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NOAAFSYB-A  72-1 


,*^'''°"^o^ 


Fishery  Bull 

National  Oceanic  and  Atmospheric  Administration  •  National  Mar 


Vol.  72,  No.  1  January  1974 

KITTREDGE,  J.  S.,  FRANCIS  T.  TAKAHASHI,  JAMES  LINDSEY.  and  REUBEN 

LASKER.  Chemical  signals  in  the  sea:  Marine  allelochemics  and  evolution 1 

FULLENBAUM,  RICHARD  F.,  and  FREDERICK  W.  BELL.  A  simple  bioeconomic 

fisheiT  management  model:  A  case  study  of  the  American  lobster  fishery 13 

OLLA,  BORI  L.,  ALLEN  J.  BEJDA,  and  A.  DALE  MARTIN.  Daily  activity,  move- 
ments, feeding,  and  seasonal  occurrence  in  the  tautog,  Tautoga  onitis 27 

LENARZ,  W.  H.,  W.  W.  FOX,  JR.,  G.  T.  SAKAGAWA,  and  B.  J.  ROTHSCHILD. 
An  examination  of  the  yield  per  recmit  basis  for  a  minimum  size  regulation  for 
Atlantic  yellowfin  tuna.  Thniiiius  albacares 37 

FLEMINGER,  A.,  and  K.  HULSEMANN.  Systematics  and  distribution  of  the  four 

sibling  species  comprising  the  genus  Pontellina  Dana  (Copepoda.  Calanoida) 63 

HUGHES,  STEVEN  E.  Stock  composition,  growth,  mortality,  and  availability  of 

Pacific  saury,  Cololabis  saira,  of  the  northeastern  Pacific  Ocean 121 

ANAS,  RAYMOND  E.  Hea\y  metals  in  the  northern  fur  seal,  Callorhiinis  ursinus, 

and  harbor  seal,  Phoca  vituUita  ricliardi 133 

WAHLE,  ROY  J.,  ROBERT  R.  VREELAND,  and  ROBERT  H.  LANDER.  Bio- 
economic contribution  of  Columbia  River  hatchery  coho  salmon.  1965  and  1966 
broods,  to  the  Pacific  salmon  fisheries 139 

POWELL,  GUY  C,  KENNETH  E.  JAMES,  and  CHARLES  L.  HURD.  Ability  of 
male  king  crab.  Paralithodes  camtschatica,  to  mate  repeatedly,  Kodiak,  Alaska,  1973.  171 

WICKHAM,  DONALD  A.,  and  GARY  M.  RUSSELL.  An  evaluation  of  mid-water 

artificial  structures  for  attracting  coastal  pelagic  fishes 181 

GRANT,   GEORGE   C.   The  age   composition   of  striped   bass  catches  in  Virginia 

Rivers,  1967-1971,  and  a  description  of  the  fishery 193 

PEARCY,  WILLIAM  G.,  and  SHARON  S.  MYERS.  Larval  fishes  of  Yaquina  Bay. 

Oregon:  A  nurser>'  ground  for  marine  fishes?  . 201 

PARK,  TAISOO.  Calanoid  copepods  of  the  genus  Aetideus  from  the  Gulf  of  Mexico  .  .  215 

LIGHTNER.  DONALD  V.  Normal  postmortem  changes  in  the  brown  shrimp,  Pe)iaeus 

aztecHH    223 

STRUHSAKER,  PAUL,  and  ROBERT  M.  MONCRIEF.  Bothii^  thonip.s(>,ii  (Fowler) 

1923.  a  valid  species  of  flatfish  (Pisces;  Bothidae)  from  the  Hawaiian  Islands 237 

Note 

CABLE,  WAYNE  D.,  and  WARREN  S.  LANDERS.  Development  of  eggs  and  em- 

biyos  of  the  surf  clam,  Spisula  Holidissinia,  in  synthetic  seawater 247 


Seattle,  Wash. 


U.S.  DEPARTMENTOFCOMMERCE 

Frederick  B.  Dent,  Secretary 

NATIONAL  OCEANIC  AND  ATMOSPHERIC  ADMINISTRATION 

Robert  M.  White,  Adminisfrator 

NATIONALMARINE  FISHERIES  SERVICE 
Robert  W.  Schoning,  Director 


Fishery  Bulletin 

The  Fishery  Bulleiin  carries  original  research  reports  and  technical  notes  on  investigations  in  fishery  science, 
engineering,  and  economics.  The  Bulletin  of  the  United  States  Fish  Commission  was  begun  in  1881;  it  became  the 
Bulletin  of  the  Bureau  of  Fisheries  in  1904  and  the  Fishery  Bulletin  of  the  Fish  and  Wildlife  Service  in  1941.  Separates 
were  issued  as  documents  through  volume  46;  the  last  document  was  No.  1103.  Beginning  with  volume  47  in  1931  and 
continuing  through  volume  62  in  1963,  each  separate  appeared  as  a  numbered  bulletin.  A  new  system  began  in  1963 
with  -volume  63  in  which  papers  are  bound  together  in  a  single  issue  of  the  bulletin  instead  of  being  issued  individually, 
Beginning  with  volume  70,  number  1,  January  1972,  the  Fishery  Bulletin  became  a  periodical,  issued  quarterly.  In  this 
form,  it  is  available  by  subscription  from  the  Superintendent  of  Documents,  U.S.  Government  Printing  Office,  Washington, 
D.C.  20402.  It  is  also  available  free  in  limited  numbers  to  libraries,  research  institutions.  State  and  Federal  agencies, 
and  in  exchange  for  other  scientific  publications. 


EDITOR 

Dr.  Reuben  Lasker 

Scientific  Editor,  Fishery  Bulletin 

National  Marine  Fisheries  Service 

Southwest  Fisheries  Center 
,  La  Jolla,  California  92037 


Editorial  Committee 

Dr.  Elbert  H.  Ahlstrom 

National  Marine  Fisheries  Service 

Dr.  William  H.  Bayliff 

Inter-American  Tropical  Tuna  Commission 

Dr.  Daniel  M.  Cohen 

National  Marine  Fisheries  Service 

Dr.  Howard  M.  Feder 
University  of  Alaska 

Mr.  John  E.  Fitch 

California  Department  of  Fish  and  Game 

Dr.  Marvin  D.  Grosslein 
National  Marine  Fisheries  Service 


Dr.  J.  Frank  Hebard 

National  Marine  Fisheries  Service 

Dr.  John  R.  Hunter 

National  Marine  Fisheries  Service 

Dr.  Arthur  S.  Merrill 

National  Marine  Fisheries  Service 

Dr.  Virgil  J.  Norton 
University  of  Rhode  Island 

Mr.  Alonzo  T.  Pruter 

National  Marine  Fisheries  Service 

Dr.  Theodore  R.  Rice 

National  Marine  Fisheries  Service 

Dr.  Brian  J.  Rothschild 

National  Marine  Fisheries  Service 

Mr.  Maurice  E.  Stansby 
National  Marine  Fisheries  Service 

Dr.  Maynard  A.  Steinberg 
National  Marine  Fisheries  Service 

Dr.  Roland  L.  Wigley 

National  Marine  Fisheries  Service 


Kiyoshi  G.  Fukano,  Managing  Editor 


The  Secretary  of  Commerce  has  determined  that  the  publication  of  this  periodical  is  necessary  in  the 
transaction  of  the  public  business  required  by  law  of  this  Department.  Use  of  funds  for  printing  of 
this  periodical  has  been  approved  by  the  Director  of  the  Office  of  Management  and  Budget  through 
May  31,  1974. 


Fishery  Bx^^ 


LIBRARY 
CONTEN'l^y  2  0  1974 

Vol.  72,  No.  1  I      Woods  Hole,  M^'^     j^^^^^.^  ^^._^ 

KITTREDGE,  J.  S.,  FRANCIS  T.  TAKAHASHI,  JAMES  LINDSEY,  and  REUBEN 

LASKER.  Chemical  signals  in  the  sea:  Marine  allelochemics  and  evolution 1 

FULLENBAUM,  RICHARD  F..  and  FREDERICK  W.  BELL.  A  simple  bioeconomic 

fishery  management  model:  A  case  study  of  the  American  lobster  fishery 13 

OLLA,  BORI  L.,  ALLEN  J.  BEJDA,  and  A.  DALE  MARTIN.  Daily  activity,  move- 
ments, feeding,  and  seasonal  occurrence  in  the  tautog,  Tautoga  ojiitis 27 

LENARZ,  W.  H.,  W.  W.  FOX,  JR.,  G.  T.  SAKAGAWA.  and  B.  J.  ROTHSCHILD. 

An  examination  of  the  yield  per  recruit  basis  for  a  minimum  size  regulation  for 
Atlantic  yellowfin  tuna.  Tliuinuis  albacares 37 

FLEMINGER,  A.,  and  K.  HULSEMANN.  Systematics  and  distribution  of  the  four 

sibling  species  comprising  the  genus  Pontellina  Dana  (Copepoda.  Calanoida) 63 

HUGHES,  STEVEN  E.   Stock  composition,  growth,  mortality,  and  availability  of 

Pacific  saury,  Cololabis  saira,  of  the  northeastern  Pacific  Ocean 121 

ANAS,  RAYMOND  E.  Heavy  metals  in  the  northern  fur  seal,  CaU(i)-hi)tus  ursi)iHs, 

and  harbor  seal,  Pltoca  rituliiia  richardi 133 

WAHLE,  ROY  J.,  ROBERT  R.  VREELAND,  and  ROBERT  H.  LANDER.  Bio- 
economic contribution  of  Columbia  River  hatchery  coho  salmon,  1965  and  1966 
broods,  to  the  Pacific  salmon  fisheries 139 

POWELL,  GUY  C,  KENNETH  E.  JAMES,  and  CHARLES  L.  HURD.  Ability  of 

male  king  crab,  Paralithudes  ca nitschatica ,  to  mate  repeatedly,  Kodiak,  Alaska,  1973.  171 

WICKHAM,  DONALD  A.,  and  GARY  M.  RUSSELL.  An  evaluation  of  mid-water 

artificial  structures  for  attracting  coastal  pelagic  fishes 181 

GRANT,   GEORGE    C.   The  age   composition   of  striped   bass   catches   in   Virginia 

Rivers,  1967-1971.  and  a  description  of  the  fishery 193 

PEARCY,  WILLIAM  G.,  and  SHARON  S.  MYERS.  Larval  fishes  of  Yaquina  Bay, 

Oregon:  A  nursery  ground  for  marine  fishes? 201 

PARK,  TAISOO.  Calanoid  copepods  of  the  genus  Aetideus  from  the  Gulf  of  Mexico  .  .  215 

LIGHTNER,  DONALD  V.  Normal  postmortem  changes  in  the  brown  shrimp,  Peiiaei(s 

aztt'cn!<    223 

STRUHSAKER,  PAUL,  and  ROBERT  M.  MONCRIEF.  Bofluis  thompsmn  (Fowler) 

1923,  a  valid  species  of  flatfish  (Pisces;  Bothidae)  from  the  Hawaiian  Islands 237 

Note 

CABLE,  WAYNE  D.,  and  WARREN  S.  LANDERS.  Development  of  eggs  and  em- 
bryos of  the  surf  clam,  Spisida  solidissima,  in  synthetic  seawater 247 


For  sale  bv  the  Superintendent  of  Documents.  U.S.  Government  Printing 
Office.  Wasliington.  DC.  20402  -  Subscription  price:  $10.85  per  year 
(S2.75  additional  for  foreign  mailing).  Cost  per  single  issue  -  $2.75. 


CHEMICAL  SIGNALS  IN  THE  SEA: 
MARINE  ALLELOCHEMICS  AND  EVOLUTIO 


J.  S.  KiTTREDGE,'-  FRANCIS  T.  TaKAHASHI,^ 

James  Lindsey,^  and  Reuben  Lasker'^ 


ABSTRACT 


Observations  in  chemical  ecology  suggest  the  coevolution  of  "natural  products"  of  plants  and 
the  chemoreceptors  of  herbivorous  insects.  We  have  reviewed  evidence  which  suggests  that 
this  coevolution  extends  back  to  the  primordial  protistans.  Thus,  the  evolutionary  pressure 
for  the  development  of  a  chemosensory  capability  probably  derived  from  the  presence  of 
metabolic  products  in  the  milieu.  These  products  are  considered  to  have  been  both  cues  to 
the  location  of  prey  and  "membrane  irritants"  evolved  in  the  initial  phase  of  chemical 
protection.  Sometime  later  this  chemosensory  capability  provided  several  functions  in  the 
evolution  of  metazoans,  i.e.  the  precursors  of  developmental  signals,  hormone  function,  and 
synaptic  transmission. 

We  consider  that  most  of  the  extant  "natural  products"  of  plants  and  marine  invertebrates 
are  protective  allomones.  A  feature  of  allomone  function  that  has  been  termed  "antifeedant" 
or  "feeding  inhibitor"  may  represent  the  "cryptic  odors"  of  Haldane.  We  provide  evidence 
that  the  naphthoquinones  with  a  juglone  or  naphthazarin  structure  have  this  activity.  Octo- 
pus ink  has  a  "cryptic  odor"  effect  on  moray  eels.  Marine  Crustacea  have,  however, 
evolved  an   ability  to  perceive  the  orthoquinone   precursors  of  the  ink,   a  warning  signal. 

Evidence  for  an  array  of  sex  pheromones  in  a  crab  and  a  cycloid  swimming  pattern  in  a 
copepod  that  may  enable  it  to  follow  a  chemical  gradient  indicate  the  complexity  of 
behavioral  responses  to  chemical  cues. 


The  earliest  form  of  interaction  between  organ- 
isms was  probably  by  means  of  chemical 
agents.  This  interaction  involved  both  conflict 
and  cooperation  and  its  existence  implies  detec- 
tion of  these  agents.  Haldane  (1955)  first 
suggested  that  chemical  communication  is  the' 
most  primitive  form  of  communication,  orgin- 
ating  with  primordial  unicellular  organisms.  He 
reasons  that  this  primordial  protistan  com- 
munication was  a  necessary  prelude  to  the  evo- 
lution of  metazoans  and  thus  is  a  lineal  pre- 
decessor of  synaptic  transmission  and  hormone 
reception.  This  early  chemical  communication 
may  have  evolved  as  an  accessory  to  the  active 
transport  mechanism  of  the  cell  membrane 
or  as  a  "membrane  sensitivity"  to  metabolic 
by-products    (Wynne-Edwards,    1962).    That   a 


'  This  work  was  supported  by  NSF  grant  GB-27703; 
ONR  Contract  N00014-7I-C-0103;  NOAA  Institutional 
Sea  Grant  2-35  187;  PHS  NB  08599. 

-  Marine  Biomedical  Institute,  University  of  Texas 
Medical  Branch,  Galveston,  TX  77550. 

3  Zoology  Department,  Oregon  State  University, 
Corvallis,  OR  97331. 

*  Department  of  Biological  Sciences,  University  of 
California   at   Santa   Barbara,   Santa   Barbara,  CA   93106. 

5  Southwest  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  La  Jolla,  CA  92037. 


more  detailed  understanding  of  transducer 
physiology  is  central  to  further  advances  in 
neurobiology  has  been  emphasized  by  Delbriick 
(1970).  He  considers  the  stimulus-response 
system  represented  by  chemoreception  or 
synaptic  transmission  to  be  homologous. 

We  wish  to  examine  some  of  the  recent  con- 
cepts of  chemical  ecology  and  to  present 
examples  from  the  marine  environment.  Studies 
of  chemoreception  are  providing  evidence  for 
the  pervasive  function  of  chemical  signals  in 
the  environment.  The  "membrane  sensitivity" 
concept  of  Wynne-Edwards  may  provide  a  clue 
to  both  the  initial  evolution  of  a  transducer 
function  and  the  continuing  evolution  of 
receptor  sites  of  greater  diversity  and  specificity. 
It  is  evident  that  this  diversity  has  resulted  from 
a  continual  interplay  of  chemical  counter- 
measures  and  the  development  of  neurosensory 
and  behavioral  adaptations  to  these  agents. 

ALLELOCHEMICS 

At  all  levels  of  life  we  are  finding  examples 
of    attack,    defense,    and    behavioral    response 


Manuscript  accepted  July  1973. 

FISHERY  BULLETIN:  VOL.  72,  NO.  1,  1974 


1 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


based  on  chemical  agents.  These  interactions 
and  the  characterization  of  the  chemical  agents 
involved  are  the  subject  of  the  newly  developing 
field  of  chemical  ecology  (Sondheimer  and 
Simeone,  1970).  Chemicals  that  are  syntheized 
and  released  by  one  individual  of  a  species  to 
alter  the  behavior  of  other  members  of  the 
species  are  termed  pheromones.  These  signals 
range  in  their  function  from  trail  markers  and 
territorial  markers  through  alarm  and  defense 
signals  to  those  which  control  caste  structure  in 
social  insects  and  the  sex  pheromones  that  are 
calling  signals  and  aphrodisiacs.  Chemicals  also 
have  a  wide  range  of  interspecific  interactions. 
A  substance  produced  by  one  organism  may 
influence  the  behavior  of  members  of  other 
species.  A  flower  scent  that  enhances  pollina- 
tion is  a  well-known  example.  This  field  of 
chemical  ecology  has  been  termed  allelo- 
chemics,  and  the  chemical  agents  have  been 
subdivided  on  the  basis  of  function  into  allo- 
mones,  which  give  adaptive  advantage  to  the 
producing  organism,  and  kairomones,  which 
give  adaptive  advantage  to  the  receiving 
organism  (Whittaker  and  Feeny,  1971).  The 
allomones  include  the  repellents  produced  by 
many  plants  and  animals,  suppressants  which 
inhibit  competitors  (e.g.,  fungal  antibiotics), 
venoms,  inductants  (e.g.,  gall  producing  agents), 
and  attractants  (e.g.,  chemical  lures).  The  kairo- 
mones include  attractants  (e.g.,  the  scent  of  a 
prey),  inductants  (e.g.,  the  factor  that  stimulates 
hyphal  loop  development  in  nematode-trapping 
fungi),  danger  signals  (e.g.,  predator  scents, 
secondary  plant  substances  indicating  toxicity), 
and  stimulants  (e.g.,  hormones  that  induce 
growth  in  the  receiving  organism). 

The  diverse  natural  products,  coumarins, 
quinones,  flavonoids,  acetylenes,  terpenoids, 
saponins,  cardiac  glycosides,  alkaloids,  thiols, 
and  cyanogenic  glycosides,  which  were  long 
considered  metabolic  waste  products,  are  now 
recognized  to  be  allelochemic  agents.  Examina- 
tion of  the  function  of  these  natural  products 
provides  some  insight  into  their  evolution.  Some 
of  these  compounds  are  toxic,  some  are 
chemical  lures,  others  inhibit  the  growth  of 
competitive  plant  species,  but  the  bulk  of  these 
compounds  probably  function  as  "feeding  inhi- 
bitors" of  herbivores  (Gilbert,  Baker,  and  Norris, 
1967;  Munakata,  1970).  The  coevolution  of 
butterflies  and  plants  is  considered  by  Ehrlich 
and    Raven    (1964).    They   emphasize   the   role 


of   reciprocal    selective    responses   during   this 
evolution    and    conclude   that    "the    plant-her- 
bivore interface  may  be  the  major  zone  of  inter- 
action   responsible    for    generating    terrestrial 
organic  diversity."  The  "accidental"  evolution 
of  a  metabolic  sequence  resulting  in  the  produc- 
tion of  a  noxious  substance  by  a  plant  provided 
a    selective    survival    advantage    in    the   clone 
carrying  this  capability.  Decreased  predation  by 
herbivores     on    those     individuals    containing 
the    highest    concentrations    of   the    new    sub- 
stance resulted  in  genetic  selection  for  increased 
synthesis  and  storage  of  the  noxious  substance. 
Such      "protected"      species      experience      an 
explosive  increase  because  of  their  protection 
from    contemporary    phytophagous    organisms. 
The    first    evolutionary    response    of   the    her- 
bivores must  have  been  the  development  of  the 
capability  to  detect  the  compound,  i.e.  sensitive 
external    chemoreceptors.    Later    evolutionary 
events   led   to  the  development   in   some   indi- 
viduals of  a  tolerance  for  the  noxious  substance. 
The  herbivores  which  developed  this  tolerance 
then  had  access  to  a  large  food  supply  for  which 
there  was  no  competition.  The  ability  to  detect 
the  substance  then  had  an  altered  function,  the 
feeding  inhibitor  was  now  a  feeding  stimulant. 
The   present   evidence   of  the   repeated    occur- 
rence of  this  cycle  is  the  existence  of  tightly 
coupled    herbivorous    insects    and    their    host 
plants,     presumably     arising     through     coad- 
aptation. 

In  1955  Haldane,  in  a  consideration  of 
chemical  communication  and  visual  signals, 
wondered  if  cryptic  odors  had  ever  evolved. 
While  most  of  the  feeding  inhibitors  that  have 
evolved  are  probably  irritants,  many  may  be 
cryptic  odors.  It  is  likely  that  the  two  activities 
may  only  differ  in  the  membrane  affected.  The 
term  irritant  implies  membranic  sensitivity 
and,  of  those  membranes  of  an  organism  in 
immediate  contact  with  the  environment,  the 
chemosensory  membranes  are  likely  the  most 
sensitive  to  chemical  irritation.  In  an  environ- 
ment in  which  a  major  fraction  of  the  informa- 
tion flow  is  chemical,  any  agent  capable  of 
disrupting  the  chemosensory  organs  of  a  preda- 
tor would  provide  an  ideal  mechanism  for  "hid- 
ing" from  that  predator.  Cryptic  odors  may  be 
either  "negative  odors"  altering,  for  protracted 
periods,  the  membrane  potential  of  the  dendrites 
and  blocking  their  normal  generator  potential, 
or  they   may  be  the  chemical  equivalent  of  a 


KITTREDGE  ET  AL.:  CHEMICAL  SIGNALS  IN  THE  SEA 

"white  noise,"  producing  an  "uncoded"  array  of 
spikes  in  the  chemosensory  neurons. 

The  best  description  of  behavior  suggesting 
a  "cryptic  odor"  in  the  marine  environment  is 
that  given  by  MacGinitie  and  MacGinitie  (1968). 
The  ink  of  an  octopus  is  considered  a  "smoke 
screen";  however,  it  can  also  affect  the  olfactory 
sense.  The  MacGinities  observed  that  after  a 
moray  eel  swam  through  the  ink  cloud  of  an 
octopus  it  could  no  longer  "recognize"  an 
octopus.  The  moray  eel  apparently  requires 
both  visual  and  olfactory  input  for  this  recogni- 
tion. They  state,  "We  were  surprised  to  find 
that  the  real  effect  of  the  ink  of  an  octopus 
is  to  paralyze  the  olfactory  sense  of  its  enemies." 
The  melanin  of  the  ink  is  a  polymer  of  oxidized 
L-DOPA.  The  polymerization  proceeds  through 
three  orthoquinones,  dopaquinone  (6,  Figure 
1),  dopachrome  (7),  and  indole-5,  6-quinone  (8). 
In  the  biosynthesis  of  melanin,  this  oxidation  is 
catalyzed  by  polypheny  1  oxidases;  however, 
heavy  metal  ions  can  also  catalyze  the  oxidation, 
and  it  can  be  readily  demonstrated  that  the 
trace  of  heavy  metal  ions  in  seawater  will  rapidly 
convert  L-DOPA  to  melanin.  The  octopus  ink 
loses  its  potency  with  time,  a  factor  that  would 
indicate  that  the  biological  activity  of  the  ink  is 
due  to  the  presence  of  the  unstable  monomer 
orthoquinones  in  the  fresh  ink  (Kittredge, 
Takahashi,    and    Lindsey,    unpublished    data). 

The  observation  of  Gilbert  et  al.  (1967)  that 
juglone  (5-hydroxy-l,4-naphthoquinone)  (1. 
Figure  1)  is  a  deterrent  to  feeding  by  the  bark 
beetle,  Scolytus  multistriatus,  suggested  a 
similar  function  for  the  polyhydroxynaphtho- 
quinones  occurring  in  the  echinoderms.  These 
spinochromes  are  all  derivatives  of  juglone  (1) 
or  naphthazarin  (2).  They  occur  as  soluble  salts 
in  the  tissues  and  may  be  present  in  considerable 
amounts  in  the  larvae.  They  also  occur  as 
insoluble  calcium  salts  in  the  spines  and  tests 
(Thompson,  1971).  The  echinoids  have 
received  the  closest  attention,  but  P.  J.  Scheuer 
and  his  group  have  demonstrated  the  presence 
of  these  compounds  in  the  other  four  classes 
of  this  phylum — the  holothurians,  asteroids, 
ophiuroids,  and  crinoids  (Singh,  Moore,  and 
Scheuer,  1967).  They  also  demonstrated  the 
presence  of  a  substituted  2,5-benzoquinone 
(3)  in  the  genus  Echinothnx  (Moore,  Singh,  and 
Scheuer,  1966).  The  crinoids  are  interesting  in 
that  they  contain  primarily  a  series  of  poly- 
hydroxyanthroquinones    (e.g.,    rhodocomatulin, 


OH    0 
I       II 


0 


I     II 

OH    0 
(1) 


I       II 
OH    0 

(2) 


HO- 


O 

'Sr^cH; 


.CH 


0 

(3) 


HO\.^,^^0^/Ar 


H  0  •^^^'-^^-•^^^^O  H 
nu  II       II       UM 

0      COfCHglgCHj 
(4) 


00' 

I       II 
OH    0 

(5) 


0^, 
0 


.CH2-CH-COOH 

NHo 


(6) 


0< 
0' 


to- 


H 
(7) 


COOH 


(8) 


Figure  1. — Structures  of  compounds  typical  of  those 
which  may  function  as  "cryptic  odors."  (1)  juglone.  (2) 
naphthazarin,  (3)  2,  5-dihydroxy-3-  ethylbenzoquinone, 
(4)  rhodocomatulin,  (5)  fiavone,  (6)  dopaquinone,  (7) 
dopachrome.  (8)  indole-5, 6-quinone. 

4)  (Sutherland  and  Wells,  1967;  Powell,  Suther- 
land, and  Wells,  1967;  Powell  and  Sutherland, 
1967;  Matsuno  et  al..  1972;  Erdman  and 
Thomson,  1972). 

Utilizing  the  "feeding  response"  of  the  lined 
shore  crab,  Pachygmpsus  crassipes,  which 
consists  of  a  rapid  lateral  movement  of  the 
mouthparts  when  presented  with  a  feeding 
stimulus,  we  have  bioassayed  the  "feeding 
inhibitor"  activity  of  juglone  and  eight  repre- 
sentative spinochromes.  The  "feeding  stimulus" 
was  a  20-iul  aliquot  of  a  3-mM  solution  of 
taurine  in  seawater  administered  from  a  repeat- 
ing syringe  close  to  one  of  the  antennules  of  the 
crab.  Initially  the  crabs  were  immersed  in  a 
l-/uM  solution  of  the  naphthoquinone  and  tested 
for  a  feeding  response.  Five  experimental  and 


FISHERY  BULLETIN:  VOL.  11.  NO.  1 


one  control  crab  were  utilized  for  each  compound. 
No  feeding  responses  were  observed  in  any  of 
the  test  crabs  while  all  of  the  controls  were 
positive.  A  second  series  of  bioassays  was 
designed  to  determine  the  onset  of  inhibition. 
The  crabs  were  placed  in  seawater  and  stimu- 
lated with  20  fji\  aliquots  of  a  solution  of  3  mM 
taurine  and  1  jliM  quinone.  The  stimulus  was 
administered  at  2  sec  intervals  to  alternate 
antennules.  Inhibition  of  the  "feeding  response" 
was  observed  at  approximately  10  sec.  The 
naphthazarin  derivatives  were  apparently  more 
potent  than  the  juglone  derivatives.  We  interpret 
these  results  as  indicative  of  a  "cryptic  odor" 
function;  the  crabs  cannot  detect  the  feeding 
stimulant  after  a  brief  exposure  to  the  quinone. 

Many  higher  plants  contain  juglone  or  other 
hydroxynaphthoquinones  or  benzoquinones. 
These  compounds  also  occur  in  fungi,  lichens, 
pholangids,  millipedes,  and  insects.  1,4-benzo- 
quinones  are  the  most  common  ingredient  of 
insect  defensive  secretions  and  the  2,5-sub- 
stituted  1,4-benzoquinones  are  characteristic  of 
fungi.  A  similar  "cryptic  odor"  function  may  be 
predicted  for  these  compounds. 

Norris  (1969)  compared  the  feeding  deterrent 
activity  of  a  number  of  substituted  naphthoquin- 
ones. Juglone  (1)  and  naphthazarin  (2)  were  the 
most  potent  inhibitors.  The  apparent  effective- 
ness of  the  hydroxy  groups  in  the  5-  or  5,8- 
positions  in  these  naphthoquinones  suggests  an 
examination  of  the  function  of  the  major  group 
of  secondary  plant  metabolites,  the  flavones 
(5)  (Harborne,  1972)  which  have  a  marked 
structural  similarity. 

Whittaker  and  Feeny  (1971)  predict  "that 
research  into  the  relations  of  multicellular 
marine  algae  and  their  consumers  will  reveal 
chemical  defenses  and  responses  paralleling 
those  of  higher  plants  and  animals  on  land." 
The  most  likely  candidates  to  fulfill  this  predic- 
tion are  the  highly  halogenated  hydrocarbons 
that  are  synthesized  by  algae  and  stored  in  the 
tissues  of  the  herbivorous  gastropod,  Aplysia 
caHfornica  (Faulkner  and  Stallard,  1973; 
Faulkner  et  al.,  1973).  We  would  add  to  the 
prediction  of  Whittaker  and  Feeny  that  research- 
into  the  relations  of  many  marine  inverte- 
brates and  their  predators  may  reveal  allomones. 
Some  of  the  "natural  products"  of  marine 
invertebrates  that  have  been  recently  character- 
ized and  that  may  have  this  function  are  the 
halogenated  antibiotics  that  have  been  isolated 


from,  sponges  (Sharma,  Vig,  and  Burkholder, 
1970;  Fattorusso,  Minale,  and  Sodano,  1972; 
Moody  et  al.,  1972;  Anderson  and  Faulkner, 
1973).  Steroid  saponins  that  are  toxicants  or 
irritants  have  been  characterized  from  holo- 
thuroids  and  starfish  (Yasumoto,  Nakamura, 
and  Hashimoto.  1967;  Tursch  et  al.,  1967; 
Roller  et  al.,  1969;  Tursch,  Cloetens,  and 
Djerassi,  1970;  Turner,  Smith,  and  Mackie, 
1971). 

We  recall  a  simple  demonstration  by  the 
late  C.  F.  A.  Pantin  of  the  sensitive  chemo- 
sensory  capability  of  sea  anemones  for  saponin. 
The  nematocysts  of  sea  anemones  require 
both  a  mechanical  and  a  chemical  stimulus  for 
discharge.  One  can  brush  the  surface  of  a  sea 
anemone's  tentacles  with  a  clean  glass  rod 
without  effecting  any  discharges.  If,  however 
the  glass  rod  is  first  dipped  into  a  dilute  saponin 
solution,  a  massive  discharge  is  effected. 

An  observation  by  Clark  (1921)  suggests 
the  existence  of  allomones  in  crinoids.  He 
discusses  the  avoidance  of  comatulid  crinoids 
by  fish  and  suggests  the  activity  of  glands  at  the 
base  of  the  tentacles.  The  comatulids  are 
unique  in  containing  both  polyhydroxyanthro- 
quinones  and  aromatic  polyketides  (Kent,  Smith, 
and  Sutherland,  1970;  Smith  and  Sutherland, 
1971). 

MARINE  KAIROMONES 

As  in  the  terrestrial  environment,  in- 
vertebrates utilize  chemical  cues  to  locate  hosts 
or  to  warn  of  predators.  Davenport  (1966) 
demonstrated  the  response  of  commensal  poly- 
noid  polychaetes  to  a  "host  factor"  in  the  water 
draining  from  tanks  containing  the  host  species 
of  starfish.  In  an  electrophysiological  analysis 
of  the  antennular  chemoreceptors  of  two  com- 
mensal shrimps.  Ache  and  Case  (1969)  demon- 
strated the  specificity  of  the  response  to  "host 
water"  from  the  specific  hosts,  Haliotis  spp. 
and  Stro)igyloceiitrotus  spp. 

Predatory  starfish  induce  an  escape  response 
in  a  variety  of  molluscs  (Feder,  1967),  and 
these  behavioral  responses  probably  effectively 
reduce  the  predation  on  these  species  that  can 
detect  the  predator  (Feder,  1963).  The  active 
materials  in  extracts  of  the  starfish  Marthasteria 
glaciali.s  and  Asten'a.s  nibcHs  which  induce  the 
escape  response  have  been  shown  to  be  steroid 
saponins   (Mackie,   Lasker,   and   Grant,    1968). 


KITTREDGE  ET  AL:  CHEMICAL  SIGNALS  IN  THE  SEA 

The  threshold  for  response  by  the  snail, 
Biicc'nium  uudatiim  is  0.2-0.4  X  lO"-'  M 
(Mackie,  1970).  and  the  structure  of  these 
steroid  glycosides  has  been  determined  (Turner 
et  al.,  1971). 

A  behavioral  bioassay  of  one  of  the  ortho- 
quinones  derived  from  L-DOPA,  dopachrome, 
utilizing  the  feeding  response  of  the  lined  shore 
crab  PachygmpsHS  crassipes  indicated  that  this 
quinone  might  also  be  a  "cryptic  odor."  Electro- 
physiological studies,  however,  demonstrated 
that  these  results  were  misleading.  Utilizing  a 
preparation  of  the  dactyl  chemoreceptors  of 
the  spiny  lobster  Pa)udinis  interruptus,  we 
detected  chemoreceptors  for  this  quinone  that 
were  about  a  hundred  times  as  sensitive  as  the 
general  amino  acid  receptors  in  this  prepara- 
tion (Figure  2).  While  we  have  not  explored  the 


range  of  specificity  of  these  receptors,  the 
results  suggest  that  these  crustaceans,  the 
natural  prey  of  the  octopus,  have  evolved  a 
mechanism  for  detecting  the  presence  of  the 
predator.  Our  results  with  the  bioassay  likely 
reflect  a  priority  of  responses  to  the  two  chem- 
ical stimuli  (Kittredge,  Takahashi,  and  Lindsey, 
unpublished  data). 

PHEROMONES 

Unicellular  chemical  communication, 
analogous  to  Haldane's  primordial  protistan 
communication,  is  evident  in  the  conjugation 
of  ciliates.  The  microconjugant  of  a  peritrichous 
ciliate,  which  is  free  swimming,  can  identify  the 
macroconjugant,  which  is  sessile,  by  chemicals 
released  by  the  latter.  Although  evidence  for 


I 


,VW#MWM 


2. 


<#«i^A/^M'^V'^iVi!,*)/i^SJ<^^ 


3. 


4. 


1 1- 

i         •        1  * 


5. 


50jj,  Volts 


Figure  2. — Electrophysiological  recordings  from  the  dactyl  chemoreceptors  of  a  spiny  lobster,  Panulims  interruptus.  (1) 
Seawater  blank,  (2)  IQ-'i  M  dopachrome  in  seawater,  (3)  Persisting  spikes  in  dopachrome  receptors  (continuation  of  2),  (4) 
10-3  M  taurine  in  seawater,  (5)  10"3  M  taurine  after  dopachrome  and  a  seawater  wash. 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


the  presence  of  a  large  number  of  agents  chemo- 
tropic  for  male  gametes  exists  (Machlis  and 
Rawitscher-Kunkel,  1963).  only  two  have 
been  chemically  characterized.  Sirenin.  the 
active  compound  produced  by  the  female 
gametes  of  the  water  mold  Allomyces,  has  been 
isolated  and  characterized  as  an  oxygenated 
sesquiterpene  (Machlis  et  al.,  1966),  and  its 
structure  has  been  uniquely  established 
(Machlis,  Nutting,  and  Rapoport,  1968).  It  is 
active  in  attracting  male  gametes  at  10"'"M. 
The  corresponding  work  from  the  marine  field 
resulted  in  the  characterization  of  the  active 
substance  released  by  the  female  gametes  of 
the  brown  alga  Ectocarptis  siUckIosk.'^  as  allo- 
cis-l-(cycloheptadien  -2',  5'-yl)-butene-l  (Miiller 
et  al..  1971).  The  receptor  sites  on  the  male 
algal  gametes  evidence  a  low  level  of  specificity. 
Many  lower  hydrocarbons,  esters,  alcohols, 
and  aldehydes,  at  higher  concentrations,  will 
mimic  the  natural  compounds  in  attracting 
male  gametes  (Cook,  Elvidge,  and  Bentley, 
1951;    Miiller,    1968;    Hlubucek   et   al.,    1970). 

Though  many  efforts  to  demonstrate  a  chemo- 
tactic  response  by  mammalian  sperm  to  sub- 
stances from  eggs  have  yielded  negative  results, 
such  attraction  does  occur  in  marine  forms. 
Sperm  of  the  thecate  hydroids  Cai)ipanularia 
flexuosa  and  C.  calceolifera  respond  to  a  sub- 
stance issuing  from  the  aperture  of  the  female 
gonangium.  The  response  is  species  specific 
(Miller,  1966).  Observations  by  Dan  (1950) 
suggest  the  activity  of  a  similar  substance  from 
the  eggs  of  the  medusa  Spirocodan  saltatrix 
on  the  sperm  of  this  species.  The  first  examples 
of  sperm  chemotaxis  in  vertebrates  are  described 
in  pai)ers  on  fertilization  in  the  herring  Clnpea 
by  Yanagimachi  (1957)  and  in  the  bitterling 
Acheilognathus  by  Suzuki  (1961). 

The  attraction  of  the  amoeboid  form  of  the 
slime  mold  Dictyostelium  discoideum  during 
the  aggregation  phase  which  results  in  the 
formation  of  a  multicellular  "slug"  represents 
the  best  studied  protistan  communication.  The 
attractant  is  cyclic  adenosine  monophosphate 
(Konijn  et  al.,  1968;  Barkley,  1969).  Pulses  of 
cyclic  AMP  radiate  out  through  the  soil 
moisture  at  5  min  intervals  from  the  center  of  a 
growing  aggregation.  The  gradient  and  the 
pulse  nature  of  the  signal  are  maintained  by 
each  inward  streaming  amoeba.  Each  amoeba 
secretes  a  phosphodiesterase  to  break  down  the 
cyclic  AMP  and,  on  sensing  a  pulse  of  cyclic 


AMP,  emits  its  own  pulse  of  cyclic  AMP  about 
15  sec  after  receiving  a  signal  (Cohen  and 
Robertson,  1971;  Robertson,  Drage,  and  Cohen, 
1972).  Bonner  (1969)  has  indicated  the  likely 
course  of  the  evolution  of  this  communication 
in  the  social  slime  molds.  Soil  bacteria,  the  food 
of  the  solitary  predecessors  of  the  slime  mold 
amoeba,  secrete  cyclic  AMP.  It  is  reasonable 
to  assume  that  a  mechanism  which  initially 
increased  the  feeding  success  of  these  amoebas 
developed,  due  to  selective  pressure,  the  requi- 
site high  sensitivity  of  response  to  a  chemical 
signal  necessary  for  aggregation.  This  capacity 
then  facilitated  the  evolution  of  the  social 
species.  This  is  very  close  to  Haldane's  premise 
of  the  evolution  of  chemical  communication 
prior  to  the  evolution  of  metazoans.  In  further 
support  of  Haldane's  premise  of  the  lineage  of 
hormones,  after  aggregation  is  complete 
the  "metazoan"  slug  phase  migrates  to  the  soil 
surface  and  then  certain  cells  differentiate  into 
stalk  cells  which  will  eventually  support  the 
spore  head.  Cyclic  AMP  is  apparently  the 
chemical  signal  for  the  developmental  differ- 
entiation of  some  cells  into  stalk  cells  (Bonner, 
1970). 

The  recent  rapid  growth  of  our  understanding 
of  pheromone  communication  in  insects  was 
founded  on  half  a  century  of  acute  biological 
observations  which  implicated  the  existence  of 
chemical  messengers.  The  isolation  and 
chemical  characterizations  of  a  growing  number 
of  pheromones,  and  the  concomitant  behavioral 
studies,  have  provided  the  basis  for  our 
appreciation  of  the  role  of  chemical  communica- 
tion in  the  life  cycle  of  many  species.  Among  the 
many  recent  reviews  are  those  of  Beroza  (1970) 
and  Jacobson  (1972).  Electrophysiological 
investigations  of  chemoreception  in  insects 
have  demonstrated  that  the  receptor  cells  may 
be  divided  into  two  groups,  either  "specialists" 
or  "generalists"  (Yamada,  1970).  Among  the 
"specialists"  are  the  pheromone  receptors  and 
the  receptors  for  specific  secondary  plant  sub- 
stances that  act  as  phagostimulants  (Schoon- 
aoven,  1968).  While  remarkable  success  has 
been  achieved  in  recording  the  response  of 
single  receptor  cells  as  well  as  the  summed 
receptor  potential  of  all  the  antennal  chemore- 
ceptors  (electroantennogram)  these  workers 
have  had  to  contend  with  a  technical  problem 
inherent  in  studies  with  this  material.  Evalua- 
tion of  the  response  of  a  chemosensory  organ 


KITTREDGE  ET  AL:  CHEMICAL  SIGNALS  IN  THE  SEA 


or  a  single  cell  is  difficult  when  the  stimulant 
must  be  presented  in  the  gas  phase.  Each 
species  of  stimulant  molecule  must  partition 
between  the  gas  phase  and  an  aqueous  film. 
The  active  concentration  at  the  receptor 
membrane  is  unknown.  A  study  of  the  physi- 
ology of  pheromone  reception  by  aquatic  organ- 
isms would  avoid  this  limitation. 

A  survey  of  the  literature  reveals  that,  as  in 
the  field  of  entomology,  there  exists  a  broad 
basis  of  behavioral  observations  suggesting  the 
role  of  chemical  communication  in  the  aquatic 
environment.  These  studies  suggest  that  marine 
invertebrates  are  primarily  dependent  on  chemo- 
reception  for  information  from  their  environ- 
ment. The  input  is  composed  of  a  broad  spectrum 
of  chemical  messages  ranging  from  species 
specific  pheromones  eliciting  stereospecific 
responses,  e.g.,  mating  behavior,  epidemic 
spawning,  aggregation,  or  alarm  behavior, 
through  those  kairomones  triggering  metamor- 
phosis or  migration  to  the  cues  indicating  the 
proximity  of  predators  or  prey. 

The  closest  parallel  to  insect  pheromone 
communication  observed  in  marine  organisms 
are  the  sex  pheromones  of  marine  Crustacea. 
The  first  experimental  demonstration  of 
"chemical  recognition"  by  marine  Crustacea  is 
the  description  of  the  behavior  of  male  copepods 
(Labidocem  aestiva)  by  Parker  (1902).  In  a 
series  of  elegantly  simple  experiments  he 
demonstrated  that  "they  [the  females]  probably 
give  rise  to  some  substance  that  serves  as  a 
scent  for  the  males;  in  other  words,  the  males 
are  probably  positively  chemotropic  toward  the 
females."  Moreover  Parker  noted  that  "they  [the 
males]  seldom  pass  near  the  tube  without  some 
characteristic  reaction.  Usually  they  made  one 
or  two  quick  circles  as  they  swam  by,  or  even 
a  somersault-like  motion;  these  were  observed 
fifteen  times  when  the  females  were  in  the  tube, 
never  when  they  were  not."  Lillelund  and  Lasker 
(1971)  observed  similar  swimming  behavior  in 
male  Labidocera  joUae.  Although  L.  joUae 
females  swim  in  a  seemingly  random  pattern 
with  only  occasionally  looped  excursions,  the 
males  frequently  vary  their  random  course  of  a 
few  seconds  duration  by  swimming  in  circles, 
covering  a  small  area  intensively.  Of  greater 
interest  was  the  observation  that  rather  than 
circles,  the  path  of  the  males  often  resembled  a 
curtate  cycloid.  The  males  occasionally  pro- 
gressed for  several  centimeters  in  this  curtate 


cycloid  path  (Figure  3).  These  observations, 
although  obtained  during  feeding  studies, 
suggest  an  important  aspect  of  the  physiology 
of  pheromone  response  in  small  Crustacea — the 
mechanism  of  sensing  a  chemical  gradient.  Crisp 
and  Meadows  (1962)  have  stated  that,  because 
of  the  small  distance  between  the  chemosensory 
organs  of  barnacle  cyprid  larvae,  these  larvae 
cannot    detect   a   chemical   gradient   and   thus 


1  cm 
I 1 


Figure  3. — Swimming  behavior  of  a  male  copepod 
Lahidoceru  jollae.  A'  and  B'  mark  the  termini  of  the 
tracings.  The  upper  trace  shows  both  an  occasional  circu- 
lar swimming  course,  progression  in  a  curtate  cycloid 
course  and  "doubling  back."  The  lower  trace  is  an 
extreme  example  of  the  "doubling  back"  behavior. 


FISHERY  BULLETIN:  VOL    72.  NO    1 


cannot  exhibit  chemotactic  behavior.  This 
reasoning  has  been  applied  to  all  small  marine 
Crustacea  including  copepods.  From  the  above 
observations  it  is  apparent  that  the  reasoning 
of  Crisp  and  Meadows  is  invalid  for  Labidocera 
and  probably  for  other  small  Crustacea.  The 
critical  dimension  is  the  diameter  of  the  circular 
course,  not  the  dimensions  of  the  organism.  A 
circular  swimming  i)attern  in  a  concentration 
gradient  of  a  stimulant  would  result  in  a  sinus- 
oidal variation  in  the  signal  intensity.  Altera- 
tion of  the  radius  of  curvature  of  the  swimming 
course  in  response  to  this  sinusoidal  input 
would  result  in  cycloidal  progression  in  the 
gradient.  It  appears  from  the  observations 
of  the  behavior  of  male  L.  jollae  in  the  feeding 
experiment  that  a  threshold  level  of  stimulant 
will  trigger  a  circular  swimming  pattern,  if  this 
circular  course  results  in  the  detection  of  a 
gradient,  the  circular  course  will  become  a 
curtate  cycloid  with  the  ratio  of  the  major  to  the 
minor  radius  being  a  function  of  the  intensity 
of  the  gradient.  A  frequent  observation  is  a 
doubling  back.  If  several  progressions  of  the 
cycloid  result  in  loss  of  the  gradient  signal  (as 
must  frequently  occur  in  a  medium  in  which  the 
dimensions  of  the  turbulent  flow  are  of  the 
same  scale  as  the  swimming  pattern),  the 
swimming  plots  indicate  that  the  male  Labido- 
cera can  effectively  loop  back  through  the  area 
where  the  signal  was  initially  detected  (Figure 
3).  These  observations  indicate  some  power  of 
spatial  orientation  and  short  term  memory  in 
Labidocera. 

In  crabs  the  male  is  attracted  to  the  premolt 
female.  During  this  attraction  phase  he  may 
display  a  stance  characterized  by  standing  on 
the  tips  of  his  dactyls  and  elevating  his  body.  He 
will  seize  the  premolt  female  and  place  her 
below  his  body.  He  will  protect  her  during  the 
vulnerable  molting  period  and  they  copulate 
immediately  after  molting.  Ryan  (1966)  demon- 
strated pheromone  communication  in  this  inter- 
action. Water  from  a  tank  containing  a  premolt 
female  Portunus  sanguinolentus,  when  added  to 
a  tank  containing  a  male  of  this  species,  elicited 
the  premolt  stance.  Evidence  that  the  pheromone 
is  released  from  the  antennule  glands  was 
provided  by  sealing  these  glands  and  noting  the 
absence  of  the  stimulating  factor. 

We  have  examined  this  pheromone  com- 
munication in  the  lined  shore  crab,  Pachygrap- 
sus  crassipes.  We  isolated  an  active  substance 


and  found  that  it  behaved  chromatographically 
like  the  molting  hormone,  crustecdysone.  Pure 
crustecdysone  is  active  in  stimulating  all  of  the 
precopulatory  behavior  of  male  lined  shore  crabs 
from  an  early  search  behavior  through  the 
display  stance  to  seizing  the  female.  The  thresh- 
old for  stimulating  the  stance  is  10''^  M 
(Kittredge,  Terry,  and  Takahashi,  1971).  Con- 
firmation of  the  identification  has  been  obtained 
by  injecting  tritiated  crustecdysone  into  inter- 
molt  female  Dungeness  crabs  (Cancer  niagister) 
and  detecting  its  release  as  the  females  entered 
premolt.  Recently  we  have  detected  the  presence 
of  two  additional  pheromones  released  by  the 
female  lined  shore  crabs.  Compound  A  is  released 
in  addition  to  crustecdysone  prior  to  molt.  After 
molting  compound  A  is  no  longer  released  into 
the  water,  but,  if  the  female  is  held  in  isolation 
from  male  crabs,  a  second  compound,  B,  is  re- 
leased. It  is  likely  that  the  postmolt  female  has  a 
different  message  to  transmit. 

Evolutionary  biologists  concerned  with  the 
inception  of  pheromone  communication  have 
long  been  puzzled  by  a  dilemma.  This  chemical 
communication  implies  two  new  capabilities, 
that  to  synthesize  a  messenger  compound  and 
the  ability  to  receive  the  message  and  trans- 
late it  into  a  behavioral  response.  The  improb- 
ability of  the  simultaneous  occurrence  of  these 
two  de  novo  events  suggests  a  stepwise  sequence. 
The  observation  that  the  molting  hormone  of 
Crustacea  can  function  as  a  sex  pheromone 
indicates  that  the  primordial  Arthropoda, 
through  an  evolutionary  sequence  that  resulted 
in  structuring  the  receptor  site  for  the  hormones 
on  chemosensory  membranes,  were  able  to 
initiate  pheromonal  communication  (Kittredge 
and  Takahashi,  1972). 

SUMMARY 

Evidence  from  the  literature  supports 
Haldane's  premise  that  chemical  communica- 
tion is  the  most  primitive  form  of  communica- 
tion and  thus  the  lineal  predecessor  of  synaptic 
transmission  and  hormone  function.  Trans- 
ducers of  environmental  chemical  information 
have  likely  evolved  in  response  to  the  metabolic 
products  released  by  their  prey  and  by  competi- 
tive organisms.  This  coevolution  of  "natural 
products"  and  the  respective  transducers  has 
existed  from  the  earliest  metabolic  product  that 
happened   to   be   a   membrane   irritant   to   the 


8 


KITTREDGE  ET  AL:  CHEMICAL  SIGNALS  IN  THE  SEA 


present.  We  thus  consider  it  likely  that  most 
of  the  "natural  products."  not  only  of  terrestrial 
plants,  but  also  of  marine  plants  and  inverte- 
brates, function  as  allomones,  kairomones,  or 
pheromones.  Faulkner  and  Anderson  (In  press) 
have  provided  a  review  of  the  chemistry  of  the 
"natural  products"  of  marine  organisms. 

Conceptually,  in  such  a  "chemical  environ- 
ment" the  most  effective  protection  from  a 
predator  would  be  a  "cryptic  odor,"  an  irritant 
that  disrupts  chemoreception.  These  cryptic 
odors  may  be  released  into  the  environment,  as 
is  the  active  component  of  octopus  ink,  they 
may  exist  in  the  epidermal  tissues  or  glands 
where  they  would  function  at  the  inception  of 
attack,  or  they  may  be  contained  in  the  eggs  or 
larvae.  Most  sessile  marine  invertebrates  re- 
produce by  epidemic  spawning,  the  simultan- 
eous release  of  the  gonadal  products  of  an  entire 
local  population  of  a  species.  Most  sessile 
marine  invertebrates  are  also  filter  feeders.  The 
prime  advantage  of  epidemic  spawning  is  the 
enhancement  of  fertilization.  However,  in  the 
densely  populated  benthic  environment,  a  heavy 
loss  of  eggs  or  larvae  to  filter  feeders  may  occur. 
The  presence  of  a  "feeding  inhibitor"  in  the  eggs 
or  larvae  would  reduce  such  losses.  Reiswig 
(1970)  reported  that  they  observed  epidemic 
spawning  of  the  sponge  Neofibiilana  iiolitaiigere 
on  a  Jamaican  reef.  At  the  time  they  were 
measuring  the  water  pumping  rate  of  other 
sponges.  When  the  epidemic  spawning  of  A^ 
nolitangere  started,  the  pumping  rate  of  the. 
species  under  study,  Vero)igia  sp,  abruptly 
decreased  and  remained  negligible  for  2  days. 
A',  nolitangere  is  known  to  contain  toxic  sub- 
stances. 

The  evidence  for  chemical  cooperation,  from 
gamones  to  sex  pheromones,  suggests  a  pattern 
of  increasing  complexity  in  the  function  of 
chemical  cues.  The  behavioral  response  of  even 
a  "simple"  crustacean  to  a  chemical  gradient 
appears  to  involve  at  least  some  short  term 
"memory"  or  a  type  of  "chemical-spatial" 
sense  that  we  have  not  observed  in  such  clear- 
cut  form  in  any  other  organism. 

The  study  of  the  chemical  ecology  of  the 
marine  environment  is  scarcely  in  its  infancy. 
The  chemical  characterization  of  some  of  the 
intraspecific  and  interspecific  messages  in  the 
sea  and  the  physiology  of  their  perception  are 
challenges.  Solutions  to  these  paired  problems 


will  provide  insights  into  the  evolution  of 
chemical  transduction  and  perhaps  expose  a 
hierarchy  of  perception  from  membrane 
irritation  to  synaptic  transmission. 

ACKNOWLEDGMENTS 

We  wish  to  acknowledge  the  contribution  of 
Paul  J.  Scheuer,  Department  of  Chemistry, 
University  of  Hawaii,  to  the  study  of  the  "cryptic 
odor"  activity  of  natural  marine  naphtho- 
quinones. He  generously  provided  eight  spino- 
chromes  and  contributed  observations  on  their 
structure  and  occurrence. 

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in  the  micropyle   area  of  the  herring  egg.  Annot. 
Zool.  Jap.  30:114-119. 
Yasumoto,  T.,  K.  Nakamura,  and  Y.  Hashimoto 

1967.  A  new  saponin,  holothurin  B,  isolated  from 
sea-cucumber,  Holothuria  vagahiindci  and  Holo- 
iliuria  liihiicci.  Agric.  Biol.  Chem.  31:7-10. 


11 


A  SIMPLE  BIOECONOMIC  FISHERY  MANAGEMENT  MODEL: 
A  CASE  STUDY  OF  THE  AMERICAN  LOBSTER  FISHERYi 

Richard  F.  Fullenbaum^  and  Frederick  W.  Bell-* 
ABSTRACT 


The  pressures  of  world  economic  expansion  have  led  to  more  intensive  exploitation  of  living 
marine  resources  as  a  source  of  protein.  The  exploitation  of  these  common  property  resources 
leads,  in  many  cases,  to  overfishing  and  depletion.  This  paper  attempts  to  develop  a  simplified 
management  tool  to  prevent  overexploitation  and  depletion  of  a  fishery  resource.  A  general 
resource  model  is  postulated  embracing  both  biological  and  economic  relationships.  This 
bioeconomic  model  approximates  the  operation  of  a  fishery  under  free  access  to  the  resource. 
A  Schaefer  type  yield  function  is  combined  with  a  linear  demand  function,  and  other 
standard  economic  relationships  and  simulations  are  performed  to  evaluate  the  model.  Using 
computer  simulation,  we  imposed  five  management  strategies  on  the  case  example,  the 
American  lobster  fishery.  These  strategies  include  (1)  freezing  fishing  effort  by  raising  license 
fees:  (2)  reducing  fishing  effort  to  that  necessary  to  harvest  at  the  maximum  sustainable 
yield  by  raising  license  fees:  (3)  reducing  fishing  effort  to  an  "economic  optimum""  where 
marginal  cost  of  doing  business  is  equal  to  marginal  revenue  from  sales  by  raising  license 
fees:  (4)  instituting  a  "stock  certificate  plan""  where  individual  fishermen  would  own  portions 
of  the  resource  and  trade  catch  certificates  on  the  open  market:  however,  the  total  number  of 
catch  certificates  would  not  exceed  the  maximum  sustainable  yield:  and  (5)  doing  nothing. 
The  economic  impact  in  terms  of  catch,  fishing  effort,  number  of  fishermen,  ex-vessel  prices, 
license  revenues,  and  returns  per  boat  and  fishermen  were  computed  for  each  management 
strategy  so  that  policymakers  and  industry  leaders  could  see  the  alternative  consequences  of 
these  management  positions.  The  simplified  model  also  is  available  for  use  in  evaluation  of 
other  management  schemes  that  might  be  suggested. 


In  the  past  few  years  the  world  community  has 
become  increasingly  aware  of  the  sea  and  its 
resources.  The  pressures  of  world  economic 
expansion  have  led  to  more  intensive  exploita- 
tion and,  at  the  same  time,  to  increasing  con- 
cern over  the  marine  environment.  Many  man- 
agement strategies  used  to  protect  these  re- 
sources from  overexploitation  have  resulted  in 
inefficient  use  of  gear  and  equipment  as  shown 
by  Crutchfield  and  Pontecorvo  (1969).  The 
purpose  of  this  paper  is  to  develop  a  bioeconom- 
ic model  of  living  marine  resource  exploitation 
which  can  be  used  to  assess  the  economic  im- 
pact of  alternative  management  strategies  for 
the  U.S.  inshore  American  lobster  fishery. 
The  U.S.  American  lobster  fishery  is  a  classic 


case  of  rapid  increases  in  consumer  demand 
impinging  upon  a  limited  resource  (Bell.  1972). 
It  should  be  made  quite  clear  that  this  analysis 
is  intended  to  predict  the  effects  of  alternative 
actions  without  recommending  any  specific 
policy. 

SPECIFICATION  OF  THE 
GENERAL  RESOURCE  USE  MODEL 

Before  we  are  able  to  evaluate  the  economic 
impact  of  various  management  strategies,  it  is 
necessary  to  develop  a  general  bioeconomic 
model  of  how  a  fishery  functions.  The  following 
general  model  has  been  developed  by  Fullen- 
baum,  Carlson,  and  Bell  (1971): 


'  This  article  was  first  submitted  for  publication  7 
August  1972.  At  that  time,  all  data  were  as  current  as 
could  be  obtained  for  purposes  of  the  analysis.  The  views 
of  the  authors  do  not  necessarily  represent  the  official 
position  of  the  U.S.  Department  of  Commerce. 

2  Executive  Office  of  the  President,  Office  of  Manage- 
ment and  Budget,  Washington,  DC  20503. 

3  Formerly  of  Economic  Research  Division,  National 
Marine  Fisheries  Service,  NOAA:  present  address,  Florida 
State  University,  Tallahassee,  FL  32306. 


or 


X  =  f{X,  Kx) 
Kx  =  Kg{X,  K) 
X     =giX,K) 
C    =Kn 


(1) 
(2) 

(3) 
13 


Manuscript  accepted  June  1973. 

FISHERY  BULLETIN:  VOL.  72.  NO.  1.  1974. 


FISHERY  BULLETIN  VOL.  72,  NO.  1 


TT     =  pKx  -C  =  pKgiX,K)  -Kn        (4) 


5  277',  7r<0 


(5) 


In  the  above  system,  X  is  the  biomass;  K 
equals  the  number  of  homogeneous  operating 
units  or  vessels;  x  is  the  catch  rate  per  vessel; 
C  is  total  industry  cost  (in  constant  dollars)  or 
total  annual  cost  per  vessel  multiplied  by  the 
number  of  vessels;  ^  is  equal  to  total  annual  cost 
per  vessel  (in  constant  dollars)  or  opportunity 
cost;'  77  is  industry  profit  in  excess  of  oppor- 
tunity cost;  p  is  the  real  ex-vessel  price;  and 
5  J ,  5  2  represent  the  rates  of  entry  and  exit  of 
vessels,  respectively.  Equation  (1)  represents 
the  biological  growth  function  in  which  the 
natural  yield  or  net  change  in  the  biomass  {X) 
is  dependent  upon  the  size  of  the  biomass,  X, 
and  the  harvest  rate,  Kx.  X  reflects  the  influence 
of  environmental  factors  such  as  available 
space  or  food,  which  constrain  the  growth  in 
the  biomass  as  the  latter  increases.  The  harvest 
rate  or  annual  catch,  Kx,  summarizes  all  growth 
factors  induced  by  fishing  activity.  Equations 
(2)  present  the  industry  and  firm  production 
function  for  which  it  is  normally  assumed  that 


dg 
dX 


=  g,>0  and    f^=g^<0:^ 


dg 
bK 


In   other  words, 


catch  per  vessel  increases  when  the  biomass 
increases  and  declines  when  the  number  of 
vessels  increases.  Equations  (3)  and  (4)  are  the 
industry  total  cost  and  total  profit  function, 
respectively.  Equation  (5)  is  a  very  important 
equation  since  it  indicates  that  vessels  will 
enter  the  industry  when  excess  industrial 
profits  are  greater  than  zero  (i.e.,  greater  than 
that  rate  of  return  necessary  to  hold  vessels 
in  the  fishery,  or  the  opportunity  cost)  and 
will  leave  the  fishery  when  excess  industrial 
profits  are  less  than  zero  (i.e.,  below  opportunity 
cost). 


■*  Opportunity  cost  is  defined  as  the  necessary  payment 
to  fishermen  and  owners  of  capital  to  keep  them  employed 
in  the  industry  or  fishery  compared  to  alternative  employ- 
ment or  uses  of  capital. 

■'•In  some  developing  fisheries,  it  is  possible  that  .i;2>0. 
For  example,  in  the  Japanese  Pacific  tuna  fishery,  inter- 
communication between  vessels  may  increase  the  catch 
rate  as  more  vessels  enter  the  fishing  grounds. 


The  equilibrium  condition  for  the  industry 
(n  =  0)  may  be  formulated  as  shown  below: 


P  = 


77 


g{X,K) 


(6) 


Equation  (6)  merely  stipulates  that  ex-vessel 
price  is  equal  to  average  cost  per  pound  of  fish 
landed  (i.e.,  no  excess  profits). 

There  are  two  important  properties  of  the 
system  outlined  in  (1)  -  (5).  First,  the  optimum 
size  of  the  firm  is  given  and  may  be  indexed  by 
77.  Thus,  the  firm  is  predefined  as  a  bundle  of 
inputs."  Second,  the  long-run  catch  rate  per  ves- 
sel per  unit  of  time  is  beyond  the  individual 
firm's  control."  It  is,  in  effect,  determined  by 
stock  or  technological  externalities.**  Finally, 
we  are  assuming  that  the  number  of  homo- 
geneous vessels  is  a  good  proxy  for  fishing 
effort.  Alternatively,  we  may  employ  fishing 
effort  directly  in  our  system  by  determining 
the  number  of  units  of  fishing  effort  applied  to 
the  resource  per  vessel.  This  will  be  discussed 
below. 

A  QUADRATIC  EXAMPLE  OF 
THE  RESOURCE  USE  MODEL 


By  combining  the  more  traditional  theories 
depicting  the  dynamics  of  a  living  marine  re- 
source with  some  commonly  used  economic 
relations,  we  may  derive  a  quadratic  example 
of  the  general  model  specified  above.  This 
example  effectively  abstracts  from  complications 
such  as  ecological  interdependence  and  age- 
distribution-dependent  growth  of  the  biomass 
on  the  biological  side  and,  furthermore,  assumes 
the  absence  of  crowding  externalities  (i.e.,  ^2  ~ 
0)  in  the  production  function  on  the  economic 
side. 


''  In  other  words,  because  we  are  dealing  with  a  long-run 
theory  of  the  industry,  we  are  assuming  that  variations 
in  output  result  from  the  entry  or  exit  of  optimum-sized 
homogeneous  vessels. 

^  We  have  implicitly  assumed  that  such  short-run 
changes  as  longer  fishing  seasons,  etc.,  are  all  subsumed  in 
a  long-run  context.  Normally  longer  fishing  seasons,  for 
example,  do  not  change  catch  rates  per  unit  of  time  fished; 
nor  do  they  change  costs  per  unit  of  time  fished.  They 
do,  however,  change  the  effective  level  of  K. 

*  A  technological  externality  exists  when  the  input  into 
the  productive  process  of  one  firm  affects  the  output  of 
another  firm.  In  the  context  of  fishing,  an  additional  firm 
or  vessel  entering  the  fishery  will  utilize  the  biomass 
(as  an  input)  and,  as  a  result,  in  the  long  run  will  reduce 
the  level  of  output  for  other  vessels  in  the  fleet.  (See 
Worcester  (1969)). 


14 


FULLENBAUM  and  BELL:  AMERICAN  LOBSTER  FISHERY 


The  dynamics  of  a  fish  stock  may  be  depicted 
by  the  logistic  growth  function  (Lotka,  1956).^ 


X(t)  = 


1  +  Ce 


-KLt 


where  L>0,O0,/e>0,    (7) 


Kx  =  rKX 


(11) 


where  r  is  a  technological  parameter.'-  Finally, 
the  total  revenue  function  for  the  industry  may 
take  the  following  form: 


where  L,  C,  and  K  are  assumed  to  be  environ- 
mental constants.  Differentiating  (7)  and  sub- 
stituting we  obtain, 

X  =  ^  =  kLX  -  /v'X2  =  aX  -  6X2  (g) 

at 


where 


a  =  kL,  b  =  k. 


If  (8)  is  set  equal  to  zero,  we  may  solve  for  the 
nonzero  steady-state  biomass,  alb  (i.e.,  L). 
Alternatively,  the  limit  of  X{t)  as  f  ^  °°  yields 
identical  results.  The  maximum  of  (8)  occurs 
when  X  is  equal  to  al2b.  Thus 


max  3^  =  a^l4b 


(9) 


The  introduction  of  fishing  (i.e.,  harvest  or  Kx) 
is  assumed  to  have  no  interactive  effects,  so  that 
the  instataneous  growth  rate  is  reduced  by  the 
amount  harvested:'" 


^  =  gX  -  6X2  -  Kx. 
at 


(10) 


The  economic  component  of  the  model  re- 
quires the  exact  specification  of  an  industry 
production  function  and  an  industry  revenue 
relationship.  One  hypothesis  regarding  the 
fish  catch  is  that  the  proportion  of  the  biomass 
caught  is  a  direct  function  of  the  number  of 
vessels  (or  equivalent  fishing  effort)  exploiting 
a  given  ground."  Thus,  the  total  harvest  rate  is 
given  as. 


"Graham  (1935)  was  the  first  biologist  to  apply  the 
logistic  growth  model  to  exploited  fish  populations. 

'"  Schaefer,  (1954)  was  the  first  population  dynamicist 
to  develop  the  function  specified  in  equation  ( 10). 

'•  Alternatively,  one  could  assume  that  the  proportion 
of  the  biomass  caught  declines  as  the  number  of  vessels 
increases: 


Kx  =  [\  -  (\  -  nf^]X. 


0<f<l 


With  this  specification,  ;  represents  the  proportion  of  the 
biomass  taken  by  the  first  vessel  and  also  represents  the 
percentage  taken  by  each  succeeding  vessel  of  the  remain- 
ing biomass.  This  form  was  first  developed  by  E.  W.  Carl- 
son (1970.  An  economic  theory  of  common  property  re- 
sources. Unpubl.  manuscr.  Econ.  Res.  Lab.,  Natl.  Mar. 
Fish.  Serv.,  NOAA  College  Park,  Md.). 


pKx  =  (a-  (iKx)Kx. 


(12) 


Equation  (12)  merely  stipulates  that  the  total 
revenue  is  a  quadratic  function  of  total  landings, 
Kx.  Dividing  through  by  Kx  will  give  us  the 
familiar  demand  function  where  ex-vessel  price 
is  inversely  related  to  landings,  holding  all 
other  factors  constant.'-'^  With  total  costs  equal 
to  Ktt,  the  profit  function  becomes 


77  =  (a  -  iiKx)Kx  -  Krf. 


(13) 


Given  these  formulations,  the  system  in  (10)  - 
(13)  can  be  reduced  to  two  steady-state  func- 
tions. The  first,  which  condenses  all  relevant 
biotechnological  factors,  is  the  ecological  equilib- 
rium equation.  It  plots  the  relationship  between 
the  biomass  and  the  number  of  vessels  (or  fish- 
ing effort)  needed  to  harvest  the  yield  such  that 
the  biomass  is  in  equilibrium.  We  can  derive 
this  equation  by  setting  X  equal  to  zero,  sub- 
stituting (11)  into  (10),  and  solving  for  K  in 
terms  of  X.- 


K  =  -{a-  bX). 


(14) 


Similarly,  the  second  equilibrium  function  plots 
the  relationship  between  X  and  A'  under  a  zero 
profit  state,  i.e.,  under  conditions  that  K  —  0, 
or  that  there  is  no  entry  to  or  exit  from  the  fish- 
ery. Thus,  by  setting  (13)  equal  to  zero  and 
substituting  (11)  into  (13),  we  obtain 


K  = 


a 


drX     ^V2X2 


(15) 


'•^  A  reviewer  ot  this  article  has  pointed  out  that  ; 
is  not  likely  to  be  constant  over  any  large  number  of 
years.  Since  there  are  no  time  series  observations  on  X,  r 
cannot  be  tested  to  see  whether  it  varies  over  time  or  is 
a  constant.  In  this  case,  we  are  merely  following  the 
simplified  Schaefer  model. 

13  Such  complicating  factors  as  per  capita  income  and 
its  influence  on  ex-vessel  prices  can  be  introduced  later 
as  changes  in  the  parameter,  q. 


15 


FISHERY  BULLETIN  VOL.  72.  NO.  1 


These  two  curves  are  plotted  in  Figure  !.'■♦ 
Their  intersection  at  (X*,  K*)  denotes  bio- 
economic  equilibrium.  The  direction  of  the 
arrows  describes  the  qualitative  dynamic 
changes  of  a  point  in  ])hase  space.  Figure  1  rep- 
resents the  general  case  of  exploitation.  When 
(15)  is  combined  with  (14),  however,  we  can 
simulate  either  nonexploitation  (Figure  2)  or 
extinction  as  a  possible  dynamic  result  (Figure 
3).'-''  The  state  of  the  fishery — exploited,  unex- 
ploited,  or  extinct — depends  upon  the  para- 
meters a.  b,  r,  /3,  TT,  and  a  and  their  interrela- 
tionships. This  completes  our  general  model  of 
how  a  fishery  functions.  Now  let  us  turn  to  a 
specific  application  of  the  model. 


AN  EMPIRICAL  CASE  STUDY: 

THE  U.S.  INSHORE 
AMERICAN  LOBSTER  EISHERY 

The  U.S.  inshore  American  lobster  fishery — 
principally  located  off  the  coast  of  Maine — 
represents  a  good  case  study  for  a  number  of 
reasons.  First,  the  American  lobster  is  consid- 
ered a  high  quality  seafood  item  and  is  a  popu- 
larly consumed  species  for  which  demand  has 
been  increasing  rapidly  (Bell,  1972).  Second,  be- 
cause of  intensive  fishing  pressure,  the  resource 


''•  In  steady  state,  the  reader  should  be  aware  that  we 
have  not  constrained  the  population  stock  to  its  initial 
size  or  any  other  size.  Using  the  Schaefer  model  (i.e., 
steady  state),  the  stock  size  varies  inversely  with  fishing 
effort,  T.  Even  in  a  dynamic  context,  the  biomass  would 
asymptotically  approach  the  steady -state  solution. 

'■'  It  should  be  pointed  out  that  Schaefer  (1954)  discuss- 
es economic  transitional  states  which  are  very  similar 
to  the  bioeconomic  model  presented  in  this  paper.  He 
states: 

"To  arrive  at  a  particular  function  to  describe  the 
change  of  the  intensity  of  fishing  with  the  size  of  the 
population,  we  may  consider  that  the  incentive  for  new 
investment  is  proportional  to  the  return  to  be  expected, 
in  which  case  there  will  be  a  linear  relation  between 
the  percentage  rate  of  change  of  fishing  intensity  and 
the  difference  between  the  level  of  fish  population  and 
its  economically  critical  level,  b.  This  function  will, 
then,  be 


dF 

where  k-^is  a  constant." 


b) 


(11) 


has  shown  signs  of  overexploitation."'  Third,  the 
inshore  lobster  fishery  is  one  of  the  few  grounds 
for  which  enough  data  are  available  so  that 
some  rough  measures  of  needed  biological  and 
economic  ])arameters  can  be  derived.  Fourth, 
according  to  Dow  (1961),'^  the  inshore  lobster 
fishery  is  a  relatively  closed  population  as  our 
production  model  assumes.  Last,  we  believe 
that  over  the  long  run  the  American  lobster 
population  has  not  had  a  great  divergence 
from  the  steady-state  model  employed  in  our 
analysis.  The  gross  divergence  from  the 
steady-state  assumption  is  significant  only 
when  fishing  effort  changes  dramatically  from 
period  to  period.  For  modest  changes  in  fishing 
effort,  the  steady-state  assumption  will  not 
yield  biased  estimates.  A  check  on  the  fishing 
effort  series  for  the  American  inshore  northern 
lobster  fishery  reveals  a  steady  and  gradual 
increase.  The  alternative  methods  of  Pella  and 
Tomlinson  (1969)  do  yield  biased  parameters 
due  to  nonlinear  fitting  methods.  Gulland's 
(1961)  method  yields  bia.sed  parameters  since 
effort  is  averaged  and  then  used  as  an  indepen- 
dent variable.  Therefore  effort  in  period  t  is  not 
indei)endent  of  effort  in  period  t  -\-  1  which 
violates  classical  statistical  assumptions  under- 
lying least  squares.  Also  the  predictive  value 
(using  the  steady-  state  assumption)  or  goodness 
of  fit  is  certainly  at  an  acceptable  level,  R"^  = 
0.962  (infra).  Our  discussion  will  be  subdivided 
on  the  basis  of  production-related  and  demand- 
related  estimates. 

The  Production  Eunction  and 
the  Supply  of  American  Lobsters 

There  are  four  parameters  on  the  supply  side 
for  which  initial  estimates  are  required:  a,  b,  r. 


His  process  of  transitional  states  is  implicit  in  our  dia- 
grams in  Figure  3  since  adjustment  (i.e.,  transitional 
states)  will  occur  anywhere  in  phase  space  to  the  equilibri- 
um values  where  X  =  0  and  K  =  0. 


"*  U.S.  landings  of  trap-caught  American  lobsters  in- 
creased from  approximately  23  million  pounds  in  1950 
to  a  peak  of  over  29  million  pounds  by  1957.  Since  1957 
landings  have  fallen  off,  reaching  a  low  of  22  million 
pounds  in  1967.  In  1969  lobster  production  had  recovered 
to  26.9  million  pounds.  Despite  the  poor  performance 
of  production  over  the  1950-69  period,  the  number  of 
lobster  traps  fished  per  year  (i.e.,  a  proxy  for  fishing 
effort)  has  increased  secularly  from  approximately  579,000 
in  1950  to  over  1,060,000  in  1969.  Because  of  these  past 
events,  several  bills  have  been  presented  in  the  Maine 
Legislature  to  apply  some  sort  of  stringent  licensing 
scheme  to  limit  entry. 

'^  Dow,  R.  1971.  Effort,  environment,  supply,  and  yield 
in  the  Maine  lobster  fishery.  Unpublished  manuscript  sub- 
mitted to  the  U.S.  Fish  and  Wildlife  Service,  Washington, 
D.C.  125  p.  (May  be  obtained  from  Sea  and  Shore  Fish- 
eries, Maine.) 


16 


FULLENBAUM  and  BELL:  AMERICAN  LOBSTER  FISHERY 


Figure  1. — Exploitation. 


Figure  2. — Non-exploitation. 


i 

TT 

\               K=-[a-bX]                       \ 

\ 

>- 

Figure  3. — Extinction. 


17 


FISHERY  BULLETIN  VOL.  72.  NO.  1 


and  7r.'»*  The  first  three  can  be  developed  by 
combining  statistical  estimation  and  indepen- 
dently derived  data.  Assume  that  the  biomass 
is  instantaneouslv  in  equilibrium  (i.e.,  dX_^  q) 

dt 

Then,  taking  the  inverse  of  (14)  and  substituting 
it  for  X  in  (11),  we  obtain: 


(il2b,     it  follows  that  the  following  parameters 
may  be  estimated  (designated  by  *): 


Kx  =  cK-  dK^ 


(16) 


r  =  C/2X 

b  =  [d/p2]  -1 

a  =  cblr. 


(18) 
(19) 
(20) 


where 


and 


C  =  J,d 


If 
b 


X  =  c  -  dK. 


(17) 


Equation  (16)  is  the  familiar  parabolic  yield 
function  postulated  by  Schaefer  (1954).'^  Notice 
that  both  the  harvest  rate,  Kx,  and  output  per 
vessel,  X,  may  be  specified  solely  in  terms  of  the 
number  of  vessels  or  fishing  effort.  Similarly, 
the  common  property  resource  externality,  as 
given  in  (17),  is  a  function  only  of  the  level  of  K. 
Over  a  longer  period  of  time  the  basic  assump- 
tion underlying  equations  (16)  and  (17)  may 
reflect  a  valid  representation;  i.e.,  effort  or  K 
is  the  only  instrumental  variable  affecting  out- 
put. There  are  three  different  parameters  em- 
bedded in  estimates  of  c  and  (/.  The  only  way 
that  0,  b,  and  r  can  be  derived  is  if  some  inde- 
pendent biological  information  is  given.  More 
specifically,  suppose  that  we  have  an  estimate 
of  the  biomass  consistent  with  maximum  sus- 
tainable yield,  call  it  X° .  Since  X°  is  equal  to 


Thus,  (17)  will  be  estimated  subject  to  one 
modification  concerning  the  introduction  of  an 
environmental  variable.  Several  biologists, 
including  Dow  et  al.  (1961),-"  have  argued  that 
a  long-term  trend  of  declining  seawater  tem- 
perature is  partially  responsible  for  the  decline 
in  U.S.  coastal  catches. -•  It  will  be  assumed  in 
this  study  that  seawater  temperature  (°F) 
affects  the  a  term  in  the  growth  function  so  that, 


^  =  aCF)X-bX^, 


(21) 


where  °F  is  equal  to  the  mean  annual  sea- 
water temperature,  in  degrees  Fahrenheit 
Boothbay    Harbor,    Maine,    with  . 


9a 


a(   F) 


a'>0. 


Seawater  temperature  can  easily  be  incorporat- 
ed into  (17)  in  the  following  way: 


c  -dK  +  z(  F), 


(22) 


"*  An  alternative  approach  suggested  by  Thomas  (1970) 
uses  the  Beverton-Holt  model  in  developing  a  yield/ 
recruit  relationship.  However,  because  a  stock-recruit- 
ment equation  is  not  specified,  it  cannot  be  incorporated 
•nl'>  our  bioeconomic  model  at  this  time. 

"*  The  reader  should  recognize  that  it  does  not  follow 
that  (17)  can  be  derived  from  a  generalized  growth  equa- 
tion [X  =  F(X)  -  K\  =  0]  and  production  function 
Kx  =  l\X,K).  Only  under  certain  specifications  of  the 
previous  two  functions  will  it  follow  that  .v  can  be  defined 
as  a  unique  function  of  K  (or  X)  only.  In  addition,  this 
production  function  could  have  been  more  generally  speci- 
fied as  Kx  -  rK^XP.  However,  two  compelling  factors 
make  it  desirable  to  employ  this  function.  First,  there 
are  no  observations  on  the  biomass,  X,  so  that  empirical 
tests  cannot  be  made  to  estimate  B.  Second,  the  equation 
Kx  =  rKX  combined  with  the  logistic  gives  an  excellent 
empirical  fit  to  past  behavior  in  the  fishery  (i.e.,  R-  =  0.962 
for  yield  function  equation  23).  In  addition,  Schaefer 
makes  the  same  assumption  as  we  did,  and  this  assump- 
tion is  generally  accepted  as  plausible  for  most  fisheries. 
In  conclusion  it  is  difficult  for  us  to  imagine  how  a  differ- 
ent assumption  could  lead  to  superior  predictive  results 
(i.e.,  goodness  of  fit). 


where  z  represents  the  change  in  output  per 
boat  as  a  result  of  a  one-degree  change  in  water 
temperature. -- 

Data  on  the  number  of  traps  fished  per  year 
for  the  entire  inshore  American  lobster  fishery 


'-"  Dow,  R.,  D.  Harriman,  G.  Ponlecorvo,  and  J.  Storer. 
1961.  The  Maine  lobster  fishery.  Unpublished  manuscript 
submitted  to  the  U.S.  Fish  and  Wildlife  Service,  Washing- 
ton, D.C.  71  p.  (May  be  obtained  from  Sea  and  Shore 
Fisheries,  Maine.) 

-•  Higher  seawater  temperature  can  affect  the  natural 
yield  of  lobsters  by  providing  a  climate  in  which  molting 
is  facilitated.  A  larger  number  of  molts  will  tend,  ccwris 
paribus,  to  increase  the  yield  associated  with  any  given 
level  of  the  biomass. 

--  Implicit  in  the  way  the  effect  of  seawater  temperature 
is  measured  is  the  relationship: 

[a  =  <;o  +  d(°¥)]. 


18 


FULLENBAUM  and  BELL:  AMERICAN  LOBSTER  FISHERY 


are  available  for  the  1950-69  period  (see  Appen- 
dix Table).-^  Output  per  trap  was  regressed 
against  the  number  of  traps  and  seawater  tem- 
perature on  the  assumption  that  the  number  of 
traps  per  boat  was  constant.  The  regression 
estimates  yielded  the  following  results: 

X  =  -31.82  -  0.00002807(T)  +  1.846(°F)  (23) 


(6.55) 


(4.99) 


R2  =  0.962 
D-W  =  2.38 

where  T  =  562. 8( A'):  d  =  0.0156;  c  =  -  31.82 
+  1.846(°F).  In  (23).  T  is  equal  to  the  number 
of  traps  fished  per  year,  and  f-ratios  are  in 
parentheses.-^  Both  T  and  °F  are  statistically 
significant  at  the  5%  level  and  exhibit  the  cor- 
rect sign;  the  Durbin-Watson  statistic  indicates 
no  significant  autocorrelation. 

The  only  step  required  to  obtain  the  biotech- 
nological  parameters  is  an  estimate  of  the  bio- 
mass  consistent  with  ma.ximum  sustainable 
yield.  It  has  been  calculated  that  (assuming  a 
temperature  of  46°F)  the  fishable  stock  of  U.S. 
inshore  American  lobsters  consistent  with 
maximum  sustainable  yield  is  equal  to  31  mil- 
lion pounds.'--^  For  the  Gulf  of  Maine  (where 
most  of  the  resource  is  located),  estimates  of  the 
biomass  were  made  through  sampling  experi- 
ments.'-*' 

Finally,  on  the  basis  of  recent  cost  studies, 
we  have  derived  an  estimate  of  n  for  1966  equal 


23  The  assumption  of  a  constant  number  of  traps  per 
boat  is  necessary  in  order  to  solve  for  a  coefficient  on 
"K".  and  thereby,  to  obtain  the  biotechnological  paramet- 
ers embedded  in  the  yield-effort  relationship.  The  rela- 
tionship for  1966,  derived  on  the  basis  of  cost  data  ob- 
tained from  the  National  Marine  Fisheries  Service's  Divi- 
sion of  Financial  Assistance  was  562.8  traps  per  full-time 
equivalent  northern  lobster  boat.  However,  it  should  be 
pointed  out  that  when  the  stock  is  large  and  the  catch 
high,  it  may  pay  to  increase  the  number  of  traps  per 
boat:  therefore,  this  might  bias  the  number  of  "standard- 
ized boats",  but  not  total  amount  of  effort. 

-''  However,  the  reader  should  note  that  the  empirical 
estimates  themselves  (1950-69)  make  no  assumption  with 
respect  to  the  relation  between  K  and  T.  \  was  regressed 
on  T  and  °F.  Only  in  the  simulation  was  a  relationship 
assumed  (T  =  562.SK). 

-•^  U.S.  Department  of  the  Interior.  1970.  Joint  master 
plan  for  the  northern  lobster  fishery.  Unpublished  man- 
uscript. 130  p.  (May  be  obtained  from  the  National  Marine 
Fisheries  Service,  Washington.  D.C.) 

-6  No  attempts  were  made  to  run  the  simulation  model 
with  varying  sizes  of  the  MSY  biomass  as  this  would  un- 
necessarily complicate  this  paper  which  is  intended  to  be 
simplistic  as  possible. 


to  $12,070.27,28  Therefore,  on  the  supply  side, 
the  estimated  parameters  for  1969  are  the  fol- 
lowing: 


a 
b 
r 


1.85379 

2.9899  X  10-^ 

5.1562  X  10-4 

$13,191  (see  footnote  27). 

The  Demand  Function  for 
American  Lobsters 


Only  knowledge  of  d  and  /j  is  needed  in  order 
to  complete  the  empirical  component  of  the 
study.  The  estimation  procedure  is  rather 
straightforward.  We  may  specify  the  following 
demand  function  for  all  lobsters: 


C 

N 


=  F-m(P'/CPI)  +  g(y/AO 


(24) 


where  C  is  equal  to  consumption  of  all  lobsters, 
P'  is  the  money  ex -vessel  price  of  American  lob- 
sters, Y  is  aggregate  U.S.  personal  income 
(1967  prices),  A'  is  U.S.  population,  and  CPI  is 
the  consumer  price  index.  Since  there  are  no 
exports  of  lobster,  the  following  identity  holds: 


C  =  1+  Q    +  Q. 


(25) 


where  /,  Q^,  and  Q^^  are  the  level  of  imported 
lobsters,  U.S.  production  of  all  other  lobsters, 
and  U.S.  production  of  inshore  American  lob- 
sters, respectively.  Given  (25),  equation 
(24)  may  be  solved  in  terms  of  P,  or, 


P  = 


CPI 


If  Qq,  /,  Y,  CPI.  and  N  are  held  constant,  equa- 
tion (26)  gives  a  unique  relationship  between 
the  ex-vessel  price  of  American  lobsters  and 
quantity  landed. 

Using  data  over  the  1950-69  period  (see 
Appendix  Table),  the  parameters  of  equation 
(24)  were  estimated  using  least  squares: 


-'  Cost  data  from  the  National  Marine  Fisheries  Serv- 
ice's Division  of  Financial  Assistance  (1966)  reveal  the 
following  cost  breakdown  for  a  representative  lobster 
boat:  operating  expenses,  $4,965.16:  fixed  expenses, 
$1,180.20:  returns  to  capital  and  labor,  $5,825.48.  This 
gives  a  total  of  $12,070.84.  The  latter  figure  was  updated 
to   1969  by  income  increases  in  Maine  to  obtain  $13,191. 

28  We  will  assume  that  rf  remains  constant  in  real 
terms.  This  is  equivalent  to  keeping  our  estimate  of  it".  Tf 
constant,  while  deflating  all  nominal  variables  on  the 
demand  side. 


19 


FISHERY  BULLETIN  VOL.  72.  NO.  1 


^=  -0.0632  -0.005029(^j 
(2.06) 


0.00051^  (27) 


(5.38) 


«2  =  0.816 

D-W  =  0.619 

All  of  the  independent  variables  are  significant 
at  the  0.05  level.  However,  the  Durbin-Watson 
statistic  indicates  the  strong  possibility  of  posi- 
tive autocorrelation.  Nonetheless,  we  will  use 
these  estimates  as  rough  approximations  to 
obtain  the  price-dependent  relationship  as 
shown  in  (26).  Given  1969  values  of  exogenous 
variables  (A^  -  199.100,000;  Y  -  $567,635 
million;  CPI  =  109.8  with  a  base  of  1967  = 
100;  Q     +  I  =   158.8  million  pounds),  we  have. 


P=  1.179  -  (0.99853  X  10-^)Q.^. 


(28) 


Thus  initial  values  for  a  (1.179)  and  ^  (0.99853 
X  IQ-^)  have  been  obtained.-" 


-9  For  purposes  of  simplification,  the  parameters  of 
the  model  are  all  assumed  constant.  Certainly,  one  could 
argue  that  the  parameters,  so  tacitly  assumed  to  be 
constants,  are  at  best  random  variables.  Therefore,  a 
stochastic  treatment  might  be  used  with  criteria  like 
maximal  expected  present  value  or  minimal  maximum 
expected  loss  for  evaluating  the  management  alternatives 
rather  than  simple  deterministic  computations.  Possibly, 
the  parameters  are  random  variables  and  conditional  on 
some  of  the  suggested  management  alternatives.  For 
example,  freezing  effort  might  accelerate  /■,  leading  to 
shifts  in  season  or  age  structure  harvested,  hence  a  change 
in  ulh. 


HOW  THE  MODEL  WORKS:  THE 
IMPACT  OF  CRITICAL  VARIABLES 

To  illustrate  the  power  of  the  model  in  ex- 
plaining the  impact  of  changes  in  critical 
variables,  we  may  derive  initial  quantitative 
estimates  of  the  ecological  equilibrium  and 
economic  steady-state  functions.  In  this  section 
we  will  illustrate  the  power  of  the  model  in 
explaining  the  impact  of  changes  in  critical 
variables.  The  year  1969  is  selected  for  initial 
quantitative  estimates  of  the  ecological  equi- 
librium and  economic  steady-state  functions. 
Table  1  shows  what  happens  to  the  value  of 
{X*,  K*)  as  well  as  the  equilibrium  harvest 
level.  {Kx)*,  when  the  following  changes  take 
place: 

a)  A  25%  increase  in  opportunity  costs  of  labor 
caused  by  the  development  of  greater  regional 
industrial  activity; 

b)  A  25%  increase  in  the  supply  of  other  lobsters 
traceable  to  the  discovery  of  a  new  lobster 
ground; 

c)  A  5%  increase  in  personal  per  capita  income; 
and 

d)  A  decrease  in  water  temperature  from  48° 
to47°F. 

Notice  that  these  changes  are  for  illustrative  pur- 
poses; however  they  do  come  about  on  a  routine 
basis  in  the  real  world.  Perhaps  25%  changes 
in  selected  variables  do  not  come  about  in  one 
year  so  the  reader  can  view  the  new  equilibrium 


Table    1.  —  The    impact    of   exogenous    shocks    to    the    inshore    American    lobster 
fishery  on  the  effort,  catch,  and  biomass. 


Vessels, 

Traps 

Catch 

Biomass 

full-time 

equivalent 

K* 

£* 

Kx* 

X* 

Nuinhcr 

Niiiiibcr 

Million 

poiiiuls 

Initial  equilibrium  (1969) 

1,936 

1 ,089,000 

28.56 

28.62 

(computed  by  model) 

New  equilibrium: 

(a)    Increase  (25°o)  in  opportunity 

1,531 

861,718 

28.1 

35.6 

cost  of  labor 

(b)    Increase  (25°o)  in  exogenous 

947 

533,000 

22.3 

45.7 

supply  of  lobsters 

(c)    Increase  (5°o)  in  personal  per 

2,182 

1,228,310 

27.4 

28.0 

capita  income 

(d)    Decline  in  water  temperature  by  1° 

1,851 

1,041,710 

26.8 

29.0 

(e)    Changes  (a)-(d)  simultaneously 

905 

509,356 

20.7 

45.9 

20 


FULLENBAUM  and  BELL:  AMERICAN  LOBSTER  FISHERY 


positions  shown  in  Table  1  to  result  over  a 
period  of  years  from  the  1969  initial  e(iuilibrium. 
We  may  incorporate  all  of  the  four  changes 
given  separately  in  (a)  -  (d)  to  ascertain  their 
net  impact.  The  strength  of  the  simulation 
model  is  that  we  can  study  the  separate  and 
combined  influences  on  the  fishery  of  important 
variables.  Because  we  have  both  positive  and 
negative  influences  on  fishing  effort,  it  is  likely 
to  be  such  that  complete  extinction  of  a  particu- 
lar species  would  be  somewhat  difficult.-'" 


ECONOMIC  IMPACT  OF  SELECTED 
MANAGEMENT  ALTERNATIVES 

Up  to  this  point,  we  have  been  concerned 
largely  with  building  a  bioeconomic  model  that 
considers  all  important  variables.  The  model  is 
based  upon  the  fact  that  open  access  to  the 
American  lobster  fishery  is  permitted.  However, 
all  States  restrict  gear  to  pots  and  traps.  Each 
State  (Maine,  Massachusetts,  New  Hampshire, 
and  Rhode  Island)  has  a  minimum  length  re- 
quirement; permitted  minimum  lengths  vary 
from  S'/h  to  S-'/ie  inches.  We  are  taking  the 
array  of  existing  regulations  as  given.  We  shall 
consider  the  economic  impact  of  five  alternative 
policies  that  could  be  adopted  to  manage  or  to 
limit  entry  to  the  entire  American  lobster  fish- 
ery. These  management  strategies  assume  that 
some  central  authority  such  as  a  regional  com- 
mission could  impose  these  regulations. •'!  The 
specific  objectives  of  these  management  strate- 
gies will  be  discussed  below.  All  strategies 
have  two  objectives  in  common  which  are  (1) 
to  protect  the  resource  from  overex])loitation  and 
(2)  to  allow  maximum  freedom  for  operators  to 
function  in  a  free  enterprise  fashion.  Further, 
the  following  strategies  are  meant  to  be  illustra- 
tive and  do  not  exhaust  all  possible  alternatives. 
Also,  two  other  management  strategies  sug- 
gested by  Reeves  (1969)  and  Sinclair  (1960)  will 


30  This  is  subject  to  two  qualifications.  First,  since  we 
are  plotting  only  equilibrium  relationships,  extinction  is 
a  possible  dynamic  outcome  (as  was  mentioned  previously). 
Second,  we  have  implicitly  assumed  that  in  the  case  of 
American  lobster,  the  rate  of  technological  advance  is 
minimal.  This  is  a  fairly  realistic  assumption  for  the  in- 
shore trap  fishery.  However,  in  general.  /  =  r(i),  with 
^'>0. 

31  With  the  steady-state  assumption,  the  management 
policies  would  in  fact  maximize  the  present  value  of  the 
stream  of  net  benefits  over  time. 


be  reviewed.  As  other  management  strategies 
are  suggested  both  inside  and  outside  govern- 
ment, the  model  formulated  above  may  be  used 
to  predict  their  impact. 

Some  Possible  Alternative  Management 
Strategies  for  Inshore  American  Lobsters 

1.  Freeze  on  existing  (1969)  fishing  effort  by 
placing  a  lice)ise  fee  on  traps:  Under  this 
scheme,  the  regulatory  authority  would  calcu- 
late a  license  fee  on  traps  which  would  keep 
the  level  of  fishing  effort  constant  despite  an 
increase  in  the  demand  for  lob.sters.-'-  A  license 
fee  could  not  be  levied  on  the  individual  vessel 
because  this  would  not  control  the  number  of 
traps  fished  per  vessel.  The  increased  cost  of 
operations  due  to  the  license  fee  would  make  it 
uneconomical  for  vessels  to  enter  the  fishery 
even  though  ex-vessel  prices  have  increased. 
In  essence,  the  license  fee  would  siphon  off 
increased  revenue  (or  profits)  from  an  increase 
in  ex-vessel  prices  assuming  the  latter  increases 
faster  than  cost  of  operations.  For  purposes  of 
illustration,  let  us  assume  that  we  desire  to 
manage  the  inshore  American  lobster  fishery 
commencing  in  1974.  Given  the  estimated  trend 
in  important  variables  in  the  fishery  (i.e.,  n, 
I,  Qq,  Y,  N,  CPI)  to  the  year  1974,  it  would  be 
necessary  to  place  an  estimated  annual  license 


32  The  model  can  derive  the  "correct  tax"  (or  license 
fee)  in  a  number  of  ways.  Suppose,  the  regulatory  author- 
ity wishes  to  freeze  effort  at  some  specified  level  K^.  We 
can  derive  the  equilibrium  yield  consistent  with  K'\ 
call  it  (A^.v)",  from  the  yield-effort  relationship.  The  total 
tax  and  the  tax  per  vessel  are  then  respectively  given  by: 

7'^.  -(a-/i(/..Y)0)(A-.v)0-AOf 

K 

In  similar  fashion,  if  the  regulatory  authority  wishes  to 
freeze  effort  at  a  level  consistent  with  maximum  sustain- 
able yield,  we  can  obtain  the  tax  that  will  insure  this 
level  of  exploitation. 

The  only  other  taxing  scheme  that  requires  further  ex- 
planation is  a  tax  that  will  insure  marginal  cost  pricing. 
Long-run  industry  marginal  cost  can  be  defined  as: 


ff/  J^\  where 


dK.\ 


is   the   first    derivative   of  (16).  Total 


industry  cost  can  then  be  redefined  as, 

ydKx/bK/ 

This  expression  can  be  substituted  into  the  total  revenue 
function  and  solution  for  K,  Kx  can  be  found  by  iteration. 
The  tax  consistent  with  these  solutions  can  then  be  derived 
by  using  the  formulas  given  above,  i.e.,  Tx,  TxIK. 


21 


FISHERY  BULLETIN  VOL.  72,  NO.  1 


fee  of  $3.34  (in  1972  dollars)  on  each  lobster 
trap  fished.  This  is  shown  in  Table  2.  The  reg- 
ulatory authority  would  collect  over  $3.5  mil- 
lion in  license  fee  revenue  which  could  be  used 
to  finance  resource  research,  enforcement,  and 
surveillance.  It  should  be  emi)hasized  that 
these  calculations  are  merely  rough  estimates 
and  only  serve  to  give  the  reader  some  idea  of 
the  magnitude  of  such  license  fee.  The  illustra- 
tive license  fee  is  also  based  upon  an  extra- 
polation of  trends  5  yr  ahead  of  1969.  If  we 
did  nothing,  it  is  estimated  that  the  catch  would 
be  lower  and  more  fishermen  and  traps  would 
be  employed  in  the  fishery  by  1974.  Obviously, 
the  situation  would  worsen  as  demand  for  lob- 
sters expanded  and  the  fishery  became  increas- 
ingly overfished.  The  license  fee  plan  does  have 
many  disadvantages.  First,  a  license  fee  on 
traps  fished  does  not  really  get  at  the  utilization 
rate.  One  might  expect  that  a  license  fee  on  an 
individual  trap  might  induce  fishermen  to  fish 
each  trap  more  intensively  and  thereby  reduce 
their  number  of  traps.  At  this  point,  we  do  not 
have  any  information  on  utilization  rates 
whereby  the  tax  could  be  adjusted  upward  if 
utilization  increased.  Second,  enforcement  and 
surveillance  might  be  difficult  along  the  coast- 
line   from    Maine    to    North    Carolina.    Third, 


and  most  important,  the  quantitative  tools  and 
projected  figures  needed  to  calculate  a  license 
fee  are  at  best  crude  and  would  have  to  be  used 
for  calculations  each  year. 

2.  Reduce  the  existing  level  of  fishing  effort 
to  that  necessary  to  liarvest  MSY  by  placing  a 
Hcoise  fee  on  traps:  With  this  scheme,  the 
regulatory  authority  would  calculate  a  license 
fee  on  traps  which  would  reduce  the  level  of 
existing  effort  to  that  necessary  to  harvest  maxi- 
mum sustainable  yield  (i.e.,  estimated  to  be 
about  1,011,910  traps)  despite  an  increase  in 
demand  for  lobsters.-''^  Because  we  are  actually 
reducing  fishing  effort  as  opposed  to  freezing  it 
at  the  1969  level,  the  estimated  1974  license 
fee  per  trap  must  be  higher  or  $5.58  (in  1972 
dollars).  Actual  catch  will  not  be  significantly 
higher.  The  regulatory  authority  would  receive 
approximately  $5.6  million  in  license  fee  reven- 
nue.  However,  this  plan  has  the  same  disadvan- 
tages of  a  general  license  fee  plan  indicated 
under  alternative  one. 

3.  Reduce  the  existi)ig  level  of  fishing  effort 
to  that  )iecessarjj  to  make  the  marginal  cost  of 


33  The  fishing  effort  needed  to  harvest  MSY  was  ob- 
tained from  equation  (23)  with  the  1950-69  average 
water  temperature. 


Table  2. — The  impact  of  various  management  schemes  imposed  on  the  inshore  American  lobster  fishery  in  1974. 


Impact 

after  the  imposition 

of  selected  mane 

igement  strategies  for 

1974 

(1) 

(2) 

(3) 

(4) 

(5) 

Estimated 

Issue  "stock 

values  before 

Freeze  at 

Reduce 

Reduce 

certificate" 

Economic 

imposition  of 

1969  level 

fishing 

fishing 

to  vessel 

Do 

variables 

management 

of  fishing 

effort 

effort 

owner  while 

nothing 

strategies 

effort 

to  £max 

%o  MC  =  P 

freezing  effort 

( 1 969) 

at  1969  level 

Catch  (million  lb) 

28.6 

28.6 

28.7 

23.9 

28.6 

28.1 

Value  of  catch 

28.0 

36.8 

36.9 

31.9 

36.8 

36.4 

(million  $) 

Vessels  (full-time 

1,900 

1,900 

1,798 

1,060 

1,900 

2,070 

equivalent) 

Traps  (million) 

1.069 

1.069 

1.011 

0.597 

1.069 

1.165 

Ex -vessel  price 

0,98 

1.29 

1.29 

1.33 

1.29 

1.30 

Total  license  fees 

0 

3.56 

5.58 

13.3 

0 

0 

collected  (million  $) 

License  fee/vessel  ($)'- 

0 

1,877 

3,119 

12,622 

0 

0 

License  fee  /trap  ($) 

0 

3.34 

5.54 

22.43 

0 

0 

Return  per  vessel 

6,365 

8,400 

8,400 

8,400 

10,278 

8,400 

and  fisherman 

'  Projection  of  1974  impact  of  selected  management  strategies.  Assumes  that  F°  =  48°;  Y  =  $677.9  billion,  (1969  prices);  POP  = 
212.4  million;  Qo  +  /  =  183.6  million  pounds  and  fi  =  $15,292.  All  prices  and  dollar  values  projected  for  1974  ore  expressed 
in  1972  dollars. 

^  The  license  fee  per  vessel  was  obtained  by  multiplying  the  tax  per  trap  by  the  average  number  of  traps  (562.8)  fished  per 
full-time  vessel. 


22 


FULLENBAUM  and  BELL;  AMERICAN  LOBSTER  FISHERY 


knidiiigs  equal  to  ex-ves.sel  price  by  placitig  a 
license  fee  on  traps:  The  idea  hei'e  is  to  obtain 
the  greatest  "net  economic  benefit"  and  has 
been  suggested  by  such  economists  as  Crutch- 
field  and  Pontecorvo  (1969).''^  If  a  regulatory 
authority  were  to  try  this  for  1974,  it  would  have 
a  drastic  impact  on  the  fishery  as  the  number  of 
full-time  equivalent  vessels  and  traps  would  be 
reduced  by  approximately  47%.  To  accomplish 
this  objective  an  estimated  1974  license  fee 
of  $22.43  (in  1972  dollars)  per  trap  would  be 
needed.  This  would  yield  the  regulatory  author- 
ity appro.ximately  $13.3  million  in  revenue. 
From  an  economic  point  of  view,  it  is  argued 
that  this  management  strategy  will  result  in  the 
most  efficient  operation  of  the  fishery  if  fisher- 
men and  vessels  can  easily  move  to  other  fish- 
eries or  industries.  However,  this  strategy  may 
be  particularly  unwise  in  rural  areas  such  as 
Maine  where  labor  mobility  is  low.  A  drastic 
cutback  in  the  number  of  fishermen  may  create 
social  problems  where  the  cost  would  greatly 
exceed  any  benefits  derived  from  this  manage- 
ment strategy.  Therefore  this  management 
strategy  is  difficult,  if  not  impossible,  to  justify 
on  economic  grounds  for  many  rural  areas  where 
the  fishing  industry  is  located  and  also  has  the 
same  disadvantages  of  a  general  license  fee 
plan  on  traps  as  discussed  above. 

4.  Issue  "stock  certificates"  to  each  vessel 
ou'iier  based  upon  average  catcJt  over  last  5  ijr 
while  freezing  the  existi)ig  level  of  fishing  effort: 
Under  this  scheme,  the  historic  rights  of  each 
fishing  firm  would  be  recognized.  In  a  similar 
manner  to  a  private  land  grant  procedure,  the 
regulatory  authority  would  simply  grant  each 
fisherman  a  "private"  share  of  an  existing 
resource  or  catch.  The  stock  certificate  would 
be  evidence  of  private  ownership.  Individual 
fishermen  would  be  free  to  catch  up  to  their 
allotted  share  through  the  use  of  pots  or  other 
biologically  permissible  technology  or,  if  they 
desired,  trade  their  stock  certificates  to  others 
for  cash.  Suppose  the  regulatory  authority  were 
to  freeze  the  level  of  fishing  effort  at  the  1969 
level  and  distribute  the  estimated  catch  via  a 
stock  certificate  to  the  existing  fishermen.  It 
should  be  pointed  out  that  the  regulatory  author- 


s'* When  price  is  constant,  maximization  of  net  economic 
benefit  becomes  identical  to  the  goal  of  maximization  of 
rent  to  the  fishery.  This,  however,  is  not  the  case  when 
the  normally  downward  sloping  demand  curve  is  specified. 


ity  fixes  effort  when  it  selects  a  given  catch.  The 
selected  catch  could  be  either  MSY  or  any  other 
level  of  catch  deemed  by  the  regulatory  author- 
ity not  injurious  to  the  viability  of  the  .stock.  The 
expansion  in  demand  for  lobsters  by  1974  would 
generate  excess  profits  for  those  individual  fish- 
ermen who  were  initially  endowed  with  the 
property  right.  By  1974,  it  is  estimated  that  a 
full-time  lobsterman  would  be  earning  $10,278 
(in  1972  dollars)  a  year  of  which  $1,878  would 
be  excess  profits  (i.e.,  above  opportunity  cost). 
If  iirofits  become  excessive  a  license  fee  would 
be  levied  on  the  fishermen  holding  stock  certif- 
icates to  insure  against  increased  abnormal 
returns  and  provide  the  regulatory  authority 
with  funding  to  conduct  scientific  investigations 
and  enforcement.  It  should  be  noted  that  this 
plan  is  identical  to  the  license  fee  scheme  which 
freezes  effort  at  its  1969  level.  However,  in  the 
latter  case,  excess  profits  are  taken  by  the 
regulatory  authority  while  for  this  strategy, 
fishermen  are  allowed  to  hold  onto  the  profits 
generated  in  the  fishery.  Since  many  fisheries 
are  located  in  rural  areas  where  earnings  are 
traditionally  low,  this  strategy  might  be  justified 
on  the  basis  that  it  will  raise  income  levels  and 
thereby  help  improve  living  standards  to  com- 
parable levels  to  those  received  in  urban  areas. 
This  management  strategy  would,  of  course,  be 
popular  with  those  already  in  the  fishery.  How- 
ever, new  entrants  would  have  to  buy  .stock 
certificates  from  those  initially  in  the  fishery. 
This  would  bring  up  certain  questions  of  equity 
and  legal  precedent  which  are  beyond  the  scope 
of  this  article. 

5.  No  manage  Die  nt  strategy:  When  consider- 
ing the  economic  consequences  of  alternative 
management  strategies  (1-4),  it  is  aJways  wise 
to  assess  the  results  of  doing  nothing.  This  gives 
policymakers  a  better  ])erspective  in  evaluating 
the  benefits  from  taking  action.  The  consequence 
of  doing  nothing  would  be  overcapitalization 
by  1974  with  an  expansion  in  the  number  of  full- 
time  equivalent  fishermen  and  traps  fished. 
Approximately  96,000  excess  traps  (i.e.,  above 
that  necessary  to  take  MSY)  would  be  in  the 
fishery,  and  the  catch  would  fall  to  28.1  million 
pounds. 

The  fishery  would  grow  increasingly  over- 
capitalized, and  the  resource  would  be  greatly 
overexploited  as  demand  increased  for  lobsters 
during  the  1970"s.  On  economic  grounds,  these 


23 


FISHERY  BULLETIN  VOL.  72,  NO.  1 


results  are  hardly  ac-ceptable  because  more  fish- 
ermen and  vessels  will  probably  be  catching 
less. 

6.  Other  suggested  ma)iageme)it  sti'ategies: 
Reeves  (1969)  has  proposed  a  hike  in  license 
fees  to  eliminate  the  marginal  or  part-time 
fishermen.  He  suggests  that  the  present  $10 
yearly  fee  in  Maine  be  raised  $10  a  year  over 
the  next  9  yr  to  a  top  of  $100.  In  1969,  a  little 
less  than  one-half  of  the  lobster  fishermen  were 
part-time.  A  part-time  lobster  fisherman  is 
defined  as  one  who  gains  less  than  one-half  of 
his  aniRial  income  from  lobstering.  The  first 
step  in  most  suggested  limited  entry  schemes 
is  usually  to  restrict  the  fishery  to  full-time 
utilization  of  cai)ital  and  labor.  Two  problems 
occur  with  this  policy.  First,  the  part-time  fish- 
ermen may  represent  the  most  efficient  way  of 
taking  the  catch.  If  so,  the  full-time  fishermen 
may  be  eliminated  by  increased  license  fees. 
Second,  license  fees  do  not  directly  control  fish- 
ing effort  since  fishermen  may  fish  more  tra})s. 
However,  Reeves  also  goes  on  to  argue  strongly 
for  limiting  the  number  of  traps  each  fisherman 
is  allowed  to  set.  It  is  not  quite  clear  whether 
anyone  knows  the  optimum  number  of  tra])s 
per  vessel. 

Rutherford.  Wilder,  and  Frick  (1967)  in  their 
study  of  the  Canadian  inshore  lobster  fishery 
endorse  the  system  suggested  by  Sinclair  (1960). 
They  state: 

"An  alternative  management  system  is  that  suggested 
by  Sinclair  (1960)  for  the  salmon  fisheries  of  the  Pacific 
Coast.  This  would  use  the  licensing  of  fishermen  to 
limit  entry  into  the  fishery.  In  the  first  stage,  lasting 
about  five  years,  licenses  would  be  reissued  at  a  fee 
but  no  new  entries  would  be  licensed,  and  it  would  be 
hoped  that  during  the  period  there  would  take  place  a 
reduction  in  the  labour  and  capital  input,  to  take  the 
maximum  sustainable  catch  of  salmon  at  a  considerably 
lower  cost.  After  the  end  of  the  first  stage,  licenses 
would  be  issued  by  the  government  under  competitive 
bidding  and  only  in  sufficient  numbers  to  appro.ximate 
the  most  efficient  scale  of  effort;  the  more  competent 
fishermen  would  be  able  to  offer  the  highest  bids  and 
it  would  be  expected  that  the  auction  would  recapture 
for  the  public  purse  a  large  portion  of  the  rent  from 
the  fisheries  that  would  otherwise  accrue  to  the  fishing 
enterprises  under  the  more  efficient  production  condi- 
tions in  the  fishery. 

"An  arbitrary  reduction  in  the  number  of  fishermen 
by  restriction  of  licenses  to  a  specified  number  would 
entail  injustice  and  inequity  as  well  as  grave  administra- 
tive problems  in  determining  who  should  be  allowed  to 
continue  fishing.  The  auctioning  of  licenses  to  exploit 
a    public    property    resource    is  justifiable   in    a    private 


enterprise  system  of  production,  particularly  when  the 
state  is  incurring  heavy  expense  to  administer  and  con- 
serve the  resource:  the  recovery  by  the  state  of  some  part 
of  the  net  economic  yield  by  means  of  a  tax  on  fisher- 
men (or  on  the  catch)  would  recoup  at  least  part  of 
such  public  expenditures,  or  could  be  used  to  assist 
former  fishermen  (see  strategies  discussed  above)  for 
instance,  by  buying  their  redundant  equipment.  A  tax 
on  fishermen  through  the  auctioning  of  licenses  has, 
at  least,  the  merit  of  using  economic  means  instead 
of  arbitrary  regulations  to  achieve  a  desired  economic 
objective — the  limitation  of  fishing  effort  to  increase 
the  net  economic  yield  from  the  fishery.  Regulations 
have  to  be  enforced,  usually  at  considerable  cost, 
but  economic  sanctions  tend  to  be,  if  not  impartial, 
at  least  impersonal  and  automatic  in  their  operation." 

Actually,  this  latter  management  scheme  is 
similar  to  the  taxing  scheme,  but  uses  an 
auction  rather  than  a  direct  tax. 

Conclusions 

The  purpose  of  this  article  is  to  explain  the 
use  of  bioeconomic  models  in  assessing  alter- 
native management  strategies.  For  this  purpose 
the  data  are  less  than  optimal.  However,  this 
does  not  mean  that  we  cannot  take  steps  in  the 
direction  of  fishery  management.  In  fact,  these 
steps  must  be  taken  to  protect  the  resource 
from  destruction  and  to  achieve  a  better  use 
of  vessels  and  fishermen.  It  is  hoped  that  the 
following  conclusions  will  provide  a  helpful 
framework  in  which  to  consider  the  merits  of 
limited  entry: 

1.  For  the  inshore  American  lobster  resource, 
there  is  every  indication  that  the  fishery  has 
achieved  maximum  sustainable  yield  and  is 
fully  capitalized.  This  has  been  brought  about 
by  a  rapid  expansion  in  effort  (i.e..  traps  fished) 
produced  by  (1)  free  access  to  the  resource,  (2) 
a  rising  market  for  lobsters  of  all  species,  and 
(3)  a  secular  decline  in  seawater  temperature. 

2.  We  have  presented  the  bioeconomic  im- 
pact of  alternative  management  strategies  to 
both  conserve  the  resource  and  use  it  efficiently. 
The  choice  of  which  strategy  to  pursue  is  in  the 
public  domain  and  beyond  the  scope  of  this 
paper.  However,  the  economic  alternatives  are 
pointed  out. 

LITERATURE  CITED 

Bell,  F.  W. 

1972.  Technological  externalities  and  common  proper- 
ty resources:  an  empirical  study  of  the  U.S. 
northern  lobster  fishery.  J.  Polit.  Econ.  80:148-158. 


24 


FULLENBAUM  and  BELL:  AMERICAN  LOBSTER  FISHERY 


CrUTCHFIELD,  J.  A,,  AND  G.  PONTECORVO. 

1969.  Pacific  salmon  fisheries:  A  study  of  irrational 
conservation.  Johns  Hopkins  Press.  Baltimore. 
Md.,  220  p. 

FULLENBAUM,  R.  F.,  E.  W.  CaRLSON,  AND  F.  W.  BeLL. 

1971.  Economics    of    production    from     natural    re- 
sources: comment.  Am.  Econ.  Rev.  61:483-487. 
Graham,  M. 

1935.  Modern  theory  of  exploiting  a  fishery  and 
application  to  North  Sea  trawling.  J.  Cons.  10:264- 
274. 

GULLAND,  J.  A. 

1961.  Fishing  and  the  stocks  of  fish  at  Iceland.  Fish 
Invest.  Minist.  Agric.  Fish  Food  (G.B.)  Ser.  II, 
23(4):  1-32. 

LOTKA.  A.  J. 

1956.  Elements  of  mathematical  biology.  Dover 
Publ.,  N.Y.,  465  p. 

PeLLA,  J.  J.,  AND  P.  K.  TOMLINSON. 

1969.  A    generalized    stock    production    model.     [In 
Engl,    and    Span.]     Inter-Am.    Trop.    Tuna   Comm. 
Bull.  13:421-496. 
Reeves,  J. 

1969.  The   lobster    industry:    Its   operation,   financing. 


and     economics.     Master's     dissertation.     Stonier 
Grad.       Sch.       Banking,       Rutgers      Univ.,       New 
Brunswick,  N.J.,  170  p. 
Rutherford,  J.  B.,  D.  G.  Wilder,  and  H.  C.  Frick. 

1967.  An   economic   appraisal   of  the  Canadian   lob- 
ster fishery.  Fish.  Res.  Board  Can.,  Bull.  157,  126  p. 

SCHAEFER, M.  B. 

1954.  Some   aspects   of  the   dynamics   of  populations 
important     to     the     management     of     commercial 
marine    fisheries.    Inter-Am.    Trop.    Tuna    Comm., 
Bull.  1:27-56. 
Sinclair,  S. 

1960.   License       limitation — British       Columbia:       A 
method  of  economic  fisheries  management.  Chap- 
ter III,  p.  98.  Can.  Dep.  Fish.  256  p. 
Thomas,  J.  C. 

1970.  An  analysis  of  the  commercial  lobster  (Homants 
americanus)  fishery  along  the  coast  of  Maine, 
August  1966  through  December  1970.  Final  Rep., 
Lobster  Res.  Prog.  State  Maine,  Dep.  Sea  Shore 
Fish.,  73  p. 
Worcester,  D.  A.,  Jr. 

1969.  Pecuniary  and  technological  externality,  factor 
rents,  and  social  costs.  Am.  Econ.  Rev.  59:873-885. 


Appendix  Table — Economic  variables  associated  with  the  U.S.  inshore  American  lobster  fishery,  1950-69. 


Per  capita 

disposable 

Mean  annual 

Ex-vessel 

personal  income 

seawater  temp- 

price divided 

Per  capita 

divided  by 

Consumer 

erature  ot 

Catch 

Traps 

Catch 

Ex -vessel 

by  consumer 

consumption 

consumer  price 

price  index 

Boothboy 

Year 

by  traps 

Value 

fished 

per  trap 

price 

price  index 

Year 

of  lobsters 

index 

(1967=  100) 

Harbor,  Maine 

Thousand 

Tlunisand 

Nmnher 

Pounds 

Cems  per 

Cents  per 

Pounds 

Dollars 

Dei^rees 

pounds 

dollar  \ 

pound 

pound 

(live  weiKhrl 

Fahrenheit 

1950 

22,914 

8,283 

578,930 

39.6 

36.1 

50.1 

1950 

0.585 

1,892 

72.1 

49.3 

1951 

25,749 

9,328 

512,812 

50.2 

36.2 

46.6 

1951 

.651 

1,888 

77.8 

51.4 

1952 

24,681 

10,469 

544,730 

45.3 

42.4 

53.4 

1952 

.638 

1,909 

79.5 

50.2 

1953 

27,509 

10,687 

569,081 

48.3 

38.8 

48.5 

1953 

.710 

1,976 

80.1 

52.0 

1954 

26,628 

10,250 

628,209 

42.4 

38.5 

47.8 

1954 

.690 

1,969 

80.5 

50.3 

1955 

27,886 

11,003 

669,229 

41.7 

39.5 

49.2 

1955 

.734 

2,077 

80.2 

50.0 

1956 

25,386 

11,584 

666,887 

38.1 

45.6 

56.1 

1956 

.704 

2,141 

81.4 

48.6 

1957 

29,358 

11,263 

688,815 

42.6 

38.4 

45.6 

1957 

.806 

2,136 

84.3 

48.8 

1958 

26,143 

12,890 

753,503 

34.7 

49.3 

56.9 

1958 

.736 

2,114 

86.6 

47.4 

1959 

27,752 

14,043 

856,794 

32.4 

50.6 

58.0 

1959 

.763 

2,182 

87.3 

47.0 

1960 

29,345 

13,657 

844,110 

34.8 

46.5 

52.5 

1960 

.830 

2,185 

88.7 

47.9 

1961 

25,621 

13,662 

895,098 

28.6 

53.3 

59.5 

1961 

.810 

2,214 

89.6 

47.3 

1962 

26,728 

13,770 

909,318 

29.4 

51.5 

56.9 

1962 

.855 

2,280 

90.6 

46.6 

1963 

27,210 

15,299 

866,900 

31.4 

56.2 

61.3 

1963 

.938 

2,333 

91.7 

47.9 

1964 

26,844 

17,689 

904,233 

29.7 

65.9 

70.9 

1964 

.935 

2,459 

92.9 

46.9 

1965 

24,737 

18,764 

949,045 

26.1 

75.9 

80.3 

1965 

.884 

2,578 

94.5 

45.8 

1966 

25,606 

19,517 

947,113 

27.0 

76.2 

78.4 

1966 

.873 

2,680 

97.2 

45.7 

1967 

22,098 

18,162 

907,956 

24.3 

82.2 

82.2 

1967 

.882 

2,751 

100.0 

45.1 

1968 

26,918 

20,648 

966,335 

27.9 

76.7 

73.6 

1968 

.960 

2,827 

104.2 

46.6 

1969 

26,930 

22,997 

1,061,807 

25.4 

85.4 

77.8 

1969 

.999 

2,851 

109.8 

48.0 

Source 

Fishery 

Statistics     ol 

the    Uni 

ed     States 

,     various 

years,     U.S. 

Department     of    Commerce,     Bureau 

3f     Labor     Statistics,     and 

Robert 

Dow. 

25 


DAILY  ACTIVITY,  MOVEMENTS,  FEEDING,  AND  SEASONAL 
OCCURRENCE  IN  THE  TAUTOG,  TAUIOGA  ONITIS^ 

BoRi  L.  Olla,  Allen  J.  Bejda,  and  A.  Dale  Martin- 

ABSTRACT 

Observations  were  made  on  the  activity  and  movements  of  adult  tautog,  Taiitogu  oniiis, 
in  their  natural  habitat  using  scuba  and  by  monitoring  the  movements  of  individual  fish 
by  ultrasonic  tracking.  Results  showed  tautog  to  be  active  during  the  day  and  inactive  at 
night.  Fish  larger  than  30  cm  moved  out  from  the  night  resting  place  (home  site)  each  day 
to  feed,  while  younger  fish  (^25  cm)  remained  and  fed  in  close  proximity  to  the  home  site. 
Examination  of  digestive  tracts  from  various-sized  fish  showed  the  blue  mussel,  Mytiliis  editlis, 
to  be  the  principal  food  for  this  population.  While  older  fish  appeared  to  move  offshore 
for  the  winter,  the  younger  fish  remained  inshore,  wintering  over  in  a  torpid  state.  The 
significance  of  the  tautog's  differential  responsiveness,  food  habits,  and  daily  and  seasonal 
movements  are  discussed. 


The  tautog,  Tautoga  o)iitis  (L.),  an  inhabitant  of 
the  western  Atlantic,  ranges  from  Nova  Scotia 
to  South  Carolina,  being  most  abundant  between 
Cape  Cod  and  the  Delaware  Capes  (Bigelow 
and  Schroeder,  1953:478-484).  Its  distribution 
is  limited  primarily  to  inshore  regions  with 
individual  populations  being  highly  localized 
(Cooper,  1966).  This  fish  lives  in  close  associa- 
tion with  rocky  places,  wrecks,  pilings,  jetties, 
or  almost  any  bottom  discontinuity  and  for  part 
of  its  range,  is  a  prominent  member  of  inshore 
benthic  communities.  Unlike  the  majority  of 
labrids,  this  species  is  valued  as  a  game  fish 
and  is  an  excellent  table  fish. 

Our  aim  in  this  work  was  to  observe  and 
describe  the  behavior  of  adult  tautog  in  situ 
and  to  relate  our  findings  to  the  animal's  life 
habits  and  history.  Our  queries  primarily  con- 
cerned daily  activity  and  movements,  feeding, 
and  seasonal  occurrence.  The  study  was  carried 
out  on  a  population  residing  in  Great  South 
Bay,  N.Y.,  using  scuba  and  ultrasonic  tracking. 

MATERIALS  AND  METHODS 

The  study  area  was  along  the  south  shore  of 
Great  South  Bay,  Long  Island,  N.Y.,  extending 


'  This  work  was  supported  in  part  by  a  grant  from  the 
U.S.  Atomic  Energy  Commission,   number  AT(49-7)3045. 

-  Sandy  Hook  Laboratory,  Middle  Atlantic  Coastal 
Fisheries  Center,  National  Marine  Fisheries  Service, 
NOAA,  Highlands,  NJ  07732. 


east  from  the  Fire  Island  Inlet  Bridge  to  2  km 
east  of  the  Fire  Island  Light  (Figure  1).  Water 
depth  in  the  study  area  ranged  from  2.4  to  8.8  m 
with  the  bottom  composed  primarily  of  sand, 
gravel,  and  shell. 

Two  methods  were  employed  to  observe  the 
activity  and  movements  of  the  fish:  (1)  ultra- 
sonic tracking  of  a  single  fish  and  (2)  direct 
underwater    observations    while    using    scuba. 

Twelve  fish  were  tracked  at  different  times 
from  August  through  September  1971  and  June 
through  October  1972  (Table  1).  Fish  were 
captured  at  night  within  the  Fire  Island  Coast 
Guard  basin  by  a  scuba  diver  using  a  hand-held 
net,  and  each  fish  was  held  in  a  floating  cage 
for  periods  ranging  from.  10  to  108  h  before  a 
transmitter  was  attached. 


ATLANTIC    OCEAN 


tOOO       METERS 


Manuscript  accepted  June  1973. 

FISHERY  BULLETIN:  VOL.  72.  NO,  1,  1974. 


Figure    1. — Study  area  and  areas  (A-H)  of  tautog  move- 
ment as  presented  in  Table  1. 


27 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 

Table   1. — Locations  and  duration  of  stay  (h)  of  individual  tautog  during  their  daily  movements  as  determined  by  ultra- 
sonic tracking. 


Tautog 
no. 


Day 


Night 


1  TL  (cm) 
Age'/sex 

Release  (dote/time) 
Track  duration  (h) 
Mean  temperature 

2  TL  (cm) 
Age/sex 

Release  (date/time) 
Track  duration  (h) 
Mean  temperature 

3  TL  (cm) 
Age/sex 

Release  (date/time) 
Track  duration  (h) 
Mean  temperature 

4  TL  (cm) 
Age/sex 

Release  (dote/time) 
Track  duration  (h) 
Mean  temperature 

5  TL  (cm) 
Age/sex 

Release  (date/time) 
Track  duration  (h)  ■ 
Mean  temperature 

6  TL  (cm) 
Age/sex 

Release  (date/time) 
Track  duration  (h) 
Mean  temperature 

7  TL  (cm) 
Age/sex 

Release  (date/time) 
Track  duration  (h) 
Mean  temperature 


45 

12/9 

7-25-72/1310 

67.5 

19.2°C 

42 

10/9 

8- 1  -72/0940 

68.3 

21.2°C 

42 

10/9 

8-8-72/1215 

66.5 

20.4°C 

43 

916 

9-15-71/0830 
47.5 
22.0°C 

38 

7/9 

9-27-71/1400 

41.5 

18.1°C 

47 

11/d 

8-16-71/1830 
41.5 
21.7°C 

20 

3/9 

10-4-72/0930 

34.0 

16.8°C 


A3'(  5.0)-     Al(    2.2)        A4(   9.8)        A4(   2.6)        Al(11.4)         Al(lO.O)         Al(14.1) 
A3(10.2) 
A4(    1.9) 


Al(  0.8)        A4(11.5)         A3(   3.1)        A4(   0.5)        Al(   9.6)         Al(   9.8)         Al(   9.6) 
A4(   0.4)        A5(    2.3)         A4(   9.2) 
C   (  8.4)  A5(    1.8) 


Al(   3.0)        A4(   0.9)         A5(  6.2)        A5(0.3)        Al(11.3)         Al(11.6)         Al(10.8) 
A4(   3.0)        A9(10.3)         A9(   7.0) 


Al(  1.0)  A3(  2.5)         A4(  0.5) 

A4(  5.7)  A5(  0.8) 

A6(  0.6)  A6(  4.5) 

A7(  2.3)  A7(  0.8) 


Al(  0.3)        A5(  2.7)         A5(    1.0) 

A4(  0.2)        A6(  1.4) 

A7(  4.0) 

A8(  0.1) 


Al(    1.4)         A2(10.9)  F    (   4.1) 

A5(  0,3) 


Al(   9.4)        Al(12.5) 


Al(12,8)         Al(15.6) 


Al(16.6)         Al(15.1) 


Al(10.3)         G   (12.2) 


Al(11.5)         Al(   0.6) 


The  transmitter  emitted  pulsed  signals  at  70 
kHz  (kilohertz).  Those  used  for  small  fish  (20- 
25  cm)  measured  30  x  9  mm  (manufactured  by 
Chipman  Instruments'').  Larger  transmitters, 
65  X  14  mm  (SR-69B,  Smith-Root  Inc.)  were 
used  for  the  remaining  fish  (38-50  cm). 

The  pharyngeal  mill  apparatus  of  the  fish 
precluded  internal  insertion  of  the  transmitter. 
This  necessitated  external  attachment  through 
the  dorsal  musculature,  with  nylon  monofila- 
ment line  just  below  the  midpoint  of  the  dorsal 
fin.  On  each  side  of  the  body,  rubber  disks  (25- 
mm  diameter)  were  used  to  prevent  the  flesh 
from  tearing.  Tags  were  made  neutrally  buoy- 
ant by  the  addition  of  a  styrofoam  collar  coated 
with  silicone  sealant.  Following  attachment  of 
the   transmitter,   fish    were   held    in   a   50-liter 


•'  Reference  to  trade  names  in  this  publication  docs  not 
imply  endorsement  of  commercial  products  by  the  Na- 
tional Marine  Fisheries  Service. 


tank  for  15  to  30  min  to  insure  that  the  fish 
were  responsive  and  that  the  transmitter  was 
operating  normally. 

Fish  were  released  within  the  basin  and 
tracked  from  a  5.2-m  skiff.  The  signal  was  moni- 
tored with  hydrophone  and  sonic  receiver 
(Model  SR-70-H  and  TA-60  respectively,  Smith- 
Root  Inc.)  in  a  manner  similar  to  that  described 
by  McCleave  and  Horrall  (1970). 

The  location  of  each  fish  was  recorded  in 
relation  to  local  landmarks.  We  considered  a 
fish  active  whenever  a  change  in  transmitter 
signal  was  detected.  Direct  underwater  obser- 
vations confirmed  that  we  were  able  to  detect 
abrui)t  changes  in  the  fish's  orientation  and 
straight  line  movement  over  1  m.  The  data  were 
subse(iuently  condensed  to  indicate  the  i)res- 
ence  of  a  fish  for  a  i)eriod  of  time  at  a  specific 
location  (Table  1). 

For  each  track,  we  recorded  current  velocity, 


28 


OLLA,  BEJDA,  and  MARTIN:  ACTIVITY  OF  TAVTOGA  ONITIS 

Table    1. — Locations  and  diiralit)n  of  stay  (h)  of  individual  tautog  during  their  daily  movements  as  determined  by  ultra- 
sonic tracking,  continued. 


Tautog 

Uay 

no. 

1 

2 

3                       4 

8   TL  (cm) 

25 

Al(   7.7) 

Al(12.5) 

Al(12.5)        Al(   0.6) 

Age/sex 

4/9 

Release  (date/time) 

10-3-72/1  115 

Track  duration  (h) 

67.7 

Mean  temperature 

16.8°C 

9   TL  (cm) 

50 

D  (   0.5) 

D  (10.1) 

D   (    4.9) 

Age/sex 

14/(5 

E   (10.9) 

E   (  3.0) 

Release  (date/time) 

6-14-72/0855 

F    (  0.6) 

Track  duration  (h) 

48.8 

Mean  temperature 

14.1°C 

Renewed  track 

D  {    3.9) 

D  (16.8) 

D  (10.2) 

Dote/time 

6-19-72/1750 

E   (   3.1) 

Trock  duration  (h) 

49.9 

Mean  temperature 

15.5°C 

10  TL  (cm) 

43 

A5(   8.6) 

A5(   9.8) 

Age/sex 

9/c5 

A6(  5.6) 

Release  (date/time) 

6-27-72/1025 

Track  duration  (h) 

42.5 

Mean  tempera'ure 

17.3°C 

n    TL  (cm) 

44 

Al(    1.1) 

Age/sex 

11/9 

A2(    1.8) 

Release  (date/time) 

6-5-72/1345 

B   (  0.6) 

Track  duration  (h) 

3.5 

Mean  temperature 

13.4°C 

12   TL  (cm) 

45 

Al(  0.3) 

Age/sex 

12/9 

A5(  3.2) 

Release  (date/time) 

6-12-72/1145 

A6(  2.7) 

Track  duration  (h) 

8.3 

A8(  0.3) 

Mean  temperature 

13.8°C 

B   (    1.1) 
C  (  0.7) 

Night 


G  (   8.0)         D  (   7.9) 


D  (   7.9)         D  (   7.9) 


A5(10.2)        A5(   8.3) 


'   Location  as  presented  in  Figures  1  and  2. 

-  Hours  given  in  parentheses. 

^  Age  estimated  from  calculated  total  lengths  by  Cooper  ( 1967) . 


stage  of  tide,  cloud  cover,  water  temperature, 
and  water  transparency.  Current  velocity  was 
measured  either  with  a  Beauvert  midget  cur- 
rent meter  or  by  the  float  method.  The  current 
velocity  ranged  from  0.65  to  1.75  m/s.  Temper- 
ature was  measured  with  a  thermistor  and 
transparency  with  a  secchi  disk.  Cloud  cover 
was  visually  estimated. 

In  conjunction  with  our  tracking,  we  directly 
observed  tautog  in  the  study  area  with  scuba 
for  a  total  of  135  h  (90  h  daytime  and  45  h 
nighttime). 

To  identify  periods  of  feeding  as  well  as  the 
types  and  amounts  of  food  ingested,  we  ex- 
amined the  digestive  tracts  of  fish  collected  at 
different  times  of  the  day  and  night.  We  mea- 
sured the  relative  dige.stive  tract  fullness  of  each 
volumetrically  with  the  fullness  index  being 
the  quotient  of  displacement  volume  of  empty 
tract/displacement  volume  of  tract  with  con- 
tents. 

Determination  of  the  maximum  size  of  mussel 


that  the  tautog  could  ingest  and  of  the  maximum 
size  it  could  crush  was  made  by  inserting  dif- 
ferent size  mussels  into  the  mouth  and  into  the 
anterior  opening  of  the  pharyngeal  mill.  The 
maximum  ingestable  size  was  defined  as  the 
largest  mussel  that  could  be  completely  enclosed 
in  the  mouth.  The  maximum  crushable  size  was 
the  largest  mussel  that  could  be  partially 
grasped  by  the  pharyngeal  teeth. 

To  aid  in  describing  the  method  of  feeding 
on  mussels,  at  infrequent  intervals  over  a  16-mo 
period,  we  directly  observed  and  used  cine  anal- 
ysis of  three  individuals  25  to  38  cm,  held  in  a 
2,200-liter  aquarium. 


RESULTS 

Activity  and  Movements 

The  fish  which  we  tracked  were  active  during 
the  day  and  inactive  at  night.  There  was  some 


29 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


degree  of  variation  in  tlie  precise  time  that  activ- 
ity began  or  ceased  relative  to  morning  and 
evening  civil  twilight  (Table  2).  Activity  began 
from  10  min  before  to  69  min  after  the  start  of 
morning  twilight.  Cessation  of  activity,  however, 
was  more  variable,  ranging  from  222  min  before 
to  69  min  after  the  end  of  evening  twilight.  Al- 
though we  were  unable  to  arrive  at  the  cause  for 
this  variation,  there  were  indications  that  cloud 
cover  and  water  transparency,  both  affecting 
light  penetration,  might  play  a  role.  Our  direct 
scuba  observations  (135  h  of  observation)  on 
untagged  tautog  showed  that  the  fish  were  active 
during  the  day  and  inactive  at  night.  Activity 
as  well  as  responsiveness  at  night  were  at  such 
a  low  level  that  we  were  able  to  touch  individual 
fish  or  catch  them  easily  with  a  hand-held  net. 
Five  fish  (No.  1-5,  Table  1),  tracked  at  dif- 
ferent times  from  July  through  September  1971 
and  1972,  exhibited  similar  j^atterns  in  their 
daily  movements.  Each  morning  at  the  onset  of 
activity  or  soon  after,  the  fish  moved  out  and 
usually  remained  within  500  m  of  the  basin. 
They  spent   most  of  each  day  at  locations  in 


which  there  were  large  concentrations  of  blue 
mussel  {Mijfihis  cdnlis)  (areas  A2-A9,  Figure 
2;  Table  1).  Towards  late  afternoon  or  early 
evening,  the  fish  returned  to  the  basin  and  with- 
in 1  to  198  min  (x=  55.7),  settled  in  one  location 
and  remained  throughout  the  night  in  an  inac- 
tive state. 

Another  fish  (No.  6,  Table  1)  tracked  during 
this  period  returned  to  the  basin  the  first  night 
after  being  released,  following  the  same  i)attern 
as  fishes  1  to  5.  However,  after  s})ending  most  of 
the  second  day  in  close  proximity  to  the  basin, 
it  did  not  return  but  rather,  at  172  min  prior  to 
the  end  of  evening  twilight,  swam  6.2  km  in 
a  direct  easterly  course  to  an  artificial  reef 
(consisting  of  sunken  barges  and  tires)  where  it 
si)ent  the  night  (area  G,  Figure  1). 

Underwater  observations  made  during  July 
through  mid-October  showed  that  the  number  of 
fish,  measuring  about  30  to  50  cm,  in  close  prox- 
imity to  the  basin  increased  just  prior  to  and 
immediately  after  the  beginning  of  evening 
twilight  in  comparison  to  the  number  that  were 
present  during  the  day.  Comparing  these  obser- 


Table  2. — Onset  and  end  of  the  daily  activity  of  individual  tautog  relative  to  morning  and  evening 

civil  twilight  (MCT  and  ECT'). 


Mean  time  and 

range  (min)  to 

Onset 

of  activity 

End  of  activity 

Tautog 
no. 

Prior  to 
MCT 

Following 
MCT 

Prior  to 
ECT 

Following 
ECT 

1 

27.0 
(21.0  to  35.0) 

122.0 

(43.0  to  222.0) 

2 

20.0 
(t0.0to30.0) 

14.7 
(   8.0  to  26.0) 

3 

26.0 
(12.0  to  43.0) 

71.0 
(39.0  to  116.0) 

4 

7.0 
(4.0  to  10.0) 

78.5 
(72.0  to  85.0) 

5 

23.0 
(18.0  to  28.0) 

47.5 

(12.0  to  83.0) 

6 

54.5 
(52.0  to  57.0) 

28.0 
(   4.0  to  52.0) 

7 

35.0 

68.0 

(54.0  to  82.0) 

8 

27.0 
(13.0  to  45.0) 

75.3 
(51.0  to  88.0) 

9 

62.0 
(49.0  to  69.0) 

131.0 
(26.0  to  158.0) 

69.0 

10 

14.0 

51.0 
(28.0  to  74.0) 

'  MCT:  start  of  morning  civil  twilight. 
ECT:  end  of  evening  civil  twilight. 


30 


OLLA,  BEJDA,  and.MARTIN:  ACTIVITY  OF  TAUTOGA  ONITIS 


100  METERS 


N 

/ 


Figure  2. — Areas  demarcating  the  locations  of  tautog 
during  their  daily  movements  as  presented  in  Table  1 
(an  enlargement  of  area  A,  Figure  1). 

vations  with  our  tracks  of  similar-sized  fish,  we 
were  led  to  conclude  that  this  increase  was  the 
result  of  the  normal  nightly  return  to  the  basin. 
However  the  number  of  smaller  fish  (^25  cm) 
appeared  to  remain  the  same  throughout  the 
day  and  during  evening  twilight,  i.e.,  there  was 
no  discernible  increase  at  evening  twilight.  To 
affirm  whether  the  smaller,  younger  fish  did  in 
fact  remain  closer  to  the  basin  during  the  day 
than  the  larger,  older  ones,  we  tagged  two  fish 
20  and  25  cm  (No.  7  and  8,  Table  1),  tracking 
one  for  34  and  the  other  for  66.8  h.  These  fish 
exhibited  the  typical  habit  of  the  larger  fish  of 
being  active  during  the  day  and  inactive  at  night 
(Table  2).  However,  in  contrast  to  the  larger 
fish,  these  smaller  fish  remained  within  the 
basin  and  never  ventured  farther  than  2  m  from 
the  walls.  Examination  of  the  digestive  tract  of 
one  of  these  smaller  fish,  recaptured  after  track- 
ing had  been  terminated,  showed  the  presence 
of  mussels  throughout  the  tract,  indicating 
that  this  fish  had  been  feeding  on  mussels  at- 
tached to  the  basin  walls  or  other  substrate 
within  the  basin. 


These  data  indicate  that  tautog  occur  as  an 
essentially  localized  population  at  least  from 
July  through  mid-October.  The  basin  acts  as  a 
focal  point  for  the  population,  providing  a  suit- 
able night  habitat  for  all  fish  and  a  forage  area 
for  smaller  fish. 

Four  fish  (No.  9-12,  Table  1)  tracked  during 
June  1972  exhibited  quite  different  patterns  of 
daily  movements.  Two  of  these  (No.  9  and  10) 
ranged  farther  during  the  day  and  spent  the 
night  at  various  locations  other  than  the  basin. 
Tracking  was  discontinued  on  the  other  two 
fish  of  this  group  (No.  11  and  12)  during  the 
first  day  due  to  inclement  weather.  However, 
a  search  the  night  following  tracking  termina- 
tion and  on  three  successive  nights  failed  to 
detect  the  presence  of  either  fish  in  or  around 
the  basin.  They,  too,  evidently  spent  the  night 
at  other  locations. 

The  major  difference  in  fish  tracked  during 
June  from  all  other  fish  tracked  was  that  all 
June  fish  were  in  spawning  condition,  readily 
extruding  sperm  or  ova  during  the  tagging  pro- 
cedure. Further,  if  this  population  bears  any 
similarities  to  the  Narragansett  Bay  popula- 
tion (Cooper,  1966),  we  surmise  that  during 
June,  fish  are  still  arriving  inshore  from  their 
offshore  wintering  area  and  have  not  yet  be- 
come localized  (at  least  fish  of  the  size  we  were 
tracking). 

On  26  September  1972,  during  the  day,  we 
sighted  just  outside  the  basin  (Area  3,  Figure  2) 
a  tautog  with  a  transmitter  attached.  Although 
we  could  not  ascertain  when  this  fish  was  tagged, 
it  had  been  49  days  since  the  last  tagging.  The 
fish,  which  appeared  normally  responsive,  had 
either  remained  localized  within  this  area  for 
at  least  49  days  or  possibly  was  one  of  the  four 
fish  tagged  during  June  that  had  not  returned 
to  the  basin  at  that  time. 

Feeding 

There  were  varying  amounts  of  food  through- 
out the  digestive  tracts  of  fish  sampled  at  vari- 
ous times  of  the  day  and  just  after  evening  twi- 
light (Table  3).  The  tracts  of  fish  sampled  just 
prior  to  morning  twilight  (23-83  min),  while 
still  in  an  inactive  night  condition,  were  empty. 
Thus  it  appears  that  the  fish  feed  throughout 
the  day,  beginning  soon  after  morning  twilight 
and  continuing  up  to  evening  twilight.  Assum- 
ing that  the  fish  sampled  just  before  morning 


31 


twilight  had  fed  up  to  the  previous  evening 
twilight,  passage  through  the  digestive  tract 
while  the  animals  were  quiescent  took  8  h  or 
less. 

Examination  of  the  matter  ingested  showed 
that  70%  of  the  fish  sampled  contained  78.4  to 
100%  mussels,  by  volume,  in  various  stages  of 
digestion  (Table  3).  Next  in  abundance  were 
remains  of  various  decapod  and  cirriped  crus- 
taceans, followed  by  an  assortment  of  other  in- 
vertebrates and  debris  (vegetable  matter,  sand, 
and  gravel),  with  some  of  the  latter  probably 
being  ingested  incidentally  with  the  mussels. 
All  but  two  of  the  fish  examined  contained  over 
50%  mussels,  by  volume,  indicating  that  mus- 
sels are  the  principal  food  for  this  population. 

Observations  on  the  tautog's  method  of  feed- 
ing on  mussels,  in  both  the  field  and  laboratory, 
revealed  that  after  approaching  a  clump  of 
mussels,  the  fish  would  grasp  one  or  several  at 
a  time  with  the  anterior  canine  teeth  and  then 
tear  them  from  the  substrate  with  an  intense 
lateral  or  shaking  movement  of  the  head.  In  no 
case,  in  either  the  field  or  laboratory,  did  the 
initial  ingestion  process  involve  crushing  with 


FISHERY  BULLETIN:  VOL    11.  NO.  1 

the  canines.  After  initial  ingestion,  muscular 
contractions  in  the  bucco-pharyngeal  area  were 
clearly  seen,  evidentally  resulting  from  the 
shells  being  crushed  by  the  pharyngeal  teeth. 
When  a  clump  of  mussels  attached  by  byssal 
threads  was  too  large  to  be  processed  by  the 
pharyngeal  teeth,  the  fish  would  alternately 
ingest  and  egest  the  clump  until  it  was  sepa- 
rated into  a  smaller  crushable  size. 

The  mussels  in  the  digestive  tracts  consisted 
primarily  of  specimens  averaging  11.9  mm  in 
length  and  estimated  to  be  1  to  2  yr  old  (Table  3). 
There  was  an  obvious  selection  of  young,  small 
mussels  by  all-sized  fish. 

While  factors  such  as  ease  of  crushing  and  a 
greater  digestive  efficiency  may  be  involved  in 
the  tautog's  preference  for  small,  young  mus- 
sels, we  found  another  possible  cause  related 
to  the  limitations  imposed  by  the  dimensions 
of  the  pharyngeal  area  where  the  mussels  are 
crushed.  The  mouth  can  accommodate  much 
larger  mussels  than  the  crushing  apparatus  is 
able  to  process.  For  example  in  the  laboratory 
on  20  occasions,  we  saw  fish  that  were  starved 
for  more  than  a  day  attempting  to  eat  mussels 


Table  3. — Relative  fullness  and  contents  of  tautog  digestive  tracts. 


°o  of  total  gut  content! 

Median 

%  of 

Time  of 

Fish 

Decapod 

length  of 

mussels 

capture 

length 

Fullness 

and  cirriped 

mussels 

less  than 

(EDT) 

(cm) 

index ' 

Mussels 

crustaceans 

Other 

(mm) 

30  mm 

0400-0500    . 

23.5 
23.5 
45.0 
37.0 
46.0 

1.0 
1.0 
1.0 
1.0 
1.0 

0800-0830 

24.0 

0.8 

85.7 

5.8 

8.5 

14 

100.0 

27.5 

0.7 

100.0 

12 

100.0 

26.5 

0.7 

99.5 

0.5 

14 

100.0 

34.0 

0.8 

62.5 

37.5 

16 

100.0 

1200-1300 

31.0 

0.6 

89.6 

4.5 

5.9 

15 

100.0 

36.5 

0.5 

65.3 

27.0 

7.7 

8 

100.0 

37.5 

0.6 

78.5 

16.1 

5.4 

16 

100.0 

21.0 

0.7 

98.6 

1.4 

11 

100.0 

24.5 

0.7 

100.0 

5 

100.0 

32.0 

0.4 

95.2 

4.8 

15 

100.0 

29.0 

0.4 

54.5 

36.4 

9.1 

10 

100.0 

1600-1700 

40.0 

0.7 

99.1 

0.6 

0.3 

8 

100.0 

32.0 

0.4 

92.2 

6.0 

1.8 

8 

100.0 

32.5 

0.6 

31.3 

68.1 

0.6 

8 

100.0 

1930-2000 

44.0 

0.4 

90.4 

9.6 

14 

88.1 

36.0 

0.6 

45.9 

41.3 

12.8 

12 

87.5 

46.0 

0.6 

65.7 

32.9 

1.4 

10 

53.8 

37.0 

0.6 

92.3 

7.7 

15 

100.0 

42.5 

0.4 

94.0 

6.0 

16 

72.7 

-20.0 

0.6 

78.4 

21.6 

11 

100.0 

'  Fullness  index   —  volume  empty  tract/volume  of  tract  with  contents. 
-  Fish  no.  7  (Table  1)  captured  at  end  of  track. 


32 


OLLA.  BEJDA,  and  MARTIN:  ACTIVITY  OF  TAUTOGA  ONITIS 


larger  than  could  be  crushed  by  the  pharyngeal 
teeth.  The  fish  would  ingest  the  mussel,  unsuc- 
cessfully attempt  to  crush  it,  and  then  egest 
it,  the  process  being  repeated  20  to  30  times. 
We  also  found  in  a  preliminary  determination 
of  the  maximum  crushable  size  that  fish,  34  to 
53  cm,  could  crush  mussels  that  were  only  0.47 
times  the  maximum  size  they  could  ingest. 

Seasonal  Movements 

Direct  observations  made  during  the  day  with 
scuba  from  October  1971  through  May  1972 
and  from  October  1972  through  January  1973 
indicated  that  there  was  a  difference  in  the 
seasonal  movement  between  small  fish  (^25  cm, 
2-3  yr  old)  and  large  fish  (>25  cm,  >4  yr  old). 
The  ages  of  fish  were  estimated  from  calculated 
total  lengths  by  Cooper  (1967).  Tautog  of  vary- 
ing sizes  were  observed  in  close  proximity  to 
the  basin  on  12  October  1971,  at  an  average 
water  temperature  of  17.0°C  (range:  15.2°- 
19.5 °C).  On  1  November  with  the  water  temper- 
ature averaging  10.0°C  (range:  8.9°-10.6°C), 
no  large  tautog  were  sighted,  but  about  25 
small  ones  were  seen  swimming  within  1  m  of 
the  basin  walls.  Small  fish  were  still  active  on 
18  November  (water  temperature  10.0°  C: 
9.7°-10.1°C).  On  9  December  1971,  and  5 
January  1972,  with  temperatures  ranging  from 
4.0°  to  5.5°C,  a  total  of  approximately  40  small 
tautog  was  sighted  within  the  basin.  These  fish 
appeared  lethargic  and  rested  against  the  basin 
walls.  When  prodded  by  a  diver,  they  moved 
only  a  few  feet  before  settling  to  the  bottom 
once  again. 

Both  large  and  small  fish  were  sighted  on  10 
May  1972  with  an  average  temperature  of 
10.6°C  (range:  8.5°-11.5°C)  and  appeared  nor- 
mally active. 

Diving  observations  the  following  fall  and 
winter  substantially  supported  the  fact  that 
small  fish  wintered  inshore.  On  2  October  1972, 
we  sighted  normally  active  large  and  small 
tautog  (water  temperature  16.8°C:  16.2°- 
17.7° C).  On  26  October  with  the  temperature 
averaging  10.0°C  (range:  9.6°-10.5°C),  we 
found  no  large  fish  but  sighted  at  least  30  small 
fish  which  appeared  normally  active.  During 
dives  on  27  November  and  29  December  1972, 
and  9  January  1973,  with  the  temperature  rang- 
ing 2.0°  to  4.8°C,  we  sighted  approximately  35 
small  fish  (^  25  cm)  lying  in  a  torpid  state  on 


the  bottom  between  pilings  and  the  basin  walls 
or  in  bottom  depressions  within  10  cm  of  the 
wall.  Some  of  these  fish  were  partially  covered 
with  silt.  Opercular  movements  were  so  shallow 
as  to  be  almost  undiscernible.  Examination  of 
the  digestive  tracts  of  five  fish  captured  during 
this  period  showed  that  the  fish  had  not  eaten 
for  some  time  as  indicated  by  the  empty  and 
flaccid  condition  of  the  tracts. 

We  concluded  from  these  observations  that 
fish  at  least  larger  than  25  cm  moved  offshore 
to  winter,  agreeing  with  the  conclusions  of 
Cooper  (1966)  for  a  population  residing  in  Nar- 
ragansett  Bay,  Rhode  Island.  However,  small 
fish  (approximately  ^25  cm)  remained  inshore 
throughout  the  year  in  close  proximity  to  the 
home  site. 


DISCUSSION 

The  tautog's  pattern  of  being  active  during 
the  day  and  inactive  at  night  is  a  typical  labrid 
trait  having  been  observed  in  a  number  of  spe- 
cies. For  example,  field  observations  in  the  Pa- 
cific by  Hobson  (1965,  1968,  1972)  showed  this 
pattern  to  be  present  in  five  species  (Bodiaiius 
diplotaeiiia,  Halichoeres  )iicholsi,  Labroides 
phthirophagus,  Thalassoma  duperrey,  and  T. 
lucasanum).  Th*  pattern  was  presumed  to  be 
present  in  Hali^oeres  dispilus,  Hemipteronotus 
mundiceps,  and  H.  pavoninus  since  the  fish  were 
observed  in  the  active  state  during  the  day  but 
not  sighted  at  night,  having  apparently  buried 
under  sand  or  rested  in  crevices.  Field  obser- 
vations in  the  Atlantic  by'^arck  and  Davis 
(1966)  on  Bodianus  rufus,  Clepticus  parrai, 
Lachitolaimus  ma.vimus,  and  Thalassoma  bi- 
fasciatum  also  show  the  typical  labrid  day  ac- 
tive/night inactive  pattern. 

Whether  a  labrid  species  spends  the  night 
buried  under  sand  or  lying  in  cracks  or  crevices, 
all  appear  to  be  in  a  state  of  low  responsiveness. 
Tauber  and  Weitzman  (1969)  investigated  the 
level  of  responsiveness  of  the  slippery  dick, 
Irideo  bivittata,  at  night.  They  found  the  fish 
to  be  in  a  state  that  resembled  the  mammalian 
sleep  phase  characterized  by  decreased  respon- 
siveness to  altering  stimuli,  diminished  or  ir- 
regular respiration,  and  eye  movement  activity. 

The  low  level  of  responsiveness  present  at 
night  in  labrids  and  other  species  with  a  similar 
habit   has   wide   ramifications    with    regard   to 


33 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


susceptibility  to  environmental  stress.  The  prob- 
ability that  fish  would  be  able  to  respond  and 
escape  potentially  lethal  environmental  pertur- 
bations during  the  inactive  night  phase  would 
be  less  than  if  the  same  stress  were  applied  dur- 
ing the  day.  Physiological  responses  would  also 
differ.  Differential  susceptibility  to  stresses  as 
related  to  the  daily  rhythm  has  been  clearly 
established  (for  discussion  and  review,  see 
Reinberg.  1967). 

During  most  of  the  summer  and  into  early 
fall,  fish  of  the  colony  we  studied  had  a  fairly 
well  defined  home  range  (Gerking,  1959)  with 
the  basin  acting  as  a  focal  point  or  home  site, 
providing  a  suitable  night  habitat  for  all-sized 
fish.  While  larger  fish  (^30  cm)  moved  out 
each  day  to  feed,  the  smaller  fish  (^25  cm) 
foraged  along  or  in  close  proximity  to  the 
basin  walls.  The  adaptation  of  young  fish  re- 
maining close  to  the  home  site  may  relate  to 
effectively  protecting  them  against  predators. 
On  one  occasion  while  diving  in  early  July  1972, 
we  observed  three  striped  bass  {Moroue  .sa.r- 
atilis,  80-90  cm)  actively  pursuing  and  attempt- 
ing to  capture  young  tautog  (^25  cm)  from  a 
group  of  30  to  40.  The  tautog  were  within  1  m 
of  the  basin  wall  at  the  onset  of  the  attack. 
They  escaped  from  the  predators  by  swimming 
directly  to  the  wall  where  they  remained  in 
crevices.  The  older  fish,  not  as  susceptible  to 
predation,  moves  out  to  feed,  resulting  in  a 
fuller  utilization  of  the  potential  energy  re- 
sources of  the  area  and  in  the  probable  reduc- 
tion of  feeding  competition  among  individuals. 
The  reduction  in  the  probability  of  feeding  com- 
petition seemed  especially  critical  since  all 
sizes  studied  preferred,  to  a  large  extent,  simi- 
lar-sized mussels.  This  daily  movement  of  the 
larger  fish  out  of  the  basin  also  seemed  to  make 
the  home  site  a  nursery  for  young  fish. 

Our  obsen^ations  that  tautog  larger  than  30 
cm  (approximately  5  yr  or  older)  were  not 
present  in  the  vicinity  of  the  basin  after  the 
end  of  October  circumstantially  agree  with  the 
finding  of  Cooper  (1966)  that  Narragansett 
Bay  fish  of  similar  size  wintered  offshore.  In 
contrast,  our  results  showed  that  younger  fish 
remained  inshore  throughout  the  year,  winter- 
ing at  the  home  site  in  a  torpid,  nonfeeding 
state.  It  is  apparent  that  the  younger  fish  are 
highly  dependent  on  the  home  site  throughout 
the  year  for  at  least  the  first  3  to  4  and  perhaps 
5  yr  of  their  life.  The  habit  of  remaining  inshore 


over. the  winter  is  not  unknown  in  labrids. 
Green  and  Farwell  (1971)  found  various-sized 
cunner,  Tautogolabrus  adspersus,  lying  in  a 
torpid  state  inshore  when  temperatures  fell 
below  5°C. 

Although  tautog  feed  readily  on  other  types 
of  food,  the  most  abundant  food  available  and 
found  most  frequently  in  the  digestive  tract 
was  mussels.  Mussels  were  predominantly  less 
than  30  mm  long,  indicating  an  average  age  of 
1  to  2  yr  (Savage,  1956).  The  next  most  abun- 
dant food  found  in  the  digestive  tract  was  vari- 
ous crustaceans,  with  only  negligible  amounts 
of  other  items.  It  seemed  that,  on  the  basis  of 
our  diving  observations,  the  crustacean  popula- 
tion, in  terms  of  a  potential  alternate  food 
source  for  the  tautog  in  this  area,  did  not  ap- 
proach the  abundance  of  mussels  in  the  1  to  2 
yr  class.  We  surmise  that  the  equilibrium  of  the 
population,  in  terms  of  food  resources,  is  highly 
dependent  on  a  single  food  item,  with  no  alter- 
nate potentially  serving  as  a  sustaining  element. 

Environmental  perturbations  that  would 
directly  affect  1-  to  2-yr-old  mussels  or  any  of 
the  pre-adult  stages,  would  lead  to  a  high  prob- 
ability of  stress  in  the  tautog  population.  This 
would  be  especially  true  for  young  fish  (3  yr  or 
less)  since  they  seem  especially  dependent  upon 
the  home  site.  This  dependence  on  the  home  site 
raises  the  question  of  whether  or  not  it  is 
within  their  capability  to  move  out  and  seek 
new  feeding  areas  and  if  so,  how  successful 
would  they  be. 

Another  obvious  limiting  element  of  the 
population  is  a  suitable  physical  structure 
which  all-sized  tautog  require  during  their 
night  inactive  phase  and  upon  which  young 
tautog  seem  totally  dependent.  In  areas  where 
food  resources  are  in  relative  abundance  to 
support  a  population,  the  introduction  of  a 
suitable  physical  habitat  could  lead  to  the  es- 
tablishment of  new  discrete  colonies. 

ACKNOWLEDGMENTS 

We  wish  to  thank  the  U.S.  Coast  Guard,  Fire 
Island,  New  York,  and  Charles  Entenmann  for 
their  assistance  and  cooperation.  Our  apprecia- 
tion is  extended  to  James  Johnson,  National 
Marine  Fisheries  Service,  and  Case  Groot, 
Fisheries  Research  Board  of  Canada,  for  their 
advice  and  encouragement  concerning  the  ultra- 
sonic tracking  portion  of  the  study.  In  addition, 


34 


OLLA,  BEJDA.  and  MARTIN:  ACTIVITY  OF  TAUTOGA  OMTIS 

we  wish  to  thank  Ralph  Sheprow  for  his  tech- 
nical assistance  during  the  study. 


LITERATURE  CITED 


BiGELOW,  H.  B..  AND  W.  C.  SCHROEDER. 

1953.  Fishes  of  the  Gulf  of  Maine.  U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  53,  577  p. 
Cooper,  R.  A. 

1966.  Migration  and  population  estimation  of  the 
tautog,  Taiitoga  onitis  (Linnaeus),  from  Rhode 
Island.  Trans.  Am.  Fish.  Soc.  95:239-247. 

1967.  Age  and  growth  of  the  tautog.  Tautoga  onitis 
(Linnaeus),  from  Rhode  Island.  Trans.  Am.  Fish. 
Soc.  96: 134-142. 

Gerking,  S.  D. 

1959.  The   restricted   movement   of  fish    populations. 
Biol.  Rev.  (Camb.)  34:221-242. 
Green,  J.  M.,  and  M.  Farwell. 

1971.  Winter    habits    of   the    cunner,    Taiitogolabrus 
adspersus  (Walbaum  1792),  in  Newfoundland.  Can. 
J.  Zool.49:1497-1499. 
HOBSON,  E.  S. 

1965.  Diurnal-nocturnal     activity     of    some     inshore 


fishes  in  the  Gulf  of  California.  Copeia   1965:291- 
302. 

1968.  Predatory  behavior  of  some  shore  fishes  in 
the  Gulf  of  California.  U.S.  Fish  Wildl.  Serv.,  Res. 
Rep.  73,  92  p. 

1972.  Activity    of   Hawaiian    reef   fishes    during    the 
evening  and  morning  transitions  between  daylight 
and  darkness.  Fish.  Bull.,  U.S.  70:715-740. 
McCleave,  J.  D.,  AND  R.  M.  Horrall. 

1970.  Ultrasonic  tracking  of  homing  cutthroat  trout 
(Salmo  clarki)  in  Yellowstone  Lake.  J.   Fish.  Res. 
Board  Can.  27:715-730. 
Reinberg,  a. 

1967.  The  hours  of  changing  responsiveness  or  sus- 
ceptibility. Perspect.  Biol.  Med.  11:111-128. 
Savage,  R.  E. 

1956.  The   great   spatfall   of  mussels   (Mytilus   edulis 
L.)   in  the  River  Conway  estuary   in  spring    1940. 
G.  B.  Minist.  Agric.  Fish.  Food.,  Fish.  Invest.  Ser. 
II.  20(7):  1-22. 
Starck,  W.  a.,  II,  AND  W.  p.  Davis. 

1966.  Night  habits  of  fishes  of  Alligator  Reef,  Florida. 
Ichthyol.  Aquarium  J.  38:3 13-356. 
Tauber,  E.  S.,  AND  E.  D.  Weitzman. 

1969.  Eye  movements  during  behavioral  inactivity  in 
certain  Bermuda  reef  fish.  Commun.  Behav.  Biol. 
Part  A  3:131-135. 


35 


AN  EXAMINATION  OF  THE   YIELD  PER  RECRUIT 

BASIS   FOR  A   MINIMUM   SIZE   REGULATION   FOR 

ATLANTIC  YELLOWFIN  TUNA,    IHUNNUS  ALBACARES 


W.  H.  Lenarz.  W.  W.  Fox,  Jr.,  G.  T.  Sakagawa, 
AND  B.  J.  Rothschild' 


ABSTRACT 

Some  of  the  conceptual  foundations  of  yield-per-recruit  analysis  as  a  management  tool 
and  as  applied  to  the  Atlantic  yellowfin  tuna  fishery  were  critically  explored.  Problems 
examined  include:  (1)  estimating  the  current  state  of  the  fishery  in  terms  of  a  knife-edged 
recruitment  approximation,  (2)  inferring  consequences  of  management  action  from  the 
yield-per-recruit  isopleth,  (3)  the  difficulty  in  achieving  a  maximum  yield  per  recruit  when 
there  exist  several  gear  types  exploiting  different  size  ranges,  (4)  the  difficulty  in  obtaining 
projected  increases  in  yield  per  recruit  when  the  killing  and  discarding  (dumping)  of  fish 
smaller  than  the  optimum  size  occurs,  and  (5)  the  possible  interaction  between  a  size  limit 
and  the  projection  of  the  maximum  sustainable  yield. 

In  employing  yield-per-recruit  analysis  to  the  Atlantic  yellowfin  tuna  fishery,  two  ap- 
proaches were  taken  —  one  approach  makes  use  of  a  wide  range  of  parameter  estimates  and 
a  number  of  simplifying  assumptions,  but  little  data,  and  the  other  approach  makes  use 
of  considerably  more  data,  but  is  more  confined  in  the  parameter  estimates  and  uses  fewer 
of  the  simplifying  assumptions.  The  general  results  of  both  approaches,  assuming  no  dump- 
ing occurs,  indicate  that  only  minor  increases  in  yield  per  recruit  would  occur  if  the  size 
at  recruitment  is  increased  from  our  estimate  of  the  present  size  at  recruitment  and  fishing 
effort  remains  constant;  an  increase  in  fishing  effort  without  changing  other  aspects  of  the 
fishery  would  not  appreciably  increase  yield  per  recruit;  and  an  increase  in  size  at  recruit- 
ment and  in  fishing  effort  would  result  in  modest  gains  in  yield  per  recruit.  Specifically 
meeting  the  request  of  the  International  Commission  for  the  Conservation  of  Atlantic 
Tunas,  we  recommended  that  a  minimum  size  limit  regulation  in  the  vicinity  of  55  cm 
(3.2  kg)  be  enacted. 


The  second  regular  meeting,  in  Madrid,  Spain, 
on  2-7  December  1971,  of  the  commission  of 
ICCAT  (International  Commission  for  the  Con- 
servation of  Atlantic  Tunas)  authorized  the 
"Council  to  recommend  to  the  Contracting  Par- 
ties that  they  prohibit  landing  of  yellowfin 
weighing  less  than  a  minimum  weight  some- 
where between  3.2  and  10  kg."  This  recommen- 
dation was  based  on  studies  by  members  of  the 
Subcommittee  on  Stock  Assessment  that  showed 
that  theoretically  the  size  at  first  capture 
which  maximizes  the  yield  per  recruit  of  yellow- 
fin is  between  10  and  25  kg. 

A  special  ICCAT  working  group  on  stock 
assessment  of  yellowfin  tuna  met  in  Abidjan, 
Ivory  Coast,  12-16  June  1972,  to  consider  fur- 
ther scientific   aspects   of  size   regulation   and 


other  matters  pertaining  to  the  Atlantic  yellow- 
fin fishery  (ICCAT,  1972).-  Studies  on  yield 
per  recruit  were  presented  by  Hayasi,  Honma, 
and  Suzuki  (1972) ;■'  Joseph  and  Tomlinson 
(1972);^  and  Lenarz  and  Sakagawa  (1972)." 
A  similar  study  was  published  by  Wise  (1972) 


'  Southwest   Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  LaJolla,  CA  92037. 


-  ICCAT.  1972.  Report  of  the  meeting  of  the  special 
working  group  on  stock  assessment  of  yellowfin  tuna 
(Abidjan,  June  12-16,  1972).  Manuscript  on  file  at  ICCAT 
General  Mola  17,  Madrid,  1  Spain. 

•^  Hayasi,  S.,  M.  Honma,  and  Z!  Suzuki.  1972.  A  com- 
ment to  rational  utilization  of  yellowfin  tuna  and  albacore 
stocks  in  the  Atlantic  Ocean.  Far  Seas  Fisheries  Research 
Laboratory,  Orido  1000,  Shimizu,  Japan.  Unpublished 
manuscript. 

-*  Joseph,  J.,  and  P.  K.  Tomlinson.  1972.  An  evaluation 
of  minimum  size  limits  for  Atlantic  yellowfin.  Inter- 
American  Tropical  Tuna  Commission,  La  JoUa,  Calif. 
Unpublished  manuscript. 

5  Lenarz,  W.,  and  G.  Sakagawa.  1972.  A  review  of  the 
yellowfin  fishery  of  the  Atlantic  Ocean.  Southwest  Fish- 
eries Center,  National  Marine  Fisheries  Service,  La  Jolla, 
Calif.  Unpublished  manuscript. 


Manuscript  accepted  June  1973. 

FISHERY  BULLETIN:  VOL.  72.  NO.  1.  1974. 


37 


FISHERY  BULLETIN,  VOL.  72.  No.  1 


before  the  meeting.  The  report  of  the  meeting 
may  be  considered  as  a  summary  of  these  pa- 
pers, which  indicated  that  increases  in  size  at 
recruitment  would  probably  increase  yield  per 
recruit  but  not  by  more  than  about  10% . 

The  special  ICCAT  working  group  also  ex- 
amined available  evidence  on  the  practicability 
of  minimum  size  regulations.  Scientists  of  the 
group  were  concerned  that  since  the  gears  that 
fish  for  yellowfin  in  the  Atlantic  supposedly 
kill  most  fish  that  are  captured,  a  minimum 
size  regulation  would  reduce  the  number  of 
small  yellowfin  that  are  landed  but  would  not 
have  the  desired  effect  of  reducing  mortality 
rates  of  small  yellowfin.  This,  of  course,  as- 
sumes that  schools  of  yellowfin  containing  yel- 
lowfin less  than  any  minimum  size  would  actual- 
ly be  set  upon.  In  this  connection  the  group 
noted  that  the  conditions  which  must  be  met 
before  minimum  size  regulations  can  be  effec- 
tive are:  (1)  the  fishermen  must  be  able  to 
estimate  the  size  of  yellowfin  in  a  school,  and 
(2)  there  must  be  little  or  no  mixing  of  small 
yellowfin  with   large  yellowfin  within  schools. 

Very  little  evidence  is  available  from  the  At- 
lantic on  these  subjects.  Ten  sami)les  were  pre- 
sented at  the  Abidjan  meeting  that  indicated 
considerable  mixing  of  small  yellowfin  (<5  kg) 
with  large  yellowfin  (>5  kg)  within  schools. 
The  working  group  also  took  note  of  a  study  on 
the  subject  by  Calkins  (1965)  when  size  regula- 
tions were  being  considered  by  the  lATTC 
(Inter-American  Tropical  Tuna  Commission) 
for  the  yellowfin  fishery  in  the  eastei'n  tropical 
Pacific.  Calkins,  working  with  only  one  hypo- 
thetical minimum  size  out  of  a  range  of  12.7  to 
25.0  kg,  concluded  that  a  12.7-kg  size  regulation 
would  be  seriously  complicated  by  size  varia- 
tion within  sets.  He  also  noted  that  a  consid- 
erable amount  of  small  yellowfin  are  often  cap- 
tured in  sets  that  include  skipjack.  Thus  it  ap- 
pears that  it  would  not  be  possible  to  fish  for 
skii)jack  without  killing  some  small  yellowfin. 
Evidence  based  on  the  few  samples  from  the 
Atlantic  indicated  that  sets  would  include 
yellowfin  tuna  larger  and  smaller  than  5  kg; 
thus  even  if  a  minimum  size  regulation  were  set 
at  this  value  it  would  be  difficult  to  prevent 
the  capture  offish  smaller  than  5  kg. 

The  working  group  recommended  that  more 
data  should  be  collected  on  the  subject  from 
the   Atlantic.   The   working  group   also   noted 


that  a  reduction  in  the  size  at  first  recruitment 
should  be  prevented  and  that  minimum  size 
regulations  of  3.2  kg  that  have  been  passed  by 
several  African  nations  should  help  prevent  a 
reduction  in  size  at  recruitment. 

The  population  dynamics  of  Atlantic  yellow- 
fin tuna  are  complex  because  the  fishery  is 
prosecuted  by  several  types  of  gear:  bait  boats, 
small  purse  seiners,  large  purse  seiners,  and 
longliners.  These  gears  tend  to  capture  differ- 
ent sizes  of  fish  and  thus  affect  the  population 
in  different  ways.  FAO  (1968)  noted  that  long- 
line  gear  tends  to  capture  large  yellowfin  while 
the  other  gears  capture  small  yellowfin.  Lenarz 
(1970).''  with  more  recent  data,  showed  that 
American"  purse  seine  gear  tends  to  capture 
relatively  more  large  yellowfin — in  significant 
quantities — than  was  indicated  for  the  earlier 
surface  fishery.  Joseph  and  Tomlinson  (1972, 
see  footnote  4)  presented  data  that  indicated 
small  purse  seiners  of  France-Ivory  Coast- 
Senegal  (FIS)  tend  to  capture  relatively  more 
small  yellowfin  than  the  large  FIS  and  Ameri- 
can purse  seiners.  The  differences  among  size 
selectivity  of  the  four  gears  necessitates  con- 
sideration of  the  physical  makeup  of  the  fleet 
when  e.xamining  size  regulations.  Therefore, 
considerable  attention  was  paid  to  this  aspect 
of  the  problem  during  the  study. 

The  above  paragraph  might  be  taken  to  imply 
that  adequate  data  are  available  respecting  the 
relative  quantities  and  size  distributions  of  fish 
caught  by  the  various  gears.  It  is  our  feeling 
that  the  adequacy  of  the  data  needs  to  be  dem- 
onstrated. We  cannot  place  much  faith  in  the 
details  of  the  relative  size  distributions  per 
unit  effort  among  the  various  fishing  units,  but 
we  do  feel  that  the  general  orders  of  magnitude 
are  essentially  correct.  We  should  also  point 
out  that  with  the  improvement  in  data  over  the 
last  several  years,  the  interpretations  which 
accrue  from  the  data  and  our  appreciation  of 
the  considerable  complexity  of  the  fishery  are 
more  evident. 

Definitions  of  Minimum  Size 

Because  this  paper  discusses  minimum  size, 
it  is  necessary  to  define  the  term  explicitly  to 


"  Lenarz,  W.  1970.  Estimates  of  yield  per  recruit  of 
Atlantic  yellowfin  tuna.  Southwest  Fisheries  Center, 
National  Marine  Fisheries  Service,  La  Jolla,  Calif.  Un- 
published manuscript. 

"  Refers  to  vessels  registered  in  Canada,  Panama,  and 
the  U.S.A. 


38 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


avoid  ambiguity  and  to  prevent  possible  mis- 
applications of  the  results  of  this  study.  "Mini- 
mum size"  may  be  viewed  from  two  aspects: 
absolute  minimum  size  and  effective  minimum 
size.  Absolute  minimum  size  is  defined  as  the 
smallest  fish  in  the  catch  and  is  related  to  the 
concept  of  knife-edged  recruitment  in  defining 
the  size  at  recruitment  to  the  fishery.  Recruit- 
ment is  defined  as  the  act  of  becoming  vulner- 
able to  fishing.  In  the  case  of  knife-edged  re- 
cruitment, no  fish  are  vulnerable  to  fishing  prior 
to  the  size  at  recruitment.  Fish  that  are  larger 
than  the  size  at  recruitment  are  full}^  vulner- 
able to  fishing.  Since  most  recruitment  is  size 
specific,  hence  sequential,  the  term  effective 
minimum  size  is  also  needed.  Effective  mini- 
mum size  is  that  size  whose  corresponding  age 
is  used  as  the  lower  bound  for  integration  of  the 
yield  equation  as  if  recruitment  were  knife- 
edged,  and  which  gives  the  same  yield  per  re- 
cruit as  the  sequential  recruitment  case. 

Approaches  to  Yield  -  Per-Recruit  Analysis 

This  paper  examined  several  of  the  concepts 
involved  in  yield-per-recruit  analyses  because 
the  question  of  what  is  the  optimum  minimum 
size  for  a  given  rate  of  exploitation  is  usually 
interpreted  through  such  analyses.  Both  the 
classical  approach,  in  which  fishing  mortality 
is  constant  with  knife-edged  reciiiitment.  and 
the  more  complex  approach,  in  which  fishing 
mortality  is  size  specific,  are  explored. 

Throughout  the  paper  we  have  intentionally 
kept  mathematical  notation  to  a  bare  minimum. 
We  believe  that  most  of  the  equations  used  are 
well  known  to  readers  actively  involved  in 
stock  assessment.  Readers  who  are  not  familiar 
with  the  equations  can  find  excellent  descrip- 
tions in  the  cited  literature. 

Employing  the  classical  approach  to  yield- 
per-recruit  analysis  involves:  (1)  estimating 
the  age  or  size  at  recruitment  which  represents 
an  approximation  of  the  current  state  of  the 
fishery  in  terms  of  knife-edged  recruitment; 
(2)  finding  the  age  or  size  at  recruitment  which 
maximizes  the  yield  per  recruit  at  a  given  level 
of  fishing  mortality;  (3)  imposing  some  regula- 
tion on  the  fishery  such  to  achieve  as  its  effec- 
tive minimum  size,  the  age  or  size  at  reci-uit- 
,  ment  which  maximizes  the  yield  per  recruit. 
The  advice  from  the  yield-per-recruit  isopleth 
(in  terms  of  the  optimal  age  or  size  at  recioiit- 


ment)  may  be  interpreted  as  either  a  knife- 
edged  absolute  minimum  size  or  as  an  effective 
minimum  size.  Since  for  the  fishery  under  con- 
sideration (and  for  many  other  fisheries  as  well) 
recruitment  is  not  knife-edged,  then  we  are 
talking  about  an  effective  minimum  size.  Now, 
on  the  other  hand,  if  we  assume  that  the  abso- 
lute minimum  size,  the  regulated  size,  and  the 
effective  minimum  size  are  all  the  same,  then 
we  will  have  an  inappropriate  estimate  of  the 
yield  per  recruit,  and  the  optimum  may  not  be 
achieved.  Somehow  we  need  to  determine  the 
relationship  between  the  effective  minimum 
size  and  the  regulated  size;  in  some  instances 
they  can  roughly  be  the  same;  but  this  equality 
will  usually  not  obtain  if  the  regulated  size  is 
chosen  to  be  the  absolute  minimum  size  in 
the  catch. 

The  more  complex  approach,  which  estimates 
size-specific  fishing  mortality,  circumvents  the 
first  difficulty  encountered  in  the  classical  ap- 
proach, i.e.,  determining  a  knife-edged  approxi- 
mation to  the  current  state  of  the  fishery.  The 
problem  still  remains,  however,  as  to  interpre- 
tation of  the  advice  from  the  yield-per-recruit 
isopleth  in  terms  of  an  effective  minimum  size. 
Joseph  and  Tomlinson  (1972,  see  footnote  4) 
used  the  more  complex  approach  in  a  recent 
study  on  minimum  size  regulations  for  the  At- 
lantic yellowfin  fishery.  We  have  updated  their 
analysis  by  using  data  made  available  at  the 
Abidjan  meeting  and  have  also  examined  the 
sensitivity  of  the  methodology  to  various  sources 
of  errors  in  the  data. 

DATA,  PARAMETERS,  AND 
COMPUTER  PROGRAMS 

Data 

Catch-  and  length-frequency  data  for  each 
type  of  gear  for  the  1967-71  period  were  ob- 
tained from  the  report  of  the  meeting  of  the 
special  ICC  AT  working  group  (Tables  10,  11, 
and  12  of  ICCAT,  1972,  see  footnote  2)  with 
the  exception  of  length-frequency  data  of  the 
1967-68  FIS  fishery  and  1971  Japanese  long- 
line  fishery.  Length  frequencies  for  the  1967-68 
FIS  fishery  were  compiled  from  various 
ORSTOM  (Office  de  la  Recherche  Scientique  et 
Technique  Outre-Mer)  publications  (Lenarz 
and  Sakagawa,   1972,  see  footnote  5).   Length 


39 


FISHERY  BULLETIN,  VOL.  12.  NO.  1 


frequencies  from  the  1971  Japanese  longline 
fishery  are  assumed  to  be  the  same  as  those  of 
the  1970  Japanese  longline  fishery;  this  as- 
sumi)tion  appears  justifiable  because  year  to 
year  changes  in  length  frequencies  from  long- 
line  fisheries  tend  to  be  less  than  differences  in 
length  frequencies  between  longline  fisheries 
and  surface  fisheries. 

Length-frequency  data  were  available  only 
from  the  Jai)anese  longline  fishery,  FIS  surface 
fisheries,  and  American  large  purse  seine  fishery. 
Thus  it  was  necessary  to  make  several  assump- 
tions before  estimating  the  length  frequencies 
of  the  total  catch  of  yellowfin  in  the  Atlantic. 
Length  frequencies  for  longline  fisheries  other 
than  Japan  are  assumed  to  be  the  same  as 
Japan's.  Length  frequencies  for  the  bait  boat 
and  small  purse  seine  fisheries  other  than  FIS 
were  assumed  to  be  the  same  as  the  FIS  fish- 
ery. Length  frequencies  for  the  large  purse 
seine  fisheries  other  than  FIS  and  American 
were  assumed  to  be  the  same  as  those  two 
fisheries. 

Parameters 

The  growth  equation  [L  =  194.8  X  (1  - 
g-0.42  (<  -  o.62))j  presented  in  LeGuen  and 
Sakagawa  (1973)  and  length-weight  relation- 
ship {W  =  0.0000214L2-9736)  given  by  Lenarz 
(19713)*^  were  used,  where  L  is  fork  length  in 
cm,  t  is  age  in  years,  and  W  is  weight  in  kg. 

The  annual  instantaneous  coefficient  of  nat- 
ural mortality  (M)  is  a  difficult  parameter  to 
estimate  and  due  to  a  lack  of  data  only  pre- 
liminary estimates  have  been  made  for  the  pa- 
rameter in  the  Atlantic.  We  assume  as  most 
authors  have  that  M  is  constant  over  the  ex- 
ploited phase.  Estimates  of  M  =  2.61  and  1.50 
for  the  Atlantic  were  made  by  Pianet  and  LeHir 
(1971)  based  on  data  from  bait  boats  and  seiners, 
respectively.  These  estimates  seem  unreason- 
ably high  perhaps  because  their  data  were  only 
from  the  Pointe  Noire  region  which  is  a  small 
area  compared  to  the  total  region  in  the  Atlan- 
tic where  yellowfin  tuna  are  found.  Hennemuth 
(1961)  estimated  that  M  is  0.8  in  the  Pacific 
while  Davidoff  (1969)  chose  the  upper  bound 


of  Hennemuth's  estimate,  1.0.  Hennemuth's 
work  was  based  on  estimates  of  instantaneous 
coefficient  of  total  mortality  (Z)  made  from  age 
compositions  of  catches  by  primarily  bait  boats 
and  an  estimate  of  instantaneous  coefficient  of 
fishing  mortality  (F)  from  Schaefer  (1957). 
Since  bait  boats  appear  to  be  selective  for  small 
yellowfin,  F  and  Z  are  not  constant,  and  meth- 
ods of  ageing  yellowfin  have  not  been  proven 
correct,  Hennemuth's  estimate  must  be  con- 
sidered a  first  approximation.  However,  his 
estimate  seems  reasonably  consistent  with  what 
is  thought  to  be  the  life  span  of  yellowfin.  We 
assumed  for  the  purposes  of  our  calculations 
here  that  M  is  0.8  as  is  conventional  (based  on 
Hennemuth's  work  in  the  Pacific);  we  also  used 
values  of  0.6  and  1.0  to  encompass  what  we 
believe  is  the  range  of  reasonable  values. 

Pianet  and  LeHir  (1971)  also  estimated  an 
average  F  of  0.88  for  the  segment  of  the  At- 
lantic yellowfin  tuna  population  that  is  exploit- 
ed in  the  Pointe  Noire  region.  As  we  have  indi- 
cated, their  estimate  is  not  representative  for 
the  population  as  a  whole. 

Our  range  of  estimates  of  Z  for  1967-71  is 
0.91  to  1.82  (Lenarz  and  Sakagawa,  1972,  see 
footnote  5).  If  we  assume  that  M  =  0.8  for  the 
Atlantic  population,  then  F  is  0.11  to  1.02.  We 
believe  that  F  is  about  0.6  for  recent  years. 
However,  we  used  a  range  of  F  values  in  our 
study. 

Computer  Programs 

Most  of  the  calculations  were  performed  on 
the  Burroughs  6700-'  computer  at  the  Univer- 
sity of  California  at  San  Diego.  Programs  used 
in  the  analysis,  except  for  FRG708  (Paulik 
and  Bayliff,  1967),  were  written  by  the  authors; 
they  are  as  follows: 

1.  Simplified  Beverton  and  Holt  yields  per 
recuit— YPER. 

2.  Accuracy  of  knife-edged  approximations 
of  age  at  entry  and  interactions  between  mini- 
mum size  and  catch  quota  regulations — 
GXPOPS. 

3.  Yield-per-recruit  isopleths  under  knife- 
edged  recruitment — FRG708. 


**  Lenarz,  W.  1971a.  Length-weight  relations  for  five 
Atlantic  scombrids.  Southwest  Fisheries  Center,  National 
Marine  Fisheries  Service,  La  Jolla,  Calif.  Unpublished 
manuscript. 


"  Reference  to  trade  names  does  not  imply  endorsement 
by  the  National  Marine  Fisheries  Service,  NOAA. 


40 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


4.  Size-specific   rates  of  fishing   mortality — 
COHORT. 

5.  Yield-per-recruit    isopleths   for   multigear 
fisheries  with  size-specific  F — MGEAR. 

6.  Optimum  size  at  recruitment  under  differ- 
ent   levels   of  effort   by   two   gears — OPSIZE. 

ANALYSIS 

As  previously  mentioned  in  the  introduction, 
we  use  two  approaches  in  analyzing  the  data, 
the  knife-edged  recruitment  approach  and  the 
size-specific  F  approach. 

Knife-Edged  Recruitment  Approach 
Introduction 

Two  commonly  used   models  for  computing 
yield  per  recruit  and  determining  the  size  at 
recruitment  which  maximizes  yield  per  recruit 
are   those    of  Beverton    and    Holt    (1957)    and 
Kicker  (1958).  We  employed  both   models  for 
knife-edged  approximation  analyses — the  sim- 
plified Beverton  and  Holt  model,  making  use  of 
a  wide  range  of  parameter  estimates  or  extra- 
polations from  fisheries  for  similar  species,  and 
the  Ricker  model,  making  use  of  the  best  param- 
eter estimates  and  giving  a  more  detailed  an- 
alysis of  yield  per  recruit.  We  used  the  Ricker 
model  instead  of  the  Beverton  and  Holt  model 
for   calculating   yield-per-recruit    isopleths   be- 
cause the  Ricker  model  allows  the  use  of  expo- 
nents  in   the   length-weight    relationship   with 
values  other  than  3.  It  is  important  to  stress 
that   the   material    in   the   simplified    Beverton 
and    Holt    model    involves   fewer   assumptions 
than  the  material  in  subsequent  sections.  This 
is  important  because  as  our  approach  becomes 
more   complex   the   data   requirements   become 
more  rigorous.  It  can  be  argued  that  we  have 
sufficient  data  for  this  simplified  approach.  In 
the  more  complex  approaches  this  assertion  be- 
comes more  tenuous;  because  we  use  more  as- 
sumptions in  the  more  complex  approaches  we 
do    not    necessarily    obtain    more    information, 
even  though  it  may  appear  that  way.  However, 
it  should   be   noted  that  the  assumption   of  a 
constant  rate  of  mortality  over  the  fishable  life 
span  contained  in  the  simplified  approach  may 
be  important,  and  we  believe  that  it  is  not  ful- 
filled. These  analyses  are  followed  by  sections 
discussing    the    problems    of   determining    the 


proper   parameters    which    represent   the   cur- 
rent situation  of  the  fishery. 

Simplified  Beverton  and  Holt  Model 

The  Beverton  and  Holt  yield-per-recruit 
model  may  be  simplified  such  that  relative  yield 
per  recruit,   Y\  is  a  function  of  three  ratios: 

C  =  i,:iL^ 

Q  =  MIK 

E  =  FI(F  +  M) 

Y'=  YI(RW^) 

and  where  //  is  the  size  (length)  at  recruit- 
ment, W^ ,  L^ ,  and  K  are  parameters  of  the 
von  Bertalanffy  growth  equation,  Y  is  yield  in 
weight,  and  R  is  recruitment.  Y'  is  tabulated  in 
Beverton  and  Holt  (1966),  but  more  extensive 
calculations  were  performed  with  program 
YPER.i"  Beverton  and  Holt  (1959)  concluded 
that,  within  reason,  there  exists  a  common 
ratio  between  M  and  K  within  related  species 
groups.  Therefore,  a  range  of  estimates  for  the 
various  parameters  is  utilized  along  with  other 
information  obtained  by  examining  parameter 
estimates  for  M  and  K  for  yellowfin  tuna  from 
areas  other  than  the  Atlantic. 

The  range  of  values  for  the  various  parameters 
is  as  follows:  K  =  0.28  to  0.53  and  L^   =  175.2 
to  223.0  cm  from  LeGuen  and  Sakagawa  (1973), 
Z   =    0.91  to  1.82  from  Lenarz  and  Sakagawa 
(1972,  see  footnote  5),  and  M  =  0.6  to  1.0.  From 
these  ranges  of  e.stimates,  a  maximum  range  for 
E  is  0.0  to  0.67  and  for  Q  is  1.13  to  3.57.  Using 
our  most  reasonable  parameter  estimates  of  K 
=  0.42,  M  =  0.8,  and  Z  =   1.4,  however,  a  rea- 
sonable range  for  E  and  Q  was  established  by 
allowing  either  the  numerator  or  denominator 
of  the  ratio  to  be  one  of  our  most  reasonable 
estimates — the  reasonable  ranges  are  E  =  0.12 
to  0.56  and  Q  =    1.42  to  2.86.  With  K  =  0.42, 
M  =  0.8,  and  Z  =   1.4,  our  most  reasonable  es- 
timates of  £■  and  Q  are  0.43  and  1.9.  respectively. 
Table  1  contains  optimal  values  of  size  (cm) 
at  recruitment,     /*/,    for  the  maximum  range 
of  estimates  of  E  and  Q  (deleting  the  impossible 
E  =  0.0)  for  the  range  and  most  reasonable  es- 
timates of   L^.  The  dashed  lines  enclose  the 


,1  f.^n.A"'"^  ^^'"^^  °f  '••  Table  lib  of  Beverton  and 
Holt  (1966)  was  slightly  higher  than  computed  by  YPER- 
this  may  be  due  to  differing  methods  of  rounding 


41 


FISHERY  BULLETIN.  VOL   72.  NO.  1 


Table  \. — Optimal  values  of  .size  at  recruitment  (cm)  as  a  function  of  the  rate  of 
exploitation  (E)  and  the  ratio  of  M  to  K  (Q)  for  three  estimates  of  L^..' 

E 
Q  0.1  0.2  0.3  0.4  0.5  0.6  0.7 


=    175.2  cm 


1.0 

56.6 

1.5 

49.4 

2.0 

43.8 

2.5 

39.4 

3.0 

35.9 

3.5 

32.9 

1.0 

62.9 

1.5 

54.9 

2.0 

48.7 

2.5 

43.8 

3.0 

39.9 

3.5 

36.6 

1.0 

72.0 

1.5 

62.9 

2.0 

55.8 

2.5 

50.2 

3.0 

45.7 

3.5 

41.9 

73.1 

84.4 

94.3 

102.3 

109.5 

64.1 

74.8 

83.4 

90.8 

97.1 

57.1 

66.9 

74.8 

81.5 

87.2 

51.7 

60.4 

67.8 

73.9 

79.4 

47.1 

55.4 

62.0 

67.6 

72.7 

""43.3  "■ 

51.0 

57.1 

62.4 

66.9 

=    194.8  cm 


81.2 

94.3 

104.8 

113.8 

121.8 

r"7r3~  ■ 

83.2 

92.7 

100.9 

107.9     1 

1      63.5 

74.4 

83.2 

90.6 

97.0     1 

j      57.5 

67.2 

75.4 

82,2 

88,2      j 

1      52.4 

61.6 

69.0 

75.2 

80.8      1 

—js--- 

56.7 

63.5 

69.4 

74,4 

=  223.0  cm 


115.8 
102.8 
92,5 
84.1 
77,1 
71.1 


128.8 

114,4 

102,8 

93.5 

85.7 

79.1 


147,4 
130,9 
117,7 
107,0 
98,1 
90.5 


'    Dashed     lines    encompass    our    reasonable    range    of    values; 
our  most  reasonable  estimate. 


underlined    value    is 


reasonable  range  of  estimates  (deleting  the  un- 
reasonably low  E  —  0.12),  and  the  underlined 
value  in  the  center  of  Table  1  is  our  most  reason- 
able estimate.  One  can  see  in  Table  1  that  the 
values  are  all  greater  than  the  approximate 
absolute  minimum  size  of  32.5  cm'^  for  the  At- 
lantic yellowfin  tuna  fishery  over  the  range  of 
the  estimates  of  L^  . 

For  the  moment  let  us  assume  that  recruit- 
ment is  knife-edged  at  32.5  cm  (0.67  kg)  and 
that  the  fishery  can  be  regulated  such  to  obtain 
a  knife-edged  recinaitment  at  any  desired  size. 
Therefore,  the  maximum  possible  increases  in 
yield  per  recruit  may  be  computed.  Our  smallest 
reasonable  values  for  optimal  size  at  recruit- 
ment are  47.1  cm  (2.0  kg),  52.4  cm  (2.8  kg),  or 
60.0  cm  (4.1  kg)  depending  on  L^.  The  respec- 
tive predicted  values  of  yield  per  recruit  are 
2.0%  ,  3.1%  ,  and  4.3%  higher  than  when  size  at 
recruitment  is  32.5  cm.  Our  largest  reasonable 
estimates  of  optimal  size  at  recruitment  are  97.1 
cm  (17  kg),  107.9  cm  (24  kg),  or  123.5  cm  (36 
kg).  The  respective  predicted  increases  in  yield 


"  The  value  of  32.5  cm  represents  our  selection  for  an 
approximate  absolute  minimum  size  for  the  Atlantic 
yellowfin  tuna  fishery,  which  also  agrees  with  that  chosen 
by  Joseph  and  Tomlinson  ( 1972,  see  footnote  4). 


per  recruit  are  65%  ,  73%  ,  and  82%  .  The  predict- 
ed increase  in  yield  per  recruit  using  all  of  our 
most  reasonable  parameter  estimates,  i.e.,  rais- 
ing 32.5  cm  to  83.2  cm  (11  kg),  is  23%.  The 
bounds  on  an  increase  in  yield  per  recruit,  2% 
to  82%  ,  and  the  most  likely  value  of  23% ,  are 
estimated  under  the  assumptions  of  knife-edged 
recruitment,  and  that  size  at  recruitment  rep- 
resents an  absolute  minimum  size.  The  Atlantic 
yellowfin  tuna  fishery,  however,  does  not  have 
knife-edged  recruitment. 

We  used  equation  lb  of  this  paper  to  obtain 
our  most  reasonable  estimate  of  the  1967-71 
average  effective  minimum  size  for  the  Atlantic 
yellowfin  tuna  fishery  from  average  lengths 
given  in  Table  15  of  Lenarz  and  Sakagawa 
(1972,  see  footnote  5).  The  estimate  of  average 
effective  minimum  size  is  about  55  cm  (3.2  kg). 
Nearly  all  the  values  within  the  dashed  lines  in 
Table  1,  however,  are  greater  than  55.  The  only 
smallest  reasonable  estimate  of  optimal  effective 
minimum  size  greater  than  55  cm  is  60.0  cm 
with  Lqo  —  223.0  cm.  An  increase  from  55  to 
60.0  cm  would  give  an  increase  in  yield  per  re- 
cruit <  0.2%  .  The  large.st  reasonable  estimates  of 
optimal  effective  minimum  size  predict  increases 
in  yield  per  recruit  of  28%  ,  36%  ,  or  45%  with  in- 


42 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


creases  from  55  cm  to  97.1,  107.9,  and  123.5  cm, 
respectively  depending  on  L^ .  The  increase  in 
yield  per  recruit  by  increasing  the  effective 
minimum  size  from  55  to  83.2  cm,  our  most 
reasonable  estimate,  is  only  7.9%  . 

From  the  above  analysis  using  a  wide  range 
of  parameter  estimates,  we  can  conclude  with 
reasonable  assurance  that  virtually  any  increase 
in  the  effective  minimum  size  will  cause  an  in- 
crease in  yield  per  recruit.  Our  most  likely 
estimate  of  this  increase  in  yield  per  recruit  is 
only  7.9%  which  is  bounded,  with  reasonable 
parameter  estimates,  by  0%  and  45%  . 

Ricker  Model 

Ricker  model  yield-per-recruit  isopleths  were 
calculated  using  values  of  M  of  0.6,  0.8.  and  1.0 
to  illustrate  our  estimates  of  actual  (rather  than 
relative)  yield  per  recruit  (Figures  1,  2,  and  3). 
As  will  be  mentioned  in  the  next  section  it  is 
difficult  to  estimate  the  location  of  the  fishery 
on  the  graphs,  i.e.,  when  fishing  mortality  is 
size  specific  it  is  not  a  trivial  matter  to  make 
reasonable  estimates  of  age  at  recruitment, 
t^,  and  a  constant  total  mortality  coefficient, 
Z.  Our  most  reasonable  estimates,  taken  from 
Lenarz  and  Sakagawa  (1972,  see  footnote  5),  of 
these  parameters  are:  t '.  is  1.41  yr  and  Z  is 
1.4. 


0.5  10  1.5  2.0  2.5  30 

INSTANTANEOUS    FISHING   MORTALITY  (F) 


35 


5  10  15  2,0  2  5 

INSTANTANEOUS  RATE  OF  FISHING  MORTALITY  (F) 

Figure  2. — Yield-per-recruit  isopleths  as  functions  of  fish- 
ing mortality  and  age  (and  weight)  at  recruitment  when 
M  =  0.8. 


-60.5 


48.0 


229 


Figure  1. — Yield-per-recruit  isopleths  as  functions  of  fish- 
ing mortality  and  age  (and  weight)  at  recruitment  when 
M  =  0.6. 


5  10  1.5  20  25 

INSTANTANEOUS  RATE  OF  FISHING  MORTALITY   (F) 

Figure  3. — Yield-per-recruit  isopleths  as  functions  of  fish- 
ing mortality  and  age  (and  weight)  at  recruitment  when 
M  =  1.0. 


The  results  (Figures  1,  2,  and  3)  show,  for 
example,  that  with  M  =  0.6  and  Z  remaining 
constant  (1.4),  an  increase  in  age  at  recruitment 
from  1.41  to  1.83  yr  (or  77.5  cm)  raises  the  yield 
per  recruit  about  20%  ;  if  iV/  =  0.8,  the  same 
change  raises  the  yield  per  recruit  on  the  order 
of  10%  ;  and  if  M  =    1.0,  the  same  change  does 


43 


FISHERY  BULLETIN,  VOL.  72.  NO.  1 


not  change  yield  per  reci*uit.  If  age  at  reciniit- 
ment  is  held  constant  and  fishing  mortality  is 
doubled,  when  M  =  0.6  yield  per  reci-uit  de- 
creases by  some  20%  ;  when  M  =  0.8  yield  per 
recruit  increases  on  the  order  of  5%  ;  and  when 
M  =  1.0  yield  per  recruit  increases  about  30%. 
If  effort  is  doubled  and  age  at  recruitment  is 
raised  to  1.83  yr,  when  M  =  0.6  or  M  =  0.8 
yield  per  recruit  increases  on  the  order  of  20%  ; 
and  when  M  =  1.0  yield  per  recruit  increases  by 
about  40% . 

Estimation  of  t 

r 

In  employing  a  knife-edged  approximation  to 
size-specific  recruitment  protracted  over  some 
time  period,  the  first  problem  is  to  determine 
the  proper  age  at  recruitment  {t^')  such  that 
the  integration  reflects  the  same  yield  per  re- 
cruit as  the  size-specific  recruitment  case.  There 
are  two  problems  in  doing  so.  First,  there  are 
two  values  for  t^.'  that  will  give  the  same  yield 
per  recruit  as  the  size-specific  recruitment  case, 
unless  eumetric  fishing  obtains.  Often,  however, 
this  may  be  of  little  consequence,  since  one  of 
the  two  values  for  t  '  could  be  obviously  infea- 
sible.  Second,  t  '  will  depend  on  the  fishing 
mortality. 

Two  estimators  of  t  '  are  provided,  at  least 
implicitly,  by  Beverton  and  Holt  (1957):  (1)  the 
age  corresponding  to  the  mean  selection  length, 
and  (2)  the  resultant  of  a  formula  depending  on 
Z  and  the  average  age,  T  (or  average  length. 
/).  in  the  catch.  The  mean  selection  length  is 
the  50%  selection  length  if  the  selection  curve  is 
symmetrical,  and  it  is  not  dependent  on  the 
magnitude  of  the  fishing  mortality  coefficient, 
F.  The  second  estimator  of  t  '   is 

r 


t; - 1  -HZ 

or,  in  terms  of  length 

i;  =  J-K{L^-J)jZ. 


(la) 


(lb) 


These  two  equations  were  obtained  from  manip- 
ulations of  the  Beverton  and  Holt  yield  equation. 
Several  computations  of  yield  per  recruit 
with  the  program  GXPOPS  were  made  utilizing 
F  =  0.1  and  F  -  2.0.  M  =  0.8,  the  von  Bert- 
alanffy  equation  for  Atlantic  yellowfin  tuna, 
and  an  arbitrary  age-specific  selection  curve 
(Figure   4)    in   order  to   demonstrate   the  two 


1.0,- 


0.8 


06 


04 


0.2 


50%   SELECTION    AT  21  mo. 


|<— F  =  20    tr'  =  24  mo 


F  =  0  I     tr    =  19  mo. 


10 


20 


30  40 

AGE    (mo) 


50 


60 


70 


Figure  4. — Arbitrary  age-specific  recruitment  curve. 

problems  and  to  evaluate  the  two  estimators  of 
t  ', .  At  F  —  0.1,  the  values  of  t !  giving  the 
same  yields  per  recruit  as  the  selection  curve 
are  <8  mo  (^q  of  the  von  Bertalanffy  growth 
curve  is  7.48  mo)  or  24  mo,  and  19  or  45  mo  for 
F  =  2.0.  Since  the  state  of  the  simulated  fishery 
is  not  eumetric  for  either  value  of  F,  there  are 
two  knife-edged  approximation  locations.  The 
effect  of  the  magnitude  of  F  on  the  true  t  ' 
is  obvious,  with  the  lower  value  increasing  from 
<8  to  19  mo  and  the  upper  value  increasing 
from  24  to  45  mo  as  F  is  changed  from  0.1  to 
2.0.  The  reasonable  values  for  t  '  to  approx- 
imate the  selection  curve,  however,  are  24  mo 
for  F  =  0.1  and  19  mo  for  F  =  2.0,  a  change  of 
5  mo. 

Estimator  1,  the  mean  selection  age,  is  21 
mo  and  is  shown  along  with  the  reasonable 
values  in  Figure  4.  Using  21  mo  for  t^'  would 
result  in  yields  per  recruit  that  are  4%  and  15% 
too  high  for  F  =  0. 1  and  F  =  2.0  respectively. 
Estimator  1  does  not  change  with  F,  of  course, 
but  in  this  case  it  lies  intermediate  between  the 
true  t^'  values.  Estimator  2  gives  19  mo  for  F 
=  0.1  and  18  mo  for  F  =  2.0.  We  emphasize 
that  this  estimator  does  depend  on  the  magni- 
tude of  F. 

Neither  estimator  is  exact  in  this  examj^le 
where  the  catches,  their  ages,  and  the  selection 
curve  are  known  without  error.  This  places 
doubt  on  their  estimates  from  the  usual  catch 
at  age  data  where  considerable  random  error 
would  be  involved.  Encouraging,  though,  is 
that  both  estimators  indicate  the  proper  direction 
that  the  fishery's  selectivity  should  proceed  to 
approach  the  optimal  yield  per  recruit — about 


44 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


15  mo  for  F  =  0.1  and  30  mo  for  F  =  2.0.  Since 
estimator  1  requires  size-selective  data  not  fre- 
quently available  and  does  not  respond  to 
changes  in  F,  estimator  2  appears  to  be  the 
most  attractive  for  knife-edged  approximations. 
The  Atlantic  yellowfin  tuna  fishery,  however, 
has  a  much  more  complex  recruitment  pattern 
and  size-specific  F  than  this  simple  example 
owing  to  the  diverse  gear  types.  The  mix  of 
relative  F  among  the  various  gear  types  makes 
the  determination  of  the  appropriate  current 
t  '  somewhat  tenuous. 

r 
Estimation  of  Constant  Z 

The  yield-per-recruit  isopleths  shown  in  Fig- 
ures 1,  2,  and  3  were  calculated  under  the 
assumption  that  fishing  mortality  and  Z  are 
constant  after  the  fish  are  recruited.  The  value 
of  Z  was  also  estimated  under  the  same  assump- 
tion. The  section  on  size-specific  fishing  mortal- 
ity will  indicate  that  F  is  not  a  constant,  but  is 
related  to  size.  Thus  our  estimate  of  a  constant 
Z  may  not  be  realistic  but  may  be  a  more 
reasonable  approach  to  estimating  yield  per 
recruit  than  the  size-specific  F  approach  given 
the  quality  of  the  data.  It  is  the  average  of  values 
of  Z  estimated  for  the  FIS  bait  boat  and  purse 
seine  fisheries  (Lenarz  and  Sakagawa,  1972, 
see  footnote  5).  The  size-specific  F  section  indi- 
cates that  F  decreases  with  size  for  bait  boats 
and  increases  with  size  for  purse  seiners.  Bever- 
ton  and  Holt  (1956)  gave  examples  that  indi- 
cated that  when  F  decreases  with  age,  constant 
Z  will  be  overestimated  and  when  F  increases 
with  age,  constant  Z  will  be  underestimated. 
Hopefully  we  have  obtained  a  reasonable  esti- 
mate by  taking  the  average  of  Z's  for  the  two 
gears. 

Size-Specific  I  Approach 
Estimates  of  Length  Frequencies 

Length  frequencies,  numbers  of  yellowfin 
caught  by  5-cm  intervals  starting  at  35  cm  (32.5 
cm  ^  fork  length  <37.5  cm),  were  estimated  for 
each  gear  and  the  total  fishery  for  two  overlap- 
ping periods,  1967-71  and  1969-71  (Figure  5). 
The  first  period  was  used  with  the  hope  that 
the  effect  caused  by  unequal  strength  of  year 
classes  would  be  minimized  by  averaging.  The 
second  period  was  used  because  it  was  felt  that 


700r 


o    1969-71 
•    1967  -  71 


40 


60 


80  100  120 

FORK  LENGTH  (cm.) 


140 


160 


180 


Figure  5. — Average  length  frequencies  for  the  Atlantic 
yellowfin  tuna  fisheries  for  two  periods,  1967-71  and 
1969-71. 


300 


Q    250 
UJ 

o 

z 
< 

-•    200 

z 
li. 

3      150 

_) 

UJ 

>- 

\k      100 


o 
o 
o 


50 


OL 


o  BAITBOAT 

•  SMALL  PURSE  SEINE 
A  LARGE  PURSE  SEINE 
A  LONGLINE 


40 


60 


140 


80  100  120 

FORK   LENGTH  (cm) 

Figure  6. — Average  length  frequencies  (1967-71) 
tic  yellowfin  tuna  caught  by  four  gear  types. 


160 


180 


of  Atlan- 


the  data  are  more  accurate.  Length  frequencies 
of  the  two  periods  are  quite  similar  and  produce 
similar  estimates  of  size-specific  fishing  mortal- 
ity and  estimates  of  yield  per  recruit.  Thus,  to 
avoid  redundancy,  only  the  data  for  the  1967-71 
period  are  used.  Figure  6  and  Table  2  show  the 
length  frequencies  for  each  gear.  The  curves  are 
as  described  earlier  (see  introductory  section.) 

Estimates  of  Size-Specific  Fishing  Mortality 

Size-specific  instantaneous  coefficients  of  fish- 
ing mortality  were  estimated  with  the  method  of 
Gulland  (1965)  and  Murphy  (1965)  as  suggested 


45 


FISHERY  BULLETIN,  VOL.  72.  NO.  1 
Table  2. — Basic  data  on  size  (age)  composition  of  catch  of  yellowfin  tuna  from  the  tropical  Atlantic  Ocean. 


Weight 

Age 

1967-71  average 

>  number  of  yell 

Dwfin  landed 

Midpoint  of 

at  beginning 

ot  beginning 

size  interval 

of  interval 

of  interval 

Small  purse 

Large  purse 

(cm) 

(kg) 

(yr) 

Bait  boats 

seiners 

seiners 

Longliners 

Total 

35 

0.67 

1 .0579 

1,886 

372 

100 

2,358 

40 

1.03 

1.1325 

14,551 

5,445 

9,057 

29,053 

45 

1.49 

1 .2093 

72,972 

21,782 

28,372 

123,126 

50 

2.08 

1.2888 

246,924 

89,614 

36,684 

7 

373,229 

55 

2.79 

1.3710 

245,206 

146,883 

83,153 

22 

475,264 

60 

3.66 

1.4562 

251,017 

110,755 

59,648 

451 

421,871 

65 

4.69 

1.5445 

165,328 

42,427 

35,891 

647 

244,293 

70 

5.90 

1 .6363 

197,855 

49,929 

26,992 

2,151 

276,927 

75 

7.30 

1.7317 

143,885 

36,942 

23,263 

5,435 

209,525 

80 

8.90 

1.8310 

128,810 

37,082 

15,528 

5,694 

187,114 

85 

10.72 

1.9348 

89,637 

31,143 

13,338 

12,025 

146,143 

90 

12.77 

2.0432 

64,128 

31,135 

9,818 

13,049 

118,130 

95 

15.06 

2.1568 

70,422 

22,248 

10,062 

1 1 ,665 

114,397 

100 

17.61 

2.2761 

63,619 

36,483 

13,323 

15,074 

128,499 

105 

20.43 

2.4017 

45,582 

48,274 

11,647 

34,071 

139,574 

110 

23.54 

2.5343 

36,414 

42,283 

24,296 

40,209 

143,202 

115 

26.95 

2.6748 

29,227 

21,268 

21,466 

44,034 

115,995 

120 

30.67 

2.8240 

18,877 

18,311 

15,144 

42,859 

95,191 

125 

34.72 

2.9832 

22,228 

23,711 

15,018 

57,358 

118,915 

130 

39.10 

3.1538 

15,152 

20,612 

16,238 

58,544 

1 10,546 

135 

43.84 

3.3376 

7,142 

18,304 

18,504 

44,690 

88,640 

140 

48.95 

3.5368 

4,137 

15,790 

13,569 

52,070 

85,566 

145 

54.43 

3.7542 

3,393 

17,301 

17,886 

55,582 

94,162 

150 

60.31 

3.9935 

3,459 

20,222 

16,711 

45,648 

86,040 

155 

66.60 

4.2595 

1,511 

12,057 

14,926 

39,108 

67,602 

160 

•  73.30 

4.5590 

793 

8,754 

10,678 

24,489 

44,714 

165 

80,44 

4.9017 

634 

7,803 

6,633 

13,659 

28,729 

170 

88.03 

5.3021 

327 

2,470 

2,918 

6,265 

1 1 ,980 

175 

96.07 

5.7838 

209 

2,132 

1,383 

241 

3,965 

180 

104.59 
113.60 

6.3883 

7.2004 

49 

1,429 

361 

55 

1 ,894 

Total 

1,945,374 

942,961 

573,207 

625,102 

4,086,645 

by  Lenarz  ( 1971b). '^  We  followed  the  modifica- 
tion of  Joseph  and  Tomlinson  (1972,  see  foot- 
note 4)  by  using  the  inverse  of  the  von  Bertalanffy 
growth  equation  to  convert  size  distributions  to 
age  distributions.  This  method  assumes  that 
there  is  a  reasonably  accurate  relationship  be- 
tween length  and  age  of  yellowfin  tuna.  This 
assumption  has  not  been  verified.  Ageing  by 
modal  progression  would  probably  be  more  satis- 
factory, if  more  complete  length  composition 
data  were  available  on  a  monthly  or  quarterly 
basis. 

The  reverse  iterative  i)rocedure  with  com- 
puter program  COHORT  and  M  =  0.8  was  used 
to  estimate  size-specific  values  of  fishing  mortal- 
ity (F)  starting  at  the  180-cm  interval.  Four 
initial  values  of  F  were  tried:  0.2,  0.4,  0.6,  and 
0.8  (Figure  7).  Estimates  of  F  tend  to  converge 


as  size  of  the  yellowfin  tuna  decreases  with  the 
range  of  initial  values  tried  as  is  characteristic 


'2   Lenarz,    W.     1971b.    Yield    per  recruit    of    Atlantic 

yellowfin  tuna  for  multigear  fisheries.  Southwest  Fisheries 

Center,    National     Marine     Fisheries  Service,     La    Jolla. 
Calif.  Unpublished  manuscript. 


>|   '   I   I   I   I   I   I Ill 

40  60  80  100  120  140  160  180 

FORK  LENGTH  (cm.) 

Figure  7. — Estimates  of  size-specific  instantaneous  fishing 
mortality  coefficients  (F)  with  several  initial  F  values. 


46 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


of  the  methodology  (Tomlinson,  1970).  Calcula- 
tions of  yield  per  reciniit  using  initial  values 
of  F  of  0.2  and  0.8  are  shown  in  Figures  8  and 
9  as  functions  of  initial  values  of  F,  effort,  and 
size  at  recioiitment.  The  values  of  yield  per 
recruit  do  not  vary  significantly  (<10%)  with 
changes  in  the  initial  values  of  F,  and  the  rela- 
tive values  are  quite  similar.  Values  of  size  speci- 
fic F  are  shown  for  each  gear  in  Figure  10  when 
initial  values  of  F  are  0.2  and  0.8.  When  the 
initial  value  of  F  is  0.8.  values  of  F  for  small 
purse  seiners  increase  sharply  with  size  from 
170  to  180  cm.  This  does  not  occur  when  the 
initial  value  of  F  is  0.2.  Intuitively  we  do  not 
expect  an  increase  in  F  with  size  past  170  cm 
and  thus  choose  to  use  the  results  when  the 
initial  value  of  F  is  0.2  in  the  remainder  of  the 


0.5- 


7i- 


O     INITIAL  F  =  0.8 
•     INITIAL   F  =  0,2 

I         I         I  I 


J I 


10  15  20  2  5 

MULTIPLIER  OF  EFFORT 


30 


35 


Figure  8. — Yield-per-recruil  (kg)  of  Atlantic  yellowfin 
tuna,  when  size  at  recruitment  is  32.5  cm,  as  a  function  of 
the  multipUer  of  fishing  effort. 


32.5  52.5  72.5  92.5  112.5  1325 

FORK  LENGTH  AT  RECRUITMENT  (cm.) 

Figure  9. — Yield-per-recruit  (kg)  of  Atlantic  yellowfin 
tuna,  with  the  current  level  of  fishing  effort,  as  a  function 
of  length  at  recruitment. 


>- 

_l 
< 

I- 

cr 
o 


to 


3 

o 


< 


< 


O   BAITBOAT 

•  SMALL  PURSE  SEINE 
A  LARGE  PURSE  SEINE 
A  LONGLINE 


80  100  120  140 

FORK    LENGTH  (cm) 


Figure  10. — Estimates  of  size-specific  instantaneous  fish- 
ing mortality  coefficients  (F)  by  gear  type  when  initial 
values  of  F  are  ( A)  F  =  0.2.  ( B)  F  =  0.8. 


paper.  Validity  of  the  estimates  of  F  depends  on 
the  validity  of  the  assumption  that  recruitment 
has  been  fairly  constant  for  the  cohorts  included 
in  the  analysis.  The  special  ICCAT  working 
group  noted  that  the  cohort  which  entered  the 
surface  fisheries  in  1969  appears  to  be  weaker 
than  the  following  two  cohorts  (ICCAT,  1972. 
see  footnote  2).  Although  inclusion  of  5  yr  of 
data  in  the  analysis  may  minimize  the  source 
of  error,  future  studies  should  examine  the  sensi- 
tivity of  the  results  to  errors  of  this  type. 

Estimates  of  Yield  Per  Recruit 

Results  of  the  yield-per-recruit  calculations 
using  the  estimates  of  size-specific  F  when  the 
initial  value  of  F  is  0.2  and  with  M  =  0.8  are 
shown  by  gear  in  Table  3.  Yield-per-recruit 
isopleths  and  the  line  of  eumetric  fishing  (size 
at  recruitment,  /  ^,  which  maximizes  yield  per 
recruit  at  a  given  effort)  for  the  entire  fishery 


47 


Table  3. — Estimates  of  yield  per  recruit    (kg)    when  M  =  0.8,  initial  F 

Sakagawa  (1973)  is  used. 


FISHERY  BULLETIN,  VOL.  72,  NO.  1 
0.2,  and  growth  curve  of  LeGuen  and 


BAIT  ROATS 

MINIMUM  t;i7E 

MULTJOLIFO  OF  FFrOPT 

CM     KG 

0.? 

0.4 

O.A        1.0        1.4 

1.8 

2.0 

a.s 

3.0 

3.5 

12?. S 

34.6 

117. S 

30.6 

U2.5 

26.9 

107. S 

23. S 

10?. 5 

20.4 

97.5 

17.6 

9?. 5 

15.0 

87.5 

12.7 

S?.5 

10.7 

77.5 

•3.9 

7'. 5 

7.3 

67.5 

5.9 

62.5 

4.7 

57.5 

3.7 

52.5 

2.8 

47.5 

2.1 

42.5 

1.5 

37.5 

1.0 

32.5 

0.7 

O.OR 
0.09 

o.n 

0.13 
O.IS 
0.17 
0.19 
0.20 
0.22 
0.24 
0.26 
0.27 


29 
30 
31 
31 


0.31 
0.31 
0.31 


0.15 
0.17 
0.21 
0.24 
0.27 
0.31 


,35 
,38 
,41 
,45 
,48 


O.Sl 

0.53 
0.56 


57 
5ft 
5ft 


21 
24 
29 
33 

38 


0.58 
0.58 


0.44 
0.50 
0.54 
0.58 
0.63 
0.68 
0.72 
0.75 
0.78 
0.79 
O.ftO 
O.ftO 
0.80 
0.80 


0.31 
0.36 


,43 
,50 
,57 
,66 

,75 
,81 
,88 


0.95 


.02 
.08 
.12 
.15 
.15 


1.15 
1.15 
1.15 
1.15 


0.39 
0.46 
0.55 
0.64 
0.73 
0.85 
0.96 
1.04 
1.12 
1.22 


30 
38 


1.41 
1.43 
1.42 
1.42 
1.41 
1.41 
1.41 


0.46 
0.54 
0.65 
0.75 
0.86 
1.01 
1.15 
1.24 
1.34 
1.45 
1.54' 
1.62 
1.65 
1.66 
1.63 
1.61 
1.60 
1  .60 
1  .60 


0.49 
0.5ft 
0.69 
0.80 
0.92 
1.08 
1.23 
1.32 
1.43 
1.55 
1.64 
1.73 
1.76 
1.76 
1.72 
1.69 
1.6ft 
1.67 
1.67 


0.56 
0.66 
0.80 
0.92 
1.06 
1.24 
1.41 
1.52 
1.64 
1.78 
1.87 
1.96 
1.98 
l."36 
1.R8 
1.84 
1.82 
1.81 
1.81 


0.62 
0.71 

o.8q 

1.0? 
1.17 
1.38 
1.58 
1.69 
1.8? 
1.97 
2.07 
2.14 
2.16 
2.11 
2.00 
1.94 
1.91 
1.90 
1.90 


0.68 
0.80 
0.96 
l.U 
1.27 
1.50 
1.72 
1.84 
1.98 
2.13 
2.?3 


30 
30 
22 

08 
00 


1.97 
1.96 
1.95 


SMALL    PU9SF    5FINJEWS 


MINIMUM  SI7E 


MULTIPLIFP  OF  FFFORT 


CM 


KG 


127.5 

34.6 

117.5 

30.6 

112.5 

26.9 

107.5 

2  3.5 

102.5 

20.4 

Q7.5 

17.6 

o='.5 

15.0 

87.5 

12.7 

82.5 

10.7 

77.5 

8.9 

72.5 

7.3 

67.5 

5.9 

6?. 5 

4.7 

57. S 

J. 7 

5?. 5 

2. ft 

47.5 

2.1 

42.5 

1.5 

37.5 

1.0 

32.5 

0.7 

0.2 

0.34 
0.35 
0.36 
0.3fl 
0.40 
0.41 
0.41 
0.42 
0.42 
0.43 
0.43 
0.43 
0.43 
0.43 
0.44 
0.44 
0,44 
0.44 


0.4 

0.58 
0.60 
0.61 
0.64 
0.67 
0.69 
0.70 
0.71 
0.71 
0.71 
0.71 
0.72 
0.71 


,71 
,72 
,71 
,71 
,71 
,71 


0.6 

0.75 
0.77 
0.79 
0.83 
0.87 
0.89 
0.90 
0.91 
0.91 
0.91 
0.91 
0.91 
0.90 
0.90 
0.89 
0.89 
0.«8 
0.88 
0.88 


1.0 

0.97 
0.99 
1.01 
1.06 
1.1? 
1.14 
1.15 
1.16 
1.16 
1.15 
1.14 
1.13 
1.11 
1.10 
1.08 
1.06 
1.06 
1.06 
1.06 


1.4 

1.09 
1.11 
1.13 
1.20 
1.27 
1.30 
1.30 
1.31 
1.30 
1.29 
1.27 
1.24 
1.22 
1.19 
1.16 
1.13 
1.12 
1.12 
1.12 


1.8 

1.16 
1.18 
1.20 
1.28 
1.37 
1.40 
1.39 
1.40 
1.39 
1.37 
1.34 
1.30 
1.27 
1.23 
1.19 
1.15 
1.14 
1.13 
1  .  13 


2.0 

1.19 
1.71 
1.73 
1.32 
1.41 
1.44 
1.43 
1.44 
1.43 
1.40 
1  .36 
1.32 
1  .78 
1.74 
1  .20 
I.IS 
1.14 
1.13 
1.13 


2.5 

1.24 
1.27 
1.28 
1.38 
1.49 
1.52 
1.50 
1.51 
1  .49 
1.45 
1.41 
1.35 
1  .30 
1.24 
1.19 
1.14 
I. 11 
1.11 
1.11 


3.0 

1  .28 
1.  30 
1.31 
1.43 
1.55 
1.59 
1.56 
1.56 
1.53 
1.49 
1.43 
1.36 
1.29 
1.23 
1.17 
l.U 
1.08 
1.08 
1.0« 


3.5 

1.31 
1.33 
1.34 
1.47 
1.60 
1.64 
1.61 
1.60 
1.57 
1.51 
1.44 
1.35 
1.28 
1.21 
1.14 
1.07 
1.05 
1.04 
1.04 


MINIMUM  SI7E 


CM 


KG 


0.4 


L4RGF  PURSE  SEINERS 
MULTTPLIEP  OF  EFFORT 


0.6 


1.0 


1.4 


1.8 


2.5 


3.0 


3.5 


122.5 

34.6 

0.31 

0.54 

0.69 

0.89 

0.99 

1.05 

1.07 

1.10 

1.1? 

1.12 

117.5 

30.6 

0.32 

0.55 

0.71 

0.90 

1.01 

1.06 

1  .08 

1.11 

1.1? 

1.13 

112.5 

?6.9 

0.33 

0.56 

0.73 

0.92 

1.03 

1.09 

1.11 

1.14 

1.16 

1.17 

107.5 

23.5 

0.34 

0.58 

0.74 

0.94 

1.04 

1.10 

1.12 

1.15 

1.17 

1.18 

102.5 

20.4 

0.14 

0.58 

0.74 

0.93 

1.0? 

1.06 

1.08 

I.IO 

1.10 

1.10 

97.5 

17.6 

0.35 

0.58 

0.74 

0.9? 

1.00 

1.04 

1.05 

1.06 

1.06 

1.06 

92.5 

15.0 

0.35 

0.58 

0.73 

0.91 

0.99 

1.02 

1.03 

1.03 

1.03 

1.02 

ft7.5 

12.7 

0.35 

0.58 

0.73 

0.90 

0.97 

1  .00 

1  .00 

1.00 

0.99 

0.97 

82.5 

10.7 

0.35 

0.5ft 

0.73 

0.89 

0.96 

0.98 

0.9B 

0.97 

0.95 

0.93 

77.5 

8.9 

0.35 

0.58 

0.72 

0.88 

0.93 

0.45 

0.95 

0.^3 

0.91 

0.88 

?2.5 

7,3 

0.35 

0.57 

n.7? 

0.86 

o.q? 

0.92 

0.92 

0.90 

0.87 

0.84 

67.5 

5.9 

0.35 

0.57 

0.71 

0.85 

0.89 

0.89 

0.88 

0.86 

0.87 

0.79 

6  7.  S 

4.7 

0.35 

0.57 

0.71 

0.84 

0.87 

0.87 

0.86 

0.83 

0.80 

0.76 

57.5 

3.7 

0.35 

0.57 

0.70 

0.8? 

O.ftS 

0.84 

0.82 

0.79 

0.75 

0.71 

57.5 

2.8 

0.35 

0.57 

0.69 

0.80 

O.ft? 

0.80 

0.  79 

0.75 

0.71 

0.67 

47.5 

2.1 

0.35 

0.56 

0.68 

0.78 

0.79 

0.77 

0.75 

0.71 

0.66 

0.62 

47.5 

1.5 

0.35 

0.56 

0.68 

0.78 

0.79 

0.76 

0.7S 

0.70 

0.65 

0.61 

37.5 

1.0 

0.35 

0.56 

0.68 

0.78 

0.79 

0.76 

0.75 

0,70 

0.6S 

0.61 

37.5 

0.7 

0.35 

0.56 

0.68 

0.78 

0.79 

0.76 

0.74 

0.70 

0.65 

0.61 

48 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 

Table  3. — Estimates  of  yield  per  recruit    (kg)    when  M  =  0.8.  initial  F  =  0.2,  and  growth  curve  of  LeGuen  and 

Sakagawa  ( 1973)  is  used. — Continued. 


LONG  LINFRS 

MINIMUM 

SIZE 

MUl TIPLIEC  OF  FFFOPT 

CM 

KG 

0.? 

0.4 

0.6 

l.O 

1.4 

1.8 

2.0 

2.5 

3.0 

3.5 

1??.5 

^'..f. 

0.80 

1.40 

1.8*. 

2.49 

2.87 

3.12 

3.21 

3.38 

3.49 

3.57 

117.5 

30.6 

0.82 

1.44 

1.90 

2.53 

2.90 

3.14 

3.23 

3.38 

3.47 

3.54 

11?. S 

?6.<5 

0.84 

1.46 

1.93 

?.54 

2.90 

3.12 

3.19 

3.32 

3.39 

3.43 

107.5 

?3.5 

0.85 

1.48 

1.93 

2.52 

2.84 

3.02 

3.08 

3.17 

3.20 

3.21 

10?. s 

?0.4 

0.86 

1.48 

1.93 

2.49 

2.78 

2.93 

2.97 

3.03 

3.03 

3.01 

97.5 

1  7.6 

0.86 

1.47 

1.90 

2.43 

2.69 

2.81 

2.83 

2.85 

2.8? 

2.76 

9?. 5 

15.0 

0.86 

1.46 

1.89 

2.38 

2.62 

2.71 

2.72 

2.71 

2.66 

2.58 

87. S 

12.7 

0.86 

1.46 

1.87 

2.34 

2.55 

2.62 

2.63 

?.<9 

2.5? 

2.43 

8?. 5 

10.7 

0.86 

1.45 

1.85 

2.?9 

2.48 

2.52 

2.52 

2.46 

?.36 

2.25 

77.5 

8.9 

0.85 

1.43 

1.82 

2.23 

2.38 

2.40 

2.38 

2.29 

?.17 

2.04 

7?. 5 

7.3 

0.85 

1.41 

1.79 

?.17 

2.29 

2.28 

2.24 

2.13 

1.99 

1  .85 

67.5 

5.9 

0.84 

1.39 

1.75 

2.09 

2.18 

2.13 

2.09 

1.95 

1.70 

1.63 

6?. 5 

4.7 

n,84 

1.38 

1.72 

2.03 

2.09 

2.03 

1.98 

1.82 

1.64 

1.48 

57.5 

3.7 

0.83 

1.35 

1.67 

1.95 

1.97 

1.88 

1.81 

1.63 

1.44 

1.27 

5?. 5 

2.8 

0.82 

1.33 

1.63 

1.86 

1.85 

1.73 

1.66 

1.46 

1.2^ 

1.09 

i.7.5 

2.1 

0.82 

1.31 

1.60 

1.81 

1.77 

1.64 

1.56 

1.35 

1.15 

0.98 

^?.S 

1.5 

0.8? 

1.31 

1.59 

1.79 

1.75 

1.61 

1.53 

1.32 

1.1? 

0.94 

37.5 

1.0 

0.82 

1.31 

1.59 

1.78 

1.74 

1.60 

1.52 

1.31 

i.n 

0.94 

3?. 5 

0.7 

0.82 

1.31 

1.59 

1.78 

1.74 

1.60 

1.52 

1.31 

i.n 

0.94 

are  shown  in  Figure  11.  Table  3  and  Figures  8, 
9,  and  11  indicate  that  if  size  at  recruitment 
remains  constant  at  32.5  cm,  very  little  increase 
in  yield  per  recruit  ('^5%)  can  be  expected  if 
effort  is  increased,  and  if  effort  remains  constant, 
very  little  (~10%  )  increase  in  yield  per  recruit 
can  be  expected  by  increasing  size  at  reciiiit- 
ment.  However,  if  fishing  effort  is  doubled  (i.e., 
multiplier  =  2.0)  and  size  at  recruitment  in- 
creased to  55  cm  (3.2  kg),  yield  per  recruit 
would  increase  15%  ,  or  if  size  at  recruitment 
is  increased  to  77.5  cm  (~10  kg),  yield  per  re- 
cruit would  increase  about  30%  (Table  3).  Since 
the  line  of  eumetric  fishing  shows  that  optimum 
size  at  recruitment  changes  with  fishing  effort, 
any  "minimum  size"  regulation  must  be  geared 
to  fishing  effort. 


If  fishermen  are  unable  to  distinguish  the  size 
of  yellowfin  before  capturing  them  and  a  mini- 
mum size  regulation  prevents  their  landing,  then 
the  discarding  of  dead  yellowfin  will  occur. 
Table  4  presents  landings  per  recruit  by  gear 
and  Figure  12  the  landings  per  recruit  for  the 
total  fishery  when  killing  and  discarding 
("dumping")  of  all  yellowfin  smaller  than  the 
size  limit  occurs.  If  the  minimum  size  limit  is 
55  cm  and  effort  remains  the  same,  then  a  2.7% 
decrease  in  landings  per  recruit  would  occur; 
and  a  13%  decrease  in  landings  per  recruit  would 
occur  if  the  minimum  size  is  set  at  77.5  cm.  If 
effort  is  doubled  and  the  minimum  size  is  55 
cm,  then  a  1%  increase  in  landings  per  recniit 
would  occur;  with  a  minimum  size  of  77.5  cm, 
a   16%    decline  in  landings  per  recruit  would 


30    4.0    4  5      50        5  5 


1,0  1.5  2.0  2.5 

MULTIPLIER   OF   EFFORT 


3.0 


3.5 


Figure  11. — Yield-per-recruit  (kg)  isopleths  for  the  entire 
Atlantic  yellowfin  tuna  fishery.  Dotted  curve  is  the  line 
of  eumetric  fishing. 


00 


0.5  1.0  1.5  2.0  25  3.0 

MULTIPLIER  OF  FISHING  EFFORT 


Figure  12. — Landings-per-recruit  (kg)  isopleths  for  Atlan- 
tic yellowfin  tuna  when  all  fish  less  than  the  minimum  size 
that  are  caught  are  discarded  dead. 


49 


FISHERY  BULLETIN,  VOL.  72.  NO.  1 

Table  4. — Landings  per  recruit    (kg)    when  M  =   0.8,  initial  F-  =   0.2,  growth  curve  of  LeGuen  and  Sakagawa 
(1973)  is  used,  and  yellowfin  less  than  the  minimum  size  are  caught  and  discarded  dead. 


Riir    R04TS 

MIMIMIJM 

<:I7E 

MULTIPLIEO    OF 

FFFORT 

CM 

KG 

0.? 

0.4 

0.6 

1.0 

1.4 

1.8 

2.0 

?.5 

3,0 

3,5 

laa.s 

Ju.h 

0.07 

0.1? 

0.15 

0.18 

0.18 

0.17 

0.16 

0.14 

0,12 

0.10 

117.5 

30.6 

0.08 

0.14 

0.18 

0.2? 

0.2? 

0.22 

0.21 

0.19 

0,16 

0.14 

11?. s 

?6.9 

0.10 

0.17 

0.2? 

0.27 

0.29 

0.28 

0.?8 

0.?5 

0,22 

0.19 

107.5 

?J.5 

0.12 

o.?o 

0.26 

0..33 

0.36 

0.36 

0.16 

0.33 

0,3(1 

0.?7 

10?. 5 

?0.i. 

0.14 

0.24 

0.31 

0.40 

0.44 

0.45 

0.44 

0.42 

0,39 

0.35 

97.5 

W.6 

0.16 

0.27 

0.36 

0.48 

0.53 

0.56 

0.56 

0.54 

0,51 

0.47 

9?. 5 

15.0 

0,18 

0.31 

0.41 

0.S5 

0.63 

0.66 

0.67 

0.66 

0,63 

0.59 

87.5 

12.7 

0.  19 

0.34 

0.45 

0.61 

0.70 

0.74 

0.75 

0.75 

0,7-) 

0.69 

8?. 5 

10.7 

0.21 

0.37 

O.SO 

0.68 

0.79 

0.84 

O.Sh 

0.87 

0,85 

0,81 

77.5 

d.'J 

0.23 

0.41 

0.55 

0.76 

0.89 

0.97 

0.99 

1.01 

1  ,00 

0.97 

7?. 5 

7.3 

o.?s 

0.44 

0.60 

0.84 

0.99 

1.08 

l.U 

1.15 

1,1=; 

1,12 

67.5 

5.9 

0.27 

0.48 

0.66 

0.9? 

1.10 

1.22 

1.25 

1.31 

1.33 

1.32 

ft?. 5 

'..7 

0.?8 

0.51 

0.70 

0.98 

1.18 

1.31 

1.35 

1.41 

1  ,46 

1.46 

57. S 

3.7 

0.?9 

0.54 

0.74 

1.05 

1.27 

1.42 

1,48 

1.57 

1.6? 

1.64 

5?. 5 

^.8 

0.30 

0.56 

0.77 

1.10 

1.34 

1.51 

1.57 

1.69 

1,7*^ 

1,79 

A7.5 

^.\ 

0.31 

0.57 

0.79 

1.14 

1.39 

1.58 

1.65 

1.79 

1,87 

1.92 

A?. 5 

1.5 

0.31 

0.58 

0.80 

1.15 

1.41 

1.59 

1.67 

1.81 

1  ,90 

1.95 

37.5 

1.0 

0.31 

0.58 

0.80 

1.15 

1.41 

1.60 

1.67 

1,81 

1 ,9n 

1.95 

3?. 5 

0.7 

0.31 

0.58 

0.80 

1.15 

1.41 

1.60 

1.67 

1.81 

1  ,90 

1.95 

SM4I  L  PH3SF  SEINERS 


MIMIMIIM  SI?F 


r^^ 


KG 


122.5 

34.6 

117.5 

30.6 

112.5 

26.9 

107.5 

23.5 

102.5 

20.4 

97.5 

17.6 

92.5 

15.0 

87.5 

12.7 

82.5 

1U.7 

77.5 

8,9 

72.5 

7.3 

67.5 

5,9 

62.5 

4,7 

57.5 

J, 7 

5?. 5 

2.8 

47.5 

2.1 

4?. 5 

1.5 

37.5 

1.0 

32.5 

0.7 

0.? 


0,31 
0.32 


33 
35 


0.37 
0.38 
0.39 
0.40 
0.40 
0.41 
0.41 
0.4? 
0.4? 
0.43 
0.43 
0.44 
0.44 
0.44 
0.44 


0.4 

0.47 
0.49 
0.51 
0.55 
0.58 
0.61 
0.62 
0.63 
0.64 
0.65 
0.66 
0.67 
0,68 
0.69 
0.70 
0.71 
0.71 
0.71 
0.71 


MULTTPL lEP  OF  EFFORT 
0.6        1,0        1.4 


0,54 
0,57 
0,60 
0.65 
0.70 
0.73 
0.75 
0.76 
0.78 
0.80 
0.31 
0.82 
0.83 
0.85 
0.87 
0.88 
0.88 
0,88 
0,88 


56 
60 


0,64 
0,71 


78 
82 
84 


0.87 
0.90 
0.92 
0.94 
0.96 
0.98 
1.01 
1.04 
1.05 


05 
06 
06 


0.50 
0.55 
0.59 
0.68 
0.76 
0.81 
0.84 
0.88 
0,91 
0,94 
0.96 
0.99 
1.01 
1.05 
1.10 
1.11 
1.12 
1,1? 
1,12 


1,8 

0,43 
0,48 
0.53 
0,6? 
0,71 
0,77 
0.80 
0.84 
0.88 
0.91 
0.94 
0.98 
1.00 
1.05 
1.10 
1.13 
1.13 
1.13 
1.13 


2,0 

0.40 
0,44 
0.49 
0.58 
0.68 
0.74 
0,78 
0.8? 
0.85 
0.89 
0.9? 
0.96 
0.98 


04 
10 
13 
13 
13 
13 


2.5 

0.31 
0.36 
0.41 
0.50 
0.60 
0.66 
0.70 
0.75 
0.79 
0.83 
0.86 
0.90 
0.93 
1.00 
1.07 
1.10 
1.11 
1.11 
l.U 


3,0 

0,25 
0.29 
0.33 
0.42 
0.52 
0.59 
0.6? 


,67 
,71 


0,76 
0,79 
0,84 
0,87 
0,95 


03 
07 
08 
08 


l.OH 


3.5 

0.19 
0.23 
0.27 
0.35 
0.45 
0.51 
0.55 
0,60 
0.64 
0.69 
0.7  3 
0.77 
0.81 
0,89 
0,98 
1.03 
1.04 
1.04 
1.04 


MiMlMijM  SIZF 


LAPGF  PUSSE  SEINERS 
MULTIPLIER  OF  EFFORT 


CM 


KG 


122.5 

34.6 

117.5 

30.6 

112.5 

26.9 

107.5 

23.5 

102.5 

20.4 

97.5 

17.6 

92.5 

15.0 

87.5 

12.7 

82.5 

10.7 

77.5 

8.9 

7?. 5 

7.3 

67.5 

5.9 

6?. 5 

4.7 

57.5 

3.7 

5?. 5 

2.8 

47.5 

2.1 

4?. 5 

1.5 

37.5 

1.0 

3?. 5 

0.7 

0.? 

0.?a 

0.?9 
0.3O 
0.31 
0.3? 
0.32 
0.33 
0.33 
0.33 
0.33 
0,34 
0,34 
0,34 
0,35 
0,35 
0.35 
0.35 
0.35 
0.35 


0.4 

0.43 
0.45 
0.47 
0,49 
0.50 
0.51 
0.51 
0.52 
0.52 
0.53 
0.53 
0.54 
0.54 
0.55 
0.56 
0.56 
0.56 
0.56 
0.56 


0.6 

0.50 
0.52 
0.55 
0.58 
0.59 
0.60 
0.61 
0.62 
0.62 
0.63 
0.64 
0.65 
0.65 
0.66 
0.68 
0.68 
0.68 
0,68 
0,68 


1,0 

0.51 
0.54 
0.59 
0.63 
0.64 
0.66 
0.67 
0.68 
0.69 
0,70 
0.71 
0.72 
0.74 
0.75 
0.77 
0.77 
0.78 
0.78 
0,78 


1,4 

0.46 
0.50 
0.54 
0.59 
0.61 
0.63 
0.64 
0.65 
0.67 
O.^n 
0,70 
0,71 
0.73 
0.75 
0.77 
0.78 
0.79 
0.79 
0.79 


1.8 

0.39 
0.43 
0.48 
0.53 
0.55 
0.57 
0.59 
0.60 
0.62 
0,63 
0,65 
0,67 
0,69 


71 

74 
75 


0,7b 
0,76 
0,  76 


2.0 

0.36 
0.39 
0,44 
0,50 
0,5? 
0,54 
0,56 
0,57 
0,59 
0,60 
0,6? 
0,64 
0,66 
0.69 
0.73 
0.74 
0.74 
0.74 
0.74 


2.5 

0.28 
0.31 
0,36 
0.42 
0.44 
0.46 
0.48 
0.50 
0.51 
0.53 
0.55 
0.57 
0.60 
0.63 
0.67 
0.69 
0.70 
0.70 
0.70 


3.0 

0.21 
0.25 
0.29 
0.35 
0,37 
0,  39 
0,41 
0,4? 
0.44 
0.46 
0,49 
0.51 
0.54 
0.58 
0.6? 
0.64 
0.65 
0.65 
0.65 


3.5 

0,16 
0,19 
0.24 
0.28 
0.31 
0,33 
0.35 
0.36 
0.39 
0.40 
0,43 
0.45 
0.48 
0.53 
0.58 
0.60 
0.61 
0.61 
0.61 


50 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 

Table  4. — Landings  per  recruit    (kg)    when  M  =   0.8,  initial  F  =   0.2,  growth  curve  of  LeGuen  and  Sakagawa 
( 1973)  is  used,  and  yellowfin  less  than  the  minimum  size  are  caught  and  discarded  dead. — Continued. 


LONG  LINFRS 

MINIMUM 

SI7F 

MULTIPLIER  OF  FFFORT 

CM 

KG 

0.? 

0.4 

0.6 

1.0 

1,4 

1.8 

?.0 

?.5 

3.n 

3.5 

12?. =5 

34.6 

0.7? 

i.n 

1.34 

1.43 

1.33 

1.16 

1.07 

0.85 

0.67 

0.5? 

117. S 

30.6 

0.74 

1.18 

1.41 

1.53 

1.43 

l.?7 

1.18 

0.96 

0.76 

0.60 

11?. "5 

?6.9 

0.77 

1.?? 

1.47 

1  .61 

1.53 

1.37 

l.?8 

1.06 

0.86 

0.69 

107.5 

?3.S 

0.79 

l.?5 

1.51 

1.68 

1.61 

1.45 

1.37 

1.15 

0.94 

0.77 

10?. S 

?0.4 

O.RO 

l.?8 

1.55 

1.7? 

1.67 

1.5? 

1.43 

l.?l 

1.01 

0.84 

97. S 

17.6 

0.81 

l.?9 

1.56 

1.74 

1.69 

1.54 

1.46 

l.?4 

1.04 

0.86 

9?. 5 

IS.O 

0.81 

l.?9 

1.57 

1.76 

1.70 

1.56 

1.48 

l.?6 

1.06 

0.88 

87. S 

1?.7 

0.81 

1.30 

1.58 

1.77 

1.7? 

1.58 

1.49 

l.?8 

1.08 

0.90 

8?.S 

10.7 

0.81 

1.30 

1.58 

1.78 

1.73 

1.59 

1.51 

1.30 

1.10 

0.9? 

77.5 

^^.9 

0.8? 

1.31 

1.59 

1.78 

1.74 

1.60 

1.51 

1.30 

1,10 

0.93 

7?. 5 

7.3 

0.8? 

1.11 

1.59 

1.78 

1.74 

1.60 

1.5? 

1.31 

0.93 

67. S 

5.9 

0.8? 

1.31 

1.59 

1.78 

1.74 

1.60 

1.5? 

1.31 

0.94 

6?.S 

4.7 

n.ft? 

1.31 

1.59 

1.7H 

1.74 

1.60 

1.5? 

1.31 

0.94 

57.5 

3.7 

0.8? 

1.31 

1.59 

1.7B 

1.74 

1.60 

1.5? 

1.31 

0.94 

5?. 5 

?.8 

0.8? 

1.31 

1.59 

1.78 

1.74 

1.60 

1.5? 

1.31 

0.94 

^7.5 

?.l 

0.8? 

1.31 

1.59 

1.78 

1.74 

1.60 

1.5? 

1.31 

0.94 

'.P. 5 

1.5 

0.8? 

1.31 

1.59 

1.78 

1.74 

1.60 

1.5? 

1.31 

0.94 

37.5 

l.P 

0.8? 

1.31 

1.59 

1.78 

1.74 

1.60 

1.5? 

1.31 

0.94 

3?. 5 

0,7 

0.8? 

1,31 

1.59 

1.78 

1,74 

1.60 

1.5? 

1.31 

0.94 

occur.  Therefore,  if  effoi't  is  constant  the  pre- 
dicted gain  with  no  dumping  is  greater  than  the 
possible  loss  through  dumping  if  the  minimum 
size  were  55  cm.  but  at  77.5  cm  the  opposite  is 
true.  At  both  size  limits  we  predict  a  greater 
gain  with  no  dumping  than  possible  loss  through 
dumping  if  effort  is  doubled. 

Assuming  constant  recruitment,  yield  per 
recruit  per  unit  effort  is  a  measure  of  fishing 
success.  Table  5  presents  the  estimated  yield 
per  recruit  per  effort  by  gear  assuming  no  dump- 
ing. Increasing  the  size  at  recruitment  to  77.5 
cm  at  the  current  level  of  effort  would  result  in 
a  17%  decrease  for  bait  boats,  a  9%  increase 
for  small  purse  seiners,  a  12%  increase  for  large- 
purse  seiners,  and  a  25%  increase  for  longliners. 
Yield  per  recruit  per  effort  would  drop  by 
about  35%  for  each  of  the  gears  if  effort  doubled 
and  size  at  recruitment  increased  to  77.5  cm. 
If  effort  doubled  and  size  at  recioiitment  re- 
mained 32.5  cm,  yield  per  recruit  per  effort 
would  decrease  by  30%  for  bait  boats,  50%  for 
purse  seiners,  and  60%  for  longliners. 

Changes  in  the  average  weight  of  landings 
should  be  considered  because  average  weight 
affects  the  values  of  landings  particularly  in 
light  of  size-specific  changes  in  the  value  of 
yellowfin  tuna.  Table  6  presents  estimates  of 
the  average  weight  of  catches  by  gear.  Figure 
13  shows  average  weight  isopleths  for  the  en- 
tire fishery.  If  effort  remained  constant  and  size 
at  recruitment  increased  to  77.5  cm,  the  average 
weight  of  the  catch  of  the  total  fishery  would 
increase  from  17.7  kg  to  30.3  kg.  If  effort  doubled 


and  size  at  recruitment  increased  to  77.5  cm, 
the  average  weight  would  increase  to  24.2  kg. 

Sensitivity    of   Results    to    Errors    when    Ageing 
Large  Yellowfin 

The  growth  curve  used  in  this  study  was 
based  on  the  use  of  modal  progressions  to  age 
yellowfin.  Unfortunately  while  this  method  is 
probably  reasonably  accurate  for  ageing  yellow- 
fin less  than  about  130  cm  long,  beyond  this 
size  it  becomes  increasingly  difficult  to  separate 
modes,  and  there  is  a  reasonable  probability 
that  ages  are  increasingly  underestimated  with 
increases  in  size.  In  addition,  because  tuna 
apparently  spawn  over  a  large  portion  of  the 
year,  the  exact  meaning  of  age  is  not  always 
clear.  Alternative  methods,  such  as  ageing  by 


0,0 


Q5 


LO  1.5  aO  2.5 

MULTIPLIER   OF  EFFORT 


30 


35 


Figure    13. — Average  weight  (kg)  isopleths  for  the  entire 
Atlantic  vellowfin  tuna  fishery. 


51 


FISHERY  BULLETIN,  VOL.  72,  NO.  1 


Table  5. — Estimates  of  yield  per  recruit  per  effort  (kg)  when  M  =  0.8,  initial  F 

LeGuen  and  Sakagawa  (1973)  is  used. 


0.2,  and  growth  curve  of 


BAIT  RnaTS 


MINIMUM  SIZF 


MULTIPLIf^R  OF  FFFORT 


CM 


KG 


0.? 


0.4 


0.6 


\  .0 


1  .'. 


1.8 


?.0 


2.5 


"t.O 


l.S 


\??.s 

34.6 

117. 5 

30.6 

11?. 5 

26.9 

107.5 

23.5 

10?. S 

20.4 

97.5 

17.6 

9?. 5 

15.0 

87.5 

12.7 

8?. 5 

10.7 

77.5 

8.9 

7?. 5 

7.3 

67.5 

5.9 

6?. 5 

4.7 

57.5 

3.7 

52.5 

2.8 

47.5 

2.1 

42.5 

1.5 

37.5 

1.0 

3?. 5 

0.7 

0.40 
0.47 
0.55 
0.64 
0.73 
0.84 
0.94 
1.01 
1.09 
1.19 
1.28 
1.37 
1.43 
1.49 
1.54 
1  .57 
1.57 
1.57 
1.57 


0.37 
0.43 
0.51 
0.60 
0.68 
n.78 
0.88 
0.95 
1.03 
1.12 
1  .?0 
1.28 
1.34 
1.39 
1.42 
1  .44 
1  .44 
1.44 
I  .44 


35 

40 


0.48 
0.56 


64 
74 


0.83 
0.90 


97 
06 
13 
21 
25 
30 


1.32 


33 
33 
33 
33 


31 
36 


0.43 
0.50 
0.57 


66 

75 
81 

88 


0.95 
1.02 
1.08 
1.12 


,15 
,15 


1.15 
1,15 
1.15 
1.15 


2« 
33 


0.39 
0.45 


,5? 
,61 


0.69 
0.74 

o.an 

0.S7 


93 
98 

01 
02 
02 
01 
01 


1.01 
1.01 


25 
30 
36 
42 
48 
56 
64 


0.69 
0.74 
0.81 
0.85 
0.90 
0.92 
0.92 
0.91 
0.90 
0.89 
0.89 
0.89 


0.24 
0.29 
0.35 
0.40 
0.46 
0.54 
0.61 
0.66 
0.72 
0 


78 

82 
86 

88 


0.88 
0.86 
0.84 
0.84 


84 
84 


0.22 
0.26 
0.3? 
0.37 
0.42 
0.50 
0.57 
0.61 


66 
71 
75 


0.78 
0.79 


78 
75 
74 
73 


0.72 
0.72 


0.21 
0.24 
0.30 
0.34 
0.39 
0.46 
0.53 
0.56 
0.61 
0.66 
0.69 
0.71 
0.72 
0.70 
0.67 
0.65 
0.64 
0.63 
0.63 


0.19 
0.23 
0.28 
0.3? 
0.36 
0.43 
0.49 
0.53 
0.57 
0.61 
0.64 
0.66 
0.66 
0.64 
0.60 
0.57 
0.56 
0.56 
0.56 


MINIMUM  SIZE 


SMALL  PU'SF  SEINERS 
MULTIPLIEP  OF  FFFORT 


CM 


KG 


0.? 


0.6 


1.0 


1.4 


1.8 


2.0 


2.5 


3.0 


3.5 


122.5 

34.6 

1.72 

.46 

.26 

0.97 

0.78 

0.65 

0.60 

0.50 

0.43 

0.38 

117.5 

30.6 

1.77 

,50 

.29 

0.99 

0.79 

0.66 

0.61 

0.51 

0.43 

0.38 

112.5 

?0.9 

1.8? 

.54 

,31 

1,01 

0.80 

0.67 

0.61 

0.51 

0  .44 

0.38 

107.5 

23.5 

1,91 

.61 

,38 

1,06 

0.85 

o.ri 

0.66 

0.55 

0.48 

0.42 

102.5 

20,4 

1  .9Q 

.69 

,45 

1.12 

0.90 

0.76 

0.70 

0.59 

0.5? 

0.46 

97.5 

17.6 

2.05 

.73 

.48 

1.14 

0.93 

0,78 

0.72 

0.61 

0.53 

0.47 

92.5 

15.0 

2.07 

.74 

.49 

1.15 

0.93 

0,77 

0.72 

0.60 

0.52 

0.46 

87,5 

12.7 

2.10 

.76 

,51 

1.16 

0.93 

0,78 

0.72 

0.60 

0,52 

0.46 

82.5 

10.7 

2.12 

.78 

.52 

1.16 

0.93 

0.77 

0.71 

0.60 

0,51 

0.45 

77.5 

8.9 

2,13 

.78 

.52 

1.15 

0,92 

0.76 

0.70 

0.58 

0.50 

0.43 

72.5 

7.3 

2.14 

,79 

.52 

1.14 

0.91 

0.74 

0.68 

0.56 

0.48 

0.41 

67.5 

5.9 

2,16 

,79 

.51 

1.13 

0,80 

0.72 

0.66 

0.54 

0.45 

0.39 

62.5 

4.7 

2.16 

,78 

.50 

1.11 

0.87 

0.70 

0.64 

0.52 

0.43 

0.37 

57.5 

3.7 

2.17 

.79 

.50 

1.10 

0,85 

0,68 

0.62 

0.50 

0.41 

0.35 

52.5 

2.8 

2.19 

.79 

.49 

1.08 

0.83 

0.66 

0.60 

0.48 

0.  39 

0.33 

'•7.5 

2.1 

2.19 

.78 

.48 

1.06 

0.81 

0.64 

0.58 

0.45 

0.37 

0.31 

42.5 

1.5 

2.19 

.78 

.47 

1.06 

0.80 

0.63 

0.57 

0.45 

0.36 

0.  10 

37.5 

1.0 

2.19 

,  ?8 

.47 

I  .06 

0.80 

0.63 

0.57 

0  .44 

0,36 

0.30 

32.5 

0.7 

2.19 

,78 

.47 

1.06 

0.80 

0.63 

0.57 

0.44 

0,  lf> 

0.30 

LAPOF  PUPSF  SEI^JFPS 


MINIMUM  SIZE 


MULTIPLIER  OF  FFFORT 


CM 


KG 


0.2 


0.4 


0.6 


1.0 


1.4 


1  ,8 


2.0 


2.5 


3.0 


3.5 


122.5 

34.6 

117.5 

30.6 

112.5 

2b. 9 

107.5 

23.5 

102.5 

20.4 

97.5 

17.6 

92.5 

15.0 

87.5 

12.7 

82.5 

10.7 

77.5 

8.9 

72.5 

7.3 

67.5 

S.9 

62.5 

4.7 

57.5 

3.7 

52.5 

2.8 

47.5 

2.1 

42.5 

1.5 

37,5 

1.0 

32,5 

0.7 

1.57 
1.61 
1  .66 
1.71 
1.72 
1.73 
1.74 
1.74 
1.74 
1.75 
1.75 
1.75 
1.76 
1.76 
1.76 
1.76 
1  .76 
1  .76 
I  .76 


1.34 
1.37 
1,41 
1  .44 
1  ,44 
1.45 
1.45 
1.45 
1  .44 
1  .44 
1  .44 
1,43 
1,43 
1  ,42 
1,42 
1  .40 
1  .40 
1  .40 
1  .40 


1.16 
1.18 
1.21 
1.24 
1.23 
1.23 
1.22 
1.22 
1.21 
1,20 
1,20 
1.19 
1.18 
1.17 
1.15 
I  .14 
1.14 
1,14 
1  .  14 


0.89 
0.90 
0.92 
0.94 
0.93 
0.92 
0.91 
0.90 
0.89 
0.88 
0.86 
0.85 
0.84 
0.82 
0.80 
0.78 


78 
78 
78 


0.71 
0.72 
0.74 


75 
73 
72 


0.71 
0.69 


68 
67 
65 
64 


0.62 
0.60 
0.59 
0.57 
0.56 
0.56 
0.56 


0.58 
0,59 
0.60 
0.61 
0.59 
0.58 
0.57 
0,56 
0.54 
0.53 
0.51 
0.44 
0.48 
0.46 
0.45 
0.43 
0.42 
0.42 
0.42 


0.53 
0.54 


55 
56 
54 


0.53 
0.51 
0.50 
0.49 
0.47 
0.46 
0.44 
0.43 
0.41 
0.40 


38 
37 


0.44 
0.44 
0.46 
0.46 
0.44 
0.43 
0.41 
0.40 
0.39 
0.37 
0.36 
0.34 
0.33 
0.32 
0.  30 
0.28 


0.37 
0.37 


28 
28 
?8 


0.37 
0.37 
0.39 
0.39 
0.37 
0,35 
0.34 
0.33 
0.32 
0.30 
0.29 
0.27 
0.27 
0.25 
0.24 
0.22 
0.2? 
0.2? 
0.22 


0.32 


3? 
33 
34 


0.32 
0.30 
0.29 
0.28 
0.27 
0.25 
0.24 
0.?3 
0.22 
0,20 
0.19 
0.18 
0.18 
0.17 
0.17 


52 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 

Table  5. — Estimates  of  yield  per  recruit  per  effort   (kg)  when  M  = 

LeGuen  and  Sakagawa  ( 1973)  is  used. 


0.8,  initial  F 
-Continued. 


=  0.2,  and  growth  curve  of 


LONG  LINFW5 

MINIMUM 

S17E 

MULTIPLIED  OF 

FFFORT 

fM 

Kb 

0.? 

0.4 

0.6 

1.0 

1.4 

1.8 

2.0 

2.5 

3.0 

3.5 

1??.S 

34.  fc 

4.00 

3.51 

3.10 

2.49 

2.05 

1.74 

1.61 

1.35 

1.16 

1.02 

117. S 

30.6 

4.1? 

3.60 

3.17 

2.53 

2.07 

1.75 

1.61 

1.35 

1.16 

1.01 

11?. 5 

?b.9 

4.?1 

3.66 

3.21 

?.54 

2.07 

1.73 

1.60 

1.3  3 

1.13 

0.98 

107. S 

?J.5 

4.?7 

3.69 

3.?? 

2.5? 

2.03 

1  .68 

1.54 

1.27 

1.07 

0.92 

10?. s 

?0.4 

4.31 

3.70 

3.21 

2.49 

1.99 

1.63 

1.4Q 

1.21 

1.01 

0.86 

97. =5 

17.6 

4.31 

3.68 

3.17 

2.43 

1.92 

1.56 

1.4? 

1.14 

0.94 

0.79 

"JP.S 

15.0 

4.30 

3.66 

3.14 

2.38 

1.87 

1.50 

1.36 

1  .08 

0.89 

0.74 

«7.5 

1?.7 

4.30 

3.64 

3.11 

2.34 

1.8? 

1.46 

1.31 

1.04 

0.84 

0.69 

8?. 5 

10.7 

4.?9 

3.6] 

3.08 

2.29 

1.77 

1.40 

l.?6 

0.98 

0.79 

0.64 

77. S 

tt.y 

4.?7 

3.57 

3.03 

?.?3 

1.70 

1.33 

1.19 

0.9? 

0.7? 

0.58 

7?.S 

7.3 

4.?4 

3.5  3 

2.98 

2.17 

1.63 

1.26 

1.12 

0.85 

0.66 

0,53 

67.5 

5.9 

4.2! 

3.49 

2.91 

?.09 

1.55 

1.19 

1.05 

0.78 

0.60 

0.47 

6?. 5 

4.7 

4.19 

3.45 

2.86 

2.03 

1.49 

1.13 

0.9^ 

0.73 

0.55 

0.42 

57.5 

3.7 

4.15 

3.39 

2.79 

1.95 

1.40 

1.04 

0.91 

0.65 

0.48 

0.36 

5?. 5 

2.B 

4.1? 

3.33 

2.72 

1.86 

1.3^ 

0.96 

0.83 

0.58 

0.42 

0.31 

47.5 

d.\ 

4.09 

3.29 

2.67 

1.81 

1.26 

0.91 

0.78 

0.54 

0.38 

0.28 

42.5 

1.5 

4.0» 

3.?7 

2.65 

1.79 

1.25 

0.89 

0.76 

0.53 

0.37 

0.27 

37.5 

1.0 

i.  .08 

3.?7 

2.65 

1.78 

1.24 

0.89 

0.76 

0.5? 

0.37 

0.27 

3?. 5 

0.7 

4.0A 

3.?7 

2.65 

1.78 

1.24 

0.89 

0.76 

0.5? 

0.37 

0.27 

FMTI3F  FI5HFSY 

MINIMUM 

5I7F 

MULTIPLIfo  OF 

FFF09T 

CM 

KG 

0.? 

0.4 

0.6 

1.0 

1.4 

1.8 

7.0 

2.5 

3.0 

3.5 

1??.5 

34.6 

7.7(1 

6.68 

5.86 

4.65 

3.82 

3.22 

2.98 

2.51 

2.17 

1.91 

117.5 

30.6 

7.97 

6.90 

6.04 

4.78 

3.91 

3.29 

3.05 

2.57 

?.21 

1.94 

11?. 5 

?b.9 

8.25 

7.1? 

6.7? 

4.90 

4.00 

3.36 

3.11 

2.61 

?.?'^ 

1.97 

107.5 

?3.5 

8.53 

7.34 

6.40 

5.0? 

4.08 

3.42 

3.16 

2.65 

2.27 

1.99 

10?. 5 

?0.4 

8.75 

7.51 

6.53 

5.10 

4.  14 

3.46 

3.19 

2.67 

2.28 

2.00 

97.5 

17.6 

8.9? 

7.64 

6.62 

5.16 

4.17 

3.48 

3.?0 

2.67 

2.28 

1.99 

9?. 5 

15.0 

9.04 

7.73 

6.69 

5.19 

4.19 

3.48 

3.21 

2.67 

2.27 

1.96 

fi7.5 

1?.7 

9.14 

7.80 

6.74 

5.21 

4.19 

3.48 

3.20 

2.65 

2.26 

1.96 

a?. 5 

10.7 

9.24 

7.86 

6.78 

5.2? 

4.18 

3.46 

3.18 

2.62 

2.?2 

1.92 

77.5 

e,9 

9.34 

7.9? 

6.81 

5.2? 

4.16 

3.42 

3.14 

2.58 

2.18 

1.88 

7?. 5 

7.3 

9.4? 

7.96 

6.82 

5.19 

4.1? 

3.38 

3.09 

2.52 

2.1? 

1.82 

67.5 

5.9 

9.49 

7.99 

6.8? 

5.15 

4.06 

3.30 

3.01 

2.44 

2.04 

1.74 

6?. 5 

4.7 

9.54 

7.99 

6.80 

5.10 

4.00 

3.?3 

2.94 

2.37 

1.97 

1.66 

57.5 

3.7 

9.58 

7.98 

6.75 

5.01 

3.88 

3.11 

2.81 

2.25 

1.84 

1.55 

5?. 5 

2.R 

9.60 

7.95 

6.68 

4.90 

3.75 

2.98 

2.68 

2.11 

1.71 

1.42 

47.5 

2.1 

9.61 

7.91 

6.61 

4. 81 

3.65 

2.87 

2.58 

2.01 

1.67 

1.33 

4?. 5 

1.5 

9.60 

7.90 

6.59 

4.78 

3.6? 

2.84 

2.54 

1.98 

1.59 

1.31 

37.5 

1.0 

9.60 

7.89 

6.59 

'♦.77 

3.61 

2.83 

2.53 

1.97 

1.5P 

1  .30 

3?. 5 

0.7 

9.60 

7.89 

6.59 

4.77 

3.61 

2.83 

2.53 

1.97 

1.58 

1.30 

the  examination  of  hard  parts,  are  extremely 
difficult  and  not  easily  interpreted  for  tropical 
species  such  as  the  yellowfin  tuna. 

The  marked  increase  in  estimates  of  size-speci- 
fic F  beyond  130  cm  for  the  purse  seine  gears  is 
a  possible  result  of  underestimating  ages  of  older 
yellowfin.  To  examine  this  possibility,  the 
growth  curve  of  LeGuen  and  Sakagawa  (1973) 
was  modified.  It  was  hypothetically  assumed 
that  the  percentage  of  underestimation  of  the 
time  interval  within  a  size  interval  increased 
linearly  from  0%  at  135  cm  to  100%  at  180  cm. 
The  resulting  growth  curve  is  compared  to  the 
original  in  Figure  14. 

Values  of  size-specific  F  were  then  estimated 
as  before  with  initial  values  of  0.2  and  0.8.  The 
value  of  0.2  gave  the  most  reasonable  results 
for  reasons  similar  to  those  given  before.  Values 
of  size  specific   F  for  each  gear  are  shown  in 


o  LE  GUEN  a  SAKAOAWA 
•  HYPOTHETICAL 


5      6 
AGE  (YEARS) 


Figure  14. — Growth  curves  of  Atlantic  yellowfin  tuna. 
Upper  curve  is  from  LeGuen  and  Sakagawa  (1973).  Lower 
curve  is  a  modification  of  the  upper  curve  (see  text). 


53 


FISHERY  BULLETIN,  VOL.  72.  NO.  1 

Table  6. — Estimates  of  average  weight  of  catch   (kg)  when  M  =  0.8,  initial  F  =  0.2,  and  growth  curve  of 

LeGuen  and  Sakagawa  (1973)  is  used. 


MINI"UM    <;I7F 


C" 


<& 


RAIT     ROATS 
MULTTPLIFTR    OF    F^FOPT 
0.6  1.0  I.'. 


1.8 


?.n 


?.5 


1.0 


3.5 


133. S 

3'*. 6 

^8,87 

47.71 

46.73 

45.1ft 

44.0  3 

43.14 

42.78 

42.01 

41.41 

40,91 

117. S 

30.6 

45.55 

44.i.7 

43.56 

4?. 12 

41.06 

40.24 

39.90 

39.19 

38.61 

38.14 

11?. S 

?6.<J 

41.63 

40.64 

39.ftO 

3fl.47 

37.49 

36.72 

36.40 

35.71 

35.15 

34.68 

107.5 

?J.S 

3ft. 03 

37.10 

36.32 

35.08 

34.15 

33.42 

33.10 

32.43 

31.87 

31.40 

10?. S 

?0.A 

34,67 

33. HO 

33.07 

31.91 

31.0? 

30.31 

30.0  1 

29.35 

28.79 

28.31 

97.5 

17.6 

31.19 

30.39 

29.71 

28.63 

27.80 

?7.12 

26.83 

26.19 

25.65 

25.19 

<5?.5 

15.0 

?fl.34 

?7.59 

26.96 

25.95 

25.16 

24.53 

24.25 

23.64 

23,12 

22.67 

87.5 

1?,7 

?6.?1 

?5.51 

24.91 

23.95 

23.19 

22.58 

22.31 

21.72 

21,21 

20.77 

fl?.5 

10.7 

?3.ftO 

?3.13 

22.57 

?1.6S 

20.93 

20.34 

20.08 

19.50 

19,00 

18.57 

77.5 

8.9 

?1.1? 

?0.51 

19.9ft 

19.12 

18.44 

17.87 

17.62 

17.06 

16.58 

16.16 

72.5 

7.3 

1ft. ft9 

1ft. 31 

17.82 

17.00 

16.35 

15.81 

15.57 

15.03 

14.56 

14.16 

67.5 

5.9 

16.57 

16.04 

15. 5ft 

14.81 

14.20 

13.68 

13.45 

12.93 

12.4« 

12.09 

6?. 5 

'*.7 

IS. Oft 

14.57 

14,13 

13.39 

12,80 

12.29 

12.07 

11.57 

11.13 

10.75 

57.5 

3.7 

13.31 

1?.H? 

12.40 

11.70 

11.13 

10.64 

10.42 

9.93 

9.50 

9.13 

5?. 5 

2.R 

11.97 

n.so 

11.10 

10.41 

9.85 

9.37 

9.16 

8.67 

a. 25 

7.88 

47.5 

?.l 

10. ft? 

10.42 

10.02 

9.35 

8.80 

ft. 33 

8.11 

7.63 

7.21 

6.85 

A?. 5 

1.5 

10.57 

10.13 

9.73 

9.07 

8.51 

8.04 

7.ft3 

7.35 

6.91 

6.56 

37.5 

1.0 

10.51 

10.07 

9.67 

9.01 

8.46 

7.98 

7.77 

7.29 

6.87 

6.50 

3?. 5 

0.7 

10.51 

10.06 

9.67 

9.00 

8.45 

7.98 

7.76 

7.?8 

6.86 

6.50 

5M4LL    PIJ9SF    SEINESS 


MINIMUM    S[7F 


MIILTIPLTFP    OF    FFFOPT 


CM 


KG 


n.2 


0.4 


0.6 


1.0 


1.4 


1.8 


2.0 


2.5 


3.0 


3.5 


122.5 

34.6 

63.08 

60.94 

58.99 

55.67 

53.0? 

50.93 

50.04 

48. ?0 

46.76 

45.59 

1  17.5 

30.6 

60.95 

50.69 

56.65 

53.18 

50.44 

48.28 

47.36 

45.47 

43.98 

4?, 78 

112.5 

?6.9 

58.6? 

56.24 

54.09 

50.47 

47.62 

45.38 

44.44 

43.48 

40.94 

39.69 

107.5 

23.5 

54,53 

51.97 

49.68 

45.87 

42.91 

40.61 

39.65 

37.65 

36.10 

34.85 

102.5 

20.4 

50.69 

48.0  1 

45.65 

41.78 

38.82 

36.55 

35.61 

33.67 

32.18 

31.00 

97.5 

17.6 

48.15 

45.42 

43.03 

39.15 

36.22 

33.99 

33.07 

31.19 

29.74 

?8,60 

92.5 

15.0 

46.71 

43.96 

41.55 

37.66 

34.74 

32.53 

31.61 

29.75 

28,32 

?7.19 

87.5 

12.7 

44.78 

41.99 

39.57 

35.67 

32.76 

30.55 

29.64 

27.79 

26,37 

?5,24 

82.5 

10.7 

42.99 

40.17 

37.73 

33.8? 

30.92 

28.72 

?7.a? 

25.97 

24.55 

?3.43 

77.5 

8.9 

41.01 

38.17 

35.71 

31.79 

28.89 

26.71 

25.81 

23.97 

22.55 

21.41 

72.5 

7.3 

39.2? 

36.35 

33.88 

29,96 

27,07 

24.89 

24.00 

22.16 

20,74 

19.60 

67.5 

5.9 

37.0? 

34,12 

31.65 

27,73 

24,86 

22.69 

21.80 

19.97 

1R.55 

17.41 

62.5 

4.7 

35.35 

32,44 

29.96 

26,06 

23.20 

21.05 

20.16 

18.34 

16.93 

15.79 

57.5 

3.7 

31.69 

28,79 

26.34 

22.51 

19.73 

17.65 

16.79 

15.04 

13,68 

12.59 

52.5 

2.8 

?7.97 

25.13 

??,75 

19.09 

16.46 

14.52 

13.72 

12.10 

10.86 

9.88 

47.5 

2.1 

?6.14 

23.35 

?1.0? 

17.47 

14.93 

13.07 

12.31 

10.77 

9.60 

ft. 67 

42.5 

1.5 

?5.7? 

22.94 

20,63 

17.10 

14.59 

12.74 

11.99 

10.47 

9,31 

8.39 

37.5 

1.0 

?S.6? 

22.84 

20.54 

17.01 

14.50 

12.66 

11.91 

10.39 

9.23 

8.32 

32.5 

0.7 

25.61 

22.84 

20.53 

17.00 

14.50 

12.65 

11.90 

10.39 

9.23 

8.32 

LAPGK  PIIP5F  SEINERS 


MINIMUM  slZf^ 


MULTIPLIER  OF  EFFORT 


CM 


KG 


0.? 


0.6 


1  .0 


1.4 


1.8 


2.0 


2.5 


3.0 


3.5 


122.5 

34.6 

63.26 

61.49 

59.84 

56.92 

54.48 

52.45 

51.57 

49.68 

48.15 

46.90 

117.5 

30.6 

61.30 

59.40 

57.62 

54.  4  ? 

51. 8H 

49.72 

48.78 

46.77 

45.16 

43.83 

112.5 

?6.9 

58.69 

56.61 

54.69 

51.30 

48.50 

46.19 

45.19 

43.07 

41.37 

39.98 

107.5 

?3.5 

55.99 

53.75 

51.68 

48.07 

45.11 

4?. 70 

41.66 

39,47 

37.72 

36.31 

102.5 

20.4 

54.78 

52.46 

50.33 

46.62 

43.59 

41.13 

40.07 

37.84 

36.07 

34.63 

97,5 

17.6 

53.40 

SI. 00 

48.79 

44.96 

41,84 

39.30 

38,21 

35.92 

34.10 

32.62 

92.5 

15.0 

52.39 

49.92 

47.65 

43.73 

40.53 

37,94 

36.83 

34.48 

32.62 

31.10 

87,5 

12.7 

51.41 

48,87 

46,54 

42.52 

39,24 

36,59 

35.45 

33,05 

31.13 

29.57 

82.5 

10.7 

SO. 10 

47,48 

45,07 

40.91 

37.54 

34,80 

33.63 

31.15 

29.16 

27,54 

77.5 

8.9 

48,65 

45.9? 

43,43 

39.13 

35,64 

32.82 

31.61 

29,05 

27.00 

25.32 

72.5 

7.3 

46.6? 

43.77 

41.16 

36.69 

33.07 

30.15 

28.90 

26.27 

24.16 

22.45 

67.5 

5.9 

44,46 

41.48 

38.78 

34.14 

30.43 

27.44 

26.17 

23.50 

21.38 

19,66 

6?. 5 

4.7 

41.92 

38.81 

36.01 

31.24 

27.46 

24.46 

23.18 

20.53 

18.44 

16.77 

57.5 

i.7 

38,35 

35.1? 

32.23 

27.39 

23.62 

20.67 

19.44 

16.90 

14.94 

13.40 

5?. 5 

2.8 

34,39 

31.08 

28.17 

23.39 

19.74 

16.96 

15.82 

13.50 

11,75 

10.41 

47.5 

2.1 

3?. 9) 

29.60 

26.69 

21.96 

18.39 

15.68 

14.58 

12.35 

10,69 

9.42 

4?. 5 

1.5 

31.85 

28.53 

25.64 

20.94 

17.43 

14.78 

13.70 

11.54 

9.93 

8.71 

37.5 

1.0 

31.52 

28.21 

25.31 

20.63 

17,13 

14.50 

13.43 

11.29 

9.70 

8.49 

32.5 

0.7 

31.52 

28.20 

25.31 

20,62 

17.13 

14.50 

13.43 

11.29 

9.70 

8.49 

54 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 

Table  6. — Estimates  of  average  weight  of  catch  (kg)  when  M  =  0.8,  initial  F  =  0.2,  and  growth  curve  of 

LeGuen  and  Sakagawa  (1973)  is  used. — Continued. 


JlrjlK'U"    SIZf 


KG 


MUI.TIPLIFP    OF     FFFOWT 


0.? 


0.6 


1.0 


l.^. 


l.B 


?.0 


2.S 


3. ft 


S.S 


ie^.'=' 

3'*.6 

5Q.30 

57. 9P 

56.63 

54.33 

52.38 

50.73 

50.00 

48.41 

47. in 

46.00 

1)7.5 

30.6 

57.53 

5'<.05 

54.68 

5?.?3 

50.16 

48.41 

47.63 

45.96 

44.57 

43,41 

11?. 5 

?b.9 

55.76 

54.18 

52.71 

50.11 

47.91 

46.05 

45.23 

43.45 

41.97 

40.74 

107.5 

?3.5 

54.18 

5?. 51 

50.96 

48.20 

45.87 

43.90 

43.03 

41.14 

39.58 

38.26 

10?. 5 

?0.4 

5?.pfi 

51.13 

49.50 

46.61 

44.16 

42.09 

41.18 

39.19 

37.53 

36.13 

97.5 

17.6 

5?. 31 

50.51 

48.85 

45,89 

43.38 

41.25 

40.31 

38.26 

36.55 

35.11 

9?. 5 

15.0 

51. «5 

50.0? 

48.3? 

45.30 

42.74 

40.56 

39.60 

37.49 

35.7? 

34.23 

R7.5 

12.7 

51,33 

49.46 

47.72 

44.6? 

41.98 

39.74 

38.74 

36.55 

34.71 

33.14 

«?.5 

10.7 

50.84 

48.93 

47.15 

43.98 

41.27 

38.95 

37.92 

35.65 

33.73 

3?. 09 

77.5 

8.9 

50.61 

48.68 

46.88 

43.66 

40.91 

38.56 

37,50 

35.19 

33.22 

31,54 

7?. 5 

7.3 

50.39 

48.44 

46.61 

43.35 

40.56 

38,16 

37.09 

34.7? 

32.70 

30.96 

67.5 

5.9 

50.30 

48.34 

46.51 

43, ?3 

40.41 

38,00 

36.91 

34.5? 

32.47 

30.70 

6?. 5 

4.7 

50.28 

48.31 

46.48 

43.19 

40.37 

37.94 

36.86 

34.45 

32.40 

30.62 

57.5 

3.7 

50. ?6 

48. ?9 

46.45 

43.16 

40.34 

37.91 

36.82 

34.40 

32.34 

30.56 

5?. 5 

a.'t 

50. ?6 

48. ?9 

46.45 

43.16 

40.34 

37.91 

36.82 

34.40 

32.34 

30.56 

47.5 

?.l 

50.26 

48. ?9 

46.45 

43.16 

40.34 

37.91 

36.82 

34.40 

32.34 

30.56 

A?. 5 

1.5 

50. ?6 

48. ?9 

46.45 

43.16 

40.34 

37.91 

36.82 

34.40 

32.34 

30.56 

37.5 

1.0 

50. ?6 

48. ?0 

46.45 

43.16 

40.34 

37.91 

36.82 

34.40 

32.34 

30.56 

3?. 5 

0.7 

50. ?6 

48.29 

46.45 

43.16 

40.  34 

37.91 

36.82 

34.40 

32.34 

30.56 

Figure  15.  The  values  of  F  of  large  fish  are 
relatively  smaller  than  those  estimated  with 
the  original  growth  curve. 

Results  of  the  yield-per-recruit  calculations 
are  shown  in  Table  7.  The  results  indicate  that 
if  effort  is  held  constant  and  size  at  recruitment 
is  increased  to  the  optimum,  less  than  a  3% 
increase  in  yield  per  recruit  would  occur.  If 
size  at  recruitment  is  constant  and  effort  is 
doubled,  yield  per  recruit  would  increase  by 
about  28%  which  is  considerably  more  than 
when  the  original  growth  curve  is  used.  If  size 
at  recruitment  is  increased  to  77.5  cm  and  ef- 
fort doubled,  a  44%  increase  in  yield  per  recimit 
would  occur. 


•  SMALL  PURSE  SEINE 
A  LARGE  PURSE  SEINE 
A  LONGLINE 


80  100  120  140 

FORK    LENGTH   (cm) 

Figure    15. — Estimates  of  size-specific   F  when  its  initial 
value  is  0.2  and  using  the  modified  growth  curve. 


Table  7. — Estimates  of  yield  per  recruit   (kg)  for  the  entire  fishery  when  M  =  0.8,  initial  F  =  0.2.  and 

hypothetical  growth  curve  is  used. 


FNTIRF    FISHFOY 

MiMlMUM 

S17F 

MULTIPLI'^P    OF 

FFFORT 

CM 

KG 

0.? 

0.4 

0.6 

1.0 

1.4 

1.8 

2.0 

2.5 

3.0 

3.5 

122.5 

34.6 

0.80 

1,48 

2.06 

?.99 

3.70 

4.?4 

4.47 

4.95 

5.3? 

5.61 

117.5 

30.6 

0,84 

1.55 

2.15 

3.1? 

3.85 

4.41 

4.65 

5.13 

5.50 

5.79 

112.5 

26.9 

0,«8 

1.6? 

2.25 

3.?5 

4.00 

4.58 

4.82 

5.30 

5.67 

5.97 

107.5 

23.5 

0.9? 

1.70 

2.35 

3.39 

4.15 

4.74 

4.98 

5.46 

5.83 

6.11 

102.5 

?0.4 

0.96 

1.76 

2.43 

3.49 

4.27 

4.85 

5.09 

5.57 

5.93 

6.21 

97.5 

17.6 

0.98 

1.80 

2.49 

3.56 

4.35 

4.93 

5.17 

5.64 

5.99 

6.25 

92.5 

15.0 

l.nn 

1.84 

2.53 

3.6? 

4.40 

4.98 

5.21 

5.68 

6.01 

6.26 

87.5 

12.7 

1.02 

1.87 

2.57 

3.66 

4.44 

5.01 

5.24 

5.69 

6.01 

6.25 

82.5 

10.7 

1.04 

1.89 

2.60 

3.69 

4.47 

5.03 

5.25 

5.69 

5.99 

6.?1 

77.5 

8.9 

1.05 

1.92 

2.63 

3.7? 

«..48 

5.03 

5.24 

5.65 

5.93 

6.12 

72.5 

7.3 

1.07 

1.94 

2.66 

3.74 

4.48 

5.01 

5.21 

5.59 

5.84 

6.01 

67.5 

5.9 

1  .08 

1.96 

2.68 

3.74 

H.47 

4.96 

5.15 

5.49 

5.70 

5.83 

62.5 

4.7 

1.09 

1  .98 

2.69 

3.74 

4.44 

4.91 

5.08 

5.39 

5.57 

5.66 

57.5 

3.7 

1.11 

1.99 

2.69 

3.71 

4.37 

4.80 

4.95 

5.20 

5.32 

5.37 

52.5 

2.8 

1.11 

1.99 

2.69 

3.67 

4.28 

4.66 

4.79 

4.98 

5.05 

5.05 

47.5 

2.1 

1.1? 

1.99 

2.68 

3.63 

4.21 

4.55 

4.66 

4.81 

4.84 

4.81 

42.5 

1.5 

1.1? 

1.99 

2.67 

3.6? 

4.18 

4.51 

4.61 

4.75 

4.77 

4.73 

37.5 

i.n 

1.1? 

1.99 

?.67 

3.61 

4.18 

4.50 

4.60 

4.73 

4,75 

4.71 

3?. 5 

0.7 

1.1? 

1  .9^ 

?.'^7 

3.^1 

4.17 

4.50 

4.60 

4.73 

4.75 

4.70 

55 


FISHERY  BULLETIN,  VOL.  72,  NO.  1 


Sensitivity   of  Results   to  Errors   in   Estimates  of 
Natural  Mortality 

Size-specific  values  of  F  were  estimated  using 
values  of  M  of  0.6  and  1.0  and  an  initial  value  of 
F  =  0.2.  The  results  are  compared  to  size-s])ecific 
F  when  M  =  0.8  in  Figure  16.  Although  the 
absolute  values  differ  considerably,  the  same 
general  trends  appear  in  each  curve.  The  ratio 
of  FIM  varies  about  threefold. 

Results  of  yield-per-recruit  calculations  are 
shown  in  Tables  8  and  9  and  Figures  17  and  18. 
There  is  a  steeper  horizontal  gradient  when 
M  =  1.0  and  a  steeper  vertical  gradient  when 
M  =  0.6  than  when  M  =  0.8.  That  is,  yield  per 
recruit  is  more  sensitive  to  changes  in  effort 


40 


60 


80  100  120  140 

FORK  LENGTH  (cm.) 


160 


180 


Figure    16. — Estimates  of  size-specific    F  when  its  initial 
value  is  0.2  and  using  values  for  M  of  0.6,  0.8,  and  1 .0. 


Table  8. — Esliniales  of  yield  per  recruit   (kg)   for  the  entire  fishery  when  M  =  0.6,  initial  F  =  0.2,  and  growth 

curve  of  LeGuen  and  Sakagawa  (1973)  is  used. 


FMTIOF  FISHFRY 

MINIMUM 

SIz-R 

MULTIPLIFW  OF 

FFFORT 

CM 

KG 

0.? 

0.4 

0.6 

l.n 

1.4 

1.8 

?.n 

?.5 

3.0 

3.5 

1??.5 

3<..6 

3.5? 

5.8? 

7.34 

9.07 

9.93 

10.39 

10.55 

10.81 

10. 9« 

11.10 

117.5 

30.6 

3.61 

5.94 

7.47 

9. IB 

10.00 

10.43 

10.58 

10.81 

10. 9S 

11.04 

11?. 5 

?6.9 

3.70 

6.06 

7.58 

9.?6 

10.04 

10.44 

10.56 

10.76 

10.86 

10.9? 

107.5 

?3.5 

3.79 

6.16 

7.68 

9.30 

10.03 

10.38 

10.48 

10.63 

10.70 

10.7? 

10?. 5 

?0.4 

3.85 

6.?4 

7.74 

9.31 

9.98 

10. ?8 

10.36 

10.47 

10.49 

10.48 

97.5 

17.6 

3.90 

6.?B 

7.77 

9.?8 

9.9] 

10.16 

10.?? 

10. ?8 

10. ?7 

10.?? 

<5?.S 

15.0 

3.93 

6.31 

7.77 

9.?4 

9.8? 

10.03 

10.07 

10.09 

10.04 

9.97 

87.5 

1?.7 

3.95 

6.33 

7.77 

9.18 

9.70 

9.87 

9.90 

9.87 

9.79 

9.68 

8?. 5 

10.7 

3.97 

6.33 

7.74 

9.09 

9.55 

9.66 

9.66 

9.58 

9.45 

9.31 

77. S 

6.9 

3.99 

6.33 

7.70 

8.95 

9.33 

9.38 

9.35 

9.?0 

9.01 

8.8? 

7?. 5 

7.3 

u.no 

6.31 

7.63 

8.79 

9.08 

9.06 

8.99 

8.78 

8.54 

8.30 

67.5 

5.9 

it. 01 

6.?7 

7.53 

8.57 

8.75 

8.64 

8.54 

8.?5 

7.94 

7.65 

6?. 5 

<».7 

4.01 

6.23 

7.44 

8.37 

8.47 

8.?9 

8.16 

7.80 

7.45 

7.13 

57.5 

3.7 

4.00 

6.15 

7.?8 

8.05 

8.01 

7.73 

7.55 

7.11 

6.70 

6.33 

5?. 5 

?.R 

3.98 

6.06 

7.10 

7.70 

7.54 

7.16 

6.95 

6.43 

5.97 

5.56 

A7.5 

2.1 

3.96 

5.99 

6.96 

7.45 

7.?0 

6.75 

6.5? 

5.95 

5.46 

5.04 

4?. 5 

1.5 

3.95 

5.96 

6.9? 

7.37 

7.09 

6.6? 

6.38 

5.80 

5.30 

4.87 

37.5 

1.0 

3.95 

5.96 

6.90 

7.35 

7.06 

6.59 

6.35 

5.77 

5.?6 

4.83 

3?. 5 

0.7 

3.95 

5.96 

6.90 

7.34 

7.06 

6.59 

b.34 

5.76 

5.?6 

4.83 

Table  9. — Estimates  of  yield  per  recruit   (kg)  for  the  entire  fishery  when  M   =  1.0,  initial  F 

curve  of  LeGuen  and  Sakagawa  ( 1973)  is  used. 


0.2,  and  growth 


FrJTIRf  FISHFPY 

MINIMUM 

SI/c 

MUl  TlPLlFt'  OF 

FFFORT 

CM 

Kb 

0.? 

n,4 

0.6 

l.n 

1.4 

1.8 

?.o 

?.5 

3.0 

3.5 

1??.5 

34.6 

0.66 

1.18 

1  .6? 

?.?6 

?.7? 

3.0  6 

3.19 

3.47 

3.67 

3.84 

117.5 

30.6 

n.f-Q 

1  .?4 

1.68 

?,36 

?.83 

3.18 

3.3? 

3.60 

3.81 

3.98 

11?. 5 

?6.9 

0.7? 

1  .?9 

1.76 

?.45 

?.94 

3.30 

3.45 

3.74 

3.96 

4.13 

107.5 

?3.5 

0.7S 

1  .35 

1  .H3 

?.5S 

3.06 

3.4? 

3.57 

3.87 

4.09 

4.?7 

10?. 5 

?0.4 

0.77 

1  .39 

1.89 

?.6  3 

J. 15 

3.5? 

3.67 

3.97 

4.?0 

4.37 

97.5 

17.6 

0.79 

I  .43 

1  .93 

?.69 

3.?1 

3.59 

3.74 

4.04 

4.?7 

4.44 

9?. 5 

IS.O 

0.81 

1.45 

1.97 

?.73 

3.?6 

3.64 

3.79 

4.09 

4.31 

4.48 

87.5 

1?.7 

0.8? 

1  .47 

1  .99 

?.76 

3.?9 

3.67 

3.8? 

4.1? 

4.34 

4.50 

8?. 5 

10.7 

0.83 

I  .4^ 

?.o? 

?.79 

3.3? 

3.7U 

3.85 

4.14 

4.35 

4.51 

77.5 

■1.9 

0.85 

1.51 

?.05 

2.H? 

3.35 

3.7? 

3.86 

4.14 

4.34 

4.49 

7?. 5 

7 . 3 

0.86 

1.53 

?.07 

?.84 

3.36 

3.7? 

3.«6 

4.13 

4.3? 

4.45 

67.5 

5.9 

0.87 

1  .55 

?.09 

?.86 

1.  37 

3.7? 

3.85 

4.10 

4.?7 

4.38 

6?. 5 

4.7 

0,88 

1.56 

?.10 

?.86 

3.-36 

3.70 

3.8^ 

4.06 

4.?1 

4.31 

57.5 

3.7 

o.aq 

1.57 

?.ll 

?.«6 

3.34 

3.65 

3.76 

3.97 

4.09 

4.16 

5?. 5 

?.H 

0.90 

1  .58 

?.ll 

?.8<. 

3.30 

3.58 

3.68 

3.85 

3.94 

3.99 

47.5 

?.l 

0.90 

1  .58 

?.ll 

?.8? 

3.?6 

3.5? 

3.61 

3.76 

3.83 

3. 85 

4?. 5 

1.5 

0.90 

\   .58 

?.10 

?.81 

3.?4 

3.50 

3.59 

3.71 

3.79 

3.80 

37.5 

1.0 

0.90 

1.58 

?.10 

?.81 

3.?4 

3.50 

3.58 

3.7? 

3.  78 

3.79 

3?. 5 

0.7 

0.90 

1  .58 

?.10 

?.81 

3.?4 

3.50 

3.58 

3.7? 

3.78 

3.7s. 

56 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


1.5  kg    2,0  kg     2  5  kg  3.0  kg 


40  kg 


10  1.5  2.0  2.5 

MULTIPLIER  OF    EFFORT 


35 


Figure     17. — Yield-per-recruit     isopleths    for    the    entire 
Atlantic  yellowtin  tuna  fishery  with  M  =  1.0. 


5      7  8 


0.5 


1.0  15  2.0  2  5 

MULTIPLIER  OF    EFFORT 


3.0 


3.5 


Figure     18. — Yield-per-recruit    isopleths    for    the    entire 
Atlantic  yellowfin  tuna  fishery  with  A/  =  0.6. 


when  M  =  1.0  and  more  sensitive  to  changes  in 
size  at  recruitment  when  M  =  0.6  than  when 
M  =  0.8.  When  M=  1.0  and  effort  is  constant 
an  increase  in  size  at  recruitment  to  77.5  cm 
does  not  change  yield  per  recioiit.  However, 
when  M  =  0.6,  the  same  change  in  size  at  re- 
cruitment causes  a  22%  increase  in  yield  per 
recruit.  When  M  =  1.0  and  size  at  recruitment 
is  held  constant,  a  doubling  of  effort  causes  a 
29%  increase  in  yield  per  recruit.  When  M  =  0.6, 
the  same  change  causes  a  14%  decrease  in  yield 
per  recruit.  When  M  =  1.0  and  size  at  reci-uit- 
ment  is  increased  to  77.5  cm.  a  doubling  of  effort 
causes  a  39%  increase  in  yield  per  reciTiit.  When 
M  =  0.6,  the  same  changes  cause  a  27%  increase 
in  yield  per  recruit. 

DISCUSSION 

The  use  of  results  of  our  study  must  be  based 
on  three  further  assumptions:  (1)  the  composi- 


tion of  the  fleet  will  not  change;  (2)  either  the 
gear  is  currently  dispersed  so  that  all  qualitative 
characteristics  of  the  population  are  available  to 
capture  by  each  gear,  or  that  the  dispersal  of 
gear  as  it  now  stands  will  not  change;  and  (3) 
recruitment  is  constant. 

Relation  Between  Composition  of  Fleet 
and  Optimum  Size  at  Recruitment 

The  preceding  text  has  assumed  that  the 
composition  of  the  fleet  remains  constant.  The 
history  of  the  fishery  reveals  that  the  composi- 
tion has  been  a  very  dynamic  process  and  there 
is  no  reason  to  believe  that  it  will  not  continue 
to  be.  Since  each  fishing  gear  has  a  different 
curve  of  size-specific  F,  changes  in  the  fleet 
composition  will  cause  changes  in  size-specific 
F  for  the  entire  fleet.  These  changes  will  cause 
changes  in  the  yield-per-recruit  isopleths. 

To  illustrate  the  influence  of  changes  in  fleet 
composition  on  management  strategy,  the 
optimum  size  at  recruitment  was  estimated  for 
441  combinations  of  baitboat  and  longline  effort. 
For  simplicity,  effort  of  purse  seiners  is  not 
included,  i.e.,  we  excluded  tw^o  variables — 
small  and  large  purse  seiners.  Multipliers  of 
effort  for  each  gear  ranged  from  0  to  2.0  with 
increments  of  0.1. 

The  results  (Table  10)  show  a  considerable 
range  in  the  estimates  of  optimum  size  at  re- 
cruitment and  that  minimum  size  regulations 
must  be  adjusted  to  changes  in  the  composition 
of  the  fleet  to  maintain  maximum  yield  per 
recruit.  As  an  example,  with  a  1.0  level  of  effort 
by  both  gears,  the  minimum  size  should  be 
about  72.5  cm.  If  this  were  instituted  as  a  mini- 
mum size  regulation,  the  bait  boat  effort  might 
decline  to  about  0.2  because  of  the  extreme  loss 
of  catch.  The  minimum  size,  therefore,  should  be 
lowered  to  67.5  cm.  Now  the  longline  effort 
might  increase  by  about  80%  due  to  the  decrease 
in  competition  from  bait  boats — the  minimum 
size  should  be  increased  to  77.5  cm.  Finally, 
suppose  an  innovation  occurs  in  bait  fishing 
such  that  non-nominal  effort  again  increases 
to  about  0.7 — the  minimum  size  should  be  raised 
further  to  about  82.5  cm.  These  changes  could 
occur  slowly  allowing  for  a  smooth  transition 
of  the  minimum  size  regulations.  When 
economics  are  involved,  however,  the  changes 
might  be  precipitous  causing  the  confusion  in 
the  above  example.  If  the  possible  changes  in 


57 


FISHERY  BULLETIN.  VOL.  72,  NO.  I 


Table  10. — Optimum  size  (cm)  at  recruitment  for  441  combinations  of  multipliers  of  effort  by 

bait  boats  and  longliners. 


Bait  boat 

multi 

plier 

Longline 

multiplier 

0 

0.1 

0.2 

0.3 

0.4 

0.5 

0,6 

0.7 

0.8 

0.9 

1.0 

1.1 

1,2 

1.3 

1.4 

1.5 

1.6 

1.7 

1.8 

1.9 

2.0 

0 

32.5 

32.5 

32.5 

32.5 

32.5 

32.5 

37.5 

37.5 

42.5 

42.5 

42.5 

42.5 

47.5 

47.5 

47.5 

47.5 

52.5 

52.5 

52.5 

52.5 

52.5 

0.1 

32.5 

32.5 

32.5 

37.5 

37.5 

42.5 

42.5 

42.5 

47.5 

47.5 

47.5 

47.5 

52.5 

52.5 

52.5 

52.5 

52.5 

52.5 

57.5 

57.5 

57.5 

0.2 

32.5 

37.5 

42.5 

42.5 

42.5 

47.5 

47.5 

47.5 

47.5 

52.5 

52.5 

52.5 

52.5 

52.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

0.3 

32.5 

42.5 

47.5 

47.5 

47.5 

47.5 

52.5 

52.5 

52.5 

52.5 

52.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

62.5 

62.5 

62.5 

0.4 

32.5 

47.5 

52.5 

52.5 

52.5 

52.5 

52.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

0.5 

32.5 

52.5 

52.5 

52.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

67.5 

67.5 

67.5 

0.6 

32.5 

57.5 

57.5 

57.5 

57.5 

57.5 

57.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

0.7 

32.5 

57.5 

57.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

0.8 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

62.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

72.5 

72.5 

72.5 

72.5 

0.9 

62.5 

62.5 

62.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

1.0 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

67.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

1.1 

67.5 

67.5 

67.5 

67.5 

67.5 

72.5 

72,5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

77.5 

77.5 

77.5 

1.2 

67.5 

67.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72,5 

72.5 

72.5 

72.5 

72.5 

72.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

1.3 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

72,5 

72.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

1.4 

72.5 

72.5 

72.5 

72.5 

72.5 

72.5 

77.5 

77.5 

77,5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

1.5 

72.5 

72.5 

72.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77,5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

82.5 

82.5 

1.6 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

1.7 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

1.8 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

77.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

1.9 

77.5 

77.5 

77.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

2.0 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

82.5 

composition  of  both  small  and  large  purse  sein- 
ers are  included,  the  attempts  to  achieve  some 
reason  in  the  minimum  size  regulation  based 
on  ma.ximum  yield  per  recruit  can  become  quite 
unwieldly. 

Dispersion  of  Gear  and  Yield  Per  Recruit 

The  second  assumption  could  be  important. 
For  example,  in  the  eastern  Pacific  yellowfin 
tuna  fishery  effort  has  expanded  farther  off- 
shore. Evidence  suggests  that  larger  fish  were 
farther  offshore  and  were  not  previously  fully 
available  to  the  fishery.  A  possible  consequence 
of  this  phenomenon  is  a  change  in  yield  per 
recruit.  Upon  analysis  of  the  data,  the  Inter- 
American  Tropical  Tuna  Commission  concluded, 
however,  that  the  possible  increase  is  minor 
(Joseph,  pers.  commun.).  The  surface  gears  have 
been  fishing  quite  close  to  shore  in  the  Atlantic. 
The  possibility  of  offshore  dispersal  of  the  sur- 
face fleets  and  the  effects  of  such  a  change  on 
yield  per  recruit  are  unknown. 

Interaction  Between  Minimum  Size  and 
Catch  Quota  Regulations 

If  recruitment  is  not  constant,  then  the  inter- 
action between  minimum  size  and  catch  quota 
regulations  should  be  examined.  Catch  quotas 


are  frequently  based  on  assessments  of  the 
maximum  sustainable  average  yield  (MSAY), 
usually  through  a  production  model  type  analy- 
sis. The  shape  of  the  total  yield  curve,  however, 
may  be  strongly  dependent  on  the  age  at  re- 
cruitment, t^.'.  Therefore,  the  interaction  be- 
tween the  two  types  of  regulation  should  be 
examined  before  a  singular  action  is  taken.  As 
an  illustration,  consider  a  population  consisting 
of  six  age-groups  with  the  growth  curve  and 
natural  mortality  coefficient  (M  =  0.8)  similar 
to  that  of  the  Atlantic  yellowfin  tuna  fishery, 
and  assume  also  that  recruitment  is  knife-edged 
at  19  mo.  Figure  19  (lower  curve)  shows  the 
total  annual  yield  as  a  function  of  fishing  mor- 
tality with  an  assumed  arbitrary  stock-recnait- 
ment  function.  Assume  further  that  the  fishery 
is  operating  at  an  F  =  1.0.  The  yield  per  recruit 
a.t  F  =  1.0  and  t^'  —  19  mo  is  5.39,  but  the  maxi- 
mum yield  per  recruit  is  6.11  at  t  '  =  27  mo. 
If  singular  action  were  taken  to  increase  t  '  to 
27  mo,  the  upper  total  yield  curve  in  Figure  19 
would  result.  Not  only  did  the  yield  per  recruit 
increase,  but  so  did  the  total  yield  at  F  =  1.0. 
In  addition,  the  MSAY  increased,  but  occurs 
at  a  much  higher  value  for  F.  A  phenomenon 
such  as  this  may  have  occurred  inadvertantly 
in  the  eastern  tropical  Pacific  with  the  introduc- 
tion of  purse  seiners  which  gave  a  better  yield 
per  recruit  than  the  existing  bait  boats  (Joseph, 
1970). 


58 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 

5.0 

4.0 


10  20 

FISHING    EFFORT 


30 


Figure    19. — Annual    equilibrium   yield    as   a  function    of 
fishing  effort  at  two  different  ages  at  recruitment,  t^'. 


The  above  result  of  singular  action  on  the 
minimum  size  regulation  resulted  in  a  fortuitous 
increase  in  total  yield  and  MSAY.  This  result 
may  not  always  occur,  however.  Consider  that  if 
the  fishery  were  operating  with  t  '  at  27  mo  and 
F  =  0.2.  then  the  yield  per  recruit  would  be 
2.77.  The  optimal  yield  per  recruit  is  3.02  at  a 
t  '  of  19  mo.  If  singular  action  were  taken  to 
lower  the  ^  '  to  19  mo,  a  slight  loss  of  total  yield 
would  occur  even  with  the  improved  yield  per 
recruit.  Even  more  disconcerting  would  be  the 
loss  in  potential  MSAY  of  28%.  The  fishery 
would  be  suboptimized  in  a  sense.  Since  the 
MSAY  is  usually  estimated  from  a  time  series 
of  catch  and  effort  data,  the  actual  potential 
which  could  have  been  realized  had  t  '  remain- 
ed  at  27  mo  would  likely  be  underestimated. 
It  is  likely  that  yield  per  recruit  studies  would 
continue  as  the  fishery  developed  effort  beyond 
F  =  0.2,  such  that  eventually  the  upper  curve 
might  be  attained;  this  is  because  the  optimal 
age  at  recruitment  increases  asymptotically  as 
F  increases.  The  low  initial  forecasts  of  MSAY, 
however,  could  hamper  development  of  the 
fishery. 

An  even  worse  consequence  of  singular  action 
on  yield  per  recruit  is  illustrated  in  Figure  20. 
Assume  the  fishery  is  operating  at  about  0.6 
unit  of  effort  with  an  age  at  recruitment  such 
'to  obtain  curve  A,  but  the  yield  per  recruit  is 
adjusted  to  maximal  for  the  age  at  recruitment 
giving  curve  B.  The  actual  MSAY  of  curve  A 


1,0  2,0 

FISHING    EFFORT 


3,0 


Figure  20. — Annual  equilibrium  yield  as  a  function  of  fish- 
ing effort  at  two  different  ages  at  recruitment  (see  text). 


might  never  be  realized  since  the  maximum 
equilibrium  yield  in  curve  B  is  also  at  0.6  unit 
of  fishing  effort.  This  case  represents  true  sub- 
optimization. 

CONCLUSIONS 

Although  there  are  some  uncertainties  in  our 
knowledge  of  the  parameters  that  enter  into 
calculations  of  yield  per  recruit  of  yellowfin  in 
the  Atlantic,  it  is  possible  to  come  to  some  con- 
clusions from  our  results. 

The  least  amount  of  data  and  assumptions 
is  involved  in  the  simplified  Beverton  and  Holt 
method.  Results  from  this  method  (Table  1) 
show  that,  in  all  but  a  few  extreme  cases  in  a 
wide  range  of  growth  and  mortality  parameter 
values,  an  increase  in  the  effective  minimum 
size  would  result  in  an  increase  in  yield  per 
recruit.  However,  our  most  reasonable  estimates 
of  the  parameters  indicated  that  at  the  current 
level  of  fishing,  an  increase  in  the  effective  mini- 
mum size  could  only  result  in  about  an  8% 
increase  in  yield  per  recruit.  We  conclude  that 
even  if  the  quality  of  our  data  is  poor  an  increase, 
probably  minor,  in  yield  per  recruit  of  Atlantic 
yellowfin  would  occur  if  the  effective  minimum 
size  is  increased  and  if  it  is  assumed  that  small 
yellowfin  tuna  were  not  dumped. 

We  next  assumed  that  our  most  reasonable 
estimate  of  growth,  constant  Z,  and  effective 
minimum  size  are  correct  and  constructed  yield- 
per-recruit  isopleths  with  the  Ricker  method  for 


59 


FISHERY  BULLETIN,  VOL.  72.  NO.  1 


several  values  of  natural  mortality.  The  results 
(Figures  1-3)  indicated  that  yield  per  recruit 
would  increase  from  0  to  20%  if  effective  mini- 
mum size  is  increased  and  effort  remains  con- 
stant. Again,  our  most  reasonable  estimate  of 
the  increase  is  only  8%  .  The  results  also  indicate 
that  little  if  any  increase  in  yield  i)er  recruit 
would  occur  if  fishing  effort  is  doubled  and 
effective  minimum  size  is  unchanged.  However, 
if  the  effective  minimum  size  is  increased  and 
effort  is  doubled,  a  modest  (20  to  40%  )  increase 
in  yield  per  recruit  could  occur.  All  these  results 
again  assume  that  there  would  be  no  dumping 
of  small  yellowfin  tuna. 

We  finally  assumed  that  the  available  data 
are  accurate  enough  to  also  make  reasonably 
accurate  estimates  of  size-specific  F.  When 
using  our  most  reasonable  parameter  estimates 
and  holding  effort  constant,  an  increase  in  size 
at  recruitment  to  55  cm  (3.2  kg)  would  obtain  a 
3.9%  increase  in  yield  per  recruit  and  to  77.5  cm 
(8.9  kg)  would  cause  less  than  a  10%  increase  in 
yield  per  recruit.  Increasing  the  size  at 
recruitment  to  55  cm  with  M  =  0.6  would 
cause  a  7%  increase  in  yield  per  recruit,  but  with 
M  =  1.0  only  a  1%  increase  would  occur.  In- 
creasing the  size  at  recruitment  to  77.5  cm  with 
M  =  0.6  would  increase  yield  per  recruit  by  22%  , 
but  with  M  —  1.0  no  increase  would  occur. 
When  size  at  recruitment  is  held  constant  and 
fishing  effort  is  doubled,  our  best  estimate  of  the 
change  in  yield  per  recruit  is  a  6%  increase. 
Our  estimates  ranged  from  a  14%  decrease  to  a 
29%  increase.  It  seems  safe  to  agree  with  the 
report  of  the  Abidjan  meeting  that  if  conditions 
remain  constant,  there  is  little  to  be  gained  on 
a  yield-per-recruit  basis  from  increases  in  fish- 
ing effort.  With  a  doubling  of  fishing  effort  and 
an  increase  in  size  of  recruitment  to  55  cm,  our 
most  reasonable  estimate  is  a  15%  increase  in 
yield  per  recruit,  with  a  range  of  a  1%  decrease 
to  a  35%  increase.  When  size  at  recruitment  is 
increased  to  77.5  cm  and  fishing  effort  is  doubled, 
our  most  reasonable  estimate  of  the  change 
in  yield  per  recruit  is  a  30%  gain;  however,  the 
estimates  range  from  27  to  44%  .  Thus  it  appears 
that  if  it  is  possible  to  increase  the  size  at 
recruitment,  a  doubling  of  effort  would  i)roduce 
a  modest  increase  in  yield  per  recruit.  These 
results,  it  must  be  noted,  assume  that  small 
yellowfin  tuna  are  not  dumped. 

It  is  interesting  to  note  that  the  same  general 
conclusions   would    be   made   using   either  the 


knife-edged  recruitment  or  size-specific  F 
approaches.  The  size-specific  F  approach,  in 
addition,  allows  us  to  examine  more  precisely 
the  effects  of  an  absolute  minimum  size  regula- 
tion and  the  effects  on  each  gear.  The  general 
conclusions  from  both  aspects  of  this  study  also 
agree  fairly  well  with  those  of  Joseph  and  Tom- 
linson  (1972,  see  footnote  4).  It  is  not  surprising, 
however,  that  results  from  the  size-specific  F 
approach  agree  with  theirs  because  they  used 
similar  methodology  and  data.  Both  estimates 
suggest  that  under  present  conditions  the  fisheiy 
is  near  the  point  of  maximum  yield  per  recruit. 
Specifically  addressing  the  recommendations 
outlined  in  the  introduction  section  of  this  paper 
for  considering  a  minimum  size  between  3.2 
and  10  kg,  we  offer  the  following  results  based 
on  our  most  reasonable  parameter  estimates: 

1.  Minimum  size  limit  55  cm  (3.2  kg): 

a)  Current  levels  of  fishing  mortality: 

i)  No  dumping  results  in  a  4%  increase 
in  landed  yield  per  recruit 

ii)  100%  dumping  results  in  a  3%  de- 
crease in  landed  yield  per  recruit 

b)  Doubling  fishing  mortality: 

i)  No  dumping  results  in  a  15%  in- 
crease in  landed  yield  per  recruit 

ii)  100%  dumping  results  in  a  1%  in- 
crease in  landed  yield  per  recruit 

2.  Minimum  size  limit  77.5  cm  (8.9  kg): 

a)  Current  levels  of  fishing  mortality: 

i)   No  dumping  results  in  a  9%    in- 
crease in  landed  yield  per  recruit 
ii)   100%  dumping  results  in  a  13%  de- 
crease in  landed  yield  per  recruit 
b.   Doubling  fishing  mortality: 

i)   No  dumping  results  in  a  31%   in- 
crease in  landed  yield  per  recruit 
ii)   100%  dumping  results  in  a  16%  de- 
crease in  landed  yield  jier  recruit. 

The  55-cm  (3.2  kg)  minimum  size  limit  would 
likely  be  of  more  benefit  to  the  tuna  fishery  than 
the  larger  minimum  size  limit  of  77.5  cm  (8.9 
kg)  since  less  dumping  would  occur.  Therefore, 
there  would  likely  be,  on  the  average,  an  increase 
in  landed  yield  per  recruit  at  the  current  or 
greater  levels  of  fishing  mortality;  whereas, 
if  a  larger  size  limit  were  adopted,  there  would 
likely  be,  on  the  average,  a  decrease  in  landed 
yield   per   recruit   at   current   levels   of  fishing 


60 


LENARZ  ET  AL.:  YIELD  PER  RECRUIT  OF  ATLANTIC  YELLOWFIN  TUNA 


mortality  and  less  of  an  increase  (perhaps  even 
a  decrease)  in  landed  yield  per  recruit  than  with 
the  55-cm  (3.2  kg)  minimum  size  and  an  increase 
in  fishing  mortality. 

The  results  of  this  paper  were  obtained  using 
reasonable  assumptions  and  all  available  data  on 
Atlantic  yellowfin  tuna.  As  we  increased  the 
number  of  assumptions  we  increased  the  number 
of  conclusions.  We  think  that  it  is  unlikely  that 
use  of  tecnhiques  not  used  in  this  paper  would 
result  in  conclusions  that  are  significantly  differ- 
ent from  ours.  That  is,  an  increase  in  effective 
minimum  size  would  result  in  a  minor  increase 
in  yield  per  recruit,  an  increase  in  effort  without 
increasing  effective  minimum  size  would  not 
appreciably  increase  yield  per  recruit,  and  an 
increase  in  effective  minimum  size  and  effort 
would  result  in  modest  gains  in  yield  per  re- 
cruit. We  wish  to  emphasize  that  these  conclu- 
sions are  based  on  a  number  of  assumptions. 
We  consider  the  assumptions  reasonable,  but 
because  they  are  assumptions  any  management 
decisions,  including  the  decision  of  taking  no 
action,  should  be  followed  with  careful  evaluation 
of  the  results. 


ACKNOWLEDGMENTS 

We  are  indebted  to  James  Joseph  and  Patrick 
Tomlinson  of  the  Inter-American  Tropical  Tuna 
Commission  for  their  useful  comments  on  this 
paper.  This  study  would  not  have  been  possible 
without  the  many  valuable  contributions  of  data 
and  ideas  by  scientists  of  the  nations  that  parti- 
cipate in  the  International  Commission  for  the 
Conservation  of  Atlantic  Tunas. 


LITERATURE  CITED 

Beverton,  R.  J.  H.,  AND  S.  J.  Holt. 

1956.  A  review  of  methods  for  estimating  mortality 
rates  in  exploited  fish  populations,  with  special 
reference  to  sources  of  bias  in  catch  sampling.  Rapp. 
P.-V.  Reun.  Cons.  Perm.  Int.  Explor.  Mer  140:67-83. 

1957.  On  the  dynamics  of  exploited  fish  populations. 
Fish.  Invest.  Minist.  Agric.  Fish.  Food.  (G.B.). 
Ser.  II,  19,533  p. 

1959.  A  review  of  the  lifespans  and  mortality  rates 
of  fish  in  nature,  and  relation  to  growth  and  other 
physiological  characteristics.  //;  G.  E.  W.  Wolsten- 
holme  and  M.  O'Connor  (editors).  Ciba  Founda- 
tion Colloquia  on  Ageing  5:142-180.  J.  &  A. 
Churchill  Ltd.,  Lond. 


1966.  Manual  of  methods  for  fish  stock  assess- 
ment. Part  II  -  Tables  of  yield  functions.  FAO 
(Food  Agric.  Organ.  U.N.)  Fish.  Tech.  Pap.  38 
(Revision  1),  67  p. 

Calkins.  T.  P. 

1965.  Variation   in   size   of  yellowfin  tuna   (Thunnus 
alhacares)      within      individual      purse-seine      sets. 
[In  Engl,  and  Span.]  Inter-Am.  Trop.  Tuna  Comm., 
Bull.  10:463-524. 
Davidoff,  E. 

1969.  Variations  in  year-class  strength  and  estimates 
of  the  catchability  coefficient  of  yellowfin  tuna, 
Thunnus  alhacares,  in  the  eastern  Pacific  Ocean. 
[In  Engl,  and  Span.]  Inter-Am.  Trop.  Tuna  Comm., 
Bull.  14:1-44. 

Food  and  Agriculture  Organization. 

1968.  Report  of  the  meeting  of  a  group  of  experts 
on  tuna  stock  assessment  (under  the  FAO  expert 
panel  for  the  facilitation  of  tuna  research).  FAO 
(Food  Agric.  Organ.  U.N.).  Fish.  Rep.  61,  45  p. 

Gulland,  J.  A. 

1965.  Estimation  of  mortality  rates.  Annex  to  Arctic 
Fish.  Working  Group  (Gadoid  Comm.),  Int. 
Counc.  Explor.  Sea  3,  9  p. 

Hennemuth,  R. 

1961.  Year  class  abundance,  mortality  and  yield-per- 
recruit  of  yellowfin  tuna  in  the  eastern  Pacific  Ocean 
1954-59.  [In  Engl,  and  Span.]  Inter-Am.  Trop. 
Tuna  Comm..  Bull.  6: 1-5  1. 

Joseph.  J. 

1970.  Management  of  tropical  tunas  in  the  eastern 
Pacific  Ocean.  Trans.  Am.  Fish.  Soc.  99:629-648. 

LeGuen,  J.  C,  AND  G.  T.  Sakagawa. 

1973.  Apparent    growth    of  yellowfin   tuna   from   the 
eastern   Atlantic   Ocean.  Fish.    Bull.,   U.S.    71:175- 
187. 
Murphy,  G. 

1965.  A  solution  of  the  catch  equation.  J.  Fish.  Res. 
Board  Can.  22: 191-202. 
Paulik  ,  G.  J.,  AND  W.  H.  Bayliff. 

1967.  A  generalized  computer  program  for  the  Ricker 
model  of  equilibrium  yield  per  recruitment.  J.  Fish. 
Res.  Board  Can.  24:249-259. 

PlANET,  Y..  AND  Y.  Le  HiR. 

1971.  La  campagne  thoniere  1970  a  Pointe-Noire. 
[Engl.  Abstr.]  Doc.  Sci.  Cent.  ORSTOM  (Off. 
Rech.  Sci.  Tech.  Outre-Mer)  Pointe-Noire,  Nouv. 
Ser.  17:1-15. 

Ricker,  W.  E. 

1958.  Handbook  of  computation  for  biological  statis- 
tics offish  populations.  Fish.  Res.  Board  Can.,  Bull. 
119,  300  p. 

SCHAEFER. M.  B. 

1957.  A  study  of  the  dynamics  of  the  fishery  for  yel- 
lowfin tuna  in  the  eastern  tropical  Pacific  Ocean. 
[In  Engl,  and  Span.]  Inter-Am.  Trop.  Tuna  Comm., 
Bull.  2:245-285. 
Tomlinson,  P.  K. 

1970.  A  generalization  of  the  Murphy  catch  equation. 
J.  Fish.  Res.  Board  Can.  27:821-825. 
Wise.  J.  P. 

1972.  Yield-per-recruit  estimates  for  eastern  tropical 
Atlantic  yellowfin  tuna.  Trans.  Am.  Fish.  Soc. 
101:75-79. 


61 


SYSTEMATICS  AND  DISTRIBUTION  OF  THE  FOUR  SIBLING 
SPECIES  COMPRISING  THE   GENUS  PONTELLINA   DANA 

(COPEPODA,  CALANOIDA) 

A.  Fleminger  and  K.  Hulsemann' 

ABSTRACT 

A  global-scale  study  on  systematics  and  distribution  of  the  epipelagic  copepod  genus  Pontel- 
lina  (Family  Pontellidae)  was  carried  out  on  materials  sorted  from  about  2,000  zooplankton 
samples  collected  at  stations  scattered  throughout  the  circumglobal  warm-water  belt.  Four 
distinctive  species  were  found  and  described,  three  being  new  to  science. 

Each  species  was  examined  for  evidence  of  conspicuous  polytypy  and  geographical  varia- 
tion. Morphology  and  geographical  distribution  were  utilized  comparatively  to  perceive  re- 
lationships that  would  shed  light  on  the  nature  of  selection  pressures  operating  on  external 
morphology.  Morphology  and  distribution  were  also  considered  to  determine  phylogenetic 
relationships  within  the  genus. 

The  geographic  distribution  of  the  four  species  was  considered  relative  to  major  near-sur- 
face hydrographic  features  characterizing  tropical  and  subtropical  latitudes  and  especially 
the  occurrence  of  eutrophic  and  oligotrophic  areas  in  each  ocean. 

Sets  of  similarly  collected,  quantitative  samples  were  used  to  determine  the  relative  abun- 
dance of  each  species,  and  co-occurrences  among  the  species  were  tested  by  recurrent  group 
analysis.  The  trophic  role  of  each  species  was  considered  and  conclusions  tested  by  a  limited 
series  of  observations  on  stomach  contents. 


Geographical  perspective,  too  often  absent 
from  studies  on  marine  plankton,  is  a  powerful 
tool  for  dealing  with  sibling  species.  Evidence 
of  reproductively  isolated  populations  that  are 
morphologically  similar  in  planktonic  calanoids 
and  other  zooplankton  as  well  has  been  present- 
ed in  a  number  of  studies  combining  geograph-' 
ical  distribution  and  morphology  (e.g.,  Schmaus, 
1917;  Johnson,  1935;  Bowman,  1955,  1967; 
Brodsky,  1959;  Foxton,  1961;  Jones,  1966; 
Fontaine,  1967;  Fleminger,  1967b;  Frost  and 
Fleminger,  1968;  Mullin,  1969;  Jaschnov, 
1970).  Our  resolution  of  the  sibling  species 
comprising  the  genus  Pontellina  Dana  is  of- 
fered as  an  additional  example. 

In  contrast  to  the  22  nominal  species  by  our 
count  comprising  Poiitellopsis  Brady,  the  pontel- 
lid  genus  most  similar  in  morphology,  P(>)itel- 
lina  has  been  universally  regarded  as  monotypic 
since  Giesbrecht's  (1892)  monumental  review 
of  planktonic  marine  copepods.  Mori  (1937) 
presented   evidence   of  polytypy   in   Pontellina 


'  Scripps    Institution    of    Oceanography,    University    of 
California  at  San  Diego,  P.O.  Box  1529,  La  Jolla,  CA  92037. 


Manuscript  accepted  July  1973. 

FISHERY  BULLETIN:  VOL.  72,  NO.  1,  1974. 


with  his  description  of  a  unique  male  distin- 
guished by  an  unusual  chela.  Apparently  in- 
fluenced by  Sewell's  views  on  copepod  ontogeny 
(1929,  1932),  Mori  ascribed  the  specimen 
taken  off  Japan  to  pliunata,  suggesting  that  it 
represented  the  fully  mature  state  and  that 
previous  descriptions  of  the  plumata  male  were 
based  on  incompletely  mature  specimens.  Our 
study  was  prompted  by  the  appearance  of  other 
seemingly  minor  morphological  features  dis- 
tinguishing adult  individuals  of  both  sexes  that 
correlated  with  indications  of  distinctive  geo- 
graphical distributions  among  the  observed 
forms. 

In  this  paper  we  redefine  the  genus  and 
describe  its  four  species.  The  distribution  of 
each  species  is  considered  in  the  context  of  our 
geographical  records.  Distribution  is  also  dis- 
cussed with  respect  to  morphological  similarities 
among  the  species  and  relationships  to  general 
oceanic  circulation.  Detailed  considerations 
and  views  regarding  environmental  conditions 
that  shape  these  distributions  and  the  circum- 
stances yielding  the  contemporary  Pontellina 
speciation  pattern  will  be  presented  separately 
elsewhere. 


63 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


MATERIALS  AND  METHODS 

Materials 

Plankton  samples  examined  for  the  genus 
Pnntdlitta  in  the  course  of  this  study  were  ob- 
tained from  three  major  sources:  the  zooplankton 
collections  of  Scripps  Institution  of  Oceanog- 
raphy. R.  Scheltema's  collection  of  Atlantic 
zooplankton  maintained  at  the  Woods  Hole 
Oceanographic  Institution,  and  quantitative 
sortings  of  Pontelliiia  from  the  International 
Indian  Ocean  Expedition  plankton  collections, 
processed  and  furnished  by  the  Indian  Ocean 
Biological  Centre,  Cochin,  India.  Additional 
collections  or  specimens  were  obtained  with 
the  kind  cooperation  of  the  National  Marine 
Fisheries  Service;  the  U.S.  Naval  Oceanographic 
Office;  T.  K.  S.  Bjornberg,  University  of  Sao 
Paulo,  Brazil;  A.  DeDecker,  Division  of  Sea 
Fisheries,  Cape  Town,  Republic  of  South 
Africa;  B.  Kimor,  Israel  Oceanographic  and 
Limnological  Research  Ltd.,  Haifa,  Israel; 
J.  E.  H.  Legare,  Instituto  Oceanografico,  Cu- 
mana,  Venezuela;  D.  J.  Tranter,  CSIRO,  Cron- 
ulla,  Australia. 

Geographical  distribution  of  the  samples  is 
shown  in  Figure  la,  and  the  localities  yielding 
Pontellina  are  listed  by  species  in  Table  1.  These 
collections  broadly  outline  most  major  sectors 
of  the  Pacific,  Indian,  and  Atlantic  Oceans,  the 
South  Atlantic  being  the  notable  omission. 
Most  of  the  samples  were  taken  with  open  con- 
ical plankton  nets  V2  to  1  m  in  diameter  at  the 
mouth.  Nets  were  towed  obliquely,  vertically, 
or  horizontally  between  the  surface  and  200  m 
of  depth.  Stations  were  occupied  irrespective  of 
time  of  day  or  cloud  cover. 

Sample  Analysis 

Plankton  samples  were  examined  in  rect- 
angular plastic  trays  (5  X  7.5  X  1  cm)  at  16  X 
magnification  with  the  aid  of  a  stereomicro- 
scope.  The  entire  sample  was  scanned  if  the 
settling  volume  did  not  exceed  20  cc.  Otherwise 
volumetric  subsamples  were  drawn,  generally 
with  the  aid  of  a  10-cc  piston  pipette,  after  stan- 
dardizing the  total  volume  and  stirring  vigorous- 
ly. Usually  more  than  2%  of  the  total  sample 
was  examined,  the  actual  percentage  varying 
inversely  with  the  size  of  the  original  sample. 

Estimates    of   abundance    and    frequency    of 


occurrence  were  obtained  from  particular 
sets  of  quantitative  samples  (Figure  lb)  selected 
for  homogeneity  of  sampling.  In  the  case  of 
Pacific  zooplankton  samples  collecting  proce- 
dures followed  standard  CalCOFI  (California 
Cooperative  Oceanic  Fisheries  Investigations) 
sampling  practices  (cf.  Smith,  1971).  The  Indian 
Ocean  samples  (Figure  lb)  are  a  composite  of 
quantitative  Indian  Ocean  Standard  Net  tows 
(Currie,  1963)  obtained  by  various  participants 
in  the  International  Indian  Ocean  Expedition. 
Preliminary  quantitative  processing  of  these 
samples  was  carried  out  by  the  Indian  Ocean 
Biological  Centre,  Cochin,  India  (Tranter, 
1969).  The  Centre  provided  us  with  specimens 
of  PontelUua  sorted  from  known  fractions  of 
the  original  samples.  Standard  quantitative 
sampling  from  the  Atlantic  Ocean  was  unavail- 
able to  us. 

Specimen  Analysis 

For  routine  examinations  specimens  were 
mounted  loosely  in  a  drop  of  glycerol.  To  en- 
hance examination  of  fine  denticles  and  spines, 
soft  tissue  was  removed  by  warming  specimens 
in  a  10%  aqueous  solution  of  KOH  at  about 
90 °C  for  1  to  2  h.  After  a  brief  rinse  in  distilled 
water  the  cuticle  was  transferred  to  35%  ethanol, 
then  to  70%  ethanol  for  1  min  and  then  stained 
in  a  solution  of  1%  Chlorazol  Black  E  dissolved 
in  70%  ethanol.  Intensive  staining  usually  re- 
quires not  more  than  V2  min  and  should  be  fol- 
lowed immediately  by  a  1-min  rinse  in  distilled 
water. 

Examinations  and  dissections  were  carried 
out  under  stereomicroscopes  at  12  X  to  100  X 
magnification  and  under  compound  micro- 
scopes at  various  magnifications  up  to  600  X  . 
All  drawings  were  made  with  the  aid  of  a 
compound  microscope  equipped  with  a  drawing 
attachment. 

Several  females  and  males  of  each  species 
were  studied  under  a  scanning  electron  micro- 
scope after  preparation  by  the  critical  point 
drying  method  (Cohen,  Marlow,  and  Garner, 
1968). 

Measurements 

For  each  species  intact  specimens  with  a 
reasonably  straight  urosome  were  chosen  at 
random  from  localities  scattered  over  the  entire 


64 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


Figure  la. — Geographical  distribution  of  sampling  stations.  Each  open  circle  represents  one  or  more  samples.  Over- 
lapping stations  and  replicate  sampling  are  omitted  for  the  purpose  of  clarity.  Areas  intensively  surveyed  are  shown 
symbolically  as  evenly  spaced  grid. 


40°  N 

20°  N 
0° 
20°  S 

— '40°S 


92°  W 


Figure  lb.  —  Distribution  and  identification  of  sets  of  quantitative  zooplankton  samples  used  to  estimate  the  frequency 
of  Poniellina  in  the  Pacific  Ocean.  Sets  were  selected  for  similarity  of  sampling;  i.e.,  each  set  obtained  by  the  same 
procedures  and  stations  occupied  in  a  closely  ordered  sequence  during  the  same  cruise.  Dots  indicate  the  sampling 
localities.  Indian  Ocean  localities  represent  Indian  Ocean  Standard  Net  samples  collected  during  the  International 
Indian  Ocean  Expedition  that  were  examined  quantitatively  for  Pontellina  in  the  course  of  this  study.  See  Table  14  for 
summary  of  sampling  data  and  Materials  and  Methods  for  analytical  details. 


65 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 
Table  1. — Localities  yielding  Pontellina  listed  by  species. 


Location 

and 
station 


Source  of 

collecting 

data' 


Location 

and 
station 


Source  of 

collecting 

data' 


PONTELLINA  PLATYCHELA 


Atlantic  Ocean: 
RV  Alaska  4: 
Amazon  Exp.: 
RV  AtUintis  11-20: 


-31: 


Circe  II  Exp.: 
RV  David  Starr 
Jordan  57: 


-32: 


B 

12 

14 

15 

16,  24,  25,  26, 

F 

31, 

34, 

35, 

38,  39,  42,  49, 

41, 

43, 

47, 

48,  49,  50,  54, 

85, 

86, 

88, 

89,  90,  94A,  98, 

Cato  6  Exp.: 

RV  Chain  35: 
RV  Chain  60: 
La  Creuse  Exp.: 
Lusiod  VII  Exp. 

RV  Oregon: 


RV  Thomas 

Washington: 
10°29'N  64°12'W 


29,  46. 

17,  19. 

2,  6,  9,  10, 

27,  28,  29, 

50,  56,  60. 

25,  38,  40, 

55,  56,  57. 

60,  61,  84, 

108,  110,  112. 

34  (26°  1  rS  38°46'W),  46  (34°37'S 

47°58'W). 

19,29,33,39,43. 

13,  16. 

4,  5,  7,  10. 

69H-4,  73  H-5,  79(00°56'N  11°29'W), 

80  H-12,  81  H-13. 

1289(17°10'N  74°20'W),  1291 

{17°50'N  72°00'W),  1292  (18°08'N 

74°35'W),  1293  (19°55'N  74°10'W), 

1294  (19°45'N  74°45'W). 


Cumand,  Venezuela). 


PONTELLINA  PLUM  ATA 


Atlantic  Ocean 

RV  Alaska  1 

2 

4 

5 

Amazon  Exp 

RV  Atlantis  IIU 

■20 

-31 


-32: 


Bjornberg: 
Cato  6  Exp. 


RV  Chain  49: 

60: 
Cyprus: 
RV  Delaware: 
la  Creuse  Exp.: 
Lusiad  VI I  Exp. 

N-3  Cruise: 
RV  Oregon: 


RV  Theodore 
N.  Gill  2: 

5: 
7: 
8: 
Pacific  Ocean: 
Aries  I  Exp.: 
Bonacca  Exp.: 
CaiCOFI  Cruise 
5804: 

5810; 
5901: 

Capricorn  Exp.: 
Circe  I  Exp.: 


29. 

46,  56. 

10,  29,  40,  42,  46. 

42. 

19,  20. 

9,  35,  44,  48. 

2,  22. 

2,  5,  6,  7,  8,  9,  11,  13,  15,  17,  18, 
21,  23,  24,  25,  26,  28,  29,  38,  44,  57. 
61,  62,  63,  64,  66,  67,  68,  72,  73,  74, 
87,  118D,  119. 

M  242  (11°24'S  33°19'W). 
33  (25°16'S  49°01'W),  34  (36°11'S 
38°46'W),  36  (30°06'S  39°2rW), 
39  {30°26'S  35°20'W),  40  {30°56'S 
3r21'W),  41  (32°28'S  28°17'V\/), 
48  (30°10'S  39°23'W),  49  (25°50'S 
39°24'W),  50  (24°33'S  41°02'W). 

3,  5,  8,  9,  10,  11,  14,  15,  16,  17, 
19,  20,  21,  22,  23,  26,  27. 

17. 

10-20  (off  coast  of  Israel). 

7,  19,  20,  25. 

3,  4,  5,  7,  10. 

21  (30°23'S  02°47'W),  24  (30°09'S 

04°42'W),  52  (19°13'S  13°44'W). 

4  (30°55'N  79°21'W). 

1291  (17°50'N  72°00'W),  1292 

(18°08'N  74°35'W),  1294(19°45'N 

74°45'W). 

41. 

3,  4. 

4,  5. 

5,  9. 


30(09°20'S  127°05'W). 

22.  A 

80.110,  60.110,  100.80.  E 

100.70,  120.90. 

100.70. 

1,2,3,28,29,30,31,32,33,35.  A 

3,  4.  B 


9,  11,  12,  13,  14. 

025(10°30'N  119°43.5'W),  076 
(03°20'N  119°42'W),  116(7°30'N 
119°43.5'W),  123(07°00'N  120°40'W), 
130(09°3rN  120°39'W),  132 
(09°45'N  120°12'W). 


60: 

071  (02°00'N  117°17'W),  122 
(04°00'N    116°41'W),  134  (07°05'N 
116°58'W). 

EASTROPAC  Exp.: 

RV  Argo  1 1 : 

197,  215,  234,  242,  250,  266,  282, 
287,  291,  299,  303,  308,  320,  328. 

D 

RV  David  Starr 

F 

Jordan  12: 

053,  059,  063. 

D 

RV  Rockawav  13: 

056. 

D 

B 

EQUAPAC  Exp.: 

A 

RV  Horizon: 

19,  20,  21,  22,  23,  24,  25,  26,  27, 
29,  30,  31,  32,  34,  35,  36,  37,  38, 
39,  40,  41. 

A 

RV  Stranger: 

3,  5,  11,  15,  17,  19,  21,  23. 

A 

Monsoon  Exp.: 

1,2,  3,  4,  5,  7,  35,  37,  38,  39,  40. 

A 

Muddouber  Exp.: 

TDS-86. 

B 

Naga  Exp.  SI lA: 

160,  164,  169,  169A. 

B 

B 

SUB: 

5,  10,  16,  17,  20,  24,  27,  29,  31,  36, 
38,  41,  50,  58,  62,  66,  78,  86. 

NAVOCEANO  RV  H 

itnt 

1968: 

12,  14. 

B 

1969  (Apr.): 

8,  31-6. 

1969  (May): 

9. 

H 

1969  (Oct.): 

3. 

1969  (A-14): 

6,  16. 

NAVOCEANO  RV 

Silas  Bcni: 

1-10,  1-11,  1-12,  1-16,  1-20. 

B 

B 

Piquero  IV  Exp.: 

12,  16,  17. 

B 

F 

V  Exp.: 

40D,  43D,  44,  45D,  46,  47N,  47D,  48, 
49,  50D. 

Scon  IV  Exp.: 

1,  2,  35D,  6. 

B 

V   Exp.: 

5. 

Scorpio  1 1  Exp.: 

92,  96,  98,  112,  114,  118,  120,  122, 
138,  140,  144,  146,  148,  152,  154, 
160,  164,  166,  168,  170,  172,  174, 
176,  180,  182. 

B 

Shellback  Exp.: 

47,  51,  103. 

A 

TO-58-1  Cruise 

(Scot): 

27,  29,  37,  56B. 

B 

TO-60-2  Cruise 

(Step  1): 

62. 

B 

RV  Townsend  Cromwell 

51:  064  (03°30'S  120°45'W), 

085  (02°29'N  120°49'W). 

TRANSPAC  Exp.:  85A,  87A,  87B,  89A,  92A,  92B,  94A, 

96A,  98A,  98B,  lOOA,  102A, 
106A,  108A,  llOA,  112A,  1  18A, 
118B,    122A,    126A,    126B,    132A,    134A, 
142A,  143A. 

24,  24A,  25,  25A,  27,  27A,  28,  28A, 
31A,  32,  32A,  33,  35. 


Troll  Exp.: 

29,  30A,  31 
32°15'N  117°16'W  (15-VIII-1962). 
Indian  Ocean: 

Circe  II  Exp.:  Camera  3. 

Ill  Exp.:  22,  25,  27,  28,  29,  38. 

RV  Diamantina:  3/93/63  (27°30'S  110°00'E). 

Dodo  VI  Exp.:  13,  65,  70,  74,  81. 

RV  Gascovne:  Gl/5/63  (27°30'S  1  10°00'E), 

G  1/32/63  (28°55'S  110°00'E). 
International  Indian  Ocean  Exp. 
RV  Anton  Brimn 

A:  6,  8,  9A,   11. 

1:  30,  33,  51,  53,  57,  58,  60,  67,  70,  78. 

2:  106,   108,    110,   111,   112,   116,   117,  118, 

120,   121,   127,   134,   135,   137,   141,   142, 
143. 
3:  149. 


66 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 

Table  1. — Continued 


Location 

Source 

of 

Location 

Sc 

urce 

of 

and 

collecting 

and 

CO 

Meet 

ng 

station 

data 

station 

data 

1 

4A: 

189. 

NAVOCEANO  RV  H 

lint 

5: 

283,  284,  295,  302,  312,  315,  318,  320, 
322,  324,  326A,  327B. 

1968 

1969  (May): 

14. 
9. 

B 

6: 

328,  333. 

1969  (Oct.): 

2,  3. 

7: 

370,  371. 

1969  (A. 14): 

7,  9. 

8: 

404,  413,  415. 

NAVOCEANO  RV 

RV  Argo 

Silas  Bent: 

Ml,  1-12,  116,  1-17,  1-18,  1-20. 

B 

(Lusiad  Exp.): 

3,  8,  9,  10,  12,  15,  17,  18,  20,  34,  40, 

C 

Piquero  V  Exp.: 

40D,  45D,  48. 

B 

41,  44,  45,  46,  49,  55,  61,  65,  71,81, 

Scan  IV  Exp.: 

1,2,  3,  35D,  HF  18,  DSDP  17,  48D. 

B 

86,  96. 

V  Exp.: 

4,5. 

RV  Diamuniina 

Scorpio  1 1  Exp.: 

156, 

B 

2  0962): 

61,  100. 

C 

Shellback  Exp.: 

100,  105. 

A 

)   (1963): 

4,  47. 

TO-58-1  Cruise 

3(1963): 

113. 

(Scot): 

14. 

B 

2  (  1  964) : 

lOOA. 

TRANSPAC  Exp.: 

87B,  92A,  96A,  98B. 

A 

5  ( 1 964) : 

212. 

Troll  Exp.: 

24A,  25,  25A,  26,  27A,  28,  30,  30A, 

A 

1   (1965): 

60. 

31A,  32,  32A. 

RV  Dncovery  1: 

5031,  5038. 

c 

Indion  Ocean: 

RV  Discovery  3: 

5267A,  5269A,  5275,  5371A,  5387, 

Circe  III  Exp.: 

22,  23,  25,  26,  27,  29. 

B 

5400B,  5412A,  5437A,  5548. 

Dodo  VI  Exp.: 

12,  70,  81,  Mombasa  Harbor. 

A 

RV  Kagoshimu  Mam 

International  Indian 

Ocean  Exp. 

3: 

7,  15,  16,  24,  30. 

c 

RV  Anton  BriiHU 

RV  Kistnu  13: 

296,  301. 

c 

A: 

6,  7,  lOA,  11. 

C 

RV  Kayo  Mani 

1: 

25,  28,  29,  30,  32,  33,  34,  35,  36,  43 

14: 

19. 

c 

51,  52,  53,  55,  56,  57,  58,  68,  69,  70 

16: 

20. 

71,  72,  73,  75,  76,  79. 

RV  Meieur: 

90,  93B,  95B,  114,  1 16A,  116B, 
126A,  130A,  137,  138,  144,  151,  157, 
168,  173,  181. 

c 

2: 
4A: 

106,  108,    109,  110,    111,   112,    113, 
120,  121,  123,  142. 
189,  198. 

114, 

RV  Oshoro  Marii 

5: 

283,  284,  323,  287A,  323A,  327B,  327C. 

1: 

3,  17,  44,  45,  50. 

c 

6: 

328,  333,  336 

7: 

7,  8. 

7: 

358,  367,  371. 

11: 

3,  10,  19,  23. 

8: 

413,  414. 

RV  Vmitaka  Mam 

RV  Argo 

23: 

1-7. 

c 

(Lusiad  Exp.): 

3,  12,  41,  46,  49,  55,  65,  71,  81,  85. 

C 

24: 

6303. 

RV  Diamautina 

RV  Vciruna  30: 

1775. 

c 

2  (  1 962) : 

61. 

RV  Vitiaz  35: 

5198A,  5198B,  5200,  5205,  5207, 
5208,  5217,  5221,  5224,  5278. 

c 

1   (1963): 
RV  Discovery 

47. 

C 

36: 

5336. 

1: 

5031,5038. 

C 

Lusiad  1  Exp.: 

2,  4. 

A 

3: 

5267,  5269A,5385,5412A. 

II  Exp.: 

5,  8,  9,  10,  11,  12,  13,  15,  19,  20,  29, 

RV  Kistna: 

296,  298,  301,  304,  514,  515. 

C 

39,  45,  51,  61,  62,  66,  76,  88,  96. 

RV  Meteor: 

90,  91,  93A,  93B,  95B,  96,  106,  114, 

c 

V  Exp.: 

VI  Exp. 
Monsoon  Exp.: 


Pacific  Ocean: 
Aries  I  Exp.: 
CalCOFI  Cruise 

5810: 

Capricorn  Exp.: 
Circe  1 1  Exp.: 


40,  42,  43,  45,  46,  47,  50,  59,  60,  64, 
68,  73,  76,  78,  84,  92,  96,  100,  104. 
1,  8. 
7,  10,  11,  12,  18,  19. 

PONTELLINA  MORII 


30  (09°20'S  127°05'W). 

153.70. 
2,  4,5,  35. 
9,  11,  12,  14. 


E 
A 

B 


RV  David  Starr  Jordan 


57: 


60: 


116  (07^30'N  119°43.3'W),  123 

(07°00'N  120°40'W). 

122  (04°00'N  116°4rW),  134(07°05'N 

116°58'W). 

197,  211,  234,  320,  328. 


RV  Natal  6. 

RV  Oshoro  Man,  11: 

RV  Pioneer  442: 

RV  Uniitaka  Maru  23 

RV  Varitna  30: 

104: 

106: 

RV  Vitiaz  35: 

Lusiad  I  Exp.: 
II  Exp.: 

V  Exp.: 

VI  Exp.: 

Monsoon  Exp.: 


116A,  130A,  137,  138,  145,  151,  154, 
157,  161B,  168,  186,  198. 
163,  174.  C 

3,  13,  19.  C 

1,35.  C 

1-7.  C 

1775.  C 

2007,  2009. 
2041. 

5224.  C 

2.  A 

1,  10,   11,  13,  14,   16,  27,  55,  62,  66,  90. 
43,  45,  58,  60,  66,  68,  76,  78. 
1,  8. 
7,  11,  14.  A 


EASTROPAC  Exp. 
RV  Argo  II: 

RV  Rockawav  13:  071,  095,  099,  103. 
EQUAPAC  Exp.: 

RV  Horizon:  20,  21,  25,  30,  31,  32,  35. 

RV  Stranger:  11,  17,  19. 
RV  Islander  VI 

(CSIRO):  2/50/70  (15°47'S  137°28'E),  1/9/71 
(12°24'S  138°11'E). 

La  Pared  Exp.:  17F. 

Monsoon  Exp.:  1,  3,  6, 

Noga  Exp.  SUA:  83,  127A,  164,  169,  169A. 

SUB:  5,  10,  16,  17,  20,  24,  27,  31,  36,  41, 
46,  66,  78,  86. 


B 
A 
B 


Pacific  Ocean: 
Bonacco  Exp.: 


CalCOFI  Cruise 

5801: 
5804: 

5807: 

5901: 
6108: 
Capricorn  Exp.: 


PONTELLINA  SOBRINA 


27,  31,  32,  33,  34,  35,  36,  37,  39,  41, 
42,  43,  .44,  45,  46,  47,  48,  49,  50,  51, 
52,  53,  54,  55,  56,  57,  58. 

153.50. 

Gulf  of  Panama. 

Gulf  of  Panama. 

157.10. 

BPT  14. 

2,  4,  6,  35. 


67 


Table  1. — Continued 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Lcxation 

ond 
station 


Source  of 

collecting 

data' 


Location 

and 
station 


Source  of 

collecting 

data' 


Circe  II  Exp.:  9,  11,  12,  14. 

R'^ Davtcl  Siarr  Jordan 


B 


57: 


60: 


65: 

Dragon  Exp.: 

EASTROPAC  Exp.: 
RV  Argo  11: 
RV  David  Slarr 


002  {13°42'N    120°I3'W),  012  (13°16'N 
119°23'W),  025  (10°30'N    119°43.5'W), 
064  (04°00'N    120°43'W),  076  (03°20'N 
119°42'W),     108    (06°32'N     119°50'W), 
132  (09°45'N  120°12'W). 
056  (03°22'S   119°30'W),  067  (01°36'N 
117°22'W),    071     (02°00'N     117°17'W), 
122  (04°00'N  116°41'W),  132  (06°34"N 
116°22.3'W),  134(07°05'N  116°58'W), 
148  (09°27.7'N  117°49'W),  156 
(10°36'N   n7°17'W). 
170  (00°28'N  96°58'W). 
N-1. 

234,  291,  299. 


Jordan  12: 
RV  Roikawav  13 
El  Golfo  II  Exp.: 
Harpoon  Exp.: 
La  Creuse  Exp.: 

Muddauber  Exp.: 
Piquero  V  Exp.: 
Shellback  Exp.: 
RV  Townsend  Cr 
51: 


TO-58-1  Cruise 

(Scot): 
TO-58-2  Cruise: 


033,  037,  041,  059,  063,  077,  100. 

048,  056,  060,  064,  071,  075,  083. 

XVIII  Bl-Dl,  B2-D1,  A6-D1,  Bl-Nl.  B 

13  (16°00'N  95°12'W). 

15,  16,    17,   18,  21,  OT-1,  OT-6,  OT-12     B 
OT-14. 

125-4,  126-1,  TDS-86.  B 

40D,  43D,  44.  B 

47,  51,  63,  67,  185.  A 

oniWL'll 
051  (03°15'S  118°23'W),  061  (02°30'S 
119°47'W),  064  (03°30'S  120°45'W), 
076  (02°28'S  121°42'W),  079  (02°42'N 
121°49'W). 

16,  17,   27,  29,  31,  32,  33,  35,  36,  37,    B 
38,  42,  45,  46,  48,  56. 

9,  16.  B 


'    A   Snyder  and  Fleminger,  1965 
B   Snyder  and  Fleminger,  1972 
C   Anonymous,  1969 
D   Love,  1972 
E   Fleminger,  1967a 
F   Scheltemo,  1971  (only  chart) 

G  Anderson,  Gehringer,  and  Cohen,  1956;  Anderson  and  Gehringer, 
H  Collier,  Drummond  and  Austin,  1958 

area  of  its  geographical  distribution.  Total 
length  (TL),  prosome,  i.e.,  cephalosome  and 
thorax  combined  (P),  and  urosome  (U)  were 
measured  with  an  ocular  micrometer  at  50  X 
magnification  under  a  stereoscopic  microscope; 
smaller  structures  were  measured  under  a  com- 
pound microscope  at  100  X  to  400  X  magnifica- 
tion. The  morphological  terms  and  abbreviations 
in  general  follow  those  of  Fleminger  (1967b). 

Measurements,  drawings,  and  descriptions 
refer  to  the  right  side  or  to  appendages  from 
the  right  side  unless  stated  otherwise.  TL  and 
the  length  of  U  were  measured  (Figure  2a)  to 
the  distal  end  of  the  right  furcal  ramus,  without 
allowance  for  any  telescoping  of  segments.  The 
length  and  width  of  the  furcal  rami  were  mea- 
sured in  dorsal  view.  In  the  adult  female,  the 
right  ramus  is  fused  to  the  anal  segment;  the 
length  was  obtained  from  the  distance  between 
the  medial  notch  indicating  the  place  of  fusion 
with  the  anal  segment  and  the  insertion  of  the 
second  innermost  furcal  seta  (Figure  2d).  The 
length  of  the  left  furcal  ramus  was  also  measured 
from  the  medial  junction  with  the  anal  seg- 
ment to  the  insertion  of  the  second  innermost 
furcal  seta  from  the  median.  In  both  males  and 
immature  females  the  lengths  of  the  right  and 
left  furcal  rami  were  measured  from  the  lateral 
margin  at  the  proximal  end  to  the  insertion  of 
the   second   innermost   seta   at   the   distal    end 


1958,  1959a,  1959b 

(Figure  2c).  For  all  stages  the  right  furcal 
ramus  was  measured  across  its  maximum  width 
(Figure  2c). 

The  segments  of  the  fifth  legs  (P5)  of  the 
female  were  measured  from  the  anterior  side 
(Figure  2f).  The  length  of  the  exopod  (Re)  was 
taken  as  extending  from  the  junction  with  the 
second  basal  segment  (B2)  to  the  base  of  the 
longest  distal  seta;  the  endopod  (Ri)  was  mea- 
sured from  the  junction  with  B2  to  the  tip  of  the 
medial  spine.  The  length  of  the  point  on  the 
fifth  thoracic  segment  (ThV)  is  taken  in  lateral 
view  as  the  distance  between  its  tip  and  its 
base  where  the  point  is  delineated  by  a  distinct 
step  or  turn  to  the  posterior  (Figure  2g).  The 
length  of  the  spermatophore  sac  was  measured 
as  the  distance  from  the  distal  end  to  the  outer 
margin  of  the  proximal  convolution  taking  care 
to  position  the  spermatophore  to  avoid  diminu- 
tion by  an  oblique  angle  of  view  (Figure  2b). 
Measurements  of  segments  13-17  and  the  suc- 
ceeding three  free  segments  of  the  male  right 
antennule  (Al)  were  taken  from  intact  specimens 
positioned  in  lateral  view  (Figure  2e).  P5  of  the 
male  was  measured  from  the  posterior  side: 
the  length  of  the  second  free  segment  of  the 
left  leg  extends  from  the  junction  with  B2  to 
the  distal  margin  near  the  seta  (Figure  2h);  the 
length  and  width  of  the  proximal  segment  of 
the  chela  are,  respectively,  the  shortest  distance 


68 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


u 


TL 


c 

1 4 

LfL 

00 

RtW 

RtL 


LfL 


RtL 


RtW 


19-21 


f 


Re 


LfRel 


tRelW 


RtRelL 


Figure  2.  —  Measurements  taken  from  Poniellina  specimens,  a.  dorsal  view,  female;  b.  abdomen  with  spermato- 
phore,  ThIV-V,  lateral  view,  female;  c.  anal  segment  and  furcal  rami,  dorsal  view,  male;  d.  urosome,  dorsal  view, 
female;  e.  right  Al,  segments  13-25  male;  f.  right  P5,  anterior  view,  female;  g.  spine  on  right  ThIV-V,  lateral  view, 
female;  h.  left  P5,  posterior  view,  male;  i.  chela  of  right  P5,  posterior  view,  male.  L  =  length;  Lf  =  left;  P  =  prosome 
length;  Pt  =  spine;  Re  =  exopod;  Rel  =  first  exopodal  segment;  Ri  =  endopod;  Rt  =  right;  Sp  =  spermatophore; 
TL  =  total  length;  U  =  urosome  length;  W  =  prosome  width. 


69 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


between  the  shallow  swelling  in  the  proximal 
lateral  corner  and  the  distal  margin,  and  the 
distance  between  the  proximal  medial  corner 
and  the  tip  of  the  large  lateral  prong  (Figure  2i). 
Types  and  reference  specimeins  have  been 
deposited  with  the  Smithsonian  Institution, 
U.S.  National  Museum,  Washington,  D.C. 

GENUS  PONT  ELLIN  A  DANA 

Pontella  Dana,  1846  (in  part),  p.  184,  type  not 
designated;  Dana,  1849,  p.  26.  type  not 
designated. 

Pontellina  Dana,  1853  (in  part),  p.  1135,  type 
not  designated;  Giesbrecht,  1889,  j).  29, 
type  by  monotypy,  PoiitelUiia  plumata 
(Dana);  Giesbrecht,  1892,  p.  73,  497; 
Giesbrecht  and  Schmeil,  1898,  p.  149. 

Calanops  Claus,  1863,  p.  211,  type  by  mono- 
iy^y,  CahiHopsi  messineyisis  C\a.\x%  =  Pontel- 
lina plumata  (Dana),  Giesbrecht,  1889,  p. 
29. 

Pseudopo)itia  Claus,  1892,  p.  861,  864,  type  by 
monotypy,  Psendopoutia  plumata  (Dana) 
=  Pseudopontella  plumata  (Dana),  Claus, 
1893,  p.  278. 

Pseudopo)itella  Claus,  1893,  p.  278,  type  by 
monotypy,  Pseadopoiitilla  plumata  (Dana) 
=  Pontellina  plumata  (Dana),  Giesbrecht 
and  Schmeil,  1898.  p.  149. 

Not  Pontellina  Claus,  1892.  p.  851;  1893.  p.  272. 

Diagnosis 

Relatively  small  pontellids,  less  than  2  mm 
in  TL.  Prosome  in  dorsal  view  broadly  oval, 
less  than  twice  as  long  as  maximum  width; 
forehead  lacking  headhooks;  ThIV-V  corners 
symmetrical;  rostrum  proximally  protuberant, 
bifurcate  at  base,  and  extending  ventrad  as 
slender,  elongate,  flexible  filaments;  in  lateral 
view,  filaments  more  than  10  times  longer  than 
wide  at  maximum  width;  ventral  eye  present 
but  inconspicuous,  scarcely  produced,  and  lack- 
ing a  distinctive  lens.  In  Al  (except  sexually 
modified  right  Al  of  male)  segments  13.  14,  and 
15  separate  and  about  equal  in  length.  A2  with 
Re  about  as  long  as  Ril,  length  of  Ril  less  than 
4  times  maximum  width. 

Female  lacking  distinctive  dorsal  lenses  in 
forehead.  Furcal  rami  weakly  asymmetrical, 
right  ramus  fused  to  anal  segment.  P5  with 
monomerous  Re  bearing  1  lateral  and  3  terminal 
setae,  in  addition  to  one  medial  setiform  process 
fused  to  Re  and  serrated  along  medial  margin; 


Ri  monomerous  and  terminating  in  one  or  two 
apical  spines.  A2  and  mandible  (Mnd)  with 
elongate  setae  reaching  beyond  thorax  when 
extended  i)osteriad. 

Male  with  one  j^air  of  dorsal  lenses  in  fore- 
head. 

Additional  Description 

Both  sexes  with  cephalic  groove  and  agree- 
ing in  meristic  features  of  all  ai:)pendages  except 
for  those  modified  by  sexual  maturation.  Non- 
sexually  modified  appendages  agree  with  those 
of  Pontellina  plumata  as  shown  by  Giesbrecht 
(1892,  pi.  25,  fig.  1,  6,  7,  9,  12-14,  18,  20,  21,  23- 
25).  Segmentation,  setation,  and  spination  of 
nonsexually  influenced  appendages  are  virtually 
identical  among  the  four  species  and,  except 
for  Al,  closely  resemble  those  of  Pontellopsis. 
They  are  as  follows: 

Al:        17  free  segments;  segments  2-5,  6-8, 

24-25  fused,  9-11  partly  fused. 
A2:        2    basal    segments;    Re:    3    segments 
with  1.  4,  3  setae,  respectively;  Ri: 
2  segments;  Le:  6,  Li:  6  +  2  setae. 
Mnd:     palpus  1  seta;  Re:  5  segments  with  a 
total   of  6   setae;    Ri:    2   segments 
with  4  and  6  setae,  respectively. 
Mxl:     Lil:  14  spines;  Li2:  3  spinelike  setae; 
Li3:    small,   3   setae;    B2:    3    +    2 
setae;  Ri:  4  +  1  setae;  Re:  8  setae; 
Le:  1-1-8  setae. 
Mx2:     lobe  1:3  +   1  setae;  lobes  2-5:  2  +   1 

setae  each;  Ri:  6  -H  1  setae. 
Mxp:     5-segmented,  fingered  lobe  on  Bl  with 

2,  2.  3  setae. 
PI:        trimerous  Re:   1.  1.  4  Si;   1  St;   1,  1, 

2  Se;    trimerous   Ri:    1,   2.   4    Se; 
1  St;  0,  0,  1  Se. 

P2  and  P3:     trimerous  Re:  1,  1,  5  Si;  1  St; 

1,   1,  3  Se;   bimerous  Ri:   3,  5,  Si; 

ISt;  0.  2Se. 
P4:        trimerous  Re:   1,  1,  5  Si;   1  St;   1,   1, 

3  Se;  bimerous  Ri:  3,  4  Si;   1  St; 
0,  2Se. 

Se  of  PI  smooth;  Se  of  Rel  and  Re2  of  P2 
with  toothed  medial  margin;  Se  of 
Re3  with  toothed  medial  and  lateral 
margins;  in  Se  of  P3  and  P4  also 
both  margins  toothed. 

St  of  Re  3  of  PI  to  4  with  toothed  lateral 
margin. 

Bl  of  PI  to  4  with  1  Si;  B2  ususally  without 
setae. 


70 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


Right  Al  in  male  with  segments  13-17  swol- 
len, 13-14  and  16-17  fused;  length  of  swollen 
section  varies  considerably  due  to  either  tele- 
scoping of  segments  or  expansion  of  articula- 
tions. Distal  three  free  segments  slender  and 
consisting  of  segment  18  followed  by  a  com- 
pound segment  formed  by  fusion  of  segments 
19-21,  and  ending  in  a  compound  segment  fusing 
segments  22-25. 

Mandibular  blade  (Giesbrecht  1892.  pi.  25, 
fig.  14)  bearing  a  one-pointed  apical  (ventral) 
tooth,  a  two-pointed  subapical  tooth,  two  deeply 
cut  two-pointed  medial  teeth,  and  three  basal 
(dorsal)  teeth;  basal  seta  lacking;  dorsal  acces- 
sory bristles  exceed  teeth  in  length;  patches  of 
spinules  appear  on  anterior  side  of  blade. 

P5  segmentation  in  both  sexes  typically 
pontellid;  B2  of  male  bearing  a  large  plumose 
seta  on  posterior  surface,  Ri  lacking.  Re  bi- 
merous;  right  leg  with  elongate  Bl,  cheliform 
Re;  left  leg  with  reduced  Bl  fused  to  precoxa, 
distal  segment  of  Re  armed  with  four  short  seti- 
form  processes. 

Spermatophore  with  relatively  long  neck 
bearing  one  full  counterclockwise  turn  relative 
to  proximal  end,  helix  occurring  between  sper- 
matophore sac  and  place  of  attachment  located 
in  a  cement  mass  overlying  genital  pore  of 
female.  Elongate  spermatophore  neck  may  also 
be  connected  secondarily  to  right  side  of  genital 
segment  proximal  to  helix,  thereby  orienting 
sac  dorsad  or  anterodorsad  with  helix  and  sac 
flanking  right  side  of  genital  segment.  When 
secondary  lateral  cementation  absent,  neck, 
helix,  and  sac  hang  free  from  ventral  side  of 
genital  segment. 

PONTELLINA  PLUMATA  (DANA) 

(Figures  3  and  4) 

Pontella  plumata  Dana,  1849,  p.  27  (type  local- 
ity not  designated);  Brady  (in  part),  1883, 
p.  92,  pi.  37,  fig.  1-10  only." 

Pontella  turgida  Dana,  1849,  p.  28  (type  local- 
ity not  designated). 

Pontelli)ia  plumata:  Dana,  1853,  p.  1135;  Dana, 
1855,  pi.  79,  fig.  10;  Giesbrecht,  1889,  p.  29; 
Giesbrecht,  1892,  p.  497,  pi.  4,  fig.  1,  pi.  25, 
fig.  1,  4,  6,  7,  9,  12-14,  18,  20,  21,  23-26,  36, 
pi.  40,  fig.  49-53;  Mori  (in  part),  1937, 
p.  99,  pi.  47,  fig.  7-11  only;  Grice,  1962,  p. 
240,  pi.  34,  fig.   11-15;    Brodsky,   1962,  p. 


147,  fig.  47;  Park,  1968,  p.  569,  pi.  13,  fig. 

15-16. 
Poiitclliiia  turgida:  Dana,  1853,  p.  1136;  Dana, 

1855,  pi.  79,  fig.  11,  12. 
Calaiiops   mesMnensis  Glaus,   1863,  p.  212,  pi. 

2,  fig.  11,  pi.  36,  fig.  13-16,  pi.  37,  fig.  10 

(Messina). 
Pontellopsis  speciosus  Brady,  1915,  p.  138,  pi. 

10,  fig.  1-8  (Durban  Bay).  NEW  SYNONY- 
MY. 
Pontellopsis  aequalis  Mori,   1932,  p.   172,   175, 

pi.  4,  fig.  7-13  (25°20'50"N,  124°7'30"E). 
not  Pontella  plumata:  Brady  (in  part),  1883,  p. 

93,  pi.  37,  fig.  11  only, 
not  Po)itelli)ia  navalium  Oliveira,  1947,  p.  472, 

fig.  12;  Vervoort,  1965,  p.  191. 

Specimens  seen:  1,259  adult  females,  917  adult 
males. 

Standard  measurements:  specimens  randomly 
selected  from  localities  spanning  the 
observed  geographical  area  of  distribution. 

Total  length  (TL),  mm: 


Standard 

Mean 

error          Speci- 

(x)             Range 

Sx             mens 

Female 

1.69           1.44-1.94 

0.0126            75 

Male 

1.51           1.34-1.92 

0.0130            67 

Prosome- 

■urosome  length  ratio  (PUR): 

Median                Range 

Specimens 

Female 

3.28:1              2.92-3.72 

1                   75 

Male 

3.07:  1              2.84-3.93 

1                   52 

Diagnosis 


Female 


Posterior  corner  of  ThIV-V  in  lateral  view 
produced  into  conspicuous  spiniform  process  of 
characteristic  shape  (Figure  3  a,  b,  d-g).  Ventral 
margin  of  spine  more  or  less  continuous  with 
ventral  margin  of  ThIV-V,  transition  with  dor- 
sal margin  abrupt  and  stepped;  junction  of 
distal  end  of  spine  and  thicker  basal  portion 
usually  set  off  by  weak  shoulder,  spine  extending 
posteriad,  sometimes  tilted  weakly  ventrad  or 
dorsad.  In  dorsal  view  spine  more  or  less  con- 
tinuous with  posterior  tapering  of  corner, 
shoulder  or  constriction  sometimes  present; 
spine  usually  directed  posteriad  and  slightly 
laterad,  sometimes  straight  or  turned  slightly 
mediad. 


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0.2  mm 


b.g 

0.2  mm 
a.d.e.f 
0.2mm 


c,h 


C 


lc=J 


Figure  3. —  Pontellma  plumata  s.str.,  adult  female:  a.  ThIV-V,  genital  segment,  lateral  view  (TRANSPAC  96A); 
b.  habitus,  lateral  view,  swimming  legs  incomplete  (same  station  as  a,  different  specimen);  c.  rostral  filaments, 
lateral  view  { Atlantis  //-31-2);  d.  range  of  variation  observed  in  ThIV-V,  lateral  view  (left  to  right:  Lusiad  VI-8; 
Chain  49-11;  Lusiad  11-66;  Cham  49-11,  different  specimen;  Atlantis  //-31-73;  same  station,  different  specimen); 
e.  ThIV-V,  urosome,  dorsal  view  (same  specimen  as  a);  f.  range  of  variation  observed  in  ThIV-V,  dorsal  view 
(top  to  bottom:  Scorpio  11-118;  Chain  49-11;  same  station,  different  animal;  Chain  49-20);  g.  habitus,  dorsal  view 
(same  specimen  as  b);  h.  lateral  margin  of  right  furcal  ramus  of  various  specimens,  dorsal  view  (left  to  right: 
Atlantis  //-31-2;  Troll  28A;  Atlantis  //-20-22;  Dodo  VI-65;  Troll  25;  Scorpio  11-182). 


72 


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Genital  segment  bearing  anterolateral  and 
posterolateral  clusters  of  hairs  on  both  sides  of 
segment  (Figure  3  a,  e);  anterior  cluster  larger, 
best  seen  in  dorsal  view.  Posterior  cluster  less 
prominent,  of  similar  or  coarser  hairs.  A  row  of 
relatively  long,  fine  hairs  encircling  segment 
near  distal  margin. 

Male 

In  lateral  view  posterior  corner  of  ThIV-V 
somewhat  angular,  apex  usually  bearing  one 
minute  denticle  (Figure  4e-h).  Chela  of  right 
P5  with  proximal  segment  extending  disto- 
laterad  as  a  relatively  slender  digitiform  pro- 
cess opposing  apex  of  distal  falcate  segment 
(Figure  4i);  base  of  distolateral  digitiform 
process  flanked  by  small  anterior  process, 
triangular  in  lateral  view,  and  small  angular 
posterior  process  bearing  a  sensoriiform  seta 
(Figure  4j);  in  lateral  view  posterior  basal 
process  and  digitiform  process  with  relatively 
straight  margins  intersecting  at  an  angle  great- 
er than  70°  (Figure  4j);  in  posterior  view  two 
basal  processes  overlapping,  both  extending 
toward  center  of  lumen  of  chela;  additional 
sensoriiform  setae  on  proximal  segment  of 
chela:  one  anteromedial  near  articulation  with 
distal  segment;  on  distal  segment:  one  proximo- 
medial,  one  mediosubapical,  and  three  lateral. 
Left  P5  (Figure  4i)  with  proximal  segment  of 
Re  (Rel)  short  relative  to  other  three  species 
below.  Length  of  right  furcal  ramus  exceeds 
left  Rel  by  1.55-1.85  times,  46  specimens  (see 
Figure  30). 


Additional  Description 


Female 


Right  furcal  ramus  fused  to  anal  segment, 
varying  directly  with  prosome  length,  relatively 
longer  than  that  in  Indian  and  Pacific  congeners 
described  below  (Figure  25);  ratio  of  length  to 
width  highest  in  genus,  usually  1.5  times  longer 
than  wide  (median  1.56:1,  range  1.28-1.74:1, 
134  specimens),  showing  apparent  overlap  only 
with  the  equatorial  Atlantic  congener  (see 
Figure  27);  lateral  margin  of  right  furcal  ramus 
with  small  pointed  projection  somewhat  vari- 
able in  shape  and  size  just  anterior  to  base  of 
outermost  seta  (Figure  3e,  h).  Glandlike  tissue 
within  right  furcal  ramus  with  associated  duct- 
like structure  extending  toward  lateral  point. 


Left  furcal  ramus  not  fused  and  appreciably 
longer  than  right  ramus  (see  Figure  19). 

P5  (Figui-e  4a,  c,  d)  with  inner  margin  of  Re 
lacking  hair.  Ri  polymorphic  with  one  or  two 
apical  spines  fused  to  segment,  spines  on  left 
and  right  Ri  may  differ  in  number  in  same 
specimen  (Figure  4b,  Table  7);  Re  2  to  3  times 
longer  than  Ri,  median  2.37:1,  range  1.97- 
3.08:1,  59  specimens,  differing  strongly  from 
Indian  and  Pacific  congeners  (see  Figure  29). 

Attached  spermatophore  observed  on  four 
specimens  (see  Figure  33  a,  b;  Table  5),  hanging 
free  from  single  place  of  attachment  in  vicinity 
of  genital  pore,  neck  with  small  helical  turn 
near  place  of  attachment  and  larger  helical  turn 
at  origin  of  sac. 

Male 

Right  furcal  ramus  not  fused  to  anal  segment, 
about  equal  in  length  to  left  ramus  (see  Figure 
19),  varying  directly  with  prosome  length  (see 
Figure  26);  ratio  of  length  to  width  relatively 
high  (median  2.30:1,  range  2.0-2.53:1,  44  speci- 
mens), but  showing  more  overlap  with  congeners 
than  found  among  females  (see  Figure  28). 

Types 

Unknown,  presumed  to  be  lost.  Reference 
specimens  from  the  Atlantic,  Pacific,  and  Indian 
Oceans  have  been  deposited  in  the  U.S.  National 
Museum,  Smithsonian  Institution. 


Reference  Specimens 

4d.  49,  Atlantis  //-31-5,  lat.  39°13.0'N,  long. 
63°26.5'W,  14  Jan.  1967,  ¥4-m  net, 
oblique  tow,  maximum  cable  out  200  m. 

2c5,  29,  Capricorn  31,  lat.  06°31'N,  long.  124° 
41'W,  13  Feb.  1953,  1-m  net,  oblique 
tow,  maximum  cable  out  200  m. 

2(5,2  9,  TRANSPAC  134A,  lat.  23°26.3'N, 
long.  161°49.6'W,  17  Nov.  1953,  1-m 
net,  oblique  tow  between  surface  and 
129  m  est. 

2  d,  4  9,  Lusiad  V-76,  lat.  02°01'S,  long.  91°58'E, 
24  Apr.  1963,  1-m  net,  oblique  tow, 
maximum  cable  out  280  m. 

2d  Lusiad     V-104,     lat.     03°01'S,     long. 

52°58'E,  10  May  1963,  1-m  net.  oblique 
tow,  maximum  cable  out  280  m. 


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0.2  mm 

I 1 

e,h 

0.2  mm 
I 1 

0.2  mm 


a,b,i,j,k 
0.1  mm 


cd 


Figure  4. —  Poniellina  pluinuta,  s.str.  Adult  female:  a.  P5  anterior  view  (TRANSPAC  96A);  b.  P5  Ri  of  other 
specimens,  right  side  above,  left  side  below  (left  to  right:  Scorpio  11-146;  Lusiad  11-66;  La  Creuse  3;  same  station, 
different  specimen;  Atlantis  //-31-6;  Lusiad  V-45);  c.  enlargement  of  P5  apex;  d.  enlargement  of  P5  Re  distal 
process  (TRANSPAC  96A).  Adult  male:  e.  habitus,  lateral  view  (Atlantis  //-31-28);  f.  ThIV-V,  part  of  urosome, 
P5.  lateral  view  (TRANSPAC  92B);  g.  variation  observed  in  ThIV-V,  lateral  view  (left  to  right:  Dodo  VI-70; 
Gill  8-9;  La  Creuse  7;  Gascoync  G 1/5/63;  Circe  NT-38;  Monsoon  18).  h.  habitus,  dorsal  view  (same  as  e);  i.  P5, 
posterior  view  (same  as  f);  j.  P5  chela,  lateral  view  (same  as  f);  k.  mandible,  gnathobase,  lateral  view. 


74 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


Remarks  on  Synonymy  and  Variability 

Dana  (1849,  1853,  1855)  described  the  male 
and  female  of  P.  plumata  as  separate  species 
based  on  specimens  obtained  from  several 
equatorial  localities  (in  the  Atlantic  Ocean: 
lat.  08°30'N  to  00°,  long.  23°  to  18°W; 
00°15'N,  31°00'W;  01°00'  to  04°30'S,  17°30' 
to  21°30'W;  04°30'S,  25°00'W).  Our  efforts  to 
use  his  descriptions  and  illustrations  to  sepa- 
rate the  two  species  in  our  Atlantic  collections 
were  fruitless.  Moreover,  Dana's  specimens  of 
Pontellina  are  apparently  lost  (T.  E.  Bowman, 
in  litt.). 

The  present  concept  of  P.  plumata  originates 
from  Giesbrecht's  (1892)  redescription  and 
synonymy  which  have  been  generally  accepted. 
Hence  we  regard  his  description  of  the  species 
as  the  basis  for  the  type  species  of  the  genus. 

Several  authors  have  noted  morphological 
variation  in  jo/« /»afo,  observations  that  may  indi- 
cate that  they  had  examined  specimens  of  two 
or  more  of  the  four  species  we  recognize  in  the 
genus.  Thus,  Dana  (1853)  reported  that  the 
furcal  rami  were  relatively  longer  in  males 
from  the  Cape  of  Good  Hope  region  than  in 
males  from  the  Pacific  Ocean.  Giesbrecht  (1892) 
found  that  the  posterolateral  corners  of  ThIV-V 
were  longer  in  males  from  the  Pacific  than  in 
those  from  waters  off  Naples.  Tanaka  (1964) 
mentions  differences  in  the  posterolateral  cor- 
ners of  ThIV-V  in  both  sexes  of  plumata.  Mori 
(1937)  believed  the  differences  he  encountered 
in  specimens  of  Pontelliua  were  a  function  of 
ontogeny.  On  the  other  hand,  a  number  of 
authors  have  published  illustrations  which 
appear  to  be  based  solely  on  plu))iata  specimens 
(e.g.,  Giesbrecht,  1892;  Brodsky,  1962;  Grice, 
1962;  Park,  1968). 

Distribution 


dance  estimates  ranged  from  0.002  to  0.4  adults 
per  m-'  water  strained,  the  median  being  0.02.  In 
the  sets  of  samples  selected  for  quantitative 
analysis  (Figure  lb)  the  species  appeared  in- 
frequently and  in  minimal  numbers  in  the 
eastern  tropical  Pacific.  In  the  remainder  of  the 
equatorial  Pacific  and  in  the  Indian  Ocean 
plumata  was  found  in  about  half  of  the  samples 
examined. 

Values  of  mean  abundance  in  temporally 
and  geographically  related  sets  of  samples  usual- 
ly exceeded  0.02  per  m-'  of  water  strained  (see 
Figure  35,  Table  14).  With  regard  to  the  Atlan- 
tic Ocean  our  impressions  from  the  available 
nonquantitative  collections  is  that  the  abundance 
of  plumata  is  not  appreciably  different  from 
that  in  the  Indian  and  Pacific  Oceans. 

The  widespread  co-occurrence  of  three  sibling 
species  (described  below)  imposes  serious  reser- 
vations on  the  use  of  previously  published 
records  of  plumata.  It  would  be  best  to  consider 
earlier  records  primarily  as  evidence  of  the 
occurrence  of  the  genus,  a  useful  attribute  con- 
sidering the  virtual  absence  of  the  genus  at 
latitudes  above  40°. 

PONTELLINA  PLATYCHELA  SP.N. 

(Figures  6  and  7) 

Specimens  seen:  168  adult  females,  466  adult 
males. 

Standard  measurements:  specimens  randomly 
selected  from  localities  spanning  the 
observed  geographical  area  of  distribution. 

Total  length  (TL),  mm: 

Standard 
Mean  error  Speci- 

(x)  Range 


Female 
Male 


1.70 
1.56 


error 

1.54-1.96       0.0173 
1.41-1.74       0.0089 


mens 

30 

57 


Prosome-urosome  length  ratio  (PUR): 


P.  plujuata  exhibits  a  warm-water  circum- 
global  distribution  bounded  in  the  north  and 
south  roughly  by  the  subtropical  convergence 
zones  of  each  hemisphere  (Figure  5).  Adults 
were  frequent  in  occurrence  but  relatively  low 
in  abundance.  For  example,  in  131  zooplankton 
samples  containing  the  species  from  the  Indian 
and  Pacific  Oceans  (Indian  Ocean  Standard  Net 
and  CalCOFI  Standard  Net  zooplankton  sam- 
ples; tows  through  the  epipelagic  layer)  abun- 


Median 

Range 

Specimens 

Female 

3.44:1 

3.19-3.89:1 

30 

Male 

3.22:1 

2.86-3.55:1 

49 

Diagnosis 

Female 

Posterolateral  corner  of  ThIV-V  ending  in  a 
relatively  minute  dentiform  process  extending 
posteriad    or    weakly    medioposteriad    (Figure 


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FISHERY  BULLETIN:  VOL.  72.  NO.  1 


20°     ■-'•--'' ■■'•     60'  100°  140°  180°  140°  100°  60°  20°  0°  20° 

Figure  5.  —  Poniellina  plitniaia  s.str.     Geographical  distribution  of  captures  recorded  during  the  present  study. 


6a-c,  f-h);  in  dorsal  view  denticle  not  sharply 
set  off  from  tapering  lateral  margin  of  ThIV-V. 
Genital  segment  (Figure  6f,  g)  with  several 
isolated  lateral  sensory  hairs  and  line  of  slender 
hairs  along  distal  margin,  lacking  lateral  clus- 
ters of  coarse  hairs. 

Male 

Posterolateral  corners  of  ThIV-V  in  lateral 
view  tending  to  be  rounded  and  lacking  denticle 
(Figure  7c,  d).  Chela  of  P5  differing  markedly 
from  that  in  pluniata  due  to  strong  antero- 
posterior expansion  of  both  segments  (Figure 
7a,  b);  distal  segment  spatulate:  in  proximal 
segment  base  of  laterodistal  digitiform  process 
greatly  expanded;  in  posterior  view  posterior 
basal  process  barely  differentiated  but  sensori- 
iform  seta  present,  anterior  basal  process  rel- 
atively small,  and  extending  toward  center  of 
lumen  of  chela.  Left  P5  (Figure  7a)  with  proxi- 


mal segment  of  Re  (Rel)  somewhat  longer  than 
that  in  phonata,  length  of  right  furcal  ramus 
exceeds  Rel  by  1.3-1.5  times,  21  specimens 
(see  Figure  30). 

Etymology 

The  name  platychela  is  derived  from  the  Greek 
words  platys  ( =  broad)  and  chela  ( —  crab's  claw) 
and  refers  to  the  relatively  large  chela  of  the 
adult  male. 

Types 

Holotype:  Adult  male,  TL  1.52  mm,  PUR 
3.22:1;  sorted  from  plankton  sample  taken  at 
Atlantis  77-31  stn.  48,  lat.  00°56'N,  long. 
25°20'W,  12  Feb.  1967,  %-m  net,  oblique  tow, 
maximum  cable  out  200  m.  USNM  No.  141613. 

AUotype:  Adult  female,  TL   1.72  mm,  PUR 


76 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


0.2mnn 
I 1 

b.f 

0.2  mm 

I \ 

a,c,d,g,h 
0.2mm 


e, 


d 


Figure  6. — Pontellina  platychela,  sp.n.,  adult  female:  a.  ThIV-V,  genital  segment,  lateral  view  (Atlantis  //-20-28); 
b.  habitus,  lateral  view  (Atlantis  //-20-2);  c.  range  of  variation  in  ThIV-V,  lateral  view  (left  to  right:  Lusiad  VII-81 
H13;  Atlantis  //-31-40;  Lusiad  VII-81  H13,  different  specimen;  Atlantis  11-20-31;  same  station,  different  specimen); 
d.  rostrum,  lateral  view  (same  as  a);  e.  P5,  anterior  view  (same  as  a);  f.  habitus,  dorsal  view  (same  as  b);  g.  ThIV-V, 
urosome,  dorsal  view  (same  as  a);  h.  ThIV-V,  dorsal  view,  another  specimen  (Atlantis  //-20-31);  i.  P5  Ri  of  other 
specimens,  right  side  above,  left  side  below  (all  four  specimens  Lusiad  VII-69  H4). 


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FISHERY  BULLETIN:  VOL.  72,  NO.  1 


0.2  mm 
I 1 


c,d 
0.2mm 


a,b 


Figure  7. — PontelUna  platychela  sp.n.,  adult  male:  a.  P5,  posterior  view  (Atlantis  //-20-24);  b.  P5  chela,  lateral  view 
(same  as  a):  c.  ThIV-V  and  P5,  lateral  view  (Atlantis  11-20-27);  d.  range  of  variation  in  ThIV-V  (left  to  right:  3  specimens 
Amazon  17;  La  Creuse  7;  Oregon  1293). 


3.52:1;  right  furcal  ramus  length  0.110  mm, 
width  0.075  mm;  from  same  sample  as  male. 
USNM  No.  141614. 

Paratypes:  3c5 ,  89  from  same  sample.  USNM 
No.  141615. 

Reference  specimeji.s:  56,  5 (^  ,  Oregon  stn. 
1293.  lat.  19°55'N,  long.  74°  lO'W,  23  Apr.  1955, 
G  III  net  towed  between  surface  and  2m. 
USNM  No.  141616. 

Distribution 

P.  platychela  was  found  only  in  epipelagic 
tows  taken  in  equatorial  latitudes  of  the  Atlantic 
Ocean  (Figure  8).  The  species  appeared  regular- 
ly in  samples  collected  between  lat.  10° S  and 
10° N.  The  more  extensive  sampling  available  to 
us  from  north  of  the  equator  indicates  that  few 
platychela  extend  as  far  as  lat.  21°  or  22°N  and 
that  the  species  disappears  abruptly  at  high- 
er latitudes.  We  anticipate  that  in  the  vicinity 
of  the  Gulf  Stream  its  northward  occurrence 
may  be  extended  somewhat  by  examination  of 
additional  samples,  paralleling  occurrences 
to  the  south  in  the  Brazil  Current. 


Additional  Description 


Female 


Right  furcal  ramus  somewhat  shorter  than  in 
plumata    (see   Figure   27),  typically    1.4   times 


78 


longer  than  wide  (median  1.44:1,  range  1.28- 
1.55:1,  35  specimens),  lateral  process  anterior 
to  proximal  seta  lacking,  but  interior  of  ramus 
with  glandlike  tissue  and  ductiike  structure 
leading  to  lateral  margin  as  in  plumata. 

P5  (Figure  6e)  essentially  as  in  plumata 
including  proportional  length  relationship  of 
Re  and  Ri,  median  2.27:1,  range  1.69-2.91:1, 
49  specimens  (see  Figure  29);  Ri  polymorphic 
with  one  or  two  apical  spines  fused  to  segment, 
in  same  specimen  spines  on  left  and  right  Ri 
may  differ  in  number  as  in  plumata  (Figure  6i, 
Table  7). 

Attached  spermatophore  observed  in  one 
specimen  (see  Figure  33c-e,  Table  5);  neck 
cemented  to  ventral  side  of  genital  segment  in 
vicinity  of  genital  pore  and  buried  within  large 
irregular  mound  of  cement  extending  across 
entire  length  of  genital  segment  and  right 
ventral  side  of  anal  segment,  neck  extending 
to  right  anterolateral  side  of  anal  segment  along 
with  continuation  of  cement  fixing  it  to  anal 
segment,  large  helical  counterclockwise  turn 
following  emergence  of  neck  from  cement 
orienting  succeeding  sac  anterodorsad. 

Male 

Right  furcal  ramus  as  in  plu  mata  (see  Figures 
19,  26),  but  relatively  wider  (see  Figure  28), 
ratio  of  length  to  width  typically  2:1  (median 
2.06: 1,  range  1.91-2.34: 1,  37  specimens). 

Our  impression  from  the  available  Atlantic 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  POSTELLINA 


20°     -... -i  :-..-  .-.,     60°  10'^°  140°  180°  '40°  100°  60°  20°  0°  20° 

Figure  8. —  PontelUna  platychela  sp.n.     Geographical  distribution  of  captures  recorded  during  the  present  study. 


collections  is  that  the  abundance  of  platychela 
is  generally  similar  to  the  numbers  of  Pt>)itel- 
li)m  in  the  Indian  and  Pacific  Oceans  (cf.  Tables 
14,  18),  i.e.,  typically  less  than  0.2  adults  per 
m^  of  water  strained. 

PONTELUNA  MORII  SP.N. 

(Figures  9  and  1 1) 

PontelUna  plumata:  Mori  (in  part),  1937,  p.  99, 
pi.  48,  fig.  1-12  only;  Dakin  and  Colefax, 
1940,  p.  99,  fig.  139.  NEW  SYNONYMY. 

Specimens  seen:  433  adult  females,  284  adult 
males. 

Standard  measurements:  specimens  randomly 
selected  from  localities  spanning  the  ob- 
served geographical  area  of  distribution. 

Total  length  (TL),  mm: 


Standard 

Mean 

error 

Speci- 

(x) 

Range 

sx 

mens 

Female 

1.61 

1.38-1.88 

0.0145 

54 

Male 

1.44 

1.26-1.68 

0.0 100 

58 

Prosome-urosome  length  ratio  (PUR): 


Median 

Range 

Specimens 

Female 

3.64:1 

3.39-4.10:1 

35 

Male 

3.34:1 

2.87-3.73:1 

50 

Diagnosis 

Female 

Posterolateral  corner  of  ThIV-V  ending  in  a 
short  spiniform  process  extending  posteriad  or 
somewhat  medioposteriad;  in  contrast  to  pluma- 
ta junction  of  spine  and  ThIV-V  corner  relatively 


79 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


0.2  mm 
I 1 

b.d 

0.2  mm 

I 

a,c,e,f 
0.2  mm 


g,h,i 


H 


Figure  9. —  PonwIUnu  luarii  sp.n.,  adult  female:  a.  ThIV-V  and  genital  segment,  lateral  view  (Lusiad  V-66);  b. 
habitus,  lateral  view  (Circe  III  NT-27);  c.  variation  in  ThIV-V,  lateral  view  (left  to  right:  Troll  31A,  2  specimens 
Lusiad  11-66);  d.  habitus,  dorsal  view  (Circe  III  NT-26);  e.  ThIV-V  and  urosome,  dorsal  view  (same  as  a);  f.  variation 
in  ThlV-V,  dorsal  view  (top:  Troll  31A;  bottom:  Lusiad  11-66);  g.  P5,  anterior  view  (Lusiad  V-66);  h.  variation 
observed  in  lateral  margin  of  right  furcal  ramus,  dorsal  view  [left  to  right:  Scan  IV-3;  TO-58-1  (Scot)  14;  Lusiad 
11-13;  Lusiad  11-10;  Lusiad  V-4?];  i.  P3  Ri  in  other  specimens,  right  side  above,  left  side  below  (left:  Troll  30; 
right:  Silas  Bent  1-12). 


80 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


abrupt  in  both  dorsal  and  lateral  views  (Fig- 
ure 9a-f),  right  and  left  sides  symmetrical 
(Table  2),  spine  small,  not  exceeding  0.035  mm 
irrespective  of  TL  (Figure  10),  spine  roughly 
one-half  as  long  as  that  in  its  congener  from  the 
eastern  equatorial  Pacific  described  below. 
Genital  segment  with  posterolateral  cluster 
of  coarse  hairs  on  both  sides,  lacking  antero- 
lateral cluster  found  in  pin  mata  although  several 
fine  hairs  may  occur  at  this  site  (Figure  9a,  e): 
posterior  margin  of  segment  bordered  by  fine, 
long  hairs  as  in  plumata. 

Male 

ThIV-V  typically  ending  posteriorly  in  a 
small  spiniform  process  (Figure  lib,  c)  similar 
to  female.  P5  with  chela  of  plumata-type  but 
both  segments  showing  distinctive  features; 
distal  segment  short,  not  reaching  opposing 
disto-lateral  digitiform  process  on  proximal 
segment  (Figure  lid),  apex  of  distal  segment 
with  prominent  triangular  spur  on  posterior 
side  (Figure  lld-f);  proximal  segment  in  lateral 
view  with  basal  process  posterior  to  digiti- 
form process  acuminate,  intersection  of 
posterior  basal  process  and  digitiform  process 
usually  in  form  of  a  deep  angular  notch;  in 
posterior  view  proximal  segment  with  axis 
of  posterior  basal  process  extending  somewhat 
parallel  to  digitiform  process  and  not  overlap- 
ping anterior  basal  process,  latter  angled  to- 
ward articulation  between  proximal  and  distal 
segments.  Left  P5  with  Rel  longer  than  that  in 
plumata  (see  Figure  30). 


Additional  Description 


Female 


Right  furcal  ramus  considerably  shorter 
than  in  plumata  relative  to  prosome  (see  Figui'e 
25),   right  furcal  ramus  with   median  ratio  of 


1.5 


1.4  - 


E    1,3 

e 


o 

CO 

o 
q: 

Q. 


1,2 


o 


LJ 


-11,1- 


10 


I  9 


s 


€9 


% 


a    c 


^^    9 


e      9€ 

2 

»   c 


€>9     9 
9    ^ 


mom 
€)  left 
»  right 

sobrina 
A  left 
Aright 


2-A     A-2 


4v 


A 
i^ 


9     ^     i^     t\     t. 
2 


.02  03  ,04  ,05 

LENGTH  OF   Th  E-I  SPINE,  mm 


.06 


Figure  10. — Length  of  prosome  (ordinate)  plotted 
against  length  of  ThIV-V  spine  (abscissa)  for  females  of 
PonteUina  morii  and  P.  sobrina. 


length  to  width  1.25:1,  range  1.12-1.44:1,  46 
specimens;  lateral  edge  of  right  ramus  with 
small  point  variable  in  shape  just  anterior  to 
base  of  outermost  seta  (Figure  9e,  h),  glandular 
tissue  within  ramus  as  in  plumata. 

P5  with  Re  bearing  hairs  along  median  mar- 
gin (Figure  9g);  Ri  relatively  longer  than  that 


Table  2.  —  Length  of  posterior  spine  on  thoracic  segment  IV-V  in  adult  females  of 

Poiiicllina  iiiorii  and  P.  sobrina. 


Species 

,v  ( m  m ) 

Range  (mm) 

\ 

N 

P.  morii 

left  side 

0.0263 

0.018-0.035 

0.00  to 

38 

right  side 

0.0275 

0.020-0.035 

0.0032 

40 

combined 

0.0269 

0.018-0.035 

0.0037 

78 

P.  sohniui 

left  side 

0.0409 

0.033-0.050 

0.0032 

33 

right  side 

0.0404 

0.028-0.049 

0.0032 

32 

combined 

0.0407 

0.028-0.050 

0.0045 

65 

81 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


0.2  mm 
a.b.c 

0.2  mm 


cl,e,f,g,h 


'I^CV 


Figure  11. — PoiUelUna  morii  sp.n.,  adult  male:  a.  right  Al,  dorsal  view  (Lusiad  11-66);  b.  variation  in  ThIV-V  spine, 
lateral  view  (left  to  right:  Shellback  105;  Troll  25;  Lusiad  11-55;  Troll  32A;  2  specimens  Monsoon  6);  c.  ThIV-V,  P5 
and  first  two  segments  of  urosome,  lateral  view  (Lusiad  V-78);  d.  P5,  posterior  view  (same  as  a);  e.  P5  chela,  lateral 
view  (same  as  c);  f.  apex  of  distal  segment  of  P5  enlarged  (same  as  c);  g.  aberrant  chela  showing  a  weakened  subapical 
spur  on  distal  segment,  posterior  view  {Anion  Britnn  /-58);  h.  aberrant  chela,  lateral  view  (same  as  g). 


in  plinnata,  Re  being  less  than  1.8  times  longer 
than  Ri,  median  1.45:1,  range  1.22-1.76:1,  55 
specimens  (see  Figure  29);  Ri  typically  with 
two  relatively  equal  apical  spines  (Figure  9g, 
i;  Table?). 

Attached  spermatophore  observed  in  four 
specimens  (see  Figure  33f-h,  Table  5),  appear- 
ance and  orientation  similar  to  that  in  platy- 
chela  except  for  less  cement  on  ventral  side  of 
urosome,  especially  on  anal  segment. 

Male 

Right   furcal    ramus   differing   from  that   in 


plumata  in  having  a  relatively  shorter  length 
(see  Figure  26),  median  length-to-width  ratio 
1.93:1,  range  1.80-2.07:1,  39  specimens,  but 
overlapping  extensively  with  its  congener  from 
the  eastern  equatorial  Pacific  (described  below). 
Left  P5  with  Rel  considerably  longer  than 
that  in  plumata:  in  morii  length  of  left  P5 
Rel  to  length  of  right  furcal  ramus  ranges 
from  1.08  to  1.26:1,  20  specimens  (see  Figure 
30). 

Etymology 

This     patronym     commemorates     the     late 


82 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


Takamochi  Mori  who  first  called  attention  to 
the  distinctiveness  of  this  species  and  for  his 
pioneering  contributions  to  our  knowledge  of 
Pacific  Calanoida. 

Types 

Holotype:  Adult  male,  TL  1.36  mm,  PUR 
3.25:1;  sorted  from  plankton  sample  taken 
at  Lusiad  II  stn.  66,  lat.  01°54'N,  long.  79°0rE, 
30  Aug.  1962,  1-m  net.  oblique  tow.  maximum 
cable  out  280  m,  USNM  No.  141621. 

Allotype:  Adult  female,  TL  1.56  mm,  PUR 
3.87:1,  right  furcal  ramus  length  0.090  mm, 
width  0.080  mm,  from  same  sample  as  male. 
USNM  NO.  141622. 

Paratypes:  56,  59  from  same  sample.  USNM 
No.  141623. 


Reference  specimens:  2d,  29,  Lusiad  V 
stn.  76,  lat.  02°01'S,  long.  91°58'E,  24  Apr.  1963, 
1-m  net,  oblique  tow,  maximum  cable  out  280  m. 
USNM  No.  141625.  2d  29.  Capricorn  stn.  2, 
lat.  02°54'N,  long.  168°40'E,  28  Nov.  1952,  1-m 
net,  oblique  tow,  maximum  cable  out  200  m. 
USNM  No.  141624. 

Distribution 

P.  mcmi  was  found  primarily  at  Indian 
and  Pacific  Ocean  localities  distributed  in  a 
zonal  band  lying  roughly  between  lat.  20 °N 
and  20° S  (Figure  12).  Occurrences  at  higher 
latitudes  are  few  and  mostly  in  the  vicinity  of 
western  boundary  currents;  e.g.,  in  the  Kuroshio 
Current  region  just  east  of  Japan  and  east  of 
southern  Africa  in  the  region  of  the  Mozam- 
bique and   Agulhas   Currents.   In  the  eastern 


20°       0°       20° 


20°     .=....„.,    60°      .  100°  140°  180°  140°  100°  60°  20°  0°  20° 

Figure  12. —  Puntellina  morii  sp.n.     Geographical  distribution  of  captures  recorded  during  the  present  study. 


83 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Pacific  niorii  approached  the  Americas  in  the 
vicinity  of  Baja  California  and  also  at  the 
latitudes  of  the  Gulf  of  Guayaquil. 

Among  the  72  quantitatively  analyzed  sam- 
ples containing  niorii  estimates  of  abundance 
ranged  from  0.003  to  0.5  individuals  per  m-*, 
the  median  being  0.01.  In  the  sets  of  samples 
selected  for  quantitative  analysis  (Figure  lb) 
mean  abundance  in  the  Indian  Ocean  exceeded 
0.04  individuals  per  m'*,  5  or  more  times  higher 
than  that  found  in  sets  of  samples  from  the 
Pacific  Ocean  (Figure  35,  Table  14);  frequency 
of  occurrence  in  the  Indian  Ocean  (~30%)  was 
also  higher  than  in  the  Pacific  Ocean  (^20%). 

PONTELLINA  SOBRINA  SP.N. 

(Figures  13  and  14) 

Specimens  seen:  421  adult  females,  364  adult 
males. 

Standard  measurements:  specimens  randomly 
selected  from  locations  spanning  the 
observed  geographical  distribution. 

Total  length  (TL).  mm: 


Standard 

Mean 

error 

Speci- 

f^j 

Range 

■iX 

mens 

Female 

1.57 

1.42-1.78 

0.0134 

50 

Male 

1.41 

1.18-1.64 

0.0118 

56 

Prosome-urosome  length  ratio  (PUR): 


Median 

Range 

Specimens 

3.73:1 

3.17-4.16:1 

33 

3.43:1 

3.06-3.75:1 

51 

Diagnosis 


Female 


Most  similar  in  appearance  to  morii.  Spini- 
form  process  strongly  demarcated  from  ThlV- 
V  corner  and  typically  symmetrical  as  in  morii, 
but  spine  almost  twice  as  long  (Figure  10, 
Table  2);  in  dorsal  view  weakly  curved  spines 
extending  posterolaterad  (Figure  13g).  Genital 
segment  with  two  lateral  clusters  of  hairs  on 
both  sides,  anterior  cluster  consisting  of  fine 
hairs,  posterior  cluster  consisting  of  coarse 
hairs  (Figure  13  a,  g);  posterior  margin  of  seg- 
ment with  border  of  long  fine  hairs  as  in  all 
preceding  species. 


Male 


ThIV-V  (Figure  14a.  b)  as  in  female.  P5 
(Figure  14c,  d)  most  similar  to  that  in  morii 
with  notable  differences  present  in  chela. 
Distal  segment  of  chela  relatively  long,  apex 
extending  beyond  apex  of  laterodistal  digitiform 
process  of  proximal  segment.  Moreover,  distal 
segment  lacking  subapical  spur  (Figure  14c,  d); 
in  lateral  view  posterior  basal  process  and  digiti- 
form process  of  i)roximal  segment  separated 
by  rounded  notch  (Figure  14d);  proximal 
segment  in  posterior  view  as  in  morii.  Left 
P5  with  Rel  longer  than  that  in  plumata  (see 
Figure  30). 

Additional  Description 

Female 

Right  furcal  ramus  somewhat  shorter  relative 
to  its  width  as  well  as  to  length  of  prosome  (see 
Figures  25,  27),  median  ratio  of  right  furcal 
ramus  length  to  width  1.12:1,  range  1.02-1.31:1, 
66  specimens;  lateral  edge  of  right  ramus  usual- 
ly with  broad  point  immediately  anterior  to 
base  of  outermost  seta  (Figure  13h),  glandular 
tissue  within  ramus  as  in  plumata. 

P5  (Figure  13i)  similar  to  that  in  morii  except 
that  ratio  of  lengths  of  exopod  to  endopod  tends 
to  be  smaller,  median  1.29:1,  range  1.07-1.50:1. 
52  specimens  (see  Figure  29);  Ri  typically  with 
two  relatively  equal  apical  spines  (see  Table  7). 

Attached  spermatophore  observed  in  27  speci- 
mens (see  Table  5),  not  differing  appreciably  in 
general  features  from  those  observed  in  morii. 

Male 

Right  furcal  ramus  similar  to  that  in  morii 
in  both  relative  length  (see  Figure  26)  and  in 
proportion  of  length  to  width,  median  1.88:1. 
range  1.71-2.07: 1,  40  specimens  (see  Figure  28); 
Rel  of  left  P5,  compared  to  length  of  right  furcal 
ramus,  relatively  longer  than  that  in  morii  (see 
Figure  30),  this  ratio  in  .'«)briiia  ranging  from 
0.96-1.17:1,21  specimens. 

Etymology 

The  name  sobri)ia,  Latin  for  cousin,  was  chosen 
to  acknowledge  the  close  morphological  relation- 
ship to  Diorii. 


84 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


0.2nnm 
I 1 

b,f 

0.2mm 
I 1 

a,c,cl,e,g 
0.2mm 


h,i 


d 


h 


Figure  13. — Pontellimi  sobrina  sp.n.,  adult  female:  a.  ThIV-V,  urosome,  lateral  view  (Bonacca  35);  b.  habitus, 
lateral  view  (same  as  a);  c.  variation  in  ThIV-V  spine,  lateral  view  (left  to  right:  EASTROPAC  Jordan  037;  2 
specimens  Bonacca  31,  Shellback  51):  d.  variation  in  left  ThIV-V,  lateral  view,  specimen  with  two  spines  (Bonacca 
50);  e.  variation  in  left  ThIV-V,  dorsal  view  (La  Creuse  OT-6);  f.  habitus,  dorsal  view  (same  as  a):  g.  ThIV-V  and 
urosome,  dorsal  view  (same  as  a);  h.  variation  in  lateral  margin  of  right  furcal  ramus,  dorsal  view  (left  to  right: 
La  Creuse  OT-6;  La  Creuse  18;  La  Creuse  OT-14;  La  Creuse  17;  La  Creuse  OT-14,  different  specimen;  2 
specimens  La  Creuse  18;  Bonacca  33);  i.  P5,  anterior  view  (same  as  a). 


85 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


0.2  mm 
0.2mm 


a,b 


Figure  14. — Poniellina  sobrina  sp.n.,  adult  male:  a. 
ThIV-V,  part  of  urosome  and  P5,  lateral  view  [TO-58-1 
(Scot)  33] ;  b.  variation  observed  in  ThlV-V  spine,  lateral 
view  (left  to  right:  Bonacca  55;  Bonacca  43;  2  specimens 
Bonacca  51);  c.  P5,  posterior  view  (La  Creuse  21); 
d.  chela  P5,  lateral  view  (Shellback  5 1). 


Types 

Holotype:  Adult  male.  TL  1.42  mm,  PUR 
3.44:1,  sorted  from  plankton  sample  taken  at 
Bonacca  stn.  51,  lat.  13°44'N,  long.  90°51'W, 
19  Aug.  1963,  Vz-m  net,  oblique  tow,  maximum 
cable  out  200  m.  USNM  No.  141617. 

Allotype:  Adult  female,  TL  1.52  mm,  PUR 
3.75:1,  right  furcal  ramus  length  0.080  mm, 
width  0.075  mm,  from  same  sample  as  male. 
USNM  No.  141618. 


Paratypes:  56,  59  from  same  sample.  USNM 
No.  141619. 

Reference  specimens:  56,  59,  La  Creuse  stn. 
15,  lat.  08°41.2'N,  long.  79°31.2'W,  4  May  1962, 
GV  net  towed  between  0  and  4  m.  USNM  No. 
141620. 

Distribution 

P.  sobrina  is  obviously  indigenous  to  the 
eastern  tropical  Pacific  Ocean  (Figure  15).  The 
species  was  found  only  at  Pacific  stations  east 
of  long.  130°W.  Occurrences  at  latitudes  higher 
than  20°  were  restricted  to  a  few  samples  taken 
near  the  mouth  of  the  Gulf  of  California.  Thus, 
the  apparent  boundaries  coincide  in  general  with 
the  North  and  South  Equatorial  Currents,  and 
its  westernmost  limits  lie  in  the  path  of  the 
Equatorial  Countercurrent. 

In  31  quantitative  samples  containing  sobrina 
abundance  varied  from  0.01  to  0.66  individuals 
per  m•■^  the  median  being  0.04.  In  the  sets  of 
samples  selected  for  quantitative  analysis 
(Figure  lb)  sobritia  showed  mean  abundance 
values  (ranging  from  0.02  to  0.09  individuals  per 
m^)  similar  to  those  of  morii  in  the  Indian  Ocean 
and  to  plionata  outside  of  the  eastern  tropical 
Pacific  (see  Figure  35,  Table  18). 


DEVELOPMENTAL  STAGES 
AND  BREEDING 

Immature  specimens  of  Pontellina  were  sort- 
ed routinely  together  with  adults.  They  were 
neither  as  abundant  nor  as  frequent  as  the 
adults,  a  difference  that  is  at  least  partially 
attributable  to  escapement  of  younger  stages 
through  the  relatively  coarse  mesh  (~0.5  mm)  of 
most  of  the  nets  used  to  obtain  our  samples. 
General  Pontelli)ia  habitus  characteristics  such 
as  appearance  of  the  prosome  in  dorsal  view, 
rostrum,  strong  Mx2,  and  relatively  long 
setae  on  A2  and  Mnd  served  to  distinguish 
the  specimens.  The  number  of  swimming  legs 
and  body  segments  as  well  as  total  body  length 
were  used  to  determine  their  ontogenetic  stage. 
Identification  to  species  was  reasonably  certain 
only  for  stage  V  copepodids;  details  are  present- 
ed below.  Specimens  of  stages  III  and  IV 
were  tentatively  assigned  to  species  on  the 
basis  of  their  geographical  origin.  The  following 


86 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


20°  0°  20° 


■?0°     -.... ...;...,  ,.,     60°  lOO"  140°  180°  140°  100°  60°  20°  0° 

Figure  15.  —  Pontellina  sobrina  sp.n.  Geographical  distribution  of  captures  recorded  during  the  present  study. 


20° 


notes  and  Table  3  summarize  ontogenetic 
characteristics  of  stages  II  through  V  prevailing 
in  the  genus. 

Stage  II 

TL  0.72-0.76  mm  (5  specimens).  Rostral  fila- 
ments and  dorsal  ocelli-like  structures  present; 
prosome  with  4  free  segments,  urosome  with 
2  segments.  Re  of  PI  and  P2  bimerous,  Ri  of 
PI  and  P2  and  both  rami  of  P3  unimerous,  P4 
consisting  of  a  pad  with  folds,  short  setae  and 
an  incipient  Ri;  P5  lacking. 


Stage  III 


(Figure  l6c) 


TL    0.82-0.88    mm    (20    specimens).    Neither 
sexes  nor  species  distinguishable.  Prosome  with 


5  segments,  urosome  with  2  segments.  Re  of 
P3  bimerous,  Ri  of  P3  as  well  as  both  rami  of 
P4  unimerous.  P5  lobiform,  bearing  one  apical 
seta. 


Stage  IV  Female 


(Figure  l6a) 


TL  0.90-1.10  mm  (22  specimens,  probably 
including  all  four  species).  Urosome  with  3 
segments.  Re  of  P3  and  P4  bimerous,  Ri  uni- 
merous. Re  of  Po  unimerous;  right  Re  and  elon- 
gate seta  on  mediodistal  corner  of  Re  slightly 
larger  than  those  of  left  P5;  Ri  lobiform,  in- 
completely separated  from  B2. 

Stage  IV  Male 

(Figure  l6b) 

TL  0.95-1.10  mm  (22  specimens,  probably 
including    all    four    species).    Male    resembles 


87 


FISHERY  BULLETIN:  VOL.  72,  NO.  I 


Table  3. — Ontogenetic  development  in  copepodite  stages  of  Pontellina. 


Ill 


IV  : 


IV, 


V  • 


Thoracic  segments 
Free  abdominal  segments 
Rostrol  filaments 
Dorsal  ocelli 
Right  Al 


PI  Re  segments 
Ri  segments 

P2  Re  segments 
Ri  segments 

P3  Re  segments 
Ri  segments 

P4  Re  segments 

Ri  segments 
P5   Re  segments 


Ri  segments 


4 

5 

5 

5 

5 

5 

2 

2 

3 

3 

4 

3 

present 

present 

present 

present 

present 

present 

present 

present 

present 

present 

present 
segments 

13-16 
swollen 

present 

2 

2 

2 

2 

3 

3 

1 

1 

1 

1 

2 

2 

2 

2 

2 

2 

3 

3 

1 

1 

1 

1 

2 

2 

1 

2 

2 

2 

3 

3 

1 

1 

1 

1 

2 

2 

lobe, 

1 

2 

2 

3 

3 

1  seta 

lobe. 

1 

1 

1 

2 

2 

1  seta 

absent 

lobe, 

1 

1 

2 

1 

1  seta 

right  leg 

right  leg 

right  leg 

right  leg 

slightly 

slightly 

larger 

with  5 

larger 

larger 

than  left 

setae. 

than  left 

than  left 

left  leg 
with  6 
setae 

absent 

absent 

rudimen- 
tary 

1 

absent 

1 

corresponding  stage  of  female,  but  P5  with  Ri 
absent  or  appearing  as  a  small  distal  swelling 
on  B2.  Right  Re  also  slightly  larger  than  left. 


Stage  V  Female 


(Figure  17a-l) 


TL  1.18-1.48  mm  (40  specimens,  all  species 
represented).  ThIV  and  V  almost  completely 
separated.  Urosome  with  3  segments,  genital 
segment  largest  and  with  weak  ventral  swelling. 
Furcal  rami  incompletely  separated  from  anal 
segment.  Lateral  margin  of  right  furcal  ramus 
proximal  to  first  seta  lacking  protrusion.  Left 
and  right  Al  symmetrical.  Re  of  P3  and  P4 
trimerous,  Ri  bimerous.  P5  with  proportions  of 
Re  and  Ri  showing  similarity  to  those  of  adult. 
Re  unimerous  with  5  setae  on  right  leg,  6  setae 
on  left  leg;  proximal  Si  of  left  side  notable  for 
its  size  and  curved  shape,  an  asymmetry  lacking 
in  the  adult. 


Stage  V  Male 


(Figure  18a-q) 


TL  1.20-1.44  mm  (40  specimens,  all  species 
represented).  ThIV  and  V  almost  completely 
separated.  Urosome  with  4  segments.  Furcal 
rami  incompletely  separated  from  anal  segment. 


0.2  mm 


a  -c 

Figure  16.  —  Pontellina  sp.  copepodite  stages:  a.  stage 
IV  female,  P5,  anterior  view;  b.  stage  IV  male,  P5, 
posterior  view;  c.  stage  III  copepodid,  P5. 

Right  Al  with  segments  13-16  slightly  swollen, 
segments  distal  to  swelling  partly  fused.  P5 
trimerous,  slightly  curved  medially;  right  leg 
longer  than  left  leg,  Ri  not  developed. 

In  other  genera  of  Pontellidae,  as  well  as  in  a 
number  of  other  heterarthrandrid  families 
(Diaptomidae,  Temoridae,  Centropagidae,  Pseu- 
dodiaptomidae)  we  note  that  fusion  of  urosomal 
segments  I  and  II  in  the  female  first  appears  in 
the  stage  V  copepodid  (Gurney,  1931;  Johnson, 
1935;  Crisafi,  1960;  Lawson  and  Grice,  1970; 
Grice,  1971).  Morphological  features  of  the  geni- 
tal plate,  antrum,  and  internal  structures  such 
as  the  seminal  receptacles  (Fahrenbach,  1962; 
Frost  and  Fleminger,  1968)  are  lacking  in  the 
stage  V  female.  We  also  note  that  in  most 
amphascandrid  families  (e.g.,  Calanidae,  Para- 


88 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


0.2  mm 
a-h 

0.2mm 


I  - 


d 


Figure  17. — Copepodite  stage  V,  females:  a-d.  ThIV-V,  right  P5  and  urosome,  lateral  view;  e-h.  anal  segment,. furcal 
rami,  dorsal  view;  i-1.  P5,  anterior  view.  Poniellina  pliiinaia:  a,  e  {Atlantis  //-31-1);  i  (Lusiad  V-60).  P.  platychela: 
b,  f,j  (Atlantis  //-20-42).     P.  niorii:  c,  g,  k  (Dodo  VI,  near  Mombasa  Harbor).     P.  sobrina:  d,  h,  I  [TO-58-1  (Scot)  56] . 


calanidae,  Pseud ocalanidae,  Aetideidae, 
Euchaetidae.  Phaennidae,  Scolecithricidae)  but 
not  in  Eucalanidae  (Johnson,  1937;  Sewell. 
1929;  Bjornberg,  1967;  and  our  unpublished 
observations  of  all  species)  fusion  of  urosomal 
segments  I  and  II  seems  to  be  delayed  until  the 
appearance  of  the  sexually  mature  female.  This 
pattern  has  been  documented  by  a  number  of 
ontogenetic  studies  on  individual  species  (With, 
1915;  Nicholls.  1934;  Campbell,  1934;  Marshall 
and  Orr,  1955;  Matthews,  1964;  and  our  un- 
published observations). 


Notes  on  Individual  Species 

PoiitelliiiJ  pliiiiiata 

(Figures  17a,  e,  i;  18a,  e,  i,  m,  p) 

Copepodite  stage  V  female:  TL  x  1.38  mm. 
range  1.26-1.48  mm,  10  specimens.  Postero- 
lateral corner  of  ThV  (Figure  17a)  produced 
into  a  strong  point  similar  to  the  adult.  Furcal 
rami  symmetrical  (Figures  17e,  19),  length  of 
right  ramus  relative  to  width  greater  than  that 
in  morii  (Figure  20).  P5  Ri  shorter  than  in  niorii 


89 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


0.2  mm 
I 1 

a-q 


Figure  18. — -Copepodite  stage  V,  males:  a-d.  ThIV-V,  right  P5  and  urosome,  lateral  view;  e-h.  anal  segment, 
furcal  rami,  dorsal  view;  i-m.  P5,  posterior  view;  n-q.  range  of  variation  in  ThIV-V,  lateral  view.  Puntellinu  phimata: 
a,  e,  i  (Lusiad  V-43):  m  (Monsoon  2,  atypical  P5  with  Ri);  p  (left  to  right:  Atlantis  11-31-74:  Atlantis  II-H-l;  Atlantis 
//-31-28;  Atlantis  //-31-23;  Gascoyne  Gl/32/63;  Troll  25A).  P.  platychelu:  b  (Atlantis  //-31-60);  f ,  j  (Atlantis  ll-}\- 
15);  n  (left  to  right:  Oregon  1289;  Atlantis  //-31-50;  Atlantis  //-20-42;  Atlantis  //-31-57).  P.  morii:  c,  g,  k  (Lusiad  V-43); 
q  (left  to  right:  EQUAPAC  Horizon  31;  Lusiad  V-68;  Anion  Britun  II-5S:  Anton  Bniun  /-60).  P.  sobrina:  d,  h,  I:  La 
Creuse  18);  o  [left  to  right:  EASTROPAC  Rockaway  064;  TO-58-1  (Scot)  29;  TO-58-1  (Scot)  38;  EASTROPAC 
Rockaway  071;  TO-58-1  (Scot)  36;  EASTROPAC  Rockaway  056]. 


[ 


90 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


platychela 


30 
20 


S    lOf 


3       0 

o 

UJ 

L^  20 


10 

0 

20 

10 


- 

— 

Y-,. 

plumata 

1 

1 

r-r+wto??:^ 

- 

— 

morii 

- 

^^^^^ 

c 

^i 

1 

_ 

— 

:V^^\XN>>^ 

sobrina 

- 

~^~ 

1 

..u 

0.15    0.10   0.05 

<-)H 


0     005   0.10    015   020 
+  ) 


Figure  19. —  Frequency  distribution  of  differences  in  length 
of  left  furcal  ramus  and  right  furcal  ramus  for  the  four 
species  of  Poniellina.  Gray  with  heavy  outline  =  adult 
females;  left-diagonal  hatch  with  light  outline  =  adult 
males;  right-diagonal  hatch  with  dotted  outline  =  stage 
V  females. 


,09 


E    08 

E 

t- 
Q 


07 


4  plumata 
o  morii 


♦      ♦♦ 


O  O  O        O  O         ♦-S     4-2 

o  3-4  4      3-4  ♦  ♦ 

O  0-7     O  f-2  f-3     ^ 

o  o 


.13  14  .15 

LENGTH,  mm 


16 


17 


Figure  20. — Width  of  right  furca  (ordinate)  plotted  against 
length  (abscissa)  for  female  stage  V  copepodids  of  Pont  el- 
Una  pi II mala  and  P.  morii. 


relative  to  length  of  right  furcal  ramus  (Figure 
21).  Re  to  Ri  length  ratio,  median  3.0:1.  range 
2.3-3.5:1,  19  specimens  (Figure  22);  left  P5 
with  medialmost  seta  on  Re  small  and  gently 
curved  (Figure  17i)  relative  to  that  in  morii 
(Figure  17k). 

Copepodite  stage  V  male:  TL  x  1.30  mm, 
range  1.20-1.44  mm,  10  specimens.  Postero- 
lateral corner  of  ThV  ending  in  a  broad  point 
(Figure  18a,  p).  Terminal  segment  of  right  P5 
about  3.1  times  longer  than  wide  (Figure  18i), 
endopod  rarely  pre.sent  (Figure  18m).  Furcal 
rami  (Figure  18e)  similar  in  relative  length 
and  width  to  those  of  female. 


07 


06 


I     05 


in 

0. 


04 


O 

I 


o 

UJ     03 


O 


O 

OO 
O      2-0         O 

O         O 
O  0-2 


0-2 


O        O        O 


♦  plumata 
o  morii 


♦ 

♦  2-^        4 

♦  2-4    ♦♦ 

2-4  ♦         ♦ 

♦ 


13  14  15  .16 

LENGTH  OF  RIGHT  FURCAL  RAMUS,   mm 


.17 


Figure  21.  —  Length  of  P3  Ri  (ordinate)  plotted  against 
length  of  right  furcal  ramus  (abscissa)  for  female  stage  V 
copepodids  of  Poniellina  plumaia  and  P.  morii. 


go 
o 

UJ 

q: 


plumata 


I — T 


-rn 


n-n 


I \ I I I L 


1.5 


111 


20 


2.5 


3.0 


Re 


P5-H^,  St.S:  Females 
Ri 


Figure  22. — Frequency  distribution  of  P5  Re:Ri  ratio  for 
female  stage  V  copepodids  of  Poniellina  plumaia  and  P. 
morii. 


91 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Poiitc'lliiiii  pUttychela 
(Figures  17b,  f,  j;  18b,  f,  j,  n) 

Copepodite  stage  V  female:  Th  x  1.37  mm, 
range  1.18-1.46  mm.  10  specimens.  ThV  postero- 
lateral corners  rounded  and  ending  in  a  small 
denticle  (Figure  17b)  as  in  adult.  Furcal  rami 
(Figure  170  and  P5  (Figure  17j)  resembling 
those  of  p/«»mfa.  _ 

Copepodite  stage  V  male:  TL  x  1.30  mm, 
range  1.24-1.36  mm,  10  specimens.  Margin  of 
posterolateral  corner  of  ThV  with  weak  denticle 
(Figure  18b,  n).  P5  with  distinctive  right  leg 
(Figure  18j).  Re  considerably  broader  than  in 
the  other  three  species,  about  1.6  times  as  long 
as  wide.  Furcal  rami  (Figure  18f)  as  in  plianata. 

Poiitelliiui  niorii 

(Figures  17c,  g,  k;  18c,  g,  k,  q) 

(Notes  based  on  specimens  from  localities  in  the 
Indian  Ocean.) 

Copepodite  stage  V  female:  TL  x  1.28  mm, 
range  1.18-1.36  mm,  10  specimens.  ThV  corner 
typically  with  a  small  spiniform  point  (Figure 
17c)  resembling  that  in  the  adult.  Ri  of  P5 
(Figure  17k)  longer  than  in  plumata  (Figure 
21),  typically  with  2  spines;  Re:Ri  length  ratio 
considerably  less  (median  2.1:1,  range  1.7- 
2.6:1,  20  specimens)  than  in  plumata  (Figure 
22).  Furcal  rami  symmetrical  (Figure  19), 
shorter  than  those  in  plumata  (Figure  20),  as 
in  sexually  mature  stages.  Medial  setalike  pro- 
cess of  Re  of  left  P5  (Figure  17k)  more  abruptly 
bent  (~90°)  than  that  of  the  other  three  species 
(Figure  17i). 

Copepodite  stage  V  male:  TL  x  1.21  mm, 
range  1.12-1.32  mm,  10  specimens.  Postero- 
lateral corner  of  ThV  ending  in  a  relatively 
short  spiniform  point  (Figure  18c,  q)  about  one- 
half  the  length  of  that  in  sobrina  (Figure  18d, 
o)  and  much  less  robust  than  that  in  plumata 
(Figure  18a,  p).  Di.stal  segment  of  right  P5 
distinctly  bent  mediad  (Figure  18k).  Furcal 
rami  (Figure  18g)  similar  in  relative  length  and 
width  to  those  in  female. 

Pontell/ua  sohr/i/ii 

(Figures  17d,  h,  1;  18d,  h,  1,  o) 

(Notes  based  on  juvtMiilc  specimens  from  eastern- 
most Pacific  localities  which  were  accompanied 
by  large  numl)ers  of  adults;  the  localities  are  rela- 
tively distant  from  those  yielding  worii.) 


Copepodite  stage  V  female:  TL  x  1.25  mm, 
range  1.18-1.34  mm,  10  specimens.  Differences 
between  sexually  immature  sobrina  and  morii 
females  are  relatively  weak,  e.g.,  greater  length 
of  the  ThV  point  (Figure  17d)  and  the  weaker 
bend  of  the  medial  setalike  i)rocess  on  the  left 
Re  of  P5  (Figure  171),  appear  to  be  useful,  but 
lack  confirmation  by  measurements  from  a 
geographically  representative  series  of 
specimens. 

Copepodite  stage  V  male:  TL  F  1.25  mm. 
range  1.12-1.38  mm,  10  specimens.  Postero- 
lateral corner  of  ThV  produced  into  a  relatively 
long  slender  point  (Figure  18d,  o).  Right  P5 
with  .straight  distal  segment  resembling  that 
in  plumata,  but  all  segments  in  P5  of  sobnjui 
appear  slightly  wider. 

Sex  Ratios 

In  laboratory-reared  populations  sex  ratios 
among  adult  copepods  of  several  families  have 
been  found  to  vary  widely  (for  recent  comments 
see  Heinle,  1970;  Katona,  1970;  Paffenhdfer, 
1970).  In  natural  populations,  however,  late 
immature  copepodids  have  been  found  to  pro- 
duce males  and  females  in  about  equal  numbers 
(Marshall.  1949).  Among  randomly  sorted, 
sexually  mature  adults  of  the  four  species  of 
Poutelliiia  females  consistently  outnumbered 
males  by  roughly  1.3: 1  (Table  4). 

Assuming  that  the  sexes  are  genetically  one 
to  one,  the  observed  male-to-female  ratios  in 
Poutelliua  could  be  readily  accounted  for  if 
females  live  longer  than  males,  a  likelihood 
suggested  by  many  authors  for  various  ampha- 
scandrid  copepod  genera.  In  a  small  series 
of  rearing  experiments  on  Labidocera  trispi)iosa, 
A.  Barnett  (pers.  comm.,  1972)  has  found  that 
following  the  adult  moult  females  live  2  to  3 
wk  and  males  about  1  wk. 

Table  4. — Frequency  of  sexually  mature  individuals  and 
sex  ratios  in  Pontcllina. 


9 

6 

No. 

Species 

N 

O 

0 

N 

% 

9:0 

samples 

plane  hcla 

M59 

54 

'137 

46 

1.16 

72 

pliiniiini 

1,259 

58 

917 

42 

1.37 

531 

iiioni 

433 

60 

284 

40 

1.52 

240 

sDhniui 

421 

54 

364 

46 

1.16 

113 

1  One  sample,  i.e.,  Allanlis  II  20-42,  was  omitted  because  it 
provided  the  extremely  disproportionate  capture  of  327  moles 
and  10  females. 


92 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


REMARKS  ON  SEASONAL 
OCCURRENCE  AND  BREEDING 

Captui'e  records  alone  do  not  necessarily  dis- 
close the  distribution  of  the  optimal  habitat  of  a 
planktonic  species  (Fleminger,  1972),  i.e., 
the  region  in  which  reproduction  is  usual, 
typically  successful,  and  from  which  the  progeny 
is  likely  to  become  entrained  in  a  circulation 
system  that  ultimately  provides  new  breeding 
stocks  with  suitable  conditions  for  their  off- 
spring. Our  sampling  of  PoiiteUiua  is  incomplete 
for  critical  assessment  of  the  impact  of  seasonal 
change  on  occurrence,  geographical  distribu- 
tion, or  reproduction.  Moreover,  as  a  conse- 
quence of  the  relatively  large  mesh  sizes  of  the 
nets  (see  Table  15)  sampling  of  most  juvenile 
stages  was  not  representative.  Thus  spermato- 
phore  occurrence  on  females  is  the  only  source 
of  breeding  information  available  to  us. 

In  C«/o»».s\  spermatophores  constitute  evi- 
dence of  mating  within  the  past  48  h  (Marshall 
and  Orr,  1955).  In  other  copepods,  spermato- 
phores are  lost  or  shed  soon  after  attachment; 
in  Labidocera  trispiitosa  discarding  of  the 
spermatophore  has  been  observed  to  occur  just 
prior  to  egg  laying  (G.  Theilacker,  pers.  comm., 
1970). 

Few  spermatophores  were  observed  in  Poiitel- 
Uiia  (Table  5)  suggesting  that  as  in  Calanus 
they  are  not  retained  for  an  appreciable  time 
after  attachment.  The  27  records  of  s(>b)i)ia 
females  bearing  a  spermatophore  afford  a 
glimpse  of  breeding  patterns  in  that  species. 
Spermatophore-bearing  females  appeared  in 
Febi-uary,  May,  and  August  samples.  The  local- 
ities span  most  of  the  latitudinal  extent  of 
sobrina  captures  on  record,  but  all  lie  to  the 
east  of  long.  98°W,  and  most  are  relatively  close 
to  the  mid-American  coast.  In  contrast,  the  few 
records  of  morii  and  plionata  bearing  spermato- 
phores are  widespread,  suggesting  that  both 
species  breed  over  a  more  extensive  range  in 
accordance  with  their  more  extensive  geographi- 
cal distributions. 

PHYLOGENETIC 

RELATIONSHIPS  AMONG 

THE  PONTELLINA  SIBLINGS 

Dobzhansky  (1972)  stressed  the  heuristic 
value  of  sibling  species  when  he  pointed  out 


"...  sibling  species  permit  the  dissection  of 
the  process  of  speciation  into  studiable  com- 
ponents." PoiitelUna  appears  especially  well 
suited  to  explore  the  question  of  speciation  in 
the  planktonic  biotope.  Restriction  to  shallow 
tropical  and  subtropical  oceanic  waters  apparent- 
ly limits  opportunities  for  complex  diversity 
in  i)lanktonic  calanoids  (Fleminger  and  Hulse- 
mann,  1973).  The  four  species  of  Po)itelli)ia 
satisfy  the  number  of  suitable  ranges  that  appear 
to  be  available  within  these  biogeographical 
limits. 

Three  of  these  ranges  reflect  the  geographical- 
ly limited  and  relatively  shallow  lenses  of 
Tropical  Surface  Water  (Wyrtki,  1966,  1967) 
described  from  the  eastern  equatorial  Pacific 
but  also  known  on  the  basis  of  similar  general 
features  to  prevail  in  the  equatorial  Atlantic 
Ocean  (Muromtsev,  1963)  and  in  the  equatorial 
Indian  Ocean  (Wyrtki,  1971).  The  fourth  range 
consists  of  the  series  of  deeper  lenses  of  warm 
water  beyond  Tropical  Surface  Waters  and 
lying  between  the  subtropical  convergences  in 
the  Atlantic,  Indian,  and  Pacific  Oceans. 

PonteUiiia's  position  as  a  distinctive  genus 
is  unchallenged,  being  strongly  separated 
from  its  closest  relative,  P(>)tteUopsis,  in  both 
morphology  and  habitat.  Compelling  evidence 
favoring  consideration  of  the  four  populations 
of  P(>)iteUi)ia  as  separate  species  is  furnished 
by  the  morphological  distinctions  of  each,  their 
independent  geographical  distributions,  and 
the  morphological  integrity  of  their  diagnostic 
features.  That  is,  despite  widespread  regions  of 
geographical  overlap  where  two  or  three  of  the 
species  may  be  captured  in  the  same  net  tow, 
no  evidence  of  intergradation  or  hybridization 
has  been  observed. 

Evidence  of  strongly  regionalized  habitat 
adaptation  may  be  inferred  from  the  apparent 
failure  of  each  species  to  colonize  areas  occupied 
by  its  adjacent  congener.  Failure  to  colonize 
must  be  regarded  as  significant.  All  four  species 
occur  in  surface  layers  (Wilson,  1942;  Heinrich, 
1961;  Vinogradov  and  Voronina,  1964;  Flemin- 
ger and  Hulsemann,  unpublished  data)  where 
air-sea  interactions  provide  opportunity  for 
dispersal  and  advection  with  neighboring  cir- 
culation systems,  but  the  distribution  of  each 
species  overlaps  at  most  only  a  portion  of  the 
range  of  its  neighboring  congeners. 


93 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 
Table  5 . — Adult  female  specimens  of  Pontellina  bearing  a  spermatophore. 


Total 

Sac 

Sampling 

length 

length 

Species 

date 

Latitude 

Longitude 

Station 

(mm) 

(mm) 

P.  phuychela 

III -8-66 

00°08'S 

18°31'W 

Atlanli\  //-20-42 

1.66 

0.490 

P.  plumaui 

VI-15-69 

33°49'N 

139°10'E 

Scan  IV-1 

1.66 
1.76 

0.460 
0.460 

VI  ■6-52 

01°00'S 

112°24'W 

Shellback  47 

1.50 

0.425 

111-30-69 

21°54'S 

110°02'W 

Piquero  V-49 

1.56 

0.365 

P.  n}i>iii 

IV-19-68 

05°irN 

123^58'E 

Circe  ll-NT  11 

1.58 

0.420 

VII-2-52 

05°18'S 

85°04'W 

Shellback  105 

1.86 

0.440 

P.  sohrina 

11-12-67 

00°28'N 

92°02'W 

EASTROPAC 
Riickaway  060 

1.68 

0.390 

V-12-58 

07°22'N 

92°47'W 

Scot  46 

1.56 

1.70 

0.360 
0.395 

V-4-62 

08°4rN 

79°31'W 

La  Creuse  15 

1.40 
1.44 
1.46 
1.42 

0.340 
0.385 
0.370 
0.355 

V-7-58 

09°45'N 

96°04'W 

Scot  35 

1.62 

0.410 

VIII-16-63 

09°5rN 

85°43'W 

Bonacca  42 

1.48 
1.46 

0.385 
0.320 

V-17-62 

13°07'N 

91°34'W 

La  Creuse  OT-6 

1.48 
1.50 

0.330 
0.355 

VIII-18-63 

13°29'N 

90°09'W 

Bonacca  50 

1.50 
1.62 
1.52 
1.48 

0.320 
0.360 
0.340 
0.340 

Vlll-19-63 

13°44'N 

90°51'W 

Bonacca  51 

1.50 
1.52 

0.390 
0.340 

VII 1-20-63 

13°57'N 

92°02'W 

Bonacca  58' 

1.54 
1.56 
1.48 
1.56 
1.50 
1.50 
1.52 
1.50 

0.390 
0.415 
0.355 
0.365 
0.375 
0.380 
0.395 
0.385 

*   One  additional  specimen  was  observed  in  this  sample  with  a  damaged  spermatophore. 


Morphology  and  distribution  also  support 
our  conclusion  that  the  four  species  are  phylo- 
genetically  close  and,  in  fact,  comprise  a  mono- 
phyletic  unit — or  holophyletic  in  Ashlock's 
(1971)  terminology — appearing  to  have  been 
recently  derived  from  a  single  tropical-sub- 
tropical epiplanktonic  precursor  (in  prepara- 
tion). 

Our  objective  in  this  section  is  to  examine 
the  degree  of  similarity  among  the  siblings  as  a 
basis  for  determining  phy  logenetic  relationships. 
In  the  absence  of  a  fossil  record,  inferences 
drawn  from  comparative  morphology,  geograph- 


ical distribution,  and  essential  habitat  adap- 
tation may  provide  a  relative  historical  per- 
spective for  judging  phylogeny  within  a  taxon. 
Phylogenetic  relationships  within  P(>)iteUi)io 
were  judged  both  intuitively  and  objectively 
on  the  basis  of  characters  that  showed  a  cohesive 
pattern  of  similarity  or  dissimilarity.  We  con- 
cur with  the  rebuttals  of  Throckmorton  (1965, 
1968)  and  Voris  (1971)  to  the  views  of  orthodox 
numerical  taxonomy  in  defense  of  the  weighting 
of  taxonomic  characters:  i.e.,  characters  differ 
in  their  taxonomic  usefulness,  and  the  adaptive 
significance  of  these  differences  is  not  beyond 
logic  and  comprehension. 


94 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 

Throckmorton  and  Voris  show  empirically 
that  characters  are  decidedly  not  equal  in  their 
content  of  phylogenetic  information.  Their 
operational  method  for  character  selection  rests 
upon  the  direct  and  assumption-free  advantages 
of  a  posteriori  weighting  of  correlated  sets  of 
derived  characters. 

Judging  from  the  numerous  articles  in 
Systematic  Zoology,  numerical  taxonomic 
phylogenies  derived  from  large  numbers  of 
unweighted  characters  do  not  vary  from  phylo- 
genies implicitly  or  explicitly  arranged  by 
experienced  workers  employing  sets  of  corre- 
lated adaptive  characters. 


Body  Dimensions  and  Proportions 
Total  Length  (TL) 

Intraspecific  sexual  differences  in  TL  are 
greater  than  interspecific  differences;  males  are 
about  10%  shorter  than  females  (Table  6,  Figure 
23).  In  both  sexes  morii  and  .so6?'/»fl  are  smaller 
than  platychela  and  plumata.  The  diffei'ence 
between  the  mean  TL  of  males  or  females  of 
species  belonging  to  the  same  pair  is  not  signifi- 
cant. However,  the  difference  between  the  mean 
TL  of  either  species  of  one  pair  with  that  of 
either  species  in  the  other  pair  is  highly  signifi- 
cant in  both  sexes  (Student's  f-test).  The  over- 
all difference  is  produced  largely  by  the  dis- 
tance between  the  rostrum  and  the  cephalic 
groove  and  the  length  of  the  furca  (see  below). 

Prosome-Urosome  Length  Ratio  (PUR) 

In  both  sexes  niorii  and  sobrina  occur  at  the 
high  end  of  the  PUR  distribution  (Table  6. 
Figure  24).  In  males,  morii  and  sobri)m  have 
similar   distributions   at   the   high    end    of  the 


25% 


> 
o 

-z. 

uj       0 

o 

UJ 

"^    25% 
U- 


75% 


25% 


-25% 


25%  - 


25% 


25% 


-25% 


12  14  1.6  18 

TOTAL   LENGTH,   mm 


O^  N  =  57 
platychela 

%      N  -30 


O^N  =  67 
plumata 

N  =  75 


¥ 


(T^N  =  58 
morii 

%     N  =  54 


O^N  =  56 
sobrina 

%     N=  50 


2.0 


Figure    23. — Frequency    distribution    of  total    length    for 
both  sexes  of  the  four  species  of  Pontellina. 


Table  6. — Total  length  (TL)  and  prosome-urosome  length  ratio  (PUR)  of  Pontellina  spp.  adults;  data  from  various 

geographical  localities  combined. 


Species 


TL  (mm) 


PUR 


X 

Range 

'     X 

N 

X 

Range 

'x 

N 

1.699 

1.54-1.96 

0.0173 

30 

3.438:1 

3.19-3.89:1 

0.0362 

30 

1.692 

1.44-1.94 

0.0126 

75 

3.282:1 

2.92-3.72:1 

0.0179 

75 

1.608 

1.38-1.88 

0.0145 

54 

3.643:1 

3.39-4.10:1 

0.0360 

35 

1.570 

1.42-1.78 

0.0134 

50 

3.732:1 

3.17-4.16:1 

0.0417 

33 

1.556 

1.41-1.74 

0.0089 

57 

3.223:1 

2.86-3.55:1 

0.0228 

49 

1.511 

1.34-1.92 

0.0130 

67 

3.066:1 

2.84-3.93:1 

0.0243 

52 

1.435 

1.26-1.68 

0.0100 

58 

3.339:1 

2.87-3.73:1 

0.0245 

50 

1.406 

1.18-1.64 

0.0118 

56 

3.426:1 

3.06-3.75:1 

0.0235 

51 

Moles: 

P.  platychela 
P.  plumata 
P.  morii 
P.  sobrina 

Females: 

P.  platychela 
P.  plumata 
P.  morii 
P.  sobrina 


95 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


range,  platychela  being  intermediate  and  plnnia- 
ta  occupj'ing  the  low  end.  Females  follow  the 
same  general  i)attern,  but  iiiorii  and  sob7i)ia 
show  considerably  less  overlap.  . 

Length  of  Furcal  Rami 

The  length  of  both  rami  is  directly  related  to 
prosome  length  as  well  as  TL.  Shortening  and 
fusion  of  the  right  ramus  in  adult  females  in- 
troduces asymmetry  but  the  change  does  not 
alter  the  essential  relationship  to  body  length. 
Ill  the  female  sex  (Figure  25)  niorii  and  sobrnua 
occupy  one  side  of  the  overall  distribution  of 
length  of  the  right  ramus,  platychela  and 
plumata  the  other  with  virtually  no  overlap 
between  the  two  pairs  of  species.  Males  show 
more  scatter  (Figure  26)  and  apparent  differ- 
ences in  allometry;  sohrina  and  niorii  tend  to 
diverge  with  respect  to  furcal  length  while 
plumata  and  platychela  tend  to  diverge  with 
respect  to  prosome  length. 

Examination  of  furcal  length  relative  to 
furcal  width  increases  separation  of  the  three 
equatorial  species.  It  also  enhances  separation 
of  platychela  and  the  Atlantic  samples  of  plu  ma- 


-25% 

...... 

-25% 

_M    i^ 

cr^  N  =  49 
platychela 

%      N  =  30 


o 

ID 

o 

UJ 

CE    25% 


25% 


25% 


25% 


plumata 
2     N=75 


cr^N=50 
morii 

%     N  =  35 


O^N  =  5l 
sobrina 

%     N  =  33 


2  8  I         3.0  I  32  I         3,4  1         3,6  I         3,8  I         4  0  I 

Prosome 
Urosome 

Figure  24. — Frequency  distribution  of  P:U  ratio  for  both 
sexes  of  the  four  species  of  Ponwllina. 


- 

- 

D 

1.5 

~ 

♦ 

♦ 

- 

t.     • 

♦ 

2 

- 

A 

• 

•     D 

♦ 

- 

A 

D 

♦ 

3 

E   '4 

- 

• 

•q»    ♦ 

^-2 

E 

- 

A     A 

•     D    D     D     ♦ 

D 

o 

~ 

•  ^^^    A 
4-A     A 

• 
A 

♦-2     2-» 

3    ♦-□     ♦ 

♦ 

D 
♦-2 

o 

g    1.3 

Ll 
O 

X 
H 

•     a2  a 
2-A^2A-^  •-< 
•    ^^     • 

> 

♦    ♦-s*    4-4 

♦ 

-z. 
y   ,2 

A 
A 

2 

D 

-^ , ;  -v,^ 

A 

• 

A      A     •-2 
A     ^ 
A    V2 

♦ 

♦   ♦  ♦   ♦ 

♦ 

2-A 

A      • 

♦ 

L                        3-^ 

A 

I.I 

• 
A 

♦ 

♦  plumata 

•  morn 

1  n 

1-             • 

1                1 

1                1 

1         1         1 

A  sobrina 
D  platychela 

1         1         1 

08  10  12  14  16 

LENGTH  OF  RIGHT  FURCAL  RAMUS,  mm 

Figure  25. — Length  of  P  (ordinate)  plotted  against  length 
of  right  furcal  ramus  (abscissa)  for  females  of  the  four 
species  of  Ponicllina. 

ta  as  well  as  separation  of  morii  and  the  Indo- 
Pacific  samples  of  plumata  (Figure  27).  A 
generally  similar  pattern  is  seen  in  the  males 
(Figure  28)  except  that  morii  and  sobrina  over- 
lap freely  with  respect  to  the  furcal  length: 
width  ratio. 

ThIV-V  Posterior  Spine 

Strong  sexual  dimorphism  appears  in  adults. 
Among  the  females,  plum,ata  is  unique;  the  base 
of  the  posteriorly  directed  spine  rises  roughly 
at  the  level  of  the  proximal  margin  of  the  genital 
segment,  the  spine  is  robust  and  broadly  trian- 
gular in  both  dorsal  and  lateral  views  (Figure 
3a,  d-f).  The  spines  in  the  three  equatorial 
species  are  similar  to  each  other  in  being  dimin- 
utive and  needlelike  or  dentiform.  They  differ 
primarily  with  respect  to  relative  length  of 
the  spine  (Figures  6a,  c,  g,  h;  9a,  c,  e,  f;  11;  13a, 
c,  g). 

The  ThIV-V  spine  in  males  appears  in  three 
states:  plumata  exhibits  a  minute  denticle  that 


96 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


l-5r 


1.4 


E   13 

E 


o 

IS) 

o 
tr 

CL 


♦  p/umafa 

•  morii 

A  sobrina 
□  platychela 


.2 


o 

X 

I- 

UJ 


I.I 


1.0 


09 


A  ^ 


A 

J L 


12  14  16  18  .20 

LENGTH   OF   RIGHT   FURCAL   RAMUS,   mm 


Figure  26. — Length  of  P  (ordinate)  plotted  against  length 
of  right  furcal  ramus  (abscissa)  for  males  of  the  four  species 
of  Pontellina. 


may  be  borne  on  a  weakly  produced  boss;  morii 
and  sobrina  bear  a  small  spine  resembling  that 
found  in  the  female  of  the  species;  platychela 
has  no  outgrowth  whatsoever. 


r  0  p/umata  Pacific- Ind 

an 

<>  plumata  Atlantic 

1.60 

-  •  morn 

F 

A  sobrina 

E 

UJ 

n 

140 

-  u  platychela 

-A                       • 

8„H    0^  °*yoD. 

CO 

o 
q: 

Q- 

o 

X 

120 

A 
A 

A  A 

•  '.  •  •• 
\  a5  "^ 

,•                                A 

0 

1- 

A    A 
A 

0                    C»0^0*0 

UJ 

- 

• 

0 

_i 

1  10 

\ 

• 
1     1 

1           1           1           1 

1.00 

1.20 

1.40                1.60 

1.80 

LENGTH 

RinuT     Fl  IPr  Al       DAK 

1  IC 

WIDTH  ---".-  .^-......o 

Figure  27. — Length  of  P  (ordinate)  plotted  against  length: 
width  ratio  of  right  furcal  ramus  (abscissa)  for  females  of 
the  four  species  of  Pontellina. 


o 

CO 

o 
tr 
a. 


1.40 


120 


0  plunnata  Pacific  -  Indian 
'i  plumata  Atlantic 

-  •  morii 
A  sobrina  ^ 

-  a  platyctiela 


O    1.00 


^ 


D 


D 


n 


A   2- 


.  AAjg      *"   • 


-^ 


2  •-a  .        D 

A  ^^^     0 


A 

A 


1.60 


180  2.00 

LENGTH 


220 


240 
RIGHT  FURCAL  RAMUS 


260 


WIDTH 

Figure  28. — Length  of  P  (ordinate)  plotted  against  length: 
width  ratio  of  right  furcal  ramus  (abscissa)  for  males  of  the 
four  species  of  Pontellina. 

Female  Genital  Segment 

The  distribution  of  lateral  clusters  of  spinules 
provides  the  basis  for  distinguishing  the  different 
character  states.  Two  species,  sobrina  and 
plumata,  are  similar  in  having  two  clusters  on 
each  side;  morii  has  one  cluster  and  platychela 
has  none.  There  is  preliminary  evidence  from 
examination  with  the  scanning  electron  micro- 
scope (SEM),  however,  that  the  similarity  of 
plumata  with  sobrina  may  in  fact  be  superficial. 
Cluster  size  and  spinule  size  differ  even  under 
the  light  microscope,  and  the  SEM  indicates 
the  presence  of  fine  sensoriiform  filaments  in 
sobrina  and  morii,  but  not  in  plumata  or  platy- 
chela. The  SEM  also  revealed  a  second  cluster 
consisting  of  minute  denticles  in  morii  anterior 
to  the  one  visible  with  the  aid  of  a  light  micro- 
scope (in  preparation). 

Female  Fifth  Pair  of  Swimming  Legs 

The  two  characters  found  in  P5  that  provide 
diagnostic  information,  i.e.,  the  Re:Ri  length 
ratio  (Figure  29)  and  the  distribution  of  spines 
on  the  endopod  (Table  7)  agree  in  showing 
strong  similarity  between  morii  and  sobrina 
on  the  one  hand  and  between  platychela  and 
plumata  (all  geographical  sectors  combined) 
on  the  other.  It  should  be  noted,  however,  that 
the  similarity  between  platychela  and  plumata 
is  weakened  when  the  comparison  is  restricted 
to  Atlantic  Ocean  samples  of  plumata  (in 
preparation). 

The  distribution  of  the  spines  on  the  endopod 
is  also  noteworthy  by  virtue  of  the  compelling 


97 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


10- 


0 


20- 


10- 


0 

>20 

■z. 

UJ 

O    10 

UJ 


0^ 

4oL 


20 
10 

0 


J L 


platychela 
x=  2.3100 
s=.30l8 
N  =  49 


J I 


1     1     1     1     1 

plumata 

x  =  2.3858 

s  =  .2677 

— I    N  =  59 

— 1      1 

J I 


morn 

x=  1.4555 

s  =  .l5ll 

N  =  55 

\ \ I 


\  ^ 


I      I      I      I      I 


sobrina 

x  =  l.2827 

s=.0904 

N  =  52 

I      I      I      I 


1.0 


14 


P5 


1.8        2.2 

Re 

Ri 


2.6       3.0 


.9 


Figure    29. — Frequency  distribution  of  P5  Re:Ri  ratio  for 
females  of  the  four  species  of  Pontellina. 

evidence  it  ))rovides  in  support  of  our  judgment 
that  the  four  siblings  are  valid  species  recently 
derived  from  the  same  parent  species.  The 
frequencies  and  vv^idespread  geographical 
occurrence  of  phenotypes  are  evidence  of  simple 
Mendelian  inheritance  and  indicative  of  balanced 
polymorphism.  Another  pontellid,  Labklocera 
diandra,  has  also  been  shown  to  be  polymorphic 
(Fleminger,  1967b).  In  both  Pontellina  and 
Labidocem  the  apparent  polymorphism  affects 
a  sexually  modified  appendage  before  the  onset 


of  maturity,  the  phenotypes  being  distinguish- 
able in  copepodite  stage  V.  However,  within 
its  species  group,  only  L.  diandra  displays  the 
polymorphism  which  is  visible  in  the  male  sex. 

Male  Fifth  Legs  and  Right  First  Antenna 

Segment  lengths  of  sexually  modified  appen- 
dages that  we  examined  tend  to  vary  directly 
with  prosome  length.  We  chose  the  length  of 
the  right  furcal  ramus  (Figure  25)  instead  of 
the  prosome  as  our  standard  body  length 
reference  for  comparing  morphometry  of 
sexual  appendages  because  the  furcal  ramus 
length  yielded  graphic  presentations  with  con- 
siderably less  scatter  within  each  sample. 


.20 


E 

e 

< 


< 
O 

3 


1- 
X 


^   .14 


o 


o 


.10 


♦  ♦      ♦ 

2-*   #-2  a 

4    i-s^-z   2-n    n-3 


2-*  ^^♦f  ♦-S 
♦      ♦ 


♦ 

D     D 


^-2     ''i 

no   D 

/2     /2 

n   D   D 


A 


•     • 


♦  plumata 

•  morii 

A  sobrina 
D  platychela 


Va 


•    -^'^A     •'    A 


A      A^  A-3 


A- 4 


_L 


J 


08  ,10  .12  -14  .16 

LENGTH  OF   LEFT    P5   Re1,  mm 


Figure  30. — Length  of  right  furcal  ramus  (ordinate)  plot- 
ted against  length  of  left  P5  Rel  (abscissa)  for  males  of  the 
four  species  of  Pontellina. 


Table  7. — Frequencies  (%)  of  phenotypes  varying  in  the  number  of  spines  on  the 
endopod  of  the  fifth  pair  of  swimming  legs  in  Pontellina  spp.  females. 


Species  (/V) 


Left  leg: 
Right  leg: 


I  spine 
1  spine 


1  spine 
2  spines 


2  spines 
1  spine 


2  spines 
2  spines 


plulychela  (100) 
pluinuia  (300) 
morii  (200) 
sobrina  (100) 


34 

16 

12 

38 

37 

12 

16 

34 

1 

2 

1 

96 

0 

1 

0 

99 

98 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 

Table   8. — Dimensions  of  selected  segments  of  sexually  modified  appendages  of 

Pontt'lliiui  spp.  adult  males. 


Segments  and 

species 

.v(mm) 

s 

N 

Range  (mm) 

Left  P5  Rel  length; 

plalychela 

0.1193 

0.0048 

21 

0.110-0.130 

plurnuta 

0.0988 

0.0067 

48 

0.085-0.120 

morii 

0.1221 

0.0079 

19 

0.110-0.130 

sohrina 

0.1269 

0.0060 

21 

0.120-0.140 

Right  P5  Rel  width: 

plalychela 

0.1895 

0.0109 

20 

0.170-0.210 

plumata 

0.1647 

0.0112 

47 

0.140-0.195 

morii 

0.1960 

0.0091 

20 

0.180-0.215 

sohrina 

0.1814 

0.0098 

21 

0.165-0.200 

Al  segment  18  length: 

plalychela 

0.3417 

0.0152 

26 

0.300-0.365 

plumala 

0.3364 

0.0220 

32 

0.285-0.400 

morii 

0.3063 

0.0159 

31 

0.280-0.340 

sobrina 

0.3014 

0.0137 

29 

0.280-0.335 

Length  of  Left  First  Exopodal  Segment 

This  segment  is  much  shorter  in  plumata 
than  in  the  other  three  species  (Figure  30, 
Table  8).  Small  differences  appear  among  the 
three  equatorial  species  but  they  are  inconspic- 
uous in  comparison  to  their  distribution  as  a 
group  relative  to  that  of  phi  niata. 

Width  of  Right  First  Exopodal  Segment 

As  in  the  section  above  on  the  left,  Rel,  the 

.20  r 


E 


en 


o 
cc 


:   I! 


16 


O    ,14 


O 

X 

o 


♦ 
♦     ♦     t 


♦     ♦      ^U-2 


♦-2 


D 


2-D     D  n-2  D 

£-♦    ♦    ♦    f^f    ♦    *      2-0  D'^n   a 

.       .       .,3  .,3  ♦ 

3-4    ♦    ♦    ♦   n-2      n  D 


♦    ♦ 


a 


•   • 


•  % 

2s^ 
A    ^    •     ^-4 

2-«     • 


♦  plumata 

•  morii 

A  sobrina 
D  platycliela 


A     A-2       '^     A-3 
A     A     A-2         A 


_L 


_L 


_J_ 


.14  16  18  .20 

WIDTH   OF  RIGHT   P5   Rel,  mm 


22 


Figure  31. — Length  of  right  furcal  ramus  (ordinate)  plot- 
ted against  width  of  right  P5  Rel  (abscissa)  for  males  of 
the  four  species  of  Poniellinu. 


distributions  of  the  three  equatorial  species 
broadly  overlap,  but  plumata  tends  to  be  ap- 
preciably smaller  (Figure  31,  Table  8). 

Morphology  of  Right  First  Exopodal  Segment 

The  proximal  segment  of  the  chela  appears 
in  three  essential  states:  the  swollen  condition 
of  platycliela  (Figure  7a,  b),  the  slender  condi- 
tion of  plumata  (Figure  4i,  j)  and  the  slender 
condition  characterized  by  a  more  distal  position 
of  the  posterolateral  outgrowth  shared  by  morii 
and  sobrina  (Figures  lid,  e;  14c,  d). 

Morphology  of  Right  Second  and  Third 
Exopodal  Segments 

The  distal  segment  of  the  chela  appears  in 
three  states:  the  swollen  condition  of  plalychela 
(Figure  7b),  the  shortened,  spurred  condition  of 
morii  (Figure  lid,  f)  and  the  simple  attenuated 
condition  shared  by  plumata  and  sobrina  (Fig- 
ures 4j,  14d). 

Length  of  Segment  18,  Right  First  Antenna 

Two  siblings,  plumata  and  plalychela,  broadly 
overlap  and  occupy  the  upper  half  of  the  overall 
distribution;  the  other  two,  morii  and  sobrina, 
broadly  overlap  in  the  lower  half  of  the  distri- 
bution (Figure  32,  Table- 8). 

Spermatophore  Attachment 

(Figures  33,  34) 

The  three  equatorial  species  agree  in  having 


99 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


20 


3 


< 


;  18 


<     16 

o 

cr 

3 


X 

O     14 

cr 

Ll_ 

o 

I 

UJ 


JO 


♦  plumata 

^  sobrina 
D  platychela 


♦       ^ 

♦     ♦  D 

D        2-D     D     ♦  "^    ♦     D-2 

♦     ♦     D    t^,j»^~D    ^-uX 


•     •"♦ 


•  •2    2-»^»    '^    A-2         A 

A 

•  2-»     •-2 

^    A-2         A^~^    A 
A     A     A     A  'ii     A     A 
A 


28  30  32  34  36 

LENGTH  OF  RIGHT  A1  SEGMENT   18,  mm 


Figure  32. — Length  of  right  furcal  ramus  (ordinate) 
plotted  against  length  of  segment  18  of  right  Al  (abscissa) 
for  males  of  the  four  species  of  Puiitellina. 


the  proximal  end  of  the  sac  cemented  to  the 
right  side  of  the  genital  segment,  morii  and 
sobrina  in  a  virtually  identical  fashion,  differing 
somewhat  from  the  condition  found  in  platychela. 
In  plumata,  however,  attachment  is  restricted 
to  the  proximal  end  of  the  neck,  the  remainder 
of  the  neck  and  the  entire  sac  hanging  free  from 
the  body  but  showing  helical  convolutions 
similar  to  those  present  in  the  other  congeners. 

Geographical  Occurrence 

Three  of  the  species,  morii,  sobrina,  and  platy- 
chela, were  found  primarily  in  low  latitudes 
between  20°N  and  20°S  (Figures  8,  12,  15). 
The  three  species  are  essentially  allopatric  to 
one  another,  each  predominating  in  a  geograph- 
ically different  segment  of  equatorial  circulation 
in  the  world's  oceans  (see  Table  20).  Relatively 
high  frequencies  of  abundance  or  occurrence 
coincided  with  eutrophic  equatorial  regions 
characterized  by  a  shallow  O2  minimum  layer 
(^1  ml/liter)  lying  at  or  near  the  permanent 
thermocline.  The  three  species  tend  to  concen- 
trate in  the  uppermost  20  to  30  m  of  depth  and 
virtually  disappear  below  50  m  (in  preparation). 

The  fourth  sibling,  plumata,  is  widespread  in 
subtropical  latitudes  (Figure  5)  and  may  be 
locally  abundant  in  tropical  regions  downstream 
from   areas  of  persistent  upwelling.   It  is  the 


only  species  of  the  genus  with  a  circumglobal 
range  but  tends  to  be  infrequent  to  absent  in 
tropical  areas  dominated  by  its  equatorial 
cognates  (see  Table  20).  Its  vertical  distribution 
appears  to  encompass  the  surface  to  200-m 
depth  in  subtropical  latitudes,  the  lower  limit 
shoaling  to  about  100  m  in  tropical  latitudes 
(in  preparation). 

Summation  of  Ph>  logenetic 
Similarities 

Thus  within  the  framework  of  the  17  charac- 
ters considered  above,  morii  and  sobrina  show 
the  highest  frequency  of  similar  character 
states.  In  practice  their  overall  morphological 
similarity  is  sufficient  to  require  routinely 
close  inspection  at  appreciable  magnifications 
for  reliable  separation.  Though  the  next  most 
frequently  linked  pairing,  plumata  and  platy- 
chela, show  similarity  in  about  60%  of  the 
features  in  Table  9,  at  low  magnifications  under 
a  stereomicroscope  they  are  almost  as  distinct 
from  one  another  as  each  is  from  motii  or 
sobriiia. 

As  noted  in  the  calanoid  genera,  Labidocera 
and  Clausocalaiius  (Fleminger  1967b;  Frost 
and  Fleminger,  1968),  the  distinguishing 
features  of  the  sibling  species  in  Pontellina  are 
limited  to  sexually  modified  characters,  i.e., 
the  fifth  legs,  the  genital  segment,  the  posterior 
corner  of  ThIV-V,  the  male  right  Al,  and 
the  caudal  furca. 

There  is  reason  to  regard  plumata  as  re- 
taining the  strongest  similarity  to  the  Pontellina 
ancestral  stock.  This  view  rests  upon  two  fea- 
tures: the  slightly  stronger  resemblance  of 
sexually  modified  structures  in  plu  //m^o,  especial- 
ly the  ThIV-V  spine  in  the  female,  to  those  of 
Poiitellopsis  and  of  the  more  eurytopic  circum- 
global distribution  of  plumata  in  comparison  to 
the  restricted  distributions  of  its  equatorial 
congeners. 

To  examine  the  statistical  significance  of  the 
phylogenetic  relationships  inferred  from  the 
characters  given  in  Table  9  we  have  utilized  a 
computer  program  that  detects  significant 
levels  of  co-occurrence  among  sets  of  overlapping 
functions.  The  program  has  been  informative  in 
the  detection  of  communities  as  well  as  in 
systematic  classifications  of  flexibacteria  (Fager, 
1969). 


100 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  POS'TELLINA 


0.2  mm 
a-h 


g 


h 


Figure  33. — ThIV-V  and  urosome  of  female  with  attached  spermatophore.  a,  b.  Poniellina  plumata.  c-e.  P.  platychela. 

f-h.  P.  morii.  a,  c,  f  dorsal  view;  b,  d,  g  lateral  view;  e,  h  ventral  view. 


101 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Table  9. — Shared  character  states  among  species  of  Pontellina. 


Character 


No.  of 
states 


Species  sharing 
same  state 


Species  with  unique 
character  state 


Remarks 


1 .  .vTL  9 


2.  PUR  9 


3.    Furcai  ramus  length  9 


4.    Furcai  ramus 

lengthiwidth  ratio  9 


5.  Th  IV-V  9 

6.  Th  IV-Vd 

7.  Genital  segment  9 

8.  P5  9,  Re:Ri  ratio 

9.  P5  9,  Ri  spines 

10,    P5  •,  left  Rel  length 
1  1.   P5i,  right  Rel  width 

12.  P5:;,  right  Ret  morphology 

13.  P5^,  right  Re  2-3  morphology 

14.  Al    '  right  seg.  18  length 

15.  Spermatophore  attachment 

16.  Geographical  distribution 


17.    Latitude  and  depth 
distribution 


2      morii  and  sohrina; 

phimaia  and  plaiychela 

2      iiiorii  and  sobrina; 

pliimaui  and  plaiychela 

2      morn  and  sobrina; 

phtmala  and  plaiychela 

2      niorii  and  sobrina: 

plunutia  and  plaiychela 

2      inoni  and  sobrina: 

pluiuala  and  plaiychela 

2      morn  and  sobrina: 

plumala  and  plaiychela 


2      morii  and  sobrina: 

plumala  and  plaiychela 

2      morii  and  sobrina: 

plumala  and  plaiychela 

2      morii,  sobrina.  and 

plaiychela 
2      morii  and  sobrina: 

plumala  and  plaiychela 


3  plumala  and  sobrina 

2     morii  and  sobrina: 

plumala  and  plaiychela 

4  morii  and  sobrina: 
plumala  and  plaiychela 

2      morii,  sobrina,  and 
plaiychela 

2  morii,  sobrina.  and 
plaiychela 

3  morii  and  sobrina 

3     plumala  and  sobrina 

2  morn  and  sobrina: 
plumala  and  plaiychela 

3  morii  and  sobrina 


2      morii,  sobrina,  and 
plaiychela 


plumala 


plaiychela:  morii 


plumala 
plumala 

plumala:  plaiychela 
morii:  plaiychela 

plumala:  plaiychela 

plumala:  plaiychela: 
morii:  sobrina 

plumala 


Significant  differences 
produced  by  furcai  ramus 
length 


Significant  differences 
produced  by  furcai  ramus 
length 


Minor  differences  between 
plumala  and  plaiychela 
ignored 

SEM  results  ignored 


Frequency  of  similarities  in  17  chorocters: 

morii  and  sobrina  linked  in  15  instances  or  82%. 

plaiychela  linked  with  morii  and  sobrina  in  4  instances  or  24%. 

plumala  and  plaiychela  linked  in  10  instances  or  59%. 

plumala  and  sobrina  linked  in  1  instance  or  6%. 

plumala  unique  in  7  instances  or  4l°o. 

plaiychela  unique  in  5  instances  or  29%. 

morii  unique  in  3  instances  or  18%. 

sobrina  unique  in  1  instance  or  6%. 


102 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


0  2  mm 
I 1 

a  -c 

Figure  34. — ThIV-V  and  urosome  of  female  PonielUna  sohrina  with  attached  spermatophore:  a.  dorsal  view;  b.  lateral 

view;  c.  ventral  view. 


The  program  calculates  an  index  of  affinity 
for  all  possible  pairs  of  species  as  the  geometric 
mean  of  the  proportion  of  common  character 
states  corrected  for  the  number  of  characters 
used  in  the  analysis:  i.e.,  Jl\/A  X  B  —  Viy/W , 
where  A  and  B  are  the  total  number  of  charac- 
ters recorded  for  the  two  species,  B  ^  A,  and 
J  is  the  number  of  shared  character  states. 
Values  of  the  index  above  0.5  have  been  found 
empirically  to  provide  objective  repeatable 
groupings  of  related  sets  of  values. 

A  nuniber  of  characters  listed  in  Table  9  were 
omitted  from  the  recurrent  group  analysis  to 
avoid  biasing  the  computations  with  redundant 
information.  Characters  1,  2,  and  4  were  not 
scored  since  their  morphometric  states  are 
determined  largely  by  the  value  of  character  3. 
Characters  11  and  14  were  deleted  since  they 
parallel  character  10  in  showing  a  direct  re- 
lationship to  TL  and  to  furcal  length.  In  the 
absence  of  a  fossil  record  the  distributional 
characters  16  and  17  were  not  scored  on  the 
intuitive  grounds  that  they  are  complex  deriv- 
atives of  both  1)  overall  genetic  adaptation  and 
2)  fortuitous  abiotic  historical  events  that 
might  obscure  essential  phylogenetic  patterns. 
All  of  the  scored  characters  were  weighted 
equally  and  disregard  the  preliminary  results 
from  SEM  observations. 

The  recurrent  group  analysis  reveals  only 
one  grouping  with  an  index  higher  than  0.5, 
that  of  morix  and  sobnna  (Table  10).  Similar- 
ity between  phonata  and  platychela  falls  well 
below  the  acceptable  level  of  significance.  The 
other  possible  pairings  are  dissimilar  in  most 
to  virtuallv  all  of  the  10  characters  used  in  the 


analysis.  Assuming  equal  rates  of  evolution 
the  results  indicate  that  the  divergence  of 
pliimata,  platychela,  and  the  morii-fiobiiua 
lineage  are  likely  to  be  divisions  of  greater  age 
than  that  of  morii  and  sohrina. 

GEOGRAPHICAL  VARIATION 
AND  SYMPATRY 

In  the  course  of  this  study  two  conspicuous 
and  parallel  instances  of  geographical  varia- 
tion were  encountered  in  the  fifth  legs  of  phauata 
females.  This  variation  was  expressed  in  the 
number  of  spines  at  the  distal  end  of  the  endopod 
and  the  length  of  the  exopod  relative  to  that  of 
the  endopod. 

As  noted  above  the  number  of  spines  on  the 
'  endopod  of  the  female's  fifth  leg  is  polymorphic 
throughout  Pontellina.  The  bilateral  two-spined 
morph  is  overwhelmingly  dominant  in  morii 
and  sobri)ia.  However,  four  morphs  are  common 
in  platychela  and  plumata.  Comparison  of  ran- 
domly selected  samples  of  Atlantic  specimens 
of  pluniata  with  specimens  from  the  Indian  and 
Pacific   Oceans   indicate  significant  differences 

Table  10. — Values  of  the  recurrent  group  affinity  index 
(Fager,  1969)  and  the  probability  of  obtaining  this  or  high- 
er values  by  chance  for  all  possible  pairs  of  Pontellina  spp. 
Further  discussion  in  text. 


Species  pair 


Affinity  index 


morii  and  sobrina 

0.642 

<0.001 

platychela  and  pliimaia 

0.242 

>.4 

platvchela  and  morii 

0.042 

>.8 

platychela  and  sobrina 

0.042 

>.8 

plumata  and  sobrina 

0.042 

>.8 

plumala  and  morii 

0 

103 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


in  the  frequency  of  the  four  morphs  (Table  11). 
The  bilateral  one-spined  morph  is  much  more 
frequent  than  the  bilateral  two-spined  morph  in 
the  Atlantic  Ocean  whereas  in  the  Indian  and 
Pacific  Oceans  the  frequencies  of  the  two  morphs 
are  more  alike  and  the  differences  are  not  signi- 
ficant. 

Notably,  the  frequencies  of  the  morphs  in 
platyckela  differ  significantly  from  those  of  the 
pluniata  sample  from  the  Atlantic  but  not  from 
those  of  the  Indian  and  Pacific  samples  of  phtiii- 
ata.  Of  the  j^airs  of  species  sharing  common 
boundaries  only  niorii  and  sobrina  do  not  appear 
to  have  appreciably  different  morph  frequencies 
(Table  11). 

In  the  ratio  exopod  to  endopod  length  for 
the  fifth  legs  in  females,  the  distribution  of  the 
Atlantic  sample  of  plumata  differed  significantly 
from  those  of  the  Indian  and  Pacific  Oceans 
(Table  12).  As  in  the  case  of  the  endopodal  spines, 
pairs  of  species  with  common  boundaries  show- 
ed significantly  different  distributions  of  the 
exopod-endopod  ratios. 

Extrapolating  from  the  similarity  of  Indian 
and  Pacific  Ocean  samples,  differences  between 
Atlantic  and  Indian-Pacific  populations  of 
plumata  appear  to  be  geographically  abioipt. 
Thus  they  may  be  viewed  as  refiecting  1)  local 


pressures  on  phi  mat  a  within  each  geographical 
population,  2)  restricted  gene  flow  between  the 
Indian  and  Atlantic  Ocean  populations,  3)  or 
both.  P.  plumata  showed  the  highest  frequency 
of  unique  character  states  in  PontelUna  (Table 
9).  Furthermore  it  tends  to  occupy  a  conspicuous- 
ly peripheral  position  relative  to  the  other  three 
species  in  its  dimensions  of  sexually  modified 
appendages  in  both  sexes  (e.g.,  Figures  27,  28, 
30,  31).  It  is  also  the  only  species  of  the  genus 
sharing  common  boundaries  with  the  other 
three  species  of  Poitt('lUna.  Therefore,  the  geo- 
graphical differences  between  Atlantic  and 
Indian-Pacific  populations  of  plumata  parallel 
the  extensive  character  divergence  (Mayr,  1970: 
51-53)  otherwise  distinguishing  the  species.  Con- 
sidering the  fact  that  all  morphological  structures 
involved  are  sexually  modified  it  would  appear 
that  we  are  witnessing  reinforcement  of  pre- 
mating  barriers  (Dobzhansky,  1970:376-382). 

Similar  disjunct  morphological  differences 
distinguishing  Atlantic  from  Indian  and  Pacific 
populations  of  epipelagic  calanoids  have  been 
reviewed  (Fleminger  and  Hulseraann,  1973) 
and  the  number  of  examples  increased  (Flemin- 
ger and  Hulsemann,  1973;  Fleminger,  1973). 
Similar  patterns  in  the  strength  of  divergence 
in    secondary    sexual    characters    relative    to 


Table    11. —  X^    test    of    homogeneity    in    the    distribution 
spines  on  the  endopod  of  the  fifth  legs  in  adult  females. 


of 


Number  of  spines  on  endopod 
(left  leg-right  leg): 


2-2 


1-2 


2-1 


1-1 


Population 


Number  of  specimens 


Total 


platychela.  Atlantic  Ocean 
plumata,  Atlantic  Ocean 
plumata.  Pacific  Ocean 
plumata,  Indian  Ocean 
morii,  Indian  Ocean 
morii.  Pacific  Ocean 
sobrina,  eastern  tropical 
Pacific  Ocean 


plumata  Atl.  vs.  pliiinata  Pac. 
plumata  Atl.  vs.  plumata  Ind. 
plumata  Pac.  vs.  plumata  Ind. 
platychela  vs.  plumata  Atl. 
platychela  vs.  plumata  Pac. 
platychela  vs.  plumata  Ind. 
morii  Pac.  vs.  sobrina 
morii  Ind.  and  Pac.  vs.  plumata 

Ind.  and  Pac. 
sobrina  vs.  plumata  Pac. 


38 

16 

12 

34 

100 

22 

11 

16 

51 

100 

39 

14 

15 

32 

100 

41 

11 

18 

30 

100 

94 

2 

1 

3 

100 

98 

0 

2 

0 

100 

99 

1 

0 

0 

100 

X2 


d.f. 


9.48 

3 

<0.025  p  >0.01 

11.3 

3 

0.01 

0.76 

3 

<0.9p  >0.75 

9.14 

3 

<0.05p  >0.025 

3.61 

3 

<0.5p  >0.25 

2.5 

3 

<0.75p  >0.5 

3.01 

3 

<0.5p  >0.25 

146.84 

3 

<0.001 

84.34 


<  0.001 


104 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 

Table   12. — Comparison  by  rank  test  (Tate  and  Clelland,   1957:89)  of  the  ratio  exopod  length  to  endopod  length  in  the 

fifth  legs  of  adult  females. 


Samples  tested 


Median 


Range 


N 


robs. 


1. 

phiinara,  Atlantic  Ocean 

2.54:1 

2.10-3.08:1 

21 

plumala,  Indian  and  Pacific  Oceans 

2.29:1 

1.97-2.71:1 

38 

2. 

pliiniulu,  Indian  Ocean 

2.27:1 

2.01-2.71:1 

9 

phimala.  Pacific  Ocean 

2.31:1 

1.97-2.64:1 

29 

3. 

pliimata,  Atlantic  Ocean 

2.54:1 

2.10-3.08:1 

21 

ptatychehi,  Atlantic  Ocean 

2.27:1 

1.69-2.91:1 

49 

4. 

plumata,  Indian  and  Pacific  Oceans 

2.29:1 

1.97-2.71:1 

38 

plalychela.  Atlantic  Ocean 

2.27:1 

1.69-2.91:1 

49 

5. 

sobrina,  eastern  tropical  Pacific  Ocean 

1.29:1 

1.07-1.50:1 

52 

morii,  Indian  and  Pacific  Oceans 

1.45:1 

1.22-1.76:1 

55 

856.5 


373 


967.5 


1655.5 


1911.5 


3.58 


0.38 


2.85 


0.14 


5.58 


<0.01 


0.7 


<0.01 


0.88 


<0.001 


sympatry  have  been  discussed  in  recent  studies 
on  the  calanoid  genera  Lahidocera  and  Clauso- 
calanus  (Fleminger,  1967b,  in  press;  Frost  and 
Fleminger,  1968).  The  similarity  of  the  plumata 
case  to  the  character  displacement  found  in 
North  American  chorus  frogs  (Pseudacris). 
reviewed  by  Littlejohn  (1969,  Figure  3),  is 
especially  noteworthy.  Differing  only  in  geo- 
graphical scale,  both  cases  support  the  view  of 
a  growing  number  of  workers  that  premating 
isolating  mechanisms  tend  to  be  a  product  of 
sympatry  resulting  from  expansion  of  the 
range  of  daughter  populations  that  have  diverg- 
ed in  geographical  isolation  (Alexander,  1969). 

REMARKS  ON  HABITAT 
BIOGEOGRAPHY 

Vertical  Distribution 

Essentially  similar  results  from  a  number  of 
independent  sets  of  published  observations  de- 
lineate general  features  of  the  vertical  distribu- 
tion of  P<>)itelUiia.  The  genus  has  been  found 
commonly  between  the  surface  and  200  m.  Un- 
fortunately differences  between  the  congeners 
were  not  noticed,  and  all  specimens  were  re- 
garded as  representing  a  single  species.  Though 
individuals  may  on  occasion  appear  below  200 
m,  the  largest  numbers  have  been  taken  regular- 
ly between  the  surface  and  100  m  (Vinogradov, 
1968).  Diurnal  migrations  seem  to  be  neither 
consistent  nor  extensive  in  vertical  distance 
(Wilson,    1942;     Heinrich,    1961;    Vinogradov 


and  Voronina,  1964;  Roehr  and  Moore,  1965). 
Vinogradov  and  Voronina's  report  of  a  pattern 
of  latitudinal  variation  in  the  depth  range  of 
Pontellina  is  particularly  interesting  in  the 
light  of  differences  in  the  latitudinal  distribu- 
tion of  plumata  and  the  equatorial  species.  In 
central  waters  the  daytime  80%  level  (i.e..  the 
depth  above  which  80%  of  the  population  occurs) 
was  found  at  200  m,  and  the  highest  concentra- 
tions appeared  between  50  and  100  m.  In 
equatorial  waters  of  the  eastern  Pacific  the 
daytime  80%  level  was  found  between  100  and 
150  m,  and  the  highest  concentrations  varied 
between  the  0  to  25  m  and  the  25  to  50  m  sam- 
pling sti'ata. 

Wilson's  (1942)  records  of  Pontellina  during 
Cruise  VII  of  the  CaDiegie  were  based  on  sam- 
ples collected  with  open  nets  routinely  deployed 
at  0830  h  local  time  at  three  depths  (0,  50,  and 
100  m)  and  towed  horizontally.  As  in  Vinogradov 
and  Voronina's  (1964)  results,  Wilson's  data 
also  show  variation  in  frequency  of  captures 
and  aoundance  at  the  three  depths  relative  to 
the  geographical  origin  of  the  samples  (Table  13). 

Vinogradov  and  Voronina  (1963)  and  Voro- 
nina (1964)  found  the  largest  number  of  Pontel- 
li)ia  in  equatorial  surface  waters  of  the  eastern 
Pacific  Ocean.  They  noted  that  the  genus  tends 
to  concentrate  in  upwelling  regions  along  zones 
of  divergence  and  in  the  vicinity  of  the  tropical 
convergence. 

Previous  observations  that  the  genus  Pontel- 
lina  occurs  chieflv  above   100  m  in  the  more 


105 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


eutrophic  equatorial  latitudes  but  may  typically 
extend  through  200  m  or  more  in  the  oligo- 
trophic  subtropics  must  now  be  viewed  within 
the  comi)lexity  of  thi-ee  tropical  and  one  tropical- 
subtropical  species.  In  this  context,  vertical  dis- 
tribution api^ears  to  differ  among  the  species: 
i.e.,  phiniata  probably  has  a  deeper  range  than 
its  three  tropical  congeners.  Confirmation  re- 
quires analysis  of  vertically  stratified  sampling 
from  regions  supporting  pUintata  and  one  or 
more  of  its  cognates. 

Abundance 

Interest  in  patterns  of  geographical  distribu- 
tion relative  to  phylogenetic  affinities  among 
the  species  prompted  us  to  make  preliminary 
comparisons  of  abundance  among  the  species  of 
PontelUua.  For  the  analysis  we  selected  sets 
of  similarly  collected,  quasi-synoptic,  quantita- 
tive samples  that  represented  the  epijjelagic 
layer  between  150  m  or  200  m  and  the  surface. 
The  sets  of  samples  comprise  transects  crossing 
the  equator  at  different  longitudes  in  the  Pacific 
Ocean  (Figure  lb.  Table  14).  Only  adults  were 
tabulated,  the  mesh  width  of  the  i)lankton  nets 
usually  being  too  large  (~0.5  mm)  to  retain 
younger  copepodids  (Table  15).  The  hour  of 
sami)ling  was  ignored  in  the  absence  of  appre- 
ciable differences  in  either  frequency  of  occur- 
rence or  mean  abundance  of  PontelUua  between 
samples  collected  at  day  or  night  (Tables  16,  17). 


The  mean  abundance  of  species  of  PonteUina 
ranged  from  0.01  to  0.9  per  m^  (Figure  35). 
Abundance  in  the  Pacific  followed  a  generally 
familiar  pattern.  Higher  values  api:)ear  in  the 
eastern  third  of  the  Pacific  as  well  as  in  the 
Austral-Asian  seas  and  the  Indian  Ocean  while 
lower  values  predominate  in  the  middle  and 
western  Pacific  (Figure  35). 

The  three  species,  P.  plumafa,  morii,  and 
.so6r///fl,  tend  to  vary  independently  in  abundance. 
Mean  abundance  and  frequency  of  occurrence 
values  from  the  Indian  Ocean  and  Austral- 
Asian  seas  are  similar  for  morii  and  plumata, 
though  evidence  of  finer-scale  geographical 
differences  sejiarating  the  two  si)ecies  within 
the  Indian  Ocean  have  been  noted  (Figure  38). 
Eastward  across  the  Pacific  the  abundance  and 
occurrence  of  plnmafa  persist  or  even  increase 
\x\)  to  but  not  beyond  the  boundary  of  the  eastern 
tropical    Pacific    where   sobriiia    predominates. 

P.  morii  differs  from  plumata  by  showing  a 
sharp  decrease  in  abundance  across  the  entire 
Pacific  Ocean.  However,  high  numbers  of  morii 
were  found  between  10  m  and  the  surface  south 
of  the  equator  along  long.  92 ''W.  This  is  too 
distant  for  direct  transport  from  the  main 
area  of  abundance  in  the  Indian  Ocean  and 
Austral-Asian  seas;  the  unusually  high  values 
for  morii,  1.96  per  m''  at  lat.  4°16'S  and  0.16 
per  m-'  at  lat.  12°19'S,  suggest  recruitment  by 
local  reproduction. 


Table  13. — Occurrence  of  Ponicllinu  by  sampling  depths  at  selected  stations  of 
the  Carnegie  cruise  VII  (Wilson,  1942).  Analysis  limited  to  Carnegie  stations 
providing  abundance  estimates  from  all  three  sampling  depths.  Grouping  of  the 
stations  under  a  particular  species  or  combination  of  species  determined  by  its 
geographical  origin  relative  to  the  distribution  of  species  of  PonteUina  determined 
by  the  present  study.  Values  are  the  sums  of  numerical  equivalents  of  Wilson's 
index  for  PonteUina  abundance  divided  by  the  number  of  stations  in  the  geograph- 
ical group.  Index  equivalents  are:  1  =  1-5  specimens  (trace);  2  =  6-10  specimens 
(rare);  3  =  11-24  specimens  (frequent);  4  =  25-50  specimens  (common);  5  =  >50 
specimens  (abundant). 


Probable 
dominanf 
species 


Sum  of  obundonce 
No.  stations 


0  m        50  m       1 00 


Carnegie  station 
numbers 


sohrina 

morii 

plumaia-morii 

pliimata-platy  chela 

plumalu 


2.66        0.33         1.33  35,37,38 

L83        0.0  0.50  40,41,43-45,48 

1.05         1.11        0.83  98,  99,  101,  103-108,  151,  153-160. 

LOO        1.33        0.67  22,23,27,31,32,34 

0.50        0.67        0.50  16,  18,  49-52,  56,  57,  67,  79,  94,  96,  97, 

109,112,132,133,135,136,139,140,142, 

145,  149 


106 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


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107 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Table   15. — -Above:  Maximum  linear  dimensions  of  Pontellina  cephalothorax.  Dorso-ventral  height  taken  in  lateral  view    m 
includes  Mx2  with  setal  fan  closed,  width  across  trunk  taken  in  dorsal  view  (mm). 


Below:   Mesh  width  of  nets  listed  in  Table  14. 


Copepodite 
stage 


Sex 


Typical 
specimen 

Small 
specimen 


Nets' 


Juday 
net 


III 


IV 


Adult 


0.30  X  0.28         0.38  X  0.34         0.48  X  0.44         0.61    X  0.56         0.62   X  0.60         0.70  X  0.66         0.90  X  0.75 
0.28  X  0.26         0.36  X  0.34  0.46  X  0.42  0.58  X  0.54         0.56  X  0.56         0.62  X  0.60         0.75  X  0.64 


lOSN 


CalCOFI  SN 


POFI  SN 


Mesh 

widths 

(mm) 


0.18 


0.33 


0.55/0.25  (silk) 
0.505/0.28  (nylon) 


0.66/0.31 


lOSN  =  Indian  Ocean  Standard  Net 

CalCOFI  SN  =  California  Cooperative  Oceanic  Fisheries  Investigations  Standard  Net. 

POFI  SN  =  Pacific  Oceanic  Fisheries  Investigation  Standard  Net. 


Table  16. — Comparison  by  Student-r  test  of  mean  abundance  in  day  (0601  to  1800  h  local  time)  and  night  (1801  to  0600 
h  local  time)  collections.  Samples  of  each  set  selected  for  similarity  of  geographical  origin,  collecting  procedures  and 
the  presence  of  the  species,  i.e.,  samples  negative  for  the  species  omitted.  Samples  derived  primarily  from  those  listed 
in  Table  14. 


Day 

Night 

Species 

Source  of  samples 

mean/m^ 

,v2 

N 

mean/m3 

^2 

N 

t 

P 

ptumaui 

Indian  Ocean 

0.0945 

2.7318 

70 

0.1048 

1 .7640 

48 

0.0370 

>0.9 

Austral -Asian  Seas 

0.0483 

0.1488 

12 

0,0413 

0.0784 

7 

0.6000 

>0.9 

Pacific  Ocean 

0.0770 

1.2224 

43 

0.0405 

0.1720 

41 

0.1986 

>0.8 

Atlantic  Ocean 

0.0857 

2.7429 

7 

0.0133 

0.0033 

3 

1.0251 

>0.3 

niorii 

Indian  Ocean 

0.1504 

3.7540 

56 

0.1550 

5.1996 

41 

0.0107 

>0.9 

Austral-Asian  Seas 

0.0300 

0.0400 

12 

0.0400 

0.1040 

6 

0.0081 

>0.9 

Pacific  Ocean 

0.0332 

0.0804 

22 

0.0462 

0.4721 

24 

0.0881 

>0.9 

sohrina 

Pacific  Ocean 

0.0307 

0.0858 

16 

0.0914 

2.8169 

35 

0.1423 

>0.8 

Table   17.  —  Occurrence  of  Pontellina  spp.  in  day  (0601  to   1800  h  local  time)  and 
night  (1801  to  0600  h  local  lime)  samples.  +  present,  -  absent. 


Day 


Night 


+ 


X2 


Atlantic  Ocean: 

pliinuua 

plutychela 
Eastern  Pacific  Ocean: 

phiinata 

niurii 

sobrinu 
Indian -Western  Pacific  Ocean: 

pliimata 

morii 


25 

16 

13 

22 

3.389 

23 

18 

23 

12 

0.383 

15 

19 

13 

49 

4.360 

6 

28 

13 

49 

0.015 

9 

25 

26 

36 

1.648 

08 

30 

87 

31 

0.491 

80 

58 

66 

52 

0.040 

0.1  >  p  >  0.05 

0.75  >  p  >  0.5 

0.05  >  p  >  0.025 

0.9  >  p  >  0.75 

0.25  >  p  >  0.1 

0.5  >  p  >  0.25 

0.9  >  p  >  0.75 


108 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


'  40°E-'  80°E-  'I20°E-  156°E  -  JI74°W-  ■  I26°W  'I24°W-'II3°W-'  95°  W  '    92°W 
80°E      IIO°E    '  IBCE   '  I64'>E     ISCW  II2°W   '  86°W  ' 

I ^1 ^1 1 


INDIAN  OCEAN     AUSTRAL- 
ASIAN 
SEAS 


PACIFIC     OCEAN 


Figure  35.  —  Mean  abundance  (No.  adults/m^)  and  per- 
centage frequency  of  occurrence  in  sets  of  samples  shown 
in  Figures  lb  and  38  and  listed  in  Table  14.  Confidence 
limits  of  the  means  shown  in  Table  14.  Further  discussion 
in  text. 

The  appearance  of  sobrina  is  restricted  to  the 
eastern  tropical  Pacific  where  its  abundance 
and  occurrence  resemble  the  values  for  »i(>rii 
and  plaiitata  in  their  regions  of  dominance, 
respectively. 

Quantitative  data  on  Poiitellhto  in  the 
Atlantic  Ocean  are  few.  In  six  quantitative 
samples  from  the  western  Atlantic  phiniata 
abundance  ranged  from  0.01  to  0.46  adults  per 
m-'.  Two  samples  containing  platycliela  provided 
estimates  of  0.001  and  0.08  adults  per  m''. 

Extremely  high  values  of  phunato  s.l.,  how- 
ever, have  been  reported  from  the  Atlantic. 
Judging  from  their  geographical  origin,  the 
northeastern  Gulf  of  Guinea,  these  abundance 
estimates  (Mahnken,  Jossi.  and  McCabe,  1968) 
are  probably  referrable  to  platychela.  Mahnken 
and  his  co-workers  record  the  species  at  18  of 
63  sampled  localities  scattered  offshore  from 
the  Bight  of  Benin  west  to  Cape  Palmas.  They 
indicate  areal  abundance  of  the  species  by 
contouring  selected  class  intervals  of  number 
per  1.000  m-'  water  strained.  In  lieu  of  the  actual 
estimates  per  sample  we  used  midpoints  of  each 
contoured  interval  to  calculate  the  mean  abun- 
dance. The  yield  is  a  surprisingly  high  mean 
of  1.01  individuals  per  m^,  an  order  of  magni- 
tude higher  than  our  highest  mean  values  from 
the  Pacific  and  Indian  Oceans.  Aside  from 
possible  bias  introduced  by  our  extrapolations 


several  factors  may  be  responsible  for  these 
unusually  high  values:  e.g.,  count  of  immature 
as  well  as  adult  specimens,  use  of  nets  with 
smaller  mesh  width  (0.281  mm),  use  of  surface 
tows  in  a  region  relatively  rich  in  zooplankton 
presumably  concentrated  in  the  very  shallow 
layer  of  tropical  surface  water  above  the 
permanent  thermocline,  etc. 

Summing  our  mean  values  of  pin  )nata,  niorii, 
and  sob7'iiia  in  each  meridional  set  of  samples, 
we  find  remarkably  good  agreement  between 
our  abundance  estimates  and  those  derived  by 
previous  studies  of  pluniata  s.l.  in  the  Pacific 
Ocean  (Table  18).  We  normalized  the  published 
data  to  conform  to  the  units  employed  in  the 
present  study.  Normalization  was  simplified 
by  the  following  assumptions: 

a.  we  assumed  100%  filtration  efficiency; 

b.  we  assumed  that  PonteUina   occurs  only 

above  200  m  and,  in  calculating  volume 
of  water  strained  by  the  net,  omitted 
segments  extending  below  200  m; 

c.  in  sets  of  vertically  stratified  tows  we  con- 

sidered the  overall  estimate  of  abun- 
dance as  if  it  were  from  a  continuous 
tow  sampling  between  200  m  and  the 
surface ; 

d.  we    assumed    that    previous    studies    on 

PaiitelUna  failed  to  discriminate  among 
the  different  species;  the  published 
values  were  regarded  as  representing  a 
combined  estimate  of  the  abundance  of 
all  species  of  the  genus  found  in  the 
region. 

Estimates  obtained  from  Heinrich  (1968)  and 
Vinogradov  and  Voronina  (1963)  are  about  one 
order  of  magnitude  higher  than  other  middle 
and  west  Pacific  estimates.  These  higher  values 
may  be  accounted  for  by  two  factors,  namely 
that  the  counts  include  immature  copepodids 
and  that  the  samples  were  taken  with  nets  of 
0.18-mm  mesh,  small  enough  to  retain  Pontel- 
U)ia  copepodids  of  stage  II  and  possibly  of 
stage  I  as  well  (Table  15).  Sherman's  (1963, 
1964)  counts  appear  to  have  been  derived  from 
adult  specimens,  partly  by  inference  from  his 
text  and  partly  from  the  relatively  wide  mesh 
comprising  most  of  the  filtering  cone  in  the 
POFI  (Pacific  Oceanic  Fisheries  Investigation) 
Standard  Net  (0.66  mm). 


109 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 
Table  18. —  Mean  abundance  (No.  /m^)  of  Pontellina  spp.  in  meridional  transects  crossing  the  Equator. 


Region 


Longitude 


Latitude 


Source 
of  data 


.V  no. 
adults 


V  no. 

adults  and 

juveniles 


Number 

of 
samples 


Sampling 
months 


Depth,  tow,  net 


Indian  Ocean  40°E-80°E  35°S-25°N  present  study 

(west) 
Indian  Oceon  80°E-nO°E  27°S-18°N  present  study 

(east) 

Austral-Asian         125°E135°E       12°S-12°N  present  study 

Seas 

Pacific  Ocean  156°E-164°E        )2°S-12°N  present  study 


160°E  04°S-16°30'N     Vinogradov  and 

Voronina,  1963 

176°W  14°S-13°N  Vinogradov  and 

Voronina,  1963 


0.1419 
0.0863 

0.0596 

0.0230 


120°E-175°W     04°S-30°N  Heinrich,  1968 


95°W  10°S15°N  present  study  0.0952 


0.1023 
0.3790 
0.1910 


168°E-155°W     20°S-20°N  Sherman,  1964  0.1379  — 


174°W-160°W    06°S-21°N           present  study  0.0346 

158°W                  07°S-21°N          Sherman,  1963  0.0438 

154°W                   13°S-13°N           Vinogradov  and  — 

Voronino,  1963 

140°W                   18°S-17°30'N     Vinogradov  and  — 

Voronina,  1963 

126°W                   12°S-20°N           present  study  0.0744 


0.1172 
0.1600 


233 
107 

23 

23 

17 
21 
91 


92°W 


20°S-10°N  present  study  0.0358 


59 
15 
13 

18 
29 
22 

19 

22 


Jon. -Dec. 
(1962-65) 
Jon. -Dec. 
(1962-64) 

Mar  .-May 
(1961) 

Aug. -Sept. 
(1956) 

Sep. -Dec. 

(1961) 

Sep. -Dec. 

(1961) 

W  of  160°E 
Jul. -Aug. 
(1957) 

Eof  160°E 
Nov. -Feb. 
(1957-58) 

Jan. -Apr. 

(1962) 

Aug. -Sep. 

(1956) 

June-July 
(1961) 

Sep. -Dec. 

(1961) 

Sep. -Dec. 

(1961) 

Feb. -Mar. 
(1967) 


Feb. -Mar. 
(1967) 


Feb. -Mar. 
(1967) 


200-0  m,  vert., 

lOSN' 

200-0  m,  vert., 

lOSN' 

150-0  m,  obi., 
CalCOFI  SN2  (silk) 

150-0  m,  obi., 
CalCOFI  SN2  (silk) 

500-0  m,  vert., 
Juday  80  cm 

500-0  m,  vert., 
Juday  80  cm 

500-0  m,  vert., 
Juday  80  cm 


Surface, 
POFI  SN3 

150-0  m,  obi., 
CalCOFI  SN2  (silk) 

Surface, 
POFI  SN3 

500-0  m,  vert., 
Juday  80  cm 

500-0  m,  vert., 
Juday  80  cm 

150-0  m,  obi., 
CalCOFI  SN2 
(nylon) 

150-0  m,  obi., 
CalCOFI  SN2 
(nylon) 

150-0  m,  obi., 
CalCOFI  SN2 

(nylon) 


'  lOSN  =  Indian  Oceon  Standard  Net. 

*  CalCOFI  SN  =  California  Cooperative  Oceanic  Fisheries  Investigations  Standard  Net. 

^  POFI  SN  =  Pacific  Oceanic  Fisheries  Investigation  Standard  Net. 


Disregarding  collecting  and  sample  enumer- 
ating procedures  as  well  as  differences  among 
the  individual  species,  estimates  of  mean  abun- 
dance of  Pontellina  across  the  Pacific  (Table  18) 
vary  from  0.023  to  0.379  with  a  median  of  0.1 
individuals  i)er  m-'.  For  einpelagic  copepods  this 
appears  to  be  a  rather  low  and  remarkably  uni- 
form set  of  values  that  varies  within  the 
unusually  narrow  range  of  one  order  of  magni- 
tude. Summing  the  abundance  of  the  three 
species   produces   a   notable   lack   of  any    pro- 


nounced geographical  trend  though  the  mean 
abundance  shows  moderate,  irregular  undula- 
tions along  the  equatorial  belt  crossing  the 
Indian  and  Pacific  Oceans. 

Low  abundance  and  relatively  uniform  dis- 
persion throughout  the  geographical  region 
occupied  by  each  species  suggests  that  the  spe- 
cies of  PoiiteUina  are  high-order  predators. 
This  impression  is  supported  for  adults  at  least 
by  the  exclusive  presence  of  animal  remains  in 
their  stomach  and  the  predominance  of  copepod 


110 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


fragments  (Table  19).  Though  all  of  the  species 
appear  to  be  similarly  predaceous  within  their 
respective  epiplanktonic  communities,  we  must 
conclude  that  appreciable  differences  in  the 
abundance  and  occurrence  of  the  sibling  species 
are  indicative  of  real  changes  in  habitat  con- 
ditions and  real  differences  in  the  adaptive 
optima  for  each  species. 


Remarks  on  Geographical  Distribution 

This  discussion  hinges  upon  inferences  drawn 
from  the  evidence  presented  in  the  preceding 
sections.  Chief  among  them  are  the  validity  of 
the  four  sibling  species  of  Po)itelUua  as  separate 
noninterbreeding  populations.  Based  on  mor- 
phological homogeneity  each  population  appears 
to  be  closely  adapted  genetically  to  prevailing 
environmental  conditions  in  the  geographically 
limited  hydrographic  systems  comprising  its 
particular  habitat.  Except  for  differences  be- 
tween Atlantic  and  Indian-Pacific  populations 
of  pluniata  morphological  indications  are  that 
panmixis  prevails  in  each  species. 

The  three  tropical  species,  moiii,  sobrina, 
and  platychela,  occupy  eutrophic  waters 
characterized   by    equatorial    upwelling   and   a 


shallow,  steeply  graded,  permanent  thermo- 
cline.  The  mixed  layer  overlying  the  thermocline 
is  relatively  homogeneous  in  temperature  and 
has  been  referred  to  as  Tropical  Surface  Waters 
(Wyrtki,  1966,  1967).  In  our  use  of  this  term, 
Tropical  Surface  Waters  are  restricted  to  the 
surface  layer  in  regions  where  the  permanent 
thermocline  has  a  temperature  gradient  of 
^0.1°C  per  m  and  encompasses  an  overall  de- 
crease in  temperature  from  about  24°  ±  1°C 
at  the  top  to  about  15°  ±  1°C  at  the  bottom. 
These  pools  of  warm  water  are  subjected  to 
seasonally  repetitive  changes  in  the  strength  of 
the  equatorial  Trade  Winds  (Wyrtki,  1966, 
1967;  Taft,  1971).  The  seasonal  changes  pro- 
duce monsoonlike  reverses  in  the  circulation  of 
the  equatorial  segment  inhabited  by  each  species. 
This  phenomenon  apparently  provides  a  suf- 
ficiently closed  hydrographic  circulation  to 
maintain  breeding  stocks  in  proximity  to  suit- 
able nursery  grounds  and  thus  ensures  contin- 
ual success  of  each  species. 

The  equatorial  distributions  of  the  tropical 
species  of  PoiiteUina  are  not  without  prece- 
dence. The  tropical  Atlantic  has  previously  been 
characterized  in  faunistic  terms,  for  example, 
by  a  number  of  mesopelagic  fishes  (Backus  et 
al.,    1970)    as   well    as   by   a   sergestid   shrimp 


Table  19. — List  of  identified  particles  from  microscopic  analysis  of  stomach  con- 
tents in  adult  female  Pontellimi. 


Species 


Speci-     Cope-  "Para-    Crust- 

men         pod      "Oncaea"calanus"  ocean      Algol 
number    ports         ports         ports       parts       ports 


Source  of  specimen: 
Oceon  Station 


plumatii  1  X  X 

2  X 

3  X  X  Pocific 

4  X  X  Indian 

5  X  X  Pocific 
Percentoge  no.  with  ingested  particles  in  midgut:  71  °o 


Atlantic  la  Creuse  5 
Indion     DodoVI-81 

Scorpio  II  -146 
Lusiad  V-45 
Jordan  57-076 


platychela 

1 

X 

X 

Atlantic 

Atlantis  II  20-28 

2 

X 

X 

Aflontic 

La  Creuse  5 

3 

X 

Atlontic 

Atlantis  // 31-40 

4 

X 

Atlantic 

Atlantis  // 31-54 

5 

X 

Atlantic 

Oregon  1289 

Percentage 

no. 

with  ingested  porticles  in  midgut 

63°o 

morii 

1 

X 

X 

Pocific 

Troll  30 

2 

X 

Pacific 

TRANSPAC  98B 

3 

X 

X 

Pocifrc 

EQUAPAC  H-31 

4 

X 

Indion 

Lusiad  V-45 

5 

X 

Indion 

Lusiod  11-14 

Percentoge 

no. 

with  ingested  particles  in  midgut 

63°o 

sobrina 

1 

X 

X 

Pocific 

Bonocco  35 

2 

X 

Pacific 

ColCOFI  5801:  153.50 

3 

X 

X 

Pacific 

Scot  45 

4 

X 

X 

Pacific 

Jordan  60-056 

5 

X 

X 

Pacific 

Bonocco  31 

Percentage 

no 

with  ingested  particles  in  midgut 

83°  o 

111 


FISHERY  BULLETIN:  VOL.  72.  NO.  I 


(Judkins,  1972).  Among  the  Atlantic  Foramin- 
ifera  listed  by  Be  and  Tolderlund  (1971)  as 
tropical  species  only  Candeina  )iitida  shows  a 
geographical  distribution  similar  to  that  of  P. 
platijchcla. 

In  general  species  characterizing  the  eastern 
tropical  Pacific,  unlike  sobriiia,  tend  to  follow 
the  coastline  of  the  Americas  from  about  lat. 
30° N  to  20° S  and  extend  westward  to  long. 
160°  to  180°W:  e.g.,  Euphausia  distinguenda, 
(Johnson  and  Brinton,  1963),  Eucalanus  inermis, 
(Lang,  1967),  Melamphaes  spiuifer,  (Ebeling, 
1962),  Stomiafi  colubrhins,  (Gibbs,  1969). 

These  distributions  are  meridionally  and 
zonally  more  extensive  than  the  limited  disper- 
sion observed  in  P.  sobriiia  and  others  like 
Pontella  danae,  P.  agasnizi,  and  Pontellopsis 
lubbockii  (Heinrich,  1964;  Fleminger,  1967b; 
and  unpubli.shed  records).  The  dissimilarities 
probably  relate  to  differences  in  depth  range, 
the  more  widespread  forms  having  access  to 
subsurface  currents  flowing  northward  (Woos- 
ter  and  Jones,  1970)  and  southward  (Wooster 
and  Gilmartin,  1961)  under  the  eastern  boun- 
dary currents  as  well  as  westward  in  the  tongue 
of  low  oxygen  water  accompanying  the  North 
Equatorial  Current  which  is  traceable  to  the 
Philippines  (Reid,  1965;  Wyrtki,  1966;  Tsuchi- 
ya,  1968). 

Distributions  of  epipelagic  species  in  the 
equatorial  Indian  and  Pacific  Oceans  resem- 
bling that  of  moiii  include  a  number  of  other 
copepods,  e.g.,  several  species  of  Eiicctkunts, 
(Fleminger  and  Hulsemann,  1973;  Fleminger, 
1973);  Claunucakuni^  ))iiii(>)\  (Frost  and 
Fleminger,  1968);  several  euphausiids  such  as 
Euphausia  diomediae,  E.  paragibba,  and  Sty- 
locheiron  microphthalina,  (Brinton.  1962);  and 
fishes  such  as  Scopeloyadiis  iinispiinis,  (Ebeling 
and  Weed,  1963)  and  Stomias  o//7»/,s,  (Gibbs, 
1969)  though  the  lattermost  is  also  considered 
to  inhabit  the  tropical  Atlantic. 

Although  the  ubiquitous  plumata  overlaps 
geographically  with  each  of  the  tropical  species, 
plumata  s  overall  range  lies  mostly  in  the  enor- 
mous basin  of  oligotrophic  waters  spreading 
across  the  tropics  and  subtropics  of  each  ocean, 
waters  markedly  different  in  vertical  thermal 
structure  from  those  of  its  tropical  congeners. 
The  almost  mutually  exclusive  distributions  of 
plumata  and  its  more  localized  congeners, 
platychela  in  the  equatorial  Atlantic  and  aobriua 


in  the  eastern  tropical  Pacific,  are  evidence  of 
relatively  intensive  environmental  gradients 
and  the  adaptive  response  to  appreciably  differ- 
ent environmental  optima,  which  separate  the 
distributions  of  these  pairs  of  species. 

For  example,  morii  has  been  found  at  the 
edge  of  the  south  Atlantic  as  well  as  the  edge 
of  the  eastern  tropical  Pacific;  concomitantly 
sobriiia  occurs  in  the  North  Equatorial  Current, 
but  successfully  extends  only  a  few  degrees  of 
longitude  to  the  west  of  its  habitat;  platychela 
is  adjacent  to  but  fails  to  establish  itself  in  the 
Sargasso  Sea;  finally  plumata,  despite  apparent 
circumglobal  distribution,  does  not  appear  in 
large  numbers  where  its  equatorial  congeners 
abound.  Thus,  the  optimum  habitats  appear  to 
be  regionally  distributed  and  those  that  are 
contiguous  are  sufficiently  different  to  prevent 
colonization  by  expatriated  congeners  trans- 
ported to  the  margin  of  the  habitat.  The  possi- 
bility of  interference  among  the  species  is  open 
but  in  the  light  of  available  knowledge  of 
calanoids  it  seems  intuitively  to  be  most  unlikely. 

Thus,  the  two  classes  of  epipelagic  warm- 
water  distributions  found  in  Po)itelliHa  suggest 
a  fundamental  dichotomy  in  the  circumglobal 
warm-water  belt.  The  three  tropical  species 
correlate  with  geographically  separated  shallow 
lenses  of  eutrophic  water.  Each  lens  is  known 
to  overlie  regions  of  intense  temperature  and 
oxygen  gradients  and  to  be  partially  bounded 
by  the  similarly  intense  tropical  convergences 
(Neumann  and  Pierson,  1966). 

P.  plumata,  however,  correlates  with  the 
circumglobal  warm-water  pool  that  is  largely 
oligotrophic.  The  oligotrophic  pool  tends  to  be 
deep,  the  permanent  thermocline  often  exceed- 
ing 200  m  in  depth.  Temperature  gradients  in 
the  thermocline  and  along  its  margins  at  the 
subtropical  convergence  are  relatively  weak, 
and  oxygen  is  generally  at  or  near  saturation 
(Neumann  and  Pierson,  1966).  Evidence  that 
the  Atlantic  pool  may  be  at  least  partially  iso- 
lated with  respect  to  Pontelliiia  whereas  the 
Indian  and  Pacific  pools  are  confluent  is  sug- 
gested by  morphological  differences  in  the 
plumata  populations  rejioited  above. 

The  circulation  systems  and  physical  condi- 
tions known  to  maintain  these  lenses  of  eutro- 
phic tropical  water  and  the  pools  of  oligotrophic 
tropical -subtropical  waters  are  the  obvious 
mechanisms   sustaining   the  geographical   dis- 


112 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  POSTELLINA 


tribution  of  the  four  species  of  Pontellina.  This 
is  apparent  in  the  relationship  between  the 
distribution  of  each  species  and  the  location  of 
prevailing  near-surface  isotherms  that  locate 
the  hydrographic  limits  of  these  bodies  of  water. 
The  localities  for  the  tropical  species  are  largely 
enveloped  by  the  mean  winter  season  position 
of  the  24 °C  isotherm  at  10  m  (Figure  36), 
the  lower  thermal  limit  of  Tropical  Surface 
Water.  The  10-m  depth  was  chosen  to  reduce 
the  influence  of  diurnal  fluctuations.  The  local- 
ities for  plumata,  however,  vary  broadly  be- 
tween the  position  of  the  20°  and  15° C  mean 
winter  season  isotherms  (Figure  37).  Factors 
confining  the  distributions  to  the  observed  lim- 
its, however,  are  not  obvious;  more  data  on 
depth  range^  vertical  migratory  behavior,  and 
depth  of  food  organisms  would  probably  be 
enlightening. 

Notably,    more   than    three-quarters    of   the 
samples  (77.5% )  containing  Pontellina  yielded 


specimens  of  only  one  species.  To  examine  joint 
occurrences  of  Po)itelli)ia  congeners  more  close- 
ly, all  capture  records  of  a  species  were  tallied 
by  ocean  and  grouped  with  respect  to  the  pres- 
ence or  absence  of  other  congeners  in  the  same 
sample  (Table  20).  Comparison  of  singular  and 
joint  occurrences  for  all  possible  pairings  indi- 
cates that  the  latter  are  relatively  infrequent. 
In  no  case  of  joint  occurrences  did  the  index  of 
affinity  (Fager  and  McGowan,  1963)  reach  a 
positive  value.  No  two  species  within  the  genus 
would  appear  to  occupy  the  same  spatial  habi- 
tat or,  in  other  words,  be  members  of  the  same 
community.  Thus,  the  extensive  overlapping  of 
morii  and  plumata  in  the  equatorial  Indian 
and  Pacific  Oceans  may  be  viewed  as  a  function 
of  intermingling  due  to  the  spatial  proximity 
of  the  two  habitats  and  perhaps  also  due  to  a 
greater  number  of  similarities  shared  by  these 
two  habitats  than  between  those  of  the  other 
possible  pairings  within  the  genus. 


60° 


Figure  36.  —  Comparison  of  geographical  area  enveloping  all  capture  records  of  tropical  species  of  Pontellina  with  select- 
ed mean  isotherms  at  10  ni  for  winter  season  of  each  hemisphere.  Data  from  Muromtsev  (1958,  1963)  and  Wyrtki 
(1971).  Dotted  shading  outlines  capture  records  of  P.  platychela  shown  in  Figure  8;  horizontal  shading  outlines  capture 
records  of  P.  sobrina  shown  in  Figure  15;  vertical  shading  encloses  the  capture  records  of  P.  morii  shown  in  Figure  12. 


113 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


40° 


100"  60°  20°  0°  23'  60°  100°  140°  180°  140°  100°  60° 

Figure  37. — Comparison  of  shaded  area  enveloping  all  capture  records  of  Pontellina  phiinata,  shown  in  Figure  5  with 
selected  mean  isotherms  at  10  m  for  winter  season  of  each  hemisphere.  Data  from  Muromtsev  (1958,  1963)  and 
Wvrtki  ( 1971).  Further  discussion  in  te,\t. 


Table  20. — Separate  and  joint  occurrences  among  species  of  Pontellina.  Values 
in  parentheses  are  the  index  of  affinity;  a  value  greater  than  0.5  suggests  joint  mem- 
bership in  the  same  communal  assemblage  of  species. 


phimaia 

morii 

\ohrina 

plalyc 

hela 

Total 

Indian  Ocean  and  Austra 

asian  Seas: 

phimala 

129 

96  (-7.01) 

0 

0 

225 

mom 

78 

0 

0 

78 

sohrinu 

0 

0 

0 

platychela 

0 

0 

Total 

129 

174 

0 

0 

303 

Pacifrc  Ocean: 

pluinata 

136 

46  (-3.77) 

23  (-5.20) 

0 

205 

morn 

23 

6  (-2.69) 

0 

29 

sohrinu 

85 

0 

85 

platychela 

0 

0 

Totol 

136 

69 

114 

0 

319 

Atlantic  Ocean 

phimata 

80 

0 

0 

14  (-3.93) 

94 

morn 

0 

0 

0 

0 

sohrina 

0 

0 

0 

platychela 

58 

58 

Total 

80 

0 

0 

72 

152 

All  records  com 

bined: 

pluniaia 

345 

137 

18 

4 

514 

morn 

101 

1 

0 

102 

sohrina 

85 

0 

85 

platychela 

58 

58 

Totals 

345 

238 

104 

72 

759 

114 


FLEMINGER  and  HULSEMANN:  FOUR  SIBLING  SPECIES  OF  PONTELLINA 


SOUTHWEST  MONSOON (APR- SEPT) 


No./m' 

a 

0.01 -0.1 

D 

0.1 1  -  I 

■ 

I.OI  -  10 


40°E 


NORTHEAST  MONSOON  (OCT -MAR) 


4(yE 


120° 


120° 


I.O.S.N.      SAMPLES 


Figure  38. — Abundance  of  Pontellina  morii  and  P.  plumata  in  Indian  Ocean  Standard  Net  (lOSN)  collections.  Samples 
collected  during  southwest  and  northeast  monsoon  seasons.  Dots  represent  localities  sampled.  Abundance  values  are 
estimated  number  of  adults  per  m^  water  strained. 


P.  morii  and  plumata  exhibit  distinctive  dis- 
tributions in  both  monsoon  seasons  (Figure  38) 
as  well  as  general  zonal  separation  (Figure  39), 
differences  that  are  blurred  in  charts  prepared 
without  regard  for  seasonal  variation  (e.g., 
Figures  5,  12).  During  the  southwest  monsoon, 
plumata  appeared  in  large  numbers  off  the 
Somali  coast  and  near  the  Seychelles  whereas 
morii  was  much  more  frequent  in  the  eastern 
Arabian  Sea  and  the  eastern  Bay  of  Bengal. 
In  the  northeast  monsoon  both  species  were 
abundant  in  the  Somali  Current.  However,  only 
morii  appeared  to  be  common  in  and  about  the 
Andaman  Sea  whereas  an  indication  of  large 
numbers  of  plumata  appeared  just  south  of 
Java. 

Morphological  relationships  analyzed  above 
indicate  the  species  have  common  ancestry  that 
produced  three  main  lines  of  descent  represented 
respectively  by  plumata,  platychela,  and  the 
Indian-Pacific  tropical  pair  of  siblings,  morii 
and  sobrina.  Ample  evidence  of  co-occurrence 


tvy 


plumata 

[\]  SOUTHWEST  MONSOON 
^  NORTHEAST    MONSOON 


[V 

^1 


Figure  39. — Frequency  of  occurrence  of  Pontellina 
plumata  and  P.  morii  in  the  Indian  Ocean  north  of  selected 
latitudes  compared  to  that  south  of  the  same  latitudes. 


115 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


without  intergradation  between  morii  and  so- 
biiiia  support  the  conclusion  that  both  are  valid 
species  that  have  evolved  relatively  recently. 
Morphological-geographical  patterns  provide 
inferential  evidence  that  sympatry  among  sub- 
sets of  the  four  species  have  led  to  modifications 
of  secondary  sexual  features,  presumably  in 
the  course  of  developing  premating  barriers  to 
hybridization.  Obvious  examples  of  this  emerge 
from  comparison  of  pairs  of  species  which 
have  extensive  contiguous  boundaries:  e.g., 
plumata  and  plat y chela  in  the  Atlantic  and 
pliimata  and  moni  in  the  Indian  and  Pacific 
Oceans.  In  each  pair  of  species  the  chela  on  the 
male  fifth  leg  in  the  tropical  congener  is  broad- 
ened in  contrast  to  the  slender  chela  found  in 
plumata.  In  the  females  of  each  pair  the  hair 
patches  on  the  genital  segment  are  either  miss- 
ing or  reduced  to  one  pair  in  the  tropical  species 
while  pluynata  maintains  two  prominent  pairs. 
Another  source  of  evidence  lies  in  the  geograph- 
ical variations  in  the  female  fifth  legs  of  plumata 
which  follows  a  pattern  indicative  of  character 
displacement. 


Geographical  variation  in  the  frequency  of 
morphs  in  plumata  distinguishes  Atlantic  from 
Indian  and  Pacific  populations;  relationships 
with  platychela  in  the  Atlantic  and  morii  and 
sobri)ia  elsewhere  suggest  the  variation  is  the 
result  of  character  displacement.  Three  of  the 
four  morphs  in  morii  and  sobriiia  appear  to  be 
extremely  rare. 

7.  Each  species  exhibits  a  distinctive  geo- 
graphic range  independent  of  the  other  three. 
Absence  of  conspicuous  geographical  variation 
indicates  sufficient  transport  and  advection  to 
maintain  panmixis  within  each  species  except 
the  Atlantic  and  Indian-Pacific  populations  of 
plumata. 

8.  Abundance  of  all  four  species  is  low  de- 
spite relatively  frequent  occurrence  within  the 
limits  of  the  distribution.  These  indications  of 
high-order  predation  are  supported  by  examina- 
tion of  gut  contents  in  sexually  mature  adults 
in  which  the  remains  consisted  primarily  of 
particles  from  small  copepods. 

ACKNOWLEDGMENTS 


CONCLUSIONS 

1.  The  genus  Pontelliua  represented  by  four 
species  is  epipelagic  and  occupies  oceanic  sec- 
tors of  the  circumglobal  warm-water  belt. 

2.  Three  of  the  species  occur  chiefly  in 
eutrophic  sectors  of  equatorial  latitudes  where 
the  layer  above  the  thermocline  is  relatively 
homogeneous;  the  distinctiveness  of  this  layer 
was  noted  by  Wyrtki  who  refers  to  it  as  Tropical 
Surface  Water.  One  species,  platychela,  occupies 
the  tropical  Atlantic;  .^obriua  is  in  the  eastern 
tropical  Pacific;  and  morii  is  found  in  the  tropi- 
cal Indian  and  tropical  Pacific  Oceans. 

3.  The  fourth  species,  plumata  s.str.,  occurs 
most  frequently  in  oceanic,  oligotrophic  regions 
in  tropical  and  subtropical  latitudes. 

4.  Morphological  differences  among  the  spe- 
cies are  subtle  and  restricted  to  secondary  sexual 
structures. 

5.  The  four  species  comprise  a  monophyletic 
complex  showing  three  basic  derivatives,  plu- 
mata, platychela,  and  a  third  that  underwent  a 
subsequent  episode  of  speciation  to  produce 
morii  and  sobrina. 

6.  The  female  fifth  leg  is  polymorphic  and 
represented    by    four    phenotypes    or    morphs. 


116 


This  research  was  supported  by  the  National 
Science  Foundation  Grants  GB12412,  GA31092, 
GB32076  and  by  the  Marine  Life  Research 
Group  of  Scripps  Institution  of  Oceanography. 
We  express  our  thanks  to  R.  Scheltema  of 
Woods  Hole  Oceanographic  Institution,  Woods 
Hole,  Mass..  and  to  the  Indian  Ocean  Biological 
Centre  at  Cochin,  India,  who  have  provided 
significant  quantities  of  material  from  the  At- 
lantic and  Indian  Oceans,  respectively.  We  owe 
special  debts  of  gratitude  to  E.  W.  Eager  for 
his  advice  on  data  analysis  and  to  Gillian  Mag- 
gert  who  carried  out  much  of  the  preliminary 
sorting  of  samples  and  whose  faithful  camera 
lucida  renditions  of  various  specimens  of  Pon- 
telliua first  called  our  attention  to  the  existence 
of  the  problem. 

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120 


STOCK  COMPOSITION,  GROWTH,  MORTALITY, 

AND  AVAILABILITY  OF  PACIFIC  SAURY, 

COLOLABIS  SAIRA,  OF  THE   NORTHEASTERN 

PACIFIC  OCEAN 

Steven  E.  Hughes^ 


ABSTRACT 

Recent  international  interest  in  the  Pacific  saury  (Cololahis  saint)  resource  of  the  north- 
eastern Pacific  Ocean  prompted  studies  to  determine  the  stock's  composition,  structure, 
growth,  mortaUty,  and  availability. 

During  August-September  1969-71,  data  were  obtained  from  more  than  5,000  fish 
sampled  from  19  individual  schools  captured  between  southern  California  and  Vancouver 
Island,  B.C.  Length  and  age  frequency  distributions  indicate  fish  grow  to  340  mm  in 
length  during  their  6-year  lifespan.  Larger  fish  apparently  migrate  farthest  north  and 
consequently  age  at  full  recruitment  off  Washington  is  III  or  IV,  and  II  off  Oregon. 
Spawning  is  e.xtended  over  most  of  the  year  and  the  stock  is  believed  homogeneous.  First 
maturity  appears  to  be  reached  during  the  second  year.  Numbers  of  males  and  females 
were  nearly  equal  until  age  IV  when  females  began  to  predominate.  Length-weight 
regressions  are  presented  by  sex.  Berlalanffy  growth  parameters  were  calculated:  K  =  0.42, 
Lx  =  342  mm,  and  lo  =  -0.72  years.  The  total  instantaneous  mortality  coefficient  was 
estimated  at  1.25-2.20. 

Data  on  distribution  and  availability  suggest  a  viable  domestic  fishery  on  this  species  is 
unlikely. 


In  1969,  an  investigation  of  the  distribution, 
availability,  and  biology  of  Pacific  saury, 
Cololabis  saira,  in  the  northeastern  Pacific 
Ocean  was  begun  by  our  laboratory.  This  study 
was  a  direct  result  of  a  tenfold  decrease  in 
combined  Japanese  and  Soviet  landings  of  the 
species  in  the  northwestern  Pacific  Ocean  since 
1958.  Unusually  high  market  demand  ci'eated 
international  interest  in  the  unexploited  stock 
in  the  eatern  Pacific  Ocean. 

Initial  studies  were  concerned  primarily  with 
the  development  of  sampling  and  harvesting 
gears  (Ellis  and  Hughes,  1971).  This  paper 
contains  results  of  research  on  the  biology  and 
availability  of  saury,  except  for  parasite  studies 
which  were  treated  separately  (Hughes,  1973). 
The  purpose  of  the  paper  is  to  provide  initial 
information  on  stock  composition,  growth,  and 
mortality  and  to  supplement  previous  studies 
of  distribution  and  abundance.  Data  were  ob- 
tained during  research  vessel  surveys,  conduct- 
ed primarily  during  August  and  September 
1969  off  the  California  coast,  and  during  August 


'  Northwest  Fisheries  Center.  National  Marine 
Fisheries  Service.  NOAA,  2725  Montlake  Blvd.  £.,  Seattle, 
WA  98112. 


Manuscript  accepted  July  1973. 

FISHERY  BULLETIN:' VOL.  72.  NO.  1.  1974. 


and  September  1970  and  1971  off  the  Washing- 
ton and  Oregon  coasts. 

STATUS  OF  KNOWLEDGE 

Parin  (1960)  reported  that  the  Pacific  saury 
inhabits  the  northern  Pacific  pelagic  zone  and 
has  a  continuous  range  from  Asia  to  North 
America.  Sokolovskii  (1969)  inferred  from 
studies  of  parasites  and  biological  and  mor- 
phometric  characteristics  of  the  species  that 
there  exist  within  its  total  range,  stocks  dis- 
tinguishable from  one  another — western  (Asian), 
central  (Aleutian),  and  eastern  (American) — 
that  there  is  no  clear  boundary  between  these 
stocks,  and  that  there  are  rather  wide  zones  of 
mixture  of  the  stocks.  The  eastern  stock  ranges 
from  Baja  California  to  the  Gulf  of  Alaska 
(Ahlstrom  and  Casey,  1956;  Clemens  and 
Wilby,  1961).  Novikov  and  Kulikov  (1966) 
found  that  in  the  eastern  Pacific  Ocean,  saury 
occupied  an  extensive  coastal  region  50-70 
miles  wide  between  lat.  41°  and  48°N  during 
August-October,  but  that  major  concentrations 
were  irregularly  distributed.  Their  survey 
indicated  the  most  dense  aggregations  occurred 
off  southern   Oregon  during  August,  October, 


121 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


and  November  in  water  temperatures  of  12.5 
to  13.5  °C.  Data  obtained  from  night-light 
station  observations  off  California  indicated 
that  in  the  California  Cooperative  Oceanic 
Fisheries  Investigations  area  saury  occurred 
most  frequently  in  waters  north  of  San  Fran- 
cisco in  a  band  40-120  miles  offshore  (Smith, 
Ahlstrom.  and  Casey.  1970).  Peak  availability 
occurred  during  November.  Results  of  egg 
surveys  suggested  peak  spawning  activity 
occurs  off  California  during  April,  May.  and 
June  and  that  the  standing  stock  in  the  eastern 
North  Pacific  Ocean  was  at  least  450,000  to 
500.000  tons  (Ahlstrom,  1968;  Smith  et  al.. 
1970). 

METHODS 

The  method  of  finding  schools  of  Pacific 
sauiy  was  similar  to  procedures  employed  by 
commercial  Japanese  saury  vessels.  The  Japa- 
nese technique  has  been  reviewed  by  Inoue  and 
Hughes  (1971).  The  Japanese  use  artificial 
lights  during  hours  of  darkness  to  visually 
locate  schools  near  the  surface  and  to  attract  the 
fish  alongside  the  vessel  for  eventual  capture. 
Sonar  was  also  used  to  assist  in  detecting 
concentrations  during  1970  and  1971.  Our 
surveys  were  generally  restricted  to  areas  where 
surface  water  temperatures  were  between  13° 
and  17 °C.  Typically,  they  were  conducted  along 
a  zig-zag  track  designed  to  cross  boundaries 
between  warm  and  cold  water  masses.  Once 
detected  and  concentrated  under  the  vessel's 
alluring  lights,  the  total  weight  of  each  school 
was  derived  by  estimating  the  percentage  of 
the  school  captured,  weighing  our  catch,  and 
then  computing  the  weight  of  the  remaining 
fish. 

During  1969.  surveying  was  confined  to 
waters  off  California  and  fishing  was  conducted 
with  a  Japanese-style  boke-ami  (Andreev,  1962). 
Operations  were  conducted  off  the  Washington 
and  Oregon  coasts  in  1970  and  extended  to 
include  waters  off  Vancouver  Island,  B.C., 
during  1971.  During  those  periods  fishing  was 
conducted  with  a  small  purse  seine  designed  for 
capturing  saury  (Ellis  and  Hughes,  1971). 

Table  1  summarizes  times  and  locations 
where  fishing  was  conducted  and  samples 
retained  for  biological  studies.  Catches  were 
randomly  subsampled  aboard  ship.  All  samples 
collected  were  returned  to  the  laboratory  for 


Table      1 . — Fishing   areas   and    number   of  Pacific   saury 
collected,  1969-1971. 


Coastal 
area 

Location 

Sample 

Date 

W  Long 

N  Lot 

size 

Aug  1969 

Calif. 

I24°03' 

37°49' 

220 

Aug  1969 

Calif. 

124°03' 

37°5r 

222 

Aug  1969 

Calif. 

124°03' 

37°53' 

143 

Aug  1969 

Calif. 

123°59' 

37°55' 

52 

Aug  1969 

Colif. 

123°48' 

37°58' 

31 

Sept  1969 

Calif. 

122°23' 

36°  10' 

160 

Sept  1970 

Greg. 

125°50' 

45°03' 

299 

Sept  1970 

Greg. 

125°11' 

44°33' 

300 

Sept  1970 

Greg. 

125°08' 

44°30' 

300 

Sept  1970 

Wash. 

126°02' 

47°43' 

284 

Sept  1970 

Wash. 

125°58' 

47°4r 

192 

Sept  1970 

Wash. 

126°00' 

47°39' 

191 

*Julv  1971 

Calif. 

120°00' 

33°00' 

98 

Aug  1971 

Van.  Isl. 

127°06' 

49°  16' 

105 

Aug  1971 

Wash. 

126°04' 

48°2r 

512 

Sept  1971 

Greg. 

125°0r 

44°01' 

506 

Sept  1971 

Greg. 

124°59' 

43°55' 

508 

Sept  1971 

Greg. 

125°00' 

43°54' 

508 

Sept  1971 

Greg. 

125°02' 

44°02' 

268 

Sept  1971 

Greg. 

125°04' 

43°58' 
Total 

419 
5,248 

*  Sample   captured   with    variable   mesh   gillnet.   This   sample   used 
only  in  the  growth  analysis. 

processing.  Samples  taken  in  1969  were  iced, 
whereas  those  collected  in  1970  and  1971  were 
frozen.  Only  length  frequency  data  were  taken 
from  the  1969  samples.  Biological  data  from 
individual  fish  obtained  during  1970  and  1971 
included  knob  length-  measured  to  the  nearest 
millimeter,  body  weight  to  the  nearest  gram, 
sex,  and  maturity.  Scales  were  removed  for 
later  examination. 

Sex  determination  of  fish  measuring  less  than 
230  mm  was  generally  difficult.  When  gross 
examination  of  gonads  proved  inadequate, 
samples  were  further  subsampled — the  gonads 
cross-sectioned  and  examined  for  the  presence 
of  a  lumen  under  10  X    binocular  microscopes. 

Age  was  determined  from  plastic  impressions 
of  scales  (Clutter  and  Whitesel,  1956)  examined 
with  a  microprojector  device  (Mosher,  1950). 
Age  determination  of  Pacific  saury  has  long 
been  a  point  of  contention  between  Soviet  and 
Japanese  scientists  working  in  the  western 
Pacific  (Kotova,  1958;  Hotta,  1960).  Details 
of  assessment  criteria  by  which  ages  were 
determined  for  this  report  have  been  documented 
bv  Mosher.^ 


-  Knob  length  (Kiniura,  1956) — the  distance  between 
the  tip  of  the  lower  jaw  and  the  posterior  end  of  the 
muscular  knob  on  the  caudal  base — has  been  accepted 
internationally  as  the  unit  of  length  measurement  for  saury. 

3  K.  H.  Mosher.  Age  determination  of  eastern  Pacific 
saury  using  scales.  Natl.  Oceanic  Atmos.  Admin.,  Natl. 
Mar.  Fish.  Serv.,  Northwest  Fish.  Center,  Seattle,  Wash. 
Unpubl.  inanuscr. 


122 


HUGHES:  PACIFIC  SAURY  OF  NORTHEASTERN  PACIFIC 


Preliminary  scale  studies  indicated  that  the 
samples  might  be  of  two  races  of  fish  with 
different  growth  patterns — those  with  a  wide 
zone  of  initial  growth  (distance  between  the 
focus  and  first  annulus)  and  those  with  a  much 
narrower  zone  of  initial  growth.  Similar  growth 
patterns  have  been  detected  by  Japanese  sci- 
entists on  scales  of  fish  of  the  western  stock 
of  Pacific  saury  and  interpreted  as  distinct 
spring-  and  autumn-born  "subpopulations" 
(Hotta,  1960).  Accordingly,  fish  were  classified 
as  being  either  spring-born,  autumn-born,  or 
intermediate  type  by  examining  the  initial 
growth  zone  of  the  scale.  Length-weight 
regressions  and  von  Bertalanffy  growth  in 
length  parameters  were  determined  for  fish  of 
the  spring-  and  autumn-born  scale  types  and 
compared  statistically.  In  addition,  electro- 
phoretic  techniques  (Utter,  Hodgins,  and 
Johnson,  1972)  were  emploj'ed  to  test  for 
significant  inter-area  heterogeneity  as  well  as 
heterogeneity  of  fish  with  spring-  and  autumn- 
born  scale  features. 

STOCK  COMPOSITION 

Temporal  and  spacial  variations  in  length, 
age,  sex,  and  maturity  are  treated  in  this  section. 
In  analyzing  the  sex  ratio  and  age  frequency 
data,  fish  of  the  spring-  and  autumn-born 
scale  types  were  treated  separately. 

Size  and  Age  Composition 

There  was  a  trend  toward  increasing  length 
and  average  age  with  increasing  latitude.  Mean 
lengths  in  the  California,  Oregon,  and  Washing- 
ton-Vancouver Island  areas  were  201  mm, 
238  mm,  and  277  mm,  respectively  (Figure  1). 
Length  frequency  histograms  (Figure  2)  show 
there  was  an  absence  of  fish  <  160  mm  off 
Washington-Vancouver  Island  which  were 
represented  off  Oregon  and  relatively  abundant 
off  California.  Conversely,  fish  >  300  mm  were 
absent  off  California,  represented  off  Oregon, 
and  relatively  abundant  off  Washington- 
Vancouver  Island. 

Samples  taken  off  California  exhibited  an 
unusual  quadra-modal  length -frequency  distri- 
bution believed  to  be  a  sampling  artifact  rather 
than  fluctuation  in  year-class  strength.  [Three 
of  six  schools  sampled  were  schooled  by  size 
(Figure  1)  which  produced  the  minimum  length 


mode  at  165  mm  and  the  maximum  length  mode 
at  270  mm.] 

More  symmetrical  length  distributions  were 
produced  from  the  three  schools  sampled  in 
1970  and  five  schools  sampled  in  1971  off 
Oregon.  Lengths  ranged  from  159  mm  to  293 
mm  in  1970  and  158  to  330  mm  in  1971.  Length 
distributions  for  both  years  are  similar,  being 
moderately  skewed  to  the  right  with  a  mode  at 
210  mm  in  1970  and  235  mm  in  1971. 

The  three  schools  sampled  off  Washington  in 
1970  and  two  schools  off  Washington-Vancouver 
Island  in  1971  showed  more  variation  between 
years  than  the  Oregon  samples.  A  bimodal 
distribution  was  more  apparent  in  1971,  modes 
at  245  and  305  mm,  than  the  moderately 
asymmetrical  distribution  in  1970  with  mode 
at  260  mm.  Lengths  ranged  from  160  to 
334  mm  in  1970,  and  161  to  340  mm  in  1971.  The 
upper  limit  of  this  latter  range  may  exceed  the 
previously  known  maximum  length  of  the 
species  in  the  eastern  North  Pacific  Ocean. 
Clemens  and  Wilby  (1961)  reported  lengths  to 
14  inches  (356  mm);  however,  it  is  unclear 
whether  this  is  standard  or  total  length.  The 
two  saury  measuring  340  mm  knob  length  were 
ripe  females  measuring  363  and  364  mm  in  total 
length  and  weighing  180  and  190  grams 
respectively. 


50° 


48" 


38° 


z  o 

X  X 


-j 1512 


I  J 


h284 
i|9l 


_,31 

rzt 


-<5Z 


-1222 
-1220 


100 


150  200 

KNOB    LENGTH     (mm) 


300 


Figure  1. — Lengths  (mean,  range  and  S.D.  of  mean)  of 
eastern  Pacific  saury  plotted  against  latitude  of  capture. 
Numbers  indicate  sample  size  per  school. 


123 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


A 


WASHINGTON 
1970 
N  ■  650 


llTTk 


WASHINGTON    OREGON   COMBINED 
1970 


Jl 


Ilk, 


WASHINGTON- 
VANCOUVER    ISLAND 


1971 
N  •  619 


,^.^rfltb^ 


WASHINGTON-VANCOUVER     ISLAND 
OREGON     COMBINED 
1971 


^ 


■^^ni}h 


ITO       I9C      ZIO        230      250       270       290       310         220       240      260      280        300       320      340  160      200       220       240       260       280      300      320      340 

IQ  KNOB     LENGTH        (mm) 


CALIfOflNIA        1969 
N.  823 


Mll^l^ 


140      150       (70        190       210       2)0       !50      270       290 
KNCB    LENGTH    (mn) 


Figure    2. — Length  frequency  distributions  of  eastern  Pacific  saury  captured  off 
the  Pacific  coast  of  North  America  during  August-September  1970-71. 


Figure  2  also  shows  length-frequency  dis- 
tributions for  combined  Washington-Oregon 
samples  in  1970  and  Washington-Vancouver 
Island  samples  in  1971.  A  bimodal  distribution 
is  not  apparent  in  1970  but  is  distinct  in  1971. 
Little  variation  in  modes  is  noted  between  years. 

Age  frequency  was  determined  from  the  13 
saury  schools  samjjled  off  the  Oregon-Washing- 
ton-Vancouver Island  coasts  during  1970-71. 
Figure  3  histograms  indicate  the  percentage  of 
age  groups  by  area,  year,  and  areas  combined 
within  year. 

Variations  in  age  comi)osition  by  latitude 
followed  the  expected  trend  established  by 
size  composition.  Oregon  fish  were  predomi- 
nantly 1-  and  2-year-olds  while  Washington- 
Vancouver  Island  fish  were  predominantly  2-, 
3-,  4-,  and  5-year-olds.  Age  composition  of 
Oregon  samples  indicated  little  variation  be- 
tween 1970  and  1971  with  age  groups  1  and 
2  representing  89%  of  the  1970  fish  and  92%  of 
the  1971  fish.  In  contrast,  Washington  fish 
showed  considerable  variation  between  years. 
In  1970,  93%  of  the  fish  were  2-  and  3-year-olds 
while  54%  were  4-year-olds  in  1971.  Sampling 
deficiencies  probably  account  for  the  decline  in 
the  I'elative  abundance  of  the  1968  year  class 
between  1970  (2-year-old  fish)  and  1971  (3-year- 
olds).  Fish  aged  as  6-year-olds  were  represented 
in  1970  and  1971  Washington  samples,  but  it 
appears  few  fish  survive  beyond  the  age  of  5. 


Fish  of  the  spring-born  scale  type  consistently 
dominated  all  schools  sampled  (Figure  4)  and 
also  dominated  most  age  groups.  The  greatest 
variation  occurred  at  Oregon  latitudes  where 
fish  of  the  autumn-born  scale  type  comprised 
27%  of  the  1970  samples  and  12%  in  1971. 
Washington  sami)les  were  comprised  of  21% 
autumn-born  type  in  1970  and  22%  in  1971. 

Sex  Ratio  and  Maturity 

The  sex  ratio  was  examined  by  age  group  for 
variation  between  area,  year,  and  scale  type. 

Area  differences  in  age  composition  and 
difficulties  in  determining  sex  of  young  fish 
hampered  some  comparisons;  however,  numbers 
of  males  and  females  were  about  equal  through 
age  3  with  females  becoming  predominant  at 
age  4  and  beyond.  For  more  meaningful  anal- 
ysis, ages  1-3  and  4-6  were  pooled  for  each  area- 
year  category.  The  sex  ratio  of  saury  of  autumn- 
and  spring-born  scale  types  were  next  examined 
and  found  so  similar  that  statistical  treatment 
was  unnecessary.  Sex  ratios  of  area-year-age 
group  categories  are  presented  in  Table  2.  While 
the  sex  ratio  was  age-dependent,  sex  composi- 
tion differences  in  1-3  year-olds  of  Washington 
vs  Oregon  catches  in  both  1970  and  1971  and 
4-6  year-olds  of  Washington  vs  Oregon  catches 
in  1971  were  nonsignificant  (0.05  level). 

Size  and  age  at  first  maturity  could  not  be 


124 


HUGHES:  PACIFIC  SAURY  OF  NORTHEASTERN  PACIFIC 


60- 

50- 

^^                Oregon    1970 

40 

^m                      N  =  7I3 

> 

O 

^^^ 

z 

^^^ 

^    30' 

^^^ 

3 

O 

^^^ 

u 

^^§{ 

J    20- 

m 

S5 

^B 

10' 
0-' 

P 

2   3  4  5  6 


Washington     1970 
N  =  608 


12   3    4  5   6 
AGE    IN    YEARS 


Washington-  Oregon 
Combined      19  70 
N=I32I 


2  3  4   5  6 


Oregon    1971 
N=|450 


3  4  5  6 


Woshington- Vancouver 
Island  1971 

522 


Woshington-  Voncouver 
Island,  Oregon  Combined 
1971 
N  =  1905 


I    2  3  4  5  6 
AGE    IN    YEARS 


12  3  4  5  6 


Figure   3. — Age  frequency  distributions  of  eastern  Pacific  saury  captured  off  the 
Pacific  coast  of  North  American  during  August-September  1970-71. 


50- 

Oregon   1970 

Woshington    1970 

Woshington -Oregon 

pS5 

N  =  7I3 

1^- 

N  =  606 

Combined   1970 

FREQUENCY 

^ 

i 

■ 

N  =  I3I9 

1 

"1 

i 

::¥: 

J 

1^ 

ss 

mM 

m 

■  II 

:■!■: 

10- 
0- 

m 

PU  ,    , 

J 

fcM^^     ^ 

■1 

Ji 

^^^^'>i    1 

50-1 

^     Ore 

gon   1971 

:|:S 

N 

=  1450 

> 

40- 

m 

o 

M 

:•:■:• 

^ 

m 

;•:•:■ 

UJ 

3 

30 

4  ^ 

o 

m       ::: 

LlJ 

m     :W 

e 

20 

ss 

10- 

II 

■^ 

0^ 

1 

1 

> 

3 

4        5 

6 

I        2        3       4        5       6 
AGE    IN    YEARS 


Washington-  Vancouver 
Island 

1971 


Spring  Born   [ 
Fish         [ 

Autumn  Born  I 
Fish        I 


Washington-Vancouver  Island, 
Oregon  Combined 
1971 
N=  962 


12        3        4        5        6 
AGE    IN    YEARS 


Figure    4. — Age    frequency    distributions    of   eastern    Pacific   saury    showing    age 
groups  separated  into  spring-  and  autumn-born  fish. 


125 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Table     2.— 

-Sex  ratios 

of  age  groups  sampled 

in  areas  off 

the  Pacific  coast. 

1970- 197 L 

Total 

No.  fish 

Year-area 

Age 

no.  fish 

used  for 

Sex  ratio 

category 

group 

examined 

sex  ratio 

(°o  males) 

1970 

Wash. 

1-3 

578 

253 

49.4 

Greg. 

1-3 

702 

143 

43.4 

Wash. 

4-6 

28 

26 

30.8 

Greg. 

4-6 

10 

10 

0.0 

)971 

Wash. -B.C. 

1-3 

179 

100 

54.0 

Greg. 

1-3 

1,365 

1,024 

56.1 

Wash. -B.C. 

4-6 

391 

388 

37.6 

Greg. 

4-6 

8 

6 

33.3 

directly  determined  from  my  samples  since  all 
but  the  very  large  fish  were  sexually  inactive  or 
immature  upon  collection.  However,  egg 
measurements  obtained  for  ten  300-330  mm 
females  collected  off  Washington  in  1971 
showed  there  were  three  distinct  size  groujis  of 
eggs:  0.1 — 0.4  mm,  0.8 — 1.5  mm,  and  the 
mature  mode  of  1.7 — 2.0  mm.  Eleven  smaller 
specimens  collected  off  California  by  Mac- 
Gregor^  in  March  1951  and  1954  ranged 
from  196  to  204  mm  and  contained  eggs  with  a 
similar  range  (0.84 — 1.9  mm)  indicating  that 
saury  are  capable  of  reaching  first  maturity 
at  lengths  near  200  mm.  Such  fish  would 
probably  range  from  1.1  to  1.4  yrs.  old  (Table  3). 
Eighteen  of  the  19  schools  sampled  were 
composed  principally  of  apparently  mature  fish 
in  a  resting  state.  The  remaining  school  was 
predominantly  4-year-olds  with  females  out- 
numbering males  1  to  0.73,  and  96%  of  these 
were  in  spawning  condition.  Fish  displaying 
both  spring-born  and  fall-born  growth  patterns 
of  scales  were  found  in  this  school. 

LENGTH-WEIGHT  RELATION 

The  length-weight  relation  of  saury  captured 
in  1970  and  1971  was  determined  by  fitting  the 
logarithmic  form  of  the  equation  W  =  qL^ , 
where  W  is  weight  in  grams  and  L  is  knob 
length  in  millimeters,  to  mean  emperical 
weights  in  each  5-mm  length  interval. 

Separate  relationships  were  determined  for 
each  hypothesized  race  and  area-year  category 


by  sex.  Using  an  analysis  of  covariance  (Dixon 
and  Massey,  1969),  no  significant  difference  in 
the  L-W  relation  was  detected  between  years, 
areas,  or  scale  type,  but  there  was  a  significant 
difference  (0.05  level)  between  males  and 
females. 

A  total  of  1,170  males  and  1,642  females 
representing  immature,  mature  resting,  and 
ripe  saury  were  included  in  the  length-weight 
regressions  presented  in  Figure  5.  The  equation 
for  males  was  W  =  3.293  X  IQ-^L^oso  ^nd  for 
females  W  =  2.077  X  10"^  L3132  pemales 
were  slightly  lighter  than  males  at  lengths  <225 
mm  and  heavier  than  males  at  lengths  >280 
mm. 

GROWTH 

Interpretation  of  growth  was  complicated 
because  of  the  possible  racial  aspect  and 
extended  spawning  season.  Growth  was  deter- 
mined for  sexes  combined  because  of  the  high 
probability  of  error  in  determining  the  sex  of 
young  fish.  It  was  assumed  that  growth  in 
length  is  asymj)totic  and  that  the  von  Berta- 
lanffy  (1938)  growth  equation  adequately 
rei)resents  such  growth. 

Following  methods  of  Stevens  (1951), 
average  lengths  (observed  and  calculated  from 
weight  at  age)  were  fitted  to  the  equation 
It  =  L^  [1  -e-^<'-'o)]. 


140- 
130 


i 

y    90 


60' 
50 


Molls 

W- 3,293  X  10"^  L^^^ 


Ftmol** 

W=2.077  X  lO'^L^ 


•*  J.  MacGregor,  Fishery  Biologist,  Natl.  Oceanic 
Atmos.  Admin.,  Natl.  Mar.  Fish.  Serv.,  Southwest  Fish. 
Center,  La  Jolla,  Calif.,  personal  commun. 


180      200    220     240     260     280     300     320     340  200     220     240    260     280     300     320     340    360 

KNOB    LENGTH    (mm) 


Figure  5. — Length-weight  relation  of  male  and  female 
saury.  The  curve  is  fitted  to  mean-observed  weight  per 
.■^-mm  length  interval. 


126 


HUGHES:  PACIFIC  SAURY  OF  NORTHEASTERN  PACIFIC 
Table  3 


Average  observed  length   at  age,  lengths  calculated  from  weight   at  age  and  estimated  von 
BertalantTy  growth  parameters  of  hypothesized  spring-  and  autumn-born  fish. 


Spring 

born  fish 

Autumn  born  fish 

Age 

Average  observed 

Length  calculated 

Age 

Average  observed 

Length  calculated 

(years) 

len 

gth 

at  age  { 

mm) 

from  weight  at 
age  '  (mm) 

(years) 

length  at  age  (mm) 

from  weight  at 
age-     (mm) 

1.10 

183.9 

182.5 

0.75 

142.8 

151.2 

1.40 

219.0 

223.6 

1.00 

178.7 

182.1 

2.40 

245.5 

249.3 

2.00 

232.1 

235.8 

3.40 

268.8 

272.7 

3.00 

256.8 

260.6 

4.40 

308.6 

312.5 

4.00 

297.0 

303.0 

5.40 

319.8 

321.4 

5.00 

314.5 

316.8 

6.40 

319.9 

323.0 

L„=  351.43 

L„  =  360,23 

L^  =  353.45 

L„=  348.50 

K  = 

0.34 

K  =       0.36 

K  =       0.38 

K  =       0.38 

'o  =    - 

1.19 

'o  =    -0-83 

'o  =   -0-72 

'o=    -l-°2 

1       HZ  = 

1.497 

X 

10-«Z.3 

.iMa 

2        K/  = 

1.809 

X 

10-BZ.3 

.155 

Growth  was  first  compared  between  fish  of 
the  autumn-  and  spring-born  scale  type.  Table 
3  summarizes  the  respective  sets  of  length  at 
age  data  and  jn-esents  growth  parameters. 
Little  difference  is  noted  between  respective 
sets  of  length  at  age  data  for  the  two  groups  of 
fish.  Although  there  is  no  consistent  advantage 
in  using  lengths  derived  from  weights  at  age. 
it  should  be  noted  that  estimated  t^  values  are 
sensitive  to  the  method  chosen.  Regardless  of 
method,  no  significant  differences  in  growth 
parameters  L^    and    e~^    existed  between  fish 


of  spring-  and  autumn-born  scale  types.  Their 
graphic  similarity  is  shown  in  Figure  6  where 
observed  lengths  at  age  and  fitted  curves  are 
presented.  Lack  of  significant  differences  in 
growth  patterns  between  fish  of  spring-  and 
autumn-born  type  suggested  that  respective 
data  sets  be  pooled  and  that  a  single  growth 
curve  be  presented  (Figure  7).  The  resulting 
estimated  parameters  were  L^  =  342.36, 
K  =  0.41,  and  t^  =  -0.72.  The  calculated 
Lqo  is  close  to  the  maximum  observed  length 
of  340  mm.  The  estimated  age  at  95%  growth 
completion  was  6.5  years. 


2  3 

AGE      lYEARSI 


Figure  6. — Average  observed  length  at  age  and  fitted 
growth  curves  of  spring-  and  autumn-born  saury  captured 
in  offshore  waters  from  southern  California  north  to 
Vancouver,  British  Columbia  1970-71. 


Figure  7. — Average  observed  length  at  age  and  fitted 
growth  curve  of  eastern  Pacific  saury  after  pooling  data 
from  spring-  and  autumn-born  fish. 


127 


FISHERY  BULLETIN:  VOL.  72,  NO,  1 


MORTALITY 

There  are  several  limitations  to  the  data  used 
for  estimating  natural  mortality:  (1)  Sampling 
was  conducted  during  a  period  of  apparent 
migration  which  caused  the  stock  along  the 
Pacific  coast  to  become  stratified  in  size  and 
age  composition.  (2)  sampling  was  limited 
and  not  conducted  throughout  the  stock's 
entire  geographical  range,  and  (3)  age  frequency 
data  indicate  possible  variations  in  annual 
recruitment  and/or  survival  rate.  Thus,  one 
or  more  basic  assumptions  underlying  tradition- 
al mortality  models  are  violated  to  some  degree. 
Realizing  the  above  limitations  and  considering 
this  an  initial  study  of  the  adult  stock,  I  have 
generated  a-  range  of  estimates  using  several 
independent  techniques. 

A  catch  curve  analysis  (Robson  and  Chapman. 
1961)  was  applied  to  the  1970  data  since  equal 
sampling  occurred  off  Washington  and  Oregon, 
the  only  areas  sampled,  during  that  period. 


Coded 

No.  offish 

Age 

age 

in  catch 

II 

0 

A'o  =  644 

III 

1 

A^  =  313 

IV 

2 

A^  =     32 

V 

3 

A^3  =       7 

VI 

4 

A^  =       1 

=  997 


Annual  survival  rate  estimate: 


S 

Var  (.s) 

SE  (.s) 

95%  CI  (.s) 


.2876 
0.00017 
0.013 

.2876+  2(0.013) 

=   (.2616,  .3136) 


When  the  above  data  were  converted  to  a  total 
annual  in.stantaneous  mortality  rate,  Z  =  1.25 
and  95%  CI,  Z  =  (1.16,  1.34). 

The  raw  age  data  were  also  converted  to 
natural  log  form  and  treated  by  simple  linear 
regression.  The  result  was  a  significant  linear 
relationship  with  Z  =  1.67  and  95%  CI,  Z  = 
(1.41,  1.93). 

Beverton  and  Holt's  (1956)  formula  using 
length  frequency  data  was  also  applied  to  the 
1970  data.  While  this  technique  was  designed 
primarily    for    exploited    pojjulations,    its    use 


generated  another  independent  estimate  and 
enabled  the  use  of  substantial  numbers  of  fish 
which  could  not  be  aged. 

The     Beverton     and     Holt     formula     Z     = 


KiL^-L) 


where  L  is  the  average  length  of 


(L  -  L,) 

the  fish  in  the  catch  that  are  as  large  as,  or 
larger  than,  the  first  fully  recruited  length 
Lf,  estimated  Z  =  1.41  when  L^  =  342  mm, 
K  =  0.41,  L  =  248  mm,  and  L^  =  220  mm. 
Survival  rates  were  generated  for  each  of 
the  four  area-year  categories  by  subjecting 
resijective  sets  of  age  frequency  data  to  Jackson's 
(1939)  technique: 


S  = 


N^^N,^ 


+  N„ 


A^i  +  A^2  + 


+  N-1 


The  analysis  yielded  the  following  estimates: 
Oregon,  1970;  Z  =  1.58, 
Oregon,  1971;  Z  =  1.80, 
Washington,  1970;  Z  =  2.20. 
Washington-Vancouver  Island,  1971; 
Z  =  1.27. 
The     seven     individual     estimates     obtained 
indicate  a  possible  range  of  Z  from  1.25  to  2.20 
and  an  overall  average  Z  of  1.60. 

AVAILABILITY  OF  FISHABLE 
CONCENTRATIONS 

Fishable  concentrations  of  saury  (>%  ton) 
were  usually  located  in  waters  of  15°-17°C 
near  areas  of  upwelling.  Surface  temperatures 
strongly  influence  distribution  and  migration 
patterns  of  western  Pacific  saury  (Fukushima, 
1956  and  1962)  as  they  appear  to  in  the  eastern 
Pacific  (Ellis  and  Hughes,  1971).  All  studies 
indicate  sharp  thermal  fronts  affect  and  often 
dictate  patterns  of  migration  and  areas  where 
temporary  concentrations  may  form. 

Throughout  the  surveys,  high  density  areas 
capable  of  sustaining  productive  fishing  opera- 
tions were  rarely  encountered.  Most  encounters 
were  single  schools  (1-3  tons)  or  loose  aggrega- 
tions offish  dispersed  over  large  areas  of  surface 
waters.  The  average  probability  of  locating 
at  lea.st  one  fishable  concentration  during  a 
night's  oi)eration  (averaging  8  hr  of  searching- 
effort  and  70  miles  of  tracklines)  was  about  0.3. 
The  relative  densities  decreased  slightly  with 
increasing  latitudes,  but  large  saury,  which  are 
currently  in  greatest  commercial  demand,  were 


128 


HUGHES:  PACIFIC  SAURY  OF  NORTHEASTERN  PACIFIC 


more  available  in  the  northern  portion  of  the 
study  area. 

Low  availability  has  evidently  hampered 
Japanese  attempts  to  establish  new  fishing 
grounds  in  the  eastern  Pacific.  Operations  by 
about  15  Japanese  saury  vessels  in  1970  and  19 
vessels  in  1971  met  financial  failure.  Conse- 
quently, major  fishery  firms  such  as  Nihon 
Sui-san,  Hoko  Suisan,  and  Nichiro  have 
reportedly  abandoned  attempts  to  exploit  the 
eastern  Pacific  saury  resource."' 

DISCUSSION 

It  seems  pertinent  to  propose  some  general 
hypotheses  about  the  life  history  of  the  eastern 
Pacific  saury  based  on  information  presented 
here  and  in  papers  by  Ahlstrom  and  Casey 
(1956).  Ahlstrom  (1968),  and  Smith  et  al.  (1970). 

The  coastal  stratification  of  saury  by  size  and 
age  composition  during  at  least  August- 
September  is  probably  due  to  a  northerly 
migration  by  many  adults  from  California 
waters.  Sea  surface  temperatures  and  position 
of  warm-cold  fronts  strongly  influence  migra- 
tion patterns  and  rates  of  movement  of  saury 
in  the  western  North  Pacific  Ocean  (Fukushima. 
1956,  1962).  Several  factors  indicate  a  similar 
situation  exists  in  the  eastern  Pacific  Ocean. 
Our  surveys  indicated  eastern  Pacific  saury 
display  narrow  limits  of  thermal  preference 
and  are  found  most  often  near  areas  of  up- 
welling.  Furthermore,  there  is  an  excellent 
correlation  between  the  apparent  spacial  and 
temporal  distribution  of  saury  and  average 
month-by-month  sea-surface  temperature  data. 
Using  Johnson's  (1961)  12-year  monthly  means 
andathermal  preference  range  of  14.0°  to  17.0°C, 
it  is  a]:)parent  that  large  quantities  of  saury 
would  not  begin  a  northerly  migration  from 
California  waters  before  June.  Migration  into 
northern  Oi'egon  and  Washington  waters  would 
not  be  expected  to  occur  before  July.  Rapid 
warming  during  July  and  August  produces  a 
favorable  temperature  regime  along  the  coasts 
of  Washington,  Vancouver  Island,  and  into 
Queen  Charlotte  Sound.  While  temperature 
conditions     remain     favorable     in     September, 


'  J.  H.  Shohara  (Compiler).  1972.  12  Japanese  vessels 
licensed  for  distant-water  saury  fishing  [Excerpted  from 
Shin  Suisan  Shimbun  Sttkuho.  July  18  and  July  29,  1972]. 
U.S.  Dep.  Commer..  Natl.  Oceanic  Atmos.  Admin., 
Natl.  Mar.  Fish.  Serv.,  Foreign  Fish.  Inf.  Release  72-27, 
p.  3.  (Processed.) 


seasonal  cooling  occurs  off  Vancouver  Island 
and  Washington  during  October  and  continues 
through  Oregon  and  northern  California  waters 
in  November.  Thus,  it  appears  that  in  addition 
to  influencing  the  time  and  patterns  of  saury 
migration,  temperature  conditions  could  also 
restrict  the  bulk  of  the  stock  to  oceanic  areas 
between  Baja  California  and  Queen  Charlotte 
Sound  or  the  southern  Gulf  of  Alaska. 

From  the  data  presented,  the  degree  of 
migration  appears  to  be  dependent  on  size  and 
age  of  fish,  and  many  young  adults  and 
juveniles  apparently  remain  in  California 
waters  throughout  the  year. 

Fish  exceeding  300  mm  in  length  (primarily 
ages  4,  5,  and  6)  reach  maturity  during  the 
migration  in  August  and  release  their  mature 
mode  of  eggs  (1.8-2.0  mm)  in  late  August  or 
September.  Since  Hatanaka's  (1956)  work  on 
maturity  in  the  western  North  Pacific  Ocean 
(three  modes  of  eggs,  0.6,  1.1,  and  1.9  mm)  is  in 
close  agreement  with  this  study,  it  seems 
reasonable  that  eastern  Pacific  saury  release 
modes  of  eggs  at  about  the  same  intervals — 2 
months  between  the  first  and  middle  mode. 
Thus,  the  second  spawning  of  large  fish  would 
probably  take  place  in  October  or  November 
and  the  third  spawning  during  the  winter  while 
off  California.  Younger  adults,  sexually 
inactive  during  August-September,  probably 
mature  and  spawn  during  the  following  winter 
and  spring  while  in  more  southerly  waters, 
primarily  off  California.  It  is  not  known 
whether  2-  and  3-year-old  fish  spawn  more  than 
one  mode  of  eggs  per  year. 

The  above  hypothesis  would  account  for  the 
reported  low  abundance  of  eggs  in  California 
waters  during  August-September  (Smith  et  al., 
1970)  when  most  spawning  saury  occupy  a 
northerly  regime.  The  spawning  of  younger 
age  groups  coincides  with  peak  egg  abundance 
in  California  during  April,  May,  and  June. 
Such  an  extended  spawning  season  would 
account  for  spring-born,  autumn-born,  and 
some  intermediate  growth  patterns  detected 
from  scale  samples,  as  well  as  the  fact  that 
three-quarters  of  the  samples  displayed  the 
spring-born  growth  characteristic. 

There  seems  to  be  little  likelihood  that  spring- 
and  fall-born  fish  constitute  different  races, 
since  both  types  were  observed  spawning  to- 
gether in  the  same  school.  Furthermore, 
statistical    comparisons    of   length-weight    and 


129 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


growth  parameters  failed  to  disclose  any 
significant  differences  between  these  groups. 
These  results  are  in  line  with  unpublished 
results  of  Utter  whose  biochemical  gene  fre- 
quency studies  gave  no  indication  of  hetero- 
geneity between  spring-born  and  fall-born 
saury.*'  Biochemical  techniques  also  indicated 
intra-area  homogeneity  of  fish  in  waters  be- 
tween southern  California  and  Vancouver 
Island.  Additional  samples  would  have  been 
desirable  for  a  more  complete  racial  study; 
however,  results  of  this  initial  study  strongly 
suggest  the  eastern  Pacific  saury  stock  is  basi- 
cally represented  by  a  single  gene  pool. 

Growth,  maturity,  and  mortality  studies 
indicate  that  saury  (1)  display  rapid  growth 
during  the  first  year  of  life,  (2)  are  capable  of 
attaining  maturity  during  the  second  year,  and 
(3)  probably  do  not  survive  beyond  6  years  of 
age.  Results  indicate  the  total  mortality  co- 
efficient (Z)  is  between  1.25  and  2.20.  Since 
fishing  mortality  has  remained  insignificant, 
Z  would  be  a  result  of  natural  mortality  {M), 
assuming  migration  during  the  sampling  period 
has  not  significantly  confounded  the  situation. 
Intuitively,  it  seems  Z  is  a  reasonable  approxi- 
mation of  M  since  sampling  was  conducted  over 
a  wide  geographical  area  during  the  middle  of 
the  migratory  period.  No  previous  estimates 
of  natural  mortality  have  been  published  for 
the  eastern  Pacific  saury  stock;  however, 
Novikov  (1969)  reports  natural  mortality  in 
the  western  Pacific  to  be  about  50% .  Con- 
verting to  instantaneous  mortality  for  direct 
comparison,  his  e.stimate  would  be  about  0.70. 

ACKNOWLEDGMENTS 

Robert  Larsen,  Ma.ster  of  the  research 
vessel  J(>h)i  N.  Cohh,  and  his  entire  crew 
rendered  exceptional  service  and  helpful 
suggestions  during  the  field  operations  in 
1970-71.  I  also  thank  George  Hirschhorn  of 
the  Northwest  Fisheries  Center  for  valuable 
assistance  in  the  growth  studies. 

LITERATURE  CITED 

Ahlstrom,  E.  H. 

1968.  An  evaluation  ot"  the  fishery  resources  available 


'•  F.  Utter,  Biochemical  Geneticist,  Natl.  Oceanic  Atmos. 
Admin.,  Natl.  Mar.  Fish.  Serv.,  Northwest  Fish.  Center, 
Seattle,  Wash.,  personal  commun. 


to  California  fishermen.  Univ.   Wash.,   Publ.   Fish., 
New  Ser.  4:65-80. 
Ahlstrom,  E.  H.,  and  H.  D.  Casey. 

1956.  Saury  distribution  and  abundance,  Pacific 
Coast,  1950-55.  U.S.  Fish  Wildl.  Serv.,  Spec.  Sci. 
Rep.  Fish.  190,  69  p. 

Andreev,  N.  N. 

1962.  Stick-held   dip   net   for   saury  fishing.   In   N.   N. 

Andreev,  Spravochnik   po  orudiyam  leva,  setesna- 

stnym       materialam       i       proniyslovomu       snarya- 

zheniyu  (Handbook  of  fishing  gear  and  its  rigging). 

Pishchepromizdat,  Moscow,  p.  459-462.  (Translated 

by   Israel   Program  Sci.  Transl.,    1966,   p.  418-420; 

available    U.S.    Dep.    Commer.,    Natl.    Tech.    Inf. 

Serv.,  Springfield,  Va.  as  TT  66-5  1046.) 
Bertalanffy,  L.  Von 

1938.  A     quantitative     theory     of     organic     growth 

(Inquiries  on  growth  laws.  II.)   Hum.  Biol.    10:181- 

213. 
Beverton,  R.  J.  H.,  AND  S.  J.  Holt. 

1956.  A   review  of  methods  for  estimating  mortality 

rates    in    exploited    fish    populations,    with    special 

reference  to  sources  of  bias  in  catch  sampling.  Rapp. 

P.-V.    Reun.   Cons.    Perm.   Int.    Explor.    Mer,    140, 

Part  1:67-83. 
Clemens,  W.  A.,  and  G.  V.  Wilby. 

1961.  Fishes  of  the  Pacific  coast  of  Canada.  2d  ed. 
Fish.  Res.  Board  Can.  Bull.  68,  443  p. 

Clutter,  R.  I.,  and  L.  E.  Whitesel. 

1956.  Collection  and  interpretation  of  sockeye  salmon 
scales.  Int.  Pac.  Salmon  Fish.  Comm.,  Bull.  9,  159  p. 
Dixon,  W.  J.,  and  F.  J.  Massey,  Jr. 

1969.  Introduction     to     statistical     analysis.     3d     ed. 
McGraw-Hill,  N.Y.,  638  p. 
Ellis,  I.,  and  S.  E.  Hughes. 

1971.  Pacific  saury — A  progress  report.  Natl.  Fisher- 
man Yearb.  Issue  1971  5 1(  13):67-70,  75,  77, 
84-85,  92. 

FUKUSHIMA,  S. 

1956.  On  the  size-composition  of  the  Pacific  saury, 
Calolahis  saira,  caught  in  the  North-eastern  Sea  area 
of  Japan.  [In  Jap.,  Engl,  summ.]  Bull.  Tohoku  Reg. 
Fish.Res.  Lab.  7:12-36. 

1962.  On  the  relation  between  the  pattern  of  the 
Kuroshio  Current  in  spring  and  summer  and  the 
saury  fishing  conditions  in  fall.  [In  Jap.,  Engl, 
summ.]    Bull.  Tohoku  Reg.  Fish.  Res.  Lab.  21:21-37. 

Hatanaka,  M. 

1956.  Biological  studies  on  the  population  of  the 
saury,  Cololahis  saini  (Brevoort).  Part  I.  Reproduc- 
tion and  growth.  Tohoku  J.  Agric.  Res.  6:227-269. 

HOTTA,  H. 

1960.     On    the    analysis    of    the    population    of   the 

saury  (Cololahis  sciiru)  based  on  the  scale  and  otolith 

characters,  and  their  growth.  [In  Jap.,  Engl,  summ.] 

Bull.     Tohoku     Reg.     Fish.     Res.     Lab.      16:41-64. 

Hughes,  S.  E. 

1973.     Some  metazoan  parasites  of  the  eastern  Pacific 
saury,   Cololahis  saira.  Fish.   Bull.,  U.S.  71:943-953. 
Inoue,  M.S.,  and  S.  Hughes. 

1971.  Pacific  saury  {Cololahis  saira):  A  review  of 
stocks,  harvesting  techniques,  processing  methods 
and  markets.  Oreg.  State  Univ.,  Corvallis,  Eng. 
Exp.  Stn.  Bull.  43,  102p. 


130 


HUGHES:  PACIFIC  SAURY  OF  NORTHEASTERN  PACIFIC 


Jackson,  C.  H.  N. 

1939.  The  analysis  of  an  animal  population.  J.  Anim. 
Ecol.  8:238-246. 
Johnson,  J.  H. 

1961.  Sea  surface  temperature  monthly  average 
and  anomaly  charts  northeastern  Pacific  Ocean, 
1947-58.  U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep. 
Fish.  385,  56  p. 

KiMURA,  K. 

1956.  The  standard  length  of  the  Pacific  saury, 
Cololahis  saini  (Brevoort).  [In  Jap.,  Engl,  summ.] 
Bull.  Tohoku  Reg.  Fish.  Res.  Lab.  7:1-1 1. 

KOTOVA,  L.  I. 

1958.  O  biologii  razmnozheniya  sairy  v  Yaponskom 
more  (The  biology  of  reproduction  of  the  saury  in 
the  Sea  of  Japan).  Rybn.  Khoz.  34(10):6-10. 
(Transl.  Natl.  Mar.  Fish.  Serv.,  Foreign  Fish 
(Transl.),  Wash.,  D.C.) 

MOSHER,  K.  H. 

1950.  Description  of  a  projection  device  for  use  in 
age  determination  from  fish  scales.  U.S.  Fish 
Wildl.  Serv.,  Fish.  Bull.  51:405-407. 

NOVIKOV,  N.  P.,  AND  M.  Yu.  KULIKOV. 

1966.  Perspektivnyi    raion    promysla    sairy    (Prospec- 
tive     region      for     saury      fishing).  Rybn.      Khoz. 
42(7):20-21.     (Transl.     Natl.     Mar.     Fish.     Serv., 
Foreign  Fish.  (Transl.).  Wash.,  D.C.) 
NoviKOV,  Yu.  V. 

1969.  Zapasy  sairy  i  regulirovanie  ee  promysla 
(Conditions  of  the  saury  stocks  and  the  regulation 
of    their    fisherv.)  Tr.    Vses.    Nauchn.-issled.    Inst. 


Morsk.      Rybn 
(Transl.,    Natl. 
(Transl.),  Wash.,  D.C.) 
Parin,N.  V. 

1960.  Areal    sairy 
socidae.     Pices) 


Khoz.      Okeanogr.      67: 190-200. 
Mar.    Fish.    Serv.,    Foreign    Fish. 


(Cololahis  sairu  Brev. — Scombre- 
i  znachenie  okeanograficheskikh 
faktorov  dlya  ee  rasprostraneniya  (The  range  of  the 
saury  (Cololahis  saira  Brev. — Scombresocidac, 
Pisces)  and  effects  of  oceanographic  features  on  its 
distribution).  Dokl.  Akad.  Nauk  SSSR  New  Ser. 
130(3):649-652. 
RoBSON,  D.  S.,  AND  D.  G.  Chapman. 

1961.  Catch  curves  and  mortality  rates.  Trans.  Am. 
Fish.  Soc.  90: 181-189. 
Smith,  P.  E.,  E.  H.  Ahlstrom,  and  H.  D.  Casey. 

1970.  The  saury  as  a  latent  resource  of  the  California 
Current.  Calif.  Coop.  Oceanic  Fish.  Invest.  Rep. 
14:88-130. 

SOKOLOVSKII,  A.  S. 

1969.  K  voprosu  o  stadakh   sairy   v  Tikhom  okeane 

(Populations   of  saira    in   the    Pacific   Ocean).  Izv. 

Tikhookean.     Nauchn.-issled.     Inst.     Rybn.     Khoz. 

Okeanogr.    68:203-208.    (Transl.,    1971,    Fish    Res. 

Board  Can.  Transl.  Serv.  1614.) 
Stevens,  W.  L. 

1951.      Asymptotic      regression.      Biometrics      7:247- 

267. 
Utter,  F.  M.,  H.  O.  Hodgins,  and  A.  G.  Johnson. 

1972.  Biochemical     studies     of     genetic     differences 

among  species  and  stocks  of  fish.  Int.  North  Pac. 

Fish.  Comm.,  Annu.  Rep.  1970:98-101. 


131 


HEAVY  METALS  IN  THE  NORTHERN  FUR  SEAL, 

CALLORHINUS  URSINUS,  AND 

HARBOR  SEAL,  PHOCA  VITULINA  RICHARDI 


Raymond  E.  Anas' 


ABSTRACT 

Samples  of  liver,  muscle,  and  kidney  from  fur  seal,  Callurhimts  iirsimis,  and  liver  from  harbor 
seal,  Pliocu  viiiilina  ricliarcli,  were  analyzed  for  lotal  mercury.  Liver  and  kidney  of  fur  seals 
were  analyzed  for  lead,  cadmium,  and  arsenic.  Fur  seals  were  from  the  Pribilof  Islands, 
Alaska,  and  from  off  the  Washington  coast.  Harbor  seals  were  from  the  waters  of  southern 
California,  Oregon,  Washington,  and  the  Bering  Sea.  All  of  the  samples,  including  a  fetus 
taken  3  mo  before  birth,  contained  mercury,  lead,  and  cadmium.  Arsenic  was  not  detected. 
Mercury  was  highest  in  liver,  followed  by  kidney,  then  muscle.  The  maximum  concentration 
of  mercury  in  liver  was  about  700  ppm  in  a  southern  California  harbor  seal  and  170  ppm  in 
a  fur  seal  taken  off  the  Washington  coast.  Concentrations  of  cadmium  and  lead  were  highest 
in  the  kidney  (maximums  of  1.8  ppm  lead  and  15.6  ppm  cadmium)  of  fur  seals.  Concentra- 
tions of  mercury  did  not  correlate  with  age  in  muscle  or  kidney  (P>  0.05)  but  did  correlate 
significantly  with  age  in  liver  iP  <  O.OI).  Concentrations  of  cadmium  and  lead  in  liver  and 
kidney  did  not  correlate  with  age  (P  >  0.05).  In  samples  of  liver  collected  from  harbor  seals, 
the  highest  concentrations  of  mercury  were  from  southern  California  seals. 


Heavy  metals  are  persistent  contaminants  that 
ultimately  end  up  in  the  oceans.  Little  is  known 
of  the  sublethal  effects  of  these  contaminants 
on  living  marine  resources,  but  some  heavy 
metals  are  known  to  be  harmful.  One  ppb  (part 
per  billion)  of  four  commonly  used  organo- 
mercurial  fungicides  reduced  the  photosynthetic 
rate  of  a  marine  diatom  (Harriss,  White,  and 
MacFarlane,  1970).  Skerfving,  Hansson,  and 
Lindsten  (1970)  reported  chromosome  break- 
age in  humans  who  ate  fish  containing  1-7  i)pm 
(parts  per  million)  methylmercury. 

Heavy  metals  are  added  to  the  sea  by  land 
erosion,  volcanic  activity,  and  man.  A  committee 
of  experts  selected  mercury,  lead,  cadmium,  and 
arsenic  as  the  four  inorganic  jjollutants  most 
threatening  to  the  marine  environment  (Food 
and  Agriculture  Organization  of  the  United 
Nations,  1971).  The  same  elements  were 
selected  for  this  study.  Average  levels  of  the 
four  most  critical  heavy  metals  in  the  ocean  are 
about  0.00003  ppm  (mg/1)  mercury,  0.08  ppm 
cadmium,  0.00003  ppm  lead,  and  0.003  ppm 
arsenic  (U.S.  Senate,  1970).  Williams  and  Weiss 


(1973)  found  0.00027  ppm  mercury  at  10-m 
depth  and  0.000029-0.000096  ppm  from  100-  to 
4,080-m  depth  in  water  samples  taken  430  km 
southeast  of  San  Diego,  Calif. 

Amounts  of  contaminants  in  seals  provide  us 
with  data  at  this  time  in  a  marine  species  near 
the  top  of  the  food  web  in  the  ocean.  Up  to 
172  ppm  mercury  in  liver  of  northern  fur  seals, 
CaU(>)-}uinis  in-si))t(i^  (Anas,  1970a);  66  ppm  in 
liver  of  gray  seals,  Hallchoerus  gnjpi(s  (Jones, 
Jones,  and  Stewart,  1972);  and  24  ppm  mercury 
in  liver  of  short-finned  pilot  whales,  Globi- 
cephala  scammo)n  (Hall,  Gilmailin,  and 
Mattsson,  1971)  have  been  reported.  Buhler- 
repoited  60  ppm  cadmium  in  the  kidney,  6  ppm 
cadmium  in  the  liver,  and  225  p])m  mercury  in 
the  liver  of  California  sea  lions,  Zalophus 
califnniiaHu.s.  This  report  documents  the 
amounts  of  mercury,  lead,  cadmium,  and 
arsenic  in  northern  fur  seals  and  of  mercury  in 
harbor  seals,  PJioca  vitulhia  richardi. 

Northern  fur  seals  are  a  migratory  species 
that  breed  each  summer  mainly  on  the  Pribilof 
Islands,  Alaska,  and  on  the  Commander  Islands 


'  Northwest       Fisheries 
Fisheries     Service,     NOAA, 
Seattle,  WA  98 112. 


Center,      National      Marine 
2725     Monllake     Blvd.     E., 


Manuscript  accepted  June.  1973 

FISHERY  BULLETIN:  VOL.  72.  NO.  1,  1974 


-  D.  R.  Buhler.  Environmental  Health  Sciences  Center, 
Oregon  State  University,  Corvallis.  Oregon  97331,  per- 
sonal communication. 


133 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


and  Robben  Island,  USSR.  Small  breeding 
colonies  are  found  in  the  Kurile  Islands,  Japan, 
and  on  San  Miguel  Island,  Calif.  During  winter 
and  sjiring,  fur  seals  are  pelagic  and  migrate 
as  far  south  as  southern  California  and  Japan. 
Fur  seals  feed  principally  on  fishes  and  squids 
in  offshore  areas. 

Harboi-  seals  are  a  nonmigratory  species 
found  in  the  northern  hemisphere  in  both  the 
Pacific  and  Atlantic  Oceans.  Those  collected  for 
this  study  (subspecies  )-icli(irdi)  are  found  from 
Mexico  to  the  Bering  Sea.  Harbor  seals  feed 
principally  on  fishes,  s(iuids,  and  octoi)uses  near 
coastlines. 

METHODS 

The  liver  and  kidneys  were  selected  as  the 
principal  tissues  for  this  study  because  heavy 
metals  tend  to  accumulate  in  these  organs 
(DuBois  and  Ceiling,  1959;  Curry,  1969). 
Sami)les  of  muscle  were  collected  from  fur  seals 
but  not  from  harbor  seals. 

Collection  of  Samples 

In  general,  the  sampling  was  conducted  as 
follows:  From  a  seal  liver  weighing  about  1.8 
kg.  a  kidney  weighing  about  0.5  kg,  or  muscle 
from  the  shoulder  area,  a  sample  of  about  75  g 
was  placed  in  a  new  unwashed  glass  bottle  or 
l)olyethylene  bag  and  stored  at  —  23°C. 
Analyses  were  made  about  5  mo  after  initial 
sami)ling. 

Samples  included  liver  and  muscle  from  3-mo- 
old  pups  and  2-  and  3-yr-old  male  fur  seals  from 
the  Pribilof  Islands;  liver,  muscle,  and  kidney 
from  fur  seals  (mostly  adult  females)  from 
Washington;  and  liver  from  harbor  seals  from 
California,  Oregon,  Washington,  and  the  Bering 
Sea.  Tissues  from  fur  seals  taken  on  the  Pribilof 
Islands  were  kept  in  jjolyethylene  bags;  all 
other  tissues  were  kei)t   in   new  glass  bottles. 

Analyses  of  Samples 

For  the  analysis  of  mercury,  four  rei)licate 
20-mg  samples  were  taken  from  a  piece  of 
tissue  in  the  sam])le  bottle  and  analyzed.  The 
mean  of  these  four  replicates  was  taken  as 
representative  of  the  i)articular  tissue  for  that 
analysis.  The  analytical  procedure  for  mercury 


involves  introduction  of  the  weighed  sample 
into  a  tubular  furnace  from  which  the  products 
of  combustion  and  vaporized  mercury  are 
drawn.  After  scrubbing  and  filtering  to  remove 
interfering  components,  the  mercury  vapor  is 
passed  through  a  cell  and  read  by  atomic 
absorption  spectrophotometry.'' 

For  lead,  cadmium,  and  arsenic  analyses,  a 
separate  2-g  sami)le  was  taken  for  each  metal. 
The  lead  analysis  was  carried  out  by  digesting 
the  sample  in  a  5:2  nitric-sulfuric  acid  mixture 
followed  by  dry  ashing  in  a  muffie  furnace  at 
550° C  until  all  organic  material  was  removed. 
Following  dissolution  in  5  ml  of  hydrochloric 
acid,  lead  content  was  determined  by  the 
double  extraction,  mixed  color  dithizone  method 
(Committee  on  Chemical  Procedures  of  the 
Occupational  Health  Section,  American  Public 
Health  Association,  1955). 

For  cadmium,  the  .sample  was  wet  ashed  in  a 
2:1  nitric-perchloric  acid  mixture,  and  the 
re.sultant  solution  diluted  to  a  known  volume 
with  water.  The  cadmium  was  extracted  into 
methyl  isobutyl  ketone  (MIBK)  by  means  of 
chelation  with  sodium  diethyldithiocarbamate 
(NDDC)  and  measured  by  atomic  absorption 
(Berman,  1967). 

For  arsenic,  the  sami)le  was  wet  ashed  in  an 
8:4:1  nitric-perchloric-sulfuric  acid  mixture  to 
oxidize  organic  matter  and  release  organically 
bound  arsenic.  Following  digestion,  the  sample 
was  diluted  to  25  ml  volume  with  water  and 
arsenic  determined  by  the  silver  diethyldithio- 
carbamate method  (American  Public  Health 
Association,  1971). 

Detection  limits  of  the  analyses  were  1  i)pb 
for  mercury,  0.1  ppm  for  lead,  0.01  ppm  for 
cadmium,  and  0.2  i)i)m  for  arsenic.  Recoveries 
were  over  90%  for  mercury  and  cadmium  where 
mercury  was  added  as  elemental  mercury 
dissolved  in  nitric  acid  and  cadmium  was  added 
as  cadmium  sulfate.  Lead  and  arsenic  recoveries 
wei"e  over  95%  with  lead  added  as  lead  nitrate 
and  arsenic  added  as  arsenic  trioxide. 

All  of  the  tissue  samples  were  analyzed  by 
Environmental  Health  Laboratories  Inc., 


!  Hermann,  W.  J.,  Jr.,  J.  W.  Butler,  and  R.  G.  Smith. 
1468.  A  dynamic  system  for  the  rapid  microdetermination 
of  mercury  in  undigested  biological  materials.  Presented 
at  Applied  Seminar  on  Laboratory  Diagnosis  of  Diseases 
Caused  bv  Toxic  Agents,  Washington.  D.C.,  Nov.  8-9, 
1968.  Wayne  State  Univ..  Detroit.  Mich.,  Dep.  Med., 
14  p.,  1  fig.  (Processed.) 


134 


ANAS:  HEAVY  METALS  IN  SEALS 


Farmington,  Mich.^  A  sample  of  paper  lid  liners 
from  the  glass  bottles  was  analyzed  by  the  use 
of  neutron  activation  by  Battelle  Pacific  North- 
west Laboratories,  Richland,  Wash.,  to  deter- 
mine amounts  of  mercury,  lead,  cadmium,  and 
arsenic. 

Age  Determinations 

Ages  were  assigned  to  fiir  seals  by  counting 
layers  of  dentine  in  sectioned  upper  canine 
teeth  (Scheffer,  1950;  Fiscus,  Baines,  and 
Wilke,  1964).  Errors  in  assigning  ages  to  fur 
seals  are  small  in  young  seals  but  increase 
sharply  in  animals  older  than  7  yr  (Anas, 
1970b).  Most  errors  in  older  animals,  however, 
are  only  of  a  magnitude  of  ±  2  yr.  Although 
canine  teeth  of  harbor  seals  have  layers  of  den- 
tine, it  is  not  known  if  these  layers  accurately 
portray  age.  Ages  were  not  assigned  to  harbor 
seals,  but  body  lengths  were  taken. 

RESULTS 
Heavy  Metals  in  Fur  Seal  Tissues 

Amounts  of  total  mercury  were  higher  in 
liver  than  in  muscle  or  kidney  of  fur  seals  (Table 
1).  Mercury  in  liver  ranged  from  0.4  ppm  in  a 
fetus  taken  3  mo  before  birth  (the  liver  of  the 
11-yr-old  mother  had  86  ppm),  to  0.1-0.3  ppm 
in  10  pups,  3-19  ppm  in  30  young  males,  7-78 


^  Reference    to   trade   names   does   not    imply   endorse- 
ment by  the  National  Marine  Fisheries  Service,  NOAA. 


ppm  in  two  young  females,  and  19-172  ppm  in 
36  adult  females.  For  muscle,  0.1  ppm  was 
found  in  five  pups,  0.1-0.4  ppm  in  29  young 
males,  and  0.2-0.4  ppm  in  10  adult  females. 
Mercury  in  kidney  ranged  from  0.2  ppm  in  a 
fetus  (the  mother  had  1  ppm),  to  0.7  ppm  in  a 
young  male,  and  0.6-1.6  ppm  in  eight  females,  1 
to  20  yr  old. 

A  wide  range  of  mercury  was  found  only  in 
the  liver,  so  variability  due  to  sampling  is  more 
important  for  liver  than  for  muscle  or  kidney. 
The  95%  confidence  limits  of  within-sample 
variability  for  the  20-mg  samples  of  liver  were 
±  11%  of  the  mean  values.  The  average  variabil- 
ity between  seals  within  ages  was  55  times 
greater  than  the  variability  within  the  20-mg 
samples.  Thus,  to  increase  accuracy,  larger 
samples  of  seals  are  more  important  than  addi- 
tional 20-mg  samples  from  each  piece  of  liver. 

Methylmercury  was  not  determined  in  this 
study.  However,  in  samples  of  liver  from  Cal- 
ifornia sea  lions,  about  2%  of  the  total  mercury 
was  methylmercury  (Buhler,  see  Footnote  2). 

On  the  average,  amounts  of  lead  and  cadmium 
were  higher  in  kidney  than  in  liver  (Table  2). 
Arsenic  was  not  detected  in  any  of  the  samples. 
Lead  in  liver  ranged  from  0.8  ppm  in  a  fetus 
(the  mother  also  had  0.8  ppm),  to  0.2  ppm  in  a 
young  male,  and  0.4-0.8  ppm  in  eight  females. 
Lead  in  kidney  ranged  from  0.3  ppm  in  a  fetus 
(0.8  ppm  in  the  mother),  to  1.8  ppm  in  a  young 
male,  and  0.8-1.2  ppm  in  eight  females.  Cad- 
mium in  liver  ranged  from  0.5  ppm  in  a  fetus 
(4.6  ppm  in  the  mother),  to  0.6  ppm  in  a  young 


Table  1.  —  Parts  per  million  mercury  on  a  wet  weight  basis  in  liver,  muscle, 
and  kidney  of  fur  seals  taken  off  Washington  and  on  the  Pribilof  Islands, 
1970-71. 


Age 

Year 

N 

jmber 

(years) 

Sex 

Area 

collected 

of 

seals 

Tissue 

Mercury 

0.3  (Pups) 

Mixed 

Pribilof 

1970 

10 

Liver 

0.1-      0.3 

Islands 

1970 

5 

Muscle 

0.1 

2-3 

Male 

Pribilof 

1970 

29 

Liver 

3.0-    19.0 

Islands 

1970 

29 

Muscle 

0.1—     0.4 

5-19 

Female 

Washington 

1970 

29 

Liver 

19.0-'72.0 

Coast 

1970 

10 

Muscle 

0.2-     0.4 

Fetus 

Male 

Washington 

1971 

1 

Liver 

0.4 

Coast 

1971 

1 

Kidney 

0.2 

1 

Male 

Washington 

1971 

1 

Liver 

3.7 

Coast 

1971 

1 

Kidney 

0.7 

1-20 

Female 

Washington 

1971 

8 

Liver 

7.1—132.0 

Coast 

1971 

8 

Kidney 

0.6-      1.6 

135 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Table  2.  —  Parts  per  million  cadmium  and  lead  on  a  wet 
weight  basis  in  kidney  and  liver  of  fur  seals  taken  off 
Washington,  1971.' 


Age 

(years) 

Sex 

Kid 

ney 

Liver 

of 

of 

specimens 

specimens 

Cadmium 

Lead 

Cadmium 

Lead 

Fetus 

M 

0.1 

0.3 

0.5 

0.8 

1 

M 

1.7 

1.8 

0.6 

0.2 

1 

6.9 

0.8 

0.9 

0.6 

3 

4.3 

0.8 

2.2 

0.6 

6 

15.6 

1.2 

2.6 

0.6 

8 

0.2 

0.9 

1.2 

0.5 

11 

6.2 

0.8 

4.6 

0.8 

15 

9.6 

0.9 

1.1 

0.4 

16 

1.0 

1.0 

1.7 

0.5 

20 

6.8 

0.8 

1.7 

0.7 

'    Arsenic    was    not    found    obove    the    limit    of    detection    of    0.2 
ppm  (mg/kg)  in  either  kidney  or  liver  in  any  of  the  samples. 


male,  and  0.9-4.6  ppm  in  eight  females.  Cad- 
mium in  kidney  ranged  from  0.1  ppm  in  a  fetus 
(6.2  ppm  in  the  mother),  to  1.7  ppm  in  a  young 
male,  and  0.2-15.6  ppm  in  eight  females. 

Lid  liners  from  new  glass  bottles  had  1.1  i)pm 
mercury  and  0.4  ppm  arsenic.  Lead  and  cad- 
mium were  not  detected.  The  tissues  and  lid 
liners  were  never  in  direct  contact,  but  some 
transfer  of  mercury  from  the  lid  liners  and 
glass  bottles  could  have  occurred.  However, 
the  maximum  contribution  from  the  lid  liners 
would  have  been  0.004  ppm  mercury,  so  the  data 
were  not  adjusted. 

Heavy  Metal  —  Age  Comparisons 
in  Fur  Seals 

Regression  equations  were  computed  for 
samples  from  fur  seals  collected  in  1970  and 
1971  to  determine  if  mercury  in  liver,  muscle, 
and  kidney  and  if  lead  and  cadmium  in  liver 
and  kidney  were  correlated  with  age.  Signifi- 
cant correlations  for  mercury  have  been  reported 
for  fur  seal  liver  (Anas,  1970a)  and  whole 
fishes  (Bache,  Gutenmann,  and  Lisk,  1971). 
Untransformed  data  were  used  here  because 
log  transformations  did  not  significantly 
improve  the  correlations.  Fetuses  and  pups  were 
not  included  in  the  calculations.  Only  liver 
tissues  were  collected  both  in  1970  and  1971. 
The  correlation  coefficients  in  the  two  years  for 
mercury  in  liver  were  common  (P>0.05),  so  the 
dataware  pooled.  Mercury  in  liver  had  a  signi- 
ficant positive  correlation  with  age  (P< 0.001, 
r  —  -1-0.84).  The  data  indicate  that  mercury 
accumulates  in   liver.   Mercury  in   muscle  and 


kidney  did  not  correlate  with  age  (P>0.05,  r  = 
-h  0.05  and  +0.51,  respectively).  Also,  lead  and 
cadmium  in  liver  and  kidney  did  not  correlate 
with  age  (P>0.05.  r  =  +0.19  and  -0.45  for 
lead  and  r  —  +0.17  and  +  0.04  for  cadmium  in 
liver  and  kidney,  respectively).  Sample  sizes 
were  67  for  mercury  in  liver,  39  for  mercury  in 
muscle,  and  9  for  cadmium  and  lead  in  liver  and 
kidney. 

Mercury  in  Harbor  Seal  Livers 

Harbor  seals  are  nonmigratory,  so  levels  of 
contaminants  in  this  species  are  useful  for 
locating  geographical  concentrations  of  con- 
taminants, provided  that  the  food  species  do  not 
migrate  long  distances.  Studies  suggest  that 
the  principal  food  species  of  harbor  seals  do  not 
migrate  far  (Scheffer  and  Sperry,  1931; 
Spalding,  1964;  Kenyon,  1965).  The  highest 
levels  of  mercury  were  found  in  harbor  seals  from 
San  Miguel  Island  (Table  3).  One  harbor  seal 
from  San  Miguel  Island  had  700  ppm  mercury 
in  the  liver.  The  amount  of  mercury  in  this 
sample  is  so  much  higher  than  the  amounts 
found  in  the  other  seals  that  the  possibility 
of  contamination  of  the  sample  should  be 
considered.  However,  as  far  as  is  known,  this 
sample  was  treated  no  differently  than  the 
other  samples.  The  sample  size  is  small  and  the 
ages  are  not  known,  but  the  concentrations  of 


Table  3.  —  Parts  per  million  mercury  on  a  wet  weight 
basis  in  liver  of  harbor  seals  taken  in  the  eastern  Pacific 
Ocean,  1970-71. 


Date 

Length 

Location 

collected 

Sex 

(cm) 

Mercury 

San  Miguel 

2  June  1971 

F 

161 

700 

Is.,  Calif. 

2  June  1971 

F 

153 

81 

4  June  1971 

M 

176 

124 

5  June  1971 

F 

156 

171 

Columbia  R., 

May  1971 

M 

0.3 

Oregon 

do 

M 

112 

3.2 

do 

F 

126 

68 

Washington 

2  Sept.  1971 

F 

84 

1.3 

Coast 

- 

Puget  Sound, 

24  Nov.  1970 

M 

60 

Washington 

21  June  1971 

M 

95 

12 

Pribilof  Is., 

17  Aug.  1971 

M 

135 

0.6 

Alaska 

do 

F 

140 

3.2 

do 

M 

175 

8.9 

136 


ANAS:  HEAVY  METALS  IN  SEALS 


mercury  in  San  Miguel  Island  seals  appear  to 
differ  significantly  from  those  from  the  Pribilof 
Islands.  Except  for  the  one  seal  with  700  ppm 
mercury,  the  amounts  of  mercury  found  in 
harbor  seals  from  all  areas  studied  are  within 
the  range  of  those  found  in  livers  of  fur  seals. 

ACKNOWLEDGMENTS 

The  staff  of  the  Division  of  Marine  Mammals, 
Northwest  Fisheries  Center,  National  Marine 
Fisheries  Service.  NOAA,  collected  the  fur 
seal  samples  for  this  study.  T.  C.  Newby, 
College  of  Fisheries,  University  of  Washington, 
Seattle,  Wash.,  helped  collect  the  harbor  seals. 
C.  H.  Fiscus,  H.  Kajimura,  and  A.  Y.  Roppel, 
Division  of  Marine  Mammals,  assigned  ages 
to  the  fur  seals. 

LITERATURE  CITED 

American  Public  Health  Association. 

1971.  Standard  methods  for  the  examination  of  water 
and  wastewater.  13th  ed.  Am.  Public  Health  Assoc, 
Wash.,  D.C.,  874  p. 
Anas,  R.  E. 

1970a.  Mercury    found   in   fur   seals.   Commer.    Fish. 

Rev.  32(12): 3. 
1970b.  Accuracy    in    assigning    ages    to    fur    seals.   J. 
Wildl.  Manage.  34:844-852. 
Bache,  C.  a.,  W.  H.  Gutenmann,  and  D.  J.  Lisk. 

1971.  Residues  of  total  mercury  and  methylmercuric 
salts   in   lake   trout    as   a  function  of  age.   Science 
(Wash.,  D.C.)  172:951-952. 
Berman,  E. 

1967.  Determination     of     cadmium,     thallium     and 
mercury      in      biological      materials      by      atomic 
absorption.  At.  Absorpt.  Newsl.  6:57-60. 
Committee  on  Chemical  Procedures  of  the  Occupa- 
tional Health  Section,  American  Public  Health 
Association. 

1955.  Methods   for   determining   lead   in    air    and   in 
biological  materials.  Am.  Public  Health  Assoc.  Inc., 
N.Y.,  p.  38-39. 
Curry,  A. 

1969.  Poison    detection    in    human    organs.    2d    ed. 
Thomas,  Springfield.  111.,  280  p. 


DuBois,  K.  P.,  and  E.  M.  K.  Ceiling. 

1959.  Textbook    of   toxicology.    Oxford    Univ.    Press, 
N.Y.,  302  p. 
Fiscus,  C.  H.,  G.  A.  Baines,  and  F.  Wilke. 

1964.  Pelagic  fur  seal  investigations,  Alaska  Waters, 
1962.  U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish. 
475. 59  p. 

Food  and  Agriculture  Organization  of  the  United 
Nations. 

1971.  Report  of  the  seminar  on  methods  of  detection, 
measurement  and  monitoring  of  pollutants  in  the 
marine  environment:  Supplement  to  the  Report  of 
the  Technical  Conference  on  Marine  Pollution  and 
its  Effects  on  Living  Resources  and  Fishing.  FAO, 
Fish.  Rep.  99,  Suppl.  1,  123  p. 
Hall,  J.  D.,  W.  G.  Gilmartin,  and  J.  L.   Mattsson. 

1971.  Investigation  of  a  Pacific  pilot  whale  stranding 
on  San  Clemente  Island.  J.  Wildl.  Dis.  7:324-327. 

Harriss,  R.  C,  D.  B.  White,  and  R.  B.  MacFarlane. 
1970.  Mercury     compounds     reduce     photosynthesis 
by  plankton.  Science  (Wash..  D.C.)  170:736-737. 
Jones,  A.   M.,  Y.  Jones,  and  W.  D.  P.  Stewart. 

1972.  Mercury  in  marine  organisms  of  the  Tay 
region.  Nature  (Lond.)  238: 164-165. 

Kenyon,  K.  W. 

1965.  Food  of  harbor  seals  at  Amchitka  Island, 
Alaska.  J.  Mammal.  46: 103-104. 

SCHEFFER,    T.    H.,    and    C.    C.    SpERRY. 

1931.  Food  habits  of  the  Pacific  harbor  seal,  Phoca 
richardii.  J.  Mammal.  12:214-226. 

ScHEFFER,    V.    B. 

1950.  Growth  layers  on  the  teeth  of  Pinnipedia  as  an 
indication  of  age.  Science  (Wash.,  D.C.,)    112:309- 
311. 
Skerfving,   S.,  K..  Hansson,   and  J.  Lindsten. 

1970.  Chromosome  breakage  in  humans  exposed  to 
methyl    mercury   through    fish   consumption.   Arch. 
Environ.  Health  21:133-139. 
Spalding,  D.  J. 

1964.  Comparative  feeding  habits  of  the  fur  seal,  sea 
lion    and    harbour    seal    on    the    British    Columbia 
coast.    Fish.    Res.    Board    Can..    Bull.    146,    52    p. 
U.S.  Senate. 

1970.  The  National  Estuarine  Pollution  Study:  Report 
of  the  Secretary  of  the  Interior  to  the  United 
States  Congress  Pursuant  to  Public  Law  89-753, 
the  Clean  Water  Restoration  Act  of  1966.  91st 
Congress,  2d  Sess.,  Doc.  91-58,  633  p.  U.S.  Gov. 
Prim.  Off.,  Wash.,  D.C. 
Williams,  P.  M.,  and  H.  V.  Weiss. 

1973.  Mercury  in  the  marine  environment:  concen- 
tration in  sea  water  and  in  a  pelagic  food  chain. 
J.  Fish.  Res.  Board.  Can.  30:293-295. 


137 


BIOECONOMIC  CONTRIBUTION   OF 
COLUMBIA   RIVER   HATCHERY   COHO  SALMON, 
1965   AND    1966  BROODS,  TO  THE   PACIFIC  SALMON 

FISHERIES 

Roy  J.  Wahle,'  Robert  R.  Vreeland.'  and  Robert  H.  Lander^ 


ABSTRACT 

Marked  coho  salmon,  Oncorhyiuhus  kisiiuh,  smolts  of  the  1965  and  1966  broods  were  re- 
leased from  20  hatcheries  on  four  sections  of  the  Columbia  River  and  tributaries.  Com- 
mercial and  sport  fisheries  in  marine  waters  from  Pelican,  Alaska,  to  Avila  Beach, 
Calif.,  and  on  the  Columbia  River  were  sampled  during  1967-69  for  marks. 

The  net  value  of  the  estimated  total  catch  of  hatchery  fish  was  calculated  after  adjust- 
ing for  the  effects  of  marking.  Also  estimated  for  each  brood  were  the  total  costs  of 
rearing  including  amortized  capital  outlay.  Total  benefits  of  $8.58  million  for  the  1965 
brood  and  $9.11  million  for  the  1966  brood  were  estimated  as  applicable  to  normal 
production  years  when  no  marking  takes  place.  Corresponding  costs  were  estimated 
as  $1.29  million  for  the  1965  brood  and  $1.23  million  for  the  1966  brood.  Estimated 
benefit/cost  ratios  for  the  20  Columbia  River  coho  salmon  hatcheries,  as  operated  under 
production  regimes  prevailing  during  the  study,  may  prove  useful  in  decisions  affecting 
management  policies.  The  ratios  are  6.6/1  for  the  1965  brood,  7.4/1  for  the  1966  brood, 
and  7.0/1  for  both  broods  combined. 


Use  of  the  Columbia  River  has  expanded  tre- 
mendously in  the  past  30  years  through  Federal- 
ly financed  and/or  licensed  water  use  projects. 
This  expansion  has  depleted  valuable  stocks  of 
Pacific  salmon,  0)icorhyuchus  spp.,  and  steel- 
head  trout,  Salmo  gairdneri,  through  the  loss 
and  deterioration  of  natural  stream  habitat. 
Therefore,  mitigative  measures — hatcheries, 
fish  ladders,  and  spawning  channels — to  sup- 
plement the  declining  natural  production  of 
Columbia  River  salmon  and  steelhead  trout 
have  been  Federally  funded. 

To  counteract  the  severe  loss  of  salmon  and 
steelhead  trout  environment  in  the  Columbia 
River  basin,  the  U.S.  Government  began  financ- 
ing the  Columbia  River  Develojjment  Program 
in  1949.  The  Program  is  a  cooperative  effort  of 
the  fish  management  agencies  of  the  states  of 
Oregon.  Washington,  and  Idaho  and  the  Federal 


'  Columbia  River  Fisheries  Program  Office,  National 
Marine  Fisheries  Service,  NOAA,  811  Northeast  Oregon 
St.,  Portland,  OR  97208. 

-  Northwest  Fisheries  Center,  National  Marine  Fish- 
eries Service,  NOAA.  2725  Montlake  Blvd.  E.,  Seattle, 
WA  98102. 


Government.  The  Columbia  Fisheries  Program 
Office,  National  Marine  Fisheries  Service,  Port- 
land, Oreg.,  administers  the  Program,  which  is 
designed  to  increase  production  of  salmon  and 
steelhead  in  the  Columbia  River.  The  Program's 
major  thrust  has  been  to  improve  the  runs  of 
salmon  and  steelhead  by  protecting  and  improv- 
ing stream  environment  and  by  production  of 
fish  in  hatcheries.  The  main  accomplishment  is 
the  con.struction  or  modernization  of  21  salmon 
and  steelhead  hatcheries  on  the  lower  Columbia 
River  and  tributaries. 

There  are  two  major  reasons  for  the  concen- 
tration of  effort  on  salmon  and  steelhead  trout. 
First,  their  life  histories  allow  successful  hatch- 
ery i^roj^agation.  Second,  these  sjiecies  are  his- 
torically and  economically  important  to  the 
United  States.  Annual  catches  of  Pacific  salmon 
have  ranked  first  or  second  for  the  past  3 
decades  in  landed  value  of  commercial  finfishes 
to  United  States  fishermen.  Chinook  salmon,  O. 
fsliaivytscha,  and  coho  salmon,  O.  kisKtch,  land- 
ings have  accounted  for  35%  of  the  6-yr  average 
(1966-71)  commercial  value  ($70  million)  for 
salmon — $12.5   million  for  chinook  and  $11.9 


Manuscript  accepted  June  1973 

FISHERY  BULLETIN:  VOL.  72.  NO.  1,  1974 


139 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


for  coho  (Lyles,  1968,  1969;  National  Marine 
Fisheries  Service.  1971;  Riley,  1970,  1971; 
Wheeland,  1972).  In  addition,  the  net  economic 
value  of  marine  and  freshwater  sport  fishing  for 
salmon  in  the  U.S.  in  1970  was  estimated  at 
$77.7  million.  This  fishery  was  made  up  of  64% 
coho  and  32%  chinook.^ 

In  1950  five  salmon  hatcheries,  representing 
the  entire  Columbia  River  production  of  hatch- 
ery coho  salmon,  released  about  1  millicjn  juve- 
niles typified  by  a  short  rearing  period,  poor  nu- 
trition, and  low  survival.  In  contrast,  the  num- 
ber of  hatcheries  rearing  coho  increased  to  20  by 
1966-67,  and  annual  releases  averaged  20  mil- 
lion smolts.  These  salmon  benefited  from  ad- 
vances in  fish  culture,  especially  nutrition, 
applied  during  the  early  1960's  and  were  char- 
acteristically large  and  healthy  with  a  high  sur- 
vival potential  (Cleaver,  1969a). 

In  1962  the  Columbia  Fisheries  Program 
Office  started  a  marking  study  to  estimate  the 
contribution  of  Columbia  River  hatchery-reared 
fall  Chinook  salrnon  to  the  Pacific  coast  fisheries. 
In  1965  this  study  was  exj^anded  to  include  coho 
salmon.  Accordingly,  representative  (10%  )  sam- 
ples from  all  Columbia  River  hatcheries  rearing 
1965-  and  1966-brood  coho  salmon  were  marked. 
Sampling  for  these  marked  coho  took  place  from 
1967  through  1969  in  the  sport  and  commercial 
fisheries  from  Alaska  to  California.  A  contribu- 
tion study  of  this  magnitude  had  never  before 
been  undertaken.  The  information  to  be  gained 
from  this  study  was  critically  needed  to  deter- 
mine if  increa.sed  Federal  funding  for  Columbia 
River  hatcheries  was  economically  justified. 

The  objectives  of  this  report  are  to  (1) 
describe  the  design  and  operations  of  marking 
and  release  procedures,  (2)  estimate  the  contri- 
bution (catch)  to  Pacific  salmon  fisheries  during 
1967,  1968,  and  1969  for  the  1965-66  brood  coho 
salmon  hatchery  releases,  and  (3)  develop  bene- 
fit/cost ratios  for  these  two  broods. 

BIOLOGICAL  EVALUATION 

Experimental  Design 

Procedures     were     basically     the     same     as 


3  George  K.  Tanonaka.  1972.  A  general  comparison  of 
the  commercial  and  sport  salmon  fisheries  of  the  United 
States,  1940-70.  Natl.  Mar.  Fish.  Serv.,  Northwest  Fish. 
Center,  Seattle,  Wash.  (Unpubl.  manuscr.)  15  p.,  7  tables, 
4  fig.,  App.  A-B. 


described  by  Worlund,  Wahle,  and  Zimmer 
(1969)  for  the  fall  chinook  salmon  study  but 
will  be  summarized  here.  The  Columbia  River 
was  divided  into  four  sections.  These  sections 
will  be  defined  later.  Releases  of  marked  fish 
were  intended  to  identify  and  estimate  the 
catches  from  each  section.  Execution  of  the  plan 
dejiended.  as  for  the  evaluation  of  fall  chinook 
salmon  hatcheries,  on  the  cooperation  of  many 
l)eople  in  the  following  agencies: 

Alaska  Department  of  Fish  and  Game 
Fisheries  Research  Board  of  Canada 
Washington  Department  of  Fisheries 
Fish  Commission  of  Oregon 
Oregon  State  Game  Commission 
California  Department  of  Fish  and  Game 
National  Marine  Fisheries  Service 
Bureau  of  Sjwrt  Fisheries  and  Wildlife 
The  basic  plan  was  to  mark  the  same  propor- 
tion of  juvenile  coho  salmon  released  at  each 
hatchery  and  to  sample  for  marks  in  commercial 
and  sport  fisheries.  Total  catches  of  fish  from 
all  hatcheries  then  could  be  estimated  from  (1) 
fractions   of  marked   fish   in   each    release,    (2) 
numbers  of  each  type  of  mark  actually  recovered, 
(3)  fractions  of  the  total  catches  sampled  for 
marks  by  time  and  area  in  each  fishery,  and  (4) 
information  on  any  bias  associated  with  appli- 
cation or  detection  of  marks. 

Allocation  of  Marks 

The  20  hatcheries  involved  in  this  study  are 
distributed  over  much  of  the  mainstem  Columbia 
River  accessible  to  anadromous  fish  (Figure  1). 
Klaskanine  River  Salmon  Hatchery,  the  lower- 
most station,  and  Leavenworth  National  Fish 
Hatchery,  the  uppermost,  are  on  tributaries 
about  25  km  and  800  km  (15  and  500  miles), 
respectively,  above  the  Columbia  River  mouth. 
Some  hatcheries  (Bonneville,  Cascade,  OxBow, 
and  Little  White  Salmon)  are  adjacent  to  the 
main  Columbia  River  and  release  their  fish  al- 
most directly  into  it.  In  contrast,  fish  released 
at  the  Toutle  River  station  must  travel  65  km 
(40  miles)  to  reach  the  Columbia  River. 

Four  different  marks  were  available  (from  the 
Pacific  Marine  Fisheries  Commission)  for  the 
1965  brood  of  coho  salmon.  The  Columbia  River 
was  therefore  divided  into  four  sections — Lower 
River,  Middle  River,  Upper  River,  and  Upper- 
most River — and  one  mark  was  assigned  to 
each    (Table    1).    The   adipose-right    maxillary 


140 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 


90  KILOHCTERt 


14  Coscode 

15  OiBow* 

16  Corson* 

17  Little  Wliite  Solmon 

18  Willocd 

19  KhcKitol 


20   Leovenworth 


1  Kloskonine  5    Toulle 

2  Groys    River  6  Loxer  Kolomo 

3  Biq  Creek  7  Kolomo  Foils 

4  EloKomin  8   Lewis  River 

9  Speelyoi 
10  Eoqle   Creek 
I  1   Sondy 
12   Wosliougol 
1  3  Bonneville 

*  Did  not  porticipote    in    1966  brood   study 

mark  (Ad-RM)  was  used  for  hatcheries  in  the 
Lower  River  section — Columbia  River  mouth 
to  Cowlitz  River.  The  adipose-only  finclip  (Ad) 
was  allotted  to  hatcheries  in  the  Middle  River 
section — the  Cowlitz  River  to  Bonneville  Dam. 
Hatcheries  in  the  Upper  River  section — Bonne- 
ville Dam  to  The  Dalles  Dam — were  issued  the 
adii)ose-left  maxillary  mark  (Ad-LM).  Leaven- 
worth National  Fish  Hatchery,  the  only  study 
hatchery  in  the  Uppermost  River  section — above 
The  Dalles  Dam — was  assigned  the  dorsal-adi- 
pose finclip  (D-Ad). 

The  same  marks  were  used  for  the  1966 
brood  with  one  exception;  at  Leavenworth 
National  Fish  Hatchery,  maxillary  marks  were 
added  to  the  D-Ad  finclip.  Juveniles  with  D-Ad- 
RM  marks  were  released  at  the  hatchery  and 
those  with  D-Ad-LM  were  trucked  downstream 
and  released  below  Bonneville  Dam.  The  pur- 
pose of  the  two  marks  and  release  sites  was  to 
examine  differential  mortality  due  to  passage 
through  dams;  results  will  be  treated  in  a  sub- 
sequent report. 

Sources  of  Variation  and  Error 

To  evaluate  variations  between  broods  and 
river   sections,   two   broods    (1965-66)    of  coho 


HCNARTDAH 


Figure  1. — Location  and  grouping  by 
river  section  of  Columbia  River  hatch- 
eries participating  in  this  study. 


salmon  were  included  in  the  study,  and  each 
river  section  was  allotted  a  specific  mark.  Mor- 
tality due  to  marking,  the  most  important 
source  of  error,  was  evaluated  by  comparing 
marked/unmarked  ratios  in  hatchery  releases 
and  returns.  To  evaluate  the  dilution  effect  of 
returning  wild  fish  on  the  marked/unmarked 
ratio  at  study  hatcheries,  oxytetracycline  (TM- 
50)  was  added  to  the  diet  of  both  broods  of 
coho  salmon  reared  at  Big  Creek  (Ad-RM 
mark)  and  Eagle  Creek  (Ad  finclip)  hatcheries. 
Tetracycline  deposits  a  permanent  mark  on  the 
bone  structure  of  feeding  juvenile  salmon  and, 
at  spawning,  this  mark  is  readily  detected  on 
coho  vertebrae  under  ultraviolet  light  (Weber 
and  Ridgway,  1967).  Thus,  wild  coho  were 
identifiable  and  were  subtracted  from  the  total 
unmarked  returns  to  Big  Creek  and  Eagle 
Creek  hatcheries. 

Marked  fish  were  held  at  Klickitat  State 
Salmon  Hatchery  to  evaluate  the  degree  of 
mark  regeneration.  Markers  at  all  participating 
hatcheries  were  asked  to  record  naturally  miss- 
ing fins  and  maxillary  bones.  Catch  samplers 
were  alerted  to  possible  regeneration  so  they 
could  look  for  malformed  fins. 

Rearing  techniques  at  different  hatcheries 
varied  within  as  well  as  between  river  sections. 


141 


The  limited  number  of  marks  available  pre- 
cluded individual  hatchery  comparisons  as 
made  from  data  of  the  fall  chinook  salmon 
study  (Cleaver.  1969b;  Worlund.  Wahle,  and 
Zimmer.  1969;  Lander,  1970;  Henry,  1971). 
The  size  of  fish  at  release  reflects  partially  the 
differences  in  rearing  techniques.  In  both  wild 
and  hatchery  salmon  stocks,  it  is  well  known 
that  large  smolts  survive  better  and  contribute 
more  to  catches,  other  factors  being  reasonably 
equal,  than  do  small  smolts  (Ricker,  1962; 
Fredin,  1964;  Johnson,  1970).  The  average  size 
of  fish  in  releases  varied  considerably  between 
hatcheries,  somewhat  between  river  sections, 
and  slightly  between  broods.  Again,  the  limited 
number  of  marks  prevented  evaluation  of  the 
effect  of  size  at  release  on  contribution,  but 
average  weights  are  included  to  complete  the 
data  record  (Appendix  Tables  la  and  lb). 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 

Estimating  Procedures 

Simple  numerical  examples  explain  the  basic 
estimating  procedures.  A  more  formal  account 
was  reported  in  the  chinook  salmon  study 
(Worlund,  Wahle,  and  Zimmer,  1969). 

The  first  quantities  to  be  estimated  were  the 
numbers  of  marked  and  unmarked  fish  in  hatch- 
ery releases.  This  was  done  with  data  from  a 
10-part  sampler  (see  "Marking  and  Release 
Procedures").  The  device  was  precalibrated 
from  a  number  of  trials  with  known  numbers  of 
fish  to  find  the  average  number  and  percentage 
retained  by  a  single  closed  pocket.  The  follow- 
ing example  illustrates  the  fish  enumeration 
procedure.  Suppose  a  precalibrated  pocket  is 
found  to  remove  a  10.1%  sample.  Also,  suppose 
after  passing  all  the  fish  in  a  pond  through  the 
sampler,   the   number  of  fish   retained   by   the 


Table  1.^ — Grouping  of  Columbia  River  hatcheries  participating  in  study  and 
type  of  mark  assigned  to  each  group. 


River  section  and  hatchery- 


.1/ 


Hatchery  location 


KLaskanine  (FCO) 
Grays  River  (WDF) 
Big  Creek  (FCO) 
Elokomin  (WDF) 


Klaskanine  River 

Grays  River 

Big  Creek,  Columbia  River 

Elokomin  River 


Middle  River  (Cowlitz  River  to  Bonneville  Dam) 


Toutle  (WDF) 
Lower  Kalama  ( WDF ) 
Kalama  Falls  (WDF) 
Lewis  River  (WDF) 
Speelyai  (WDF) 
Sandy  (FCO) 
Eagle  Creek  (FCO) 
Washougal  (WDF) 
Bonneville  (FCO) 


Green  River,  Toutle  River 

Hatchery  Creek,  Kalama  River 

Kalama  River 

Lewis  River 

Speelyai  Creek,  Lewis  River 

Cedar  Creek,  Sandy  River 

Eagle  Creek,  Clackamas  River 

Washougal  River 

Tanner  Creek,  Columbia  River 


Upper  River  (Bonneville  Dam  to  The  Dalles  Dam) 


Cascade  (FCO) 

OxBow  (FCO) 

Carson  (BSFW) 

Little  White  Salmon  (BSFW) 

Willard  (BSFW) 

Klickitat  (WDF) 


Eagle  Creek,  Columbia  River 
Herman  Creek,  Columbia  River 
Tyee  Springs,  Wind  River 
Little  White  Salmon  River 
Little  White  Salmon  River 
Klickitat  River 


Uppermost  River' (above  The  Dalles  Dam) 

Leavenworth  (BSFW)  Icicle  Creek,  Wenatchee  River 


Mark 


2/ 


Lower  River  (Columbia  River  mouth  to  Cowlitz  River) 


Ad-RM 


Ad  only 


Ad-LM 


D-Ad 
D-Ad-LM 
D -Ad-RM 


1/  Acronyms  designate  the  following  agencies:   FCO  =  Fish  Commission  of 
Oregon,  WDF  -   Washington  Department  of  Fisheries,  and  BSFW  =  Bureau  of 
Sport  Fisheries  and  Wildlife. 

2/  Ad  =  adipose  fincllp,  D  =  dorsal  flnclip,  LM  =  left  maxillary  bone 
clip,  and  RM  =  right  maxillary  clip. 


142 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 


closed  pocket  is  found  to  be  6.060.  The  total 
number  of  fish  in  that  pond  is  then  estimated  as 
6.060/0.101  =  60.000.  Suppose  further  that  of 
the  6.060  fish  retained  by  the  pocket.  606  fish 
are  found  to  be  marked.  Then  606/6.060  =  10% 
of  the  estimated  60.000  fish  in  the  pond,  or  6,000 
fish  are  estimated  to  be  marked  and  54.000  un- 
marked. The  total  release,  numbers  marked  and 
unmarked,  and  proportion  marked  were  esti- 
mated for  a  hatchery  by  summing  data  from  all 
ponds.  Finally,  estimates  of  the  foregoing  quan- 
tities for  all  fish  released  into  a  given  river  sec- 
tion were  obtained  by  summing  the  estimates 
for  appropriate  hatcheries. 

To  estimate  actual  recoveries  with  a  certain 
mark  during  a  specific  sampling  period  in  a 
given  fishery,  the  total  catch  (of  marked  and 
unmarked  fish)  during  that  period  was  multi- 
plied by  the  fraction  of  sampled  fish  observed 
with  that  mark  during  the  same  period.  For 
example.  16  Ad-RM  marks  were  detected  dur- 
ing June  1-30,  1968,  from  9,827  coho  salmon 
examined  at  Crescent  City,  Calif.,  in  a  catch  of 
31,082  from  the  commercial  troll  fishery.  Thus. 
16/9.827  (approximately  0.2%)  of  the  sample 
had  Ad-RM  marks.  The  total  marked  catch  for 
that  period  and  landing  port  was  estimated  to 
be  about  0.2%  of  the  31.082  fish  caught  or  62 
Ad-RM  marks  (actual  calculations  were  carried 
to  eight  places  to  avoid  rounding  errors).  Simi- 
lar calculations  were  made  for  each  period.  The 
results  then  were  summed  for  all  periods  and 
appropriate  landing  locations  to  estimate  the 
seasonal  recovery  of  a  certain  mark  in  the  given 
fishery  (e.g..  Ad-RM  marks  in  the  California 
troll  fishery  during  1968). 

The  catch  of  unmarked  hatchery  fish  for  each 
ocean  sport  and  commercial  fishery,  and  the 
Columbia  River  fisheries,  was  estimated  for 
each  year  and  brood  by  dividing  the  estimated 
catch  of  fish  having  a  specific  mark  by  the 
expected  marked/unmarked  ratio.  The  latter 
was  calculated  from  the  ratio  at  release  and 
the  estimated  relative  survival  of  marked  fish. 
Suppose  an  estimated  2,000  1965-brood  Ad-RM 
marks  were  recovered  in  1968  in  the  California 
ocean  sport  fishery,  the  marked/unmarked  ratio 
was  0.1  for  all  hatcheries  where  Ad-RM  marks 
were  released,  and  the  survival  of  marked  fish 
was  estimated  to  be  80%  that  of  unmarked  fish; 
then  the  estimated  catch  of  unmarked  fish 
would  be  (2,000)/(0.1  X  0.80)  =  25,000  fish. 


The  catch  of  hatchery  fish  released  from  a 
given  river  section  was  estimated  by  summing 
estimates  for  marked  and  unmarked  hatchery 
fish  from  each  type  of  fishery.  Nondetection  of 
certain  marks  in  ocean  fisheries  complicated 
the  estimation  of  the  hatchery  contribution. 

The  relative  survival  of  marked  fish  was 
estimated  by  comparing  marked/unmarked 
ratios  at  release  and  return,  as  noted  earlier  for 
tetracycline  (internal)  and  finclip  (external) 
marking  at  the  Big  Creek  and  Eagle  Creek  sta- 
tions. At  the  Big  Creek  station  for  the  1965 
brood,  for  example,  the  pond  sampling  pro- 
cedures just  described  gave  an  estimated 
marked/unmarked  ratio  at  release  of  0.12083 
(for  the  Ad-RM  finclip).  Enumeration  at  the 
hatchery  of  all  internally-  and  externally- 
marked  returns  ("jacks"  or  age  2  males  in  1967 
plus  age  3  males  and  females  in  1968)  gave  a 
marked/unmarked  ratio  of  0.09885.  The  sur- 
vival of  marked  fish  between  the  time  of 
release  and  at  return  to  the  hatchery  was  there- 
fore estimated  to  be  0.09885/0.12083  = 
0.8181  that  of  unmarked  fish. 

With  estimates  of  all  these  quantities  at  hand, 
it  remained  only  to  estimate  the  average  weight 
and  unit  value  of  fish  caught  to  calculate  their 
total  economic  value.  Weight  data  were  collected 
from  a  predetermined  number  of  fish  through- 
out the  season  at  different  landing  locations 
from  which  a  given  fishery  operated.  Resulting 
means  were  assumed  to  be  representative. 

Assumptions 

The  foregoing  method  of  estimating  catches 
of  hatchery  fish  requires  certain  assumptions. 
These  are  considered  after  presentation  of  the 
data  (see  "Bias  Associated  with  Marks"  and 
"SUMMARY").  The  main  assumptions  are: 

1.  A  marked  fish  is  identifiable  as  a 
marked  fish  throughout  life. 

2.  All  fish  detected  and  reported  with  the 
kind  of  mark  applied  are  hatchery  fish. 

3.  All  coho  salmon  sampled  in  ocean  fish- 
eries are  in  their  third  and  final  year  of  life. 

4.  Marked  and  unmarked  fish  have 
the  same  maturity  schedules. 

5.  The  same  proportion  of  releases  is  marked 
at  each  hatcherj'  in  a  given  river  section. 

6.  Marked  and  unmarked  fish  from  a  given 
river  section  are  equally  vulnerable  to  capture 


143 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


(i.e.,  have  the  same  distribution  by  time  and 
area) . 

Field  Operations 
Marking  and  Release  Procedures 

Artificial  propagation  procedures  were  simi- 
lar at  all  coho  salmon  hatcheries  during  the 
study  period.  Adults  normally  returned  to  the 
hatcheries  during  September-November  and 
were  spawned  during  October-November.  Fry 
generally  reach  the  free-swimming  stage  in 
March.  The  fish  were  released  as  smolts  13  mo 
later  at  an  average  length  of  12-15  cm  (4.5-6 
inches)  and  were  available  during  the  following 
year  to  the  fisheries  from  central  British  Colum- 
bia to  central  California. 

The  marking  phase  of  this  study  began  in 
May  1966  and  ended  in  June  1967.  About  10% 
of  the  1965-  and  1966-brood  coho  salmon  were 
marked.  A  modified  sampling  tool  (Worlund, 
Wahle,  and  Zimmer,  1969)  was  used  to  obtain 
a  random  sample  for  marking.  The  "10-part 
sampler"  consisted  of  a  cylindrical  liner  con- 
taining a  circular  metal  frame  divided  into  10 
equal  pie-shaped  sections  with  a  zipper-bot- 
tomed net  pocket  hung  from  each  section.  When 
a  10%  sample  was  to  be  taken,  the  zippers  on  all 
but  one  of  the  pockets  were  opened,  the  frame 
and  liner  were  placed  in  a  water-filled  tub.  and 
about  18  kg  (40  pounds)  of  fish  were  placed 
into  the  liner.  The  closed  net  pocket  retained 
the  desired  sample  when  the  line  and  frame 
were  lifted.  The  fish  that  passed  through  the 
open  net  pockets  remained  in  the  tub  and  were 
placed  into  another  pond.  This  procedure  was 
followed  until  all  the  coho  in  each  pond  were 
processed. 

Fish  to  be  marked  were  anesthetized  with 
MS-222'  (tricaine  methanesulfonate).  The  fins 
and  maxillary  bones  were  clipped  with  bent- 
nosed  scissors.  Marked  fish  were  held  in  hatch- 
ery troughs  until  they  recovered  from  the  anes- 
thetic, then  returned  to  the  group  from  which 
they  came.  To  insure  that  fins  and  maxillary 
bones  were  actually  removed,  quality  control  of 
marking  was  maintained  by  periodic  random 
sampling  of  the  marked  fish  throughout  the 
marking  operation. 


■*  Reference  to  trade  names  in  this  publication  does  not 
imply  endorsement  of  commercial  products  by  the  National 
Marine  Fisheries  Service. 


The  entire  coho  salmon  production  of  each 
hatchery  was  sampled  to  estimate  the  propor- 
tion and  numbers  of  marked  fish  released.  The 
"10%"  samples  removed  initially  by  the  cali- 
brated pocket  were  set  aside  then  resampled  to 
obtain  a  "1%"  sample  which  was  sorted  into 
marked  and  unmarked  groups,  counted,  and 
weighed.  The  counts  together  with  an  estimate 
of  the  proportion  removed  by  the  particular 
pocket  of  the  sampler  were  used  to  estimate  the 
numbers  of  marked  and  unmarked  fish  released. 

In  Table  2,  the  estimated  numbers  of  marked 
and  unmarked  fish  released  and  the  percentages 
marked  are  summarized  for  each  mark  type  and 
brood  year.  Detailed  data  for  each  hatchery 
are  given  in  Appendix  Tables  la  and  lb.  Over 
40  million  coho  salmon  of  both  broods  were 
released  from  the  study  hatcheries.  The  number 
of  marked  fish  released  by  section  for  the  1965- 
and  1966-brood  years  combined  were  Lower 
River,  0.9  million;  Middle  River,  1.7  million; 
Upper  River,  1.3  million;  and  Uppermost  River, 
0.2  million.  A  total  of  39.1  million  coho  from 
both  broods  was  released  from  the  study  hatch- 
eries in  the  Lower,  Middle,  and  Upper  River 
sections.  Of  these,  9.8%  were  marked.  About 
0.9  million  coho  were  released  from  the  Upper- 
most River  section,  of  which  21.1%  were 
marked. 

Recovery  of  Marks  in  Fisheries 

The  mark-sampling  phase  of  this  study  was 
designed  in  1963  for  fall  chinook  salmon  and 
was  expanded  to  include  coho  in  1967,  1  year 
before  the  1965-brood  coho  were  expected  to 
appear  in  great  numbers  in  the  fishery.  This 
advanced  sampling  was  done  for  two  reasons: 
(1)  to  locate  the  sampling  problem  areas  and 
correct  any  deficiencies  before  the  major 
appearance  of  the  1965-brood  coho  in  the  fish- 
eries and  (2)  to  assist  the  Washington  Depart- 
ment of  Fisheries  in  recovering  their  marked 
1964-brood  Puget  Sound  coho.  This  phase  of 
the  investigation  ended  in  1969.  Catch  sampling 
covered  major  ocean  fisheries  from  Pelican, 
Alaska,  southward  to  Avila  Beach,  Calif.,  and 
Columbia  River  fisheries.  Sampling  for  marks 
in  each  area  consisted  of  recording  numbers  of 
fish  examined  for  marks  and  the  recoveries  of 
each  type  of  mark  detected.  Lengths  and 
weights  of  marked  coho  salmon  from  both 
broods  were  recorded  also.  The  sampling  sea- 


144 


WAHLE.  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Table  2. — Estimated  numbers,  percentage  marked,  and  marked  to  unmarked  ratios  of  1965-  and  1966- 
brood  coho  salmon  released  from  evaluation  hatcheries  by  river  sections. 


Brood 
year 

River  section  and 
(In  parentheses)  mark 

Marked 
released 

Unmarked 
released 

Total 
released 

Proportion 
marked 

Marked/ 
unmarked 

1965 

Lower  River  (Ad-RM) 

■yC6,29h 

4,670,794 

5,179,088 

0.09SI 

0.1088 

Middle  River  (Ad) 

845,674 

7,895,360 

8,741,034 

0.0967 

0.1071 

Upper  River  (Ad-LM) 

837,829 

7,670,539 

8,506,368 

0.0985 

0.1092 

Uppermost  River  (D-Ad) 

Subtotal  1965  brood 

101,73^ 

402,272 

504,006 

0.2018 

0.2529 

2,293,531 

20,638,965 

22,932,496 

0.1000 

0.1111 

1966 

Lower  River  (Ad-RM) 

385,630 

3,569,807 

3,955,437 

0.0975 

0.1080 

Middle  River  (Ad) 

764,262 

6,965,703 

7,729,965 

0.0989 

0.1097 

Upper  River  (Ad-LM) 

493,110 

4,544,676 

5,037,786 

0.0979 

0.1085 

Uppermost  River  {Ti-AA-IM}-' 

96,643 

466 

97,109 

0.9952 

207.3884 

Uppermost  River  (D-Ad-RM) 
Subtotal  1966  brood 

78,092 

269,355 

3h7,kk7 

0.2248 

0.2899 

1,817,737 

15,350,007 

n,l67,7kk 

0.1059 

0.1184 

TOTAL  BOTH  BROODS 

4,111,268 

35,988,972 

40,100,240 

0.1025 

0.1142 

1/     Released  below  Bonneville  Dam. 


sons  were  stratified  into  relatively  small  time 
units  (usually  2-\vk  periods). 

The  main  fisheries  sampled  were  ocean  sport 
and  commercial,  Columbia  River  sport  and 
commercial,  and  Puget  Sound  fisheries.  The 
ocean  fisheries  were  stratified  further  by  port  of 
landing.  The  Alaska  and  British  Columbia  troll, 
purse  seine,  and  gillnet  fisheries;  Columbia 
River  commercial  and  sport  fisheries;  and  Puget 
Sound  sport  and  commercial  fisheries  were 
stratified  by  area  of  catch.  The  specific  fisheries 
sampled  are  listed  in  Table  3  and  shown  in 
Figure  2. 

Catch  data  for  each  time-location  stratum 
were  provided  by  management  agencies.  The 
catch  of  coho  salmon  in  numbers  of  fish  was  an 
estimate  for  most  fisheries.  Commercial  catches 
were  estimated  either  from  (1)  the  total  weight 
of  landings  and  an  estimate  of  average  fish  size 
or  (2)  total  salmon  landings  (numbers)  and  an 
estimate  of  species  composition.  Estimates  of 
sport  catches  were  from  measures  of  total 
effort  and  catch  per  unit  of  effort  or  from  salm- 
on punch  cards  together  with  independent 
sampling  by  the  management  agency. 

About  20%  of  each  time-location  stratum 
was  sampled  for  marks.  Table  4  gives  the  annual 


total  catch  of  both  broods  of  coho  salmon  by 
year  and  number  sampled  for  marks  each  year. 
During  the  3  years  of  sampling,  15.4%  of  the 
total  catch  of  21.1  million  coho  were  examined 
for  marks.  The  actual  mark  sampling  percent- 
ages were  18.3,  13.5,  and  14.3%  for  1967, 
1968,  and  1969,  respectively. 

Enumeration  of  Returns  to  Hatcheries 

An  estimate  of  the  numbers  returning  to 
hatcheries  was  required  to  measure  the  total 
hatchery  output  and  marking  mortality.  All 
returns  to  most  hatcheries  were  e.xamined  for 
marks;  at  some  hatcheries,  the  numbers  marked 
and  unmarked  were  calculated  after  a  known 
percentage  of  the  total  return  was  sampled  for 
marks.  A  breakdown  of  the  returns  to  each  of 
the  study  hatcheries  is  in  Appendix  Tables  2a 
and  2b. 

Estimation  of  Total  Catch 
from  Hatcheries 
Actual  Recoveries 

Tables  5a  and  5b  summarize  marked  recov- 
eries  by  brood  year,   mark,  year  of  recovery, 

145 


FISHERY  BULLETIN:  VOL.  72.  NO.  I 

Table  3. — Areas  where  catches  were  examined  for  marked  coho  salmon  of  Columbia  River  origin  by  port  or  zone  of  landing  and 

type  of  fishery. 


Type  of  fishery- 


Area  sampled 


Sport 


Commercial 


Rod  and  reel 


Troll 


Gill  net 


Dip  net 


Purse  seine 


British  Columbia Alaska  area.  Zones  29,  40-'t3,   Zones  29,  UO-i+3  Zones  U0-U3. 

and  Area  C.i/ 
Washington  ocean Sekiu Seattle Grays  Harbor. 

Heah  Bay Neah  Bay Willapa  Bay. 

LaPush LaPush . 

Westport Westport . 

Ilwaco Ilwaco. 

Puget  Sound  and 

Juan  de  Fuca  Strait Zones  6-12 Zones  1-15 Zones  1-12. 

Oregon  ocean Warrenton Astoria. 

Tillamook Tillamook. 

Pacific  City Pacific  City. 

Depoe  Bay Depoe  Bay. 

Newport Newport . 

Florence Florence . 

Winchester  Bay....  Winchester  Bay. 

Coos  Bay Coos  Bay. 

Gold  Beach Bandon. 

Brookings Port  Orford. 

Gold  Beach. 
Brookings . 

California  ocean Crescent  City Crescent  City. 

■  Trinidad Trinidad. 

Eureka Eureka . 

Shelter  Cove. .....  Fort  Bragg. 

Fort  Bragg Albion. 

Albion Point  Arena. 

Bodega  Bay Bodega  Bay. 

San  Francisco Point  Reyes. 

Half  Moon  Bay San  Francisco. 

Santa  Cruz Half  Moon  Bay. 

Monterey Moss  Landing. 

Morro  Bay Monterey. 

Avlla Morro  Bay. 

Avlla. 
Columbia  River 
and  tributaries Zones  1-6 Zones  1-7 Klickitat  River. 

Cowlitz  River. 

Kalama  River. 

Lewis  River. 

Toutle  River. 
Washougal  River. 

1/  Canadian  catch  3-12  miles  off  Washington,  Oregon,  and  California. 


river  section  of  origin,  and  fishery.  All  marks 
from  the  Uppermost  River  section  (Leaven- 
worth Hatcheiy  in  Appendix  Table  4)  are  com- 
bined as  D-Ad  marks  in  Table  5b.  During  the 
3  years  of  sampling,  37,632  marked  coho  salm- 
on were  recovered.  More  marked  1965-  than 
1966-brood  coho  were  caught,  but  more  were 
released  from  the  1965  brood.  Carson  National 
F^ish  Hatchery  and  OxBow  Salmon  Hatchery, 
while  participating  in  the  study  for  the  1965 
brood,  did  not  do  so  for  the  1966  brood  (Table 
2).  The  fraction  of  marked  releases  actually 
recovered  for  the  1965  brood.  0.0089,  was 
slightly  less  than  for  the  1966  brood.  0.0093 
(Tables  2,  5a,  and  5b). 


146 


Estimated  Recoveries 

As  explained  under  "Estimating  Procedures," 
the  total  catch  offish  with  a  particular  mark  was 
estimated  for  each  stratum  (fishery,  port  of  land- 
ing or  area  of  capture,  and  time  period)  from 
actual  mark  recoveries  and  the  sampling  frac- 
tion. It  was  assumed  that  a  random  sample  of 
coho  salmon  was  examined  in  each  stratum  and  , 
that  in  each  sample  all  the  marked  fish  were  in- 
spected. The  total  catch  for  each  mark  in  each 
fishery  was  estimated  by  summing  over  the 
time  periods  and  appropriate  ports  of  landing 
or  areas  of  capture. 

The  estimated  catches  and  hatchery  returns 


WAHLE,  VREELAND.  and  LANDER:  BIOECONOMIC  CONTRIBUTION 
140"  1350  130"  125° 


Figure  2. — Ports  and  zones  sampled  for  marked  coho  salmon  of  Columbia  River  origin. 


147 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


of  marked  fish  are  summarized  in  Tables  6a  and 
6b  by  region  of  recovery,  fishery,  brood  year, 
and  mark.  The  marks  from  the  Uppermost 
River  section  (Appendix  Table  5a)  are  com- 
bined in  Table  6b.  The  total  estimated  catch  of 
marked  fish  from  both  broods  was  179,096.  A 
total  of  33,910  marked  coho  salmon  returned 
to  the  study  hatcheries  during  the  3  yr  of  sam- 
pling. 

Bias  Associated  with  Marks 

To  proceed  from  the  estimated  catch  of 
marked  fish  to  the  total  catch  of  hatchery  fish, 
we  must  be  sure  that  our  assumptions  (see 
"EXPERIMENTAL  DESIGN")  are  satisfied. 
Some  elements  (e.g.,  loss  of  maxillary  bones 
due  to  hooking,  loss  of  fins  due  to  injury)  cannot 
be  evaluated;  others  (e.g.,  mark  regeneration, 
natural  marks,  relative  survival  of  marked  fish) 
can  be  appraised  more  adequately. 

Mark  Regeneration  (Assumption  1)  and  Quality 
of  Marking 

We  have  three  indications  of  the  permanence 
of  fin  and  maxillary  marks.  First,  about  550 
marked  coho  salmon  of  the  1966  brood  were 
held  for  2  yr  at  the  Klickitat  station  for  fin 
regeneration  studies.  We  examined  these  fish 
periodically  throughout  the  retention  period  and 
observed  no  adipose  regeneration.  However,  we 
noted  a  4.5%  complete  maxillary  regenei'ation. 
Second,  the  appearance  of  D-Ad  marks  in  the 
releases  of  the  1966-brood  coho  from  Leaven- 
worth National  Fish  Hatchery  indicated  maxil- 
lary regeneration;  the  maxillary  bone  was 
clipped  from  all  1966-brood  Leavenworth  coho 
marked,  vet  5%  of  the  marked  coho  released  had 


only  a  D-Ad  finclip.  During  marking  of  the 
Leavenworth  coho,  100  marked  fish  per  marker 
were  examined  at  irregular  periods  each  day  to 
check  mark  quality.  No  undipped  maxillaries 
were  observed.  This  caused  us  to  disregard  fail- 
ure to  clip  maxillaries  as  a  reason  for  the 
appearance  of  the  D-Ad  marks.  Therefore,  we 
believe  the  D-Ad  marks  occurred  mainly  be- 
cause of  maxillary  regeneration.  Finally,  the 
percentage  of  D-Ad-only  marks  in  the  1969 
lower  Columbia  River  commercial  catch  of 
1966-brood  Leavenworth  Hatchery  marked 
fish  was  6.5%  .  This  is  very  close  to  the  percen- 
tage of  D-Ad-only  marks  in  the  release.  Because 
of  these  indications,  we  are  assuming  that  mark 
regeneration  caused  little  bias  in  this  study. 

Natural  Marks  (Assumption  2) 

The  catch  of  hatchery  fish  would  be  over- 
estimated if  marks  identical  to  those  used  in  this 
study  occurred  naturally.  To  ensure  that  no 
natural  marks  existed  in  hatchery  stocks,  coho 
salmon  returns  at  most  Columbia  River  and 
some  Puget  Sound  hatcheries  were  examined 
for  2  yr  before  the  study.  Approximately  35,000 
returns  were  examined  and  no  marks  identical 
to  those  we  planned  to  use  were  observed.  Also, 
fish  markers  at  all  participating  hatcheries  ex- 
amined approximately  3.5  million  coho  for 
naturally  missing  fins  and  maxillary  bones.  Only 
26  were  found  to  have  naturally  missing  adipose 
fins  and  none  had  naturally  missing  dorsal  fins 
or  maxillary  bones. 

The  possible  occurrence  of  natural  marks 
from  other  river  systems  is  more  difficult  to 
evaluate.  Comparisons  of  the  percentage  of 
each  mark  caught  in  the  lower  Columbia  River 


Table  4. — Estimated  catches  of  coho  sahnon  and  number  ot  fish 
examined  for  marks,  1967-69.1 


Gate 

;h  of  coho  salmor 

1 

Sampled 

1965  brood 

1966  brood 

All  ages 

for  marks 

1967 
1968 
1969 

22,91+6 

8,587,969 

0 

0 

20,1+57 
h,933,706 

7,539,255 
8,608,1+26 
1+, 966,  589 

1,381,255 

1,158,932 

710,753 

Total 

8,610,915 

i+,95't,l63 

21,lll+,270 

3,250,91+0 

1/     From  all  areas   sampled   (Table   3)» 


148 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Table  5a. — Number  of  marked   1965-brood  Columbia  River  coho  salmon  by  release  section  recovered  in  the  fisheries  by  year, 

region  of  capture,  and  type  of  fishery,  1967-68. 

Washington  nriti<;h       c-     y 

California         Oregon  (without       Puget  Sound  "  ,    ^,      .,  '   ,  Columbia  River 

■D,      4.   o       J  \  Columbia  Alaska 

Puget  Sound; 

River  section  and 


(In  parentheses)  mark 

Year 

Sport 

Com- 

Com- 

Com- 

Com- 

Com- 

Com- 

Sport 

Commercial 

TOTALS 

clal 

Sport 

mer- 
cial 

Sport 

mer- 
cial 

Sport 

mer- 
cial 

mer- 
cial 

mer- 
cial 

Main 

Trlb. 

Gill 
net 

Dip 
net 

Lower  River  (Ad-RM) 

1967 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

1 

0 

15 

0 

16 

1968 

101 

1+91 

135 

1,049 

212 

1+01 

0 

5 

72 

♦ 

0 

3 

107 

5 

2,581 

Middle  River  (Ad) 

1967 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

4 

20 

1 

0 

25 

1968 

156 

968 

1,822 

5,106 

2,187 

3,339 

0 

67 

790 

« 

2 

41 

778 

1 

15,257 

Upper  River  (Ad-LM) 

1967 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

1968 

16 

131 

77 

697 

321+ 

489 

0 

1 

65 

♦ 

0 

0 

180 

65 

2,045 

Uppermost  River  (D-Ad) 

1967 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

2 

0 

2 

1968 

6 

23 

52 

194 

119 

144 

0 

0 

9 

* 

0 

0 

67 

0 

614 

TOTALS 

1967 
1968 

0 

279 

0 

1,613 

0 
2,086 

0 
7,046 

0 
2,842 

0 
4,373 

0 
0 

0 

73 

0 
936 

0 
* 

5 
2 

20 
44 

18 
1,132 

0 

71 

43 
20,497 

*No  sampling . 

Table  5b. — Number  of  marked   1966-brood  Columbia  River  coho  salmon  by  release  section  recovered  in  the  fisheries  by  year, 

region  of  capture,  and  type  of  fishery,  1968-69. 


River   section  and 
(in  parentheses)  mark 


British   S.  E. 


Washington 
California    Oregon      (without   Puget  Sound 

Puget  Sound)  Columbia  Alaska 


Columbia  River 


Year 


Com-        Com-       Com-         Com-   Com- 

Sport  mer-  Sport  mer-  Sport  mer-   Sport  mer-   mer- 

clal       cial       cial         cial   cial 


Com- 


TOTALS 


Sport   Commercial 


cial  Main  Trlb.  Gill   Dip 
net    net 


Lower  River  (Ad-RM) 


Middle  River  (Ad) 


Upper  River  (Ad-LM) 


Uppermost  River   (D-Ad) 


1968 
1969 


0 
22 


1968  0 

1969  191 


1968 
1969 


1968 
1969 


0 
14 


0 

158 


0  0 

107     911 


0 
432 


0 
432 


0  0  0  0  0 

905  1,578  4,479  2,120  1,865 


0 
102 


0 
1+0 


0  0 

86      662 


0 
31 


0 
118 


0 

525 


0 

52 


0 

356 


0 

67 


0 

0 


0 

15 


0 

32 


0 

312 


0 
9 


0 

1 


1 

0 

2 

1 

6 

158 

0 
3 

5 
2,307 

17 

1 

34 
33 

12 
759 

0 
18 

63 
12,278 

2 
0 

1 
1 

6 

233 

16 
53 

25 
2,042 

0 
0 

0 
0 

3 

50 

0 

0 

365 

TOTALS 


1968  0  000000  0  0 

1969  233  1,205  1,802  6,170  3,179  2,720    2     17     354 


*No   sampling. 


20         37  27     16  IOC 

1        35      1,200    74    16,992 


commercial  fishery  with  the  percentage  of  each 
mark  caught  in  each  ocean  fishery  give  an  indi- 
cation of  the  occurrence  of  natural  marks.  After 
making  these  comparisons,  we  noted  a  prepon- 


derance of  Ad-only  marks  especially  in  the 
Oregon  sport  fishery  for  the  1965  brood  and  the 
California  sport  and  commercial  fisheries  for 
the  1966  brood.  In  these  fisheries,  we  observed 


149 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 

Table  6a. — Estimated  number  of  marked   1965-brood  coho  salmon  in  catches  and  hatchery  returns  by  type  of  mark, 

region  of  recovery,  type  of  fishery,  and  year  of  capture,  1967-68. 


Region 


Fishery  type 


D-Ad 


Ad-LM 


Ad 


Ad-RM 


Total 


1967  1968   I96T   1968   1967    1968   1967    1968   1967    1968 


Ocean  fisheries: 

British  Columbia 

Washington 

Oregon 

C£Llif  ornia 

Subtotail 

Freshwater  fisheries: 

Columbia  River 

Total 

Columbia  River  escapement: 
Study  hatcheries 


Commercial. . . 

Sport 

Commercial. . . 

Sport 

Commercial. . . 

Sport 

Commercial. . • 

Sport 

Commercial. . . 

Sport 

Commercial. . . 

All  fisheries 


U6 
677 
636 
226 
736 

18 
109 


0   921 
0  1,527 


0 

238 


7  2,686 


k59 
1,809 
2,051 

265 

2,530 

30 

789 


6,339 
ii,i+90 
14,382 

7,9'+'+ 

17,821 

299 

5,55^+ 


581 
1,206 
1,716 

i+20 
3,564 

331 
2,617 


2,104 
5,829 


0 
846 


19,733 
44,096 


0   1,957 
0   8,478 


344    290 
2   4,907 


25 

130 


16 
825 


7,425 
15,182 
18,785 

8,855 

24,651 

678 

9,069 


0  24,715 
0  59,930 


369   306 

139  6,816 


0    8,779         346     69,026         155     11,276         508    91,767 


38        138    1,125    1,882    4,391      9,399    1,568      1,864    7,122    13,283 


Table  6b. — Estimated  number  of  marked   1966-brood  coho  salmon  in  catches  and  hatchery  returns  by  type  of  mark, 

region  of  recovery,  type  of  fishery,  and  year  of  capture,  1968-69. 


Region 


Fishery  type 


D-Ad 


Ad-LM 


Ad 


Ad-RM 


Total 


1968  1969   1968   1969    1968    1969   1968    1969   1968    1969 


Ocean  fisheries: 

British  Columbia 

Washington 

Oregon 

California 

Subtotal 

Freshwater  fisheries: 

Columbia  River 

Total 

Columbia  River  escapement: 
Study  hatcheries 


Commercial. . , 

Sport 

Commercial. . . 

Sport 

Commercial. . . 

Sport 

Commercial. . . 

Sport 

Commercial. . . 

Sport 

Commercial. . . 

All  fisheries 


7 
242 
281 
148 
645 
23 
224 


0       413 

0    1,157 


0 

283 


77 

2,333 

1,456 

392 

2,930 

38 

465 


2,970 
9,324 
7,782 
7,304 
19,952 
611 
6,024 


278 
2,178 
1,807 

492 

4,261 

58 

728 


45 
58 


2,763 
4,928 


35 
2,470 


0    17,239 
0    36,728 


541 
125 


397 

3,104 


31 

57 


2,728 
7,074 


20 
1,619 


6     1,853       103     10,196        666     62,468 


3,332 
14,077 
11,326 

8,336 

27,788 

730 

7,441 


0    23,143 
0    49,887 


617  452 

246    12,476 


11,441         863     85,958 


624      1,075     2,191      5,769     2,067      1,771     4,890      8,615 


samplers  recording  partially  regenerated  Ad-LM 
and  Ad-RM  as  Ad-only  marks.  We  attribute 
the  preponderance  of  Ad-only  marks  in  the 
above  mentioned  fisheries  to  the  reluctance  of 
samplers  to  distinguish  between  partially  regen- 
erated maxillaries  and  maxillaries  lost  through 
injury. 


Age  and  Maturity  Schedules 
(Assumptions  3  and  4) 

Godfrey  (1965)  noted  that  ocean  catches  of 
coho  salmon  in  the  regions  sampled  in  this  study 
are  all,  or  nearly  all,  age  3  adults.  Johnson 
(1970)     estimated    that    the    ocean     catch    of 


150 


WAHLE.  VREELAND.  and  LANDER:  BIOECONOMIC  CONTRIBUTION 


marked  1964-brood  coho  from  Big  Creek 
Hatchery  (Figure  1)  contained  only  3%  age  2 
coho.  This  available  evidence  indicates  that 
Assumption  3  (all  coho  in  ocean  fisheries  are 
in  their  third  and  final  year  of  life)  is  reasonably 
satisfied. 

A  comparison  was  made  of  marked  and  un- 
marked returns  (Appendix  Tables  2a  and  2b) 
to  hatcheries  in  the  same  river  section  where 
released  to  test  Assumption  4  (marked  and  un- 
marked fish  have  the  same  maturity  schedules). 
Appendix  Table  3  shows  the  percent  of  2-yr-old 
coho  salmon  in  the  marked  and  unmarked  re- 
turns by  river  section  and  brood  year.  Un- 
marked strays  to  other  river  sections  could  not 
be  identified  by  origin,  so  it  was  necessary  to 
assume  that  straying  was  the  same  for  marked 
and  unmarked  returns.  The  D-Ad  comparison 
(Leavenworth  Hatchery)  was  not  made  because 
passage  difficulties  at  John  Day  Dam  in  1969 
led  to  no  returns  of  adults  to  Leavenworth 
Hatchery.  The  nearly  equal  percentages  of  2-yr- 
olds  in  the  marked  and  unmarked  returns  by 
river  section  and  brood  year  indicate  that 
Assumption  4  is  satisfied. 

Marked  Proportions  at  Release  and  Capture 
(Assumptions  5  and  6) 

Inspection  of  mark  proportion  data  in 
Appendix  Tables  la  and  lb  shows  the  variabil- 
ity between  hatcheries  to  be  small  enough  to 
consider  Assumption  5  (same  proportion  of 
releases  marked  at  each  hatchery  in  a  given 
river  section)  reasonably  well  satisfied.  At  pre- 
sent, no  data  exist  to  support  Assumption  6 
(equal  vulnerability  to  capture  for  marked  and 
unmarked  fish  from  a  given  river  section),  but 
it  is  intuitively  satisfied.  Fish  marked  by  clip- 
ping maxillary  bones  and/or  the  adipose  fin 
would  not  seem  to  be  more  vulnerable  to  cap- 
ture by  fishing  gear  than  unmarked  fish. 

Relative  Survival  of  Marked  Fish 

Worlund,  Wahle,  and  Zimmer  (1969)  found 
that  marked  fall  chinook  salmon  did  not  survive 
as  well  as  unmarked  chinook.  We  also  found 
this  for  coho  salmon.  To  determine  the  un- 
marked catch  of  hatchery  fish,  we  must  account 
'for  the  lower  survival  of  marked  fish.  The  rela- 
tive survival  values  for  both  broods  and  each 
mark  type  of  coho  were  calculated  as  explained 


under  "Estimating  Procedures."  Oxytetracy- 
cline  (TM-50)  was  used  to  mark  both  broods  of 
coho  at  Eagle  Creek  and  Big  Creek  hatcheries 
to  obtain  survival  values  for  Ad  and  Ad-RM 
marked  coho,  respectively.  Returns  to  three 
hatcheries.  Little  White  Salmon,  Cascade,  and 
Klaskanine,  on  streams  having  no  wild  spawn- 
ing populations  were  used  to  obtain  relative 
survival  values  for  both  broods  of  Ad-LM  and 
Ad-RM  marked  coho.  Finally,  the  marked  to 
unmarked  ratios  at  release  and  return  for  each 
river  section  were  combined  to  obtain  survival 
values  for  each  mark  type  in  both  brood  years. 

The  relative  survival  estimates  are  in  Appen- 
dix Table  6.  Marked  coho  salmon  that  strayed 
to  sections  other  than  where  they  were  released 
(Appendix  Tables  2a  and  2b)  were  excluded  from 
the  marked  returns  in  computing  relative  sur- 
vival (see  "Bias  Associated  with  Marks").  There- 
fore, the  median  value  for  each  of  the  mark 
types  for  both  brood  years  combined  was  arbi- 
trarily used  to  obtain  reasonable  approxima- 
tions for  relative  survival.  The  same  value  was 
used  for  Ad-LM  and  Ad-RM  marked  coho.  The 
median  va'ues  for  the  Ad-only  and  Ad-maxillary 
marked  coho  were  89  and  72%,  respectively. 

The  relative  survival  of  D-Ad  marked  1965- 
brood  coho  salmon  from  Leavenworth  National 
Fish  Hatchery  (Uppermost  section)  was  obtained 
from  TM-50  marking  data.  In  1967  and  1968, 
a  total  of  174  D-Ad-TM-50  marked  and  1,305 
TM-50-only  marked  1965-brood  coho  returned 
to  Leavenworth.  From  these  values,  the  marked 
to  unmarked  relative  survival  of  1965-bi-ood 
D-Ad  marked  coho  was  calculated  to  be  53% . 
Few  hatchery  returns  of  1966-brood  Leaven- 
worth coho  were  obtained  because  of  passage 
difficulties  at  John  Day  Dam  due  to  construc- 
tion of  fish  ladders  and  mortalities  caused  by 
trapping  at  Priest  Rapids  Dam.  Hence,  a  rela- 
tive survival  estimate  for  the  D-Ad-RM  and  D- 
Ad-LM  marks  could  not  be  calculated.  The  value 
for  the  D-Ad  marked  1965-brood  coho  (53%) 
was  therefore  used  to  estimate  the  1966-brood 
Leavenworth  catch  of  unmarked  fish. 

Final  Estimates  Corrected  for  Marking 

One  marked  fish  represented  about  9  un- 
marked ones  at  release  but  about  11-20  (depend- 
ing on  the  mark)  at  return  (Tables  2,  6a,  and  6b). 
The  foregoing  estimates  of  relative  survival  for 
unmarked  fish  were  applied   (see  "Estimating 


151 


Procedures")  to  estimate  the  catch  of  unmarked 
hatchery  fish,  then  marked  fish  were  added  to 
estimate  the  total  catch. 

An  additional  calculation  was  required  before 
estimating  the  unmarked  catch  associated  with 
the  marked  1966-brood  Leavenworth  Hatchery 
fish  because  of  the  recovery  of  1966  brood  D-Ad- 
only  marks.  The  recovery  was  due  to  either 
regeneration  or  nondetection  of  D-Ad-maxillary 
marks  (see  "Bias  Associated  with  Marks"). 
Therefore  the  estimated  catch  of  1966  brood 
D-Ad  marks  had  to  be  apportioned  between  the 
estimated  catches  of  D-Ad-RM  and  D-Ad-LM 
marks  before  calculating  the  catch  of  unmarked 
1966-brood  fish.  The  D-Ad  marks  were  appor- 
tioned by  the  ratio  of  their  occurrence  at  the 
time  of  release.  At  Leavenworth  Hatchery,  5,081 
D-Ad  marks  were  estimated  to  have  been  re- 
leased with  the  D-Ad-RM  marks.  Below  Bonne- 
ville Dam,  4,393  D-Ad  marks  were  estimated  to 
have  been  released  with  the  D-Ad-LM  marks. 
This  is  a  total  release  of  9,474  D-Ad  mai'ks  of 
which  54%  (5,081/9,474)  came  from  D-Ad-RM 
marks  and  46%  (4,393/9,474)  came  from  D-Ad- 
LM  marks.  These  ratios  were  used  to  apportion 
the  estimated  catch  of  6G6  D-Ad  marks  (Appen- 
dix Table  5a)  between  the  D-Ad-RM  and  D-Ad- 
LM  marked  fish  in  each  of  the  fisheries.  For 
example,  88  D-Ad  marked  coho  (Appendix 
Table  5a)  were  estimated  to  have  been  caught  in 
the  Washington  sport  fisheries  in  1969.  Using 
the  occurrence  percentages  of  the  D-Ad  marks  at 
release,  88  X  0.54  =  48  were  calculated  to  be  from 
D-Ad-RM  marks  and  88X0.46  =  40  were 
calculated  to  be  from  D-Ad-LM  marks.  This 
apportioning  was  done  for  each  fishery  and  re- 
sults are  in  Appendix  Table  4b. 

The  estimated  catches  of  marked  fish  used  to 
calculate  the  catches  of  unmarked  hatchery  fish 
are  in  (1)  Table  6a  for  the  estimated  1965  brood 
D-Ad,  Ad-LM,  Ad.  and  Ad-RM  marks  captured 
in  the  ocean  and  Columbia  River  fisheries;  (2) 
Table  6b  for  the  estimated  ocean  and  Columbia 
River  catches  of  1966  brood  Ad-LM,  Ad,  and  Ad- 
RM  marked  fish;  and  (3)  Appendix  Table  5b  for 
the  catches  of  marked  1966-brood  Leavenworth 
coho  salmon.  Appendix  Table  7  presents  the 
resulting  estimated  catches  of  unmarked  hatch- 
ery fish. 

The  estimated  total  catch  of  Columbia  River 
hatchery  fish  (Appendix  Table  8)  was  obtained 
by  adding  the  estimated  catch  of  marked  fish 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 

(Tables  6a  and  6b)  to  the  estimated  unmarked 
catches  (Appendix  Table  7).  The  resulting  catch 
estimates  may  affect  management  decisions  in 
years  when  no  marking  studies  take  place. 
Therefore,  as  a  final  step,  we  divided  the  esti- 
mated catch  of  each  mark  in  each  fishery  (Tables 
6a  and  6b)  by  the  estimated  relative  survival  for 
that  mark  (see  "Relative  Survival  of  Marked 
Fish")  to  obtain  a  theoretical  catch  of  marked 
fish  assuming  no  marking  mortality.  The  results 
were  then  added  to  the  estimated  unmarked 
catch  (Appendix  Table  7)  to  obtain  a  theoretical 
total  catch  of  Columbia  River  hatchery  coho 
salmon.  The  results  are  in  Table  7  by  region  of 
recovery,  type  of  fishery,  and  year  of  capture. 
The  table  includes  the  estimated  sport  catches 
of  hatchery  fish  in  Columbia  River  tributaries 
where  no  creel  census  took  place.  This  is  broken 
down  in  detail  by  year  of  capture,  brood,  and 
stream  in  Appendix  Table  9. 

An  estimated  total  of  2,188,172  Columbia 
River  hatchery  coho  would  have  been  caught 
during  the  3  years  of  sampling  had  no  marking 
taken  place.  This  is  about  16%  of  the  total  catch 
in  areas  sampled  (Table  3)  of  1965-  and  1966- 
brood  coho  caught  during  1967-69  (Table  4) — 
13%  for  the  1965  brood  and  21%  for  the  1966 
brood.  Another  useful  statistic  is  the  catch/1,000 
fish  released.  For  the  combined  1965  and  1966 
broods,  this  was  55/1,000—50/1.000  for 
the  1965  brood  and  61/1,000  for  the  1966  brood 
(Tables  2  and  7). 

ECONOMIC  EVALUATION 

A  main  purpose  of  this  paper  is  to  develop 
benefit/cost  ratios  for  the  1965  and  1966  broods 
of  coho  salmon  from  Columbia  River  hatcheries. 
To  develop  these  ratios,  estimates  must  be  made 
of  (1)  the  costs  of  rearing  the  40.1  million  smolts 
released  (Table  2)  and  (2)  the  value  of  the  theo- 
retical catch  of  2,188,172  coho  (Table  7).  The 
rearing  costs  will  be  presented  first. 

Cost  Accounting 

Production  costs  are  broken  down  into  two 
categories:  (1)  amortized  construction  costs  or 
capital  costs  and  (2)  operational  costs. 

Capital 

The  "annual  imputed  capital  charge"  for  each 
hatchery  was  computed  by  amortizing  the  capi- 
tal expenditures  at  each  hatchery  into  30  equal 


I 


152 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Table  7. — Theoretical  catch  of  1965-  and  1966-brood  hatchery  coho  salmon  by  region  of  recovery,  type  of  fishery, 

and  year  of  capture,  1967-1969.' 


Region 


Fishery  type 


1967 


1965  brood 


1968 


Total 


1968 


1966  brood 


1969 


Total 


Ocean  fisheries: 

British  Coliimbla. . . . 
Washington 

Oregon 

California 

Subtotal 

Freshwater  fisheries: 
Columbia  River 

Total 


Commercial. . .  0 

Sport 0 

Commercial. . .  0 

Sport 0 

Commercial. . .  0 

Sport 0 

Commercial...  0 

Sport 0 

Commercial...  0 

Sport 18,739 

Commercial...  1,929 

All  fisheries  20,668 


88,755 
182,372 
226,212 
10i^,063 
300, 004 

8,750 
113,700 


88,755 
182,372 
226,212 
104,063 
300, 004 
8,750 
113,700 


0 
0 
0 
0 
0 
0 
0 


38,821+ 
171,035 
136,016 

96,371 
332,075 

8,393 
86,573 


38,824 
171,035 
136,016 

96,371 

332,075 

8,393 

86,573 


295,185 
728,671 


10,627 
82,831 


295,185 
728,671 


29,366      15,584 
84,760        3,087 


275,799 
593,488 


10,855 
151,377 


275,799 
593,  J^8 


26,439 
154,464 


1,117, 31**      1,137,982       18,671       1,031,519       1,050,190 


1/  Corrected  for  differential  fincllp  mortality  and  assuming  no  marking  had  taken  place. 


annual  payments  using  an  interest  rate  of  3.5%  .^ 
This  rate  was  the  average  3-  to  5-yr  government 
bond  interest  rate  weighted  by  the  total  annual 
capital  outlay  at  all  hatcheries  from  1949  (incep- 
tion of  Columbia  River  Development  Program) 
through  1970.  All  outlays  prior  to  this  period 
are  assumed  to  be  depreciated  out  completely. 
The  imputed  capital  charge  for  each  study  hatch- 
ery was  apportioned  among  the  broods  and 
species  present  by  using  the  percentage  of  time 
spent  caring  for  each  group  of  fish.  The  total 
annual  imputed  capital  charges  for  the  1965- 
and  1966-brood  coho  salmon  are  $271,600  and 
$235,600,  respectively. 

Operation 

The  operation  and  maintenance  costs  at  each 
hatchery  are  divided  into  two  categories.  They 
are  fish  food  and  drugs  and  other  operational 
costs.  The  cost  of  fish  food  and  drugs  is  appor- 
tioned between  each  brood  and  species  according 
to  the  pounds  of  each  brood  and  species  pro- 
duced. The  operational  costs  other  than  food  and 
drugs  include  costs  for  labor,  personal  services, 
travel,  transportation  of  items,  communication 
services,  equipment,  supplies  and  materials, 
and  administration.  These  costs  are  allocated  to 
each  brood  and  species  in  the  same  manner  as 
the  capital  costs.  The  operational  costs  appor- 


^  The  "annual  imputed  capital  charge"  is  the  estimated 
cost  of  government  funds  over  the  life  of  the  project. 


tioned  to  the  1965-  and  1966-brood  coho  are 
$1,020,700  and  $991,000,  respectively.  The  total 
costs  applicable  to  rearing  the  1965-  and  1966- 
brood  coho  are  then  $1,292,300  and  $1,226,600, 
respectively. 

Benefits 

To  determine  the  benefit  provided  by  hatchery 
releases  of  1965-  and  1966-brood  coho  salmon  to 
the  commercial  and  sport  fisheries,  an  estimate 
of  the  net  economic  value  to  these  fisheries  must 
be  made.  Additional  information  is  critically 
needed  to  improve  the  basis  for  estimating 
values  for  fishery  resources;  however,  the 
values  used  in  this  report  are  based  on  the  best 
information  now  available  and  the  limitations  of 
these  values  are  discussed. 

Commercial 

Ex-vessel  market  prices  have  been  used  to 
represent  estimated  net  values  for  commercially 
caught  fish.  There  are  two  quite  different  rea- 
sons why  this  method  can  provide  satisfactory 
estimates. 

The  Columbia  River  salmon  production  from 
hatcheries  included  in  this  study  provide  only  a 
portion  of  the  total  salmon  production.  Use  of 
the  ex-vessel  price  in  the  standard  benefit-cost 
technique  would  require  the  deduction  of  all 
associated  costs.  However,  excess  capacity 
typically  exists  in  the  fishing  sector,  so  little  or 


153 


FISHERY  BULLETIN;  VOL.  72.  NO.  1 


no  additional  fishing  effort  would  be  needed  to 
land  the  production  from  these  hatcheries. 
While  this  provides  an  adequate  reason  to  omit 
fishing  costs  for  hatchery  fish,  this  would  not  be 
true  for  total  salmon  production. 

A  stronger  basis  for  omitting  costs  necessary 
to  land  fish  and  using  the  ex-vessel  price,  results 
from  current  fishery  management  policies.  Regu- 
lated inefficiency  has  been  used  in  salmon  fish- 
eries to  prevent  overharvest  thus  excluding  effi- 
cient fishing  methods.  This  process  probably 
results  in  dissipation  of  at  least  75%  of  potential 
net  benefits  and  may  be  as  high  as  95%  (Richards, 
1969).'*  Since  the  market  prices  used  result  from 
normal  market  activities  and  thus  represent  the 
market  value  of  the  fish  resource  to  users,  this 
potential  benefit  could  be  realized  if  society 
elects  to  change  management  methods  and 
reduce  fishing  costs. 

Several  inadequacies  exist  in  the  use  of  the  ex- 
vessel  price  as  a  representation  of  the  net  value 
for  commercially  caught  fish.  The  first  inade- 
quacy is  that  the  ex-vessel  market  price  fails  to 
completely  measure  market  value.  Gear  or  sup- 
plies furnished  by  processors  and  bonuses  paid 
are  examples  of  values  that  are  not  included  in 
estimated  market  values.  A  second  inadequacy 
exists  since  ex -vessel  values  fail  to  completely 
measure  potential  production.  For  example,  a 
large  share  of  the  catch  is  now  taken  on  troll 
gear  and  many  sublegal  size  fish  are  caught.  In 
the  removal  from  the  gear  and  release  of  these 
sublegal  fish,  many  sustain  injuries  that  result 
in  death  or  reduced  growth.  This  wa.stage  sig- 
nificantly reduces  the  total  production  from  the 
resource  to  society.  Also,  estimated  market 
values  do  not  include  other  ty])es  of  benefits. 
For  example,  ex-vessel  prices  may  not  always 
be  determined  in  markets  with  adequate  com- 
petition to  indicate  total  benefits,  resulting  in 
a  producer  surplus  (i.e.,  additional  profits  to 
fish  buyers).  Benefits  due  to  employment  and 
income  generated  for  coastal  communities  and 
the  regional  and  national  economy  are  not 
included.  Consumer  surj^lus  or  benefits  to  con- 
sumers that  are  not  included  in  market  prices 
are  also  omitted. 

These  factors  indicate  that  using  the  ex-vessel 
price  for  commercially  caught  fish  is  a  reason- 


able estimate  of  benefits  that  could  be  realized. 
If  all  factors  were  included,  this  could  prove  to 
be  a  quite  conservative  estimate  of  total  benefits. 
Tables  8a  and  8b  present  the  net  value  of  com- 
mercially caught  1965-  and  1966-brood  coho 
salmon  by  ocean  regions  and  Columbia  River 
commercial  fisheries.  Two  calculations  were 
required  to  obtain  the  net  value.  The  theoretical 
commercial  catch  was  multiplied  by  the  average 
Ad  marked  coho  weight  to  obtain  the  total 
pounds  of  Columbia  River  coho  caught  by  region. 
The  total  pounds  were  then  multiplied  by  the 
average  ex-vessel  price  paid  in  each  region  to 
obtain  the  net  value  of  the  coho  catch  to  that 
region. 

Sport 

The  net  value  for  salmon  and  .steelhead  sport 
fishing  is  estimated  to  be  $20  per  day  of  fishing. 
This  value  results  from  reconciling  the  existing 
research  that  is  closely  related  to  estimated  net 
economic  values  of  Columbia  River  sport  caught 
salmon.  The  maximum  potential  benefits  from 
sport  fishing  at  a  single  market  price  is  predicted 
at  $20  per  fishing  day  by  Brown,  Singh,  and 
Richards  (1972).'  A  single  market  price  is  in- 
tended to  be  comparable  with  typical  conditions 
that  underlie  normal  market  price  determina- 
tion. The  original  data  for  this  report  were  from 
a  1962  survey  in  Oregon  with  results  published 
in  1964.  The  net  value  that  resulted  in  maximum 
benefits  was  estimated  at  $8  per  day  of  fishing 
in  the  original  analysis  (Brown.  Singh,  and 
Castle,  1964).  However,  Brown  and  Nawas  (in 
press)  developed  research  techniques  that  more 
efficiently  utilize  available  information.  When 
these  techniques  were  used  in  an  analysis  of  the 
1962  survey  data,  an  estimated  value  of  $20  per 
day  was  derived.  This  is  the  estimated  value 
used  in  this  report. 

Two  other  reports  support  the  revised  Oregon 
results.  The  estimated  net  economic  value  for 
the  1967  sport  salmon  fisheries  of  Washington 
resulted  in  a  recommended  value  of  $28  per  day 
of  fishing  (Mathews  and  Brown,  1970).  An  eval- 
uation of  the  net  economic  values  for  the  Idaho 
sport  fisheries,  based  on  a  1968  survey,  resulted 


**  Jack  A.  Richards.  1969.  An  economic  evaluation  of 
Columbia  River  anadromous  fish  programs.  U.S.  Dep.  Int.. 
Fish  Wildl.  Serv..  Bur.  C  ommer.  Fish.,  Working  paper  17, 
274  p.  (Processed.) 


'  William  G.  Brown,  Ashok  K.  Singh,  and  Jack  A. 
Richards.  1972.  Influence  of  improved  estimating  tech- 
niques on  predicted  net  economic  values  for  salmon  and 
steelhead.  (Oreg.  State  Univ.,  Corvallis),  Agric.  Exp.  Stn. 
unpubl.  manuscr..  26  p.  (Typescript.) 


154 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 


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WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 


in  estimates  comparable  to  those  originally  re- 
ported forthe  1962  Oregon  survey  (Gordon,  n.d.)-^ 

The  value  of  $20  per  day  is  believed  to  be  a 
reasonable  estimate  based  on  existing  research 
information.  However,  limitations  associated 
with  this  estimated  value  should  be  recognized. 
A  range  of  values  is  needed  for  sport-caught  fish 
that  reflect  differences  in  quality  variables  such 
as  distance  from  metropolitan  areas,  environ- 
mental conditions,  species  involved,  and  success 
level.  The  reports  mentioned  here  not  only  indi- 
cate an  average  value  for  these  different  vari- 
ables but  involve  different  time  periods,  geo- 
graphic areas,  and  research  methods.  This  is 
also  an  estimated  market  value  and  does  not  in- 
clude other  values  such  as  consumer  surplus  (i.e., 
benefits  to  consumers  that  are  not  measured  by 
market  prices),  benefits  due  to  employment  and 
income  generated  in  local  communities  and  the 
regional  and  national  economy,  and  benefits  to 
nonusers  who  may  not  fish  but  may  want  fish- 
ing preserved  and  available. 

Since  the  value  per  fishing  day  is  an  average 
of  various  quality  factors,  no  values  by  species 
are  estimated  directly.  The  only  method  present- 
ly available  to  determine  values  for  fish  is  by 
success  levels.  This  requires  careful  interpreta- 
tions; for  example,  greater  success  results  in 
lower  values  per  fish.  This  means  that  higher 
total  values  would  result  with  poorer  success 
since  the  number  of  fish  involved  at  the  esti- 
mated market  price  is  not  fully  taken  into 
account.  For  this  report,  success  is  assumed  to 
be  estimated  at  an  average  of  the  total  landings 
of  all  species.  This  is  probably  reasonable  since 
mostly  ocean  fishing  and  entire  seasons  are 
involved. 

Limitations  of  estimated  sport  and  commercial 
values  need  to  be  emphasized.  The  estimated 
market  price  of  $20  per  fishing  day  excludes  con- 
sumer surplus  whereas  the  estimated  number  of 
fishing  days  does  not.  Consequently,  multiply- 
ing market  prices  by  actual  participation  is  not 
comparable  with  the  ex-vessel  prices  used  for 
values  of  commercially  caught  fish  since  these 
values  do  not  contain  consumer  surplus.  There- 
fore extreme  caution  should  be  observed  in  com- 
paring values  between  fish  species  or  total  val- 
ues of  sport  and  commercial  fishing. 


**  Douglas  Gordon,  (n.d.).  An  economic  analysis  of  Idaho 
sport  fisheries.  Univ.  Idaho,  Coll.  Forestry.  Wildl.  and 
Range  Sci.,  Idaho  Coop.  Fish.  Unit.,  Review  draft,  60  p. 
(Processed.) 


To  obtain  values  for  the  1965-  and  1966-brood 
sport-caught  coho  salmon,  the  estimated  market 
value  of  $20  per  day  of  fishing  is  divided  by  the 
success  level  in  each  region.  This  value  per  fish 
is  then  multiplied  by  the  number  of  coho  taken 
in  each  region.  The  results  are  presented  in 
Tables  8a  and  8b. 

Benefit/Cost 

The  total  net  economic  values  of  the  1965-  and 
1966-brood  coho  salmon  were  $8,508,590  and 
$9,065,579,  respectively.  Benefits  were  also  de- 
rived from  the  sale  of  excess  1965-  and  1966- 
brood  coho  carcasses  at  the  study  hatcheries. 
The  revenue  from  carcass  sales  is  used  to  pur- 
chase additional  fish  food.  This  allows  additional 
fish  to  be  reared,  thus  providing  future  benefits 
to  society. 

Coho  carcasses  were  sold  at  Fish  Commission 
of  Oregon  and  Washington  Department  of  Fish- 
eries hatcheries.  The  values  of  the  1965-  and 
1966-brood  coho  carcasses  sold  are  $75,035  and 
$40,973,  respectively.  When  these  values  are 
added  to  the  net  economic  values,  total  benefits 
of  $8,583,625  for  the  1965  brood  and  $9,106,552 
for  the  1966  brood  are  obtained.  The  benefit  to 
cost  ratios  are  then  $8.583.625/$l,292,300  or 
6.6/1  and  $9,106,552/$1,226,600  or  7.4/1  for 
the  1965  and  1966  broods,  respectively.  The 
average  benefit  to  cost  ratio  is  7.0/1. 


SUMMARY 

When  this  marking  study  was  designed,  four 
marks  were  available  from  the  Pacific  Marine 
Fisheries  Commission.  The  Columbia  River  was 
divided  into  four  sections.  Each  section  was 
assigned  a  specific  mark.  All  study  hatcheries 
within  a  given  section  (except  Leavenworth 
station  in  the  Uppermost  River  section)  marked 
approximately  10%  of  their  coho  salmon  produc- 
tion with  the  assigned  mark  (Table  2).  Two 
broods,  1965  and  1966,  of  coho  salmon  were  in- 
cluded in  the  study.  During  the  2-year  marking 
phase,  4.1  million  of  the  40.1  million  total  coho 
production  were  marked  (Table  2).  Approxi- 
mately 22.9  million  1965-brood  and  17.2  million 
1966-brood  coho  were  released  (Table  2). 

Sampling  for  marks  was  conducted  in  most 
coho  salmon  fisheries,  with  few  exceptions,  from 
Avila  Beach,  Calif.,  to  Pelican,  Alaska  (Figure 


157 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


2  and  Table  3).  During  1968  and  1969,  there  was 
no  sampling  done  in  the  southeast  Alaska  troll 
and  gill  net  fisheries.  During  the  3  yr  of  mark 
sampling,  an  average  of  15.4%  of  the  coho  catch 
was  examined  for  marks  (Table  4).  A  total  of 
37,632  marked  coho  was  recovered  from  1967 
through  1969  (Tables  5a  and  5b). 

The  appropriateness  of  the  estimating  pro- 
cedures used  to  determine  hatchery  contribution 
is  dependent  on  the  validity  of  six  assumptions. 
Additional  studies  and  data  collections  previous- 
ly described  were  incorporated  into  the  marking 
experiment  to  help  test  the  assumptions.  The 
first  assumption,  permanence  of  fin  marks,  was 
tested  by  holding  marked  fish  in  fresh   water 
over  a  period  of  months.  Little  total  regeneration 
occurred,  but  maxillary  regeneration  caused  con- 
fusion between  maxillary-adipose  and  adipose- 
only  marked  coho  salmon.  The  second  assump- 
tion, origin  offish  marked  with  hatchery  marks, 
was  tested  by  examining  returning  adult  coho 
prior  to  the  marking  study  and  coho  fingerlings 
at  the  time  of  marking  for  natural  marks.  No 
noteworthy  numbers  of  naturally  missing  adi- 
pose  fins   or   maxillary   bones   were   observed. 
Prior  to  this  study,  a  number  of  age  studies  have 
supported  that  Assumption  3,  all  adult  coho  are 
3  yr  old,   is  valid   (Godfrey,   1965).  The  mark 
sampling  data  (Appendix  Tables  2a  and  2b)  in- 
dicate that  the  fourth  assumption,  same  maturi- 
ty schedule  for  marked  and  unmarked  fish,  is 
valid.   Appendix   Tables    la   and    lb   show   the 
validity  of  Assumption  5,  hatcheries  in  a  given 
section   have   the   same   proportion   of  marked 
releases.  Assumption  6,  equality  of  ocean  dis- 
tribution could  not  be  tested  because  regenera- 
tion and  nondetection  of  maxillary  marks  dis- 
torted the  picture. 

A  total  of  179,096  marked  1965-  and  1966- 
brood  coho  salmon  were  estimated  to  have  been 
caught.  An  additional  33,910  marked  coho 
returned  to  study  hatcheries  to  spawn  (Tables 
6a  and  6b).  The  theoretical  estimated  catch 
assuming  no  marking  had  taken  place  was 
2,188,172  coho  and  comprised  about  16.1%  of 
the  total  catch  of  1965-66  brood  coho  in  the  fish- 
eries sampled  (Table  7). 

The  estimated  costs  of  rearing  the  1965  and 
1966  broods  of  coho  salmon  are  $1,292,300  and 
$1,226,600,  respectively.  The  estimated  benefits, 
including  carcass  sales,  received  from  the  har- 
vest of  these  two  broods  of  coho  are  $8,583,625 


158 


and  $9,106,552,  respectively.  The  benefit  to  cost 
ratios  are  then  6.6  to  1  for  the  1965  brood  and 
7.4  to  1  for  the  1966  brood. 

ACKNOWLEDGMENTS 

Many   agencies   and   individuals   assisted   in 
planning  and  implementing  the  hatchery  evalu- 
ation study.  The  Canadian  Government  financed 
and  conducted  a  program  of  mark  sampling  in 
the  British  Columbia  fisheries.  The  State  agen- 
cies  provided   research   and   management   per- 
sonnel   and    necessary   catch   data.    Donald    D. 
Worlund,   National   Marine   Fisheries   Service, 
developed  the  design  of  this  study  and  was  the 
primary       mathematical       consultant.       Jack 
Richards,   National   Marine   Fisheries  Service, 
developed  the  justification  for  the  sport  and  com- 
mercial economic  evaluation.  Robert  C.  Lewis, 
Fish    Commission    of    Oregon,    improved    the 
method    of   amortizing    hatchery    construction 
costs.  Harold  Godfrey,  Fisheries  Research  Board 
of  Canada;  Gary  Finger,  Alaska  Department  of 
Fish  and  Game;  Emanual  A.  LeMier,  Samuel  G. 
Wright,  and  Harry  Senn,  Washington  Depart- 
ment   of   Fisheries;    Fred    E.    Locke,    Oregon 
Game  Commission;  Ernest  R.  Jeffries,  Earl  F. 
Pulford,  and  Roy  E.  Sams,  Fish  Commission  of 
Oregon;  Paul  T.  Jensen,  L.  B.  Boydstun,  and 
William  H.  Sholes,  California  Fish  and  Game 
Department;  Harlan  E.  Johnson  and  Warner  G. 
Taylor,  Bureau  of  Sport  Fisheries  and  Wildlife; 
Arthur  H.  Arp,  Dean  A.  Eggert,  Steven  K.  01- 
hausen,  William  D.  Parente,  Joe  H.  Rose,  and 
Paul    D.   Zimmer,    National    Marine   Fisheries 
Service;  and  many  members  of  their  respective 
agencies  gave  their  time  and  effort.  Helpful  edi- 
torial comments  were  contributed  by  Frederick 
Cleaver,  George  M.  Kaydas,  Richard  T.  Pressey, 
John  L  Hodges,  Kenneth  Henry,  Roger  Pearson, 
and  Paul  Macy,  National  Marine  Fisheries  Ser- 
vice;   and    William    G.    Brown,    Oregon    State 
University. 

LITERATURE  CITED 

Brown,  W.  G.,  and  F.  Nawas. 

In  press.  Effect  of  aggregation  upon  the  estimation  and 
specification  of  outdoor  recreation  demand  function. 
Western  Agric.  Econ.  Assoc,  Annu.  Proc. 
Brown,  W.  G.,  A  Singh,  and  E.  N.  Castle. 

1964.  An  economic  evaluation  of  the  Oregon  salmon 
and  sleelhead  sport  fishery.  Oreg.  State  Univ.,  Agric. 
Exp.  Stn.,  Tech.  Bull.  78,  47  p. 


WAHLE,  VREELAND.  and  LANDER:  BIOECONOMIC  CONTRIBUTION 


C LEAVER,  F. 

1969a.  Recent  advances  in  artificial  culture  of  salmon 

and  steelhead  trout  of  the  Columbia  River.  U.S.  Fish 

Wildl.  Serv.,  Fish.  Leafl.  623,  5  p. 
1969b.    Effects    of   ocean    fishing   on    1961-brood    fall 

Chinook   salmon  from  Columbia   River  hatcheries. 

Fish  Comm.  Oreg.,  Res.  Rep.  1(1):  1-76. 
Fredin,  R.  a. 

1964.  Ocean  mortality  and  maturity  schedules  of  Kar- 
luk  River  sockeye  salmon  and  some  comparisons  of 
marine  growth  and  mortality  rates.  U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  63:551-574. 

Godfrey,  H. 

1965.  Salmon  of  the  North  Pacific  Ocean— Part  IX. 
Coho,  Chinook  and  masu  salmon  in  offshore  waters. 
1.  coho  salmon  in  offshore  waters.  Int.  North  Pac. 
Fish.  Comm.,  Bull.  16:1-39. 

Henry,  K.  A. 

1971.  Estimates  of  maturation  and  ocean  mortality  for 
Columbia  River  hatchery  fall  chinook  salmon  and 
the  effect  of  no  ocean  fishing  on  yield.  Fish.  Comm. 
Oreg.,  Res.  Rep.  3:13-27. 

Johnson,  A.  K. 

1970.  The  effect  of  size  at  release  on  the  contribution 
of  1964-brood  Big  Creek  Hatchery  coho  salmon  to 
the  Pacific  coast  sport  and  commercial  fisheries. 
Fish  Comm.  Oreg..  Res.  Rep.  2(  1  );64-76. 

Lander,  R.  H. 

1970.  Distribution  in  marine  fisheries  of  marked  Chi- 
nook salmon  from  the  Columbia  River  Hatchery 
Program,  1963-66.  Fish  Comm.  Oreg.,  Res.  Rep. 
2(l):28-55. 


Lyles,  C.  H. 

1968.  Fisheries  statistics  of  the  United  States,  1966. 
U.S.  Fish  Wildl.  Serv.,  Stat.  Dig.  60,  676  p. 

1969.  Fisheries  statistics  of  the  United  States,  1967. 
U.S.  Fish  Wildl.  Serv.,  Stat.  Dig.  61,  486  p. 

Mathews,  S.  B.,  and  G.  S.  Brown. 

1970.  Economic  evaluation  of  the  1967  sport  salmon 
fisheries  of  Washington.  Wash.  Dep.  Fish.,  Tech. 
Rep.  2,  19  p. 

National  Marine  Fisheries  Service. 

1971.  Fisheries  statistics  of  the  United  States  1968. 
Stat.  Dig.  62,  576  p. 

RiCKER,  W.  E. 

1962.  Comparison  of  ocean  growth  and  mortality  of 
sockeye  salmon  during  their  last  two  years.  J.  Fish. 
Res.  Board  Can.  19:531-560. 
Riley,  F. 

1970.  Fisheries  of  the  United  States  .  .  .  1969.  U.S. 
Fish  Wildl.  Serv.,  Curr.  Fish.  Stat.  5300,  87  p. 

1971.  Fisheries  of  the  United  States,  1970.  U.S.  Dep. 
Commer.,  Natl.  Ocean.  Atmos.  Admin.,  Natl.  Mar. 
Fish.  Serv.,  Curr.  Fish.  Stat.  5600.  79  p. 

Weber,  D.,  and  G.  J.  Ridgway. 

1967.  Marking  Pacific  salmon  with  tetracycline  anti- 
biotics. J.  Fish.  Res.  Board  Can.  24:849-865. 
Wheeland,  H.  a. 

1972.  Fisheries  of  the  United  States,  1971.  U.S.  Dep. 
Commer..  Natl.  Ocean.  Atmos.  Admin.,  Natl.  Mar. 
Fish.  Serv.,  Curr.  Fish.  Stat.  5900,  101  p. 

Worlund,  D.  D.,  R.  J.  Wahle,  and  P.  D.  Zimmer. 

1969.  Contribution  of  Columbia  River  hatcheries  to 
harvest  of  fall  chinook  salmon  (Oncorhyncluis 
ishawylscha).  U.S.  Fish  Wildl.  Serv.,  Fish.  Bull. 
67:361-391. 


159 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Appendix  Table    la. — Estimated  numbers,  percent  marked,  and  mean  weights  of  1965- 
brood  coho  salmon  released  from  study  hatcheries. 


Hatchery  group 

and 
s )  mark 

Number  of  fish 

Percent 
marked 

Mean         , 
weight^-' 

(in  parenthese 

Marked 

Unmarked 

Total 

Lower  River   (Ad- 

RM) 

Elokomin 

118,137 

1,170,725 

1,288,862 

0.0917 

11+ 

Big  Creek 

164,759 

1,363,618 

1,528,377 

0.1078 

29 

Grays  River 

106,986 

91+6,1+1+1 

1,053,1+27 

0.1016 

23 

KLaskanine 

118,1+12 

1,190,010 

1,308,1+22 

0.0905 

33 

Total  Ad-RM 

508,291+ 

l+,670,79'+ 

5,179,088 

0.0981 

25 

Middle  River   (Ad 

) 

Bonneville 

81,1+02 

786,1+25 

867,827 

0.0938 

22 

Washougal 

21+5,1+89 

2,152,336 

2,397,825 

O.IO2I+ 

21+ 

Sandy                 , 
Eagle  Creek-/ 
Lewi si/ 

85,871 

868,250 

95l+,121 

0.0900 

27 

69,988 

610,113 

680,101 

0.1029 

16 

65,i+53 

61+9,1+90 

71l+,9l+3 

0.0915 

28 

Kalama  Falls 

11+8,21+2 

l,l+3l+,022 

1,582,261+ 

0.0937 

27 

Lower  Kalama 

37,069 

315,1+63 

352,532 

a.  1052 

27 

Toutle 

112,160 

1,079,261 

1,191,1+21 

0.091+1 

25 

Total  Ad 

81+5,671+ 

7,895,360 

8, 7^1 '031+ 

0.0967 

19 

Upper  River   (Ad- 

LM) 

KLickitat 

1,  / 

11+6,123 

1,365,131+ 

1,511,257 

0.0967 

16 

Little  White  Salmon^ 

357,^+07 

3,290,31+8 

3,61+7,755 

0.0980 

15 

Willard 

-- 

— 

-- 

— 

19 

Carson, 
OxBow^/ 

158,868 

l,i+77,931 

1,636,799 

0.0971 

15 

^+7,578 

l+2l+,892 

1+72,1+70 

0.1007 

29 

Cascade 

127,853 

1,112,231+ 

1,21+0,087 

0.1031 

26 

Total  Ad-LM 

837,829 

7,670,539 

8,508,368 

0.0985 

19 

Uppermost  River 

(D-Ad) 

Leavenworth 

l0l,73it 

1+02,272 

50l+,006 

0.2018 

25 

TOTAL  ALL  HATCHERIES 

2,293,531 

20,638,965 

22,932,1+96 

0.1000 

-- 

1/ 

i 


Mean  weights  in  grams  per  fish.   Values  in  total  lines  are  averages  weighted 

by  total  release  at  each  hatchery  In  that  river  section. 

Additional  70,198  fish  released  with  LM  mark. 

Includes  release  from  Speelyai  hatchery. 

Includes  release  from  Willard  hatchery. 

Released  from  Bonneville  hatchery. 


160 


WAHLE,  VREELAND,  and  LANDER;  BIOECONOMIC  CONTRIBUTION 
Appendix  Table 


lb. — Estimated  numbers,  percent  marked,  and  mean  weights  of  1966- 
brood  coho  salmon  released  from  study  hatcheries. 


Hatchery  group  and 

Number  of  fish 

Percent 
marked 

Mean    , 
weigh ti/ 

(in  parentheses)  mark 

>ferked 

Unmarked 

Total 

Lower  River  (Ad-RM) 

Elokomin 
Big  Creek 
Grays  River 
Klaskanine 
Total  Ad-RM 

85,319 

122,552 

60,852 

116,907 
385,630 

761,349 
1,159,780 

530,173 
1,118,505 
3,569,807 

846,668 
1,282,332 

591,025 
1,235,1+12 
3,955,437 

0.1008 
0.0956 
0.1030 
0.0946 
0.0975 

28 
23 
27 
28 
2E 

Middle  River  (Ad) 

Bonneville 
Washougal 
Sandy       , 
Eagle  Creek^ 
Lewis^Z 
Kalama  Falls 
Lower  Kalama 
Toutle 
Total  Ad 

146,457 
85,741 
98,702 

130,384 
85,442 
85,022 
38,792 
93,722 

764,262 

1,361,388 
769,789 
920,106 

1,028,499 
882,958 
789,515 
357,123 
856,325 

6,965,703 

1,507,845 
855,530 

1,018,808 

1,158,883 
968,400 
871+,  537 
395,915 
950,047 

7,729,965 

0.0971 
0.1002 
0.0969 
0.1125 
0.0882 
0.0972 
0.0980 
0.0986 
0.0989 

24 

25 
22 
20 

27 
28 

27 
24 
2H 

Upper  River  (Ad-LM) 

Klickitat         ,  , 
Little  White  Salmon-^ 
Willard 

79,864 
369,935 

770,023 
3,339,807 

849,887 
3,709,742 

0.0940 
0.0997 

28 
20 
17 

Carson?/ 

-- 

~ 

— 

— 

~ 

OxBow2/ 
Cascade 

Total  Ad-LM 

43,311 
493,110 

434,846 

i+78,157 
5,037,786 

0.0905 
0.0979 

23 
20 

Uppermost  River  (D-Ad-RM, 

D-Ad-LM^ ) 

Leavenworth 
LeavenworthE/ 

78,092 
96,643 

269,355 
466 

347,447 
97,109 

0.2248 
0.9952 

23 
23 

TOTAL  ALL  HATCHERIES 

1,817,737 

15,350,007 

17,167,7'+'+ 

0.1059 

— 

1/ 

I 


Mean  weights  in  grams  per  fish.   Values  in  total  lines  are  averages  weighted 

by  total  release  at  each  hatchery  in  that  river  section. 

Additional  126,323  fish  released  with  LM  mark,  87,733  released  with  An  mark, 

and  127,514  released  with  RM  mark. 

Includes  release  from  Speelyal  hatchery. 

Includes  releases  from  Willard  hatchery. 

Honpartlclpating  for  I966  brood. 

Released  below  Bonneville  Dam. 


161 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Appendix   Table   2a. — Number  of  marked   and  unmarked    1965-brood  coho  salmon 
recovered  at  hatcheries  in  each  section  ot  the  Columbia  River  in  1967  and  1968. 


Recovery  location, 
by  hatchery 


Marked  and 
unmarked 


Origin 


Middle  River- -Continued 
Lewis  River 

Kalama  Falls 

Lower  Kalama 

Toutle 


Unmarked 

-- 

Ad-LM 

Upper  river 

Ad 

Lewis 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Kalama  Falls 

Ad-RM 

Lower  river 

Unmarked 

-_ 

Ad-LM 

Upper  river 

Ad 

Lower  Kalama 

Ad-RM 

Lower  river 

Unmarked 
Ad-LM 

Upper  river 

Ad 

Toutle 

Ad-RM 

Lower  river 

Upper  River 


Year  of  return 


1,072 

0 

88 

0 

1,891+ 

0 

235 

0 

1,176 

0 

107 

0 

10,1+51 

0 

865 

0 

521+ 
0 

89 
0 

1,915 

0 

227 

0 

l+,i+17 

0 

1+16 

0 

2l+,931 

0 

2,030 

0 

Klickitat 

Unmarked 

— 

916 

1,398 

Ad-LM 

Klickitat 

1+1 

117 

Ad 

Mid  river 

6 

27 

Ad-RM 

Lower  river 

0 

0 

Little  White  Salmon 

Unmarked 

__ 

1,0U1+ 

5,1+03 

Ad-LM 

Little  White  Salmon 

1+6 

1+19 

Ad 

Mid  river 

8 

58 

Ad-RM 

Lower  river 

0 

0 

OxBow 

■   Unmarked 

__ 

■(♦) 

103 

Ad-LM 

OxBow 

(») 

3 

Ad 

Mid  river 

(*) 

2 

Cascade 

Unmarked 

„_ 

7,21+7 

7,227 

Ad-LM 

Cascade 

5I+9 

576 

Ad 

Mid  river 

1+1+ 

IOI+ 

Ad-RM 

Lower  river 

5 

21 

roermost  River 

Leavenworth 

Unmarked 

__ 

310 

1,81+9 

D-Ad 

Leavenworth 

38 

138 

♦Returns  not  examined. 


162 


WAHLE.  VREELAND.  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Appendix  Table  2a. — Continued. 


Recovery  location, 
by  hatchery 


Marked  and 
unmarked 


Origin 


Year  of  ret ur n 
"I96B      1969" 


Middle  Rlver--Contlnued 
Lewis  River 

Kalama  Falls 
Lower  Kalama 
Toutle 


Upper  River 
Klickitat 

Little  White  Salmon 


Cascade 

Uppermost  River 
Leavenworth 


Unmarked 

-- 

Ad-LM 

Upper  river 

Ad 

Lewis  River 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Kalama  Falls 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Lower  Kalama 

Ad-RM 

Lower  river 

Unmarked 

-_ 

Ad-LM 

Upper  river 

Ad 

Toutle 

Ad-RM 

Lower  river 

Unmarked 

-- 

Ad-LM 

Klickitat 

Ad 

Mid  river 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Little  White  Salmon 

Ad 

Mid  river 

Ad-RM 

Lower  river 

Unmarked 



Ad-LM 

Cascade 

Ad 

Mid  river 

Ad-RM 

Lower  river 

Unmarked 
D-Ad 
D-Ad-LM 
D -Ad-RM 


1,911 

0 

233 

0 

1,592 

0 

148 

0 

1,887 

0 

192 

0 

0 

200 

0 


2,91+5 

0 

302 

0 

10,696 
0 

888 

1 

2,739 

1 

263 

1 

23,664 

0 

2,093 

0 


Leavenworth 
Leavenworth 
Leavenworth 


181 

1,347 

15 

163 

2 

13 

0 

0 

5,036 

8,131 

341 

666 

kh 

105 

1 

2 

2,144 

1,374 

146 

83 

41 

22 

3 

14 

69 

32 

1 

0 

7 

0 

0 

0 

163 


FISHERY  BULLETIN:  VOL    72.  NO.  1 


Appendix   Table   2b. — Number  of  marked   and   unmarked    1966-brood  coho  salmon 
recovered  at  hatcheries  in  each  section  of  the  Columbia  River  in  1968  and  1969. 


Recovery  location, 
by  hatchery 


Marked  and 
unmarked 


Origin 


Year  of  return 
1968      1969 


)wer  River 


Elokomln 

Unmarked 

-- 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Elokomin 

Big  Creek 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Big  Creek 

Grays  River 

Unmarked 

.. 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Grays  River 

KLaskanine 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Klaskanlne 

ddle  River 
Bonneville 

Washougal 

Sandy 

Eagle  Creek 


Unmarked 

-- 

Ad-LM 

OxBow 

Ad 

Bonneville 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Washougal 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Sandy 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Eagle  Creek 

Ad-RM 

Lower  river 

LM 

Eagle  Creek 

4,527 

3 

2 

280 

6,316 

1 

10 

532 

5,682 

0 

0 

430 

7,719 
0 

5 

489 

5,375 
0 
0 

518 

5,310 

2 

10 

516 

0,473 

0 
0 

788 

2,623 

0 

0 

172 

7,034 

90 

585 

26 

3,115 
148 

567 

24 

2,204 

0 

237 

0 

9,060 
0 

1,033 
7 

4,134 

27 

422 

20 

3,079 

11 

267 

13 

929 

2 

85 

1 
77 

1,799 
0 

191 
0 

221 

164 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Appendix  Table  2b. — Coniiiuicd 


Recovery  location, 
by  hatchery 


Marked  and 
unmarked 


Origin 


Year  of  return 

TgEi  19SB" 


ower  River 


Elokomin 

Unmarked 

-- 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Elokomin 

Big  Creek 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Big  Creek 

Grays  River 

Unmarked 

._ 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Grays  River 

ICLaskanine 

Unmarked 

-_ 

Ad-LM 

Upper  river 

Ad 

Mid  river 

Ad-RM 

Klaskanlne 

Iddle  River 
Bonneville 

Washougal 

Sandy 

Eagle  Creek 


Unmarked 

— 

Ad-LM 

OxBow 

Ad 

Bonneville 

Ad-RM 

Lower  river 

Unmarked 
Ad-LM 

Upper  river 

Ad 

Washougal 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Sandy 

Ad-RM 

Lower  river 

Unmarked 

__ 

Ad-LM 

Upper  river 

Ad 

Eagle  Creek 

Ad-RM 

Lower  river 

LM 

Eagle  Creek 

533 

0 

0 

1+1 

1,616 
0 

3 
105 

10,51+0 

0 

26 

936 

10,573 
0 

5 
1,079 

1,363 

3 

1+1 

1+0 

2,651 
0 
0 

213 

7,201 

0 

0 

527 

l+,l5l 
0 

1 

365 

7,1+01 

1+68 

188 

5 

16,602 

735 

787 

1+1+ 

22,098 

0 

2,651 

0 

1+3,261+ 

3 

'+,316 

3 

6,021 

18 

661+ 
11+ 

5,222 

21+ 

517 

32 

593 

0 

63 

0 

2,371 

5 

222 

2 

58 

215 

165 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Appendix  Table  3. — Percentage  of  iwo-year-old  coho  salmon  in  the 
marked  and  unmarked  returns  to  Columbia  River  hatcheries  by  river 
section  and  brood  vear,  1965-66. 


River  section  and 

Percent 

of 

2-year-olds 

(in  parentheses)  mark 

Brood 

Marked 

Unmarked 

Lower  (Ad-RM) 

1965 

hi 

51 

1966 

3h 

3h 

Middle  (Ad) 

1965 

32 

29 

1966 

27 

28 

Upper  (Ad-LM) 

1965 

36 

ko 

1966 

36 

1^0 

Appendix  Table  4. — Actual  number  of  marked  coho  salmon  of  the  1966  brood  from  Leavenworth  National 
Fish  Hatchery  recovered — by  type  of  mark,  year  of  recovery,  region  of  capture,  and  type  of  fishery,  1968-69. 


Region 


Fishery  type 


D-Ad 


D-Ad-RM 


D-Ad 


■U^ 


Total 


1968   1969   1968  1969   1968   1969   1968   1969 


British  Columbia. 
Washington 

Oregon 

California 

Columbia  River... 

Total . . . 


Commercial. . . . 

Sport 

Commercial. . . . 

Sport 

Commercial . . . . 

Sport 

Commercial. . . . 

Sport 

Commercial. . . . 

All  fisheries. 


0 
0 

0 
0 

0 
0 

0 
3 


18 
30 

20 
3^+ 

2 
19 

0 
2 


0 
0 

0 
0 

0 
0 

0 
0 


5 

7 

5 
32 


0 

15 


0 
0 

0 
0 

0 
0 

0 
0 


29 
30 

6 

52 

3 

13 

0 
33 


0 
0 

0 
0 

0 
0 

0 
3 


52 

67 

31 
118 

6 

1+0 

0 

50 


125 


73 


167 


365 


1/  Released  below  Bonneville  Dam. 


166 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Appendix  Table  5a. — Estimated  number  of  marked  coho  salmon  of  the  1966  brood  from  Leavenworth  National 
Fish  Hatchery  recovered  —  by  type  of  mark,  year  of  recovery,  region  of  capture,  and  type  of  fishery,  1968-69. 


Region 


Fishery  type 


D-Ad 


D-Ad-RM 


D-Ad 


■U^ 


Total 


1968   1969   1968   1969   1968   1969   1968    1969 


British  Columbia. 
Washington 

Oregon 

California 

Columbia  River... 

Total . . . 


Commercial. . . . 

Sport 

Commercial. . . . 

Sport 

Commercial. . . . 

Sport 

Commercial. . . . 

Sport 

Commercial. . . . 

All  fisheries. 


0 
0 

0 
0 

0 
0 

0 
6 


123 

lilt 
184 

7 
137 

0 
7 


0 
0 

0 
0 

0 
0 

0 
0 


23 
30 

15 
176 

2 
35 

0 

90 


0 
0 

0 
0 

0 
0 

0 

0 


131 
128 

19 
285 

Ik 
52 

0 

186 


0 
0 

0 
0 

0 
0 

0 
6 


242 
281 

lk8 
645 

23 
224 

0 
283 


660 


371 


822 


1,853 


1/     Released  below  Bonneville  Dam. 


Appendix  Table  5b. — Estimated  recovery  of  D-Ad-RM  and  D-Ad-LM  marked  1966-brood  coho  salmon  from 
Leavenworth  National  Fish  Hatchery  after  redistribution  of  the  D-Ad-only  marks. 


i^^ 


Region 


Fishery  type 


D-Ad-RM 


D-Ad' 


Total 


1968   1969   1968    1969    1968    1969 


British  Colvunbia. 
Washington 

Oregon 

California 

Columbia  River. . . 

Total . . . 


Commercial 

Sport 

Commercial 

Sport 

Commercial 

Sport 

Commercial 

Sport 

Commerc  ial 

All  fisheries. . 


71 
96 

77 
275 

6 
109 

0 

94 


0 
0 

0 
0 

0 
0 

0 
3 


171 

185 

0 
0 

71 
370 

0 
0 

17 
115 

0 
0 

0 

189 

0 
6 

242 
281 

148 
645 

23 
224 

0 

283 


728 


1,125 


1,853 


1/  Released  below  Bonneville  Dam. 


167 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Appendix  Table  6. — Relative  survival  of  marked  1965-  and  1966-brood  coho  salmon 

by  mark  type  and  hatchery  groups. 


Cascade, 

Tetracycline 

Little  White, 

All 

Brood 

Mark 

group 

Klaskanine 

hatcheries 

1965 


Ad-LM 

Ad 

Ad-RM 


1966 


Ad-LM 

Ad 

Ad-RM 


- 

.69^ 

.69^ 

^ 

— 

.9^ 

^ 

.79^ 

•  79 

_ 

.683/ 

•  72 

3^/ 



.89^ 

^ 

.1^ 

.72 

1/  Eagle  Creek  National  Fish  Hatchery. 

2/  Big  Creek  Salmon  Hatchery. 

3/  Cascade   Salmon  Hatchery,   Little  White  Salmon  National  Fish  Hatchery. 

\J  Klaskanine  River  Salmon  Hatchery. 

5/  Klickitat  State  Salmon  Hatchery,   Cascade  Salmon  Hatchery,    Little  White  Salmon 

National  Fish  Hatchery. 

6/  Bonneville  Salmon  Hatchery  returns  not   included  in  calculations . 


Appendix  Table  7. — Estimated  catch  of  unmarked    1965-  and    1966-brood  hatchery  coho  salmon  by 

region,  fishery  type,  brood  year,  and  year  of  capture. 


Region 


Fishery  type 


1967 


1965  brood 


1968 


Total 


1968 


1966  brood 


1969 


Total 


Ocean  fisheries: 

British  Columbia... 
Washington 

Oregon 

California 

Subtotal 

Freshwater  fisheries: 
Columbia  River 

Total 


Commercial 

Sport 

Commercial 

Sport 

Commercial 

Sport 

Commercial 


Sport 

Commercial 


Sport 

Commercial. . . 


3,928 
1,733 


80,101 

163,997 
203,620 

93,759 

270,127 

7,878 

102,523 


0     265,634 
0     656,371 


3,21+6 
7't,5't8 


80,101 
163,997 
203,620 

93,759 

270,127 

7,878 

102,523 


265,634 
656,371 


7,174 
76,281 


0 

0 
0 
0 
0 
0 
0 


34,981 
153,837 
122,210 

86,658 

298,453 

7,529 

77,724 


0   248,024 
0  533,368 


6,516       4,771 

2,775   136,057 


34,981 
153,837 
122,210 

86,658 

298,453 

7,529 

77,724 


248,024 
533,368 


11,287 
138,832 


All  fisheries   5,66l   999,799   1,005,460   9,291   922,220   931,511 


168 


WAHLE,  VREELAND,  and  LANDER:  BIOECONOMIC  CONTRIBUTION 

Appendix  Table  8. — Estimated  total  catch  of  1965-  and   1966-brood  hatchery  echo  salmon  by  region,  fishery 

type,  brood  year,  and  year  oF  capture. 


Region 


Fishery  type 


1967 


1965  brood 


1968 


Total 


1968 


1966  brood 


1969 


Total 


Ocean  fisheries: 

British  Columbia. . . . 
Washington , 

Oregon 

California 

Subtotal 

Freshwater  fisheries: 
Columhia  River 

Total 


Commercial 

Sport 

Coramerc  ial 

Sport 

Commercial 

Sport 

Commercial 


Sport 

Commercial 


Sport 

Commercial. . 


4,297 
1,872 


87,526 

179,179 
222,405 
102,614 
294,778 
8,556 
111,592 


290,349 
716,301 


3,552 
81,364 


87,526 
179,179 
222,405 
102,614 
294,778 
8,556 
111,592 


290, 349 
716,301 


7,849 
83,236 


38,313 
167,91^+ 
133,536 

94,994 

326,241 

8,259 

85,165 


7,133 
3,021 


271,167 
583,255 


5,223 
148,533 


38,313 
l67,91i^ 
133,536 

94,99^ 
326,241 

8,259 
85,165 


271,167 
583,255 


12,356 
151, 55^+ 


All  fisheries       6,169       1,091,566       1,097,735       10,154       1,008,178       1,018,332 


Appendix  Table  9. — Estimated  1967-69  sport  catch  in  Columbia  River  tributaries  (where  no  creel 
census  was  made)  of  1965-  and  1966-brood  hatchery  coho  salmon. 


1965  brood 

1966  brood 

Estimation 

stream 

1967 

1968 

Total 

1968 

1969 

Total 

method 

Icicle  River 

50 

15 

65 

10 

10 

20 

1/ 

Klickitat  River 

5 

6 

11 

5 

0 

5 

2/ 3/y 

Little  White  Salmon  R. 

m 

8 

119 

7 

2 

9 

2/3/5/ 

Wind  River 

2 

0 

2 

— 

— 

-- 

2/ 3/y 

Washougal  River   (upper) 
(lower ) 

10,382 
1,385 

2,048 
273 

12,430 
1,658 

2,493 
332 

872 
116 

3,365 
448 

i/ 3/ 5/ 
i/3/1/ 

Elokomln  River 

59 

75 

134 

92 

115 

207 

2/3/4/ 

Grays  River 

10 

218 

228 

265 

213 

478 

2/3/v 

Sandy  River 

513 

944 

l,i*57 

l,i+57 

1,198 

2,655 

3/i±/6/ 

Eagle  Creek   (Clackamas) 

928 

1,709 

2,637 

\,lkk 

1,1+33 

3,177 

3/4/6/ 

Big  Creek 

4lO 

l^h 

1,164 

603 

496 

1,099 

3/V6/ 

KLaskanine  River 

53it 

983 

1,517 

1,31+6 

1,106 

2,452 

3/5/6/ 

TOTAL 

l'+,389 

7,033 

21,422 

8,35lt 

5,561 

13,915 

1/     Estimates  from  discussions  with  Gene  Nye,  Washington  Department  of  Fisheries,   and  local 

fishery  personnel. 
2/     Catches  from  Washington  Department   of  Fisheries  punch  card  returns  1967-1969- 
3/     Age  groups  broken  down  by  using  jack  to  adult  ratios   obtained  in  creel  census  on  Lewis, 

Kalama,    Cowlitz,   and  Toutle  Rivers. 
4/     70?^  of  catch  apportioned  to  hatchery  production. 
5/     Entire  catch  assumed  hatchery. 
5/     Catches  from  Oregon  State  Game  Commission  punch  card  returns  I967-I969. 


169 


ABILITY  OF  MALE  KING  CRAB,  PARALITHODES  CAMTSCHATICA, 
TO  MATE  REPEATEDLY,  KODIAK,  ALASKA,  1973 

Guy  C.  Powell.'  Kenneth  E.  James.-  and  Charles  L.  Hurd'' 


ABSTRACT 

An  experiment  lo  test  abilities  of  male  king  crab  to  mate  repeatedly  in  an  environment 
approximating  natural  conditions  was  conducted  during  the  spring  of  1970.  Twenty-four  males 
of  varying  size  and  shell  age  were  placed  into  separate  undersea  compartments  for  intervals 
up  to  56  days  with  222  females.  The  ability  of  males  to  mate  repeatedly  was  determined  by 
introducing  females  in  mating  condition  to  males  at  the  rate  of  one  every  5  days. 

No  difference  in  mating  capabilities  of  males  of  different  types  was  evident  until  after  expo- 
sure to  seven  females.  At  this  point  egg  fertility  and  relative  fullness  of  brood  chamber  of  the 
females  mated  to  the  small  old-shell  males  decreased  significantly.  Large  new-shell  males 
showed  a  marked  decline  in  mating  ability  after  the  ninth  mating.  One  small  new-shell  male 
mated  with  13  females. 


Owing  to  declining  stocks  within  the  Kodiak 
Island  fishery,  commercial  harvest  of  king  crab 
has  declined  from  96  to  11  million  pounds  over 
the  past  seven  years.  1965-1971.  To  determine 
the  level  of  king  crab  brood  stocks  necessary  for 
perpetuation  of  a  maximum  sustained  yield  fish- 
ery, the  reproductive  capabilities  of  the  king 
crab  are  being  studied  in  detail. 

In  1964,  biologists  of  the  Alaska  Department 
of  Fish  &  Game  determined  experimentally  that 
recently-molted  sublegal  (smaller  than  146  mm 
carapace  length)  male  king  crabs  were  capable 
of  mating.  Eleven  males  ranging  from  120  to 
144  mm  carapace  length  mated  51  females  in  16 
days  (Powell  and  Nickerson.  1965).  Observa- 
tions on  individual  males  were  not  obtained.  In 
1971.  males  as  small  as  85  mm  carapace  length 
were  found  to  be  capable  of  mating  (Powell. 
Shafford.  and  Jones,  1972).  Of  3.402  males  ob- 
served mating  in  nature  from  1963  to  1971.  how- 
ever, only  two  were  smaller  than  100  mm 
(Powell.  Rothschild,  and  Buss^). 


'  Alaska  Dept.  of  Fish  &  Game,  Commercial  Fisheries 
Div.,  Box  686,  Kodiak,  AK  99615. 

-  Bio-Statistics  Div.,  Dept.  of  Preventive  Medicine, 
Stanford  University  Medical  Center,  Stanford.  CA  94305. 

■'  Alaska  Dept.  of  Fish  &  Game.  Commercial  Fisheries 
Div..  Box  234.  Homer,  AK.  99603. 

*  Powell,  Guy  C.  Brian  J.  Rothschild,  and  James  A. 
Buss.  1972.  A  study  of  king,  ParaUthodcs  canushaiica 
(Tilesius)  brook  stocks,  Kodiak  Island,  Alaska,  1963-1971. 
30  p.  (Processed) 


Several  authors  have  reported  old-shell  males 
congregated  with  adult  females  during  the  mat- 
ing season  and  indicated  they  may  be  capable 
breeders  because  new-shell  males  were  separate 
from  the  females  at  the  time  (Gray  and  Powell, 
1966;  Miyahara  and  Shippen,  1965). 

Currently  the  reproductive  success  or  failure 
of  any  particular  brood  year  is  not  readily  appar- 
ent until  approximately  8  yr  later  when  males 
are  entering  the  fishery.  At  this  late  date,  it  is 
doubtful  that  we  can,  with  any  precision,  eval- 
uate the  degree  to  which  each  of  the  limiting 
factors  contributes  to  the  success  or  failure;  con- 
sequently we  are  unable  to  determine  if  resul- 
tant abundance  levels  are  attributable  to  initial 
magnitude  of  egg  production,  environment,  or 
effects  of  commercial  fishing. 

Prior  to  1970,  managers  assumed  that  any 
level  of  harvest  of  males  was  acceptable  as  long 
as  the  7-inch  size  limit  (carapace  width  outside 
spines)  was  observed. 

In  recent  years,  we  observed  that  the  propor- 
tion of  adult  females  without  eggs  and  with 
partial  broods  had  increased  and  that  some  of 
the  female  population  was  not  being  serviced 
(unpublished  Alaska  Department  of  Fish  & 
Game  data).  Large  adult  females  have  approxi- 
mately nine  times  more  eggs  than  small  ones 
(Haynes.  1968)  and  initial  examination  of  un- 
published Department  of  Fish  &  Game  data 
reveals  that  the  incidence  of  adults  without  eggs 
and  with  partial  broods  is  greater  among  the 


Accepted  tor  publication  June  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO.  1.  1974 


171 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


larger  individuals.  In  order  to  place  more  males 
on  the  mating  grounds  and  to  stabilize  annual 
harvests,  a  quota  system  was  initiated  in  1970. 

It  is  important  to  know  whether  that  segment 
of  the  male  population  harvested  by  the  commer- 
cial fishery,  i.e.,  large  males  and  old-shell  males 
(Nickerson,  Ossiander,  and  Powell.  1966)  pos- 
sess greater  mating  capabilities  than  smaller 
protected  males  which  molt  during  the  mating 
season.  Also  of  significance  is  the  question  of 
whether  undersized  males  would  be  adequate  in 
numbers  and  ability  to  mate  all  females  if  larger 
males  were  removed  by  the  fishery.  Recent  in- 
creases in  the  numbers  of  adult  females  with 
broods  of  reduced  size  appear  related  to  simul- 
taneous increased  exploitation  rates  and  may 
result  from  matings  with  males  which  had 
mated  several  times  previously.  Our  experiment 
was  designed  to  gain  insight  into  these  phenom- 
ena and  to  obtain  more  complete  data  for 
individual  males,  especially  comparative  data 
on  mating  ability  for  old-shell  males  and  recently 
molted  new-shell  males. 

In  this  paper,  mating  refers  to  the  actual  fer- 
tilization of  the  eggs.  Hence,  the  term  "mating 
capability"  refers  to  the  ability  of  the  male  to 
fertilize  the  eggs  of  the  females  to  which  he  is 
exposed. 

METHODS  AND  MATERIALS 

Experimental  Equipment  and  Location 

The  experiment  was  conducted  in  undersea 
l^ens,  the  sides  and  top  of  which  were  covered 
with  nylon  mesh;  the  bottoms  were  open  to 
allow  crabs  to  dig  in  the  substrate  as  they  would 
do  in  nature.  Each  pen  was  8'  X  8'  X  4'  and  each 
divided  into  four  equal  sized  compartments. 
Compartments  were  numbered  1  through  28  and 
situated  in  40  ft  of  water  on  a  level  stretch  of 
muddy-sand  bottom  east  of  Near  Island  adjacent 
to  an  area  where  king  crabs  normally  mate.  The 
study  location  is  one  mile  from  the  city  of 
Kodiak,  Alaska.  Pens  were  designed  and  located 
to  simulate  natural  conditions.  Environmental 
factors  such  as  daily  tidal  currents,  pressures, 
light  intensities,  temperatures,  and  salinities 
were  considered  important  in  that  they  might  in- 
fluence mating.  For  this  reason,  undersea  pens 
were  considered  superior  to  aquaria. 

The  mating  study  was  conducted  in  compart- 
ments 1  through  24  while  25  through  28  were 


used  to  store  crabs.  Females  were  held  in  storage 
prior  to  and  after  the  completion  of  mating. 

Fishery  biologists  and  trained  technicians 
utilizing  scuba  observed  the  crabs  underwater 
every  day.  Individual  crabs  were  identified  by 
tagging  with  permanent  "isthmus"  loop  tags 
(Gray,  1965)  prior  to  being  placed  in  the  pens. 


Experimental  Procedures 

The  experiment  was  designed  to  compare 
mating  capabilities  of  four  size  shell-age  classes 
of  male  king  crabs  (small  new-shell,  small  old- 
shell,  large  new-shell,  and  large  old-shell)  by 
studying  the  effects  of  repeated  matings  on  the 
ability  of  these  males  to  mate  successfully  with 
additional  females.  A  5-mm  range,  145-149,  was 
used  as  a  dividing  ])oint  between  small  and 
large  males  at  the  juncture  of  legal  and  under- 
size  crabs.  Those  144  mm  or  less  (commercially 
undersize  males)  were  classified  as  small  while 
those  150  mm  or  larger  were  classified  as  large 
(Table  1).  Small  males  averaged  140  mm,  large 
males  167. 

Most  males  used  in  the  experiment  were 
captured  by  scuba  divers.  A  few  of  the  males  of 
required  size,  however,  were  not  available  by 
diving  (the  preferred  method  of  collecting)  and 
therefore  were  taken  from  the  catches  of  com- 
mercial pots  and  trawls. 

All  females  used  in  the  study  were  in  premolt 
condition  and  were  in  the  pre-copulatory  em- 
brace (Powell  and  Nickerson,  1965):  i.e.,  they 
had  already  been  selected  for  mating  by  males 
in  the  natural  environment.  The  use  of  these 
females  (called  "graspees")  was  our  method  of 
insuring  that  females  were  ready  to  mate  with 
males  when  introduced  into  the  ])ens.  Females 
from  natural  mating  areas  near  the  pens  were 
captured  by  scuba  divers  a  day  or  two  before 
they  were  needed  and  ranged  in  length  from  104 
to   181  mm,  with  an  average  size  of  134  mm. 

Table  1. — Size  relationships  of  experimental  crabs. 


No.  of 


Coropoce  length  (mm) 


Mole  king  crabs 

female 
partners 

Range                   Meon 

Class 

Number 

Male    Female    Male    Female 

Small  old-shell 

4 

29 

136-144   107-181     142         133 

Large  old  -shell 

9 

82 

156-193    1  14-175     178         134 

Small  new-shell 

4 

35 

136-142   1 15-150     139         135 

Large  new -shell 

10 

76 

150-168   104-160     158         134 

Total 

27' 

222 

Three  extra  males  replaced  three  original  males  which  died. 


172 


POWELL.  JAMES,  and  HURD:  MATING  ABILITY  OF  MALE  KING  CRAB 


Females  were  separated  from  the  males  which 
held  them  and  placed  in  storage  ready  for  use 
in  the  experiment.  The  average  length  of  females 
increased  as  the  study  progressed  because  older 
females  mate  later  in  the  season. ^  Females  cap- 
tured 15  March  through  15  April  averaged  128 
mm.  while  those  captured  20  April  to  20  May 
averaged  140. 

Twenty-four  females  were  paired  randomly 
with  the  24  males  in  the  pens  at  the  beginning 
of  each  of  the  14  separate  5-day  periods  begin- 
ning 16  March  and  continuing  through  24  May. 
On  days  when  a  complete  set  of  24  females  could 
not  be  captured,  those  which  had  been  were  in- 
troduced to  males  which  previously  had  had  the 
largest  number  of  female  partners.  Incomplete 
sets  of  females  exist  for  early  and  late  spawning 
periods — 1,  2,  3,  12,  13,  and  14 — when  mating 
crabs  were  relatively  scarce.  In  addition,  12  fe- 
males escaped  from  six  compartments  on  9  May 
when  two  pens  were  accidentally  lifted;  as  many 
as  three  females  were  lost  from  a  single  com- 
partment. During  the  middle  of  the  mating  sea- 
son, 31  March  through  5  May,  females  were 
abundant;  consequently  each  male  received  a 
female  for  each  of  the  eight  consecutive  periods 
within  this  interval.  Females  were  introduced 
to  males  as  soon  after  capture  as  possible;  none 
were  held  more  than  two  days  and  many  were 
introduced  the  same  day. 

Females  were  left  with  males  until  mating 
was  completed  and  eggs  were  known  to  be  fer- 
tilized; consequently  males  commonly  shared 
their  compartments  with  several  females  at  a 
time.  Approximately  10  days  after  eggs  were 
deposited  on  the  pleopods,  a  sample  of  approxi- 
mately 1,000  was  obtained  from  each  female  to 
determine  success  of  fertilization.  Each  sample 
consisted  of  several  separate  groups  of  eggs 
taken  from  scattered  locations  within  the  egg 
mass.  Samples  were  preserved  in  Bouin's  solu- 
tion. Fertilized  eggs  developing  for  7  to  10  days 
at  approximately  37 °F  showed  cleavage  when 
viewed  microscopically.  When  eggs  were  known 
to  be  fertilized  (i.e.,  advanced  cleavage  stages 
observed),  females  were  separated  from  their 
experimental  male  partners  and  placed  in  stor- 
age compartments  25-28. 


Divers  made  observations  at  daily  intervals 
recording  data  on  underwater  slates.  Observa- 
tions included  collecting  and  measuring  shed 
exoskeletons  to  determine  day  of  molting,  exam- 
ining recently-molted  females  to  determine  rela- 
tive fullness  of  the  brood  chamber,  and  recording 
activities  of  mating  and  feeding. 

RESULTS 

Relative  success  of  male  copulation  was 
measured  in  two  ways.  First,  relative  fullness 
of  brood  chamber  was  determined  subjectively 
by  visually  deciding  what  proportion  of  the 
brood  chamber  was  filled  with  eggs  and  record- 
ing same  on  a  scale  of  zero  to  one  hundred  (Table 
2).  The  second,  percent  of  eggs  fertilized,  was 
determined  in  two  steps;  (1)  a  prompt  micro- 
scopic viewing  of  several  hundred  eggs  to  obtain 
quick  estimates,  followed  later  by  (2)  a  careful 
microscopic  examination  of  100  eggs  (Table  3). 

Both  measures  of  mating  success  provided 
compatible  results  and  revealed  that  infertile 
eggs  are  scattered  throughout  the  egg  mass 
rather  than  being  grouped  separately  from  fer- 
tile eggs. 

The  raw  data,  ij,  for  each  of  the  two  measure- 
ment variables  were  transformed  so  that  they 
would  be  more  normally  distributed,  using  the 
formula:'' 


z  =  y/n  +  1/2  sin 


-1/v  +  3/8* 


n  +  3/4 


In  this  case,  n  is  equal  to  100,  since  both 
methods  of  measurement  are  based  on  a  scale  of 
100. 

A  covariance  analysis  was  performed  relating 
z  to  X.  the  number  of  females  mated.  This 
analysis  fits  a  least  squares  regression  line  z  — 
0/  -I-  b,-  X  for  each  of  the  four  groups,  where  a,-, 
bj  represent  the  intercept  and  slope  respectively 
for  the  ith.  group.  The  results  of  this  analysis  are 
presented  in  Table  4.  Slopes  for  each  group 
appear  to  be  significantly  different  from  zero, 
except  for  percent  of  eggs  fertilized  in  large  old- 
shell  and  small  new-shell  males.  The  more  nega- 
tive the  slope  of  the  regression  line,  the  less  the 


'"  Determined  from  3,402  observations  of  grasping  pairs 
of  king  crabs  captured  over  a  9-year  period,  1963-1971. 
See  page  257  National  Geographic  Magazine.  Vol.  139, 
No.  2,  Feb.  1971  for  photograph  of  grasping  pairs. 


•>  Thoni,  H.  Transformation  of  variables  used  in  the 
analysis  of  experimental  and  observational  data,  a  review. 
Technical  Report  No.  7.  Statistical  Laboratory,  Iowa  State 
University.  Ames.  Iowa,  July  1967. 


173 


FISHERY  BULLETIN:  VOL.  72.  NO    1 


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POWELL.  JAMES,  and  HURD:  MATING  ABILITY  OF  MALE  KING  CRAB 


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175 


FISHERY  BULLETIN:  VOL.  72,  NO.  I 

Table  4. — Comparison  of  king  crab  mating  ability,  slopes  and  slope  contrasts  for  relative  fullness  of  brood  chamber  and 

percent  of  eggs  fertilized. 


Relative  fullness  of  brood  chamber 


Percent  of  eggs  fertilized 


Male  class 


Slope 


Standard 
deviation 
of  slope 


F  Value  for 
Test  of  slope    =    0 


Slope 


Standard 
deviation 
of  slope 


f  Value  for 
Test  of  slope  =  0 


Small  old-shell 
Large  old-shell 
Small  new-shell 
Large  new-shell 

/)i    =    -1.416 
/)2    =    -0.616 
/)3    =    -0.328 
hi    =    -0.677 

0.234 
0.112 
0.164 
0.116 

F 
F 
F 
F 

=    36.5       P  <  .0001 
=    30.3       P  <  .0005 
=      3.9       P  =  .05 
=    33.9       P  <  .0001 

/'I 

/>2 

=    -1.171 
=    -0.087 
=    -0.036 
=    -0.637 

0.202 
0.107 
0.142 
O.IOO 

F  =  33.5       P  < 
F  =        .7        P  = 
F=        .1        P  = 
F  =  40.4        P  < 

0.0001 
.32 
.75 
.0001 

Test  for  equality 
of  slopes 

hi    =    />2    =    /'3    =    /'4 

F 

=    4.07,  P    =    0.01 

F    =    11.74,  P 

=  .0001 

Slope  Contrasts 

Contrast 
estimate 

Standard 

deviation 

of  estimate 

f  Value 

for  test  of 

contrast    =    0 

Contrast 
estimate 

Standard 
deviation 
of  contrast 

F  Value 
for  test  of 
contrast    = 

0 

Old-shell  vs. 
new-shell  -1.028 

b\  +  h2  —  h^—  hi 

Large  vs.  small  -0.450 

hi  +  hs  —  b2~  hi 


0.329 


0.329 


9.80       P  =  O.OOI 


f   =    1.9 


P  =  0.17 


-0.585 


-0.482 


0.287 


0.287 


f   =    4.1       P  =  0.04 


F  =    2.8       P  =  0.10 


mating  ability  of  the  males  in  that  particular 
group.  A  test  of  the  hypothesis  of  equality  of 
slopes  {bi  =  b2  =  b^  =  64)  yields  an  F  ratio  of 
4.1  for  relative  fullness  of  brood  chamber  and 
11.7  for  percent  of  eggs  fertilized,  significant  at 
the  1  and  0.01  percent  level  respectively.  In  or- 
der to  determine  the  significance  of  the  size  shell- 
age  classifications,  contrasts  of  old-shell  versus 
new-shell  and  small  versus  large  were  computed 
as  shown  in  Table  4.  These  contrasts  indicate 
that  the  major  contribution  to  the  inequality  in 
slopes  comes  from  the  difference  in  shell  age. 
Size  did  not  appear  to  be  a  significant  factor  as 
is  indicated  by  P  values  of  0.17  and  0.10  respec- 
tively for  relative  fullness  of  brood  chamber  and 
percent  of  eggs  fertilized.  Within  the  shell-age 
contrast,  the  small  old-shell  males  contribute 
the  most  in  the  form  of  a  more  negative  slope, 
indicating  that  these  males  have  much  less 
mating  ability  than  the  other  three  groups. 

The  data  pre.sented  thus  far  give  a  comparison 
of  the  mating  abilities  of  the  four  size  shell-age 
groups.  A  linear  approximation  was  assumed 
for  each  group  and,  although  this  procedure  is 
not  exact,  it  is  sufficiently  close  for  comparative 
purposes.  Graphs  of  the  curves  for  mating  abil- 
ity versus  number  of  matings  indicate  that  small 
old-shell  and  large  new-shell  males  have  the 
least  linear  relationship  of  the  four  groups.  The 
points  i)lotted  in  Figures  1  and  2  are  the  means 


of  the  transformed  variables  for  each  successive 
mating.  A  point  may  represent  as  few  as  one  or 
as  many  as  ten  observations,  as  shown  in  Tables 
2  and  3.  The  original  0  to  100  scale  is  attached 
to  the  graphs  to  make  them  easier  to  read;  thus 
after  the  means  are  computed,  they  are  trans- 
formed back  to  the  original  scale. 
The  slopes  of  the  functions  were  approximated 
by  computing  the  means  of  the  transformed 
measurement  variables  for  each  x  and  fitting 
empirical  curves  to  the  data  points.  Figures  1 
and  2  show  the  relationship  between  percent  of 
eggs  fertilized  and  relative  fullness  of  brood 
chamber  respectively  and  are  presented  primar- 
ily as  an  aid  to  fisheries  management.  The 
results,  however,  are  quite  consistent  with  those 
given  in  Table  4.  The  graphs  show  a  marked  de- 
cline in  the  mating  ability  of  small  old-shell 
males  after  approximately  the  seventh  mating 
and  a  decline  in  the  ability  of  large  new-shell 
males  after  the  tenth  mating.  Figure  2  indicates 
that  partial  clutches  result  from  mating  with 
small  old-shell  and  large  new-shell  males  which 
had  mated  several  times  previously. 

The  least  squares  regression  lines  for  large 
old-shell  males  and  small  new-shell  males  are 
also  plotted  in  Figures  1  and  2.  These  groups 
show  little  decrease  in  mating  ability  as  the 
number  of  matings  increases,  particularly  for 
the  percent  of  eggs  fertilized.  The  slope  of  the 


176 


POWELL.  JAMES,  and  HURD:  MATING  ABILITY  OF  MALE  KING  CRAB 


100 


90  - 
=        80 


70- 


60 


50 


40 

CO 

30 

o 

UJ 

?0 

z 

UJ 

o 

(r 

UJ 

10 

a. 

00 


SMALL 

OLD   SHELLS 


SMALL 

NEW    SHELLS 


LARGE 

OLD    SHELLS 


Pgfg  P 

oints 

Small 

Old 

Shells 

X 

Large 

Old 

Shells 

* 

Small 

New 

Shells 

+ 

Large 

New 

Shells 

• 

LARGE 

NEW    SHELLS 


1  I \ T 

3  6  9  12 

NUMBER    OF   SUCCESSIVE    FEMALES    MATED 


I 
15 


Figure  I. —  Mating  ability  of  male  king  crabs  expressed  as  percentage  of  eggs  fertilized. 


100 


z 

3 

90 

>- 

IT 

80 

UJ 

OD 

z 
< 

70 

I 

o 

Q 

60 

<■> 

O 

IT 

m 

50 

-I 

3 


40- 
30  - 

20 


UJ    10 


< 

bJ 
q: 


00- 


J\ 


SMALL 

NEW  SHELLS 


LARGE  \ 

NEW  SHELLS-^2^ 


SMALL 

OLD  SHELLS - 


\ 


-LARGE 
OLD  SHELLS 


Data  Points 

Small 

Old 

Shells 

X 

Large 

Old 

Shells 

* 

Small 

New 

Shells 

+ 

Large 

New  Shells 

• 

I  I 

6  9 

NUMBER  OF  SUCCESSIVE    FEMALES    MATED 


"T" 
12 


15 


Figure   2. —  Mating  ability  of  male  king  crabs  expressed  as  relative  fullness  of  brood  chamber  of 

mated  females. 


177 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


regression  line  for  large  old-shell  males  for 
relative  fullness  of  brood  chamber  is  quite  steep 
(-0.616)  and  nearly  approaches  the  slope  for 
large  new-shell  males  (-0.677);  however,  there 
are  no  points  in  the  vicinity  of  zero  to  indicate 
that  mating  ability  for  large  old-shell  males 
drops  off  suddenly  after  a  certain  number  of 
matings.  Furthermore,  the  other  measurement 
variable  indicates  that  the  mating  ability  of 
large  old-shell  crabs  does  not  decline  at  a  signif- 
icant rate  when  exposed  to  a  maximum  of  18 
females. 

DISCUSSION 

This  study  indicates  that  all  classes  of  males 
tested  i)ossessed  considerable  ability  to  mate 
repeatedly  at  the  approximate  rate  of  one  female 
every  5  days.  Mating  ability  of  small  old-shell 
and  large  new-shell  male  king  crabs  decreases 
markedly  after  approximately  the  seventh  to 
ninth  mating.  The  decline  for  large  old-shells 
and  small  new-shells  is  not  as  noticeable. 

Although  the  analysis  of  covariance  for  this 
experiment  does  not  indicate  significant  differ- 
ences in  mating  ability  attributable  to  size,  one 
should  be  hesitant  in  saying  categorically  that 
size  is  not  a  relevant  factor.  By  examining  the 
individual  slopes  in  the  graphs,  it  is  evident 
that  certain  combinations  of  age  and  size  have 
a  marked  effect  on  mating  ability  and  one  must 
realize  that  when  a  given  factor  is  examined,  the 
other  factor  is  averaged  out. 

The  knowledge  obtained  as  a  result  of  this 
investigation  represents  just  a  beginning  in  the 
understanding  of  the  mating  of  king  crabs.  To 
what  extent  these  findings  are  applicable  to 
mating  in  nature  remain  uncertain.  The  effects 
of  holding  experimental  crabs  in  undersea  pens 
must  be  understood  before  realizing  full  appli- 
cation of  the  data  to  practical  management  of 
the  fishery. 

Holding  males  in  pens  could  adversely  affect 
mating  ability  of  some  classes,  particularly  later 
matings  after  prolonged  captivity,  while  simul- 
taneously enhancing  ability  of  others  by  forcing 
partners  into  constant  close  association  with 
one  another.  Larger  females  used  later  in  the 
experiment  may  also  have  affected  results. 

Even  though  size  does  not  appear  to  be  a  sig- 
nificant factor  in  mating  ability  as  far  as  the 
number  of  repeated  matings  is  concerned,  and 


even  though  small  males  appear  to  be  capable 
breeders,  it  remains  a  possibility  that  in  some 
instances  in  nature  small  males  may  not  serve 
adequately  as  brood  stock.  Measurements  of 
6,804  king  crabs  captured  by  divers  as  mating 
pairs,  1963-1971,  reveal  that  small  young  fe- 
males are  the  first  to  mate  each  season  followed 
three  months  later  by  large  old  females  (Powell, 
Rothschild,  and  Buss.  1972).  Further,  males 
mating  in  nature  with  "pubescent"  females  (i.e., 
those  mating  for  the  first  time  and  therefore  the 
smallest  found)  are  older  and  larger,  averaging 
42  mm  more  than  females,  with  grasping  ob- 
served as  early  as  January  9  (Powell,  Shafford, 
and  Jones,  1972). 

Apparently  male  size  and  male-female  ratios 
are  not  the  only  factors  affecting  mating  in 
nature.  The  presence  in  recent  years  of  high  in- 
cidence of  adult  females  without  eggs  and  with 
partial  clutches  within  certain  locations  of  the 
Kodiak  fishery  seem  to  be  fishery-related  because 
they  occur  only  in  areas  of  intense  fishing  (Pow- 
ell, 1969'). 

Adult  female  king  crabs  form  mating  congre- 
gations in  shallow  water  from  January  through 
April  and  these  congregations  are  intermittently 
distributed  throughout  the  thousands  of  square 
miles  of  shallow  habitat.  For  mating  to  be  suc- 
cessful in  each  congregation,  adequate  numbers 
of  capable  males  must  be  present  during  the 
relatively  brief  matable  period  following  female 
ecdysis,  otherwise  delayed  mating  may  adverse- 
ly affect  the  success  of  ovulation  and  subsequent 
fertilization  (Kurata,  1961;  McMullen.  1969; 
and  Wallace,  Pertuit,  and  Hvatum,  1958). 

The  ratio  of  males  to  females  necessary  for 
complete  mating  success  in  nature  appears  de- 
pendent upon  factors  other  than  just  numbers 
alone.  The  rate  at  which  females  molt  and  spa- 
tial distribution  and  size  differences  of  adults 
inhabiting  the  location  are  also  believed  impor- 
tant. The  greater  the  rate  of  female  molting,  the 
greater  the  number  of  males  required.  Male 
crabs  select  partners  as  early  as  16  days  prior  to 
mating  and  continually  grasp  them  until  copu- 
lation occurs  soon  after  female  ecdysis  (Powell, 
Rothschild,  and  Buss,  1972).  Because  of  pre- 
mating  "grasping"  behavior,  it  is  possible  that 
females  molt  without  male  partners  though  a 


■  Powell  Ciuv  C.  1969.  Some  aspects  of  king  crab  biol- 
ogy. Proc.  Am.'  Fish.  Soc.  West.  Div.  Meeting,  Jackson 
Hole,  WY,  June  1969.  (Processed) 


178 


POWELL,  JAMES,  and  HURD:  MATING  ABILITY  OF  MALE  KING  CRAB 


favorable  male-female  ratio  exists,  because  all 
males  are  either  preoccupied  grasping  other 
females  or  resting  between  subsequent  matings. 

King  crabs  segregate  to  varying  degrees 
according  to  size,  sex.  age,  and  time  of  year.  Com- 
mercial fishing  is  concentrated  in  areas  inhabited 
by  large  males  with  total  effort  varying  accord- 
ing to  factors  such  as  accessibility.  Thus  crop- 
ping of  males  may  be  excessive  in  one  area  but 
not  in  another.  Incidence  of  nonovigerous  adult 
females  is  lowest  in  areas  where  sublegal  sized 
males  are  abundant,  but  is  often  high  in  ex- 
ploited areas  with  few  adult  males  (unpublished, 
Alaska  Dept.  Fish  &  Game). 

Size  differences  between  partners,  presence 
of  competing  males,  and  time  of  year  also  must 
be  considered  in  evaluating  the  reproductive 
potential  of  mating  populations. 

It  is  conceivable  that  even  with  many  young 
adult  males  present,  a  population  of  large  old 
females  may  be  inadequately  serviced  partly 
because  the  few  surviving  large  males  may, 
through  aggressive  behavior,  keep  smaller 
males  away.  To  what  extent  competitive  be- 
havior exists  is  presently  unknown  but  large 
old  males  commonly  are  found  mating  small 
young  females  in  nature.  Of  the  14  matings  in 
this  experiment,  where  females  were  larger 
than  males,  79  percent  produced  partial 
clutches. 

Small  males  probably  produce  less  reproduc- 
tive material  (sperm)  than  large  males,  and  as 
a  result,  may  be  less  capable  of  fertilizing  the 
greater  masses  of  eggs  of  large  females. 


LITERATURE  CITED 

Gray.G.  W.,  Jr. 

1965.  Tags  for  marking  king  crabs.  Prog.-Fish  Cult. 
27:22 1-227. 

Gray,  G.  W.,  Jr.,  and  G.  C.  Powell. 

1966.  Sex  ratios  and  distribution  of  spawning  king 
crabs  in  Alitak  Bay,  Kodiak  Island,  Alaska  (Deca- 
poda.  Anomura.  Lithodidae).  Crustaceana  10:303- 
309. 

Haynes,  E.  B. 

1968.  Relation  of  fecundity  and  egg  length  to  carapace 
length  in  the  king  crab.  Paralithodcs  camtschuticu. 
Proc.  Natl.  Shellfish.  Assoc.  58:60-62. 

KURATA,  H. 

1961.  King  crab  investigations  in  the  eastern  Bering 
Sea  in  1961.  (Prelim,  transl.)  I.N.P.F.C.  (Int.  North 
Pac.  Fish.  Comm.)  Doc.  48  1,  6  p. 

McMuLLEN,  J.  C. 

1969.  Effects  of  delayed  mating  on  the  reproduction 
of  king  crab,  Paralithodcs  camischatica.  J.  Fish. 
Res.  Board  Can.  26:2737-2740. 

MiYAHARA,  T.,  AND  H.  H.  ShIPPEN. 

1965.  Preliminary  report  of  the  effect  of  varying 
levels  of  fishing  on  eastern  Bering  Sea  king  crabs, 
Paralithodcs  camischatica  (Tilesius).  Rapp.  P-V. 
Reun.  Cons.  Perm.  Int.  Explor.  Mer  156:5  1-58. 

NiCKERSON,  R.  B..  F.  J.  OSSIANDER,  AND  G.  C.  PoWELL. 

1966.  Change  in  size-class  structure  of  populations  of 
Kodiak  Island  commercial  male  king  crabs  due  to 
fishing.  J.  Fish.  Res.  Board  Can  23:729-736. 

Powell,  G.  C,  and  R.  B.  Nickerson. 

1965.  Reproduction  of  king  crabs.  Paralithodcs  cuini- 
schatica  (Tilesius).  J.  Fish.  Res.  BoardCan.  99: 10 1- 1 1 1 . 
Powell,  G.  C,  B.  Shafford,  and  M.  Jones. 

1972.   Reproductive     biology     of    young     adult     king 
crabs  Paralithodcs  camtschatica  (Tilesius)  at  Kodiak 
Alaska.  Proc.  Natl.  Shellfish.  Assoc.  63:77-87. 
Wallace,  M.  M..  C.  J.  Pertuit,  and  A.  R.  Hvatum. 

1949.  Contribution  to  the  biology  of  the  king  crab, 
Paralithodcs  camtschatica  Tilesius.  U.S.  Fish  Wild. 
Serv.,  Fish.  Leafl.  340,  50  p. 


179 


I 


AN  EVALUATION  OF  MID-WATER  ARTIFICIAL  STRUCTURES 
FOR  ATTRACTING  COASTAL  PELAGIC  FISHESi 

Donald  A.  Wickham  and  Gary  M.  Russell^ 


ABSTRACT 

Mid-water  artificial  structures  positioned  off  Panama  City,  Fla.  during  August  1970  were 
evaluated  to  determine  their  ability  to  attract  coastal  pelagic  fishes.  Quantitative  and  quali- 
tative experimental  results  were  obtained  using  scuba  divers  and  purse  seine  catches.  The 
feasibility  of  using  artificial  structures  to  facilitate  the  commercial  harvest  of  coastal  pelagic 
fishes  with  purse  seines  was  established  and  the  methods  described.  Average  catch  values  of 
398  kg  (875  lb)  per  structure  were  obtained  during  a  period  when  coastal  pelagic  fishes  were 
unavailable  to  the  local  fishery.  A  greater  total  production  was  obtained  from  structures 
fished  daily  compared  with  those  allowed  to  soak  for  3  days  before  being  fished.  Experi- 
mental purse  seine  collections  established  that  fish  leave  the  structures  at  night  with  new 
recruitment  occurring  daily.  No  significant  differences  were  obtained  from  preliminary  exper- 
iments to  evaluate  the  effects  of  structure  size  and  color  on  attraction  effectiveness.  A  work- 
ing hypothesis  is  presented  to  describe  apparent  behavioral  mechanisms  involved  in  the 
attraction  of  some  species  of  coastal  pelagic  schooling  fish  to  objects  in  the  sea.  This  study 
indicates  that  artificial-structure  fish-attraction  has  potential  for  development  as  a  tech- 
nique to  facilitate  the  harvest  of  the  latent  coastal  pelagic  fishery  resources  in  the  Gulf  of 
Mexico. 


Artificial  structures  have  been  shown  to  be  effec- 
tive for  attracting  concentrations  of  pelagic 
fishes  (Hunter  and  Mitchell,  1968).  Klima  and 
Wickham  (1971)  visually  evaluated  the  species 
and  number  of  coastal  pelagic  fishes  attracted 
to  experimental  artificial  structures  in  the  north- 
eastern Gulf  of  Mexico.  These  observations  es- 
tablished the  feasibility  of  attracting  large 
numbers  of  coastal  pelagic  fishes  with  artificial 
structures;  however,  many  questions  concern- 
ing structure  attraction  characteristics  and 
dynamics  as  well  as  their  actual  usefulness  in 
augmenting  conventional  harvesting  methods 
for  these  species  still  remained  unanswered. 

Studies  were  conducted  during  August  1970, 
in  5  to  10  fathoms  (9  to  18  m)  of  water  offshore 
of  Shell  Island,  Panama  City,  Fla.  to  obtain 
quantitative  samples  for  evaluating  the  validity 
of  scuba-diver  estimates  of  structure-attracted 
fish  aggi-egations,  to  evaluate  methods  for  using 
a  conventional  purse  seine  for  capturing  struc- 
ture-attracted fish,  and  to  obtain  catch-produc- 
tion values  for  single  structures.  We  also  evalu- 


'  Contribution  No.  234,  Southeast  Fisheries  Center, 
Pascagoula  Laboratory,  National  Marine  Fisheries  Service. 

-  Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Pascagoula,  MS  39567. 


ated  effects  of  structure  soak  time  and  size-color 
differences  on  attraction  effectiveness.  Day  and 
night  samples,  plus  scuba-diver  observations  of 
fish  behavior,  provided  additional  clues  to  the 
dynamics  of  the  coastal  pelagic  fish  aggregations 
attracted  to  artificial  structures. 


MATERIALS  AND  METHODS 

Our  fish  attraction  devices  were  three-dimen- 
sional structures.  Each  structure  was  construct- 
ed from  vinyl-cloth  covered,  wood  and  wire 
frame  panels.  Two  panels  were  fastened  along 
one  side,  permitting  the  structure  to  be  stored 
flat,  but  opened  into  a  three-dimensional  right 
prism  when  deployed  for  fish  attraction.  Two 
sizes  of  structures  were  used.  The  small  struc- 
ture panels  were  0.9x1.5  m  (3x5  ft)  in  size 
and  the  large  structures,  with  twice  the  surface 
area  of  the  smaller  structures,  were  1.8  X  1.5  m 
(6X5  ft).  All  structures  were  white  except 
those  painted  for  specific  experiments. 

Structures  were  positioned  4-6  m  (15-20  ft) 
beneath  the  surface.  The  structure  design  and 
mooring  arrangement  are  illustrated  in  Figure  1. 
Structures  were  spaced  at  approximately  0.8-km 


Manuscript  accepted  May  1973. 

FISHERY  BULLETIN:  VOL.  72.  NO.  1.  1974. 


181 


FISHERY  BULLETIN:  VOL    72.  NO.  1 


(0.5-mile)  intervals.  Their  arrangement  in  the 
experimental  site  is  shown  in  Figure  2.  The 
eight  structure  mooring  locations  were  used 
with  different  .structures  as  required  for  specific 
exj)eriments. 

The  15-m  (49-ft)  single  boat-rig  bait  purse 
seiner,  Gidf  Ranger,  was  chartered  to  make 
quantitative  collections  at  selected  artificial 
structures  using  a  tom-weight  type  purse  seine, 
22  m  (12  fathoms)  deep  and  110  m  (60  fathoms) 
in  length,  with  3.2  cm  (lV4-inch)  stretched  mesh 
webbing.  A  6-m  (20-ft)  inboard -outdrive  power 
boat  was  used  as  a  diving  platform  and  for  pick- 
ing up  and  resetting  structures  sampled  by  the 
purse  seine. 

Daily  visual  estimates  of  the  number  and 
species  of  fisti  present  at  each  structure  were 
made  independently  by  scuba  divers.  We  ob- 
tained quantitative  data  from  selected  structures 
by  collecting  all  the  fish  around  these  structures 
with  the  purse  seine.  Diver  estimates  and  purse 
seine  catch  data  are  given  in  Table  1. 

Scuba  divers  made  visual  estimates  of  the  fish 
aggregation  at  a  structure  prior  to  beginning  the 
purse  seine  set.  The  structure  anchor  was  picked 


Figure      1. —  Artificial     structure     design     and     mooring 
arrangement. 

up  by  the  divers  as  soon  as  the  seiner  began 
setting  its  net.  When  pursing  was  half  completed, 
the  structure  counterweight  was  retrieved  to 
l^revent  its  being  tangled  in  the  jiurse  line.  After 
the  purse  rings  were  up,  the  dive  boat  would 
take  the  structure  aboard,  pass  over  the  cork- 
line,  and  reset  the  structure  clear  of  the  net. 

The  captain  of  the  Gulf  Ranger  estimated  the 
catch  weight  after  each  purse  seine  set  and  the 
biologist  aboard  sanij^led  each  catch  to  provide 


30'I0' 


Figure  2. — Map  of  experimental  site  with  numbered  circles  illustrating  positions  where 
artificial  structures  were  deployed.  Stage  II  is  a  Navy  research  platform  west  of  the  study 
area. 


182 


WICKHAM  and  RUSSELL:  EVALUATION  OF  MID-WATER  ARTIFICIAL  STRUCTURES 


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data  on  species  composition.  It  was  not  practical 
to  totally  weigh  each  catch  as  it  came  aboard  or 
to  keep  the  fish  from  individual  sets  separated 
for  later  weighing;  consequently  the  captain's 
catch  weight  estimates  had  to  serve  as  our  quan- 
titative standard.  The  accuracy  of  the  captain's 
estimates  was  established  by  comparing  the 
daily  total  of  his  estimates  with  the  daily  fish 
house  landing  records  for  the  G/iIf  Ranger  (Table 
2).  We  believed  the  accuracy  of  these  estimates 
()•-  =  0.97)  justified  our  utilizing  them  for  eval- 
uating diver  estimates  and  for  quantifying 
experimental  data  (Figure  3). 

RESULTS 
Diver  Estimates 

The  validity  of  scuba-diver  observations  was 
evaluated  by  comparing  the  divers'  estimates  of 
the  total  number  and  species  composition  of  fish 
present  at  a  structure  with  data  obtained  from 
the  purse  seine  catch  at  that  structure.  Numer- 
ical estimates  obtained  by  the  divers  for  coastal 
pelagic  school  fish  were  converted  to  weight, 
utilizing  a  catch  average  of  approximately  22 
fish  per  kilogram  to  permit  comparison  with 
purse  seine  catch  data. 

The  comparison  of  diver  estimates  with  the 
captain's  estimates  for  the  corresponding  purse 
seine  catches  are  plotted  in  Figure  4  for  data 
collected  17-21  August  1970  (Table  1).  Data 
from  24  August  to  27  August  were  not  included 
in  this  comparison  because  schools  of  little  tunny 
{Euthijiunm  oUetteratus)  began  following  the 
purse  seiner  and  were  occasionally  observed 
attacking  and  scattering  the  structure-attracted 
fish  schools  before  the  purse  seine  set  was  com- 
pleted. A  linear  regression  analysis  of  the  mean 
for  each  set  of  paired  diver  estimates  {Y=  76.5  + 
0.56X;  ?•-  =  0.68)  indicates  that  although  con- 
siderable variation  does  exist,  fish  schools  less 
than  182  kg  (400  lb)  tend  to  be  slightly  overesti- 
mated while  the  larger  schools  are  increasingly 
underestimated.  A  linear  regression  analysis 
was  also  calculated  for  each  diver's  individual 
estimates  and  these  calculations  indicated 
that  estimates  made  by  diver  2  tend  to  be  more 
accurate  than  the  more  conservative  estimates 
made  by  divers  1  and  3. 

The  purse  seine  catch  sample  data  indicated 
scuba  divers   were  able  to   identify  the  major 


J 


184 


WICKHAM  and  RUSSELL:  EVALUATION  OF  MID-WATER  ARTIFICIAL  STRUCTURES 

Table  2. —  Diver  estimates,  purse  seiner  captain's  estimates,  and  fish  house  landing  totals  for  daily  catches  from  artificial 

structures. 


No. 
daytime 

Total  average  diver 
estimates  for 

Total  purse  seiner                       Fish 
captain's  daily                        house 

Fish  house 

landings 

by 

species 

Date 

1970 

sets 

structures  sampled 

catch  estimates                     landings 

Round  scad 

Spanish  sardine 

Aiiiiusi 

17 

4 

1,227 

2,227                                2,193 

830 

1,363 

18 

4 

1,057 

1,091                                    909 

614 

295 

19 

8 

2,568 

3,841                                4,045 

1,830 

2,215 

20 

4 

1,227 

1,500                                1,545 

727 

818 

21 

4 

830 

955                                   852 

432 

420 

Total 

24 

6,909 

9,614                                9,544 

4,433 

5,111 

'21 

4 

1,136 

1,159                                1,034 

761 

273 

'25 

5 

2,034 

1,386                                1,682 

716 

966 

'26 

5 

3,182 

1 ,068                                   693 

443 

250 

'27 

6 

3,523 

1,114                                1,194 

489 

705 

Total 

20 

9,875 

4,727                                4,603 

2,409 

2,194 

9-day  total 

44 

16,784 

14,341                                 14,147 

6,842 

7,305 

Data  not  used  for  scuba-diver  estimates-purse  seiner  catch  comparisons. 


species  attracted  to  the  structures.  They  were 
not,  however,  able  to  determine  accurately  the 
pei'cent  species  composition  for  the  schools  of 
mixed  coastal  pelagic  fishes.  These  mixed 
schools  contributed  over  95%  of  the  catch  weight 
taken  from  each  structure.  The  mixed  coastal 
pelagic  school  fish  consisted  of  round  scad 
(Decapterns  pioictatus)  and  Spanish  sardine 
(Sardiitella  anchovia).  The  bait  fish  occurred  at 
each  structure  in  mixed  schools  of  varying  per- 
cent species  composition.  The  difficulty  encoun- 
tered by  the  divers  in  obtaining  accurate  percent 
species  composition  data  for  this  group  was 
probably  the  result  of  behavioral  differences  " 
between  the  species.  Round  scad  usually 
approached  closer  to  the  divers  than  Spanish 
sardine,  which  tended  to  concentrate  on  the  side 
of  the  school  farthest  away  from  the  divers. 

Jacks  usually  represented  less  than  5%  of  the 
total  catch  weight  and  consisted  primarily  of 
small  15-cm  (6-inch)  blue  runner  {Caranx 
crysos),  crevalle  jack  (C.  hippos),  and  bar  jack 
(C.  ruber).  Among  the  species  which  comprised 
the  major  components  of  Klima  and  Wickham's 
(1971)  jack  group,  amberjack  {Seriola  sp.)  were 
only  occasionally  observed  and  rainbow  runner 
{Elagatis  bipi)i)iulata)  were  notable  by  their 
absence  in  this  series  of  experiments.  The  jacks 
are  not  treated  separately'  in  our  paper  because 
of  their  minor  contribution  to  the  total  number 
and  weight  of  the  structure-attracted  fish  aggre- 
gations. 

Comparison    of   diver    estimates    and    purse 


seine  catch  data  indicates  that  although  purse 
seine  data  are  quantitatively  superior  both 
sampling  techniques  are  complementary  and, 
combined,  provide  a  more  complete  picture  of 
the  experimental  environment  than  either  singu- 
larly. Where  diver  estimates  provided  the  only 
available  data  they  are  considered  sufficient  to 
permit  rough  evaluation  of  the  experimental 
results  in  terms  of  their  commercial  significance. 


FISH       HOUSE     LANDING      (pounds) 

leOO         ZZX        2700         3150         3600 


Figure  3. — Relationship  between  the  daily  total  of  the 
Gulf  Ranger  captain's  estimates  of  structure-purse  seine 
catches  and  the  daily  fish  house  landing  records.  Statistical 
evaluation  of  this  data  by  linear  regression  analysis  yields 
Y  =  216.4  +  O.S16X\  r-  =  0.97.  N  =  number  of  set  es- 
timates in  each  daily  total. 


185 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


400 


800 


1200 


CATCH      (pounds) 
1600         2000  2400 


1600 


1400 


1200 


:iooo 


800 


;  600 


400 


200 


"1 — r 


1 — \ — r 


2800  3200  3600 

— I — I — 1 — 1 — r- 


4000 


O     DIVER  2 
X       DIVER  3 


200 


400 


600 


800  1000  1200 

CATCH     (kilogroms) 


1400 


1600 


1800 


3200 


2800 


o 
< 


2400 


2000 


-  1600    -o 


1200 


800 


-  400 


Figure  4. — Relationship  between  divers"  estimates  of  bait  fish  school  size  and  the  captain's 
estimate  of  the  purse  seine  catch  at  each  structure.  A  linear  regression  analysis  of  the  average 
paired  diver  estimates  yields  Y  =  76.5  +  0.56A';  /?-  =  0.684.  A  linear  regression  analysis  of 
the  estimates  made  by  each  diver  yields  Y  =  11  .b  +  0.?04A',-  r-  =  0.285  for  diver  one; 
Y  =  55.3  +  0.683A':  r^  =  0.704  for  diver  two;  and  Y  =  98.4  +  0.501A';  r-^  =  0.42  for  diver 
three. 


Recruitment  Patterns  and  Production 

Our  observations  indicate  a  rapid  reci-uit- 
ment  with  fish  being  observed  at  structures  the 
day  following  placement.  To  obtain  estimates  of 
production  and  recruitment  of  bait  fish  to  the 
structures,  we  made  daily  diver  estimates  and 
purse  seine  collections  at  four  selected  structures. 
Four  other  structures,  also  observed  daily  by 
divers,  were  set  on  after  being  in  position  for  3 
days.  During  this  period  (17-21  August  1970). 
our  structures  produced  an  average  of  398  kg 
(875  lb)  per  set.  These  catch  rates  are  not  ex- 
tremely large,  but  they  were  made  when  bait  fish 
were  not  seasonally  available  to  the  local  beach 
seine  fishery.  No  bait  was  being  landed,  excei)t 
for  fish  captured  around  our  structures.  The 
total  daily  diver  estimates  and  purse  seine  col- 
lections are  plotted  in  Figure  5,  along  with  the 
3-day  accumulative  totals,  to  allow  comparison 


of  production  between  the  four  structures  fished 
daily  and  the  four  structures  set  on  once,  follow- 
ing the  3-day  soak  period.  Our  day  3  catch  results 
indicate  no  significant  advantage  in  catch  size 
was  realized  by  allowing  the  structures  to  soak 
for  3  days.  The  potential  total  catch,  assuming 
daily  sets  had  been  made  on  the  3-day  soak  struc- 
tures, indicated  from  our  consistently  conserva- 
tive diver  estimates  was  three  times  larger  than 
the  actual  catch  after  3  days'  soaking.  The  total 
accumulative  catch  from  the  four  structures  set 
on  daily  was  also  approximately  three  times 
larger  than  the  actual  catch  from  the  four  3-day 
soak  structures  even  though  diver  estimates 
indicated  smaller  total  fish  concentrations  were 
present  at  the  .structures  set  on  daily.  These 
results  show  that  a  greater  total  production 
was  obtained  by  making  daily  sets.  This  high 
rate  of  daily  attraction  and  the  apparent  lack 
offish  accumulation  provided  further  indications 


186 


WICKHAM  and  RUSSELL:  EVALUATION  OF  MID-WATER  ARTIFICIAL  STRUCTURES 


that  fish  were  being  attracted  to  the  structures 
on  a  daily  basis. 

Comparison  of  Day  and  Night  Collections 

A  series  of  day  and  night  sets  were  conducted 
to  determine  whether  fish  leave  the  structures  at 
night.  Divers  estimated  the  quantities  of  fish 
at  four  selected  structures  which  were  then  set 
on  during  daylight  hours.  The  quantity  offish  at 
four  other  structures  was  estimated  by  divers 
just  before  dark  and  fish  around  these  structures 
were  collected  after  dark.  Diver  estimates,  and 
day  and  night  catch  results,  are  plotted  in  Figure 
6.  The  diver  estimates  were  conservative  for 
structures  set  on  during  the  day,  with  estimates 
for  both  days  being  less  than  the  actual  catch  for 
three  of  the  four  structures.  The  divers  frequent- 
ly estimated  that  concentrations  of  fish  present 
at  the  structures  fished  at  night  were  larger 
than  at  the  structures  fished  in  the  daylight. 
Nighttime  collections  however,  consistently  pro- 
duced only  45.5  kg  (100  lb)  or  less  of  mixed 
species.  These  results  provided  further  evidence 
that  bait  fish  leave  the  structures  at  night  and 
that  new  recruitment  was  occurring  daily.  The 
nighttime  sets  were  made  during  the  new  moon 
and  we  lack  data  on  whether  bait  fish  also  leave 
the  structures  at  night  during  the  full  moon. 

Size  and  Color  Evaluation 

The  success  of  bait  fish  attraction  with  arti- 
ficial structures  appeared  to  be  dependent  upon 
the  visibility  of  the  structure.  We  evaluated  two 
sizes  of  structures  to  determine  whether  dou- 
bling the  structure  size  would  increase  the  num- 
ber of  fish  attracted.  An  analysis  of  variance  for 
purse  seine  capture  data  (F  —  0.75<  Fo.90(i,5) 
=  4.06)  and  diver  estimates  revealed  no  sig- 
nificant difference  in  attraction  by  structure 
size. 

Structure  attraction  was  also  evaluated  in 
terms  of  color  visibility.  We  compared  a  white 
structure  with  ones  painted  fluorescent  green, 
blue,  and  yellow  since  Kinney  (1970)  reported 
that  fluorescent  paints  provide  greater  visibility 
under  water.  Structure  position  was  rotated 
daily  so  that  a  structure  of  each  color  occupied 
each  of  the  four  positions.  An  analysis  of  vari- 
ance for  catch  data  (F=0.026<Fo.90(3.9)  =  2.8) 
and    diver    estimates    revealed    no    significant 


-  2800 

E 
o 

I  2400 

o  2000 

uj 

S 


O^      OIVEB     CSTIM4TE     (TOTALl 

PU«Se      3CINE     C4TCM    (TOTALl 


*-     STWUCTUBCS      1,2,7,9 
B  -    STBUCTUBCS       3,4,9,6 


^ 


6000      s 


A        B 

3      D4Y 

ACCUMULATIVE 

TOTAL 


Figure  5.  —  Total  of  daily  average  diver  estimates  and  purse 
seine  catch  weights,  17-19  August  1970.  (A)  Structures 
estimated  by  divers  and  fished  daily  by  purse  seine.  (B) 
Structures  estimated  daily  by  divers  but  fished  by  purse 
seine  only  on  day  three. 

difference  in  the  number  of  fish  attracted  to  the 
structures  on  the  basis  of  color.  During  these 
color  evaluation  studies,  the  bait  fish  schools 
were  occasionally  scattered  by  little  tunny. 
These  predator  attacks  may  have  affected  the 
catch  data;  however  our  diver  estimates  were 
not  affected  and  also  indicate  no  significant 
color  preference. 

Divers  reported  the  experimental  changes  in 
size  and  color  extended  the  visible  range  of  a 
single  structure  less  than  2.1  m  (6  ft)  which  ap- 
parently was  not  sufficient  to  significantly 
improve  the  structures'  attraction  capabilities. 

Structure  placement  (Figure  3)  in  relation  to 
the  distance  offshore  (water  depth)  or  to  the 
along-shore  current  direction  tended  to  have 
some  effect  on  the  number  of  fish  attracted,  with 
larger  numbers  of  fish  being  attracted  to  struc- 
tures positioned  offshore  than  to  those  positioned 
inshore.  Structures  positioned  on  the  eastern 
end  of  the  experimental  area  also  tended  to 
attract  more  fish  than  those  on  the  western  end. 
These  general  patterns  probably  vary  with 
seasonal  changes  in  water  temperature  and  pre- 
vailing current  direction.  Our  experiment  was 


187 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


a   600 
bj 

9 


-2600 
-  2000 


DAY     SET 
I  NIGHT    SET 
]  DIVERS'  AVERAGE     ESTIMATE 


M 


I 


-  2600 

-  2000 


i 


1 


Figure  6. — Average  diver  estimates  and  day  and  night  purse  seine  catch  weights  for  each  structure  on  (A)  August  20,  and 
(B)  August  21,  1970.  No  diver  observations  or  purse  seine  sets  were  made  at  structure  three  on  August  21  due  to  an  after- 
noon squall. 


not  designed  to  evaluate  the  effects  of  structure 
placement  on  fish  attraction  and  further  studies 
would  be  necessary  to  meaningfully  evaluate 
these  effects. 

Responses  to  Moving  Structures 

A  bait  fish  school  was  observed  by  Klima  and 
Wickham  (1971)  to  have  remained  with  a  free 
drifting  artificial  structure  moving  slower  than 
the  current.  One  of  our  structures  (Structure 
No.  8.  19  August  1970).  with  a  school  of  bait  fi.sh 
in  attendance,  was  also  observed  dragging  its 
anchor  and  moving  slowly  with  the  current.  This 
structure  was  towed  for  20  min  at  a  speed  of 
ai)proximately  2  knots  against  a  0.5  knot  current 
for  a  distance  of  ai)proximately  0.8  km  (0.5  mile) 
in  order  to  return  it  to  its  experimental  mooring 
location.  The  structure  moved  up  to  the  surface 
while  being  towed,  but  the  fish  swam  along  with 
it,  trailing  out  behind  when  the  towing  speed 
was  increased.  After  the  structure  was  re- 
anchored  in  position,  the  fish  school  began 
swimming  around  it  in  the  usual  manner.  Divers 


estimated  that  over  half  the  original  number  of 
fish  remained  around  the  structure  after  towing. 
A  purse  seine  set  made  on  this  structure  after 
repositioning  produced  545  kg  (1,200  lb)  offish. 

Behavior  Observations  at  Structures 

Our  observation  of  bait-fish-school  behavior 
at  the  structures  is  in  general  accordance  with 
the  behavior  described  by  Klima  and  Wickham 
(1971).  The  bait-fish  schools  normally  main- 
tained a  position  up-current  from  the  structures 
and  were  observed  continuously  feeding  on  crab 
larvae  and  other  particulate  material  in  the 
water.  During  very  slow  or  zero  current  condi- 
tions, the  bait  fish  would  often  mill  about  in  a 
loose  aggregation  (Figure  7)  or  form  long 
streaming  schools  making  large  looping  passes 
out  and  around  the  structures  in  all  directions. 
The  schools  would  frequently  swim  beyond  the 
divers'  range  of  visibility,  remaining  out  of  sight 
for  periods  up  to  3  min  or  longer  before  stream- 
ing back  in  and  around  the  structures  from  a 
different  direction. 


188 


WICKHAM  and  RUSSELL:  EVALUATION  OF  MID-WATER  ARTIFICIAL  STRUCTURES 


Figure  7.  —  Underwater  photograph  of  a  mixed  school  of  round  scad  (Decapicnis  punctaius) 
and  Spanish  sardine  (Scudinclla  anchovia)  swimming  past  an  artificial  structure. 


A  different  pattern  of  behavior  was  observed 
by  the  divers  when  the  bait-fish  schools  were 
threatened  by  the  presence  of  feeding  predators, 
i.e.,  Spanish  mackerel  (Scomberoniorus  macu- 
latus),  king  mackerel  (S.  cavalla),  little  tunny 
(E.  alletteixitus).  and  bluefish  {Poniatomus  salt- 
atrix).  On  these  occasions,  relatively  small  bait- 
fish  schools,  i.e.,  100  kg  (220  lb)  or  less,  would 
form  a  milling  ring  with  the  structure  in  the 
center  or  swirl  in  a  tight  group  in  quick  passes 
close  to  the  structure  as  the  predators  made 
darting  attacks  on  the  school.  Larger  schools 
would  usually  be  split  by  the  attacking  predators 
with  one  group  of  bait  fish  moving  to  the  struc- 
ture and  circling  it  as  described  above  while  the 
remaining  fish  moved  off  in  tight,  fast-darting 
groups. 

Behavioral  Mechanisms 

Different  sizes  and  species  of  fish  apparently 
associate  with  objects  in  the  sea  for  different 
reasons  involving  different  behavioral  mechan- 
isms. Hypotheses  advanced  to  explain  the  asso- 
ciation of  fishes  with  floating  objects  were 
reviewed  by  Gooding  and  Magnuson  (1967).  The 


initial  attraction  of  pelagic  fishes  to  objects 
probably  results  from  their  visually  detecting 
the  object  in  the  optical  void  of  the  pelagic  en- 
vironment, since  fish  beyond  the  visual  range  of 
a  structure  or  structure-attracted  fish  school  are 
not  attracted  (Hunter  and  Mitchell,  1967).  Sig- 
nificantly improving  the  visual  characteristics  of 
an  object  apparently  increases  the  rate  and  num- 
ber of  fish  it  attracts  (Hunter  and  Mitchell, 
1967;  Klima  and  Wickham,  1971).  Objects,  how- 
ever, must  serve  a  meaningful  function  beyond 
that  involved  in  the  ;initial  visual  attraction  in 
order  for  pelagic  fish  to  remain  in  association 
with  them.  To  tentatively  explain  this  behavior 
in  mixed  schools  of  round  scad  (D.  puuctatus) 
and  Spanish  sardine  (S.  anchovia)  around 
artificial  structures,  Klima  and  Wickham  (1971) 
proposed  the  hypothesis:  "Floating  objects  and 
underwater  structures  provide  spatial  references 
around  which  fish  can  orient  in  the  otherwise 
unstructured  jielagic  environment."  This  tenta- 
tive hypothesis  was  given  some  support  by  our 
study,  but  it  must  be  modified  and  expanded  to 
account  for  our  additional  behavioral  observa- 
tions. Our  studies  indicate  that  although  coastal 


189 


FISHERY  BULLETIN:  VOL.  72.  NO    1 


pelagic  bait  fish  are  capable  of  ranging  beyond 
sight  of  an  object  for  periods  of  several  minutes 
or  longer,  they  apparently  require  periodic 
visual  reconfirmation  of  the  object's  position  in 
order  to  maintain  their  orientation  with  it. 
This  assumption  is  supported  by  our  observa- 
tions that  structure-attracted  fish  aggregations 
leave  the  structures  at  night  when  low  light 
levels  inhibit  visual  contact.  Our  observations 
of  coastal  pelagic  bait-fish  behavior  around 
artificial  structures  also  indicate  that  the  struc- 
tures can  apparently  be  useful  to  these  species 
for  predator  avoidance.  Schools  of  bait  fish 
associated  with  an  artificial  structure  have  been 
observed  to  be  immediately  attacked  by  j^reda- 
tors  upon  removal  of  the  structure  from  the 
water.  Bait-fish  schools  threatened  by  the  pres- 
ence of  feeding  predators  were  observed  to  form 
a  tight  ball  or  ring  around  the  stinicture  or  swirl 
in  tightly  packed  formation  making  quick  dart- 
ing passes  near  the  structure.  On  several  occa- 
sions, we  have  observed  the  attack  behavior  of 
a  predator  to  be  interrupted  at  the  moment  the 
bait  fish  darted  past  the  structure.  Mitchell  and 
Hunter  (1970)  describe  laboratory  experiments 
in  which  splitnose  rockfish  (Sebastes  diploproa) 
and  opaleye  (Girella  idgriccuin)  were  pursued 
more  often,  for  longer  periods,  and  captured 
more  frequently  by  ocean  whitefish  (Caulolatilus 
princeps)  in  an  aquarium  when  kelp  was  absent 
than  when  it  was  present. 

Our  ))resent  supposition  as  to  the  possible 
mechanisms  involved  in  the  association  of  some 
species  of  coastal  pelagic  schooling  fish  with  ob- 
jects in  the  sea  are  summarized  in  the  following 
working  hypothesis:  "Objects  in  the  sea  i)rovide 
visual  stimuli  which  attract  certain  species  of 
pelagic  schooling  fish  and  are  used  in  conjunc- 
tion with  natural  optomotor  responses  to  provide 
a  spatial  reference  for  orientation  in  the  other- 
wise relatively  unstructured  pelagic  environ- 
ment; however,  in  the  presence  of  feeding  preda- 
tors stimulus  priorities  are  restructured  such 
that  the  objects  become  useful  for  predator 
avoidance."  An  increasing  body  of  subjective  evi- 
dence is  available  to  support  much  of  this  con- 
jecture, but  its  verification  lacks  the  requisite 
quantitative  experimental  evidence. 

Purse  Seine  Operations 

The  feasibility  of  harvesting  structure-attract- 
ed coastal   pelagic  bait  fish   with  conventional 


tom-weight  type  purse  seines  was  evaluated 
during  our  development  of  the  quantitative  col- 
lection procedures.  Fish  aggregations  normally 
showed  little  disturbance  during  purse  seine  sets 
while  the  structure  remained  in  the  water.  Fish 
stayed  with  the  structure  even  when  it  floated 
at  the  surface  after  the  counterweight  was  lifted 
to  .prevent  its  tangling  the  purse  line.  The  fish 
showed  distress  and  attempted  to  escape  the  net 
only  when  the  structure  was  removed  from  the 
water  and  the  diving  boat  prepared  to  pass  over 
the  corkline  and  reset  the  structure.  The  only 
deviation  from  this  pattern  was  observed  when 
bait  fish  were  attacked  by  predators,  i.e.,  little 
tunny  (E.  alletteratus),  which  on  several  occa- 
sions were  following  the  seiner.  On  these  occa- 
sions, the  predators  scattered  the  bait  fish  during 
the  set  and  then  escaped  before  the  net  was  com- 
pletely closed. 

During  our  experimental  collections,  we 
utilized  an  additional  small  boat  and  several 
men  to  handle  the  structures  during  the  purse 
seine  operations.  Sets  have  been  made,  however, 
using  only  the  seine  skiff  and  its  operator  to 
retrieve  and  reset  the  structures.  These  trials 
indicate  that  in  a  commercial  fishing  operation 
using  artificial  structures,  fishing  procedures 
can  be  modified  so  that  additional  men  and 
equipment  should  not  be  required.  The  applica- 
bility of  structure-attraction  techniques  for  aug- 
menting purse  seining  during  commercial  fish- 
ing operations,  although  technically  feasible, 
remains  dependent  upon  the  production  poten- 
tial of  structures  and  their  recruitment  charac- 
teristics in  the  geographical  area  under  consid- 
eration. 

SUMMARY  AND  CONCLUSIONS 

An  evaluation  of  our  diver  estimates  and  purse 
seine  catch  data  indicates  that  a  combination  of 
these  techniques  provides  a  more  complete  de- 
scription of  the  artificial  structure  experimental 
environment  than  either  singularly.  Our  com- 
parative results  support  the  contention  by  Klima 
and  Wickham  (1971)  that  quantitative  diver 
estimates  tend  to  be  conservative  where  large 
fish  schools  are  involved.  Our  divers  were  able 
to  qualitatively  determine  the  major  species 
present  at  a  structure,  but  were  unable  to  reli- 
ably establish  the  percent  species  composition 
in  mixed  species  schools. 


190 


WICKHAM  and  RUSSELL:  EVALUATION  OF  MID-WATER  ARTIFICIAL  STRUCTURES 


The  quantity  offish  attracted  to  the  structures 
during  our  study  was  not  as  large  as  the  schools 
reported  by  Klima  and  Wickham  (1971).  Coastal 
pelagic  school  fish,  however,  were  seasonally  un- 
available to  the  local  fishery  during  the  study 
period  and  the  fish  captured  around  our  struc- 
tures were  the  only  bait  fish  being  landed. 

The  rapid  rate  of  recruitment  during  our  study 
was  similar  to  the  pattern  of  recruitment  re- 
ported by  Klima  and  Wickham  (1971)  with  fish 
being  observed  at  the  structures  the  day  follow- 
ing placement.  Our  experimental  results  indi- 
cated that  the  fish  were  recruited  to  the  struc- 
tures daily  and  no  significant  accumulation  in 
the  fish  population  was  observed  when  the  struc- 
tures were  allowed  to  soak  for  3  days.  Conse- 
quently, a  greater  total  production  was  obtained 
from  the  structures  by  making  daily  sets.  Com- 
parative day  and  night  sets  provided  further 
evidence  that  fish  schools  dispersed  from  struc- 
tures at  night  during  the  new  moon  and  new  fish 
were  being  recruited  each  day. 

We  were  unable  to  significantly  improve  the 
rate  or  number  of  fish  attracted  to  a  structure 
either  by  doubling  its  size  in  relation  to  our 
standard  structure,  or  by  painting  it  with  fluo- 
rescent colors.  The  experimental  changes  in  size 
and  color  apparently  did  not  extend  the  visible 
range  of  a  structure  sufficiently  to  significantly 
increase  the  number  of  fish  attracted.  Further 
study  is  required  to  determine  whether  multiple 
structure  units  might  be  successful  as  a  means 
for  significantly  improving  the  effective  range 
of  structure  attraction. 

The  feasibility  of  harvesting  structure-attrac- 
ted coastal  pelagic  bait-fish  schools  with  con- 
ventional tom-weight  purse  seines  was  es- 
tablished by  the  success  of  our  quantitative 
collection  procedures.  The  incidence  of  success- 
ful purse  seine  sets  was  greatly  improved  using 
the  artificial  structure  techniques  since  the 
coastal  pelagic  fish  schools  remained  in  associa- 
tion with  the  structures  during  the  sets  and 
made  no  attempt  to  escape. 


Our  experience  during  this  study  indicates 
that  artificial-structure  fish  attraction  techniques 
can  be  developed  to  facilitate  the  harvest  of  the 
latent  coastal  pelagic  resources  in  the  Gulf  of 
Mexico.  Artificial-structure  fish  attraction  tech- 
niques may  also  have  sport  fishing  applications, 
potential  for  development  as  a  method  for  pro- 
viding ground  truth  for  fishery  survey  remote 
sensor  evaluation  and  as  a  method  for  monitor- 
ing fish  movements  and  relative  changes  in 
abundance  in  certain  geographical  areas.  These 
potential  applications  for  artificial-structure 
fish  attraction  techniques  will  be  the  subject  of 
future  investigations. 

ACKNOWLEDGMENTS 

We  would  like  to  thank  John  W.  Watson,  Jr. 
for  his  contributions  during  all  phases  of  the 
field  work,  especially  for  his  assistance  as  a  diver. 
Charles  Roithmayr  and  Wayne  Adkison  provided 
valuable  assistance  by  obtaining  purse-seine 
catch  samples  and  recording  data  aboard  the 
chartered  purse  seiner  Gulf  Ranger. 

LITERATURE  CITED 

Gooding,  R.  M.,  and  J.  J.  Magnuson. 

1967.  Ecological   significance  of  a   drifting  object   to 
pelagic  fishes.  Pac.  Sci.  21:486-497. 
Hunter.  J.  R..  and  C.  T.  Mitchell. 

1967.  Association  of  fishes  with  flotsam  in  the  offshore 
waters  of  Central  America.  U.S.  Fish.  Wild!.  Serv.. 
Fish.  Bull.  66: 13-29. 

1968.  Field  experiments  on  the  attraction  of  pelagic 
fish  to  floating  objects.  J.  Cons.  3 1 :427-434. 

Kjnney,  J.  S. 

1970.  Visibility  of  colors  underwater.  Mar.  Tech.  Soc. 
6th  Annu.  Conf.  Expo.  1:627-636. 

Klima,  E.  F.,  and  D.  A.  Wickham. 

1971.  Attraction  of  coastal  pelagic  fishes  with  artificial 
structures.  Trans.  Am.  Fish.  Soc.  100:86-99. 

Mitchell,  C.  T.,  and  J.  R.  Hunter. 

1970.  Fishes  associated  with  drifting  kelp,  Macrocys- 
tis  pyrifera,  off  the  coast  of  southern  California  and 
northern  Baja  California.  Calif.  Fish  Game. 
56:288-297. 


191 


THE  AGE  COMPOSITION  OF  STRIPED  BASS 

CATCHES  IN  VIRGINIA  RIVERS,  1967-1971, 

AND  A  DESCRIPTION  OF  THE  FISHERY^ 

George  C.  Grant^ 


ABSTRACT 

The  age  composition  of  Virginia  catches  of  the  striped  bass,  Morone  saxatilis,  is  being 
monitored  as  one  of  the  parameters  important  in  rational  management  of  the  species.  Catches 
of  pound  nets  and  fyke  nets,  relatively  nonselective  gear  types  used  in  estimates  of  age  struc- 
ture, weie  sampled  semimonthly  in  three  Virginia  rivers  from  July  1967  through  June  1971. 

Seasonal  changes  in  age  compt)sition  are  slight  with  older,  migratory  striped  bass  occurring 
more  frequently  in  winter  and  spring  catches.  Young  fish  are  not  caught  by  these  nets  in 
significant  numbers  until  the  spring  following  the  year  of  their  hatch.  An  age  group  that  is 
dominant  in  summer  usually  continues  its  dominance  through  the  spring  of  the  following  year. 

Differences  in  age  composition  of  striped  bass  catches  among  rivers  and  years  occur  as  a 
result  of  variable  year  class  strength.  Although  one-year-olds  normally  dominate 
catches,  two-year-olds  may  predominate  either  through  local  failure  of  a  year  class  or  by 
continued  dominance  of  a  relatively  strong  year  class. 

A  brief  description  of  the  striped  bass  fishery  in  Virginia  is  included. 


Closer  management  of  anadromous  fish  stocks 
may  become  necessary  as  a  protective  response 
to  increasing  human  populations  along  the 
Atlantic  coast  of  the  United  States.  Because  of 
their  reproductive  migrations  into  river  systems, 
these  anadromous  fishes  may  be  most  directly 
affected  by  the  expanding  megalopolis  of  the  east 
coast  and  the  increased  pollution  of  coastal 
waters. 

One  valuable  anadromous  species  is  the  striped 
bass,  Morone  saxatilis  (Walbaum).  Although 
the  biology  and  habits  of  striped  bass  are  fairly 
well  studied  (Raney,  1952),  effective  manage- 
ment of  the  stocks  has  been  hampered  by  the 
absence  of  data  on  population  parameters  such 
as  age  composition  and  mortality. 

An  investigation  of  striped  bass  in  Virginia-^ 
was  initiated  in  1967  after  a  review  of  results 
from  the  Chesapeake  Bay  Cooperative  Striped 
Bass  Program  (Lewis,  1961;  Mansueti,  1961; 
Massmann  and  Pacheco.  1961)  and  follows  the 
suggestions  of  Sykes  (1961)  for  further  research 
on  striped  bass.  This  paper  considers  the  age 


'  Contribution  No.  590  from  the  Virginia  Institute  of 
Marine  Science. 

-  Virginia  Institute  of  Marine  Science,  Gloucester  Pt., 
VA  23062. 

■*  Supported  in  part  with  Anadromous  Fish  Act  (P.L. 
89-304)  funds,  through  the  Bureau  of  Sport  Fisheries  and 
Wildlife,  Projects  AFS4  and  AFS6  (Virginia). 


composition  of  striped  bass  catches  in  Virginia 
and  briefly  describes  the  fishery. 

DESCRIPTION  OF  THE  FISHERY 

The  coastal  Virginia  fishery  for  striped  bass  is 
scattered  and  diverse.  It  includes  trawlers, 
pound  nets,  fyke  nets,  haul  seines,  gill  nets  and 
sport  fishing  gear. 

In  the  commercial  fishery,  pound  nets  are 
fished  at  permanent  locations  and  are  most 
consistently  in  use.  They  are  lifted  only  during 
brief  periods  for  cleaning,  to  prevent  possible 
ice  damage,  or  because  of  nuisance  factors  such 
as  abundant  jellyfish.  Fyke  nets,  hung  and 
fished  much  like  small  pound  nets  in  Virginia 
waters,  are  usually  located  farther  upriver  than 
the  pound  nets.  Catches  are  relatively  small  and 
the  gear  is  employed  more  sporadically  than 
pound  nets.  Trawlers  are  limited  to  offshore 
fishing  by  law.  Therefore  striped  bass  are 
available  to  this  gear  only  in  winter  months, 
when  they  are  migrating  along  the  coast.  Striped 
bass  availability  to  trawlers  increases  during 
severe  winters  when  the  river  populations 
migrate  to  the  warmer  coastal  waters  (Grant 
et  al.,  1970).  Gill  net  mesh  size  and  manner 
of  fishing  vary  with  the  season  in  the  striped 
bass  fishery.  Small  mesh  "spot  and  perch  nets" 


Manuscript  accepted  Julv.  IV73 

FISHERY  BULLETIN:  VOL.  72.  NO.  1.  1974, 


193 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


VZVs  -  3V2"  stretch  mesh)  are  anchored  in  the 
summer  and  staked  from  late  fall  to  winter. 
Large  mesh  "shad  nets"  (51/2  "  stretch  mesh)  are 
staked  or  drifted  in  late  winter  and  spring.  Haul 
seines  are  used  sporadically  throughout  the 
warmer  months,  but  most  effectively  in  the 
spring. 

Sport  fishing  for  striped  bass  is  intensive  in 
the  lower  Chesaj^eake  Bay.  especially  along  the 
Chesapeake  Bay  Bridge-Tunnel  in  spring  and 
fall.  The  sport  fishery  extends  from  the  mouth 
of  the  Bay  to  the  freshwater  regions  of  major 
river  systems  from  March  through  December. 
Attraction  of  small  striped  bass  to  the 
numerous  lighted  piers  extends  sport  fishing 
well  beyond  daylight  hours. 

Commercial  landings  of  striped  bass  in  Vir- 
ginia^ for  the  40-yr  period  1930-1969  show  a 
ninefold  increase  from  a  low  of  0.3  million 
pounds  in  1934  to  2.8  million  pounds  in  1966 
(Figure  1).  The  overall  trend  in  landings  (and 
striped  bass  populations)  has  been  rising  during 
this  period.  Two  definite  peaks  of  abundance  are 
evident,  one  in  the  late  1940's  and  the  other  in 
the  1960's.  Not  included  in  these  landings  are 
sport  catches,  which  have  increased  to  as  much 
as  50  percent  of  the  total  catch  in  certain  areas 
(Grant,  unpublished  data).  Averaged  commer- 
cial landings  .in  the  most  recent  years  have 
declined;  continuation  or  reversal  of  this  decline 
depends  on  contributions  to  subsequent  catches 
by  successful  year  classes  such  as  those  of  1966 
and  1970  (Grant  and  Joseph,  1969;  Grant, 
Burrell,  and  Kriete,  1971). 

AGE  COMPOSITION 

Methods  and  Materials 

Pound  nets  and  fyke  nets  trap  striped  bass 
over  their  entire  size  range,  except  for  the 
young-of-the-year  which  are  incompletely 
recruited  to  the  gear.  These  two  gear  types 
were,  therefore,  considered  to  be  essentially 
nonselective  (allowing  for  escapement  of  Age 
0  fish)  and  were  sampled  for  estimates  of  the 
age  composition  of  striped  bass  stocks  residing 
in  the  James,  York,  and  Rappahannock  rivers. 
Although  differences  in  the  age  composition  of 


2.8  n 


'■["l"l"T"f'|"l"l'  T  '['  I'  I    I 
1930         1935         1940 


I  'I'  I   I  I  I   I  I   I   I   I   I 
1945         1950         1955 


I    I    I    I    I    I    I    I    IT 
1960        1965 


■*  Data  from  K.00  ( 1970)  and  from  annual  summaries  of 
regional  fisheries  statistics  published  by  the  Bureau  of 
Commercial  Fisheries. 


Figure  1. — Annual  landings  of  striped  bass  in  Virginia, 
1930-69.  Moving  averages  (indicated  by  heavy  line  for 
6-yr  average  and  light  line  for  3-yr  average)  incorporate  an 
interpolated  value  of  1,321,000  pounds  for  1943. 

catches  by  pound  and  fyke  nets  did  occur,  no 
consistency  was  evident  in  these  differences,  so 
catches  were  pooled  for  analysis.  Rappahannock 
River  samples  were  taken  from  pound  nets  only. 

The  scale  method  was  used  for  age  determina- 
tions. Scales  were  first  used  in  age  analysis  of 
striped  bass  populations  by  Scofield  (1931); 
this  method  was  fully  developed  and  validated 
for  striped  bass  by  Merriman  (1941).  Samples 
of  approximately  50  striped  bass  were  obtained 
from  each  river  system  semimonthly.  Scales 
were  removed  from  individual  fish  at  the  site 
specified  by  Merriman  (1941).  Cellulose  acetate 
impressions  of  scale  sculpturing  were  prepared 
using  five  or  six  scales  from  each  fish.  Annuli 
were  counted  at  a  magnification  of  15  x  with 
all  scales  being  read  at  least  twice  and  instances 
of  disagreement  re-examined. 

Annuli  on  the  scales  of  Virginia  strijied  bass 
form  between  April  and  June,  coincident  with 
the  spawning  season  and  hatch  of  a  new  year 
class.  The  growth  year  of  local  populations, 
therefore,  may  be  considered  to  extend  from 
July  to  June.  Young-of-the-year  do  not  become 
Age  I  fish  until  late  spring  of  the  year  following 
their  hatch.  In  this  paper,  July  1  is  designated 
as  the  start  of  each  year  so  that  a  member  of 
the  1966  year  class  caught  between  1  July  1967 
and  30  June  1968  would  be  called  Age  I.  Season- 
al designations  are  used  as  follows:  winter 
(Jan. -Mai'.),  s])ring  (A])r.-June),  summer  (July- 
Sej^t.).  fall  (Oct. -Dec);  these  quarterly  periods 


194 


GRANT:  AGE  COMPOSITION  OF  STRIPED  BASS 

were  chosen  on  the  basis  of  water  temperatures 
and  are  more  meaningful  in  the  present  context 
than  terrestrial  seasons. 

Seasonal  Age  Composition 
James  River 

Catches  in  the  James  River  (Table  1)  typify 
the  seasonal  pattern  observed  in  all  three  rivers. 
The  age  group  that  dominated  July-September 
catches  generally  continued  to  dominate  through 
the  following  June,  i.e.,  for  a  complete  sampling 
year  that  began  in  July. 

Striped  bass  older  than  Age  III  were  present 
throughout  the  1967-1968  sampling  year  and 
were  most  abundant  in  spring.  In  other  years, 
these  mature  fish  appeared  in  April;  some  re- 
mained in  the  river  through  summer,  but  none 
were  taken  during  the  fall  and  winter.  Young- 
of-the-year  were  generally  absent  from  catches, 
except  for  the  appearance  of  the  1969  year  class 
in  spring  months  of  1970. 


York  River 

The  general  pattern  of  dominance  observed  in 
the  James  River  was  repeated  in  the  York  (Table 
2).  An  exception  occurred  in  winter  months  of 
1970,  when  icing  of  the  river  severely  reduced 
catches  and  the  small  sample  consisted  mostly 
of  older  fish.  A  more  notable  exception  was  the 
dominance  of  young-of-the-year  striped  bass  in 
spring  months  of  1971. 

Mature  striped  bass  older  than  Age  III 
rarely  appeared  during  warmer  months  in  the 
York  River.  Seventy-eight  percent  of  these  older 
individuals  were  taken  in  winter  and  spring 
months,  7.5%  in  the  summer  quarter. 

Rappahannock  River 

Only  one  seasonal  shift  in  age  group  domi- 
nance occurred  in  Rappahannock  River  catches 
of  striped  bass  during  the  four-year  sampling 
period.  Older  fish  dominated  in  winter  months 
of  1970  (Table  3),  as  observed  in  the  York  River. 


Table    1. — Age   composition   of  striped  bass  caught   by   nonselective   fishing  gear   in   the 
James  River  within  quarterly  periods,  July  1967-June  1971. 


Num 

ber  in  Age 

Group 

Quarterly 
Period 

0 

1 

II 

III 

IV 

V 

VI 

^VJI 

N 

(1967) 
July-Sept 

— 

— 

35 

24 

1 

1 

1 

1 

63 

Oct -Dec 

(1968) 

Jan-Mar 

1 

19 
9 

122 
8 

10 
4 

2 

1 

3 

4 

157 
26 

Apr  June 

_ 

22 

39 

34 

8 

2 

8 

26 

139 

°o  Subtotal 

0.3 

13.0 

53.0 

18.7 

2.9 

1.0 

3.1 

8.1 

July-Sept 

— 

70 

189 

94 

27 

4 

1 

3 

388 

Oct -Dec 

(1969) 

Jan-Mar 

—               97 

(no  samples) 

89 

13 

— 

— 

— 

— 

199 

0 

Apr -June 

_ 

154 

108 

16 

19 

10 

8 

12 

327 

%  Subtotal 

0 

35.1 

42.2 

13.5 

5.0 

1.5 

1.0 

1.6 

July-Sept 

— 

31 

235 

58 

3 

4 

— 

3 

334 

Oct -Dec 

(1970) 

— 

8 

85 

13 

— 

— 

z 

z 

106 

Jan-Mar 

— 

1 

3 

2 

6 

Apr -June 

19 

33 

81 

29 

10 

3 

2 

14 

191 

%  Subtotal 

3.0 

11.5 

63.4 

16.0 

2.0 

1.1 

0.3 

2.2 

July-Sept 

1 

98 

57 

64 

12 

1 

1 

1 

235 

Oct -Dec 

(1971) 

Jan-Mar 

-               33 
(no  samples) 

8 

6 

— 

— 

— 



47 
0 

Apr -June 

(no  samples) 

0 

%  Subtotal 

0.4 

46.5 

23.0 

24.8 

4.3 

0.4 

0.4 
Total  N 

0.4 
umber  Aged 

2,218 

195 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Table    2. — Age   composition   of  striped   bass   caught    by    nonselective   fishing   gear   in   the 
York  River  within  quarterly  periods,  July  1967-June  1971. 


Nurr 

ber  in  Age 

Goup 

Quarterly 
Period 

0 

1 

II 

III 

IV 

V 

VI 

SVII 

.V 

(1967) 
July-Sept 

— 

317 

22 

4 

— 

— 

— 

— 

343 

Oct -Dec 

(1968) 

Jan-Mar 

— 

112 
16 

20 
13 

1 
11 

— 

— 

— 

— 

133 
40 

Apr -June 

2 

119 

21 

2 



_ 

_ 

2 

146 

°o  Subtotal 

0.3 

85.2 

11.5 

2.7 

0 

0 

0 

0.3 

July-Sept 

— 

84 

126 

5 

— 

1 

— 

2 

218 

Oct -Dec 

( 1 969) 

Jan-Mor 

1 
1 

274 
178 

210 
151 

27 
40 

4 
14 

4 

1 

1 

516 
390 

Apr -June 

11 

191 

75 

15 

3 

3 

1 

6 

305 

°b  Subtotal 

0.9 

50.9 

39.3 

6.1 

1.5 

0.6 

0.1 

0.6 

July-Sept 

— 

221 

149 

13 

2 

2 

— 

— 

387 

Oct -Dec 

(1970) 
Jan-Mar 

8 

225 

1 

200 
4 

47 
6 

11 

1 

2 

1 

3 

497 
12 

Apr -June 

41 

84 

33 

10 

2 

3 

2 

_ 

175 

°c  Subtotal 

4.6 

49.6 

36.0 

7.1 

1.5 

0.7 

0.3 

0.3 

July-Sept 

— 

223 

48 

2 

— 

— 

— 

— 

273 

Oct -Dec 

(1971) 

Jan-Mar 

13 
13 

425 
82 

65 
13 

16 
8 

6 
1 

1 

— 

3 

525 
121 

Apr -June 

145 

131 

9 

12 

7 

_ 

2 

2 

308 

%  Subtotal 

13.9 

70.2 

11.0 

3.1 

1.1 

0.1 

0.2 
Total  N 

0.4 
umber  Aged 

4,389 

Seasonal    occurrence    of   striped    bass    older 
than  Age  III  was  similar  to  that  observed  in  the 
York.  Eighty-three  percent  of  these  individuals 
were  taken  in  winter  and  spring  months,  11.2% 
in  the  summer  months. 

Young-of-the-year  first  appeared  in  fall 
catches,  but  significant  numbers  were  not  taken 
until  the  following  spring.  This  seasonal  pattern 
was  similar  to  observations  from  the  York 
River. 

Differences  in  Age  Composition  between 
Years  and  Rivers 

Differences  between  both  years  and  rivers  in 
the  age  structure  of  Virginia  striped  bass 
catches  are  shown  in  Figure  2,  where  age 
comi)osition  data  have  been  combined  into 
sampling  year  totals  within  river  systems.  James 
River  catches  were  dominated  by  Age  II  striped 


bass  in  three  of  the  four  sampling  years,  and  by 
Age  I  fish  (1969  year  class)  in  1970-1971. 
Rappahannock  River  catches,  on  the  other 
hand,  were  dominated  by  Age  I  striped  bass  in 
three  of  the  four  years,  and  by  Age  II  fish  in 
1968-69.  Age  I  fish  dominated  York  River 
catches  in  all  four  years.  Except  for  the  con- 
tinued domination  of  Rappahannock  River 
catches  by  the  1966  year  class  during  the  1968- 
69  sampling  year,  age  composition  in  the  York 
and  Rappahannock  rivers  was  similar. 

Among  the  1965-1969  year  classes  which 
progressed  through  the  fishery  as  Age  I  and  II 
fish  during  the  four-year  sampling  period,  the 
1966  year  class  appears  to  have  contributed 
most  heavily  to  the  York  and  Rappahannock 
river  catches.  The  1967  year  class  was  strongest 
in  the  James  River.  Dominance  of  year  classes 
in  the  various  years  and  river  systems  is  sum- 
marized in  Table  4. 


196 


GRANT:  AGE  COMPOSITION  OF  STRIPED  BASS 

Table    3. — Age  composition   of  striped   bass  caught   by    nonselective   fishing  gear   in   the 
Rappahannock  River  within  quarterly  periods,  July  1967-June  1971. 


Nun- 

ber  in  Age 

Group 

Quarterly 
Period 

0 

1 

II 

III 

IV 

V 

VI 

S=VII 

N 

(1967) 
July-Sept 

— 

124 

11 

2 

— 

— 

— 

— 

137 

Oct -Dec 

(1968) 

Jan-Mar 

2 

280 

84 

48 

25 

11 
17 

2 

4 

6 

19 

1 
23 

344 
178 

Apr -June 

6 

217 

12 

2 

— 

1 

— 

1 

239 

%  Subtotal 

0.9 

78.5 

10.7 

3.6 

0.7 

0.8 

2.1 

2.8 

July-Sept 

— 

81 

220 

1 

2 

— 

— 

— 

304 

Oct -Dec 

(1969) 

Jan-Mar 

4 

124 
36 

256 

139 

8 

14 

1 
4 

1 

— 

3 

393 

197 

Apr -June 

30 

121 

146 

8 

_ 

1 

_ 

11 

317 

°o  Subtotal 

2.8 

29.9 

62.8 

2.6 

0.6 

0.2 

0 

1.2 

July-Sept 

— 

156 

110 

47 

3 

3 

— 

— 

319 

Oct -Dec 

(1970) 

Jan-Mar 

— 

152 
17 

113 
35 

32 

40 

3 
2 

1 

— 

4 

300 
99 

Apr -June 

28 

142 

20 

44 

4 

5 

1 

10 

254 

°o  Subtotal 

2.9 

48,0 

28.6 

16.8 

1.2 

0.9 

0.1 

1.4 

July-Sept 

— 

123 

87 

7 

10 

1 

— 

— 

228 

Oct -Dec 

(1971) 

Jan-Mar 

8 
3 

200 
127 

86 
64 

4 
16 

1 
14 

1 

1 

4 

1 

300 
230 

Apr -June 

86 

149 

30 

7 

14 

1 

1 

5 

293 

°'o  Subtotal 

9.2 

57.0 

25.4 

3.2 

3.7 

0.3 

0.6 
Total 

0.6 
Number  Aged 

4,132 

DISCUSSION 

Seasonal  and  Annual  Age  Composition 
of  River  Catches 

Seasonal  variation  in  the  age  composition 
of  striped  bass  catches  is  slight  (Tables  1-3) 
when  viewed  over  a  sampling  year  begun  in 
July.  Most  of  the  seasonal  variation  occurs 
among  subdominant  age  groups,  specifically 
the  appearance  of  young-of-the-year  in  the 
fall  and  the  annual  return  of  older,  mature 
stocks  in  winter  and  spring.  A  year  class  that  is 
dominant  in  summer  tends  to  remain  dominant 
through  the  following  spring.  Changes  in 
year  class  dominance  from  one  year  to  another 
usually  occur  in  summer,  so  age  group  domi- 
nance tends  to  remain  constant. 

Annual  differences  in  age  composition,  on 
the  other  hand,  can  be  striking.  Although  Age  I 
striped  bass  are  expected  to  predominate  in 
pound   net  and  fyke   net  catches,   strong  year 


classes  may  continue  to  dominate  catches  a 
second  year  as  Age  II  individuals.  This  occurred 
in  the  Rappahannock  River  as  a  result  of  the 
strong  1966  year  class  (Figure  2). 

The  predominance  of  Age  II  striped  bass 
catches  from  the  James  River  during  three  of 
the  four  sampling  years  differs  from  the  age 
composition  observed  in  the  York  and  Rappa- 
hannock rivers.  Partial  explanations  are 
available  for  two  of  these  cases:  1)  the  1965 
year  class  dominated  1967-68  catches  because 
of  the  local  failure  of  the  1966  year  class  (Grant 
and  Joseph.  1969);  2)  the  1966  year  class 
dominated  1968-1969  catches  after  entering 
the  James  from  other  rivers  where  it  was  an 
unusually  successful  year  class. 

The  Virginia  Fishery  and 
Cycles  of  Abundance 

The  appearance  of  a  dominant  year  class  of 
striped  bass  in  Chesapeake  Bay  waters  is 
reflected  in  subsequent  catches  within  the  Bay 


197 


FISHERY  BULLETIN:  VOL,  72.  NO.  1 


75- 


50- 


20- 


0- 
75- 


50- 


25- 


-I 
a. 


JULY      1970- 
—  JUNE     1971 


:t7n    mn 


JULY     1969- 
-JUNE     1970 


Im^TT— I 


so- 


ts 
< 

H 

S     25 

o 

a: 


75- 


50- 


25- 


i 


JULY  1968- 
-JUNE   1969 


K?7-7I — . f      I      I      I 


JULY     1967- 
-JUNE   1968 


E3  JAMES    R 

O  YORK      R 

□  RAPPAHANNOCK    R 


|1 


^ 

2 


_E1 


21       >  7n 


n        ra       Ez 

AGE        GROUP 


Figure  2. — ^^Age  composition  of  sampled  pound  and  fyive 
net  catches  in  the  James,  York,  and  Rappahannock  rivers, 
July  1%7-June  1971. 

(Tiller,  1950;  Vladykov  and  Wallace,  1952; 
Murphy,  1960;  Shearer,  Ritchie,  and  Frisbie, 
1962)  and  along  the  migration  route  in 
coastal  states  from  Virginia  to  New  England 
(Merriman,  1941;  Schaefer,  1968).  Schaefer 
(1968)  concluded  that  Chesapeake  Bay  is 
the  primary  source  of  striped  bass  caught  in 
the  surf  of  Long  Island,  and  that  Hudson  River 
stocks  may  significantly  contribute  to  these 
populations  only  when  dominant  year  classes 
from  Chesapeake  Bay  are  unavailable.  Yet 
it  is  generally  believed,  although  still  debatable, 
that  only  a  small  proportion  of  those  striped 
bass  originating  in  Chesapeake  Bay  enter  the 
coastal  migration  (Vladykov  and  Wallace,  1952; 
Mansueti,  1961;  Massmann  and  Pacheco,  1961; 
Grant  etal.,  1970). 

Koo  (1970)  has  shown  an  apparent  six-year 


Table   4. — Summary   of  the   year   classes  of  striped  bass       ■ 
that  dominated  catches  in  Virginia  rivers,  1967-1971. 


River 

Samp 
1967-68 

ing  Year 
1968-69 

(Ju 

y  through  J 
1969-70 

une) 
1970-71 

James 

York 

Rappa 

ha 

nnock 

1965 
1966 
1966 

1966 
1967 
1966 

1967 
1968 
1968 

1969 
1969 
1969 

Table  5 — Contribution  of  age  groups  I-III  to  pound  net 
and  fyke  net  catches  of  striped  bass  in  three  Virginia 
rivers,  1967-1971. 


Sampling  Year 

Perce 

ntage 
Age 

of  Samp 
Groups 

ed  Catch  in 
I-III 

(July-June) 

James 

York 

Rappahannock 

1967-1968 
1968-1969 
1969-1970 
1970-1971 

84.7 
90.8 
90.9 
94.3 

99.4 
96.3 
92.7 
84.3 

92.8 
95.3 
93.4 
85.6 

cycle  of  abundance  in  Maryland.  Such  a  cycle 
could  result  from  the  appearance  of  a  dominant 
year  class  every  six  years,  followed  by  three 
years  of  high  catches  (Ages  I-III),  then  three 
of  relatively  low  catches.  The  younger  age 
groups  (I  to  III)  contribute  most  to  Virginia 
pound  net  and  fyke  net  catches  of  striped  bass 
(Table  5),  as  expected  for  nonselective  fishing 
gear.  Over  90%  of  sampled  individuals  were 
from  age  gi-oups  I  to  III,  except:  1)  84.7%  in 
the  James  River  during  the  first  year  of  sam- 
pling due  to  catches  of  large  numbers  of  older 
fish,  particularly  the  1958  year  class;  2)  84.3%  in 
the  York  River  in  the  1970-1971  sampling  year; 
and  3)  85.6%  in  the  Rappahannock  River  in 
the  same  year.  The  last  two  exceptions  occurred 
because  of  contributions  by  the  latest  dominant 
year  class  (1970 — then  Age  0). 

Although  the  age  composition  of  Virginia 
catches  would  seem  to  conform  to  Koo's  (1970) 
six-year  cycle,  no  such  cycle  is  apparent  in 
Virginia  landings  (Figure  1),  even  though  the 
dominant  year  classes  mentioned  by  Koo  (1970) 
were  also  successful  ones  in  Virginia.  The 
difference  between  Maryland  and  Virginia 
landings,  relative  to  this  six-year  cycle,  might 
stem  from  local  successes  of  year  classes  inter- 
spersed among  those  appearing  at  six-year 
intervals.  In  addition  to  the  1958,  1964  and 
1970  cyclically  dominant  year  classes,  certain 
Virginia  rivers  have  produced  large  hatches  of 
striped  bass  in  1961  and  1966  (Grant  and 
Joseph,  1969;  Grant,  Burrell,  and  Kriete,  1971). 
Catches  of  these  aperiodically  strong  year  clas- 


198 


GRANT:  AGE  COMPOSITION  OF  STRIPED  BASS 


es  tend  to  obscure,  or  even  eliminate,  peaks  in 
landings  contributed  by  Koo's  Chesapeake- 
wide  dominant  year  classes.  Thus  only  long- 
term  trends  in  abundance  remain  evident 
(Figui'e  1). 

ACKNOWLEDGMENTS 

The  author  acknowledges  with  thanks  the 
following  colleagues  for  their  helpful  dis- 
cussions and  assistance:  Edwin  B.  Joseph, 
Victor  G.  Burrell,  Jr..  C.E.  Richards.  William 
H.  Kriete,  Jr.,  George  R.  Thomas,  and  James 
C.  Owens.  Reviews  of  the  manuscript  by 
Jackson  Davis  and  John  V.  Merriner  were 
most  helpful.  Also  appreciated  are  the  drafting 
of  figures  by  Jane  Davis,  photography  by  Ken 
Thornberry  and  manuscript  typing  by  Louise 
DeBolt  and  Linda  Jenkins. 

LITERATURE  CITED 

Grant,  B.  C,  V.  G.  Burrell,  Jr.,  and  W.  H.  Kriete,  Jr. 
1971.     Age  comiiosilion  and  magnitude  of  striped  bass 
winter     gill-net     catches     in     the     Rappahannock 
River,    1967-1970.   Proc.  24th  Annu.  Conf.   South- 
eastern Assoc.  Game  Fish.  Comm.,  p.  659-667. 
Grant,  G.  C,  V.  G.  Burrell,  Jr.,  C.  E.  Richards,  and 
E.  B.  Joseph. 

1970.  Preliminary  results  from  striped  bass  tagging  in 
Virginia,  1968-1969.  Proc.  23rd  Annu.  Conf.  South- 
eastern Assoc.  Game  Fish  Comm.,  p.  558-570. 
Grant,  G.  C,  and  E.  B.  Joseph. 

1969.  Comparative  strength  of  the  1966  year  class  of 
striped  bass,  Roccus  saxalilis  (Walbaum),  in  three 
Virginia  rivers.  Proc.  22nd  Annu.  Conf.  South- 
eastern Assoc.  Game  Fish  Comm..  p.  501-509. 

Koo,  T.  S.  Y. 

1970.  The  striped  bass  fishery  in  the  Atlantic  states. 
Chesapeake  Sci.  11:73-93. 


Lewis,  R.   M. 

1961.  Comparison    of  three   tags    on   striped   bass   in 
the  Chesapeake  Bay  area.  Chesapeake  Sci.  2:3-8. 
Mansueti,  R.  J. 

1961.     Age,  growth,  and  movements  of  the  striped  bass, 
Roccus  saxalilis,  taken  in  size  selective  fishing  gear  in 
Maryland.  Chesapeake  Sci.  2:9-36. 
Massmann,  W.  H.,  and  a.  L.  Pacheco. 

1961.  Movements  of  striped  bass  tagged  in  Virginia 
waters  of  Chesapeake  Bay.  Chesapeake  Sci.  2:37-44. 

Merriman,  D. 

1941.  Studies   on   the   striped   bass   {Roccus  saxalilis) 
of  the  Atlantic  coast.  U.S.   Fish  Wild!.  Serv..  Fish. 
Bull.  50;  1-77. 
Murphy,  G.  J. 

1960.  Availability  of  striped  bass  during  summers  of 
1958  and  1959  as  reflected  in  commercial  haul 
seine  catch.  Chesapeake  Sci.  1:74-75. 

Raney,  E.  C. 

1952.  The  life  history  of  the  striped  bass.  Roccus 
saxalilis  (Walbaum)  Bull.  Bingham  Oceanogr. 
Collect..  Yale  Univ.  14(l):5-97. 

SCHAEFER,  R.  H. 

1968.  Size,  age  composition  and  migration  of  striped 
bass  from  the  surf  waters  of  Long  Island.  N.Y.  Fish 
Game  J.  15:1-51. 

SCOFIELD,    E.    C. 

193  1.     The  striped  bass  of  California  (Roccus  Imcaius). 
Calif.  Fish  Game,  Fish  Bull.  29,  84  p. 
Shearer  ,  L.  W.,  D.  E.  Ritchie,  Jr..  and  C.  M.  Frisbie. 

1962.  Sport  fishing  survey  in  1960  of  the  lower 
Patuxent  estuary  and  the  1958  year-class  of  striped 
bass.  Chesapeake  Sci.  3:1-17. 

Sykes,  J.  E. 

1961.  The  Chesapeake  Bay  cooperative  striped  bass 
program.  Chesapeake  Sci.  2: 1-2. 

Tiller,  R.  E. 

1950.  A  five-year  study  of  the  striped  bass  fishery  of 
Maryland,  based  on  analyses  of  the  scales.  Chesa- 
peake Biol.  Lab.  Publ.  85: 1-30. 
Vladykov,  V.  D.,  and  D.  H.  Wallace. 

1952.  Studies  of  the  striped  bass,  Roccus  saxalilis 
(Walbaum)  with  special  reference  to  the  Chesapeake 
Bay  region  during  1936-1938.  Bull.  Bingham 
Oceanogr.  Collect.,  Yale  Univ.  14(  1):  132- 177. 


199 


LARVAL  FISHES  OF  YAQUINA  BAY,  OREGON: 
A  NURSERY  GROUND  FOR  MARINE  FISHES? 

WiLUAM  G.  Pearcy  and  Sharon  S.  Myers' 

ABSTRACT 

Based  on  a  survey  of  planktonic  fish  larvae,  the  Yaquina  Bay  estuary  appears  important  as  a 
spawning  or  rearing  ground  only  for  Cliipea  harengus  pallasi  (Pacific  herring)  and  a  variety  of 
small  cottids,  gobies,  and  stichaeids.  Other  investigators,  however,  have  found  an  abundance 
of  juvenile  Paroplirys  vctiihis  (English  sole),  Citharichihys  stigiuaeus  (sanddab),  HyponicsHs 
pretiosus  (surf  smelt),  Plutichthys  siellatiis  (starry  flounder)  and  embiotocids  (surf  perches), 
indicating  that  the  bay  is  an  important  nursery  area  for  these  species. 

Of  the  44  types  of  larval  fishes  found  in  the  bay,  C.  h.  pallasi  and  Lepidogobius  lepidits 
(bay  goby)  were  co-dominants  each  year,  1960-1970,  comprising  90%  of  all  larvae  collected. 
There  was  no  evidence  of  trends  in  abundances  or  species  composition  during  the  11-yr  study. 

Maxima  of  planktonic  fish  eggs  and  L.  gobiiis  larvae  occurred  in  the  summer:  maxima  of  all 
larvae  combined  and  most  species  of  larvae  occurred  in  the  winter  and  spring.  High  densities 
of  larval  herring  were  found  in  February  and  March,  and  peak  numbers  appeared  earlier 
in  the  lower  than  the  upper  estuary. 

Larvae  of  C.  h.  pallasi,  L.  lepidus,  and  Cotius  asper  were  common  at  all  stations  from  0.5 
to  8  nautical  miles  up  the  estuary,  but  not  in  the  adjacent  open  ocean.  Larvae  of  many  species 
that  were  found  in  the  estuary  in  small  numbers  were  more  abundant  in  offshore  waters. 
Although  English  sole  and  sanddab  were  rare  in  the  bay  as  larvae,  juveniles  were  numerous. 


This  is  a  study  of  the  species  composition, 
relative  abundance,  seasonal  and  annual  occur- 
rence and  distribution  of  larval  fishes  in  an 
Oregon  estuary.  It  was  undertaken  to  increase 
the  extremely  limited  knowledge  of  fish  larvae 
in  estuaries  of  the  Pacific  Northwest  and  to 
evaluate  the  role  of  these  estuaries  as  spawning 
and  nursery  grounds. 

According  to  Clark  (1967)  and  McHugh 
(1966,  1967)  the  young  of  up  to  70%  of  the  eco- 
nomically important  Atlantic  species  of  fishes 
inhabit  estuaries  during  part  of  their  early  life. 
Many  species  spawn  offshore  and  young  stages 
subsequently  move  into  brackish  estuaries. 
Although  the  Pacific  coast  is  known  for  its  runs 
of  anadromous  salmonids  which  migrate 
through  estuaries,  "There  is  no  counterpart  on 
the  Pacific  coast  of  the  mass  inshore  movement 
of  larvae  and  young  of  offshore-spawning  nek- 
tonic  species  into  brackish  nursery  grounds 
that  is  such  a  striking  feature  of  the  ecology  of 
most  Atlantic  coast  and  Gulf  of  Mexico 
estuaries."  (McHugh,  1967).  Thus  the  number 
of  species  that  are  dependent  on  estuaries  may 


'   School  of  Oceanography,  Oregon  Stale  University,  Cor- 
vallis,  OR  97.131. 


not  be  as  great  on  the  Pacific  as  the  Atlantic 
coast. 

Oregon's  estuaries  are  few  in  number  and 
include  but  a  small  area.  For  this  reason  man's 
infringement  on  them  for  recreation,  land 
development,  harbors,  agriculture,  and  waste 
disposal  will  be  intense.  This  study  evaluates 
some  long-term  trends  of  the  relative  abundance 
of  larval  fishes.  Hopefully  it  will  facilitate  future 
comparisons  of  faunal  changes  within  this 
estuarine  habitat. 

THE  ESTUARY 

Yaquina  Bay  (Figure  1)  is  a  small  tidal 
estuary  on  the  central  Oregon  Coast.  It  extends 
inland  about  37  km  and  has  an  area  of  about 
11.6  km-.  A  channel  is  dredged  to  a  depth  of  7.9 
m  to  McLean  Point  and  to  3.7  m  to  the  town  of 
Toledo.  Tides  are  mixed,  semidiurnal  with  a 
mean  tidal  range  of  1.7  m  (Kulm  and  Byrne, 
1967).  According  to  Zimmerman  (1972)  the  bay 
has  an  exchange  ratio  of  52%  and  a  flushing  time 
of  13.3  tidal  cycles  during  the  summer.  The 
estuary  is  well-mixed  with  little  vertical  strati- 
fication in  the  summer  when  freshwater  runoff 
is  low,  and  is  partially  mi.xed  (4-19"/on  salinity 


Manuscript  accepted  June.  1973. 

FISHERY  BULLETIN,  VOL.  72,  NO.  1,  W74 


201 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


I24»00  W. 


TOLEDO 


44' 
96' 
N. 


CONTOUR     INTERVAL     12    FEET 
DATUM     MEAN     LOWER    LOW    WATER 

Contour!    complied    from      U.  S 
C.  AGlS      I9S3    •moom  tliMt 


44" 
36 

N. 


124*  00' W. 


Figure  1. — Yaquina  Bay  estuary,  showing  location  of  stations:  Bridge,  Buoy  15,  21,  29,  and  39. 


difference  from  surface  to  bottom)  during  other 
seasons  (Burt  and  McAlister,  1959;  Kulm  and 
Byrne,  1967;  Zimmerman,  1972).  Salinity  is 
lowest  and  also  most  variable  during  the  winter 
period  of  high  precipitation.  Temperatures, 
however,  are  most  variable  during  the  summer, 
owing  to  periodic  advection  of  cold  upwelled 
waters  into  the  bay  and  to  local  heating  (Fro- 
lander.  1964;  Frolander  et  al..  1973). 

SAMPLING  METHODS 

A  12.5  cm  diameter  Clarke-Bumpus  (CB) 
Sampler  with  nylon  (Nitex")"  net  of  0.233  mm 
mesh  aperture  was  used  to  collect  393  plankton 
samples  from  January  1960  to  December  1970 
and  to  provide  a  long  time  series  for  analysis 
at  one  station  (Buoy  21)  located  in  Yaquina 
Bay  about  4.3  nautical  miles  from  the  ocean 
(Figure  1).  In  addition,  both  the  CB  and  a  20.2 
cm  diameter  nonclosing  Bongo  Sampler  were 
towed  together  at  five  stations  (Bridge  and 
Buoys  15,  21,  29,  and  39)  from  June  1969  to 
June    1970   (223   tows).   The  bongo  had   nylon 


2  Reference  to  trade  names  does  not  imply  endorsement 
by  the  National  Marine  Fisheries  Service. 


nets  with  0.233  mesh  on  one  side  and  a  0.571 
mesh  on  the  other  and  was  attached  1  m  below 
the  CB  on  the  same  towing  cable.  The  CB  net 
was  61.6  cm  long  with  the  filtering  area  of  the 
mesh  to  mouth  area  ratio  of  6.2:1.  The  bongo 
nets  were  cylindrical-conical,  177  and  161  cm 
long  for  the  0.233  and  0.571  mesh  nets  respec- 
tively. Both  bongo  nets  had  a  filtering  area  to 
mouth  area  ratio  of  10.5: 1. 

Samples  were  collected  from  small  boats, 
generally  at  weekly  intervals  during  the  sam- 
pling period.  Oblique-step  tows  were  made  at  2 
knots.  At  the  three  deep  stations  (Bridge,  Buoys 
15  and  21)  the  net  was  towed  horizontally  at 
each  of  three  depths  for  4  min:  about  1  m  above 
the  bottom,  at  mid-depth  and  1  m  below  the 
surface.  At  the  two  shallow  stations  in  the  upper 
estuary  the  nets  were  towed  at  each  of  two 
depths  for  6  min:  1  m  above  the  bottom  and  1  m 
below  the  surface.  Tows  were  made  during  day- 
light, in  mid-channel,  against  tidal  currents, 
and  did  not  coincide  with  any  particular  tidal 
stage.  However,  several  24-h  series  of  CB  tows 
(123  tows)  were  made  during  the  11-yr  period 
to  assess  diel  and  tidal  variations  at  single 
stations. 


202 


PEARCY  and  MYERS:  LARVAL  FISHES  OF  YAQUINA  BAY 


Samples  were  also  collected  with  the  bongo 
nets  (0,233  and  0.571  mm  mesh)  in  the  open 
ocean  off  Yaquina  Bay  from  June  1969  to  June 
1970,  often  within  a  day  of  the  bay  sampling.  A 
total  of  113  step  oblique  tows  was  made  at  four 
stations  1,  3,  5,  and  10  miles  from  the  coast. 

Volume  of  water  filtered  during  each  tow 
was  estimated  by  flowmeters  in  the  mouth  of 
the  nets.  TSK  meters  were  mounted  on  the 
inside  wall  of  the  bongo  frames.  Meters  were 
calibrated  periodically  by  towing  them  over  a 
measured  distance.  Samples  were  preserved  in 
the  field  with  Formalin.  In  the  laboratory  entire 
samples  were  sorted  for  fish  larvae  with  the  aid 
of  2V4 -power  illuminated  magnifier.  Fish  eggs 
were  sorted  from  the  1960-1968  CB  samples. 

SPECIES  COMPOSITION 

Larval  fishes  representing  17  families  were 
found  in  Yaquina  Bay  during  the  11-yr  studies. 
These  included  45  distinct  types  of  larvae,  22  of 
which  were  identified  to  species  (Table  1).  Most 
families  were  represented  by  only  one  or  two 
species  or  types.  The  family  Cottidae,  however, 
was  represented  by  14  different  larval  types, 
by  far  the  most  for  any  family.  The  family  with 
the  next  largest  number  of  types  was  Pleuronec- 
tidae  with  6  identified  species. 

THE  11-YR  SERIES 

Relative  Abundances 

Table  2  summarizes  the  occurrence  and 
average  density  of  different  fish  larvae  collected 
during  the  11-yr  CB  series  at  Buoy  21.  Two 
species,  Clnpea  harengiix  pallasi  (Pacific  her- 
ring) and  Lepidogobius  lepidus  (bay  goby), 
were  clearly  the  most  abundant  larvae.  Com- 
bined they  accounted  for  90%  of  all  the  fish 
larvae  collected  in  the  393  samples. 

These  two  species  were  consistently  the  co- 
dominants  during  all  years  of  the  sudy  (Table 
3).  C.  h.  pallasi  ranked  first  in  abundance  during 
8  yr.  L.  lepidus  ranked  first  in  3  yr  and  second 
in  the  8  yr  that  C.  h.  palla.^i  was  dominant. 
Cottus  asper  (prickly  sculpin)  ranked  third  in 
abundance.  Leptocottus  armatus  (Pacific  stag- 
horn  sculpin),  Gobiidae  type  1,  and  Hypomesus 
pretiosus  (surf  smelt)  alternated  in  the  fourth, 
fifth,  and  sixth   positions.  Average  number  of 


Table     1. —  Species     composition     of    fish     larvae     from 
Yaquina  Bay  from  all  samples  examined,  1960-1970. 

Clupeidae 

Cltipca  hurciiKiis  pallasi 
Engraulidae 

EnKiaitli''  morilax 
Osmeridae 

H\  potncsus  pii'iiosus 
Gobiesocidae 

Gohicsox  nwandricus 
Gadidae 

Microiiadti^  proxiniWi 
Gasterosteidae 

Aiilorhynchus  ttavidus 
Syngnathidae 

Svni;iHilhm  i;iisci>lincan<\ 
Stichaeidae 

LumpeiuiS  sugilta 

Annplarchiis  sp. 

ChiroUiphis  sp. 

2  unknown  types 
Pholidae 

Pholis  (irnara 
Ammodytidae 

Ainmodyles  hexaptenis 
Gobiidae 

LcpuloKohiiis  It'dpiitiis 

1  unknown  type 
Scorpanenidae 

SchasU'\  spp. 
Hexagram  mi  doe 

Hi'xaiirainini)^  sp. 

Ophioddii  eU>ui;aiiis 
Cottidae 

Leplocollus  armalus 

Conns  asper 

Scarpaenichthys  nianuoratus 

Enophrys  bison 

HeniiU'pidoiiis  spp. 

9  unknown  types 
Agonidae 

2  unknown  types 
Cyclopteridae 

3  unknown  types 
Bothidae 

Cilharichihys  sp. 
Pleuronectidae 

Psellichthys  melanosticiiis 
Platichlhys  stellalus 
Glyiocephaliis  zuchinis 
Isopsetta  isolepis 
Parophrys  vetulus 
Lyopsetta  exilis 


these  larvae  per  m''  varied  from  year  to  year,  but 
no  obvious  long-term  trends  in  the  relative 
abundance  of  these  species  suggested  environ- 
mental changes  or  species  succession.  (Similar- 
ly, Frolander  et  al.  [in  press]  found  no  evidence 
for  persistent  changes  of  zooplankton  abun- 
dances in  Yaquina  Bay  over  the  same  time 
period.) 

In  order  to  learn  if  all  six  of  the  common 
species  were  more  abundant  in  some  years 
than  others,  rank  correlations  were  calculated 
from  annual  abundances  in  Table  3.  Cliipea  h. 
pallasi  and  L.  lepidus  were  both  caught  in 
large  numbers  in  1967.  but  the  Coefficient  of 
Concordance,  W,  (Tate  and  Clelland,  1957) 
indicated  little  agreement  among  ranking  of 
vears  (P  >  0.2).  In  other  words,  there  was  no 


203 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Table  2. —  Fish  larvae  collected  in  CTarke-Bumpus  nets  during  1960-1970  at  Buoy  2] 

ranked  by  abundance. 


No.  of  Tows 

Total  No. 

Total  No.  larvae   — 

Months  of 

occurred 

collected 

total 

volume  of  water 

occurrence 

item 

in  out  of  393 

filtered       m-'xlO'' 

Clupeu  harentiiis  palUiM 

76 

2,174 

510 

l-V 

LepidoKobiiis  lepidus 

98 

1,287 

302 

IV-X 

Ci>llu\  a\per 

47 

129 

30 

l-V 

LeptocoUKs  armatus 

42 

53 

12 

Vlll-lll 

Gobiidae  type  1 

27 

49 

11 

Vll-lll,  VI 

H\,  pomcsu.s  preliosiis 

23 

39 

9.1 

VIII-IX,  XI-IV 

Lninpcnus  siiaina 

8 

29 

6.8 

l-ll 

Enaphrys  his  on 

12 

20 

4.7 

l-lll 

AntmodyU's  hexapienis 

10 

15 

3.5 

l-lll 

Anopkinhiis  sp. 

10 

12 

2.8 

ll-lll 

Cottidae  type  1 

8 

10 

2.3 

ll-lll,  Vi-VII 

Ennraiilis  itiordax 

6 

7 

1.6 

VII-IX. 

Pholis  oriuilu 

7 

7 

1.6 

l-lll 

Parophrys  venilus 

4 

6 

1.4 

ll-lll 

Plaiichihy^  \ielUmis 

3 

3 

0.7 

V-VI 

Cyclopteridae  type  1 

3 

3 

0.7 

VI,  VII,  XII 

Cottidae  type  lOA 

3 

3 

0.7 

II,  XI 

Cottidae  type  5 

3 

3 

0.7 

VIM,  IX 

Cilhuncluhys  sp. 

2 

2 

0.5 

ll-lll 

Cyclopteridae  type  2 

2 

2 

0.5 

VI-VII 

S\Kiitilhus  i;risi'i>Unealus 

2 

2 

0.5 

VII-VIII 

Cottidae  type  lOB 

1 

1 

0.2 

1 

Cottidae  type  1  1 

1 

1 

0.2 

III 

Schasics  spp. 

1 

1 

0.2 

1 

Hexagrammidoe 

1 

1 

0.2 

II 

evidence  that  "good"  or  "bad"  years  occurred 
simultaneously  for  different  species  of  larvae. 

SEASONAL  VARIATIONS 

Total  Eggs  and  Larvae 

The  average  monthly  catch  of  pelagic  fish 
eggs  at  Buoy  21  was  highest  in  the  summer, 
with  highest  values  ( >  2/m^)  from  July  to  October 
(Figure  2).  Eggs  of  the  northern  anchovy 
{Engraulis  mordax)  were  sometimes  abundant 
during  this  season.  Numbers  of  fish  larvae, 
on  the  other  hand,  peaked  early  in  the  year, 
from  February  to  June,  and  few  larvae  were 
taken  after  June.  C.  h.  pallasi  and  L.  lepidus 
larvae  were  the  main  contributors  to  these  large 
larval   catches.   These  two   species,   and   many 


others    found    in    the    estuary,    have    demersal 
eggs. 

This  seasonal  maximum  of  fish  larvae  in  the 
first  half  of  the  year  in  Yaquina  Bay  is  similar 
to  the  seasonality  reported  in  the  Straits  of 
Georgia,  British  Columbia  by  Parsons,  LeBras- 
seur,  and  Barraclough  (1970). 

Individual  Species 

The  seasonal  occurrence  of  larvae  collected 
at  Buoy  21  is  summarized  in  Table  2.  The 
majority  of  the  larval  species  were  most  com- 
mon in  the  winter  or  spring,  including  C.  It. 
pallasi,  Coitus  asper,  Hypomesus  pretiosus, 
Paropltrys  retulus,  Anintodytes  hexapterus, 
Luinpenus  sagitta,  Auoplarchus  sp.,  Pholis 
oruata,    and    Euophi-ys    bisou.    L.    lepidus    was 


Table    3.  —  Average   abundance   of  the  six   most   common   fish   larvae   by   year,    1960-1970, 

Clarke-Bumpus  samples.  Buoy  21. 


Avera 

ge  number  of  larvae  per 

lO'^m^ 

water  filtered 

Item 

1960 

1961 

1962 

1963 

1964 

1965 

1966 

1967 

1968 

1969 

1970 

Clupc'u  )iarenHUS 

174 

542 

278 

279 

1,230 

335 

273 

1,136 

961 

526 

506 

pallasi 

Li'pidoKohiiis 

312 

230 

37 

1  14 

326 

402 

161 

1,169 

471 

74 

132 

lepidus 

Cdiuis  asper 

17 

35 

24 

38 

41 

48 

35 

68 

5 

20 

14 

Gobiidae  type  1 

11 

1 

2 

50 

24 

0 

0 

11 

0 

34 

14 

Leplocollits 

17 

6 

12 

34 

12 

7 

18 

17 

5 

10 

2 

armatus 

Hypomesus 

5 

7 

0 

23 

4 

4 

18 

3 

0 

44 

7 

pretiosus 

204 


PEARCY  and  MYERS:  LARVAL  FISHES  OF  YAQUINA  BAY 

the  only  common  species  with  a  distinct  peak 
of  larval  abundance  in  the  summer  (April- 
September).  Several  species  were  collected 
most  months  of  the  year:  considering  all  years 
together,  larvae  of  Hyponiesus  pretiosus  were 
found  every  month  but  May,  June,  July  and 
October,  L.  arniatus  every  month  except 
April-July,  and  Gobiidae  type  1  every  month 
but  April,  May  and  July. 

Pacific  Herring 

Catches  of  C.  It.  pallasi  larvae  during  each 
January-June  period,  1960-1970,  are  illus- 
trated for  Buoy  21  in  Figure  3.  Herring  larvae 
were  common  from.  Febi-uary-April,  with  peak 
numbers  usually  in  February  and  March. 
Though  sampling  variability  and  the  limited 
number  of  samples  precluded  annual  com- 
parisons of  abundance,  no  obvious  long-term 
trends,  such  as  decreasing  catches,  are  evident 
during  this  11-yr  period,  nor  is  there  good 
evidence  for  large  fluctuations  in  larval  num- 
bers. This  suggests  a  fairly  stable  population  of 
spawning  herring  over  this  time  period. 

The  initial  occurrence  of  larval  herring 
varied  among  years,  from  January  to  March, 
suggesting  annual  differences  in  time  of  spawn- 
ing or  hatching  times  (e.g.,  contrast  1969  and 
1970  with  1961-1963).  This  variability  may 
be  related  to  water  temperature.  The  surface 
temperature  of  first  larval  occurrence  varied 
from  7.3°C  to  10.5°C  (average  =  9.0°C).  To 
estimate  date  of  first  spawning,  incubation 
time  was  calculated  from  a  curve  of  incubation 
times  vs.  temperature  (Outram,  1955;  Taylor, 
1971;  Steinfeld,  1972).  Incubation  was  estimated 
to  range  between  12  and  17  days  for  the  first 
herring  larvae  caught  during  these  years  using 
surface  water  temperatures  at  Buoy  21.  (Because 
herring  spawn  in  shallow  water,  often  inter- 
tidally  [Steinfield.  1972;  Taylor,  1971;  Hard- 
wick,  1973] ,  surface  temperatures  were  used.) 
Surface  temperatures  averaged  for  the  date  of 
first  herring  larval  occurrence  and  the  previous 
17  days  (2-3  observations)  were  plotted  against 
time  of  first  larval  occurrence  after  January  1 
(Figure  4).  This  revealed  a  surprising  relation- 
ship: Years  of  earliest  occurrence  of  larvae  (i.e., 
1969  and  1970)  had  lowest  water  temperatures 
(<  8°C)  preceding  first  catches,  and  most  years 
of  latest  occurrence  (i.e.  1961.  1963,  1965,  1966) 
had    highest    temperatures    (>9.2°C)    during 


0  - 


2  - 


_.*_ 


A     I     S     I     0     I     N     I      D 


Figure  2. — Average  monthly  catches  offish  eggs  and  larvae 
in  Clarke-Bumpus  samples  at  Buoy  21.  Each  point  rep- 
resents a  monthly  average  for  fish  eggs  each  year,  1960- 
1968,  and  for  fish  larvae  each  year,  1969-1970.  No  samples 
were  available  from  April-July  1966. 

incubation  of  the  first  hatch.  Thus,  factors  other 
than  water  temperature  appear  to  be  important 
in  determining  the  time  of  the  initial  spawning 
of  herring  in  Yaquina  Bay. 

Steinfeld  (1972)  observed  from  egg  surveys 
in  Yaquina  Bay  that  herring  had  four  major 
spawnings  during  February  and  March  1970. 
These  occurred  at  about  2-wk  intervals  starting 
in  early  February,  the  most  intensive  spawnings 
coinciding  with  highest  tides.  Newly  hatched 
larvae  would  therefore  be  expected  in  most  of 
the  catches  throughout  the  larval  periods. 
Measurements  of  larvae  contributing  to  early 
and  late  peaks  in  1964  and  1967  showed  that 
recently  hatched  larvae  (6-8  mm)  were  indeed 
present  in  April,  but  as  expected,  the  percentage 
of  small  larvae  was  lower  later  in  the  year. 

HORIZONTAL  VARIATIONS 

The  average  number  of  larvae  collected  at  the 
different  stations  in  both  the  estuary  and  the 
open  ocean  are  listed  in  Table  4,  permitting 
comparison  of  horizontal  variations  of  relative 
abundance  at  nine  stations  from  8  miles  up  the 


205 


FISHERY  BULLETIN;  VOL.  72.  NO.  1 


cr 

LlJ 
CL 

cc 

UJ 


10- 


ii- 


10 


0.1  r 


I- 


0.1 


I  - 


l|- 


"1 r 


1        r 


1969 


1966 


1965 


1964 


1963 


1962 


•f'l' 


^ 


1961 


I       r 


Figure  3. — Number  of  Pacific  herring  larvae  per  m'*  caught 
in  Clarke-Bumpus  nets  at  Buoy  21  during  January -June 
periods,  1960-1970. 


10 


0)    g 

Q. 

E 

0) 


1 

1 

,1963 

,1966 
,1965 

/968, 

*I96I 

— 

1964^ 

^1967 

— 

. 

I960, 

,1962 

- 

,/5/c 

,1969 

- 

JAN. 

1             FEB. 

1              MAR. 

Figure  4. — Average  surface  temperature  at  Buoy  21  during 
and  14-17  days  prior  to  first  catches  of  herring  larvae  vs. 
date  of  first  catches  of  herring  larvae,  1960-1970. 


estuary  to  10  miles  off  the  coast.  Within  the 
estuary,  larvae  of  C.  /;.  pallasi,  L.  lepidus,  and 
CottKs  anper  usually  ranked  first,  second,  and 
third  respectively  in  the  catches  at  all  five 
stations,  from  0.5  to  8  nautical  miles  up  the  es- 
tuary. L.  lepidiis  was  the  only  common  species 
revStricted  to  the  bay;  it  was  most  numerous  in 
the  upper  estuary.  Larvae  of  C.  h.  pallasi  were 
abundant  in  the  bay  and  rare  outside  the  bay. 
Some  of  the  other  species  that  are  considered 
to  be  primarily  bay  forms  are  Cottus  asper, 
found  in  greatest  numbers  in  the  upper  estuary, 
and  Eiiopliiys  bison,  Leptocottns  armatus  and 
Pholis  ornata,  found  mainly  in  the  lower 
estuary. 

Many  of  the  larvae  found  in  the  bay  were  found 
in  greater  numbers  offshore.  Larvae  of  the  surf 
smelt,  H.  pretiosKs,  were  sometimes  abundant 
in  the  lower  estuary  where  juvenile  H.  pretiosus 
were  also  numerous.  Osmerids  were  most  abun- 
dant 1  mile  offshore.  We  assume  that  these 
were  mainly  H.  pnfiosKs,  a  si)ecies  known  to 
spawn  in  the  surf  zone.  Consequently,  the  surf 
smelt  larvae  found  in  the  bay  may  be  carried 
there  by  tidal  exchange.  Larvae  of  A.  hexap- 
terus,  Sebastes  spp.,  pleuronectids,  gadids,  and 
cyclopterids  were  all  found  in  higher  numbers 
offshore  than  in  the  bay.  Parophryx  vetulus  was 
only  found  offshore. 

Eiigraulis  niordax  larvae  were  found  through- 
out the  bay  and  to  3  miles  offshore.  They  were 
not  found  5  or  10  miles  offshore.  This  larval 
di.stribution,  and  the  large  numbers  of  anchovy 


206 


PEARCY  and  MYERS:  LARVAL  FISHES  OF  YAQUINA  BAY 

Table  4, —  Average  number  of  larvae  per  lO-'nv'  filtered  in  bongo  nets  (mesh  0.233  and 
0.571  mm  combined)  calculated  from  total  number  of  specimens  collected  ^  total  volume 
filtered  for  entire  year.  Only  species  represented  by  five  or  more  larvae  are  listed.  June 
1%9-June  1970. 


BAY 

OFFSHORE  (mi) 

39 

29 

21 

15 

BR 

1 

3 

5 

10 

A.  BAY  ONLY 

LepiciofiohiHs  U-pidiis 

)06.0 

340.5 

113.4 

92.9 

6.4 

0 

0 

0 

0 

Lumpeniis  sa^itui 

0 

0 

0.5 

1.1 

1.3 

0 

0 

0 

0 

Anoptarchiis  spp. 

0 

0.6 

0.7 

1.1 

1.0 

0 

0 

0 

0 

B.  PRIMARILY  BAY 

Chipca  h.  pallasi 

509.2 

428.2 

442.6 

556.0 

183.3 

0.3 

0.5 

0 

0 

Gobiidoe  type  1 

0.5 

0.9 

13.7 

5.3 

1.3 

0.6 

0.3 

0 

0 

Coitus  usper 

40.7 

42.3 

21.0 

10.1 

9.2 

0.6 

0 

0 

0 

Enophrys  bison 

0 

0 

2.3 

9.6 

18.8 

0.3 

0 

0 

0 

Leplocoitus  arma!u\ 

0.7 

1.6 

10.0 

7.2 

3.8 

0.3 

0 

0 

0 

Cottidae  Type  1 

0 

0 

0.5 

1.3 

1.3 

0.6 

0.5 

1.0 

0.3 

Pholis  ornutu 

0 

0 

0.8 

1.3 

1.3 

0.3 

0.5 

0 

0 

C,  PRIMARILY  OFFSHORE 

Eni;ruulis  monlax 

0.5 

1.0 

0.5 

0.3 

0.2 

2.1 

1.1 

0 

0 

H}  ponu'sus  pn'tiosus-Osmeridi 

1.0 

0.6 

3.0 

15.7 

27.2 

100.9 

18.6 

4.6 

0.3 

Gadidae 

0 

0 

0.5 

0 

0.2 

0.6 

4.5 

0.7 

1.1 

Ammodytes  hexapterus 

0 

0 

0 

0.5 

0.5 

1.8 

13.0 

2.0 

2.5 

Sebasies  spp. 

0 

0 

0 

0.5 

0.8 

6.9 

4.2 

1.5 

19.6 

Ophiodon  elonf;urus 

0 

0 

0 

0.3 

0 

0.6 

0.8 

0.7 

0 

Hemilepidotus 

0 

0 

0 

0 

0.2 

1.5 

2.9 

0 

1.2 

Cottidae  type  12 

0 

0 

0 

0.3 

0.5 

0.9 

0 

0 

0 

Agonidae 

0 

0 

0 

0 

1.0 

0.3 

0.5 

0.2 

0 

Cyclopteridae 

0 

0 

0.2 

0.3 

0.2 

0.6 

3.2 

0.2 

0.5 

Pseilichthys  inelunoslUliis 

0.2 

0 

0.5 

0 

0.5 

5.1 

31.1 

3.4 

0.5 

Isopseita  isolepis 

0 

0 

0 

0 

0.2 

0.6 

36.1 

5.1 

1.1 

Lyopselta  extlis 

0.2 

0 

0 

0 

0 

0 

9.0 

0 

0.3 

Citharichthys  sp. 

0 

0 

0 

0.5 

0.5 

1.0 

0 

0 

0 

D.  OFFSHORE  ONLY 

Stenobrachius  teucopsarus 

0 

0 

0 

0 

0 

0.3 

0.5 

1.0 

1.6 

Cottidae  type  16 

0 

0 

0 

0 

0 

0 

2.4 

0 

0.3 

Cottidae  unident,  spp. 

0 

0 

0 

0 

0 

1.8 

9.6 

7.1 

0.6 

Parophrys  veluliis 

0 

0 

0 

0 

0 

1.2 

9.0 

11.9 

8.9 

Blennoids 

0 

0 

0 

0 

0 

3.3 

4.5 

0 

0 

eggs  within  the  bay,  is  peculiar  since  Richard- 
son (1973)  reported  that  anchovy  larvae  were 
abundant  well  offshore,  usually  in  Columbia 
River  plume  waters,  and  not  near  the  coast. 


Pacific  Herring 


Abundance 


Herring  larvae  were  abundant  at  all  five 
stations  during  February  and  March  1970  (Fig- 
ure 5).  A  peak  in  catches  occurred  in  late 
January  at  the  three  stations  closest  to  the 
ocean,  and  conversely,  higher  numbers  occurred 
later  (April  and  May)  at  the  upper  estuarine 
stations.  These  trends  suggest  earlier  spawning 
near  the  mouth  and  later  spawning  in  the  upper 
estuary.  Based  on  intertidal  surveys,  Steinfeld 
(1972)  found  herring  eggs  near  the  mouth  from 
February  5  to  20,  1970,  and  in  the  upper  estuary 
above  Buoy  21  from  March  8  to  24.  1970.  The 
trend  for  earlier  spawning  near  the  mouth  of 


the  estuary  was  therefore  found  in  both  larval 
and  egg  surveys.  However,  the  fact  that  Stein- 
feld did  not  find  any  spawn  before  February  5 
while  we  collected  many  larvae  between  January 
23  and  February  10  indicates  that  intertidal 
surveys  may  miss  substantial  areas  of  eggs, 
perhaps  from  subtidal  spawning. 

Comparison  of  Nets 

Catches  of  herring  larvae  in  the  three  types  of 
nets  (CB  and  bongo  with  0.233  mm  mesh  and 
bongo  with  0.571  mm  mesh)  were  usually  sim- 
ilar on  a  m'^  basis,  especially  at  high  densities 
of  larvae  (Figure  5).  The  type  of  net  catching 
the  highest  or  the  lowest  number  of  larvae 
altei'nated  among  tows.  We  had  not  expected 
catches  by  the  CB  to  compare  favorably  with 
the  bongo  in  view  of  the  known  avoidance 
capability  of  Atlantic  herring  larvae  (Bridger, 
1956;  Tibboetal.,  1958). 

The  percentage  of  herring  larvae  of  different 


207 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


sizes  caught  at  Buoy  29  in  the  three  nets  during 
the  1970  larval  season  is  shown  in  Figure  6. 
Little  difference  is  apparent  in  the  proportion 
of  different  sizes  of  larvae  in  the  different  nets. 
All  curves  show  that  the  number  of  larvae 
caught  between  6  and  8  mm  was  less  than  be- 
tween 8  and  10  mm.  This  is  probably  explained 
by  hatching  of  some  larvae  at  lengths  over  8 
mm,  and  hence  is  a  true  reflection  of  relative 
abundance,  rather  than  lack  of  retention  of 
the  smallest  larvae  by  the  nets.  Larvae  larger 
than  20  mm  were  not  caught  at  all  in  the  CB 
samples,  presumably  because  of  the  capability 
of  large  larvae  to  avoid  this  gear. 

TIDAL-DIEL  VARIATIONS 

Figure  7  illustrates  the  variations  in  CB 
catches  of  fish  eggs  and  larvae  during  several 
diel  sampling  periods  at  Buoy  21.  In  Figure  7A, 
peaks  in  both  egg  and  larval  abundance  occurred 
during  periods  of  low  water  (Mann-Whitney  U 
test.  P  <0.01).  Similarly,  highest  catches  of 
herring  larvae  coincided  with  times  of  low 
water  in  Figure  7B  {P  =  0.06).  In  neither  of 
these  figures  is  a  day-night  difference  evident 
(P  >  0.2).  In  Figure  7C,  however,  catches  of 
herring  larvae  were  not  correlated  with  tidal 
stage  (P  >0.2),  but  highest  catches  coincided 
with  darkness  (P  <0.01);  all  but  one  of  the  9 
nighttime  catches  exceeded  the  14  daytime 
catches. 

Therefore,  both  tidal  and  diel  factors  may 
influence  catches.  We  believe  the  high  catches 
associated  with  low  water  were  caused  by  tidal 
excursion  of  water  with  high  density  of  eggs 
or  lai-vae.  In  other  words,  the  center  of  abun- 
dance of  L.  lepidus  larvae  and  fish  eggs  (Figure 
7A)  and  C.  h.  pallasi  (Figure  7B)  was  up  the 
estuary  from  Buoy  21  at  high  tide.  The  ability 
of  larger  larvae  to  avoid  plankton  nets  during 
the  daytime  (see  Figure  6;  Tibbo  et  al.,  1958; 
Bridger,  1956;  and  Colton,  Honey,  and  Temple, 
1961)  was  thought  to  explain  the  high  catches 
after  dark  in  Figure  7C,  but  this  interpretation 
was  not  supported  by  the  similar  size-frequency 
distributions  of  day-  and  night-caught  larvae. 


Q 
UJ 
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1969 


1970 


THE  ESTUARY  AS  A  NURSERY 

The  results  of  this  study  on  the  i)lanktonic 
fish  larvae  tentatively  support  McHugh's  (1966, 


Figure  5. — Number  of  Pacific  herring  per  m^  caught  in 
Clarke-Bumpus  nets  with  0.233  mm  mesh,  the  bongo  net 
with  0.233  mm  mesh  and  the  bongo  net  with  0.571  mm 
mesh  at  five  stations  in  Yaquina  Bay,  June  1969-June  1970. 


208 


PEARCY  and  MYERS:  LARVAL  FISHES  OF  YAQUINA  BAY 

1967)  contention  that  estuaries  of  the  Pacific 
coast  may  be  less  important  as  nursery  grounds 
than  eastern  seaboard  estuaries.  But  such  a 
conclusion  is  unwarranted  without  a  comparison 
of  larval  abundances  within  the  estuary  with 
those  in  adjoining  open  ocean  to  learn  if  larvae 
are  restricted  to  or  concentrated  in  estuaries. 
High  numbers  of  larvae  within  the  estuary  are 
not  necessarily  pi-oof  of  estuarine  dependance, 
as  they  may  be  more  abundant  in  the  ocean. 
Conversely,  low  densities  of  a  species  inside  the 
estuary  may  indicate  importance  if  it  is  absent 
elsewhere.  A  comparison  of  larval  catches  in 
Yaquina  Bay  with  the  open  ocean  is  possible 
since  we  collected  fish  larvae  at  stations  1,  3,  5, 
and  10  miles  off  Yaquina  Bay,  using  the  same 
bongo  nets  during  the  same  sampling  period 
as  the  bay  sampling.  The  results  of  this  compari- 
son (Table  4)  corroborate  our  earlier  suggestion: 
with  the  exception  of  the  Pacific  herring  the 
estuary  does  not  appear  to  be  important  to  the 
pelagic  larvae  of  commercial  fishes.  Most  of 
the  larvae  that  were  restricted  to  or  were  most 
common  in  the  estuary  were  of  small,  non-food 
species  of  cottids,  stichaeids,  and  gobies.  Larvae 
of  all  the  pleuronectids  collected  were  more 
common  offshore  than  inside  the  estuary. 

Thus  the  Pacific  herring  was  the  only  species 
of  commercial  interest  that  appeared  to  use  the 
estuary  extensively  as  both  a  spawning  and  a 
nursery  ground.  In  California,  herring  spawn  in 
bays  and  estuaries  (Hardwick,  1973).  Since 
Pacific  herring  are  known  to  comprise  more  or 
less  distinct  populations  with  adults  returning 
to  the  same  bay  to  spawn  (Stevenson,  1955; 
Rounsefell,  1930),  estuaries  may  be  vital  to  the 
maintenance  of  herring  along  some  portions  of 
the  west  coast. 

Feeding  conditions  for  herring  are  undoubt- 
edly related  to  their  use  of  estuaries  as  nurs- 
eries. Russell  (1964)  found  that  Yaquina  Bay 
is  used  as  a  feeding  ground  for  1  to  4  yr-old 
herring  which  fed  mainly  on  the  copepods 
Acartia  clausii  and  Pseudocalaiiui<  sp.,  both 
abundant  within  the  bay.  A.  clausii,  which  is 
thought  to  maintain  indigenous  populations 
in  Yaquina  Bay,  is  especially  abundant  in  the 
upper  estuary  (Buoys  21  and  29)  early  in  the 
spring  when  densities  of  adults  and  immatures 
exceed  30,OOOm-5  (Zimmerman,  1972  Froland- 
er  et  al..  1973).  The  numbers  of  copepod  eggs, 
nauplii,  and  copepodites,  important  food  for 
Atlantic  herring  larvae,   probably   exceed  this 


100 


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10 


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UJ 
Q. 


CLARKE-BUMPUS  233 


-^    BONGO  233 
-a    BONGO  571 


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o'^ 


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I         ,        7        I        I       f^      c\j      c\j     (\j 

~         00         C\J        (\J 

LENGTH   OF   LARVAE    (mm) 

Figure  6. —  Catches  of  different  lengths  of  herring  larvi 
at  Buoy  29  expressed  as  a  percentage  of  the  total  catc 
for  each  of  the  Clarke-Bumpus  and  bongo  nets  with  0.2J 
mm  mesh  and  the  bongo  net  with  0.571  mm  mesl 
February  10-March  13,  1970. 


density  during  the  early  spring  and  provid 
adequate  food  for  larval  herring  (Blaxter,  196c 
Bainbridge  and  Forsyth,  1971;  Sherman  an 
Honey,  1971). 

Our  planktonic  survey  of  fish  larvae  was  n( 
adequate  to  assess  completely  the  estuary  as 
nursery  ground.  First,  plankton  nets  are  sele( 
five  and  only  weakly  swimming  pelagic  larv£ 
were  effectively  sampled.  Other  young  stag( 
may  not  have  been  fully  susceptible  to  captui 
because  they  actively  avoid  the  nets.  Secondl; 
the  young  of  some  species  may  have  been  preser 
but  simply  unavailable  for  sampling  because  ( 
their  distributions.  These  may  include  youn 
that  migi'ate  into  the  estuary  after  metamo: 
phosis,  benthic  forms,  or  young  that  reside  i 
shallow  areas  of  the  estuary. 

For  example,  viviparous  embiotocids  (PJiai 
erudoii  furcatus,  Rhacochilus  vacca,  an 
Embiotoca  lateralis)  are  common  species  i 
Yaquina  Bay.  Mature  females  of  all  these  specif 
are  numerous  in  the  middle  and  upper  estuar 


201 


[0) 


\D) 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


[O 


—    10 


9  AUG  63  I  /O  AUG  63 


T 

12  24  12 

21  FEB  64  I  22  FEB  64 


1 \  r 

12  24  12 

,?(9  /i^/I/?  67   I  21  MAR  67 


Figure  7. — Diel  variations  in  the  CB  catches  at  Buoy  21:  A.  9-10  August 
1963;  solid  line  =  fish  larvae:  dashed  line  =  fish  eggs.  B.  21-22  February 
1964:  solid  line  =  herring  larvae.  C.  20-21  March  1967:  solid  line  =  herring 
larvae.  The  tidal  height  above  mean  lower-low  water  and  period  of  darkness 
(hatched  bar)  are  shown  above  each  figure.  Dates  and  noon  and  midnight 
are  indicated  below  each  figure. 


during  the  spring  when  they  give  birth  to  young 
which  use  the  estuary  as  a  nursery  (Beardsley, 
1969;  Wares,  1971).  Because  of  their  pelagic 
nature  and  swimming  abilities,  young  embiot- 
ocids  are  not  readily  captured  in  small  plankton 
nets  or  trawls.  Beardsley  (1969)  and  Westr- 
heim  (1955)  also  found  many  juvenile  starry 
flounder  {Flatichthys  stcllufus)  in  Yaquina 
Bay,  and  Haertel  and  Osterberg  (1967)  con- 
cluded that  the  starry  flounder  use  the  upper 
Columbia  River  estuary  as  a  nursery  ground. 

A  trawl  survey  of  juvenile  fishes  of  Yaquina 
Bay  by  Wm.  Johnson  (pers.  comm.),  conducted 
during  the  same  period  and  at  the  same  stations 
as  our  plankton  survey,  provided  useful  in- 
formation on  the  juvenile  fishes  caught  in  mid- 
channel  of  the  estuary  near  the  bottom.  Relative 
abundances  of  the  young  fishes  caught  are 
shown  in  Table  5.  Three  species  were  dominant: 
HypomeHiis  pretiosus,  Paroplirya   vetulus,  and 


Citharichthys  stigmaeus.  They  comprised  79% 
of  the  total  number  of  fishes  collected.  Of  these, 
only  the  abundant  H.  pretiosus  was  also  com- 
mon in  plankton  collections  (Tables  2,  3,  and  4). 
Lepidogobius  lepidus,  Cottus  asper,  and  Lepto- 
cottus  armatiis,  though  presumbly  benthic  as 
juveniles,  were  not  abundant  in  the  trawl 
collections  despite  their  abundance  as  pelagic 
larve.  Johnson  (pers.  comm.)  caught  large  num- 
bers of  juvenile  L.  an)iati<s  in  shoal  areas  of 
Yaquina  Bay  with  a  beach  seine,  indicating 
that  juveniles  of  some  species  may  reside  main- 
ly in  shallow  water. 

Young  of  both  ParopJirys  vcfiilHs  and  Citluir- 
ichtltys  stlgniaciis  were  abundant  within 
Yaquina  Bay,  indicating  that  the  bay  provides 
a  nursery  for  these  species.  Peak  numbers  of 
P.  vetidns  (15-45  mm)  were  found  between 
April  and  June  at  Buoy  21,  but  young  were 
captured  at  all  stations  from   Buoy   15  to  39. 


210 


PEARCY  and  MYERS:  LARVAL  FISHES  OF  YAQUINA  BAY 


Cithcu'iclitliys  stignuwus  (30-80  mm)  were  con- 
centrated in  the  lower  estuary  and  were  rarely 
captured  up-estuary  of  Buoy  21.  They  were 
most  common  in  May  and  June.  Hypomesus 
pretiosHs  (35-50  mm)  were  abundant  at  all 
trawling  stations,  but  only  in  January  and 
February  (Johnson,  pers.  comm.). 

The  importance  of  estuaries  as  nursery 
grounds  for  flounder,  and  especially  for  Par- 
(iphrys  vi'tuliis,  has  been  emi)hasized  by  others. 
Westrheim  (1955)  reported  appreciable  num- 
bers of  small  Parophrys  vetulus,  Cithanchthys 
s())-didiix-^  and  Platichthys  stellatus  (starry  floun- 
der) in  Yaquina  Bay.  Sand  sole  (Psettichthyyi 
ni(Io)i(>><ticti(s)  were  also  encountered  frequently. 
Although  no  adults  of  the  commercially  impor- 
tant English  sole  were  caught,  juveniles  (20- 
180  mm)  were  common  until  autumn  when 
most  emigrated  from  the  bay.  Olsen  and  Pratt 
(1973)  also  reported  that  juvenile  English 
sole  were  abundant  in  lower  Yaquina  Bay  from 
April  to  Sei^tember  1971,  emigrating  to  offshore 
areas  in  October.  Based  on  the  incidence  of  a 
parasitic  infection,  apparently  acquired  only 
in  estuaries,  they  concluded  that  estuaries  are 
likely  to  be  the  exclusive  nursery  grounds  for 
Parophrys  vetulus  on  the  Oregon  coast,  a 
conclusion  that  is  supported  by  the  absence  of 
0-age  English  sole  in  Demory's  (1971)  ocean 
trawling  survey  off  the  Oregon-Washington 
coast.  Misitano  (1970)  and  Eldridge  (1970) 
found  large  numbers  of  English  sole  in  Humboldt 
Bay,  California.  Villadolid  (1927,  as  cited  in 
Misitano,  1970)  captured  0-age  English  sole  by 
trawling  in  San  Francisco  Bay  but  found  none 
off  the  coast.  Shallow  protected  waters  along  the 
indented  British  Columbia  coastline  also  provide 
nursery  grounds  for  this  species  (Ketchen, 
1956).  Bays  and  estuaries  are  therefore  vital  as 
nurseiy  areas  for  P.  vetulus  in  their  first  year 
of  life,  perhaps  because  the  sediments  in  these 
protected  waters  provide  an  ideal  feeding  hab- 
itat for  the  young  as  opposed  to  coarse  sand 
sediments  at  similar  depths  along  the  open 
coast. 

Sexually  mature  (ripe)  P.  vetulus  were  not 
caught  in  Humboldt  or  Yaquina  Bay  but  are 
known  to  spawn  offshore  (Westrheim,  1955; 
Harry.  1959;  Jow,  1969).  Young  larvae  were 
uncommon   in  plankton  collections  from  these 


Table  5. — Relative  abundance  (7c)  ot  juvenile  fishes 
collected  at  four  stations  in  Yaquina  Bay  (Bridge  to 
Buoy  29)  in  a  1.8-m  beam  trawl  (1.5  mm  stretch  mesh), 
January-June,  1970  (courtesy  Wm.  Johnson). 


Hypomesus  preiiostis 
Parophrys  vetulus 
Citharichthys  siif-niaeus 
Enophrys  bison 
CI  u  pea  h.  pal  las  i 
Ammodytes  hexaplerus 
Leplocoitus  annatus 
HexaKrammos  decaf^rainnuis 
Pholis  ornata 
Raja  hinuculala 
Platichthys  stellatus 
Heniilepidotus  heiuilepidotus 
Lumpenus  sa>>itta 
Eiigraulis  mordax 
Lepidoi>ohiiis  lepidus 
Cyiuatofiaster  aggregata 
Sehastes  nielaiiops 
Artedius  fenestralis 
P\ettichthys  mehmostictus 
Ophiodon  eloitf;atiis 
Syanathus  i;riseolineatus 
Pallas  Ilia  barhatu 
Syinphurus  airicauda 
Artedius  harriniitoui 
Anoplarchus  purpurescens 
Phanerodoii  furcatus 
Einbiotoca  lateralis 
Occella  verrucosa 
G obi e SOX  maeandricus 


36.2 

24.6 

18.2 

4.1 

3,6 

2.5 

2.3 

1.1 

1.0 

0.7 

0.7 

0.7 

0.7 

0.6 

0.5 

0.5 

0.4 

0.4 

0.4 

0.3 

0.3 

0.1 

<0.1 

<0.1 

<0.1 

<0.1 

<0.1 

<0.1 

<0.1 


'■'■  Probably     C.    siifiinaeus, 
by  others  in  Yaquma  Bay. 


the    species    usually     Found 


bays  (Eldridge,  1970;  Misitano,  1970).  In  our 
study  P.  vetulus  larvae  were  common  offshore 
but  were  absent  or  rare  in  Yaquina  Bay  (Table 
4).  Therefore  young  English  sole  must  be  trans- 
ported into  the  bay  from  offshore  waters  as  late 
larval  stages  or  migrate  in  as  juveniles.  In 
Humboldt  Bay,  Misitano  (1970)  captured  meta- 
morphosing English  sole  (average  length,  23 
mm)  by  midwater  trawling,  especially  after 
dark.  These  larvae  were  active  swimmers  in 
aquaria  but  usually  resided  on  the  bottom.  As 
a  result  they  would  be  relatively  inaccessible  to 
daytime  plankton  collections. 

The  question  remains,  however,  how  these 
larvae  enter  estuaries.  Currents  off  the  northern 
Pacific  coast  during  the  winter  and  spring  are 
largely  inshore  and  northerly  (Burt  and  Wyatt, 
1964;  Wyatt,  Burt,  and  Pattullo,  1972)  and 
would  transport  buoyant  fish  eggs  such  as  those 
of  English  sole  (Budd.  1940;  Ketchen,  1956; 
Alderdice  and  Forrester,  1968)  toward  and 
then  along  the  coast.  Retention  in  estuaries 
would  seem  to  require  active  behaviorial  re- 
sponses by  the  larvae,  such  as  a  change  in  depth 
distribution  to  enhance  transport  into  and  reduce 
advection  out  of  estuaries.  Since  a  two-layered 
transport  system  prevails  in  Yaquina  Bay  dur- 
ing the  winter  (Kulm  aiid  Byrne,   1967;   Burt 


211 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


and  McAlister.  1959)  and  since  Kulm  and  Byrne 
(1967)  found  that  marine  sand  was  transported 
by  strong  currents  6  miles  up  the  Yaquina  Bay 
estuary  during  the  winter,  the  season  when  P. 
vetulus  enter  the  estuary,  then  descent  of  larvae 
into  deep  water,  where  net  transport  exists  up 
the  estuary,  may  result  in  transport  into  and  re- 
tention within  estuaries  of  English  sole  and 
other  species,  as  found  for  other  larval  fish 
(Pearcy,  1960;  Pearcy  and  Richards.  1962;  and 
Graham,  1972). 

In  conclusion,  Yaquina  Bay,  like  many  east 
coast  estuaries,  is  an  important  nursery  for 
the  young  of  several  species  of  marine  fishes. 
This  was  not  apparent  from  a  survey  of  plank- 
tonic  larvae,  however.  Only  the  larvae  of  Pacific 
herring,  a  species  that  spawns  in  bays,  were 
abundant  in  our  plankton  collections  in  Yaquina 
Bay.  Although  the  pelagic  larvae  of  flatfishes 
were  much  more  common  in  offshore  than 
estuarine  waters,  the  juveniles  of  several  species 
move  into  the  estuary  in  large  numbers. 


ACKNOWLEDGMENTS 

We  are  indebted  to  H.  F.  Frolander  who  has 
tenaciously  conducted  the  plankton  survey  of 
Yaquina  Bay  since  1960  and  provided  the 
11-yr  series  of  collections  and  to  Joan  Flynn 
who  curated  these  collections.  We  are  also 
grateful  to  William  Johnson,  University  of 
Rhode  Island,  who  generously  supplied  his 
data  on  juvenile  fishes,  to  Peter  Rothlisberg, 
Greg  Lough,  and  Dean  Satterlee  who  were 
essential  for  field  sampling  in  1969  and  1970,  to 
Elbert  AhLstrom,  Elaine  Sandknop,  Maxwell 
Eldridge,  and  James  Blackburn  who  helped  to 
identify  fish  larvae  and  to  Sally  Richardson, 
Charles  Miller,  and  William  McNeil  for  their 
helpful  criticisms  of  the  manuscript. 

This  research  was  supported  by  NOAA  In- 
stitutional Sea  Grant,  Contract  No.  2-35187. 


LITERATURE  CITED 


Alderdice,  D.  F.,  andC.  R.  Forrester. 

1968.  St)me  effects  of  salinity  and  temperature  on 
early  development  and  survival  of  the  English 
Sole  (Purophrys  vciulu.s).  J.  Fish.  Res.  Board  Can. 
25:495-521. 


Bainbridge,  v.,  and  D.  C.  T.  Forsyth. 

1971.     The   feeding   of  herring   larvae   in   the   Clyde. 

Rapp.   P.-V.    Reun.   Cons.   Perm.    Int.    Explor.    Mer 

160:104-113. 
Beardsley,  a.  J. 

1969.  Movement  and  angler  use  of  four  foodfishes 
in  Yaquina  Bay,  Oregon.  Ph.D.  Thesis,  Oregon 
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Blaxter,  J.  H.  S. 

1965.     The  feeding  of  herring  larvae  and  their  ecology 
in   relation  to  feeding.  Calif.  Coop.  Oceanic   Fish. 
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Bridger.  J.  P. 

1956.  On  day  and  night  variations  in  catches  of  fish 
larvae.  J.  Cons.  22:42-57. 

BUDD,  P.  L. 

1940.     Development  of  the  eggs  and  early  larvae  of 
six  California  fishes.     Calif.  Dep.  Fish  Game,  Fish. 
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Burt,  W.  V.,  and  W.  B.  McAlister. 

1959.     Recent  studies  in  the  hydrography  of  Oregon 
estuaries.  Fish  Comm.  Oreg.  Res.  Briefs  7(1):  14-27. 
Burt,  W.  V.,  and  B.  Wyatt. 

1964.     Drift    bottle    observations    of    the    Davidson 
Current  off  Oregon.  //;  K.  Yoshida  (editor).  Studies 
on  oceanography,   p.    156-165.  Univ.  Tokyo  Press, 
Tokyo. 
Clark,  J. 

1967.     Fish   and   man.  Conflict   in  the  Atlantic   estu- 
aries. Am.  Littoral  Soc,  Spec.  Publ.  5,  78  p. 
CoLTON,  J.  B.,  Jr.,  K.  A.  Honey,  and  R.  F.  Temple. 

1961.     The   effectiveness   of  sampling   methods    used 
to   study   the   distribution   of  larval   herring  in   the 
Gulf  of  Maine.  J.  Cons.  26: 180-190. 
Demory,  R.  L. 

1971.  Depth  distribution  of  some  small  flatfishes  off 
the  northern  Oregon-southern  Washington  coast. 
Res.  Rep.  Fish  Comm.  Oreg.  3:44-48. 

Eldridge,  M. 

1970.  Larval  fish  survey  of  Humboldt  Bay.  M.S. 
Thesis,  Humboldt  State  Coll.,  Areata,  52  p. 

Frolander,  H.  F. 

1964.     Biological     and     chemical     features     of    tidal 
estuaries.   J.    Water   PoUut.   Control    Fed.    36:1037- 
1048. 
Frolander,  H.  F.,  C.  B.  Miller,  M.  J.  Flynn,  S.  S.  Myers, 
and  S.  T.  Zimmerman. 

1973.  Seasonal   cycles  of  abundance   in   zooplankton 
populations   of  Yaquina    Bay,    Oregon.    Mar.    Biol. 
(Berl.) 
Graham,  J.  J. 

1972.  Retention  of  larval  herring  within  the  Sheep- 
scot  estuary  of  Maine.  Fish.  Bull.,  U.S.  70:299-305. 

Haeriel,  L.,  and  C.  Osterberg. 

1967.     Ecology    of  zooplankton,    benthos    and   fishes 
in  the  Columbia  River  estuary.  Ecology  48:459-472. 
Hardwick,  J.  E. 

1973.  Biomass  estimates  of  spawning  herring,  Clupea 
harcngiis  palhisi,  herring  eggs,  and  associated  vege- 
tation in  Tomales  Bay.  Calif.  Fish  Game  59:36-61. 

Harry,  G.  Y.,  Jr. 

1959.  Time  of  spawning,  length  at  maturity,  and 
fecundity  of  the  English,  Petrale.  and  Dover  Soles 
(Parophrys    vcliihis,    Eopsctta  jordani.    and    Micro- 


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PEARCY  and  MYERS:  LARVAL  FISHES  OF  YAQUINA  BAY 


stunius  pacificus,  respectively).   Fish  Comm.  Oreg., 
Res.  Briefs  7(1) :5- 13. 
Jow,  T. 

1969.  Results  of  English  sole  tagging  off  California. 
Pac.  Mar.  Fish.  Comm.,  Bull.  7;  15-33. 

Ketchen,  K.  S. 

1956.     Factors  influencing  the  survival  of  the  lemon 
sole    (Parophrys   vetulus)    in   Hecate   Strait,    British 
Columbia.  J.  Fish.  Res.  Board  Can.  13:647-693. 
KuLM,  L.  D.,  AND  J.  V.  Byrne. 

1967.     Sediments  of  Yaquina  Bay,  Oregon.  In  G.  H. 
Lauff  (editor),   Estuaries,   p.   226-238.   Am.   Assoc. 
Adv.  Sci.  Publ.  83. 
McHuGH,  J.  L. 

1966.  Management  of  estuarine  fisheries.  Am.  Fish. 
Soc,  Spec.  Publ.  3:133-154. 

1967.  Estuarine  nekton.  In  G.  H.  Lauff  (editor). 
Estuaries,  p.  581-620.  .Am.  Assoc.  Adv.  Sci.  Publ. 
83. 

MiSITANO,  D.  A. 

1970.  Aspects  of  the  early  life  history  of  English 
sole  {Parophrys  vt'tulus)  in  Humboldt  Bay,  Cali- 
fornia. M.  S.  Thesis,  Humboldt  State  Coll.  Areata, 
57  p. 

Olsen,  R.  E.,  and  1.  Pratt. 

1973  Parasites  as  indicators  of  English  Sole  (Par- 
ophrys vetulus)  nursery  grounds.  Trans.  Am.  Fish. 
Soc.  102:405-411. 

OUTRAM,  D.  N. 

1955.     The  development   of  the  Pacific  Herring  egg 
and  its  use  in  estimating  age  of  spawn.  Fish.  Res. 
Board  Can.  Pac.  Biol.  Stn.,  Nanaimo,  B.  C,  Circ. 
40,  10  p. 
Parsons,  T.  R.,  R.  J.  LeBrasseur,  and  W.  E.  Barraclough. 
1970.     Levels  of  production  in  the  pelagic  environ- 
ment  of  the   Strait  of  Georgia,   British  Columbia: 
A  review.  J.   Fish.  Res.  Board  Can.  27:1251-1264. 
Pearcy,  W.  G. 

1962.     Ecology  of  an  estuarine  population  of  winter 
flounder     Pseudopleuronectes     americanus     (Wald- 
baum)  Parts  I-IV.  Bull.  Bingham  Oceanogr.  Collect., 
Yale  Univ.  18(1):  1-78. 
Pearcy,  W.  G.,  and  S.  W.  Richards. 

1962.     Distribution    and    ecology    of    fishes    of    the 
Mystic    River    estuary,    Connecticut.    Ecology    43: 
248-259. 
Richardson,  S.  L. 

1973.  Abundance  and  distrubition  of  larval 
fishes  in  waters  off  Oregon,  May-October  1969, 
with  special  emphasis  on  the  northern  anchovy. 
EngrauUs  mordax.  Fish.  Bull.  U.S.  71:697-71 1. 

ROUNSEFELL,  G.  A. 

1930.     Contribution    to    the    biology    of   the    Pacific 


herring,    Clupea  pallasii,   and  the  condition  of  the 

fishery  in  Alaska.  U.S.  Bur.  Fish.  Bull.  45:227-320. 
Russell,  H.  J.,  Jr. 

1964.     The    endemic    zooplankton    population    as    a 

food   supply    for   young   herring   in   Yaquina    Bay. 

M.S.  Thesis,  Oregon  State  Univ.,  Corvallis,  42  p. 
Sherman,  K.,  and  K.  A.  Honey. 

1971.  Seasonal  variations  in  the  food  of  larval 
herring  in  coastal  waters  of  central  Maine.  Rapp. 
P.-V.  Reun.  Cons.  Perm.  Int.  Explor.  Mer  160: 
121-124. 

Steinfeld,  J.  D. 

1972.  Distribution  of  Pacific  herring  spawn  in  Ya- 
quina Bay,  Oregon,  and  observations  on  mortality 
through  hatching.  M.  S.  Thesis,  Oregon  State  Univ., 
Corvallis,  75  p. 

Stevenson, J.  C. 

1955.  The  movement  of  herring  in  British  Columbia 
waters  as  determined  by  tagging.  With  a  descrip- 
tion of  tagging  and  tag  recovery  methods.  Rapp. 
P.-V.  Reun.  Cons.  Perm.  Int.  Explor.  Mer  140:33-34. 

Tate,  M.  W.,  and  R.  C.  Clelland. 

1957.  Nonparametric  and  shortcut  statistics  in  the 
social,  biological,  and  medical  sciences.  Interstate 
Printers  and  Publishers,  Inc.,  Danville,  111.,  171  p. 

Taylor,  F.  H.  C. 

1971.     Variation  in  hatching  success  in  Pacific  herring 
(Clupea  pallasii)   eggs   with   water   depth,   tempera- 
ture, salinity  and  egg  mass  thickness.  Rapp.  P.-V. 
Reun.    Cons.    Perm.    Int.    Explor.    Mer    160:34-41. 
TiBBO,  S.  N.,  J.  E.  H.  Legare,  L.  W.  Scattergood,  and 
R.  F.  Temple. 

1958.  On  the  occurrence  and  distribution  of  larval 
herring  (Clupea  harengus  L.)  in  the  Bay  of  Fundy 
and  the  Gulf  of  Maine.  J.  Fish.  Res.  Board  Can. 
15:1451-1469. 

Wares,  P.  G. 

1971.  Biology  of  the  pile  perch  (Phacochilus  vacca) 
in  Yaquina  Bay,  Oregon.  U.S.  Bur.  Sport  Fish. 
Wildl.  No.  51,21  p. 

Westrheim,  S.  J. 

1955.  Size  composition,  growth,  and  seasonal  abun- 
dance of  juvenile  English  sole  (Parophrys  vetulus) 
in  Yaquina  Bay.  Res.  Briefs  Fish  Comm.  Oreg. 
6:4-9. 

Wyatt,  B.,  W.  V.  Burt,  and  J.  G.  Pattullo. 

1972.  Surface  currents  off  Oregon  as  determined 
from  drift  bottle  returns.  J.  Phys.  Oceanogr.  2:286- 
293. 

Zimmerman,  S.  T. 

1972.  Seasonal  succession  of  zooplankton  popula- 
tions in  two  dissimilar  marine  embayments  on  the 
Oregon  coast.  Ph.D.  Thesis,  Oregon  State  Univ., 
Corvallis,  207  p. 


213 


CALANOID  COPEPODS  OF  THE  GENUS   AETIDEUS 
FROM  THE   GULF  OF  MEXICOi 

Taisoo  Park2 


ABSTRACT 

The  copepod  population  known  previously  as  belonging  to  Aciidcus  annaius  (Boeck)  in 
the  Gulf  of  Mexico  and  Caribbean  Sea  is  recognized  as  a  separate  species.  The  males  of 
Aetideus  ciciiius   Farran   and   Aciidciis  giesbrechti  Cleve   are  fully   redescribed  with   figures. 


The  genus  Aetideus  Brady,  1883,  comprised 
four  species  (A.  armatus,  A.  bmdyi,  A.  aciitioi, 
and  A.  giesbn'chti)  when  Sars  (1925)  estab- 
lished the  genus  Enaetideus  to  distinguish  the 
last  three  species  from  the  first.  A  new  species 
has  since  been  added  to  each  genus,  A.  pacificus 
and  E.  ausfralis.  Bradford  (1971)  reviewed  the 
genera  Aetideus  and  Euaetideus  on  the  basis 
of  specimens  from  the  Atlantic  and  Pacific 
Oceans.  Having  found  a  close  similarity  be- 
tween the  males,  she  proposed  the  merging  of 
the  two  genera.  In  agreement  with  her  pro- 
posal, the  name  Euaetideus  is  considered  here 
as  a  junior  synonym  of  Aetideus. 

In  the  Gulf  of  Mexico,  three  species  of 
Aetideus  (A.  armatus,  A.  acutus,  and  A.  gies- 
brechti) have  been  recorded  (Owre  and  Foyo, 
1967;  Park,  1970).  During  the  examination  of 
plankton  samples  obtained  from  the  Gulf  of 
Mexico  by  the  RV  Alamiuos  in  September 
1971.  all  of  these  species  were  found,  including 
the  males. 

A.  armatus  had  been  known  to  have  world- 
wide distribution  (Vervoort,  1957)  until  Brad- 
ford (1971)  recognized  a  population  in  the 
Southern  Hemisphere  and  two  in  the  North 
Pacific  as  separate  species.  Bradford  also  noted 
differences  between  the  northern  and  southern 
forms  of  A.  armatus  in  the  Atlantic,  but  the 
differences  were  not  considered  as  taxonomical- 
ly  significant.  When  examined  in  detail  in  the 
light  of  Bradford's  findings,  the  Gulf  of  Mexico 
population  of  A.  armatus,  however,  was  found 
to  be  significantly  different  from  either  the 
northern  or  southern  Atlantic  form  of  the  spe- 


'  This  study  was  supported  bv  National  Science  Founda- 
tion Grant  GA-27485. 

-  Department  of  Marine  Sciences,  Texas  A&M  Uni- 
versity, Galveston.  TX  77550. 


cies,  or  from  any  other  known  species  of  the 
genus.  Therefore,  it  is  described  here  as  a  new 
species. 

A.  acutus  and  A.  giesbrechti  found  in  this 
study  were  in  agreement  with  the  descriptions 
by  Grice  (1962)  and  Park  (1968)  for  the  Pacific 
forms.  The  males  of  these  species  have  not 
been  fully  described,  except  for  brief  descrip- 
tions by  Giesbrecht  (1892)  and  Bradford  (1971). 

AETIDEUS  MEXICAN  US, 
NEW  SPECIES 

Type. — Holotype  female,  U.S.  National  Mu- 
seum No.  143777;  allotype  male  USNM  No. 
143778;  30  female  and  7  male  paratypes, 
USNM  No.  143779.  Type  locality,  lat.  25°15'N, 
long.  89°11'W,  in  the  Gulf  of  Mexico  (sam- 
pling depth,  about  500-0  m). 

Female. — Body  lengths  of  31  type  specimens, 
1.66-1.84  mm.  Proportional  lengths  of  pro- 
some  and  urosome  about  78:22.  Viewed  dorsal- 
ly,  body  slender,  with  a  round,  slightly 
produced  forehead  (Figure  lA).  Laterally,  dor- 
sal margin  of  forehead  broadly  vaulted  at  level 
of  mouth  (Figures  IB,  D).  Two  rostral  rami 
separated  by  a  U-shaped  notch  (Figure  IG). 
Distance  between  tips  of  rostral  rami  exceed- 
ing depth  of  notch  (1.07-1.15:1).  Metasomal 
process  extending  straight  backward;  although 
variable  in  length,  generally  reaching  about 
distal  end  of  genital  segment.  Dorsally,  genital 
segment  (Figure  IH)  wider  than  long,  with  its 
widest  part  close  to  its  proximal  end.  Shape 
of  spermatheca  (Figures  IC,  F)  similar  to 
A.  armatus  as  described  by  Bradford  (1971), 
with  short  wide  neck  connecting  proximal  and 
distal    sacs;    space   between   two   sacs   slightly 


Manuscript  accepted  July  1973. 

FISHERY  BULLETIN:  VOL.  72.  NO.  I.  1974. 


215 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Figure    1.  —  Actidcus  lucxuanus,  new  species.  Female:   A,  habitus,  dorsal;  B,  habitus,  lateral;   C,   posterior  part  of 

body,  lateral;   D,  forehead,  lateral;   E,   posterior   part  of  body,  dorsal;    F,  last  metasomal   and  first   two  urosomal 

segments  of  another  specimen,  lateral;  G,  rostrum,  anterior;   H,  urosome,  dorsal:   I,  first   pair  of  legs,  anterior;  J, 
second  leg,  anterior;  K,  third  leg,  anterior;  L,  fourth  leg,  anterior. 


wider    than    connecting    neck.    Caudal    ramus 
about  2.4  times  as  long  as  wide. 

Antennules  extending  beyond   distal   end  of 
caudal    ramus    by    last    two    segments.    Other 


216 


cephalic  appendages  as  in  A.  pacificiis  as  de- 
scribed by  Park  (1968).  In  most  of  the  speci- 
mens dissected  the  first  pair  of  legs  were  asym- 
metrical, with  the  external  margin  of  the  right 


PARK:  .4£r/D£t'5  0FTHEGULFOF  MEXICO 


basis  produced  distally  into  a  large  tooth-like 
process  (Figure  II).  Second  to  foux-th  legs 
(Figures  IJ-L)  similar  to  A.  pacificu.^,  but  coxa 
of  fourth  leg  without  spinules  at  base  of  inter- 
nal seta.  Terminal  exopodal  spines  of  second 
to  fourth  legs  with  15-17  teeth. 

Male. — Body  lengths  of  eight  type  specimens, 
1.58-1.68  mm.  Proportional  lengths  of  prosome 
and  urosome  about  75:25.  Body  slender,  with 
forehead  slightly  produced  (Figure  2A).  Ros- 
strum  reduced.  Metasomal  process  pointing 
straight  backward,  reaching  about  distal  end 
of  genital  segment  (Figures  2D,  E).  Second 
to  fourth  urosomal  segments  and  caudal 
rami  (Figure  2E)  with  width: length  ratios  of 
1:0.98-1.05,  1:1.08-1.15,  1:1.12-1.19,  and  1:1.82- 
2.00,  respectively.  Antennules  reaching  about 
distal  end  of  fourth  urosomal  segment,  nine- 
teenth and  longest  segment  (Figure  2G)  with 
width: length  ratio  of  1:4.9-5.1.  On  second  leg 
(Figure  2M),  endopod  reaching  distal  end  of 
second  exopodal  segment.  On  second  and  third 
legs  (Figure  2N),  terminal  exopodal  spines 
longer  than  third  exopodal  segments,  with 
about  29  and  23  teeth,  respectively.  Second  to 
fourth  segments  of  fifth  leg  (Figure  20)  with 
width: length  ratios  of  1:3.7-4.2,  1:8.3-8.7,  and 
1:9.0-9.7,  respectively. 


AETIDEUS  ACUTUS  FARRAN,  1929 


Male. — Body  length,  1.22-1.36  mm  according 
to  48  randomly  selected  specimens.  Propor- 
tional lengths  of  prosome  and  urosome  about 
79:21.  Dorsally,  forehead  (Figure  3B)  more 
produced  than  in  A.  ine.vicaitufi.  Rostrum  re- 
duced. Metasomal  process  with  wide  base,  dis- 
tinctly curved  downward  when  viewed  laterally 
(Figure  3E)  and  slightly  curved  inward  in 
dorsal  view  (Figure  3D).  Second  to  fourth  uro- 
somal segments  and  caudal  rami  with  width: 
length  ratios  of  1:0.83-0.88,  1:0.75-0.81,  1:0.78- 
0.81,  and  1:1.64-1.83,  respectively. 

Antennules  reaching  about  distal  end  of 
third  urosomal  segment,  nineteenth  and  long- 
est segment  (Figure  3F)  with  width: length 
ratio  of  1:3.31-3.52.  Other  cephalic  appendages 
similar  to  A.  nie.vicanus.  On  second  leg  (Figure 
3L),  endopod  reaching  distal  end  of  second 
exopodal  segment.  Terminal  exopodal  spines  of 
second  and  third  legs  (Figure  3M)  longer  than 
their  third  exopodal  segments,  with  about  23 
and  18  teeth,  respectively.  Terminal  exopodal 
spines  of  fourth  legs  (Figure  3N)  shorter  than 
their  third  exopodal  segments,  with  about  16 
teeth.  Second  to  fourth  segments  of  fifth  leg 
(Figure  30)  with  width: length  ratios  of  1:3.41- 
3.78,  1:6.72-7.33,  and  1:6.00-6.60,  respectively. 


Remark.'^. — The  female  of  A.  nie.vicaitus  is  dis- 
tinguished from  A.  annatu.'i  by  the  slender 
body,  long  antennules  which  extend  beyond  the' 
caudal  rami  by  two  segments  and,  particularly, 
the  fourth  leg  which  lacks  spinules  at  the  base 
of  the  coxal  seta  found  in  all  other  species  of 
the  genus  (Bradford,  1971).  The  male  of  A. 
mexicaiius  is  very  close  to  that  of  A.  armatu.'i 
as  described  by  Bradford  but  seems  to  differ 
from  it  in  the  proportions  of  the  caudal  rami 
and  of  the  second  to  fourth  segments  of  the  fifth 
legs.  However,  the  importance  of  these  charac- 
ters in  the  distinction  between  the  two  species 
is  yet  to  be  determined. 


Di.'^tribHtio)i. — A.  mexicaitH.'<  was  found  in  a 
number  of  plankton  samples  taken  from  the 
upper  500  m  in  the  Gulf  of  Mexico  by  the  RV 
Alantii/os  in  September  1971.  A.  arniatus  re- 
corded from  the  Caribbean  Sea  by  Park  (1970) 
belongs  to  this  new  species. 


Remarks. — The  male  of  A.  acutus  was  first  de- 
scribed very  briefly  by  Bradford  (1971).  The 
present  specimens  seem  to  be  in  agreement 
with  her  descriptions.  The  male  of  A.  acutus 
is  easily  distinguished  from  those  of  A.  niexi- 
caiius  and  A.  gie.sbrechti  by  its  considerably 
smaller  size.  In  the  shape  of  the  forehead,  meta- 
somal process,  and  antennule,  it  is  closely  re- 
lated to  A.  gieahrechti,  but  differs  from  this 
species  in  the  relative  lengths  of  the  urosomal 
segments  and  caudal  rami. 

The  female  specimens  of  A.  acutus  in  the 
present  study  (1.48-1.62  mm  in  body  length 
according  to  80  randomly  selected  specimens) 
are  identical  with  the  specimens  described  by 
Park  (1968)  from  the  Pacific,  and  can  be  readily 
recognized  by  the  shape  of  the  spermatheca 
(Figure  3A).  The  appendages  are  similar  to 
those  of  A.  pacificus  as  described  by  Park  (1968), 
except  that  the  maxillule  carries  3-1-3  +  6  setae 
on  the  endopod. 


217 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Figure  2.  —  Aetidcus  incxicuuHs,  new  species.  Male:  A,  habitus,  dorsal:  B,  habitus,  lateral;  C,  forehead,  lateral: 
D,  posterior  part  of  body,  lateral;  E,  posterior  part  of  body,  dorsal:  F,  antennule,  setae  omitted:  G,  19th  segment 
of  antennule;  H,  antenna;  I,  mandible;  J,  maxillule;  K,  maxilliped:  L,  first  leg,  anterior:  M,  second  leg,  anterior; 
N,  third  leg,  anterior;  ().  fifth  leg.  anterior.  (1.  and  W,  length  and  width  of  segment.) 


218 


PARK:  /l£r/Det'5  0FTHEGULF0F  MEXICO 


Figure  3. —  Aciideus  acuiiis.  Femnle;  A,  posterior  part  of  body,  lateral.  Male:  B,  habitus,  dorsal;  C.  habitus,  lateral; 
D.  posterior  part  of  body,  dorsal;  E,  last  metasomal  and  genital  segments,  lateral;  F,  19th  segment  of  antennule; 
G,  antenna;  H,  mandible;  I,  maxillule;  J,  maxilliped;  K,  first  leg,  anterior:  L,  second  leg,  anterior;  M,  third  leg, 
anterior;  N.  fourth  leg.  anterior;  O.  fifth  leg.  anterior. 


219 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


Figure  4. — Actidcus  tiicshrechii.  Female:  A,  posterior  part  of  body,  lateral.  Male:  B,  habitus,  dorsal;  C,  posterior 
part  of  body,  dorsal;  D.  posterior  part  of  body,  lateral;  E,  habitus,  lateral;  F,  19th  segment  of  antennule;  G, 
first  leg,  anterior;  H,  second  leg,  anterior;  I,  fifth  leg,  anterior. 


Dixtrihiition. — A.  aciifiis  was  originally  de- 
scribed from  off  New  Zealand  (Farran,  1929). 
The  species  has  so  far  been  known  to  occur  on 
the  Great  Barrier  Reef  (Farran.  1936),  in  the 
Malay  Archipelago  (Vervoort.  1957),  off  the 
Pacific  coast  of  Middle  Japan  (Tanaka,  1957; 
Tanaka  and  Omori,  1970).  in  the  tropical  Pa- 
cific (Grice,  1962).  the  northwestern  Pacific 
(Brodsky,  1962),  the  central  North  Pacific 
(Park,  1968),  the  northeast  Atlantic  (Grice  and 
Hulsemann,    1965),    the    Caribbean    Sea    and 


Gulf  of  Mexico  (Park,  1970),  and  in  the  west- 
ern Indian  Ocean  (De  Decker  and  Mombeck, 
1965;  Grice  and  Hulsemann,  1967).  In  the 
Gulf  of  Mexico,  A.  acutus  is  the  most  common 
of  all  three  Acfidcus  species  so  far  known  to 
occur,  and  it  is  mainly  found  in  the  upper  500  m. 

AETIDEUS  GIESBRECHTI 
CLEVE,  1904 

Male. — Body  length.  1.52-1.60  mm  according 
to    50    randomly    selected    specimens.    Propor- 


220 


PARK:  ^£7/D£f5  0FTHEGULFOF  MEXICO 


tional  lengths  of  prosome  and  urosome  about 
77:23.  Dorsally,  forehead  (Figure  4B)  produced 
as  in  A.  acutiis.  Rostrum  reduced.  Metasomal 
process  (Figures  4C,  D)  as  in  A.  aciitiix. 
Second  to  fourth  urosomal  segments  and  caudal 
rami  with  width: length  ratios  of  1:0.93-0.95, 
1:0.85-0.86.  1:0.88-0.89,  and  1:2.27-2.38,  re- 
spectively. 

Antennules  reaching  about  distal  end  of 
third  urosomal  segment,  nineteenth  and  long- 
est segment  (Figure  4F)  with  width: length 
ratio  of  1:3.75-3.86.  Other  cephalic  appendages 
as  in  A.  acutus.  On  second  leg  (Figure  4H), 
endopod  extending  beyond  distal  end  of  second 
exopodal  segment.  Terminal  expodal  spine 
longer  than  third  exopodal  segment,  with  about 
24  teeth.  Second  to  fourth  segments  of  fifth 
leg  (Figure  41)  with  width: length  ratios  of 
1:3.34-4.00,  1:6.00-6.25,  and  1:5.00-6.65,  re- 
spectively. 

Rei)iark>i. — The  male  of  A.  giesbrechti  is  close 
to  A.  niexiccuiKs  in  size  but  can  be  distin- 
guished from  it  by  the  more  produced  forehead, 
wide  and  curved  metasomal  process,  relatively 
short  urosomal  segments,  wide  nineteenth  seg- 
ment of  the  antennule,  and  long  endopod  of 
the  second  leg. 

A.  giesbrechti,  including  the  male,  was  first 
described  with  figures  by  Giesbrecht  (1892) 
under  the  name  of  A.  armatus.  Although  the 
female  has  been  reported  by  many  authors,  the 
male  has  since  been  found  only  by  Bradford 
(1971).  The  female  specimens  found  in  the' 
present  study  (1.84-2.08  mm  in  body  length 
according  to  76  randomly  selected  specimens) 
are  in  agreement  with  the  descriptions  given 
by  Grice  (1962)  for  the  Pacific  specimens.  The 
appendages  are  identical  with  those  of  A.  acutus, 
but  the  females  of  the  two  species  are  different 
in  the  form  of  spermatheca  (Figure  4A). 

Distribution. — As  reviewed  by  Vervoort  (1957). 
A.  giesbrechti  has  been  found  throughout  the 
world's  oceans,  except  for  the  high  latitudes. 
In  the  Gulf  of  Mexico  the  species  is  quite  com- 
mon in  the  upper  500  m. 


LITERATURE  CITED 

Bradford,  J.  M. 

1971.     Aetideus    and    Euactidcus    (Copepoda:    Cala- 


noida)     from     the    Atlantic     and    Pacific    Oceans. 
N.  Z.  J.  Mar.  Freshwater  Res.  5: 12-40. 
Brodsky.  K.  a. 

1962.     On   the   fauna   and   distribution  of  Calanoida 
in  surface  waters  of  the  north-western  Pacific    [In 
Russ.]      Issled.   Dal'nevost.   Morei  SSSR.   8:91-166. 
De  Decker,  A.,  and  F.  J.  Mombeck. 

1965.     South    African    contribution    to    the    Interna- 
tional Indian  Ocean  Expedition:  (4)  A  Preliminary 
report   on  the   planktonic  Copepoda.     S.  Afr.  Div. 
Sea  Fish.  Invest.  Rep.  51:10-67. 
Farran, G.  p. 

1929.  Crustacea.  Part  X.  Copepoda.  Brit.  Antarctic 
(Terra  Nova)  Exped.  1910.  Nat.  Hist.  Rep.  Zool. 
8(3):203-306. 

1936.     Copepoda.   Great    Barrier   Reef  Exped.    1928- 
29.     Sci.  Rep.  5(3): 73- 142. 
Giesbrecht,  W. 

1892.     Sytemtik      und      Faunistik      der     pelagischen 
Copepoden     des     Golfes     von     Neapel     und     der 
angrenzenden  Meeres-abschnitte.  Fauna  Flora  Golf. 
Neapel.  Monogr.  19:1-830. 
Grice,  G.  D. 

1962.  Calanoid  copepods  from  equatorial  waters  of 
the  Pacific  Ocean.  U.S.  Fish  Wildl.  Serv.,  Fish. 
Bull. 61:171-246. 

Grice,  G.  D.,  and  K.  Hulsemann. 

1965.  Abundance,  vertical  distribution  and  tax- 
onomy of  calanoid  copepods  at  selected  stations 
in  the  northeast  Atlantic.  J.  Zool.  146:213-262. 
1967.  Bathypelagic  calanoid  copepods  of  the  west- 
ern Indian  Ocean.  Proc.  U.S.  Natl.  Mus  122(3583): 
1-67. 
Owre,  H.  B.,  and  M.  Foyo. 

1967.  Copepods  of  the  Florida  Current.  Fauna  Cari- 
baea;  Number  1.  Crustacea,  Part  1:  Copepoda, 
137  p. 

Park,T. 

1968.  Calanoid  copepods  from  the  central  North 
Pacific  Ocean.  U.S.  Fish  Wildl.  Serv.,  Fish.  Bull. 
66:527-572. 

1970.     Calanoid   copepods   from   the   Caribbean   Sea 
and  Gulf  of  Mexico.  2.  New  species  and  new  rec- 
ords    from     plankton     samples.     Bull.     Mar.     Sci. 
20:472-546. 
Sars,  G.  O. 

1924.     Copepodes     particulierement    bathypelagiques 
provenant    des   campagnes   scientifiques    du    Prince 
Albert  F""  de  Monaco.     Result.  Camp.  Sci.  Monaco 
69,  408  p.,  127  plates. 
Tanaka,  O. 

1957.     The    pelagic    copepods    of    the    Izu    region, 
Middle    Japan.    Systematic     account     III.     Family 
Aetideidae   (Part    1).     Publ.   Seto   Mar.   Biol.   Lab. 
6:31-68. 
Tanaka.  O.,  and  M.  Omori. 

1970.     Additional  report  on  calanoid  copepods  from 
the   Izu   region.  Part   3-A.   Eiiaetideiis,  Aetideopsis, 
CInridius,  Gaidnis,  and  Gaetanus.     Publ.  Seto  Mar. 
Biol.  Lab.  18:109-141. 
Vervoort,  W. 

1957.  Copepods  from  Antarctic  and  sub-Antarctic 
plankton  samples.  B.A.N.Z.  Antarctic  Res.  Exped. 
1929-1931.    Rep.,    Ser.    B    (Zool.    Bot.)    3,    160    p. 


221 


NORMAL  POSTMORTEM  CHANGES 
IN  THE   BROWN   SHRIMP,  PENAEUS  AZTECUS^ 

Donald  V.  Lightner- 

ABSTRACT 

A  study  was  carried  out  to  determine  the  normal  rates  and  patterns  of  gross  and  histologic 
postmortem  changes  in  the  brown  shrimp  (Penaeus  aztecus  Ives).  Experimental  shrimp 
were  held  at  10°,  20°.  or  30°C  in  water-saturated  air  or  in  seawater  at  a  salinity  of  30<yoo. 
Observations  were  made  at  0,  2,  4,  8,  12,  24,  48,  and  72  h  postmortem. 

The  first  change  observed  grossly  was  the  onset  of  a  rigorlike  stiffening  of  the  abdominal 
musculature.  This  stiffening  was  noted  at  2  h  postmortem  at  30°C,  but  disappeared  by  12  h 
postmortem.  The  condition  appeared  later  and  persisted  longer  at  the  lower  temperatures. 

Histologically,  the  tubule  epithelium  of  the  hepatopancreas  was  the  first  tissue  to  show 
autolytic  change.  The  autolysis  in  the  remaining  tissues  examined  occurred  in  the  following 
order:  foregut  and  midgut  epithelium,  heart,  neurons  and  nerve  fibers,  antennal  gland 
epithelium,  gill  epithelium,  epidermis,  muscle,  and  lastly  connective  and  cuticular  tissue 
elements.  In  all  tissues  the  rate  of  autolysis  was  temperature-dependent. 


Shrimp  from  the  Gulf  of  Mexico  represent  one 
of  the  most  valuable  fishery  products  of  the 
United  States.  Their  popularity  as  a  food  item 
and  for  use  as  sportfishing  bait  in  some  coastal 
areas  has  resulted  in  recent  studies  aimed  at 
developing  methods  of  artificially  culturing 
these  animals.  Despite  the  enormous  value  of 
shrimp  as  a  seafood,  little  is  known  about  their 
histology  and  the  rates  and  patterns  of  post- 
mortem change. 

Postmortem  biochemical  changes  in  the 
muscle  of  brown  shrimp  (Penaeus  aztecus  Ives) 
were  reported  by  Flick  and  Lovell  (1972).  They 
reported  that  the  compounds  ATP,  ADP,  AMP, 
IMP,  and  glycogen  decreased  with  time  post- 
mortem, while  inosine,  hypoxanthene,  and  lac- 
tic acid  increased.  The  latter  compounds  were 
suggested  as  being  partly  responsible  for  flavor 
deterioration  of  ice-stored  shrimp.  Tissue  pH 
values  increased  from  7.4  to  8.2  after  10  days 
in  ice-stored  shrimp  (0°C),  and,  according  to 
these  authors,  even  with  advanced  bacterial 
spoilage,  increases  in  pH  are  usually  observed 
in  fish  and  shellfish.  Shrimp  tails  remained 
tender  and  soft  during  the  entire  storage  period 
of  10  days  (at  0°C)  and  did  not  exhibit  any  of 


'  Contribution  No.  369,  Gulf  Coastal  Fisheries  Center, 
Galveston  Laboratory,  National  Marine  Fisheries  Service, 
NOAA,  Galveston,  TX  77550. 

-  Gulf  Coastal  Fisheries  Center,  Galveston  Laboratory, 
National  Marine  Fisheries  Service,  NOAA,  Galveston, 
TX  77550. 


Manuscript  accepted  July  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  1. 


the  characteristics  commonly  associated  with 
rigor  mortis  (Flick  and  Lovell,  1972). 

In  the  only  histologic  study  of  postmortem 
change  in  an  invertebrate  animal.  Sparks  and 
Pauley  (1964)  reported  the  normal  postmortem 
changes  in  the  oyster,  Crassostrea  gigas.  The 
digestive  tubules  of  the  oyster  underwent  the 
most  rapid  autolytic  change  in  dead  oysters 
held  at  14°-16°C,  while  the  Leydig  tissue,  gut, 
stomach,  mantle,  gill  and  palps  autolyzed  some- 
what less  rapidly.  The  gonads  were  the  most 
resistant  of  all  oyster  tissue  to  autolysis  with 
ova  and  sperm  appearing  relatively  normal  even 
after  all  other  tissues  had  undergone  extensive 
autolysis. 

There  are  certainly  a  number  of  factors  which 
influence  the  rate  of  autolysis  in  a  dead  animal. 
Some  of  these  factors  include  water  tempera- 
ture, dissolved  oxygen  concentration,  pH,  bac- 
terial flora  of  the  water  and  of  the  animal,  and 
the  physiological  condition  of  the  animal  at 
the  time  of  death.  It  has  been  demonstrated  in 
man  and  other  animals  that  postmortem  chang- 
es occur  in  a  regular  and  irreversible  pattern 
and  at  a  relatively  constant  rate  from  one  indi- 
vidual to  another  when  factors  causing  varia- 
tion in  the  rate  and  pattern  are  considered 
(Sparks  and  Pauley,  1964).  Differentiation  of 
histological  changes  due  to  disease  from  those 
due  to  postmortem  autolysis  or  poor  fixation 
is  possible  once  the  normal  rates  and  patterns 


223 


I  ISIll  R^    mi  I  1   1  IN:  \  Ol  .  7:.  NO,  I 


of  post  iiuMttMii  rliaiiu'os  uiuKm'  \  arious  comlilioiis 
■dw  known. 

Tho  pivsonl  stuily  was  luuUMtakon  1o  di'tiT- 
n\\\w  (lio  normal  rates  ami  patterns  orpostnioi- 
teni  I'lianiie  in  penaei(i  slirinip  as  an  aid  in  ilis- 
tinjiuishini;'  gross  and  histologie  elianges  due 
to  aiitt>lysis  1V(mu  ehanges  liue  to  disease. 

MATHRIALS  AND  Ml-  1  HODS 

.luxiMiile  blow  11  shrimp  averaiiing  "lO  mm  in 
total  lenjith  (\'\\i  of  rc^strum  to  tip  of  ti'lsoii) 
were  obtained  live  iVom  a  eommereial  bait  ilealei" 
and  were  held  in  500-liter  tiberu'lass  tanks  for 
several  ilays  pritn*  to  beini;  killed.  Control 
shrimp  were  killed  by  immersion  in  tixative. 
Tlu^  remaininii'  shrimp  were  killed  by  plaeiiii:' 
the  shrimp  between  wft  towels  in  an  enamel 
tray  for  ;>0  min.  The  slirimji  were  removed 
after  oO  min  and  plaeed  \\\\o  100-ml  glass  jars. 
Two  groui>s  at  three  temperatures  (10'"\  20  \  ami 
SOT)  were  studied:  one  in  air  ami  the  other  in 
seawater.  Shrim{)  lield  in  air  were  introilueed 
wet  into  test  jars  ami  tiie  jars  were  sealed. 
Shrimp  held  in  water  were  introdueed  into  the 
test  jars  ami  enough  Instant  Oeeaiv'  artitieial 
seawater  (at  .'U"t  "'/(ut  salinity')  was  atldeil  to  till 
the  jars.  ,lars  were  heUl  in  wire  baskets  at 
midlevel  in  eonstant  temperature  baths. 

Samples  for  antemortem  examination  were 
taken  at  0  h  while  those  for  postmortem  exam- 
ination were  taken  at  2.  1.  S.  12.  24.  48.  and  72 
h.  Vouv  eontrol  shrimp  were  taken  for  study 
and  tw(i  shrimp  (one  tVom  seawater  and  one 
from  air)  were  taken  from  the  10  \  20  \  and  ;UV  C" 
baths  at  eaeh  of  the  remaining  sampling  times. 

General  appearance,  color,  odor,  aiul  eomli- 
tion  of  the  hepatopanereas  were  noted  at  eaeh 
sampling  period.  Tissues  for  microscopic 
examination  were  preserved  in  lO^'c  buffered 
Formalin,  prejiared  for  microscopy  with  stan- 
dard paraftin  embedding  and  sectioning 
methods,  anil  stained  with  liematoxylin  ami 
eosin. 

RKSl  LTS 

Gross  Observ  ations 

The  tirst  change  observed  w  as  the  onset  of  a 
rigorlike  condition  of  the  abdomen  which 
appeared  at  about  2  h  after  tieath  at  oO  'C  and  at 


I  \ni  I  1.  liiiu-  ot  oiiMl  ol  .1  I  igDi  like  sliUcnini;  o{ 
shninp  .iIhIihuiiuiI  mustulaiuii'  ,il  1(V\  20'\  aiui  30'\'  in 
an  and  seawater. 


Tempera 

ture  {" 

C) 

H  poslmorletii 

10 

"C 

20 

■■'c 

r 

30 

*C 

Air 

Water 

Air 

Wafe 

Air 

Water 

0 

— 

— 

— 

— 

— 

_ 

2 

— 

— 

-1- 

— 

+ 

+ 

4 

— 

— 

+ 

- 

+ 

+ 

8 

— 

— 

+ 

-1- 

+ 

+ 

12 

— 

+ 

— 

-1- 

— 

— 

24 

-1- 

+ 

+ 

+ 

— 

- 

48 

+ 

+ 

— 

— 

— 

— 

72 

+ 

+ 

— 

— 

— 

— 

-I-   =  stiff 
—   =  flaccid 

t  and  2  1  h  at  20  and  \0'\\  respectively.  Tlie 
abdomen  became  flaccid  at  12  and  48  h  after 
tleath  in  shiimi^  held  at  SO'^  and  20^X".  but  at 
lO'T  the  abdomen  remained  rigid  at  72  h  after 
death  (Table  1). 

C'olor  change  ami  the  api)earance  of  spoilage 
odor  were  tirst  observed  at  4  h  after  death  at 
oOH\  The  general  appearance  of  the  shrimp 
changed  from  the  usual  semitransparent  to  a 
wliitish-opaque  at  about  the  same  time  the  first 
trace  of  odor  was  detected  (Tables  2  and  o).  At 
20  '  ami  lO'X'  the  first  color  change  and  appear- 
ance of  odor  were  notetl  at  12  h  and  24  li. 
respectively.  At  all  three  temperatures  tlie  color 
of  the  shrimp  changed  from  opaque  to  an  orange- 
red  and  finally  to  red  with  some  blackened 
areas  (Table  2).  The  intensity  of  spoilage  odor 
increased  along  with  the  color  change  (Tables  2 
and  a). 

Fluid  leakage  from  the  hepatopanereas  was 
tirst  observed  at  4  h  at  oO'T  and  at  about  8  and 
12  h  postmortem  at  20'  and  10 T.  Enzymatic 
cligestion  of  hepatopanereas  and  surrounding- 
tissues  was  grossly  eviilent  at    12  h  at  oOT  as 

1  AHi  E    2. — Times   lit'  posUiioi tciii    color   chaniic   of  whole 
shrimp  at  10'\  20'\  and  3lVX"  in  .m  .uid  se.iw.iiei. 


Temperoture  C'C) 


H  postmortem 


10-^C 


20  ^X 


30 -X 


Air       Water 


Water       Air       Water 


0 
2 

4 
8 

12 
24 
48 


— 

— 

— 

— 

0 

0 

— 

— 

— 

— 

0 

0 

0 

— 

— 

0 

LR 

LR 

LR 

0 

LR 

LR 

Rb 

Rb 

LR 

LR 

R 

Rb 

Rb 

R 

Rb 

R 

Rb 

R 

Rb 

Rb 

'  Rctcrcncc  to  trade  names  in  liiis  pul-ihcalion  does  not 
imply  endorsement  of  commercial  product. 


—    =  normol 

0  =  opaque 

LR  =  orange  to  light  red 

R  =  red 

Rb  =  red  with  blackened  edges  of  cuticle  or  blackened  appendages 


224 


LIGHTNER:  POSTMORTEM  CHANGES  IN  BROWN  SHRIMP 


Table    3. — Time   ui'  appearance   of    poslmortem   spoilage- 
odor  in  whole  shrimp  held  at  10",  20",  and  30"C  in  air  and 


Table     4. — Rate     of     poslmortem     histologic    change 
shrimp  held  in  air  or  seawater  at  three  temperatures. 


a.H 

epatop 

ancrea-s 

Temperature  ("'C) 

H  postmortem 

Tempera 

ure  (°C) 

H  posfmortem 

10 

C 

20 

'-C 

30 

-c 

Air 

Water 

Air 

Water 

Air 

Water 

10 

'-C 

20 

"C 

30 

"C 

Air 

Water 

Air 

Water 

Air 

Woter 

0 

- 

- 

- 

- 

— 

— 

2 

0 

0' 

0 

0 

0 

0 

0 

— 

— 

+ 

— 

+ 

+ 

2 

2.5' 

2,5 

2.5 

2.5 

3 

3.5 

8 

— 

— 

+  + 

— 

+ 

+ 

4 

4 

4 

4 

4 

4 

4 

12 

— 

— 

+  + 

— 

+  + 

+  + 

8 

4 

3.5 

4,5 

5 

4.5 

4  5 

24 

+ 

+ 

+  + 

+  + 

+  + 

+  + 

12 

3.5 

4 

5 
5 

5 
5 

48 

+  + 

+ 

+  +  + 

+  +  + 

+  +  + 

+  +  + 

24 

5 

4 

5 

5 

72 

+  + 

+  + 

+  +  + 

+  +  + 

+  +  + 

+  +  + 

48 
72 

5 
5 

5 
5 

5 
5 

5 
5 

5 

5 

5 
5 

—    =  normal 

+   =  odor 

indicated  by  a  loo.sening  of  the  junction  of  the 
cephalothorax  and  abdomen.  By  48  h  the  junc- 
tion was  very  loose  and  Vjy  72  h  the  tissues  of 
the  junction  appeared  mostly  liquified.  At  IC 
and  20 'C  the  same  process  was  observed  but  at 
a  proportionately  slower  rate. 

Histological  Observations 

Since  the  same  patterns  of  autolysis  were  seen 
in  .shrimp  held  at  all  three  temperatures,  the 
differences  l>eing  a  function  of  time  (Table  4), 
only  the  histological  re.sults  from  the  30 '-C 
portion  will  be  presented  in  the  text.  The  only 
significant  histological  differences  between 
groups  held  in  air  and  water  noted  were  the 
more  rapid  tissue  decomposition  due  to  increased 
bacterial  action  in  animals  held  submerged  in 
seawater. 

Digestive  Tract 

According  to  Roberts  (1966j,  the  digestive 
tract  in  shrimp  is  composed  of  three  divisions: 
flj  the  foregut,  which  includes  the  mouth, 
esophagus,  stomach,  and  associated  glands; 
(2)  the  midgut  and  hepatopancreas;  and  (3) 
the  hindgut.  Of  these  organs  the  hepatopancreas, 
the  foregut,  and  midgut  were  studied  in  detail. 
The  hindgut  was  not  .studied. 

Hepatopancreas 

The  glandular  hepatopancreas  is  the  first 
organ  to  undergo  autolytic  change  (Figure  la). 
This  organ  is  a  compound  tubularacinar  exocrine 
gland  composed  of  tubules  which  end  in  blind 
sacs  or  acini.  The  tubules  and  acini  are  lined 
with  a  simple  low  to  high  columnar  epithelium 
(Figure  Ibj.  Autolysis  of  the  epithelium  of  this 


b.  Midgut  epithelium. 

Temperoture  (^•'C) 


H  postmortem 


0 

2 

4 

8 

12 

24 

48 

72 


lO'C 


20 ''C 


30 -C 


Air       Water       Air       Water       Air       Water 


0* 

r 

2 
4 

5 
5 
5 


0 

1 

1-2 

4-5 

2 

5 
5 


0 
1 
1-2 

4 
5 
5 
5 


0 
1-2 

3 
5 
5 


c.  Abdominal  muscle. 


Temperoture  (°C) 

H    postmortem 

10 

'C 

20 

'C 

30 

■-C 

Air 

Water 

Air 

Woter 

Air 

Water 

0 

0* 

0 

0 

0 

0 

0 

2 

0 

0 

0 

0 

0 

0 

4 

1 

1 

2 

1 

1.5 

1 

8 

0 

1 

2 

2 

2 

2 

12 

1 

1 

2.5 

2.5 

3 

3 

24 

3 

3 

3.5 

3 

3.5 

3.5 

48 

2.5 

3 

4 

4 

3.5 

4.5 

72 

4 

3.5 

4.5 

4 

4.5 

4 

d.  Epidermis. 

Temperature  CC) 

H  postmortem 

10 

°C 

20 

"C 

30 

•c 

Air 

Water 

Air 

Water 

Air 

Water 

0 

0* 

0 

0 

0 

0 

0 

1 

0 

0 

0 

0 

0 

0 

2 

0 

0 

0 

0 

0 

0 

4 

0 

1 

— 

— 

2 

2 

8 

1 

1 

— 

2 

3 

3 

12 

2 

2 

3 

3 

4 

4 

24 

3 

3 

3 

3 

4 

— 

48 

3 

3 

4 

4 

5 

5 

72 

5 

5 

5 

5 

5 

5 

-  No  observation  made. 

Average  assigned  values  from  a  scale  of  0  to  5  denoting  the 
general  histological  appearance  of  the  tissue  or  organ. 


0       = 


3  = 

4  = 

5  = 


appearance,    like  the  control,   no  post- 
pyknotic    nuclei,    slight   stoining 


Normal   histologic 

mortem  change. 

Slight    chonge,    scattered 

differences. 

AAore   advanced  cellular  chonge  with   increases   in   nuclear 

pyknosis,    koryrhexis,    koryolysis,    some   cytolysis;    loss    of 

normal    appearance    or    structure    of    the    tissue    or    organ. 

Further  odvonced  change  with  no  normal  oppeoring  areas. 

Advonced    autolytic    change,    tissue    or   organ    represented 

by  cellular  debris  or  by  its  fibrous  or  cuticulor  stroma. 

Complete    outolysis,    tissue    or    organ    no    longer    demon- 

stroble. 


225 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


VffSSi. 


:.-^t>^ 


■•.>    .'^i^ 


^^^       ^^^■'- 


''    _* 


»^ 


'^- 


^^ 


I 


Figure  1. — a.  Normal  stomach  (S)  and  hcpatopancieas  (H).  25  X.  b.  Normal  hepatopancreas.  120  X.  c.  Hepatopancreas 
at  2  h  postmortem  showing  edematous  swelling  between  adjacent  tubules.  Autolysis  is  more  advanced  nearer  the  center  of 
the  organ  (upper  right)  than  at  the  periphery  (left).  IIOX.  d.  Hepatopancreas  at  4  h  postmortem  showing  tubules  on  lon- 
gitudinal section.  Note  the  progression  of  autolylic  change  in  the  tubules  from  the  periphery  of  the  organ  (bottom)  to  the 
autolyzed  center  (top).  1 10  X  .  e.  Hepatopancreas  showing  near  complete  autolysis  (4  h  postmortem).  Note  network  of  con- 
nective tissue  stroma  (arrows)  remaining  after  autolysis  of  tubule  epithelium.  120  X.  f.  Hepatopancreas  at  8  h  postmortem 
showing  advanced  autolysis.  Intensely  pyknotic  nuclei  are  present  in  the  remaining  epithelial  cells  near  the  periphery  of 
the  organ.  Tissue  debris  and  remnants  of  the  connective  tissue  stroma  are  present  nearer  the  organ's  center  (upper  right). 
120  X. 


226 


LIGHTNER:  POSTMORTEM  CHANGES  IN  BROWN  SHRIMP 


organ  proceeds  so  rapidly  that  by  2  to  4  h 
postmortem,  the  epithelium  of  tubules  near  the 
center  of  the  organ  showed  advanced  autolysis. 
These  tubules  showed  desquamation  and  cytoly- 
sis  of  the  lining  epithelium  and  replacement 
with  eosinophilic  debris  (Figures  Ic  and  Id). 
Nearer  the  periphery  of  the  organ,  the  condition 
of  the  tubules  and  tubule  epithelium  appeared 
progressively  more  normal,  with  the  most 
normal  appearing  tubules  and  acini  at  the 
periphery  (Figures  Ic  and  Id).  In  the  band  of 
tissues  between  the  normal  appearing  periphery 
and  the  lysed  core,  all  stages  of  cell  death  were 
observed.  A  thin  band  of  tissue  in  this  area  con- 
tained tubules  whose  epithelial  cells  possessed 
scattered  pyknotic  nuclei  and  had  slight  cyto- 
plasmic staining  differences  (Figure  le).  Deeper 
to  this  layer  the  epithelial  cells  of  tubules  and 
acini  possessed  scattered  pyknotic  nuclei  and 
had  slight  cytoplasmic  staining  differences 
(Figure  le).  The  cytoplasm  of  these  cells  was 
highly  vacuolated  and  stained  variably  with 
hematoxylin  and  eosin  but  generally  much  less 
basophilicily  than  normal  (Figure  Ic).  At  this 
time  the  s])aces  between  adjacent  tubules  and 
acini  had  become  swollen  (Figures  Ic  and  Id). 
Slightly  deeper  to  this  layer  epithelial  cell  nu- 
clei had  undergone  karyoi*rhexis  or  karyolysis 
and  disappeared.  Many  of  the  cells  of  this  area 
had  lysed  and  the  cellular  debris  stained  red 
with  eosin.  The  supportive  stroma  of  the  hepato- 
pancreatic  tubules  remained  intact  in  some 
areas  after  the  epithelium  had  autolyzed, 
thereby  masking  the  former  site  of  the  hepato- 
pancreatic  tubules  (Figure  le). 

By  8-12  h  i)ostmortem  even  the  tubules  and 
acini  at  the  peripheiy  of  the  organ  showed  ad- 
vanced autolytic  change,  and  the  tissue  debris 
and  remnants  of  supportive  stroma  in  the  center 
of  the  organ  were  liquified  (Figure  If).  The 
connective  tissue  capsule  of  the  organ  had  be- 
come ruptured  and  few  recognizable  tubules 
were  present.  Past  12  h  no  trace  of  the  hepato- 
pancreas  was  present,  and  surrounding  tissues 
had  also  been  partially  or  completely  digested, 
presumably  by  enzymes  released  from  the  auto- 
lyzed hepatopancreas. 

Foregut  and  Midgut 

Autolytic  changes  in  the  foregut,  particularly 
the  epithelium  of  the  stomach  (Figure  la), 
proceeded  at  approximately  the  same  rate  as 


changes  in  the  hepatopancreas.  Nuclear  changes 
within  epithelial  cells  were  observed  at  2  h 
postmortem  with  considerable  change  by  4  h. 
By  8  to  12  h  the  epithelium  of  the  stomach  had 
undergone  nearly  complete  autolysis  and  had 
disappeared,  leaving  only  the  cuticular  elements 
of  the  stomach  lining  intact.  The  cuticular 
elements  of  the  esophagus  and  stomach  per- 
sisted for  the  duration  of  the  study  (72  h). 

The  midgut  extends  from  the  pyloric  stomach 
to  the  sixth  abdominal  segment  where  it  joins 
with  the  hindgut  (Roberts,  1966).  It  is  without 
a  lining  cuticle.  The  first  autolytic  change  in 
the  midgut  was  observed  in  the  lining  epithelium 
at  2  to  4  h,  when  the  epithelial  cells  began  to 
show  changes  such  as  scattered  pyknotic  nuclei, 
changes  in  staining  reaction  from  a  pale  baso- 
philic reaction  to  a  more  eosinophilic  one,  and 
the  "blebing"  of  the  apical  ends  of  epithelial 
cells  into  the  gut  lumen  (Figure  2a).  The  epithe- 
lium usually  remained  attached  to  the  basement 
membrane  at  2  h.  but  in  some  areas  portions  of 
the  midgut  epithelium  had  been  sloughed  into 
the  gut  lumen  (Figures  2b  and  2c).  Sloughed 
epithelial  cells  were  rounded  and  had  intensely 
pyknotic  nuclei  and  a  uniform  eosinophilic 
cytoplasm.  At  this  time  the  gut  lumen  usually 
contained  a  fibrous,  eosinophilic  coagulum 
(Figure  2b).  The  gut  wall  basal  to  the  lining 
epithelium  showed  no  appreciable  changes  by 
4h. 

By  8  to  12  h  the  midgut  epithelium  had  been 
sloughed  into  the  gut  lumen  (Figure  2d).  The 
epithelial  cells  in  the  gut  lumen  were  rounded, 
and  some  had  pyknotic  nuclei,  but  they  were 
mostly  anucleate.  Many  of  the  epithelial  cells 
had  lysed  and  left  behind  amorphous  masses  of 
eosinophilic  debris  (Figure  2d).  Changes  in  the 
cellular  elements  of  the  wall  of  the  midgut 
became  apparent  by  8-12  h.  These  changes  con- 
sisted primarily  of  a  decrease  in  nuclear  number 
in  the  muscle  and  connective  tissue  cells  present 
and  pyknosis  of  those  nuclei  remaining  (Figure 
2d).  In  general,  the  cytoplasm  of  the  cells 
present  showed  increased  eosinophilia. 

No  trace  of  the  lining  epithelium  was  present 
after  24  h  (Figure  2e).  The  coagulum,  which 
was  present  in  the  gut  lumen  of  some  animals 
at  2-8  h,  was  still  present.  Also  present  in  the 
gut  lumen  were  large  numbers  of  bacteria 
(Figure  2e).  No  nuclei  were  present  in  the  gut 
wall,  and  the  cellular  elements  remaining 
stained  intensely  with  eosin. 


227 


FISHERY  BULLETIN:  VOL    12.  NO.  1 


■.& 


.-^ 


'^ 


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y 


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.*%.    J-.*v 


.A.-*' 


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Figure  2. — a.  Cross  section  of  midgut  at  2  h  postmortem.  The  appearance  is  near  normal  e.xcept  for  the  "blebing"  of  the 
apical  ends  of  some  of  the  epithelial  cells  (arrows)  and  a  few  pyknotic  nuclei.  250  X.  b.  Midgut  showing  more  advanced 
autolytic  change  at  2  h  postmortem.  Some  epithelial  cells  have  been  sloughed  into  the  gut  lumen  where  an  eosinophilic 
coagulum  (C)  has  formed.  240  X.  c.  Midgut  at  4  h  postmortem.  Most  of  the  epithelial  cells  possess  pyknotic  nuclei,  and 
some  of  the  cells  have  been  sloughed  into  the  gut  lumen.  210X.  d.  Midgut  at  8  h  postmortem.  Sloughed  epithelial  cells 
are  rounded  and  are  either  anucleate  or  have  pyknotic  nuclei.  An  eosinophilic  coagulum  is  present.  160  X  .  e.  Midgut  at  24 
h  postmortem.  An  eosinophilic  coagulum  is  present  in  the  gut  lumen  as  are  numerous  bacteria.  No  trace  of  the  gut  epithe- 
lium remains.  The  muscle  and  tibrocyle  cells  of  the  gut  wall  are  anucleate.  190  X.  f.  Site  of  midgut  at  48  h  postmortem. 
Bacteria  and  debris  have  filled  the  gut  lumen.  Only  fibrous  elements  of  the  gut  wall  remain.  150  X  . 


228 


LIGHTNER:  POSTMORTEM  CHANGES  IN  BROWN  SHRIMP 


By  48  h,  the  gut  wall  had  become  thin  and 
was  frequently  interrupted.  The  gut  lumen  was 
filled  with  bacteria  and  other  debris  (Figure  2f). 
By  72  h,  all  traces  of  the  gut.  including  the  gut 
wall,  had  disappeared  leaving  the  former  site 
of  the  gut  marked  only  by  masses  of  bacteria 
and  amorphous  eosinophilic  cellular  debris. 

Heart  and  Major  Vessels 

In  shrimp  the  heart  lies  immediately  dorsal 
and  slightly  caudad  to  the  large  hepatopancreas. 
Only  the  thin  connective  tissue  coverings  of  the 
two  organs  separate  them.  Hence,  autolysis 
of  the  hepatopancreas  and  release  of  its  proteo- 
lytic enzymes  results  in  a  rapid  destruction 
of  the  rather  loose  tissues  of  the  shrimp  heart 
(Figure  3a).  The  hepatopancreas  showed  con- 
siderable autolytic  change  by  4  h  postmortem 
leaving  the  heart  barely  recognizable  (Figure 
3b).  By  8  h  the  heart  was  not  distinguishable 
from  the  other  tissue  debris  present  at  the  heart's 
former  location  in  the  cephalothorax.  Vessels 
in  the  vicinity  of  the  hepatopancreas  and  heart 
also  disappeared  by  4-8  h,  but  vessels  elsewhere, 
such  as  in  the  abdomen,  persisted  much  longer, 
some  still  recognizable  after  24  h.  However,  by 
48  h  vessels  were  not  usually  demonstrable 
anywhere  in  the  body  of  a  shrimp. 


to  that  of  vertebrate  striated  muscle  (Figure  4a). 
The  muscles  of  the  cephalothorax  in  the  vicinity 
of  the  hepatopancreas  underwent  rapid  autolytic 
change,  apparently  due  to  digestion  by  enzymes 
released  on  lysis  of  the  hepatopancreas.  Further 
from  the  hepatopancreas,  the  rate  of  autolytic 
change  in  the  muscle  was  much  slower.  The 
earliest  observed  postmortem  change  in  the 
muscle  was  at  4  h  when  some  individual  muscle 
fibers  had  a  slightly  "frayed"  appearance. 
There  was  a  pronounced  swelling,  presumably 
edematous,  between  adjacent  muscle  fibers 
(Figure  4b).  By  8-12  h,  muscle  cell  nuclei  had 
become  pyknotic.  After  24  h  muscle  cells  had 
become  anucleate,  highly  eosinophilic,  and  the 
edematous  swelling  between  adjacent  muscle 
cells  had  decreased.  Cross  striations  within 
muscle  fibers  were  especially  evident  (Figures 
4d,  4e,  and  4f). 

In  some,  but  not  all,  of  the  shrimp  studied, 
bacterial  growth  was  evident  between  muscle 
bundles,  especially  in  the  vicinity  of  the  gut. 
The  presence  of  large  numbers  of  bacteria 
greatly  increased  the  rate  of  tissue  deterioration 
(Figure  4c),  while  muscle  not  heavily  invaded 
by  bacteria  remained  recognizable  as  muscle 
tissue  at  72  h  (Figure  4f). 

Integument 


Musculature 

Shrimp   locomotory   muscle   is   striated   and 
presents  a  histologic  appearance  that  is  similar 


The  integument,  consisting  of  epidermis  and 
an  overlying  cuticle,  underwent  rapid  degen- 
eration in  the  area  of  the  cephalothorax  that 
surrounds    the    hepatopancreas,    leaving    only 


r   »^v 


% 


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Figure  3. — a.  Normal  heart.   llOx.  b.  Heart  al  4  h  postmortem  showing  considerable  autolytic  change  and  loss  of  struc- 
tural detail.  100  X  . 


229 


FISHERY  BULLETIN:  VOL.  72.  NO.  I 


1 


KV« 


\ 


-~I1i 


'.. 


^^Blr** 


B 


'^^mm^ 


I 


m 


D 


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Figure  4. — a.  Normal  abdominal  muscle.  220  x  .  b.  Muscle  al  4  h  postmortem  showing  edematous  swelling  between  muscle 
bers.  Sarcoplasmic  staining  reaction  is  more  eosinophilic  than  normal  and  there  has  been  a  decrease  in  the  number  of 
nuclei  although  few  pyknotic  nuclei  are  shown.  150  X  .  c.  Muscle  showing  advanced  autolytic  change  due  to  the  presence  of 
large  amounts  of  bacteria  (12  h  postmortem).  190  X  .  d.  Muscle  at  24  h  postmortem.  Edematous  swelling  has  decreased,  but 
the  muscle  fibers  have  become  anucleale.  Note  the  prominence  of  cross  striations.  240X.  e.  Muscle  al  48  h  postmortem. 
240  X  .  f.  Muscle  fibers  with  prominent  cross  striations  are  still  recognizable  at  72  h  postmortem.  250  X  . 


230 


LIGHTNER:  POSTMORTEM  CHANGES  IN  BROWN  SHRIMP 


the  cuticle  remaining  by  4  h.  Distant  from  the 
hepatopancreas,  the  epidermis  showed  pyknotic 
nuclei  and  cell  rounding  by  4  to  8  h  (Figures  5a 
and  5b).  A  slight  hemocytic  response  was 
present  at  this  time  in  the  subepidermal  tissue 
layers  representing  the  only  inflammatory- 
like  response  observed  in  the  study. 

The  epidermis  had  frequently  become  de- 
tached from  the  overlying  cuticle  by  12  to  24 
h  postmortem  and  many  of  the  epidermal  cells 
had  lysed,  with  those  remaining  having  pyknotic 
nuclei  (Figure  5c).  By  24  to  48  h  nearly  all 
traces  of  the  epidermis  had  been  lost  and  in 
some  animals  examined  only  cellular  debris  or 
clumps  of  bacteria  marked  its  former  location 
(Figure  5d).  Though  usually   interrupted,  the 


cuticle  was  the  most  resistant  structure  to 
autolytic  change  and  showed  only  slight  histo- 
logical change  by  72  h. 

Gills 

The  shrimp  respiratory  system  consists  of 
paired  gills  in  the  branchial  chambers  of  the 
cephalothorax.  The  structure  of  the  gills  is 
dendrobranchiate  (Barnes.  1963).  The  gills  are 
covered  by  a  thin  cuticle  underlain  by  a  thin 
epithelium  and  other  supportive  cells  (Figure 
6a). 

A  peritrichous  ciliated  protozoan  (Figure  6b), 
presumably  a  commensal  on  shrimp  (especially 
common  on  the  gills  but  also  found  elsewhere  on 


•  -^^^v* 


5^ 


^  v_ 


B 


}Cmm  •*#•>  V^^S?:* 


*^  ^^ 

Figure  5. — a.  Integument  consisting  of  epidermis  and  overlying  cuticle  at  4  h  postmortem.  Some  of  the  epidermal  cells 
possess  pyknotic  nuclei.  A  few  hemocytes  are  present  in  the  subepidermal  tissues  (arrows).  480x.  b.  Integument  at  8  h 
postmortem.  Inflammatory  cells  are  present  in  the  subepidermal  tissue.  There  is  an  increase  in  nuclear  pyknosis  in  the 
epidermis  and  in  the  subepidermal  tissue.  300  X.  c.  Epidermis  and  cuticle  at  24  h  postmortem.  All  of  the  epidermal  cells 
have  intensely  pyknotic  nuclei,  as  does  all  the  subepithelial  tissue.  600  X  .  d.  Integument  at  48  h  postmortem.  The  cuticle  is 
present,  but  the  epidermis  is  represented  by  debris  (arrows).  750  X  . 


231 


FISHERY  BULLETIN:  VOL    72.  NO.  1 


the  body  surface),  increased  rapidly  in  numbers 
for  2  to  4  h  after  death  of  the  shrimp.  They 
were  absent  by  8  h  postmortem. 

The  cellular  elements  of  the  gills  underwent 
fairly  rapid  autolytic  change.  By  8-12  h  scat- 
tered pyknotic  nuclei  were  present  (Figure  6c). 
By  24  h  the  cellular  elements  of  the  gills  were 
for  the  most  part  anucleate,  with  some  portions 
of  the  gills  having  only  eosinophilic  debris 
within  the  lamellar  cuticle  (Figure  6d).  By 
48  h  the  thin  cuticle  of  gill  lamellae  had  begun 
to  deteriorate  and  hence  the  gill  lamellae  sec- 
tioned transversely  began  to  lose  their  typical 
"dumbbell"  appearance  (Figure  6e).  By  72  h 
the  gills  were  usually  no  longer  demonstrable 
histologically,  but  in  one  of  four  animals  exam- 
ined portions  of  the  gills  were  still  evident 
(Figure  60- 

Nerve  Tissue 

The  nervous  system  of  shrimp  is  composed  of 
a  large  ventral  nerve  cord  and  segmental  gang- 
lia from  which  smaller  nerve  branches  originate 
to  innervate  the  tissues.  At  the  anterior  end  of 
the  ventral  nerve  tract  is  the  supraesophageal 
ganglion,  which  anteriorly  receives  the  large 
optic  nerve  tracts. 

Neuron  perikaryons  in  the  ganglia  (Figure 
7a)  underwent  the  most  rapid  autolytic  change 
of  the  various  elements  of  shrimp  nerve  tissue. 
After  2  to  4  h,  these  cells  showed  considerable 
rounding,  pyknotic  or  karyolytic  nuclei,  and  a 
change  in  cytoplasmic  staining  from  highly 
basophilic  to  a  lesser  basophilic  to  almost  eosin- 
ophilic (Figure  7b).  By  8  h  no  trace  of  neuron 
perikaryons  was  evident. 

The  nerve  tracts  of  the  ventral  nerve,  its 
branches,  and  the  optic  nerves  autolyzed  less 
rapidly  than  did  neuronal  perikaryons.  How- 
ever, nerve  cell  processes  (axons  and  dendrites) 
within  the  nerve  tract  autolyzed  more  rapidly 
than  did  the  supportive  neurolemmal  and  glial 
cells,  and  were  no  longer  demonstrable  histo- 
logically by  12  to  24  h  (Figure  7c).  The  support- 
ive glial  cells  of  the  nerve  tracts  persisted  with- 
out noticeable  change  to  8  to  12  h,  but  these 
cells  became  anucleate  or  underwent  autolysis 
after  24  h,  and  their  former  presence  was 
represented  only  by  debris  and  an  occasional 
pyknotic  nucleus  (Figure  7d). 

After  24  h  postmortem,  the  basic  structural 


arrangement  of  the  nerve  tract  remained  rec- 
ognizable due  to  the  persistence  of  neurolemmal 
fibers  (Figures  7d  and  7e),  which  persisted  to 
72  h  at  the  sites  of  the  optic  nerve  and  ventral 
nerve  tracts. 

Antennal  Gland 

The  antennal  gland  of  crustaceans  had  been 
demonstrated  to  be  imi)ortant  in  ion  regulation 
(Robertson,  1959).  The  antennal  or  hemocoelic 
excretory  gland  in  shrimp  is  located  in  the 
cephalothorax  above  the  supraesophageal  gang- 
lion (Young,  1959).  The  gland  is  composed  of  a 
collection  of  tubules  and  a  bladder  (Figures  8a 
and  8b).  By  4  h  some  sloughing  of  tubule  epi- 
thelium was  evident  (Figure  8b),  but  for  the 
most  part  the  histologic  appearance  of  the  organ 
remained  normal.  At  12  h,  however,  most  of  the 
nuclei  of  the  tubule  epithelium  were  intensely 
pyknotic  (Figure  8c),  and  by  24  h  the  organ  had 
disappeared  or  had  become  difficult  to  recognize 
(Figure  8d).  No  trace  of  the  gland  was  found 
after  48  h  postmortem. 

Gonadal  Tissue 

Since  the  animals  used  in  this  study  were 
immature  juvenile  shrimp,  the  gonads  were 
small,  poorly  differentiated  and  were  located  in 
the  cephalothorax  lateral  and  slightly  caudad  to 
the  hepatopancreas.  The  terminal  ampule  of 
male  shrimp  was  poorly  developed  and  in  female 
shrimp  the  ovarian  lobe,  which  extends  into 
the  abdomen  in  older  shrimp,  had  not  yet 
develoj^ed. 

The  rate  of  autolysis  in  the  gonads  of  the 
shrimp  studied  was  rapid,  due  to  their  close 
proximity  to  the  hepatopancreas.  Gonadal 
tissue  was  not  recognizable  histologically  after 
4  to  8  h  postmortem. 

DISCUSSION 

The  rigorlike  stiffening  observed  in  this 
study  may  represent  true  rigor  mortis.  Sparks 
(1972)  i)ostulated  that  rigor  mortis  or  a  similar 
phenomenon  may  occur  in  some  invertebrates 
with  well  organized  skeletal  systems  and  as- 
sociated skeletal  muscles.  He  based  his  opinion 
on  the  observation  that  many  arthropods,  which 
are   flaccid   after   somatic   death,   subsequently 


232 


LIGHTNER:  POSTMORTEM  CHANGES  IN  BROWN  SHRIMP 


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Figure  6. — a.  Normal  gills.  120  x  .  b.  An  unidentitied  ciliated  protozoan  abundant  on  the  gills  at  4  h  postmortem.  240  X  .  c. 
Gills  at  12  h  postmortem.  Note  the  absence  of  the  protozoan  and  the  presence  of  pyknotic  nuclei  in  the  cellular  elements. 
130  X.  d.  Gills  at  24  h  postmortem.  Except  for  a  few  pyknotic  nuclei  only  the  cuticle  and  cellular  debris  remain.  160  X.  e. 

Gills  at  48  h  postmortem.  The  tissue  is  still  recognizable  as  gills:  however,  the  lamellae  are  losing  their  usual  "dumbbell" 
appearance  and  contain  only  eosinophilic  cellular  debris.  190  X.  f.  Gills  at  72  h  postmortem.  GUIs  were  recognizable  his- 
tologically only  from  this  one  of  four  animals  examined.  120  X  . 


233 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


s        . 


B^ 


■--^J 


Figure  7. — a.  Cross  section  of  an  abdominal  segment  ganglion  on  the  ventral  nerve  (0  h  control).  Neuron  perikaryons 
(N)  are  present  ventral  to  the  large  ventral  nerve  tract  (T).  1 10  X  .  b.  Sagittal  section  of  an  ahdominal  segment  ganglion  at 
4  h  postmortem.  The  neuron  perikaryons  are  rounded  and  have  pyknolic  nuclei.  Nerve  cell  processes,  neurolemmal 
and  glial  cells  in  the  nerve  tract  show  no  apparent  autolysis.  220  X.  c.  Cross  section  of  the  ventral  nerve  at  12  h  postmor- 
tem. Nerve  cell  processes  are  not  evident  and  neurolemmal  and  glial  cells  possess  pyknotic  nuclei.  200  X  .  d.  Cross  section 
of  the  ventral  nerve  at  24  h  postmortem.  Only  supportive  fibrous  tissue  elements  and  eosinophilic  debris  remain.  190  X. 
e.  Cross  section  of  ventral  nerve  at  48  h  postmortem.  Fibrous  elements  are  still  present.  200  X  .  f.  Ventral  nerve  in  cross 
section  at  72  h  postmortem.  The  Hbrous  elements  of  the  nerve  are  still  present.  120  X  . 


234 


LIGHTNER:  POSTMORTEM  CHANGES  IN  BROWN  SHRIMP 


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Figure  8. — a.  Normal  antenna!  gland.  100  X  .  b.  Anlennal  gland  at  4  h  postmortem.  A  few  epithelial  cells  have  been  sloughed 
into  the  tubule  lumens.  100  X.  c.  The  tubule  epithelium  of  the  antennal  gland  at  12  h  postmortem  showing  intense  nuclear 
pyknosis.  150  X.  d.  Antennal  gland  at  24  h  postmortem.  The  tubule  epithelium  has  lysed  filling  the  tubule  lumens  with 
eosinophilic  debris  and  nuclear  remnants.  150  X  . 


become  rigid.  Whether  this  was  due  to  desic- 
cation of  the  tissues  or  actual  rigor  of  the  mus- 
cles was  not  determined.  In  the  present  study, 
freshly  killed  juvenile  shrimp  became  rigid 
in  sealed  glass  jars  containing  water-saturated 
air  and  when  totally  submerged  in  water.  Desic- 
cation was  not  possible.  The  time  of  onset  of 
rigidity  was,  as  in  vertebrates,  temperature- 
dependent,  occurring  earlier  at  higher  tempera- 
tures than  at  lower  temperatures. 

Flick  and  Lovell  (1972)  in  studying  post- 
mortem biochemical  changes  in  penaeid  shrimp 
reported  that  shrimp  tails  remained  soft  and 
did  not  exhibit  any  of  the  characteristics  com- 
monly associated  with  rigor  mortis  during  a 
storage  period  of  10  days  at  0°C.  Perhaps  the 
effect  of  freezing  or  near-freezing  temperature 
on  shrimp  muscle  either  masks  or  inhibits  the 
onset  of  physical  rigor. 


The  rate  of  autolysis  of  the  hepatopancreas  is 
extremely  rapid.  The  organ  is  a  large,  multi- 
functional organ  believed  to  produce  the  bulk 
of  enzymes  used  in  the  digestive  process  in 
shrimp  and  to  have  some  absorptive  and  storage 
function.  The  hepatopancreas  connects  to  the 
midgut  near  its  origin  from  the  pyloric 
stomach.  The  gut  is  a  short,  nearly  straight  tube. 
and,  hence,  enzymatic  digestion  must  occur  as 
rapidly  as  possible  if  the  shrimp  is  to  utilize 
its  food  efficiently.  Even  careful  handling  of 
shrimp  to  avoid  stress  before  fixation,  opening 
of  the  cuticle  over  the  hepatopancreas,  or  exci- 
sion and  bisection  of  the  gland  to  enhance  fixa- 
tion, frequently  failed  to  provide  adequate 
penetration  and  fixation  of  the  organ  when 
Formalin  fixatives  were  used.  The  remaining 
tissues  of  shrimp  are  generally  adequately  fixed 
for  light  microscopy  with  Formalin,  provided 


235 


FISHERY  BULLETIN:  VOL.  72,  NO.  1 


that  small  jiieces  of  tissue  are  used  or  that 
the  cuticle  is  opened  on  smaller  shrimp  that  are 
fixed  whole. 

The  relative  rates  and  patterns  of  postmortem 
change  in  shrimp  are  similar  to  those  described 
for  the  oyster  (Sparks  and  Pauley,  1964)  and 
for  mammals  (Cruickshank.  1912;  Smith  and 
Jones,  1966).  In  mammals,  oysters,  and  shrimp, 
tissues  that  ])roduce  large  amounts  of  proteoly- 
tic enzymes  such  as  the  mammalian  i)ancreas 
and  lining  epithelium  of  the  stomach,  oyster 
digestive  tubules,  and  shrimp  hepatopancreas 
and  gut  ejiithelium  autolyze  the  most  rajMdly. 
Tissues  that  autolyze  nearly  as  rapidly  are 
high  lipid  containing  tissues  such  as  nerve 
tissue.  In  the  shrimp  and  in  mammals,  muscle, 
connective,  and  epidermal  tissues  undergo  the 
least  rapid  autolysis. 


LITERATURE  CITED 


Barnes,  R.  D. 

196.^.     Invertebrate    zoology. 
Phila.,  632  p. 


W.    B.    Saunders   Co. 


Cruickshank,  J. 

1^12.     The     histological     appearances     occurring     in 
organs    undergoing    autolysis.   J.    Pathol.    Bacteriol. 
16:167-184. 
Flick,  G.  J.,  and  R.  T.  Lovell. 

1972.     Post-mortem     biochemical     changes     in     the 
muscle  of  Gulf  shrimp,  Penaeus  aztecus.     J.  Food 
Sci.  37:609-611. 
Roberts,  N.  L. 

1966.     Morphology  and  histology  of  the  stomach  of 
the    while   shrimp,    Pciuwus  flnviatilis   (Say,    1817). 
Ph.D.  Thesis.  Univ.  South.  Mississippi.  Hattiesburg, 
78  p. 
Robertson,  J.  D. 

19? 9.    Osmotic  and  ionic  regulation.    In  T.  H.  Water- 
man (editor).  The  physiology  of  Crustacea,  Vol.   1, 
p.  317-339.  Academic  Press,  N.Y. 
Smith,  H.  A.,  and  T.  C.  Jones. 

1966.     Veterinary  pathology.    3d  ed.    Lea  &  Febiger, 
Phila..  1192  p. 
Sparks,  A.  K. 

1972.     Death    and    postmortem    change.       //(    A.    K. 
Sparks,    Invertebrate    pathology    noncommunicable 
diseases,  p.  1-19.  Academic  Press,  N.Y. 
Sparks,  A.  K.,  and     G.  B.  Pauley. 

1964.     Studies  of  the  normal  postmortem  changes  in 
the   oyster,   Cnissosircu  ,i,'wv.v   (Thunberg).  J.   Insect 
Pathol.  6:78-101. 
Young,  J.  H. 

1959.  Morphology  of  the  white  shrimp,  Penaeus 
seiiferus  (Linnaeus  1758).  U.S.  Fish.  Wildl.  Serv., 
Fish.  Bull.  59:1-168. 


236 


BOTHVS  IHOMPSOM  (FOWLER)  1923,  A  VALID 

SPECIES  OF  FLATFISH  (PISCESiBOTHIDAE) 

FROM  THE  HAWAIIAN  ISLANDS 

Paul  Struhsaker  and  Robert  M.  Moncrief' 

ABSTRACT 

Boihiis  ihumpsoni  (Fowler)  1923  is  resurrected  from  the  synonymy  of  B.  hleekeri  Steindach- 
ner  and  redescribed.  B.  ihonipsuni  differs  from  all  other  recognized  species  of  the  genus  in 
possessing  11-17  gill  rakers  on  the  lower  limb  of  the  first  gill  arch  and  115-147  lateral  line 
scales.  B.  ihumpsoni  is  endemic  to  the  Hawaiian  Islands  where  it  inhabits  the  outer  shelf  in 
depths  of  70- 115  m. 


Fowler  (1923)  proposed  Platophry^  thonipi^oiti 
on  the  basis  of  a  single  specimen  obtained  by 
John  W.  Thompson.  Although  no  exact  locality 
data  were  given,  we  assume  the  specimen  was 
from  the  Honolulu  market.  PlatopJirys  is  now 
considered  a  synonym  of  BotJiu.s,  while  Norman 
(1934),  without  comment,  relegated  Bathus 
thonipsoui  to  the  synonymy  of  B.  hhtkeri  Stein- 
dachner.  Gosline  and  Brock  (1960)  followed 
Norman  in  listing  B.  bleekeri  from  the  Hawaiian 
Islands.  Previously,  only  the  holotype  of  B. 
thompsoni  was  available  for  study.  Our  examina- 
tion of  numerous  specimens  collected  by  the 
National  Marine  Fisheries  Service  (NMFS) 
during  recent  bottom  trawling  surveys  in  the 
60-700  m  depth  range  of  the  Hawaiian  Islands 
demonstrates  that  B.  thoinpsoui  should  be 
recognized  as  a  valid  species. 

MATERIAL  AND  METHODS 

All  specimens  were  collected  with  12.5-m 
(headrope)  shrimp  trawls  during  bottom  trawl- 
ing surveys  in  the  Hawaiian  Islands  with  the 
NMFS  RV  Toicnsend  Cromwell.  Sampling 
effort  and  general  ichthyological  results  of  these 
surveys  are  given  by  Struhsaker  (1973).  Most 
specimens  examined  (one  exception  from  Maui) 
were  from  the  north  coast  of  the  island  of  Oahu. 

The  following  description  is  based  on  a  series 
of  29  male  (55.8-114.4  mm  SL)  and  31  female 
(39.1-103.7  mm  SL)  specimens  all  of  which  are 
housed    in   the   National    Museum    of  Natural 


'    Southwest  Fisheries  Center.  National  Marine  Fisheries 
Service,  NOAA,  Honolulu.  HI  968  12. 


History  (USNM)  and  Bernice  P.  Bishop 
Museum  (BPBM).  Additionally,  33  uncata- 
logued  specimens  cleared  and  stained  by  the 
method  described  by  Taylor  (1967)  were  utilized 
in  vertebral  and  gill  raker  counts,  and  more  un- 
catalogued  specimens  were  examined,  obtaining 
supplementary  dorsal,  anal,  and  caudal  ray 
counts. 

Measurements  and  counts  are  usually  as 
defined  by  Norman  (1934),  Hubbs  and  Lagler 
(1958),  and  Gutherz  (1967).  Standard  length 
was  taken  from  tip  of  snout  to  end  of  hypural 
plate  on  the  blind  side.  Horizontal  eye  diameter 
was  taken  between  edges  of  the  bony  orbits.  Snout 
to  axis  of  greatest  depth  was  taken  from  the 
snout  to  a  vertical  line  at  the  greatest  body  depth. 
The  last  two  dorsal  and  anal  rays  are  each 
associated  with  pteiygiophores  and  are  counted 
as  two.  Lateral  line  scale  rows  just  above  the 
lateral  line  and  pored  lateral  line  scales  were 
counted.  Vertebral  counts  were  taken  from  radio- 
graphs and  from  cleared  and  stained  speci- 
mens. Gill  rakers  were  counted  as  discussed 
below. 

To  evaluate  morphometric  characters,  mea- 
surements in  original  units  and  as  percent  of 
standard  length  were  plotted  as  functions  of 
standard  lengths. 

RESULTS 

Description 

Although  a  figure  of  B.  thompsoui  did  not 
accompany  the  original  description,  Fowler 
(1928),  in  listing  the  species  for  Oceania,  pro- 
vided a  figure  of  the  type  (PI.  IV,  C)  which  is 


Manuscript  accepted  June  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO. 


1.  1974. 


237 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


housed  in  the  BPBM  (3398).  Measurements  of 
the  106.8  mm  SL  male  holotype  (Fowler  gave 
an  undefined  length  of  134  mm)  expressed  as 
percent  of  standard  length  are  given  in  Table 
1.  We  obtained  the  following  counts  on  this 
specimen:  dorsal  rays  86;  anal  rays  62;  caudal 
rays  16;  pectoral  rays  (both  sides)  12;  lateral- 
line  scale  rows  130;  pored  lateral-line  scales 
83;  gill  rakers  19  (5  +  14).  Prowler  (1923)  gave 
counts  of  132  scale  rows  and  20  gill  rakers  (6 
-I-  14).  Otherwise,  our  counts  agree  with  his. 

Photographs  of  recently  collected  female 
(106.4  mm  SL)  and  male  (114.4  mm  SL)  speci- 
mens (both  BPBM  14102)  are  shown  in  Figures 
1  and  2. 

Counts 

Dorsal  and  anal  ray  counts,  expressed  as 
bivariate  relations,  for  101  specimens  are  given 
in  Table  2.  Dorsal  rays  ranged  from  84  to  95 
{X  —  87.9)  and  anal  rays  ranged  from  64  to 
70  (A'  =  66.3).  Although  the  dorsal  ray  counts 
are  skewed  to  the  right,  the  distribution  does  not 
deviate  significantly  from  a  normal  distribution 
(P>0.2;  Kolomogorov-Smirnov  test  for  good- 
ness of  fit,  D  =  0.0702). 

There  were  considerably  fewer  pored  lateral- 
line  scales  (Table  3)  {X  =  80.9)  than  the  numbe£ 
of  vertical  scale  rows  above  the  lateral  line  (X 
=  131.6). 

There  was  a  tendency  towards  more  pectoral 
rays  (Table  3)  on  the  ocular  side  (X  =  12.24) 
than  on  the  blind  side  {X  =  11.49).  The  upper 
pectoral  ray  on  the  ocular  side  is  reduced  and 
sometimes   inconspicuous.   The  upper  pectoral 


ray  on  the  blind  side  is  also  reduced,  but  easily 
visible. 

BotJiKs  thompso)ii  appears  to  be  unique  among 
si)ecies  of  BotJius  in  usually  jjossessing  16  caudal 
rays.  Of  163  specimens  examined  (Table  3),  2 
(1.2%  )  had  15  rays,  157  (96.3%  )  had  16  rays,  and 
4  (2.5%  )  had  17  rays.  The  caudal  rays  are  usually 
associated  with  the  four  hypural  elements.  Of 
31  cleared  and  stained  specimens  having  16 
rays,  11  had  a  caudal  ray  formula  of  4-4-4-4 
(dorsal  element  counted  first).  Other  formulae 
obtained  and  number  of  specimens  are  as  follows 
(rays  articulating  between  elements  are  enclosed 
by  parentheses):  4-4-3-(l)-4,  (6  specimens); 
4-4-3-5,  (5  specimens) ;  3-(  l)-4-4-4,  (4  specimens) ; 
3-(l)-4-3-(l)-4,  (2  specimens);  3-(l)-4-3-5,  (1 
specimen);  3-(l)-4-3-5,  (1  specimen);  4-4-3-5, 
(1  specimen).  Two  specimens  with  15  rays 
had  formulae  of  4-4-3-4  and  3-(l)-4-4-3. 

None  of  the  caudal  rays  of  B.  thompsoiii  was 
associated  with  the  neural  and  haemal  spines 
of  the  penultimate  vertebra  or  articulated  in  the 
space  between  the  spines  and  hypural  elements. 
Thus,  B.  thompsoni  differs  from  certain  other 
species  of  Botlius  which  have  rays  associated 
with  the  neural  and  haemal  spines  of  the  penul- 
timate vertebra  or  which  occur  in  the  interspace 
between  the  spines  and  hypural  elements.  Gutherz 
(1970)  gives  a  formula  of  1-4-4-3-4-1  for  larval 
BotliHs  (species  not  determined)  from  the 
western  North  Atlantic.  We  obtained  the  same 
formula  for  12  cleared  and  stained  specimens 
of  B.  pa)ithe7HHUs  (Riippell)  from  the  Hawaiian 
Islands.  In  these  specimens  the  first  and  last 
rays  most  often  articulated  in  the  interspace 
between  the  spines  and  hypural  elements.  These 


Table  1. — Bothiis  thompsoiu:  Measurements  of  13  characters  for  holotype,  29  males,  and  31  females  expressed  as  percent 
of  standard  length.  Holotype  excluded  from  regression  statistics  (a  =  ordinate  intercept,  h  =  regression  coefficient). 


Holotype 

Range  percent 

Range  percent 

BPBM  3398 

standard 

standard 

percent  of 

length 

length 

Characters  measured 

standard  length 

for  males 

a 

h 

;-2 

for  females 

(/ 

b 

r2 

Heed  length 

28.5 

25.7-29.5 

0.646 

0.270 

0.965 

26.0-29.6 

1.100 

0.264 

0.983 

Snout  length:   to  upper  eye 

23.9 

14.0-21.5 

-5.865 

0.252 

0.961 

13.0-16.6 

-  1.022 

0.162 

0.968 

to  lower  eye 

6.3 

4.4-   6.2 

0.315 

0.048 

0.821 

4.8-   6.8 

-0.171 

0.569 

0.857 

Orbit  diameter:    upper 

11.6 

9.1-12.6 

2.255 

0.084 

0.828 

8.2-12.4 

1.656 

0.087 

0.896 

lower 

9.6 

7.6-10.9 

2.222 

0.071 

0.811 

8.0-11.5 

2.263 

0.067 

0.874 

Interorbitol  distance 

14.9 

7.713.5 

-5.856 

0.182 

0.958 

5.1-  8.6 

-  1.112 

0.088 

0.949 

Length  of  upper  jaw 

10.3 

8.0-10.6 

1.102 

0.081 

0.856 

8.2-10.4 

0.770 

0.084 

0.943 

Greatest  body  depth 

60.8 

57.7-66.0 

-  1.046 

0.629 

0.968 

57.0-67.3 

-0.057 

0.632 

0.973 

Least  depth  caudal  peduncle 

11.2 

9.7-11.4 

0.042 

0.107 

0.970 

9.2-11.6 

0.195 

0.104 

0.981 

Length  of  pectoral  fin:    ocular  side 

21.7 

19.0-24.7 

4.661 

0.159 

0.912 

18.8-24.9 

4.925 

0.153 

0.924 

blind  side 

18.4 

15.3-18.7 

2.294 

0.141 

0,928 

14.0-18.5 

0.826 

0.155 

0.930 

Length  of  anal  fin  base 

75.2 

73.4-77.4 

2.373 

0.734 

0.958 

71.9-84.8 

-3.634 

0.814 

0.966 

Snout  to  greatest  body  depth 

46.3 

41.6-48.6 

-4.156 

0.497 

0.959 

41.4-50.0 

0.341 

0.452 

0.961 

238 


STRUHSAKER  and  MONCRIEF:  BOTHVS  THOMPSOSl 


Figure  1. — A  106.4  mm  SL  female  Boihu.s  ihonipsoni. 


Figure  2. — A  1 14.4  mm  SL  male  Boihu.s  ihompsoni. 


data  indicate  that  B.  thompsoni  exhibits  a  more 
variable  caudal  ray  formula  than  B.  pant'herinus. 

The  first  two  and  last  two  caudal  rays  of  B. 
thompsoni  are  usually  simple.  Of  a  sample  of 
20  specimens,  only  2  ( 10%  )  had  either  the  second 
or  penultimate  ray  divided. 

The  arrangement  of  gill  rakers  in  B.  thomp- 
soni is  shown  in  Figure  3,  and  counts  are  given 


in  Table  3.  There  are  3-9  reduced  gill  rakers 
associated  with  the  epibranchial  and  1-4  reduced 
gill  rakers  associated  with  the  hypobranchial.  A 
series  of  9-14  well-developed  gill  rakers  is 
principally  associated  with  the  ceratobranchial. 
The  reduced  gill  rakers  associated  with  the 
epibranchial  comprise  the  counts  for  the  upper 
limb  of  the  gill  arch.  The  first  well-developed 


239 


FISHERY  BULLETIN:  VOL.  72.  NO.  I 


Table  2. — Dorsal  and  anal  ray  counis  for  101  specimens  ot 
liolhiis  ilioinpsdiii. 

Number  of  dorsal  rays  Total  nuin- 

Number  of ■ ber  of 

anal  rays  84    85    86    87    88    89    90    91     92    93    94    95  specimens 

70 __]_ 1  2 

69  ____-l-l----  2 

68  -__-1314l—  —  —  10 

67  --2577531-  —  -  30 

66  -37398  —  —  —  —  —  —  30 

65  2-873-------  20 

64  21211-------  7 

Total 
number  of 
specimens  4      4     19     16    21     19      7      8      2     -     -      1  101 


raker  occurs  at  the  angle  of  the  arch  and  is 
included  in  the  counts  forthe  lower  limb,  although 
stained  material  reveals  this  raker  to  be  more 
closed  associated  with  the  epibranchial.  The 
last  one  or  two  well-developed  rakers  are 
associated  with  the  hypobranchial. 

The  number  of  gill  rakers  in  the  size  range 
examined  is  apparently  independent  of  size. 
A  regression  coefficient  calculated  for  28 
females  was  not  significant  (P>  0.4). 

Vertebral  counts  were  obtained  from  96 
specimens.  There  are  usually  10  abdominal 
vertebra  (94  specimens),  but  two  individuals  had 
11  (28  caudal  vertebrae  in  both  cases).  Counts 
of  caudal  vertebrae  (including  urostyle)  were  27 
(7),  28  (69),  and  29  (18).  while  total  vertebral 
counts  were  37  (7),  38  (69),  and  39  (20). 


Figure   3. — A  typical  first  gill  arch  from  the  ocular  side 
of  Bcihus  iliiimpsoni. 


Measurements 

The  measurements  obtained  from  29  male  and 
31  female  specimens  for  13  characters  are 
summarized  in  Table  1.  Linear  regressions  were 
calculated  in  original  units  of  measurement 
(mm)  with  standard  length  as  the  independent 


Table  3. —  Bailius  iliomp.soni:  Counts  for  eight  characters. 


Characters 


Frequency  of  occurrence 


10       II       12       13       14       15       16 


19      20      21       22      23      24      N 


Caudal  rays 
Pectoral  rays 

{ocular  side) 
Pectoral  rays 

(blind  side) 
Gill  rakers 

(upper  limb) 
Gill  rakers 

(lower  limb) 
Gill  rakers  (total) 


157 


5      29      29      21 


1  7      32      22 

2  29      31         1 


3      21      22      27      13 
1 


13      24 


17 


-       163  16.0) 

63  12.24 

63  11.49 

91  5.92 

91  14.38 

5      91  20.30 


70-    72-     74- 

71       73      75      76 


90-    92- 
78      80      82     84      86      88      91      93 


Pored  lateral  line 
scales 


31       80.9 


114-  116-  118-  120-  122-  146- 

115    117    119    121     123    124    126  128    130    132    134    136    138    140    142    144    147 


Lateral  line  scale 
rows 


17 


63    131.6 


240 


STRUHSAKER  and  MONCRIEF:  BOTHUS  THOMPSONI 


variable.  Plots  of  all  regressions  are  linear  and 
exhibit  high  )^  values. 

The  regressions  obtained  for  the  13  measured 
characters  were  subjected  to  analysis  of 
covariance  to  test  for  sexual  dimorphism. 
Highly  significant  differences  (P< 0.001)  were 
found  between  the  regression  coefficients  for  two 
characters  (which  are  related):  interorbital  dis- 
tance (Figure  4)  and  snout  to  upper  eye.  Juvenile 
and  adult  male  specimens  of  B.  thonipsoni  are 
similar  to  many  Bothus  spp.  males  in  possessing 
a  much  greater  interorbital  distance  than  females 
of  the  same  species.  Male  B.  fliompsoni  exhibit 
positive  allometric  growth  of  the  interorbital 
distance,  this  measurement  being  about  7.5%  - 
9.0%  of  standard  length  at  a  length  of  50-60  mm 
and  about  12% -14%  ofstandard  length  at  a  length 
of  100-115  mm.  In  female  specimens  longer 
than  50  mm  the  interorbital  distances  were  6.0%  - 
8.6%  'ofstandard  length.  Interorbital  distances  of 
5.3%  and  5.1%  ofstandard  length  were  noted  in 
two  specimens  39  mm  and  48  mm  long.  As  ex- 
pected, male  B.  thonipficnii  exhibited  positive 
allometric  growth  of  the  snout  to  upper  eye 
distance. 

Among  the  remaining  11  characters  subjected 
to  analysis  of  covariance,  there  were  no  signifi- 
cant differences  between  regression  coefficients. 
There  were  significant  differences  (P<0.05)  in 
the  elevations  of  the  regressions  between  sexes 
for  four  characters.  Both  the  upper  and  lower 
orbit  diameters  of  males  tend  to  be  larger  than  for 
females;  the  differences  in  adjusted  means  for 


FEM 

ILES    — ' ■ 

" 

•    • 

-— — % 

•  ___^.— 

-—*    • 

^^„^— -«- 

^^u— ■ 

, 

^^>^ 

1 

• 

^t-'  • 

%  .- 

L<^ 

,  ^ 

f^ 

• 

60  70  60  90 

STANDARD  LENGTH   (mm) 


Figure   4. — Plots  of  the  interorbital   distance  of  29  male 
and  3  1  female  specmiens  of  Boihiis  ihonipsciii. 


the  two  characters  are  0.35  and  0.40  mm,  re- 
spectively. Females  tend  to  have  a  greater  body 
dei)th  and  a  greater  snout  to  greatest  body  depth 
distance.  The  differences  in  adjusted  means  for 
these  two  characters  are  1.1  and  1.0  mm, 
respectively. 

In  both  sexes,  the  pectoral  fins  of  the  ocular 
side  tend  to  be  longer  than  those  of  the  blind  side 
(Table  1).  The  pectoral  fins  of  both  sexes  exhibit 
negative  allometric  growth.  This  is  most  pro- 
nounced on  the  ocular  size  where  the  pectoral 
length  is  about  24%  -25%  of  standard  length  at 
40-60  mm  and  about  18%  -21%  ofstandard  length 
at  a  length  of  100-115  mm.  There  is  only  slight 
negative  allometric  growth  of  the  pectoral  fin 
on  the  blind  side  where  this  structure  varies 
from  14.0%  to  18.7%  ofstandard  length. 

All  other  morphometric  characters  examined 
exhibited  approximately  isometric  growth. 

Two  of  the  measurements  we  obtained  for  the 
holotype  (Table  1)  do  not  fall  within  the  ranges 
we  obtained  from  our  study  series:  interorbital 
distance  and  snout  to  upper  eye. 

Other  morphological  characters 

Botlius  thonipsoiii  has  cycloid  scales  on  the 
blind  side  and  on  most  of  the  ocular  side  (Figure 
5A).  Ctenoid  scales  occur  on  the  proximal 
portions  of  the  dorsal  and  anal  rays.  There  are 
2-3  rows  of  ctenoid  scales  at  the  bases  of  the  dor- 
sal and  anal  fins  (Figure  5B).  Fowler  (1923) 
stated  that  the  holotype  had  ctenoid  scales  on 
the  cheeks  and  postorbital  region.  In  addition, 
we  find  that  there  is  a  patch  of  about  15  ctenoid 
scales  below  the  curved  portion  of  the  lateral 
line  in  the  holotype.  A  scale  from  this  region  is 
shown  in  Figure  5C.  The  occurrence  of  ctenoid 
scales  on  the  cheek  and  in  the  vicinity  of  the 
curved  portion  of  the  lateral  line  is  a  variable 
character.  Of  25  specimens  (67.5-106.4  mm  SL) 
from  our  study  series,  six  had  ctenoid  cheek 
scales,  three  had  ctenoid  scales  on  the  cheek 
and  near  the  lateral  line,  and  one  had  ctenoid 
scales  near  the  lateral  line  only.  The  presence 
of  ctenoid  scales  in  these  two  regions  does  not 
appear  to  be  related  to  size  or  sex.  The  cycloid 
scales  are  small  and  nonimbricated,  but  the 
ctenoid  scales  at  the  dorsal  and  anal  fin  bases 
overlap  to  a  slight  degree.  The  ctenii  of  the 
ctenoid  scales  generally  occur  in  two  rows:  a 
primary  row  of  well-developed  ctenii  and  a 
secondary   row  of  smaller  ctenii   basal   to  the 


241 


FISHERY  BULLETIN:  VOL.  72.  NO.  1 


Figure  5. — Scales  of  Boihus  ilioiiip.soni:  A,  cycloid 
scale  from  above  the  lateral  line;  B,  ctenoid  scale 
from  near  the  dorsal  fin  base;  and  C,  ctenoid  scale 
from  below  the  curved  portion  of  the  lateral  line  in 
the  holotype. 


primary  row  (Figure  5B  and  C).  The  number  of 
ctenii  on  cheek  scales  varies  from  5  to  8,  while 
scales  from  the  dorsal  and  anal  fin  bases  at  the 
greatest  body  depth  have  15  to  25  ctenii. 

The  general  arrangement  of  teeth  in  the  upper 
and  lower  jaws  is  shown  in  Figure  6.  There 
are  usually  three  rows  of  teeth.  The  outer  row 
consists  of  a  few,  stout  conical  teeth  in  the 
anterior  portion  of  the  jaws.  The  middle  row 
consists  of  more  numerous,  but  less  stout,  conical 
teeth.  The  inner  row  consists  of  depressed,  poor- 
ly ossified  conical  teeth  subequal  in  number  to 
those  in  the  middle  row  (except  on  the  blind  side 


of  the  upper  jaw).  The  inner  row  of  teeth  are 
movable,  being  held  in  place  by  flesh  and  not 
inserted  in  the  jaw  bones. 

The  number  of  outer  teeth,  and,  to  a  lesser 
extent,  the  middle  teeth,  vary  according  to  jaw 
bone  and  size  of  specimen.  This  is  illustrated  in 
Figure  7  where  the  number  of  teeth  are  plotted 
by  standard  length  for  10  females  49.2-106.4  mm 
SL  and  10  males  55.8-114.5  mm  SL.  The  increase 
in  number  of  outer  teeth  with  size  is  ai)parent 
for  all  jaw  bones  except  the  dentary  on  the  ocular 
side.  There  also  appear  to  be  more  outer  teeth  in 
the  premaxillary  of  the  ocular  side  of  the  males. 


242 


STRUHSAKER  and  MONCRIEF:  BOTHUS  THOMPSON! 


The  teeth  in  the  middle  row  also  exhibit  a  general, 
but  less  well-defined,  increase  in  numbers  with 
size. 

There  are  no  fleshy  papillae  along  the  edges 
of  the  eyes  such  as  reported  for  male  B.  pcvtther- 
imis  (Norman,  1934).  There  is  a  single  promi- 
nent, blunt  protuberance  on  the  snout  of  males 
greater  than  60  mm  SL.  This  stnacture  is 
represented  in  females  by  a  small  knob.  The 
anterior  edge  of  the  lower  orbit  tends  to  be  more 
developed  and  rugose  in  males  than  in  females. 

Coloration  of  fresh  specimens 

The  blind  side  of  both  sexes  is  white,  but  tending 
to  dusky  white  in  males  greater  than  about  80 
mm  SL,  especially  on  the  cheek  and  above  the 
cheek.  The  ground  color  of  the  ocular  side  is 
light  olive  green.  There  is  a  single  prominent 
dark  spot  on  the  lateral  line  posteriad  about  60% 
of  the  standard  length.  There  are  two  secondary 
dark  ocelli  near  the  pectoral  fin.  There  are  14-15 
olive  green  ocelli  broadly  distributed  along  the 
dorsal  and  ventral  borders  of  the  trunk.  There 
are  numerous  light  blue  ocelli  and  spots  dis- 
tributed over  the  trunk,  head,  and  dorsal,  anal, 
caudal,  and  ventral  fins.  The  pectoral  fins  are 
almost  clear.  In  males,  the  light  blue  spots  are 
more  numerous  and  elongated  along  the  anterior 
profile  and  between  the  eyes. 

Comparison  with  Other  Species  oi  Bothns 

A  definitive  discussion  of  the  relation  of  B. 
th()))tps())ii  to  other  species  of  Bothus  must  await 
further  study  of  the  genus  on  a  worldwide  basis. 
B.  tJiompsoiii  differs  from  all  recognized 
species  of  Bothus  (Fowler,  1933;  Norman,  1934; 
Chabanaud,  1942;  Stauch,  1966;  Gutherz.  1967; 
Amaoka,  1969;  Topp  and  Hoff,  1972)  in  possess- 
ing 11-17  gill  rakers  on  the  lower  limb  of  the 
first  arch  (11  or  fewer  in  other  species)  and 
115-147  scale  rows  above  the  lateral  line 
(apparently  100  or  fewer  in  other  species:  Nor- 
man, 1934).  It  may  also  be  unique  in  that  it 
usually  has  only  16  caudal  rays  as  opposed  to 
17  in  other  species.  This  character,  however, 
apparently  has  been  examined  only  rarely  by 
earlier  authors  and  few  data  on  the  numbers 
and  arrangements  of  the  caudal  rays  are  avail- 
able (Chabanaud,  1942;  Amaoka,  1969;  Gutherz, 
1970).  The  figures  given  by  Norman  (1934)  for 
B.  leopardinus  (Giinther)  and  B.bleekeri  indicate 


Figure  6. — The  arrangement  of  teeth  in  Baihiis  ihompsoni. 

caudal  ray  counts  of  16.  However,  a  count  of  16 
is  also  indicated  for  B.  ovalis  (Regan)  which 
Amaoka  (1964)  has  shown  to  be  the  young  of 
B.  myriaster  (Temminck  and  Schlegel).  B. 
inyriaster  has  17  caudal  rays  (Amaoka,  1969). 
Chabanaud  (1942)  described  B.  biidkeri  from  the 
Red  Sea  and  gave  caudal  ray  counts  of  16  for 
the  holotype  and  17  for  the  two  paratypes.  A 
sample  of  368  adult  and  lai*val  specimens  of 
B.  panthcrhiKs  from  the  Hawaiian  Islands  had 
the  following  caudal  ray  counts:  16  (2.7%),  17 
(95.7%  ),  18  (1.6%  ).  Further  examination  of  this 
character  is  required. 

We  have  not  examined  specimens  of  B.  bleekeri, 
and  we  separate  this  species  from  B.  thompsniii 
on  the  basis  of  the  description  given  by  Norman 
(1934).  In  addition  to  the  differences  in  gill 
raker  and  lateral  line  scale  row  counts  dis- 
cussed above,  B.  thompso)n  has  more  pectoral 
rays  on  the  ocular  side  (10-14  vs.  8-9).  Adult 
male  specimens  of  B.  tho))ipso)u  do  not  have 
elongated  pectoral  rays  (ocular  side),  whereas 
male  B.  bleekeri  have  elongated  pectoral  rays. 

Two  other  species  of  Bothus,  B.  panthennus 
and  B.  mcnicKs  (Broussonet),  occur  in  the 
Hawaiian  Islands.  Adult  specimens  of  B.  thomp- 
suiii  may  be  separated  from  similar  life  history 
stages  of  the  former  two  species  on  the  basis  of 
body  profile  alone.  Other  useful  characters  for 


243 


FISHERY  BULLETIN:  VOL.  12.  NO.  I 


distinguishing  B.  thompsoiu  from  B.  ptDitheri- 
nus  and  B.  maiicua  (in  addition  to  counts  of  the 
lateral  line  scale  rows,  lower  gill  rakers,  and 
caudal  rays)  are  as  follows.  Cycloid  scales  are 
present  on  the  ocular  side  of  B.  thonipsoiii 
(except  at  the  bases  of  the  dorsal  and  anal  fin, 
and  occasionally  on  the  cheeks  and  in  the 
vicinity    of   the    lateral    line)    as    opposed    to 


ctenoid  scales  on  the  ocular  side  for  B.  paiither- 
imis  and  B.  ihuiicks.  Adult  males  of  the  latter 
two  species  have  elongated  pectoral  fin  rays  on 
the  ocular  side,  while  male  specimens  of  B. 
thonipsoni  do  not.  Bothus  niaiicHs  possess 
more  dorsal  and  anal  fin  rays  than  do  B.  thomp- 
sdiii  and  B.  paiitJwriinis  (97-102  vs.  84-96  and 
77-82  vs.  64-74,  respectively;  Hawaiian  Island 


UJ 
UJ 


o 


ffi 

Z 


60 

50 

40 

30 

20 

10 

0 
60 

50 

40 

30 

20 

10 

0 
40 

30 

20 

10 

0 
40 

30 

20 
10 


FEMALES 

k  MIDDLE  TEETH 
•  OUTER  TEETH 

MALES 

1 1 1        I        1 

T               1 
k 

A 

1        1        1        1        i 

A 

PREMAXILLARY-  BLIND  SIDE 

• 

• 

• 
•    • 

• 

•        i     .  1        1     .   J 

• 
• 

• 

1           1 

1 •—L 

• 

• 

•                            • 
• 

1               111^. 

■■     ■  T 

I 

1 

1              I              1 

\ 1 -I 

■  I 

1 

1 

1 
A 

A 

i 

A 

A 

k 

A 

A 

A 

*     A 

A 

*       A 

A 

A 

A 
• 

• 

A 
•   • 

• 

PRE^flAXILLARY- OCULAR  SIDE 

• 

• 

1 

• 

• 

fl 

• 

m^^- 

•    • 

• 

1              1              1 

1 •_! L- 

1 

1 

1 

1 

1 
A 

'        A    ' 

A 
A       . 

1— 

■  ■■      1 
A 

1 
A 

I 
A 

1 
A 

A 

A       * 

A 

A 

A 
A 

A 

A 

A 

- 

DENTARY  -  BLIND  SIDE 

• 

• 

•b 

• 

• 

• 

• 

•  • 

1 •"— 

, 

— •-I-.- 

•i 

1               1 

•  ^*- 

-•^ 

1 

1 

1 

1 

1 

! 

I 

1               1               1 
A 

'            '           I 

1 

1 

A 
•' — 

A 
• 

A       A 

*  A 

•  '    » 

A 
A 

A 

A 

A 

A 

A 

— •-^- 

A 
*- 

*A 

-•-* 

A 
• 

DENTARY -OCULAR  SIDE 

-J — • — •L 

§• 

-L» •!- 

40        50        60        70        80        90        100        110        120  40        50        60        70        80        90        100        110        120 

STANDARD  LENGTH   (mm) 


Figure    7. — Numbers    of   teeth    in    the    outer    and    middle    tooth    rt)ws    in    Butinis    ilioinp.soni 


244 


STRUHSAKER  and  MONCRIEF:  BOTHUS  THOMPSONI 


specimens).  Bothus  thonipsoi/i  has  10-14 
pectoral  rays,  whereas  this  count  is  9-11  for 
both  B.  paiitlieri)tns  and  B.  niaiictts. 

With  regard  to  other  Indo-Pacific  species 
recognized  by  Norman  (1934),  B.  thompsoni 
differs  from  B.  nnjriaster  in  that  the  pectoral 
fins  of  males  are  not  elongated  in  the  former 
species.  The  combination  of  cycloid  and  ctenoid 
scales  on  the  ocular  side  of  B.  thonipsoni  dif- 
ferentiates it  from  B.  assimilis  (Giinther)  which 
has  onl}^  cycloid  scales  and  from  B.  leopardinus 
(Giinther)  which  has  only  ctenoid  scales  on  the 
ocular  side  (Norman.  1934).  Norman  (1934) 
considers  also  that  B.  coiisteUatns  (Jordan, 
ill  Jordan  and  Goss)  is  very  doubtfully  distinct 
from  B.  leoparduius. 

Although  no  illustration  was  given  of  B. 
budkeri  (Chabanaud.  1942)  from  the  Red  Sea, 
it  differs  from  B.  fhotiipi<(>)ii  in  having  a  lesser 
body  depth,  fewer  dorsal  and  anal  rays,  fewer 
gill  rakers  on  the  lower  limb  of  the  first  arch,  and 
only  ctenoid  scales  on  the  ocular  side. 

Fowler  (1933)  described  five  species  of  Bothus 
from  the  Phili])pines  and  China  Sea.  The 
generic  placement  of  several  of  these  species  is 
questionable.  At  any  rate,  none  of  them  could 
be  confused  with  B.  thoinp.^oiii. 


Ecology 

With  the  exception  of  one  specimen  caught  at 
a  depth  of  72  m  off  Maui,  all  specimens  of 
B.  thompsoiii  taken  to  date  have  come  from 
depths  of  90-113  m  off  the  north  coast  of  Oahu 
where  bottom  temperatures  ranged  from  24.5° 
to  26.0°C.  About  580  specimens  (32-107  mm 
SL)  have  been  obtained  at  13  stations  where 
catches  ranged  up  to  275  individuals  per  haul. 
An  analysis  of  dispersion  for  this  species 
(Struhsaker.  1973)  shows  it  to  have  a  highly 
clumped  distribution.  The  type  of  bottom  in  the 
area  of  capture  is  primarily  muddy  sand 
interspersed  with  patches  of  sponge,  broken 
shell,  and  rubble.  Bothus  thompsoni  was  often 
taken  with  20-30  other  species  of  fishes;  it 
usually  comprised  less  than  8%  of  the  total 
catch,  but  occasionally  ranged  up  to  30%.  Nu- 
merically dominant  species  taken  with  B.  thomp- 
soni include  Tmchiiiocephaliis  niyops,  Priacaii- 
thus  spp.,  Aiitigoiiia  cos.  Parupeneus  chyysoiie- 
mus,  and  Lagocephalus  hypselogeueioii.  Struh- 


saker and  Higgins  (rnanuscr.-)  have  shown 
that  B.  thompsoni  is  the  third  most  abundant 
larval  flatfish  (after  Engyprosopo)i  .ve)icuidrus 
Gilbert  and  B.  paiitlierinus)  taken  in  offshore 
mid  water  hauls  near  Oahu.  They  also  presented 
evidence  that  B.  thompsoni  may  spawn  through- 
out the  vear. 


ACKNOWLEDGMENTS 


We  thank  John  E.  Randall  for  the  photo- 
graphs used  in  Figures  1  and  2  and  for  review- 
ing the  manuscript.  We  are  also  indebted  to 
Elbert  H.  Ahlstrom  and  C.  Richard  Robins 
for  comments  on  the  manuscript.  The  NMFS 
Systematics  Laboratory  provided  the  radio- 
graphs. The  illustrations  are  by  Tamotsu 
Nakata  and  Robert  Bonifacio. 


MATERIAL  EXAMINED 


USNM  208494:  TC-33-52  (R/V  Towusend 
Ci'omwell,  cruise  33,  station  52);  1  male  (109.2 
mm  SL);  lat.  19°58.3'  N,  long.  156°28.5'  W; 
depth  72  m,  13  Nov.  1967.  USNM  208495: 
TC-36-15;  4  females  (93.7-99.1  mm  SL);  lat. 
21°37.7'  N,  long.  158°08.8'  W;  depth  113  m. 
2  May  1968.  USNM  208496:  TC-36-20;  7 
females  (39.5-72.8  mm  SL),  12  males  (55.8- 
81.2  mm  SL);  lat.  21°36.8'  N,  long.  158°  12.5' 
W;  depth  110  m,  3  May  1968.  USNM  208497: 
TC-40-115;  10  females  (56.9-87.3  mm  SL), 
5  males  (70.0-84.5  mm  SL);  lat.  21°36.8'  N, 
long.  158° 08.2'  W;  depth  102  m,  8  Nov.  1968. 
USNM  208498:  TC-40-116;  4  females  (56.0- 
105.4  mm  SL),  3  males  (58.6-104.5  mm  SL); 
lat.  21°36.8'  N,  long.  158°  11.6'  W;  depth  112 
m.  1  Dec.  1968.  USNM  208499:  TC-40-119; 
5  females  (78.6-91.2  mm  SL),  7  males  (86.2- 
99.2  mm  SL);  lat.  2r36.8'  N,  long.  158°  11.2' 
W;  depth  96  m,  1  Dec.  1968.  BPBM  14102; 
TC-40-125;  1  female  (106.4  mm  SL),  1  male 
(114.4  mm  SL);  lat.  21°36.8'  N,  long.  158°11.6' 
W;  depth  102  m,  10  Nov.  1968. 


-  Struhsaker.  P.,  and  B.  E.  Higgins.  Unpubl.  manuscr. 
Post-larval  flatfishes  (Pisces:Pleuronectiformes):  Observa- 
tions on  the  identity  and  ecology  of  11  Hawaiian  species. 
Southwest  Fisheries  Center.  National  Marine  Fisheries 
Service.  NOAA,  Honolulu.  Hawaii  968  12. 


245 


FISHERY  BULLETIN:  VOL.  12.  NO.  1 


LITERATURE  CITED 


Amaoka,  K. 

1964.  Development  and  growth  of  the  sinistral 
flounder,  Bothus  inyriaster  (Temminck  and 
Schlegel)  found  in  the  Indian  and  Pacific  Oceans. 
Bull.  Misaki  Mar.  Biol.  Inst..  Kyoto  Univ.  ^.W- 
29. 
1969.  Studies  on  the  sinistral  flounders  found  in  the 
waters  around  Japan — taxonomy,  anatomy  and 
phylogeny.  J.  Shimonoseki  Univ.  Fish.  18:65-340. 
Chabanaud,  p. 

1942.    Notules  ichthyologiques.  Bull.  Mus.  Natl.  Hist. 
Nat.  Paris  14:395-402. 
Fowler,  H.  W. 

1923.     New  or  little   known  Hawaiian  fishes.  Occas. 

Pap.  Bernice  Pauahi  Bishop  Mus.  8(7),  20  p. 
1928.   Fishes    of   Oceania.    Mem.    Bernice    P.    Bishop 

Mus.  10,  540  p. 
1933.  Descriptions    of   new    fishes   obtained    1907    to 
1910,     chiefly     in     the     Philippine     Islands     and 
adjacent  seas.  Proc.  Acad.  Nat.  Sci.  Phila.  85:233- 
367. 
GOSLINE,   W.   A.,  AND  V.    E.    Brock. 

1960.  Handbook    of    Hawaiian    fishes.  Univ.    Hawaii 
Press,  Honolulu,  372  p. 

GUTHERZ,    E.    J. 

1967.  Field    guide    to    the    flatfishes    of    the    family 


Bothidae  in  the  western  North  Atlantic.  U.S.  Fish 
Wildl.Serv.,  Circ.263,47  p. 
1970.  Characteristics  of  some  larval  bothid  flatfish, 
and  development  and  distribution  of  larval  spot- 
fin  flounder,  Cydopsciia  Jimhriaici  (Bothidae).  U.S. 
Fish  Wildl.  Serv.,  Fish.  Bull.  68:261-283. 
HuBBS,  C.  L.,  AND  K.  F.  Lagler. 

1958.     Fishes  of  the  Great  Lakes  region.  Revised  ed. 
Cranbrook  Inst.  Sci.,  Bull.  26,  213  p. 
Norman,  J.  R. 

1934.      A    systematic    monograph    of    the    flatfishes 
(Heterosomata).  Vol.  I.  Psettodidae,  Bothidae,  Pleuro- 
nectidae.  Br.  Mus.  (Nat.  Hist.),  Lond.,  459  p. 
Stauch,  a. 

1966.  Quelques  donnees  sur  les  Bothus  de  TAtlan- 
tique  et  description  d'une  espece  nouvelle  Bothus 
guibei:  n.  sp.  (Pisces  Teleostei,  Heterosomata).  Bull. 
Mus.  Natl.  Hist.  Nat.  Paris  38:118-125. 

Struhsaker,  p. 

1973.   A  contribution  to  the  systematics  and  ecology 

of    Hawaiian    bathyal    fishes.    Ph.D.    Diss.,    Univ. 

Hawaii,  Honolulu,  482  p. 
Taylor,  W.  R. 

1967.  An  enzyme  method  of  clearing  and  staining 
small  vertebrates.  Proc.  U.S.  Natl.  Mus.  122(3596), 
17  p. 

Topp,  R.  W.,  and   F.  H.  Hoff,  Jr. 

1972.  Flatfishes  (Pleuronectiformes).  Mem.  Hour- 
glass Cruises,  Fla.  Dep.  Nat.  Resour.,  Mar.  Res. 
Lab.4(2):l-135. 


246 


NOTE 


DEVELOPMENT  OF  EGGS  AND  EMBRYOS 

OF  THE  SURF  CLAM,  SPISULA  SOLIDISSIMA, 

IN  SYNTHETIC  SEAWATER 

The  eggs  of  the  surf  clam,  Spisula  solidissima, 
have  been  used  extensively  for  investigations  of 
egg  structure  and  embryonic  development  of 
bivalves.  Allen  (1951)  has  pointed  out  the  ad- 
vantages of  the  use  of  surf  clam  eggs  for 
research  of  this  nature.  These  studies  have  been 
limited,  however,  to  areas  where  natural  sea- 
water  was  readily  available,  due  to  the  unsuit- 
ability  of  most  synthetic  seawaters  for  support- 
ing the  embryonic  development  of  bivalves 
(David  A.  Nelson,  NMFS,  Milford,  Connecticut 
and  Gerald  Zaroogian,  Environmental  Protec- 
tion Agency  Laboratory,  West  Kingston,  Rhode 
Island,  pers.  comm.). 

Experimental  Observations 

We  recently  reared  Spisi'.lo  solidissima  em- 
bryos in  a  synthetic  seawater  formulation  de- 
veloped by  Zaroogian,  Pesch,  and  Morrison 
(1969)  as  a  culture  medium  in  which  to  rear 
oyster  embryos.  Our  observations  were  made  in 
salinities  of  25  and  30  'Voo  at  10°,  15°,  and  20°C 
water  temperatures.  Within  these  ranges  we 
found  20°C  to  be  the  optimum  temperature  for 
development,  allowing  us  to  rear  eggs  to  the 
5-day-old  stage  (early  veliger)  with  almost 
100%  survival  and  no  signs  of  larval  abnormali- 
ties. At  20°C  polar  body  formation  occurs  in 
about  45  min  and  the  two-cell  stage  in  about 
90  min.  The  early  veliger,  or  straight-hinge 
stage,  is  reached  in  less  than  24  h.  At  15 °C  all 
stages  of  development  are  normal  but  somewhat 
delayed,  with  development  to  the  straight- 
hinge  stage  requiring  more  than  24  h.  At  10°C 
the  rate  of  development  of  all  stages  is  greatly 
retarded  and  many  abnormal  embryos  are 
present.  The  majority  of  fertilized  eggs  held  at 
10  °C  requires  more  than  96  h  to  develop  to  the 
straight-hinge  stage. 

At  20° C  we  found  that  development  of  fer- 
tilized  eggs   in    synthetic    seawater   was   com- 


parable  to   the  best   development   observed   in 
natural  seawater. 

This  study  did  not  involve  testing  embry- 
onic development  of  S.  fiolidissima  in  synthetic 
seawater  over  a  wide  range  of  salinities,  but 
was  limited  to  those  salinities  currently  in  use 
in  other  research  programs  within  this  labora- 
tory. It  appeared  that  there  was  no  difference  in 
survival  and  development  of  eggs  to  the  5-day- 
old  stage  at  salinities  of  25  and  30  "/oo.  the  only 
salinities  tested.  In  earlier  work,  however, 
Stickney  (in  Yancey  and  Welch,  1968)  reported 
that  S.  solidissima  eggs  failed  to  develop  under 
experimental  conditions  in  salinities  of  less  than 
23  'Voo  in  natural  seawater. 

Since  the  synthetic  seawater  formulation 
developed  by  Zaroogian,  Pesch,  and  Morrison 
(1969)  can  be  readily  prepared,  its  general 
acceptance  could  lead  to  a  wider  utilization  of 
surf  clam  eggs  by  embryologists  and  cytologists 
with  standardization  of  techniques  and  compar- 
ability of  results  not  always  possible  when 
natural  seawaters  from  different  locations  are 
used. 

LaRoche,  Eisler,  and  Tarzwell  (1970),  in 
studies  of  bioassay  procedures  for  oil  and  oil 
dispersant  toxicity  evaluation,  suggested  the  use 
of  Zaroogian 's  seawater  as  a  standard  testing 
medium  in  place  of  natural  seawater,  the  com- 
position of  which  varies,  especially  in  regard  to 
the  presence  of  trace  metals,  dissolved  organics, 
and  particulate  matter.  They  recommended  the 
use  of  Zaroogian 's  seawater  because  of  its 
ability  to  support  spawning  adults  and  larvae 
of  the  American  oyster,  Crassostrea  virginica, 
for  at  least  48  h  without  visible  adverse  effects, 
and  adult  mummichog,  Fundulus  heteroclitus, 
grass  shrimp,  Palaemonetes  vulgaris,  and  sand- 
worm,  Nereis  virens,  for  extended  periods. 
Thus,  when  sufficient  research  has  been  per- 
formed in  this  area,  it  may  be  possible  not  only 
to  hold  adult  animals  but  also  to  rear  the  eggs 
and  larvae  of  these  animals  in  the  same  syn- 
thetic seawater.  This  would  be  an  obvious  ad- 
vantage in  assessing  comparative  tolerances  to 
pollutants  of  different  life  stages. 


247 


Collection  and  Maintenance  of 
Surf  Clams  in  the  Laboratory 

Although  some  information  on  the  collection 
and  maintenance  of  surf  clams  in  the  labora- 
tory and  their  reproductive  cycle  has  been  pub- 
lished (Loosanoff  antl  Davis,  1963;  Ropes,  1968; 
Yancey  and  Welch.  1968),  we  feel  it  pertinent 
to  this  pai)er  that  it  be  reviewed  and  our  own 
observations  added. 

Adult  surf  clams  can  be  purchased  from  bio- 
logical supi)ly  houses  or  collected  in  their  nat- 
ural habitat.  The  range  of  S.  soUdissuiia  is 
along  the  Atlantic  Coast  of  North  America,  from 
the  Gulf  of  St.  Lawrence  to  Cape  Hatteras 
(Yancey  and  Welch,  1968).  South  of  Cape  Hat- 
teras the  surf  clam  is  represented  by  Spi>inla 
solidissinta  raveiieli.  similar  to  S.  soUdissima 
but  a  smaller  species.  S.  soUdissiiua  is  found  in 
sandy  bottoms  from  the  low-tide  line  to  depths 
of  500  ft  in  waters  of  oceanic  salinity.  They  are 
present  in  shallow  water  beds,  at  various  points 
along  their  range,  and  are  easily  hand-gathered 
along  the  coasts  of  Delaware,  New  Jersey,  Long 
Island  (New  York),  Rhode  Island,  and  Massa- 
chusetts. Our  collections  have  come  mainly  from 
Little  Narragansett  Bay  and  the  area  of  Point 
Judith,  in  Rhode  Island. 

Surf  clams  can  also  be  obtained  from  com- 
mercial clam  boats  working  the  beds,  but  our 
observations  have  shown  that  hand-gathered 
clams  are  more  suitable  for  laboratory  purposes; 
those  obtained  from  commercial  sources  are 
often  damaged  by  the  action  of  the  hydraulic 
dredge  used  in  harvesting.  They  suffer  high 
mortalities  soon  after  introduction  into  the 
laboratory  and  long-term  survival  of  those  re- 
maining also  seems  inferior  to  that  of  hand- 
gathered  stocks. 

We  feel  that  the  best  working  size  for  labora- 
tory animals  to  be  used  as  a  source  of  gametes 
is  4  to  5  inches.  Larger  ones  require  more  space 
and  do  not  survive  as  well  in  crowded  tanks. 
Smaller  animals  are  more  difficult  to  spawn, 
even  though  we  have  found  some  specimens  as 
small  as  5  cm  to  have  viable  sex  products. 

Ropes  (1968),  in  a  study  of  the  rej^roductive 
cycle  of  offshore  surf  clam  populations,  found  a 
biannual  cycle  during  3  years  of  the  4-year 
period  covered  by  his  study.  This  biannual  cycle 
was  characterized  by  a  major  mid-year  spawn- 
ing and  a  minor  late-year  spawning.  He  found 
ripe  clams  as  early  as  May  and  as  late  as  Octo- 


ber during  3  years  of  the  study.  This  pattern  of 
ripeness  may  vary  between  inshore  and  off- 
shore populations,  depending  on  local  tempera- 
ture conditions.  We  found  ripe  clams  only  from 
June  to  August  in  inshore  Rhode  Island  waters. 

Surf  clams  can  be  collected  prior  to  their 
natural  spawning  period  and  conditioned  to 
ripeness  in  the  laboratory.  Conditioning  refers 
to  a  procedure  of  gradually  raising  the  water 
temperatures  at  which  bivalves  are  maintained 
as  a  means  of  achieving  gonad  ripeness  prior 
to  the  time  one  would  expect  to  find  ripe  ani- 
mals in  the  field  (Loosanoff,  1954). 

We  have  collected  animals  with  unripe 
gametes  from  early  winter  through  late  spring 
(December  to  May)  and  conditioned  them  at 
15 °C.  This  temperature  equals  or  exceeds  that 
at  which  gametogenesis  takes  place  in  natural 
populations  (Ropes,  1968).  Such  animals  col- 
lected in  early  winter  and  conditioned  in  the 
laboratory  have  been  spawned  as  early  as 
March. 

Ripe  surf  clams  held  in  the  laboratory  at  15  °C 
have  never  spawned  spontaneously;  thus,  the 
spawning  threshold  of  this  animal  in  the  labo- 
ratory would  appear  to  be  higher  than  15 °C.  We 
do  feel,  however,  even  though  we,  as  yet,  lack 
quantitative  data  to  substantiate  it,  that  ripe 
animals  held  at  15 °C  tend  to  resorb  their 
gametes  more  quickly  than  those  held  at  a 
lower  temperature  following  conditioning.  Ripe 
animals  collected  in  June  and  held  at  10°C  con- 
tained viable  sex  products  in  December. 

Ropes  (1968)  reported  that  offshore  popula- 
tions spawn  at  lower  temperatures  than  we 
found  in  our  laboratory  populations.  He  also 
noted  that  abrupt  rises  in  water  temperature 
were  not  clearly  a  cause  of  spawning  in  natural 
populations.  A  rapid  increase  in  temperature  is 
certainly  an  important  factor  in  stimulating 
spawning  in  the  laboratory.  Clams  conditioned 
at  15 °C  spawned  when  the  temperature  was 
raised  quickly  to  18-20 °C.  However,  these  clams 
were  less  responsive  than  those  held  in  damp 
refrigeration  (approximately  2°C,  covered  with 
a  wet  towel  to  prevent  drying)  overnight  prior 
to  exposure  to  18-20 °C.  Refrigerated  clams  nor- 
mally spawned  within  an  hour  after  exposure 
to  1*8-20°C,  while  those  conditioned  at  15°C 
and  exposed  to  water  at  18-20°C  did  not. 

Eggs  and  sperm  can  also  be  obtained  by  strip- 
ping the  sex  products  from  the  gonads  using  a 


248 


method  described  by  Costello  et  al.  (1957).  This 
invalves  removing  one  shell  and  gill,  exposing 
the  visceral  mass,  and  slicing  into  the  gonad 
which  overlays  the  digestive  glands  and  viscera. 
Care  should  be  taken  to  avoid  cutting  into  the 
underlying  intestines  and  digestive  glands,  as 
the  presence  of  body  fluids  in  the  cultures  of 
eggs  appears  to  be  detrimental  to  embryonic 
development.  The  eggs  and  sperm  are  washed 
into  separate  collecting  containers.  Most  of  the 
tissue  and  debris  collected  along  with  the 
gametes  can  be  removed  by  selective  screening. 

Stripped  eggs  tend  to  be  more  irregular  in 
shape  than  naturally  spawned  eggs  but  soon 
become  spherical.  Previous  investigators 
(Loosanoff  and  Davis,  1963)  have  reported  the 
diameter  of  spawned  mature  eggs  to  average 
56.5  jj.  Our  measurements  of  rounded  stripped 
eggs  from  ripe  clams  have  agreed  with  this. 

To  fertilize  the  eggs  a  small  quantity  of 
sperm  suspension  is  added  to  the  egg  suspension 
and  mixed  by  rapid  stirring;  care  must  be  taken 
to  add  only  a  small  quantity  of  sperm  as  Spi- 
siila  eggs  are  quite  susceptible  to  polyspermy  at 
high  sperm  concentrations  (Allen,  1951).  Fol- 
lowing fertilization  the  germinal  vesicle  breaks 
down  and  a  thin  membrane  forms  a  short  dis- 
tance above  the  surface  of  the  egg. 

In  conclusion  we  would  like  to  point  out  that 
this  is  the  first  time  to  our  knowledge  that 
Spisiila  soUdissinia  embryos  have  been  reared  in 
synthetic  seawater,  although  they  have  been 
previously  reared  in  the  laboratory  in  natural 
seawater.  Not  all  synthetic  seawaters  currently 
available  are  suitable  for  this  purpose  but  that 
developed  by  Zaroogian,  Pesch,  and  Morrison 
has  consistently  given  us  good  results.  We  feel 
that  the  ability  to  rear  these  embryos  in  syn- 
thetic seawater  will  enhance  the  value  of  surf 
clam  eggs  and  embryos  in  embryological  and 
cytological  research  by  offering  a  standardized 


rearing  medium  and  a  comparability  of  results 
not  always  possible  when  natural  seawaters 
from  different  locations  are  used,  as  well  as 
making  possible  the  use  of  these  organisms  in 
bioassay  procedures  where  the  composition  of 
the  seawater  must  be  known. 

Literature  Cited 

Allen.  R.  D. 

1951.  The  use  of  Spisiila  solidissimci  eggs  in  cell  re- 
search.   J.  Cell.  Comp.  Physiol.   37:504-505. 
Costello,    D.    P.,    M.    E.    Davidson,   A.   Eggers,   M.   H. 
Fox,  AND  C.  Henley. 

1957.  Mollusca  (Pelecypoda)  Maciru  (now  Spisula) 
solidi.ssinui.  In  D.  P.  Costello,  M.  E.  Davidson,  A. 
Eggers,  M.  H.  Fox,  and  C.  Henley,  Methods  for 
obtaining  and  handling  marine  eggs  and  embryos, 
p.  113-116.  Mar.  Biol.  Lab.,  Woods  Hole,  Mass. 
LaRoche,  C,  R.  Eisler,  and  C.  M.  Tarzwell. 

1970.     Bioassay  procedures  for  oil  and  oil  dispersant 
toxicity  evaluation.     J.  Water  Pollut.  Control  Fed. 
42:1982-1989. 
Loosanoff,  V.  L. 

1954.     New  advances  in  the  study  of  bivalve  larvae. 
Am.  Sci.  42:607-624. 
Loosanoff,  V.  L.,  and  H.  C.  Davis. 

1963.   Rearing    of    bivalve    mollusks.    In    .Adv.    Mar. 
Biol.  1:1-136. 
Ropes,  J.  W. 

1968.     Reproductive  cycle  of  the   surf  clam,    Spisula 
solicli.ssinia,    in    offshore    New    Jersey.       Biol.    Bull. 
(Woods  Hole)  135:349-365. 
Yancey,  R.  M.,  and  W.  R.  Welch. 

1968.  The  Atlantic  Coast  surf  clam — with  a  partial 
bibliography.  U.S.  Fish  Wildl.  Serv.,  Circ.  288,  14  p. 

Zaroogian,  G.  E.,  G.  Pesch,  and  G.  Morrison. 

1969.  Formulation  of  an  artificial  seawater  media 
suitable  for  oyster  larvae  development.  Am.  Zool. 
9:549. 

Wayne  D.  Cable 
Warren  S.  Landers 

Middle  Ailaiuic  Cousud  Fisheries  Center 
Milford  Laboratory 

National  Marine  Fisheries  Service,  NOAA 
Milford.  CT  06460 


249 


ERRATUM 

Fishery  Bullethi.  Vol.  71,  No.  3 

Paul,  A.  J.,  and  Howard  M.  Feder,  "Growth,  recruitment,  and  distribution  of  the  littleneck  clam, 
Protothaca  staminea,  in  Galena  Bay,  Prince  William  Sound,  Alaska,"  p.  665-677. 
1)  Page  665,  left  column,  first  paragraph.  The  last  sentence  should  read: 

"Feder  and  Paul  (1973)  and  R.  Nickeron  (Alaska  Department  of  Fish  and  Game,  pers.  comm.) 
suggested  that  a  small  clam  fishery  is  feasible  in  Prince  William  Sound  since  paralytic  shellfish 
poison  (P.S.P.)  does  not  seem  to  be  a  problem  there,  and  many  beaches  with  sizable  populations 
of  P.  staminea  and  the  butter  clam,  Saxidomus  giganteus,  occur  in  the  area." 


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Fishery  Bulletin 

National  Oceanic  and  Atmospheric  Administration  •  National  Marine  Fisheries  Service 


Vol.  72,  No.  2 


April  1974 


KANWISHER,  JOHN,  KENNETH  LAWSON,  and  GUNNAR  SUNDNES.  Acous- 
tic telemetry  from  fish  251 

SOUTAR,  ANDREW,  and  JOHN  D.  ISAACS.  Abundance  of  pelagic  fish  during 
the  19th  and  20th  centuries  as  recorded  in  anaerobic  sediment  off  the  Cali- 
fornias  . '. 257 

MacGREGOR,  JOHN  S.  Changes  in  the  amount  and  proportions  of  DDT  and  its 
metabolites,  DDE  and  DDD,  in  the  marine  environment  off  southern  Califor- 
nia, 1949-72  275 

HIROTA,  JED.  Quantitative  natural  history  of  Pleurobrachia  bachei  in  La 
Jolla  Bight 295 

CLARKE,  THOMAS  A.  Some  aspects  of  the  ecology  of  stomiatoid  fishes  in  the 
Pacific  Ocean  near  Hawaii   

ADRON,  J.  W.,  A.  BLAIR,  and  C.  B.  COWEY.  Rearing  of  plaice  (Pleuronectes 
platessa)  larvae  to  metamorphosis  using  an  artificial  diet 353 

BEN-YAMI,  M.,  and  T.  GLASER.  The  invasion  of Saurida  undosquamis  (Richard- 
son) into  the  Levant  Basin  —  An  example  of  biological  effect  of  interoceanic 
canals   .  .     359 

KEMMERER,  ANDREW  J.,  JOSEPH  A.  BENIGNO,  GLADYS  B.  REESE,  and 
FREDERICK  C.  MINKLER.  A  summary  of  selected  early  results  from  the 
ERTS-1  menhaden  experiment   375 

MOSER,  H.  GEOFFREY,  and  ELBERT  H.  AHLSTROM.  Role  of  larval  stages  in 
systematic  investigations  of  marine  teleosts:  The  Myctophidae,  a  case  study  .     391 

APRIETO,  VIRGINIA  L.  Early  development  of  five  carangid  fishes  of  the  Gulf  of 
Mexico  and  the  south  Atlantic  Coast  of  the  United  States  415 

KAPLAN,  EUGENE  H.,  J.  R.  WELKER,  and  M.  GAYLE  KRAUS.  Some  effects 
of  dredging  on  populations  of  macrobenthic  organisms 445 

MUSICK,  JOHN  A.  Seasonal  distribution  of  sibling  hakes,  Urophycis  chuss  and 
U.  tenuis  (Pisces,  Gadidae)  in  Nev^'  England 481 

MILLER,  JOHN  M.,  and  BARBARA  Y.  SUMIDA.  Development  of  eggs  and  larvae 
of  Caranx  mate  (Carangidae)  497 

STICKNEY,  ROBERT  R.,  GARY  L.  TAYLOR,  and  RICHARD  W.  HEARD,  III. 
Food  habits  of  Georgia  estuarine  fishes.  I.  Four  species  of  flounders  (Pleuro- 
nectiformes:  Bothidae)   515 


(Continued  on  hack  cover) 


Seattle,  WA 


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NATIONAL  OCEANIC  AND  ATMOSPHERIC  ADMINISTRATION 

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NATIONAL  MARINE  FISH ER I ES  SERVICE 
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i 


Fishery  Bulletin 

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and  in  exchange  for  other  scientific  publications. 


EDITOR 

Dr.  Reuben  Lasker 

Scientific  Editor,  Fishery  Bulletin 

National  Marine  Fisheries  Service 

Southwest  Fisheries  Center 
La  Jolla,  California  92037 


Editorial  Committee 

Dr.  Elbert  H.  Ahlstrom 

National  Marine  Fisheries  Service 

Dr.  William  H.  Bayliff 

Inter-American  Tropical  Tuna  Commission 

Dr.  Daniel  M.  Cohen 

National  Marine  Fisheries  Service 

Dr.  Howard  M.  Fcder 
University  of  Alaska 

Mr.  John  E.  Fitch 

California  Department  of  Fish  and  Game 

Dr.  Marvin  D.  Grosslein 
National  Marine  Fisheries  Service 


Dr.  J.  Frank  Hebard 

National  Marine  Fisheries  Service 

Dr.  John  R.  Hunter 

National  Marine  Fisheries  Service 

Dr.  Arthur  S.  Merrill 

National  Marine  Fisheries  Service 

Dr.  Virgil  J.  Norton 
University  of  Rhode  Island 

Mr.  Alonzo  T.  Pruter 

National  Marine  Fisheries  Service 

Dr.  Theodore  R.  Rice 

National  Marine  Fisheries  Service 

Dr.  Brian  J.  Rothschild 

National  Marine  Fisheries  Service 

Mr.  Maurice  E.  Stansby 
National  Marine  Fisheries  Service 

Dr.  Maynard  A.  Steinberg 
National  Marine  Fisheries  Service 

Dr.  Roland  L.  Wigley 

National  Marine  Fisheries  Service 


Kiyoshi  G.  Fukano,  Managing  Editor 


The  Secretary  of  Commerce  has  determined  thot  the  publication  of  this  periodical  is  necessary  in  the 
transaction  of  the  public  business  required  by  low  of  this  Department.  Use  of  funds  for  printing  of 
this  periodical  has  been  approved  by  the  Director  of  the  Office  of  Management  and  Budget  through 
May  31,  1974. 


Fishery  Bulletin 


CONTENTS 

Vol.  72,  No.  2  April  1974 

KANWISHER,  JOHN,  KENNETH  LAWSON,  and  GUNNAR  SUNDNES.  Acous- 
tic telemetry  from  fish  251 

SOUTAR,  ANDREW,  and  JOHN  D.  ISAACS.  Abundance  of  pelagic  fish  during 
the  19th  and  20th  centuries  as  recorded  in  anaerobic  sediment  off  the  Cali- 
fornias 257 

MacGREGOR,  JOHN  S.  Changes  in  the  amount  and  proportions  of  DDT  and  its 
metabolites,  DDE  and  DDD,  in  the  marine  environment  off  southern  Califor- 
nia, 1949-72 275 

HIROTA,  JED.  Quantitative  natural  history  of  Pleurobrachia  bachei  in  La 
Jolla  Bight 295 

CLARKE,  THOMAS  A.  Some  aspects  of  the  ecology  of  stomiatoid  fishes  in  the 
Pacific  Ocean  near  Hawaii   337 

ADRON,  J.  W.,  A.  BLAIR,  and  C.  B.  COWEY.  Rearing  of  plaice  (Pleuronectes 
platessa)  larvae  to  metamorphosis  using  an  artificial  diet 353 

BEN-YAMI,  M.,  and  T.  GLASER.  The  invasion  ofSaurida  undosquamis  (Richard- 
son) into  the  Levant  Basin  —  An  example  of  biological  effect  of  interoceanic 
canals   359 

KEMMERER,  ANDREW  J.,  JOSEPH  A.  BENIGNO,  GLADYS  B.  REESE,  and 
FREDERICK  C.  MINKLER.  A  summary  of  selected  early  results  from  the 
ERTS-1  menhaden  experiment   375 

MOSER,  H.  GEOFFREY,  and  ELBERT  H.  AHLSTROM.  Role  of  larval  stages  in 
systematic  investigations  of  marine  teleosts:  The  Myctophidae,  a  case  study  .     391 

APRIETO,  VIRGINIA  L.  Early  development  of  five  carangid  fishes  of  the  Gulf  of 
Mexico  and  the  south  Atlantic  Coast  of  the  United  States   415 

KAPLAN,  EUGENE  H.,  J.  R.  WELKER,  and  M.  GAYLE  KRAUS.  Some  effects 
of  dredging  on  populations  of  macrobenthic  organisms 445 

MUSICK,  JOHN  A.  Seasonal  distribution  of  sibling  hakes,  Urophycis  chuss  and 
U.  tenuis  (Pisces,  Gadidae)  in  New  England  481 

MILLER,  JOHN  M.,  and  BARBARA  Y.  SUMIDA.  Development  of  eggs  and  larvae 
of  Caranx  mate  (Carangidae)   497 

STICKNEY,  ROBERT  R.,  GARY  L.  TAYLOR,  and  RICHARD  W.  HEARD,  III. 
Food  habits  of  Georgia  estuarine  fishes.  I.  Four  species  of  flounders  (Pleuro- 
nectiformes:  Bothidae)  515 

(Continued  on  next  page) 
Seattle,  WA 


For  sale  by  the  Superintendent  of  Documents,  U.S.  Government  Printing 
Office,  Washington,  D.C.  20402  —  Subscription  price:  $10.85  peryear  ($2.75 
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(Contents-continued) 


ALVARINO,  ANGELES.  Distribution  of  siphonophores  in  the  regions  adjacent  to 
the  Suez  and  Panama  Canals 527 

RAJU,  SOLOMON  N.  Three  new  species  of  the  genus  Monognathus  and  the  lepto- 
cephali  of  the  order  Saccopharyngiformes 547 

POTTHOFF,  THOMAS.  Osteological  development  and  variation  in  young  tunas, 
genus  Thunnus  (Pisces,  Scombridae),  from  the  Atlantic  Ocean 563 

FRENCH,  ROBERT  R.,  and  RICHARD  G.  BAKKALA.  A  new  model  of  ocean  mi- 
grations of  Bristol  Bay  sockeye  salmon 589 

Notes 

BALDRIDGE,  ALAN.  Migrant  gray  whales  with  calves  and  sexual  behavior  of 
gray  whales  in  the  Monterey  area  of  central  California,  1967-73 615 

BROOKS,  A.  L.,  C.  L.  BROWN,  JR.,  and  P.  H.  SCULLY-POWER.  Net  filter- 
ing efficiency  of  a  3-meter  Isaacs-Kidd  midwater  trawl 618 

DOW,  ROBERT  L.  American  lobsters  tagged  by  Maine  commercial  fishermen, 
1957-59 622 


ACOUSTIC  TELEMETRY  FROM  FISH 

John  Kanwisher,'  Kenneth  Lawson,'  and  Gunnar  Sundnes^ 

ABSTRACT 

Methods  are  described  for  monitoring  physiological  parameters  such  as  temperature  and  electrocardio- 
gram from  free  swimming  fish.  Information  is  telemetered  as  sound  radiating  from  an  acoustic  transmitter 
implanted  on  the  fish.  Limitations  of  the  technique  and  construction  details  of  representative  devices  are 
covered.  Uses  in  both  behavior  and  physiology  are  considered. 


Acoustic  telemetry  allows  an  investigator  to 
study  the  behavior  and  physiology  of  fish  under 
conditions  which  approximate  their  natural 
state.  Improvements  in  electronic  techniques 
permit  construction  of  devices  the  size  of  one's 
little  finger;  these  devices  can  transmit  data  such 
as  heartbeat  and  temperature  over  ranges  of  sev- 
eral hundred  meters  for  as  long  as  a  month.  We 
describe  here  the  use  and  constraints  on  sound  as 
a  means  of  transmitting  these  data.  We  then  dis- 
cuss, in  detail  sufficient  for  duplication,  the  con- 
struction of  sample  devices  for  transmitting,  re- 
ceiving, and  interpreting  the  data.  Finally,  we 
show  how  these  devices  have  been  applied  to 
specific  experimental  problems,  and  discuss  the 
results  we  have  obtained. 

SOUND  AS  A  TELEMETRY  MEDIUM 

For  ranges  beyond  a  few  meters  through  water, 
sound  is  the  only  practical  form  of  energy  for 
telemetry.  It  travels  with  little  loss,  whereas 
radio  waves  and  light  are  rapidly  absorbed.  Sev- 
eral properties  of  sound  in  water  are  important. 
For  example  greater  ranges  are  possible  in  fresh 
water  than  salt  (one  rarely  has  a  choice  in  this). 
Low  frequencies  transmit  further  than  high.  For 
ranges  up  to  several  hundred  meters,  any  fre- 
quency below  100  kHz  is  suitable.  If  a  range  of 
several  kilometers  is  needed,  the  frequency 
should  be  less  than  20  kHz.  Low  frequencies, 
however,  involve  longer  wave  lengths  which  im- 
plies larger  transducers.  In  the  small  devices 


necessary  for  fish  work  these  are  difficult  to  use. 
Thus  we  most  frequently  employ  frequencies  be- 
tween 40  and  80  kHz.  Only  in  large  tuna  could  we 
use  a  transmitter  big  enough  to  work  efficiently 
at  20  kHz.  It  had  an  open  sea  range  of  8  km. 

The  interfering  background  noise,  which 
tends  to  obscure  the  signal,  varies  greatly  at  dif- 
ferent places.  In  general,  the  shallow  water 
tropics  are  noisiest.  At  Coconut  Island  in  Hawaii 
the  natural  acoustic  energy  may  be  100  times 
greater  than  that  at  Friday  Harbor  in  Puget 
Sound.  Most  of  the  noise  appears  to  be  from  bot- 
tom animals  such  as  snapping  shrimp.  Man-made 
noise,  like  that  from  boat  motors,  can  also  be 
troublesome. 

Relative  motion  between  a  sound  source  and 
the  receiver  produces  a  Doppler  shift  in  the  ap- 
parent frequency  such  that 

^/"      relative  velocity 


'Woods  Hole  Oceanographic  Institution,  Woods  Hole,  MA 
02543.  Contribution  No.  3277  from  the  Woods  Hole  Oceanographic 
Institution.  This  work  was  supported  by  National  Science  Founda- 
tion Grant  G  A  31987X. 

^University  of  Trondheim,  Trondheim,  Norway. 


/      velocity  of  sound  in  water 

The  velocity  of  sound  in  water  is  1,500  m/s.  A 
relative  velocity  of  1  knot  shifts  frequency  0.03%. 
This  is  only  significant  when  frequency  is  inter- 
preted critically,  as  in  the  depth  transmitter  to  be 
described. 

Additional  complications  arise  from  the  inter- 
ference effects  due  to  multiple  sound  paths  be- 
tween transmitter  and  receiver.  These  are  fre- 
quently troublesome  in  small  enclosures  where 
sound  reflects  from  the  walls.  Nulls  in  the  sound 
field  are  produced  which  represent  momentary 
loss  of  signal.  The  ear  has  little  trouble  interpret- 
ing periodic  signals  such  as  electrocardiogram 
(EKG),  but  in  a  transcribed  record  these  effects 
can  be  confusing  (see  Figure  2). 

These  remarks  are  meant  to  make  one's  ambi- 
tions more  modest  when  considering  acoustic 


Manuscript  accept  October  1973. 

FISHERY  BULLETIN:  VOL.  72,  NO.  2,  1974. 


251 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


telemetry,  particularly  for  work  in  the  open  sea. 
It  is  not  possible  to  send  across  oceans  with  a 
miniscule  device.  But  almost  any  small  amount 
of  energy  will  work  in  laboratory  tanks.  The  low 
power  transmitters  described  here  are  useful  at 
distances  of  at  least  100  m. 

CONSTRUCTION 

Heartbeat  Transmitters 

The  cylindrical  form  of  our  devices  is  dictated 
by  the  transducers  and  batteries,  both  of  which 
are  round.  A  stainless  steel  tube  is  chosen  into 
which  the  battery  fits.  The  electronics  are  then 
packaged  to  this  inside  diameter.  They  are  cast  in 
epoxy  resin  in  one  end  of  the  tube,  with  the 
heartbeat  lead  or  thermistor  coming  out  of  the 
plastic.  The  tubular  transducer  is  fit  either  inside 
or  outside  the  tube,  and  similarly  embedded  in 
plastic  to  assure  electrical  insulation.  The  bat- 
tery is  held  in  place  with  a  watertight  cap  on  the 
other  end.  The  metal  case  forms  the  indifferent 
reference  electrode  to  the  one  placed  near  the 
heart.  With  the  exception  of  the  transducers 
(Penn  Engineering  &  Manufacturing  Co.  Inc.,  % 
Aquadyne,  Inc.,  Falmouth,  Mass.)  parts  used  in 
these  devices  are  routine.  Parts  for  a  heartbeat 
transmitter  cost  about  $15.00. 

Large  Heartbeat  Transmitter 

A  vertebrate  heart  produces  an  electric  field 
when  it  beats.  A  millivolt  level  signal  from  an 
electrode  near  the  heart  is  amplified  by  Qi  in  the 
schematic  of  Figure  1.  The  larger  voltage  is  used 
to  vary  the  frequency  of  an  oscillator  (Q2  and  Qs). 
Another  amplifier  (Q4  to  Q7)  after  the  oscillator 
drives  a  transducer  at  this  frequency  producing 


i.z.j.i.s.e. 


2N5I38 
2N5133 


T,     —    TRANSDUCER,    PZT-4   CERAMIC   CYLINDER      2.25  cm   0,D. 
FREQUENCY    ^-     50I.HZ  ',;|7cmL0NG 

FREQUENCY    DEVIATION   =   200hz /mv  lSJEK  G     INPUT 


Figure  1. — Large  heartbeat  transmitter. 


sound  in  the  water.  With  a  carrier  frequency  of  50 
kHz  the  typical  excursions  are  a  few  hundred 
hertz.  Thus  the  EKG  voltage  is  transformed  into 
variations  of  the  sound  frequency.  Another  gain 
stage  before  the  heartbeat  amplifier  can  make 
the  transmitter  sufficiently  sensitive  to  send 
signals  of  100  /uv  or  less.  In  this  way  we  have  been 
able  to  follow  the  electromyograms  in  the  red  and 
white  muscles  of  fish.  Figure  2  is  an  example  of 
an  EKG  recorded  from  free  swimming  Atlantic 
cod,  Gadus  morhua,  and  Atlantic  salmon,  Salmo 
salar.  The  various  sequential  details  of  the 
heartbeat  are  clearly  shown.  The  transmitter  is  2 
cm  in  diameter  and  8  cm  long. 

Small  Heartbeat  Transmitter 

Similar  performance  at  the  cost  of  greater  ef- 
fort at  miniaturization  can  be  had  with  the  sim- 
pler and  smaller  transmitter  shown  in  Figure  3, 
which  is  1.5  cm  by  7  cm.  Reduced  power  consump- 
tion allows  the  same  battery  life  (3  wk)  as  the 
larger  transmitter.  Be  replacing  Ra  in  either 
transmitter  with  a  thermistor,  temperature  will 
control  the  carrier  frequency.  The  heartbeat  can 
still  be  transmitted  as  variations  around  this 
changing  frequency. 

Depth  Transmitter 

The  depth  of  a  fish  has  been  a  difficult  variable 
to  transmit  because  of  the  lack  of  practical  pres- 
sure sensors.  Some  information  about  depth  has 
been  discerned  from  water  temperature.  The  re- 
cent appearance  of  small  sensitive  silicon  pres- 
sure sensors  has  made  direct  measurement  of 
depth  feasible.  We  have  built  a  depth  transmitter 
around  such  a  device  (Figure  4). 

The  DC  output  voltage  from  the  pressure  sen- 
sor is  increased  by  an  operational  amplifer,  A. 
These  larger  voltage  excursions  control  the  fre- 
quency of  an  oscillator  in  the  same  way  as  amp- 
lified heartbeat  signals.  The  thermistor  in  Qi 
compensates  the  oscillator  against  frequency  var- 
iations due  to  temperature.  The  resistor  in  paral- 
lel with  this  thermistor  must  be  empirically  cho- 
sen to  optimize  this  compensation.  This  allows 
the  received  frequency  to  be  interpreted  as  pres- 
sure. The  frequency  change  is  1000  Hz/m  of  depth. 
A  20°C  change  in  temperature  causes  an  equiva- 
lent pressure  error  equal  to  5  cm  of  water.  The 
circuit  is  a  voltage  controlled  oscillator,  useful 
with  any  millivolt-level  DC  signals.  This  instru- 


252 


KANWISHER,  LAWSON,  and  SUNDNES:  ACOUSTIC  TELEMETRY  FROM  FISH 


ATLANTIC    COD  -  GADUS  MORHUA 


C        D 


PR  PR  T     P      R 

T 


PR  T  P     R 


1  SEC 


ATLANTIC    "t^hV-UOV^- SALMO  SALAR 

. 1  SEC . 


J,.^ i 


\ 1- 


j^   _Y-|-- — I — t^/^^l +- 


"h^^ 


V^~/-~-  ^-ry-^- ^ |~Atj'^v_-^J^j^.^-^'^-^(sJ^,^^,Y — -'1.\\«vA\|\v^-4-,.\- 


•  •  •  •  •  • 


Figure  2.— Examples  of  electrocardiogram  from  free  swimming  Atlantic  cod  and  Atlantic  salmon.  The  experimenter  approached  the 
aquarium  at  A  and  looked  over  at  B.  slowing  the  heart  rate.  When  he  went  away  the  heart  started  at  the  maximum  rate  at  C,  since  the  T  wave 
is  piled  on  the  next  P  wave  at  D.  The  Atlantic  salmon  also  showed  a  slowing  at  E  from  the  same  source.  It  was  chased  at  F,  resulting  in  a 
quickly  accelerating  heart  rate  from  exercise.  Noise  while  swimming  is  an  acoustic  artifact  from  reflections  in  the  tank. 


ment  has  an  operating  life  of  1  wk.  We  are  using  it 
to  study  gas  pressure  in  swim  bladders.  With  a  less 
sensitive  sensor  we  can  determine  pressures  at 
depths  equal  to  1,000  m. 

Receiver 

Much  of  our  work  has  been  done  with  tunable 
superheterodyne  receivers.  These  employ  a 
mechanical  filter  to  set  bandpass.  Nearly  equiv- 
alent results  can  be  had  from  the  simpler  circuit 
of  Figure  5.  The  hydrophone  contains  a  frequency 
selective  preamplifer  with  a  voltage  gain  of  100. 
Amplification  within  the  hydrophone  is  impor- 
tant to  eliminate  interference  from  motor  igni- 
tion and  radio  stations.  Power  for  this  preamp- 
lifer comes  down  the  same  wire  that  carries  sig- 
nals to  the  receiver. 

The  preamplified  signal  is  amplified  another 
100  times  in  Ai  (}h  of  a  1437  dual  operational 


amplifier).  Its  output  is  mixed  with  a  local  oscil- 
lator in  Q3  to  produce  a  signal  at  the  audio  differ- 
ence frequency.  This  is  amplified  10  times  in  A2 
and  used  to  drive  headphones.  A  l-fiv  signal  at 
the  receiving  hydrophone  is  clearly  audible. 

RESULTS 
General 

We  originally  developed  our  telemetry  so  it 
could  be  used  with  ease  for  human  cardiac 
monitoring.  Work  with  fish  only  required 
miniaturization.  The  usual  method  is  to  have  the 
receiver  output  played  through  a  speaker  in  the 
laboratory.  This  allows  one  to  notice  occasional 
events  of  interest.  Such  more  or  less  casual 
monitoring  has  greatly  reduced  the  need  for  ob- 
servational patience.  In  this  way  we  have  ob- 
tained cues  related  to  feeding  and  behavioral  in- 


253 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


100  p( 


lOOpf 
NPO 


150  fBj 


lOOpf 


2.2  mh      1_ 


1.4  V 

MALLORY 
#RM  450  R 
BATTERY 


T,—  TRANSDUCER,  PZT-4  CERAMIC    CYLINDER     1.27cm  O.D. 

1.02cm    ID. 
FREQUENCY  =  50  kHz  1.41  cm  LONG 

FREQUENCY    DEVIATIONS   200  h; /mv^' EKG  INPUT 


fatigue  can  result  in  an  increased  heart  rate  for 
as  long  as  10  to  20  h  while  this  debt  is  being 
repaid.  Thus  one  gets  a  substantiation  of  the 
already  recognized  biochemical  changes  in  mus- 
cle glycogen  and  lactic  acid.  When  remote 
monitoring  shows  a  rapid  heart  rate  one  cannot 
tell  if  the  fish  is  swimming  at  that  moment  or  is 
reflecting  a  previous  exhaustion. 

Behavior 


Figure  3. — Small  heart  beat  transmitter. 

teraction.  At  such  times  we  could  direct  our  at- 
tention more  intently.  Generally  we  have  found 
that  heart  rate  changes  are  related  to  specific  de- 
tails of  a  fish's  physiology  and  also  its  behavior. 

The  transmitter  can  usually  be  carried  in  the 
stomach  of  the  fish.  It  is  readily  inserted  into  an 
animal  which  has  been  anaesthetized  with 
MS-222.3  The  EKG  lead  is  brought  out  under  the 
last  gill  arch.  It  is  pushed  under  the  skin  im- 
mediately over  the  heart.  The  receiving  hyd- 
rophone is  placed  against  the  fish  so  the  trans- 
mitter can  be  monitored.  There  is  no  difficulty  in 
interpreting  when  the  lead  placement  for  op- 
timum EKG  signal  has  been  reached.  The  lead  is 
then  sutured  in  place. 

The  gills  can  now  be  flushed  with  anaesthetic- 
free  water  and  the  fish  soon  released.  The  entire 
operation  takes  3  or  4  min.  The  fish  will  have 
been  under  anaerobic  stress  because  no  water  has 
been  flowing  over  the  gills.  Most  specimens  ap- 
pear to  fully  recover  in  a  few  hours. 

If  drag  is  not  important  the  transmitter  can  be 
sutured  to  the  outside  of  the  fish.  This  method 
has  allowed  us  to  work  with  plaice,  Pleuronectes 
platessa,  whose  stomachs  were  too  small.  It  was 
also  convenient  for  some  Atlantic  cod  and  Atlan- 
tic salmon  that  repeatedly  threw  up  a  stomach 
tag. 

Physiological  Response 

When  a  fish  is  swimming  we  find  an  expected 
increase  in  heart  rate,  reflecting  the  increased 
oxygen  transport  of  the  cardiovascular  system. 
In  an  Atlantic  cod  this  is  a  measure  of  both  the 
instantaneous  exertion,  and  also  of  any  previ- 
ously incurred  oxygen  debt  (Wardle  and  Kan- 
wisher,  In  press).  Chasing  a  fish  to  maximum 


We  were  not  prepared  for  the  large  component 
of  behavioral  response  observed  in  the  heart  rate 
of  all  fish.  Cardiac  arrest  is  a  well  known  re- 
sponse in  conditioning.  We  found  it  to  occur  with 
the  subtlest  of  cues,  once  the  fish  had  recovered 
from  initial  handling.  This  can  best  be  described 
by  two  anecdotes. 

A  plaice,  which  had  not  eaten  for  many 
months,  had  settled  into  the  sand  on  the  bottom 
of  a  60-ft  circular  laboratory  aquarium.  It  was 
mid-winter  with  low  water  temperatures  and  the 
fish  appeared  to  be  doing  the  equivalent  of  hiber- 
nating. In  spite  of  this  outward  lethargy  it  re- 
sponded to  doors  opening,  relays  clicking,  and  to 
any  other  sort  of  human  activity  in  the  vicinity. 

It  was,  not  unexpectedly,  most  sensitive  to  vis- 
ual cues.  We  gradually  reduced  these  to  smaller 
objects  moved  in  the  visual  field  of  the  fish.  The 
most  sensitive  response  came  early  in  the  morn- 
ing before  local  laboratory  activity  had  started. 
At  this  time  we  could  come  quietly  up  to  the  tank 
and  push  a  pencil  a  few  centimeters  over  the 
edge.  The  plaice,  \V2  m  below  responded  by  stop- 
ping its  heart  for  8  or  9  s. 

Another  incident  concerned  a  venerable  cod  of 
more  than  a  year  in  captivity.  It  had  been  re- 


S  22K  I  22K 


2N5813 
„N  1200i       iZOOie]      n 

Q,'         {k\%'     ;k(   —    ° 


5|  '0.11  ;i4 
2 


♦  .  4.05  V 
MALLORY 
#TR  133R 
BATTERY 


"■1.2  „f 


2N3663  J?- 

1    V'tL' 


SEMICONDUCTOR 
PRESSURE  TRANSDUCER 
KULITE#T0S-360-25 


FAIRCHILD    OP   AMP 
#110    776 


R         SELECTED  TO  NULL  OFFSETS  IN  A 

1  THERMISTOR.        2K^25°C 

T,        AS  USED  IN   LARGE   HEARTBEAT 
TRANSMITTER 

B        CMOS  BUFFER  SOLID  STATE  SCIENTIFIC 
jjf  SCL4441AF 

FREQUENCY=«55  kH; 


'Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


Figure  4. — Pressure  transmitter. 


254 


KANWISHER,  LAWSON.  and  SUNDNES:  ACOUSTIC  TELEMETRY  FROM  FISH 


peatedly  handled  for  blood  samples  and  had 
largely  accommodated  to  the  presence  of  people. 
Its  heart  slowed  only  when  the  fish  was  physi- 
cally touched. 

At  one  point  we  started  toward  the  fish  with  a 
dip  net.  This  was  one  which  the  fish  had  never 
seen.  It  stopped  swimming,  faced  the  approaching 
strange  net,  and  extended  its  fins  in  what  we  had 
come  to  recognize  as  a  fright  response.  Its  heart 
stopped  for  19  s. 

We  detail  these  because  we  feel  that  such 
acoustic  telemetry  will  be  a  valuable  adjunct  to 
behavior  and  sensory  studies.  When  we  have 
monitored  three  fish  simultaneously  some  ele- 
ments of  social  interaction  showed  in  their  vari- 
able heart  rate.  In  particular,  competition  for 
food  was  easily  discerned  after  a  few  simultane- 
ous observations  of  feeding  and  listening  to  the 
EKG.  In  this  manner  we  hope  to  build  up  a  be- 
havioral repertoire  which  will  allow  us  to  inter- 
pret data  from  a  fish  swimming  free  in  the  ocean 
where  it  cannot  be  observed. 

The  potential  effect  of  behavior  on  such 
physiology  as  oxygen  consumption  had  been  pre- 
viously shown  by  erratic  increases  when  a  fish 
was  confined  in  a  respirometer  (Sundnes,  1957a, 
b).  This  could  be  overcome  by  keeping  cod  in  a 
laboratory  aquarium  for  many  weeks,  while  it 
became  used  to  people  and  capture.  Veteran  fish 
were  found  to  increase  their  O2  consumption  and 
also  showed  immediate  color  changes  whenever 
strangers  were  in  the  laboratory.  We  were  reluc- 
tant to  accept  the  respiratory  data  until  substan- 
tiated by  simultaneous  observations  of  cardiac 
response. 

Some  species  are  difficult  to  acclimate  to  cap- 
tivity. Atlantic  salmon  were  brought  directly 
from  a  fish  farm  and  wired  for  EKG  transmitting. 
They  swam  for  several  weeks  at  the  maximum 
sustainable  speed  until  they  died.  From  this  we 
could  only  learn  the  maximum  heart  rate.  A  5-kg 
salmon  showed  60  to  62  beats/min. 

Later  we  have  had  fish  which  were  hand  fed  in 
a  laboratory  tank  for  over  a  year.  When  these  fish 
were  tagged  they  were  immediately  returned  to 
familiar  surroundings.  They  soon  joined  in  feed- 
ing frenzy  and  showed  cardiac  arrest  when 
frightened.  When  they  were  chased  the  heart 
rate  quickly  increased,  as  shown  in  Figure  2.  Rest- 
ing rates  below  30  beats/min  were  common. 

This  approach  was  not  successful  with  skipjack 
tuna,  Katsuwonus  pelamis,  in  Hawaii.  These 


2.5  K 
SENSITIVITY 


Tl 


2N5B 
5 


I— »-»— gl'ZNiaoo 

1       i  IHYDRO- 

a      ;|,jK    PHONE 


RCA         S-^ 

JPPT*        -6. 
,25  i 

270 


100- 


}22 


T    —  AS  USED  IN  LARGE 

HEARTBEAT   TRANSMITTER 


437     <     1 
♦  4001 
#7 

FREQUENCY       50 kHi 
CAPACITORS      DECIMAL  VALUES 

IN    Mf 

WHOLE   NUMBERS 

IN    of 
A,*  A  J  MOTOROLA   OP  AMP 
#MC1'»37L 


Figure  5. — Simple  beat  frequency  oscillator  receiver. 

fast,  probably  warm-blooded  fish  were  able  to 
either  get  rid  of  our  transmitter,  or  died  in  the 
effort.  Their  heart  rates,  however,  were  from  80 
to  240  beats/min.  This  reflects  their  near  mam- 
mallike metabolic  rate.  They  recovered  from 
fatigue  in  less  than  1  h,  much  like  man.  We  have 
used  a  new  miniature  tag  (7  mm  diameter  x  35 
mm  long)  successfully  on  mackerel,  Scomber 
japonicus. 

CONCLUSIONS 

We  have  tried  to  outline  the  possibilities  and 
methods  of  acoustic  telemetry  from  fish.  It  is  a 
valuable  adjunct  in  both  laboratory  and  open 
water  studies.  In  many  cases,  such  as  monitoring 
the  body  temperatures  of  a  free-swimming  tuna, 
it  is  the  only  way  to  get  the  desired  data  (Carey 
and  Lawson,  1973).  The  burgeoning  solid  state 
technology  promises  a  rapid  advancement  in 
methodology  beyond  the  relatively  simple  ele- 
ments we  have  presented  here. 


LITERATURE  CITED 

Carey,  F.  G.,  and  K.  D.  Lawson. 

1973  Temperature  regulation  in  free-swimming  bluefin 
tuna.  Comp.  Biochem.  Physiol.  44A:375-392. 
Sundnes,  G. 

1957a.  On  the  transport  of  live  cod  and  coalfish.  J.  Cons. 

22:191-196. 
1957b.  Notes  on  the  energy  metabolism  of  the  cod  (Gadus 
callarias  L.)  and  the  coalfish  (Gadus  virens  L.)  in  relation  to 
body  size.  Fiskeridir.  Skr.  Ser.  Havunders.  11(9),  10  p. 
Wardle,  C.  S..  and  J.  W.  Kanwisher. 

In  press.  The  significance  of  heart  rate  in  free  swimming 
cod.  J.  Mar.  Physiol.  Behav. 


255 


ABUNDANCE  OF  PELAGIC  FISH  DURING  THE  19TH  AND  20TH 

CENTURIES  AS  RECORDED  IN  ANAEROBIC 

SEDIMENT  OFF  THE  CALIFORNIAS 

Andrew  Soutar  and  John  D.  Isaacs^ 

ABSTRACT 

Anaerobic  sediment  preserves  a  chronographic  record  of  the  bioclimatological  conditions  in  coastal 
seas.  Of  the  myriad  elements  within  this  record,  the  accumulation  of  pelagic-fish  debris  is  of  particular 
interest.  The  deposition  of  scales  of  the  Pacific  sardine,  the  northern  anchovy,  the  Pacific  hake,  the 
Pacific  saury,  and  the  Pacific  mackerel  in  the  sediment  of  the  Santa  Barbara  Basin,  Alta  California, 
and  the  Soledad  Basin,  Baja  California,  is  generally  in  accord  with  available  population  estimates.  The 
relation  between  scale  deposition  and  population,  when  applied  to  the  sedimentary  record  over  the  past 
150  yr,  suggests  that  major  pelagic-fish  productivity  between  1925  and  1970  was  substantially  below 
pre-1925  levels. 


Man  in  his  search  for  an  environmental  perspec- 
tive has  unearthed  a  number  of  natural  chrono- 
graphic records.  These  include  the  well-known 
growth  rings  of  trees  (Fritts,  1972),  the  deposition 
of  annual  strata  in  the  snowfields  of  Greenland 
and  Antarctica  (Murozumi  et  al.,  1969),  the  in- 
cremental growth  of  coral  and  stromatolites 
(Knutson  et  al.,  1972;  Panella  et  al.,  1968),  and  the 
formation  of  annual  layers  in  certain  lacustrine 
and  marine  sediments  (Seibold,  1958). 

Perhaps  no  richer  records  exist  than  those  finely 
laminated  deposits  encountered  beneath  the  sea 
in  regions  of  anaerobic  sedimentation.  A  web  of 
circumstance  involving  productivity  and  topog- 
raphy serves  to  produce  and  protect  such  records, 
but  no  factor  can  be  more  important  than  the  ex- 
clusion of  burrowing  animals  from  the  sediment 
by  a  persistently  low  dissolved  oxygen  concentra- 
tion in  the  bottom  water.  Here  such  diverse  and 
informative  fragments  of  the  air-sea-land  system 
as  the  tests  of  the  microplankton,  skeletal  and 
integument  debris  from  the  nekton,  air-  and 
river-borne  detritus,  natural  radioisotopes,  and 
more  recently,  anthropogenic  products  fall  in  se- 
quential association  to  a  common  resting  place. 
Undisturbed,  these  threads  of  information  ac- 
cumulate to  form  a  remarkable  sedimentary 
chronicle  combining  the  rhythmic  pulse  of  the 
seasons  with  the  vagaries,  trends,  and  inconsis- 
tencies of  ocean  life,  chemistry,  and  currents. 


Of  the  myriad  elements  within  the  anaerobic 
sediment  record,  the  temporal  framework  and  the 
distribution  of  pelagic  fish  scales  at  depth  in  the 
sediment  in  the  Santa  Barbara  Basin,  Alta 
California  (Figure  la),  and  in  the  Soledad  Basin, 
Baja  California  (Figure  lb),  compose  a  particularly 
relevant  set — relevant  not  only  in  relation  to  the 
continuing  importance  of  pelagic  fish  as  a  resource 
off  the  Californias,  but  also  as  a  potential  indi- 
cator of  long-term  productivity  and  change.  Such 
knowledge  of  ocean  conditions  within  the  broader 
context  of  the  North  Pacific  gyre  and  the  Northern 
Hemisphere  climate  can  aid  man  in  his  search  for 
a  rational  interaction  with  his  environment,  guide 
him  toward  a  wise  stewardship  of  marine  re- 
sources, and  aid  him  in  discriminating  between 
those  changes  that  he  produces  by  his  interven- 
tions and  those  that  are  a  part  of  the  natural  order. 

Time  in  the  laminated  sediment  of  the  Santa 
Barbara  Basin  can  be  estimated  through  the  se- 
rial assignment  of  the  year  of  deposition  to  each 
laminae  pair  (Figure  2a).  It  was  suggested  that 
the  regular  alternation  of  sediment  density  is  a 
direct  response  to  the  monsoonal  climate  affecting 
southern  California  (Emery,  1960).  Confirmation 
of  this  and  the  laminae  pair  sequence  as  a  yearly 
depositional  record  has  come  through  the  correla- 
tion of  regional  rainfall  and  sediment-laminae 
patterns. 2  As  indicated  (Figure  3),  the  essentially 
random  pattern  of  southern  California  seasonal 


'Scripps  Institution  of  Oceanography,  University  of  California 
at  San  Diego,  La  JoUa,  CA  92037. 


Manuscript  accepted  June  1973. 

FISHERY  BULLETIN;  VOL.  72,  NO.  2,  1974. 


^Soutar,  A.,  J.  D.  Isaacs,  P.  A.  Crlll.  Recent  paleoclimatology 
and  paleoecology  of  the  Santa  Barbara  Basin.  Unpubl.  manuscr. 


257 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 


120°  1 5' 
34°30' 


lacoo' 


34°  15' 


II9''45' 
1  34°30 


CALIFORNIA 


34°00 


34°I5' 


I20°00 


34°00' 


Figure  la.— Santa  Barbara  Basin,  California.  The  basin  lies 
under  the  Santa  Barbara  Channel  and  reaches  a  maximum 
depth  of  589  m  (Hulsemann  and  Emery,  1961).  Pertinent 
box-core  locations  (230,241,239,  and  265)  are  shown. 

rainfall  can  be  simply  transformed  into  a  clear 
reflection  of  the  serial  pattern  of  varve  thickness. 
This  transformation  corresponds  to  factors  such  as 
upstream  aggradation  (Schumm,  1969)  which 
could  cause  a  considerable  delay  in  basin  sedimen- 
tation. 

Further  development  of  the  anaerobic-sediment 
chronology  has  been  possible  through  the  close 
agreement  of  Pb-210  and  Th-228/Th-232 
radiometric  ages  and  the  varve-sequence  year 
(Koide  et  al.,  1972,  1973;  Krishnaswami,  1973) 
(see  Figure  4a,  b).  These  relatively  short-term 
radiochronologic  tools  can  be  used  to  considerable 
advantage  in  the  Soledad  Basin  sediment.  Though 
this  basin  is  morphologically  and  oceanogra- 
phically  similar  to  the  Santa  Barbara  Basin  in 
that  there  is  virtually  no  dissolved  oxygen  in  the 
bottom  water,  the  absence  of  consistent  seasonal 
rainfall  inhibits  the  formation  of  distinct  sequen- 
tial varves  (Figure  2b).  Nevertheless,  a  reasonable 
time  framework  can  be  estimated  for  the  near- 
surface  sediment  of  the  Soledad  Basin  from  the 
measurement  of  Pb-210  and  the  Th-228/Th-232 
ratio  at  depth  (Koide  et  al.,  1973)  (see  Figure  4c,  d). 

The  distribution  of  pelagic  fish-scale  debris  can 
be  determined  within  the  time-sediment  frame- 
work. Specifically,  large  (20  x  20  cm)  cores 
were  frozen,  then  cut  into  longitudinal  sections 


measuring  5  x  15  x~40  cm.  X-radiograph  rep- 
resentations were  obtained  for  each  of  the  sec- 
tions, and  by  means  of  recognizable  stratigraphic 
patterns  5-yr  block  templates  were  drawn.  In  the 
case  of  the  Santa  Barbara  Basin  sediment,  specific 
laminae  can  be  identified  within  cores  and  be- 
tween cores  as  to  the  year  of  deposition;  therefore, 
precise  templates  can  be  constructed.  This  is  par- 
ticularly so  for  the  time  period  1860-1970  in  which 
the  laminae  are  well  defined.  The  period  from 
some  time  before  1810  to  1860  is  partly  obscured 
by  bioperturbation  apparently  supported  by  a 
marginal  increase  in  bottom-water  dissolved  ox- 
ygen. Only  general  sedimentation  rates  are  avail- 
able for  the  Soledad  Basin  sediment;  therefore 
linear  estimates  of  the  5-yr  blocks  were  made  for 
the  core  slab  from  which  the  radiometric  ages 
were  obtained.  These  estimates  were  carried  out 
to  the  90-yr  hmit  of  the  Pb-210  method  and  were 
transferred  by  available  stratigraphic  markers  to 
the  other  core  sections.  Furthermore,  these  linear 
estimates  were  continued  to  the  bottom  of  the  core, 
an  additional  80  estimated  years.  It  should  be 
noted  that  the  Th-228/Th-232  method  permits  age 
estimates  in  the  uppermost  sediment  of  the  Sol- 
edad Basin  that  are  comparable  in  accuracy  to 
those  in  the  Santa  Barbara  Basin.  The  templates 


II4°00' 


113°00' 


112-00 


26°00' 


25°00' 


26°00 


25°00' 


CONTOURS  IN  METERS 

AFTER     D'ANGLEJ0N.I965 


II4*>00' 


I13°00 


II2»00 


Figure  lb.— Soledad  Basin,  Baja  California.  This  basin  lies  in  a 
trough  trending  northwest  from  Cabo  San  Lazaro.  The  maxi- 
mum depth  is  nearly  520  m  and  it  occurs  in  the  vicinity  of  core 
244. 


258 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 


Core  239 


34*'  14.0'N 
120**  01.5'W 


cm 


Figure  2a.— Radiograph  of  core  239,  Santa  Barbara  Basin.  The 
radiograph  was  obtained  from  a  frozen  core  slab  approximately  2 
cm  thick.  The  darker  laminae  are  the  more  dense  (negative  print 
of  radiograph  transparency).  Each  pair  of  laminae  are  consid- 
ered to  be  a  single  year  with  the  denser  sediment  representing 
detritus  brought  in  by  winter  rains  (Soutar  et  al,  in  prep.). 

SO  constructed  were  fitted  to  the  frozen  core  sec- 
tions by  means  of  morphologic  and  stratigraphic 
markers,  and  the  sections  were  split  into  the  5-yr 
blocks.  These  sediment  blocks  were  subsequently 
treated  with  a  buffered  dilute  H2O2  solution  and 
gently  washed  on  a  500/u  screen.  The  retained 


coarse  fraction  was  transferred  to  vials  and  stored 
wet  with  ethanol  as  a  preservative.  Identification 
and  enumeration  of  the  material  was  carried  out 
at  low  magnification. 

The  presence  of  fish  scales  in  contemporary 
laminated  sediment  should  not  be  unexpected, 
particularly  to  those  acquainted  with  the 
stratified  diatomite  of  the  Monterey  Formation 
cropping  out  along  the  Coastal  Range  of  Califor- 
nia (David,  1943).  In  some  instances  whole  or  par- 
tial skeletons  offish  are  present  in  these  deposits. 


Core  244 


25°  13.8' N 
1I2°40.6'W 


960 
1950 


SLUMP 


[    1  cm 


Figure  2b. — Radiography  of  core  244,  Soledad  Basin.  Although 
laminae  are  present  there  are  no  consistent  patterns  that  would 
suggest  varves.  There  is,  however,  enough  information  to  physi- 
cally correlate  between  slabs  and  to  identify  irregular  sedimen- 
tation events. 


259 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


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Such  are  likely  victims  of  mass  mortality  result- 
ing from  an  invasion  of  hydrogen  sulfide  water  or 
red  water  situations  which,  while  reported  in 
Walvis  Bay,  South  Africa  (Brongersma-Sanders, 
1957),  do  not  seem  characteristic  of  the  present 
coastal  waters  off  the  Californias.  On  the  other 
hand,  the  occurrence  of  separate  scales  is  likely 
the  incidental  result  of  serious  if  not  fatal  trophic 


interactions.  Previous  investigation  has  indicated 
that,  with  few  exceptions,  fish  scales  are  deposited 
in  Santa  Barbara  Basin  as  individual  events 
(Soutar,  1967). 

Interstitial-water  measurements  (Sholkovitz, 
1973)  indicate  an  increase  of  dissolved  phosphate 
within  the  anaerobic  sediment  from  20  m  moles 
POi"  near  the  surface  to  levels  in  excess  of  100 


260 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 


Figure  3. — Comparison  of  Santa  Barbara  regional  rainfall, 
smoothed  Santa  Barbara  regional  rainfall,  and  total  varve 
thickness.  Spearman  rank-correlation  coefficient  between 
Santa  Barbara  regional  rainfall  and  total  varve  thickness  is  0.26 
(P  =  0.02,  n  =  99).  The  highly  variable  pattern  of  seasonal 
rainfall  is  smoothed  by  the  filter: 


Y,= 


i"^ 


a-4)i-,- 


where  Yf  =  smoothed  seasonal  rainfall  at  year  t;  R/  =  actual 
seasonal  rainfall  at  year  i;  and  r  =  a  time  constant  (years).  Thus 
Yf  is  the  sum  of^  of  year  t  rainfall  and  exponentially  decreasing 
portions  of  previous  year's  rainfall.  The  function  tends  to  damp- 
en rapid  oscillations  and  lag  slower  oscillations  at  a  slightly 
lower  amplitude.  The  value  of  ris  derived  by  multiple  regression 
analysis.  Varve  thickness  at  year  t  is  the  dependent  variable  and 
rainfall  at  year  t,  year  t-l,  year  t-2,  etc.  are  the  independent 
variables.  T  is  found  by  fitting  a  log  linear  line  to  the  regression 
coefficients.  The  Spearman  rank-correlation  coefficient  between 
the  filtered  rainfall  and  the  total  varve  thickness  is  0.50  {n  =  99). 
Due  to  the  autocorrelation  induced  by  the  filter,  no  probability  is 
assigned.  Mean  Santa  Barbara  regional  rainfall  is  42.2  cm,  and 
mean  varve  thickness  is  1.74  mm  (at  60%  water  by  weight). 


M  moles  at  depth.  Since  the  composition  of  fish 
scales  is  essentially  an  intermixture  of  micro- 
crystalline  apatite  and  a  collagen-ichthylepidin 
matrix  ( Wallin,  1957),  a  potential  for  the  degrada- 
tion of  the  scale  record  is  present.  However, 
ichthylepidin,  an  albuminoid  approaching  keratin 
in  composition,  is  unlikely  to  be  degraded  in  an 
anaerobic  environment  (Kaplan  and  Rittenberg, 
1963).  Thus  the  organic  matrix  may  contribute 
significantly  toward  the  preservation  of  scales. 
The  distinctly  higher  frequencies  of  scales  at  core 
depths  in  excess  of  2  m  further  suggest  a  non- 
degraded  record  (Soutar  and  Isaacs,  1969). 

The  record  of  scale  deposition  in  the  Santa  Bar- 
bara Basin  (16  subcore-sample  mean,  1810-1970) 
and  the  Soledad  Basin  (4  subcore-sample  mean, 
1780-1970)  is  in  part  presented  (Figure  5a,  b)  and 
statistically  summarized  (Table  1)  for:  Sardinops 
caerulea  (Pacific  sardine),  Engraulis  mordax 
(northern  anchovy),  Merlucciusproductus  (Pacific 
hake),  Colalabis  saira  (Pacific  saury),  and 
Scomber  japonicus  (Pacific  mackerel). 

Of  particular  interest  are  those  portions  of  the 
scale  record  covering  the  past  few  decades  for 
which  population  estimates  exist.  Considerable 
attention  has  been  directed  towards  the  elucida- 
tion of  the  historical  population  levels  of  the 
Pacific  sardine.  Estimates  of  the  population  (fish  2 
yr  and  older)  derived  from  the  solution  of  a  fishery 
catch  equation  extend  from  1930  up  to  1959  (Mur- 


phy, 1966).  These  biomass  estimates  presented  in 
single-  and  5-yr  averages  (Figure  6)  document  the 
historical  decline  of  the  fishery  and  the  popula- 
tion. Comparison  of  the  5-yr  averages  of  the 
biomass  and  the  scale-deposition  rate  in  the  Santa 
Barbara  Basin  sediment  indicates  a  parallel  but 
offset  decline.  The  derived  age  frequency  of  the 
sedimented  scales  (Table  2)  indicates  that  most 
(92%)  of  the  contributing  fish  were  less  than  2  yr 
old,  suggesting  a  relatively  fast  response  on  the 
part  of  the  sediment  to  particular  year-class  sizes. 
Comparison  of  the  5-yr  averages  of  the  year-class 
size  (numbers  of  2-yr-old  fish  entering  the  fishery) 
and  the  scale-deposition  rate  indicates  a  direct 
proportional  relationship  (Figure  7  and  Table  3). 
Population  estimates  for  the  central,  southern, 
and  total  populations  of  the  northern  anchovy  for 
the  years  1951  to  1966  have  been  made  (Smith, 
1972).  The  estimates  of  the  total  spawning  pop- 
ulation presented  in  single-  and  5-yr  averages, 
and  the  5-yr  averages  for  the  subpopulations, 
record  the  recent  ascendancy  of  the  anchovy. 
Comparison  is  made  of  these  population  estimates 
with  the  northern  anchovy  scale-deposition  rate 
in  the  Santa  Barbara  and  Soledad  Basin  sedi- 
ments (Figure  8  and  Table  4).  In  the  three  5-yr 
intervals  having  sufficient  information,  the  scale 
deposition  is  proportional  to  the  spawning 
biomass.  The  direct  relation  to  spawning  biomass 
may  be  associated  with  the  relatively  rapid  mat- 


Table  1. — Statistical  summary  of  scale  deposition 
(numbers/10='cm*/yr)  for  Santa  Barbara  Basin  sediment, 
1810-1970,  and  Soledad  Basin  sediment,  1780-1970.^ 


Sediment 

Mean 

Median 

Variance 

Maximum 

Minimum 

Santa  Barbara  Basin 

(N=32) 

Pacfic  sardine 

3.6 

2.8 

13.6 

15.2 

0 

Northern  anchovy 

10.0 

9.8 

27.8 

19.4 

2.0 

Pacific  hake 

24.8 

21.8 

310.1 

73,0 

5.5 

Pacific  saury 

0.8 

0.3 

3.2 

8.4 

0 

Pacific  mackerel 

0.3 

0.2 

0.2 

1.9 

0 

Other 
Total 

8.5 
48.1 

8.1 
44.7 

24.3 
532.6 

17.8 
108  1 

0 
21.0 

Soledad  Basin 

(N=38) 

Pacific  sardine 

0.4 

0.2 

0.4 

3.0 

0 

Northern  anchovy 

9.2 

7.5 

43.5 

26.4 

0.6 

Pacific  hake 

6.1 

6.1 

8.3 

12.0 

1.3 

Pacific  saury 

0.3 

0 

0.8 

3.9 

0 

Pacific  mackerel 

0.3 

0 

0.3 

1.6 

0 

Other 

2.9 

2.2 

4.0 

6.8 

0 

Total 

19.2 

17.9 

52.4 

39.0 

5.6 

'In  the  case  of  the  Santa  Barbara  sediment,  the  statistics  are  drawn  from  a 
16subcoreset  representing  a  combinedareaof  980  cm^.  The  statistics  for 
the  Soledad  Basin  are  drawn  from  a  4  subcore  set  having  a  combined  area 
of  260  cm2. 


261 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


SANTA  BARBARA  BASIN  C-2S2-I 
TH-BES/TH-B3B  ACTIVITY 


0.70 

1 1                  1 ♦ 1 1 1                  1 ♦ 

0-« 

\ 

a 
1—1 

0-10 

*  \     1371-1370 

\^       1S7013EB 

< 

or 

-0-ao. 

\  *    1^TH-13EB 

1— 1 

s 

1- 

-o-so 

\  +    19EB-13&4 

-0-80 . 

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a 

v.   ia&4-ia5 

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♦\  13EB-1360 

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\ 

-1-70 

\ 

-8-00 

\ 

\ 

Q_ 

O  1-00. 

LD 
D 

_|   O-BO.. 


SANTA  BARBARA  BASIN  C-^39B2-S 
PB-210  ACTIVITY 


iaSB-1300 


000       e-oo       <oo       600 


1-00        10-00        1^-00        14.00        16-00        16.00       50-00 


0.00  4-00  B'OO        12-00        lB-00       20-00       24-00 


1-00        3E-00        3E-00        40-00 


DEPTH  IN  CENTIMETERS  IN  SEDIMENT 


DEPTH  IN  CENTIMETERS  IN  SEDIMENT 


Figure  4a,b-— Santa  Barbara  Basin  Th-228/Th-232  activity  and  Pb-210  activity  at  sediment  depth.  An  excess  of  both  the  thorium 
isotopic  ratio  Th-228/Th-232  and  the  lead  isotope  Pb-210  are  present  in  coastal  surface  sediments  (Koide  et  al,  1972, 1973).  In  the  case  of 
Pb-210  (22-3  yr  half  life),  the  varve  age  estimate  and  the  radiometric  age  estimate  may  be  directly  compared-  The  thorium  ratio  on  the 
other  hand  cannot  be  directly  estimated  as  function  of  time  but  may  be  calibrated  against  the  accepted  varve  age. 


BAJA  CALIFORNIA  C-E44  Bl-4 
TH-P2a/TH-B32  ACTIVITY 


BAJA  CALIFORNIA  C-B44  Bl-4 
PB-210  ACTIVITY 


1-80 

\ 

— 1 

1-60. 

+ 

\  + 
\    + 

l-«. 

+ 

■ 

LD 
\ 

CL 
D 

1-ao 

l-OO 

\ 

• 

LD 
O 

0-eo 

♦      \ 

•f 

■■ 

o-eo 

\  ♦ 

+ 

+ 

o-o 

\ 

+ 

o-ao 

^ 

\ 

0-00 

* 

— 1 

J^ 

♦-'    '         ♦               < 

0-00  2-00  4-00  G-00         8-00        lO-OO       15-00        14-00       lB-00        lfi-00       50-00 


0-00       4-00       B-00     12-O0     ie-00     ao-oo     ?4.oo     ae-oo     ^-oo     3B-oo     4o-oo 


DEPTH  IN  CENTIMETERS  IN  SEDIMENT 


DEPTH  IN   CM-  (MINUS  SLUMP) 


Figure  4c,d.— Soledad  Basin  Th-228/Th-232  activity  and  Pb-210  activity  at  sediment  depth.  The  information  gained  from  the  study  of 
these  radiometric  tools  in  the  Santa  Barbara  sediment  may  be  applied  to  the  anaerobic  sediment  of  the  Soledad  Basin.  Here,  despite  the 
absence  of  consistent  laminae,  the  radiometric  ages  provide  the  basis  for  a  time  framework-  It  should  be  noted  that  the  scatter  of  Pb-210 
points  at  the  lower  end  (circa  1880)  signals  the  merging  with  the  supported  background  activity  (U-238  series)- 


262 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 


Table  2. — Derived-age'  frequency  of  Pacific  sardine,  northern 
anchovy,  and  Pacific  hake  scales  in  sediment  of  the  Santa  Bar- 
bara and  Soledad  Basins. 


Age 

in  years 

Sediment 

0 

1 

2 

3 

4 

5 

6  + 

Santa  Barbara  Basin 
Pacific  sardine 
Northern  Anchovy 
Pacific  hal<e 

163 

62 

685 

46 
110 
592 

9 

78 
15 

8 

48 
3 

7 

18 

0 

2 

1 
1 

7 
9 
0 

Soledad  Basin 
Pacific  sardine 
Northern  anchovy 
Pacific  hake 

13 
139 
208 

1 
16 
22 

1 

12 
1 

0 
36 

1 

0 

(older 
0 

0 

than 

1 

0 
3yr) 
0 

'The  derived  age  is  an  estimate  of  age  based  on  the  measurement  of  scale 
width.  The  scale  width  is  a  more  reliable  feature  of  sedimented  scales  than 
is  the  scale  length  as,  for  example,  in  the  case  of  the  sardine  the  exposed 
"wing"  of  the  scale  is  often  separated  The  scale  width  is  converted  to  an 
estimate  of  standard  length  and  the  estimate  of  standard  length  is  con- 
verted to  an  age  estimate  by  the  growth  curve. 


uration  of  the  northern  anchovy.  Considering 
that  50%  of  the  anchovy  mature  in  2  to  3  yr  (Clark 
and  Philhps,  1952),  then  the  derived-age  fre- 
quency of  the  anchovy  scales  (Table  2)  suggests 
that  for  Santa  Barbara  35%  and  for  Soledad  24% 
of  the  contributing  anchovy  are  mature. 

No  direct  population  estimates  are  available  for 
the  Pacific  hake;  however,  larval  abundances 
thought  to  be  proportional  to  the  adult  biomass 
have  been  provided.^  In  view  of  the  estimate  that 
54%  or  more  of  the  scale  information  in  the  sedi- 
ment is  derived  from  hake  less  than  one  year  old,  a 
proportional  relationship  between  larval  abun- 
dance and  scale  deposition  might  be  anticipated. 
However,  this  comparison  for  the  inshore  region  of 
southern  California  and  southern  Baja  California 
from  1950  to  1965  indicates  a  non-systematic  rela- 
tionship (Table  5).  One  explanation  of  the  incon- 
sistency may  be  that  between  1950  and  1965  the 
inshore  larval  populations  were  generally  low  and 
had  no  strong  trend.  It  should  also  be  noted  that 
the  inshore  and  total  abundances  are  in  them- 
selves not  entirely  consistent,  and,  in  fact,  the 
total  larval  abundances  tend  toward  an  inverse 
relationship  with  the  scale-deposition  rate. 

Information  on  the  spawning  population  of  the 
Pacific  saury  for  the  period  1950  to  1966  has  been 
reported  (Smith  et  al.,  1970).  Comparison  of  the 
spawning  biomass  and  the  scale-deposition  rate 
(Table  6)  indicates  a  sparse  but  sensible  relation. 

Egg  abundances  and  catch  information  for  the 
Pacific  mackerel  which  could  reflect  the  popula- 


tion are  available,  but  the  extremely  low  rate  of 
scale  deposition  for  this  species  limits  an  evalua- 
tion (Table  7). 

The  generally  consistent  relationships  between 
the  available  estimates  of  pelagic  fish  populations 
and  scale  deposition  provide  an  entree  into  the 
past.  Such  relationships  are  perhaps  not  un- 
reasonable considering  the  strategic  location  of 
the  basins  adjacent  to  major  spawning  grounds. 
The  short  time  over  which  population  estimates 
and  scale-deposition  rates  may  be  compared  in  the 
case  of  the  anchovy,  hake,  saury,  and  mackerel  is 
presently  a  limitation;  nevertheless,  relative 
measures  of  high  and  low  spawning  biomass  may 
be  made  from  the  sedimentary  information.  The 
record  for  the  Pacific  sardine,  however,  should  be 
amenable  to  direct  interpretation  in  terms  of 
year-class  size  and  projected  biomass,  with  the 
exception  perhaps  of  those  times  when  scale  dep- 
osition far  exceeds  our  experience. 

Consideration  of  the  scale  record  (Figure  5)  as  a 
population  record  affords  a  fascinating  look  into 
the  flow  of  ocean  life  at  the  higher  trophic  level. 
The  historical  decline  of  the  sardine,  seen  in  per- 
spective, appears  as  a  subdued  finale  to  a  move- 
ment that  had  begun  in  1890,  thirty  years  before 
the  inception  of  the  fishery,  and  this  movement  in 
turn  belongs  to  a  theme  extending  into  the  mil- 
lennia (Soutar  and  Isaacs,  1969).  Levels  of  year- 
class  success  in  excess  of  10^°  fish  occurring  in  the 
late  1930's,  which  are  historically  considered  im- 
pressive, appear  in  broader  context  to  be  at  most 
moderate.  Even  higher  levels  of  success  suggested 
by  the  sedimentary  record  between  1855  and  1865 
afforded  insufficient  reserve  against  a  precipitous 
and  natural  decline.  Nor  can  the  virtual  absence  of 
the  sardine  from  the  waters  off  Alta  California  be 


Table  3. — Comparison  of  Pacific  sardine  population  (Murphy, 
1966)  and  scale-deposition  rate  in  the  Santa  Barbara  Basin 
sediment.' 


2  yr  old 

year  annual 

2  yr  and  older 

class 

Scale-deposition 

Year 

annual  biomass 

in  year  spawned 

rate 

interval 

(10^  metric  tons) 

(10^) 

(no./IO^cm^/yr) 

1959-55 

0.25 

1.7 

0 

1954-50 

0.63 

2.1 

0 

1949-45 

0.64 

3.3 

0.4 

1944-40 

1,84 

3.5 

0.5 

1939-35 

1.71 

9.1  ■ 

3.1 

1934-30 

23.52 

6.8 

2.0 

^Smith,  P.E.  CalCOFI— the  first  twenty-five  years.  Unpubl. 
manuscr. 


'The  Spearman  rank-correlation  coefficient  between  the  2-yr  and  older 
biomass  and  the  scale-deposition  rate  is  0.81 ,  n  =  6;  and  for  the  2-yr-old 
year  class  and  the  scale-deposition  rate  Is  0.99,  n  =  6.  While  these  are 
highly  suggestive  of  a  significant  relationship,  no  probabilities  are  as- 
signed due  to  inherent  autocorrelation  in  these  series. 
^Incomplete  data. 


263 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


2 
U 


o 
in 

o 

o 
o 


< 
u 
tn 


>- 


s 
u 


o 

o 
o 
o 


in 
ui 
_i 
< 
u 
in 


17.50 

15-00 
15.50    , 
10-00 

7-SO 

5-00 

S-SO 


0-00 


PACIFIC  5ARDItv£.  SANTA  BARBARA  BASIN 


19B0   1370   19B0   1350   1940   1930   13S0   1910   1300   1S30   ISBO   1B70   IflEO   1B50   1&40   iflSO   IBEO   IBIO   IBOO 


35-00 
3O-0O 
SS-00 
50-00     , 


NORTHERN    ANCHOVr.    SANTA    BARBARA    BASIN 


1980       1970       19E0       19SO       1940        1930       13g0        1910        130O       1B90       laBO       1870       1860       ISSO       1840       1830       1850        1810 


PACIFIC  HAKE.  SANTA  BARBARA  BASIN 


1980   1970   1380   1950   1940   1930   1350   1910   1900   1B30   IflBO   1870   1880   1H50   1B40   1B30   1850   1810 


Figure  5a. — Histogram  plot  of  the  scale-deposition  rate  of  the  Pacific  sardine,  the  northern  anchovy,  and  the  Pacific  hake  in  sediment 

of  Santa  Barbara  Basin,  1810  to  1969. 


considered  an  unnatural  circumstance.  The  levels 
of  year-class  success  between  1865  and  1880  were 
likely  as  low  as  those  estimated  after  1940.  It  may 
be  argued  that  in  the  previous  period  the  sardine 
had  moved  offshore  or  migrated  southward, 
thereby  causing  a  decline  in  scale  deposition. 
However,  abandonment  by  a  substantial  popula- 
tion of  a  major  spawning  ground  would  seem  prob- 
lematic, and  in  regard  to  a  southern  immigration 
it  can  be  said  that  during  the  apparent  year-class 
failures  from  1865  to  1880  no  substantial  sardine 
population  occupied  the  southern  waters  near  the 
Soledad  Basin,  Baja  California.  Indeed,  the  only 
time  the  sardine  appears  even  moderately  in- 


fluential in  these  waters  is  the  period  1920  to 
1935,  coincidental  with  the  development  of  the 
fishery  to  the  north.  While  the  evidence  from  pre- 
vious decades  makes  it  impossible  to  accuse  the 
sardine  of  avoidance,  the  coincidence  may 
nevertheless  underline  the  naturally  intermittent 
occurrences  of  abundant  sardine  populations  in 
California  waters. 

As  in  the  case  of  the  sardine,  one's  view  of  the 
distribution  of  the  anchovy  through  time  is  col- 
ored by  perspective.  The  sediments  in  both  the 
Santa  Barbara  and  Soledad  Basins  have  re- 
sponded to  the  recent  increase  in  the  anchovy 
population.  This  response  appears  as  part  of  a 


264 


SOUTAR  ;ind  ISAACS:  ABUNDANCE  OF  PFLAGIC  FISH 


>- 


u 


a 
ui 

o 
o 
o 


Lfl 
U 
_l 
< 

u 

Ul 


a: 


2 
U 


o 

LTl 

O 
O 
O 


< 

u 
m 


17.50 
15-00    , 
15-50    , 
10-00     . 

7-50 

5-00 

8-50 


0-00 


PACIFIC  SARDINE.  SDLEDAD  BASIN 


1^0   1970   laeo   1950   1940   1930   19B0   1910   1900   1B30        IBBO   1870   IBEO   1B50   1B.40   1830   18S0   1810   1800   1790   1780   1770 


NORTHERN  ANCHOVY,  SOLEDAD  BASIN 


SO-00 

lS-00 

10-00 

S-00 


0-00 


1980   1970   19E0   1950   19-SO   1930   1920   1910   190O   1B90   IBBO    870   1860   1850   18->0   1830   IBeO   IBIO   IBOO   1790   17B0 


PACIFIC  HAK.E.  SOLEDAD  BASIN 


19B0   1970   1360   1^0   1900   1330   19SO   1310   1900   1B90   1880   1B70   1860   1B50   IBAO       1830   1880   IfllO   1800   1790   1780 

Figure  5b- — Histogram  plot  of  the  scale  deposition  rate  of  the  Pacific  sardine,  the  northern  anchovy,  and  the  Pacific  hake  in  sediment  of 

the  Soledad  Basin  from  about  1780  to  1969. 


significant  pattern  of  similarity  in  scale  deposi- 
tion (Table  8).  The  recorded  increase  in  the  an- 
chovy population,  while  substantially  above  re- 
cent historical  levels,  when  compared  to  the  in- 
ferred population  reached  in  most  of  the  19th  and 
the  early  part  of  the  20th  centuries,  appears  mod- 
erate. Furthermore,  in  contrast  to  the  sardine,  the 
population  of  the  anchovy  has  been  of  comparable 
density  in  the  waters  of  the  Californias  over  the 
past  two  centuries.  This  then  supports  contempor- 
ary observations  that  the  northern  anchovy  is  re- 
gionally adapted  and  is  capable  of  successful  popu- 
lation responses  covering  at  least  the  southern 
half  of  the  California  Current. 

The  inferred  distribution  of  the  Pacific  hake. 


although  made  tenuous  by  the  lack  of  clearly  sup- 
portive population  information,  is,  in  the  case  of 
Santa  Barbara  Basin,  strongly  suggestive  of  the 
anchovy  with  an  indication  of  a  recent  increase 
from  low  levels  between  1920  and  1965  and  with 
substantially  higher  levels  before  1920  (Table  8, 
Figure  5).  The  inferred  hake  population  in  the 
water  near  Soledad  Basin  corresponds  with  the 
levels  inferred  for  Santa  Barbara  back  to  the 
1930's  and  in  this  regard  is  consistent  with  recent 
observations  of  essentially  equal  larval  abun- 
dance in  both  areas.  However,  levels  of  inferred 
population  before  1930  at  Santa  Barbara  are  con- 
siderably above  those  of  Soledad,  the  latter  show- 
ing a  consistent  level  over  the  past  200  years. 


265 


Table  4. 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 

-Comparison  of  the  northern  anchovy  population  (Smith,  1972)  and  the  scale-deposition  rate  in  the  Santa  Barbara  and 

Soledad  Basin  sediment.' 


Central  subpopulation 

Southern  subpopulation 

Total  population 

Scale-deposition 

Seal 

e-deposition 

5-yr  average 

5-yr  average 

5-yr  average 

rate.  Santa 

rate, 

Year 

spawning  biomass 

spawning  biomass 

spawnmg  biomass 

Barbara  Basin 

Soledad  Basin 

interval 

(lO''  metric  tons) 

(10«  metric  tons) 

(10^  metric  tons) 

no./10^cm2/yr 

no 

/103cm2/yr 

1969-1965 

2470 

20.92 

2502 

4.9 

27.0 

1964-1960 

2.95 

1.18 

429 

10.0 

10.3 

1959-1955 

1.34 

0.37 

1  85 

5.4 

3.6 

1954-1950 

0.54 

0.47 

1.04 

3.3 

0.6 

1949-1945 

— 

— 

— 

3.4 

1.5 

1944-1940 

— 

— 

22.37 

4.7 

3.0 

'As  defined  (Vrooman  and  Smith,  1971)  the  central  subpopulation  area  includes  southern  Alta  California  inshore,  offshore,  and  seaward  and  Baja 
California  inshore,  offshore,  and  seaward.  The  southern  subpopulation  area  includes  southern  Baja  California  inshore,  offshore,  and  seaward.  Inshore 
includes  0-80  miles:  offshore  includes  80-160  miles,  and  seaward  includes  160-280  miles. 
2|ncomplete  data. 

Table  5. — Comparison  of  Pacific  hake  larval  abundance  ( Ahlstrom,  1969;  Smith,  in  prep.)  and  scale-deposition  rate  in  Santa  Barbara 

and  Soledad  Basin  sediment. 


Scale-deposition 

Scale-deposition 

California  coastal 

Southern  Baja  coastal 

Total  (inshore 

rate 

rate 

Year 

inshore  area 

inshore  area 

and  offshore) 

Soledad  Basin 

Santa  Barbara  Basin 

interval 

(5-yr  average) 

(5-yr  average) 

(5-yr  average) 

no./103cm2/yr 

no./103cm2/yr 

1969-1965 

'3,500 

'880 

'10.360 

'21.3 

'2.5 

1964-1960 

480 

590 

3,810 

7.3 

6.9 

1959-1955 

600 

420 

11,850 

5.8 

4.6 

1954-1950 

540 

880 

1 2,660 

5.5 

4.0 

'Incomplete  data. 


Consideration  of  the  relationships  of  the  three 
major  species  provides  further  insight  into  the 
distribution  of  pelagic  fish  through  time.  Most  if 
not  all  investigators  have  found  the  hypothesis 
that  the  Pacific  sardine  and  the  northern  anchovy 
are  direct  competitors  unavoidable.  This 
hypothesis  is  not  supported  by  the  less-than- 
significant  positive  correlation  between  the  scale 
deposition  of  the  two  species  in  the  Santa  Barbara 
sediment  (Table  8).  However,  fluctuations  in  rela- 
tive abundance  of  even  closely  competitive  species 
in  the  marine  environment  may  follow  quite  dif- 
ferent rules  than  mere  abundance  or  autecologic 
correlation.  The  abundance  of  species  may  be  di- 
rectly related  to  advantageous  conditions.  How- 
ever, whenever  an  advantageous  or  disadvan- 
tageous series  of  years  is  of  critical  duration  (de- 
termined by  specific  differences  in  life  history)  the 
abundances  may  be  inversely  related.  In  this  con- 
text the  apparent  decline  and  subsequent  recovery 
of  the  sardine  population  between  1865  and  1890 
from  levels  which  appear  substantially  above  his- 
torical experience,  in  the  presence  of  what  also 
appears  to  be  substantial  anchovy  populations, 
may  not  be  entirely  enigmatic. 

The  associations  of  the  anchovy,  hake,  and  sar- 
dine in  the  Santa  Barbara  sediment  (Table  8)  is 
further  suggestive  of  periods  favorable  or  unfavor- 


able to  these  three  species.  This  is  in  contrast 
to  the  Soledad  sediment  from  which  it  may  be 
inferred  the  anchovy  alone  is  able  to  maintain 
high  population  levels.  Some  idea  of  the  total 
pelagic-fish  productivity  off  the  Californias  may 
be  gained  by  combining  the  inferred  populations 
of  the  anchovy,  hake,  and  sardine  into  a  total 
spawning  biomass  estimate  (Figure  9).  This 
biomass  estimate  suggests  that  the  central 
California  and  presumably  the  northern  Baja 
California  regions  can  become  a  dominant  center 
of  pelagic  fish  productivity.  Even  though  signifi- 
cant densities  of  northern  anchovy  have  been  pre- 
sent in  the  water  above  Soledad  Basin,  available 
information  (Table  4)  suggests  these  represent  a 
relatively  smaller  southern  subpopulation.  The 


Table  6. — Comparison  of  the  Pacific  saury  population  (Smith  et 
al.,  1970)  and  the  scale-deposition  rate  in  the  Santa  Barbara  and 
Soledad  Basin  sediments. 


Total  population 

Total  scale- 

Total  scale- 

spawning  biomass 

deposition  rate, 

deposition  rate, 

Year 

CalCOFI  area 

Santa  Barbara  Basin 

Soledad  Basin 

interval 

(10*  metric  tons) 

no./10^  cm2/yr 

no./10^  cm2/yr 

1969-1965 

'0.21 

'1.1 

'0.0 

1964-1960 

0.12 

0.3 

0.0 

1959-1955 

0.18 

1.1 

0.0 

1954-1950 

0.23 

2.2 

0.6 

'Incomplete  data. 


266 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 


u 

n 

h- 
LJ 


Z 

a 


10.00  . 
9-00  , 
S-OO 
7.00 
S.OO 
S.OO 
4.00 
3-00 
S.OO 
1.00  . 
0.00 


PACIFIC   SARDINE   BIDMASS 


lO-OO     ^ 

9.00 

e.Qo 

1 

7.QO 
B.OO 

u 

5-00 
4-00 

g 

l-l 

2 

3.00 

a. 00 

1.00 

PACIFIC   SARDItvE    BIDMASS 


laao   1970   laGO   19S0   1940   1930 


19B0   1970   19G0   1350   1940   1330   13S0 


SARDINES.    2    YR.    OLDS   VS-    YR.    SPAWNED 


esono-oo 

2SS00-00 

in 

a 

50000-00 

17500-00 

> 

15000-00 

^ 

*"• 

lSSOO-00 

b 

1 

in 

10000-00 

_i 

7500-00 

1 

5000-00 

Jl 

1 

psno-no 

■       1|.  ' 

■ 

0-00 

[ 

H 

01 

_l 
< 

a 


D 
2 


O 
LO 

z 
a 
1—1 

_i 
-I 


25000-00 
22500-00 
20000-00 
17500-00 
15000-00 
12500.00  . 
10000.00  , 
7500.00  . 
5000.00  ., 
2SOO-0O  ., 
0-00 


SARDINES.  2  YR.  DLDS  VS-  YR.  SPAWNED 


laeo   1970   1360   1350   1340   1330   13E0 


13B0   1370   19G0   1550   1340   1530   1320 


Figure  6. — Yearly  estimates  of  Pacific  sardine  biomass  2-yr  and  older  and  year  class  size  at  2  yr  old  (after  Murphy,  1966).  The  yearly 
population  estimates  (left)  are  grouped  into  5-yr  block  averages  (right)  that  correspond  to  the  sampling  intervals  in  the  sediment. 


Table  7. — Comparison  of  Pacific  mackerel  larval  abundance  (Ahlstrom,  1969;  Smith,  in  prep.),  fishery  landings  (Fitch,  1952),*  and 

scale-deposition  rate  in  Santa  Barbara  and  Soledad  Basin  sediment. 


Southern  California 

Scale-deposition 

Seal 

B-deposition 

Southe 

rn  California 

Southern  Baja 

Total  (inshore 

landings 

rate. 

rate. 

Year 

coastal 

inshore  area 

coastal  inshore  area 

and  offshore) 

(5-yr  average) 

Santa  Barbara  Basin 

Soledad  Basin 

interval 

(5-y 

average) 

(5-yr  average) 

(5-yr  average) 

(metric  tons) 

no./IO^cm^/yr 

no 

/lO^cm^/yr 

1969-1965 

2 

2 

2 

1,660 

20 

20 

1964-1960 

560 

21,000 

38,600 

17,830 

0 

0 

1959-1955 

1.260 

3,060 

16,100 

18,390 

0-2 

0 

1954-1950 

650 

10,100 

19.000 

10,780 

0.2 

0.8 

1949-1945 

— 





21,660 

0.6 

0 

1944-1940 

— 





35,020 

0.4 

1.6 

1939-1935 

— 

— 



45,430 

0.2 

1.6 

1934-1930 

— 

— 

— 

1.6 

0.8 

'Also  subsequent  Gal.  Dept.  Fish  and  Game  landing  statistics, 
^incomplete  data. 


267 


FISHFRY  BULLETIN:  VOL.  72.   NO.  2 


PACIFIC  5ARDI^E  SCALE  DEP-  RATE  (S-  B- ) 
V5-  BIDMA55  2  YRS-  AND  OLDER  (1930-1959) 


a. 

\ 

u 


o 

LD 

O 
O 
O 

\ 

LH 
U 
_l 
< 
U 


>- 
\ 


o 

o 
o 
o 

vH 

\ 

in 

< 

u 
m 


s-oo^ 

PACIFIC  SARDINE  SCALE 
VS-  TWD  YR.  DLD5 

DEP-  RATE  IS- 
I  1930-1959 

B-) 

4-50 

4.00 

3. so 

/ 

3.00 

/ 

£-50 

2.00 

1-50 

1. 00 

0.5D 
0.00 

1 •  m   • • •— 

O'OO       i'OO       a. CO       3.00       4.00       s-oo       e.oo       7.00       s-oo       9-00     10.00 


0*00  1.00         £.00  3.00 


1.00       5.00       e.oo       7.00       e.oo       9.00     lo.oo 


MILLION  METRIC  TONS 


BILLIONS 


Figure  7a, b. — Scatterplot  of  the  5-yr  averages  of  the  Pacific  sardine  biomass  (after  Murphy,  1966)  and  the  scale-deposition  rate  in 
Santa  Barbara  sediment,  1930  to  1959.  The  plot  of  biomass  versus  scale  deposition  though  indicating  a  significant  relationship 
(Spearman  rank-correlation  coefficient  is  0.81,  n  =  6)  shows  considerable  scatter.  If,  on  the  other  hand,  the  year-class  size  at  2  yr  of  age 
is  plotted  against  the  scale-deposition  rate  in  the  year  spawned,  the  scatter  is  markedly  reduced  and  a  highly  significant  relationship 
emerges  (Spearman  rank-correlation  coefficient  is  0.99,  n=  6).  The  reduction  in  scatter  can  be  explained  through  the  observation  that 
most  of  the  scales  encountered  in  the  sediment  were  derived  from  younger  fish. 


>- 
\ 


o 

m 

o 
o 
o 

\ 


< 


IS-OO 

NORTHERN  ANCHOVY,   5-  B-  SCALE  DEP- 
VS-  CENT-  AND  TOTAL  BIOMASS   (1950- 

RATE 
19G4) 

i3<90 

y 

/ 

l£-00 

CENT.  X 

U}-50 

/ 

^ 

9-00 

/     y^ 

7.S0 

X              y^     TOTAL 

6-ao 

/         3^ 

4-^ 

/y^ 

3-00 

/y^ 

1-5D 

^ 

0-00 

q: 
\ 

u 


o 
ui 

o 
o 
o 

H 

\ 

LD 

u 

< 

u 


NORTHERN  ANCHOVY, 
VS-  SO-  AND  TOTAL 

SLO-  SCALE  DEP-  RATE 
BIDMASS    (1950-1964) 

13-50 

/ 

ie-00 

/  so- 

/ 

UJ.SD 

J 

/ 

9-00 

/ 

/ 

7-5D 

/ 

/ 

6-00 

/ 

/      TOTAL 

4.ao 

•  /            o/ 

/ 

3-00 

/     / 

1.50 

/       / 

0-00 

/  *   /^ 

0-00    O.SD    1.00    1.50    £.00    £.SD    3.00    3. SO    4.00    4.50    5. 00 


MILLION  METRIC  TONS 


).00         0.50         1.00  1.50         £.00         £.50         3-00         3.50  4.0O         4.50         5. 00 

MILLION   METRIC    TONS 


Figure  7c,d. — Scatterplot  of  the  5-yr  averages  of  the  northern  anchovy  spawning  population  estimates  (after  Smith,  1972)  and  the 
scale-deposition  rates  in  Santa  Barbara  and  Soledad  Basin  sediment,  1950  to  1965.  The  scale-deposition  rates  in  both  the  basins  vary 
airectly  with  increasing  population  estimates  of  the  northern  anchovy.  The  relatively  steep  slope  of  the  southern  subpopulation  (S) 
relative  to  the  central  subpopulation  (CNT)  reflects  the  smaller  southern  population. 


268 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 

NO-     ANCHOVY,     TOTAL    POPULATION 
lO-OO     , 

9-00 


a 

00 

7 

no 

LD 

LJ 

1— 

e 

00 

u 

t— ( 

a^ 

5 

00 

1— 

UJ 

2 

4 

00 

z 

□ 

3 

00 

_J 

2 

2 

00 

o-oo 


u 


k 


LT) 


U 


UJ 

2 


_l 
2 


NO-  ANCHOVY,  TOTAL  POPULATION 


9-00 

8-00 

7.00 

G.OO     , 

5.00 

4.00 

3.00      . 

2.00 

1.00 

0.00 

19B0        1970        19G0        1950 


19S0       1970       19S0       1950 


NO.    ANCHOVY,    CENT-    5UBP0P- 


NO-    ANCHOVY,    50-    5UBP0P- 


m 

z 
a 


u 
a. 


UJ 

2 


Z 
D 


_J 
_J 
n 

2 


9-00 

B-OO 

7.00 

G.OO 

5.00 

4.00 

3-00     . 

2.00     . 

1-00 

0-00 

19B0   1970   19G0   1950 


10.00 

g.oo 

e.oo 

1- 

7.00 
6.00 

u 

l-t 

1. 

5-00 
4.00 

n 

_l 
_l 

2 

3.00 
2-00 

1.00 
0.00     , 

-1  1 

1980   1970   19G0   1950 


Figure  8. — Yearly  estimates  of  the  northern  anchovy  biomass  (after  Smith,  1972).  The  yearly  total  population  estimates  (upper  left) 
are  grouped  into  5-yr  block  averages  (upper  right).  Also  given  are  the  central  and  southern  subpopulation  5-yr  block  averages  (lower). 

Table  8. — Rank-correlation  coefficients'  between  the  scale  occurrences  of  the  Pacific  sardine,  the  northern  anchovy,  and  the  Pacific 

hake  in  sediment  of  Santa  Barbara  and  Soledad  Basins  in  =  32). 


Pacific  sardine 

Northern 

anchovy 

Pacific 

hake 

Santa  Barbara                  Soledad 

Santa  Barbara 

Soledad 

Santa  Barbara 

Soledad 

Pacific  sardine 

Santa  Barbara 

-002 

0.34 

0.05 

0.49 

0.19 

Soledad 

0.20 

-0.19 

-0.09 

020 

Northern  anchovy 

Santa  Barbara 

0.37 

0.65 

-0.08 

Soledad 

0.26 

-0.46 

Pacific  hake 

Santa  Barbara 

0.17 

Soledad 

'While  the  correlation  coefficients  above  0.35  appear  significant,  nevertheless  due  to  autocorrelation  inherent  in  these  time  series  the  probabilities 
associated  with  these  coefficients  are  likely  to  be  greater  than  if  the  series  were  internally  independent. 


269 


FISHERY    BULLETIN:  VOL.  72,  NO.  2 


Lfl 

z 
a 


u 
1—1 


Z 

a 


25.00 

SS-50 

30-00 

17.50 

15-00 

lS-50 

10-00 

7.50 

5-00 

2.S0 

0-00 


SARDINE.    ANCHOVY,    AND   HAKE    B I DMA55- -CENTRAL    AREA 


1980       1970       1960       1950       ISaO       1930       1930       1910       1900       1B90       1B90       1970       igGO       1B50       18-10       1830       1830       1910       1900       1790 


35.00  ^ 
23.50 
30-00 
17-50 
15-00 
13-50 
10-00  , 
7-50 


SARDINE.    ANCHOVY,    AND   HAf<,E    BIDMAS5- -SOUTHERN    AREA 


1980       1970       1960       1950       1940       1930       1930       1910       1900       1890       1880       1970       IGEO       1B5C       IS-JO       1830       1830       1810       1800       1790 

Figure  9. — Combined  biomass  estimate  for  the  Pacific  sardine,  the  northern  anchovy,  and  the  Pacific  hake  in  Alta  California  and 
southern  Baja  California  waters,  1810  to  1969.  The  biomass  estimates  are  derived  directly  from  the  information  in  Tables  3, 4,  and  5.  In 
the  case  of  the  hake  the  average  population  level  for  the  years  1950-1965  was  assumed  to  be  0.9  x  IC^  metric  tons  (P.E.  Smith,  pers. 
comm.).  One  half  of  this  population  has  been  assigned  to  the  central  region;  the  other  half  has  been  assigned  to  the  southern  region.  The 
actual  relations  used  in  the  biomass  calculation  are  as  follows: 

Sardine — Santa  Barbara  (central  population)  and  Soledad  (southern  population):  sinceN^  =  2.27S^2  +  2.15  andB/=  0.38N;  -0.40 
(Spearman  rank-correlation  coefficient  is  0.97,  n  =  6;  see  also  Sette,  1969);  then  Bt  =  0.85S^2  +  0.40 

Anchovy— Santa  Barbara:  Bt  =  0.36S^  -  0.64;  and  Soledad:  Bt   =  0.08S^  -I-  0.29 

Hake— Santa  Barbara  and  Soledad:  Bt  =  0.08S( 
where  N  is  number  of  2-yr  olds,  B  is  annual  spawning  biomass,  S  is  scale  deposition  rate,  and  subscript  t  refers  to  year.  The  mean 
spawning  biomass  estimates  for  the  sardine,  anchovy,  and  hake  are  3.5, 3.0,  and  2.0  million  tons  for  the  central  population  and  0.7, 1.0, 
and  0.5  for  the  southern  area. 


importance  of  the  central  region  would  also  likely 
extend  to  the  north  through  the  seasonal  migra- 
tion of  these  fish. 

The  projected  mean  biomass  level  for  the  three 
main  species  off  California  over  the  past  30  years 
is  roughly  2  million  metric  tons  and  over  the  past 
150  yr  is  8  million  metric  tons.  Thus  the  recent  rise 
of  the  anchovy  population  may  simply  be  a  return 
to  reasonably  productive  conditions.  It  is  ironic 


that  most  of  man's  experience  in  the  waters  off  the 
Californias  appears  to  be  associated  with  low 
pelagic-fish  productivity.  Conceding  a  significant 
effect  of  the  fishery  on  the  Pacific  sardine  does  not 
mitigate  the  synchronous  low  population  levels  of 
the  anchovy  and  the  hake.  As  a  matter  of  perspec- 
tive, it  should  be  emphasized  that  most  of  the 
understanding  regarding  the  California  Current 
system  and  pelagic  fish,  particularly  that  from 


270 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 


a. 


5 


a 

01 

o 
o 
o 


Ld 

_j 
< 
u 

01 


17.50 
1S.D0  . 
15-50  .. 
10-00     ., 

7-50     , 

5-00     . 

5-50 

O-OO 


PACIFIC  5AURY,  SANTA  BARBARA  BASIN 


■r>^ 


laeo  1970  isGo  laso  is^o  1930  i3so  laio  laoo  isao  laeo  ie7o  ibbo  ibso  i84o  leao  laeo  laio 


17.50 

15-00 
IS-SO    , 
10-00 

7-50     .. 

5-00 

S-50     , 


O-OO 


PACIFIC  MACKEREL,  SANTA  BARBARA  BASIN 


1380   1370   1360   1950   13^   1330   1950   1310   1900   1B90   IBBO   1S70   1360   IBSO   1B40   1B30   1850   IBID   ISOO 


Figure 


lOa.b.— Histogram  plot  of  the  scale-deposition  rate  of  Pacific  saury  and  Pacific  mackerel  in  sediment  of  the  Santa  Barbara 

Basin,  1810  to  1969. 


^ 


u 


o 

01 

o 
o 
o 


01 
u 
_l 
< 

u 

01 


17-50 

PACIFIC    SAURY 

.    Sni.EDAD   BASIN 

15-00 

12-50 

« 

lO-OO 

7-50 

5-00 

, 

2-50 

1      . 

1  1 

L         .«.             J              .1                  I .,                                                           ..,_.      1              .1                  1 M « 

13B0   1370   19EO   1950   1940   1330   1320   1310   1300   1B30   IBBO   1S70   IflBO   IBSO   1B40   1S30   ISSO   ISIO   IBOO   1730   1780 


17-50 
15-00  , 
12-50 
10-00 

7-50 

S-OC 


PACIi^IC    MACKEREL,    SDLEDAD   BASIN 


I   ,1   I   .1 


13B0   1970   1360   1950   1340   1330   1320   1310   1300   1S90   IBBO   lfl70   1S60   IBSO   1840   1830   1820   1810   1900   1790   1780 

Figure  10c,d.— Histogram  plot  of  the  scale-deposition  rate  of  Pacific  saury  and  Pacific  mackerel  in  sediment  of  the  Soledad  Basin  from 

about  1780  to  1969. 


271 


FISHERY   BULLETIN:  VOL.   72,  NO.  2 


ui 

UJ 

_i 
< 

u 
in 

>- 
> 


u 
z 
< 
\ 

LD 
U 

_/ 
< 
U 

in 

u 

z 

3 

< 


2-50  . 

3-S5 

S-00 

1-75 

1-50 

1-S5 

1-00 

0-75 

0-SO 


SARDINE/ANCHOVY  RATIO.  SANTA  BARBARA  BASIN 


laeo   1970   1360   1950   1340   1930   19S0   1910   1900   lfl90   IBBO   1B70   IBGO   1B50   IflJO   1H30   IBSO   laiO 


E-SO 

SARDINE/ANCHOVY  RA 
t 

TI( 

:. 

SDLEDAD  BASIN 

a-2s 

5-00 

1-75 

1-50 

1-25 

1-00 

0-75 

0-SO 

0-25  . 

0-CC 

„  n-^ 

,1    1 ^-T 

.1 „ 1— n ^^4 . — ,.— .  .,. « 

19B0   1970   13E0   1950   19-10   1930   1950   1910   1900   1B90   IBBO   1B7Q   IBGO   IBSO   1B40   1830   IBSO   IBIO   IBOO   1790   1760 

Figure  11. — The  ratio  of  Pacific  sardine  scales  to  northern  anchovy  scales  in  the  sediments  of  the  Santa  Barbara  and  Soledad  Basins. 


intensive  efforts  over  the  past  20  yr,  has  been 
gleaned  from  unproductive  times,  and  there  is  yet 
limited  appreciation  of  the  capacity  of  the  system. 
In  regard  to  this  point,  a  level  of  15  million  metric 
tons  is  suggested  for  the  1890's. 

The  scale  records  of  two  other  pelagic  fish  serve 
to  underscore  the  preceding  observations.  The 
record  of  the  Pacific  saury  (Figure  10a,  c)  indicates 
an  intrusion  by  this  fish  during  the  1940's  into  the 
coastal  waters.  It  would  appear  the  saury  found 
these  waters  attractive  in  the  anomalous  paucity 
of  the  more  regular  inhabitants.  Although  the 
information  in  the  case  of  the  Pacific  mackerel  is 
meager,  the  scale  record  (Figure  10b,  d)  resembles 
that  of  the  saury  in  that  the  higher  scale  occur- 
rences are  near  the  ends  of  the  record. 

The  records  preserved  in  the  sediments  display 


a  panorama  of  pelagic-fish  abundance  in  the 
California  Current  over  the  past  150  yr.  Interpre- 
tations of  these  records  in  the  limited  light  of  pres- 
ent knowledge  point  in  both  disturbing  and  excit- 
ing directions:  disturbing,  in  revealing  the  mag- 
nitude and  duration  of  the  effort  needed  to  encom- 
pass such  a  system;  exciting,  in  the  temporal 
glimmer  of  its  flow  and  potential.  The  character  of 
pelagic-fish  abundance  in  California  Current 
waters  is  perhaps  best  summarized  in  graphic 
form  (Figure  11).  The  records  of  the  two  critical 
species,  the  Pacific  sardine  and  the  northern  an- 
chovy, when  treated  as  a  simple  ratio  exhibit  a 
marked  cyclical  distribution  (Santa  Barbara)  and 
a  unique-event  distribution  (Soledad).  The  basic 
factors  which  gave  rise  to  these  distributions  are 
most  likely  interspecific  and  autecologic.  The 


272 


SOUTAR  and  ISAACS:  ABUNDANCE  OF  PELAGIC  FISH 


former  is  susceptible  to  scrutiny  through  the 
analysis  of  the  projected  fish  populations  through 
time.  The  latter  is  no  less  susceptible,  for  the  sed-  ■ 
iments  contain  a  rich  record  of  fossil  microplank- 
ton  which  promises  to  further  define  oceanic  con- 
ditions off  the  Californias  in  relation  to  pelagic- 
fish  productivity. 

ACKNOWLEDG  MENTS 

This  report  is  a  contribution  of  the  Marine  Life 
Research  Group,  Scripps  Institution  of  Oceanog- 
raphy. Gratitude  is  expressed  to  Peter  A.  Grill  for 
his  statistical  calculations,  computer  graphics, 
and  patience.  The  support  of  the  National  Science 
Foundation  (GA-27306)  is  gratefully  acknow- 
ledged. 

REFERENCES 

Ahlstrom,  E.  H. 

1969.  Distributional  atlas  of  fish  larvae  in  the  California 

Current  region:  jack  mackerel,  Trachurus  symmetricus, 

and  Pacific  hake,  Merluccius  productus,  1951  through 

1966.  Calif.  Coop.  Oceanic  Fish.  Invest.  Atlas  11:88-99. 

Brongersma-Sanders,  M. 

1957.  Mass  mortality  in  the  sea./n  J.  W.  Hedgpeth  (editor), 
Treatise   on   marine   ecology   and   paleoecology,   p. 
941-1010.  Geol.  Soc.  Am.  Mem.  67,  Vol.  1. 
Clark,  F.  N.,  and  J.  B.  Phillips 

1952.  The  northern  anchovy  (Engraulis  mordax  mordax)  in 
the  Cahfomia  fishery.  Calif.  Fish  Game  38:189-207. 
D'Anglejan-Castillon,  B. 

1965.  Marine  phosphorite  deposits  of  Baja  California,  Mex- 
ico, present  environment  and  history.  Ph.D.  Thesis, 
Univ.  Calif.,  San  Diego,  Scripps  Inst.  Oceanogr. 
David,  L.  R. 

1943.  Miocene  fishes  of  southern  California.  Spec.  Pap. 
Geol.  Soc.  Am.  43:1-193. 
Emery,  K.  O. 

1960.  The  sea  off  Southern  California.  A  modern  habitat  of 
petroleum.  John  Wiley  &  Sons,  N.Y.,  366  p. 

Fitch,  J.  E. 

1952.  The  decline  of  the  pacific  mackerel  fishery.  Calif. 
Fish  Game  38:381-403. 
Fritts,  H.C. 

1972.  Tree  rings  and  climate.  Sci.  Am.  226(5):92-100. 
Hulsemann,  J.,  AND  K.  O.  Emery. 

1961.  Stratification  in  recent  sediments  of  Santa  Barbara 
Basin  as  controlled  by  organisms  and  water  character.  J. 
Geol.  69:279-290. 

Kaplan,  I.  R..  and  S.  C.  Rittenberg. 

1963.  Basin  sedimentation  and  diagenesis.  In  M.  N.  Hill 
(editor),  The  sea.  Vol.  3,  p.  583-619.  John  Wiley  and  Sons, 
NT. 
Knutson,  D.  W.,  R.  W.  Buddemeier,  and  S.  V.  Smith. 

1972.  Coral  chronometers:  seasonal  growth  bands  in  reef 
corals.  Science  (Wash.,  D.C.)  177:270-272. 


KoiDE,  M.,  A.  SouTAR,  and  E.  D.  Goldberg. 

1972.  Marine  geochronology  with  Pb-210.  Earth  Planet. 
Sci.  Lett.  14:442-446. 

Koide,  M.,  K.  W.  Bruland,  and  E.  D.  Goldberg. 

1973.  Th-228/Th-232  and  Pb-210  geochronologies  in 
marine  and  lake  sediments.  Cjeochim.  Cosmochim.  Acta 
37:1171-1187. 

Krishnaswami,  S.,  D.  Lal,  B.  S.  Amin,  and  A.  Soutar. 

1973.  Geochronological  studies  in  Santa  Barbara  Basin: 
Fe-55  as  a  unique  tracer  for  particulate  settling.  Limnol. 
Oceanogr.  18:763-770. 

MuROzuMi,  M.,  T.  J.  Chow,  and  C.  Patterson. 

1969.  Chemical  concentrations  of  pollutant  lead  aerosols, 
terrestrial  dusts  and  sea  salts  in  Greenland  and  Antarctic 
snow  strata.  Geochim.  Cosmochim.  Acta  33:1247-1294. 

Murphy,  G.  I. 

1966.  Population  biology  of  the  Pacific  sardine  (Sardinops 
caerulea).  Proc.  Calif.  Acad.  Sci.  34:1-84. 

Panella,  G.,  C.  MacClintock,  and  M.  N.  Thompson. 

1968.  Paleontological  evidence  of  variations  in  length  of 
synodic  month  since  Late  Cambrian.  Science  (Wash., 
DC.)  162:792-796. 

SCHUMM,  S.  A. 

1969.  Geomorphic  implications  of  climatic  changes. /«  R.  J. 
Chorley  (editor),  Water,  earth,  and  man,  p.  525-534. 
Methuen  and  Co.,  Ltd.,  Lond. 

Seibold,  E. 

1958.  Jahreslagen  in  sedimenten  der  mittleren  Adria. 
Geol.  Rundsch.  47:100-117. 

Sette,  O.  E. 

1969.  A  perspective  of  a  multi-species  fishery.  Calif.  Coop. 
Oceanic  Fish.  Invest.  Rep.  13:81-87. 

Sholkovitz,  E.  R. 

1973.  Interstitial  water  chemistry  of  the  Santa  Barbara 
Basin  sediments.  Geochim.  Cosmochim.  Acta 
37:2043-2073. 

Smith,  P.  E. 

1972.  The  increase  in  spawning  biomass  of  northern  an- 
chovy, Engraulis  mordax.   Fish.  Bull.,  U.S.  70:849-874. 

Smith,  P.  E.,  E.  H.  Ahlstrom,  and  H.  D.  Casey. 

1970.  The  saury  as  a  latent  resource  of  the  California 
Current.  Calif.  Coop.  Oceanic  Fish.  Invest.  Rep. 
14:88-100. 

Soutar,  A. 

1967.  The  accumulation  offish  debris  in  certain  California 
coastal  sediments.  Calif.  Coop.  Oceanic  Fish.  Invest.  Rep. 
11:136-139. 

Soutar,  A.,  and  J.  D.  Isaacs. 

1969.  History  offish  populations  inferred  from  fish  scales  in 
anaerobic  sediments  off  California.  Calif.  Coop.  Oceanic 
Fish.  Invest.  Rep  13:63-70. 

Vrooman.  a.  M.,  and  P.  E.  Smith. 

1971.  Biomass  of  the  subpopulations  of  northern  anchovy 
Engraulis  mordax  Girard.  Calif.  Coop.  Oceanic  Fish.  In- 
vest. Rep.  15:49-51. 

Wallin,  O. 

1957.  On  the  growth  structure  and  developmental  physiol- 
ogy of  the  scale  of  fishes.  Inst.  Freshwater  Res.  Drottning- 
holm.  Rep.  38:385-447. 


273 


CHANGES  IN  THE  AMOUNT  AND  PROPORTIONS  OF  DDT  AND  ITS 
METABOLITES,  DDE  AND  DDD,  IN  THE  MARINE  ENVIRONMENT 

OFF  SOUTHERN  CALIFORNIA,  1949-72 


John  S.  MacGregori 


ABSTRACT 

This  paper  is  about  the  contamination  of  the  ocean  and  its  biota  off  southern  Cahfornia  by  the  pesticide, 
DDT.  The  accumulation  of  DDT  and  the  changes  in  proportions  of  DDT  and  its  metabolites  in  the  ocean 
are  described  for  the  years  1949  to  1972  especially  as  they  are  reflected  in  the  myctophid  fish, 
Stenobrachius  leucopsarus.  This  time  period  was  characterized  by  continuous  dumping  of  DDT  wastes 
into  the  ocean  by  a  large  manufacturer  of  DDT  and  the  cessation  of  this  dumping  in  1970.  Aspects  and 
implications  of  the  pesticide  pollution  problem  in  the  marine  environment  are  discussed. 


In  January  and  May  1970,  the  Fishery-Ocean- 
ography Center,  La  Jolla,  Calif.,  collected 
samples  of  fish  off  southern  California  and  Baja 
California  as  their  part  in  a  survey  of  chlorin- 
ated hydrocarbon  (CHC)  pesticides  in  marine 
fishes  by  the  U.S.  fish  and  Wildlife  Service 
Bureau  of  Commercial  Fisheries  (now  the  Na- 
tional Marine  Fisheries  Service).  Each  sample 
consisted  of  the  livers  of  several  specimens  of  a 
single  species  from  one  locality.  The  samples 
were  sent  to  the  Environmental  Protection  Agen- 
cy Laboratory  at  Gulf  Breeze,  Fla.,  for  analysis. 
The  results  (Duke  and  Wilson,  1971)  showed 
that  off  southern  Baja  California  9  samples  (170 
fish)  contained  an  average  of  0. 14  parts  per  million 
(ppm)  wet  weight  of  DDT  and  its  metabolites;  in 
Sebastian  Vizcaino  Bay  (central  Baja  California) 
3  samples  (29  fish)  averaged  1.2  ppm;  along  the 
southern  California  coast  south  of  Oceanside  and 
at  two  offshore  banks  15  samples  (179  fish)  aver- 
aged 13  ppm;  in  Santa  Monica  Bay  8  samples  (65 
fish)  averaged  370  ppm.  Two  samples  (26  fish)  of 
Pacific  hake,  Merluccius  productus,  taken  by  a 
Russian  trawler  off  northern  California  and 
Oregon  averaged  2.7  ppm,  and  fish  sampled 
farther  to  the  north  by  the  Seattle  Laboratory 
contained  less  than  1  ppm  or  no  detectable  DDT 
residues  in  the  livers.  The  highest  levels  of  DDT 
and  its  metabolites  were  found  in  the  Los  Angeles 
area  with  DDT  levels  declining  greatly  in  samples 


'Southwest  Fisheries  Center,  National  Marine  Fisheries  Ser- 
vice, NOAA,  P.  O.  Box  271,  La  Jolla,  CA  92037. 


taken  to  the  north,  south,  and  offshore  from  Los 
Angeles. 

Previous  pesticide  residue  surveys  of  marine 
birds  and  fish  (Keith  and  Hunt,  1966;  Risebrough 
et  al.,  1967;  Risebrough  et  al.,  1968)  had  been 
confined  primarily  to  central  California  and  did 
not  reveal  the  extent  of  DDT  pollution  in  the  ocean* 
off  Los  Angeles.  Risebrough  et  al.  (1967)  reported 
one  sample  of  northern  anchovy,  Engraulis  mor- 
dax,  taken  off  Los  Angeles  that  contained  12.7 
ppm  DDT  and  its  metabolites  compared  with  addi- 
tional samples  of  anchovies  and  three  other 
species  offish  taken  north  of  Los  Angeles  to  San 
Francisco  that  ranged  in  DDT  residue  content  be- 
tween 0.2  and  2.8  ppm. 

In  the  spring  of  1969,  Keith,  Woods,  and  Hunt 
(1970)  investigated  the  breeding  pelican, 
Pelecanus  occidentalis,  colony  on  Anacapa  Island, 
about  35  nautical  miles  west  of  Santa  Monica  Bay, 
and  found  extensive  reproductive  failure  caused 
by  thin-shelled  eggs  which  broke  under  the  brood- 
ing pelicans.  They  found  that  the  contents  of  a 
composite  sample  of  many  broken  eggs  contained 
1,818  ppm  DDT  residues  (lipid  basis)  while  nine 
intact  eggs  averaged  1,215  ppm.  They  also  sam- 
pled pelican  eggs  from  three  breeding  colonies  in 
the  Gulf  of  California  and  found  DDT  residues 
averaging  58,  61,  and  105  ppm.  Jehl  (1970)  sam- 
pled pelican  eggs  from  Los  Coronados  Islands, 
about  95  nautical  miles  south  of  Anacapa.  These 
contained  810  ppm  DDT  residues.  At  San  Martin 
Island  250  nautical  miles  south  of  Anacapa,  egg 
residues  were  192  ppm. 


Manuscript  accepted  October  1973. 

FISHERY   BULLETIN:  VOL.  72,  NO.  2,   1974. 


275 


FISHERY   BULLETIN:  VOL.  72,  NO. 


More  recent  data  (Southern  California  Coastal 
Water  Research  Project,  1971)2  for  thep,p'DDE 
content  of  the  mussel,  Mytilus  calif ornianus ,  show 
that  two  samples  taken  on  the  Palos  Verdes 
Peninsula,  near  Los  Angeles,  contained  61  and 
151  ppm  of  p.p'DDE  while  samples  taken  at  a 
greater  distance  from  Los  Angeles  declined 
greatly  to  between  0.3  and  3  ppm  at  San  Diego, 
Point  Conception,  and  on  the  farther  outlying  is- 
lands. 

Burnett  (1971)  determined  DDT  residues  in 
samples  of  the  sand  crab,  Emerita  analoga,  from 
19  locations  along  the  coast  between  northern 
Baja  California  and  San  Francisco.  Only  in  those 
crabs  from  the  Los  Angeles  area  did  he  find  values 
greater  than  1  ppm  (up  to  7.2  ppm).  The  DDT 
values  fell  off  rapidly  north  and  south  of  Los 
Angeles  and  averaged  about  0.1  ppm  at  most  of 
these  locations. 

These  results  of  the  above  studies  demonstrate 
that  geographical  proximity  to  Los  Angeles  was 
accompanied  by  greatly  elevated  levels  of  DDT 
and  its  metabolites  in  marine  organisms. 

High  DDT  residues  in  marine  life  in  the  ocean 
off  Los  Angeles  had  an  adverse  effect  on  the 
fishing  industry.  In  June  1970,  canned  jack  mack- 
erel, Trachurus  symmetricus,  shipped  from  Los 
Angeles  was  condemned  by  the  U.S.  Food  and 
Drug  Administration  in  New  York  for  high  DDT 
content  (13  ppm).  The  FDA  had  set  a  maximum 
tolerance  of  5  ppm  on  fish  products.  In  the  follow- 
ing year  jack  mackerel  was  withheld  from  dis- 
tribution by  the  packers,  and  jack  mackerel  and 
Pacific  bonito,  Sarda  chiliensis,  were  condemned 
by  the  FDA  in  the  Los  Angeles  area.  In  December 
1970,  the  FDA  seized  about  8,000  lb  of  white 
croaker,  also  called  kingfish,  Genyonemus 
lineatus,  that  had  been  caught  near  Los  Angeles. 
These  contained  19  ppm  DDT  residues. 

While  the  fishing  industry  was  unable  to  pin- 
point any  particular  area  of  heavy  DDT  contami- 
nation of  pelagic  fish  off  southern  California,  it 
seemed  to  be  fairly  well  defined  for  the  more 
sedentary  bottom  dwelling  species.  Although  the 
total  DDT  in  the  flesh  of  the  Santa  Monica  Bay  fish 
samples  taken  in  May  1970  ranged  from  12  to  57 
ppm,  about  30  nautical  miles  away  at  Farnsworth 
Bank  on  the  west  side  of  Santa  Catalina  Island, 


^Southern  California  Coastal  Water  Research  Project,  1971. 
Comments  on  the  policy  for  water  quality  control  proposed  by  the 
State  Water  Resources  Control  Board.  Presented  at  the  State 
Water  Resources  Control  Board  public  hearing,  San  Diego, 
Calif.,  2  Dec.  1971,  27  p. 


DDT  in  the  flesh  of  a  sample  of  sculpin,  Scorpaena 
guttata,  and  in  flesh  samples  of  four  species  of 
rockfishes,  Sebastes  spp.,  had  a  range  of  only  0.23 
to  0.49  ppm;  and,  a  sample  of  white  croakers  taken 
off  Oceanside,  40  nautical  miles  south  of  Los 
Angeles,  contained  only  0.61  ppm  of  DDT  residues 
in  the  flesh. 

The  pelagic  fish  were  not  good  indicators  of  the 
source  of  pesticide  contamination  because  they 
are  much  more  migratory  than  the  bottom  dwell- 
ing species,  and  the  area  in  which  they  are  caught 
is  not  necessarily  the  area  in  which  they  were 
contaminated.  Even  though  this  would  also  mean 
that  their  exposure  to  heavy  contamination  would 
be  of  shorter  duration  than  for  bottom  fishes  living 
in  these  areas,  they  still  built  up  high  concentra- 
tions of  DDT  in  the  flesh  because  pelagic  fish  tend 
to  store  fat  throughout  the  body  rather  than  in  the 
liver  as  do  bottom  dwelling,  more  sedentary 
species.  The  DDT  residues  are  stored  in  the  fats, 
and  the  distribution  of  the  total  body  load  of  DDT 
residues  in  the  fish  is  roughly  related  to  the  dis- 
tribution of  fat. 

Although  we  have  no  flesh  sample  analyses 
from  pelagic  fish  to  illustrate  this  point,  concen- 
trations of  DDT  were  found  to  be  two  to  six  times 
higher  in  the  livers  of  samples  of  four  different 
species  of  bottom  dwelling  fish  taken  in  1970  along 
the  coast  between  San  Diego  and  Oceanside  than 
they  were  in  the  livers  of  a  sample  of  jack  mackerel 
from  the  same  area,  and  seven  to  19  times  higher 
than  in  the  livers  of  a  sample  of  Pacific  sardine, 
Sardinops  sagax,  taken  in  San  Diego  Bay  at  about 
the  same  time.  And  even  among  bottom  fish  taken 
from  the  same  area  at  the  same  time,  those  that 
have  more  oil  in  the  flesh  seem  to  carry  relatively 
more  of  the  total  DDT  load  in  the  flesh.  For  five 
species  of  bottom  dwelling  fishes  taken  from  Santa 
Monica  Bay  in  1970,  there  is  an  inverse  relation 
between  the  ratio  of  DDT  in  the  liver  to  DDT  in  the 
flesh  and  the  percent  of  oil  in  the  flesh  as  given  in. 
Table  1. 

Because  of  the  prevalence  of  winds  from  the 
Pacific,  and  the  concentration  of  agriculture  in  the 
inland  valleys,  we  considered  it  unlikely  that  the 
heavy  DDT  contamination  in  the  ocean  off  Los 
Angeles  was  caused  by  airborne  pesticide  resi- 
dues. Surface  runoff  was  also  an  unlikely  source. 
Southern  California's  arid  climate,  the  damming 
of  rivers,  the  large  population  and  importation  of 
water  have  resulted  in  a  condition  in  which  the 
annual  discharge  by  sewers  into  the  ocean  is  at 
least  twice  the  average  annual  surface  runoff  of 


276 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 


Table  1.— Relation  between  ratio  of  DDT  in  liver  to  DDT  in  flesh  and  percent  of  oil  in  flesh  of 
five  species  of  bottom  dwelling  fishes  from  Santa  Monica  Bay  in  1970. 


Number 

Total  DDT 

Rat 

io  of  DDT 

Liver 

Flesh 

Percent  oil 

Species 

of  fish 

(ppm) 

(ppm) 

Liver:flesh 

in  flesh 

Bocaccio, 

Sebastes  paucispinis 

9 

590 

12 

49:1 

1.4 

Starry  rockfjsh. 

S.  constellatus 

5 

1,030 

57 

18:1 

1.8 

Vermilion  rockfish, 

S.  miniatus 

10 

163 

16 

10:1 

2.2 

Dover  sole. 

Microstomus  paclficus 

13 

63 

13 

5:1 

3.6 

Sablefish, 

Anoplopoma  fimbria 

10 

103 

23 

4:1 

6.0 

water.  The  "rivers"  of  southern  California  are  its 
sewers,  and  the  two  largest  of  these,  in  the  400 
million  gallons  (1.51  million  m^)  per  day  class,  are 
the  outlets  of  the  Hyperion  treatment  plant  that 
serves  the  city  of  Los  Angeles  and  those  of  the 
White  Point  treatment  plant  that  serves  Los 
Angeles  County. 

The  Hyperion  plant  empties  into  the  head  of  an 
underwater  canyon  in  the  northern  half  of  Santa 
Monica  Bay,  and  the  White  Point  plant  empties 
into  the  ocean  off  Palos  Verdes  Peninsula.  Fish 
samples  that  showed  very  high  DDT  residues 
came  from  southern  Santa  Monica  Bay  about 
midway  between  the  two  sewer  outfalls. 

The  County  Sanitation  Districts  of  Los  Angeles 
County  (CSDLAC)  began  a  monitoring  program  to 
test  for  CHC  pesticides  in  its  sewerage  system  in 
December  1969  (Carry  and  Redner,  1970).  They 
found  that  very  high  concentrations  of  DDT  were 
present  in  the  sewer  system.  In  March  1970,  they 
began  to  sample  the  sewer  trunk  lines  in  order  to 
pinpoint  the  sources  of  DDT  input  into  the  sewer 
system. 

They  soon  discovered  that  the  source  of  most  of 
the  DDT  pollution  was  the  Montrose  Chemical 
Corporation,  a  major  manufacturer  of  DDT,  lo- 
cated in  the  city  of  Torrance.  Los  Angeles  Times 
staff  writer,  John  Dreyfus,  reported  (7  October 
1970),  after  interviewing  a  Montrose  official,  that 
at  that  time,  Montrose  was  the  only  manufacturer 
of  DDT  left  in  the  United  States,  and  that  it  ac- 
counted for  two-thirds  of  the  world's  sales  of  DDT. 

The  CSDLAC  found  that  water  samples  taken 
from  the  sewers  immediately  upstream  from 
Montrose  contained  34  parts  per  billion  (ppb)  of 
DDT  and  its  metaboHtes  (DDD  and  DDE)  in  a  flow 
of  25.3  million  gallons  (95.8  thousand  m'^)  per  day 
or  7.2  lb  (3.27  kg)  of  total  DDT  per  day,  while 
samples  taken  immediately  downstream  con- 


tained 2,950  ppb  in  a  flow  of  26.6  million  gallons 
(100.7  m3)  per  day  or  654  lb  (297  kg)  of  total  DDT 
per  day  (Carry  and  Redner,  1970). 

In  April  1970,  Montrose  began  hauling  most  of 
its  processing  wastes  to  a  storage  area,  which 
caused  a  considerable  drop  in  CHC  entering  the 
CSDLAC  disposal  plant.  However,  in  May  180  lb 
(81.6  kg)  per  day  CHC,  of  which  150  lb  (68.0  kg) 
was  DDT  and  its  metabolites,  were  still  found  to  be 
entering  the  White  Point  plant.  The  primary 
source  of  this  was  found  to  be  the  sewer  trunk  line 
serving  Montrose  Chemical  Corporation.  Because 
the  composition  of  the  total  DDT  sampled,  14% 
DDT,  48%  DDD,  and  38%  DDE,  was  different  from 
the  Montrose  effluent  previously  sampled, 
74% DDT,  5% DDD,  and  21%  DDE,  CSDLAC  per- 
sonnel concluded  that  the  primary  source  of  pollu- 
tion was  from  old  deposits  in  the  sewer  lines. 

Between  11  December  1970,  and  1  July  1971, 
567,000  lb  (257,000  kg)  of  deposits,  of  which  7,700 
lb  (3,500  kg)  were  total  DDT,  were  removed  from 
the  interceptor  system  that  served  Montrose 
(Redner  and  Payne,  1971).  The  cleaning  of  this 
section  of  the  sewer  lines  also  stirred  up  old  de- 
posits which  were  washed  down  into  the  sewerage 
disposal  plant,  resulting  in  an  increase  in  total 
DDT  entering  the  plant.  By  October  1971,  the 
total  CHC  entering  the  disposal  plant  had  de- 
creased to  60  lb  (27  kg)  a  day  of  which  28  lb  ( 13  kg) 
was  total  DDT  and  the  remaining  32  lb  (14  kg) 
polychlorinated  biphenyls  (PCB). 

Since  March  1971,  an  average  of  22,000  gallons 
(83.3  m^)  a  day  of  alkaline  waste  from  the  Mon- 
trose plant  has  been  trucked  to  the  Sanitation 
District's  landfill  on  Palos  Verdes  Peninsula,  and 
another  700  gallons  (25.9  m^)  of  acid  waste  has 
been  trucked  to  a  quarry.  The  alkaline  waste  was 
found  to  contain  about  3,000  ppm  of  total  DDT 
(Redner  and  Payne,  1971)  or  about  550  lb  (250  kg) 


277 


FISHERY    BULLETIN:  VOL    72,  NO    2 


per  day.  The  acid  waste  was  not  tested,  but  if  the 
concentration  of  DDT  was  similar  to  that  in  the 
alkaline  waste,  it  would  amount  to  an  additional 
175  lb  (79  kg)  of  DDT  residues  per  day. 

The  average  inflow  of  DDT  into  the  White  Point 
sewerage  plant  during  December  1969  through 
March  1970  was  estimated  at  652  lb  (296  kg)  per 
day.  The  amount  measured  in  the  sewers  at  the 
Montrose  plant  was  647  (293  kg)  per  day.  The 
amount  trucked  out  as  alkaline  waste  only  was 
estimated  at  550  ( 250  kg)  per  day.  Considering  the 
difficulties  in  sampling  such  large  volumes  of 
material  and  the  fact  that  the  samples  were  taken 
in  different  localities  at  different  times,  there  is 
remarkable  agreement  among  them. 

It  is  difficult  to  determine  just  how  much  DDT 
finally  was  pumped  into  the  ocean  after  treatment 
at  the  sewerage  plant.  Some  of  it  was  undoubtedly 
removed  in  grit,  grease  skimming  operations,  and 
in  dried  sludge. 

At  the  Hyperion  treatment  plant  (city  of  Los 
Angeles),  the  digested  sludge  is  pumped  into  the 
ocean,  although  some  of  it,  at  least  in  the  past,  has 
been  used  for  fertilizer.  The  DDT  input  into  the 
Hyperion  plant  was  estimated  to  be  on  the  order  of 
0.6  lb  (0.27  kg)  a  day  (tests  by  Hyperion  personnel 
cited  in  Los  Angeles  Times,  7  October  1970)  so, 
insofar  as  the  DDT  input  into  the  ocean  is  con- 
cerned, it  has  had  little  impact.  The  White  Point 
treatment  plant  has  never  discharged  its  sludge 
into  the  ocean  (Terry  Hindrichs,  Southern 
California  Coastal  Water  Research  Project,  pers. 
commun.)  except  during  a  short  period  of  heavy 
rains  in  1955.  Until  1959,  digested  sludge  was 
spread  on  nearby  fields  to  air  dry.  Since  1959  a 
centrifuge  has  been  used  to  partially  dry  sludge. 
The  resulting  cakes  have  been  used  for  fertilizer  or 
landfill. 

CSDLAC  personnel  were  unable  to  get  reliable 
estimates  of  the  DDT  content  of  their  effluent  into 
the  ocean  until  December  1970  (Carry  and  Red- 
ner,  1970),  long  after  Montrose  stopped  dumping 
most  of  their  wastes.  Nine  samples  that  they  took 
from  the  effluent  into  the  ocean  in  December 
showed  that  the  average  total  CHC  entering  the 
ocean  was  130  lb  (59  kg)  a  day.  The  influent  into 
the  sewerage  disposal  plant  in  December  had  a 
load  of  153  lb  (69  kg)  per  day.  The  influent  samples 
were  taken  after  the  grit  chambers  so  any  CHC 
removed  in  grit  would  not  have  been  included.  If 
we  assume  that  sludge  removal  accounted  for  a 
15%  loss  of  CHC  in  December  1969  through  March 
1970,  between  influent  (average  652  lb  or  296  kg 


per  day)  and  effluent  into  the  ocean,  then,  the 
ocean  discharge  would  have  been  about  552  lb 
(250  kg)  per  day  of  CHC  for  these  months.  This  is 
about  100  short  tons  (91  metric  tons)  per  year  or 
about  10  times  the  amount  of  pesticides  estimated 
to  be  carried  into  the  Gulf  of  Mexico  each  year  by 
the  Mississippi  River  (Butler,  1969). 

Montrose  received  a  permit  to  dump  its  wastes 
into  the  CSDLAC  sewer  system  in  1953,  but  it  had 
been  dumping  for  a  few  years  before  that  accord- 
ing to  company  personnel.  The  continuous  dump- 
ing of  large  quantities  of  DDT  wastes  into  the 
ocean  at  a  single  point  over  a  period  of  about  20  yr 
presented  an  unparalleled  opportunity  to  study 
the  effects  of  DDT  on  the  ocean  environment.  Un- 
fortunately the  one-time  opportunity  to  take  ad- 
vantage of  the  situation  was  not  fully  realized 
until  some  time  after  the  dumping  had  stopped, 
and  no  large-scale  coordinated  investigation  was 
undertaken  to  exploit  this  ecological  windfall. 

An  investigation  of  pesticide  pollution  of  the 
marine  environment  was  initiated  at  the  Fishery 
Oceanography  Center  (FOC),  La  Jolla,  in  1970. 
Personnel  at  FOC  have  collected  samples  of  bot- 
tom muds,  fishes,  and  other  biological  samples 
primarily  from  the  ocean  off  Los  Angeles  in  order 
to  study  the  effects  of  heavy  DDT  pollution  in  the 
marine  environment. 

Collections  of  marine  organisms  taken  for  other 
purposes,  some  dating  back  to  1949,  were  avail- 
able for  study.  Most  of  the  present  paper  is  based 
on  DDT  levels  found  in  specimens  from  one  of 
these  collections  of  a  myctophid  fish,  Stenob- 
rachius  leucopsarus,  found  in  the  ocean  off  south- 
ern California  in  an  attempt  to  trace  the  historical 
buildup  of  DDT  and  its  metabolites  in  the  marine 
environment  as  reflected  in  this  species. 


MATERIALS 

The  California  Cooperative  Oceanic  Fisheries 
Investigations  (CalCOFI)  has  taken  plankton 
samples  over  an  extensive  area  off  California  and 
Baja  California  since  1949.  These  samples  were 
obtained  over  a  predetermined  pattern  of  stations 
in  order  to  determine  the  species  present,  their 
numbers,  and  their  distribution.  The  most  inten- 
sive sampling  took  place  during  the  1950's;  during 
the  1960's  the  number  of  CalCOFI  cruises  was 
reduced  considerably. 

All  fish  and  fish  eggs  are  routinely  sorted  out  of 
the  collections  for  identification.  About  600 


278 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 


specimens  of  the  myctophid  fish,  S.  leucopsarus, 
that  had  been  sorted  from  the  plankton  collec- 
tions, were  selected  for  this  study  to  give  best  areal 
and  temporal  coverage. 

Initially  a  few  plankton  samples,  which  were 
available  in  much  greater  quantity,  were  tested 
for  pesticides.  However,  the  plankton  species 
composition  varied  in  time  and  with  locality,  and 
it  was  felt  that  the  samples  might  not  be  compara- 
ble. The  plankton  samples  also  appeared  to  con- 
tain both  Aroclor  1242^  and  Aroclor  1254  (poly- 
chlorinated  biphenyls  (PCB)  manufactured  by 
Monsanto  Corporation)  while  the  myctophids 
generally  contained  only  Aroclor  1254  in  quan- 
tity. Plankton  samples  can  include  man-produced 
debris  that  contains  relatively  large  amounts  of 
CHC  or  other  organic  chemicals  which  interfere 


^Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


with  analysis,  while  individual  myctophids  are 
relatively  free  of  such  material.  Myctophids  do  not 
undergo  any  more  horizontal  movement  than 
other  plankton  organisms,  and,  if  they  use  their 
motility  at  all,  at  least  in  the  coastal  waters,  it  is 
probably  to  maintain  position  over  the  deeper  ba- 
sins. In  addition,  they  tend  to  contain  more  pes- 
ticide than  the  invertebrate  constituents  of  the 
plankton  with  which  they  are  taken,  and  they  are 
convenient  material  to  work  with. 

The  myctophids  tested  for  pesticide  residues 
ranged  in  standard  length  (SL)  from  14  to  77  mm. 
They  are  apparently  short-lived  fish.  Fish  of  the 
year  can  be  followed  through  their  first  year  and 
into  their  second  by  length-frequency  distribu- 
tions (Figure  1).  Most  of  the  myctophids  tested 
appeared  to  be  comparable  in  DDT  content  to 
other  fish  taken  at  the  same  time  and  place,  but 
the  amounts  in  smaller  fish  were  erratic.  Some 


10 


20  I 


o 


LU 


60 


70 


80 


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h 


f  T  T  r  r  T 1 


:7 


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h 


1 1 1 1 1 1 1 1 1 


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;.v;-; 

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rj.Ti 

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h 
J 

% 

r 

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— 

M.I, 

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1  1  1  1  J  r  1  1 

0         50         50         5         10        0         5         0         50         50         50         50         50         50         50        5 

NUMBER    OF    FISH    BY    MONTH 
MAY  JUNE  JULY  AUG.         SEPT.         OCT         NOV.       DEC.  JAN.  FEB.      MAR.      APR. 


Figure  1. — Length-frequency  distribution  of  Stenobrachius  leucopsarus  by  month.  Shaded  area  is  entering  year  class. 


279 


FISHERY   BULLETIN:   VOL.  72.  NO.  2 


were  comparable  to  larger  fish,  while  others  con- 
tained less  DDT  than  might  be  expected  in  larger 
fish  taken  at  the  same  time  and  in  the  same  local- 
ity. 

This  variation  in  pesticide  content  appeared  to 
be  related  to  the  "fat"  content  (hexane  extractable 
portion  of  the  fish)  of  the  specimens.  The  fat  con- 
tent of  the  fishes  (Figure  2)  increased  very  rapidly 
and  with  considerable  variation  to  30  mm  length, 
6.5%  fat  of  the  dry  weight  of  the  fish  in  an  18-mm 
specimen  to  42.5%  in  a  29-mm  specimen)  where  it 
began  to  level  off.  In  mature  fish  the  fat  is  about 
49%  of  dry  weight  and  16%  of  wet  weight.  There  is 
no  apparent  seasonal  fat  cycle.  For  comparison  of 
DDT  in  time  and  space,  only  myctophids  30  mm  or 
longer  were  used. 

METHODS 

The  myctophids  used  in  this  study  were  pre- 
served in  Formalin  which  had  no  apparent  effect 
on  the  pesticides  to  be  analyzed.  The  specimens 
were  measured  and  weighed  and  placed  in  tared 
disposable  pipets  that  had  been  plugged  with  glass 
wool  at  the  small  end,  or  for  larger  fish  in  similarly 
prepared  glass  tubing  of  appropriate  size.  The  fish 
were  dried  in  an  oven  at  65^0  to  constant  weight 
and  reweighed  to  obtain  dry  weight.  Each  fish  was 


20 


•••    ••••"^,    •,• 


w  *      V      A 


CO 


cPcP 


J^ 


"h 


J L 


20 


30  40  50  60 

STANDARD    LENGTH  (mm) 


Figure  2. — Increase  in  percent  fat  with  increase  in  length  for 
Stenobrachius  leucopsarus.  Dark  circles  equal  fat  as  a  percent  of 
dry  weight;  open  circles,  as  a  percent  of  wet  weight.  Fat  equals 
hexane  extractable  substances.  Pesticide  values  forfish  less  than  30 
mm  standard  length  (SL)  were  not  used  because  of  the  greater 
variation  in  these  values  than  in  larger  fish  in  which  fat  content  was 
more  stabilized. 


macerated  in  the  tube  and  extracted  into  a  15-ml 
graduated  centrifuge  tube  with  10  ml  of  hexane. 
The  remains  of  the  fish  in  the  pipet  were  dried  and 
reweighed  to  obtain  the  weight  of  material  ex- 
tracted. 

The  extract  in  the  centrifuge  tube  was  mixed  to 
uniformity,  and  an  aliquot  equal  to  20  mg  or  less  of 
fat  removed.  This  was  reduced  in  volume  if  neces- 
sary and  passed  through  an  activated  alumina 
column  as  described  by  McClure  (1972).  The 
cleaned  up  sample  was  again  reduced  in  volume  if 
necessary  and  injected  into  a  model  402  Hewlett 
Packard  gas  chromatograph  (GLC)  with  a  Ni^^ 
electron  capture  detector.  The  6-foot  glass  column 
contained  1.5%  OV-17/1.95%QF-l,  on  100/120 
mesh  Supelcoport. 

DDT  gets  its  name  from  its  former  chemical 
designation,  p,p'-dichlorodiphenyltrichloro- 
ethane.  The  current  chemical  designations  for 
DDT  and  its  metabolic  products  mentioned  in  this 
paper  are: 


p,p -DDT 

p,p -DDD  (TDE) 

p,p -DDE 

p,p, -DDMU 

Kelthane  (Dicofol) 


1 ,  l-dichloro-2,2-bis(p-chloro- 

phenyDethane 
l,l-dichloro-2,2-bis(p-chloro- 

phenyDethane 
l,l-dichloro-2,2-bis(p-chloro- 

pheny  1  )ethy  lene 
l-chloro-2,2-bis(p-chlorophe- 

nyl)ethylene 
l,l-bis(p-chlorophenyl)-2,2, 

2-trichloroethanol 


For  the  ortho-para  isomers  of  DDT,  DDD,  DDE, 
and  DDMU  substitute  2(o-chlorophenyl)-2-('p- 
chlorophenyl)  for  2,2-bisrp-chlorophenyl).  In  this 
paper  total  DDT  includes  p,p 'DDT,  o,p 'DDT, 
p,p 'DDD,  o,p 'DDD,  andp.p'DDE.  While o,p'DDE 
andp,p'DDMU  are  present,  although  not  as  major 
constituents  of  the  fish  samples,  both  have  the 
same  short  retention  times  on  the  column  used 
and  are  interfered  with  by  a  number  of  other  un- 
knowns as  tends  to  be  true  of  anything  having  a 
shorter  retention  time  than  p,p 'DDE  in  these 
samples;  therefore  they  were  omitted  because  of 
the  difficulty  in  identification  and  quantification. 
Kelthane  was  also  omitted  because  it  breaks  down 
on  this  column  (Morgan,  1967)  to  a  material  that 
has  a  low  response  and  an  even  shorter  retention 
time  than  DDMU. 

For  the  purposes  of  this  paper  we  assume  that 
DDT  is  metabolized  (O'Brien,  1967;  Morgan,  1967; 
Menzie,  1969)  as  follows: 


280 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 


DDT 


< 


DDE ^-(little  or  no  metabolism) 

DDD »-DDMU ►►(continued  metabolism) 

Kelthane—»-Dichlorobenzophenone— ♦-(continued  metabolism) 


Since  we  have  no  measurements  of  Kelthane,  the 
scope  of  this  paper  includes  only  the  measurement 
of  the  metabolism  of  DDT  to  DDE  and  DDD.  As 
mentioned  earlier,  the  effluent  from  the  Montrose 
plant  was  already  partly  metabolized  (Carry  and 
Redner,  1970).  In  seven  samples  taken  between  14 
August  and  24  November  1970,  the  total  DDT 
portion  of  the  effluent  contained  74%  (range 
62-84)  of  DDT,  5%  (3-7)  of  DDD,  and  21%  (9-35)  of 
DDE.  During  this  period  the  effluent  contained  2 
lb  or  less  of  DDT  per  day.  The  proportions  of  DDT, 
DDD,  and  DDE  at  the  time  when  dumping  was 
650  lb  (295  kg)  per  day  were  73:2:25. 

At  the  beginning  of  this  investigation  some  pes- 
ticides were  separated  on  other  columns  to  con- 
firm the  identification  of  DDT  and  its  metabolites. 
Additional  confirmation  was  obtained  by  dehy- 
drochlorinating  samples  with  alcoholic  KOH 
which  converts  DDT  and  DDD  to  their  respective 
ethylene  derivatives,  DDE  and  DDMU,  but  does 
not  change  the  PCB,  Aroclor  1254. 

Because  there  are  so  many  possible  sources  of 
variance  to  the  estimates  of  pesticide  content,  we 
cannot  obtain  a  precise  measure  of  this  error. 
Based  on  the  least  accurate  measurements  made 
in  the  course  of  analysis,  the  standard  error  of  the 
amount  of  pesticide  in  a  sample  should  be  about 
plus  or  minus  10% .  The  error  may  be  increased  by 
shortcomings  in  methodology  and  by  the  presence 
of  other  peaks  that  interfere  with  those  to  be  quan- 
tified. At  low  pesticide  values  the  error  increases, 
and  it  may  be  more  like  plus  or  minus  100%  at 
values  on  the  order  of  10  ppb.  However,  the  abso- 
lute error  is  only  a  few  parts  per  billion  also  and 
makes  little  difference  when  values  that  differ  by 
orders  of  magnitude  are  being  compared. 

In  the  myctophid  samples,  Aroclor  1254  seemed 
to  be  the  only  substance  that  contributed  peaks  on 
the  chromatogram  of  any  significance  which  could 
interfere  with  quantification  of  the  DDT  series. 
Six  Aroclor  1254  peaks  span  the  retention  time 
range  ofp,p'DDE,  o,p'DDD,  o,p'DDT,  p,p'DDD, 
andp,p'DDT  (Figure  3).  In  all  the  marine  sam- 
ples examined,  o,p 'DDT  and  o,p 'DDD  are  present 
in  either  very  small  quantities  or  not  detectable 
at  all  unless  the  samples  contain  very  large  quan- 
tities ofp,p'DDT  orp.p'DDD.  In  the  myctophid 
samples,  Aroclor  1254  seems  to  maintain  its  in- 


tegrity very  well.  There  is  no  apparent  selective 
breakdown  of  its  components,  and  the  pattern  of 
peaks  from  myctophid  samples  containing  this 
PCB  and  very  little  pesticide  closely  resemble  the 
Aroclor  1254  standard  (Figures  3  and  4). 


RETENTION  TIME    IN  MINUTES 

Figure  3. — A.  Aroclor  1254  standard;  column:  1.5% 
OV-17/1.95%  QF-1, 100/120  mesh  Supelcoport.B.  Sample  of  two 
Stenobrachius  leucopsarus  each  20  mm  standard  length  (SL)  taken 
in  July  195 1 .  at  CalCOFI  station  70. 100.  About  0.54  ppm  Aroclor 
1254  with  peak  no.  5  increased  slightly  by  0.2  ppm  DDE  and  peak 
no.  10  by  0.3  ppm  DDT.  Less  highly  chlorinated  Aroclor  peaks  no. 
1,  2,  and  3  may  be  breaking  down  in  the  environment;  more  highly 
chlorinated  peaks  (no.  4  through  10)  tend  to  maintain  their  integrity 
of  pattern.  Same  column  as  A.  C.  Standard  of  six  DDT  analogs. 
Same  column  as  A.  D.  Sample  of  a  33-mmS.  leucopsarus  taken  in 
November  1955  at  CalCOFI  station  83.40.  This  sample  contains 
2.3  ppm  total  DDT.  Because  of  the  high  DDT  content  of  this 
sample,  it  was  not  concentrated  as  much  as  sample  B.  It  probably 
contains  at  least  half  as  much  Aroclor  1254  as  sample  B.  Same 
column  as  sample  A. 


281 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


RETENTION  TIME    IN    MINUTES 

Figure  4. — A.  Aroclor  1254  standard;  column;  4%  SE-30/6% 
QF-1,  100/120  mesh  Supelcoport.  B.  Sample  of  a  28-mmS.  leucop- 
sarus  taken  in  November  1955  at  CalCOFI  station  83.55.  Aroclor 
1254,  4.2  ppm;  pesticides  not  measured.  Same  column  as  A.  C. 
Standard  of  six  DDT  analogs.  Same  column  as  A.  D.  Sample  of 
one  37-mm  S.  leucopsarus  taken  in  March  1954  at  CalCOFI  sta- 
tion 85.45.  1.0  ppm  total  DDT.  Same  column  as  A. 

It  is  apparent  (Figure  3)  that  the  seventh  of  the 
Aroclor  peaks  is  not  interfered  with  by  the  DDT 
series.  The  two  ortho-para  prime  peaks  bracket- 
ing it  are  generally  small  or  absent.  Therefore,  it 
may  be  used  to  correct  the  DDT  series  for  PCB 
interference  and  to  quantify  the  Aroclor  1254. 

An  estimate  of  peak  area,  peak  height  times 
width  at  one-half  peak  height,  was  used  in 
quantification.  Increasing  chart  speed  makes  it 
possible  to  measure  the  width  more  accurately. 
Peak  area  rather  than  peak  height  is  a  more  accu- 
rate measurement  of  the  combined  effects  of  two 
CHC  when  their  retention  times  are  about  the 
same.  Because  GLC  operating  conditions  may 
thange  gradually  during  a  sample  run,  one  pes- 
ticide standard  was  injected  for  every  two  samples 


Area  of 

Combined  peaks 

Aroclor 

p.p'DDE  +  Aroclor 

no.  5 

0.247 

p,p  DDD 

0 

o,p 'DDT  +  Aroclor 

no.  8 

0.547 

p,p 'DDD  +  Aroclor 

no.9 

0.737 

p.p' DDT  +  Aroclor 

no.  10 

0.957 

so  that  each  sample  would  have  an  adjacent  stan- 
dard for  quantification. 

To  correct  the  areas  of  the  combined  peaks  of  the 
DDT  series  and  Aroclor  1254  to  the  area  repre- 
senting pesticide  only,  we  letX  equal  the  area  of 
each  peak  at  the  respective  retention  time  of  each 
of  the  DDT  series  and  Y  equal  the  area  of  Aroclor 
peak  no.  7.  Then  for  our  operating  conditions  and 
Aroclor  standard,  the  areas  allotted  to  the  compo- 
nents were: 

Area  of 
DDT  series 

X- 0.247 
X 

X-  0.547 

X- 0.737 

X-  0.957 

An  estimate  of  Aroclor  1254  was  obtained  by  mul- 
tiplying the  area  of  the  no.  7  Aroclor  peak  by  12.3 
and  quantifying  against  the  area  of  thep,p'DDE 
standard,  or  multiplying  by  9.6  and  quantifying 
against  the  area  of  the  p,p 'DDT  standard.  The 
subtractive  corrections  for  the  DDT  series  were 
confirmed  in  part  for  a  few  samples  by  calculating 
values  both  before  and  after  dehydrochlorination 
with  alcoholic  KOH. 

In  a  few  samples  taken  far  from  the  sewer  out- 
fall and  in  the  earlier  years,  Aroclor  1254  was  high 
enough  to  mask  out  the  DDT  residues  except  for 
slight  increases  in  some  peak  areas  (Figure  3).  In 
such  cases  the  pesticides  were  present  in  such 
small  quantities  that  it  made  no  appreciable  dif- 
ference in  the  overall  results  what  small  values 
were  assigned  to  them.  The  illustrated  example  is 
an  extreme  case  of  masking. 

In  most  of  the  samples  the  DDT  residues  domi- 
nated the  PCB  peaks  and  over  the  range  of  the  six 
pesticide  standards  (Figure  3),  only  peaks  no.  6 
and  7  of  Aroclor  1254  were  evident.  If  DDT  re- 
sidues were  high,  peak  no.  6  was  evident  as  a 
widening  of  the  base  of  thep.p'DDE  peak  (Figure 
3). 

RESULTS  AND  DISCUSSION 

The  pattern  of  CalCOFI  stations  from  which  the 
samples  were  obtained  extends  across  the  north 
flowing  coastal  countercurrent  out  into  the  south 
flowing  California  Current  cutting  across  the 
counterclockwise  eddy  or  eddies  that  develop  be- 
tween the  two  currents.  At  a  depth  of  200  m  the 


282 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 


California  Current  is  usually  farther  offshore 
than  at  the  surface  (Wyllie,  1966).  In  April  and 
May  this  current  moves  inshore  eliminating  the 
countercurrent  at  the  surface  and  sometimes  at 
200  m.  When  the  California  Current  is  offshore, 
the  surface  countercurrent  develops;  when  it 
moves  onshore,  the  surface  countercurrent  is  ab- 
sent although  the  southern  California  eddy  usu- 
ally persists. 

The  currents,  and  consequently  the  distribution 
of  the  sewer  discharge,  are  influenced  locally  by 
such  factors  as  the  configuration  of  the  coast,  the 
presence  of  islands,  the  topography  of  the  ocean 
floor,  and  the  short  range  effects  of  winds  and 
tides. 

The  total  DDT  data  for  the  myctophids  were 
divided  into  four  time  periods,  and  the  average 
DDT  value  determined  for  all  specimens  taken  at 
each  station,  or  combined  stations  if  they  were 
very  close  together,  for  each  time  period  (Figures 
5-8).  The  total  DDT  content  of  the  fish  tended  to  be 
high  near  the  sewer  outlet  and  decreased  away 
from  the  outlet.  Total  DDT  values  increased  with 
the  passage  of  time. 

Total  DDT  for  the  purpose  of  this  discussion 
consists  of  DDT,  DDE,  and  DDD.  Although  total 
DDT  content  in  the  myctophids  increased  with 
time,  this  did  not  hold  true  for  each  of  the  three 
constituents.  DDT  increased  for  a  few  years  until 


metabolism  and  dispersion  equalled  input  and 
then  leveled  off.  DDD  acted  in  a  similar  manner 
but  at  a  lower  level.  Most  of  the  increase  in  total 
DDT  after  the  first  few  years  was  caused  by  the 
increase  in  the  persistent  metabolite,  DDE.  The 


ColCOFI     STATION    NUMBERS 


Figure  6. — Average  total  DDT  at  CalCOFI  stations  off  southern 
California  for  the  4  yr  1953-56. 


s 

3 


97.80        .75  70  .65  .60         ,55  50  .45  40  .35       50 


CalCOFI     STATION    NUMBERS 


CalCOFI    STATION  NUMBERS 


Figure  5. — Average  total  DDT  at  CalCOFI  stations  off  southern 
California  for  the  3  yr  1950-52. 


Figure  7.— Average  total  DDT  at  CalCOFI  stations  off  southern 
California  for  the  4  yr  1957-60. 


283 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


s 

Z 


9780       .75         .70  .65  .60         .55  50  45  10  35        .30 


ColCOFI     STATION  NUMBERS 


Figure  8. — Average  total  DDT  at  CalCOFI  stations  off  southern 
California  for  the  6  yrl%  1-66. 


increase  inp,p'DDE  relative  top,p'DDT  for  the 
years  1950-51  through  1965-66  in  the  myctophids 
was: 


Year 

Ratio  of  DDE  to  DDT 

1950-51 

0.33:1.00 

1952-53 

0.36:1.00 

1954-55 

0.69:1.00 

1956-57 

1.06:1.00 

1959-60 

1.14:1.00 

1961-62 

2.02:1.00 

1963-64 

2.39:1.00 

1965-66 

3.96:1.00 

(1970) 

(4.74:1.00) 

(1972) 

(8.80:1.00) 

These  data  show  a  12-fold  increase  in  the  amount 
of  DDE  relative  to  DDT  from  1950-51  to  1965-66. 
The  ratio  for  the  fish  taken  in  1970,  65-70  nautical 
miles  southeast  of  the  sewer  outlet  (in  La  Jolla 
Canyon)  indicates  a  continuing  increase  in  the 
ratios,  although  there  were  only  two  fish  in  the 
sample.  The  1972  sample,  consisting  of  only  five 
myctophids,  was  taken  west  of  Santa  Catalina 
Island  and  about  25-30  nautical  miles  south 
southwest  of  the  sewer  outfall  about  2  yr  after  the 
dumping  of  DDT  into  the  sewer  system  had 
stopped.  The  high  ratio  may  reflect  in  part  con- 
tinued metabolism  of  DDT  without  replenish- 
ment. 


Because  there  are  no  data  on  the  amount  of  DDT 
discharged  into  the  ocean  through  the  White  Point 
sewer  outfall  each  year,  I  have  assumed  that  it 
was  constant  and  discharged  continuously 
throughout  the  year.  Under  these  circumstances 
the  amount  of  DDE  (and  DDD)  entering  the 
marine  environment  should  gradually  have  in- 
creased in  the  earlier  years  until  the  input  of  DDT 
equalled  the  amount  of  DDT  metabolized,  when 
the  input  of  DDE  (and  DDD)  would  also  be  con- 
stant. This  is  indicated  by  the  initial  slower  in- 
crease in  ratios  of  DDE  to  DDT. 

If  we  assume  that  the  same  amount  of  pesticide 
is  released  into  an  environment  each  year  and 
that  it  is  released  continuously  throughout  the 
year  we  may  empirically  represent  the  accumula- 
tion of  the  pesticide  in  the  environment  by  the 
formula 

Y  =Ka  -S^) 

in  which  Y  equals  the  amount  of  pesticide  accumu- 
lated at  the  end  ofX  years; /^  equals  the  maximum 
amount  of  pesticide  that  could  be  accumulated  by 
the  organism  under  the  prevailing  conditions;  and 
S  equals  the  "survival"  rate  of  the  pesticide  for  1 

yr- 

In  some  of  the  years  from  1949  to  1966,  Cal- 
COFI cruises  were  limited,  and  fewer  samples 
were  taken.  Also  the  fish  were  not  uniformly  sam- 
pled with  respect  to  distance  from  the  sewer  out- 
fall in  each  of  the  years.  But,  by  averaging  the 
p,p' DDE  content  of  all  fish  taken  in  each  year  and 
grouping  years  by  twos,  a  rough  indication  of  the 
increase  in  p,p 'DDE  was  obtained  to  compare 
with  theoretical  values  of  the  formula,  Y  =  K 
(1  -  SX)  (Figure  9). 

The  almost  linear  increase  inp,p'DDE  indicates 
that  its  metabolism  is  very  low.  In  fact, 
metabolism  in  this  case  would  include  p,p' DDE 
lost  by  removal  from  the  area  under  study,  and, 
therefore,  the  data  indicate  that  very  little  was 
lost  from  this  area  during  the  years  in  which 
dumping  occurred. 

Because  of  the  apparent  lack  of  metabolism  of 
p,p' DDE,  this  metabolite  of p,p 'DDT  should  give 
the  best  picture  of  areal  and  temporal  buildup  of  a 
CHC  in  the  ocean  as  a  result  of  the  sewer  dis- 
charge. 

Data  on  p,p'DDE  content  of  the  myctophids, 
year  of  capture  (with  1949  equal  to  year  1),  and 
distance  in  nautical  miles  from  the  sewer  outlet  to 
the  place  of  capture  were  fitted  to  the  formula: 


284 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 


Figure  9. — Increase  in  p,p' DDE  in  the  ocean  off  southern 
California,  1949-70.  The  points  are  averages  of  all  stations  com- 
bined in  2-yr  groupings.  Because  the  same  patterns  of  stations  were 
not  run  each  year,  myctophids  were  not  obtained  from  the  same 
stations  or  the  same  number  of  stations  each  year.  Also  pesticide 
concentrations  were  more  dependent  on  distance  from  the  point 
source  of  contamination  than  on  year.  This  makes  the  coarse  group- 
ing of  data  necessary  when  increase  in  DDE  with  time  only  is 
considered.  The  two  theoretical  lines  are  computed  to  the  formula 
Yf.  =  K(\-S^).  in  which  Yc  =  computed  value  ofp.p'DDE,  K  = 
value  at  which  metabolism,  excretion,  and  dispersal  of  DDE  equals 
input,  S  =  survival  of  DDE  for  1  yr,  and  X  =  year  with  1949 
considered  as  year  no.  1.  The  data  indicate  thatp.p'DDE  is  very 
stable.  For  the  98%  survival  curve,  which  more  closely  fits  the  data. 
90%  of  the  equilibrium  value  would  not  be  attained  for  1 14  yr. 


log  y  =  log  a  +  6  log  X  +  c  log  X' 

in  which  Y  =  calculated  value  of  DDE  in  parts  per 
billion,  X  =  distance  from  sewer  outfall  in  nauti- 
cal miles,  andX'  =  year.  The  data  were  grouped 
for  greater  ease  of  computation  and  to  minimize 
individual  variations  which  tend  to  distort  the 
actual  values  transformed  from  log-log  calculated 
values  if  not  minimized  by  averaging. 

The  values  determined  for  the  above  equation 
are: 

log  a  3.054 

6  (distance)    -1.062  (SE  0.057) 

c  (year)  1.423  (SE  0.122) 

The  correlation  coefficients  are: 


multiple 
partial  (6) 
partial  (c) 


0.978 

-0.829 

0.522 


all  of  which  are  significant  atP  of  less  than  0.001. 


The  computed  lines  did  not  fit  the  data  for  1949, 
1950,  and  1951  very  well.  These  years  were  left 
out  of  the  calculations  because  the  input  of  DDE 
was  rising  relatively  rapidly  at  this  time  and  did 
not  begin  to  stabilize  until  about  1953.  Also  in 
these  earlier  years,  the  influence  of  the  sewer  dis- 
charge of  pesticide  extended  out  to  only  about  100 
nautical  miles  from  the  outfall.  In  the  following 
years  the  influence  of  the  sewer  discharge  in- 
creased rapidly  to  between  300  and  400  nautical 
miles  from  the  outfall  before  becoming  indistin- 
guishable from  the  ocean  background.  Although 
there  are  no  extensive  data  for  any  one  station 
throughout  the  period  under  study,  we  can  now 
calculate  values  for  a  theoretical  station  20  nauti- 
cal miles  from  the  sewer  outfall  from  the 
DDE-time-distance  formula  and  in  conjunction 
with  the  observed  changes  in  ratios  among  the 
various  DDT  analogs,  obtain  a  description  of  the 
metabolism  of  DDT  in  the  marine  environment  as 
reflected  in  the  myctophid  fish,  S.  leucopsarus. 

Because  o,p'DDE  was  not  quantified,  we  used 
onlyp,/?  'DDE,  p,p  'DDT,  and  p,p  'DDD  in  the  ratios. 
In  more  than  300  myctophids  30  mm  or  longer  in 
standard  length  in  which  the  above  three  con- 
stituents and  o,p  'DDT  and  o,p  'DDD  were  measur- 
able, o,p'DDT  and  o,p'DDD  averaged  22.3%  of 
p,p'DDT  and p,p 'DDD.  In  samples  of  commercial 
DDT  that  were  tested  o,p 'DDT  averaged  about 
25%  of  p,p 'DDT. 

From  the  calculated  values  of  DDE  and  ratios  of 
DDE  to  DDT,  we  can  calculate  that  at  our 
theoretical  20  mile  station  DDT  accumulates  in 
the  fish  up  to  1.077  ppm  when  input  equals 
metabolism.  From  this  we  may  calculate  that: 

Yt   =  1.077(1  -  0.708^) 

in  which  Y,  equals  calculated  p,p' DDT  and  X 
equals  the  year  with  1949  equal  to  year  1.  From 
the  values  obtained  (Table  1,  Figure  10)  we  may 
recalculate  values  for  DDE.  These  values  remain 
essentially  the  same  as  those  calculated  from  the 
DDE-time-distance  formula  for  the  later  years 
but  make  allowances  for  lower  input  from  DDT  for 
the  earlier  years  if  we  use  the  formula: 

2.0467^   =  0.368X  -  1.077  +  1.077(0.708^) 
or  Ye    =  0.18QX  -  0.526  +  0.526(0.708^) 

in  which  Ye  -=  calculated  p,p 'DDE  andX  equals 
the  year  and  in  which  we  assume  that  there  is  no 
further  metabolism  of  DDE. 


285 


FISHERY   BULLETIN:  VOL.   72.  NO.  2 


CC 
LU 
Q- 

t— 
cr 

Q. 


3.5- 


3.0 


2.5 


2.0 


1.5 


1.0 


0.5 


0.0"- 


DDE 

DDT 

-DDD 


•/ • ^ 


•  • 


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I'll 


1950 


1955 


i-r,- 


I    '    I   I    I   I   I 


■■■A 


I    I     I     I 


I960 
YEAR 


1965 


1970 


Figure  10.— Trends  of  p.p'DDE  (squares),  p.p'DDT  (circles), 
and  p.p'DDD  (triangles)  in  the  ocean  off  southern  California, 
1949-72,  at  a  theoretical  station  20  nautical  miles  from  the  point 
source  of  pesticide  contamination.  Computed  lines  show  persistant 
DDE  increasing  until  dumping  of  DDT  wastes  ceased  in  1970. 
Both  DDT  and  DDD  increase  for  several  years  and  then  level  off 
when  metabolism,  excretion,  and  dispersion  equal  input.  Points  are 
based  on  calculated  total  value  of  the  three  analogs  distributed 
among  them  on  the  basis  of  the  observed  ratios  of  the  three  analogs 
to  each  other  for  each  year.  The  1972  ratios  were  affected  by  sewer 
cleaning  operations  that  caused  large  quantities  of  DDD  to  enter 
the  ocean. 

From  the  calculated  values  of  DDT  and  the 
DDD:DDT  ratios  we  may  estimate  values  for 
DDD.  From  these  it  appears  that  DDD  accumu- 
lates in  the  fish  up  to  0.303  ppm  where  input 
equals  metabolism.  From  this  we  may  calculate 
that  Frf  =  0.303(1  -  0.525^).  However,  this  for- 
mula is  based  on  a  constant  input  equivalent  to 
0.189  ppm.  The  actual  input  from  metabolism  of 
DDT  was  only  0.028  ppm  the  first  year  and  in- 
creased to  0.181  by  the  10th  year,  and  0.188  by  the 
20th  year.  By  adjusting  for  these  increasing  in- 
puts we  obtain  accumulative  values  for  DDD,  for 
DDMU,  and  other  metabolites  of  DDD  (Table  2, 
Figure  10). 


The  percent  distribution  of  total  DDT  among 
p,p'DDT,p,p'DDE,  andp,p'DDD  did  not  appear  to 
change  in  myctophids  with  distance  from  the 
sewer  outfall.  Therefore  the  percent  distribution 
which  is  based  on  large  numbers  of  fish  in  most 
years  can  be  used  to  prorate  the  total  p.p'DDT 
obtained  from  the  curves  to  obtain  "observed"  val- 
ues ofp,p'DDT,p,p'DDE,  andp.p'DDD  (Table  1, 
Figure  10).  Both  the  curves  and  their  observed 
values  are  based  on  observed  percent  changes  in 
the  composition  of  total  DDT  transformed  to  ppm 
values  of  the  three  constituents  at  a  theoretical 
station  20  nautical  miles  from  the  sewer  outfall. 

It  should  be  emphasized  that  the  above  descrip- 
tion of  metabolism  is  only  an  indication  of  what  is 
taking  place  in  the  ocean.  It  neither  describes  the 
metabolism  of  DDT  in  the  myctophid  fish  nor  the 
metabolism  in  the  marine  environment,  but 
rather  refiects  selective  storage  of  DDT  and  its 
environmental  metabolites  in  one  species  offish. 

Three  factors  determine  the  amount  of  CHC 
found  in  myctophid  fishes:  1)  The  CHC  present  in 
the  fish's  environment  during  its  brief  life  span;  2) 
the  selective  absorption  of  CHC  through  the  gills 
and  the  ingestion  of  selected  food  particles;  3)  and 
the  selective  storage,  metabolism  and  excretion  of 
CHC.  Factors  2  and  3,  above,  should  remain  con- 
stant for  each  generation  of  fish.  Therefore,  the 
changes  in  composition  of  total  DDT  probably 
reflect  changes  occurring  in  the  environment. 
However,  the  percent  composition  found  in  the 
myctophids  may  not  represent  the  percent  com- 
position in  the  environment  because  of  the  selec- 
tive nature  of  intake  and  excretion. 

Some  of  the  DDT  was  changed  to  DDE  and  DDD 
before  entering  the  ocean.  Sixteen  samples  of 
sewer  discharge  from  the  Montrose  Chemical 
Corporation  taken  between  14  August  1970,  and 
12  May  1971,  averaged  74%DDT,  209^^ DDE,  and 
6%DDD  (Redner  and  Payne,  1971).  Although 
these  samples  represented  discharges  averaging 
less  than  0.5  lb  (0.23  kg)  a  day,  samples  taken 
earlier  in  1970  when  dumping  was  estimated  at 
640  lb  (290  kg)  per  day  also  had  ratios  of  73:25:2. 
These  percent  ratios  are  very  much  like  the 
74:23:2  distribution  in  the  myctophids  in  1949  and 
the  70:23:7  distribution  in  1950. 

Although  some  DDT  was  converted  to  DDD  and 
DDE  before  it  left  Montrose,  most  of  the 
metabolism  took  place  after  it  was  discharged 
from  the  plant.  This  is  indicated  by  the  percent 
distribution  of  DDT,  DDE,  and  DDD  in  the  myc- 
tophids in  1970,  16:75:9,  by  the  bottom  fish  taken 


286 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 


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287 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


in  Santa  Monica  Bay  in  1970,  8:87:6,  and  by  a 
bottom  sediment  sample  taken  near  the  sewer  out- 
fall in  1971, 6:82: 12.  Samples  of  sewer  water  taken 
in  1970  that  derived  their  DDT  content  from  sewer 
sediments  had  ratios  of  14:38:48  (Redner  and 
Payne,  1971). 

A  few  specimens  of  another  myctophid, 
Triphoturus  mexicanus,  also  showed  a  change  in 
CHC  ratios  with  time.  Twenty-one  specimens 
taken  between  1950  and  1959  contained  an  aver- 
age of  699'f  DDT,  99f  DDD,  and  22*7^ DDE,  while  12 
specimens  taken  between  1961  and  1970  con- 
tained 23% DDT,  15%DDD,  and  62% DDE.  These 
fish  were  taken  between  Los  Angeles  and  south- 
ern Baja  California  (lat  26°20'N).  This  species  has 
a  more  southern  distribution  than  Stenobrachius 
leucopsarus,  and  therefore  the  population  was  less 
influenced  by  the  sewer  discharge. 

One  might  expect  that  DDE  would  be  more 
abundant  in  samples  taken  farther  from  the  sewer 
outfall,  indicating  older  deposits,  but  this  is  not 
the  case.  The  proportions  are  very  similar  in  all 
samples,  even  those  taken  outside  of  the  influence 
of  the  sewer.  For  the  fish  samples  taken  in  1969-70 
for  the  survey,  the  percentages  are  given  in  Table 
3. 

Each  sample  contained  several  fish  of  the  same 
species,  and  only  the  livers  were  tested.  Where  the 


Table  3.— Distribution  of  p.p'DDE,  p.p'DDD,  and  p.p'DDT  in 
fish  samples  by  area  taken,  1969-70. 


Number 

of 
samples 

Percent 

as 

Location 

DDE 

DDD 

DDT 

Southern  Baja  California 

8 

80.6 

8.9 

10.5 

Sebastian  Vizcaino  Bay 

3 

74.2 

8.8 

17.0 

Cortez  Bank 

4 

86.5 

4.7 

8.8 

Southern  California  coast 

6 

86.0 

5.1 

8.9 

Farnsworth  Bank 

6 

86.9 

5.6 

7.5 

Santa  Monica  Bay 

8 

86.6 

5.8 

7.6 

pesticide  levels  were  very  high,  the  proportions 
were  remarkably  similar  among  samples.  For  the 
eight  Santa  Monica  Bay  samples,  the  DDE  ranged 
from  85.2  to  87.7%,  DDD  from  5.1  to  6.6%,  and 
DDT  from  5.7  to  9.1%. 

The  high  proportions  of  DDE  relative  to  DDT 
and  DDD  seem  to  be  typical  of  fishes,  porpoises, 
and  crustaceans  in  the  ocean  off  southern  Califor- 
nia (Tables  4  and  5).  In  six  adult  pelicans  taken  on 
Anacapa  Island  in  1969  (Keith  et  al.,  1970),  DDE 
made  up  99%  of  the  total  DDT  found  in  the  fat,  and 
93%  in  eggs  taken  at  the  same  time.  Lament, 
Bagley,  and  Reichel  (1970)  tested  10  pelican  eggs 
from  the  same  place  and  year  and  found  that  DDE 
constituted  96%  of  the  total. 

Stout  (1968)  gives  data  for  17  samples  repre- 
senting seven  species  of  marine  fishes  taken  off 
Washington  and  Oregon.  In  these,  DDE  averaged 


Table  4. — Percent  distribution  of  total  DDT  and  ratio  of  DDD  to  DDT  in  rockfishes  and 
sablefish  from  Santa  Monica  Bay.  Major  dumping  of  DDT  wastes  into  sewer  system  stopped  in 
April  1970.  Samples  of  May  1970  and  August  1971  are  averages  of  five  separate  samples  each 
for  fat,  liver,  and  flesh.  In  each  of  these  15  samples  the  ratio  of  DDE  to  DDT  was  greater  than 
one. 


Percent 

Total 

distributior 

Ratio 

Part 
tested 

DDT 
(ppm) 

Species 

DDE 

DDD 

DDT 

DDD;DDT 

May  1970; 

Sebastes  paucispinis 

Liver 

519.0 

86.3 

5.6 

8.1 

0.69:1.00 

S.  paucispinis 

Flesh 

11.6 

80.6 

8.8 

10.6 

.82 

S.  miniatus 

Liver 

162.0 

87.0 

5.6 

7.4 

.75 

S.  miniatus 

Flesh 

16.0 

92.3 

trace 

7.7 

.0? 

S.  constellatus 

Liver 

1,026.0 

87.7 

5.5 

6.8 

.80 

S  constellatus 

Flesh 

57.2 

88.2 

5.5 

6.3 

.86 

S.  constellatus 

Fat 

2,588.0 

85.0 

7.0 

8,0 

.87 

Anoplopoma  fimbria 

Liver 

103.0 

87.3 

5.8 

6.9 

.85 

A.  fimbria 

Flesh 

23.4 

81.2 

10.1 

8.7 

1.15 

August  1971: 

S.  paucispinis  and 

S.  mystmus 

Liver 

156.0 

84.0 

10.3 

5.7 

1.78 

A.  fimbna 

Liver 

38.0 

84.2 

12.9 

3.9 

4.45 

January  1972: 

S.  paucispinis 

Liver 

17.0 

78.5 

15.5 

6.0 

2.58 

S.  paucispinis 

Flesh 

.20 

81.4 

12.7 

5.9 

2.15 

S.  paucispinis 

Fat 

115.0 

78.8 

16.1 

5,1 

3.15 

August  1971: 

Bottom  sample 

Mud 

82.0 

72.0 

6.0 

2.00 

288 


MacGREGOR:    AMOUNT  AND  PROPORTIONS  OF  DDT 

Table  5. — Distribution  ofp.p'DDE.p.p'DDD  andp.p'DDT  in  various  animals  from  southern  California  marine  waters.  Porpoises 
found  dead  on  beach  north  of  San  Diego,  various  dates  May  1970.  Fishes  and  crustaceans  taken  in  net  haul  in  San  Pedro  Channel 
4  August  1971. 


Organ 
tested 

Standard 
length 
(mm) 

Wet 
weight 

(g) 

Total 
DDT 

Percent 

as 

Species 

(ppm) 

DDE 

DDD 

DDT 

Porpoises: 

Lagenorhynchus  obliquidens 

flesh 

84. 

92.0 

2.3 

5.7 

Delphinus  sp. 

flesh 

208. 

86.5 

58 

7.7 

Delphinus  sp 

flesh 

31. 

85.0 

7.2 

7.8 

Delphinus  sp. 

liver 

44. 

90.7 

4.8 

4.5 

Delphinus  sp. 

liver 

300. 

92.0 

4.0 

4.0 

Delphinus  sp. 

head  oil 

196. 

898 

2.6 

7.6 

Delphinus  sp. 

blubber 

497. 

88.5 

3.4 

8.1 

Fishes: 

Leuroglossus  stilbius 

whole 

84 

5.20 

.49 

75.9 

11.6 

12.4 

Melanostigma  pammelas.  eelpout 

whole 

89 

2.40 

5.63 

87.9 

2.7 

9.4 

Argyropelecus  sp..  hatchetflsh 

whole 

30 

.50 

.09 

49.5 

7.6 

42.9 

Cyclothone  acclinidens 

whole 

48 

.36 

2.01 

80.7 

4.7 

14.6 

Cyclothone  acclinidens 

whole 

43 

.37 

.64 

76.1 

6.9 

17.0 

Cyclothone  acclinidens 

whole 

47 

.39 

2.46 

83.2 

5.9 

10.9 

Cyclothone  acclinidens 

whole 

38 

.18 

3.56 

89.5 

4.5 

6.0 

Cyclothone  acclinidens 

whole 

34 

.15 

1.55 

84.9 

8.5 

6.6 

Crustaceans: 

Gnathophausia  gigas.  pelagic  mysid 

whole 

.42 

.55 

76.7 

7.2 

16.1 

Sergestes  sp. 

whole 

.64 

4.38 

85.1 

6.1 

8.8 

Sergestes  sp. 

whole 

.38 

4.59 

82.9 

6.1 

11.0 

Nematoscelis  sp..  euphauslld 

whole 

.019 

.35 

90.3 

4.3 

5.4 

Nematoscelis  sp..  euphauslld 

whole 

.043 

.26 

90.2 

3.0 

4.9 

52%  (26-81),  DDD  20%,  and  DDT  28%  of  total 
DDT. 

Keith  and  Hunt  (1966)  list  DDT  content  for 
samples  of  mammals,  birds,  and  freshwater  fishes 
taken  throughout  California.  The  proportion  of 
DDE  tends  to  be  high  in  categories  that  include 
birds  of  prey  and  fish  eating  birds,  but  varies  con- 
siderably in  their  other  samples.  In  their  warm- 
water  fish  samples  and  the  fish  eating  birds,  white 
pelican,  western  grebe,  and  common  egret,  DDD  is 
unusually  high.  This  may  be  because  of  the  former 
use  of  DDD  as  a  spray  on  some  California  lakes 
(Murphy  and  Chandler,  1948;  Brydon,  1955;  Hunt 
and  Bischoff,  1960). 

Following  the  cessation  of  DDT  dumping  into 
the  ocean  off  Los  Angeles  in  1970,  a  change  oc- 
curred in  the  DDD:DDT  ratios  found  in  fish  sam- 
ples. The  five  S.  leucopsarus  taken  in  April  1972 
contained  79%  DDE,  12% DDD,  and  9% DDT.  Each 
of  the  five  specimens  contained  more  DDD  than 
DDT.  In  the  period  1949-70,  only  8  out  of  more 
than  500  S.  leucopsarus  tested  contained  more 
DDD  than  DDT.  The  five  myctophids  taken  in 
April  1972  ranged  from  40  to  50  mm  SL,  indicat- 
ing that  most  or  all  of  their  growth  had  taken  place 
since  dumping  stopped  in  1970. 

The  shift  in  DDD:DDT  ratios  also  appeared  in 
some  other  species.  The  ratios  in  rockfishes  and 
sablefish,  Anoplopoma  fimbria,  taken  in  Santa 


Monica  Bay  in  May  1970,  indicated  that  DDT  was 
more  abundant  than  DDD  while  15  and  20  mo 
later  the  reverse  was  true  (Table  4,  Figure  11). 
The  pelagic  crustaceans  and  fish  taken  in  the 
midwater  trawl  in  August  1971  (Table  5)  did  not 
show  the  increased  DDD  to  DDT  ratio  as  did  the 
bottom  fish  taken  at  that  time,  or  the  five  S. 
leucopsarus  taken  in  April  1972.  A  mud  sample 
taken  in  August  1971  (Table  4,  Figure  12)  about  3 
nautical  miles  from  the  White  Point  sewer  outfall 
contained  about  twice  as  much  DDD  as  DDT. 

The  work  of  Burnett  (1971)  on  DDT  residues  in 
the  sand  crab  along  coastal  California  showed  that 
the  high  ratios  of  DDD  to  DDT  were  a  local  condi- 
tion. Twelve  samples  taken  in  November  1970  and 
February  197 1  from  eight  stations  on  either  side  of 
the  White  Point  sewer  outfall  between  33°22'N 
and  34°28'N  contained  more  DDD  than  DDT  in  all 
but  two  samples.  The  11  stations  north  and  south 
of  this  area  all  contained  less  DDD  than  DDT.  The 
four  samples  taken  closest  to  the  outfall  averaged 
more  than  three  times  as  much  DDD  as  DDT. 

This  shift  in  DDD:DDT  ratios  was  undoubtedly 
caused  by  the  deposits  in  the  sewer  system. 
CSDLAC  cleaning  operations  started  in  De- 
cember 1970,  and  ended  in  July  1971.  Although 
large  quantities  of  these  deposits  were  removed 
directly  from  the  sewers,  additional  large  quan- 
tities were  moved  through  the  system  to  the  White 


289 


FISHERY   BULLETIN;  VOL.  72.  NO.  2 


RETENTION   TIME    IN    MINUTES 

Figure  1 1. — Chromatogram  of  DDT  analog  standard  and  of  a  fat 
sample  from  Sebastes  paucispinis  taken  in  Santa  Monica  Bay  7 
January  1972.  p.p'DDE  (98  ppm)  is  off  scale.  Following  cessation 
of  dumping  of  DDT  wastes  and  flushing  out  of  sewer  lines  in  1970, 
p.p'DDD  (15  ppm)  has  exceeded p,p' DDT  (6.1  ppm)  in  most  fish 
specimens  tested.  Prior  to  cessation  of  dumping  and  flushing  of 
sewer  lines,  DDT  was  almost  always  present  in  greater  quantities 
than  DDD. 

Point  plant  and  out  into  the  ocean.  Sewer  water 
from  these  deposits  contained  48%  DDD  as  op- 
posed to  2-6%  in  the  original  Montrose  discharges, 
and  although  the  total  amount  of  DDT  and  its 
metabolites  was  much  less  than  before  April  1970, 
the  total  amount  of  DDD  entering  the  ocean  ap- 
peared to  be  several  times  greater  than  it  had  been 
before  the  dumping  stopped  in  April.  This  would 
account  for  the  increase  in  DDD  in  the  myctophids 
taken  in  1972  rather  than  the  expected  decrease 
indicated  by  the  calculated  line  (Figure  10,  Table 
1).  A  mud  sample  taken  from  the  ocean  floor  a  few 
miles  from  the  sewer  outfall  in  July  1971,  just 
after  the  sewer  cleaning  operations  ceased  con- 
tained 6%DDT,  82%  DDE,  and  12%  DDD  (Figure 
12).  This  compares  favorably  with  the  myctophids 
taken  in  April  1972,  9:79:12,  and  the  S.  pauci- 
spinis fat  samples  (Figure  11)  taken  in  January 
1972,  5:79:16,  and  indicates  that  the  fish  reflect 
the  values  of  these  analogs  in  the  environment 
fairly  well. 


8        9        10 
RETENTION    TIME    IN    MINUTES 

Figure  12. — Chromatogram  of  DDT  analog  standard  and  sample 
of  mud  from  the  ocean  floor  in  the  Los  Angeles  area  taken  in  August 
1971,  16  mo  after  most  dumping  of  DDT  wastes  stopped.  DDD 
greatly  exceeds  DDT.  This  may  have  resulted  from  the  sewer 
cleaning  operations,  or  it  may  have  been  the  condition  existing 
before  and  merely  reflect  what  the  biota  can  excrete  more  easily.  In 
the  Sebastes  chromatogram  (Figure  11),  the  o.p'DDE  peak  is 
within  the  limits  of  the  right  proportions  top.p'DDE  for  it  to  be 
considered  o.p'DDE.  In  the  mud  sample  it  is  much  too  high  and 
may  be  DDMU  (a  metabolite  of  DDD)  which  has  the  same  reten- 
tion time  on  this  column  as  o.p'DDE. 

The  most  noticeable  difference  between  the  pes- 
ticide metabolites  in  the  fish  (Figure  11)  and  the 
mud  (Figure  12)  were  the  two  prominent  peaks 
preceding  p.p'DDE.  The  peak  at  the  locus  of 
o,p'DDE  also  may  contain  DDMU,  a  metabolite  of 
DDD.  The  other  peak  could  be  a  metabolite  of 
Kelthane.  However,  several  dozen  additional  mud 
samples  tested  subsequently  did  not  contain  these 
peaks  except  for  expected  amounts  of  o,p 'DDE. 
The  mud  sample  (Figure  12)  was  run  while  we 
were  experimenting  with  methods  of  determining 
pesticide  content  of  the  mud  samples.  The  subse- 
quent samples  were  run  after  we  had  settled  on  a 
different  method  that  gave  maximum  recovery  of 
DDT,  DDD,  and  DDE  without  special  regard  to 
other  CHC.  These  subsequent  mud  samples 
yielded  chromatograms  almost  identical  with 
those  offish  and  other  biological  samples  from  the 
same  general  area. 


290 


MacGREGOR:  AMOUNT  AND  PROPORTIONS  OF  DDT 


There  was  also  a  large  decrease  between  May 
1970  and  January  1972,  in  total  pesticides  in  the 
fish  taken  in  Santa  Monica  Bay  (Table  4).  The  S. 
paucispinis  taken  in  1972  were  smaller  than  those 
taken  in  1970  which  may  account  in  part  for  the 
lower  values.  The  five  specimens  taken  in  January 
1972,  averaged  312  mm  total  length.  Phillips 
(1964)  gives  the  total  length  of  this  species  at  age  2 
as  267  mm  and  at  age  3  as  343  mm.  Thus,  most  of 
the  growth  of  these  specimens  had  taken  place 
since  dumping  stopped. 

On  land  where  soil  has  been  subjected  to  DDT 
spraying  for  long  periods  of  time,  the  situation  is 
very  different.  In  New  York  State  vineyard  soils 
(Kuhr,  Davis  and  Taschenberg,  1972)  the  residues 
consisted  of  73%  DDT  and  27%  DDE  after  24  yr  of 
spraying  with  DDT.  In  Oregon  (Kiigemagi  and 
Terriere,  1972)  samples  of  soil  from  one  orchard 
contained  80%DDT,  17%DDE,  and  3%DDD  after 
25  yr  of  spraying,  while  soil  samples  from  another 
orchard  in  a  different  area  contained  78%  DDT, 
14% DDE,  and  8%  DDD  after  24  yr.  Forests  in  New 
Brunswick,  Canada  (Yule,  1973)  were  sprayed 
heavily  from  1956  to  1967  in  which  year  spraying 
with  DDT  ceased.  Many  samples  taken  of  soils  in 
this  area  in  1968  contained  92% DDT  and  8%  DDE. 
Three  years  later  a  second  sampling  of  the  soils  in 
the  same  locality  contained  90%  DDT  and 
10% DDE.  DDD  was  present  only  in  trace  amounts 
in  both  sampling  years. 

As  a  general  rule  soil  samples  from  land  areas 
that  have  been  sprayed  with  DDT  tend  to  contain 
a  much  higher  proportion  of  DDT  than  DDE  or 
DDD  even  after  many  years.  This  is  not  neces- 
sarily true  of  the  fauna  that  inhabit  the  land  un- 
less their  contamination  is  the  result  of  recent 
spraying.  Keith  and  Hunt  (1966)  give  examples  of 
a  number  of  species  of  mammals  and  birds  in 
which  the  proportions  of  the  three  analogs  vary 
greatly. 

Within  some  species  of  birds,  which  are  more 
wide  ranging  than  mammals,  there  seems  to  be 
remarkable  uniformity  in  the  proportions  of  the 
three  analogs.  Martin  and  Nickerson  ( 1972 )  tested 
125  10-bird  samples  of  starlings  from  throughout 
the  (48)  United  States.  These  samples  averaged 
91%DDE,  3% DDD,  and  6% DDT.  Although  the 
total  residues  ranged  from  0.05  to  15  ppm,  in  only 
two  samples  did  the  amount  of  DDD  exceed  DDT, 
and  in  only  one  did  the  amount  of  DDT  exceed 
DDE. 

The  proportions  of  the  three  analogs  of  DDT  in 
the  starlings  is  very  similar  to  the  proportions 


found  in  the  fish  taken  in  Santa  Monica  Bay  in 
1970  (Table  4),  in  the  porpoises  found  dead  on  the 
beach  in  1970,  and  the  small  fishes  and  inverte- 
brates taken  off  Los  Angeles  in  the  mid-water 
trawl  in  1971  (Table  5).  And,  in  fact,  except  in 
cases  of  recent  contamination  by  DDT,  most  fauna 
have  tended  to  approach  these  proportions  in  re- 
cent years.  This  is  in  spite  of  the  fact  that  soil 
samples  from  areas  of  land  that  have  long  his- 
tories of  spraying  with  DDT  almost  without  excep- 
tion contain  very  high  proportions  of  DDT.  From 
this  it  would  appear  that  the  selective  storage, 
metabolism,  and  excretion  of  DDT  is  somewhat 
similar  for  all  animals. 

When  investigators  first  became  aware  of  the 
pesticide  problem,  methods  of  measuring  residues 
were  considerably  less  refined  than  they  are  at 
present,  and  few  samples  were  run.  Very  little 
work  has  been  done  on  preserved  specimens  from 
these  earlier  years.  But,  in  view  of  the  similarity 
in  proportions  of  DDE  and  DDT  in  so  many  differ- 
ent species  in  recent  years,  it  seems  probable  that 
the  increase  in  DDE  and  the  change  in  ratios  of 
DDE  and  DDT  inS.  leucopsarus  are  descriptive  of 
the  general  change  in  these  analogs  that  has 
taken  place  in  the  earth's  environment. 

There  was  no  pattern  discernible  in  the  dis- 
tribution of  Aroclor  1254.  In  472  myctophid  sam- 
ples taken  between  1949  and  1966,  the  median 
values  of  Aroclor  1254  fluctuated  around  0.17  ppm 
and  showed  no  trend  with  time.  Sixty-eight  per- 
cent of  the  samples  contained  less  than  0.25  ppm. 
The  only  indication  of  an  areal  relationship  was 
that  while  the  three  stations  closest  to  the  White 
Point  sewer  outfall,  and  the  city  of  Los  Angeles 
(CalCOFI  stations  87.35,  90.28,  and  90.30)  consti- 
tuted only  8%  of  the  total  samples,  they  accounted 
for  34%  ( 12  out  of  35)  of  the  myctophids  containing 
more  than  Ippm  of  Aroclor  1254.  However,  there 
were  some  samples  taken  175-200  nautical  miles 
offshore  that  contained  more  than  1  ppm,  and 
there  were  others  taken  near  shore  in  the  Los 
Angeles  area  that  contained  none  or  traces  only. 
These  higher  values  could  result  from  the  myc- 
tophids ingesting  nondigestible  particles  of 
man-made  substances  either  while  feeding  or  ac- 
cidentally while  in  the  cod  end  of  the  plankton  net. 

In  the  larger  fish  taken  in  the  Los  Angeles  area, 
the  high  values  of  the  DDT  residues  tend  to  mask 
the  presence  of  Aroclor  1254.  What  might  be  re- 
corded as  a  trace  amount  could  actually  be  a 
rather  significant  amount  in  view  of  the  dilute 


291 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


solutions  of  sample  used  in  such  cases  in  order  to 
keep  the  DDT  residue  recordings  on  scale. 

SUMMARY 

1.  Between  1949  and  1970,  total  DDT  increased 
in  the  ocean  off  southern  California.  The  major 
source  of  this  insecticide  apparently  was  wastes 
discharged  into  the  Los  Angeles  County  sewer 
system  by  a  major  manufacturer  of  DDT. 

2.  As  measured  in  the  myctophid  fish,  Steno- 
hrachius  leucopsarus,  p,p'DDT  andp,p'DDD  in- 
creased for  several  years  until  metabolism,  excre- 
tion, and  dispersion  equalled  input,  at  which  point 
the  content  of  these  CHC  stabilized  in  the  fish. 

3.  The  more  persistent,  less  easily  metabolized 
p,p'DDE  continued  to  increase  in  S.  leucopsarus 
throughout  the  time  period  under  study.  The 
amount  ofp,p'DDE  decreased  with  distance  from 
the  sewer  outfall. 

4.  During  the  earlier  years  the  abundance  of  the 
other  analogs  in  decreasing  order  wasp.p'DDT, 
p,p'DDE,  andp,p'DDD.  During  the  later  period 
through  1970,  the  more  persistent  p,p' DDE  be- 
came more  abundant  than  p,p 'DDT.  Following 
cessation  of  dumping,  in  1970,p,p'DDD  became 
more  abundant  than  p,p  DDT  in  the  myctophids 
and  most  of  the  other  fish  species  tested. 

ACKNOWLEDGMENTS 

I  am  especially  indebted  to  E.  H.  Ahlstrom  for 
sacrificing  part  of  his  collection  of  the  myctophid 
fish,  S.  leucopsarus,  for  the  present  study.  Shirley 
Imsand  donated  the  five  myctophids  taken  in  1972 
on  the  University  of  Southern  California  MV  Vel- 
ero  IV.  Carol  Talkington  assisted  in  some  of  the 
analyses.  I  am  indebted  also  to  R.  Lasker  for  his 
invaluable  criticism  and  guidance  in  the  prepara- 
tion of  the  paper  and  to  V.  McClure  and  W.  Rommel 
for  technical  advice  and  assistance.  This  work  was 
supported  in  part  by  NOAA,  Office  of  Sea  Grant, 
under  grant  #UCSD  2-35208  with  the  Institute  of 
Marine  Resources,  University  of  California. 

LITERATURE  CITED 

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1971.  DDT  residues:  Distribution  of  concentrations  in 


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Martin,  W.  E.,  and  P.  R.  Nickerson. 

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292 


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293 


QUANTITATIVE  NATURAL  HISTORY  OF 
PLEUROBRACHIA  BACH  EI  IN  LA  JOLLA  BIGHT 

Jed  Hirota' 

ABSTRACT 

An  assessment  of  the  quantitative  natural  history  oi  Pleurobrachia  bachei  A.  Agassiz  was  made  by 
estimating  growth  rates,  metabolic  rates,  distribution,  abundance,  occurrence  of  prey,  predators  and 
parasites,  population  parameters,  and  net  production.  These  were  then  integrated  to  give  an  indica- 
tion of  the  ecological  significance  of  this  animal  in  the  plankton. 

Rates  of  somatic  growth  and  digestion  of  prey  were  observed  in  laboratory  experiments  and  applied 
to  field  data.  A  comparison  of  growth  curves  of  P.  bachei  at  20°  and  15°C  showed  development  rates 
from  hatching  to  the  same  diameter  which  were  10-15  days  faster  at  20°C.  In  addition,  a  much  higher 
mortality  of  the  ctenophores  was  observed  at  20°C.  Maximum  growth  rate  coefficients  on  a  daily  basis 
were  0.21-0.47  and  were  for  2.5-  to  6.5-mm  ctenophores  (0.1-2  mg  bodily  organic  weight).  Studies 
on  the  rates  of  digestion  of  six  frequently  ingested  prey  species  by  various  sizes  of  P.  bachei  showed 
marked  differences  between  species.  Although  Labidocera  was  the  largest  prey  offered,  it  was  di- 
gested the  fastest  per  unit  weight. 

The  horizontal,  offshore  distribution  of  P.  bachei  postlarvae  often  showed  maxima  within  5  km 
from  the  shore  and  decreased  about  tenfold  by  10  km.  Patterns  of  water  movement  in  La  Jolla  Bight 
were  described  as  a  prerequisite  to  the  distributional  studies.  The  near-surface  current  velocities 
showed  counterclockwise  rotational  motion  over  the  submarine  canyon  complex  of  La  Jolla  Bay; 
otherwise  the  water  generally  moved  onshore  and  towards  the  north  at  speeds  of  about  5  km/ day.  The 
high  abundances  of  the  animal  nearshore  are  believed  to  be  caused  in  part  by  these  water  move- 
ments. The  ctenophores  occurred  in  the  upper  50-60  m,  living  mostly  in  the  upi>er  15  m  in  the  day 
and  at  about  30  m  at  night.  The  range  of  average  abundances  of  postlarvae  was  from  1,000/m^  and 
1,000  mg  organic  matter/m^  in  August  to  being  nearly  absent  in  December. 

Hyperoche  mediterranea,  a  parasitic  amphifwd,  and  Beroe  sp.,  a  potential  predator,  showed  pat- 
terns in  seasonal  abundance  similar  to  that  of  P.  bachei  postlarvae,  except  that  H.  mediterranea  was 
absent  in  winter  and  spring.  The  higher  frequency  of  occurrence  of  endoparasites  with  larger  sized 
hosts  and  few  multiple  infections  suggests  that  the  parasites  are  adapted  to  prevent  overexploitation 
of  hosts.  The  stomach  contents  of  postlarvae  showed  a  pattern  of  larger  prey  in  larger  ctenophores, 
and  within  some  prey  sp>ecies  increasing  frequency  of  occurrence  in  larger  ctenophores  was  observed, 
e.g.,  Acartia  tonsa.  The  diel  emd  seasonal  variations  in  stomach  contents  were  also  considered.  Prey 
selection  by  P.  bachei  may  be  determined  by  the  following  attributes  of  prey:  density,  size,  avoidance 
and  escapement  behavior,  strength  and  protective  spination. 

Size-specific  instantaneous  mortality  rates,  the  mean  schedule  of  live  births,  and  somatic  growth 
rates  were  used  to  estimate  population  parameters  and  compute  rates  of  net  production.  The  highest 
rate  of  population  growth  was  0.02  on  a  per  day  basis,  which  would  enable  a  population  doubling  in 
about  35  days.  The  first  50-100  eggs  laid  by  young  postlarvae  are  most  important  to  replace  the 
population.  The  mean  and  range  of  annual  net  production  by  postlarval  P.  bachei  are  5.24  and 
2.32-7.65  g  organic  matter  per  square  meter;  mean  values  for  eggs  and  larvae  are  0.08  and  0. 10  g/m*, 
respectively.  The  mean  annual  net  production  of  all  stages  is  5.4  g/m^,  with  95%  confidence  limits  for 
the  mean  being  4.4-6.5  g/m^. 

The  ecological  significance  and  functional  role  of  P.  bachei  are  as:  Da  seasonally  dominant 
carnivorous  zooplankter  which  preys  selectively  on  small  crustaceans  and  may  regulate  their  abun- 
dances; 2)  a  vehicle  which  provides  shelter  and  nutrition  for  parasites  and;  3)  an  organism  which 
transfers  a  substantial  amount  of  organic  matter  and  potential  energy  in  the  food  web  of  La  Jolla 
Bight. 

Ecological  studies  may  be  grouped  into  four  species  populations,  3)  communities,  and  4) 
categories,  depending  on  the  level  of  complexity  ecosystems.  The  long-term  objective  in  ecology  is 
being  considered:  1)  single  individuals,  2)  single         the  description  of  ecosystems.  More  specifically, 

two  important  objectives  in  studies  of  ecosystems 


are:  the  elucidation  of  complex  interactions  be- 

'Scripps  Insti^tution  of  Oceanography  Institute  of  Marine  Re-  tween  species  in  a  food  web  and  the  understanding 

sources.  La  Jolla,  CA  92037;  present  address  University  of  ^ 

Hawaii,  Institute  of  Marine  Biology,  Kaneohe,  HI  96744.  and  prediction  of  the  dynamic  processes  that  OCCUr 


Manuscript  accepted  September  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO.  2.  1974. 


295 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


in  this  web.  To  obtain  this  information,  one  ap- 
proach is  the  investigation  of  basic  trophic  rela- 
tionships among  the  various  developmental 
stages  of  different  species  in  the  food  web  (e.g.  for 
herring,  Hardy,  1924)  and  the  quantitative  mea- 
surement of  matter  or  energy  transferred  along 
these  paths  (e.g.,  for  a  lake,  Lindeman,  1942). 
From  the  four  categories  of  complexity  I  chose  to 
study  Pleurobrachia  bachei  A.  Agassiz  at  the 
single  species  population  level.  I  have  attempted 
to  integrate  three  basic  aspects  of  the  population 
ecology  oi Pleurobrachia  into  a  study  of  its  quan- 
titative natural  history:  1)  the  structure  of  its  food 
web,  2)  the  population  parameters  and  attributes 
which  most  affect  the  population  growth  rate,  and 
3)  the  trophic-dynamic  aspect  of  the  quantitative 
transfer  of  organic  matter.  In  previous  work 
(Hirota,  1972)  the  culture  and  metabolism  of  P. 
bachei  have  been  described. 

Studies  on  the  trophic-dynamics  of  marine 
planktonic  food  webs  have  concentrated  on  the 
measurement  of  primary  production  and  the  fac- 
tors which  influence  its  level.  MuUin  (1969)  sug- 
gested that  similar  production  studies  of  total  zoo- 
plankton  or  of  single  species  are  few,  because  no 
simple,  direct  methods  exist  for  the  measurement 
of  secondary  production  in  situ.  He  stated  that  two 
basic  approaches  exist  for  these  studies:  the 
laboratory  "carbon  balance"  study  and  the  popula- 
tion dynamics  approach.  A  somewhat  more  direct 
measurement  could  be  made  as  a  modification  of 
the  approach  used  in  lakes  by  Haney  (1971).  In 
situ  population  feeding  rates  (measured  using 
food  particles  labeled  with  isotopes)  multiplied  by 
the  population  gross  growth  efficiency  is  the  rate 
of  net  production.  This  method  has  the  advantages 
of  being  more  direct  and  made  in  nature,  but  it  is 
impractical  for  complex  marine  plankton  com- 
munities with  their  numerous  and  relatively 
large,  mobile  species.  It  also  requires  detailed 
knowledge  of  factors  which  affect  gross  growth 
efficiency. 

Most  marine  planktonic  species  are  not  amena- 
ble to  culture  in  the  laboratory  for  entire  life  cy- 
cles, and  results  of  laboratory  experiments  may 
fail  to  represent  accurately  activity  in  nature. 
Present  field  sampling  techniques  and  variability 
in  plankton  studies  are  often  such  that  it  is  neither 
possible  to  obtain  sequential  samples  from  the 
same  target  population  nor  calculate  the  rates  of 
biological  activity.  In  spite  of  these  difficulties  and 
such  severe  limitations  (Hall,  1964),  more  and 
better  data  are  needed  in  different  ecosystems 


from  their  functionally  distinct  component  species 
before  a  clear  understanding  of  the  structure  and 
dynamics  of  food  webs  is  obtained  and  generaliza- 
tions of  predictive  nature  concerning  the  systems 
can  be  made. 

Studies  on  the  population  dynamics  and  produc- 
tion of  marine  zooplankton  (reviews  by  Mann, 
1969  and  Mullin,  1969)  almost  exclusively  pertain 
to  "herbivorous"  calanoid  copepods.  At  present  lit- 
tle information  exists  on  the  production  rates  of 
carnivorous  marine  zooplankters  (McLaren,  1969; 
Petipa,  Pavlova,  and  Mironov,  1970;  Sameoto, 
1971),  and  the  study  of  Sergestes  lucens  (Omori, 
1969)  is  one  with  the  supportive  catch  data  of  a 
commercial  fishery.  The  lack  of  data  for  higher 
trophic  levels  is  in  part  the  result  of  an  inability  to 
culture  and  maintain  delicate  or  large,  mobile 
forms.  Nearly  all  laboratory  data  on  the 
long-term  metabolism  and  life  cycles  of  zooplank- 
ton species  come  from  successful  rearing  of  one  or 
more  generations  of  facultative  herbivorous 
copepods  (see  Hirota,  1972  for  references).  Hamil- 
ton and  Preslan  (1970)  and  Gold  (1971)  have  cul- 
tured ciliate  protozoans. 

The  genus  Pleurobrachia  (Tentaculata,  Cydip- 
pida)  includes  about  12  species  (see  Ralph  and 
Kaberry,  1950  for  the  most  recent  summary  of  the 
species),  some  of  which  may  be  synonymous.  The 
current  taxonomic  status  of  the  synonymies  in 
this  genus  is  uncertain,  because  there  are  few  sets 
of  general  characteristics  which  have  been  set  up 
as  important  for  the  separation  of  species.  In  par- 
ticular, some  possibly  distinct  species  have  been 
grouped  with  the  boreal  species  P.  pileus  O. 
Miiller  of  the  North  Atlantic.  One  of  these,  P. 
bachei,  is  the  boreal  form  which  inhabits  the 
Pacific  coast  of  North  America  from  Puget  Sound 
to  San  Diego.  This  species  is  believed  synonymous 
with  P.  pileus,  based  on  the  works  of  Moser  (1909) 
and  Mayer  (1912).  However,  I  agree  with  Torrey 
(1904),  Bigelow  (1912),  and  Esterly  (1914)  thatP. 
bachei  is  a  distinct  and  separate  species.  This  dis- 
tinction is  supported  by  work  in  progress  on  the 
differences  between  these  two  forms  in  both 
meristic  and  metric  characters  (Hirota  and  Greve, 
unpubl.  data). 

Studies  of  spatial  distribution,  vertical  migra- 
tion, seasonal  variations  in  numerical  abun- 
dance, and  natural  history  in  the  planktonic 
ctenophores  have  provided  some  data  on  natural 
populations,  but  information  on  population 
dynamics  and  rates  of  production  are  especially 
needed.  Patterns  of  the  geographic  distribution  of 


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HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


Pleurobrachia  species  and  other  ctenophores 
have  been  described  (Moser,  1909;  Mayer,  1912), 
but  no  attempt  was  made  to  relate  abundance 
quantitatively  to  geographic  location.  Only  a  few 
workers  have  studied  vertical  distribution  of 
ctenophores  (Esterly,  1914;  Russell,  1927; 
Alvarino,  1967;  Rowe,  1971)  and  only  the  study  of 
P.  pileus  in  Kaneohe  Bay,  Oahu  (Rowe,  1971) 
could  show  that  diel  vertical  migration  occurs. 
Pleurobrachia  pileus  in  Kaneohe  Bay  follow  the 
"normal"  pattern  for  zooplankton  with  the 
ctenophores  living  at  depth  during  the  day  and 
moving  up  near  the  surface  at  night.  However, 
the  vertical  displacement  of  the  migrants  was 
only  on  the  order  of  10  m  because  the  bay  is  very 
shallow.  More  is  known  about  quantitative  sea- 
sonal changes  in  numerical  abundance  of  P. 
pileus  (Wear,  1965;  Eraser,  1970;  Greve,  1971) 
and  P.  bachei  (Esterly,  1914;  Parsons,  LeBras- 
seur,  and  Barraclough,  1970).  There  are  also 
numerous  qualitative  reports  of  ctenophore 
swarms  in  coastal  waters  (Chopra,  1960;  Ra- 
jagopal,  1963;  Eraser,  1970).  Eraser  (1962,  1970) 
reviewed  the  role  of  ctenophores  and  salps  in 
marine  food  webs  and  their  natural  history. 
Greve  (1970,  1972)  provided  laboratory  studies  of 
the  effects  of  temperature,  salinity,  and  food  on 
growth  of  P.  pileus  and  a  field  study  (Greve, 
1971)  of  variations  in  abundance  of  P.  pileus  and 
two  of  their  predators,  Bero'e  gracilis  and  B. 
cucumis.  These  studies  did  not  relate  seasonal 
variations  in  abundance  to  rates  of  population  re- 
cruitment, growth,  mortality,  net  production,  or 
advection. 

In  order  to  describe  the  quantitative  natural 
history  of  P.  bachei  as  outlined  above,  it  was 
necessary  to  sample  natural  populations  and  to 
carry  out  laboratory  experiments.  The  field  work 
was  needed  for  data  on  the  food  web  and  for  de- 
mographic purposes,  and  the  laboratory  data 
were  used  to  calculate  metabolic  rates  which 
could  not  be  measured  from  field  samples. 
Metabolic  rates  measured  or  calculated  from  in- 
dividuals reared  from  eggs  to  adults  in  the 
laboratory  were  applied  to  field  populations.  Pre- 
liminary field  studies  were  then  made  of  the  var- 
iations in  abundance  of  P.  bachei  as  a  function  of 
distance  from  shore.  The  vertical  distribution  was 
determined  by  sampling  with  opening-closing 
bongo  nets  (McGowan  and  Brown,  1966^)  while 


^McGowan,  J.  A.,  and  D.  M.  Brown.  1966.  A  new  opening- 
closing  paired  zooplankton  net.  Scripps  Inst.  Oceanogr.  Ref. 
66-23.  (Unpubl,  Manuscr.) 


tracking  parachute  drogues  in  those  locations 
where  ctenophores  were  most  abundant.  Erom 
the  data  on  water  movement  and  the  horizontal 
and  vertical  distributions  of  P.  bachei,  sampling 
stations  and  sample  depths  (the  maximum  depth 
to  which  a  net  sample  is  taken)  were  allocated  for 
a  study  of  spatial  and  seasonal  variations  in 
numerical  abundance,  standing  stocks  and  net 
production.  Size  or  stage-specific  instantaneous 
mortality  rates  were  calculated  from  the  ob- 
served size-frequency  distribution  in  field  sam- 
ples and  development  rates  calculated  from 
laboratory  growth  data.  Standing  stocks  per  unit 
area  of  sea  surface  were  calculated  as  the  sum- 
mation of  the  organic  weight  (ash-free  dry 
weight)  of  all  individuals  in  a  sample  multiplied 
by  the  ratio  of  maximum  sample  depth  to  the  vol- 
ume of  water  filtered.  The  organic  weights  were 
estimated  from  regression  equations  of  bodily 
weight  on  bodily  diameter.  Rates  of  net  produc- 
tion per  24-h  day  were  calculated  from  the  esti- 
mated standing  stocks  of  each  stage  and  the 
stage-specific  instantaneous  rates  of  mortality 
and  growth  on  a  daily  basis.  Eor  a  given  set  of 
stage-specific  instantaneous  mortality  rates,  and 
using  the  mean  schedule  of  live  births  derived 
from  laboratory  data,  the  following  population 
parameters  were  calculated:  T,  r,  d,  b,  Cx  which 
are  the  generation  time,  instantaneous  rate  of 
natural  increase,  death  and  birth  rates,  and  sta- 
ble age  distribution,  respectively.  More  than 
12,000  specimens  of  P.  bachei  were  counted  and 
measured  during  the  seasonal  study,  of  which 
1,352  postlarvae  in  10  size  classes  contained  par- 
tially digested  food  organisms  and  1,007  postlar- 
vae contained  internal  parasites  of  the  hyperiid 
amphipod,  Hyperoche  mediterranea.  Attempts 
were  made  to  quantify  changes  in  the  absolute 
numbers  and  the  proportions  of  various  prey 
categories  with  changes  in  bodily  size  of  P. 
bachei.  A  study  of  the  seasonal  variation  in  num- 
bers of  parasites,  percent  hosts  parasitized,  and 
the  frequency  distribution  of  numbers  of  para- 
sites per  host  and  percent  hosts  parasitized  at  dif- 
ferent host  sizes  is  also  presented. 

GROWTH    IN    CULTURE    AND 
METABOLIC  RATES 

Methods 

Techniques  for  the  laboratory  culture  of  P. 
bachei  at  15°C  have  been  described  previously 


297 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


(Hirota,  1972);  culturing  has  also  been  done  at 
20°C  to  examine  the  effect  of  temperature  on 
growth  rates.  The  rates  at  which  different  prey 
species  were  digested  were  measured  in  the 
laboratory  in  order  to  make  corrections  for  preda- 
tion  by  P.  bachei  on  the  most  abundant  crusta- 
ceans during  field  sampling  with  nets  (Judkins 
and  Fleminger,  1972,  discuss  feeding  by  Sergestes 
in  nets). 

Six  ctenophores  were  cultured  from  eggs  at  20'^C 
and  about  20  /.(g  C/liter  as  prey  for  the  adult 
ctenophores  in  order  to  evaluate  the  effect  of 
temperature  on  growth  rate  (the  surface  tempera- 
ture in  summer  is  about  20°C).  The  basic  tech- 
niques were  the  same  as  described  previously 
(Hirota,  1972,  Table  1),  except  that  adult 
Paracalanus  parvus  replaced  Artemia  nauplii  as 
food  for  2-  to  3-mm  ctenophores.  In  this  manner, 
it  was  possible  to  raise  ctenophores  without  "arti- 
ficial" foods  of  any  kind  and  instead  raise  them  on 
prey  species  which  they  utilize  in  nature.  In  addi- 
tion, antibiotics  (streptomycin  sulfate  and  penicil- 
lin G  each  at  concentrations  of  50  mg/liter)  were 
added  after  4  wk  of  culturing  at  20°C  when  several 
specimens  appeared  very  weak  or  moribund. 
When  changes  in  bodily  diameter  indicated  that 
the  last  two  specimens  might  also  die,  the  experi- 
mental temperature  was  changed  back  to  15°C  to 
determine  whether  or  not  recovery  might  occur 
and  whether  the  mortality  effect  was  due  to  lethal 
temperature. 

In  order  to  determine  whether  or  not  a  prey  spe- 
cies found  in  the  gut  of  Pleurobrachia  sampled 
with  nets  was  eaten  prior  to  or  during  capture,  a 
number  of  observations  were  made  of  the  rate  at 
which  five  prey  species  were  ingested  and  digested 
after  initial  entanglement  with  the  tentacles.  The 
time  elapsed  to  achieve  one  of  four  scores  was 
recorded  during  observations  with  a  dissecting 
microscope  through  the  transparent  bodily  wall  of 
the  ctenophore.  These  scores  are:  (4)  the  prey  en- 
ters the  mouth  and  is  in  the  distal  half  of  the 
stomach;  (3)  the  prey  is  moved  into  the  proximal 
half  of  the  stomach  but  no  digestion  of  the  prey  is 
indicated;  (2)  the  prey  is  being  digested  and  as- 
similated, as  indicated  by  less  than  10%  of  the 
bodily  tissues  clearing  and  the  occurrence  of  prey 
tissues  in  the  aboral,  transverse,  and  pharyngeal 
canals;  (1)  the  prey  is  almost  fully  digested  and 
assimilated,  as  indicated  by  transparent  skeletal 
remains  (crustacean  exoskeletons  are  not  di- 
gested) and  the  presence  of  digested  tissues 
throughout  the  canal  network.  The  elapsed  time 


to  achieve  a  given  score  was  then  compared  to  the 
maximum  time  period  a  prey  organism  was  at  risk 
in  the  net  sample  with  the  ctenophores.  This  time 
period  is  the  elapsed  time  from  the  start  of  the  tow 
until  preservative  was  added  to  the  sample  jar. 
Those  prey  found  in  the  ctenophore  stomachs 
whose  score  required  more  time  than  the  max- 
imum period  at  risk  are  presumed  to  have  been 
eaten  in  nature  prior  to  capture  by  the  net. 

Results  and  Discussion 

The  growth  curve  of  bodily  diameter  up  to  6  mm 
at  20°C  indicates  similar  patterns  as  is  the  case  for 
15°C  (Hirota,  1972,  Figure  1),  except  that  the  de- 
velopment rates  to  the  same  bodily  diameter  are 
10-15  days  faster  at  20°C  (Figure  1).  The  other 
important  differences  are:  1)  very  much  higher 
mortality  rates  at  20°C  than  at  15°C,  2)  60%  mor- 
tality despite  the  addition  of  antibiotics  on  day  29, 
and  3)  the  recovery  and  prolonged  growth  and  sur- 
vival of  two  specimens  after  the  temperature  was 
lowered  to  15°C  from  20°C  when  growth  had 
ceased  at  20°C.  Note  that  there  is  a  lag  of  over  a 
week  before  the  apparent  effect  of  lowered  tem- 
perature is  indicated  by  a  response  in  bodily  diam- 
eter. The  significance  of  the  effect  of  temperature 
on  growth  rate  will  be  discussed  below. in  relation 
to  the  stratification  of  water  temperature  in  na- 
ture, the  diel  vertical  distribution  of  the 
ctenophores,  and  the  effect  of  these  distributions 
on  seasonality  in  the  standing  stocks  and  net  pro- 
duction of  the  ctenophores. 

Using  the  data  for  growth  in  bodily  diameter  at 
15°C  (Hirota,  1972,  Figure  1),  it  is  possible  to  cal- 
culate rates  of  growth  in  bodily  organic  weight 
from  regressions  of  organic  weight  on  bodily 
diameter  (Figure  2).  A  curve  for  the  mean  growth 
in  organic  weight  and  the  ranges  for  weight  at  a 
given  age  and  age  at  a  given  weight  are  shown  in 
Figure  3.  The  mean  growth  rates  are  highest  from 
0.1  to  2  mg  (2.5  and  6.5  mm  diameter,  respec- 
tively); the  exponential  growth  rate  coefficients  on 
a  daily  basis  are  0.21-0.47.  Below  0.1  mg  and  over 
2  mg  the  exponential  growth  rates  are  slower,  the 
values  being  0.12-0.17  and  0.04-0.17,  respec- 
tively. The  range  for  weight  at  a  given  age  is  about 
tenfold  and  for  age  at  a  given  weight  about  15 
days. 

The  rates  of  digestion  of  five  prey  species  are 
shown  in  Table  1.  These  data  show  that  undi- 
gested prey  present  in  ctenophore  stomachs 
(scores  4  and  3)  can  be  ingested  during  a  0.3-  to 


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10 


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E 


or 

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10 


20  30  40  50  60 

DAYS   AFTER   HATCHING 


Figure  1. — Growth  in  bodily  diameter  o{ Pleurobrachia  bachei 
at  20°C,  expressed  as  a  function  of  age  in  days.  Each  symbol 
represents  measurements  of  a  different  individual.  The  point 
indicated  by  AB  refers  to  the  starting  date  with  antibiotic  addi- 
tions and  the  points  indicated  by  15°C  refer  to  change  of  the 
experimental  temperature  from  a  constant  20°C  to  a  constant 
15°C.  All  ctenophores  died  after  the  last  observation  shown  for 
each  individual,  except  that  one  which  was  still  alive  after  80 
days. 

5-min  period  at  risk  while  both  the  predator  and 
prey  are  being  sampled  by  nets.  Partial  or  fully 
digested  states  (scores  2  and  1),  however,  required 
more  than  9  and  15  min,  respectively.  Prey  of 
scores  2  and  1  in  ctenophore  stomachs  are,  there- 
fore, very  likely  to  have  been  ingested  by 
ctenophores  prior  to  capture  by  nets  in  samples  of 
short  duration  (i.e.,  less  than  5  min).  Only  prey  of 
these  scores  were  used  in  the  study  of  stomach 
analyses  presented  below,  unless  the  prey  were 
too  small  to  be  retained  by  the  0.363-mm  meshes 
of  the  net  and,  therefore,  were  not  at  risk  to  preda- 
tion  during  the  sampling.  Examples  of  these  smal- 
ler prey  species  not  at  risk  are  nauplii  of  Acartia 
and  all  stages  of  Euterpina  acutifrons,  a  copepod 
of  0.7  mm  length. 

Measurements  of  the  organic  weight  of  six 
species  of  "important"  planktonic  marine  crusta- 
ceans in  La  Jolla  Bight  are  given  in  Table  2.  The 
first  four  species  are  copepods  and  the  remainder 
are  cladocerans.  Note  that  for  adults,  Labidocera 
is  tenfold  larger  than  Acartia  and  Evadne  and 
about  twentyfold  larger  than  Paracalanus, 
Corycaeus,  and  Penilia. 

A  trend  exists  in  the  data  for  scores  2  and  1  when 
the  respective  medians  for  the  elapsed  time  to 
achieve  these  scores  are  expressed  per  unit  bodily 
organic  weight  for  each  prey  species  (Table  1). 
Labidocera  trispinosa  is  the  most  easily  digested 
prey  per  unit  bodily  mass  although  it  is  the 
largest.  Acartia  is  digested  slightly  faster  than 


e 


I- 

X 
UJ 


< 

CI 
(T 
O 


luvj 

- 

I 

Mill 

III 

1    1   1  1  1  iii{     — r 

1   M  1  iiri 

10 

— 

/ 

1 

w 

3.2IID 

-2.386- 

-f 

- 

oA 

0.1 

z 

^ 

9n 

0.01 

— 

/ 

/ 

0.001 

'-/ 

/ 

/L 

-W  =  1,9400  -  i.eio 

- 

0.0001 


J — I   I  I  1 1  III 1 I   I  I  1 1  III 


I   I  I  I  III 


0.1  0.5       I  5       10 

DIAMETER   IN   mm 


50     100 


Figure  2. — The  relationship  between  bodily  organic  weight  and 
bodily  diameter  of  P.  bachei  on  a  double  logarithmic  scale.  The 
open  circles  represent  data  on  field-collected  ctenophores  from 
La  Jolla,  Calif;  the  triangles  represent  data  on  laboratory  cul- 
tured ctenophores;  and  the  diamonds  and  squares  represent  data 
on  ctenophores  grown  in  the  deep  tank  facility  at  Scripps  Institu- 
tion during  experiments  1  and  2,  respectively.  The  lowest  four 
values  are  calculated  from  determinations  of  organic  carbon.  In 
the  equations  the  upper  line  is  for  ctenophores  larger  than  3  mm 
and  the  lower  line  for  those  smaller  than  3  mm.  In  both  equations 
W  =  log  10  (bodily  organic  weight  in  milligrams)  and£>  =  logio 
(bodily  diameter  in  millimeters). 

Paracalanus  and  each  of  these  faster  than  either 
Corycaeus  or  Penilia.  Part  of  the  cause  for  the 
delay  in  digestion  of  Corycaeus  and  Penilia 
relative  to  the  above-mentioned  calanoid 
copepods  is  the  protective  spination.  In  addition  to 
stout  furcal  spines,  caudal  rami,  and  very  sharp 
projecting  corners  of  the  last  thoracic  joint, 
Corycaeus  has  a  large,  smooth  cephalothorax 
which  encloses  much  of  the  bodily  tissues  and  may 
retard  penetration  of  digestive  enzymes.  The  spi- 


299 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


nation  causes  great  difficulty  for  the  movement  of 
this  prey  into  the  proximal  half  of  the  gut  where 
digestion  occurs.  For  example,  the  median  time  for 
score  3  of  Acartia  is  significantly  shorter  than  the 
corresponding  median  ofCorycaeus  as  determined 
by  a  [/-test  rP<0.05).  Similarly,  the  rigid  bifur- 
cate rostrum,  caudal  spines,  and  denticulate 
carapace  oiPenilia  are  often  hooked  into  the  gut 
wall  of  the  ctenophore  and  delay  passage  of  the 
prey  to  the  site  of  digestion.  Contrary  to  this  delay 
in  the  passage  ofCorycaeus  and  Penilia,  the  rela- 
tively smooth-bodied  calanoids  are  translocated 
quite  easily  by  peristalsis  of  the  gut.  More  detailed 
studies  might  indicate  differences  in  the  integu- 
ment to  penetration  by  the  digestive  enzymes  or 
perhaps  differences  in  the  specificity  of  the  en- 
zymes for  protein  or  lipid  components  of  the  sub- 
strate. 

FIELD  ECOLOGY  OF  P.  BACHEI 

Study  Area  and  Previous  Plankton  Work 

The  study  location  is  La  Jolla  Bight  (long. 
117'20'W,  lat.  33'N),  including  the  coastal  waters 
(hereafter  coastal  waters  refers  to  that  area 
bounded  by  the  shoreline  and  a  line  parallel  to  it 
out  to  a  distance  of  about  8  km)  south  to  Point 
Loma  and  north  to  Oceanside  (Figure  4).  The 
major  physiographic  features  of  the  area  are:  1) 
Point  La  Jolla,  which  extends  about  2  km  west  of 
the  shoreline  at  Scripps  Institution  and  forms  the 
southern  boundary  of  La  Jolla  Bight;  2)  two  sub- 
marine canyons  (La  Jolla  and  Scripps  Canyons)  in 
La  Jolla  Bight  which  bring  water  over  100  m  deep 
within  2  km  of  shore;  3)  numerous  kelp  beds  lo- 
cated both  north  and  south  of  Point  La  Jolla  gen- 
erally in  10-  to  20-m  depth  and  extending  out  to  1 
km  from  shore.  The  area  is  not  strongly  influenced 
by  precipitation  and  runoff,  so  that  seasonal  and 
annual  variations  in  salinity  are  within  32-34  Vco 
(Fager,  1968).  The  range  of  sea-surface  tempera- 
ture is  14-2 IX  annually  and  approximates  the 
temperature  difference  between  the  surface  and 
50  m  in  July  (Mullin  and  Brooks,  1967).  The  tides 
are  of  a  mixed  semidiurnal  type  with  a  diurnal 
inequality  and  total  daily  range  that  change  twice 
each  month.  Within  a  given  month  the  maximum 
daily  tidal  range  is  about  2  m  and  the  minimum 
about  1  m.  Wind  velocities  are  highly  variable; 
storms  with  wind  speeds  greater  than  about  7  m/s 
generally  come  from  the  southwest  to  the  north- 
west quadrant.  Santa  Ana  winds  blow  occasion- 


en 

£ 


X 


< 

tr 
o 


V     0.01  - 


Q 
O 
CD 


0.0001 


0.001  - 


10 


20         30        40        50        60        70 
DAYS   AFTER   HATCHING 


80 


90       100 


Figure  3. — Growth  in  bodily  organic  weight  of  Pleurobrachia 
bachei  at  15°C  during  the  second  laboratory  generation,  expres- 
sed as  a  function  of  age  in  days.  The  values  for  bodily  organic 
weight  at  different  ages  were  calculated  from  the  observed 
growth  in  diameter  and  a  regression  of  organic  weight  on  diame- 
ter. The  horizontal  and  vertical  bars  indicate  the  ranges  for  age 
at  weight  and  weight  at  age,  and  the  numbers  in  parentheses  are 
the  number  of  specimens  observed  in  the  data. 


ally  from  the  northeast  in  fall,  and  diel  variations 
in  wind  velocities  predominate  in  the  east-west 
directions. 

Previous  plankton  work  in  the  study  area  in- 
clude the  extensive  phytoplankton  work  of  Allen 
(1928,  1941),  the  California  Cooperative  Oceanic 
Fisheries  Investigations  programs,  and  the  plank- 
ton study  off  La  Jolla  by  the  Food  Chain  Research 
Group  (Strickland,  1970).  In  general  these  previ- 
ous studies  provide  basic  information  on  species 
lists  and  levels  of  abundance  and  variability  of 
phytoplankton,  microzooplankton,  and  macrozoo- 
plankton.  In  these  coastal  waters,  however,  very 
little  information  is  available  on  the  patterns  of 
water  circulation,  variations  in  abundance  of  or- 
ganisms in  relation  to  variations  in  the  physical 
parameters  (e.g.,  tidal  motion,  wind  velocities 
etc.),  or  the  organization  and  interaction  of  the 
species  which  inhabit  this  coastal  region. 


300 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 

Table  1. — Rate  of  digestion  experiments  at  20°C  for  individual  adults  of  five  prey  species  and 
various  sizes  of  Pleurobrachia  bachei.  Medians  and  ranges  are  given  for  the  diameters  of  the 
ctenophores  used  in  the  trials  and  for  the  elapsed  time  in  minutes  from  the  prey  entanglement  with 
the  tentacles  until  each  score  of  digestion  is  achieved.  The  values  in  parentheses  are  the  medians 
for  the  elapsed  time  to  achieve  scores  2  and  1  divided  by  the  bodily  organic  weight  of  each  respective 
prey.  Refer  to  the  Methods  for  details. 


Diameter 
(mm) 


Md 

10.9 

W 

7.6-12.4 

Md 

6.4 

W 

2.0-11.7 

Md 

7.2 

W 

2.0-11.7 

Md 

7.5 

W 

4.0-10.3 

Md 

8.0 

W 

5.4-12.0 

Prey 


Trials 


Labidocera 
trispinosa 


Acartia 
tonsa 


Paracalanus 
parvus 


Corycaeus 

anglicus 


Penilia 
avirostris 


12 


Score  of  digestion 

4 

3 

2 

1 

1.00 

2.67 

20 

46 

0.42-2.84 

1.58-8.50 

14.5-35 

37->60 

(0.23) 

(0.53) 

0.50 

1  83 

15 

25 

0.25-1.50 

0.92-3.00 

10-29 

18-45 

(2.08) 

(3.47) 

1.00 

2.29 

12 

21 

0.25-2.00 

1.00-6.00 

9-27 

15-37 

(3.16) 

(5.53) 

0.33 

3.0 

16 

30 

0.04-1.50 

1.0-6.0 

9->35 

18-37 

(5.3) 

(10.0) 

1.83 

4.8 

>40 



0.42-2.84 

0.83->9 

21->50 

— 

(10.1) 

— 

Table  2. — The  mean  and  range  of  organic  weight  of  six  prey 
species  of  Pleurobrachia  bachei.  F,  M,  A,  CV,  and  J  refer  to 
females,  males,  adults,  fifth  copepodids  and  juveniles,  respec- 
tively. 


Prey  category 

Mean           Range 

(mq)           (uq) 

Number  of 
observations 

Labidocera 
trispinosa 

F 
M 
CV 

88                85-94 
86                83-89 
29                   - 

3 
2 

1 

Acartia 
tonsa 

A 

7.2            6.2-7.9 

8 

Paracalanus 
pan/us 

A 

3.8            3.7-3.8 

2 

Corycaeus 

anglicus 

F 
M 

2.2               — 
3.4           3.0-3.5 

1 
3 

Penilia 
avirostris 

A 

J 

3.6            3.3-4.0 
1.2            1.1-1.2 

3 
2 

Evadne 
tergestina 

A 

74            6.8-8.2 

3 

Methods 

The  three  main  physical  parameters  considered 
in  the  course  of  the  field  studies  are  current  veloc- 
ity, water  temperature,  and  tidal  stage.  Current 
velocities  in  La  Jolla  Bight  were  measured  on  five 
,  occasions  between  November  1969  and  June  1970 
by  tracking  surface  floats  attached  to  parachute 
and  "vane"  drogues  (vane  drogues  were  made  of 


Figure  4. — The  study  area:  La  Jolla  Bight  and  ac^jacent  waters. 
Sampling  stations  1-5  and  6  are  located  1.6  and  10  km  offshore, 
respectively.  The  juncture  of  Scripps  Canyon  with  La  Jolla  Can- 
yon is  near  station  5.  The  depth  contours  are  in  fathoms. 


301 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


parachute  silk  attached  to  a  wooden  frame,  creat- 
ing three  intersecting  planes  normal  to  each 
other;  each  plane  covers  about  9  m^)  set  at  depths 
in  or  near  the  thermocline  (about  15-m  depth). 
During  the  field  studies  surface  temperatures 
were  measured  by  bucket  thermometer  to  the 
nearest  0.1°C,  and  the  vertical  distribution  of 
temperature  was  measured  by  mechanical 
bathythermograph  (BT)  or  salinity-temper- 
ature-depth recorder  (STD).  Tidal  heights  for  the 
time  of  particular  events  are  taken  from  tide  cal- 
endars for  predicted  tides  by  the  U.S.  Coast  and 
Geodetic  Survey  for  La  JoUa. 

For  studies  of  the  offshore  and  seasonal  dis- 
tributions of  P.  bachei  two  types  of  nets  were 
used.  The  net  to  collect  postlarval  ctenophores 
(i.e.,  ctenophores  larger  than  0.5  mm  in  diameter) 
is  a  ring  net  of  0.5  m  diameter  and  0.363-mm 
mesh  apertures.  This  net  was  used  for  oblique 
sampling.  The  second  net  is  a  0.17-m  diameter 
ring  net  of  0.035-mm  mesh  apertures  equipped 
with  a  20-cm  metal  collar  that  attaches  the  net 
onto  the  wire.  This  net  was  towed  vertically,  and 
it  was  used  for  sampling  the  eggs  and  larvae  of 
Pleurobrachia  and  the  smaller  zooplankters 
which  were  available  as  prey  but  not  sampled 
quantitatively  by  the  0.363-mesh  net.  Both  nets 
were  equipped  with  a  calibrated  TSK  (Tsurumi- 
Seiki  Kosakusho)  flowmeter^  to  measure  volumes 
of  water  filtered. 

Two  studies  of  the  vertical  distribution  of  P. 
bachei  were  made,  the  first  during  3-6  November 
1969  and  the  second  during  22  May-1  June  1970. 
In  both  cases,  0.7-m  diameter  paired, 
opening-closing  bongo  nets  with  mesh  apertures 
of  0.053  and  0.153  mm  were  used.  In  each  vertical 
profile  of  abundance,  four  to  six  depth  intervals 
were  sampled  at  10-  to  20-m  intervals  for  shal- 
low depths  and  at  greater  intervals  below  50  m. 
Thus,  a  set  of  four  to  six  pairs  of  samples  com- 
prised each  vertical  profile.  The  volumes  of  water 
filtered  were  between  5  and  50  m^,  as  determined 
from  calibrations  of  numerical  settings  on  the  net 
release  gear  against  the  calculated  cubic  meters 
of  water  filtered  using  a  TSK  flowmeter. 

In  all  cases  net  samples  were  preserved  with  10 
ml  of  40%  formaldehyde  solution,  buffered  with 
calcium  carbonate,  in  about  750  ml  of  seawater. 
This  solution  is  about  0.5%  formaldehyde.  Pre- 
liminary experiments  with  preservation  of 


Pleurobrachia  showed  this  to  be  the  best  concen- 
tration and  type  of  preservative.  Relatively  small 
changes  occur  in  length  frequencies  of  P.  bachei 
after  27  mo  in  this  preservative  (Table  3). 

A  preliminary  survey  of  the  horizontal,  offshore 
distribution  (the  distribution  of  numerical  abun- 
dance of  Pleurobrachia  in  samples  taken  at  in- 
creasing distances  from  the  shore)  was  made  on  28 
August  1969.  Samples  were  taken  at  10  stations 
with  closely  spaced  intervals  out  to  11  km  from 
shore  off  Scripps  Institution.  Results  of  this  study 
showed  that  the  ctenophores  occurred  in  highest 
abundances  within  3  km  of  shore. 

Samples  were  taken  in  the  following  manner 
during  the  two  field  studies  of  the  vertical  and 
offshore  distributions  of  P.  bachei  mentioned 
above.  In  both  studies  of  vertical  distributions, 
about  10  sets  of  four  to  six  pairs  of  samples  were 
taken  alongside  or  between  parachute  and  vane 
drogues.  Each  sample  set  permitted  the  descrip- 
tion of  abundances  at  various  depth  intervals  for 
one  time  of  the  day.  In  the  study  of  November  1969 
the  offshore  distribution  sampling  consisted  of  six 
transects  of  stations  perpendicular  to  shore.  The 
transects  were  about  3-8  km  apart,  beginning  off 
Del  Mar  and  ending  off  Point  Loma.  Each  transect 
consisted  of  three  or  more  stations  located  between 
1  and  13  km  from  shore.  In  the  second  study  the 
offshore  distribution  sampling  consisted  of  two 
transects  of  seven  and  nine  stations  out  to  50  km 
from  shore.  In  all  offshore  distribution  studies  rep- 
licate samples  were  taken  at  each  station  except 
in  five  cases  where  time  prohibited  it  or  second 
samples  were  lost. 

Table  3. — Changes  in  size-frequency  distribution  of  Pleuro- 
brachia with  duration  in  2%  Formalin-seawater  preservative. 
Samples  A  and  B  were  analyzed  16  and  12  days  after  sampling, 
respectively,  and  a  second  time  after  27  months  as  indicated  in 
columns  A'  and  B'.  The  variable  indicated  is  the  number  of 
occurrences  of  each  size  class.  One  specimen  in  sample  A  was 
lost. 


'Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service. 


Mean 

diameter 

A 

a' 

B 

B' 

(mm) 

'/) 

0 

0 

1 

0 

1 

10 

10 

64 

69 

2 

28 

24 

28 

28 

3 

23 

23 

17 

15 

4 

12 

11 

3 

1 

5 

5 

4 

1 

2 

6 

11 

14 

4 

3 

7 

5 

6 

1 

3 

8 

6 

8 

2 

0 

9 

2 

1 

1 

1 

10 

2 

2 

2 

2 

11 

0 

4 

0 

0 

12 

5 

1 

0 

0 

13 

2 

2 

0 

0 

302 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEl  IN  LA  JOLLA  BIGHT 


From  8  March  to  1  May  1970  sampling  for  the 
seasonal  variations  in  the  coastal  plankton  was 
done  at  stations  located  between  Del  Mar  and 
Scripps  Institution  1-3  km  from  shore.  Results  of 
the  study  of  current  velocities  during  22  May  to  1 
June  1970  indicated  that  the  plankton  were  ad- 
vected  northward  on  the  order  of  tens  of  kilome- 
ters per  week.  Therefore  from  18  June  1970  to  2 
June  1971  the  sampling  stations  for  seasonal  vari- 
ations in  the  coastal  plankton  were  changed  to 
those  six  stations  in  Figure  4.  Five  stations  are 
located  1.6  km  from  shore  about  8  km  apart  be- 
tween Oceanside  and  Scripps  Institution,  and  the 
sixth  station  is  located  about  8  km  beyond  the 
station  off  Scripps.  Replicate  samples  were  taken 
at  stations  1-5  with  each  of  the  two  kinds  of  ring 
nets  described  above.  Samples  with  only  the 
0.363-mm  mesh  net  were  taken  at  station  6. 
Analysis  of  the  0.363-mm  mesh  net  samples,  as 
described  below,  was  carried  out  on  samples  at  all 
stations  from  8  March  through  29  August  1970 
(this  period  includes  the  seasonal  maximum  in 
abundance).  From  29  August  1970  to  2  June  1971 
mainly  samples  from  stations  1,  3,  5,  and  6  were 
analyzed  once  it  became  apparent  that  the  varia- 
tions between  the  five  stations  parallel  to  shore 
could  be  about  as  well  accounted  for  by  variations 
at  stations  1,  3,  and  5. 

Samples  were  taken  on  two  occasions  for  special 
studies  related  to  the  diel  variation  in  predation 
by  Pleurobrachia,  their  stomach  contents  in  net 
tows  of  short  duration  and  their  selectivity  of  prey 
species  with  which  they  co-occur.  During  a  field 
study  from  23  to  27  July  1971,  five  sets  of  tripli- , 
cate  samples  were  taken  with  the  0.5-m  net  of 
0.363-mm  mesh  in  the  upper  50  m  off  Del  Mar. 
Three  of  these  sets  were  taken  at  midnight  and 
two  sets  at  midday.  All  samples  were  sorted  and 
counted  as  described  below.  The  ctenophores  were 
measured  and  the  stomach  contents  identified  to 
determine  whether  diel  variations  exist  in:  1)  the 
proportion  of  ctenophores  which  contain  prey  and 
2)  the  numbers  and  kinds  of  prey  which  occur  in 
stomachs  during  the  day  and  at  night.  This  study 
is  important  because  all  other  information  about 
the  stomach  contents  of  P.  bachei  during  the  sea- 
sonal study  were  derived  entirely  from  samples 
taken  between  0900  and  1600  h.  On  25  August 
1970  a  pair  of  samples  was  taken  at  the  surface 
with  the  0.363-mm  mesh  net  on  station  5  at 
1500  h.  The  tows  were  for  60  s  duration  and  the 
maximum  period  which  prey  were  at  risk  is  95  s. 
Samples  were  sorted  and  counted  and  the  stomach 


contents  of  ctenophores  identified  for:  1)  compari- 
son of  these  prey  species  to  other  data  from  field 
samples  of  longer  sample  durations  and  periods  at 
risk,  and  2)  calculations  of  the  electivity  indices  of 
prey  on  a  numerical  and  organic  weight  basis. 
Counts  were  made  of  all  zooplankters  in  2.5%  sub- 
samples  of  each  net  tow,  and  the  proportions  of 
prey  in  stomachs  and  in  the  net  samples  were  used 
to  calculate  electivity  indices  (Ivlev,  1961). 

Whole  samples  of  each  of  two  replicates  per  sta- 
tion taken  with  the  0.363-mm  mesh  net  were 
sorted  at  6-12x  magnification  under  a  dissecting 
microscope,  and  all  postlarval  ctenophores  were 
counted  and  measured  in  polar  diameter  with  an 
ocular  micrometer.  These  procedures  apply  to  all 
field  samples  taken  for  the  offshore  distribution, 
seasonal  distribution,  and  special  sets  of  samples 
taken  for  the  analysis  of  diel  variations  in  feeding 
and  prey  selectivities.  For  the  sets  of  samples 
taken  during  the  seasonal  study,  postlarvae  of  one 
or  the  other  replicate  sample  selected  at  random 
were  dissected  and  the  contents  of  stomachs  iden- 
tified and  given  one  of  four  scores  described  above. 
All  specimens  were  examined  if  there  were  less 
than  about  100/sample,  but  during  a  few  periods  of 
high  abundances  subsamples  of  about  50  speci- 
mens were  taken.  For  each  of  30  sampling  dates 
between  8  March  1970  and  2  June  1971,  data  on 
stomach  contents  of  about  100  specimens  were 
obtained,  except  on  those  dates  with  very  few 
specimens  captured  in  all  samples  lumped  to- 
gether. For  these  same  ctenophores  which  were 
measured  and  dissected,  counts  were  also  made  of 
the  numbers  of  larval  and  early  juvenile  stages  of 
the  facultative  endoparastic  amphipod,  H. 
mediterranea.  Also  enumerated  in  these  samples 
of  the  seasonal  study  were  the  numbers  of  adult 
and  late  juvenile//,  mediterranea,  which  were  not 
attached  to  ctenophores,  and  the  numbers  of 
Bero'e  sp. 

Each  replicate  sample  of  the  eggs  and  larvae 
of  P.  bachei  taken  at  station  5  with  the  0.035 
mm  mesh  net  was  concentrated  to  400  ml  by 
settling  overnight,  siphoning  off  the  excess 
water  and  transferring  it  to  a  graduated  cylinder. 
Each  of  two  subsamples  of  20  ml  was  removed 
by  Stempel  pipet,  examined  under  12-25x 
magnification  and  the  numbers  of  eggs  and  lar- 
vae counted.  Numbers  per  square  meter  of  sea 
surface  were  calculated  as  ten  times  the  total 
numbers  in  both  subsamples  times  the  ratio  of 
the  sample  depth  in  meters  to  the  volume  of 
water  filtered  in  cubic  meters. 


303 


iiT'ig 


32"'56 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

II7°I7'  15' 


Date      Time  Height,  cm 

3       1630  134 

2324  2 1 

0606  146 

1200  67 

1730  137 

2354  21 

0630  159 

1236  46 

1818  140 

0018  24 

0648  175 

1306  21 

1906  143 


32°  52 


32°  52 


117°  19 


32°  56 


-    54 


52 


50 


II7°I9 


Figure  5. — Trajectories  of  two  drogues  during  the  field  study  of  3-6  November  1969.  Observed 
positions  of  the  drogues  are  indicated  by  the  open  circles,  and  the  date  and  time  of  the  triangulation  are 
indicated  by  the  one-four  digit  sequence  of  numbers  near  the  circles.  The  date  and  predicted  times 
(Pacific  standard  time)  and  heights  of  tides  in  centimeters  are  given  in  the  inset. 


Estimates  of  the  standing  stocks  of  food  avail- 
able to  P.  bachei  were  obtained  from  counts  of  prey 
taxa  in  subsamples  of  the  0.035-mm  mesh  net 
samples  at  station  3,  the  centrally  located  station 
(Figure  4).  These  pairs  of  replicate  samples  were 
treated  in  a  manner  similar  to  the  counts  of 
ctenophore  eggs  and  larvae,  except  that  counts  of 
all  zooplankters  were  made  in  a  5-ml  subsample 
of  a  500-ml  sample.  Over  100  specimens  were 
counted  in  each  subsample.  The  counts  of  numbers 
were  converted  to  mass  of  organic  carbon  using 
the  data  from  six  species  (Table  2)  which  fre- 
quently occur  in  these  waters,  data  in  the  litera- 
ture, and  approximations  by  proportions  of  body 
volumes  relative  to  the  known  mass  of  species  for 
which  data  exist. 

Counts  of  ctenophores  in  samples  for  vertical 
distribution  studies  were  made  as  follows.  First, 
all  large  ctenophores  which  could  be  seen  by  the 
unaided  eye  were  removed  with  pipets  from  one  of 
the  pair  of  bongo  net  samples  selected  at  random. 
When  no  further  specimens  could  be  found  by  eye, 
subsamples  of  5-12.5%  of  the  whole  sample  were 
taken  by  Stempel  pipet  or  Folsom  splitter  and 
examined  under  12-25  x   magnification  for  all 


sizes  of  ctenophores,  including  larvae  and  eggs. 
The  diameters  were  measured  as  described  above. 
Numbers  per  cubic  meter  were  calculated  by  ap- 
propriate corrections  for  subsample  fraction  and 
volume  of  water  filtered. 

Results 

Physical  Parameters  and  Distribution 
of  Pleurobrachia 

Patterns  in  the  currents  of  La  Jolla  Bight  ap- 
pear to  be  affected  by:  1)  the  configuration  of  the 
coastline  (especially  in  the  Point  La  Jolla-La  Jolla 
Cove  complex,  2)  the  bottom  topography  and 
bathymetry  in  the  La  Jolla  Canyon-Scripps  Can- 
yon complex,  and  3)  the  surface  tides.  During  the 
first  field  study  in  November  1969  a  pair  of 
drogues  drifted  toward  Point  La  Jolla,  paralleling 
the  axis  of  La  Jolla  Canyon  during  an  ebb  tide 
(Figure  5).  Both  changed  directions  several  times 
over  La  Jolla  Canyon  and  made  a  complete  coun- 
terclockwise rotation  before  moving  northward 
nearly  parallel  to  shore.  Note  that  the  rotational 
motion  and  major  changes  in  direction  occur  over 


304 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


II7»20' 


1  32"  45' 


Figure  6. — Trajectories  of  drogues  during  studies  on  12-15  March  and  4-5  April  1970.  Observed 
positions  of  the  drogues  are  indicated  by  open  circles,  triangles  and  squares,  and  the  date  and  time  of 
the  triangulation  are  indicated  by  the  one-four  or  two-four  digit  sequence  of  numbers  near  the 
symbols.  The  respective  dates  and  predicted  times  (Pacific  standard  time)  and  heights  of  tides  in 
centimeters  are  given  in  each  inset. 


or  near  La  Jolla  Canyon.  The  surface  tides  as- 
sociated with  the  commencement  of  the  rotational 
motion  were  slack  ebb  tides,  and  completion  of  the 
loops  during  rotation  occurred  during  flood  tides. 
From  1800  h  3  November  until  2300  h  4  November 
wind  speeds  were  less  than  3  m/s  with  variable 
direction.  From  0240  h  5  November  until  0600  h  6 
November  the  winds  increased  to  a  steady  3-5  m/s 
from  the  south  southeast  to  south  southwest.  The 
northward  drift  of  the  drogues  after  0400  h  5 
November  may  have  been  a  response  to  changes  in 
the  wind  velocity.  Some  changes  in  direction  oc- 
curred on  the  northward  drift  of  the  drogues  once 
they  were  beyond  the  submarine  canyon  complex, 
but  these  were  relatively  slight.  While  the 
drogues  were  over  shallow  water,  the  mean  drifts 
were  slightly  onshore  during  flood  tides  and 
slightly  ofFshore  during  ebbs.  The  net  eastward 
drift  was  about  0.3  km  and  the  westward  drift 
about  1  km  relative  to  a  line  true  north  at  0400  h  5 
November. 


During  two  other  drogue  studies  on  12-15 
March  and  4—5  April  1970  drogues  were  tracked 
for  1  to  2  days.  The  study  of  March  1970  provided 
the  best  information  associating  the  surface  tides 
with  changes  in  direction  (Figure  6).  A  drogue  set 
in  the  axis  of  La  Jolla  Canyon  drifted  slowly  to- 
ward the  southeast  along  the  canyon  axis  until 
flood  tides  changed  its  direction  to  northeasterly. 
On  the  following  slack  flood  tide  the  drogue  slowed 
and  then  moved  off'shore  toward  the  west  on  the 
next  ebb  and  smaller  flood.  The  onshore- offshore 
motions  occurred  during  the  following 
flood-slack-ebb  sequences  but  are  not  as  well  as- 
sociated with  the  surface  tide  as  in  the  first  cycle. 
During  this  drogue  study  the  weather  was  foggy, 
especially  in  the  early  morning  hours,  and  the 
winds  were  less  than  3  m/s  during  the  day  from  the 
northwest.  At  night  and  in  the  early  morning 
hours  offshore  winds  were  about  2-4  m/s.  Note 
that  the  east- west  horizontal  translation  during  a 
tidal  cycle  is  on  the  order  of  1-2  km.  This  effect  will 


305 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Figure  7. — Trajectories  of  four  drogues  during  the  study  of  22  May  to  1  June  1970.  Observed  positions  of  the  drogues  are  indicated  by 
circles  and  triangles  for  each  pair  of  drogues,  and  the  date  and  time  of  the  triangulation  are  indicated  by  the  one-four  or  two-four  digit 
sequence  of  numbers  near  the  symbols.  Reset  drogues  indicated  by  primes  refer  to  other  drogues  placed  into  the  water  after  ones  placed 
earlier  either  ran  a<ground  or  broke  down.  Refer  to  the  text  for  further  details. 


be  considered  below  as  one  of  the  physical  vari- 
ables which  may  affect  the  offshore  distribution  of 
Pleurobrachia  and  present  a  bias  in  the  sampling 
program  for  estimates  of  ctenophore  abundance  in 
the  coastal  waters.  In  the  study  during  April  1970 
three  drogues  set  in  a  line  about  1  km  apart  in  a 
north-south  direction  moved  southeast  toward 
Point  La  Jolla  on  flood  tide  and  changed  direction 
on  ebb  tide,  moving  west  or  southwest  (Figure  6). 
After  moving  beyond  Point  La  Jolla  all  drogues 
continued  toward  the  south.  Note  that  after  0800  h 
the  two  drogues  closest  to  the  shore  apparently 
became  detached  from  their  surface  floats  in  kelp 
beds,  because  only  the  floats  were  recovered  at  the 
end  of  the  study,  1800  h  5  April.  No  dramatic 
changes  in  direction  occurred  with  changes  in  the 
surface  tide  for  the  drogues  off  Pacific  Beach. 
Wind  data  were  not  recorded  for  this  study,  but  the 
weather  reports  for  4-5  April  indicated  easterly 


winds  at  6  m/s  in  the  morning  becoming  westerly 
at  4^7  m/s  in  the  afternoon. 

The  current  velocities  measured  with  drogues 
in  La  Jolla  Bight  for  periods  up  to  a  week 
confirmed  the  presence  of  a  counterclockwise  gyre 
over  or  nearby  the  La  Jolla  Canyon  complex  (Fig- 
ure 7).  The  four  drogues  moved  northward,  gener- 
ally paralleling  the  shore  and  finally  ran  aground 
or  broke  down  near  Encinitas  and  Carlsbad,  sea- 
sonal sampling  stations  3  and  2,  respectively. 
Drogues  which  ran  aground  or  lost  the  subsurface 
parachute  or  vane  were  reset  nearby  the  other 
drogues.  Drogues  no.  2  and  3  were  reset  about  5 
km  from  shore,  and  they  continued  to  move 
northward  parallel  to  shore  until  they  were  lost. 
Drogues  no.  1  and  4,  however,  tended  to  move 
offshore.  Drogue  no.  1  made  a  large  counter- 
clockwise loop  about  16  km  long  and  returned  to 
cross  its  original  path  about  5  days  later.  Mean 


306 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


AUGUST       SePTEMBER     OCTOBER       NOVEMBER      DECEMBER      JANUARY       FEBRUARY        MARCH  APRIL 


Figure  8. — Distribution  of  water  temperature  during  the  seasonal  study  at  stations 

located  1.6  km  from  shore. 


wind  velocities  during  the  study  were:  southwest- 
erly at  3  m/s  from  23  to  26  May,  northwesterly  at 
5  m/s  from  27  to  28  May,  and  northwesterly  at  3 
m/s  from  29  May  to  1  June.  The  range  on  any 
given  day  was  0-7  m/s.  No  clear  pattern  of  the 
effect  of  wind  velocity  on  drogue  trajectory  was 
observed. 

From  these  studies  the  limited  data  for 
"near-surface  waters"  indicated  predominantly 
northerly  flow  near  the  coast  with  some  counter- 
clockwise rotational  motion  in  La  Jolla  Cove  and 
off  Oceanside.  Some  data  also  showed  small  scale 
onshore-offshore  motion  associated  with  the  sur- 
face tidal  cycle.  South  of  Point  La  Jolla  the  cur- 
rents on  one  occasion  indicated  southerly  flow  and 
little  east^west  motion  associated  with  tidal  cy- 
cles. The  larger  scale  rotational  motion  off  Ocean- 
side  was  not  associated  with  a  promontory  and  a 
submarine  canyon  complex  and  remains  to  be  ex- 
plained by  other  means. 

The  water  temperature  in  the  upper  50  m  for  the 
period  from  May  1970  to  June  1971  was  measured 
by  BT  casts  at  stations  1-5.  Since  the  stations 
were  located  in  water  of  different  depths,  only  the 
upper  20  m  values  were  represented  by  averages 
for  all  stations.  Data  at  30  m  were  from  stations  2, 
3,  and  5;  data  at  50  m  were  only  from  station  5. 
Thermal  stratification  began  in  May  and  June 
and  reached  maximal  development  in  August  and 
early  September  (Figure  8).  The  12.5°C  isotherm 
rose  to  the  surface  in  January,  and  at  this  time  the 
smallest  gradients  were  found.  Note  that  the  an- 
nual temperature  range  at  the  sea  surface  was 
almost  identical  to  the  range  of  temperature  in 
mid- August  between  the  surface  and  20  m. 

The  vertical  distribution  of  P.  bachei  on  3-6 
November  1969  (Figure  9)  showed  three  main  fea- 
tures: 1)  very  low  abundances  below  50  m  for  those 
profiles  which  sampled  that  deep,  2)  the  pattern  of 
vertical  distribution  indicates  that  P.  bachei 


NUMBER    PER    m' 
0      10     0      10     O      10     0      10     0      10     0      10     0      10     0      10     0      10     0      10 


5-1600  '"      -6-0535 


3rd  4  th 

2115-      0100- 
2350      0320 


4th 
0905- 
1153 


4  th 
1402- 
1612 


4lh 
2100- 
2345 


5th 
0120- 
0500 


5th 

0900- 

1145 


5th 
1253- 
1530 


5lh  6  th 

1615-      0155- 
1853        0350 


NOVEMBER 


Figure  9. — The  vertical  distributions  of  Pleurobrachia  bachei 
and  temperature  during  the  study  of  3-6  November  1969.  The 
scale  of  numerical  abundance  is  given  at  the  top,  and  the  scale  of 
temperature  and  the  time  interval  required  to  sample  each 
profile  are  given  at  the  bottom  of  the  figure.  Note  that  the  depth 
is  given  with  a  change  of  scale  below  100  m.  The  hatched  lines 
below  each  profile  indicate  the  sea  bottom  and  the  numbers  at 
the  last  sample  depth  give  the  approximate  numbers  of 
ctenophores  per  square  meter  of  sea  surface.  The  dashed  line 
between  successive  profiles  connects  the  centers  of  gravity  of  the 
distributions. 

occurred  nearer  the  surface  during  the  day  and 
deeper  at  night,  and  3)  the  extent  of  the  "vertical 
migration"  as  measured  by  diel  vertical  displace- 
ment of  the  center  of  gravity  of  the  population  was 
less  than  20  m.  The  modal  class  of  ctenophore  sizes 
at  all  depths  was  8  mm  with  a  range  from  4  to  12 
mm.  Neither  larvae  nor  eggs  were  found  in  these 
bongo  net  samples.  Vertical  separation  of  differ- 
ent size  classes  of  ctenophores  was  slight,  the  20- 
to  40-m  depth  interval  consisting  of  a  modal  size 
class  at  9  mm  and  the  0-  to  5-m  interval  consist- 
ing of  a  modal  size  class  at  6  mm.  Note  that  the 
relatively  small  vertical  movements  of  P.  bachei 
enabled  these  animals  to  spend  part  of  the  day  in 
or  above  the  thermocline  near  17°C  and  part  of  the 


307 


FISHERY   BULLETIN:  VOL.  12.  NO.  2 


NUMBER  PER  m^ 


20  10 

TEMPERATURE,  °C 

Figure  10. — The  vertical  distributions  o{  Pleurobrachia  and 
temperature  during  the  study  of  22  May  to  1  June  1970.  Profiles 
are  during  the  evening  of  26  May  and  the  following  morning.  The 
times  of  sampling,  the  depth  of  the  water,  and  the  numbers  of 
ctenophores  per  square  meter  of  sea  surface  are  also  indicated. 


night  at  about  13°C.  In  addition,  individuals  may 
have  been  displaced  from  each  other  horizontally 
during  the  migration  by  currents  moving  at  dif- 
ferent velocities  at  different  depths  (Hardy,  1935). 
A  physical  process  of  this  nature  superimposed  on 
the  biological  activity  of  diel  vertical  migration 
may  help  account  for  the  observed  variations  in 
numbers  of  ctenophores  per  square  meter.  Profiles 
taken  from  0900  to  1530  h  5  November  and  from 
0155  to  0350  h  6  November  indicated  abundances 
threefold  or  fourfold  higher  than  at  other  times.  It 
is  apparent  that  following  a  target  population 
with  drogues  will  have  limited  success  over  in- 
creasingly longer  time  periods,  even  for  cases  in 
which  vertical  migration  is  restricted  to  shallow 
depths. 

The  vertical  distribution  of  Pleurobrachia  on 
the  evening  of  26  May  1970  and  the  following 
morning  (Figure  10)  showed  patterns  similar  to 
those  observed  in  November  1969,  but  with  more 
clearly  defined  vertical  migration  from  about  40  m 
at  night  to  about  10  m  the  next  morning.  Note  that 
very  low  abundances  occurred  below  65  m  day  or 
night.  The  size  frequency  distribution  of 
ctenophores  in  these  samples  was  more  rectangu- 
lar than  in  the  previous  November,  with  a  range  of 
1-12  mm  and  the  5-9  mm  sizes  being  most  fre- 
quent. Again  no  larvae  or  eggs  were  found  in  these 
bongo  samples,  and  it  is  suspected  that  these  smal- 
ler, more  delicate  stages  may  have  been  broken 
during  sampling  or  they  did  not  occur  in  sufficient 
abundance  to  be  counted  in  small  subsamples. 


1000 


100 


E 

o 
o 

q:       0- 


DEL  MAR 


100  — 


10 


S.I.O. 


100  -' 


10 


J L 


_L 


cc 

UJ 
QD 

3 


1000  — 


TORREY  PINES 
100 


X 


OCEAN        ,,„,. 
BEACH      V'^^^ 


100 


PACIFIC  BEACH 
100 


.t. 


ot 


^ 


10  — 


■t 


POINT 
LOMA 


I 


-t 


10       0       10       0 
DISTANCE  OFFSHORE,  km 


10 


Figure  11. — The  horizontal,  offshore  distribution  oi  Pleuro- 
brachia postlarvae  on  6  November  1969  at  stations  along  six 
transects  perpendicular  to  shore.  Note  the  tenfold  greater  abun- 
dance off  Del  Mar  and  Torrey  Pines  and  the  break  of  scale  in 
order  to  account  for  absence  data.  The  vertical  bar  represents  the 
range  of  values  for  the  replicate  samples,  and  dots  indicate  that 
the  range  is  less  than  the  size  of  the  dot;  the  open  symbols  off 
Point  Loma  without  any  vertical  bar  are  single  observations. 

Thermal  stratification  was  more  pronounced  than 
in  November  1969,  and  these  ctenophores  experi- 
ence a  7°C  average  temperature  differential  dur- 
ing the  course  of  diel  migration. 

The  horizontal,  offshore  distribution  of  postlar- 
valP.  bachei,  as  deduced  from  three  field  studies, 
indicated  higher  abundances  at  the  shoreward 
stations  and  lower  abundances  offshore  (Figures 
11  and  12).  Note  that:  1)  data  are  presented  on 
semilogarithmic  plots  to  the  same  linear  scale  of 
distance  offshore,  2)  there  is  a  tenfold  lower  abun- 
dance scale  shift  for  stations  located  south  of 
Scripps  Institution  in  Figure  11,  and  3)  breaks 
occur  in  the  scale  of  abundance  to  account  for 


308 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


10000 


0    5     10   0  10         20        30        40        50        60 

DISTANCE   OFFSHORE,  km 

Figure  12. — The  horizontal,  offshore  distribution  of 
Pleurobrachia  postlarvae  on  28  August  1969  (circles)  and  29-30 
May  1970  (triangles  and  squares).  The  profile  indicated  by  the 
triangles  is  off  Scripps  Institution  and  that  indicated  by  squares 
is  off  Encinitas,  about  20  km  to  the  north.  Note  that  both  dis- 
tributions are  plotted  to  the  same  scale  of  distance  as  in  Figvu^e 
11  and  that  the  scale  of  abundance  is  broken  in  order  to  account 
for  absence  data.  The  vertical  bar  represents  the  range  of  values 
for  the  replicate  samples,  and  solid  symbols  indicate  that  the 
range  is  less  than  the  size  of  the  symbol;  open  symbols  without 
any  vertical  bar  are  single  observations. 

samples  with  absences.  Shifts  were  found  in  the 
offshore  locations  of  the  highest  ctenophore  abun- 
dances at  different  positions  along  the  coast  (Fig- 
ure 11).  All  sampling  over  the  six  lines  of  stations 
was  completed  between  0700  and  2300  h,  6 
November.  At  the  northernmost  station  at  Del 
Mar,  highest  values  were  closest  to  shore  and  de- 
creased over  tenfold  by  6.4  km.  Off  Torrey  Pines, 
Scripps  Institution,  Pacific  Beach,  and  Point  Loma 
the  observed  maxima  were  located  between  3.2 
and  6.4  km.  The  exceptional  case  was  the  max- 
imum abundance  observed  beyond  10  km  off 
Ocean  Beach.  The  surface  tides  associated  with 
these  six  lines  of  stations  were  slack  flood  tide  at 
Del  Mar  and  Ocean  Beach,  slack  ebb  at  Scripps 
Institution,  flood  at  Pacific  Beach  and  ebb  at  Tor- 
rey Pines  and  Point  Loma  (refer  to  the  inset  of 
Figure  5  for  the  times  and  heights  of  tides).  The 
nearshore  maximal  abundance  at  Del  Mar  may 


represent  the  slack  flood  tide  onshore  movement  of 
water  and  ctenophores,  while  the  ebb  and  slack 
ebb  tides  at  Torrey  Pines  and  Scripps  Institution, 
respectively  may  have  caused  offshore  movements 
of  surface  water  and  ctenophores  such  that  the 
maximal  abundances  occurred  at  3.2  km.  After 
sampling  the  outer  stations  off  Scripps  Institu- 
tion, a  strong  southerly  wind  about  10  m/s  gener- 
ated short  period  swells  1-2  m  high.  Increased 
wind  stress  and  turbulence  may  have  altered  the 
current  pattern  south  of  Point  La  Jolla  and  added 
considerable  variation  to  the  expected  pattern  of 
the  distribution.  The  presence  of  high  abundances 
of  salps  in  the  net  tows  at  stations  off  Ocean  Beach 
and  Point  Loma,  which  were  not  present  north  of 
Scripps  Institution,  indicated  that  the  water  to  the 
south  was  different  in  faunal  composition  than  the 
normal  coastal  assemblage.  On  28  August  1969 
and  29-30  May  1970,  the  offshore  distributions 
indicated  a  tenfold  decrease  in  abundance  in  the 
first  10  km  from  shore  (Figure  12).  The  maximal 
abundances  between  1  and  2  km  were  associated 
with  slack  flood  or  flood  tides  nearing  slack  flood. 
The  secondary  peak  at  5  km  on  28  August  oc- 
curred during  sampling  on  midebb  tide,  and  it  may 


1000  rr 


100 


E 
cc 

UJ 

a. 
cr 

UJ 
CD 

Z) 


10  - 


"1    I    I    I    rgn     \    I — I — \ — 1 — \ — \ — \ — r 

POSTLARVAE 


I  — 


i 


J I k_J L 


STA  I 
STA.  2 
STA.  3 
STA.  4 
STA.  5 
BETWEEN  STA.  4-5 


J-AiihULl-eii i<!>4fe(i4— ' 


JFMAMJJASONDJ     FMAMJ 


1970 


1971 


Figure  13. — Seasonal  variation  in  abundance  of  Pleurobrachia 
postlarvae  from  8  March  1970  to  2  June  1971  at  stations  located 
1.6  km  from  shore.  The  solid  line  connects  the  medians  of  each 
sample  date.  Note  the  break  of  scale  to  account  for  absence  data. 
Each  type  of  symbol  represents  a  different  station,  except  for 
those  sample  dates  prior  to  May  1970.  Refer  to  the  text  for  details 
of  the  field  sampling. 


309 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


100,000 


10,000 


cr 

a!    1,000 

(T 
liJ 

m 

s 


100 


n — I — I — I — I — I — I — I — I — I — I — I — I — I — I — r 
EGGS 

Q 


J     F    M    A    M     J     J 
1970 


-!••*•* 


JI 


ASONDJ     FMAMJ 
1971 


J LLl 


J     FMAMJ 
1970 


D     J    F     M     A    M    J 
1971 


Figure  14. — Seasonal  variation  in  abundance  of  Pleurobrachia  eggs  and  larvae  from  8  March  1970  to  2 
June  197 1  at  station  5  located  1.6  km  offshore  at  Scripps  Institution.  The  solid  line  connects  the  mean  of 
the  replicate  samples  for  each  sampling  date.  The  vertical  bar  represents  the  range  of  values  for  the 
replicate  samples,  and  solid  symbols  indicate  that  the  range  is  less  than  the  size  of  the  symbol;  open 
symbols  without  any  vertical  bar  are  single  observations. 


represent  the  offshore  movement  of  the  high 
ctenophore  abundance  while  field  sampling  was 
taking  place.  Note  the  secondary  peak  in  abun- 
dance which  was  25  km  from  shore.  Deviations 
from  an  exponential  decay  function  are  perhaps 
the  result  of  coastal  water  eddies  (Figure  7), 
which  move  offshore  with  their  surface-living 
species  and  give  rise  to  offshore  aggregations  in 
moderate  abundance.  An  important  question  to 
resolve  is  whether  or  not  the  expatriated  or  ad- 
vected  aggregations  are  able  to  survive,  grow, 
and  reproduce  as  well  in  offshore  areas  as  they  do 
in  the  coastal  waters. 

Seasonal  variations  in  abundance  of  P.  bachei 
postlarvae,  larvae,  and  eggs  on  semilogarithmic 
plot  indicated  different  patterns  between  these 
stages  in  life  history  (Figures  13  and  14).  Recall 
that  egg  and  larval  abundances  are  based  on  sam- 
ples from  station  5  only,  whereas  those  of  postlar- 
vae are  based  on  the  replicate  tows  of  three  to  five 
stations.  Note  the  wide  range  for  the  median  in 
abundance  of  postlarvae  (Figure  13),  which  usu- 
ally was  on  the  order  of  one-fifth  to  five  times  the 
overall  median.  In  several  instances  the  values 
from  different  stations  were  closer  to  each  other 
than  they  were  to  their  respective  replicate  sam- 
ple at  the  same  station.  This  indicates  that  spatial 
heterogeneity  within  a  station  on  the  scale  of  100 
m  was  often  as  large  as  the  spatial  plus  temporal 
heterogeneity  between  stations  on  the  scale  of  8 


km  apart  in  distance  and  1  h  apart  in  time  to  32 
km  apart  in  distance  and  5  h  apart  in  time.  The 
95%  confidence  limits  for  the  mean  of  replicate 
samples  at  one  station  is  the  mean  multiplied  and 
divided  by  2.15  (determined  by  two-way  analysis 
of  variance  estimate  of  the  mean  square  error 
using  90  pairs  of  replicate  samples  at  five  stations 
from  18  June  1970  to  2  June  1971).  The  95% 
confidence  limits  for  the  mean  of  all  stations  at  one 
sampling  date  is  the  mean  multiplied  and  divided 
by  6.23  (also  determined  by  the  two-way  ANOVA 
referred  to  above).  The  ratio  of  the  95%  confidence 
limits  for  the  mean  of  all  stations  at  one  sampling 
date  to  that  for  the  mean  of  replicate  samples  at 
one  station  is  8.4  (the  ratio  is  equal  to  6.23^/2.152). 
This  latter  residual  variability  is  comprised  of 
time-dependent  physical  variations  plus  spatial 
variation  and  is  1.8  times  larger  than  replicate 
sample  error  (1.8  =  8.4/2. 15^).  The  seasonal  pat- 
tern of  postlarvae  showed  high  abundances  in 
May  to  October  1970,  low  values  in  Novem- 
ber-January and  moderate  densities  in  Feb- 
ruary-June 1971.  Note  that  median  abundances 
in  March-June  1970  were  one  or  two  orders 
of  magnitude  higher  than  the  same  interval  in 
1971.  The  seasonal  distribution  of  larval  abun- 
dance was  180^  out  of  phase  with  that  of  postlar- 
vae for  most  of  1970  (Figure  14).  In  1970  larval 
numbers  were  low  during  the  summer  maximum 
of  postlarvae  and  highest  in  November  when  post- 


310 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 

larvae  were  in  very  low  abundance.  The  abun- 
dance of  eggs  was  generally  the  same  as  that  for 
larvae,  except  for  the  absence  of  eggs  in  April  1970 
and  the  high  abundances  of  eggs  relative  to  larvae 
in  August-September.  There  were  about 
1,000-10,000  eggs/m2  in  August-September, 
which  are  presumed  to  be  spawned  by  the  high 
abundance  of  postlarvae.  The  hatching  time  of 
eggs  is  about  24  h  at  15°C,  so  that  the  low  densities 
of  larvae  during  this  time  were  the  result  of  large 
seasonal  changes  in  hatching  success,  increased 
mortality  rates  of  larvae,  or  both,  assuming  that 
the  observed  abundances  were  not  determined 
mainly  by  physical  processes.  The  data  on  sea- 
sonal variation  in  length  frequency  distributions 
of  postlarvae  considered  below  will  provide  some 
information  to  support  the  interpretation  of  in- 
creased larval  mortality.  From  the  abundance  of 
eggs,  larvae,  and  postlarvae  at  station  5  it  was 
calculated  that  on  13  March,  1  May,  31  July,  21 
August,  5  November,  and  27  January  the  eggs  and 
larvae  made  up  89-99%  of  the  numbers  of  indi- 
viduals per  square  meter.  On  13  August  the  eggs 
and  larvae  constituted  69%  of  the  total  population. 
The  sample  dates  in  which  the  eggs  and  larvae 
made  up  a  very  low  percentage  of  the  population 
are  those  in  June  1970  and  April- June  1971. 

During  the  seasonal  study  18  pairs  of  replicate 
samples  were  taken  between  31  July  1970  and  2 
June  1971  at  both  stations  5  and  6, 1.6  and  10  km 
off  Scripps  Institution,  respectively.  The  mean 
abundance  of  postlarvae  per  cubic  meter  was  cal- 
culated at  each  respective  station  on  each  sam- 
pling date,  and  a  f/-test  was  performed  on  these 
means  to  determine  whether  or  not  medians  of 
mean  abundance  over  time  were  significantly  dif- 
ferent at  stations  5  and  6.  The  null  hypothesis  is  no 
significant  difference,  with  a  one-tailed  alternate 
hypothesis  that  the  median  of  station  5  is  greater 
than  that  of  station  6.  Results  indicate  sig- 
nificantly greater  median  abundance  at  station 
5  than  at  6  (P<0.025).  The  median  difference  is  a 
factor  of  4.2  and  the  mean  difference  is  a  factor  of 
4.8.  This  result  supports  the  three  offshore  dis- 
tribution studies  which  indicated  decreasing 
abundance  with  increasing  distance  from  shore. 
However,  the  observed  decrease  in  abundance  in 
the  first  10  km  from  shore  was  about  tenfold  for 
the  offshore  distribution  studies  and  about  half 
this  for  the  seasonal  study.  The  discrepancy  of  a 
factor  of  two  is  probably  real  and  may  be  caused  by 
sampling  bias  in  relation  to  stage  of  the  tide  and  to 
seasonal  changes  in  the  patterns  of  currents.  The 


TIDAL  HEIGHT,  cm 

Figure  15. — The  relationship  between  abundance  of  postlarval 
Pleurobrachia  bachei  and  the  tidal  height.  The  abundances  are 
in  number  per  square  meter  of  sea  surface  (Y),  and  the  heights 
are  in  centimeters  (X)  for  samples  at  all  stations  located  1.6  km 
from  shore.  The  data  are  for  all  stages  of  the  tide. 

more  accurate  measure  of  variations  in  abun- 
dance with  distance  offshore  should  be  found  in 
the  seasonal  comparisons,  but  more  carefully 
planned  sampling  could  now  be  carried  out  to  bet- 
ter sort  out  variations  due  to  small  scale  tidal 
motions,  larger  scale  "true"  spatial  variations 
offshore,  and  the  effect  of  other  types  of  motion  and 
the  wind  on  patterns  of  abundance. 

When  all  of  the  180  samples  for  the  seasonal 
study  (15  samples  on  five  sampling  dates  are  ex- 
cluded from  the  analysis  as  five  or  fewer 
ctenophores  occurred  in  all  samples  lumped  per 
date)  are  plotted  against  predicted  tidal  height  in 
centimeters  for  all  tidal  stages  (Figure  15),  the 
resulting  least  squares  regression  is  Y  =  0.89X  -I- 
88.36.  Y  is  the  number  of  ctenophores  per  square 
meter  andX  is  the  tidal  height  in  centimeters.  The 
slope  of  the  line  is  significantly  different  from  zero 
in  a  two-tailed  ^-test  (P<0.01).  It  is  surprising  to 
find  a  significant  positive  regression  coefficient. 
The  strength  of  the  test  is  in  the  many  degrees  of 
freedom  and  the  removal  of  15  samples  which 
might  otherwise  tend  to  pull  the  line  down  toward 
a  zero  slope  because  of  frequent  absence  data  at 
any  tidal  height.  This  result  is  unexpected  be- 
cause the  tidal  currents  are  probably  not  the  same 
at  different  locations  along  the  coast.  Variations 
exist  in  depth,  bottom  topography,  exposure  to 
wind,  strike  of  the  beach,  etc.  The  pattern  of  circu- 
lation will  also  be  differentially  affected  by  spatial 
and  temporal  variations  in  the  wind  field.  The 
results  suggest  that  over  an  annual  average, 
abundance  at  any  one  time  and  place  of  sampling 
could  be  affected  by  as  much  as  a  factor  of  four  due 
to  tidal  variations  alone  at  locations  1.6  km  from 
shore.  This  average  range  due  to  tidal  effects  is 
about  the  same  magnitude  as  the  annual  average 
difference  between  mean  abundances  of  stations  5 


311 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


ID 
Q. 
O 


< 


UJ 

o 


50 
0 

50 
0 

50 
0 

50 


8  MAR.  '70 
258 


^L^ 


8  OCT.  '70 
411 

*—t — I 1 I f I I 


\^D^ 


12  MAR.  '70        \- 
27 


_j I — I — 1_ 


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353 


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22  OCT.  '70 
748 


5  NOV  '70 
74 


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2  APR.  '70 
237 


„I 1 I I L_ 


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25  NOV.  '70 
93 


I  MAY  '70 
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30  MAY  '70 
915 


18  JUNE  '70 
668 


2  DEC.  '70 
30 


LI 


//  JAN.  '71 
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Ik= 


27  JAN.    71 
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\ I 1 1 I I 


rh-n — 


2  JULY  '70 
391 


14  JULY  '70 
672 


8  FEB.  '71 
336 


12  MAR.   71 
40 


31  JULY  '70 
798 


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2/ AUG.  '70       L 
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29  AUG.  '70 
1117 


16  SEPT  '70 
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2      4       6      8      10      12 


WHOLE  YEAR 
12.665 

^ — : — I — J 

2      4      6      8      10     12 


MEAN   DIAMETER,  mm 

Figure  16. — Seasonal  variations  in  the  size  frequency  distribu- 
tions of  Pleurobrachia  bachei  captured  by  the  0.363-mm  mesh 
0.5-m  net,  expressed  as  the  percentage  in  each  size  class  of  total 
numbers  of  all  sizes  on  each  sampling  date.  Each  histogram  is 
based  on  all  sample  data  from  each  respective  sampling  date. 
The  date  and  number  of  individuals  measured  are  given  with 
each  histogram. 


and  6,  whose  difference  should  be  less  influenced 
by  tidal  currents  and  represents  the  order  of  true 
spatial  variation  within  the  first  10  km  from 
shore. 

The  size-frequency  distributions  of  postlarvae 
for  the  8  March  1970-2  June  1971  period  indicate 
that  most  of  the  year  the  1-  to  2-mm  size  classes 
made  up  the  highest  proportion  of  all  postlarvae 
(Figure  16).  The  lower  abundance  of  the  0.25-mm 
class  relative  to  the  1-mm  class  is  the  result  of 
sampling  gear  mesh  selectivity  caused  by  the  ina- 


bility of  the  0.363-mm  mesh  to  retain  larvae 
quantitatively.  At  sporadic  intervals  the 
size-frequency  distributions  show  drastic 
changes,  and  these  are  attributed  to  immigration 
of  individuals  in  advected  water.  Between  14  July 
and  21  August  1971  note  the  decline  in  proportion 
of  1  and  2  mm  sizes  and  a  shift  in  modal  class  from 
1  to  7  mm.  During  this  same  period  the  occur- 
rences of  eggs  and  larvae  showed  that  while  up  to 
9,000  eggs/m^  were  present  in  the  water,  seven  of 
eight  samples  for  larvae  indicated  none  present 
(Figure  14).  Assuming  that  these  changes  in 
size-frequency  distribution  over  the  4-wk  period 
are  the  result  of  biological  activity  rather  than 
sampling  error  and  advective  change,  it  is  con- 


en 

E 


cr 

UJ 
Q. 


X 


o 

< 

q: 
o 


J     FMAM     JJA     SONDJFMAMJ 
1970  1971 

Figure  17. — Seasonal  variations  in  standing  stocks  of  postlar- 
vae, larvae,  and  eggs  at  station  5.  Each  type  of  line  connects  the 
respective  mean  values  for  the  replicate  samples  at  each  sam- 
pling date.  The  vertical  bar  represents  the  range  of  values  for  the 
replicate  samples,  and  solid  symbols  indicate  that  the  range  is 
less  than  the  size  of  the  symbol;  the  open  symbols  without  any 
vertical  bar  are  single  observations. 


312 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


eluded  that  the  ctenophore  population  was  releas- 
ing eggs  into  the  water  but  that  the  larvae  were 
eaten  or  died  from  other  causes  as  fast  as  they 
were  hatching  from  eggs.  A  feedback  control 
mechanism  which  can  account  for  the  presumed 
high  mortality  of -larvae,  high  abundance  of  eggs, 
and  rapid  growth  of  postlarvae  is  discussed  below. 

The  calculated  development  rate  from  1.5  to  6.5 
mm  in  30  days  from  field  sample  data  is  about  10 
days  slower  than  the  growth  rates  in  laboratory 
cultures  at  both  15°  and  20°C. 

Patterns  in  the  seasonal  distribution  of  stand- 
ing stocks  of  postlarvae,  larvae,  and  eggs  at  sta- 
tion 5  (Figure  17)  are  similar  to  the  respective 
seasonal  variations  in  numerical  abundance. 
Postlarval  values  in  1970  increased  from  March  to 
a  seasonal  maximum  of  1,500  mg  organic 
matter/m^  in  August,  then  decreased  to  a 
minimum  in  December.  The  range  over  the  year 
for  standing  stock  of  postlarvae  was  about  four 
orders  of  magnitude.  Note  that  the  mean  standing 
stock  of  larvae  was  high  relative  to  that  of  postlar- 
vae in  April  and  November  1970  and  the  following 
winter  months.  Except  for  a  few  instances  in  Au- 
gust and  September,  the  mean  standing  stock  of 
larvae  was  about  twofold  to  tenfold  greater  than 
that  for  eggs.  The  crops  for  postlarvae  were  about 
equal  to  those  of  the  larvae,  except  from  May  to 
October  when  they  were  much  greater. 

Seasonal  Variations  in  Parasites,  Predators, 
and  Prey 

Coincident  with  seasonal  variations  in  the 
abundance  and  size  frequency  distribution  of  post- 
larval  P.  bachei  are  variations  in  abundance  of  the 
hyperiid  amphipod,  H.  mediterranea  (Figure  18). 
The  data  shown  are  from  station  5  off  Scripps 
Institution,  but  patterns  in  the  seasonal  distribu- 
tion 16  and  32  km  to  the  north  (stations  3  and  1, 
respectively)  are  essentially  the  same.  Plots  of 
abundance  per  square  meter  on  a  semilogarithmic 
scale  are  for  postlarval  ctenophores,  attached  en- 
doparasitic  larvae  and  early  juveniles  of  H. 
mediterranea,  and  unattached  free-living  late 
juvenile  and  adult  H.  mediterranea.  The  appear- 
ance of  Hyperoche  in  the  plankton  is  associated 
with  P.  bachei  when  the  abundance  of  hosts  ex- 
ceeded about  100  ctenophores/m^,  which  was 
May-June  to  November  1970.  Prior  to  June  1970 
and  after  January  1971  H.  mediterranea  was 
sparse  enough  to  be  absent  in  6  to  10  samples  of 


1000  p-i — r 


p.  bachei  '__ 

o — o  Attached  Hyperoche  _ 
O — O  Unattached  Hyperoche- 


100  — 


cr 
a. 
or 

LjJ 
GD 


Figure  18. — Seasonal  variations  in  numerical  abundance  of 
postlarval  Pleurobrachia  bachei  and  attached  (endoparasitic) 
and  unattached  (free-living)  Hyperoche  mediterranea  at  station 
5.  Values  are  expressed  as  number  per  square  meter  of  sea 
surface  in  logarithmic  scale,  and  the  lines  connect  respective 
means  at  each  sampling  date.  The  vertical  bar  represents  the 
range  of  values  for  the  replicate  samples,  and  solid  symbols 
indicate  that  the  range  is  less  than  the  size  of  the  symbol. 
Hyperoche  was  absent  after  December  1970. 

15-20  m^  each.  Maximal  abundance  of  Hyperoche 
occurred  about  a  week  after  the  ctenophore 
maximum,  and  may  represent  an  "overshoot" 
phenomenon  in  a  density-dependent,  para- 
site-host system.  Note  that  the  larger  am- 
phipods  occurred  in  highest  abundance  when  most 
postlarval  ctenophores  were  at  6-8  mm  sizes.  Lit- 
tle concerning  the  dynamic  aspect  of  this 
parasite-host  interaction  can  be  deduced  from  the 
data  because  of  uncertainties  in  immigration  and 
emigration  over  time.  In  August  and  September 
1969-72  the  occurrence  of  Hyperoche  in  and  onP. 
bachei  has  been  noted  during  plankton  sampling. 
The  co-occurrence  and  relative  abundance  of 
these  two  species  is  predictable  and  should  follow 
the  same  pattern  from  year  to  year,  with  temporal 
shifts  in  the  maxima  and  minima,  depending  on 
the  type  of  "meterological  year"  and  the  sequence 
of  events  that  occur  in  the  plankton  during  the 
increase  and  decline  of  the  ctenophore 
summer-fall  maximum.  The  important  problems 
to  resolve  are  where  the  amphipods  occur  in  the 
winter-spring  months,  and  whether  the  observed 
seasonal  pattern  of  co-occurrence  is  determined 


313 


FISHFR^    Bl  I  I  FTIN:  \  Ol     ':.  NO.  2 


"T — I — I — r 


O  STA.  I 

0STA.2  _ 

D  STA.  3 

ASTA.4 

O  STA.  5 

•  ALL    STATIONS"! 


>k»k 


V'     A     M 


1971 


Figure  19. — Seasonal  variation  in  the  percentage  of  postlarval 
Pleurvbrachia  bachei  parasitized  hy  Hyperoche  mediterranea  at 
five  stations  located  1.6  km  from  shore.  The  line  connects  the 
mean  value  at  each  sampling  date,  and  the  various  types  of  ojjen 
symbols  represent  different  stations. 


suit  is  caused  hy  the  seasonal  distrihution  of  para- 
sites in  relation  to  the  seasonal  distribution  of 
length  frequency  of  postlarval  P/t'j/ro6rac/j;a  (see 
Figures  16  and  18).  Note  that  the  6-8  mm  sizes 
with  highest  frequency  of  infection  are  at  the  size 
range  for  beginning  reproduction  as  adults  indi- 
cated by  results  from  laboratory  cultures.  Also 
notice  that  only  about  I'l  of  all  postlarvae  in  the 
1-  to  2-mm  size  classes  were  parasitized.  These 
are  the  sizes  of  ctenophores  which  reproduce  at  an 
early  age  with  small  numbers  of  eggs.  Secondly, 
the  distribution  of  percentages  of  total  occur- 
rences and  total  numbers  of  parasites  for  single 
infection  and  multiple  infection  show  a  decreasing 
occurrence  of  multiple  infection,  such  that  over 
9(y~c  of  the  occurrences  and  numbers  of  parasites 
are  as  one.  two,  or  three  parasites  per  host. 

Seasonal  variations  in  abundance  of  Bfrot'  sp., 
a  known  predator  of  other  ctenophores,  show  a 
pattern  very  similar  to  that  of  P.  bachei  (Figure 
20).  The  data  plotted  are  numbers  per  2  m^  (the 
sum  of  numbers  per  square  meter  of  each  repli- 
cate sample  I  at  station  5.  The  distributions  show 
seasonal  maximum  values  in  July- October  with 
secondary  high  abundances  in  winter  months. 
This  pattern  of  seasonal  co-occurrence  is  similar 


by  a  periodic  convergence  of  w-ater  types  contain- 
ing//vperoc /it'  and  Pleurobrachia. 

Data  from  all  stations  during  the  seasonal  study 
were  plotted  as  the  percentage  of  postlarval 
Pleurobrachia  containing  one  or  move  Hyperoche. 
The  mean  percentage  over  time  shows  that  Au- 
gust w'as  the  month  of  highest  percentage  hosts 
parasitized  (Figure  19);  at  this  time  over  one  in 
three  postlarvae  were  infected.  The  rate  of  in- 
crease of  percentage  infection  appears  to  be  faster 
than  the  decrease,  although  the  range  of  3  mo 
time  around  the  maximum  was  the  same  for  both. 
The  very  large  variability  on  some  sample  dates 
was  more  a  result  of  differences  in  percentages 
between  stations  than  an  artifact  of  sample  size, 
since  several  hundred  ctenophores  were  ex- 
amined per  sample  date. 

The  frequency  distributions  of  the  percentages 
of  total  occurrences  and  of  total  numbers  of  para- 
sites for  single  and  multiple  infection  and  for  dif- 
ferent sizes  of  hosts  show  two  interesting  results 
(Table  4).  First,  there  is  a  central  tendency  in  the 
percentages  of  total  occurrences  of  parasites,  and 
in  the  total  number  of  parasites,  with  6-8  mm 
sizes  being  the  most  frequently  infected.  This  re- 


10000 


E 

CM 

q: 

bJ 

a. 

bJ 

m 


JJASONDJF 
1971 


Figure  20. — Seasonal  variation  in  the  numerical  abundance  of 
p)ostlarvalP/ewro6racAia  bachei  and  postlarval  Beroe  sp.  at  sta- 
tion 5.  Values  are  expressed  for  simplicity  as  the  numbers  per  2 
m^  (the  sum  of  numbers  i>er  square  meter  in  the  replicate  sam- 
ples*. The  range  for  the  mean  of  replicate  samples  has  been 
indicated  previously  (e.g..  Figures  13  and  18). 


314 


HIROTA;  NATURAL  HISTORY  OF  PLELROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


Table  4. — The  frequency  distribution  of  the  number  of  parasites  per  host  for  14  size 
classes  of  postlarval  Pleurobrachia  bachei,  the  percentage  of  total  occurrences  At 
and  of  total  numbers  'B*  of  parasites  for  each  size  class,  and  the  percentages  of  total 
occurrences  <C)  and  of  total  numbers  <Di  of  parasites  for  single  and  multiple 
infections.  The  blank  spoces  indicate  absences. 


Mean 

Numoer  of  parasites  per  hos- 

aiameter 

(mm) 

1 

2 

3 

4 

5              6              7 

5 

A 

3 

2 

9 

2 

r     a  r 

1.09 

:  -4 

0.92 

-3 

42 

10 

7 

1 

5.96 

6.19 

4 

100 

30 

8 

1 

13.80 

13.37 

5 

82 

35 

9 

3 

1 

12.91 

13.94 

6 

147 

29 

11 

7 

2              1 

1 

19.66 

20.63 

7 

145 

31 

10 

3 

1 

18.87 

18.21 

8 

119 

36 

7 

4 

16.48 

16.22 

9 

56 

14 

1 

1 

7^ 

6.61 

10 

20 

6 

1 

2.68 

2.49 

11 

4 

3 

0.70 

0.71 

12 

1 

1 

020 

0.36 

13 

1 

0-10 

0.07 

>13 

1 

0.10 

0.14 

C 

72.29 

19.66 

5.36 

2.09 

0.30        0.10        0.10 

0.10 

0 

51  78 

28.16 

11  52 

5.97 

1.07        0.43        0.50 

0.57 

to  that  of  P.  bachei  and//,  mediterranea,  except 
that  Beroe  persists  through  the  year  rather  than 
being  absent  for  the  winter  and  spring  months. 
The  patterns  in  the  seasonal  distribution  of  Beroe 
and  P.  bachei  at  station  3  were  much  the  same  as 
at  station  5,  except  that  the  abundance  of  Beroe 
was  fourfold  lower  at  station  3,  and  the  secondary- 
high  abundances  of  Beroe  in  the  winter  and 
spring  months  at  station  5  was  not  as  well  de- 
fined at  station  3. 

The  partially  digested  stomach  contents  of  P. 
bachei  captured  at  the  surface  in  tows  of  short 
duration  '60  s  duration,  95  s  maximum  period  at 
risk  to  feeding  in  the  net)  showed  that  the  same 
species  groups  occur  as  in  tows  of  fivefold  longer 
duration.  These  species  are  :  li  copepods — L.  tri- 
spinosa,  A.  tonsa,  P.  parvus,  C.  anglicus,  E. 
acutifrons,  and  2 '  cladocerans — Evadne  nord- 
manni,  E.  spinifera.  E.  tergestina,  and  P.  avi- 
rostris.  The  results  provide  evidence  to  support 
the  contention  isee  results  of  stomach  contents 
below)  that  the  prey  in  stomach  contents  of  P. 
bachei  captured  in  tows  of  short  duration  are 
those  which  were  ingested  and  digested  in  nature 
prior  to  capture  by  the  net.  The  same  species 
would  probably  occur  in  stomachs  of  P.  bachei  if 
the  ctenophores  were  pipetted  from  the  sea  sur- 
'face  and  preser\'ed  immediately.  Seven  species 
of  zooplankton.  which  were  retained  quantita- 
tively in  the  0.363-mm  mesh  net  as  adults,  were 


considered  in  calculations  of  electivity  indices.  In 
the  Ivlev  electivity  index.  E  =  r  -  pj  ''r  -  pj,  r 
and  p  being  the  proportions  of  a  food  item  in  the 
stomach  and  in  the  environment  respectively. 
Paracalanus  parvus,  C.  anglicus,  and  E.  acuti- 
frons, which  occurred  frequently  in  the  stomachs 
but  passed  through  the  net,  were  not  included  in 
the  calculations.  The  results  on  the  basis  of  num- 
bers show  moderate  positive  selection  for  Acartia, 
Labidocera,  andE.  tergestina;  high  positive  selec- 
tion for  E.  nordmanni  a.ndE.  spinifera;  and  mod- 
erate and  strongly  negative  selection  for  Penilia 
and  Sagitta  'Table  5).  The  indices  on  the  basis  of 
organic  weight  show  the  same  trends,  but  the 
values  for  both  copepods  and  Evadne  are  in- 
creased somewhat,  and  that  for  Penilia 
decreased,  due  to  differences  in  bodily  weights. 
Penilia  has  a  negative  electivity  and  was  a  slowly 
digested  prey  species  (Table  1),  whereas 
Labidocera  and  Acartia  have  positive  electivity 
indices  and  were  more  rapidly  digested.  Prey 
selection  by  Pleurobrachia  is  more  complex  than 
dependence  on  prey  digestibility  alone.  Data  on 
the  stomach  contents  of  P.  bachei  during  the  sea- 
sonal study  and  observations  in  the  laboratorv*  of 
avoidance  behavior  and  prey  protective 
mechanisms  will  be  discussed  below  in  the  con- 
text of  prey  selection. 

In  the  study  of  diel  variation  in  feeding,  differ- 
ences in  the  percentage  of  ctenophores  with 


315 


Table  5. — Electivity  indices  for  seven  species  of  zooplankton 
which  are  retained  by  the  0.363-mm  mesh  net  as  adults.  The 
range  for  the  mean  is  calculated  from  the  replicate  samples  from 
the  proportion  of  the  numbers  and  the  proportion  of  the  calcu- 
lated organic  weight  present  in  the  sample  and  in  the  stomach  of 
the  ctenophores.  Refer  to  the  text  for  further  details. 


On  a 

numbers  basis 

On  an  o 

ganic  weight  basis 

Prey  Species 

E 

range  E 

E 

range  E 

Acartia  tonsa 

0.191 

0.118-0.264 

0.464 

0.434-0.495 

Labidocera 
trispinosa 

0.130 

0.099-0.160 

0413 

0.408-0.419 

Evadne 
tergestina 

0.244 

0.183-0.305 

0  506 

0.430-0,582 

E.  nordmanni 

0.806 

0.748-0.864 

0.953 

0.936-0.970 

E.  spinifera 

0.770 

0.748-0.792 

0.776 

0.659-0.893 

Penilia 
avirostris 

-0.345 

-0.300to -0.391 

-0.055 

-0.143to +0.033 

Sagitta 
euneritica 

-1.000 

-1.000  to -1.000 

-1.000 

-1.000  to -1.000 

Table  6. — Diel  variation  in  the  percentage  of  ctenophores  which 
have  empty  stomachs.  The  numbers  in  parentheses  are  the 
numbers  of  specimens  examined  per  sample. 


Replicate 

Midnight  station 

Midday 

station 

sample 

A 

B 

c 

A 

B 

1 

70 

62 

75 

69 

62 

(27) 

(40) 

(8) 

(16) 

(32) 

2 

76 

76 

57 

77 

64 

(38) 

(41) 

(46) 

(13) 

(14) 

3 

71 

90 

62 

71 

67 

(55) 

(10) 

(26) 

(24) 

(18) 

empty  stomachs  at  midnight  and  midday  were 
small,  the  medians  being  71%  and  68%,  respec- 
tively (Table  6).  These  medians  are  not 
significantly  different  as  determined  by  a  two- 
tailed  U-test  (P>>0.20).  It  is  concluded  that  no 
day-night  differences  exist  in  the  proportion  of 
the  postlarval  ctenophores  feeding,  at  least  at  the 
time  of  this  study. 

The  prey  categories  most  frequently  found  dur- 
ing the  diel  study  in  both  day  and  night  stomach 
contents  were  copepods  and  cladocerans — A. 
tonsa,  unidentified  copepods,  P.  parvus,  copepod 
nauplii,  Clausocalanus  spp.,E.  tergestina,  C.  ang- 
licus,  Oithona  spp.,£J.  acutifrons,  Oncaea  spp.,  and 
unidentified  material.  In  these  samples  A.  tonsa 
was  over  50%  of  all  prey  by  numbers.  The  species 
which  were  present  in  stomachs  of  P.  bachei 
captured  at  night  include  the  same  groups  cap- 
tured during  the  day,  the  larger  and  deeper-living 


FISHERY   BUM  tTlN:  VOl     72.  NO.   2 

copepods,  euphausiids  and  other  crustaceans 
being  absent  in  the  stomachs.  If  redundancy  in  the 
presence  of  prey  species  day  and  night  (a  qualita- 
tive aspect)  occurs  at  other  times  of  the  year,  then 
the  prey  species  of  Pleurobrachia  could  be  ade- 
quately described  by  stomach  analyses  of 
ctenophores  captured  during  the  daytime.  How- 
ever, in  quantitative  aspect  diel  variations  of  per- 
centages of  each  species  may  vary.  For  two  of  the 
species  most  frequently  present,  A.  tonsa  and  P. 
parvus,  the  results  are  different.  As  determined  by 
a  two-tailed  U-test,  there  is  no  significant  differ- 
ence in  median  percentage  Acartia  of  the  total 
number  of  prey  for  day  vs.  night  samples  (P>0.20); 
however,  the  same  test  ior  Par acalanus  indicates 
significant  day-night  differences  (P<0.05),  there 
being  more  frequent  occurrences  at  night  than 
during  the  day.  Further  investigation  of  prey 
selection  by  Pleurobrachia  in  relation  to 
time-space  distributions  of  prey  and  predators  is 
important  for  understanding  the  ecology  of  P. 
bachei  but  beyond  the  scope  of  the  present  study. 

The  stomach  contents  (on  the  basis  of  numbers 
and  mass  of  organic  carbon)  of  postlarval 
Pleurobrachia  in  10  size  classes  over  the  period  8 
March  1970  to  2  June  1971  indicated  some  pat- 
terns in  the  frequency  distribution  of  prey 
categories  (Table  7).  The  patterns  or  trends  exist 
as  four  types:  (I)  decreasing  frequency  with  in- 
creasing ctenophore  size,  (II)  increasing  frequency 
with  increasing  ctenophore  size,  (III)  little  change 
in  frequency  with  increasing  ctenophore  size,  and 
(IV)  non-systematic  change  and  low  frequency  of 
occurrence  for  all  ctenophore  sizes.  Examples  of 
each  pattern  type  are:  (I)  E.  acutifrons,  copepod 
eggs,^.  spinifera;  (IDA.  tonsa,  L.  trispinosa;  (III) 
Oithona  spp.,  C.  anglicus,  P.  parvus,  copepod 
nauplii;  (IV)  Rhincalanus  nasutus,  euphausiid 
calyptopis,  brachyuran  zoea,  Sagitta  euneritica. 

These  results  are  subject  to  several  sources  of 
bias,  three  of  which  are:  1)  the  occurrence  of  the 
stomach  contents  of  ctenophore  prey  in  the 
stomachs  of  ctenophores,  2)  the  numbers  of  obser- 
vations per  ctenophore  size  category  and  the 
number  of  total  occurrences  per  prey  category,  and 
3)  seasonal  variations  in  the  length- 
frequency  distributions  of  ctenophores  and  their 
co-occurrences  with  prey.  The  diatom  and  dino- 
flagellate  prey  categories  may  be  biased  toward 
higher  frequencies  of  occurrence  if  some  of  these 
types  of  organisms  which  occur  in  the  stomachs  of 
herbivores  are  released  into  the  gut  of  a 
ctenophore  during  digestion.  Fortunately,  these 


316 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 

Table  7. — Stomach  contents  over  the  period  8  March  1970  to  2  June  1971  for  10  size  classes  of  postlarval  Pleurobrachia  bachei.  Data 
are  the  percentage  by  numbers  (upper  value)  and  by  carbon  mass  (lower  value)  of  each  prey  category  in  the  stomachs  for  each  size  class 
of  ctenophore  calculated  separately.  The  first  10  prey  categories  are  given  in  ascending  order  of  body  mass;  thereafter  the  order  is  by 
taxonomic  group  (e.g.,  copepods,  cladocerans,  crustaceans,  chaetognaths,  etc.).  The  numbers  indicated  in  parentheses  below  each  size 
class  are  the  number  of  ctenophore  stomachs  examined  per  size  class.  Total  numbers  and  total  carbon  refer  to  values  of  all  prey  in  each 
ctenophore  size  class.  Carbon  mass  is  not  calculated  for  protozoans. 


Size 

class,  mean 

diameter 

(mm) 

Prey  category 

1 
(189) 

2 

(211) 

3 
(235) 

4 
(190) 

5 
(158) 

6 
(150) 

7 
(105) 

8 
(68) 

9 
(24) 

>10 
(22) 

Euterpina           %N 
acutifrons         %C 

20.85 
9.15 

18.33 
5.56 

15.36 
2.98 

15.58 
3.05 

7.41 
0.80 

5.54 
0.71 

4.05 
0.40 

4.00 
0.23 

0 

7.06 
1.00 

Oithona  spp. 

6.81 
2.18 

3.33 
0.47 

5.03 
0.24 

3.43 
0.14 

4.04 
0.27 

0.98 
0.06 

0.40 
0.01 

4.67 
0.12 

5.17 
0.58 

2.35 
0.17 

Oncaea  spp. 

0.85 
0.50 

2.33 
0.91 

0 
0 

1.25 
0.13 

0 
0 

0.33 
0.06 

1.21 
0.15 

1.33 
0.06 

0 

0 

Corycaeus 
anglicus 

426 
2.58 

933 
9.76 

950 
5.25 

8.41 
4.44 

9.76 
3.45 

4.56 
1.80 

5.26 
1.60 

7.33 
0.77 

3.45 
1.43 

14.12 
4.46 

Paracalanus 

parvus 

1.70 
2.40 

3.00 
2.22 

4.47 
2.01 

3.43 
1.23 

6.40 
2.11 

3.91 
1.16 

4.86 
1.24 

6.00 
0.67 

5.17 
1.07 

7.06 
2.17 

Acartia 
tonsa 

10.64 
39.59 

21.67 
48.04 

25.14 
36.94 

29.91 
39.21 

36  03 
33.66 

47.23 
43.17 

55.87 
37.49 

49.33 
16.80 

60.34 
53.78 

47.06 
37.62 

Calanus 
helgolandicus 

0 

0 

0.28 
3.18 

1.25 
7.83 

1.01 
10.14 

0.65 
2.85 

0.81 
4.61 

0.67 
3.26 

0 

1.18 
6.97 

Labidocera 
trispinosa 

0 

0 

2.51 
29.33 

2.49 
28.44 

3.37 
30.60 

2.93 
37.24 

4.45 
37.50 

5.33 
21.96 

1.72 
10.52 

2.35 
25.08 

Metridia 
pacifica 

0 

0 

0 

0 

0 

0 

0 

1.33 
4.89 

0 

1.18 
13.94 

Rhincalanus 
nasutus 

0 

0.33 
0.05 

0 

0 

0.34 
4.78 

0 

0 

0 

1.72 
23.90 

0 

Clausocalanus  spp 

0 

0 

0.56 
0.37 

0.62 
0.27 

0.67 
0.36 

0.33 

0.17 

0 

0.67 
0.06 

0 

0 

Ctenocalanus 

0 

0 

0 

0 

0 

0.33 

0 

0.67 

0 

0 

vanus 

0.09 

0.06 

Tortanus 
discaudatus 

0 

0 

0 

0.31 
0.45 

0.34 
0.17 

0 

0 

0 

0 

0 

Copepod  eggs 

14.47 
6.12 

10.67 
3.20 

8.38 
1.66 

4.36 
0.70 

2.69 
0.33 

1.30 
0.07 

0.81 
0.05 

2.00 
0.09 

3.45 
0.49 

0 

Copepod  nauplii 

11.91 
0.78 

6.67 
0.25 

335 
0.08 

4.05 
0.08 

9.43 
0.13 

4.89 
0.07 

5.67 
0.06 

4.67 
0.02 

3.45 
0.05 

0 

Unidentified 
copepods 

4.26 
5.60 

4.00 
3.03 

2.79 
1.27 

3.12 
1.26 

2.02 
0.57 

2.28 
0.64 

1.21 
0.25 

1.33 
0.13 

3.45 
0.96 

0 

Evadne 
nordmanni 

5.96 
16.47 

7.00 

11.12 

6.70 
6.42 

5.61 

4.77 

1.01 
0.60 

4.89 
2.90 

5.26 
2.24 

1.33 
0.27 

8.62 
5.02 

8.24 
4.10 

Evadne 
splnifera 

2.13 
5.88 

1.00 
1.59 

0.56 
0.54 

0.31 
0.26 

0.67 
0.40 

0.33 
0.19 

0 

0 

0 

0 

Evadne 
tergestma 

0.85 
2.35 

1.33 
2.12 

1.96 
1.87 

2.80 
2.39 

1.68 
1.00 

6  84 
4.06 

4.45 
1.90 

0.67 
0.14 

0 

1.18 
0.58 

Evadne  spp 

0 

2.67 
4.24 

3.91 
3.75 

3.43 
2.92 

0 

0 

0 

0 

0 

0 

Pen  ilia 
avirostrls 

0.42 
0.56 

0.67 
0.50 

2.51 
1.15 

2.18 
0.88 

3.03 
0.86 

2.93 
0.83 

0.40 
0.08 

1.33 
0.13 

1.72 
0.48 

4.71 
1.11 

Podon 
polyphemoides 

0 

0.67 
1.06 

0.28 
0.27 

1.25 
1.06 

1.35 
0.80 

0.33 
0.19 

0 

0 

0 

0 

Euphauslld 
calyptopis 

0 

0 

0  28 
0.46 

0 

0 

0.33 
0.33 

0 

0 

1.72 
1.72 

0 

Clrriped  nauplii 

0 

0 

0 

0 

0.34 
0.02 

0 

0 

0 

0 

0 

Mysids 

0 

0 

0 

0 

0 

0 

0.40 
12.34 

0 

0 

0 

Brachyuran 
zoea 

0 

0 

0 

0 

0.34 
0.96 

0.65 
1.84 

0 

1.33 
1.30 

0 

1.18 
2.79 

(Continued) 


317 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


Table  7. — Continued 


Size 

class,  mean 

diameter 

mm) 

Prey  category 

1 
(189) 

2 

(211) 

3 
(235) 

4 
(190) 

5 
(158) 

6 
(150) 

7 
(105) 

8 
(68) 

9 

(24) 

>10 

(22) 

Unidentified 
crustaceans 

383 
2.52 

1,67 
063 

1.12 
0.25 

1-56 
0.32 

1,35 
0,19 

0,98 
0,14 

040 
0  04 

2-00 
0-10 

0 

0 

Sagitta 
euneritica 

0 

0.33 
2.14 

0 

0 

0,34 
6.10 

0 

0.40 
0-01 

0-67 
48-88 

0 

0 

Oikopleura  spp. 

0.42 
202 

0 

1.12 
1  83 

0 

1.01 
1  03 

1  30 
1,32 

0 

0 

0 

0 

Echinopluteus. 
doliolids 

0 

0 

0 

0 

0 

0 

0 

0 

0 

2.36 

Fish  eggs 

0 

0.67 
2.77 

0 

0 

0,34 
0,53 

0 

0 

0 

0 

0 

Sarcodina 

0 

0 

0 

0.31 

034 

0.65 

0 

0 

0 

0 

Noctiluca 
scintillans 

0 

0 

0 

0 

0 

0 

0,40 

0 

0 

0 

Dinoflagellates 

0.85 

0 

1,12 

0,31 

0,67 

1,95 

081 

0 

0 

0 

Diatoms 

0 

0 

0 

0,62 

0 

0 

1-62 

0 

0 

0 

Unidentified 
material 

9.79 
1.29 

4.33 
0.33 

3.07 
0.14 

3.43 
0.14 

4  04 
0,11 

3.58 
0.10 

1-21 
002 

3.33 
0.03 

0 

0 

Total  numbers 

235 

300 

358 

321 

297 

307 

247 

150 

58 

85 

Total  carbon,  ug 

178.47 

396.48 

78476 

791.93 

1045,87 

1087.39 

1215-87 

1534.41 

209.17 

358.80 

taxa  made  up  less  than  2%  of  any  one  category  by 
numbers  and  less  on  a  mass  basis  because  of  their 
small  size.  The  number  of  observations  per 
ctenophore  size  category  are  similar  for  classes 
1-6,  but  thereafter  they  decrease  sevenfold.  There 
are  few  observations  in  the  last  two  size  classes, 
because  these  sizes  are  relatively  infrequent  and 
occur  in  high  numbers  only  during  July- August. 
Some  of  the  larger  copepods  (e.g.,  Calanus,  Met- 
ridia,  and  Rhincalanus)  occur  relatively  infre- 
quently in  stomachs,  perhaps  because  of  their  rel- 
ative rarity  and  spatial  separation  from  the 
ctenophores.  Other  infrequent  groups  such  as  fish 
eggs,  cirriped  nauplii,  euphausiids,  etc.,  may  not 
be  spatially  separated  but  are  perhaps  rare,  not 
selected  as  prey  or  are  unavailable  because  of 
temporal  separation  during  different  seasons. 
Whatever  the  reasons  for  the  infrequent  occur- 
rence of  these  groups  in  the  stomachs  of 
Pleurobrachia,  the  data  for  these  prey  are  much 
less  reliable  and  many  more  observations  are  re- 
quired to  establish  patterns  of  occurrence  with 
size  of  the  ctenophore  predator.  The  potential  ef- 
fect of  seasonal  variations  in  size-frequency  dis- 
tribution of  ctenophores  and  co-occurrence  of  prey 
on  patterns  of  stomach  contents  is  suggested  when 
the  annual  data  are  examined  separately  by  sea- 


sons. The  results  indicate  that  some  prey  are  very 
seasonal  in  occurrence,  while  many  are  present 
throughout  the  year.  The  seasonal  data  are  given 
(Table  8)  for  only  those  categories  which  showed 
strong  seasonal  variations.  The  first  two  prey 
were  most  frequent  in  summer-fall,  E.  tergestina 
in  summer-winter,  the  next  four  in  fall  and  the 
last  one  in  winter-spring.  Note  the  differences  in 
occurrence  of  three  species  of  Evadne  regarding 
seasonal  separation  and  predation  by  different 
sizes  oi Pleurobrachia. 

When  all  stomach  content  data  are  grouped  to 
include  all  sizes  of  postlarval  Pleurobrachia  and 
prey  categories  are  ordered  by  rank  of  occurrence, 
the  results  show  that  A.  tonsa  and  £.  acutifrons 
account  for  nearly  one-half  of  all  prey  items 
(Table  9).  Thereafter,  the  percentage  contribu- 
tion from  each  category  decreases  to  less  than  1% 
by  the  sixteenth  category,  at  which  point  the 
cumulative  percentage  is  94.2%.  On  a  mass  basis 
Calanus,  Labidocera,  and  Sagitta  join  Acartia  as 
the  main  large  prey  items.  While  these  larger 
items  may  afford  good  growth  to  a  few  individu- 
als, most  of  the  ctenophore  population  is  being 
nourished  by  A.  tonsa,  E.  acutifrons  and  sev- 
eral other  species  of  copepods  and  cladocerans. 

Variations  in  the  standing  stock  of  food  avail- 


318 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


Table  8. — Seasonal  variations  in  the  stomach  contents  of  ctenophores 
for  eight  prey  categories.  All  values  are  expressed  as  the  number  of 
occurrences  per  1,000  stomachs.  The  seasons  spring  (SP),  summer 
(SU),  fall  (F)  and  winter  (W)  are  groups  of  three  months  starting  with 
February  1970  and  ending  in  January  1971;  the  following  spring  1971 
is  also  included.  The  dashed  lines  indicate  absence  of  data. 


Size 

class,  mean  diameter  (mm) 

Prey  category 

1 

2 

3 

4 

5 

6 

7 

8 

9 

>10 

Paracalanus 

SP 

0 

100 

154 

0 

200 

0 

0 



0 



parvus 

SU 

46 

50 

52 

44  146 

67 

91 

91 

91 

300 

F 

0 

22 

85 

55 

79 

98 

125 

26 

111 

0 

W 

33 

0 

0 

182  400 

0 

125 

429 

— 

500 

SP 

0 

0 

0 

83 

0 

0 

0 

3,000 

333 

250 

Labidocera 

SP 

0 

0 

0 

0 

0 

0 

500 



0 



trispinosa 

SU 

0 

0 

21 

0 

49 

0 

45 

318 

91 

100 

F 

0 

0 

66 

77 

79 

88 

125 

26 

0 

250 

W 

0 

0 

0 

91 

0 

0 

0 

0 

— 

0 

SP 

0 

0 

0 

0 

125 

0 

0 

0 

0 

0 

Evadne 

SP 

0 

0 

0 

0 

0 

0 

0 



0 



tergestina 

SU 

0 

0 

21 

44 

0 

100 

0 

0 

0 

0 

F 

42 

0 

47 

55 

56 

167 

139 

26 

0 

250 

W 

0 

364 

0 

91 

0 

91 

125 

0 

— 

0 

SP 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Calanus 

SP 

0 

0 

0 

0 

0 

0 

0 

— 

0 

— 

helgolandicus 

SU 

0 

0 

0 

0 

0 

33 

0 

0 

0 

100 

F 

0 

0 

9 

44 

34 

10 

28 

26 

0 

0 

w 

0 

0 

0 

0 

0 

0 

0 

0 

— 

0 

SP 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Evadne 

SP 

0 

0 

0 

0 

0 

0 

0 



0 



spinitera 

SU 

0 

8 

0 

0 

0 

0 

0 

0 

0 

0 

F 

21 

43 

18 

11 

22 

10 

0 

0 

0 

0 

w 

33 

0 

0 

0 

0 

0 

0 

0 

— 

0 

SP 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Penilia 

SP 

0 

0 

0 

0 

0 

0 

0 

— 

0 

— 

avlrostris 

SU 

0 

8 

0 

0 

49 

100 

0 

45 

0 

300 

F 

21 

22 

85 

77 

79 

59 

14 

26 

111 

250 

w 

0 

0 

0 

0 

0 

0 

0 

0 

— 

0 

SP 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Podon 

SP 

0 

0 

0 

0 

0 

0 

0 



0 

— 

polyphemoides  SU 

0 

8 

0 

0 

0 

0 

0 

0 

0 

0 

F 

0 

22 

9 

44 

45 

10 

0 

0 

0 

0 

w 

0 

0 

0 

0 

0 

0 

0 

0 

— 

0 

SP 

0 

0 

0  . 

0 

0 

0 

0 

0 

0 

0 

Evadne 

SP 

0 

0 

0 

0 

0 

0 

0 

— 

0 

— 

nordmanni 

SU 

0 

58 

72 

59 

0 

0 

0 

0 

0 

0 

F 

62 

22 

19 

0 

0 

29 

14 

0 

0 

0 

w 

30 

1,000 

1 ,333  909 

0 

364 

1,500 

286 

— 

0 

SP 

111 

143 

538  333  375 

1,600 

0 

0 

1,667 

1,750 

able  to Pleurobrachia  from  18  June  1970  to  2  June 
1971  showed  a  twentyfold  range,  with  high  val- 
ues in  May  to  early  November  and  low  values 
from  mid-November  to  mid-March  (Table  10). 
The  food  concentrations  were  about  10-30  mg 
C/m^  during  the  summer-fall  maxima  in  num- 
bers and  standing  stocks  of  Pleurobrachia 
postlarvae.  The  decrease  in  abundance  of 
Pleurobrachia  during  November  and  December 
(see  Figure  13)  was  associated  with  a  fivefold  de- 
crease in  the  standing  stock  of  prey.  The  winter 
increase  of  P.  bachei  occurred  while  food  con- 
centration doubled  from  the  minimum  in  De- 


cember. The  higher  food  concentrations  in  May 
and  June  do  not  seem  to  cause  increases  in 
ctenophore  abundance. 

DISCUSSION 

The  vertical  distribution  of  P.  bachei  in  La  Jolla 
Bight  is  related  to  the  diel  light-dark  cycles,  but 
in  reverse  to  the  pattern  for  most  migrating  zoo- 
plankton;  the  pattern  is  the  result  of  one  or  more 
causes  of  differing  selective  advantage  to  the  tem- 
poral persistence  of  this  species.  Four  potential 


319 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


Table  9. — Rank  order  in  frequency  of  occurrence  by  numbers  of 
all  developmental  stages  per  prey  category  in  all  sizes  of 
Pleurobrachia  postlarvae  and  the  corresponding  estimates  of 
total  carbon  mass  per  prey  category. 


Table  10. — Seasonal  variations  in  the  calculated  standing 
stocks  of  prey  for  Pleurobrachia  at  station  3. 


Prey  category 


Frequency     Percent       ug  C 


Percent 


Acartia  tonsa 

815 

34.56 

2,644.23 

34.78 

Euterpina  acutifrons 

270 

11.45 

114.04 

1.50 

Corycaeus  anglicus 

180 

7.63 

225.73 

2.97 

Copepod  nauplii 

139 

589 

6.95 

0.09 

Copepod  eggs' 

129 
(1,649) 

5.47 

49.47 

0.65 

Evadne  nordmanni 

122 

5.17 

256.20 

3.37 

Paracalanus  parvus 

101 

4.28 

108.80 

1.43 

Unidentified 

89 

3.77 

8.90 

0.12 

Oithona  spp. 

83 

3.52 

15.99 

0.21 

Unidentified  copepods 

62 

2.63 

62.00 

0.82 

Evadne  tergestina 

61 

2.59 

128.10 

1.68 

Labidocera  trispinosa 

58 

2.46 

2,085.54 

27.43 

Penilia  avirostris 

45 

1.91 

45.00 

059 

Unidentified  crustaceans 

34 

1.44 

17.00 

022 

Evadne  spp. 

33 

1.40 

69.30 

0.91 

Oncaea  spp. 

19 

0.81 

8.86 

0.12 

Dinoflagellates 

17 

0.72 

— 

— 

Calanus  helgolandicus 

14 

0.59 

355.00 

4.67 

Evadne  spinitera 

14 

0.59 

29.40 

0.39 

Podon  polyphemoides 

12 

0.51 

25.20 

0.33 

Oikopleura  spp. 

12 

0.51 

43.20 

0.57 

Clausocalanus  spp. 

8 

0.34 

11.74 

0.15 

Brachyuran  zoea 

6 

0.25 

60.00 

0.79 

Diatoms 

6 

0.25 

— 

— 

Sagitta  euneritica 

4 

0.17 

822.4 

10.82 

Sarcodina 

4 

0.17 

— 

— 

Metridia  pacifica 

3 

0.13 

125.0 

1.64 

Rhincalanus  nasutus 

3 

0.13 

100.2 

1.32 

Euphausiid  calyptopis 

3 

0.13 

10.80 

0.14 

Fish  eggs 

3 

0.13 

16.50 

0.22 

Ctenocalanus  vanus 

2 

0.08 

2.00 

0.03 

Tortanus  discaudatus 

2 

0.08 

5.40 

0.07 

Cirriped  nauplii 

0.04 

0.2 

0.003 

Mysids 

0.04 

150.0 

1.97 

Echinopluteus 

0.04 

— 

— 

Doliolids 

0.04 

—  . 

— 

Noctiluca  scintillans 

0.04 

— 

— 

Total 

2,358 

7,603.15 

'The  frequency  value  refers  to  the  nunnber  of  groups  of  copepod  eggs 
and  the  value  in  parenthesis  below  it  refers  to  the  total  number  of  eggs. 


advantages  of  migration  to  P.  bachei  are  the  abil- 
ity to:  1)  seek  locations  and  depths  with  favorable 
food  types  and  concentrations,  2)  seek  locations 
and  depths  with  few  predators  and  parasites,  3) 
avoid  lethal  or  near-lethal  surface  temperature 
after  the  downward  migration  at  night  and  in- 
crease the  rate  of  development  by  living  in 
warmer  water  during  the  day,  and  4)  maintain  the 
pattern  of  high  abundance  close  to  shore  and  de- 
crease the  chance  of  drifting  offshore.  No  data 
have  been  collected  on  quantitative  changes  in  the 
abundance  of  prey  and  predators  with  P.  bachei 
during  vertical  migration;  such  information 
would  enable  qualitative  evaluation  of  the  effect 
of  these  changes  on  the  pattern  of  vertical  dis- 
tributions. Limited  data  from  the  study  of  diel 
changes  in  the  species  composition  of  prey  in 
stomachs  of  ctenophores  indicated  no  major 
changes  between  day  and   night,   although 


Sample  date 


Mean 
(mg  C/m3) 


Range 
(mg  C/m^) 


18  June  1970 
14  July 
13  August 
29  August 
22  September 
5  November 
18  November 
16  December 

11  January  1971 
8  February 

12  March 
4  May 

2  June 


10.9 

10.8-11.0 

10.7 

10.4-11.1 

15.5 

6.0-25.0 

17.8 

16.4-19.1 

27.8 

20.2-35.4 

15.7 

13.4-17.9 

5.8 

3.4-  8.1 

2.7 

2.6-  2.8 

6.8 

3.7-  9.9 

6.0 

2.2-  9.7 

5.2 

5.1-  5.3 

58.4 

52.2-64.6 

9.3 

9.3-  9.4 

Paracalanus  occurred  more  frequently  in 
stomachs  of  ctenophores  captured  at  night. 
Another  major  study  would  be  required  to  quan- 
tify changes  in  the  temporal  and  spatial 
co-occurrence  of  Pleurobrachia  with  their  prey 
and  predators.  The  data  on  vertical  and  seasonal 
distribution  of  P.  bachei  and  the  thermal 
stratification  of  water;  the  failure  of  laboratory 
cultures  at  20°C;  and  growth  experiments  in  the 
deep  tank  facility  at  14.5°  and  19.5°C  are  inter- 
preted to  indicate  that  vertical  migration  for  this 
ctenophore  is  beneficial  for  survival  and  would 
optimize  the  rates  of  development  and  increase  of 
bodily  mass.  A  constant  temperature  of  20°C  was 
detrimental  to  survival  and  growth  of  bodily 
weight  (Figure  1),  relative  to  conditions  at  15°C.  It 
is  suspected  that  in  August  when  the  ctenophore 
abundance  is  highest  and  the  maximum  thermal 
stratification  occurs,  vertical  migration  from  the 
surface  to  20-m  depth  increases  the  chance  of 
survival  by  lowering  the  ambient  temperature  at 
night  by  nearly  10°C.  In  addition,  the  detrimental 
effect  of  high  temperature  on  somatic  growth  may 
be  decreased  and  the  ctenophores  develop  at  some 
rate  intermediate  to  the  rate  at  12°  and  22°C. 
Growth  experiments  using  the  deep  tank  facility 
in  which  stratification  of  temperature  is  made  to 
simulate  conditions  in  nature  might  support  some 
of  these  speculations.  Alternatively,  laboratory 
growth  experiments  could  be  made  in  which 
temperature  is  varied  with  a  semidiurnal  period. 
Another  complication  in  these  experiments,  if 
they  are  to  simulate  conditions  in  the  field,  is  the 
co-occurrence  of  the  parasite  Hyperoche  and  its 
possible  temperature-dependent  effect  on  the 
growth  and  survival  of  P.  bachei. 

A  consequence  of  diel  vertical  migration  in  the 


320 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEl  IN  LA  JOLLA  BIGHT 


coastal  waters  off  southern  California  is  the  po- 
tential effect  on  the  horizontal,  offshore  distribu- 
tion of  a  species.  Stevenson  (IGSS)"*  summarized 
some  wind  data  for  the  Newport  Beach  to  Los 
Angeles  Harbor  area,  which  show  that  in  the  sea 
breeze-land  breeze  diel  variation  of  wind  velocity 
there  is  a  stronger  sea  breeze  component  from  the 
west-northwest  quadrant  during  the  afternoons 
and  a  more  variable  and  weak  wind  in  the  morn- 
ings. Robert  Arthur  has  suggested  that  a  possible 
result  of  the  diel  variation  in  wind  velocity  and  the 
observed  pattern  of  vertical  migration  in  P. 
hachei  may  in  part  account  for  the  maintenance  of 
high  ctenophore  abundances  close  to  shore.  By 
living  in  the  wind-mixed  layer  during  the  day 
with  a  westerly-northwesterly  sea  breeze, 
ctenophores  are  moved  shoreward.  At  night 
through  the  early  morning  hours  the  weaker  land 
breeze  moves  the  surface  waters  offshore,  but  by 
living  deeper  at  night  the  net  offshore  movement 
of  ctenophores  should  be  relatively  smaller  than 
the  shoreward  displacement.  The  frequent  strand- 
ing or  grounding  of  drogues  nearshore  suggests  a 
net  onshore  movement  of  water.  One  mechanism 
of  horizontal,  seaward  transport  is  the  rip  cur- 
rents, but  these  are  probably  important  only  a  few 
hundreds  of  meters  seaward  of  the  surf  zone  and 
are  dependent  on  the  size  of  sea  swells.  It  is  not 
known  how  important  stranding  is  as  a  source  of 
mortality  to  Pleurobrachia,  but  in  summer 
months  Pelagia  (Scyphozoa)  are  frequently 
stranded  on  La  Jolla  beaches  and  are  broken  apart 
in  the  surf  zone.  Other  macrozooplankton,  such  as 
salps  and  Velella,  periodically  occur  on  the  beach 
and  in  waters  near  the  shore.  It  is  not  clear  what 
cues  or  mechanisms  the  ctenophores  use  to  main- 
tain their  distribution  to  within  1  km  of  shore 
without  most  being  washed  into  the  surf  and 
killed.  A  number  of  net  tows  taken  near  the  end  of 
Scripps  Institution  pier  and  just  seaward  of  the 
surf  zone  indicate  absence  of  P.  bachei. 

The  estimates  of  abundance  of  P.  bachei  at  fixed 
stations  located  alongshore  2-3  km  from  the 
shoreline  are  subject  to  variability  in  time  and 
space  from  several  causes.  At  a  single  station  the 
abundance  will  be  affected  by:  1)  spatial 
heterogeneity  and  patchiness  on  the  scale  of 
100-m  horizontal  distance  and  20-  to  50-m  depth 
over  the  course  sampled  during  a  tow,  2)  the  stage 


••Stevenson.  R.  E.  1958.  An  investigation  of  nearshore  ocean 
currents  at  Newport  Beach,  California.  UnpubL  Rep.  to  Orange 
Cty.  Sanit.  Dist.,  108  p. 


of  the  tides  and  the  tidal  current  velocity  (see 
Figure  15),  and  3)  the  water  temperature 
stratification  and  near-surface  drift  due  to  the 
wind.  The  magnitude  of  replicate  sample  error  is 
one-half  to  twice  the  mean,  and  the  variability  in 
abundance  due  to  the  presumed  horizontal  motion 
generated  by  the  tides  and  wind  for  the  annual 
average  is  about  the  same  as  replicate  sample 
error. 

For  estimates  of  abundance  on  a  given  sampling 
date  at  stations  1.6  km  from  the  shore  at  different 
locations  along  the  coast,  "true  spatial"  variabil- 
ity exists  in  addition  to  replicate  sampling  error 
and  aliasing  due  to  physical  effects  of  tides  and  the 
wind.  It  is  difficult  to  sort  out  quantitatively  the 
separate  error  components  due  to  physical  effects 
and  true  spatial  effects  alone,  because  the  time 
period  for  the  physical  effects  to  bias  sampling 
(about  6  h)  is  about  the  same  as  that  required  to 
move  through  space  and  sample  different  stations. 
Variability  around  the  mean  of  all  stations  at  one 
sampling  date  includes  variations  due  to  replicate 
sampling  error,  variations  due  to  physical  effects, 
and  variations  due  to  true  spatial  differences.  The 
relative  magnitudes  of  these  components  of  varia- 
tion estimated  from  the  95%  confidence  limits  of 
the  two-way  analysis  of  variance  and  the  regres- 
sion of  abundance  on  tidal  height  are:  1)  the  95% 
confidence  limits  about  the  mean  of  all  stations  at 
a  given  time  of  sampling  is  the  mean  multiplied 
and  divided  by  6.23,  2)  the  95%  confidence  limits 
about  the  mean  of  replicate  samples  is  the  mean 
multiplied  and  divided  by  2.15,  3)  the  range  of  the 
expected  abundance  from  the  regression  equation 
over  the  observed  values  of  tidal  heights  is  four- 
fold, or  a  range  of  about  one-half  to  twice  the 
overall  annual  mean,  and  4)  the  residual  true  spa- 
tial variation  calculated  by  difference  is  the  mean 
multiplied  and  divided  by  1.45  (i.e.,  6.232  =  2.15^ 
X  2^  X  1.45^).  In  terms  of  the  relative  contribution 
of  these  three  components  to  the  total  variability, 
the  values  are  2.2:1.9:1  for  replicate  sampling 
error,  physical  effects,  and  true  spatial  variation, 
respectively.  The  relative  contribution  of  replicate 
sampling  error  vs.  physical  plus  true  spatial  vari- 
ations to  the  total  variability  of  all  stations  on  one 
sampling  date  is  1:1.8.  These  results  from  a  sam- 
pling program  not  designed  specifically  to  sepa- 
rate each  effect  suggest  that  physical  effects  on 
sampling  bias  and  the  replicate  sample  error  are 
important  relative  to  real  spatial  differences  of 
abundance  between  stations  equidistant  from 
shore.  A  synoptic  sampling  program  with  two  or 


321 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


more  ships  would  better  enable  separation  of  the 
total  variability  into  variations  from 
time-dependent  physical  effects,  true  spatial  dif- 
ferences, and  replicate  sample  error.  It  is  indeed 
discouraging  that  confidence  limits  for  the  mean 
of  replicate  samples  could  not  be  reduced  below 
about  one-half  to  twice  the  mean,  even  with  a  t 
value  based  on  90  degrees  of  freedom.  Zooplank- 
tologists  may  continue  to  be  plagued  with  the  ina- 
bility to  reduce  field  sampling  variability  much 
below  this  level,  given  reasonable  time  and  man- 
power limitations  and  no  significant  changes  in 
sampling  methodology.  Because  of  their  large  size 
and  lack  of  rapid  escapement,  postlarvalP.  bachei 
are  as  easy  to  sample  accurately  as  any  zooplank- 
ter  is  likely  to  be. 

Seasonal  changes  in  abundance  of  P.  bachei 
postlarvae  observed  in  La  Jolla  Bight  during  my 
study  (Figure  13)  agree  with  the  earlier  work  of 
Esterly  (1914)  off  San  Diego  and  work  by  Parsons 
et  al.  (1970)  in  the  Strait  of  Georgia,  British  Co- 
lumbia (the  values  reported  in  the  Strait  of  Geor- 
gia work  are  numbers  of  Pleurobrachia  plus 
Philidium  per  cubic  meter).  These  two  studies 
showed  that  seasonal  maxima  occurred  in  July  or 
August;  high  densities  were  from  June  to  Sep- 
tember and  lower  values  and  absences  were  ob- 
served from  October  to  March.  Esterly  (1914) 
noted  that  P.  bachei  were  more  abundant  at  tem- 
peratures above  18°C  than  below;  they  were  espe- 
cially abundant  at  about  19°C  in  August.  He  also 
noted  that  although  P.  pileus  and  P.  bachei  are 
similar  in  morphology,  their  distributional  pat- 
tern and  temperature  optima  are  widely  different. 
In  the  Atlantic  P.  pileus  was  abundant  at  lower 
temperatures  during  the  year  (<15°C);  in  the 
Pacific  the  reverse  seemed  to  be  the  case. 

Seasonal  studies  of  P.  pileus  in  Wellington 
Harbor,  New  Zealand  (Wear,  1965)  and  the  North 
Sea  region  (Russell,  1933;  Fraser,  1970;  Greve, 
1971)  show  that  it  differs  from  P.  bachei  in  the 
season  of  maximal  abundance.  In  Wellington 
Harbor  P.  pileus  was  dominant  in  the  winter 
plankton,  and  it  was  the  most  variable  plank- 
tonic  species.  P.  pileus  was  absent  in  February- 
March,  rare  (1-10/20-min  tow)  in  April-May,  and 
December-January,  common  (20-100/tow)  in 
June  and  September- November  and  abundant 
(500-1,000/tow)  in  July- August  (note  that  this  is 
the  winter  in  New  Zealand).  Critical  temperature 
for  the  occurrence  of  P.  pileus  was  between  15° 
and  16°C.  When  the  temperature  fell  below  this 
level,  P.  pileus  occurred  in  great  abundance;  in 


early  summer  at  temperatures  above  16°C  they 
were  rare  or  absent.  In  the  North  Sea  off 
Plymouth,  P.  pileus  occurred  in  a  bimodal  sea- 
sonal distribution  with  early  summer 
(May-June)  and  fall  (October)  maxima  (Russell, 
1933).  In  the  North  Sea  near  Helgoland  P.  pileus 
occurred  with  a  May- June  maximum  at  10-15°C 
and  a  less  distinct  fall  peak  (Greve,  1971). 
Long-term  mean  seasonal  distributions  in  the 
Scottish  North  Sea  showed  a  clear  November 
maximum  with  a  less  distinct  secondary  mode  in 
June  (Fraser,  1970);  however,  the  month  of  the 
seasonal  maximum  can  be  as  early  as 
July-August  in  "abnormal"  years  compared  to 
the  expected  fall  maximum  of  normal  years. 
Highest  numerical  abundance  of  postlarval  P. 
pileus  in  the  North  Sea  was  on  the  order  of 
10-20/m3  (Fraser,  1970;  Greve,  1971).  This  is 
about  the  same  as  the  maximum  of  40/m^  I  found 
for  P.  bachei  postlarvae,  but  through  most  of  the 
year  the  population  of  P.  bachei  was  dominated 
by  numbers  of  larvae  and  eggs.  Contrary  to  the 
annual  or  biannual  spawning  patterns  of  P. 
pileus  in  the  North  Atlantic  (Fraser,  1970),  P. 
bachei  produced  eggs  throughout  the  year  except 
for  spring  and  some  summer  months. 

Important  differences  exist  between  P.  pileus 
and  P.  bachei  in  addition  to  the  pattern  of  sea- 
sonal distributions  and  the  surface  temperature 
at  the  season  of  maximum  abundance.  Patterns 
in  the  seasonal  co-occurrence  of  Bero'e  with 
Pleurobrachia  and  the  parasitism  of  each 
Pleurobrachia  species  are  different  for  P.  pileus 
and  P.  bachei.  In  the  North  Sea,  P.  pileus 
occurred  in  patterns  of  seasonal  abundance  which 
were  180°  out  of  phase  with  the  abundance  of 
Beroe  (Russell,  1933;  Greve,  1971).  In  La  Jolla 
Bight  abundances  of  P.  bachei  and  Bero'e  sp.  gen- 
erally increased  and  decreased  in  phase  without 
time  lags.  The  seasonal  patterns  for  the  co- 
occurrence of  Bero'e  with  P.  pileus  and  P.  bachei 
suggest  that  Bero'e  and  other  predators  may  over- 
exploit  P.  pileus  temporarily  to  decrease  the 
population  abundance  seasonally,  whereas  Bero'e 
and  P.  bachei  appear  to  co-occur  in  a  less  intense 
predator-prey  association.  In  the  North  Sea,  P. 
pileus  were  parasitized  by  nematodes  (Greve, 
1971)  and  cercaria  of  Opechona,  a  trematode 
(Fraser,  1970).  In  La  Jolla  Bight,  P.  bachei  were 
parasitized  by  H.  mediterranea.  Farther  to  the 
north  Hyperoche  mediterranea  is  replaced  by  H. 
medusarum  (Bowman,  1953),  and  P.  bachei  is 
parasitized  by  this  species  in  waters  off  northern 


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HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEl  IN  LA  JOLLA  BIGHT 


California  (Brusca,  1970). 

Off  southern  California,  the  strongest  equator- 
ward  surface  flow  occurs  during  spring  and  sum- 
mer, and  south  of  Point  Conception  the  semiper- 
manent cyclonic  eddy  produces  a  northward  in- 
shore circulation  (Wyley,  1966).  Beneath  the 
California  Current,  the  undercurrent  is  a  sub- 
thermocline  poleward  flow  of  water  of  relatively 
high  temperature  and  salinity;  for  example  in  Au- 
gust 1966  the  undercurrent  at  lat.  31°N,  long. 
177°W  was  close  to  the  continental  slope,  being 
about  20  km  wide  and  300  m  thick  (Wooster  and 
Jones,  1970).  This  undercurrent  below  200  m  sur- 
faces well  inshore  of  the  main  stream  in  late  fall 
and  early  winter  when  northerly  winds  are  weak 
or  absent  (Reid  et  al.,  1958). 

The  seasonal  distributions  of  P.  bachei  in  La 
Jolla  Bight  showed  some  features  which  are  con- 
sistent with  seasonal  changes  in  the  vertical 
movement  of  the  California  undercurrent  (also 
called  the  Davidson  Current).  Postlarvae  de- 
creased by  over  two  orders  of  magnitude  from  the 
end  of  October  through  December,  and  reappeared 
at  moderate  abundance  in  late  January  and  Feb- 
ruary. For  larvae  and  eggs,  the  timing  and  mag- 
nitude of  the  winter  decrease  were  about  the  same, 
but  the  frequency  of  absences  was  less  than  for 
postlarvae  (see  Figures  13  and  14).  Another  vari- 
able associated  with  the  presumed  winter  shoal- 
ing of  the  undercurrent  is  the  fivefold  decrease  in 
prey  standing  stock  from  early  November  to  the 
middle  of  December  (Table  10).  A  subsurface  cur- 
rent which  rises  to  the  surface  in  winter  is  ex- 
pected to  contain  relatively  low  crops  of  animals 
and  plants,  and  poleward  advection  of  water  from 
the  south  should  cause  decreases  in  abundance  of 
Pleurobrachia. 

Studies  of  stomach  contents  of  P.  pileus  in  the 
Scottish  North  Sea  (Fraser,  1970)  and  in  Kaneohe 
Bay,  Oahu  (Rowe,  1971)  indicate  that  this 
ctenophore  is  predominantly  a  crustacean  feeder, 
especially  of  copepods,  cladocerans,  and  cirriped 
nauplii.  In  the  Scottish  North  Sea,  P.  pileus  fed 
about  809c  of  the  time  on  Acartia,  Calanus, 
Evadne,  invertebrate  eggs,  Temora  longicornis, 
Oithona,  unidentified  copepods,  cirriped  larvae, 
Spiratella,  andPodon.  In  Kaneohe  Bay  75%  of  the 
prey  were  nauplii  of  barnacles  and  copepods  and 
the  appendicularian  Oikopleura  longicauda 
(Rowe,  1971).  The  evidence  indicated  that 
Pleurobrachia  very  rarely  fed  on  fish  eggs  and 
larvae.  The  North  Sea  study  included  seasonal 
and  annual  data,  the  differences  between  which 


Fraser  attributed  to  differences  in  the  composition 
of  the  plankton  rather  than  prey  selectivity  by 
Pleurobrachia. 

The  gut  contents  of  P.  bachei  in  La  Jolla  Bight 
generally  agree  with  the  results  for  P.  pileus  in 
that  they  fed:  1)  predominantly  on  crustaceans, 
especially  copepods;  2)  very  rarely  on  fish  eggs  and 
larvae;  and  3)  on  a  broad  spectrum  of  organisms 
some  of  which  appear  seasonally  for  only  limited 
periods.  The  major  difference  between  the  results 
from  the  three  study  areas  is  that  in  Kaneohe  Bay 
Pleurobrachia  fed  on  relatively  few  prey 
categories,  the  number  being  about  one-fifth  that 
in  my  study  and  the  North  Sea  study.  The  three 
most  frequent  foods  on  a  numerical  basis  were:  1) 
barnacle  and  copepod  nauplii,  Oikopleura  and 
other  copepods  in  Kaneohe  Bay;  2)  Acartia, 
Calanus,  and  Evadne  in  the  Scottish  North  Sea, 
and  3)  Acartia,  Euterpina,  and  Corycaeus  in  La 
Jolla  Bight.  Both  studies  of  P.  pileus  gut  contents 
considered  the  postlarvae  as  a  homeogeneous 
group.  I  have  treated  the  postlarvae  of  P.  bachei 
as  being  made  up  of  10  separate  size  classes  to 
show  that  some  changes  do  occur  in  prey  fre- 
quency during  ontogeny  (Table  7).  All  studies  of 
ctenophore  gut  contents  have  been  inadequate  to 
describe  quantitatively  the  developmental  stages 
of  prey  species  eaten  by  different  life  history 
stages  of  ctenophores,  including  the  larvae.  Great 
difficulties  and  amounts  of  work  would  be  re- 
quired for  such  a  study  (each  copepod  species  has 
13  developmental  stages  counting  the  eggs).  Many 
important  biological  interactions  probably  occur 
during  different  developmental  stages  during  on- 
togeny, yet  we  know  very  little  about  them. 

Feeding  rate  experiments  with  9-  to  10-mm 
diameter  P.  bachei  (Bishop,  1968)  have  shown 
differences  between  mean  ingestion  rates  of 
copepodids  of  Epilabidocera  amphitrites  and 
Pseudocalanus  minutus;  P.  bachei  also  fed  at  a 
faster  rate  on  copepodids  and  adults  of  P.  minutus 
than  on  their  nauplii.  These  results  showed  that 
rates  of  feeding  depend  on  prey  size  and  other 
differences  between  the  same  stages  of  different 
prey  species  and  between  different  developmental 
stages  of  one  species.  The  study  of  feeding  be- 
havior of  P.  pileus  indicated  that  this  ctenophore 
regulates  its  feeding  rate  by  changing  the  average 
size  of  the  tentacles  in  response  to  different  con- 
centrations of  Artemia  nauplii  (Rowe,  1971). 

During  laboratory  culturing  and  rate  of  diges- 
tion of  prey  experiments,  differences  were  ob- 
served in:  1)  the  avoidance  and  escape  behavior  of 


323 


prey,  2)  the  protective  spination  of  various  species, 
3)  the  strength  and  sensory  acuity  of  larger  zoo- 
plankters,  and  4)  the  active  search  patterns  of 
"setting  out"  tentacles  by  the  ctenophore.  Each  of 
these  four  factors  in  addition  to  other  variables, 
which  are  determined  by  the  relative  abundance 
and  movement  of  species  in  nature,  have  some 
bearing  on  the  selection  of  prey  by  Pleurobrachia. 
The  first  consideration  is  time-space  co- 
occurence  of  prey  with  the  ctenophore.  Since 
the  ctenophores  are  neritic  and  mostly  live  close  to 
shore  in  the  upper  50-60  m,  they  will  occur  with 
surface-living  holoplanktonic  and  meroplank- 
tonic  species,  only  coexisting  with  deeper-living, 
migratory  species  at  night.  Secondly,  the 
ctenophores  will  most  frequently  encounter  the 
most  abundant  organisms  in  numbers  per  unit 
volume.  Size  and  swimming  activity  of  the  prey 
are  also  important  to  determine  the  chance  of  en- 
counter with  the  tentacles.  Bodily  length  deter- 
mines the  likelihood  of  retention  of  a  given  or- 
ganism by  the  tentacle  net,  and  swimming  activ- 
ity determines  how  often  the  prey  will  encounter  a 
given  ctenophore  if  swimming  in  a  random  man- 
ner. Rowe  (1971)  has  shown,  using  Artemia 
nauplii,  that  the  instantaneous  feeding  rate  of  P. 
pileus  follows  the  form  for  effusion  of  an  ideal  gas; 
this  requires  the  assumption  that  prey  move  about 
randomly.  However,  I  have  seen  P.  bachei  make 
at  least  three  different  types  of  settings  of  its  ten- 
tacles in  apparent  attempts  to  alter  the  pattern  of 
search  for  prey:  1)  a  double  helix  set  like  two 
interwoven  corkscrews  perpendicular  to  a  level 
surface  with  the  body  at  the  uppermost  end,  2)  a 
pair  of  spirals  parallel  to  a  level  surface  with  the 
ctenophore  body  at  the  outer  end  of  the  spiral,  and 
3)  linear  and  curved  sets  which  are  placed  at  dif- 
ferent angles  with  respect  to  the  vertical  and  with 
the  ctenophore  body  either  heading  up  or  down. 
The  types  of  tentacle  settings  may  be  adaptive 
responses  to  the  nonrandom  swimming  patterns  of 
different  zooplankton  species,  some  of  which  move 
more  in  a  horizonal  or  a  vertical  plane.  It  is  at  this 
point  that  animal  behavior  becomes  very  impor- 
tant. Species  which  co-occur  with  Pleurobrachia 
and  are  relatively  abundant  (up  to  several 
hundred  per  cubic  meter)  are  not  necessarily 
eaten  by  this  ctenophore,  because  these  potential 
prey  probably  use  their  sensory  acuity  and 
locomotive  power  to  avoid  danger.  One  outstand- 
ing example  is  S.  euneritica,  a  species  which  is 
very  fast  and  difficult  to  catch  compared  to  most 
zooplankton;  it  had  a  highly  negative  electivity 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 

index  (Table  9).  Assuming  that  a  prey  organism 
has  just  made  contact  with  the  ctenophore  tenta- 
cles, three  possible  outcomes  have  been  observed 
in  the  laboratory  for  different  species:  1)  the  prey 
is  too  strong  and  breaks  away  from  the  tentacle 
hold;  2)  the  prey  provides  a  strong  escape  re- 
sponse, becomes  further  entangled  and  is  eaten; 
and  3)  the  prey  provides  little  or  no  escape  re- 
sponse, remains  nearly  motionless  and  "plays 
dead,"  often  being  dislodged  from  the  tentacle  hold 
and  not  eaten.  A  species  which  is  too  powerful  for 
P.  bachei  to  capture  is  H.  mediterranea.  The 
adults  of  this  amphipod  can  break  away  from  the 
entanglement  and  also  have  the  ability  to  exploit 
the  ctenophores  as  a  predator.  Prey  which  provide 
a  strong,  "calanoid  escape  response"  are  almost 
always  further  entangled  by  swirls  of  the  tentacle 
branches  and  are  eaten.  The  immediate  strug- 
gling and  pulling  away  appears  to  signal  the 
ctenophore  of  a  successful  prey  capture,  much  as  I 
would  expect  that  a  spider  detects  the  impact  and 
vibrations  of  the  prey  struggling  on  its  web.  The 
copepods  such  as  Acartia,  Labidocera,  Calanus, 
etc.,  exhibit  strong  escape  responses  when  stimu- 
lated by  contact  or  approaching  danger.  Two  prey 
species  were  observed  to  exhibit  the  motionless  or 
"play  dead"  response.  These  are  C.  anglicus  and 
P.  auirostria.  Penilia  is  also  one  of  the  species 
which  has  a  negative  electivity  index  or  is  taken 
less  frequently  than  in  proportion  to  abundance  in 
the  water.  Once  the  prey  is  brought  to  the  mouth  of 
the  ctenophore,  the  next  limitations  are  the 
configuration  of  the  prey  body  and  appendages 
plus  the  protection  from  external  spination.  Bodi- 
ly shapes  such  as  those  ofSagitta  and  zoea  larvae 
of  Porcellanidae  (a  family  of  crabs)  create  difficul- 
ties for  their  ingestion  by  Pleurobrachia.  Large 
Sagitta  must  be  bent  in  half  and  ingested  at  the 
middle  section  first  (observations  are  from  the 
laboratory  work;  gut  contents  from  field  sampled 
ctenophores  show  that  this  event  is  very  infre- 
quent). The  long  anterior  and  posterior  spines  of 
the  porcellanid  zoeae  prevent  full  ingestion  and 
digestion  entirely,  although  the  prey  probably  do 
not  survive  the  capture.  Many  other  decapod  lar- 
vae possess  stout  spines  and  very  thick  exoskele- 
tons  (e.g.,  Emerita  larvae),  which  prevent  inges- 
tion and  would  retard  digestion  as  well.  Some 
brachyuran  zoeae  which  have  dorsal  and  lateral 
spines  have  been  observed  to  cut  open  the 
ctenophore  gut  wall  during  ingestion.  Recall  that 
brachyuran  zoeae  only  make  up  0.25%  of  the  total 
number  of  prey  in  ctenophore  guts  (Table  7). 


324 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


DEMOGRAPHY  AND  NET 
PRODUCTION 

Methods 

Computations  of  stage-specific  instantaneous 
mortality  rates  (hereafter  referred  to  as  mortality 
rates  or  mortalities)  were  made  in  order  to  use 
these  values  in  other  calculations  to  estimate 
population  parameters  and  rates  of  net  produc- 
tion. Mortalities  were  calculated  using  field  data 
on  stage  frequencies  treated  as  a  composite  of  all 
samples  taken  on  each  sampling  date  and  labora- 
tory data  on  rates  of  development,  with  tempera- 
ture and  food  concentrations  being  similar  to  aver- 
age values  observed  in  the  field  study  area.  The 
growth  or  development  rate  data  are  from 
laboratory  cultures  at  15°C  and  35  /jg  C/liter  food 
concentration.  The  mortalities  were  computed  by 
a  computerprogram  (Fager,  1973)  which  solves  an 
equation  to  fixed  level  or  error  by  a  specified 
number  of  iterative  calculations. 

N,+  1 IN^  =  t,  (1  -  e  ~'^^v  +  1  )lt,  +  1  (e  ^'x  -  1).  (1) 

The  variables  ^r  and  tx^^  i  are  the  duration  of 
development  in  days  for  stage  x  andx+1,  respec- 
tively; variables  A^v  andA^v+i  are  the  numbers  of 
each  stage  in  the  composite  divided  by  the  respec- 
tive duration  of  development.  The  mortality  rate 
on  a  per  day  basis  from  stage  x  to  stage  x  + 1  is  M; 
for  an  organism  with  continuous  growth,  such  as  a 
ctenophore,  a  "stage"  is  a  size  category.  Positive, 
mortalities  can  be  calculated  only  when  Nx  ex- 
ceeds A'^;^  + 1 .  Implicit  in  the  calculation  are  the 
assumptions  that:  1)  successive  stages  of  the  or- 
ganisms were  born  during  a  period  of  constant 
recruitment  and  2)  successive  stages  have  lived 
together  in  spatial  proximity,  or  emigration  is 
balanced  by  immigration  in  the  water  parcel.  . 

The  life  table  calculations  were  based  on  the 
estimated  mortalities  for  different  time  periods  of 
field  sampling  and  the  mean  schedule  of  live 
births  from  laboratory  cultures  at  IS'^C.  The  equa- 
tions used  to  calculate  population  parameters  and 
stable  age  distributions  are  from  Birch  (1948). 

The  rate  of  net  production  per  day  of  each  de- 
velopmental stage  is  a  function  of  the  numbers 
and  weights  of  the  animals  and  their  instantane- 
ous rate  of  tissue  growth  and  of  mortality  on  a  per 
day  basis;  the  rate  of  net  production  by  a  species 
population  of  a  given  age  structure  is  simply  the 


sum  of  the  rates  for  each  stage.  These  rates  are 
calculated  from  the  equation  of  Ricker  (1958), 
which  relates  the  rate  of  net  production  to  the 
mean  daily  standing  stock  and  the  rates  of  growth 
and  mortality. 


NP,  =  G,B,il  -  e 


Gi-M 


)/(M,-G,)  =  G,Bi.(2) 


In  this  equation  0 ,  and  M,  are  the  mean  exponen- 
tial coefficients  or  mean  instantaneous  rates  of 
growth  and  mortality  of  the  ith  stage  on  a  per  day 
basis.  The  variables  Bi  and  B,  are  the  calculated 
standing  stocks  per  sample  in  milligrams  organic 
matter  per  square  meter  of  the  ith  stage  at  the 
beginning  of  the  day  (B, )  and  the  average  over  a 
24-h  period  (Bi ).  This  function  equates  the  rate  of 
net  production  per  day  for  the  ith  stage  (NP,  has 
units  of  milligrams  organic  matter  per  square 
meter  over  a  24-h  period)  to  the  instantaneous 
rate  of  tissue  growth  times  the  standing  stock  at 
the  beginning  of  the  day  (the  beginning  of  the  day 
is  the  time  a  field  sample  is  taken)  corrected  for 
differential  increases  due  to  tissue  growth  and 
differential  decreases  due  to  mortality.  For 
further  details  refer  to  the  work  of  Ricker  (1958) 
and  Mullin  and  Brooks  (1970).  Note  that  the  rate 
of  net  production  per  day  is  actually  an  average 
value,  because  it  is  calculated  using  means  for 
growth  and  mortality  rates. 

The  rates  of  net  production  for  postlarvae  and 
larvae  of  P.  bachei  were  calculated  according  to 
Equation  (2)  above.  No  values  for  mortality  rates 
of  eggs  were  calculated,  but  the  hatching  time  of 
eggs  at  15°C  is  about  24  h.  In  calculation  of  the  net 
production  of  eggs  per  day,  it  is  assumed  a  steady 
state  in  the  standing  stock  of  eggs  with  a  hatching 
time  of  24  h.  This  is  equivalent  to  the  assumption 
that  the  rate  of  net  production  of  eggs  per  day  is 
equal  to  the  standing  crop  at  the  time  of  sampling 
the  eggs. 

From  calculations  of  the  net  production  per  day 
of  postlarvae  for  each  replicate  sample  at  each 
station,  the  mean  value  and  the  variance  of  the 
mean  are  calculated  according  to  standard 
parametric  statistics.  At  a  given  station,  the  total 
amount  of  organic  matter  produced  over  some  in- 
terval of  time,  i^,  equals  the  product  of  the  mean 
rate  per  day  and  the  time  interval  in  days.  For 
calculations  of  the  annual  net  production  (ANP), 
it  is  assumed  that  the  mean  rate  per  day  on  a  given 
sampling  date  at  one  station  applies  linearly  over 
an  interval  of  time  equal  to  the  sum  of  one-half 


325 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


the  period  between  the  given  sampHng  date  and 
the  previous  sampling  date  plus  one-half  the 
period  between  the  given  sampling  date  and  the 
next  following  sampling  date. 

The  ANP  equals  the  sum  of  all  net  production 
increments  over  the  year. 


tn=n 

ANP  =  SUM  NP  t„  (tn  4  ;  -t,  -  ;  )/2. 

tn  —  J- 


(3) 


In  the  equation  tn  refers  to  the  nth  sample  date, 
^Ptn  refers  to  the  mean  rate  of  net  production  per 
day  on  the  nth  sample  date,  and  ANP  is  the  mean 
value  of  the  annual  net  production  for  any  life 
history  stage  being  considered.  For  the  first  and 
last  sampling  dates  of  the  year,  the  mean  rates  per 
day  were  applied  over  one-half  the  following 
sampling  date  interval  and  one-half  the  previous 
sampling  date  interval,  respectively.  Calculations 
using  Equation  (3)  were  carried  out  separately  for 
postlarvae,  larvae,  and  eggs  at  station  5  off 
Scripps,  and  the  total  for  all  life  history  stages  is 
the  sum  of  the  annual  values  for  the  eggs,  larvae, 
and  postlarvae  at  that  station.  ANP  was  also  cal- 
culated at  stations  1,  3,  and  6  for  postlarvae  only. 
The  variance  of  the  mean  value  of  the  ANP  at  a 
given  station  was  calculated  as  the  product  of  the 
variance  of  the  mean  rate  of  net  production  per 
day  and  the  square  of  the  time  interval  over  which 
it  was  applied,  summed  for  all  time  intervals  dur- 
ing the  year.  The  equation  was  derived  from  the 
variance  formula  of  a  dependent  variable  which 
equals  the  product  of  two  independent  variables 
(net  production  over  a  time  interval,  a  t,  equals 
the  product  of  the  mean  net  production  per  day 
and  zi^),  by  solving  for  the  square  of  the  differen- 
tial of  net  production  over  a  time  interval  a^  The 
covariance  term  is  zero  since  the  daily  net  produc- 
tion and  time  interval  between  sampling  dates  are 
independent.  The  term  for  the  square  of  the  mean 
daily  net  production  multiplied  by  the  variance  of 
A  Ms  presumed  to  be  small,  because  sampling  dur- 
ing the  year  was  within  a  few  hours  at  the  same 
time  of  the  day  for  all  sampling  dates. 

t„=n 


Var(ANP)=SUM  Var(A^P^J(^„4i-^„_im.(4) 

n  ^  1 


The  symbols  are  as  given  above  in  Equation  (3), 
and  Var  (ANP)  and  Nd,x{NPtn)  refer  to  the  var- 


iance of  mean  annual  net  production  and  the  var- 
iance of  mean  daily  net  production  on  sampling 
date  tn,  respectively. 

Results 

During  the  field  study  from  8  March  1970  to  2 
June  1971, 100  mortality  values  were  obtained  for 
postlarvae  and  larvae.  On  any  one  sampling  date 
it  was  not  possible  to  calculate  mortality  values 
for  all  size  classes,  especially  with  small  sample 
sizes  in  older  stages.  Therefore,  the  mortalities 
from  all  sample  dates  were  grouped  into  seven 
time  periods  and  seven  size  classes  (excluding 
eggs)  in  order  to  obtain  an  estimate  of  mortality 
for  each  class  over  time.  The  mortalities  were 
grouped  according  to  the  subjective  criterion  that 
medians  of  a  group  would  differ  from  any  other  by 
at  least  50%.  The  mortalities  for  size  classes  were 
set  by  the  comparisons  of  mean  numbers  per  class 
between  successive  classes. 

For  the  time  period  of  1  May  to  18  June  1970  a 
life  table  calculation  is  given  in  Table  11.  The 
mean  hatching  success  of  eggs  is  94%.  The  Ix 
values  are  the  probability  that  an  individual  born 
will  survive  to  the  beginning  of  each  age  interval. 
The  instantaneous  mortality  rates  which  were 
used  to  construct  the  / ,:  schedule  are  as  follows:  1) 
0.170  for  larvae  ofage  1-19  days,  2)  0.021  for  stage 
1-2  mm  postlarvae  ofage  19-45  days,  3)  0.150  for 
stage  3-4  mm  postlarvae  of  age  45-53  days,  4) 
1.047  for  stage  5  mm  postlarvae  ofage  53-54  days, 
5)  0.572  for  stage  6  mm  postlarvae  ofage  54-55 
days,  6)  0.378  for  stage  7-8  mm  postlarvae  ofage 
55-63  days,  and  7)  0.260  for  stage  9-13  mm  post- 
larvae ofage  greater  than  63  days.  These  mortal- 
ity rates  were  applied  equally  for  each  age  inter- 
val over  the  duration  of  the  respective  stages.  Note 
that  up  to  age  53  days  (4.5  mm)  the  first  45  live 
births  give  a  net  reproduction  of  1 .0405  (60%  of  the 
total),  enough  to  replace  the  population.  The  next 
53  live  births  add  23%  of  the  total  net  reproduc- 
tion. The  enormous  potential  reproductive  capac- 
ity at  age  61-63  days  and  older  is  not  fully  realized 
because  of  the  miniscule  numbers  which  survive 
to  this  age.  These  results  show  the  great  impor- 
tance of  early  reproduction  in  size  classes  1-2  mm 
toward  the  net  reproduction. 

The  population  parameters  and  stable  age  dis- 
tributions in  May-June  and  three  other  time 
periods,  each  with  its  own  schedule  of  survival  and 
the  mean  schedule  of  births,  are  shown  in  Table 
12.  For  the  1  May  to  18  June  period,  the  observed 


326 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


Table  11. — The  life  table  for  Pleurobrachia  bachei  during  1 
May- 18  June  1970  based  on  laboratory  growth  and  reproduction 
data  at  15°C  and  calculated  mean  rates  of  mortality  for  this 
period.  The  symbols  dx.lx.  bx  andx  represent  the  age  interval  in 
days,  survival  to  the  beginning  of  the  age  interval,  the  numbers 
of  live  births  during  the  age  interval,  and  the  pivotal  age,  respec- 
tively. 


dx 

1x 

bx 

1xbx 

Ubxx 

0-1 

1 .0000 

1-3 

.9400 

3-5 

.6691 

5-7 

.4762 

7-9 

.3390 

9-11 

.2413 

11-13 

.1717 

13-15 

1222 

15-17 

0870 

17-19 

.0619 

19-21 

.0441 

21-23 

.0423 

23-25 

.0405 

1 

0.0405 

0,9720 

25-27 

,0388 

0 

27-29 

.0372 

0 

29-31 

.0357 

1 

.0357 

1,0710 

31-33 

0342 

0 

33-35 

0328 

0 

35-37 

.0315 

0 

37-39 

0302 

0 

39-41 

.0290 

0 

41-43 

.0277 

6 

.1662 

69804 

43-45 

0266 

15 

.3990 

17.5560 

45-47 

.0256 

3 

.0768 

3.5328 

47-49 

,0189 

13 

.2457 

11.7936 

49-51 

.0140 

4 

.0560 

2.8000 

51-53 

.0103 

2 

.0206 

1.0712 

53-55 

.0077 

53 

.4081 

22.0374 

55-57 

.00152 

102 

.1550 

8.6800 

57-59 

.00071 

8 

.0057 

.3306 

59-61 

.000336 

53 

.0178 

1.0680 

61-63 

.000158 

353 

.0558 

3.4596 

63-65 

.000074 

325 

.0240 

1.5360 

65-67 

.000044 

302 

.0133 

.8778 

67-69 

.000026 

204 

.0053 

.3604 

69-71 

.000015 

557 

,0084 

.5880 

71-73 

000009 

298 

,0027 

.1944 

73-75 

.000006 

960 

,0058 

.4292 

75-77 

,000003 

1026 

,0031 

.2356 

77-79 

.000002 

1319 

,0026 

2028 

Ro  - 

=  1,7481 

85.7768 

mean  age  distribution  in  field  samples  was  66.7% 
eggs,  20.0%  larvae,  8.7%  1-  to  2-mm  postlarvae, 
and  4.7%  all  other  stages.  The  field  age  distribu- 
tion is  unlike  the  stable  age  distribution  in  that 
the  proportions  of  eggs  and  larvae  are  reversed 
and  the  proportion  of  late  stages  is  sevenfold 


higher  than  in  the  stable  age  distribution.  The 
population  growth  rates  (r)  in  other  time  periods 
predict  decreases  of  population  abundance  from  8 
March  to  2  April  (r  =  -0.105)  and  increases  in  14 
July  to  21  August  (r  =  0.020)  and  in  October  (r  = 
0.0115).  Eggs  and  larger  ctenophores  were  again 
more  frequent,  and  larvae  less  frequent  in  the  field 
during  July- August  than  calculated  for  the  stable 
age  distribution. 

For  postlarvae  the  mean  rate  of  net  production 
per  day  for  all  stations  located  1.6  km  from  the 
shore  (Table  13)  followed  the  seasonal  variation  in 
the  standing  stocks.  The  maximum  rate  of  net  pro- 
duction on  13  August,  212  mg  organic  matter  m'^ 
day  ,  was  about  20%  of  the  standing  crop.  About 
two-thirds  of  ANP  occurred  during  August.  The 
variance  of  the  mean  ANP  is  quite  large,  but  since 
the  confidence  limits  for  the  mean  are  determined 
by  standard  deviations,  the  95%  confidence  inter- 
val for  the  mean  ANP  is  4,200-6,280  mg  organic 
matter  m~^  yr  \ 

Mean  ANP  of  postlarvae  at  stations  1,  3,  and  5 
(1.6  km  from  shore)  and  at  station  6  (10  km  from 
shore)  are  given  in  Table  14.  Note  that  "annual" 
net  production  at  the  stations  1,  3,  and  5  are  for 
0.956  yr  and  at  station  6  for  0.84  yr;  these  values 
were  not  corrected  to  a  full  year  by  proportion, 
because  statistical  tests  based  on  variances  would 
not  be  valid.  Tests  for  differences  of  variances 
(F-ratio)  and  means  (f-tests)  between  stations  1, 
3,  and  5  were  made.  The  variance  of  station  3  was 
significantly  different  from  that  of  stations  1  and  5 
rP<0.01),  but  the  variances  of  stations  1  and  5 
were  not  different  from  each  other  (P>0.05). 

The  difference  between  means  of  all  pairs  of 
contrasts  for  stations  1,  3,  and  5  are  significant 
(P<<0.01).  The  net  production  at  station  6  located 
10  km  from  shore  off  Scripps  Institution  was  about 


Table  12. — Summary  of  population  parameters  for  P.  bachei  during  four  time  periods  in  1970.  The 
symbols /Jo,'",  T,B,  b,d  andCx  refer  to  net  reproduction,  instantaneous  rate  of  population  growth, 
generation  time,  finite  birth  rate,  instantaneous  birth  rate,  instantaneous  death  rate  and  stable 
age  distribution  respectively.  The  percentages  of  eggs  (E),  larvae  (L),  1-2  mm,  and  s  3  mm  stages 
are  given  in  that  order  for  the  stable  age  distribution. 


Time  period 

«o 

r 

T 

B 

b 

d 

Cx 

8  Mar.-2  Apr. 

0.0058 

-0.105 

49.0 

0.2485 

0.2617 

0.3667 

1  May-18  June 

1.7481 

00115 

48.6 

0.2348 

0.2328 

0.2213 

23.3  E 
69.0  L 
7.0  1-2  mm 
0.7  3  3  mm 

14July-21  Aug. 

2.9271 

0.020 

53.7 

0.248 

0.248 

0.228 

24.6  £ 
69.3  i. 
5.6  7-2  mm 
0.5  3  3  mm 

8-22  Oct. 

1.7565 

0.0115 

490 

0.2348 

0.2328 

0.2213 

Same  as  1  May-18  June 

327 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


Table  13. — Seasonal  variation  of  the  mean  rate  of  net  produc- 
tion per  day  (NPtn  is  in  mg  organic  matter  rii^  day"')  for  postlar- 
va\  Pleurobrachia  bachei  at  stations  located  1.6  km  from  shore  in 
La  Jolla  Bight.  The  mean  annual  net  production  is  given  as  the 
sum  of  the  mean  rate  per  day  multiplied  by  the  appropriate  time 
interval,  A  <;  the  variance  of  the  mean  annual  net  production  is 
also  given.  Note  that  the  sum  is  for  0.956  yr. 


Sampling 

Number  of 

NPtn 

NPtn(^t)  Var(/VPrn)Af2 

date 

samples 

18  June  1970 

10 

5.188 

36.316 

270.5065 

2  July 

10 

5.356 

69.628 

216.5228 

14  July 

10 

9.080 

131.660 

639.0759 

31  July 

10 

38.396 

575.940 

35.286.5025 

13  Aug 

10 

212.287 

2,229.014 

102.152  1706 

21  Aug- 

8 

70.454 

563,632 

11.169.1520 

29  Aug. 

10 

22.712 

295.256 

2,370,3264 

16  Sept. 

6 

21.416 

428.320 

2,824,7200 

8  Oct. 

6 

10.843 

195.174 

7,217,9748 

22  Oct. 

6 

41.882 

586.348 

91,135,2960 

5  Nov. 

6 

1.775 

23.962 

141,4260 

18  Nov. 

6 

0.350 

4.725 

7,4322 

2  Dec. 

10 

0.114 

1.596 

0.7291 

16  Dec. 

10 

0.0003 

0.006 

0.0003 

11  Jan.  1971 

6 

0.321 

6.741 

14.4207 

27  Jan. 

6 

0.962 

13.468 

87.1612 

8  Feb. 

8 

1.745 

25.302 

102.6440 

25  Feb. 

6 

0.240 

3.840 

4.9306 

12  Mar. 

6 

1.148 

24.108 

221.5584 

7  Apr. 

6 

1.018 

20.360 

48.4800 

20  Apr. 

6 

0.202 

2.727 

2.8978 

4  May 

6 

0.061 

0.854 

0,1764 

18  May 

6 

0.044 

0.638 

0,1051 

2  June 

6 

0.002 

0.015 

0  0004 

SUM 

5.239.63 

253,914,2097 

sevenfold  lower  than  that  at  station  5  (1.6  km  off 
Scripps  Institution)  and  fivefold  lower  than  the 
mean  for  all  stations  located  1.6  km  from  shore. 
For  these  comparisons,  the  production  at  station  6 
was  extrapolated  to  0.956  yr.  The  net  production  of 
larvae  and  eggs  at  station  5  contributed  only 
about  3%  of  the  sum  of  net  production  of  eggs, 
larvae,  and  postlarvae  at  that  station. 

For  stations  1,3,  and  5  the  annual  mean  ratio  of 
the  net  production  per  day  of  postlarvae  to  their 
mean  daily  standing  stock  (B,  of  Equation  (2))  are 
0.197,  0.196,  and  0.211,  respectively.  The  mean 
ratios  are  based  on  32,  43,  and  54  observations  for 
stations  1,  3,  and  5,  respectively.  There  are  no 
significant  differences  between  the  variances 
(F-ratio  tests)  of  all  paired  contrasts  of  stations 
(P>0.05).  There  are  no  significant  differences  be- 
tween all  paired  contrasts  of  station  means 
(P>0.50).  The  overall  annual  mean  ratio  at  these 
three  stations  is  0.202,  with  95%  confidence  limits 
for  the  mean  being  0.187-0.217.  Thus,  the  ratio  of 
production  to  biomass  on  the  day  of  maximal  pro- 
duction was  no  greater  than  the  annual  mean. 

In  order  to  estimate  the  food  chain  efficiency 
(defined  for  any  trophic  level  L  as  the  steady  state 
ratio  of  yield  to  predators  at  level  L -I- 1  to  the  net 


production  of  trophic  level  L-1)  of  the  transfor- 
mation of  materials  or  energy  by  trophic  levels, 
the  two  parameters  stated  above  must  be  known: 
1 )  the  net  production  of  potential  food  at  level  L-1 
and  2)  the  yield  to  predators  from  the  level  L, 
which  in  steady  state  is  the  total  net  production  of 
level  L  minus  losses  to  decomposers.  This  concept 
can  be  extended  to  include  more  than  three  trophic 
levels,  e.g.,  the  square  root  of  the  ratio  of  ingestion 
by  secondary  carnivores  to  net  primary  production 
might  be  termed  the  equal  transfer  efficiency  of 
herbivores  and  primary  carnivores. 

In  practice  it  is  very  difficult  to  accurately 
"measure"  the  secondary  production  of  the  entire 
herbivore  trophic  level  in  the  sea,  and  such  data 
are  not  available  in  my  study  area.  Further,  the 
estimates  of  net  production  by  P.  bachei  could  not 
be  partitioned  into  the  fractional  losses  to  decom- 
posers and  as  yield  to  predators.  Therefore,  two 
simplifying  assumptions  were  made  in  calculat- 
ing the  transfer  efficiency  for  the  macrozooplank- 
ton  of  La  Jolla  Bight:  1 )  all  of  the  net  production  by 
P.  bachei  resulted  in  yield  to  predators  and  none  to 
decomposers  and  2)  the  efficiency  was  constant 
and  equal  from  the  primary  producer  level 
through  the  first-order  carnivore  level  of  P. 
bachei.  Given  these  limiting  assumptions,  the 
efficiency  calculated  is  referred  to  as  the  "equal 
transfer  efficiency."  Thus,  if  net  production  data 
were  not  available  for  trophic  levels  between 
primary  producers  and  the  trophic  level  of  in- 

Table  14. — Summary  of  "annual"  net  production  (ANP)  values 
(in  mg  organic  matter  in^  time"')  of  Pleurobrachia  bachei,  at  four 
stations  in  La  Jolla  Bight.  The  value  at  station  6  is  for  0.84  yr;  all 
other  values  are  for  0.956  yr.  The  standard  deviation  of  ANP  for 
each  respective  value  is  also  given.  Values  are  for  postlarvae 
unless  otherwise  specified.  The  mean  production  for  larvae  and 
eggs  at  stations  1-5  were  calculated  assuming  that  the  same 
fraction  of  production  would  be  as  larvae  and  eggs  at  all  stations 
as  at  station  5. 


Number 

of 

Station 

sample  dates 

ANP 

SD 

1 

24 

2.320 

104 

3 

24 

4,320 

377 

5 

25 

7.650 
144  Larvae 
111  Eggs 

125 

18 

6 

6 

17 

950 

85 

Mean  of 

24 

5,240 

504 

station  1-5 

Mean  of 

24 

5.240 

station  1-5 

99  Larvae 

plus  eggs  and 

76  Eggs 

larvae 

5,415 

504 

328 


HIROTA:   NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEI  IN  LA  JOLLA  BIGHT 


terest,  a  general  equation  to  calculate  equal  trans- 
fer efficiency  for  n  transfers  is 


ETE  ^(NPL/NPP)^'^ 


(5) 


In  the  equation  ETE  is  the  equal  transfer 
efficiency,  NPL  is  the  net  production  of  trophic 
level  L  (which  is  equal  to  ingestion  by  level  L  +  1), 
NPP  is  the  net  primary  production,  and  n  is  the 
number  of  transfers  from  primary  producers  (the 
zeroth  trophic  level)  through  trophic  level  L.  This 
equation  was  derived  from  the  works  of  Schaefer 
(1965)  and  Ryther  (1969).  The  equal  transfer 
efficiency  calculated  in  this  manner  for  n>2  says 
nothing  about  the  efficiency  of  a  given  trophic 
level,  but  only  the  equal  efficiency  of  all  trophic 
levels  from  primary  producers  through  trophic 
level  L. 

The  equal  transfer  efficiency  from  primary  pro- 
ducers through  P.  bachei  was  calculated  using  es- 
timates of  annual  net  primary  production  in  the 
coastal  waters  of  southern  California,  ANP  of  P. 
bachei,  and  the  weighted  mean  number  of  trans- 
fers from  primary  producers  through  P.  bachei. 
The  mean  number  of  transfers  was  calculated 
from  the  percentage  contribution  from  each  of  21 
prey  categories  to  the  total  numbers  of  prey  (these 
21  categories  are  989c  of  the  total  numbers  of  prey 
in  the  stomachs  of  P.  bachei  over  a  year)  and  best 
guesses  as  to  the  number  of  transfers  from  prim- 
ary producers  to  each  of  the  21  prey  species.  The 
mean  and  range  of  ANP  by  all  stages  of  P.  bachei 
extrapolated  to  365  days  (5,700  and  8,300-2,500 
mg  organic  matter)  were  converted  from  units  of 
organic  matter  into  organic  carbon  by  taking  50% 
of  the  organic  matter  as  organic  carbon.  The  mean 
and  range  of  annual  net  primary  production  (400 
and600-200gC  m  yr  )  were  estimated  from  the 
mean  and  range  of  the  rates  per  day  in  southern 
California  coastal  waters  (Eppley,  Reid,  and 
Strickland,  1970;  W.  Thomas,  pers.  commun.)  and 
multiplication  by  365.  The  expectation  of  the 
number  of  transfers  from  primary  producers 
through  P.  bachei  is  2.3  with  an  upper  limit  of  the 
estimate  equal  to  2.5.  These  fractions  occur  be- 
cause species  of  animals  often  do  not  fall  into  a 
single  trophic  level,  and  this  is  in  fact  the  case 
with  P.  bachei;  some  of  its  prey  organisms  are 
herbivorous  and  some  are  themselves  carnivor- 
ous. The  equal  transfer  efficiency  was  calculated 
and  presented  in  a  matrix  for  the  means  and 
ranges  of  the  three  variables  stated  above  (Table 


Table  15. — Calculations  of  the  equal  transfer  efficiency  in  per- 
cent for  different  numbers  of  transfers  from  primary  producers 
through  Pleurobrachia.  given  the  observed  range  and  mean  of 
annual  net  production  of  P.  bachei  and  the  estimated  range  and 
mean  of  annual  net  primary  production  in  g  C  m^  yr"'.  In  each 
group  of  three  values,  the  first  is  for  the  highest  value  of 
ctenophore  net  production  (4.1  g  C  m^  yr  '),  the  second  is  for  the 
mean  (2.8  g  C  m^  yf )  and  the  third  is  for  the  lowest  value  ( 1 .2  g  C 


Net  primary 

Number  of  transfers 

produ 

ction 

20 

2.25 

25 

200 

14.3 

17.8 

21  1 

11.8 

15.0 

18.1 

7.7 

10.3 

12.9 

400 

10.1 

13.0 

16.0 

8.4 

11.0 

13,7 

5.5 

7.6 

9.8 

600 

8.3 

10.9 

136 

6.8 

9.2 

11.7 

4.5 

6.3 

8.3 

15).  Note  that  the  range  of  equal  efficiency  is  found 
on  the  diagonal  from  the  lower  left  to  the  upper 
right  of  the  table.  The  overall  central  value  is  an 
equal  efficiency  of  11%.  This  efficiency  of  transfer 
involves  phytoplankton,  herbivores,  and  those 
primary  carnivores  on  which  P.  bachei  feeds,  P. 
bachei,  and  the  predators  and  parasites  of  P. 
bachei.  This  efficiency  equals  the  nth  root  of  the 
ratio  of  ingestion  by  predators  of  P.  bachei  to  net 
primary  production. 

DISCUSSION 

Life  table  parameters  of  P.  bachei  show  adap- 
tive value  in  the  interdependence  of  the  schedule 
of  births  and  the  rates  of  development  and  mortal- 
ity on  population  growth.  Early  reproduction 
makes  a  very  important  contribution  to  net  repro- 
duction and  population  growth  rate,  but  only  in 
relation  to  the  rates  of  development  and  mortality. 
The  larvae  have  relatively  high  rates  of  mortality 
and  lower  rates  of  growth  compared  to  other 
stages.  The  1-  to  2-mm  postlarvae  have  the  low- 
est rate  of  mortality  and  grow  slowly,  but  they  are 
able  to  reproduce  at  an  early  age  and  thereby 
contribute  an  important  fraction  of  net  reproduc- 
tion. The  3-  to  7-mm  stages  have  very  rapid  tis- 
sue growth  (instantaneous  rates  of  0.21-0.47)  but 
do  not  contribute  many  young  to  the  population. 
Instead,  these  larger  stages  are  important  to  net 
production  of  organic  matter  because  of  their 
rapid  growth  and  high  abundance  in  summer.  The 
stages  larger  than  8  mm  are  able  to  produce 
enormous  numbers  of  young,  but  few  survive  to 


329 


FISHERY    BULLETIN:  VOL.  72.  NO.   2 


this  size  in  nature.  Regulation  of  population 
growth  rate  would  be  very  sensitive  to  changes  in 
mortality  rates  during  production  of  the  first 
50-100  young  and  again  during  the  production  of 
the  several  hundred  young  by  later  stages. 

The  seasonal  occurrence  of//,  mediterranea  and 
the  frequency  distribution  of  single  and  multiple 
infections  and  of  the  percentage  of  cases  for  differ- 
ent stages  of  hosts  show  two  kinds  of  patterns  that 
are  related  to  life  history  episodes:  1 )  the  parasites 
do  not  often  attack  the  1-  to  2-mm  stage  postlar- 
vae  which  are  important  to  net  reproduction  as 
discussed  above  and  2)  the  parasites  occur  mainly 
as  one  or  two  individuals  per  host  and  most  fre- 
quently in  6-  to  8-mm  postlarvae.  The  early 
stages  of  parasites  infect  the  larger  hosts  more 
frequently  than  the  smaller  hosts  because  of  sea- 
sonal availability  and  perhaps  also  because  of  the 
ability  of  the  larger  hosts  to  better  accommodate 
the  extra  metabolic  burden.  The  "strategy"  of  the 
parasites  appears  to  be  infection  of  larger  hosts 
with  few  young  to  provide  sufficient  food  and  shel- 
ter during  their  development,  but  not  overexploit 
each  host  with  too  many  parasites.  The  larger 
stages  of  hosts  are  buffered  against  local  extinc- 
tion by  adult  parasites,  because  suitable  hosts  be- 
come more  difficult  to  locate  the  faster  they  die. 
The  total  ctenophore  population  has  some  protec- 
tion from  overexploitation  of  postlarvae  by  para- 
sites and  other  predators  in  the  presence  of  rela- 
tively large  numbers  of  eggs  and  larvae  and  the 
ability  of  young  postlarvae  to  reproduce  soon  after 
development  to  1-mm  size. 

The  calculated  population  growth  rates  of  P. 
bachei  indicate  that  the  minimum  time  for  a  popu- 
lation doubling  is  about  35  days  (0.693/0.02).  This 
suggests  that  rapid  increases  of  Pleurobrachia 
observed  on  a  time  scale  less  than  a  month  are 
probably  due  to  gross  advective  change  if  refer- 
ence of  a  "bloom"  is  made  to  total  abundance  of  all 
stages.  However,  the  growth  in  bodily  size  of 
Pleurobrachia  from  2  mm  to  6-7  mm  diameter 
may  occur  in  about  2  wk,  and  this  may  account  for 
the  visual  impression  of  a  bloom.  Regarding  indi- 
vidual and  potential  population  growth  rates  the 
salp  Thalia  democratica  as  another  macrozoo- 
plankter,  is  much  faster  than  P.  bachei  (Heron, 
1972a,  b). 

The  statistical  treatment  of  variances  for  mean 
net  production  per  day  describes  precision  of  the 
estimates,  which  probably  is  not  the  same  as  inac- 
curacy in  the  estimates.  For  example,  it  is  ques- 
tionable whether  growth  rates  in  the  laboratory 


under  constant  temperature,  food  concentration, 
and  food  type  are  accurate  estimates  of  the  rates  in 
nature.  Variation  during  a  day  in  ambient  condi- 
tions appear  to  be  at  least  as  important  or  more 
important  than  the  average  condition  (e.g.,  temp- 
erature). The  rates  of  tissue  growth  and  mortality 
both  depend  on  the  duration  of  development 
within  a  stage,  and  they  are  not  fully  independent 
variables  although  they  are  treated  as  such  in 
Equation  (2).  Another  error  ignored  in  the  statis- 
tical treatment  is  the  variance  of  the  standing 
stock  calculated  for  each  replicate  sample.  I  as- 
sumed in  the  calculation  of  the  net  production  per 
day  for  each  replicate  sample  at  one  station  that 
the  variance  for  the  best  estimate  of  the  crop  is 
negligible  compared  to  the  deviations  between  the 
best  estimates  from  the  regression  equations  for 
each  sample.  The  net  production  per  day  for  each 
replicate  sample  is  based  on  the  mean  rates  of 
growth  and  mortality  and  the  best  single  estimate 
of  the  standing  crop. 

The  variance  for  the  mean  value  of  the  ANP 
depends  on  the  variance  of  the  mean  net  produc- 
tion per  day  and  the  square  of  the  time  interval 
over  which  the  rate  is  linearly  applied  (Equation 
(4)).  Assuming  that  the  data  on  net  production  per 
day  would  have  a  Poisson  distribution  (variance 
equals  the  mean),  reasonably  small  95% 
confidence  limits  for  the  annual  net  production 
(ANR±ANP/10)  are  obtained  with  repHcate  sam- 
ples if  each  of  ten  sampling  dates  is  spaced 
evenly  during  the  year.  The  limits  are  relatively 
insensitive  to  whether  the  seasonal  distribution  of 
production  is  rectangular  and  continuous,  rectan- 
gular and  discontinuous,  or  triangular  and  discon- 
tinuous. The  important  considerations  to 
minimize  the  confidence  limits  for  the  mean  an- 
nual production  are:  1)  the  number  of  observations 
per  sampling  date,  2)  the  number  of  sampling 
dates,  and  3)  the  time  interval  between  sampling 
dates  in  relation  to  the  seasonal  maximum  abun- 
dance and  rate  of  production.  The  number  of  ob- 
servations per  sampling  date  is  determined  by  the 
number  of  replicate  samples  and  the  number  of 
stations.  More  stations  and  replicate  samples  im- 
prove the  accuracy  in  estimating  the  mean  and 
should  decrease  the  variance  of  the  overall  mean 
for  a  given  sampling  date.  The  number  of  sam- 
pling dates  minus  one  is  the  number  of  degrees  of 
freedom  for  the  ^-statistic  which  is  multiplied  by 
the  standard  deviation  of  the  mean  to  give  one  tail 
of  the  confidence  limit.  The  time  interval  between 
sampling  dates  will  affect  the  variance  for  the  net 


330 


HIROTA:  NATURAL  HISTORY  OF  PLEUROBRACHIA  BACHEl  IN  LA  JOLLA  BIGHT 


production  over  a  given  period  as  the  square  of  the 
interval;  therefore,  sampling  should  be  carried  out 
on  a  regular  basis  without  long  intervals  between 
dates  unless  previous  information  is  available  on 
the  seasonal  distribution  of  production  and  the 
relationship  between  means  and  variances. 

Three  parameters  can  influence  the  magnitude 
of  net  production  by  P.  bachei  in  addition  to  errors 
in  the  estimation  of  abundance:  1)  water  tempera- 
ture, 2)  food  supply,  and  3)  parasitism.  In  the  first 
two  cases,  it  would  appear  that  for  the  observed 
range  of  temperature  and  food  supply  in  the  study 
area  temperature  is  more  important  than  food 
supply.  A  10°C  range  of  surface  temperature  over 
the  year  or  the  temperature  change  experienced 
during  a  postulated  20-m  vertical  migration  in 
August  (see  Figure  8)  should  affect  the  rate  of 
growth  in  length  and  weight  and  survival.  Data 
are  not  sufficiently  good  for  quantitative  state- 
ments about  the  effect  of  vertical  migration  dur- 
ing August  on  rates  of  tissue  growth,  net  produc- 
tion, and  population  growth.  The  case  for  the  effect 
of  food  supply  on  rates  of  net  production  is  some- 
what better  than  for  temperature.  Rates  of  growth 
in  the  laboratory  at  15°C  are  essentially  the  same 
for  ctenophores  cultured  on  Acartia  at  35  /ug 
C/liter  and  500  yug  C/liter.  The  rates  of  growth  in 
length  and  weight  at  14.5'C  and  1-2  ^;g  C/liter  of 
mixed  natural  food  organisms  indicated  that  the 
postlarvae  grow  about  as  well  as  at  tenfold  higher 
food  concentrations.  From  field  samples  in  which 
the  calculated  food  concentration  was  about  10  Mg 
C/liter  growth  rates  in  the  laboratory  and  from 
the  field  size  frequency  distributions  agree  within 
±20%  of  the  mean  rate.  It  appears  therefore  that 
P.  bachei  postlarvae  are  very  efficient  at  the  ex- 
traction of  prey  from  the  water  at  very  low  con- 
centrations. The  estimates  of  gross  growth 
efficiency  showed  that  over  one-half  of  the  food 
ingested  was  incorporated  into  somatic  tissues. 
Perhaps  the  "passive"  feeding  mode  of  these  car- 
nivores allows  them  to  have  a  very  low  threshold 
for  the  commencement  of  feeding  activity,  espe- 
cially since  the  area  of  the  tentacles  is  very  large 
in  relation  to  the  bodily  size  of  the  ctenophore,  and 
relatively  low  metabolic  expenditure  is  generated 
while  waiting  for  prey  to  contact  the  tentacles. 

The  estimates  of  ANP  by  P.  bachei  are  also 
inaccurate,  because  no  corrections  were  made  for 
effects  of  parasitism  hy  Hyperoche  on  rates  of  tis- 
'  sue  growth  and  duration  of  development.  Since 
the  occurrence  of  parasitism  and  high  rates  of 
production  both  were  in  August  (two-thirds  of  the 


ANP  was  in  August),  correction  may  not  be  triv- 
ial. It  is  not  possible  to  make  a  quantitative  esti- 
mate of  the  error  based  on  any  data,  but  the  follow- 
ing sources  of  error  must  be  considered:  1)  the 
standing  stock,  B,,  was  overestimated  by  the 
amount  of  ctenophore  tissue  in  the  volume  that 
the  parasites  occupy;  2)  the  instantaneous  rate  of 
tissue  growth,  G,,  was  overestimated  by  the  dif- 
ference between  the  instantaneous  growth  rates  of 
nonparasitized  and  parasitized  ctenophores;  3)  the 
instantaneous  rate  of  mortality,  M, ,  was  overes- 
timated by  the  difference  between  the  durations  of 
development  of  nonparasitized  and  parasitized 
ctenophores  (see  Equations  1  and  4)  the  total  loss 
of  ctenophore  tissue  (due  to  mortality  of  all  types 
and  to  ingestion  of  tissue  by  parasites  that  does 
not  result  in  mortality)  in  one  time  increment  was 
underestimated  by  that  fractional  amount  of  tis- 
sue removed  from  the  mean  standing  crop  during 
the  time  increment  by  parasitism.  Overestima- 
tion  of  the  standing  stock  of  ctenophores  due  to 
presence  of  parasites  is  believed  to  be  negligible, 
especially  since  only  one  or  two  parasites  were 
present  in  927c  of  all  cases  (Table  4).  For  given 
values  of  standing  stock  and  rates  of  growth  and 
m.ortality(e.g.,fi,  =  100mg/m2,G,  =0.2,andM, 
=  0.5),  the  effect  of  additional  tissue  loss  due  to 
parasitism  on  the  rate  of  net  production  is  rela- 
tively small  (ca.  107c)  for  instantaneous  rates  of 
parasitism  up  to  50%  of  the  rate  of  mortality.  The 
mean  net  production  per  time  interval  was  overes- 
timated. The  actual  extent  of  the  overestimate  can 
not  be  evaluated  without  more  information  on  the 
effect  of  parasitism  on  ctenophore  growth. 

The  ratio  of  net  production  per  day  to  mean 
standing  crop  during  the  day  for  all  postlarvae  is 
the  biomass-weighted  mean  instantaneous  rate 
of  tissue  growth  (Allen,  1971),  assuming  that 
growth  and  mortality  rates  are  exponential.  The 
similarity  of  mean  values  between  stations  1,  3, 
and  5  is  due  partly  to  the  bias  of  having  used  only 
the  growth  rates  at  15°C  throughout  the  year,  but 
the  range  between  stages  of  the  mean  exponential 
growth  rate  is  at  least  tenfold.  Some  of  the  consis- 
tency in  ratios  of  production  to  mean  standing 
stock  is  due  to  similarity  in  the  length  frequency 
distributions  between  stations  and  relative  con- 
tribution of  different  stages  to  the  total  crop.  The 
overall  annual  mean  production  to  standing  stock 
value  of  0.202  indicates  that  net  production  per 
day  is  20%  of  the  mean  daily  standing  stock.  This 
value  is  within  the  range  of  values  summarized  by 
MuUin  (1969),  but  is  quite  high  considering  the 


331 


F1SHFR\    BULLETIN:  VOL    72,  NO.  2 


relatively  large  size  of  postlarvae  (e.g.,  over  10  mg 
organic  weight). 

The  11%  overall  mean  in  the  equal  transfer 
efficiency  is  surprisingly  close  to  the  values  of 
ecological  efficiency  measured  in  the  laboratory 
(Silliman,  1968;  Slobodkin,  1968);  food  chain 
efficiency  is  the  same  as  ecological  efficiency  if  all 
food  available  to  a  consumer  level  is  ingested  (the 
range  for  ecological  efficiency  is  generally  ac- 
cepted to  be  5-20%).  The  stability  and  con- 
vergence characteristics  of  these  efficiencies  must 
be  set  by  two  boundary  conditions:  1)  the 
minimum  net  production  and  food  required  to  just 
replace  the  component  species  within  a  trophic 
level  and  2)  the  age-structure  weighted  max- 
imum gross  growth  efficiency  of  the  component 
species  within  a  trophic  level.  The  upper  limit  is 
set  by  the  physiological  maximum  gross  growth 
efficiency  of  each  developmental  stage  weighted 
over  all  stages  and  species  in  proportion  to  their 
relative  abundance.  In  this  regard  the  adults  of  P. 
bachei  are  very  efficient  (60%  )  at  converting  food 
ingested  into  somatic  tissues,  and  this  is  probably 
near  the  upper  limit  of  gross  growth  efficiency. 
Low  ecological  efficiency  is  found  in  species  popula- 
tions dominated  by  older,  slowly  growing  indi- 
viduals with  low  growth  efficiency  and  low  rates  of 
mortality  (Mann,  1965).  In  nature  it  would  seem 
unlikely  that  food  chain  efficiency  through  several 
successive  trophic  levels  could  vary  widely.  For 
example,  a  low  efficiency  through  producers  to 
herbivores  means  that  less  net  herbivore  produc- 
tion would  be  available  to  first-order  carnivores, 
all  else  being  equal.  Under  these  circumstances 
the  efficiency  through  herbivores  to  first-order 
carnivores  should  also  be  low,  because  the  carni- 
vores must  search  a  larger  volume  or  area  to  feed 
and  this  decreases  growth  efficiency.  Conversely, 
a  high  efficiency  through  producers  to  herbivores 
should  perpetuate  a  high  efficiency  through  her- 
bivores to  carnivores,  unless  the  age  or  size  dis- 
tributions of  herbivores  which  yields  high  net  pro- 
duction from  producers  is  not  conducive  to  max- 
imize the  efficiency  through  herbivores  to 
first-order  carnivores  (i.e.,  the  herbivores  are 
predominantly  younger  stages  which  are  not  avail- 
able to  those  stages  of  carnivores  which  possess 
the  highest  growth  efficiency). 

There  is  some  evidence  from  lakes  and  from 
theoretical  considerations  of  growth  patterns  that 
food  chain  efficiency  is  at  least  in  some  cases  de- 
termined by  growth  efficiency  of  component 
species  in  a  food  chain  and  their  metabolic 


flexibility  in  response  to  size  and  abundance  of 
prey  (Kerr  and  Martin,  1970;  Kerr,  1971).  In  com- 
plex marine  systems  considerable  effort  must  be 
expended  before  the  predator-prey  interactions 
are  described  and  the  metabolic  rates  and 
efficiencies  are  measured.  Meanwhile,  an  expla- 
nation based  on  sound  theoretical  grounds  is 
needed  to  show  why  the  food  chain  and  ecological 
efficiencies  tend  to  converge  on  10%  and  have  a 
relatively  small  range  from  about  5  to  20%. 


SIGNIFICANCE  OF  P.  BACHEI  IN 
THE  PLANKTON 

The  coastal  waters  of  southern  California  rep- 
resent an  ecotone  which  includes  the  boundary  of 
land  and  sea.  It  is  influenced  strongly  by  physical 
processes  and  the  biota  in  the  water  from  several 
sources.  The  relatively  shallow  depths  within  the 
first  2-3  km  from  shore  emphasize  the  inter- 
dependence and  coupling  of  the  benthic  and 
planktonic  communities.  The  benthic  community 
depends  on  the  planktonic  community  for  some  of 
its  food  supply  and  for  removal  of  the  least  fit 
individuals  of  those  meroplanktonic  larvae  re- 
leased by  benthic  animals.  The  plankton  commun- 
ity receives  some  of  its  food  in  the  form  of  mero- 
planktonic larvae,  and  the  benthic  community  re- 
turns the  materials  removed  from  the  water  in  the 
form  of  regenerated  nutrients,  detritus,  and  de- 
composing tissues.  It  is  not  surprising,  therefore, 
that  Euterpina  andOithona  are  the  prey  of  young 
stages  of  newly  settled  juvenile  garibaldi,  Hyp- 
sypops  rubicunda  (Clarke,  1970)  and  also  of  P. 
bachei. 

The  pattern  of  high  standing  stocks  of  different 
trophic  levels  and  intense  biological  activity 
within  the  first  5-10  km  from  shore  is  probably 
associated  with  the  high  regeneration  rates  of 
nutrients  and  high  productivity  in  shallow  water 
(Anderson  and  Banse,  1961)  and  life  history  adap- 
tations of  coastal  water  species  to  exploit  highly 
productive  zones.  The  short  generation  times  of 
microcopepods,  parthenogenesis  in  cladocerans 
and  spined  eggs  o^Acartia  are  some  adaptations  to 
enable  rapid  exploitation  of  favorable  conditions 
in  the  plankton.  The  coastal  waters  may  be  com- 
pared to  a  chemostat.  The  rates  of  dilution  by 
physical  forces  vary  in  time  and  space,  but  the 
specific  growth  rates  of  the  organisms  plus  their 
refugial  seed  stocks  and  immigrants  enable  them 
to  persist  over  time.  The  quasi-continuous  change 


332 


HIROTA:   NATURAL  HISTORY  OF  PLEVROBRACHIA  BACHEI   IN   LA  JOLLA   BIGHT 


in  the  physical-chemical  habitat  of  the  coastal 
waters  prevents  the  formation  of  a  stable, 
time-independent  assemblage  of  organisms,  al- 
though the  system  appears  to  be  basically  com- 
posed of  the  same  recurrent  species  in  seasonally 
varying  proportions.  Occasionally  expatriates 
from  oceanic,  southern  waters,  and  northern  wa- 
ters appear  (e.g. ,  Candacia,  Eucalanus  attenuatus, 
Tortanus  discaudatus,  Velella,  etc.).  The  tran- 
sients are  joined  by  some  organisms  which  appear 
seasonally  in  this  area  during  spawning  migra- 
tions (e.g.,  gray  whale,  squid,  grunion). 

The  regulation  of  population  size  in  Pleuro- 
brachia  is  postulated  to  be  through  density- 
dependent  feedback  meahanisms  proposed 
by  Greve  (1972),  in  which  the  prey  of  larger 
ctenophores  (e.g.,  adult  stages  of  copepods)  are 
detrimental  to  survival  of  the  small  ctenophore 
larvae.  Balance  in  the  abundance  of  predators  and 
prey  is  conferred  by  selection  of  larger  copepods  by 
the  larger  ctenophores  (Bishop,  1968),  but  with 
dependence  of  ctenophore  larvae  on  copepod  naup- 
lii  for  food  supply  and  low  abundance  of  adult 
copepods  for  their  survival.  A  high  density  of 
copepod  nauplii  and  low  density  of  copepod  adults 
would  favor  occurrence  of  ctenophore  larvae  and 
early  postlarvae.  As  both  prey  and  predators  grow 
the  roles  of  predator  and  prey  become  reversed  to 
some  extent.  The  large  ctenophores  may  nearly 
deplete  the  water  of  large  copepods  to  satiate  their 
metabolic  demands,  but  this  condition  is  unstable, 
because  the  larger  ctenophores  will  become  food 
limited.  The  population  size  will  not  increase 
greatly  because  few  adult  copepods  are  available 
to  produce  eggs,  and  the  nauplii  which  are  hatched 
from  eggs  are  needed  for  food  of  larval 
ctenophores.  If  the  abundance  of  postlarvae 
should  increase  and  some  threshold  is  exceeded, 
the  ctenophore  population  also  becomes  vulnera- 
ble to  density-dependent  predation  by  Bero'e  and 
other  predators  and  infection  by  parasites. 

All  organisms  in  nature  consume  food,  recycle 
materials  through  excretion  (and  exuviation),  and 
are  themselves  consumed.  In  this  regard  the  func- 
tional role  or  ecological  significance  of  a  species 
population  is  closely  related  to  its  relative  abun- 
dance and  rates  of  turnover.  Pleurobrachia  bachei 
is  a  dominant  carnivorous  zooplankter  during 
summer  and  fall  in  the  coastal  waters  off  San 
Diego.  Its  functional  role  can  be  divided  into  three 
parts:  1)  a  predator  which  regulates  the  abun- 
dance of  small  crustaceans  (copepods  and  cladoce- 
rans)  and  removes  least  fit  individuals,  2)  a  vehi- 


cle which  provides  shelter  and  nutrition  for  para- 
sites such  asHyperoche,  and  3)  an  organism  which 
transfers  and  transforms  material  and  potential 
energy  in  the  planktonic  food  web.  As  a  predator, 
the  role  of  selective  removal  of  prey  is  an  impor- 
tant factor  for  both  the  evolution  of  size,  shape, 
behavior,  etc.  in  the  coastal  water  species  and  for 
regulating  the  abundance  and  species  composition 
of  prey.  Pleurobrachia  bachei  is  not  unique  as  a 
planktonic  form  in  providing  shelter  and  nutrition 
for  co-occuring  species;  salps  are  exploited  in  a 
similar  manner  by  copepods,  except  that  details  of 
the  life  histories  differ  (Heron,  1969).  As  a  season- 
ally dominant  carnivore,  P.  bachei  is  also  un- 
doubtedly an  important  species  which  transfers 
organic  matter  and  potential  energy  to  higher 
trophic  levels  in  the  food  web  of  La  Jolla  Bight. 

ACKNOWLEDGMENTS 

I  am  indebted  to  Michael  M.  Mullin  for  his  gui- 
dance and  suggestions  throughout  my  research, 
especially  in  laboratory  work  and  critical  evalua- 
tion of  data.  I  received  considerable  help  from  E. 
W.  Fager  and  E.  Stewart  with  computer  programs 
and  other  help  in  calculations.  E.  W.  Fager  also 
made  many  suggestions  regarding  statistical 
treatment  of  abundance  and  production  data.  T.  E. 
Bowman  kindly  identified  the  amphipod  parasite 
of  Pleurobrachia  bachei  as  Hyperoche  mediter- 
ranea.  The  drogue  studies  and  many  other  aspects 
of  field  work  were  done  jointly  with  A.  M.  Barnett 
and  D.  Kamykowski.  Their  help  in  preparation  of 
equipment  and  participation  in  cruises  is  greatly 
appreciated.  I  also  thank  my  wife  Gail  and  parents 
for  their  support  and  encouragement.  This  re- 
search was  supported  by  Marine  Life  Research 
General  Funds,  U.  S.  Atomic  Energy  Commission 
Contract  No.  AT(ll-l)  GEN  10,  P.  A.  20,  and 
National  Science  Foundation  Contract  No. 
GA-35507. 

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333 


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335 


SOME  ASPECTS  OF  THE  ECOLOGY  OF  STOMIATOID  FISHES 
IN  THE  PACIFIC  OCEAN  NEAR  HAWAII 


Thomas  A.  Clarke' 


ABSTRACT 

Forty-seven  species  of  eight  families  of  stomiatoid  fishes  were  collected  in  the  upper  1,000  m  near 
Hawaii.  Most  species  appear  to  undertake  diurnal  vertical  migrations;  only  two  definitely  did  not. 
Many  of  the  abundant  species  showed  changes  in  size  composition  within  both  day  and  night  depth 
ranges,  the  smaller  fish  occurring  shallower.  All  sizes  of  several  other  species  appeared  to  occur 
throughout  their  depth  ranges.  Seasonal  changes  in  the  size  composition  of  several  species  indicated 
that  they  spawn  principally  in  the  summer.  Several  species  appear  to  avoid  the  Isaacs-Kidd  trawl 
better  during  the  day  than  at  night.  Some  species  appeared  to  avoid  the  Isaacs-Kidd  more  than  a  larger 
trawl,  but  many  were  sampled  as  well  or  better  by  the  former.  Absence  or  rarity  of  mature  individuals 
of  several  species  indicated  that  the  larger  fish  avoided  both  trawls. 

Relationships  between  vertical  distribution  and  morphology  of  some  species  are  proposed,  and 
potential  interactions  between  species  are  considered  relative  to  the  degree  of  similarity  of  depth 
ranges  or  size-depth  patterns. 


Stomiatoids  are  a  dominant  and  diverse  group  of 
mesopelagic  fishes.  Most  previous  work  on  the 
group  has  been  of  a  systematic  or  zoogeographic 
nature,  and  only  recently  have  the  systematics  of 
some  families  come  into  order.  With  the  exception 
of  a  few  works  such  as  Kawaguchi  and  Marumo 
(1967)  and  Krueger  and  Bond  (1972),  ecologically 
pertinent  information  such  as  depth  ranges,  mi- 
gration habits,  etc.,  has  been  appended  to  other 
studies  and  is  usually  based  on  so  few  specimens  or 
inappropriate  sampling  programs  that  it  is  of 
dubious  value.  Consequently,  even  for  the  fre- 
quently collected  species,  little  is  known  of  their 
ecology — especially  in  comparison  to  knowledge  of 
the  myctophids,  another  important  group  of 
mesopelagic  fishes. 

This  paper  considers  data  on  47  species  of 
stomiatoids  collected  by  a  mid-water  trawling 
survey  in  the  central  North  Pacific  near  the 
Hawaiian  Islands.  (Specimens  of  the  Sternop- 
tychidae  and  the  gonostomatid  genus  Cyclothone 
are  being  investigated  by  other  workers,  and  the 
systematics  of  three  genera  of  the  Melanos- 
tomiatidae  are  so  confused  at  present  that  these 
genera  cannot  be  considered  in  detail  here.)  For 
many  species,  sufficient  numbers  were  collected  to 
present  reliable  estimates  of  depth  ranges,  migra- 


'Hawaii  Institute  of  Marine  Biology  and  Department  of 
Oceanography,  University  of  Hawaii,  Honolulu,  HI  96822. 


tions,  and  seasonal  changes  in  size  composition. 
The  habits  of  this  diverse  group  are  compared  with 
those  of  other  mesopelagic  fishes. 


METHODS 

All  specimens  considered  here  were  collected 
near  the  island  of  Oahu,  Hawaii  (lat.  22°20-30'N, 
long.  158°20-30'W).  Details  of  the  sampling  pro- 
gram are  given  in  Clarke  ( 1973),  and  will  be  only 
summarized  here.  Four  series  of  samples  were  col- 
lected with  a  10  foot  Isaacs-Kidd  mid-water  trawl 
(IK).  These  were  taken  at  approximately  quar- 
terly intervals  (September  1970,  December  1970, 
March  1971,  and  June  1971)  and  attempted  to 
cover  the  upper  1,000  m  of  the  water  column  both 
day  and  night  for  each  season.  Useful  information 
was  also  derived  from  a  series  of  samples  collected 
with  a  6-foot  IK  in  the  upper  400  m  at  night  and 
between  400  and  1,000  m  during  the  day  in  June 
1970,  from  a  series  of  samples  with  a  10-foot  IK  in 
the  upper  190  m  at  night  during  periods  of  new 
and  full  moon  in  September-October  1971,  and 
from  preliminary  samples  taken  in  September- 
November  1969.  Also  included  are  data  from  a 
series  of  tows  made  by  the  Southwest  Fisheries 
Center  Honolulu  Laboratory,  National  Marine 
Fisheries  Service  (NMFS),  NOAA  in  conjunction 
with  the  March  1971  IK  series;  these  sampled  the 


Manuscript  accepted  August  1973. 

FISHERY  BULLETIN:  VOL.  72.  NO.  2.  1974. 


337 


upper  200  m  at  night  with  a  modified  Cobb  pelagic 
trawl  (CT)  described  by  Higgins  (1970).  I  have  also 
examined  specimens  of  some  species  taken  near 
Hawaii  by  R.  E.  Young  with  a  modified  Tucker 
trawl  equipped  with  an  opening-closing  device. 

The  IK  and  CT  were  fished  without  opening- 
closing  devices.  Winch  and  ship  speed  were  ad- 
justed to  minimize  forward  motion  of  the  trawl 
during  descent  and  ascent.  Time-depth  recorders 
were  attached  to  the  trawls.  A  few  oblique  tows 
were  made,  but  mostly  the  trawls  were  towed  for 
2-3  h  at  the  same  depth.  Actually,  the  trawls  often 
sank  or  rose  gradually  during  the  "horizontal" 
part  of  the  tow,  but  the  range  fished  was  small 
relative  to  spacing  of  different  tows.  A  single,  most 
frequently  fished  depth  was  assigned  to  each  tow. 
The  IK  was  towed  at  about  1.75  m/s  and  the  CT  at 
about  1.5  m/s.  All  "night"  samples  were  taken 
between  2000  and  0500  h,  "day"  samples  between 
0800  and  1700  h. 

Specimens  were  identified  principally  from  data 
given  by  Grey  (1964),  Morrow  (1964a,  b,  c),  Mor- 
row and  Gibbs  (1964),  Gibbs  (1964),  Barnett  and 
Gibbs  (1968),  Goodyear  and  Gibbs  (1969),  and 
Novikova  (1967).^  Standard  length  of  all  speci- 
mens was  measured  to  the  nearest  millimeter. 
With  a  few  exceptions,  gonads  of  only  larger 
specimens  were  examined  to  determine  size  at 
maturity  and  any  seasonal  changes  in  gonad  de- 
velopment in  mature  females.  Size  at  maturity 
was  taken  as  that  of  the  smallest  female  which 
carried  obviously  ripened  ova.  For  each  species 
considered,  the  total  number  of  specimens  ex- 
amined and  the  length  range  in  millimeters  are 
given  in  parentheses  after  the  species  name. 

The  lower  limits  of  depth  ranges  of  the  species 
are,  of  course,  open  to  some  question  since  the 
trawls  were  fished  without  opening-closing  de- 
vices. The  reliability  of  estimated  depth  ranges  for 
the  more  abundant  species  (50-100  specimens)  is 
probably  fairly  high.  Catches  from  tows  within  the 
depth  range  were  obviously  greater  than  those  of 
deeper  tows  which  passed  through  the  depth 
range.  The  latter  were  comparable  with  catches  of 
short  oblique  tows  taken  during  the  program  and 
were  considered  to  be  contaminants,  i.e.,  caught 
during  ascent  or  descent,  unless  data  from  the 
opening-closing  Tucker  trawl  indicated  other- 
wise. Any  catches  below  the  "normal"  depth  range 
that  were  unexpectedly  high  or  different  in  size 


^Specimens  of  all  species  considered  here  will  be  deposited  at 
the  U.S.  National  Museum. 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

composition,  etc.,  are  discussed  under  the  species 
headings. 

Many  species  considered  here  were,  however,  so 
rarely  taken  that  there  is  considerable  doubt 
about  estimates  of  depth  ranges  and  vertical  mi- 
gration. The  chances  of  being  taken  in  a  tow  with- 
in the  actual  range  were  not  much  greater  than 
those  of  being  taken  during  descent  or  ascent  of  a 
deeper  tow.  Catches  with  the  opening-closing 
Tucker  trawl  were  helpful  in  only  a  few  cases 
since  the  species  where  greatest  doubt  exists  were 
rare  to  begin  with  and  many  were  not  captured  at 
all  or  as  frequently  by  the  Tucker  trawl. 

For  species  which  were  collected  in  sufficient 
numbers  (ca.  10/tow  or  more)  in  more  than  one  tow 
during  a  series,  changes  in  size  composition  with 
depth  were  assessed  by  comparing  the  size- 
frequency  curves  of  individual  samples  from  dif- 
ferent depths  using  the  Kolmogorov-Smirnov  test 
(Tate  and  Clelland,  1957).  Size  composition  was 
considered  significantly  different  if  the  probabil- 
ity associated  with  the  difference  between  curves 
was  0.05  or  less.  For  rarer  species,  plots  of  size  vs. 
depth  were  made  using  pooled  data  for  all  speci- 
mens. Trends  in  size  composition  with  depth  were 
noted,  but  no  statistical  significance  can  be  at- 
tached to  these. 

Only  one  species,  Vinciguerria  nimbaria,  was 
caught  consistently  in  high  enough  numbers  to 
permit  a  quantitative  consideration  of  abundance 
and  size  composition  throughout  the  water  col- 
umn (cf  treatment  of  data  on  the  more  abundant 
myctophids  in  Clarke,  1973).  Thus  considerations 
of  day-night  or  seasonal  differences  in  abundance 
in  the  remaining  species  are  subject  to  some  doubt. 
For  these,  the  data  from  each  series  were  simply 
pooled  without  any  attempt  to  weight  the  catch  of 
each  tow  for  the  relative  thickness  of  the  depth 
stratum  it  represented.  Nevertheless,  compari- 
sons between  seasonal  series  are  merited  since  the 
total  trawling  times  and  depth  coverages  for  each 
of  the  series  were  reasonably  similar.  In  compar- 
ing data  from  different  seasons,  I  have  assumed 
that  changes  were  not  a  result  of  horizontal  advec- 
tion  or  migration. 

RESULTS 

Gonostomatidae 

Diplophos  taenia  (169;  35-153  mm) 

The  day  depth  range  ofD.  taenia  was  450-610  m 
and  the  night  range  15-100  m.  The  smaller  fish 


338 


CLARKE:   ECOLOGY  OF  STOMIATOID  FISHES 


tended  to  occur  shallower  during  both  periods. 
During  the  day  those  over  70  mm  long  were  mostly 
below  525  m  and  those  over  120  mm  were  below 
575  m.  At  night  none  over  90  mm  were  caught 
shallower  than  50  m  and  none  over  120  mm  were 
above  75  m. 

Smaller  D.  taenia  (<  70  mm)  were  more  fre- 
quently taken  in  June,  July  and  September,  and 
larger  fish  appeared  most  abundant  in  March. 
This  suggests  that  spawning  is  seasonal,  but  the 
season  cannot  be  estimated  since  the  age  of  35-to 
70-mm  individuals  is  not  known.  Size  at  maturity 
was  about  140  mm.  It  was  not  possible  to  deter- 
mine the  spawning  season  from  gonad  state  of 
females  since  very  few  mature  females  were 
taken.  The  data  from  the  March  1971  series  indi- 
cated that  individuals  100-140  mm  long  avoided 
the  IK  better  than  the  CT,  but  that  neither  trawl 
sampled  larger  individuals  adequately. 

Vinciguerria  nimbaria  (2,927;  8-49  mm) 

For  most  series,  the  data  indicated  that  V.  nim- 
baria occurred  at  400-560  m  during  the  day  and 
migrated  to  20-125  m  at  night.  In  December  1970, 
two  night  tows  in  the  day  depth  range  caught 
substantial  numbers  of  V.  nimbaria — more  than 
expected  on  the  basis  of  short  oblique  tows  and 
other  night  tows  below  150  m.  The  size  composi- 
tion of  these  catches  was  within  the  range  of  that 
of  the  shallow  night  catches  and  close  to  those  of 
day  catches  at  similar  depths.  The  number  of  ma- 
ture fish  in  the  deep  night  catches  was  low,  but 
there  was  no  obvious  difference  in  sex  ratio  or 
gonad  state  between  these  and  those  of  other  tows. 
Thus  it  appears  that  a  fraction,  roughly  607c,  of 
the  population  did  not  migrate  in  December. 

The  larvae  ofVinciguerria  are  restricted  to  the 
surface  layers  and  do  not  apparently  undertake 
substantial  migrations  until  metamorphosis 
( Ahlstrom  and  Counts,  1958).  Those  collected  dur- 
ing this  study  (8-14  mm)  were  taken  mostly  at 
15-50  m  at  night.  (No  day  tows  were  taken  above 
250  m.) 

Consistent  and  frequently  significant  differ- 
ences in  size-frequency  curves  indicated  that 
smaller  V.  nimbaria  occurred  shallower  in  the 
water  column  both  day  and  night  (Figure  1).  Few 
fish  over  25  mm  were  captured  shallower  than  75 
m  at  night  and  few  less  than  20  mm  were  captured 
below  this  depth.  In  the  day,  the  small  fish  occur- 
red mostly  above  500  m  and  the  large  individuals 
were  taken  almost  exclusively  below  500  m. 


15  20         25         30         35 

STANDARD  LENGTH  (mm) 


Figure  1. — Cumulative  size-frequency  curves  for  Vinciguerria 
nimbaria  taken  at  60  m  (A,  35  individuals),  80  m  (B,  96),  100  m 
(C  dashed  line,  44),  and  125  m  (C,  solid  line,  12)  at  night  in 
September  1971.  All  pairs  were  significantly  different  (P<0.05) 
from  each  other  except  100  m  vs.  125  m. 


The  full-new  moon  series  of  night  tows  in  the 
upper  layers  during  September-October  1971,  in- 
dicated substantial  differences  in  depth  distribu- 
tion related  to  phase  of  the  moon  (Figure  2A),  but 
the  picture  was  complicated  by  the  presence  of 
many  more  larvae  and  recently  transformed 
juveniles  during  the  October  (full  moon)  series. 
Calculated  (see  Clarke,  1973)  total  numbers  in  the 


NUMBER/TOW 


60  90  120 


I 
H 
O. 
LlT 
Q 


Figure  2. — Catches  of  Vinciguerria  nimbaria  per  tow  (l'/2  h 
each)  at  several  depths  at  night  at  new  moon  (solid  circles  and 
lines)  and  full  moon  (open  circles,  dashed  lines)  during 
September-October  1971.  Left:  total  catches  including  larvae 
and  recently  transformed  juveniles.  Right:  catches  offish  larger 
than  15  mm. 


339 


FISHERY  BULLETIN:  VOL.   72,  NO.  2 


water  column  for  each  series  were  similar,  but  the 
calculated  size  compositions  indicated  that  during 
full  moon  909?^  of  the  population  were  larvae  or 
recently  transformed  juveniles  as  opposed  to  only 
50%  in  the  new  moon  series.  Since  the  tows  were 
taken  during  the  season  of  highest  recruitment  to 
the  trawlable  population  (see  below),  the  differ- 
ence possibly  was  due  to  recruitment  during  the 
intervening  2  wk. 

When  only  the  individuals  over  15  mm  were 
considered  (Figure  2B),  it  appeared  that  most  of 
the  larger  fish  occurred  about  50-75  m  deeper  at 
full  moon.  The  calculated  total  number  for  the  new 
moon  series  was  about  twice  that  for  the  full  moon 
series,  and  the  calculated  size-frequency  curves 
were  similar.  In  addition  to  moving  deeper,  V. 
nimharia  also  appeared  to  avoid  the  net  better 
during  full  moon. 

Vinciguerria  nimbaria  was  by  far  the  most 
abundant  of  the  fishes  considered  here.  Among  all 
the  species  which  occurred  in  the  upper  layers  at 
night,  V.  nimbaria  ranked  eighth  after  seven 
species  of  myctophids,  but  because  of  its  small  size, 
contributed  little  to  the  total  estimated  biomass 
(Clarke,  1973).  Calculated  total  numbers  in  Sep- 
tember and  December  were  about  twice  those  for 
March  and  June  (about  30-35/102m2  vs. 
15-18/10^m2).  The  calculated  biomass  was  about 
7-8  g/lO^m^  at  all  seasons. 

Vinciguerria  nimbaria  appears  to  spawn  prin- 
cipally in  the  summer  and  fall  and  reach  maturity 
(27  mm)  within  1  yr.  The  calculated  size  composi- 
tions indicated  that  about  759i:  of  the  population  in 
June  were  less  than  15  mm,  while  in  March,  759^ 
of  the  fish  were  over  20  mm  and  about  40^  were 
mature.  The  September  and  December  series  had 
substantial  percentages  of  small  fish,  but  about 
5(Wr  were  15-25  mm.  Among  the  mature  females 
examined,  the  proportion  bearing  ripened  ova  was 
higher  in  June  and  September  (15/16  and  7/9,  re- 
spectively) than  in  December  and  March  (5/10  and 
4/11). 

Vinciguerria  poweriae  (365;  9-35  mm) 

Only  35  V.  poweriae  were  caught  during  the 
day  by  IK  tows.  These  were  mostly  25-  to  30-mm 
fish  caught  around  500  m.  A  daytime  CT  tow  at 
300  m  caught  seven  individuals  (15-29  mm),  sug- 
gesting that  this  species  occurs  rather  shallow  in 
the  water  column  during  the  day  and  avoids  the 
net  due  to  higher  light  intensities.  At  night,  V. 


poweriae  occurred  at  100-200  m.  Few  larger  than 
20  mm  were  caught  above  150  m  and  practically 
none  under  15  mm  were  taken  below  150  m. 

Seasonal  changes  in  size  composition  indicated 
that  V.  poweriae  spawns  in  the  spring  and  sum- 
mer. All  caught  in  March  were  over  15  mm  and 
over  5(Wc  were  larger  than  the  size  at  maturity  (27 
mm).  Ten  of  11  mature  females  from  the  March 
series  carried  ripe  ova.  In  June,  few  of  any  size 
were  caught,  but  these  included  both  juveniles 
(<  15  mm)  and  mature  fish.  Three  of  the  four  ma- 
ture females  caught  in  June  were  ripe.  In  July 
and  September,  the  bulk  of  the  fish  were  9-20  mm 
and  very  few  mature.  The  few  caught  in  December 
were  all  over  15  mm.  Of  the  five  mature  females 
taken  in  September  and  December,  only  one  was 
ripe. 

Ichthijococctis  ovatiis  (45;  12-55  mm) 

All  but  nine  /.  ovatus  were  taken  during  the 
day  between  400  and  500  m.  The  night  catches 
consisted  of  two  small  fish  (15  mm)  taken  near  the 
day  depth,  two  larger  ones  taken  at  350  m,  and  five 
others  (26-35  mm)  taken  at  150  m  and  260  m. 
Since  it  seems  unlikely  that  this  species  occurs  as 
shallow  as  150-260  m  during  the  day,  at  least  some 
fraction  of  the  population  apparently  moves  into 
the  upper  layers  at  night.  /.  ovatus  matures  at 
about  35  mm. 


Gonostotna  atlanticum  (680;  10-66  mm) 

Gonostoma  atlanticum  was  taken  principally  at 
490-560  m  during  the  day  and  at  150-300  m  at 
night.  In  several  cases,  the  size-frequency  curves 
from  samples  at  different  depths  within  the  same 
series  differed  significantly  and  indicated  that  the 
smaller  fish  occurred  at  shallower  depths.  In  De- 
cember, at  night  all  fish  from  170  m  were  less  than 
30  mm,  most  from  190  to  200  m  were  30-45  mm, 
and  most  from  250  to  300  m  were  40-60  mm. 
Catches  from  day  tows  in  both  March  and  Sep- 
tember indicated  that  few  fish  less  than  50  mm 
occurred  deeper  than  500-525  m. 

Gonostoma  atlanticum  apparently  spawns  over 
most  of  the  year.  Between  90  and  100%  of  the 
mature  females  (over  50  mm)  in  each  series  car- 
ried well-developed  ova,  and  there  were  no  evi- 
dent seasonal  changes  in  size  composition  of  the 
catch. 


340 


CLARKE:  ECOLOGY  OF  STOMIATOID  FISHES 

Gonostoma  ebelingi  (306;  12-158  mm) 

Gonostoma  ebelingi  occurred  at  520-700  m  dur- 
ing the  day  and  at  125-300  m  at  night.  The  size 
composition  of  the  catches  changed  with  depth  for 
both  day  and  night  series.  The  largest  taken  shal- 
lower than  150  m  at  night  was  45  mm,  and  most 
fish  taken  below  200  m  exceeded  60  mm.  During 
the  day,  few  fish  over  100  mm  were  caught  above 
600  m,  and  none  less  than  75  mm  were  caught 
deeper. 

Female  G.  ebelingi  matured  at  about  120  mm, 
but  males,  as  far  as  could  be  told  without  histologi- 
cal studies,  appeared  to  mature  at  about  100  mm. 
There  was,  however,  no  evidence  to  suggest  that 
this  species  is  a  protandrous  hermaphrodite  as 
observed  in  G.  gracile  by  Kawaguchi  and  Marumo 
( 1967).  There  were  no  obvious  seasonal  differences 
in  the  percentages  of  ripe  females  among  mature 
females,  but  differences  in  size  composition  of  the 
catches  of  different  series  suggested  some  season- 
ality in  spawning. 

All  G.  ebelingi  caught  in  December  were  over  70 
mm.  In  March,  all  fish  were  either  less  than  50  mm 
or  over  70  mm.  In  June,  AQF/c  of  the  catch  was  20-60 
mm  and  the  rest  about  evenly  distributed  between 
61  and  150  mm.  In  September,  the  catch  was  again 
bimodal  with  all  fish  either  smaller  than  70  mm  or 
over  100  mm.  Recently  transformed  juveniles 
were  taken  only  in  March  and  September  and 
were  most  abundant  in  March.  More  data  would, 
of  course,  be  helpful,  but  it  seems  that  G.  ebelingi 
spawns  principally  in  early  spring  and  early  fall. 


Gonostoma  elongation  (1,346;  10-218  mm) 

In  all  series  but  December  1970,  G.  elongatum 
occurred  at  560-725  m  during  the  day  and  moved 
to  60-265  m  at  night.  In  December,  no  individuals 
over  115  mm  long  were  caught  in  the  upper  layers 
at  night,  but  larger  fish  were  taken  in  two  night 
tows  within  the  day  depth  range  (of  22  fish,  9  were 
117-200  mm.  Figure  3).  These  deep  night  catches 
were  not  large  relative  to  those  expected  from 
contamination,  and  consequently  may  have  re- 
sulted from  encountering  patches  in  the  shallow- 
layers.  However,  the  difference  in  size  suggests 
that  the  large  individuals  did  not  migrate. 

Size-frequency  curves  from  night  samples  at  dif- 
ferent depths  during  the  same  series  were  fre- 
quently significantly  different  and  consistently 
indicated  that  small  fish  occurred  shallower  (Fig- 


100 


50         75         100       125        150 

STANDARD  LENGTH(mm) 


200 


Figure  3. — Cumulative  size-frequency  curves  for  Gonostoma 
elongatum  taken  at  170  m  (A,  25  individuals),  190-200  m  (B,  two 
tows,  11),  265  m  (C,  13),  and  750  m  (D,  two  tows,  22l  at  night 
during  December  1970.  The  curves  were  all  significantly  differ- 
ent (P<0.05)  from  each  other. 


ure  3).  Those  caught  above  100-125  m  were  less 
than  35-40  mm,  most  caught  between  175  and  200 
m  were  60-80  mm,  and  larger  fish  were  taken 
mostly  in  tows  below  200  m.  It  was  not  clear 
whether  a  similar  pattern  existed  at  depth  during 
the  day. 

There  was  considerable  sexual  difference  in 
size  at  maturity.  Males  appeared  to  reach  matur- 
ity at  about  120  mm;  the  largest  male  was  161 
mm.  The  smallest  mature  female  was  193  mm. 
Some  small,  clearly  immature  females  (120-140 
mm)  were  found,  but  unfortunately,  no  fish  be- 
tween 161  and  193  mm  was  collected.  Although 
histological  studies  of  specimens  of  all  sizes  are 
obviously  necessary,  the  above  data  suggest  that 
some  G.  elongatum  mature  directly  as  females, 
while  others  are  protandrous  hermaphrodites. 
Kawaguchi  and  Marumo  (1967)  have  shown  that  a 
congener,  G.  gracile  is  a  protandrous  hermaphro- 
dite. Butler  ( 1964)  has  shown  that  in  some  species 
of  pandalid  shrimps,  a  group  within  which  pro- 
tandrous hermaphroditism  frequently  occurs,  the 
degree  of  hermaphroditism  varies  throughout  the 
species'  ranges.  Butler  suggests  that  this  is  a  re- 
sult of  varying  ecological  factors.  Varying  degrees 
of  protandry  may  similarly  occur  among  the 
Gonostoma  spp. 

Too  few  mature  females  were  collected  to  assess 
any  seasonal  trends  in  gonad  ripeness,  but  the 
pooled  size  composition  data  for  each  series  indi- 


341 


FISHERY  BULLETIN:  VOL    72,  NO.  2 


cated  that  the  principal  spawning  season  was  in 
the  spring  or  early  summer.  A  few  small  (10-30 
mm)  G.  elongatum  were  taken  in  March  and  June, 
but  these  were  far  more  abundant  in  July  and  Sep- 
tember. In  December,  substantial  numbers  of  35- 
to  50-mm  fish  were  taken,  but  none  were  less  than 
30  mm.  Too  few  large  individuals  were  taken  to 
indicate  any  further  trends,  but  it  seems  probable 
that  G.  elongatum  requires  several  years  to  reach 
maturity.  Krueger  and  Bond  (1972)  have  sug- 
gested a  3-yr  life  cycle  for  this  species  in  the  sub- 
tropical Atlantic. 

Danaphos  oculatus  (229;  19-41  mm) 

Danaphos  oculatus  does  not  appear  to  migrate 
vertically.  The  night  depth  range  was  430-600  m 
and  the  day  range  480-650  m.  The  day-night  dif- 
ference is  an  artifact  due  to  depth  spacing  of  the 
samples.  There  were  no  trends  in  size  composition 
with  depth.  Danaphos  oculatus  matures  at  about 
30  mm.  There  were  no  seasonal  trends  in  size 
composition  or  reproductive  condition. 

Valenciennellus  tripunctulatus  (600;  10-32  mm) 

During  the  day,  V.  tripunctulatus  was  taken 
principally  between  400  and  550  m.  The  size- 
frequency  curves  for  tows  at  500  and  525  m  taken 
in  September  1970  were  significantly  different; 
70%  in  the  shallower  tow  were  20-25  mm,  and  75% 
in  the  deeper  were  over  25  mm.  The  day  depth 
range  and  evidence  of  changes  in  size  composition 
with  depth  agree  with  results  reported  by  Krueger 
(1972)  for  V.  tripunctulatus  in  the  central  North 
Atlantic. 

Krueger's  data  show  that  V.  tripunctulatus 
remains  at  the  same  depths  during  the  night,  but 
near  Hawaii  this  species  undertakes  a  limited,  but 
definite  upward  migration.  The  night  depth  range 
was  200-330  m.  The  catches  per  effort  within  this 
range  were  roughly  equivalent  to  those  during  the 
day  at  400-500  m.  Catches  below  330  m  at  night 
were  lower  and  probably  due  to  contamination. 
All  sizes  were  taken  within  the  night  depth  range. 
Changes  in  size  composition  with  depth  were  evi- 
dent, but  numbers  sufficient  to  make  statistical 
comparisons  were  taken  at  more  than  one  depth 
only  in  December  1970.  In  that  case,  the  curve 
from  the  200-m  depth  sample  differed  signi- 
ficantly from  those  from  samples  at  270  and 
320  m.  About  90%  of  the  fish  in  the  shallower 
sample  were  10-16  mm  and  over  90%  in  the  deeper 


were  over  20  mm.  Thus  the  upward  extension  of 
the  depth  range  at  night  was  not  due  solely  to 
shallow  catches  of  postlarvae  or  juveniles  as 
Krueger  ( 1972)  has  suggested  may  be  the  case  for 
Badcock's  (1970)  earlier  observation  of  limited 
diurnal  vertical  migration  by  V.  tripunctulatus 
in  the  eastern  Atlantic. 

Valenciennellus  tripunctulatus  matures  at 
about  25  mm.  Large  proportions  of  the  mature 
females  (90-100%)  carried  well-developed  ova  at 
all  seasons.  There  were  no  obvious  seasonal  trends 
in  size  composition. 

Other  Gonostomatidae 

Two  Woodsia  nonsuchae  (39  and  106  mm)  were 
taken  at  530  and  620  m  at  night,  respectively.  A 
damaged  specimen  (22  mm)  that  was  probably  W. 
nonsuchae  was  taken  in  a  day  tow  to  875  m. 

Margrethia  obtusirostra  (18;  8-44  mm)  was 
taken  mostly  at  night  between  180  and  200  m.  The 
two  day  catches  were  in  tows  at  350  and  540  m. 
The  two  largest  specimens,  44  mm,  were  mature 
females  and  the  next  largest,  34  mm,  was  a  female 
with  ova  beginning  to  develop. 

Chauliodontidae 

Chauliodus  sloani  (147;  21-250  mm) 

Chauliodus  sloani  appeared  to  migrate  from  a 
day  depth  range  of  450-825  m  to  45-225  m  at  night. 
No  individual  over  65  mm  was  taken  above  100  m 
at  night  nor  above  500  m  during  the  day.  All  fish 
over  120  mm  were  taken  below  175  m  at  night  or 
below  600  m  during  the  day. 

The  pooled  data  from  each  series  showed 
significant  differences  in  size  composition  (Figure 
4A)  which  indicated  that  C.  sloani  spawns  princi- 
pally in  the  spring  or  early  summer  and  reaches 
lengths  of  70-100  mm  by  the  following  March. 
Individuals  less  than  40  mm  were  present  only  in 
June,  July,  and  September  and  were  most  abun- 
dant in  the  June  and  July  series.  These  were  likely 
represented  by  the  large  numbers  of  40-  to 
70-mm  fish  present  in  September  and  December 
and  70-  to  100-mm  fish  which  dominated  the 
March  samples.  Too  few  large  fish  were  collected 
to  assess  any  further  trends  in  size  composition. 
Chauliodus  sloani  almost  certainly  takes  several 
years  to  reach  maturity.  Only  the  two  largest 
specimens  (females,  225  and  250  mm)  were  ma- 
ture. The  next  largest  was  only  185  mm. 


342 


CLARKE:   ECOLOGY  OF  STOMIATOID  FISHES 

100  r 


iJ-tf 

80 

- 

-L-''Tn 

- 

/. 

rjj 

60 

f-j 

1! 

40 

1 

(B) 

11 

I© 

1 1 

1 1 

20 

w 

r 

1      A  indicus 

1            1           t 

10  20  30  40  50  60 

STANDARD  LENGTH(mm) 

Figure  4. — Left:  Cumulative  size-frequency  curves  for  the 
pooled  catches  of  Chauliodus  sloani  (exclusive  of  individuals 
over  120  mm)  in  June  1971  (A,  21  individuals),  September  1970 
(B,  42),  December  1970  (C,  13),  and  March  1971  (D,  19).  The 
curve  for  the  catch  in  July  1970  (not  shown)  did  not  differ 
significantly  from  and  was  almost  identical  with  that  for  June 
1971.  All  other  curves  differed  significantly  from  each  other 
(P<0.05).  Right:  Cumulative  size-frequency  curves  for  the 
pooled  catches  of  Astronesthes  indicus  (exclusive  of  individuals 
over  60  mm)  in  September  1970  (A,  dashed  line,  20  individuals), 
December  1970  (A,  solid  line,  41),  March  1971  (B,  128),  June 
1971  (C,  solid  line,  18),  and  July  1970  (C,  dashed  line,  27).  All 
pairs  except  June-July  and  September-December  differed 
significantly  (P<0.05). 


Stomiatidae 

Four  Stomi as  danae  (55-75  mm)  were  taken  at 
night.  Two  were  from  tows  at  100  m  and  two  from  a 
tow  at  250  m  that  extended  well  past  dawn.  A 
larger  (154  mm),  damaged  Stomias  sp.  was  taken 
in  a  night  tow  at  225  m. 

Three  specimens  (99-290  mm)  of  the  genus  Mac- 
rostomias  were  taken,  but  depth  information  on 
the  samples  was  questionable  for  all  three. 
Fedorov  and  Melchikova  (1971)  described  a  new 
species  of  Macrostomias,  M.  pacificus,  which 
they  distinguish  from  M.  longiharbatus  mostly 
on  the  basis  of  anal  fin  ray  and  photophore  counts. 
Two  of  the  specimens  I  collected  had  14  anal  rays, 
and  one  had  15.  Complete  photophore  counts  were 
possible  on  only  one  specimen  with  14  anal  rays: 
PV  =  81,  OV  =  82,  VAV  and  VAL  =  64.  The  other 
specimen  with  14  anal  rays  had  PV  =  82,  OV  =  80. 
The  estimated  PV  +  VAV  for  the  remaining 
specimen  was  148.  Thus  the  photophore  counts 
definitely  indicate  M.  longiharbatus,  while  the 
anal  ray  counts  fall  between  those  given  for  the 
two  forms  by  Fedorov  and  Melchikova  (1971).  I 
suspect  that  additional  specimens  will  indicate 
there  is  only  one  valid  species,  M.  longiharbatus. 


Astronesthidae 

Astronesthes  cyaneus  (45;  16-66  mm) 

Astronesthes  cyaneus  is  used  here  pending 
further  study  of  the  systematics  of  this  species 
group  in  the  Pacific.  The  specimens  were  closest  to 
A.  cyaneus  as  defined  by  Goodyear  and  Gibbs 
( 1969),  but  all  had  rudimentary  barbels.  Also,  the 
luminous  tissue  on  the  operculum  of  the  few  larger 
specimens  was  not  exactly  as  described  by 
Goodyear  and  Gibbs. 

Only  eight  specimens  were  caught  during  the 
day,  six  of  these  between  600  and  700  m.  Three- 
fourths  of  the  night  catches  were  at  80-100  m;  the 
few  collected  deeper  were  scattered  throughout 
the  water  column  and  were  probably  contamin- 
ants. None  of  the  specimens  were  near  maturity; 
only  eight  were  over  25  mm.  Larger  fish  undoubt- 
edly avoid  the  trawl  and  may  occur  deeper  than 
the  small  individuals.  It  appears  that  even  the 
small  ones  avoid  the  trawl  during  the  day. 


Astronesthes  indicus  (307;  11-117  mm) 

Astronesthes  indicus  was  taken  principally  at 
500-800  m  during  the  day  and  at  30-200  m  at  night 
except  in  the  December  1970  series.  In  that  series, 
no  A.  indicus  were  taken  in  the  upper  layers  at 
night,  but  21  were  taken  in  three  night  tows  at 
625-750  m,  within  the  day  depth  range.  The 
numbers  collected  in  these  tows  were  larger  than 
expected  if  they  had  been  due  to  contamination 
and  were  comparable  to  catches  of  day  tows  at  this 
time.  At  night,  no  individual  over  50  mm  was 
taken  shallower  than  125  m,  but  smaller  indi- 
viduals were  taken  with  roughly  equal  frequency 
throughout  the  night  depth  range.  The  small  fish 
also  appeared  to  occur  throughout  the  day  depth 
range,  but  large  fish  were  taken  mostly  in  tows 
near  the  deep  end. 

The  size  composition  of  the  catch  varied  consid- 
erably with  season  and  suggested  that  spawning 
occurred  principally  in  the  summer  and  fall  and 
that  about  2  yr  were  required  to  reach  50-60  mm. 
A  few  small  individuals  (<  20  mm)  were  taken  in 
July  1970,  many  in  September  and  December,  and 
none  in  March  or  June  of  1971  (Figure  4B).  The 
small  individuals  of  the  September  and  December 
samples  appear  to  be  represented  by  a  21-  to 
35-mm  group  in  March  and  a  34-  to  45-mm 
group  in  June.  A  similar  sized  group,  37-49  mm, 


343 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


was  present  in  the  July  1970  samples  and 
appeared  to  be  represented  by  a  42-to  51-mm 
group  in  September  and  a  46-  to  57-mm  group 
in  December.  The  CT  series  in  March  collected  99 
specimens,  56  of  which  were  24-36  mm  or  roughly 
equivalent  to  the  majority  of  the  IK  specimens.  Of 
the  remaining  CT  specimens,  26  were  50-76  mm- 
perhaps  representative  of  the  46-  to  57-mm  group 
in  the  December  IK  series. 

The  catch  per  effort  and  size  composition  of  IK 
catches  were  roughly  equal  for  day  and  night  indi- 
cating no  differential  avoidance.  However,  22  of 
the  35  specimens  over  60  mm  were  taken  by  the 
CT.  The  largest  taken  by  the  CT  was  89  mm  and 
only  four  larger  individuals  were  taken  by  scat- 
tered IK  tows.  Thus  it  appears  that  individuals 
over  60  mm  regularly  avoid  the  IK  and  that  larger 
ones  avoid  both  trawls.  The  largest  individual 
(117  mm)  was  a  female  that  appeared  to  be  near- 
ing  maturity.  Judged  from  the  above  data,  it  is 
likely  that  this  species  takes  at  least  3  or  4  yr  to 
mature. 


the  filament.  The  lateral  filaments  on  the  bulb 
were  much  shorter  than  the  bulb  itself.  The  sys- 
tematic status  of  this  form  is  presently  under 
study  by  other  workers  (Gibbs,  pers.  commun.). 

Twenty-four  of  the  specimens  were  taken  at 
50-200  m  at  night  and  eight  were  taken  at  500-640 
m  during  the  day.  Only  four  of  the  specimens  ex- 
ceeded 60  mm  indicating  that  the  large,  mature 
fish  consistently  avoided  both  trawls. 

Astronesthes  spp. 

Three  other  species  of  Astronesthes  were  taken. 
A.  gemmifer  (6;  91-138  mm)  was  taken  once  at 
night  at  245  m,  four  times  at  580-690  m  during  the 
day,  and  once  by  a  day  tow  to  1,150  m.  As- 
tronesthes lucifer  (10;  26-49  mm)  was  taken  five 
times  at  night  at  25-195  m,  and  by  day  at  250,  550 
(3),  and  640  m.  Astronesthes  luetkeni  (6;  26-74 
mm)  was  taken  in  only  three  tows  for  which  depth 
information  was  valid:  125  and  200  m  at  night  and 
600  m  during  the  day. 


Astronesthes  splendidus  (82;  22-110  mm) 

About  75%  of  the  A.  splendidus  collected  were 
taken  at  25-130  m  at  night.  There  was  no  obvious 
trend  in  size  composition  with  depth.  Only  16 
specimens  were  taken  during  the  day,  all  but  2  of 
these  between  600  and  800  m.  Nearly  transformed 
larvae  with  photophores  (<  25  mm)  and  small 
juveniles  were  present  only  in  June,  July,  and 
September  suggesting  summer  or  early  spring 
spawning.  These  young  may  have  been  rep- 
resented by  40-  to  60 — mm  fish  which  made  up 
85%  of  the  March  catch,  but  so  few  fish  were 
caught  in  December  that  the  connection  between 
the  two  size  groups  is  tenuous.  Only  15  of  the  82 
specimens  were  over  60  mm  and  none  were  ma- 
ture. The  size  composition  of  IK  and  CT  catches  in 
March  was  similar.  Thus  both  trawls  were  avoided 
by  most  larger  juveniles  and  consistently  by 
adults. 


Heterophotus  ophistoma  (28;  32-245  mm) 

Of  17  H.  ophistoma  taken  at  night,  15  were 
taken  between  50  and  200  m.  The  other  two  were 
nearly  transformed  larvae  taken  in  a  closing  net 
tow  at  about  630  m.  Ten  of  the  11  day  specimens 
were  taken  at  625-775  m;  one  was  taken  at  1,000 
m.  Eighteen  were  larvae  or  recently  transformed 
juveniles  (32-64  mm),  and  all  but  two  of  these  were 
taken  in  July  or  September.  The  two  largest 
specimens,  235  and  245  mm,  were  males  and  ap- 
peared to  be  mature  or  nearly  so. 

Neonesthes  microcephalus  (2;  135-147  mm) 

One  A^.  microcephalus  was  taken  at  640  m  at 
night  and  the  other  in  oblique  tow  to  1,600  m. 


Melanostomiatidae 


Astronesthes  sp.  (near  si tnilis)  (37;  21-133  mm) 

The  specimens  of  this  species  of  Astronesthes 
agreed  with  the  description  of^.  similis  by  Gibbs 
(1964)  except  for  the  barbel  tip.  Instead  of  being 
unornamented,  the  barbel  tip  of  the  Hawaiian 
specimens  had  a  dark  terminal  filament  about  as 
long  as  the  bulb  and  often  a  pale  tip  at  the  end  of 


Eustomias  bibulbosus  (20;  80-145  mm) 

Fourteen  E.  bibulbosus  were  taken  at  75-300 
m  at  night;  however,  only  two  large  (131  and  145 
mm)  individuals  were  taken  below  125  m.  During 
the  day,  six  were  taken  between  600  and  960  m. 
Sixteen  of  the  specimens  were  small  (80-102  mm), 
and  none  of  the  large  ones  were  mature. 


344 


CLARKE:   ECOLOGY  OF  STOMLATOID  FISHES 

Eustomias  bifilis  (128;  41-170  mm) 

All  but  5  of  the  92  night  catches  of  £:.  bifilis  (40 
by  IK,  51  by  CT)  were  at  15-200  m.  The  day  depth 
range  appeared  to  be  635-800  m;  only  5  of  the  29 
day  catches  were  at  greater  depths.  There  was  no 
obvious  trend  in  size  composition  with  depth.  Size 
at  maturity  was  about  140  mm. 

Eustomias  gibbsi  (28;  55-131  mm) 

All  but  three  E.  gibbsi  were  taken  at  night. 
The  night  depth  range  was  about  50-200  m,  and 
the  three  day  catches  were  at  680-800  m.  There 
was  no  obvious  trend  in  size  composition  with 
depth  among  the  night  catches.  None  of  the  speci- 
mens were  mature. 

Eustomias  spp. 

Of  the  remaining  specimens  of  Eustomias, 
about  130  were  too  badly  damaged  to  be  identified 
with  certainty.  The  great  majority  of  these  had 
pectoral  ray  and  photophore  counts  within  the 
range  of  the  three  species  considered  above  (most 
were  probably  E.  bifilis).  Some  150  other  speci- 
mens include  about  20  different  forms,  most  of 
which  cannot  be  reliably  identified  due  to  present 
uncertainties  in  the  systematics  of  the  genus. 
These  along  with  other  specimens  from  the  Cen- 
tral Pacific  will  be  considered  in  a  later,  more 
systematically  oriented  report. 


Thysanactis  dentex  (340;  39-177  mm) 

Thysanactis  dentex,  the  most  frequently  col- 
lected melanostomiatid,  occurred  principally  at 
75-200  m  at  night.  A  few  individuals  were  taken 
as  shallow  as  40  m,  and  there  were  scattered  night 
catches  throughout  the  water  column.  The  princi- 
pal day  depth  range  was  600-800  m  with  a  few 
caught  between  400  and  600  m  or  scattered  deeper 
than  800  m.  Within  both  ranges,  the  larger  fish 
tended  to  occur  deeper  and  the  smaller  shallower. 
At  night  few  over  100  mm  occurred  above  150  m, 
and  catches  of  those  smaller  than  80  mm  below 
125  m  were  low  and  probably  due  to  contamina- 
tion. During  the  day  those  over  100  mm  were 
caught  mostly  below  700  m  and  those  less  than 
100  mm  mostly  between  600  and  700  m.  Size  at 
maturity  was  about  160  mm. 


Bathophilus  spp. 

Seven  species  of  Bathophilus  were  taken.  Al- 
though data  are  incomplete  for  most,  it  seems  that 
all  occur  at  about  500-700  m  during  the  day  and 
migrate  to  the  upper  250  m  at  night.  Bathophilus 
kingi  (23;  24-95  mm)  was  taken  most  frequently. 
At  night,  18  specimens  were  taken  between  50  and 
225  m.  Three  specimens  were  taken  at  590-725  m 
during  the  day  and  one  each  at  1,000  and  1,100  m. 
Bathophilus  brevis  (3;  12-43  mm)  was  taken  only 
at  night  between  200  and  225  m.  Bathophilus  di- 
gitatus  (9;  23-91  mm)  was  taken  seven  times  at 
night  at  125-175  m  and  twice  during  the  day  at 
520  and  550  m.  Bathophilus  longipinnis  ( 10;  25-97 
mm)  was  taken  seven  times  at  night  scattered 
throughout  the  water  column  (100-1,175  m)  and 
three  times  between  520  and  590  m  during  the 
day.  Bathophilus  pawneei  (7;  30-90  mm)  was 
taken  at  night  between  40  and  195  m  and  once  at 
690  m  during  the  day.  Bathophilus  cf.  altipinnis 
?  (3;  26-59  mm;  pectoral  rays  26-28,  pelvic  rays 
15-18)  was  taken  at  170  and  265  m  at  night  and  at 
640  m  during  the  day.  A  singleB.  schizochirus  (76 
mm)  was  taken  at  265  m  at  night. 

Other  Melanostomiatidae 

Pachystomias  microdon  (33  mm)  was  taken  once 
in  a  day  tow  at  660  m.  Two  small  (55-56  mm) 
Flagellostomias  boureei  were  taken  at  500  m  (day) 
and  750  m  (night).  Five  juvenile  Echiostoma  bar- 
batum  (29-89  mm)  were  taken,  four  at  30-185  m  at 
night  and  one  in  an  oblique  day  tow  to  800  m.  Four 
species  of  Photonectes  which  were  collected  could 
be  identified  with  reasonable  certainty.  Photo- 
nectes  achirus  (9;  43-146  mm)  was  taken  at 
125-225  m  at  night  and  at  400,  550,  620,  and  1,400 
m  during  the  day.  A  single  Photonectes  caerules- 
cens  (127  mm),  which  is  likely  to  be  proven  indis- 
tinct from  Photonectes  achirus,  was  taken  in  a  day 
tow  at  800  m.  Photonectes  albipennis  (8;  22-87 
mm)  was  taken  once  at  620  m  during  the  day  and 
between  60  and  165  m  at  night.  Photonectes 
fimbria  (34  mm)  was  taken  once  at  620  m  during 
the  day.  The  above  specimens  ofPhotonectes  fit  the 
descriptions  given  in  Morrow  and  Gibbs  (1964) 
reasonably  well.  In  addition,  two  specimens  (208 
and  255  mm),  taken  at  650  m  at  night  and  490  m 
during  the  day,  were  close  to,  but  not  identical 
with,  Photonectes  margarita. 

Leptostomias  spp.  (15;  68-134  mm)  were  taken 
predominantly  at  night  between  100  and  250  m; 


345 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


four  were  taken  during  the  day  at  500-625  m. 
Melanostomias  spp.  (23;  48-238)  were  mostly 
taken  at  50-250  m  at  night  or  520-800  m  during 
the  day.  Due  to  either  damage  to  the  barbels 
(mostly  Leptostomias)  or  lack  of  data  on  the  varia- 
bility of  characters  used  to  separate  nominal 
species  in  these  genera,  definite  identifications 
cannot  be  given. 

Idiacanthidae 

Idiacanthus  fasciola  (341;  13-375  mm) 

Larval  /.  fasciola  (13-50  mm)  were  taken 
mostly  at  night  in  the  upper  200  m;  deeper  catches 
both  day  and  night  were  scattered  and  probably 
contaminants.  Males  (30-50  mm)  were  taken  prin- 
cipally between  550  and  800  m  during  the  day. 
Fourteen  of  the  20  night  captures  were  also  in  the 
day  depth  range,  but  6  were  taken  at  200-300  m. 

At  night,  females  (47-375  mm)  were  taken  prin- 
cipally between  30  and  300  m.  All  taken  below  200 
m  were  over  145  mm,  but  larger  ones  did  occur 
shallower.  In  the  December  1970  series  seven 
females  were  taken,  but  only  one  was  taken  at 
night  in  the  upper  300  m,  the  remainder  were 
taken  within  the  day  depth  range.  During  the  day, 
females  were  taken  mostly  between  600  and  800 
m,  but  one  was  caught  at  250  m  and  several  at 
400-600  m.  Too  few  were  taken  to  make  detailed 
comparisons  of  day  and  night  catch  per  effort,  but 
the  data  indicated  no  gross  differences  in  abun- 
dance or  size  frequency. 

Female  /.  fasciola  mature  at  about  250  mm, 
but  too  few  large  individuals  were  taken  to  assess 
any  seasonal  trends  in  gonad  ripeness.  There  were 
no  clear  seasonal  trends  in  size  composition  of  the 
catches.  Larvae  and  males  were  taken  most  fre- 
quently in  December.  Few  were  taken  in  March, 
with  catches  for  June,  July,  and  September  inter- 
mediate. In  July,  September,  and  December,  84- 
91%  of  the  females  were  shorter  than  150  mm, 
while  the  percentages  for  March  {597c )  and  June 
(30%  )  indicated  relatively  fewer  smaller  females. 
There  were,  however,  no  definite  size  groups 
which  could  be  traced  from  season  to  season. 

Malacosteidae 

Fhotostomias  guernei  (159;  24-158  mm) 

Photostomias  guernei  was  taken  principally  at 
346 


15-300  m  at  night  and  at  350-800  m  during  the 
day.  A  few  specimens  were  taken  in  deep  night 
tows  with  the  opening-closing  trawl  indicating 
that  the  entire  population  does  not  regularly  mi- 
grate. Small  fish  were  caught  throughout  these 
ranges,  but  only  two  fish  over  100  mm  were  caught 
above  185  m  at  night  and  none  over  80  mm  were 
taken  above  750  m  during  the  day. 

Mature  female  P.  guernei  showed  a  rather  curi- 
ous size  distribution.  Of  41  females  examined 
(46-158  mm),  11  bore  ripened  ova.  Nine  were 
64-85  mm  and  two  were  considerably  larger — 147 
and  158  mm.  Of  the  specimens  with  undeveloped 
ova,  seven  were  less  than  63  mm,  and  the  remain- 
der 93-149  mm.  Some  of  the  large  individuals 
could  possibly  have  spawned  already,  but  the  in- 
dividuals between  93  and  125  mm  were  clearly 
immature.  The  bimodal  size  distribution  suggests 
that  two  populations  were  present  in  the  samples, 
but  there  was  considerable  overlap  or  agreement 
in  photophore  and  fin  ray  counts  of  both  large  and 
small  females.  Also  there  was  no  indication  that 
one  type  of  female  had  a  different  depth  distribu- 
tion or  seasonal  pattern  than  the  other. 

Photostomias  guernei  probably  spawns  over 
most  of  the  year.  Individuals  under  40  mm  were 
most  frequently  taken  in  June,  but  were  present 
in  all  series.  There  was  no  obvious  seasonal  trend 
in  size  composition  of  the  larger  fish. 

Aristostomias  spp. 

Aristostomias  lunifer  (12;  30-151  mm)  was 
taken  only  between  120  and  260  m  at  night.  The 
largest  specimen,  a  151  mm  female,  was  mature  or 
nearly  so.  Aristostomias grimaldii  (5;  33-117  mm) 
was  taken  at  100  and  500  m  at  night  and  at  690 
and  750  m  during  the  day.  The  largest  specimen,  a 
male,  appeared  immature.  Aristostomias  poly dac- 
tylus  (10;  33-140  mm)  was  taken  at  100,  175,  320, 
and  590  m  at  night  and  at  625,  850,  875,  and  1,100 
m  during  the  day.  The  largest  individual  was  an 
immature  female.  Two  specimens  similar  to  A. 
tittmanni  (68  and  75  mm)  were  taken  at  15  and 
250  m  at  night. 

Malacosteus  niger  (133;  26-186  mm) 

Malacosteus  niger  occurred  between  520  and 
900  m  during  the  day  and  500-850  m  at  night;  the 
day-night  differences  were  due  to  sample  spacing. 
Most  were  taken  between  600  and  700  m.  The 


CLARKE:   ECOLOGY  OF  STOMIATOID  FISHES 


depth-size  plot  indicated  a  trend  for  greater  size 
with  increasing  depth,  but  since  106  of  the  133 
specimens  were  75-125  mm  any  trends  for  smaller 
or  larger  fish  are  of  dubious  significance.  The  only 
mature  females  collected  were  the  four  largest 
specimens  (172-186  mm).  There  was  no  seasonal 
trend  in  size  composition  of  the  the  catches. 

DISCUSSION 

In  spite  of  the  fact  that  the  stomiatoids  in  the 
study  area  were  quite  diverse  and  that  there  have 
been  no  really  comprehensive  studies  based  on 
extensive  sampling  programs  in  the  Pacific,  only  a 
few  species  are  either  undescribed  or  of  uncertain 
status  (with  the  exception  of  the  Eustomias  spp.). 
To  paraphrase  Gibbs  (1960),  it  is  indeed  a  reHef 
that  most  specimens  fit  descriptions  based  pri- 
marily on  Atlantic  material. 

Eight  species  were  previously  unrecorded  in  the 
Facific:  Astronesthes ge?7imifer,  Neonesthes  micro- 
cephalus,  Aristostomias  grimaldii,  A.  lunifer, 
A.,  polydactylus,  Eustomias  bibulbosus,  Photo- 
nectes  achirus,  and  Bathophilus  altipinnis.  Three 
of  the  more  commonly  collected  species  were  pre- 
viously known  only  from  a  few  specimens. 
Gonostoma  ebelingi  (Grey,  1960)  and  Eustomias 
bifilis  (Gibbs,  1960)  were  described  on  the  basis  of 
two  and  one  specimens,  respectively,  and  no  other 
specimens  have  been  reported  since.  Thysanactis 
dentex,  which  was  taken  regularly  by  the  present 
study  and  by  King  and  Iversen  ( 1962),  is  listed  by 
Morrow  and  Gibbs  ( 1964)  as  known  from  only  five 
captures  in  the  North  Atlantic.  Further  studies  of 
material  from  other  tropical  areas  will  be  nec- 
essary to  determine  if  these  species  are  for  some 
reason  present  in  high  numbers  only  in  the 
Central  Pacific. 

Inadequate  information  from  other  areas  of  the 
Pacific  does  not  permit  detailed  consideration  of 
zoogeographic  patterns  of  these  species.  Negative 
records  of  several  studies  and  reports  cannot 
necessarily  be  considered  conclusive.  It  is  likely 
that  the  majority  of  the  species  recorded  here 
occur  throughout  the  warm  water  masses.  How- 
ever, preliminary  examination  of  samples  from 
the  central  equatorial  Pacific  indicates  that  at 
least  Vinciguerria  nimbaria  and  Gonostoma 
ebelingi  do  not  occur  continuously  across  the  equa- 
torial region  and  also  confirm  Gibbs'  (1969)  state- 
ment that  Stomias  danae  is  replaced  by  S.  affinis 
'  in  equatorial  waters.  Two  species,  Vinciguerria 
lucetia  and  Idiacanthus  antrostomus,  which  ap- 


pear to  occur  in  eastern  and  equatorial  waters, 
were  not  taken  during  this  study.  Vinciguerria 
lucetia  has  been  recorded  near  Hawaii  (King  and 
Iversen,  1962;  Ahlstrom  and  Counts,  1958)  and 
Idiacanthus  antrostomus  may  also  be  expected  to 
occur  here  occasionally,  but  their  absence  from  the 
material  collected  during  the  study  indicates  that 
some  warmwater  species  do  not  normally  occur  in 
the  central  water  mass. 

It  is  clear  from  the  absence  or  extreme  rarity  of 
mature  fish,  that  neither  of  the  trawls  used  were 
adequately  sampling  the  larger  sizes  of  many 
species — particularly  the  Astronesthes  spp.  Al- 
though differences  in  day-night  catches  have  not 
been  rigorously  demonstrated,  it  also  appears  that 
many  large  species  and  individuals  avoid  the  IK 
better  during  the  day  than  at  night. 

For  most  species,  the  numbers  caught  by  the 
paired  series  of  IK  and  CT  tows  in  March  1971, 
were  not  sufficient  for  detailed  analyses,  but 
rough  comparison  of  the  catches  and  size  ranges 
(Table  1)  indicates  some  differential  avoidance. 
The  total  volume  sampled  by  the  CT  tows  was 
about  10  times  that  of  the  IK  tows  in  the  same 
depth  range.  In  10  species,  the  ratio  of  CT/IK 
catches  was  considerably  lower  than  10  (1.3-6.0) 
suggesting  that  the  IK's  greater  towing  speed  was 
more  of  an  advantage  than  the  greater  size  of  the 
CT.  In  these  cases,  the  CT/IK  ratio  was  httle  af- 
fected by  considering  only  the  fish  larger  than  the 
smallest  caught  by  the  CT;  i.e.,  the  passage  of 
smaller  fish  through  the  coarser  CT  meshes  did 
not  seem  to  be  an  important  factor. 

Three  species,  Diplophos  taenia,  Gonostoma 

Table  1.— Total  numbers  and  size  ranges  of  15  species  offish 
taken  in  nine  tows  with  the  IK  and  eight  tows  with  the  CT  in  the 
upper  200  m  at  night  during  February-March  1971.  The  tows 
with  each  net  were  roughly  equally  distributed  between  25  and 
200  m.  The  total  volume  sampled  by  the  CT  tows  was  about  10 x 
that  of  the  IK  tows. 


Species 

Total  catch 

Size  ran 

ge  (mm) 

IK 

CT 

IK 

CT 

Diplophos  taenia 

5 

62 

66-83 

61-153 

Vinciguerria  poweriae 

29 

122 

16-34 

15-33 

Gonostoma  atlanticum 

10 

40 

15-45 

20-64 

Gonostoma  ebelingi 

11 

100 

12-37 

16-162 

Gonostoma  elongatum 

97 

236 

10-139 

30-165 

Chauliodus  sloani 

4 

13 

81-162 

68-123 

Astronestties  cyaneus 

4 

13 

18-19 

17-44 

Astronesthes  indicus 

18 

83 

21-89 

24-89 

Astronesthes  splendidus 

10 

13 

29-58 

30-65 

Eustomias  bibulbosus 

0 

10 

— 

81-141 

Eustomias  bililis 

2 

49 

93-115 

52-158 

Eustomias  gibbsi 

1 

10 

77 

70-131 

Thysanactis  dentex 

17 

102 

58-173 

44-165 

Idiacanthus  fasciola 

17 

81 

58-297 

54-301 

Photostomias  guernei 

9 

26 

30-113 

40-133 

347 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


ebelingi,  and  Eustomias  gibbsi,  were  taken  in 
roughly  the  predicted  ratios,  and  the  other  two 
species  of  Eustomias  treated  here  were  clearly 
sampled  better  by  the  CT.  Size  ranges,  of  course, 
were  greatly  influenced  by  just  one  large  indi- 
vidual, but  in  general  the  CT  caught  considerably 
larger  individuals  of  the  five  species  which  it  ap- 
peared to  sample  relatively  better  in  terms  of 
numbers.  Although  not  shown  by  the  figures  in 
Table  1,  large  Astronesthes  indicus  were  also 
apparently  sampled  better  by  the  CT  (see  above). 

Of  the  47  species  considered  here,  only 
Danaphos  oculatus  and  Malacosteus  niger  clearly 
did  not  migrate  to  shallower  levels  at  night.  All 
the  other  abundant  species  migrated  to  the  upper 
layers  at  night  and,  in  spite  of  the  fact  that  no 
opening-closing  device  was  used,  even  the  data  on 
many  of  the  rarer  species  are  consistent  with  mi- 
grations of  several  hundred  meters.  It  is,  of  course, 
possible  that,  as  in  the  case  of  Photostomias 
guernei,  a  small  percentage  of  some  species  may 
not  migrate  at  any  given  time.  Diurnal  vertical 
migration  has  been  shown  to  occur  in  a  few  of  the 
species  considered  here  (e.g.,  Badcock,  1970; 
Krueger  and  Bond,  1972),  but  due  to  limited  data 
it  had  been  only  "suspected"  for  many  others.  Pos- 
sibly because  of  the  deeper  mixed  layer  and  ther- 
mocline  and  greater  transparency  of  the  water, 
migrations  in  the  tropics  are  greater  in  extent  and 
thus  more  easily  detected  than  elsewhere. 

As  with  several  species  of  myctophids  (Clarke, 
1973),  there  was  evidence  that  some  of  the 
stomiatoids  did  not  regularly  migrate  during  the 
winter.  For  Vinciguerria  nimbaria,  Gonostoma 
elongatum,  Astronesthes  indicus,  and  I diacanthus 
fasciola,  night  catches  within  the  day  depth  range 
during  December  1970  were  higher  than  expected 
if  due  to  contamination  and  indicated  that  a  frac- 
tion of  the  population  remained  at  depth.  Too  few 
of  the  latter  two  species  were  taken  to  permit 
consideration  of  any  differences  between  the  mi- 
grating and  nonmigrating  fractions.  The  evidence 
for  nonmigration  was  weak  for  G.  elongatum  but 
suggested  that  the  large  fish  did  not  migrate. 
There  were  no  obvious  differences  in  the  two  frac- 
tions of  the  population  of  V.  nimbaria.  Thus  as 
with  the  myctophids,  there  is  no  explanation  for 
the  apparent  change  in  behavior. 

Many  of  the  species  showed  trends  for  increased 
size  with  depth  both  day  and  night.  Similar  trends 
were  noted  for  many  species  of  myctophids 
(Clarke,  1973),  and  qualitative  reports  (e.g..  Bad- 
cock,  1970)  indicate  that  this  trend  is  shown  by  a 


variety  of  mesopelagic  species.  The  trend  was 
clearest  for  the  abundant  vertically-migrating 
gonostomatids,  Diplophos  taenia,  Vinciguerria 
spp.,  Gonostoma  spp.,  and  Valenciennellus 
tripunctulatus,  but  was  also  evident  for 
Chauliodus  sloani,  Astronesthes  indicus  and 
Thysanactis  dentex. 

The  size-depth  patterns  at  night  of  10  species 
are  shown  in  Figure  5  by  straight  lines  connecting 
the  coordinates  for  the  smallest  size,  upper  limit  of 
depth  range  with  those  for  the  largest  size,  lower 
limit  of  depth  range  (extremes  of  size  and  depth 
have  been  ignored).  These  are  only  rough 
approximations  of  the  size-depth  patterns;  in  real- 
ity the  patterns  are  rather  complex  polygons.  The 
straight  lines  serve  mainly  as  a  basis  for  consider- 
ing the  possible  interactions  of  the  various  species. 


STANDARD   LENGTH  (mm) 


Figure  5. — Depth-size  profiles  (see  text)  for  10  species  in  the 
upper  300  m  at  night:  Vinciguerria  nimbaria  (A),  Vi.  poweriae 
(B),  Valenciennellus  tripunctulatus  (C),  Diplophos  taenia  (D), 
Chauliodus  sloani  (E),  Thysanactis  dentex  (F),  Gonostoma  elon- 
gatum (G),G.  ebelingi  (H),  Astronesthes  indicus  (I),  andG.  atlan- 
ticum  (J). 

Two  very  similar  species,  Vinciguerria  nim- 
baria and  V.  poweriae,  showed  distinctly  different 
size-depth  patterns.  As  with  many  similar  species 
of  myctophids,  individuals  of  similar  sizes  were 
well  separated  in  the  water  column.  Where  the 
depth  ranges  overlapped,  at  100-125  m,  the  larger 
V.  nimbaria  co-occurred  with  the  smaller  V.  pow- 
eriae. Vinciguerria  nimbaria  generally  co- 
occurred  with  similar-sized  or  slightly  larger  in- 
dividuals of  several  abundant  species  of  myc- 
tophids in  the  upper  100  m,  while  V.  poweriae 
co-occurred  with  the  deeper  living  myctophids 
(Clarke,  1973). 

Although  their  size-depth  patterns  were 
slightly  different,  similar-sized  individuals  of 
Gonostoma  elongatum  and  G.  ebelingi,  two  very 
similar  species,  co-occurred  over  much  of  their 
depth  ranges.  G.  atlanticum ,  in  addition  to  being 
rather  different  from  its  congeners  in  size  range, 
color,  and  several  morphological  aspects,  also  had 


348 


CLARKE:    ECOLOGY  OF  STOMIATOID  FISHES 


a  quite  different  size-depth  pattern  and  tended  to 
co-occur  with  much  larger  individuals  of  its  con- 
geners. The  former  two  species  co-occurred 
throughout  much  of  their  depth  range  with 
similar-sized  individuals  of  three  species  of  the 
myctophid  genus  Lampanyctus.  Thus  in  the 
100-250  m  layer  at  night  similar  species  of  at  least 
two  genera  of  two  families  co-occur.  This  is  in 
contrast  to  the  upper  100  m  where  only  rather 
different  or  distantly  related  species  co-occur. 

Other  gonostomatids  exhibited  nighttime  pat- 
terns quite  different  from  any  of  the  other  species 
considered.  Danaphos  oculatus  remained  at  the 
day  depth  and  showed  no  trend  in  size  composition 
with  depth.  Valenciennellus  tripunctulatus 
occurred  much  deeper  than  similar-sized  indi- 
viduals of  any  other  species.  Diplophos  taenia 
occurred  much  shallower,  with  respect  to  size, 
than  any  of  the  species  thus  far  investigated.  It  is 
possible  that  some  of  the  shallow-living  myc- 
tophids,  e.g.,  Myctophum  spp.,  which  were  not 
adequately  sampled  by  the  trawl  also  have  pat- 
terns similar  to  that  of  Z).  taenia. 

The  larger  stomiatoids  with  fanglike  teeth,  dor- 
sal or  mental  "lures,"  or  various  adaptions  for 
swallowing  large  items,  are  generally  thought  to 
be  predators  on  small  nekton.  Near  Hawaii,  the 
dominant  "predatory"  species  exhibited  a  variety 
of  patterns  at  night.  Astronesthes  indicus,  Chau- 
liodus  sloani,  and  Thysanactis  dentex  showed 
trends  for  increased  size  with  depth.  In  the  upper 
100  m,  these  species  co-occurred  with  roughly 
similar-sized  or  slightly  smaller  individuals  of  the 
more  abundant  myctophids  and  Vinciguerria 
nimbaria.  Although  there  are,  scattered  through- 
out the  literature,  several  records  of  larger 
stomiatoids  ingesting  rather  large  prey,  it  seems 
unlikely  that  these  three  species  are  important 
predators  on  the  abundant  fishes  in  the  upper  100 
m  or  that  the  latter  are  important  items  in  the 
former's  diet.  All  sizes  of  Idiacanthus  fasciola, 
Eustomias  bifilis.  and  Astronesthes  splendidus 
appeared  to  occur  throughout  their  night  depth 
ranges.  Thus  it  would  seem  that,  if  indeed  any  of 
the  larger  stomiatoids  are  important  predators  on 
the  small  fishes  in  the  upper  100  m,  species  such  as 
these  are  more  likely  candidates. 

Malacosteus  niger  did  not  migrate,  and  its  depth 
range  was  somewhat  deeper  than  the  day  ranges 
of  most  of  the  vertically  migrating  species  consid- 
ered here.  Malacosteus  niger  has  very  poorly  de- 
veloped serial,  ventral-lateral  photophores  in 
comparison  with  most  other  stomiatoids.  The  only 


nonmigrating  species  of  myctophid,  Taaning- 
ichthys  bathyphilus,  occurs  in  the  same  depth 
range  and  has  greatly  reduced  serial  photophores 
in  comparison  with  the  other  myctophid  species. 
If,  as  Clarke  (1963)  has  suggested,  ventral-lateral 
photophores  are  a  counter-shading  device,  their 
absence  or  reduction  in  these  deep-living,  non- 
migrating  species  is  likely  related  to  lower  light 
levels  and  more  nearly  spherical  radiance  dis- 
tribution at  such  depths  even  during  the  day  in 
comparison  to  the  regime  which  most  of  the  mi- 
gi'ating  species  experience  day  or  night. 

Three  of  the  species  which  occurred  together  at 
400-600  m  during  the  day,  Danaphos  oculatus, 
Valenciennellus  tripunctulatus,  and  Ichthyococ- 
cus  ovatus,  all  have  dorsally  directed  eyes  and 
markedly  ventrally  directed  serial  photophores. 
These  characteristics  are  shared  by  the  sternop- 
tychids  of  the  genus  Argyropelecus  which  also 
occur  in  the  same  depth  range  (S.  S.  Amesbury, 
pers.  commun.).  The  argentinoid,  Opisthoproctus 
soleatus,  which  shares  the  same  day  depth  range, 
also  has  dorsally  directed  eyes  and  a  ventrally 
directed  luminescent  apparatus.  At  night,  none  of 
these  species  appear  to  undertake  extensive  mig- 
rations. Danaphos  oculatus  remains  at  the  same 
depths,  V.  tripunctulatus  undertakes  a  limited 
upward  migration,  and  /.  ovatus  either  migrates 
or  disperses  upward.  The  Argyropelecus  spp. 
either  move  upward  slightly  or  remain  at  the 
same  depths  (S.  S.  Amesbury,  pers.  commun.). 
Opisthoproctus  soleatus  was  for  some  reason 
nearly  absent  from  the  night  samples;  out  of  the 
114  specimens  only  4  were  taken  at  night. 

Several  investigators  (see  review  by  McAllister, 
1967)  have  suggested  that  the  dorsally  directed 
eyes  are  an  adaptation  for  better  detection  of  prey 
or  predators  above  the  fish  and  that  the  ventrally 
directed  light  organs  serve  to  disrupt  the 
silhouette  of  the  fish  to  predators  below.  These 
adaptive  values  would  be  realized  only  under  a 
situation  where  light  levels  were  low  but  still 
sufficient  for  vision  and  where  the  radiance  dis- 
tribution was  dominated  by  the  downwelling 
component.  Such  conditions  probably  obtain  only 
during  the  day  for  the  above  species.  This  would 
suggest  that  they  feed  primarily  during  the  day 
and  that  they  are  exposed  to  heavier  predation 
then  also.  At  least  the  former  seems  likely.  These 
species  probably  feed  on  zooplankton,  and  pre- 
liminary analyses  of  zooplankton  in  the  study 
area  indicates  that  these  species  encounter  higher 
concentrations  during  the  day  owing  to  vertical 


349 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


migrations  of  the  zooplankton.  The  situation  is 
just  the  opposite  for  most  of  the  other  fishes  which 
share  the  same  day  depth  range  and  have  neither 
upwardly  directed  eyes  nor  as  pronounced  a  ven- 
tral orientation  of  their  light  organs.  The  latter 
fishes  undertake  more  extensive  vertical  migra- 
tions at  night  and  encounter  higher  concentra- 
tions of  zooplankton  and  probably  predators  then 
rather  than  during  the  day. 

The  species  which  showed  seasonal  trends  in 
size  composition  or  gonad  ripeness  all  appeared  to 
spawn  primarily  in  the  spring  and  summer  or 
summer  and  fall.  These  were  Vinciguerria  spp., 
Chauliodus  sloani,  Astronesthes  indicus,  and  prob- 
ably A.  spendidus  and  Heterophotus  ophistoma. 
Their  seasons  of  peak  reproduction  were  thus 
similar  to  those  of  the  abundant  myctophids 
(Clarke,  1973).  The  data  onGonostoma  elongatum 
and  Idiacanthus  fasciola  suggested  rather  incon- 
clusively that  these  species  spawn  primarily  in 
the  summer  and  winter,  respectively.  Several 
fairly  abundant  species,  Gonostoma  atlanticum, 
Danaphos  oculatus,  Valenciennellus  tripunc- 
tulatus,  Eustomias  bifilis,  Thysanactis  dentex, 
Photostomias  guernei,  and  Malacosteus  niger, 
showed  no  indication  of  seasonality  in  reproduc- 
tion. Possibly  the  larvae  of  those  species  which 
exhibit  no  seasonality  either  hatch  at  a  larger  size 
or  live  at  greater  depths  than  those  of  the  seasonal 
species  and  thus  the  former's  spawning  is  not 
timed  to  any  seasonal  fluctuations  in  food  concen- 
tration or  size  distribution  in  the  upper  layers. 

ACKNOWLEDGMENTS 

I  am  indebted  to  the  many  people  who  partici- 
pated on  the  cruises  and  also  the  captain  and  crew 
of  the  RV  Teritu.  The  Cobb  trawl  samples  were 
taken  during  cruise  52  of  the  NMFS  RV  Townsend 
Cromwell.  I  thank  B.  E.  Higgins,  chief  scientist, 
and  others  at  the  Southwest  Fisheries  Center 
Honolulu  Laboratory,  NMFS,  NOAA,  for  their 
cooperation.  R.  E.  Young  and  S.  S.  Amesbury  of 
the  University  of  Hawaii  provided  specimens  and 
data  from  the  opening-closing  trawl. 

Patricia  J.  Wagner  assisted  capably  in  all  phas- 
es of  the  laboratory  analyses.  R.  H.  Gibbs,  Jr.  and 
R.  H.  Goodyear  kindly  supplied  or  confirmed 
identifications  of  many  species.  Their  assistance 
in  untangling  several  systematic  problems  is 
greatly  appreciated.  Any  errors  are  my  own. 

This  research  was  supported  by  NSF  GB-23931 
to  the  University  of  Hawaii  and  by  funds  from  the 


University  of  Hawaii,  Hawaii  Institute  of  Marine 
Biology. 

LITERATURE  CITED 

Ahlstrom,  E.  H.,  and  R.  C.  Counts. 

1958.   Development  and  distribution  of  Vinciguerria  lucetia 

and  related  species  in  the  Eastern  Pacific.  U.S.  Fish. 

Wildl.  Serv.,  Fish.  Bull.  58:363-416. 
Badcock,  J. 

1970.  The  vertical  distribution  of  mesopelagic  fishes  col- 
lected on  the  Sond  cruise.  J.  Mar.  Biol.  Assoc.  U.K. 
50:1001-1044. 

Barnett,  M.  a.,  and  R.  H.  Gibbs,  Jr. 

1968.  Four  new  stomiatoid  fishes  of  the  genus  Bathophilus 
with  a  revised  key  to  the  species  of  Bathophilus.  Copeia 
1968:826-832. 

Butler,  T.  H. 

1964.  Growth,  reproduction,  and  distribution  of  pandalid 
shrimps  in  British  Columbia.  J.  Fish.  Res.  Board  Can. 
21:1403-1452. 
Clarke,  T.  A. 

1973.  Some  aspects  of  the  ecology  of  laternfishes  (Myc- 
tophidae)  in  the  Pacific  Ocean  near  Hawaii.  Fish.  Bull., 
U.S.  71:401-434. 
Clarke,  W.  D. 

1963.  Function  of  bioluminescence  in  mesopelagic 
organisms.   Nature  (Lond.)  198:1244-1246. 

Fedorov,  V.  v.,  and  L.  I.  Melchikova. 

1971.  The  description  of  a  new  species  Macrostomias 
pacificus  Fedorov  et  Melchikova  sp.  n.  (Pisces, 
Stomiatidae)  from  the  Kuroshio  waters.  Vopr.  Ikhtiol. 
11:763-769. 

Gibbs,  R.  H.,  Jr. 

1960.  The  stomiatoid  fish  genera  Eustomias  and  Melanos- 
tomias  in  the  Pacific,  with  descriptions  of  two  new 
species.  Copeia  1960:200-203. 

1964.  Family  Astronesthidae.  In  Y.  H.  Olsen  (editor), 
Fishes  of  the  western  North  Atlantic.  Part  4,  p. 
311-350.  Mem.  Sears  Found.  Mar.  Res.,  Yale  Univ.,  1. 

1969.  Taxonomy,  sexual  dimorphism,  vertical  distribution, 
and  evolutionary  zoogeography  of  the  bathypelagic  fish 
genus  Stomias  (Stomiatidae).  Smithson.  Contrib.  Zool. 
31,  25  p. 

Goodyear,  R.  H.,  and  R.  H.  Gibbs,  Jr. 

1969.  Systematics  and  zoogeography  of  stomiatoid  fishes  of 
the  Astronesthes  cyaneus  species  group  (family  Astrones- 
thidae), with  descriptions  of  three  new  species.  Arch.  Fis- 
chereiwiss.  20:107-131. 

Grey,  M. 

1960.  A  preliminary  review  of  the  family  Gonostomatidae, 
with  a  key  to  the  genera  and  the  description  of  a  new 
species  from  the  tropical  Pacific.  Bull.  Mus.  Comp.  Zool. 
Harvard  College  122:57-125. 
1964.  Family  Gonostomatidae.  In  Y.  H.  Olsen  (editor), 
Fishes  of  the  western  North  Atlantic.  Part  4,  p. 
78-273.  Mem.  Sears  Found.  Mar.  Res.,  Yale  Univ.,  1. 
Higgins,  B.  E. 

1970.  Juvenile  tunas  collected  by  midwater  trawling  in 
Hawaiian  waters,  July-September  1967.  Trans.  Am. 
Fish.  Soc.  99:60-69. 

Kawaguchi,  K.,  and  R.  Marumo. 

1967.  Biology  of  Gonostoma  gracile  (Gonostomatidae).  I. 
Morphology,  life  history  and  sex  reversal.  Inf.  Bull. 


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CLARKE:   ECOLOGY  OF  STOMIATOID  FISHES 


Planktol.  Japan.  1967:53-69. 
King,  J.  E.,  and  R.  T.  B.  Iversen. 

1962.  Midwater  trawling  for  forage  organisms  in  the  Cen- 
tral Pacific  1951-1956.  U.S.  Fish.  Wildl.  Serv.,  Fish.  Bull. 
62:271-321. 
Krueger,  W.  H. 

1972.  Biological  studies  of  the  Bermuda  Ocean  Acre 
IV.  Life  history,  vertical  distribution  and  sound  scatter- 
ing in  the  gonostomatid  fish  Valenciennellus  tripunc- 
tulatus  (Esmark).  Rep.  to  U.S.  Navy  Underwater  Sys- 
tems Center,  Wash.,  37  p. 
Krueger,  W.  H.,  and  G.  W.  Bond. 

1972.   Biological  studies  of  the  Bermuda  Ocean  Acre 
III.  Vertical  distribution  and  ecology  of  the  bristlemouth 
fishes  (family  Gonostomatidae).  Rep.  to  U.S.  Navy  Un- 
derwater Systems  Center,  Wash.,  50  p. 
McAllister,  D.  E. 

1967.  The  significance  of  ventral  bioluminescence  in 
fishes.  J.  Fish.  Res.  Board  Can.  24:537-554. 
Morrow,  J.  E.,  Jr. 

1964a.  Family  Chauliodontidae.  In  Y.  H.  Olsen  (editor), 


Fishes  of  the   western   North   Atlantic.   Part  4,  p. 

274-289.   Mem.  Sears  Found.  Mar.  Res.,  Yale  Univ.  1. 
1964b.  Family  Stomiatidae.  In  Y.  H.  Olsen  (editor),  Fishes 

of  the  western  North  Atlantic.  Part  4,  p.  290-310.  Mem. 

Sears  Found.  Mar.  Res.,  Yale  Univ.  1. 
1964c.  Family  Malacosteidae.  In  Y.  H.  Olsen  (editor). 

Fishes  of  the  western   North  Atlantic.   Part  4,  p. 

523-549.  Mem.  Sears  Found.  Mar.  Res.,  Yale  Univ.  1. 

Morrow,  J.  E.,  Jr.,  and  R.  H.  Gibbs,  Jr. 

1964.  Family  Melanostomiatidae.  In  Y.  H.  Olsen  (editor), 
Fishes  of  the  western  North  Atlantic.  Part  4,  p. 
351-511.  Mem.  Sears  Found.  Mar.  Res.,  Yale  Univ.  1. 

NOVIKOVA,  N.  S. 

1967.  Idiacanthids  of  the  Indian  and  Pacific  oceans  (Pisces, 
Idiacanthidae).  [In  Russ.,  Engl,  summ.]  Tr.  Inst. 
Okeanol.  Akad.  Nauk  SSSR  84:159-208. 

Tate,  M.  W.,  and  R.  C.  Clelland. 

1957.  Nonparametric  and  shortcut  statistics  in  the  social, 
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Publishers,  Inc.,  Danville,  111.,  171  p. 


351 


REARING  OF  PLAICE  {PLEURONECTES  PLATESSA)  LARVAE 
TO  METAMORPHOSIS  USING  AN  ARTIFICIAL  DIET 

J.  W.  Adron,  a.  Blair,  and  C.  B.  Cowey» 

ABSTRACT 

Newly  hatched  larval  plaice  were  grown  to  metamorphosis  using  an  artificial  diet.  The  overall  survival 
rate  to  metamorphosis  was  of  the  order  of  20%.  This  compares  with  a  survival  rate  of  38%  in  control 
larvae  fed  Artemia  in  a  similar  tank  system. 

The  preparation  of  the  artificial  diet  is  described.  The  main  protein  component  was  freeze-dried  cod 
muscle  and  the  diet  contained  70.7%  crude  protein,  9.7%  lipid,  7.9%  ash,  and  5%  digestible  carbohy- 
drate. 

This  food  in  particle  sizes  ranging  from  180  to  355  m  was  introduced  automatically  into  the  inflowing 
water  of  a  cylindrical  tank  containing  200  yolk  sac  larvae.  Water  temperature  was  10±  2'C.  After  about 
13-14  days  a  relatively  high  larval  mortality  occurred,  leaving  approximately  70  established  feeding 
larvae.  Unfed  larvae  in  an  identical  control  tank  did  not  survive  beyond  this  time. 

Once  feeding  had  been  established  larval  mortalities  were  occasional  and  sporadic.  Thirty-five  days 
after  commencement  of  the  experiment  some  larvae  began  to  metamorphose,  and  56  days  from  the 
start  some  35  metamorphosed  fish  were  transferred  to  a  separate  tank.  These  fish  have  since  continued 
to  feed  and  grow  on  the  same  diet. 


The  rearing  of  marine  flatfish  from  egg  to 
metamorphosis  and  subsequently  to  more  adult 
stages  was  achieved  under  laboratory  or  hatchery 
conditions  using  live  food  {Artemia  salina)  about 
10  yr  ago  ((Shelbourne,  1964).  The  experimental 
animal  was  plaice,  Pleuronectes  platessa.  Since 
then  other  flatfish  (lemon  sole,  Microstomus  kitt; 
Dover  sole,  Solea  solea;  and  tuvhot,  Scop h thai mus 
maximus)  have  been  similarly  reared  to 
metamorphosis,  using  either  the  same  food  or- 
ganism for  sole  or  a  combination  of  organisms 
such  as  rotifers  followed  hy  Artemia  for  turbot. 

While  such  methods  have  been  applied  success-' 
fully  on  a  pilot  scale  the  ability  to  rear  these  fish  on 
an  artificial  diet  may  confer  certain  advantages 
such  as:  ( 1 )  the  ability  to  change  the  composition  of 
the  food  and  so. ultimately  arrive  at  a  composite 
ration  approaching  the  optimal  requirement  of 
the  larva;  (2)  continuity  of  a  food  supply  of  stand- 
ard quality  (the  large  scale  production  of  live  food 
other  than  Artemia  involves  cultivation  of  several 
organisms,  e.g.  rotifers,  and  food  for  rotifers.  Thus 
the  whole  cultivation  program  must  be  carefully 
synchronized  and  there  must  be  certainty  that 
production  of  food  will  keep  pace  with  the  increas- 
ing demands  of  the  growing  larval  fish.  Moreover, 


Artemia  themselves  may  vary  in  nutritional  qual- 
ity and  may  contain  variable  amounts  of  pesticide 
residues  (Bookhout  and  Costlow,  1970));  (3)  elimi- 
nation of  the  need  to  wean  metamorphosed  larvae 
from  a  natural  to  an  artificial  food.  There  can  be 
little  doubt  that  the  availability  of  compounded 
foods  has  contributed  greatly  to  the  growth  offish 
farming  procedures  for  freshwater  fish  such  as 
trout,  salmon,  and  channel  catfish  in  several  coun- 
tries. All  these  species  of  fish  have  large  eggs 
which  give  rise  to  large  fry  so  that,  compared  with 
the  early  rearing  of  marine  fish  larvae,  few  techni- 
cal problems  arise. 

The  present  paper  describes  a  partially  success- 
ful attempt  to  rear  plaice  from  egg  to  metamor- 
phosis using  artificial  food  under  small  scale 
laboratory  conditions. 

EXPERIMENTAL 

The  apparatus  used  is  shown  in  Figure  1  and 
Figure  2.  The  larval  rearing  tank  was  cylindrical 
and  measured  26  cm  in  diameter  with  a  depth  of  23 
cm.  It  was  contained  in  an  outer  vessel  which  was 
normally  full  of  sea  water.  The  bottom  of  the  tank 
was  formed  from  a  circular  piece  of  rigid  polyvinyl 
chloride  pipe  (Durapipe^)  which  fitted  closely 


'Institute  of  Marine  Biochemistry,  St.  Fittick's  Road,  Aber- 
deen ABl  3RA  Scotland. 


^Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


Manuscript  accepted  September  1973. 
FISHFRV  BULLETIN:  VOL.  72.  NO.  2.  1974. 


353 


FISHERY   BUI  l.ETIN:  VOL.  72.  NO.  2 


food   dispensef 

recess   into  which  a  clean  tank 
bottom  can  be  inserted 


nylon   screw  secumg 
tank   bottom 

removable  tank 
bottom 


nylon    mesh 


10  cm 


Figure  1. — Vertical  section  through  the  larvae  rearing  tank.  In 
use  the  tank  is  suspended  within  a  larger  plastic  vessel. 


Figure  2. — Photograph  of  one  of  the  larvae  rearing  units  in  use. 

round  the  cylindrical  tank  and  was  firmly  clipped 
onto  it  by  a  bayonet  attachment.  This  circular 
piece  of  Durapipe  was  covered  with  0.75  mm  aper- 
ture nylon  mesh  to  retain  larvae  and  possibly 
permit  uneaten  food  to  escape.  In  the  event  the 
food  tended  to  swell  after  being  in  the  water  for 
some  time  and  only  a  portion  of  it  passed  through 


the  screen  at  the  bottom  of  the  tank.  To  facilitate 
tank  cleaning  and  hygiene,  therefore,  an  exactly 
similar  cover  could  be  fitted  over  the  top  of  the 
cylindrical  tank  and  the  tank  slowly  and  carefully 
inverted  in  the  outer  vessel  so  that  the  bottom 
cover  was  now  at  the  top  and  could  readily  be 
removed  together  with  adhering  uneaten  food. 
This  cleaning  arrangement  is  not  ideal,  but  by 
permitting  the  removal  of  much  of  the  uneaten 
food  from  the  bottom  of  the  tank,  it  allowed  posi- 
tive control  over  tank  hygiene  and  water  quality. 
These  factors  have  been  a  major  obstacle  to  culti- 
vation of  larval  fish  on  artificial  diets  in  earlier 
experiments.  As  the  larvae  grew  larger  it  became 
more  and  more  possible  to  siphon  uneaten  food 
from  the  bottom  of  the  tank  without  endangering 
or  losing  larvae. 

Food  was  dispensed  into  the  tank  with  the  in- 
flowing water  by  means  of  an  automatic  feeder  of 
the  type  described  by  Adron  (1972).  This  feeder 
was  held  on  a  clamp  stand  adjacent  to  the  tank  and 
could  readily  be  removed  when  the  tank  was  being 
cleaned  by  inversion.  Approximately  15  mg  dry 
food  was  introduced  into  the  water  via  a  mixing 
chamber  at  10  min  intervals,  the  flow  rate  of  water 
being  about  150  ml/min.  The  experiment  was  car- 
ried out  at  a  temperature  of  10°  ±  2°C  with  a  light 
intensity  at  the  water  surface  of  250  lux  provided 
by  fluorescent  light. 

The  composition  of  the  food  used  is  shown  in 
Table  1.  Freeze-dried  cod  muscle  and  shrimp  meal 
were  prepared  as  in  Cowey,  Pope,  Adron,  and 
Blair  (1972).  Freeze-dried  whole  hen's  egg  was 
prepared  by  drying  homogenized  hen's  egg  in  a 
bulk  centrifugal  freeze  drier.  The  gelatin  (pre- 

Table  1. -Composition  of  diet  used  for  rearing  larval  plaice. 


Component 


g;100  g  dry  diet 


Freeze  dried  cod  muscle 

53.4 

Freeze  dried  whole  hen's  egg 

10.0 

Shrimp  meal 

10.0 

Cod  liver  oil 

4.0 

Encapsulated  vitamin  mixture 

3.3 

Vitamin  mixture 

2.8 

Mineral  mixture 

1.0 

Glucose 

5.0 

a-tocopherol 

0.4 

Sunset  yellovi;  F.C  F. 

0.1 

Furanace 

0.8  mg 

Gelatin 

10.0 

2  Water 


150  ml 


'Cowey  et  al.  1972 

^Removed  finally  by  freeze  drying 


354 


ADRON,  BLAIR,  and  COWEY:  REARING  OF  PLAICE  LARVAE 


pared  from  swine  skin  300  bloom)  and 
a -tocopherol  (500  mg  a -tocopherol  per  g)  were 
obtained  from  the  Sigma  Chemical  Co.,  Ltd.  Sun- 
set yellow  was  a  gift  from  Imperial  Chemical  In- 
dustries; it  was  included  in  the  diet  to  simulate  the 
color  of  Artemia  nauplii.  Furanace,  a  broad  spec- 
trum antibiotic  developed  specifically  for  fish 
(Shimizu  and  Takase,  1967)  was  obtained  from 
Dainippon  Pharmaceutical  Co.,  Ltd.  Half  of  the 
vitamin  supplement  was  encapsulated  in  hy- 
drogenated  coconut  oil  to  prevent  the  leaching  out 
of  the  vitamins  into  the  sea  water.  Lest  this  proce- 
dure rendered  vitamins  unavailable  to  the  larvae, 
the  other  half  of  the  supplement  was  added  with- 
out further  treatment.  To  encapsulate  the  vitamin 
mixture  28  g  were  homogenized  in  100  ml  of 
di-ethyl  ether  in  which  5  g  of  hydrogenated 
coconut  oil  MP  32-34°C  (Loders  and  Nucoline  Ltd., 
London)  had  been  dissolved.  The  homogenate  was 
dried  in  a  Bucchi  Rotary  evaporator. 

Freeze-dried  cod  muscle,  freeze-dried  whole 
egg,  and  shrimp  meal  were  finely  ground  together 
in  a  hammer  mill.  To  these  ground  components 
were  added  the  vitamin  mixture,  mineral  mix- 
ture, and  glucose.  The  cod  liver  oil  and 
Q-tocopherol  were  mixed  together  and  then 
thoroughly  mixed  with  the  dry  components,  mix- 
ing being  carried  out  in  a  Hobart  food  mixer.  The 
furanace  and  sunset  yellow  were  dissolved  in  %  of 
the  allotted  water  and  mixed  with  the  dry  compo- 
nents. The  gelatin  was  dissolved  in  the  remaining 
water  at  50°C  before  being  mixed  with  the  other 
dietary  components.  While  still  warm  the  moist 
diet  was  pressed  into  slabs  5  mm  thick  and  cooled 
to  room  temperature.  The  slabs  of  diet  were  then 
dried  in  a  bulk  freeze-drier,  ground  with  a  pestle 
and  mortar  and  graded  with  sieves,  to  give  sizes  of 
250  u-355  Id  and  180  iJ-250  fi.  For  the  first  2  days  of 
feeding  the  larvae  were  given  only  diet  of  180 
/U-250  u ;  for  the  next  8  days  increasing  quantities 
of  the  250  jU-355  /j'size  were  mixed  with  the  180 
/u-250  u  size  until  only  the  250  a/ -355  ju  size  was 
offered.  By  analysis  the  diet  contained  protein  (N 
X  6.25)  70.7%,  lipid  9.7%,  and  ash  7.9%. 

Two  hundred  newly  hatched  larvae  were  put 
into  each  of  three  tanks  on  2  April  1973.  These 
larvae  were  obtained  from  eggs  kindly  supplied  by 
White  Fish  Authority,  Hunterston;  the  eggs  had 
been  artificially  fertilized  on  12  March.  Food  was 
introduced  into  one  of  the  tanks  on  5  April; 
Artemia  nauplii  were  added  to  the  second  tank, 
while  the  third  tank  was  kept  as  an  unfed  control 
mainly  because  unfiltered  seawater  was  being 


used,  and  it  may  have  contained  enough  natural 
food  to  maintain  a  number  of  the  larvae. 

For  the  first  few  days  of  the  experiment  rela- 
tively few  mortalities  occurred  in  any  of  the  tanks 
but  then  10-12  days  after  hatching,  a  rapid  mor- 
tality occurred  in  the  unfed  control,  together  with 
relatively  high  mortalities  in  the  tanks  fed 
artificial  and  natural  {Artemia  nauplii)  diets.  By 
15  April  no  larvae  remained  alive  in  the  unfed 
control  tank,  while  the  numbers  surviving  in  the 
two  tanks  receiving  food  were  about  70  in  the  tank 
receiving  the  compounded  artificial  diet  and  about 
100  in  the  tank  receiving  Artemia  nauplii.  It 
seems  possible  that  this  high  mortality  corre- 
sponds with  the  complete  utilization  of  the  yolk 
and  that  the  fish  surviving  in  the  tanks  receiving 
food  correspond  to  Shelbourne's  "established  feed- 
ers." 

After  about  15  April  mortality  rates  fell  to  a  low 
level  in  both  the  remaining  tanks;  some  of  the 
deaths  in  the  tank  receiving  the  artificial  food 
were  a  direct  consequence  of  tank-cleaning  opera- 
tions. Fish  began  to  metamorphose  in  both  these 
tanks  as  early  as  6  May  and  by  28  May  some  35 
metamorphosed  plaice  from  the  tank  receiving  the 
artificial  compounded  diet  were  transferred  to  a 
conventional  tank  in  our  recirculated  system 
where  they  continued  to  eat  the  same  powdered 
diet.  This  represents  a  17.5%  survival  of 
metamorphosed  fish  from  hatched  larvae.  Of  the 
larvae  which  were  reared  on  Artemia  some  76 
survived  to  metamorphosis  (last  day  of  May),  rep- 
resenting 38%  of  the  original  newly-hatched  lar- 
vae. No  abnormalities  of  pigmentation  were  dis- 
cernible in  the  larvae,  possibly  because  of  the  rela- 
tively uncrowded  conditions  in  which  they  were 
reared. 

The  survival  rates  with  the  artificial  food  were 
much  lower  than  with  larvae  fed  Artemia;  this 
may  be  due  to  the  greater  acceptability  of  the  live 
moving  diet  as  compared  to  the  inert  artificial 
food;  the  higher  number  of  "established  feeders" 
obtained  when  feeding  Ar^emm  perhaps  supports 
this  view.  Both  our  survival  rates  are  considerably 
lower  than  those  achieved  by  Shelbourne  (1963) 
using  Artemia,  his  most  successful  regime  giving 
about  67%  survival  to  metamorphosis  (including 
mortalities  between  fertilization  and  hatching). 
However,  with  a  temperature  regime  somewhat 
similar  to  that  used  by  us  (his  water  bath  4)  Shel- 
bourne obtained  survival  rates  not  greatly  differ- 
ent from  our  "Artemia"  tank,  i.e.  55%  survival 
(when  egg  incubation  was  carried  out  in  the  pres- 


355 


FlSHfRY    BULI  FTIN:   VOL.  72.  NO.  2 


ence  of  antibiotics)  and  SO^c  survival  (eggs  irri- 
gated with  seawater  free  of  antibiotics  during  in- 
cubation). 

Despite  the  lower  larval  survival  rate  when  fed 
artificial  food  it  is  felt  that  this  rate  is  sufficiently 
high  to  demonstrate  the  technical  feasibility  of 
using  non-living  food  for  rearing  marine  fish  lar- 
vae. Moreover,  eggs  are  produced  in  enormous 
numbers  by  marine  fish  and  are  extremely  cheap 
so  that  a  209r  survival  rate  to  metamorphosis  is  an 
acceptable  level.  If  such  a  survival  rate  can  be 
achieved  with  the  more  exacting  larvae  of  highly 
esteemed  species  (Dover  sole,  turbot)  it  would  give 
a  considerable  impetus  to  the  cultivation  of  these 
fish. 

DISCUSSION 

Reviewing  marine  fish  larval  rearing,  May 
(1970)  named  the  provision  of  a  suitable  food  (i.e. 
"one  which  the  larvae  will  consume  and  grow  on 
and  which  can  be  supplied  in  sufficiently  large 
quantities")  as  the  prime  obstacle.  Several  at- 
tempts have  been  made  over  the  years  to  rear 
marine  fish  larvae  on  non-living,  composite  foods 
but  none  of  these  have  yet  been  successful  (Fishel- 
son,  1963;  Blaxter,  1962;  Ivanchenko  and  Ivan- 
chenko,  1969).  In  practice  we  have  had  no  great 
difficulty  in  getting  plaice  larvae  or  at  least  a 
relatively  high  proportion  of  them  to  ingest  the 
food  and  develop  on  it.  The  main  obstacle  has  been 
one  of  tank  hygiene  and  it  remains  the  overriding 
problem.  This  too  is  recognized  by  May  ( 1970)  who 
comments  on  the  use  of  non-living  food:  "un- 
eaten food  accumulates  on  the  bottom  of  the  rear- 
ing container  and  decays  rapidly,  fouling  the 
water".  Although  the  present  set-up  does  permit 
control  of  the  quantity  of  uneaten  food  in  the 
water,  any  improvements  in  tank  design  which 
release  uneaten  food  completely  while  retaining 
the  larvae  are  desirable.  Various  modifications  of 
tank  design  to  this  end  are  under  consideration. 
The  problem  is  particularly  acute  in  the  early 
stages  as  the  food  particles  tend  to  swell  in  the 
water  and  fail  to  pass  the  screen  at  the  bottom  of 
tank.  As  larvae  increase  in  size,  and  a  screen  of 
larger  mesh  size  can  be  substituted  at  the  bottom 
of  the  tank,  the  problem  becomes  less  acute. 

Some  bacteriological  control  of  water  may  be 
attained  by  sterilizing  the  incoming  water  by 
means  of  ultraviolet  light  and  such  a  device  should 
be  incorporated  into  future  experiments. 


Microencapsulation  of  the  food  may  offer  a 
further  means  of  improving  tank  hygiene.  The 
microcapsules  currently  available  seem  to  sink 
very  rapidly  through  a  water  column.  This  mili- 
tates against  their  chances  of  being  consumed  by 
larval  fish  in  a  rearing  tank.  The  development  of 
neutrally  buoyant  microcapsules,  however,  could 
lead  to  rapid  strides  in  the  controlled  cultivation  of 
larval  marine  fish. 

The  use  of  an  antibiotic  in  the  diet  calls  for  some 
comment.  The  relatively  free  use  in  animal  feeds 
of  those  antibiotics  which  are  commonly  employed 
in  human  medicine  has  obvious  social  dangers. 
Attention  has  yet  again  been  focused  on  these 
dangers  by  Williams-Smith  ( 1973).  It  must,  there- 
fore, be  emphasized  that  furanace  was  used  in 
very  low  concentrations  and  that  it  has  been  de- 
veloped specifically  for  use  in  fish.  Thus  any  resis- 
tant strains  which  could  result  from  its  use  should 
still  be  sensitive  to  antibiotics  currently  in  use  in 
clinical  medicine. 

The  diet  used  was  designed  empirically  with  the 
objects  of  providing  a  relatively  large  intake  of 
high  quality  protein,  marine  oil,  and  a  luxus  of  B 
vitamins  all  allied  to  reasonable  water  stability. 
The  diet  is  by  no  means  ideal  and  there  is  clearly 
scope  for  improvement  in  this  ration  in  many 
ways.  However,  it  does  provide  a  basic  experimen- 
tal formula  from  which  more  nearly  optimal  diets 
may  evolve. 


LITERATURE  CITED 

Adron,  J.  W. 

1972.   A  design  for  automatic  and  demand  feeders  for  ex- 
perimental fish.  J.  Cons.  34:300-305. 
Blaxter,  J.  H.  S. 

1962.  Herring  rearing-IV.  Rearing  beyond  the  yolk-sac 
stage.  Mar.  Res.  Dep.  Agric.  Fish.  Scotl.  1,  18  p. 

BOOKHOUT,  C.  G.,AND  J.  D.  COSTLOW,  Jr. 

1970.   Nutritional  effects  of  Artemia  from  different  loca- 
tions on  larval  development  of  crabs.  Helgolander  Wiss. 
Meeresunters.  20:435-442. 
CowEY,  C.  B.,  J.  A.  Pope,  J.  W.  Adron,  and  A.  Blair. 

1972.  Studies  on  the  nutrition  of  marine  flatfish.  The  pro- 
tein requirement  of  plaice  (Pleuronectes  platessa).  Br.  J. 
Nutr.  28:447-456. 

FiSHELSON,  L. 

1963.  Observations  on  littoral  fishes  of  Israel.  II.  Larval 
development  and  metamorphosis  oi Blennius  pavo  Risso 
(Teleostei,  Blenniidae).  Isr.  J.  Zool.  12:81-91. 

Ivanchenko,  L.  A.,  and  O.  F.  Ivanchenko. 

1969.  Transition  to  active  feeding  by  larval  and  juvenile 
white  sea  herring  (Clupea  harengus  pallasi  NATIO 
Maris-albi  BERG)  in  artificial  conditions.  Dokl.  Akad. 
Nauk  SSSR  184:1444-1446. 


356 


ADRON,  BLAIR,  and  COWEY;  REARING  OF  PLAICE  LARVAE 

May,  R.  C.  1-83.  Academic  Press,  N.Y. 

1970.  Feeding  larval  marine  fishes  in  the  laboratory:  a  Shimizu,  M.,  and  Y.  Takase. 
review.  Calif.  Mar.  Res.  Comm.,  Calif.  Coop.  Oceanic  1967.  A  potent  chemotherapeutic  agent  against  fish  dis- 

Fish.  Invest.  Rep.  14:76-83.  eases:  6-hydroxymethyl-2-[2-(5-nitro-2-furyl)  vinyl] 

Shelbourne,  J.  E.  pyridine  (p-7138).   Bull.  Jap.  Soc.  Sci.  Fish.  33:544-554. 

1963.  A      marine     fish-rearing     experiment     using  Williams  Smith,  H. 

antibiotics.  Nature  (Lend. I  198:74-75.  1973.  Effect  of  prohibition  of  the  use  of  tetracyclines  in 

1964.  The  artificial  propagation  of  marine  fish.  In  F.  S.  animal  feeds  on  tetracycline  resistance  of  faecal  £.  coZi  of 
Russell  (editor),  Advances  in  Marine  Biology,  vol.  2,  p.  pigs.  Nature  (Lond.)  243:237-238. 


357 


THE  INVASION  OF  SAURIDA  UNDOSQUAMIS  (RICHARDSON)  INTO 

THE  LEVANT  BASIN  -  AN  EXAMPLE  OF 
BIOLOGICAL  EFFECT  OF  INTEROCEANIC  CANALS 


M.  Ben-Yami'  and  T.  Glaser2 


ABSTRACT 


The  Red  Sea  lizardfish,  Saurida  undosquamis  (Richardson),  invaded  the  Levant  Basin  and  established 
a  population  of  considerable  commercial  importance.  Its  expansion  came  at  the  expense  of  other 
commercial  fishes  on  which  it  preys  and  with  which  it  competes.  The  explosion  of  the  Red  Sea  lizardfish 
population  in  the  Levant  Basin  was  made  possible  by  a  combination  of  changes  in  the  environmental 
conditions  (abiotic  and  biotic),  one  of  these  being  the  retreat  of,  or  the  recession  in,  the  native  hake 
population.  The  dynamic  coexistence  between  the  lizardfish  and  the  hake,  its  main  competitor,  is 
affected  by  fluctuations  in  the  abiotic  conditions  to  which  the  hake  seems  to  be  more  sensitive  than  the 
lizardfish. 


A  faunistic,  zoogeographical  approach  to  the 
marine  animal  migration  through  the  Suez  Canal 
is  common  to  most  investigators  of  the  canal's 
influence.  Animal  species  native  to  one  sea  and 
found  in  the  other  after  the  opening  of  the  canal 
serve  as  main  indicators  of  its  biological  influence 
and  of  its  effectivity  as  a  link  to  the  migrant 
species  and  as  a  barrier  to  others  (Ben-Tuvia, 
1966,  in  press;  Kimor,  19703;  Por,  1971;  Steinitz, 
H.,  1968;  Steinitz,  W.,  1929;  Thorson,  1971).  Many 
authors  listed  and  described  migrant  species 
(Barash  and  Danin,  1971-*;  Ben-Tuvia,  1953;  Col- 
lette,  1970;  Gilat,  1964;  Gohar,  1954;  Gordin, 
19665;  Holthuis  and  Gottlieb,  1958;  Kosswig, 
1951;  Steinitz,  H.,  1967;  Tortonese,  1953). 

Some  authors  have  discussed  the  Red  Sea- 
Mediterranean  animal  migrations  in  relation  to 
ecological  conditions  in  the  canal  and  in  the  adja- 
cent sea  areas  (Gilat,  1966^  1969^;  Oren,  1969, 


'Fisheries  Technology  Unit,  P.O.B.  699,  Haifa,  Israel. 

^Kibbutz  Ma'agan  Mikhael,  D.N.Hof  Hacarmel.  Israel. 

^Kimor,  B.  1970.  The  Suez  Canal  as  a  link  and  a  barrier  in 
the  migration  of  planktonic  organisms.  Submitted  to  the  Ocean 
World-Joint  Oceanographic  Assembly,  Tokyo,  13-25  Sept. 
1970,  20  p. 

■'Barash,  A.,  and  Z.  Danin.  1971.  Indo-Pacific  species  of  Mol- 
lusca  in  the  Mediterranean.  Appendix  to  Progress  Report 
1970/1971.  The  Hebrev/  University  -  Smithsonian  Institution 
Joint  Project  "Biota  of  the  Red  Sea  and  the  Eastern  Mediterra- 
nean," 8  p.  [Processed.] 

*Gordin,  H.  1966.  Migration  of  fishes  through  the  Suez  Canal 
Ms.  in  files  of  Fish.  Technol.  Unit,  Haifa,  Israel. 

^Gilat,  E.  1966.  The  animal  bottom  communities  in  the  Le- 
vant Basin  of  the  Mediterranean  Sea.  9  p.  In  files  of  Fish.  Tech 
Unit,  Haifa.  [Processed.] 

'Gilat,  E.  1969.  The  macrobenthic  communities  of  the  level 
bottom  in  the  Eastern  Mediterranean.  In  Interim  Report,  Joint 
Research  Project  "Biota  of  the  Red  Sea  and  the  Eastern  Mediter- 
ranean," p.  82-89.  The  Hebrew  University  of  Jerusalem  and  the 
Smithsonian  Institution,  Washington,  D.C.  [Processed.] 


1970;  Por,  1969«,  197P),  suggesting  that  the 
mechanism  of  the  penetration  of  some  species 
through  the  canal  and  their  expansion  in  the 
Mediterranean  is  associated  with  environmental 
conditions  (salinity,  currents,  nature  of  substrate, 
etc.). 

In  this  paper  we  discuss  the  ecology  of  the  mi- 
gration and  expansion  in  the  new  habitat  of  an 
important  commercial  fish.  We  examine  its 
dynamic  coexistence  with  its  native  competitor  in 
view  of  the  changing  environmental  conditions. 

The  Relative  Importance  of  Species 

It  is  a  well-known  fact  that,  while  some  of  the 
migrant  species  have  established  themselves  in 
the  new  environment,  creating  populations  with  a 
significant  impact  on  the  ecosystem,  other  species 
may  just  survive  under  the  new  and,  perhaps, 
hostile  conditions. 

The  relative  importance  of  a  species  in  terms  of 
biomass  and  its  role  and  weight  in  the  food  chain  is 
often  neglected  when  two  species  are  listed  as 
"common"  or  "abundant."  One  of  them  may  be  an 
important  commercial  fish  with  a  biomass  of  an 
order  of  tens  of  thousands  of  tons  or  more,  and  the 


8Por,  F.  D.  1969.  The  Canuellidae  (Copepoda  Harpacticoida) 
in  the  waters  around  the  Sinai  Peninsula  and  the  problem  of 
Lessepsian  migration  in  this  family.  In  Interim  Report,  Joint 
Research  Project  "Biota  of  the  Red  Sea  and  the  Eastern  Mediter- 
ranean," p.  34-40.  The  Hebrew  University  of  Jerusalem  and  the 
Smithsonian  Institution,  Washington,  D.C.  [Processed.] 

^Por.  F.  D.  1970.  The  nature  of  the  Lessepsian  migration 
through  the  Suez  Canal.  Paper  presented  at  the  XXIIe  Congres 
Assemblee  Pleniere  de  la  C.I.E.S.M.,  Rome. 


Manuscript  accepted  September  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO. 


1974. 


359 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


other  is,  say,  a  frequently  met  small,  commer- 
cially unimportant,  Apogon.  However,  such  dis- 
crimination should  be  made:  the  first  fish  is  a 
wholesale  consumer  and  also  a  supplier  of  impor- 
tant food  for  other  species;  the  other,  although 
frequently  collected,  occurs  in  small  numbers,  and 
whatever  its  importance  may  be  in  its  immediate 
biotope,  its  effect  on  the  whole  ecosystem  is  of  little 
consequence.  Therefore,  in  studying  the  impact  of 
one  sea  on  the  other,  number  of  migrant  species 
should  not  be  overemphasized  and  more  attention 
should  be  paid  to  species  of  ecological  importance. 

Commercial  Fish  Populations  as 
Indicators  of  the  Biological  Effect 

The  most  important  aspect  of  interrelations  be- 
tween two  seas,  especially  where  a  new  canal  is 
planned,  are  the  ecological  effects  which  influence 
the  human  ecological  conditions  and  economy.  To 
obtain  a  meaningful  picture  of  the  biological  effect 
of  the  Suez  Canal  on  both  seas,  emphasis  should  be 
put  on  changes  which  have  considerably  affected 
the  large  or  the  commercial  populations  of  either. 
Obviously,  almost  any  fish  species  which  occurs  in 
great  numbers  and  biomass  becomes  sooner  or 
later  commercially  important,  either  as  a  market- 
able product  or  as  a  food  to  commercial  piscivores. 

Changes  in  the  quantity  and  composition  of  im- 
portant commercial  fishes  are  contained  in  most 
fisheries  statistics.  Of  course,  this  can  only  be 
shown  where  fish  landings  are  reasonably  well 
recorded  and  where  the  data  obtained  may  be 
evaluated  to  eliminate  technological  and 
socioeconomical  factors. 

Commercially  Important  Red  Sea 
Migrants 
and  Their  Mediterranean  Competitors 

A  number  of  immigrant  Red  Sea  species  have 
become  commercially  important  in  the  Levant 
Basin  and/or  provide  food  for  both  Red  Sea  immi- 
grants and  native  fish  populations.  Sufficient  data 
are  available  to  discuss  the  expansion  of  the  Red 
Sea  lizardfish,  Saurida  undosquamls  (Richard- 
son), and  the  dynamics  of  its  coexistence  with  its 
main  native  competitor  Merluccius  merluccius 
(Linnaeus),  the  hake. 

Unfortunately,  other  species  which  could  serve 
perhaps  as  better  examples,  the  yellow-striped 
goatfish,  Upeneus  moluccensis  Bleeker,  and  its 
Mediterranean  counterpart  the  red  mullet,  Mul- 
lus   barbatus   Linnaeus,  or  the  barracudas, 


Sphyraena  chrysotaenia  Kiunzinger  (a  Red  Sea 
migrant),  S.  sphyraena  (Linnaeus),  and  S.  vir- 
idensis  Cuvier  (both  Atlantic  species),  cannot  be 
used  for  this  purpose  as  the  catch  statistics  do  not 
discriminate  between  the  species  of  the  same  fam- 
ily or  genus. 

From  the  information  available  on  the  Mullidae 
{Upeneus  and  Mullus),  the  following  can  be  sum- 
marized: Red  mullets  (Mullidae)  represent  one  of 
the  most  important  components  of  the  Israeli 
trawl  catches.  Their  share  in  the  total  trawl  land- 
ings varied  between  1956  and  1970  from  29  to 
46%,  (Sarid,  1951-71).  The  bulk  of  the  red  mullets 
consists  of  two  species:  the  red  mullet  and  the 
yellow-striped  goatfish.  The  latter  species  is  a  Red 
Sea  migrant.  According  to  Wirszubski  (1953)  in 
the  late  40's  the  share  of  the  yellow-striped  goat- 
fish in  the  Mullidae  catch  was  10  to  15%.  Four 
years  later,  Oren  (1957)  estimated  on  the  basis  of 
Gilat's  unpublished  data  that  Upeneus  formed 
over  83%  of  the  total  number  of  red  mullets  caught 
in  trawls  during  the  first  half  of  1956. 

These  are  two  closely  related  fish  species,  very 
similar  in  their  appearance  and  behavior  and  ap- 
parently competing  for  the  same  food  (E.  Gilat, 
pers.  comm.).  Although  the  red  mullet  evidently 
prefers  cooler  and,  thus,  in  periods,  deeper  waters 
than  the  yellow-striped  goatfish  (Ben-Yami,  1955; 
Ben-Tuvia,  in  press),  they  mostly  occupy  overlap- 
ping territories.  One  of  them-the  invader- 
succeeded  in  becoming  a  majority  during  1955 
(Ben-Yami,  1955;  Oren,  1957).  Since  1956,  fluc- 
tuations continue  to  occur  in  the  Mullus  to 
Upeneus  ratio.  Ben-Tuvia  (in  press)  estimates  the 
average  share  of  the  latter  fish  in  the  catches  of  red 
mullets  to  be  approximately  30% . 

What  are  the  reasons  for  such  fluctuations? 
What  are  the  factors  which  determine  whether  a 
fish  which  has  crossed  the  canal  will  establish 
itself  as  a  sizeable  population? 

Is  it  possible  that  after  some  years  of  blooming  a 
migrant  population  will  recede  into  its  previous 
state,  and  why?  Will  an  expanding  migrant  popu- 
lation contribute  to  the  total  fish  biomass  in  the 
new  area,  or  come  at  the  expense  of  the  other 
fishes? 

SOURCES  AND  RELIABILITY 
OF  DATA 

Fishery  Statistics 

All  fisheries  data  presented  in  the  graphs  and 


360 


BEN-YAMI  and  GLASER:  INVASION  OF  SAURIDA   UNDOSQUAMIS 

tables  are  based  on  statistics  collected  by  the  De- 
partment of  Fisheries  (Sarid,  1951-71).  These  are 
in  general  reliable,  and  the  proportion  of  the  hake 
and  the  lizardfish  in  the  total  trawl  catch  is  well 
represented.  The  figures,  however,  may  be  biased 
in  some  aspects,  and  the  following  must  be  borne 
in  mind: 

1.  The  catch  per  unit  effort  for  all  fish  and  for 
each  of  the  two  species  separately  is  expressed  in 
kilograms  per  day  at  sea  of  a  trawler.  The  Israeli 
trawlers  operating  in  the  Mediterranean  during 
1950-70  were  powered  by  110-to  240-horsepower 
engines.  The  average  power  per  trawler  varied 
with  time,  due  to  transfer  of  some  to  the  Red  Sea, 
loss  of  others,  and  acquisition  of  new  vessels  and 
engines.  It  increased  steadily  in  the  50's,  de- 
creased in  the  early  60's,  and  started  increasing 
again  during  the  recent  years  (Table  1 ).  Therefore, 
when  examining  the  data  in  Figure  5A  and  B,  it 
should  be  remembered  that  the  unit  of  effort  var- 
ied from  year  to  year. 

2.  The  total  fishing  effort  and  the  total  catches 
fluctuated  partly  because  of  the  changing 
socioeconomical  and  geopolitical  conditions, 
which  determined  the  extent  of  the  fishing 
grounds  on  which  the  Israeli  trawlers  could  oper- 
ate in  the  Mediterranean,  and  its  effect  on  the  size 
of  the  active  trawling  fleet. 

3.  The  character  and  extent  of  the  trawling 
grounds  available  to  and/or  preferred  by  the 


fishermen  partly  affect  the  data:  In  deepwater  op- 
erations the  hake  is  one  of  the  main  fish  caught 
(Ben-Yami,  1971;  Zismann,  1971),  while  the 
lizardfish  is  almost  absent.  In  shallow  water, 
trawling  depends  on  the  accessibility  of  the 
southern  trawling  grounds,  which  fluctuated  with 
the  Egypto-Israeli  relations.  On  these  grounds 
good  summer  catches  could  be  obtained  in  shallow 
waters,  conditions  preferred  by  some  skippers  to 
deepwater  trawling. 

From  1953  to  1960,  some  of  the  Israeli  trawlers 
operated  during  the  summer  months  in  the  north- 
eastern area  of  the  Mediterranean,  between  Cy- 
prus and  Turkey,  mostly  in  the  Bay  of  Tarsus. 
Their  catches  were  included  indiscriminately  in 
the  general  statistical  data.  In  these  catches, 
the  lizardfish  greatly  outweighed  the  hake.  There- 
fore, the  catch  composition  data  for  these  years 
may  be  slightly  biased  in  favor  of  the  lizardfish 
and  to  the  disadvantage  of  the  hake  as  compared 
with  the  other  years,  but  by  no  means  to  a  degree 
which  might  change  the  general  picture. 

Sea  Temperature 

In  order  to  study  effects  of  changes  in  the  en- 
vironmental factors  on  the  catches  of  the  hake  and 
the  lizardfish,  the  temperatures  recorded  from  the 
sea  between  Ashdod  and  Tel  Aviv,  an  area 


Table  1. — Changes  in  the  fishing  effort,  catch  and  catch-per-effort,  1950-1970,  in  the  Israel  Mediter- 
ranean trawling  fishery.* 


Number 

of 
trawlers 

H 

orsepow^r 

Number 
of  days 
at  sea 

Catch 

total  of 

the  selected 

boats  (tons) 

Year 

Total 

Average 

per 
trawler 

Catch/100  hp 

per  day 

(kg) 

1950 

7 

840 

120 

976 

312 

265 

1951 

19 

2.420 

127 

3,102 

1,031 

211 

1952 

14 

2,070 

146 

2,152 

667 

221 

1953 

14 

2,070 

146 

2,728 

997 

250 

1954 

17 

2.350 

139 

3,047 

1.160 

273 

1955 

22 

3,120 

142 

3.523 

1,494 

298 

1956 

16 

2,530 

158 

2,616 

1,162 

281 

1957 

16 

2.520 

158 

3,185 

1.335 

225 

1958 

20 

3.020 

151 

4,350 

1.575 

239 

1959 

23 

3,330 

145 

5,208 

1.878 

235 

1960 

17 

2,580 

152 

3,386 

1.077 

208 

1961 

15 

2,130 

142 

2,957 

874 

295 

1962 

14 

1,990 

142 

2,694 

766 

284 

1963 

13 

1,760 

135 

2,505 

647 

191 

1964 

10 

1,390 

139 

1,765 

530 

215 

1965 

13 

1,800 

138 

2,443 

676 

200 

1966 

13 

1,840 

141 

2,579 

561 

155 

1967 

14 

2,010 

143 

2,933 

720 

195 

1968 

14 

2,070 

147 

2,985 

925 

210 

1969 

14 

2.140 

153 

2,967 

979 

224 

1970 

14 

2,290 

163 

3.013 

886 

180 

'The  data  do  not  include  research  and  training  vessels,  and  vessels  which  fished  less  than  100  days  per  year  (E.  Grofit, 
private  communication). 


361 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


situated  in  the  center  of  the  trawl  grounds,  were 
examined. 

The  water  temperatures  at,  or  closely  below,  the 
75-m  depth  (Figure  1),  and  a  number  of  sea  surface 
temperatures  were  collected  during  monthly 
cruises  of  Israeli  research  vessels  (Oren  and  Hor- 
nung,  1972,  and  pers.  comm.).  During  the  21  yr, 


many  monthly  cruises  were  not  carried  out,  hence 
the  numerous  gaps  (Figure  2). 

Additional  surface  temperature  data  for  the 
period  from  1958  to  1970  are  monthly  averages  of 
daily  monitored  temperatures  at  Ashdod.  These 
were  supplied  by  the  Coast  Study  Division  of  the 
Israel  Port  Authority  (pers.  comm.). 


T°c 

26 
25 

24 
23 
22 
21 
20 
19 
18 
17 
16 
15 


J I I L. 


-i I I I I L 


J I L 


50 


52 


54 


56 


58 


60 


62 


64 


66 


68 


70 
YEAR 


Figure  1. — Sea  temperatures  at  depths  of  75  m  or  below,  collected  during  monthly  cruises  in  or  near  the  Tel 
Aviv-Ashdod  area  between  1950  and  1970  (Oren  and  Hornung,  pers.  comm.).  Dots  -  yearly  maxima;  cross  -  yearly 
minima.  In  this  graph  each  year  begins  in  January. 


30 
29 
28 
271- 


18 

- 

/N. 

17 

■•         / 

16 

■ 

15 

\                        / 

14 

i                 1                  1 

1               1               1               1               1 

1               1               1              1               I               1              1               1               1               1               1               1              1              ., 

50/51        52/53        54/55        56/57        58/59        60/61        62/63       64/65       66/67 


68/69 


70/71 
YEAR 


Figure  2. — Sea  surface  temperature.  Top  -  summer  maxima;  bottom-  winter  minima.  A  -  Data  collected  during 
monthly  cruises  in  the  area  of  Tel  Aviv-Ashdod  (Oren  and  Hornung,  pers.  comm.);  B  -  (dashed  line) — monthly 
means  of  daily  collected  data  at  Ashdod,  inshore  (Coastal  Survey  Unit,  pers.  comm.).  Each  year  starts  1  September. 


362 


BEN-YAMI  and  GLASER:  INVASION  OF  SAURIDA  UNDOSQUAMIS 


Meteorology 

Air  temperature  (monthly  averages)  and  pre- 
cipitation data  for  1950-70  were  published  by  the 
Israel  Meteorological  Service.  These  data  are 
complete  and  uninterrupted  for  the  whole  period. 
Only  those  data  which  were  collected  at  stations 
between  Tel  Aviv  and  Ashdod  (Anonymous, 
1950-71)  were  chosen  (Figures  3,  4). 

Presentation 

In  attempting  to  find  the  relationship  between 
climatic  phenomena  and  fish  catches,  it  is  simpler 
to  follow  a  calendar  based  on  seasons  with  the  year 


beginning  in  the  fall,  at  the  beginning  of  the  rainy 
season  in  this  area.  Thus,  for  the  purpose  of  this 
study,  the  environmental  and  most  of  the  fisheries 
data  are  given  according  to  years  which  start  on  1 
September  and  end  on  31  August,  i.e.,  1  Sep- 
tember 1950-31  August  1951  forms  the  year 
1950/51. 

In  some  instances,  extreme  values  rather  than 
annual  averages  may  be  influential  factors  affect- 
ing crops  or  populations.  One  year  may  be  a  rainy 
year,  but  most  of  the  rains  may  not  have  been 
timely,  etc.  For  this  purpose,  some  data  are  pre- 
sented selectively  to  emphasize  the  more  critical 
points.  Thus,  e.g.,  the  average  of  the  three  coldest 
months,  whatever  these  months  may  be  in  each 


T°C 


28 
27 
26 
25 

16 
15 
14 
13 


50/51        52/53         54/55         56/57        58/59        60/61         62/63        64/65        66/67        68/69  YEAR 


Figure  3. — Air  temperatures,  1950/51-1968/69  (Anonymous,  1950-70).  A  -  Summer  maxima,  mean  of  the 
warmest  month;  B  -  average  of  three  coldest  months.  Each  year  starts  1  September. 


MM 

900 

• 

800 

1    \ 

i             \           ■ 

^ 

700 
600 

/    »'    V       V,              /     \    / 

X              1       \                 1 

500 
400 

V >   // 

300 

.;    />.        /  \  /<l/     \  j^ 

200 

•  y^               \       /          \r                           w 

^ 

100 

¥ 

'        ■        >       i •        « 

50/51       52/53        54/55         56/57         58/59         60/61  62/63        64/65        66/67         68/69  YEAR 


Figure  4.— Precipitation,  1950/51-1968/69  (Anonymous,  1950-70).  A  -  September-January;  B  -  January-April. 

Each  year  starts  1  September. 


363 


year,  rather  than  the  annual  averages  are  used. 
Neither  the  data  presented  in  this  paper  nor  other 
available  pertinent  data  have  been  statistically 
processed.  Therefore  we  have  limited  ourselves 
to  seek  only  most  general  patterns  based  on  the 
most  obvious  dramatic  changes  and  to  point  out 
apparent  or  likely  correlations. 

THE  RED  SEA  LIZARDFISH 
The  Invasion 

Prior  to  1954,  two  species  of  lizardfish  (Synodon- 
tidae)  occurred  rather  infrequently  in  the  catches 
of  the  Israeli  Mediterranean  trawlers:  Synodus 
saurus  (Linnaeus),  a  tropical  Atlantic  and 
Mediterranean  species  (Fowler,  1936),  and  the 
Red  Sea  lizardfish,  an  Indo-Pacific  species.  The 
latter  was  first  reported  from  the  Mediterranean 
as  Saurida  grandisquamis  (Gunther)  by  Ben- 
Tuvia  (1953,  in  press),  who  found  it  for  the  first 
time  in  December  1952.  At  that  time,  neither 
species  was  of  commercial  value,  and  S.  undo- 
squamis  was  much  rarer  than  Synodus  saurus 
(Ben-Tuvia,  1953,  in  press;  Oren,  1957). 

Ben-Tuvia  (in  press)  observed  that  as  early  as 
August  1953  the  lizardfish  was  fairly  common  in 
trawl  catches  taken  in  the  Gaza-El  Arish  area, 
with  10  to  20  specimens  caught  usually  in  each 
haul. 

In  the  winter  of  1954-55,  together  with  other 
changes  in  the  composition  of  trawl  catches,  the 
proportion  of  the  Red  Sea  lizardfish  increased  to 
such  an  extent  that  the  fishermen  attempted  to 
market  them  as  a  food  fish  (Ben-Yami,  1955).  Con- 
sequently, in  1955  lizardfish  appeared  for  the  first 
time  in  the  statistics  of  landings  (Sarid,  1956). 

In  the  summer  of  1955,  unusual  numbers  of 
fingerlings  were  found  in  the  cod  ends  of  trawl 
nets.  The  bulk  of  them  consisted  of  two  Red  Sea 
species,  the  yellow-striped  goatfish  and  the 
lizardfish  (Ben-Yami,  1955). 

In  1955-56,  the  lizardfish  became  one  of  the 
main  commercial  fishes  in  Israel;  its  proportion  in 
the  total  landings  of  Israel's  marine  fishery 
reached  11%  (Sarid,  1956),  and  in  the  trawl  fishery 
landings  approximated  20%  (Figure  5).  Catch 
data  collected  during  1955  and  1956  (Oren,  1957) 
indicate  that  the  Red  Sea  lizardfish  made  its  first 
significant  appearance  in  the  trawl  catches  in  the 
fishing  grounds  off  the  Gaza  Strip  and  North 
Sinai.  By  the  end  of  summer  and  autumn  of  1955 


FISHERY  BULLETIN;  VOL.  72,  NO.  2 

it  had  expanded  all  over  Israel's  fishing  grounds. 

During  the  period  1952-60,  most  Israeli  trawl- 
ers fished  in  the  summer  months  in  the  north- 
eastern part  of  the  Mediterranean  (Gulf  of  Tarsus 
and  neighboring  waters).  The  Red  Sea  lizardfish, 
however,  was  not  found  in  those  waters  in  1952  by 
Gottlieb  and  Ben-Tuvia  (1953),  who  produced  a 
detailed  list  of  52  fish  species  caught  in  a  trawl 
catch.  By  summer  1956,  it  was  common  in  the 
trawl  catches  in  the  Bay  of  Tarsus  (Ben-Tuvia, 
pers.  comm.),  and  since  then  it  has  become  well 
established  and  is  one  of  the  most  important  com- 
mercial fish  in  that  area. 

The  quantity  of  lizardfish  caught  by  the  trawl- 
ers continued  to  increase  until  1959  when  almost 
400  tons  (20%  of  the  total  trawl  catch)  were  landed 
(Sarid,  1960).  This  was  followed  by  a  4-yr  reces- 
sion. In  1963,  the  catches  dropped  to  an  approxi- 
mately 120-ton  low,  and  since  then,  they  appar- 
ently stabilized  near  this  level  with  "normal"  an- 
nual fluctuations. 

Food  and  Habitat 
of  the  Red  Sea  Lizardfish 

The  lizardfish  is  a  demersal  piscivore.  Its  food  in 
the  Levant  Basin  was  studied  by  Bograd- 
Zismann  (1965)  and  by  Chervinsky  (1959). 
Bograd-Zismann  examined  some  1,500  stom- 
achs, of  which  859  contained  food.  Of  these, 
77.3%  contained  fish;  the  rest  contained  inverte- 
brates, mostly  crustaceans,  and  digested  matter. 
Chervinsky  examined  some  500  stomachs,  of 
which  131  contained  identifiable  food.  Large  in- 
vertebrates were  found  in  only  16  stomachs;  the 
rest  contained  fish.  Both  authors  indicate  that  the 
most  frequent  prey  of  the  Red  Sea  lizardfish  are 
clupeoid  fish-according  to  Chervinsky  (1959)  an- 
chovy, and  according  to  Bograd-Zismann  (pers. 
comm.)  mostly  anchovy,  but  also  some  sardines. 

The  second  important  group  in  the  food  of  the 
lizardfish  are  fish  of  the  family  Mullidae 
(Bograd-Zismann,  1965;  Chervinsky,  1959). 
Other  important  groups  in  the  lizardfish  food  are 
Gobiidae,  Centracanthidae  (listed  as  Maenidae 
by  Bograd-Zismann,  1965,  and  by  Chervinsky, 
1959),  and  Leiognathus  klunzingeri  (Stein- 
dachner)  (Bograd-Zismann,  1965;  Chervinsky, 
1959;  Ben-Tuvia,  1966). 

No  direct  information  is  available  on  the 
diurnal-nocturnal    feeding    activity    of   the      i 
lizardfish  in  the  Levant  Basin.  Nonetheless,  the 
high  proportion  of  anchovy  in  the  food  of  the      ' 


364 


BEN-YAMI  and  GLASER:  INVASION  OF  SAURIDA  UNDOSQUAMIS 


25 
20 
15 
10 
5 


/  \ 


-»^ 


50/51 


52/53        54/55        56/57        58/59        60/61 


62/63       64/65        66/67       68/69        70/71 

YEAR 


Figure  5. — Changes  in  the  hake — Red  Sea  lizardfish  relationship  in  catches  and  the  catch-per-unit-effort  (cpu)  in 
the  Israel  trawl  fishery  in  the  Mediterranean,  1950-70  (Sarid,  1951-71).  A  -  cpu— all  fish,  each  year  starts  1 
January;  B  -  cpu — (1)  lizardfish,  (2)  hake;  C  -  proportion  in  catch,  percent:  (1)  lizardfish,  (2)  hake.  BandC — each 
year  starts  1  September. 


lizardfish  may  indicate  that  either  the  lizardfish  is 
a  demersal  feeder,  feeding  on  clupeoids  only  when 
it  approaches  the  bottom  of  the  sea  during  the 
hours  of  light,  or  that  it  ascends  during  the  night 
to  the  upper  water  layers  where  it  could  feed  on 
these  pelagic  fish.  We  favor  the  first  hypothesis, 
for  the  lizardfish  almost  never  occurs  in  the  night 
catches  of  purse  seines  in  light  fishing.  This 
hypothesis  is  corroborated  by  observations  of 
Hiatt  and  Strasburg  (1960)  of  two  lizardfishes, 
Saurida  gracilis  and  Synodus  variegatus,  of  the 
Marshall  Islands.  The  lizardfish  lie  motionless, 
on  or  partly  buried  in  the  sand,  and  are  virtu- 
ally impossible  to  detect.  Only  when  small  fish 
come  within  a  distance  of  a  few  feet,  the  lizardfish 
seize  them  in  a  rapid  dart.  They  were  rarely  ob- 


served to  ascend  for  more  than  3  to  4  feet  while 
attacking  their  prey. 

Hayashi,  Yamaguchi,  and  Hanaoka  (1960)  and 
Toriyama  (1958)  reported  on  the  basis  of  stomach 
examinations  that  S.  undosquamis  in  Japanese 
waters  feeds  during  most  hours  of  day  and  night. 
According  to  Toriyama,  however,  feeding  activity 
is  most  intensive  during  the  early  morning  hours. 

According  to  Chervinsky  (1959),  the  lizardfish 
is  cannibalistic.  Bograd-Zismann  (1961-62)  ob- 
served that  the  occurrence  of  lizardfish  in 
stomachs  may  rather  be  a  result  of  panicky  indis- 
criminate attacking  in  the  trawl  cod  end. 

The  Red  Sea  lizardfish  in  the  Levant  Basin  pre- 
fers rather  shallow  waters.  It  is  caught  in  the  cool- 
er seasons  at  depths  generally  not  exceeding  45  fm 


365 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Figure  6. —  The  overlapping  habitats  of  the  Red  Sea  lizardfish 
and  the  hake  over  the  Israel  continental  shelf.  Top  -  summer; 
bottom  -  winter.  Depth  in  fathoms. 

(fathoms),  but  mostly  at  less  than  35  fm  (Figure  6). 
During  the  warm  season  the  lizardfish  may  spread 
over  deeper  trawling  grounds.  Occasionally  it  oc- 
curs in  catches  made  at  80  to  100  fm.  In  general, 
however,  the  lizardfish  is  of  no  commercial  signifi- 
cance over  the  deepwater  trawling  grounds 
(Ben-Yami,  1971;  Zismann,  1971). 

Spawning 

There  is  very  little  biological  information  on  the 
Red  Sea  lizardfish  in  this  area.  Bograd-Zismann 
(see  footnote  10)  and  Chervinsky  ( 1959)  found  that 
ripe,  nearly  ripe,  and  partly  spent  females  occur  in 
catches  almost  all  year  long,  though  the  former 
author  indicated  that  the  greater  proportion  of 
nearly  ripe  females  occurs  in  the  early  summer.  It 
has  to  be  borne  in  mind  that  a  fish  may  spawn  over 
a  prolonged  season,  while  the  survival  of  its  fry 
may  be  confined  to  a  much  shorter  period  con- 
trolled by  favorable,  seasonal  conditions. 

The  area  of  spawning  can  only  be  speculated  as 
being  offshore  and  in  deep  water.  This  is  based  on 
the  following  information:  Neither  larvae  nor 
juveniles  oiSaurida  were  taken  during  an  exten- 
sive survey  offish  larvae  made  using  neuston  nets 
(Ben-Yami  et  al.,  1970)  and  Isaacs-Kidd  mid- 
water  trawl  off  the  coast  of  Israel  and  Sinai  during 
1967-69.  This  survey  consisted  of  25  cruises  cover- 
ing inshore  (Haifa  Bay,  Bardawil  Lagoon),  shal- 


low water,  and  offshore  stations.  Only  once,  in 
December  1968,  were  S.  undosquamis  fry  taken: 
nine  11-20  mm  specimens  were  caught  in  deep 
water  in  the  Isaacs-Kidd  trawl,  at  a  station 
situated  7  miles  west  of  Cape  Carmel,  over  200  fm 
depth  (Lourie,  Herzberg,  and  Ben-Yami,  1969^S 
Lourie,  pers.  comm.). 

The  very  fact  that  S.  undosquamis  larvae  and 
juveniles  did  not  occur  either  among  the 
thousands  of  fish  larvae  and  juveniles  caught  in 
neuston  nets  during  day  and  night  tows  (Lourie  et 
al.,  see  footnote  11;  Lourie,  pers.  comm.)  or  in  sam- 
ples taken  by  means  of  a  light  trap  for  small 
photokinetic  organisms  (Zismann,  1969)  seems  to 
indicate  that  they  do  not  occur  in  the  surface  water 
layer,  neither  during  the  day  nor  by  night.  On  the 
other  hand,  the  capture  of  the  young  in  December, 
over  deep  water  and  apparently  deep  in  the  mid- 
water,  coincided  with  the  seasonal  temperature 
increase  at  this  level  (Oren,  1970)  (Figure  1). 

Growth 

Chervinsky  (1959)  has  measured  the  length  fre- 
quency of  the  lizardfish  between  June  and  De- 
cember 1957,  concluding  that  while  the  bulk  of  the 
lizardfish  catch  consisted  offish  between  16  and  24 
cm  long,  they  grew  fast;  2  cm  per  month.  No  males 
exceeding  24  cm  were  found,  although  females 
exceed  30  cm. 

Bograd-Zismann  (see  footnote  10)  examined  the 
scales  of  the  lizardfish.  Two  annuli  were  found  on 
the  scales  offish  22  to  30  cm  total  length  (TL).  On 
the  scales  offish  19  to  22  cm  TL,  one  annulus  was 
seen,  but  there  are  indications  that  the  year's 
growth  is  not  marked  by  a  clear  annulus.  Thus,  it 
seems  that  the  age  of  the  lizardfish  at  recruitment 
is  about  2  yr  or  may  be  3  yr,  the  bulk  of  the  fish  in 
the  catch  being  at  least  2  yr  old. 

Relation  with  Relative  Species 

To  complete  the  ecological  picture  of  the  Red  Sea 
lizardfish,  its  relationship  with  two  of  its  relatives 
should  be  mentioned:  one  is  the  Atlantic- 
Mediterranean  lizardfish,  Synodus  saurus,  and 


'"Bograd-Zismann,  L.  1961-62.  Interim  report  on  the  study 
of  the  food  of  Saurida  undosquamis  in  the  Mediterranean 
Sea.  Unpubl.  manuscr.  In  files  of  the  Isr.  Sea  Fish.  Res.  Stn., 
Haifa. 


"Lourie,  A.,  A.  Herzberg,  and  M.  Ben-Yami.  1969.  A  survey 
of  neustonic  fishes  off  the  Mediterranean  coast  of  Israel  and 
Sinai,  1968.  In  Interim  Report,  Joint  Research  Project  "Biota  of 
the  Red  Sea  and  the  Eastern  Mediterranean,"  p.  133-150.  The 
Hebrew  University  of  Jerusalem  and  the  Smithsonian  Institu- 
tion, Washington,  D.C.  [Processed.] 


366 


BEN-YAMI  and  GLASER:  INVASION  OF  SAURIDA  UNDOSQUAMIS 

the  other  is  the  Indo-Pacific  species  greater 
lizardfish,  Saurida  tumbil  (Bloch).  The  first  is  a 
quantitatively  insignificant  and  hence  noncom- 
mercial demersal  predator  in  the  Levant  Basin. 
Although  a  natural  competitor  to  the  latter,  the 
native  S.  saurus  was  superseded  by  the  invader, 
being  now  as  rare  as  ever. 

Saurida  tumbil  is  one  of  the  main  commercial 
fishes  and  dominates  in  the  south  Red  Sea  trawl 
fishery.  Another  species,  S.  undosquamis ,  is  the 
"underdog"  there,  though  not  as  rare  as  Synodus 
saurus  is  in  the  Levant  Basin.  Saurida  undo- 
squamis holds  ground  only  in  deeper  and,  evi- 
dently, cooler  waters,  while  S.  tumbil  dominates 
over  most  of  the  trawling  grounds  (Ben-Tuvia, 
1966).  On  the  other  hand,  it  is  S.  undosquamis, 
probably  the  euryecous  of  the  two,  which  spread 
into  the  northern  Red  Sea,  becoming  the  only  sig- 
nificant lizardfish  in  the  Gulf  of  Suez  and  the  Le- 
vant Basin. 


Feeding  in  Israel  Waters 

Shmida  (1964)^2  investigated  76  stomachs  of 
which  49  contained  food.  The  fish  were  from 
catches  taken  in  summer  and  spring.  While  the 
bulk  of  the  food  taken  in  spring  consisted  of  crus- 
taceans (mostly  Decapoda,  Macrura),  the  food  of 
hake  caught  in  summer  was  mostly  fish.  Shmida 
concludes  that,  in  general,  the  food  in  terms  of 
weight  was  half  crustaceans  and  half  fish.  All 
identifiable  fish  were  anchovy.  Unfortunately, 
Shmida  had  at  his  disposal  only  small  individuals, 
less  than  27  cm  long.  Larger,  faster,  and  stronger 
hake  may  have  a  different  diet  in  which  the  pro- 
portion offish  may  be  higher.  This  was  indicated 
by  a  slight  trend  of  more  fish  in  the  stomachs  of  the 
larger  hake,  even  within  the  narrow  length  range 
investigated  (Shmida,  1964). 

Habitat 


HAKE 

Another  important  commercial  fish  whose 
habitat  and  food  in  the  Levant  Basin  indicate  that 
it  is  the  main  competitor  of  the  lizardfish  is  the 
hake,  Merluccius  merluccius.  This  is  an  eastern 
Atlantic  species  which  is  also  native  to  these  wa- 
ters (Ben-Tuvia,  1953),  and  whose  biology  and 
habits  in  the  Levant  Basin  still  remain  to  be 
studied. 

In  the  Atlantic  Ocean  the  hake  is  known  as  a 
voracious  predator,  feeding  during  the  day  at  the 
bottom  and  rising  at  night  into  higher  water 
layers.  It  is  known  as  a  deepwater  species  caught 
at  depths  down  to  400  fm.  Off  the  British  Isles,  it 
seems  to  prefer  water  temperatures  of  around 
lOT. 

Spawning  and  Growth 

Near  the  British  Isles,  the  hake  spawns  mostly 
at  or  near  areas  over  the  100-fm  isobath.  Females 
spawn  up  to  a  million  eggs  each.  The  eggs  are 
pelagic,  floating  on  the  sea  surface.  Before  hatch- 
ing, which  occurs  within  a  fortnight,  the  eggs  de- 
scend to  midwater,  where  the  larvae  hatch  and 
develop.  The  yolk  is  absorbed  within  3  to  4  wk 
after  which  the  postlarvae  feed  on  zooplankton. 
The  fry  descend  to  the  bottom,  where  hake  3  to  4 
cm  long  were  taken.  They  reach  10  cm  at  the  year's 
end  and  become  mature  at  20  cm  (Marshall,  1965; 
Travis  Jenkins,  1954). 


The  hake  prefers  cool  water.  This  is  evident 
from  its  occurring  over  the  shallow  trawling 
grounds  only  during  the  cooler  season  of  the  year. 
Its  proportion  in  trawl  catches  can  be  consider- 
able, even  at  depths  less  than  20  fm,  if  the  water  is 
cold  enough.  With  the  approach  of  the  warm  sea- 
son, the  hake  retreats  to  the  deepwater  regions 
where  it  remains  available  to  trawls  at  depths 
over  100  fm  throughout  the  season  (Ben-Yami, 
1971).  Figure  6  illustrates  the  relative  distribu- 
tion of  the  lizardfish  and  the  hake  over  the  Israeli 
continental  shelf  and  their  overlapping  habitats. 

RED  SEA  MIGRANTS  AS  PREY 

OF  THE  HAKE 

AND  THE  LIZARDFISH 

As  mentioned  above,  both  our  predators  feed 
extensively  on  anchovy.  It  seems,  nevertheless, 
that  the  hake  competes  with  the  lizardfish  also  for 
other  fish,  some  of  them  Red  Sea  migrants.  Ben- 
Tuvia  (1966)  reports  that  two  of  them,  Leio- 
gnathus  klunzingeri  and  a  Red  Sea  goatfish,  Upe- 
neus  asymmetricus  Lachner  (reported  previously 
as  U.  tragula  Richardson),  are  components  of  the 
food  of  both  the  lizardfish  and  the  hake.  Leio- 
gnathus,  a  trash  fish  in  trawl  catches,  has  been, 
undoubtedly,  of  major  importance  in  the  food 


i^Shmida,  A.  1964.  T'zunat  dagim  b'Yam  Tikohn  uv'Yam 
Suf  (Food  of  fishes  in  the  Mediterranean  and  the  Red  Sea).  [In 
Hebrew.]  Unpubl.  manuscr.  In  files  of  the  Isr.  Sea  Fish.  Res. 
Stn.,  Haifa. 


367 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


chain  of  demersal  piscivores  (Ben-Tuvia,  1966), 
and  has  declined  (Ben-Tuvia,  in  press  b)  since  its 
peak  bloom  in  the  50's.  Ben-Tuvia  attributes  this 
decline  to  the  spread  of  the  lizardfish,  one  of  its 
main  predators.  The  U.  asymmetricus,  usually 
small,  does  not  occur  in  commercial  quantities, 
and  in  the  catches  it  is  classified  with  the  other  red 
mullets. 

Another  Red  Sea  migrant,  the  yellow-striped 
goatfish,  Upeneus  moluccensis  has  not  yet  been 
identified  from  the  stomachs  of  the  hake.  There 
are  good  indications  that,  ecologically,  both  the 
Upeneus  and  the  lizardfish  are  closely  related  in  a 
prey-predator  relationship.  They  occupy  the  same 
habitat,  the  goatfish  being  an  equally  rare  visitor 
at  the  deepwater  trawling  grounds  (Zismann,  in 
preparation).  Both  species  seem  to  increase  in 
catches  during  the  same  years  (Ben-Yami,  1955; 
Oren,  1957),  which  may  be  associated  with  en- 
vironmental conditions. 

It  is,  thus,  very  likely  that  in  areas  where  they 
are  both  found,  the  hake  and  the  Red  Sea 
lizardfish  compete  for  food. 

THE  MECHANISM  OF  AN  INVASION 

Ecological  "Barriers"  to 
Migrating  Species 

A  demersal  fish  expanding  from  one  sea  to 
another  through  a  man-made  canal  encounters 
several  barriers  which  it  must  overcome  before  a 
significant  population  can  be  established  in  the 
other  sea  (Figure  7).  The  "height"  of  an  ecological 
barrier  differs  for  each  separate  species.  Hypersa- 
linity,  e.g.,  which  may  be  prohibitive  to  some 
purely  marine  species,  may  not  be  a  barrier  or  may 
even  possess  attractive  environmental  qualities  to 
euryhaline  organisms.  The  height  of  an  ecological 
barrier  may  also  change  with  seasonal,  annual, 
and  multiannual  fluctuations  in  the  environmen- 
tal conditions. 

The  first  barrier  is  the  canal  itself  which  may 
represent  a  less  or  more  hostile  environment  for 
the  migrating  species.  Migration  through  the 
Suez  Canal  must  have  been  very  difficult  for  some 
and  impossible  for  other  species,  because  of  the 
complex  hydrological  conditions  in  the  canal  (the 
high  salinity  of  the  Bitter  Lakes,  freshening  of  the 
water  due  to  influx  of  fresh  water  at  some  places, 
and  the  seasonal  Nile  floods)  (Oren,  1970;  H. 
Steinitz,  pers.  comm.).  The  nature  of  the  Suez 
Canal,  as  a  barrier,  has  changed,  however,  with 


NATIVE  SEA 


THE  CANAL 


SEA  BOTTOM   & 
FOOD  DIFFERENCES 


BARRIER  III      ^    f)  S;°C« '"' 


r 


1 


BARRIER  IV     1^  COMPETITORS  & 


PREDATORS 


I 


NEW  SEA 


Figure  7. — "Barriers"  on  the  path  of  a  migrating  species  of 
demersal  fish  the  last  three  "barriers"  may  occur  in  any  order 
and/or  overlap. 


time.  Animal  migration  through  the  canal  may 
now  become  easier  (Thorson,  1971). 

The  second  barrier,  especially  for  demersal 
species,  is  the  difference  in  bottom  conditions.  The 
importance  in  the  character  of  the  substrate  for 
the  expansion  of  migrating  benthic  invertebrates 
was  emphasized  by  Gilat  (see  footnote  6)  and  Por 
( 1971).  The  type  of  bottom  influences  the  type  and 
quality  of  food  available.  Bodenheimer  ( 1966)  em- 
phasized the  negative  effect  which  lack  of  food 
may  have  on  fecundity.  De  Vlaming  (1971)  has 
shown  that  starvation  affected  the  gametogenesis 
and  gonadal  regression  in  a  goby,  Gillichthys 
mirabilis.  Undoubtedly,  it  is  not  enough  for  a  bot- 
tom fish  just  to  cross  a  canal.  To  survive  and  repro- 
duce, it  must  find  in  its  new  habitat  either  the  food 
to  which  it  is  accustomed  or  a  food  which  can 
replace  the  former  both  quantitatively  and  qual- 
itatively at  all  stages  of  its  life  cycle.  This  condi- 
tion is,  generally,  controlled  by  the  character  of 
the  sea  bottom. 

A  third  barrier  is  the  hydrological  gradient  (if 
any)  between  both  seas.  A  species  may  cross  a 
canal,  may  even  find  an  apparently  suitable 
habitat,  but  all  its  spawn  may  be  killed  by  extreme 
winter  or  summer  temperatures.  Also,  adverse 


368 


BEN-YAMI  and  GLASER:  INVASION  OF  SAURIDA   UNDOSQUAMIS 


temperature  conditions  may  affect  prespawning, 
reproductive  processes  in  fish  (De  Vlaming,  1971 ), 
while  difference  or  seasonal  changes  in  salinity 
may  affect  survival  of  a  stenohaline  species. 

Oren  (1970)  has  noticed,  e.g.,  that  after  the  crit- 
ical 1954/56  years,  the  minimum  seawater  winter 
temperatures  over  the  Israel  continental  shelf 
have  never  returned  to  their  values  of  15°C  mea- 
sured prior  to  this  period.  He  also  found  that  the 
salinities  in  the  same  area  increased  since  the 
closure  of  the  Aswan  Dam  in  1964.  It  seems,  thus, 
that  in  the  long  run,  the  hydrological  gradient 
between  the  Gulf  of  Suez,  where  the  temperatures 
and  salinities  are  higher  than  in  the  Levant  Basin 
(Kosswig,  1951;  Oren,  1957;  Ben-Tuvia,  1966)  and 
the  Mediterranean,  is  on  the  decrease. 

The  fourth  barrier  is  the  predators  and  com- 
petitors. Darwin  (1859)  emphasized  the  role  of 
prey,  predators,  and  competitors  on  the  distribu- 
tion range  of  species.  Obviously,  the  abundance 
and  distribution  of  the  native  predators  and  com- 
petitors are  affected  by  fluctuations  in  the  hy- 
drological conditions.  Therefore,  changes  in  the 
hydrological  conditions  may  affect  establishment 
of  the  migrant  species  both  directly  and,  through 
their  competitors,  indirectly. 

Human  Interference  May 
Facilitate  Invasion 

An  invasion  may  succeed  because  of  human  in- 
terference in  the  environment.  Elton  (1958)  has 
shown  that  such  interference,  especially  where 
associated  with  depletion  of  native  populations, 
considerably  increases  the  vulnerability  of  an 
area  to  invasions.  We  consider  commercial 
fisheries  to  be  an  example  of  an  extreme  interfer- 
ence. 

The  Explosion  of  the  Red  Sea 
Lizardhsh  Population 

The  lizardfish,  Saurida  undosquamis ,  is  an  im- 
portant component  of  the  Egyptian  trawl  catches 
in  the  Gulf  of  Suez  (Latif,  1971).  The  early  records 
of  lizardfish  in  the  Suez  Canal  by  Gruvel  and 
Chabanaud  (1937),  asS.  sinaitica,  S.  tumbil,  and 
S.  gracilis,  may  have  been  S.  undosquamis 
(Ben-Tuvia,  pers.  comm.). 

Fifteen  years  later,  and  83  years  after  the  open- 
ing of  the  Suez  Canal,  the  Red  Sea  lizardfish  ap- 
peared in  the  southeastern  Mediterranean  in  suf- 


ficient numbers  to  be  described  as  a  "rare"  fish 
(Ben-Tuvia,  1953).  But  within  2  to  3  yr,  it  became 
one  of  the  most  important  commercial  trawl  fishes 
forming  20%  of  the  catch.  This  recalls  the  invasion 
of  the  sea  lamprey,  Petromyzon  marinus,  in  the 
Great  Lakes  in  North  America  (Elton,  1958).  Al- 
though the  Welland  Ship  Canal  was  opened  as 
early  as  1829,  the  sea  lampreys  were  observed  in 
Lake  Erie  100  yr  later.  Then,  within  10  yr,  the 
lamprey  population  expanded  rapidly  and 
dramatically  both  in  space  and  in  number,  caus- 
ing a  collapse  of  the  lake  trout  fishery  in  Lake 
Michigan  and  Lake  Huron. 

The  population  explosion  of  the  Red  Sea 
lizardfish  was  much  faster,  for  its  1959  all-time 
record  landings  occurred  only  4  yr  after  its  first 
appearance  in  the  trawl  catch  as  a  fraction  of  a 
percent. 

Although  the  subsequent  decline  in  the 
lizardfish  catch  may  be  associated  with  decrease  of 
the  fishing  effort  (Tables  1  and  2),  particularly  in 
the  northeast  Mediterranean,  its  relatively  stable 
proportion  in  the  total  catch  indicates  that  an 
ecological  balance  was  reached  within  the  first  2 
yr  of  its  appearance  in  the  commercial  catch  (Fig- 
ures 5,  8).  Subsequent  annual  fluctuations  seem  to 
be  normal  to  natural  populations. 


Table  2.— Israel  trawl  fishery,  1948-70. 


Total 

Number 

of  trawlers 

landings 

Year 

(act 

vity  %) 

1 

(tons) 

1945 

25 

(56) 

508 

1946 

11 

(73) 

333 

1947 

12 

(67) 

258 

1948 

12 

(46) 

111 

1949 

14 

(57) 

430 

1950 

30 

(54) 

1,092 

1951 

27 

(43) 

929 

1952 

23 

(49) 

1,000 

1953 

23 

(56) 

1,286 

1954 

22 

(75) 

1,480 

1955 

27 

(63) 

1,518 

1956 

26 

(60) 

1,391 

1957 

27 

(69) 

1,550 

1958 

29 

(77) 

1,740 

1959 

27 

(92) 

1,952 

1960 

25 

(69) 

1,274 

1961 

19 

(70) 

992 

1962 

18 

(75) 

830 

1963 

17 

(74) 

706 

1964 

15 

(76) 

615 

1965 

18 

(70) 

761 

1966 

18 

(77) 

638 

1967 

16 

(87) 

741 

1968 

16 

(80) 

926 

1969 

16 

(91) 

1,028 

1970 

19 

(82) 

930 

'Activity  index  (100';): 
below  150  hp  -  210  days  at  sea  per  trawler, 
over  150  hip  -  230  days  at  sea  per  trawler. 


369 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


YEAR    PRECIPITATION 


SHARE    IN    TRAWL  CATCH 
HAKE  LIZARDFISH 


/qISIO  5  0  5   10  15 


l_-l L 


15 10   5    0  5    1015    /ft 


TEMPERATURE     YEAR 
SEA  AIR 


50/51- 


52/53- 


54/55- 


56/57- 


58/59- 


60/61- 


62/63- 


64/65- 


66/67- 


68/69- 


70/61- 


RAINY  YEAR 


DRIEST  JAN-APR 
SEASON 


VERY  RAINY 
YEAR 


DROUGHT 

RAINY  YEAR 

DRYISH 
YEAR 

V.RAINY  YEAR 


DROUGHT 


RAINY  YEAR 


DROUGHT 


RAINY  YEAR 


BELOW   75M. 
WARM  IN  AUTUMN 
&   SUMMER 


AIR   EXTRA 
WARM  IN  WIN. 


AIR  iXTRA 
COLD  IN 
WINTER 


-50/51 


AIR  EXTRA 
COLD  IN 

WINTER 


SURF.  EXTRA 
WARM  IN 
WINTER 


-52/53 


-54/55 


-56/57 


58/59 


-60/61 


-62/63 


-64/65 


-66/67 


-68/69 


-70/71 


Figure  8. — Changes  of  the  proportion  of  the  hake  and  the  Red  Sea  lizardfish  in  the  Israel  trawl  landings  and  their 

relationship  with  environmental  conditions,  1950-71. 


Hence,  in  the  case  of  the  lizardfish,  the 
population-growth  logistic  curve  (Bodenheimer, 
1966)  would  have  been  extremely  steep  in  its  cen- 
tral part  with  extremely  sharp  flexes  between  the 
first  and  the  central  sections  and,  again,  between 
the  central  and  the  third  sections  of  the  curve.  It 
can  be,  therefore,  speculated  that  this  invasion 
and  expansion  were  not  only  a  product  of  a  "nor- 
mal" population  growth  but  were  also  aided  by 
additional  factors. 


370 


The  Role  of  Environmental  Factors 

The  sudden  buildup  of  the  Red  Sea  lizardfish 
population  which  occurred  between  1954  and  1956 
was  accomplished  by  a  series  of  unusual 
phenomena:  1)  unusually  high  temperatures,  both 
of  air  and  water  (Ben-Yami,  1955;  Oren,  1957), 
especially  in  winter  (Figures  1,  2,  3);  2)  the  ex- 
tremely dry  January-April  season  of  1955  (Figure 
4),  as  well  as  a  very  pronounced  absence  of  winter 


BEN-YAMI  and  GLASER:  INVASION  OF  SAURIDA  UNDOSQUAMIS 


gales  of  anticyclonic  depression  origin,  during  the 
same  winter  (Ben- Yami,  1955);  3)  the  hake  made  a 
very  poor  appearance  in  the  1955/56  Israel  trawl 
catches  (Figures  5,  8),  decreasing  to  approxi- 
mately 40^c  of  its  20  yr  average  (Figures  5,  8)  in 
the  catch  and  to  approximately  42%  of  its  20  yr 
average  (Figure  5)  in  its  catch  per  fishing  day. 
Since  then,  such  low  catches  of  the  hake  only  oc- 
curred in  1960/61  and  in  1966/67.  In  all  three 
cases,  the  drop  in  the  hake  catches  seems  to  be 
associated  with  drought:  it  followed  the 
January-April  drought  in  1955,  in  1959/60  and 
1966/67  it  followed  a  drought  in  the  preceding 
winter  (Figure  8). 

Trawl  Fishery's  Rapid  Development 

The  rapid  intensification  of  the  Israel  trawl 
fishery  1949-54  (Table  2)  was  probably  another 
important  factor  contributing  to  the  expansion  of 
the  Red  Sea  lizardfish.  The  landings,  which  before 
1940  were  100  to  500  tons,  rose  to  approximately 
1,000  tons/year  during  1950-52  and  to  almost 
1,500  tons  in  1954,  when  the  first  commercial 
catches  of  the  lizardfish  were  taken. 

Before  1950,  the  Israeli  trawlers  did  not  fish  in 
waters  deeper  than  50  to  60  fm.  Since  1950, 
deepwater  trawling  operations  have  been  carried 
out,  and  hence  there  has  been  considerable  exploi- 
tation of  the  hake  resources  (Ben- Yami,  1971). 

DISCUSSION  AND  CONCLUSIONS 

The  set  of  conditions  which  prevailed  just  before 
and  during  the  explosion  of  the  Red  Sea  lizardfish 
population  and  which,  apparently,  facilitated  this 
explosion  included: 

1.  "Preparation"  of  the  area  due  to  the 
intensification  of  the  trawling  fishery  by  the  factor 
of  3-4  (Table  2); 

2.  Water  temperature  conditions  which  contrib- 
uted to  good  survival  of  several  strong  year 
classes  of  lizardfish; 

3.  A  combination  of  climatic  (drought)  and 
water  temperature  conditions  which  caused  the 
withdrawal  of  the  hake  from  most  of  the  trawling 
grounds,  leaving  ample  space  for  the  spread  of  the 
lizardfish. 

It  is  possible  that  the  population  of  the  Red  Sea 
lizardfish  in  the  Levant  Basin  has  been  and,  with- 
out these  conditions,  might  have  remained  "dor- 
mant" and  suppressed  by  its  competitors  and  by 
unfavorable  environmental  conditions.  It  may 


have  been  still  waiting  for  its  opportunity  to  ex- 
pand. 

The  fluctuation  in  the  abiotic  conditions,  subse- 
quent to  the  lizardfish  explosion  years,  seems  to  be 
correlated  with  the  fluctuations  in  the  catches  of 
both  the  lizardfish  and  the  hake,  though  with  an 
"anomaly"  in  1961-63  when,  in  spite  of  two  con- 
secutive warm  winters,  the  proportion  of  hake  in- 
creased in  comparison  to  the  lizardfish.  Here,  e.g., 
the  abundant  rains  of  1961-62,  or  other  factors 
might  have  intervened  (Figure  8). 

The  hake  is  much  more  sensitive  to  the  fluctua- 
tions of  physical  conditions  than  the  lizardfish,  as 
may  be  seen  from  the  shape  of  the  respective  col- 
umns in  Figure  8.  The  declines  in  the  hake  catches 
indicate  either  recessions  in  the  population  or  a 
geographical  retreat  from  the  usual  fishing 
grounds,  probably  into  deeper  and  cooler  waters, 
or  a  combination  of  both. 

An  interesting  feature  of  the  fluctuation  of  the 
hake  proportion  in  catches  is  that  so  far  they  are  in 
phase  with  those  of  the  solar  activity  index  (Fig- 
ure 8),  though  this  correlation  may  be  purely  inci- 
dental. 

The  interrelations  discussed  in  this  paper  are 
very  complex.  Different  and,  perhaps,  even  vari- 
able time  lags  have  to  be  employed  to  correlate 
abiotic,  biotic-natural,  and  man-activated 
(fisheries)  factors.  A  study  for  further  pursuit 
along  this  line  will  require  the  application  of  com- 
puter technique.  Unquestionably,  a  good  oppor- 
tunity for  studying  the  influence  of  environmental 
conditions  on  the  relationship  of  competing  mi- 
grant and  native  species  was  lost  when  data  on 
the  Mullus-Upeneus  and  Red  Sea  Barracuda- 
Atlantic  Barracuda  proportion  in  catches  were 
not  collected  during  the  past  years.  Such 
studies  should  be  undertaken  in  the  future. 

An  examination  of  the  available  statistical  data 
(Sarid,  1951-71)  could  not  establish  any  sig- 
nificant influence  of  the  appearance  of  the  Red 
Sea  lizardfish  in  the  total  trawl  catches  on  the 
landings,  catch  per  unit  effort,  or  returns  of  the 
trawl  fishery.  Undoubtedly,  the  lizardfish  is  not 
just  an  additional  inhabitant,  and  its  invasion  did 
not  enrich  the  existing  ecosystem  in  terms  of 
biomass.  It  occurs  in  the  catches  at  the  expense  of 
other  fish,  partly  its  competitors,  such  as  the  hake, 
and  partly  its  prey,  such  as  the  yellow-striped 
goatfish,  red  mullet,  etc. 

The  proportion  of  the  lizardfish  in  the  trawl 
catches  has  never,  after  its  1954-56  invasion,  been 
less  than  13%,  although  there  have  been  several 


371 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


cold  winters  since  (Figures  2,  3,  8).  This,  besides 
indicating  that  the  Red  Sea  lizardfish  is  fairly 
eurythermic,  may  also  support  Kosswig's  ( 1972)^^ 
suggestion  of  the  role  of  the  modificability  of 
species  in  new  environments.  It  is  quite  probable 
that  the  Mediterranean  stock  of  the  Red  Sea 
lizardfish  today  is  better  adapted  to  the  local  en- 
vironmental conditions  than  it  was  20  yr  ago. 

The  Red  Sea  lizardfish  proved  vigorous  enough 
to  establish  itself  in  a  niche  in  a  habitat  occupied 
by  other  species;  it  is  euryecous  enough  to  with- 
stand fluctuations  in  environmental  conditions; 
and,  barring  an  ecological  disaster,  it  is  here  to 
stay. 


ACKNOWLEDGMENTS 

The  authors'  thanks  are  extended  to  all  col- 
leagues who  have  read  this  paper  and  offered 
many  valuable  comments  and  remarks,  and  par- 
ticularly to  Adam  Ben-Tuvia,  Eliezer  Gilat,  Av- 
raham  Herzberg,  Oton  H.  Oren,  and  Sh'muel  Pi- 
santy.  Last,  but  by  no  means  least,  we  thank  Lyka 
Bograd-Zismann  for  her  reading,  correcting,  and 
editing  efforts.  Irit  Brecher  helped  with  the  draw- 
ings. 


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373 


SUMMARY  OF  SELECTED  EARLY  RESULTS  FROM 
THE  ERTS-1  MENHADEN  EXPERIMENT^ 

Andrew  J.  Kemmerer,^  Joseph  A.  Benigno,^  Gladys  B.  Reese,'  and  Frederick  C.  Minkler' 

ABSTRACT 

A  15-mo  study  was  initiated  in  July  1972  to  demonstrate  the  potential  of  using  satellite-acquired 
environmental  data  to  provide  fisheries  information.  Imagery  from  ERTS-1  (Earth  Resources  Tech- 
nology Satellite)  was  used  in  conjunction  with  aerial  photographically  sensed  menhaden  distribution 
information,  sea-truth  oceanographic  measurements,  and  commercial  fishing  information  from  a 
8,670-km^  study  area  in  the  north  central  portion  of  the  Gulf  of  Mexico.  Objectives  were  to  demon- 
strate relationships  between  selected  oceanographic  parameters  and  menhaden  distribution,  ERTS-1 
imagery  and  menhaden  distribution,  and  ERTS-1  imagery  and  oceanographic  parameters.  ERTS-1, 
MSS  Band  5  imagery  density  levels  correlated  with  photographically-detected  menhaden  distribution 
patterns  and  could  be  explained  based  on  sea-truth  secchi  disc  transparency  and  water-depth  mea- 
surements. These  two  parameters,  together  with  surface  salinity,  Forel-Ule  color,  and  chlorophyll  a, 
also  were  found  to  correlate  significantly  with  menhaden  distribution.  Eight  empirical  models  were 
developed  which  provided  menhaden  distribution  predictions  for  the  study  area  based  on  combinations 
of  secchi  disc  transparency,  water  depth,  surface  salinity,  and  Forel-Ule  color  measurements. 


A  need  of  managers  and  users  alike  of  living 
marine  resources  is  timely  synoptic  information 
about  the  distribution  and  abundance  of  the  re- 
sources. For  users,  this  need  is  particularly  criti- 
cal in  that  daily  decisions  must  be  made  about 
where  to  deploy  fishing  vessels  and  less  frequent 
decisions  about  investment  strategies  for  men  and 
equipment.  The  increasing  pressures  placed  on 
living  marine  resources  by  domestic  and  foreign 
fishing  fleets  interacting  with  environmental 
changes  demand  that  resource  managers  also  be 
kept  fully  aware  of  the  current  status  of  the 
stocks  to  prevent  possible  catastrophic  fluc- 
tuations in  specific  fish  populations.  Unfortu- 
nately, the  tools  required  to  satisfy  this  need 
economically  are  lacking,  forcing  users  to  base 
decisions  on  inituition  and  often  biased  personal 
knowledge  and  resource  managers  to  formulate 
recommendations  based  on  historical  rather  than 
current  information.  In  response  to  this  need,  a 
number  of  relatively  new  technologies  are  being 
examined  by  the  National  Marine  Fisheries 


'Contribution  No.  246,  Southeast  Fisheries  Center,  Pascagoula 
Laboratory,  National  Marine  Fisheries  Service. 

^Formerly  Southeast  Fisheries  Center,  Pascagoula  Labo- 
ratory, National  Marine  Fisheries  Service,  NOAA,  Pascagoula, 
MS  39567;  present  address:  Office  of  Resource  Research,  Na- 
tional Marine  Fisheries  Service,  NOAA,  Washington,  DC  20235. 

^Southeast  Fisheries  Center,  Pascagoula  Laboratory,  Na- 
tional Marine  Fisheries  Service,  NOAA,  Pascagoula,  MS  39567. 


Service  and,  in  particular,  the  technologies  asso- 
ciated with  aerial  and  satellite  remote  sensing, 
to  determine  if  they  can  be  used  to  provide  perti- 
nent fisheries  resource  information. 

A  15-mo  study  was  initiated  in  July  1972  to 
demonstrate  the  potential  of  using  satellite- 
acquired  information  to  predict  the  distribution 
and  abundance  of  a  fishery  resource.  The  study 
represented  a  combined  Federal  Government  and 
private  industry  effort  and  stressed  acquisition 
of  data  to: 

1.  determine  the  reliability  of  satellite  and 
high-altitude  aircraft-supported  sensors  to 
provide  information  about  selected  oceano- 
graphic parameters  in  coastal  waters; 

2.  demonstrate  the  feasibility  of  using 
remotely-sensed  oceanographic  information 
to  predict  the  distribution  and  abundance  of 
a  selected  species; 

3.  demonstrate  the  potential  of  using 
satellite-acquired  information  for  improv- 
ing the  harvest  and  management  of  a  fishery 
resource  and; 

4.  identify  necessary  sensor  techniques  or  de- 
velopments to  satisfy  selected  needs  of  re- 
source users  and  managers. 

This  paper  presents  a  summary  of  selected 
results  from  the  experiment.  Earlier  publications 
dealing  with-  the  experiment  have  stressed  its 
management  (Stevenson,  Atwell,  and  Maughan, 


Manuscript  acceped  September  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  2,  1974 


375 


FISHERY   BULLETIN:  VOL.  72.  NO.   2 


1972),  relationships  between  selected  oceano- 
graphic  parameters  and  fish  distribution  and 
abundance  (Kemmerer  and  Benigno,  1973),  and 
commercial  fishing  operations  (Maughan,  Mar- 
melstein,  and  Temple,  1973). 


EXPERIMENTAL  RATIONALE 

With  existing  technology,  fish  cannot  be  de- 
tected directly  with  sensors  aboard  orbiting  satel- 
lites. It  may  be  feasible,  however,  to  use  satel- 
lite sensors  to  measure  selected  environmental 
parameters  and  then  to  use  these  parameters  to 
predict,  and  in  some  cases  even  forecast,  the  dis- 
tribution and  abundance  of  a  fish  species.  The 
quality  of  these  predictions  or  forecasts  would 
depend  on  how  accurately  the  parameters  are 
measured  with  the  sensors,  how  precisely  the 
parameters  correlate  with  the  distribution  of 
specific  fish  populations,  and  how  accurately  the 
values  were  predicted. 

The  rationale  employed  in  the  experiment  was 
to  convert  data  obtained  with  ERTS- 1  or  aircraft- 
supported  sensors  into  oceanographic  parameter 
information,  attempt  to  derive  correlations  be- 


tween these  parameters  and  the  distribution  and 
abundance  of  a  selected  fishery  resource,  and  then 
determine  if  the  relationships  have  meaning  for 
commercial  fishing  operations  and  resource  man- 
agement. Data  obtained  with  the  satellite  were 
supplemented  with  data  obtained  with  sensors 
aboard  aircraft  to  provide  a  broader  spectrum  of 
environmental  information.  In  addition,  a  mas- 
sive sea-truth  sampling  effort  was  undertaken  to 
provide  calibration  data  for  remote  sensors  and 
backup  information  for  correlation  analyses. 

STUDY  AREA  AND  FISHERY 

The  study  area  was  a  8,670-km  rectangle 
situated  in  the  north  central  portion  of  the  Gulf  of 
Mexico  (Figure  1).  It  included  coastal  areas  of 
Alabama,  Mississippi,  and  Louisiana  and  encom- 
passed all  of  the  Mississippi  Sound,  the  southern 
portion  of  Mobile  Bay,  and  extended  offshore  from 
the  Mississippi  Sound  to  approximately  the 
18-m  depth  curve.  The  study  area  is  divided  in 
half  lengthwise  by  five  barrier  islands  which 
isolate  the  typically  turbid,  low-salinity  waters  of 
the  Mississippi  Sound  from  the  relatively  much 
clearer  oceanic  waters  of  the  offshore  portion  of 


B 


D 


TEST  SITE  COORDINATES 


LATITUDE    LONGITUDE 


SCALE  1:875,000 


A)  30O27'N 

B)  30°27'N 

C)  30°00'N 

D)  SQOQO'N 


89°30'W 
87045'W 
87045'W 
89°30'W 


N.MI, 


10 


20 


TEST  SITE  DIMENSIONS 
LENGTH:   170  KM. 
WIDTH:   51  KM. 
AREA:   8670  SQ .  KM. 


KM. 


_L 


j_ 


_L 


J 


10   20    30   AO 


Figure  1. — ERTS-1  menhaden  experiment  study  area. 


376 


KEMMERER   ET  AL.;   ERTS-I   MENHADEN   EXPERIMENT 

the  study  area.  A  comprehensive  description  of 
the  area  is  given  by  Christmas  (1973). 

The  target  fish  species  for  the  study  was  the 
small  (mean  weight  about  85  g),  herringlike, 
surface-schooHng  Gulf  menhaden  (Brevoortia 
patronus).  These  fish  occur  along  the  Gulf  of 
Mexico  coast  and  are  considered  to  be  an  estua- 
rine-dependent  species.  They  are  used  com- 
mercially as  a  source  of  fish  meal,  oil,  and  con- 
densed soluble  proteins.  In  the  Mississippi  Sound, 
menhaden  are  fished  from  about  mid-April  to 
October  by  twin  purse  seine  boats  assisted  by 
spotter  pilots  flying  light  aircraft.  The  spotter 
pilots  direct  the  purse  boats  to  the  menhaden  and 
then  through  radios  notify  the  boat  captains  when 
to  encircle  a  school  with  their  purse  seine.  Once 
a  school  is  captured  and  concentrated  in  the  net, 
a  larger  mother  or  carrier  vessel  is  brought  along- 
side and  the  fish  are  pumped  into  the  hold  of  the 

ship. 

Menhaden  are  plankton  feeders  using  a  sieve- 
like branchial  apparatus  to  strain  plants  and 
animals  from  the  water  (Reintjes,  1969).  Their 
characteristic  schooling  behavior,  which  seems 
innate  from  late  larval  stage  to  old  age,  makes 
them  particularly  available  to  commercial 
fishing.  School  size  varies  from  about  25  to  in 
excess  of  2,000  m^  (surface  area)  and  averages 
about  125  m^.  Although  Gulf  menhaden  have  been 
the  subject  of  many  investigations  (Christmas 
and  Gunter,  1960;  Gunter  and  Christmas,  1960; 
Reintjes,  Christmas,  and  Collins,  1960;  and 
Rounsefell,  1954),  little  is  known  about  their 
distribution  in  relation  to  environmental  para- 
meters. 

DATA  ACQUISITION 

Data  acquisition  events  were  divided  into  four 
operations  categories:  main  day,  secondary  day, 
special  purpose,  and  commercial  fishing  oper- 
ations. Main  day  activities  occurred  at  or  near  the 
time  of  selected  ERTS-1  overpasses  (7  August, 
25  August,  and  28  September  1972)  and  included 
an  intensive  sea-truth  sampling  effort-up  to 
144  stations  were  occupied.  Only  a  few  sea-truth 
stations  were  occupied  during  secondary  day 
missions,  which  were  conducted  weekly,  weather 
permitting,  to  record  temporal  environmental  and 
fishery  changes.  Special  purpose  missions  were 
designed  to  satisfy  limited  objectives  and  as  such 
did  not  follow  set  schedules.  Oceanographic  and 
fisheries  data  were  obtained  from  one  to  three 


commercial  fishing  vessels,  usually  on  three  days 
of  each  week,  June  through  September  1972. 

ERTS-1  and  Aircraft 
Environmental  Sensors 

A  number  of  oceanographic  parameter  sensors 
were  used  during  the  experiment  from  NP3A 
(NASA)  and  D18  Beechcraft''  (NASA/ERL)  air- 
craft at  altitudes  ranging  from  610  to  7,620  m.  The 
sensors  included  a  RC  8  camera,  RS-14  scanner, 
PRT-5  radiation  thermometer.  KA  62  multiband 
camera,  Hasselblad  EL-500  cameras,  RS-18 
thermal  IR  scanner,  multifrequency  microwave 
radiometer,  and  an  Exotech  spectroradiometer. 
The  sensors  were  configured  to  measure  sea- 
surface  temperature,  water  color  as  a  function  of 
wavelength,  surface  current  patterns,  surface 
salinity,  and  surface  turbidity  patterns. 

The  ERTS-1  satellite,  launched  on  23  July 
1972,  operates  in  a  circular  sun-synchronous 
near  polar  orbit  at  an  altitude  of  915  km.  It  circles 
the  earth  every  103  min,  completing  14  orbits  per 
day  and  providing  repetitive  coverage  of  specific 
areas  every  18  d.  Two  consecutive  orbits,  24  h 
apart,  are  required  for  complete  coverage  of  the 
study  area. 

The  only  environmental  sensor  aboard  the  satel- 
lite operating  during  the  study  was  a  multispec- 
tral  scanner  (MSS)  which  provided  images  in  four 
discrete  portions  of  the  light  spectrum  (Freden, 
1972):  Band  4,  0.5-0.6  micron;  Band  5,  0.6-0.7 
micron;  Band  6,  0.7-0.8  micron;  and  Band  7,  0.8- 
1.1  microns. 

Sea-Truth  Oceanographic  Parameter 
Measurements 

Sea-truth  measurements  during  main  day  data 
acquisition  events  were  taken  from  25  research 
boats.  Because  two  orbits  24  h  apart  of  ERTS-1 
were  required  for  complete  coverage  of  the  study 
area,  only  about  half  of  these  measurements  coin- 
cided with  the  passage  of  the  satellite.  On  7  and 
25  August  1972,  coincidental  measurements  oc- 
curred for  the  western  portion  of  the  study  area, 
resulting  in  a  24-h  difference  for  measurements 
from  the  eastern  portion.  A  main  day  occurred  on 
28  September  1972,  which  did  not  correspond  to 


^Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


377 


FISHERY   BULLETIN;  VOL.  72.  NO.  2 


either  orbit  of  ERTS-1.  Orbits  instead  occurred 
on  the  29th  (eastern  portion)  and  30th  (western 
portion)  of  September  1972,  representing  24- 
and  48-h  differences,  respectively. 

The  25  research  boats  generally  occupied  95 
stations  in  the  Mississippi  Sound  and  46  stations 
in  the  offshore  portion  of  the  study  area.  These 
stations  were  spaced  to  provide  a  sampling  density 
of  about  one  station  per  29  km^  in  the  Sound  and 
one  station  per  60  km^  in  the  offshore  waters. 
Parameters  measured  included  surface  tempera- 
ture, salinity,  chlorophyll  a,  currents,  sea  state, 
water  color,  water  depth,  and  secchi  disc  trans- 
parency. Surface  water  temperature,  salinity, 
and  chlorophyll  a  measurements  were  obtained 
from  bucket  samples.  Temperature  was  deter- 
mined immediately  in  the  bucket,  and  poly- 
propylene bottles  were  used  to  store  samples  for 
chlorophyll  a  and  salinity  measurements  in  the 
laboratory.  Color  was  estimated  with  a  Forel- 
Ule  color  comparator  (Hutchinson,  1957),  and 
current  speed  and  direction  were  measured  by 
timed  drifts  of  neutrally  buoyant  floats. 

Fisheries  Data 

Aerial  photography  provided  most  of  the 
fisheries  distribution  and  abundance  information 
augmented  periodically  with  nighttime,  low- 
light-level  television  sensor  missions  and  com- 
mercial fish-spotter  pilot  reports.  Menhaden  are 
particularly  susceptible  to  aerial  sensing  tech- 
niques because  of  their  characteristic  surface  or 
near-surface  schooling  behavior.  Discussions  on 
aerial  photography  and  low-light-level  tele- 
vision sensing  of  fish  schools  have  been  pub- 
lished by  Bullis  (1967),  Benigno  (1970),  Drennan 
(1969),  and  Roithmayr  and  Wittman  (1972). 

Photographic  fish  sensing  missions  were  flown 
to  provide  95%  coverage  of  the  study  area  at  a 
scale  of  1:16,200.  The  camera  used  was  a  Zeiss 
RMK-1523  mapping  camera  with  a  15.24-cm 
focal  length  lens  and  22.86-cm  film  format.  The 
camera  was  supplied  with  GAF-1000  blue  insen- 
sitive (2575)  film,  selected  for  its  speed  and  re- 
ported ability  to  penetrate  the  hydrosphere  (Vary, 
1969).  Photographic  missions  were  divided  into 
morning  and  afternoon  flights  corresponding  to 
sun  angles  of  15  to  50  degrees,  with  morning 
flights  covering  the  Mississippi  Sound  and 
afternoon  flights  covering  the  offshore  section  of 
the  study  area.  A  Houston-Feerless  film  viewer. 


providing  magnifications  of  3  x  to  33  x ,  was  used 
to  aid  in  the  search  of  processed  film  for  imaged 
menhaden  schools.  Fish  school  locations  were 
recorded  according  to  latitude  and  longitude  with 
an  accuracy  of  ±0.4  km.  Menhaden  schools  could 
be  subjectively  differentiated  from  other  schooling 
species  in  the  study  area  on  the  basis  of  size,  shape, 
and  color. 

Commercial  Fishing  Data 

Fishery  and  oceanographic  parameter  measure- 
ments were  obtained  June  through  September 
1972  from  one  to  three  commercial  fishing  vessels. 
These  measurements  were  taken  at  the  time 
and  location  of  capture  or  attempted  capture  of 
a  menhaden  school.  Data  collected  included  sur- 
face water  temperature  and  salinity,  secchi 
disc  transparency,  Forel-Ule  color,  number  of 
fish  captured  (visual  estimate),  date,  time,  and 
location.  Usually,  these  observations  were 
made  the  first  three  days  of  each  fishing  week 
(Monday  through  Saturday)  except  during  periods 
when  an  ERTS-1  overpass  or  main  day  occurred, 
in  which  case  the  sampling  period  was  extended 
over  the  entire  fishing  week. 


DATA  ANALYSIS  AND 
INTERPRETATION 

General  Analytical  Rationale 
and  Data  Limitations 

Because  the  overall  success  of  the  experiment 
depended  upon  finding  relationships  between 
menhaden  distribution  and  abundance  and 
oceanographic  parameters,  the  logical  point  of 
departure  was  with  these  relationships.  Thus, 
impetus  initially  was  given  to  finding  relation- 
ships between  fish  distribution  and  abundance 
and  selected  oceanographic  parameters,  and  then 
to  determine  if  parameters  which  had  fisheries 
meaning  could  be  measured  remotely  with  suf- 
ficient accuracy  for  precise  correlation  analysis. 
The  last  step  in  the  analytical  rationale  was  to 
determine  what,  if  any,  uses  these  relationships 
might  have  for  commercial  fishing  and  resource 
management. 

The  principal  data  limitation  placed  on  early 
analyses  was  a  general  lack  of  remotely  acquired 
synoptic  oceanographic  parameter  measure- 
ments. The  conversion  of  remotely  acquired 


378 


KEMMERER   ET  AL  :   ERTS-1   MENHADEN   EXPERIMENT 


oceanographic  data  into  meaningful  information 
has  proceeded  slowly  because  of  interpretation  dif- 
ficulties. Thus,  reported  fisheries  oceano- 
graphiuc-parameter  relationship  analyses  de- 
pend primarily  upon  sea-truth  measurements. 
An  essential  exception  was  the  photographically 
acquired  menhaden  distribution  and  abundance 
information. 

Oceanographic  Parameter-Fish 
Distribution  Relationships 

Analysis 

The  distribution  and  abundance  of  menhaden 
in  the  study  area,  principally  in  the  Mississippi 
Sound,  can  be  placed  into  a  simplified  systems 
context  (Figure  2).  Factors  directly  affecting  the 
system,  i.e.,  the  distribution  and  abundance  of 
menhaden,  include  fish  input,  fish  output  (includ- 
ing harvest,  death,  and  emigration),  the  environ- 
ment, and  the  innate  behavior  of  the  menhaden 
not  directly  or  immediately  influenced  by  environ- 
mental conditions.  Examples  of  this  latter 
factor  include  fish  age  and  degree  of  sexual 
maturity.  This  systems  concept  can  be  modified 
slightly  and  expressed  as  an  algebraic  argument 
as: 

A,.y  =  f(E,B,P)  (1) 

where: 

A   =  number  of  menhaden  schools, 

X  and  y    =  refer  to  school  location  coordinates, 
E   =  environmental  conditions, 
B    =  innate  fish  behavior,  and 


Environmental 
Parameters 

Menhaden 

Input                    ^ 

Menhaden 
Distribution 

and 
Abundance 

Menhaden 
^         Output 

Innate  Menhaden 
Behavior 

P   =  instantaneous  menhaden  school 
population. 

The  problem  with  the  argument  is  that  the  de- 
pendent variable  A^.vis  a  function  of  more  than 
just  the  environment,  E,  and  as  such  cannot  be 
solved  with  available  information.  To  simplify  the 
expression,  two  assumptions  were  made.  First,  it 
was  assumed  that 5  was  constant  (i.e.,  the  innate 
behavior  of  the  menhaden  did  not  vary  signifi- 
cantly) and  thus  could  be  ignored  in  the  expres- 
sion, an  assumption  which  led  to  the  development 
of  a  new  expression  where  A^^y  became  a  function 
of  E  and  P  alone.  This  assumption  appeared 
reasonable  because  only  adult  menhaden  were 
considered  in  the  experiment  while  they  were 
in  the  Mississippi  Sound,  a  relatively  short  period 
of  time.  The  second  assumption  made  was  that 
A^,y  could  be  expressed  in  relative  terms  such 
that: 


'x,y 


=  f(E) 


(2) 


This  assumption  permitted  the  normalizing  of 
Ax,y  relative  to  P  and  has  its  roots  in  many  fisheries 
catch/effort  related  expressions. 

In  the  subsequent  analyses,  the  number  of 
photographically  detected  menhaden  schools 
at  any  given  point  was  used  as  an  estimator  of 
Ax,y,  and  the  total  number  of  detected  menhaden 
schools  was  used  as  an  estimator  of  P.  If  there  was 
a  constant  sensor-caused  bias  in  the  photography 
data,  the  quotient  Ax,y/P  should  not  be  affected 
seriously,  as  the  bias  cancels.  However,  if  the 
bias  was  not  constant  but  instead  was  a  variable 
function  of  the  environment,  then  the  bias 
would  affect  the  quotient.  Whether  or  not  the 
effect  would  be  significant  would  depend  on  the 
magnitude  and  variability  of  the  bias. 

Because  of  a  concern  about  the  possibility  of  bias 
affecting  the  relationships,  a  second  approach  also 
was  used  which  should  have  reduced  sensor  bias. 
A  new  dependent  variable,  D,  was  defined  which 
reflected  only  the  distribution  of  menhaden  and 
was  related  to  the  environment  as: 


D  =  f(E) 


(3) 


Figure  2. — Simplified  systems  view  of  the  Mississippi  Sound 
menhaden  population  described  only  in  terms  of  distribution  and 
abundance. 


Inherent  in  this  expression  is  the  assumption 
that  P  does  not  affect  the  distribution  of  menha- 
den within  the  extremes  of  P  characteristic  of  the 


379 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


menhaden  population  during  the  experiment. 
Neither  photographic  nor  commercial  fishing  data 
indicated  a  major  change  in  P  on  main  days,  which 
lends  credibility  to  this  assumption.  As  defined, 
D  can  have  two  possible  outcomes:  yes,  menha- 
den are  present  and  no,  menhaden  are  not  present. 
In  the  analysis,  areas  where  menhaden  were 
detected  were  assigned  a  value  of  1  and  areas 
where  fish  were  not  detected  were  assigned  a 
value  of  0.  Although/)  is  clearly  a  discontinuous 
dependent  variable,  the  statistical  techniques 
used  in  the  analyses  converted  it  into  a  continuous 
variable  ranging  from  about  0  to  1.  The  general 
interpretation  applied  to  predicted  values  is  that 
as  the  values  approached  1,  the  chance  of  finding 
fish  increased  proportionately. 

Regression  techniques  were  used  exclusively  to 
define  relationships  between  the  abundance  and/ 
or  distribution  of  menhaden  and  available 
measurements  of  oceanographic  parameters. 
Because  remotely  sensed  oceanographic  data 
were  not  available,  environmental  conditions 
where  fish  were  detected  had  to  be  interpolated 
and,  in  some  cases,  extrapolated  from  nearby 
sea-truth  sampling  stations.  This  procedure 
probably  introduced  experimental  error  into  the 
analyses  and,  as  such,  may  have  obscured  subtle 
relationships. 


Results 

Photographically  sensed  menhaden  distribution 
and  abundance  {A^JP)  and  distribution  (D)  in- 
formation were  regressed  against  available 


oceanographic  parameter  measurements  (Table 
1).  These  analyses  reflect  only  those  data  col- 
lected on  7  August,  25  August,  and  28  September 
1972  (i.e.,  main  days)  from  the  Mississippi  Sound 
portion  of  the  study  area.  Forel-Ule  color  data 
were  not  collected  on  7  August  1972;  consequently, 
color  analysis  was  limited  to  25  August  and  28 
September.  Clouds  and  cloud  shadow  obscured 
portions  of  the  Sound  on  25  August  and  28 
September;  these  areas  were  ignored  in  the 
analysis. 

In  general,  the  two  approaches,  i.e.,  relative 
abundance  and  distribution  dependent  vari- 
ables, gave  similar  results.  The  type  of  relation- 
ship, either  positive  or  negative,  was  the  same 
in  every  case.  Their  precision  varied,  how- 
ever, which  affected  level  of  significance.  Of  the 
two  approaches,  relationships  derived  using  dis- 
tribution as  the  dependent  variable  probably  are 
the  most  reliable.  Recent  work  has  shown  that 
there  may  have  been  a  variable  bias  associated 
with  the  photographic  sensor  system  used  to 
obtain  the  fisheries  data  (Benigno  and  Kem- 
merer,  1973).  The  bias  appeared  to  relate  to 
school  size  and  atmospheric  conditions  and  ap- 
parently affected  the  number  of  schools  detected 
more  than  where  they  were  detected. 

Assignment  of  biological  significance  to  these 
correlations  is  difficult  in  that  the  parameters  may 
be  serving  as  indices  of  unmeasured  parameters. 
In  other  words,  there  is  a  question  of  concomi- 
tance. Nevertheless,  there  does  appear  to  be 
support  for  the  distribution  significant  (^  90% 
confidence  level)  correlations  presented  in  Table 
1.  Menhaden  fishermen  frequently  are  frustrated 


Table  1. — Correlations  between  menhaden  relative  abundance  (Ax.yIP)  and 
distribution  (D)  estimates  and  selected  oceanographic  parameters  (E). 


Correlation 

coefficient  (r) 

Mean  conditions 
where  menhaden 

Degrees  of 

Relative 

Distribu- 

were detected 

Parameter 

freedom 

abundance 

tion 

(±95%  confidence  limit) 

Temperature  ("C) 

195 

0.009 

0.044 

29.75  (0.33) 

Salinity  (ppt) 

195 

-0.257*" 

-0.222*" 

25.53  (1.85) 

Chlorophyll  a  (mg/m^) 

195 

0.025 

0.119- 

5.61  (1.95) 

Current  speed  (cm/s) 

195 

-0.062 

0.027 

13,61  (5,50) 

Sea  state  (m) 

195 

-0.064 

-0.103 

0,25  (0,08) 

Forel— Ule  color  (units) 

113 

-0.256— 

-0.150- 

13,69  (1.21) 

Wafer  depth  (m) 

195 

-0.216— 

-0.404"- 

1.91  (0.47) 

Secchi  disc  trans- 

195 

-0.093 

-0.146" 

1.25(0.17) 

parency  (m) 

'  90%  significance  level 
'■  95%  significance  level 
*•  99%  significance  level 


380 


KEMMERER  ET  AL.:   ERTS-1   MENHADEN   EXPERIMENT 


in  attempts  to  capture  schools  because  the 
schools  often  inhabit  waters  too  shallow  for 
efficient  boat  and  net  operations  (negative 
correlation  associated  with  depth).  Spotter  pilots 
tend  to  concentrate  their  fish-searching  efforts 
on  turbid  waters  because  of  a  relatively  high 
frequency  of  fish  encounter  in  these  waters 
(negative  correlation  associated  with  secchi  disc 
transparency).  The  positive  correlation  associated 
with  chlorophyll  a  seems  reasonable  in  that 
menhaden  are  plankton  feeders.  Salinity  is  a 
questionable  concomitant  factor  although, 
because  these  fish  are  euryhaline  organisms  and 
inhabit  estuarine  waters  throughout  most  of 
their  lives,  a  preferred  association  with  waters  of 
low  salinity  seems  plausible  (negative  correlation 
associated  with  salinity).  Christmas  and  Gunter 
(1960)  reported  that  70%  of  the  catch  from  87 
sets  in  the  Mississippi  Sound  came  from  waters 
ranging  from  5  to  24  ppt  salinity,  suggesting  also 
a  menhaden  preference  for  low  salinity  waters. 
No  biological  significance  can  be  attached  directly 
to  Forel-Ule  color  (negative  correlation)  yet, 
although  this  color  may  manifest  water  trans- 
parency and  chlorophyll  content.  Correlation 
coefficients  between  Forel-Ule  color  and  secchi 
disc  transparency  and  chlorophyll  a  were  -0.404 
and  0.369,  respectively,  significant  at  the  99% 
confidence  level. 

The  lack  of  statistical  significance  for  several  of 
the  parameters  listed  in  Table  1  should  not 
necessarily  be  construed  as  meaning  that  no 
such  correlations  exist.  For  example,  surface 
water  temperature  was  relatively  constant 
spatially  throughout  the  study  period  and  there- 
fore its  effect,  if  any,  on  the  distribution  and  abun- 
dance of  menhaden  may  not  have  been  sufficient 
to  gain  statistical  significance.  In  the  long  run, 
however,  temperature  may  be  a  very  important 
parameter.  One  also  should  be  reminded  that  the 
correlations  were  developed  from  linear  expres- 
sions for  the  sake  of  statistical  tractability. 
The  correlations,  therefore,  may  not  factually 
represent  real  world  situations  where  most 
responses  probably  are  nonlinear. 

The  concern  over  a  possible  significant  sensor 
bias  in  the  menhaden  distribution  estimates 
prompted  attempts  to  substantiate  the  results 
through  other  approaches.  The  set  of  commercial 
fishing  data  which  included  measurements  of 
selected  oceanographic  parameters  provided  the 
only  avenue  through  which  substantiation  could 
be  accomplished.  However,  these  data  were  notice- 


ably biased  in  that  environmental  measurements 
were  obtained  only  from  areas  where  catches  were 
made  or  attempted.  In  addition,  the  boats  did  not 
fish  randomly  throughout  the  study  area;  rather, 
they  fished  according  to  fish  availability,  distance 
from  home  port  (minimized  to  reduce  operating 
expense),  day  of  the  week  (tendency  to  fish 
farther  from  home  port  as  the  fishing  week 
progressed),  and  water  depth  (usually  about  2  m 
for  efficient  boat  operation).  Nevertheless,  if 
caution  is  used  in  the  analysis,  the  data  can  be 
used  to  substantiate  some  of  the  results  gained 
through  photographic  sensing  of  the  menhaden 
stocks. 

In  the  classical  statistical  situation,  one  gener- 
ally attempts  to  differentiate  between  two  pre- 
sumably different  populations,  e.g.,  with  and 
without  menhaden.  As  noted  previously,  the 
principal  problem  with  the  commercial  fishing 
data  is  that  data  were  not  obtained  from  areas 
without  fish.  However,  if  the  assumption  is 
made  that  all  other  environmental  measurements 
collected  throughout  the  study  period  (main  and 
secondary  day  events)  were  taken  at  random  in 
terms  of  temporal  and  spatial  coverage,  then  it 
is  logical  to  assume  that  these  latter  measure- 
ments included  areas  with  and  without  menhaden. 
The  commercial  fishing  data  can  then  be  handled 
as  a  "with  fish"  subset  of  the  total  data  population, 
i.e.,  with  and  without  fish. 

The  difficulty  in  this  approach  is  that  differences 
are  difficult  to  demonstrate  with  a  high  level  of 
statistical  significance  because  the  subset  (with 
fish)  is  not  discrete  from  the  total  population 
(with  and  without  fish).  The  hypotheses  which  can 
be  tested  are  that  the  means  (x)  and  standard 
deviations  (s)  of  the  subset  and  total  population 
are  different,  resulting  in  the  following  four 
general  conditions  and  accompanying  conclusions: 

1.  Means  and  standard  deviation  are  not 
significantly  different;  conclusion:  fish  dis- 
tribution is  not  related  to  the  parameter 
tested. 

2.  Means  are  significantly  different  but  stan- 
dard deviations  are  not;  conclusion:  fish  dis- 
tribution is  related  to  the  parameter  tested. 

3.  Means  are  not  significantly  different  but 
standard  deviations  are;  conclusion:  fish  dis- 
tribution is  related  to  the  parameter  tested. 

4.  Means  and  standard  deviations  are  both 
significantly  different;  conclusion:  fish  dis- 
tribution is  related  to  the  parameter  tested. 


381 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


A  note  of  caution  should  accompany  the  conclu- 
sions, however.  They  are  valid  only  for  the  data 
collected  under  the  conditions  of  the  experiment, 
and  therefore  extrapolation  to  other  areas  or  to  the 
same  area  under  different  experimental  condi- 
tions might  not  be  valid. 

The  commercial  fishing  data  demonstrated  a 
Condition  4,  i.e.,  means  and  standard  deviations 
different  with  respect  to  water  depth,  salinity, 
Forel-Ule  color,  and  secchi  disc  transparency 
(Table  2).  Temperature  and  sea  state  were  not 
tested,  and  data  were  not  available  for  chlorophyll 
a  and  currents.  The  subset  of  fishing  data  included 
measurements  from  237  "fish  sets"  and  the  total 
population  of  oceanographic  conditions  included 
measurements  from  29  June,  30  June,  6  July,  7  Au- 
gust, 25  August,  and  28  September  1972.  For  each 
parameter,  a  negative  correlation  is  indicated  as 
the  mean  parameter  values  for  the  fishing  subsets 
were  significantly  less  than  the  mean  values  for 
the  total  parameter  populations.  The  lack  of  high 
significance  levels  for  mean  salinity  and 
Forel-Ule  color  value  differences  was  not  particu- 
larly surprising  in  that  the  subset  approach  tends 
to  preclude  such  significance.  In  any  case,  the  rela- 
tionships shown  in  Table  2  substantiate  those 
shown  in  Table  1. 

A  second  approach  was  used  to  substantiate  still 
further  the  correlations  formed  between  fish  dis- 
tribution and  salinity,  Forel-Ule  color,  secchi  disc 
transparency,  and  water  depth.  Mean  parameter 
values  for  conditions  where  menhaden  were 
photographically  detected  (Table  1)  were  com- 
pared with  similar  values  from  the  fishing  subset 
(Table  2).  None  of  these  values  were  significantly 
different  at  levels  down  to  80%  (^-test). 

In  summary,  water  depth,  secchi  disc  visibility 
depth,  surface  salinity,  and  Forel-Ule  color  were 
found  to  correlate  negatively  with  the  distribution 
of  menhaden.  Chlorophyll  a  correlated  positively 


with  fish  distribution,  although  independent  data 
were  not  available  with  which  to  corroborate  this 
relationship  as  in  the  case  of  the  other  four 
parameters. 

ERTS-  Imagery  and  Fish 
Distribution  Relationships 

Analysis 

The  only  complete  docket  of  quality  ERTS-1 
MSS  imagery  coincidental  with  main  day  acquisi- 
tion events  was  from  7  August  1972.  Band  5  imag- 
ery from  25  August  1972  was  of  poor  quality  and 
no  imagery  was  available  for  28  September  1972. 

The  four  MSS  bands  from  7  August  1972  were 
examined  to  determine  if  their  density  levels  re- 
lated to  fish  distribution.  Bands  6  and  7  did  not 
contain  any  readily  apparent  useful  density  de- 
tail. Band  4,  for  reasons  which  are  still  unclear, 
seemed  to  contain  too  much  density  detail.  Den- 
sity levels  in  Band  5,  however,  appeared  to  relate 
to  menhaden  distribution. 

Results 

Figure  3a  shows  a  portion  of  the  ERTS- 1  Band  5 
imagery  covering  the  western  portion  of  the  Mis- 
sissippi Sound  and  adjacent  offshore  waters  as 
displayed  on  a  I^S  DIGICOL  video  screen. 
Superimposed  on  the  image  are  locations  of  23 
photographically  detected  menhaden  schools. 
Water  imagery  densities  were  divided  into  two 
density  ranges  and  color-enhanced  (Figure  3b). 
All  menhaden  schools  were  found  to  lie  in  the  less 
dense  range,  enhanced  as  orange.  This  density 
range  was  further  reduced  by  slicing  it  to  the  nar- 
rowest range  possible  with  the  instrument.  All  of 
the  fish  schools  can  be  found  to  either  lie  in  or 
immediately  adjacent  to  this  range,  enhanced  as 


Table  2. — Comparison  of  total  parameter  populations  (with  and  without  fish)  and  fish 
parameter  population  subsets  (with  fish). 


Total 
population 


Fishing  subset 
population 


Level  of  signi- 
ficant difference 
(%)' 


Parameter 

n 

X 

s 

n 

X 

s 

X 

s 

Water  deptfi  (m) 

354 

3.41 

1.27 

237 

2.19 

1.17 

99 

90 

Seccfii  disc  trans- 

348 

1.45 

0.71 

237 

1.10 

032 

99 

99 

parency  (m) 

Salinity  (ppt) 

357 

26.30 

4.15 

237 

2585 

2.95 

80 

99 

Forel-Ule  color 

166 

14.16 

304 

237 

13.78 

2.44 

80 

99 

(units) 

'f-tests  for  differences  between  means  for  populations  witti  unequal  variances  and  F-tests  for 
differences  between  standard  deviations  (Ostle,  1963) 


382 


KEMMERER   ET  AL.:   ERTS-I   MENHADEN   EXPERIMENT 


383 


KEMMERER   ET  AL  :   ERTS-I   MENHADEN   EXPERIMENT 


orange  (Figure  3c).  The  10  tightly  grouped  school 
location  indicators  in  the  middle-left  portion  of 
the  image  overlie  a  small  orange  enhanced  area 
making  the  latter  difficult  to  see. 

Unfortunately,  the  lack  of  additional  data  to 
test  the  persistence  of  the  relationship  between 
menhaden  distribution  and  MSS  Band  5  imagery 
density  levels  precludes  any  but  the  most  tenta- 
tive of  conclusions.  However,  the  data  are  suffi- 
cient to  warrent  an  observation  that  the  imagery 
does  appear  to  contain  information  relating  to  the 
distribution  of  menhaden  schools. 

ERTS-1  Imagery  and  Oceanographic 
Parameter  Relationships 

Analysis 

An  analysis  was  performed  on  the  MSS  Band  5 
imagery  for  7  August  1972  to  determine  if  image 
densities  could  be  explained  based  on  oceano- 
graphic parameter  measurements.  An  isodensity 
tracing  was  made  of  that  portion  of  the  imagery 
covering  the  study  area  to  provide  quantitative 
relative  density  data.  The  tracing  was  not  particu- 
larly satisfactory  because  of  instrument  limita- 
tions which  caused  more  than  one  density  range 
to  be  represented  by  the  same  color  trace,  but 
accurate  enough  to  demonstrate  relationships. 

Results 

Water  depth,  secchi  depth  visibility,  and  the 
interaction  between  the  two  parameters  (formed 
by  their  product,  Mott,  1967)  were  regressed 
against  relative  image  densities.  Simple  correla- 
tions (r)  between  these  parameters  and  image 
density  were  0.56,  0.73,  and  0.69,  respectively, 
significant  at  the  99%  confidence  level.  A  slight 
improvement  in  precision  (r  =  0.77)  was  realized 
when  the  parameters  were  combined  through 
multiple  regression  (Table  3)  into  the  following 
equation: 

Image  Density  =  0.5776  +  0.0222B  +  0.0762T 

-0.00515T  (4) 

where: 
B  =  water  depth  in  meters, 
T=  secchi  disc  transparency  in  meters, 

BT  =  interaction  formed  as  the  product  of  B  and  T 

Of  the  parameters,  secchi  disc  transparency  was 


Table  3. — Analysis  of  variance  for  the  relationship  between 
ERTS-1  image  density  and  two  oceanographic  parameters. 


Degrees  of 

Mean 

F- 

Source  of  variation 

freedom 

square 

value 

Total 

47 

0.0051 

Regression  (secchi  disc  trans- 

3 

00469 

21.040*" 

parency,  water  depth,  and 

interaction) 

Error 

44 

0.0022 

the  most  important  one  in  the  equation  as  indi- 
cated by  the  relative  magnitude  of  the  coefficients 
and  the  simple  correlation  coefficients.  The  most 
meaningful  facet  of  this  analysis  is  that  the  two 
parameters  correlating  significantly  with  image 
density  levels  also  correlated  significantly  with 
menhaden  distribution  (Tables  2  and  3).  Thus,  it 
appears  that  the  apparent  correlation  between 
menhaden  distribution  and  Band  5  density  levels 
(Figure  3)  is  more  than  a  chance  occurrence  and 
can  be  explained  based  upon  secchi  disc  transpar- 
ency and  water  depth  measurements. 

PREDICTION  MODELS  FOR 

RESOURCE  MANAGEMENT 

AND  UTILIZATION 

A  potential  management  and  utilization  benefit 
from  this  experiment  is  identification  of  an  ap- 
proach through  which  remotely  sensed  environ- 
mental data  could  be  used  to  provide  distribution 
information  about  menhaden  stocks  in  the  study 
area.  This  information  could  be  used  to  reduce 
search  time  for  commercial  concentrations  of 
menhaden  by  fishermen  and  as  a  means  to  develop 
efficient  survey  designs  by  resource  managers. 
Ideally,  distribution  information  should  be  valid 
for  the  entire  Gulf  Coast  menhaden  fishery;  how- 
ever, this  ideal  case  cannot  be  supported  with  re- 
sults from  this  experiment  but  can  be  realized  only 
through  future  experiments  specifically  designed 
to  test  demonstrated  relationships  in  other  areas. 

Model  Development 

Demonstrated  menhaden  distribution- 
oceanographic  parameter  relationships  (Table  1) 
were  placed  into  a  context  potentially  useful  to 
commercial  fishermen  and  resource  managers. 
Multiple  regression  analysis  was  used  to  develop 
eight  empirical  models  to  predict  menhaden 
distribution  (D)  in  the  study  area  based  on 


385 


FISHERY   BULLETIN:  VOL.  72.  NO.   2 


four  oceanographic  parameters:  water  depth, 
secchi  disc  transparency,  Forel-Ule  color, 
and  salinity  (Table  4).  The  models  contain  selected 
2-factor  interactions  formed  as  products  between 
parameters  and  treated  as  additional  independent 
variables.  Interaction  selection  was  based  on 
whether  or  not  an  interaction  significantly  in- 
creased the  precision  of  the  estimate  0).  The 
models  were  constructed  from  data  collected  on 
main  days  (i.e.,  7  August,  25  August,  and  28  Sep- 
tember 1972)  and  are  presented  separately  and  in 
combination  and  with  and  without  the  inclusion  of 
color  as  an  independent  variable. 

Model  Testing  and  Interpretation 

The  models  were  tested  by  playing  them  with 
oceanographic  data  collected  during  commercial 
fishing  operations  and  main  day  sea-truth  station 
data  stratified  to  include  only  those  stations  where 
menhaden  were  not  detected  photographically 
(Figure  4).  Ideally,  model  products  for  fishing  data 
should  have  grouped  close  to  1,  and  products  for 
the  "without  fish"  sea-truth  stations  should  have 
grouped  close  to  0;  obviously,  this  type  of  grouping 
is  not  demonstrated  in  Figure  4,  indicating  a  gen- 
eral lack  of  accuracy  and  precision  in  the  models. 
Product  populations,  however,  are  significantly 


1-0  1,0 

MODEL  I'm:  DICTIONS 


4 


Figure  4. — Histogram  plots  of  "with  fish"  (shaded)  and  "with- 
out fish"  (unshaded)  model  products. 


Table  4. — Empirical  regression  models  which  predict  menhaden  distribution  (D)  in  the  ERTS-1  study  area. 

B  =  water  depth  (m)  S  =  salinity  (ppt) 

T  =  Secchi  disc  transparency  (m)       C  =  Forel-Ule  color  (units) 

BT,  BS,  ST,  CT,  and  CS  =  interactions  formed  as  the  products  of  the  respective  parameters. 


Model 

Signifi- 

Inclusive 

Standard 

correla- 

cance 

dates 

error 

tion  co- 

level 

Model 

(1972) 

n 

Regression  model 

of  D 

efficient 

(%) 

D1  7  Aug.  82         D      =    1.9959-0  06645+0  7453  7-0.68208- 

0.0233S7  -  0.01448  7  +  0  02308S 

D2  25  Aug  42         D      =    5.1537  -  0.1740S  -  0.91957  -  0.0371C  - 

0.43508  +  0.0502S7  -  0.12438  7  +  0.01958S 

D3  28  Sept.  73         D      =   2.3473  -  0  0934C  -  0.81178  -  0.0358S  7  - 

0.0007CS  +  0.0528C7  +  0.05168  7  +  0.02358S 

D4  7  and  25  124       D      =   2.4691  -  0  0855S  +  0.3948  7  -  0.64778  - 

Aug  0.0054S  7  -  0.04418  7  +  0.02238S 

D5  7  Aug   and  155        D      =    1.8559-0  05775  +  0,56047-0  69548- 

28  Sept.  0.0191S7  -  0.00798  7  +  0,023285 

D6  25  Aug   and  115       D      =2.9396-0.10245  +  0.15227-0  74868- 

28  Sept.  0.00265  7  -  0  05478  7  +  0  026885 

D7  25  Aug   and  115        D      =   3.6035  -  0.09875  -0  12497  -  0.0416C  - 

28  Sept  0.67178  +  0  00875  7  -  0  04418  7  +  0.023485 

D8  7  and  25  Aug.  197        D      =    2,3759-0  07975+0.3928  7-0.70518- 

and  28  Sept  0  00865  7  -  0  03268  7  +  0  024285 


0.2492 


0.3793 


0.2443 


0.3009 


02489 


0.596 


0.630 


0.409 


0.584 


0480 


0  3118  0.488 

0  3090  0  508 


99 


99 


90 


99 


99 


99 


99 


028560,515 


99 


386 


KEMMERER  ET  AL.:   ERTS- 1   MENHADEN   EXPERIMENT 


different  for  each  model  even  though  the  distribu- 
tions overlap  without  a  wide  margin  of  difference 
between  means  (Table  5). 

A  number  of  factors  probably  contributed  to  the 
failure  of  the  models  to  group  fishing  data  closer  to 
1.  It  should  be  pointed  out  first,  however,  that  no 
seasonally  caused  variation  in  products  was 
noted,  suggesting  that  the  nonparametric  group- 
ing was  caused  by  factors  prevalent  throughout 
the  June  through  September  commercial  fishing 
sampling  period.  One  of  these  factors  may  have 
been  the  effect  of  commercial  fishing  operations  on 
the  distribution  offish  as  evidenced  by  visual  ob- 
servations made  during  the  photographic  surveys 
of  the  study  area.  Menhaden  schools  frequently 
were  observed  being  chased  by  purse  boats 
through  waters  of  varying  visual  qualities  (i.e., 
turbidity).  In  addition,  oceanographic  parameter 
measurements  generally  were  taken  from  the 
mother  vessel  rather  than  the  purse  boats,  which 
often  was  several  kilometers  distant  from  the  ac- 
tual site  offish  capture.  Another  of  these  factors  is 
that  there  is  no  biological  reason  to  suspect 
menhaden  distribution  to  be  wholly  a  determinis- 
tic function  of  environmental  conditions;  rather, 
there  most  likely  is  a  probability  associated  with 
how  and  where  fish  are  distributed  in  response  to 
these  conditions.  Also,  there  were  errors  as- 
sociated with  all  of  the  parameter  measurements 
used  to  develop  and  test  the  models  as  well  as  a 
distinct  possibility  that  other  parameters  having 
a  direct  influence  on  menhaden  distribution  might 
not  have  been  measured  (e.g.,  zooplankton 
biomass,  presence  or  absence  of  predators,  oxygen 
tensions,  etc.).  And  finally,  there  is  the  linear  ad- 
ditive nature  of  the  models  which  at  best  probably 
only  approximates  the  real  world  situation. 


Selection  of  a  best  model  was  difficult  in  that 
they  all  provide  similar  products.  On  the  basis  of 
sample  size,  number  of  parameters  (minimum), 
and  difference  between  means  (Table  5),  Model  D8 
would  have  to  be  given  selection  priority,  how- 
ever. 

A  number  of  interpretations  and  presentation 
methods  can  be  applied  to  model  products  as  long 
as  they  recognize  the  imprecision  of  the  models. 
An  example  of  one  method  applied  to  Model  D8,  for 
7  August  1972  sea-truth  data,  is  presented  in 
Figure  5.  The  categorization  of  model  products 
was  done  by  dividing  the  values  shown  in  Figure  4 
for  Model  D8  into  three  ranges  based  upon  a  direct 
comparison  of  fishing  and  nonfishing  histograms: 


high  potential  =  >  0.2 

moderate  potential      =  -1.0  to  0.2 
low  potential  =  <-1.0 

The  interpretation  applied  to  high,  moderate,  and 
low  potential  areas  is  related  to  relative  probabil- 
ity. In  high  potential  areas,  the  probability  offish 
capture  is  higher  than  in  moderate  or  low  poten- 
tial areas  and  higher  in  moderate  than  in  low 
potential  areas.  Incomplete  commercial  fishing 
reports  from  7  August  1972  indicate  that  most,  if 
not  all,  fishing  occurred  in  the  high  potential 
areas. 

An  additional  analysis  was  performed  on  the 
commercial  fishing  data  to  determine  if  relation- 
ships could  be  demonstrated  between  catch  size 
and  the  four  oceanographic  parameters  which 
made  up  the  models.  Catch  size  ranged  from  5  to 
225  and  averaged  about  38  thousand  fish.  Catch 


Table  5. — Tests  of  empirical  models  played  with  oceanographic  data  taken  near  sites  of 
commercial  fish  capture  (with  fish)  and  during  main  day  events,  the  latter  stratified  to  include 
only  those  areas  where  fish  were  not  detected  photographically  (without  fish). 


With  fish 

Without  fish 

Sig 
for 

niflcance  level 
difference  be- 

Model 

n 

D 

C.V.(%)' 

n 

D 

C.V.(%)' 

tween  means  {%f 

D1 

225 

0.202 

86 

165 

0071 

147 

99 

D2 

225 

0.371 

78 

94 

0.100 

187 

99 

D3 

225 

0.146 

184 

94 

-0.115 

132 

99 

D4 

225 

0.305 

67 

165 

0.139 

80 

99 

D5 

225 

0.175 

106 

165 

-0.017 

755 

99 

D6 

225 

0  288 

79 

165 

0089 

165 

99 

D7 

225 

0338 

70 

94 

0093 

151 

99 

D8 

225 

0.145 

163 

165 

-0,111 

160 

99 

'Coefficient  of  variation. 

'r-test  for  populations  with  unequal  variances  (Ostle,  1963). 


387 


FISHERY   BULLETIN;  VOL.   72,  NO.   2 


89°00'W 


88°30'W 


30°30'N 


30°20'N 


30°10'N 


X 


X 


a.  < 
< 

CD 

< 


BAY  ST.  LOUIS 


...   .  BILOXI  •■      OCEAN 


;"< 


SPRINGS.     .PASCAGOULaJ     V 


HIGH  POTENTIAL  AREA 


30°00'N  -^ **»«,>'<« flX)  ^ 


[        I  MODERATE  POTENTIAL  AREA 


LOW  POTENTIAL  AREA 


i 


Figure  5. — Model  D8  predictions  for  menhaden  distribution  in  the  Mississippi  Sound  on  7  August  1972,  between 

0900-1500  h  (CDT)  (based  on  95  sea-truth  measurements). 


size  was  divided  into  three  categories:  0-50, 
50-100,  and  more  than  100  thousand  fish,  and  an 
analysis  of  variance  applied  to  the  categories  to 
test  for  differences  between  mean  parameter  con- 
ditions. No  significant  differences  were  found  be- 
tween catch  size  and  salinity,  Forel-Ule  color,  and 
depth  parameters  at  significance  levels  down  to 
50%.  However,  a  significant  difference  at  95%  was 
found  between  the  first  and  third  catch  size  cate- 
gory for  averaged  secchi  disc  transparency  values 


(T 


0-50K 


=  1.09  m  and  T 


>100K 


=  1.32  m).  This  sig- 


nificance probably  does  not  have  biological  mean- 
ing, however.  It  probably  reflects  changes  in  the 
ability  of  fishermen  to  selectively  detect  and 
capture  fish  schools  with  respect  to  water  clarity. 

SUMMARY  AND  CONCLUSIONS 

The  feasibility  of  using  satellite-supported  en- 
vironmental sensors  to  predict  fish  distribution 
was  demonstrated.  ERTS-1,  MSS  Band  5  imagery 
was  shown  to  contain  density  levels  which  corre- 
lated with  menhaden  distribution.  These  density 
levels  were  further  shown  to  correlate  signifi- 
cantly with  sea-truth  measurements  of  secchi 
disc  transparency  and  water  depth,  two  pa- 
rameters which  also  correlated  significantly 
with  menhaden  distribution.  Additionally,  sur- 


face salinity,  Forel-Ule  color,  and  chlorophyll  a 
were  found  to  correlate  significantly  with  menha- 
den distribution.  Independent  tests  of  four 
oceanographic  parameter-menhaden  distribu- 
tion relationships  with  oceanographic  informa- 
tion taken  at  or  near  sites  of  commercial  menha- 
den captures  corroborated  these  relationships. 
The  correlation  between  chlorophyll  a  and 
menhaden  distribution  could  not  be  substantiated 
because  of  insufficient  data. 

Eight  empirical  regression  models  which  pre- 
dict menhaden  distribution  in  the  study  area  were 
constructed  from  combinations  of  four  oceano- 
graphic parameters:  water  depth,  secchi  disc  trans- 
parency, surface  salinity,  and  Forel-Ule  color.  Al- 
though the  models  did  not  provide  particularly 
precise  predictions  about  menhaden  distributions, 
their  predictions  nevertheless  were  statistically 
significant.  The  importance  of  the  models  is  that 
they  demonstrate  a  potential  means  or  direction 
through  which  remotely  sensed  oceanographic  in- 
formation can  be  used  to  provide  menhaden  dis- 
tribution information  on  a  real-time  basis.  This 
information  could  be  used  by  the  commercial  in- 
dustry to  reduce  spotter-pilot  search  time  by  iden- 
tifying likely  areas  for  concentrations  of  menha- 
den and  by  resource  managers  as  an  aid  in  plan- 
ning assessment  surveys. 


388 


KEMMERER  ET  AL.:   ERTSI   MENHADEN   EXPERIMENT 

ACKNOWLEDGMENTS 

The  authors  wish  to  express  their  sincere  ap- 
preciation to  Kenneth  J.  Savastano,  Fisheries  En- 
gineering Laboratory,  Mississippi  Test  Facihty 
(MTF),  for  his  programming  help  in  many  of  the 
analyses;  the  Earth  Resources  Laboratory 
(NASA),  also  at  MTF,  for  the  use  of  their  painstak- 
ingly acquired  oceanographic  data;  and  Earth 
Satellite  Corporation  for  the  use  of  their  commer- 
cial fishing  data.  This  research  was  supported  in 
part  through  NASA  Project  240. 


LITERATURE  CITED 


Benigno,  J.  A. 

1970.  Fish  detection  through  aerial  surveillance.  Tech. 
Conf.  on  Fish  Finding,  Purse  Seining,  and  Aimed  Trawl- 
ing; Reykjavik,  May  1970.  FAO  (Food  Agric.  Organ., 
U.N.),  FII:FF  70  78;  13  p. 
Benigno,  J.  A.,  and  A.  J.  Kemmerer. 

1973.  Aerial  photographic  sensing  of  pelagic  fish  schools:  A 
comparison  of  two  films.  Preprint  of  the  American  Society 
of  Photogrammetry,  American  Congress  on  Surveying 
and  Mapping,  and  National  Convention  and  Symposium 
on  Remote  Sensing  and  Oceanography,  Orlando,  Fla., 
Oct.  2-5,  1973. 
BuLLis,  H.  R.,  Jr. 

1967.  A  program  to  develop  aerial  photo-technology  for  as- 
sessment of  surface  fish  schools.  Proc.  Gulf  Caribb.  Fish. 
Inst.,  20th  Annu.  Sess.,  p.  40-43. 
Christmas,  J.  Y. 

1973.  Cooperative  Gulf  of  Mexico  estuarine  inventory  and 
study,  Mississippi.  Phase  I  Area  Description.  Spec.  Rep.  to 
the  Mississippi  Conservation  Commission  (Gulf  Coast 
Research  Laboratory,  Ocean  Springs,  Miss.),  450  p. 
Christmas,  J.  Y.,  and  G.  Gunter. 

1960.  Distribution  of  menhaden,  genus  Brevoortia,  in  the 
Gulf  of  Mexico.  Trans.  Am.  Fish.  Soc.  89:338-343. 
Drennan,  K.  L. 

1969.  Fishery  oceanography  from  space.  Proc.  6th  Space 
Congr.  Space  Tech.  Soc.  Canaveral  Counc.  Tech.  Soc, 
Cocoa  Beach,  Fla.,  p.  9.1-9.6. 
Freden,  S.  C. 

1973.  Introduction:  Performance  of  sensors  and  systems. /n 
W.  A.  Finch,  Jr.  (editor).  Earth  Resource  Technology 
Satellite-1,  Symposium  proceedings,  p.  1-6.  Goddard 
Space  Flight  Center,  Greenbelt,  Md. 


Gunter,  G.,  and  J.  Y.  Christmas. 

1960.  A  review  of  literature  on  menhaden  with  special  re- 
ference to  the  Gulf  of  Mexico  menhaden,  Brevoortia  pa- 
tronus  Goode.  U.S.  Fish.  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish. 
363,  31  p. 
Hutchinson,  G.  E. 

1957.  A  treatise  on  limnology.  Vol.  I,  Geography,  physics, 
and  chemistry.  John  Wiley  &  Sons,  N.Y.,  1015  p. 
Kemmerer,  A.  J.,  and  J.  A.  Benigno. 

1973.  Relationships  between  remotely  sensed  fisheries  dis- 
tribution information  and  selected  oceanographic 
parameters  in  the  Mississippi  Sound.  Symposium  of 
Significant  Results  Obtained  from  ERTS-1,  Goddard 
Space  Flight  Center,  Greenbelt,  Md.,  NASA,  Mar.  5-9, 
1973. 
Maughan,  p.  M.,  a.  D.  Marmelstein,  and  O.  R.  Temple. 

1973.  Application  of  ERTS-1  imagery  to  the  harvest  model 
of  the  U.S.  menhaden  fishery.  Symposium  of  Significant 
Results  Obtained  from  ERTS-1,  Goddard  Space  Flight 
Center,  Greenbelt,  Md.,  NASA,  Mar.  5-9,  1973. 
MoTT,  D.  G. 

1966.  The  analysis  of  determination  in  population  systems. 
In  K.  E.  F.  Watt  (editor),  Systems  analyses  in  ecology,  p. 
179-194.  Academic  Press,  N.Y. 

OSTLE,  B. 

1963.  Statistics  in  research.  [2d  ed.],  Iowa  State  Univ.  Press, 
Ames. 
Reintjes,  J.  W. 

1969.  Synopsis  of  biological  data  on  the  Atlantic  menhaden, 
Brevoortia  tyrannus.  FAO  (Food  Agric.  Organ.  U.N.) 
Species  Synopsis  No.  42.  (Available  U.S.  Fish  Wildl. 
Serv.,  Circ.  320,  30  p.) 
Reintjes,  J.  W.,  J.  Y.  Christmas,  Jr.,  and  R.  A.  Collins. 

1960.  Annotated  bibliography  on  biology  of  American 
menhaden.  U.S.  Fish  Wildl.  Serv.,  Fish.  Bull.  60:297-322. 
Roithmayr,  C.  M.,  and  F.  P.  Wittman. 

1972.  Low  light  level  sensor  development  for  marine  re- 
source assessment.  Preprints,  8th  Annu.  Conf  Expo., 
Mar.  Tech.  Soc,  Sept.  11-13,  1972,  Wash.,  D.C.,  p. 
277-288. 

ROUNSEFELL,  G.  A. 

1954.  Biology  of  the  commercial  fishes  of  the  Gulf  of  Mexico. 

U.S.  Fish  Wildl.  Serv.,  Fish.  Bull.  55:507-512. 
Stevenson,  W.  H.,  B.  H.  Atwell,  and  P.  M.  Maughan. 

1972.  Application  of  ERTS-1  for  fishery  resource  assessment 

and  harvest.  Eighth  International  Symposium  on  Remote 

Sensing  of  the  Environment.  Willow  Run  Lab.,  Ann 

Arbor,  Mich.,  Oct.  2-6,  1972. 
Vary,  W.  E. 

1969.  A  new  non-blue  sensitive  aerial  color  film.  Seminar 

Proceedings— New  Horizons  in  Color  Aerial  Photography; 

American  Society  of  Photogrammetry  and  Society  of 

Photographic  Scientists  and  Engineers,  June  9-11,  1969, 

p.  127-130. 


389 


ROLE  OF  LARVAL  STAGES  IN  SYSTEMATIC  INVESTIGATIONS 
OF  MARINE  TELEOSTS:  THE  MYCTOPHIDAE,  A  CASE  STUDY^ 


H.  Geoffrey  Moser  and  Elbert  H.  Ahlstrom^ 


ABSTRACT 

The  lanternfish  family  Myctophidae  is  the  most  speciose  and  widespread  family  of  mid- water  fishes  in 
the  world  ocean.  As  presently  recognized  it  contains  about  30  genera  and  300  nominal  species.  Their 
larvae  are  highly  prominent  in  the  plankton  and  make  up  about  50%  of  all  larvae  taken  in  open-ocean 
plankton  tows. 

Our  studies  of  myctophid  larvae,  on  a  worldwide  basis,  have  demonstrated  that  characters  of  the 
larval  stages  of  lanternfishes  are  of  great  utility  in  systematic  analysis.  The  genera  and  species  can  be 
recognized  on  the  basis  of  eye  and  body  shape,  the  shape  and  length  of  the  gut,  and  pigment  pattern  and 
by  the  sequence  of  photophore  development.  In  this  paper  the  larvae  of  55  species  representing  24 
genera  are  illustrated  and  used  to  demonstrate  the  usefulness  of  larvae  in  understanding  the  relation- 
ships of  species  within  genera. 

Characters  of  the  larvae  provide  insight  into  generic  affinities  of  lanternfish,  allowing  us  to  construct 
an  evolutionary  scheme  of  tribes  and  subfamilies  that  differs  in  some  aspects  from  those  proposed  on 
the  basis  of  adult  characters.  The  concept  of  using  larval  characters  in  combination  with  adult 
characters  to  delineate  phylogenetic  lines  in  myctophids  is  discussed,  as  is  our  view  of  evolutionary 
strategy  in  the  family. 


A  major  facet  of  comprehensive  systematic  inves- 
tigations is  the  search  for  functionally  unrelated 
characters.  Whether  the  independence  of  these 
characters  is  actual  or  merely  apparent,  they  con- 
stitute useful  elements  in  the  analysis  of  systema- 
tic relationships.  Ample  evidence  of  this  is  the 
higher  classification  of  teleosts  (Greenwood  et  al., 
1966)  generated  by  the  synthesis  of  a  diverse 
array  of  classical  taxonomic  characters.  The  re- 
cent surge  of  serological  and  biochemical  studies 
on  fish  has  placed  a  fresh  group  of  characters  in  the 
hands  of  systematic  ichthyologists  (De  Ligny, 
1969).  Likewise,  recent  advances  in  fish  cytogene- 
tics (e.g.,  Ohno,  1970;  Benirschke  and  Hsu,  1971; 
Ebeiing,  Atkin,  and  Setzer,  1971)  are  providing 
another  group  of  taxonomic  characters.  It  is  likely 
that  behavioral  science  will  be  still  another  source 
of  taxonomic  characters,  as  exemplified  by  the 
growing  body  of  information  on  the  acoustic  be- 
havior of  fishes  (Fish  and  Mowbray,  1970). 

One  group  of  well  known  taxonomic  characters, 
those  of  the  embryonic  and  larval  stages,  has  re- 
ceived scant  attention  from  all  but  a  few  systema- 
tic ichthyologists.  Characters  of  the  larvae  have 


'This  paper  was  presented  at  the  International  Symposium  on 
the  Early  Life  History  of  Fish  (sponsored  by  lABO,  FAO,  ICES, 
ICNAF,  and  SCOR)  held  at  Oban,  Scotland,  17-23  May  1973. 

^Southwest  Fisheries  Center,  National  Marine  Fisheries  Ser- 
vice, NOAA,  La  Jolla,  CA  92037. 


Manuscript  accepted  Agust  1973. 

FISHERY  BULLETIN:  VOL.  72,  NO.  2,  1974. 


played  a  large  role  in  the  taxonomy  of  anguil- 
liform  fishes  (Castle,  1969)  partly  because  of  the 
conspicuousness  of  eel  leptocephali  and  partly  be- 
cause of  the  unavailability  of  adults  of  many  of  the 
families.  Bertelsen's  (1951)  treatment  of  the 
ceratioid  fishes  is  a  superb  example  of  the  value  of 
utilizing  larval  stages  in  a  systematic  revision  of  a 
large  group  of  teleosts.  Apart  from  these  two 
groups,  it  is  the  larvae  of  myctophiform  fishes 
which  have  received  the  most  attention  from  tax- 
onomists.  Ege  (1953,  1957)  relied  heavily  on  lar- 
val stages  in  his  extensive  works  on  the 
Paralepididae.  Johnson  (1971)  employed  larval 
characters  in  defining  species  and  genera  of 
Scopelarchidae.  Bertelsen,  Marshall,  and  Krefft 
(pers.  commun.)  have  used  larval  stages  exten- 
sively in  their  revision  of  the  Scopelosauridae. 
Our  studies  on  the  family  Myctophidae  itself 
(Moser  and  Ahlstrom,  1970,  1972)  indicated  that 
larval  characters  can  aid  significantly  in  differen- 
tiating taxa  and  defining  evolutionary  lineages 
within  this  family. 

The  lanternfish  family  Myctophidae  is  the  most 
speciose  and  widespread  family  of  mid-water 
fishes  in  the  world  ocean.  As  presently  recognized 
it  contains  about  30  genera  and  300  nominal 
species.  Their  larvae  are  highly  prominent  in  the 
plankton  and  make  up  about  50%  of  all  larvae 
taken  in  open-ocean  plankton  tows. 


391 


FISHERY   BULLETIN:   VOL.  72.  NO.  2 


Our  studies  of  the  larvae  of  this  family  have 
included  material  from  all  oceans.  We  have  been 
able  to  identify  larvae  from  all  recognized  genera 
except  Hintonia  and  Dorsadena.  Larval  evidence 
supports  giving  generic  status  to  Metelectrona  and 
Parvilux.  Including  these,  we  have  developmental 
series  for  29  myctophid  genera  and  for  many  gen- 
era we  have  series  for  all  known  species.  This  has 
afforded  a  more  comprehensive  view  of  the  range 
and  variability  of  larval  characters,  and  we  are 
increasingly  impressed  with  the  functional  inde- 
pendence of  the  larval  and  adult  characters.  It  is 
apparent  that  the  world  of  the  larvae  and  the 
world  of  the  adults  are  two  quite  separate 
evolutionary  theaters.  Our  studies  of  larval 
lanternfishes  have  disclosed  a  full  range  of  charac- 
ters, from  generalized  to  specialized  and  from  con- 
servative to  labile,  equal  in  scope  to  those  of  the 
adults.  These  characters  fall  into  several 
categories.  An  important  group  is  the  shape  of 
various  structures  such  as  the  eye,  head,  trunk, 
guts,  and  fins,  especially  the  pectoral  fins.  Another 
group  is  the  sequence  of  appearance  and  the  posi- 
tion of  fins,  photophores,  and  bony  elements. 
Another  is  the  size  of  the  larvae  when  fins  and 
other  features  appear  and  the  size  of  the  larvae 
when  they  transform  into  juveniles.  Pigmentation 
provides  an  important  group  of  characters  based 
on  the  position,  number,  and  shape  of  melano- 
phores.  Finally,  there  are  the  highly  special- 
ized larval  characters  such  as  voluminous  fin 
folds,  elongated  and  modified  fin  rays,  chin  bar- 
bels, preopercular  spines,  etc.  It  is  our  purpose 
here  to  point  out  some  of  these  characters  and 
demonstrate  how  they  can  be  of  advantage  in 
defining  taxa  and  establishing  phylogenetic 
lineages. 

THE  SUBFAMILY  MYCTOPHINAE 

The  most  trenchant  character  of  larval  myc- 
tophids  is  eye  shape.  Our  studies  show  that 
lanternfish  larvae  fall  naturally  into  two  groups 
on  the  basis  of  eye  shape — those  with  narrow  ellip- 
tical eyes  and  those  with  round  or  nearly  round 
eyes  (Moser  and  Ahlstrom,  1970).  The  species 
composition  of  these  two  groups  agrees  closely 
with  that  of  the  two  subfamilies,  Myctophinae  and 
Lampanyctinae,  established  by  Paxton  (1972)  on 
the  basis  of  osteological  and  photophore  charac- 
ters of  adults.  Larvae  of  the  Myctophinae  have 
elliptical  eyes;  some  species  have  ventral  pro- 


longations of  choroid  tissue  and  some  have  the 
eyes  on  stalks.  Paxton  recognized  11  genera  in 
the  subfamily  Myctophinae  and  distributed  them 
into  two  tribes,  the  Myctophini  and  the  Gonich- 
thyini.  Larvae  of  the  species  in  each  of  these 
genera  generally  conform  to  a  particular  morph 
based  on  form,  pigment,  and  developmental 
pattern  and,  although  these  morphs  are  remark- 
ably diverse,  we  can  find  no  character  or  set  of 
characters  that  would  divide  the  genera  into 
tribes.  Within  each  genus  of  the  subfamily,  how- 
ever, the  larval  characters  are  indispensible  in 
delineating  groups  of  related  species  or  subgenera. 
This  is  best  illustrated  by  examining  the  impor- 
tant genera  of  the  Myctophinae. 

Protomyctophum  larvae  have  a  slender  shape 
(Figure  1).  For  all  species  exceptP.  anderssoni,  the 
gut  is  short  during  most  of  the  larval  period  and 
characteristically  there  is  a  marked  interspace 
between  the  anus  and  the  origin  of  the  anal  fin 
(Figure  lA-D).  The  gut  elongates  dramatically  in 
late  larvae,  to  fill  the  interspace.  Gut  development 
is  completely  dissimilar  in  P.  anderssoni,  where 
the  gut  is  long  at  all  larval  sizes,  in  fact  longer 
than  in  most  other  lanternfish  larvae  (Figure  IE). 
Series  of  ventral  tail  melanophores  are  formed  in 
some  species  of  both  recognized  subgenera 
(Heirops  and  Protomyctophum  sensu  stricto),  for 
example  in  P.  Protomyctophum  normani  (Figure 
lA)  and  P.  Heirops  thompsoni  (Moser  and  Ahl- 
strom, 1970).  Larvae  of  the  subgenera  can  be  sepa- 
rated, however,  on  the  basis  of  eye  shape,  the  eyes 
of  Heirops  (Figure  IC,  D)  being  characteristically 
narrower  than  those  of  Protomyctophum  sensu 
stricto  (Figure  lA,  B).  Choroid  tissue  is  absent 
from  the  ventral  surface  of  the  eye  in  all  species  of 
the  genus  except  P.  anderssoni,  which  has  a  well- 
developed  "teardrop"  (Figure  IE).  Larvae  of  P. 
anderssoni  are  so  markedly  different  from  those  of 
all  other  species  of  Protomyctophum,  which 
otherwise  form  a  rather  cohesive  group,  that  this 
species  should  be  placed  in  a  separate  subgenus  or 
perhaps  even  in  a  distinct  genus.  This  suggestion 
is  supported  by  the  unique  placement  of  certain 
photophores  and  by  the  structure  of  the  sup- 
racaudal  luminous  tissue  in  adults  of  this  species. 

Larvae  of  the  genus  Electrona  are  a  less 
homogeneous  group  but  are  united  by  a  common- 
ality of  body  shape  and  especially  gut  shape  (Fig- 
ure 2).  A  marked  interspace  is  present  between 
the  end  of  the  gut  and  the  origin  of  the  anal  fin. 
This  space  is  closed  only  at  the  termination  of  the 


392 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


-■n  -^i.  t^  ^t  ^  ^  9   *  ■*   *  * 


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Figure  1. — Larvae  of  Protomyctophum.  A.  P.  Protomyctophum  normani.  15.2  mm;  B.P.  Protomyctophum  teni- 
soni,  l4.5mm;C. P. Hieropssubparallelum,  15.2mm;D. P. Hieropschilensis.  11.0mm;E.P.  anderssoni,  15.7  mm. 


393 


FISHERY   BULLETIN:   VOL.   72,  NO.  2 


/T? 


i 


''■'""?™i*-4i'l 


■m:»- 


-  -A 


Figure  2.— Larvae  of  Electrona  and  Metelectrona.  A.  E.  antarctica,  12.7  mm;  B.  E.  carlsbergi,  11.1  mm;  C.  E. 

subaspera,  10.5  mm;  D.  M.  ahlstromi,  10.3  mm. 


394 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEM ATICS 

larval  period.  None  of  the  species  forms  photo- 
phores  during  the  larval  period  other  than  the  Br2 
pair. 

The  characters  that  most  clearly  separate  the 
three  developmental  lines  in  Electrona  are  eye 
shape  and  the  amount  of  choroid  tissue  developed 
under  the  eye.  Electrona  antarctica  has  an  elon- 
gate choroid  mass  uniquely  divided  into  two  nar- 
row eyes  (Figure  2A).  Also,  E.  antarctica  larvae 
attain  a  large  size  (20  mm),  are  the  deepest-bodied 
oiaWElectrona  larvae,  and  have  the  heaviest  pig- 
mentation. The  two  species  in  the  second  de- 
velopmental line  transform  at  a  small  size  (ca.  10 
mm  in  E.  rissoi  and  12-13  mm  in  £■.  carlsbergi), 
have  a  small  choroid  mass  under  a  moderately 
narrow  eye,  and  develop  scant  pigment  (Figure 
2B).  In  the  third  line,  consisting  of  £.  subaspera 
and  E.  paucirastra,  the  eye  is  the  least  narrow, 
has  no  choroid  tissue,  and  the  larvae  attain  a  large 
size  (20  mm)  (Figure  2C). 

The  larva  of  the  species  described  as  Metelec- 
trona  ahlstromi  (Wisner,  1963)  is  illustrated  in 
Figure  2D.  It  is  more  laterally  compressed  than 
any  species  of  Electrona  and  has  no  interspace 
between  the  anus  and  origin  of  the  anal  fin.  In 
some  features  it  resembles  the  larvae  of 
Hygophum;  it  has  a  late-forming  dorsal  fin  and  the 
gut  is  shaped  very  similarly  to  that  inH.  taaningi 
and  H.  macrochir.  Its  pigment  is  unique  and  the 
eye  is  distinct,  with  the  ventral  edge  of  the  scleral 
envelope  characteristically  squared  off.  Also,  in 
late-stage  larvae,  in  addition  to  the  Br2,  a  second 
pair  of  photophores  (PO5)  develops,  a  feature 
found  in  neither  Hygophum  nor  Electrona.  Paxton 
(1972)  synonymized  Metelectrona  with  Electrona 
and  suggested  that  M.  ahlstromi  andE.  ventralis 


are  synonyms,  however,  the  uniqueness  of  the 
larva  strongly  suggests  the  resurrection  of 
Metelectrona  as  a  valid  genus. 

The  genus  Benthosema  is  the  least  cohesive  of 
any  genus  in  the  subfamily  Myctophinae,  from  the 
viewpoint  of  larval  structure  (Figure  3).  We  can 
find  only  four  types  of  larvae  in  the  world  ocean, 
although  Nafpaktitis  (1973)  recognizes  five 
species  on  adult  characters.  We  cannot  distin- 
guish larvae  of  B.  pterota  and  B.  panamense 
although  Nafpaktitis  has  listed  a  number  of  con- 
vincing characters  that  distinguish  the  adults  of 
the  two  species.  We  find  two  highly  divergent 
species  pairs.  One  is  composed  of  B.  glaciale  and 
B.  suborbitale  with  a  narrow  eye  subtended  by  a 
lunate  choroid  mass  and  with  a  pronounced  inter- 
space between  the  anus  and  the  anal  fin  origin, 
reminiscent  of  Protomyctophum  and  Electrona 
(Figure  3A-C).  In  the  other  pair,  consisting  of  B. 
panamense-pterota  and  B.  fibulatum,  the  eye  is 
wider,  is  subtended  by  a  mere  sliver  of  choroid 
tissue  and  the  gut,  of  moderate  length,  lacks  a 
postanal  interspace  (Figure  3D,  E). 

The  one  feature  held  in  common  by  the  four 
species  is  the  development  of  some  photophores  in 
addition  to  the  Bra  during  the  larval  period.  The 
only  other  myctophine  genera  that  develop  photo- 
phores in  addition  to  the  ubiquitous  Br2  during  the 
larval  period  are  Diogenichthys,  Myctophum, 
and  Metelectrona.  This  feature  is  much  more  pre- 
valent among  genera  of  the  Lampanyctinae  and  is 
helpful  in  defining  groups  of  related  genera  there 
(Moser  and  Ahlstrom,  1972). 

In  B.  panamense-pterota  and  B.  fibulatum  the 
Dn  pair  is  formed  soon  after  the  Br2  at  about 
5.0-6.0  mm.  The  PO5  pair  is  the  third  to  appear  in 


Table  1. — Sequence  of  photophore  formation  in  larvae  of  three  species  oi Benthosema . 


Size 

No.  of 

Smallest 

larva 

photophore 

juvenile 

Species 

(mm 

) 

Photophores 

pairs 

(mm) 

B.  fibulatum 

ca.  4.0 

Br2 

1 

13.2 

5.4 

Bra 

Dn 

2 

6.0 

Bra 

Dn  PO5 

3 

6.4 

Br2 

Dn  PCs  POt 

4 

7.3 

Br2 

Dn  PO5  POi  AOai 

5 

7.7-8.7 

Br2 

Dn  PO5  PO1  AOai  PO2 

6 

ca.  10.0 

Br2 

Dn  PCs  PO1  AOai  PO2  Op2  VLO 

8 

B.  pterota 

(panamense) 

40 

Br2 

1 

11.8 

5.0 

Br2 

Dn 

2 

60 

Br2 

Dn  PO5 

3 

ca.  7  0 

Br2 

Dn  PO5  PVO1 

4 

7.1 

Br2 

Dn  PO5  PVO,  Op2 

5 

7.5 

Br2 

Dn  PO5  PVO,  Op2  VO1  PVO2 

7 

8.0 

Br2 

Dn  PO5  PVO,  Op2  VO,  PVO2  PO1 

AOai 

9 

B.  suborbitale 

4.1 

Br2 

1 

10.7 

8.3-9.2 

Br2 

PO1  PO2 

3 

9.4 

Br2 

PO,  PO2  Br,  Br3  Op2 

6 

11.5 

Br2 

PO1  PO2  Bri  Br3  Op2  PO3  PO4  PO- 

AOai 

A0a2          11 

395 


FISHERY   BULLETIN:   VOL.  72,  NO.  2 


Figure  3.— Larvae  of  Benthosema.  A.  B.  glaciale,  7.2  mm;  B.  B.  glaciate.  10.5  mm;  C.  B.  suborbitale,  9.2 

mm;  D.  B.  pterota,  8.5  mm;  E.  B.  fibulatuni,  8.7  mm. 


396 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


larvae  about  6.0  mm  long.  Thereafter  the  pattern 
diverges  as  shown  in  Table  1,  but  both  species 
gradually  add  about  a  dozen  pairs  during  the  lar- 
val period.  Specimens  of  B.  pterota  from  the  Per- 
sian Gulf  off  India,  formed  photophores  at  some- 
what larger  sizes  than  larvae  of  B.  panamense, 
but  in  the  same  sequence.  Transformation  occurs 
at  a  small  size,  10-12  mm  in  B .  panamense-pterota 
and  11-13  mm  inB.  fibulatum. 

Photophores  appear  relatively  late  in  larvae  of 
B.  suborbitale  and  S.  glaciale.  however,  the  Bri, 
Br2,  Op2,  and  PO  series  appear  in  late  larvae  of 
both  species  (Table  1).  Transformation  occurs  at 
about  9-11  mm  in  both  species.  The  larvae  of  5. 
panamense-pterota  and  B.  fibulatum  are  close  to 
the  larvae  of  Diogenichthys  in  several  characters 
including  body  shape,  gut  shape,  and  early  ap- 
pearance of  photophores. 

As  in  Benthosema,  the  larval  characters  of 
Hygophum  suggest  some  divergence  within  the 
genus,  although  all  species  have  a  highly  charac- 
teristic series  of  isthmal  melanophores,  form  the 
dorsal  fin  late  in  the  larval  period,  and  develop  no 
photophores  other  than  the  Br2,  as  larvae  (Figure 
4).  The  genus  contains  three  divergent  types  of 
larvae.  The  most  unusual  of  these  are  the  ex- 
tremely elongate  larvae  of//,  reinhardti  and//. 
atratum,  which  have  very  narrow  eyes  that  are 
underlain  by  prominent  choroid  tissue  and  are 
borne  on  short  stalks  (Figure  4A).  The  amount  of 
pigmentation  along  the  gut  and  tail  and  on  the 
myosepta  and  fin  fold  increases  throughout  the 
larval  period. 

A  second  larval  type  is  represented  by  the 
largest  number  of  species,  H.  proximum,  H. 
hygomi,  and  //.  brunni,  all  illustrated  (Figure 
4B-D),  as  well  as  H.  benoiti,  H.  hanseni,  and  an 
undescribed  form  in  our  collection.  These  larvae 
are  only  moderately  slender  and  have  unstalked 
eyes  of  moderate  width,  subtended  by  prominent 
choroid  tissue.  Melanophores  are  located  chiefly 
on  the  head  and  gut,  however  some  species  have 
pigment  on  the  myosepta  and  fin  fold.  The  trend  in 
this  group  of  species  is  for  the  early  larval  stages 
to  have  the  heaviest  pigment  and  for  melano- 
phores to  be  lost  as  development  proceeds. 

A  third  type  of  larva  is  exhibited  by  H.  mac- 
rochir,  H.  taaningi,  and  an  undescribed  form  in 
our  collection  (Figure  4E,  F).  These  are  relatively 
deep-bodied,  have  large,  relatively  wide  eyes  with 
little  or  no  choroid  tissue,  and  lack  tail  pigment. 
Also,  the  gut  has  a  highly  distinctive  form;  the 
anterior  half  has  a  very  small  diameter  and  opens 


dorsally  into  a  prominent  enlarged  posterior  sec- 
tion. In  H.  macrochir  this  enlarged  section  is 
covered  with  large  melanophores.  Larvae  of  this 
group  occur  only  in  the  Atlantic. 

The  genus  Hygophum  affords  an  excellent  ex- 
ample of  the  taxonomic  utility  of  larval  stages. 
The  juveniles  and  adults  of  some  species  are 
notoriously  difficult  to  identify.  In  contrast,  the 
larvae  of  these  species  are  highly  distinct  and  can 
be  readily  identified.  We  have  11  such  distinct 
larval  types,  whereas  only  9  species  are  currently 
known  for  the  adults.  Search  for  adults  of  the  two 
remaining  larval  types  has  led  to  the  discovery  of 
two  undescribed  species.  In  addition,  characters  of 
the  adults  of  this  genus  reveal  little  about  the 
relationships  of  the  member  species  (Becker, 
1965).  A  study  of  the  larvae,  however,  shows  that 
there  are  three  highly  distinct  subgeneric  groups, 
each  containing  from  two  to  six  closely  related 
species.  Such  an  independent  view  of  the  complete 
species  complement  of  a  genus  is  an  invaluable 
tool  in  the  formal  revision  of  that  genus. 

Larvae  of  the  species  of  Symbolophorus  are 
perhaps  the  most  cohesive  of  all  myctophine  gen- 
era (Figure  5A).  In  all  species  known  to  us  the 
pectoral  fin  is  large  and  is  supported  by  an  elon- 
gate aliform  base.  Also,  the  pelvic  fins  are  large 
and  develop  earlier  than  in  any  other  lanternfish 
genus.  The  narrow  eyes  have  choroid  tissue  and 
are  borne  on  short  stalks.  The  amount  of  pigmen- 
tation decreases  towards  the  end  of  the  larval 
period.  Most  species  attain  a  large  size — up  to  24 
mm.  The  species  differ  principally  in  the  size  at 
which  various  larval  structures  appear. 

The  closely  related  genus,  Myctophum,  has  a 
diversity  of  larval  form  unmatched  in  the  family 
(Figures  5,  6,  7).  Before  taking  up  the  bulk  of  the 
species  in  this  genus  we  must  first  examine  the 
most  aberrant  of  all  lanternfish  larvae,  that  of  M. 
aurolaternatum  (Figure  5B).  In  this  remarkable 
larva  the  eyes  are  borne  on  long  stalks  and  the  free 
trailing  section  of  the  gut  is  almost  as  long  as  the 
fish  itself.  The  dorsal  fin  forms  at  the  margin  of  the 
fin  fold.  These  characters  are  so  bizarre  that  it 
would  seem  preposterous  to  identify  it  as  a 
lanternfish  larva,  much  less  that  of  M.  aurolater- 
natum. Nonetheless,  A.  Vedel  Taning  first  sug- 
gested the  true  identity  of  this  larva  (E.  Bertelsen, 
pers.  commun.)  which  we  can  now  confirm  since 
recently  receiving  the  critical  transforming 
specimens  through  the  courtesy  of  Warren 
Freihofer  (California  Academy  of  Science).  The 
uniqueness  of  this  larva  would  certainly  suggest 


397 


FISHERY   BULLETIN:   VOL.  72.  NO.  2 


^^"^^ 


Figure  4.— Larvae  oiHygophum.  A.  H.  reinhardti,  12.8  mm;  B.  H.  proximum,  8.9  mm;  C.  H.  hygomi.  8.1 
mm;  D.  H.  brunni,  9.7  mm;  E.  H.  macrochir.  7.3  mm;  F.  H.  taaningi,  6.8  mm. 


398 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


r-ni^^^^^^^s 


>^^/^l^^ 


Figure  5. — Larvae  of  Symbolophorus  and  Myctophum.  A.  S.  calif orniense,  9.6  mm;  B.  M.  aurolater- 
natum,  26.0  mm;  C.  M.  punctatum,  13.6  mm;  D.  M.  nitidulum,  8.2  mm;  E.  M.  phengodes,  9.8  mm. 


399 


the  creation  of  a  distinct  genus  for  M.  aurolater- 
natum  and  it  is  highly  probable  that  corroborative 
characters  will  appear  after  careful  reexamina- 
tion of  the  adults. 

With  the  removal  of  M.  aurolaternatum ,  the  re- 
maining larvae  o^Myctophum  form  a  diverse,  yet 
recognizable,  group.  All  have  large  broad  pectoral 
fins  supported  on  a  highly  characteristic  fan- 
shaped  base.  The  species  may  be  divided  into  two 
groups,  those  which  form  only  the  Br2  photophores 
and  those  which  develop  additional  photophores 
during  the  larval  period.  In  the  first  group  the 
elongate  larva  of  M.  punctatum  (Figure  5C)  has 
stalked  eyes  and  a  slightly  aliform  pectoral  fin 
base,  reminiscent  of  Symbolophorus  larvae,  and 
may  be  the  closest  relative  of  that  genus  among 
the  species  of  Myctophum.  A  closely  related 
species,  M.  nitidulum,  is  also  stalk-eyed,  but  is 
deeper-bodied,  more  heavily  pigmented,  and  has  a 
more  fan-shaped  pectoral  fin  base  (Figure  5D).  It  is 
obvious  from  our  studies  thatM.  nitidulum  is  one 
member  of  a  complex,  that  includes  M.  affine  (not 
illustrated)  and  several  other  species.  The  lightly 
pigmented  larva  of  M.  phengodes  has  only  a  sug- 
gestion of  stalked  eyes  but  is  similar  in  body  shape 
toM.  nitidulum  (Figure  5E).  The  larval  characters 
substantiate  Paxton's  (1972)  decision  to  abolish 
the  genus  Ctenoscopelus,  established  for  this 
species  by  Fraser-Brunner  (1949). 

The  other  major  group  of  Myctophum  is  charac- 
terized by  the  appearance  of  the  Dn  photophore 
anterior  to  the  eye,  usually  early  in  the  larval 
period.  These  species  fall  into  three  rather  distinct 
species  groups  on  the  basis  of  body  and  eye  shape. 
The  first  is  a  group  of  four  rotund  broad-headed 
species,  which  have  large  unstalked  eyes  sub- 
tended by  a  short  mass  of  choroid  tissue.  Of  these, 
the  larvae  of  M.  asperum  are  the  most  heavily 
pigmented,  particularly  on  the  body  (Figure  6A). 
Pigment  is  confined  to  the  head  in  M.  obtusirostre, 
is  heavy  under  the  posterior  part  of  the  gut  in 


FISHERY   BULLETIN;   VOL.  72.  NO.  2 

Myctophum  sp.  (possibly  brachygnathum)  and  is 
developed  on  the  jaws,  branchistegal  membrane 
and  lower  part  of  the  pectoral  fin  base  in  Myc- 
tophum sp.  (possibly /issKnoui)  as  seen  in  Figure 
6B-D.  The  latter  three  species  form  the  PLO 
photophores  on  the  pectoral  fin  base  soon  after  the 
appearance  of  the  Dn  organs  (Table  2). 

Nafpaktitis  (1973)  has  listed  a  number  of 
characters  for  distinguishing  adult  M.  ob- 
tusirostre from  M.  brachygnathum.  He  showed 
that  M.  pristilepis  is  a  synonym  of  M.  brachyg- 
nathum. The  status  of  M.  imperceptum  Bekker 
and  Borodulina  has  yet  to  be  determined. 

A  second  larval  type  is  represented  by  M. 
selenops  (Figure  7A)  and  a  closely  related  species 
restricted  to  the  Indian  Ocean  and  Persian  Gulf 
for  which  we  can  find  no  adult  (Figure  7B).  In 
these  rotund  species,  the  head  is  relatively  longer 
and  narrower  than  in  the  previous  group  and  the 
slightly  stalked  eyes  are  narrower  and  bear  more 
elongate  choroid  tissue.  The  two  species  differ  in 
that  the  eyes  of  the  unnamed  larva  are  more 
definitely  stalked  than  in  M.  selenops.  Also  the 
pigment  pattern  is  markedly  different,  as  is  the 
size  at  which  photophores  appear.  We  have  care- 
fully examined  larvae  of  M.  selenops  from  the  At- 
lantic, Indian,  and  Pacific  Oceans,  find  them  to  be 
identical  in  all  three  oceans,  and  seriously  ques- 
tion Wisner's  (1971)  allocation  of  the  Hawaiian 
population  as  a  distinct  species,  based  on  slight 
differences  in  relative  eye  size  and  SAO  photo- 
phore orientation. 

The  third  type  of  larvae  that  develop  the  Dn 
photophores  is  represented  by  M.  spinosum 
(Figure  7C)  andM.  lychnobium  (Figure  7D).  These 
are  elongate  fusiform  larvae  with  moderately  nar- 
row unstalked  eyes,  underlain  by  a  pronounced 
choroid  mass.  M.  spinosum  is  the  more  slender  of 
the  two  and  is  extremely  heavily  pigmented,  espe- 
cially in  older  larvae.  Pigmentation  in  M.  lych- 
nobium is  confined  to  that  in  the  illustrated 


Table  2. — Sequence  of  photophore  formation  in  species  oCMyctophum  that  form  two  or  more  pairs 

during  the  larval  stage. 


Size  range 

Size 

at  first  to 

rmation 

Size  at 

Species 

(mm) 

(mm) 

transformation 

Br; 

Dn 

PLO 

PO, 

(mm) 

M.  asperum 

ca.  3.0-9.8 

42 

4.6 

9.8 

_ 

Early  transf.  1 1.4 

M.  obtusirostre 

ca.  3.0-8.9 

3.8 

4.0 

ca.  7.1 

8.9 

Late  transf.  12.5 

M.  sp.  (possibly 

fissunovi) 

ca.  3.0-7.1 

4.1 

4.1 

7.1 

— 



M.  sp.  (possibly 

brachygnathum) 

6.0-11.4 

6.0 

6.0 

ca.  9.0 

ca.  9.0 

Late  transf.  13.8 

M.  lychnobium 

3.5-12.1 

ca 

60 

6.3 

12.1 

— 

Late  transf.  14.2 

M.  spinosum 

3.5-13.7 

ca 

5.5 

7.2 

13.7 

— 

Late  transf.  14.5 

M.  selenops 

3.5-7.5 

5.1 

5.1 

6.2 

7.5 

Late  transf.  11.4 

M.  sp. 

40-9  1 

ca 

70 

9  1 

— 

— 

— 

400 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


^=^^^m^-m 


f.i:i'.-''- 


^■-^^ii^^ 


^*^i^.: 


Figure  6.— Larvae  of  Myctophum.  A.  M.  asperum,  6.8  mm;  B.  M.  obtusirostre ,  7.6  mm;  C.  M.  sp. 
(possibly  brachygnathum),  7.5  mm;  D.  M.  sp.  ipossihiy  fissunovi),  7.4  mm. 


401 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


^^^:; 


^■^^';n> 


))  n_)  //in)  ■! . ;  J , ,, 


-■— J^  '  ■"* 


ir^zh-L^ 


Figure  7. — Larvae  oi Myctophum.  A.  M.  selenops.  7.8  mm;  B.  M.  sp.,  9.1  mm;  C.  M.  spinosum,  9.0  mm; 

D.  M.  lychnobium,  9.5  mm. 


402 


MOSER  and  AHl.STROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


specimen.  Only  larvae  of  M.  lychnobium  have 
been  taken  in  the  eastern  Pacific,  whereas  both 
species  have  been  taken  in  the  central  and  west- 
ern Pacific  and  in  the  Indian  Ocean.  Taxonomists 
dealing  with  adult  characters  only,  have  placed  M. 
lychnobium  in  synonymy  with  M.  spinosum  but 
the  distinctiveness  of  the  larvae  suggests  that  the 
adult  characters  should  be  reexamined. 

The  larvae  ofM.  spinosum  andM.  lychnobium, 
although  clearly  developing  the  Dn  pair  of  photo- 
phores,  resemble  the  larvae  of  M.  punctatum  in 
body  shape  and  pigmentation,  a  species  which 
does  not  develop  the  Dn  as  larvae.  Actually,  there 
are  some  common  characters  of  pigmentation  and 
eye  structure  which  appear  in  all  of  the  groups  of 
Myctophum  species  described  above.  What  we  ap- 
pear to  be  dealing  with  is  a  mosaic  of  larval 
characters  in  a  highly  complex  genus.  The  tax- 
onomy of  Myctophum  presently  is  confused;  our 
work  on  the  larvae  should  help  define  the  number 
of  species  in  the  genus  and,  perhaps,  adult  charac- 
ters will  emerge  that  can  be  combined  with  larval 
characters  to  define  the  phyletic  lines  within  the 
genus. 

Larvae  of  the  four  genera  known  collectively  as 
the  slendertailed  myctophids  are  shown  in  Figure 
8.  Quite  obviously  there  are  two  highly  divergent 
generic  pairs.  Loweina  and  Tarletonbeania  are 
characterized  by  large  oval  eyes,  posterior  place- 
ment of  median  fins  to  accommodate  the  immense 
fin  fold,  and  elongated  lower  pectoral  rays  bearing 
spatulate  processes.  Gonichthys  and  Centrobran- 
chus  are  characterized  by  a  deep  but  markedly 
compressed  head  and  body  and  small  narrow  eyes 
with  extremely  elongate  choroid  tissue.  As  stated 
earlier,  the  larval  characters  suggest  strongly 
that  the  two  generic  pairs  are  not  closely  related 
and  should  not  be  grouped  into  a  tribe.  The 
Gonichthys-Centrobranchus  pair  is  similar  in  eye 
shape  and  gut  shape  to  some  species  of  Myc- 
tophum, however  no  species  o{  Myctophum  even 
approaches  this  pair  in  body  shape.  The  characters 
of  the  other  pair  are  so  divergent  as  to  give  no 
clue  of  their  affinities  within  the  subfamily 
Myctophinae. 

THE  SUBFAMILY 
LAMPANYCTINAE 

The  subfamily  Lampanyctinae  is  considerably 
larger  than  the  Myctophinae;  it  contains  about  19 
genera  and  200-250  species  compared  with  12 


genera  and  about  75  species  in  the  Myctophinae. 
Paxton  (1972)  divided  the  genera  into  four  tribes 
on  the  basis  of  a  combination  of  osteological  fea- 
tures and  characters  of  the  photophores.  In  a  pre- 
vious paper  (Moser  and  Ahlstrom,  1972)  we  dis- 
cussed Paxton's  placement  of  genera  in  these 
tribes  and  indicated  that  the  larval  characters 
suggested  a  somewhat  different  distribution  of 
genera  among  the  four  tribes.  For  the  purposes  of 
this  discussion  the  tribes  referred  to  here  are  those 
suggested  by  the  larval  characters. 

In  general,  the  larvae  of  the  Lampanyctinae  are 
much  less  diverse  in  larval  characters  and 
specializations  than  are  the  larvae  of  the  Myc- 
tophinae, although  exceptions  to  this  may  be 
found  in  two  of  the  lampanyctine  tribes,  the 
Diaphini  and  the  Lampanyctini. 

The  tribe  Diaphini  is  made  up  of  two  genera 
— Diaphus  contains  about  50  species  and  Lobian- 
chia  has  3  species.  Both  genera  develop  photo- 
phores, in  addition  to  the  Br2,  during  the  larval 
period;  in  fact  more  are  developed  in  Diaphus 
than  in  any  other  lanternfish  genus. 

There  are  two  basic  larval  types  in  Diaphus 
(Figure  9A,  B).  One  has  a  slender  body,  small 
head,  and  a  series  of  persistent  melanophores  on 
the  ventral  midline  of  the  tail.  The  other  type  has 
a  deeper  body,  bulbous  head,  and  a  single  persis- 
tent ventral  tail  melanophore,  or  none.  It  is  excep- 
tional for  larvae  of  either  type  to  develop  pigment 
on  the  head  and  it  never  occurs  between  the  eyes, 
as  is  common  in  Lampanyctus.  Both  types  do  form 
embedded  melanophores  at  the  base  of  the  caudal 
fin  rays. 

The  slender  type  is  restricted  to  the  species  that 
develop  a  suborbital  photophore  as  adults 
[Diaphus  sensu  stricto  of  Fraser-Brunner,  1949) 
and  is  represented  in  Figure  9A  by  D.  theta.  The 
stubby  type  is  represented  by  D.  pacificus  (Figure 
9B).  The  specimens  illustrated  for  the  two  species 
are  rather  early  larval  stages  which  have  not  yet 
formed  their  larval  photophores,  other  than  the 
Br2.  The  first  additional  pair  to  form  in  both  types 
is  the  PO5  and  then  the  POi  (Table  3).  The  large 
genus  Diaphus,  except  for  the  Atlantic  species 
ably  reviewed  by  Nafpaktitis  (1968),  is  in  a  state  of 
taxonomic  confusion.  Various  workers  (Fraser- 
Brunner,  1949;  Bolin,  1959)  have  attempted  to 
split  the  genus  into  smaller,  more  cohesive  groups; 
the  larval  evidence  would  suggest  that  at  least  two 
divergent  groups  are  present. 

The  larvae  of  the  three  species  ofLobianchia  are 


403 


FISHERY    BULLETIN:   VOL.  72.  NO.  2 


1 


Figure  8.— Larvae  of  Gonichthyini.  A.  Loweina  rara,  17.6  mm;  B.  Tarletonbeania 
crenularis,  18.9  mm;  C.  Gonichthys  tenuiculus.  7.7  mm;  D.  Centrobranchus 
choerocephalus,  7.3  mm. 


404 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


J*=P^£ 


Figure  9. — Larvae  ofDiaphus  and  Lobianchia.  A.  D.  theta,  6.9  mm;  B.  D.  pacificus,  5.2  mm; 
C.  L.  urolampus,  7.2  mm;  D.  L.  gemellari,  6.7  mm;  E.  L.  dofleini,  8.2  mm. 


405 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 
Table  3. — Sequence  of  photophore  formation  in  larvae  of  two  species  of  Diaphus. 


Species 


Size 
larva 

(mm) 


Photophores 


No.  of 

photophore 

pairs 


Smallest 

luvenile 

(mm) 


D.  theta 

6-2 

Bra  PO5 

2 

ca.  12.0 

7.6 

Br2  PO5  PO, 

3 

8.2 

Br2  PO5  PO1  VO1 

4 

8.6 
9.0 

Br2  PO5  PO1  VO,  PO2  Op2 

Br2  PCs  PO1  VOi  VO,  PO2  Op2  PO3  PO4  VO5 

6 
9 

9.2 

Br2  PCs  PO1  VOi  PO2  Op2  PO3  PO4  VO5  VLO 

10 

D.  pacificus 

5.7 
6.2 
6.5 

7.5 

Br2  PCs  PO. 

Br2  PO5  PO1  PO2  PVO1 

Br2  PO5  PO,  PO2  PVO,  PO3 

Br2  PO;  PO,  PO2  PVO,  PO3  VO, 

3 
5 
6 

7 

9.8 

deep-bodied,  have  large  broad  heads,  and  are  eas- 
ily identified  by  their  unique  wing-shaped  pec- 
toral fins  (Figure  9C-E).  The  larvae  of  all  three 
species  are  heavily  pigmented  and  develop  the 
Br2,  POi ,  and  PO5  photophores  sequentially.  In  L. 
urolampus  (Figure  9C)  and  L.  gemellari  (Figure 
9D)  the  eyes  are  large  and  nearly  round  and  the 
lower  pectoral  rays  are  delayed  in  developing.  In 
L.  dofleini  the  lower  pectoral  rays  develop  along 
with  the  produced  upper  rays  and  the  eye  is  com- 
pletely different  (Figure  9E).  With  its  narrow  el- 
liptical shape  and  unique  squarish  mass  of  choroid 
tissue,  it  is  the  single  obvious  exception  to  the  rule 
of  narrow  eyes  in  the  subfamily  Myctophinae  and 
rounded  eyes  in  the  Lampanyctinae.  All  other  lar- 
val characters  identify  this  species  as  a  Lobian- 
chia,  and  we  conclude  that  the  narrowing  of  the 
eye  in  this  species  occurred  independently  as  a 
secondary  adaptation. 

In  our  view  the  tribe  Lampanyctini  contains  the 
genera  Lampanyctus,  Triphoturus,  Steno- 
brachius,  and  Paruilux.  As  recently  as  Fraser- 
Brunner's  (1949)  review  of  the  family  Myc- 
toi)hidae,  Lampanyctus  was  still  a  catchall  genus 
with  a  number  of  disparate  subgenera.  Since  then 
the  subgenera  Stenobrachius,  Triphoturus,  and 
Lepidophanes  have  been  removed  from  Lam- 
panyctus and  afforded  generic  status.  Lepido- 
phanes has  been  further  split  into  the  genera 
Lepidophanes  and  Bolinichthys.  All  of  the 
separated  genera  have  distinctive  larval  morphs. 
With  their  removal,  the  species  oi Lampanyctus 
form  a  more  coherent  assemblage  of  40-50  species, 
and  despite  the  diversity  of  larval  specializations 
encountered  in  the  genus,  there  is  a  central  morph 
and  pattern  of  larval  development. 

Lampanyctus  larvae  are  deep-bodied  and 
bigheaded.  In  older  larvae  characteristic  pigment 
can  develop  at  a  variety  of  locations  such  as  the  tip 
of  the  lower  jaw,  between  the  eyes,  the  back  of  the 
head,  the  side  of  the  head,  the  adipose  fin,  the 


pectoral  fin,  internally  in  the  region  of  the 
cleithra,  and  along  the  myosepta.  The  pigment 
patterns  are  of  prime  importance  in  identifying 
the  larvae  to  species. 

There  are  several  rather  distinct  larval  types  in 
Lampanyctus.  One  of  these  consists  of  a  group  of 
species  whose  adults  are  characterized  by  having 
the  pectoral  fins  much  reduced  or  even  absent,  and 
has  been  separated  recently  as  a  distinct  genus 
Paralampanyctus  by  Kotthaus  (1972)  with  P. 
niger  as  type.  Previously,  Giinther  (1887)  had 
proposed  the  generic  name  Nannobrachium  for 
this  species  and  this  has  priority  over  Paralam- 
panyctus (John  Paxton,  pers.  commun.).  There  is  a 
remarkable  trend  of  jaw  specialization  in  the  lar- 
vae of  this  group  (Figure  10).  The  larva  of  L.  ritteri 
has  jaws  of  moderate  length  and  the  other  species 
shown  have  progressively  longer  jaws  with  more 
prominent  teeth,  particularly  anteriorly.  This 
trend  culminates  in  the  larva  of  Lampanyctus  sp. 
(possibly  achirus)  which  somewhat  resembles  a 
larval  billfish.  This  species  will  lack  the  pectoral 
fin  in  juveniles  and  adults,  even  though  it  is  well 
developed  in  the  larvae.  The  pectoral  fins  are  also 
large  inL.  regalis  andL.  niger  larvae,  but  will  be 
small  and  weakly  developed  in  adults.  This  dis- 
parity is  even  more  apparent  in  another  eastern 
Pacific  species,  which  lacks  pectoral  fins  as  an 
adult,  but  whose  larvae  have  the  largest  pectoral 
fins  with  the  highest  number  of  rays  that  we  have 
encountered  among  Lampanyctus  larvae.  Other 
less  spectacular  specializations  appear  in  the 
other  subgroups  0^  Lampanyctus,  but  it  appears 
that  the  larval  characters  will  be  helpful  in 
defining  the  species  composition  of  the  several 
subgenera. 

Representatives  of  other  genera  of  Lampanyc- 
tini, Triphoturus,  Stenobrachius,  andParvilux  are 
illustrated  in  Figure  llA-C.  Small  larvae  of 
Triphoturus  and  Stenobrachius  have  a  row  of 
melanophores  along  the  ventral  margin  of  the  tail 


406 


MOSER  and  AHLSTROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


^/^///;'-^//^^ 


^r?". 


Figure  10. — Larvae  of  Lampanyctus.  A.  L.  ritteri,  10.1  mm;  B.  L.  regalis,  9.1  mm;  C.  L.  njger,  8.7  mm;  D.  L.  sp. 

(possibly  achirus),  13.4  mm. 


407 


FISHERY   BULLETIN:   VOL.  72,  NO.  2 


Figure  11. — Larvae  of  Lampanyctini  and  Gymnoscopelini.  A.  Triphoturus  mexicanus.  10.5  mm;  B. 
Stenobrachius  leucopsarus,  10.4  mm;  C.  Parvilux  ingens,  14.4  mm;  D.  Bolinichthys  supralateralis ,  9.4 
mm;  E.  Ceratoscopelus  townsendi,  16.6  mm. 


408 


MOSER  and  AH  I  STROM:  ROLE  OF  LARVAE  IN  S't  STEMATICS 


but  these  coalesce  into  one  or  two  spots  in  mid- 
stage  larvae.  Triphoturus  larvae  are  character- 
ized further  by  their  distinctive  head  shape  and  by 
the  series  of  melanophores  along  the  ventral  mid- 
line below  the  gut.  Stenobrachius  larvae  add  con- 
siderable pigment  late  in  the  larval  period,  par- 
ticularly along  the  dorsum  and  on  the  myosepta 
of  the  trunk.  The  larvae  of  Parvilux  are  distinct 
in  shape  and  pigmentation.  Paxton  (1972)  placed 
this  genus  in  Lampanyctus  based  on  osteological 
characters.  In  certain  photophore  arrangements, 
however,  particularly  in  the  posterior  placement 
of  the  VLO  and  the  nonangulate  arrangement  of 
the  SAO,  the  genus  appears  to  us  to  be  more 
closely  related  to  Stenobrachius  than  to  Lam- 
panyctus. These  characters  in  addition  to  the  dis- 
tinctness of  the  larvae  would  suggest  that  the  va- 
lidity of  Parvilux  should  be  reconsidered. 

The  tribe  Gymnoscopelini  judged  from  larval 
and/or  adult  characters  contains  a  dozen  genera 
{Notoscopelus,  Lampichthys,  Scopelopsis,  Cerato- 
scopelus.  Lepidophanes.  Bolinichthys,  Lampadena, 
Taaningichthys,  Dorsadena,  Lampanyctodes, 
Gymnoscopelus,  and  Hintonia).  The  larvae 
of  these  genera  are  united  by  a  group  of  common 
characters,  including  a  distinctive,  usually 
slender,  body  outline,  a  series  of  melanophores 
on  the  dorsal  and  ventral  midlines  of  the  tail 
(in  most  genera),  and  the  development  of  a 
group  of  photophores  during  the  larval  period, 
most  notably  the  PO5,  FLO,  and  Vn.  The  larvae  of 
this  tribe  were  treated  extensively  in  a  previous 
paper  with  representative  larvae  illustrated  for  10 
of  the  12  genera  (Moser  and  Ahlstrom,  1972).  Ad- 
ditional species  of  Bolinichthys  (B.  supralateralis, 
Figure  IID), Ceratoscopelus  (C.  townsendi,  Figure 
HE),  Lampadena  (L.  luminosa.  Figure  12B), 
Lepidophanes  (L.  gaussi.  Figure  12C)  are  illus- 
trated herein.  Illustrations  of  Notoscopelus  re- 
splendens  (Figure  12 A)  and  Scopelopsis  mul- 
tipunctatus  (Figure  12D)  are  included  for  com- 
parative purposes.  It  need  only  be  mentioned  here 
that  the  clusters  of  closely  related  genera  within 
this  tribe  are  readily  apparent  from  examining 
the  larval  characters,  especially  the  sequence  of 
photophore  development,  and  these  groupings 
agree  closely  with  those  established  on  the  basis  of 
adult  characters. 

The  species  Notolychnus  valdiviae  has  so  many 
unique  adult  characters  that  Paxton  (1972)  as- 
signed it  to  the  monotypic  tribe  Notolychnini. 
Likewise  the  larva  has  a  number  of  unusual 
characters  (Figure  12E).  The  shape  of  the  eye  is 


variable  from  specimen  to  specimen;  it  can  be  nar- 
row and  elliptical  or  nearly  round,  but  most  typi- 
cally would  be  classified  as  irregular  in  shape.  The 
shape  of  the  head,  body,  and  gut  is  unusual  and 
distinctive.  The  larval  characters  are  of  little  help 
in  elucidating  the  affinities  of  this  species  within 
the  Myctophidae  and,  when  added  to  the  list  of 
unique  adult  characters,  only  magnify  the  prob- 
lem. It  would  seem  to  make  just  as  much  sense  to 
establish  a  separate  subfamily  for  Notolychnus  as 
to  place  it  in  a  monotypic  tribe  in  the  subfamily 
Lampanyctinae. 

The  larvae  illustrated  in  this  paper  comprise  55 
species  representing  24  genera.  Illustrations  are 
included  for  larvae  of  11  of  the  12  genera  in  the 
subfamily  Myctophinae;  not  included  are  illustra- 
tions of  Diogenichthys  (see  Moser  and  Ahlstrom, 
1970  for  D.  laternatus  and  D.  atlanticus).  In  the 
subfamily  Lampanyctinae  larvae  are  illustrated 
for  13  of  the  19  genera.  The  omitted  genera  {Lam- 
pichthys, Lampanyctodes,  Gymnoscopelus,  and 
Tanningichthys),  all  from  the  tribe  Gymnoscope- 
lini, are  illustrated  in  Moser  and  Ahlstrom  (1972). 
Larvae  of  Hintonia  and  Dorsadena  have  not  yet 
been  identified. 

SOME  EVOLUTIONARY 
CONSIDERATIONS 

With  this  brief  review  of  lanternfish  larvae 
completed,  let  us  now  turn  to  an  interesting  prob- 
lem of  myctophid  evolution  to  which  study  of  the 
larvae  may  contribute  importantly — the  evolu- 
tion of  photophore  pattern.  With  a  single  excep- 
tion, all  adult  myctophids  have  two  conspicuous 
rows  of  photophores  that  extend  the  length  of  the 
body  on  each  side  of  the  ventral  midline.  The 
photophores  are  grouped  and  positioned  in  a 
definite  and  often  diagnostic  pattern.  Also, 
lanternfishes  have  a  specific  pattern  of  photo- 
phores on  the  sides  of  the  body,  below  the  lateral 
line,  and  on  the  ventral  aspect  of  the  head.  The 
exception  is  Taaningichthys  paurolychnus,  which 
appears  to  lack  body  photophores  entirely.  In  ad- 
dition to  these  photophores,  some  lanternfish  gen- 
era have  photophores  positioned  in  a  pattern 
above  the  lateral  line  and  some  have  small  "sec- 
ondary" photophores  distributed  more  generally 
over  regions  of  the  body  and  head.  Another  type  of 
luminous  structure  present  on  most  myctophids 
are  discrete  glands  located  at  the  caudal  peduncle. 
Typically,  these  are  sexually  dimorphic  in  charac- 
ter and,  doubtless,  play  some  part  in  courtship 


409 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


>^^; 

L^i=^ 

k  ' 

-f|^^ 

-sa- 


'■•^-; 


^^=^^Si:j;^f5^i::JL^ 


Figure  12.— Larvae  of  Gymnoscopelini  and  Notolychnini.  A.  Notoscopelus  resplendens,  11.2  mm;  B. 
Lampadena  luminosa,  12.8  mm;  C.  Lepidophanes  gaussi,  13.5  mm;  D.  Scopelopsis  multipunctatus,  17.5 
mm;  E.  Notolychnus  valdiviae,  9.2  mm. 


410 


MOSER  and  AHl  STROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


behavior.  Finally,  some  myctophids  have  small 
patches  of  soft  whitish,  apparently  luminous,  tis- 
sue located  at  various  regions  of  the  body. 

The  most  popular  speculation  as  to  the  possible 
function  of  the  patterns  of  photophores  and  lumin- 
ous scales  is  that  they  function  in  species  recogni- 
tion (see  McAllister,  1967).  An  explanation  for  the 
universality  of  the  two  ventral  rows  was  postu- 
lated by  Clarke  (1963).  His  suggestion  that  these 
downward  directed  rows  emit  a  continuous  light  of 
ambient  wavelength,  which  conceals  the  fish  from 
deeper-living  predators  by  countershading,  has 
much  appeal. 

We  have  long  been  interested  in  the  mechanism 
by  which  such  patterns  of  photophores  could  have 
evolved  and  believe  we  have  gained  some  insight 
into  this  mechanism  through  our  studies  of  the 
larval  stages.  Our  proposal,  as  expressed  in  an 
earlier  paper  (Moser  and  Ahlstrom,  1972),  is  that 
ancestral  myctophids  had  a  generalized  arrange- 
ment of  unspecialized  photophores,  one  at  the 
posterior  margin  of  each  scale  pocket,  and  a  group 
of  similar  photophores  on  the  head.  We  further 
proposed  that  the  specific  photophore  patterns  of 
contemporary  myctophids  evolved  through  pro- 
gressive enlargement  and  specialization  of  certain 
photophores  of  the  generalized  pattern  and  con- 
current diminution  or  loss  of  the  unspecialized 
photophores.  This  idea  came  to  us  upon  discover- 
ing the  remarkable  transforming  specimens  of 
Scopelopsis  multipunctatus,  the  adults  of  which 
have  a  small  photophore  at  each  scale  pocket  and  a 
group  of  photophores  on  the  head.  In  the  adults, 
the  "primary"  organs  can  be  distinguished  only  by 
their  modified  lens-bearing  scales,  but  in  the 
transforming  specimens  (Figure  IID)  the  primary 
photophores  stand  out  clearly  as  enlarged  mem- 
bers of  the  meristic  series  of  light  organs.  It  struck 
us  that  a  similar  arrangement  of  photophores 
might  have  existed  in  the  adults  of  an  ancestral 
species,  and  led  to  the  development  of  our  ideas  on 
the  evolution  of  photophore  pattern.  Our  theory 
was  further  strengthened  by  neurological  findings 
and  by  what  we  feel  are  inherent  weaknesses  in 
Bolin's  ( 1939)  and  Fraser-Brunner's  ( 1949)  theory 
that  photophore  patterns  evolved  by  the  upward 
migration  of  organs  from  ventral  rows  of  photo- 
phores. 

Viewed  from  the  standpoint  of  our  theory  the 
subfamily  Myctophinae  would  be  considered 
highly  specialized,  since  it  is  here  that  diminution 
of  secondary  photophores  has  reached  its  highest 
degree;  they  are  totally  lacking  in  the  subfamily. 


The  individual  "primary"  photophores  are  typi- 
cally highly  developed  and  concentrated  ventrally 
on  the  body.  The  ventral  location  of  photophores  in 
Myctophinae  is  probably  related  to  their  habitat. 
That  is,  they  are  generally  shallow-living  active 
fishes  that  have  well-developed  gas  bladders  and 
it  is  plausible  that  concentration  of  photophores 
ventrally  on  the  body  evolved  as  an  adaptation  for 
countershading  and  protection  from  deeper-living 
predators.  This  view  of  the  Myctophinae  is  com- 
pletely contrary  to  those  previously  held  for  this 
subfamily.  On  the  basis  of  the  "upward  migration" 
theory  of  photophore  evolution,  myctophines  were 
thought  to  be  primitive  unspecialized  forms.  For- 
merly, we  too  subscribed  to  this  view,  and  con- 
trasting the  then  supposed  primitive  features 
such  as  low  photophore  position  and  short  jaws  of 
the  adults  with  the  highly  specialized  and  diverse 
features  of  the  larvae,  we  proposed  that  the 
evolutionary  pace  had  differed  in  the  larval  and 
adult  stages  of  the  subfamily.  Our  altered  opinion 
would  view  both  larvae  and  adults  of  the  Myc- 
tophinae as  highly  advanced  and  would  interpret 
the  low  photophores,  prominent  gas  bladders, 
short  jaws,  and  often  narrow  caudal  peduncles  as 
specialized  adaptations  of  active  surface-dwelling 
fishes. 

Our  view  of  the  Lampanyctinae  must  also  be 
revamped.  Formerly  we  considered  the  diverse 
and  often  dorsally  oriented  pattern  of  photophores 
and  accessary  luminous  tissue  to  be  highly 
specialized  features.  Possibly,  the  luminous 
scalelike  patches  and  luminous  glands  are 
specialized  adaptations,  but  we  feel  that  the  pres- 
ence of  small  secondary  photophores  and  the  dor- 
sal positioning  of  primary  photophores  in  many  of 
the  genera,  indicate  a  retention  of  the  ancestral 
condition.  The  Lampanyctinae  are  generally 
deeper-living  than  the  Myctophinae  and  many 
genera  are  lethargic  fishes  that  rest  vertically  in 
the  water  column  (Barham,  1970).  In  deeper- 
living  fishes  with  such  a  behavior  pattern  there 
would  be  little  evolutionary  advantage  in  having 
ventrally  concentrated  photophores,  and  the  fat- 
invested  swim  bladders  and  long  jaws  typical  of 
many  genera  could  have  evolved  in  relation  to 
habitat  and  activity  pattern.  It  is  interesting  that 
the  most  obvious  exception  in  the  subfamily,  the 
Diaphini,  are  active,  often  surface-dwelling  fishes 
with  relatively  short  jaws  and  ventrally  concen- 
trated photophores.  It  is  obvious  from  the  present 
paper  that  the  larvae  of  Lampanyctinae  exhibit 
much  less  diversity  than  the  Myctophinae,  but  we 


411 


FISHERY    BUllFTIN:   VOL.  72.  NO.  2 


no  longer  view  the  adult  myctophines  as  being 
more  "primitive"  than  the  adult  lampanyctines. 
We  feel  that  the  adults  of  both  subfamilies  are 
equally  specialized  and  that  these  specializations 
are  basically  related  to  their  particular  habitat. 
In  summary,  thorough  study  of  the  larvae  of  a 
teleost  family  such  as  the  Myctophidae  can  be 
most  helpful  in  species  validation,  in  analyzing 
affinities  at  all  taxon  levels,  and  in  assessing 
phylogenetic  lineages.  Also,  the  above  discussion 
would  indicate  that  larval  studies  can  provide  in- 
teresting insights  into  the  major  directions  of 
evolution  within  a  family  offish. 

ACKNOWLEDGMENTS 

George  Mattson  executed  15  of  the  illustrations 
(Figures  IE,  4A,  5A  and  D,  8A-D,  lOA,  B,  and  D, 
llA  and  E,  and  12A  and  E)  and  we  thank  him  for 
his  efforts.  The  remaining  illustrations  were  made 
by  one  of  us  (H.  G.  Moser).  Larval  specimens  came 
from  a  variety  of  sources  and  we  are  especially 
indebted  to  the  following  persons  for  their  gener- 
ous provision  of  material:  E.  Bertelsen  and  J. 
Nielsen,  Zoological  Museum,  Copenhagen;  N.  B. 
Marshall  and  A.  Wheeler,  British  Museum;  W. 
Nellen,  Institute  fiir  meereskunde,  Kiel,  Ger- 
many; R.  McGinnis  and  B.  Nafpaktitis,  Univer- 
sity of  Southern  California  (USC);  R.  J.  Laven- 
berg,  Los  Angeles  County  Museum;  R.  Rosenblatt 
and  R.  Wisner,  Scripps  Institution  of  Oceanog- 
raphy (SIO);  T.  Clarke  and  J.  Miller,  University  of 
Hawaii;  W.  Freihofer,  California  Academy  of  Sci- 
ences. We  would  like  to  thank  B.  Nafpaktitis  and 
R.  McGinnis,  USC;  R.  Wisner,  SIO;  J.  Paxton, 
Australian  Museum,  Sydney;  and  G.  Krefft, 
Fisheries  Institute,  Hamburg,  Germany,  for  shar- 
ing their  vast  knowledge  of  lanternfishes  with  us 
in  numerous  discussions.  Discussions  with  N.  B. 
Marshall,  British  Museum;  B.  Robison,  Stanford 
University;  and  A.  Kendall,  Middle  Atlantic 
Coastal  Fisheries  Center,  National  Marine 
Fisheries  Service  (NMFS),  Sandy  Hook,  have  been 
helpful  in  stimulating  some  of  the  ideas  put  forth 
herein.  We  appreciate  the  able  technical  assis- 
tance of  Elaine  Sandknop,  Elizabeth  Stevens,  and 
Patricia  Lowery,  Southwest  Fisheries  Center  La 
Jolla  Laboratory,  NMFS.  Kenneth  Raymond 
kindly  lettered  the  illustrations. 

LITERATURE  CITED 

Barham,  E.  G. 

1970.  Deep-sea  fishes  lethargy  and  vertical  orientation.  In 


G.  B.  Farquhar  (editor),  Proceedings  of  an  international 
symposium  on  biological  sound  scattering  in  the  ocean,  p. 
100-118.  Maury  Center  for  Ocean  Science,  Department  of 
the  Navy,  Wash.,  D.C.  MC  Rep.  005. 
Becker,  V.  E. 

1965.  Lanternfishes  of  the  genus  Hygop/ijzm  (Myctophidae, 
Pisces).  Systematics  and  distribution.  Tr.  Inst.  Okeanol. 
Akad.  Nauk  SSSR  80:62-103.  (In  Russ.,  Engl.  Transl.  No. 
45,  Natl.  Mar.  Fish.  Serv.,  Syst.  Lab.,  Wash.,  D.C.) 

Benirschke,  K.,  and  T.  C.  Hsu  (editors). 

1971.  An  atlas  of  mammalian  chromosomes.  Vol.  5  and 
6.  Springer-Verlag,  N.Y.,  200  p. 
Bertelsen,  E. 

1951.  The  ceratioid  fishes.  Ontogeny,  taxonomy,  distribu- 
tion and  biology.   Dana  Rep.,  Carlsberg  Found.  39,  276  p. 
BoLiN,  R.  L. 

1939.  A  review  of  the  myctophid  fishes  of  the  Pacific  coast  of 
the  United  States  and  of  Lower  California.  Stanford 
Ichthyol.  Bull.  1:89-156. 
1959.  Iniomi  Myctophidae.   Rep.  Sci.  Results  "Michael 
Sars"  North  Atl.  Deep-Sea  Exped.  1910.  4,  2(7):l-45. 
Castle,  P.  H.  J. 

1969.  An  index  and  bibliography  of  eel  larvae.  J.  L.  B. 
Smith  Inst.  Ichthyol.,  Rhodes  Univ.,  S.  Afr.  Spec.  Publ.  7, 
121  p. 
Clarke,  W.  D. 

1963.   Function   of  bioluminescence   in   mesopelagic 
organisms.  Nature  (Lond.)  198:1244-1246. 
De  Ligny,  W. 

1969.  Serological  and  biochemical  studies  on  fish 
populations.   Oceanogr.  Mar.  Biol.  Annu.  Rev.  7:411-513. 

Ebeling,  a.  W.,  N.  B.  Atkin,  and  P.  Y.  Setzer. 

1971.  Genome  sizes  of  teleostean  fishes:  increases  in  some 
deep-sea  species.  Am.  Nat.  105:549-561. 
Ege,  V. 

1953.  Paralepididae  I.  (Paralepis  and  Lestidium). 
Taxonomy,  ontogeny,  phylogency  and  distribution.  Dana 
Rep.,  Carlsberg  Found.  40,  184  p. 
1957.  Paralepididae  II.  (Macroparalepis).  Taxonomy,  on- 
togeny, phylogeny  and  distribution.  Dana  Rep.,  Carlsberg 
Found.  43,  101  p. 
Fish,  M.  P.,  and  W.  H.  Mowbray. 

1970.  Sounds  of  Western  North  Atlantic  fishes.  Johns 
Hopkins  Press,  Baltimore,  207  p. 

Fraser-Brunner,  a. 

1949.   A    classification    of  the    fishes    of  the    family 
Myctophidae.  Proc.  Zool.  Soc.  Lond.  118:1019-1106. 
Greenwood,  P.  H.,  D.  E.  Rosen,  S.  H.  Weitzman,  and  G.  S. 
Myers. 

1966.  Phyletic  studies  of  teleostean  fishes,  with  a  provi- 
sional classification  of  living  forms.  Bull.  Am.  Mus.  Nat. 
Hist.  131:341-455. 

GUNTHER,  A. 

1887.   Report  on  the  deep-sea  fishes  collected  by  H.M.S. 
Challenger  during  the  years  1873-76.  Rep.  Sci.  Res.  Voy- 
age H.M.S.  Challenger  22:335  p.,  73  plates. 
Johnson,  R.  K. 

1971.  A  revision  of  the  alepisauroid  family  Scopelarchidae 
(Pisces:  Myctophiformes).  Ph.D.  Thesis,  Scripps  Inst. 
Oceanogr.,  La  Jolla,  474  p. 

KOTTHAUS,  A. 

1972.  Die  meso-und  bathypelagischen  Fische  der 
Meteor-Rossbreiten-Expedition  1970  (2.  und  3.  Fahr- 
tabschnitt).  "Meteor"  Forsch.-Ergeb.  Dll:l-28. 


412 


MOSER  and  AHI  STROM:  ROLE  OF  LARVAE  IN  SYSTEMATICS 


McAllister,  D.  E. 

1967.  The  significance  of  ventral  bioluminescence  in 
fishes.  J.  Fish.  Res.  Board  Can.  24:537-554. 

MosER,  H.  G.,  AND  E.  H.  Ahlstrom. 

1970.  Development  of  lanternfishes  (family  Myctophidae) 
in  the  California  Current.  Part  I.  Species  with  narrow- 
eyed  larvae.  Bull.  Los  Ang.  Cty.  Mus.  Nat.  Hist.  Sci.  7, 
145  p. 
1972.  Development  of  the  lanternfish,  Scopelopsis  mul- 
tipunctatus  Brauer  1906,  with  a  discussion  of  its 
phylogenetic  position  in  the  family  Myctophidae  and  its 
role  in  a  proposed  mechanism  for  the  evolution  of  photo- 
phore  patterns  in  lanternfishes.  Fish.  Bull.,  U.S. 
70:541-564. 

Nafpaktitis.  B.  G. 

1968.  Taxonomy  and  distribution  of  the  lanternfishes,  gen- 
era Lobianchia  and  Diaphus.  in  the  North 
Atlantic.  Dana  Rep.,  Carlsberg  Found.  73,  131  p. 


1973.  A  review  of  the  lanternfishes  (family  Myctophidae) 
described  by  A.  Vedel  Taning.  Dana  Rep.,  Carlsberg 
Found.  83,  46  p. 
Ohno,  S. 

1970.  The  enormous  diversity  in  genome  sizes  offish  as  a 
reflection  of  nature's  extensive  experiments  with  gene 
duplication.  Trans.  Am.  Fish.  Soc.  99:120-130. 

Paxton,  J.  R. 

1972.  Osteology  and  relationships  of  the  lanternfishes 
(Family  Myctophidae).  Bull.  Los  Ang.  Cty.  Mus.  Nat. 
Hist.  Sci.  13,  81  p. 

WiSNER,  R.  L. 

1963.  A  new  genus  and  species  of  myctophid  fish  from  the 
South-Central  Pacific  Ocean,  with  notes  on  related  genera 
and  the  designation  of  a  new  tribe,  Electronini.  Copeia 
1963:24-28. 

197 1 .  Descriptions  of  eight  new  species  of  myctophid  fishes 
from  the  eastern  Pacific  Ocean.  Copeia  1971:39-54. 


413 


4 


EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES  OF 
THE  GULF  OF  MEXICO  AND  THE  SOUTH  ATLANTIC  COAST 

OF  THE  UNITED  STATES 

Virginia  L.  Aprieto' 

ABSTRACT 

Larvae  of  round  scad,  Decapterus  punctatus;  rainbow  runner,  Elagatis  bipinnulata;  banded  rudderfish, 
Seriola  zonata;  lookdown,  Selene  vomer;  and  leatherjacket,  Oligoplites  saurus,  collected  in  the  Gulf  of 
Mexico  and  off  the  south  Atlantic  coast  of  the  United  States  are  described  and  illustrated.  Larvae  2  to  3 
mm  long  show  general  family  characteristics  but  generic  and  specific  characters  are  differentiated  in 
later  stages.  Morphological  features  including  supraoccipital  crest,  thickness  of  the  first  interhemal 
spine,  and  body  indices;  meristic  characters;  mode  of  development  and  modification  of  the  dorsal  and 
pelvic  fins;  and  patterns  of  pigmentation  are  useful  in  distinguishing  the  family,  genera,  and  species. 
Information  on  distribution  and  spawning  is  included. 


The  family  Carangidae  consists  of  about  200 
species  of  fishes  which  vary  widely  in  form  and  are 
distributed  in  tropical  and  subtropical  waters. 
Various  attempts  by  authors  to  divide  the  family 
into  subfamilies  proved  unsatisfactory  in  view  of 
the  numerous,  weak  characters  used  for  this  pur- 
pose and  the  presence  of  many  transition  genera 
which  did  not  permit  delineation  of  groups  which 
may  have  been  proposed  as  subfamilies  (Gins- 
burg,  1952). 

Twenty-eight  species  of  carangids  have  been 
found  along  the  Atlantic  and  Gulf  coasts  of  the 
United  States  (Table  1).  The  larvae  of  some  of 
these  species  occurred  frequently  in  plankton  and 
nekton  collected  in  the  Gulf  of  Mexico  and  off  the 
south  Atlantic  coast  of  the  United  States  during 
the  multiship  cruises  in  October  to  November 
1970  and  May  to  October  1971  during  continuing 
surveys  of  marine  biological  communities  con- 
ducted by  the  National  Marine  Fisheries  Service 
(Southeast  Fisheries  Center)  and  cooperating 
agencies.  The  larval  development  of  five  species  is 
described  and  illustrated  in  the  present  work. 

Only  a  few  studies  dealing  with  early  life  his- 
tory stages  of  North  Atlantic  carangids  have  been 
carried  out  by  American  workers.  Hildebrand  and 
Cable  (1930)  described  larvae  and  early  juveniles 
of  Decapterus  punctatus  and  Seriola  dumerili. 


'College  of  Fisheries,  University  of  the  Philippines,  Quezon 
City,  Philippines. 


Fields  (1962)  described  postlarvae  of  these  species 
of  Trachinotus:  T.  carolinus,  T.  falcatus,  and  T. 
glaucus;  McKenney,  Alexander,  and  Voss  (1958) 
described  a  rather  complete  larval  series  of 
Caranx  crysos;  Berry  (1959)  described  late-stage 
larvae  and  juveniles  of  five  species  of  Caranx, 
including:  C.  crysos,  C.  bartholomaei,  C.  ruber,  C. 
hippos,  and  C  latus.  None  of  the  above  series  in- 
cluded eggs  or  yolk-sac  larvae  and  the  majority 
lacked  early-stage  larvae  as  well. 

Over  a  third  of  the  carangids  that  occur  off  the 
eastern  United  States  are  wide-ranging  species, 
and  early  life  history  series  had  been  described 
from  other  areas  for  the  following:  Selar  cru- 
menophthalmus  by  Delsman  (1926)  and  Devane- 
san  and  Chidambaram  (1941),  Naucrates  ductor 
by  Sanzo  (1931),  Caranx  dentex  by  Schnakenbeck 
(1931),  Seriola  dumerili  by  Sanzo  (1933), 
Trachinotus  glaucus  by  de  Gaetani  ( 1940),  Caranx 
hippos  by  Chacko  (1950)  and  Subrahmanyam 
(1964),  Chloroscombrus  chrysurus  and  Alectis 
crinitus  by  Aboussouan  (1968),  and  Elagatis 
bipinnulata  by  Okiyama  (1970).  Hence,  early  life 
history  series — some  complete,  some  fragmen- 
tary— were  known  for  16  of  28  species  of  caran- 
gids that  occur  along  the  Atlantic  and  Gulf  coasts 
of  the  United  States. 

A  proper  understanding  of  the  early  life  history 
of  fishes,  particularly  those  of  species  important  to 
man,  can  never  be  overemphasized.  The  presence 
of  larvae  is  indicative  of  recent  spawning,  and 


Manuscript  accepted  August  1973. 

FISHERY  BULLETIN;  VOL.  72,  NO.  2,  1974. 


415 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Table  1.— Meristic  characters  of  adult  carangids  of  the  Gulf  and  Atlantic  coasts  of  the  United  States. 


Pectoral 

Verte- 

Species 

Dorsal  fin 

An 

al  fin 

fin 

GMI  rakers 

brae 

Source 

Alectis  crinitus 

(VII)O;  1,18-19 

(11)0;  1 

,  15-16 

18-20 

5-  6  +  14-16 

_ 

Ginsburg,  1952 

Alectis  crinitus 

- 

- 

- 

- 

24 

Starks,  1911 

Caranx  bartholomaei 

VIM 

:  1.  25-28 

II:  1 

,  21-24 

1.  19-21 

6-  9+18-21 

- 

Berry,  1959 

Caranx  bartholomaei 

- 

- 

- 

- 

24 

Miller  and  Jorgensen 

1973 

Caranx  crysos 

VIII 

;  1,  22-25 

II:  1 

,  19-21 

1,  19-23 

10-14  +  23-28 

- 

Berry.  1959 

Caranx  crysos 

- 

- 

- 

- 

25 

Miller  and  Jorgensen 

1973 

Caranx  crysos 

VIII 

:  1,  23-25 

- 

- 

- 

McKenney  et  aL,  1958 

Caranx  crysos 

- 

- 

- 

- 

25 

Starks.  1911 

Caranx  hippos 

VIII 

;  1,  19-21 

II:  1 

16-17 

1,  19-20 

6-  9  +  22-27 

- 

Berry,  1959 

Caranx  hippos 

- 

- 

- 

- 

24 

Lane, 1965 

Caranx  latus 

VIII 

1,  19-22 

II;  1 

16-18 

1.  18-20 

6-   7+16-18 

- 

Berry,  1959 

Caranx  latus 

20-21 

16-18 

18-20 

16  +  17 

24 

Lane,  1965 

Caranx  lugubris 

VIM 

1,  22 

11;  1 

19 

1,  19 

6  +  20 

- 

Berry,  1959 

Caranx  lugubris 

- 

- 

- 

- 

24 

Lane.  1965 

Caranx  lugubris 

VIM 

1,22 

II:  1 

18 

- 

- 

- 

Fowler,  1936 

Caranx  ruber 

VIII 

1,  26-30 

II;  1 

23-26 

1,  18-21 

10-14  +  31-35 

- 

Berry,  1959 

Caranx  ruber 

- 

- 

- 

- 

24 

Miller  and  Jorgensen, 

1973 

Caranx  dentex 

VIM 

1,  25-26 

II:  1 

21-23 

1,  19-20 

11-13  +  26-28 

- 

Berry.  1959 

Chloroscombrus  chrysurus 

VIII 

1,  26-28 

II:  1 

25-27 

19-20 

9-11+31-35 

- 

Ginsburg,  1952 

Chloroscombrus  chrysurus 

- 

- 

- 

- 

24 

Miller  and  Jorgensen, 

1973 

Chloroscombrus  chrysurus 

VII-VIII 

1.  24-26 

II:  1 

25-26 

- 

9-10  +  32-35 

- 

Fowler,  1936 

Chloroscombrus  chrysurus 

- 

- 

- 

- 

24 

Starks,  1911 

Decapterus  macarellus 

VIII 

1,31-37 

II;  1 

27-31 

1,  21-23 

9-13  +  32-39 

24 

Berry,  1968 

Decapterus  punctatus 

VIII 

1,  29-34 

II;  1 

25-30 

1,  18-20 

11-16  +  32-44 

25 

Berry.  1968 

Decapterus  punctatus 

VIII 

1,  28-32 

II;  1 

25-27 

19-21 

12-15  +  34-40 

- 

Ginsburg,  1952 

Decapterus  punctatus 

VIII 

1,  27-31 

II;  1 

24-27 

- 

12-15  +  35-40 

- 

Fowler.  1936 

Decapterus  tabi 

VIII 

1.  29-34 

II;  1 

24-27 

1,  20-22 

10-12  +  30-33 

24 

Berry,  1968 

Elagatis  bipinnulata 

V 

-1.  25-26 

O-ll;  1 

16-17 

20-21 

10-11+25-26 

- 

Ginsburg,  1952 

Elagatis  bipinnulata 

V-VI 

1,  25-30 

II 

18-22 

1,  18-21 

9-12  +  25-29 

24 

Berry,  1969 

Hemicaranx  amblyrhynchus 

VII-VIII 

1,  27-29 

II;  1 

23-25 

19-22 

8-10  +  19-23 

- 

Ginsburg,  1952 

Hemicaranx  amblyrhynchus 

- 

- 

- 

- 

26 

Miller  and  Jorgensen, 

1973 

Naucrates  ductor 

lll-IV;  1 

-II.  26-28 

O-ll;  II 

15-16 

- 

6^18-19 

- 

Fowler,  1936 

Naucrates  ductor 

- 

- 

- 

- 

25 

Starks,  1911 

Oligoplites  saurus 

V-VI 

1,  19-21 

11;  1 

18-21 

15-17 

6-  9  +  13-15 

- 

Ginsburg,  1952 

Oligoplites  saurus 

- 

- 

- 

- 

26 

Miller  and  Jorgensen, 

1973 

Selar  crumenophlhalmus 

VIII 

1,  24-26 

II;  1 

21-23 

20-22 

9-11+27-30 

- 

Ginsburg,  1952 

Selar  crumenophlhalmus 

- 

- 

- 

- 

24 

Miller  and  Jorgensen, 

1973 

Selar  crumenophlhalmus 

VIM 

1,  26 

II;  1 

22 

- 

10-12  +  28-31 

- 

Fowler,  1936 

Selar  crumenophlhalmus 

- 

- 

- 

- 

24 

Starks.  1911 

Selene  vomer 

VIII 

1,  21-23 

0-11;  1 

18-20 

20-21 

6-  8  +  23-27 

- 

Ginsburg,  1952 

Selene  vomer 

- 

- 

- 

- 

24 

Miller  and  Jorgensen, 

1973 

Selene  vomer 

VII-VIII 

1,  21-23 

II;  1 

18-19 

- 

7-  8  +  24-28 

- 

Fowler.  1936 

Seriola  dumerili 

VII 

1,  30-35 

II;  1 

19-22 

19-22 

2-  3  +  11-13 

- 

Ginsburg,  1952 

Seriola  dumerili 

- 

- 

- 

- 

24 

Miller  and  Jorgensen. 

1973 

Seriola  dumerili 

VII 

1,  29-35 

- 

- 

11-24 

- 

Mather,  1958 

Seriola  fasciata 

VIM 

1,  30-32 

II;  1 

19-20 

19-20 

7-  8+18-20 

- 

Ginsburg,  1952 

Seriola  fasciata 

VII-VIII 

1,  29-32 

II;  1 

18-21 

- 

6+15 

_ 

Fowler,  1936 

Seriola  fasciata 

VIM 

1,  28-32 

- 

_ 

22-26 

_ 

Mather,  1958 

Seriola  rivoliana 

VII-VIII 

1.  28-32 

I-II:  1 

19-22 

19-20 

7-   8+16-18 

- 

Ginsburg,  1952 

Seriola  rivoliana 

- 

- 

- 

- 

24 

Miller  and  Jorgensen, 

1973 

Seriola  rivoliana 

VII 

1,  29 

II;  1 

21 

- 

_ 

- 

Fowler,  1936 

Seriola  rivoliana 

VII 

1,  27-33 

- 

- 

18-28 

- 

Mather.  1958 

Seriola  zonata 

VII-VIII 

1,  33-40 

I-II:  1 

19-21 

16-21 

2-  3  +  11-13 

- 

Ginsburg,  1952 

Seriola  zonata 

VIII 

1,  38-40 

- 

_ 

12-13 

_ 

Mather,  1958 

Seriola  zonata 

- 

- 

- 

_ 

24 

Starks,  1911 

Trachinotus  carolinus 

V-VI 

1,  23-27 

II;  1 

20-23 

17-19 

-      +7-11 

- 

Ginsburg,  1952 

Trachmotus  carolinus 

V-VI 

1,  22-27 

M:  1 

20-23 

1.  16-18 

4-   7+    6-13 

_ 

Fields.  1962 

Trachinotus  carolinus 

- 

- 

- 

- 

24 

Starks,  1911 

Trachinotus  falcatus 

VI 

1,  18-20 

II;  1 

17-18 

18-20 

-      +   9-13 

- 

Ginsburg,  1952 

Trachinotus  falcatus 

- 

- 

- 

- 

24 

Miller  and  Jorgensen, 

1973 

Trachinotus  falcatus 

VI 

1,  17-21 

II;  1 

16-19 

1.  17-19 

3-  8  +  12-14 

- 

Fields,  1962 

Trachinotus  glaucus 

VI 

1,  19-20 

II:  1 

16-18 

16-19 

-      +8-12 

- 

Ginsburg,  1952 

Trachinotus  glaucus 

VI 

1,  19-20 

II;  1 

16-18 

1,  15-19 

3-  8  +  9-14 

- 

Fields,  1962 

Trachurus  lathami 

VIII 

1.  28-33 

II;  1 

26-30 

21-22 

12-14  +  34-39 

_ 

Ginsburg.  1952 

Trachurus  lathami 

VIII 

1.  30 

II:  1. 

28 

- 

15  +  36 

24 

Merriman.  1943 

Uraspis  heidi 

VIII 

1,  29 

0-1 

21 

23 

6+14 

- 

Ginsburg,  1952 

Vomer  setapinnis 

VIII 

1.  20-23 

O-ll;  1 

17-19 

17-19 

5-  8  +  25-29 

- 

Ginsburg,  1952 

Vomer  setapinnis 

VIII 

1,  21-22 

II:  1 

18-20 

- 

6-  8  +  26-30 

- 

Fowler,  1936 

Vomer  setapinnis 

- 

- 

- 

- 

24 

Starks,  1911 

416 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 


data  derived  from  the  study  of  larvae  provide  use- 
ful tools  in  gaining  insight  into  the  abundance  and 
fluctuation  of  the  size  of  spawning  populations 
(Farris,  1961 ).  Patterns  of  larval  development  and 
larval  structures,  when  sufficient  groups  are 
studied,  are  potential  keys  to  possible  relations 
which  often  are  not  adequately  illustrated  in  adult 
morphology  and  osteology.  The  present  paper 
aims  to  contribute  to  the  understanding  of  the 
early  life  stages  of  members  of  the  family  Caran- 
gidae. 


MATERIALS,  METHODS, 
AND  TERMINOLOGY 

Larvae,  juveniles,  and  adults  were  largely  in 
the  collections  of  the  Miami  Laboratory,  South- 
east Fisheries  Center.  The  larvae  and  juveniles 
were  collected  with  1-m  bongo  plankton  (Posgay, 
Marak,  and  Hennemuth,  1968)  and  nekton  nets  on 
board  research  vessels  during  oceanographic  and 
biological  surveys  and  during  the  routine  sam- 
pling for  larval  fish  in  the  Gulf  Stream  off  Miami. 
Descriptions  of  vessels,  cruise  tracks,  and  sam- 
pling methods  are  available  at  the  Miami 
Laboratory,  Southeast  Fisheries  Center.  Some 
specimens  were  contributed  from  a  private  collec- 
tion and  from  the  fish  museum  of  the  Center.  One 
species  was  raised  in  the  marine  fish  larvae  rear- 
ing system  of  the  Rosenstiel  School  of  Marine  and 
Atmospheric  Science,  University  of  Miami. 

The  larval  development  of  the  carangids  in  this 
work  is  based  on  551  larval  and  early  juvenile 
specimens  ofDecapteruspunctatus,  94  ofElagatis 
bipinnulata,  86  of  Selene  vomer,  64  of  Seriola 
zonata,  and  31  of  Oligoplites  saurus.  Meristic 
characters  and  sequence  of  ossification  data  were 
taken  from  stained  and  cleared  specimens.  The 
complete  sequence  of  ossification  was  not  ob- 
served, however,  in  Selene  vomer  and  Oligoplites 
saurus  on  account  of  the  lack  of  transforming 
specimens  and  poorly  preserved  materials,  respec- 
tively. 

The  embryological  and  anatomical  terms  and 
measurements  used  in  this  study  follow  largely 
those  of  Lagler,  Bardach,  and  Miller  ( 1962),  Man- 
sueti  and  Hardy  (1967),  and  Moser  and  Ahlstrom 
(1970).  Terms  for  ossification  are  those  of  Starks 
(1911),  Suzuki  (1962),  and  Weitzman  (1962). 
Chromatophore  terminology  is  from  Fujii  (1969). 
However,  for  clarity,  certain  terms  are  defined  as 


they  relate  to  larvae  of  carangids. 

Growth  stages  beyond  the  yolk-sac  stage  are 
defined  according  to  Moser  and  Ahlstrom  (1970), 
and  the  terms  prolarva  and  postlarva  of  Hubbs 
(1943)  are  not  used.  The  larval  period  lasts  from 
hatching  to  the  attainment  of  juvenile  characters. 
The  transformation  or  metamorphosis  of  the  lar- 
vae into  juveniles  is  called  the  transitional  period 
and  the  individuals  undergoing  this  process  are 
called  transforming,  metamorphic,  or  transitional 
specimens.  The  fish  is  a  juvenile  when  it  has  the 
essential  features  of  the  adult,  particularly  the 
complete  fin  ray  counts.  The  juvenile  period  ter- 
minates with  the  attainment  of  sexual  maturity 
when  the  fish  is  considered  an  adult. 

The  dynamic  approach  of  Moser  and  Ahlstrom 
(1970)  is  adapted  in  the  description  of  larval  fish. 
Here,  a  complete  or  fairly  complete  series  of 
growth  stages  from  the  smallest  differentiated 
larvae  to  the  juvenile  is  assembled,  and  the  de- 
velopment of  each  character  is  traced  sequen- 
tially. The  method  used  for  determining  apparent 
relative  abundance  is  based  on  Ahlstrom  (1948). 

The  youngest  specimens  collected  in  the  plank- 
ton were  past  the  yolk-sac  stage.  While  eggs  were 
present  in  the  collections,  identification  is  uncer- 
tain in  view  of  the  conspicuous  absence  of  the 
intervening  yolk-sac  stages.  Perhaps,  the  yolk  sac 
ruptured  or  collapsed  at  capture  due  to  mechani- 
cal stress. 

All  specimens  used  in  this  study  are  deposited  in 
the  larval  fish  laboratory  of  the  Miami  Labora- 
tory, Southeast  Fisheries  Center  of  the  National 
Marine  Fisheries  Service. 


DESCRIPTIONS 

Rainbow  runner,  Elagatis  bipinnulata 
(Quoy  and  Gaimard) 
Figure  1 

Literature 

Larval  stages  of  this  species  from  the 
Indo-Pacific  oceans  were  illustrated  and  described 
by  Okiyama  (1970)  who  also  traced  their  de- 
velopment. Berry  (1969)  illustrated  an  18.5-mm 
juvenile  from  the  Straits  of  Florida.  Schnaken- 
beck  (1931)  illustrated  an  11.5-mm  larva  from  the 
Lesser  Antilles  under  the  name  of  Caranx  hel- 
volus. 


417 


FISHERY   BULLETIN:  VOL.  72.  NO.   2 


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418 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 


Distinguishing  Features 

Larvae  ofElagatis  bipinnulata  are  distinct  from 
those  of  other  carangids  in  having  only  two  spines 
in  the  anal  fin.  Following  transformation,  the 
terminal  dorsal  and  anal  soft  fin  rays  become 
gradually  separated  from  these  fins.  These  larvae 
are  remarkably  similar  to  those  oiSeriola  species 
in  size,  structure,  and  pigmentation.  Unlike  the 
larvae  of  Seriola,  however,  they  have  a  supraoc- 
cipital  crest,  serrations  on  the  preopercular 
spines,  and  all  the  dorsal  spines  are  about  equal  in 
length.  The  first  interhemal  spine  is  only  slightly 
swollen  and  is  not  pressed  nor  fused  with  the 
hemal  spine  of  the  first  caudal  vertebra  (Starks, 
1911).  The  larvae  transform  at  10  to  14  mm. 
the  other  interhemal  and  hemal  spines.  In  many 


carangids  the  first  interhemal  spine  is  much  en- 
larged and  pressed  against  or  fused  with  the 
hemal  spine  of  the  first  caudal  vertebra  (Starks, 
1911).  The  larvae  transform  at  10  to  14  mm. 

Morphology 

Larvae  ofE.  bipinnulata  are  deep-bodied.  Body 
depth  at  the  base  of  the  pectoral  fin  is  32%  of  the 
standard  length  at  3.8  mm;  it  attains  a  maximum 
of  40%  at  initial  notochord  flexion  and  is  never  less 
than  33%  during  the  entire  period  of  larval  de- 
velopment (Table  2). 

The  head  is  large  and  deep.  Relative  length  of 
the  head  increases  throughout  the  larval  and 
transition  periods.  Head  length  is  31.6%  at  3.8 
mm,  increases  to  35  to  49%  at  notochord  flexion, 


Table  2. — Measurements  (mm)  of  larvae  and  juveniles  ofElagatis  bipinnulata. 
(Specimens  between  dashed  lines  are  undergoing  notochord  flexion.) 


Stan- 
dard 

Snout-to- 
anus 

Head 

Head 

Body  depth 

at  base  of 

pectoral 

fin 

Orbit 
Snout 

Orbit 

Snout  to  fin  origin 

length 

distance 

length 

depth 

length 

diametei 

Predorsal 

Prepelvic 

Preanal 

3.8 

1.9 

1.2 

1.2 

1.2 

0.32 

030 

_ 

_ 

_ 

3.9 

1.96 

1.25 

1.25 

1.2 

.32 

,30 

~ 

~ 

~ 

46 

29 

1.6 

1.7 

1.5 

.48 

.55 

2.0 

2.0 

2.0 

5.0 

3.5 

2.0 

20 

2.1 

.58 

.50 

2.7 

2.0 

4,0 

5,2 

3.5 

2.1 

22 

2.1 

.59 

.60 

2.7 

2.2 

3.6 

5.9 

3.5 

2.2 

2.3 

22 

.50 

.65 

2.8 

2.4 

3.6 

6.1 

3.9 

2.1 

22 

2.3 

.52 

.65 

3.0 

25 

4.4 

62 

3.9 

2.3 

2.4 

22 

.55 

.65 

3.0 

2.5 

4.1 

7.0 

4.4 

2.5 

26 

2.4 

.60 

.70 

.35 

2.8 

4.5 

8.5 

5.1 

28 

3.0 

28 

.75 

.77 

4,0 

3.2 

5.2 

8.7 

5.3 

3.0 

3.2 

3.1 

.75 

.77 

4.1 

3.4 

5.5 

95 

60 

3.2 

3.3 

32 

.80 

1.0 

4.1 

35 

6.1 

9.7 

6.0 

3.2 

3.3 

3.3 

.85 

1.0 

4.5 

36 

62 

MO.O 

6,1 

3.8 

3.5 

3.4 

.90 

1.2 

46 

3.6 

62 

'11.0 

7.2 

3.8 

3.8 

38 

1.0 

1.0 

5.2 

40 

7.4 

Ml. 2 

7.2 

42 

40 

35 

1.1 

1.2 

5,5 

43 

7.4 

'11.5 

7.2 

4.3 

3.8 

3.8 

1.2 

1.2 

6,0 

43 

7.5 

'118 

7.3 

4.0 

36 

36 

1.1 

1.2 

60 

4.3 

7.5 

'12,0 

7.4 

4.0 

3.8 

3.8 

1,2 

1,3 

6.0 

4.5 

7.4 

'12.5 

7.5 

4.2 

38 

3.8 

1.1 

1,4 

5.9 

4.8 

7.8 

'13.0 

7.5 

4.0 

4.0 

3.9 

1.2 

1,3 

6.0 

5.0 

8-0 

'13.2 

7.8 

4.0 

40 

3.9 

1.0 

1.4 

5.8 

48 

80 

'13.3 

8.1 

4.5 

4.1 

4.2 

1.2 

1.3 

6.1 

5.0 

86 

'14.0 

8.5 

5.3 

4.9 

45 

1.5 

13 

6.3 

5.5 

90 

214.1 

8.5 

5.0 

4.9 

45 

1.5 

1.4 

6.1 

5.4 

9.0 

214.5 

9.5 

5.0 

48 

4.6 

1,7 

1.3 

6.0 

5.2 

9.8 

214.8 

9.0 

4.8 

46 

4.5 

1,7 

1.4 

6.5 

5.4 

9.8 

215.2 

9.5 

5.3 

4.7 

4.3 

1,6 

1.5 

6.5 

5.3 

9.9 

215.5 

9.0 

5.4 

4,7 

4.6 

1.6 

1.3 

6.6 

52 

9.7 

216.2 

10.0 

5.6 

4.9 

48 

1.7 

1.6 

7.0 

6.0 

11.0 

216.8 

102 

5.7 

5.0 

4,7 

18 

1.5 

8.0 

7.0 

106 

217.0 

10.0 

5.6 

5.0 

4,9 

19 

1.3 

7.0 

6.0 

10.5 

218.0 

100 

6.0 

5.0 

5,0 

1.9 

1.5 

7.5 

6.0 

11.0 

2184 

10.5 

6.0 

50 

56 

1.8 

1.5 

8.1 

5,9 

11.0 

'Transforming. 
2Juveniles. 


419 


and  averages  35%  during  the  late  larval  and  early 
juvenile  stages.  The  head  is  as  deep  as  long  at  3.8 
mm  and  is  deeper  than  long  for  most  of  the  larval 
period.  Head  depth  reaches  a  maximum  of  110%  of 
the  head  length  at  5  mm  and  averages  101%  in  the 
late  larvae.  The  dorsal  profile  of  the  snout  is 
slightly  concave  at  3.8  mm;  at  notochord  flexion,  it 
becomes  indented  at  the  anterior  and  posterior 
margins  of  the  slightly  swollen  forebrain.  These 
indentations  disappear  in  older  larvae  and  at 
transformation,  the  dorsal  profile  becomes  convex. 

The  eyes  are  round  and  large.  Relative  eye 
diameter  ranges  from  26.3  to  31.3%  of  the  head 
length.  A  low  orbital  crest  is  formed  above  the  eyes 
in  early  larvae  but  regresses  at  metamorphosis. 

A  supraoccipital  crest  is  present  throughout  the 
larval  stages.  At  15  mm,  the  crest  is  much  reduced 
and  is  no  longer  visible  externally  but  may  be 
observed  in  cleared  and  stained  specimens. 

There  are  two  series  of  preopercular  spines:  one 
along  the  margin  and  another  on  the  lateral  sur- 
face. Spines  on  the  lower  margin  are  bigger  and 
more  serrated  than  those  on  the  lateral  surface. 
All  preopercle  spines  gradually  diminish  in  size 
and  are  completely  overgrown  by  the  expanding 
preopercle  bones  following  metamorphosis. 

The  gut  is  long  and  coiled  in  a  single,  rounded 
loop  in  larvae  up  to  a  length  of  12  mm;  at  18  mm,  a 
second  loop  is  added.  Hypaxial  muscles  enclose  the 
gut  at  5  mm  and  completely  cover  the  abdominal 
cavity  except  at  the  opening  of  the  gut  at  8  mm. 

The  number  of  myomeres  is  constant — 10 
preanal  plus  14  postanal — throughout  the  larval 
and  early  juvenile  periods. 

The  first  scales  formed  are  those  found  along  the 
lateral  line  near  the  caudal  peduncle.  Lateral  line 
scales  ossify  in  a  posteroanterior  direction  at  15 
mm.  Regular  body  scales  are  not  ossified  until  the 
juveniles  are  at  least  20  mm  long. 

Pigmentation 

Larvae  are  among  the  most  intensely  pig- 
mented of  carangids.  In  the  early  larvae  (3.8-4.6 
mm),  the  most  conspicuous  pattern  of  pigmenta- 
tion includes  melanophores  along  the  bases  of  the 
dorsal  and  anal  fins  and  along  the  lateral  midline 
(Figure  lA,  B).  Small  patches  of  melanophores  are 
present  on  the  head,  jaws,  snout,  and  on  the  upper 
sides  of  the  body.  Internal  pigmentation  is  concen- 
trated on  the  dorsal  wall  of  the  peritoneum.  At  5  to 
6  mm,  melanophores  develop  profusely  all  over 
the  body  leaving  only  a  small  unpigmented  area  at 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 

the  caudal  peduncle  (Figure  1C,D).  A  row  of 
closely  spaced  pigment  cells  along  the  midventral 
line  below  the  gut  is  notable  and  distinguishes 
early  larvae  from  similarly  pigmented  larvae  of 
Seriola.  Xanthophores  (yellow)  develop  profusely 
on  the  head  and  back  in  late  larvae.  At 
metamorphosis,  iridiophores  (reflecting),  xantho- 
phores, and  melanophores  cover  the  whole  length 
of  the  body  except  on  the  jaws  and  fins,  and  an 
irregular  row  of  large  melanophores  is  formed  on 
the  upper  side  of  the  body  (Figure  IE).  The 
melanophores  are  capable  of  expansion  and  con- 
traction and  the  larvae  are  pale  or  dark  depending 
on  the  state  of  the  pigment  cells.  Iridiophores  and 
xanthophores  fade  upon  preservation.  The  only 
chroma tophores  apparent  in  preserved  specimens 
are  the  melanophores. 

Fin  Development 

Rudiments  of  all  fins  except  the  ventral  fins  are 
present  in  the  smallest  larva  (3.8  mm)  and  are 
situated  in  about  the  position  they  occupy  at  older 
stages.  The  fins  ossify  in  the  following  sequence:  1) 
caudal,  2)  first  dorsal  and  anal,  3)  second  dorsal 
and  pectoral,  4)  ventral.  All  fins  are  essentially 
complete  at  metamorphosis  (Table  3). 

In  the  pectoral  fins  the  dorsalmost  rays  are  the 
first  to  ossify  at  5  mm,  and  the  rest  of  the  rays  are 
added  ventrally.  The  full  complement  of  18  to  21 
rays  is  present  at  8  mm. 

The  pelvic  fins  ossify  at  6  mm,  and  the  full  com- 
plement of  5  rays  is  present  at  8  mm.  The  pelvic  fin 
rays  grow  fast,  and  at  transformation  they  are 
about  as  long  as  the  pectoral  fins. 

Ossification  of  the  dorsal  and  anal  fin  rays  pro- 
ceed in  an  anteroposterior  direction  in  an  orderly 
manner.  The  anteriormost  rays  are  the  first  to 
ossify  at  5  mm,  and  ossification  continues  pos- 
teriad.  The  last  two  fin  rays  are  gradually  sepa- 
rated beginning  at  metamorphosis  in  a  manner 
described  by  Berry  ( 1969).  The  full  complement  of 
7  spines  and  25  to  30  soft  rays  is  present  at  10  mm. 
The  dorsal  spines  are  of  almost  uniform  height  in 
the  larvae.  In  early  juveniles  (17  mm),  their 
height  is  about  half  that  of  the  soft  rays.  The  first 
and  second  dorsal  fins  are  continuous  throughout 
the  larval  and  transition  stages.  The  full  comple- 
ment of  2  spines  and  19  to  20  soft  rays  in  the  anal 
fin  is  completed  at  10  mm. 

Caudal  fin  formation  has  begun  in  the  smallest 
larva  (3.8  mm).  This  is  indicated  by  the  presence  of 
a  thickening  near  the  tip  of  the  notochord.  When 


420 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 

Table  3. — Meristic  characters  of  cleared  and  stained  larvae  and  juveniles  oiElagatis  bipinnulata. 


Left 

Left 

Primary  caudal 

Secondary  caudal 

Gill  rakers. 

Left  pre- 
opercular 

Standard 
length 

pectoral          pelvic 

fin 

rays 

fin 

rays 

left  first 

margin 

Dorsal  fin                       Anal  fin 

fin 

fin 

Dorsal 

Ventral 

Dorsal 

Ventral 

gill  arch 

spines 

3.8 

. 

_ 

_ 

_ 

_ 

- 

_ 

_ 

- 

7 

4.6 

- 

- 

- 

- 

2 

2 

- 

- 

0  +  5 

7 

5.4 

V 

18 

1,  10 

5 

7 

8 

- 

- 

0+11 

8 

6.0 

V 

24 

,  16 

13 

,  2 

8 

8 

2 

4 

2  +  13 

8 

7.0 

VI 

1,  25 

.  18 

17 

,  4 

9 

8 

4 

5 

4  +  15 

7 

8.0 

VI 

1.  24 

1,  19 

18 

.  5 

9 

8 

8 

9 

5+18 

6 

9.0 

VI 

1.26 

1,  20 

19 

.  5 

9 

8 

9 

9 

5  +  18 

8 

10.4 

VI 

1,  27                              1 

1.  20 

19 

,  5 

9 

8 

9 

9 

6+22 

7 

11.5 

VI 

1,  26                              1 

1,  19 

20 

,  5 

9 

8 

10 

9 

7  +  21 

5 

12.0 

VI 

1.  27                              1 

1.  20 

19 

,  5 

9 

8 

10 

10 

7  +  21 

5 

13.1 

VI 

1,  28                              1 

1,  19 

20 

,  5 

9 

8 

10 

9 

7  +  21 

4 

14.7 

VI 

1,28                              1 

1,  19 

20 

.  5 

9 

8 

10 

10 

8  +  21 

2 

15.2 

VI 

1,  27                              1 

1,  19 

20 

.  5 

9 

8 

11 

10 

8  +  23 

2 

16.0 

VI 

1,  27                              1 

1.  19 

20 

.  5 

9 

8 

11 

10 

8  +  22 

2 

17.1 

VI 

1,  27 

1,  19 

20 

,  5 

9 

8 

10 

11 

8  +  23 

1 

18.0 

VI 

1,26 

1,  19 

20 

,  5 

9 

8 

11 

11 

8  +  22 

1 

19.0 

VI 

1.27 

1,  19 

19 

,  5 

9 

8 

11 

10 

8  +  24 

1 

19.5 

VI 

1,27                              1 

1.  19 

20 

.5 

9 

8 

11 

11 

8  +  24 

1 

20.0 

VI 

1,  27                              1 

1.  19 

19 

,  5 

9 

8 

10 

10 

9  +  25 

1 

23.3 

VI 

1,  27 

1,  19 

21 

,  5 

9 

8 

11 

10 

8  +  27 

1 

the  larvae  are  4  to  5  mm  long,  the  thickening 
differentiates  into  hypural  elements,  the 
notochord  starts  flexion,  and  the  median  caudal 
rays  ossify.  The  hypural  elements  ossify  at  6  mm, 
the  full  complement  of  9  dorsal  and  8  ventral  prin- 
cipal rays  is  present  at  7  mm,  and  notochord 
flexion  is  completed  at  8  mm.  The  secondary  rays 
ossify  at  6  mm  beginning  with  the  posteriormost 
rays.  The  full  complement  of  10  to  11  dorsal  and  of 
10  to  11  ventral  secondary  rays  is  formed  at  12 
mm. 

The  last  3  vertebrae,  the  hypural  elements,  and 
5  dorsal  structures  including  the  neural  spine  of 
the  antepenultimate  vertebra,  3  median  epurals, 
and  a  specialized  neural  process  support  the 
caudal  fin.  The  supporting  structures  articulate 
with  the  principal  and  secondary  caudal  rays. 
They  are  generally  similar  to  those  occuring  in 
Trachurus  symmetricus  (Ahlstrom  and  Ball, 
1954). 

Distribution  and  Spawning 

Elagatis  bipinnulata  has  a  circumtropical  dis- 
tribution (Briggs,  1960).  It  has  been  previously 
reported  from  Texas,  Florida,  and  Long  Island 
(Ginsburg,  1952)  and  is  also  known  from  the  West 
Indies  (Jordan  and  Evermann,  1896),  Japan 
(Okada,  1966),  Hawaii  (Gosline  and  Brock,  1960), 
Africa  (Fowler,  1936),  Philippines  (Herre,  1953), 
and  the  Great  Barrier  Reef  (Marshall,  1965).  The 
larvae  were  reported  by  Okiyama  (1970)  to  be  the 
most  abundant  form  of  epipelagic  larval  carangid 
in  the  tropical  as  well  as  in  the  subtropical 


Indo-Pacific    ocean   where    spawning   occurs 
throughout  the  year  with  a  peak  in  March. 

In  the  present  study,  larvae  and  early  juveniles 
less  than  20  mm  have  been  taken  in  every  month 
except  in  May  and  December.  While  the  speci- 
mens are  too  few  to  give  conclusive  information,  it 
appears  that  spawning  may  occur  throughout  the 
year.  The  larvae  were  taken  mainly  in  offshore 
waters  in  the  eastern  Gulf  of  Mexico,  in  the  Santa- 
ren  Channel,  the  Straits  of  Florida,  and  the 
Carolina  Bight  off  New  Brunswick,  Ga.  (Figure  2). 
They  occurred  in  2.6%  of  the  net  stations  and  con- 
stituted 2.39c  of  the  young  carangids  collected. 


Figure  2. — Locations  of  collections  of  larval  carangids  during 
two  cruises  of  the  Oregon  II  from  July  to  August  and  from 
October  to  November  1970  and  a  cruise  of  the  Tursiops  in  August 
1971.  Records  of  occurrences  oiElagatis  bipinnulata  are  shown 
as  solid  circles,  those  of  Seriola  zonata  as  solid  triangles,  and 
those  of  Selene  vomer  as  solid  squares.  Open  circles  represent 
other  stations  occupied. 


421 


During  its  larval  life,  Elagatis  bipinnulata  is 
planktonic.  Some  larvae  and  juveniles  become  as- 
sociated with  the  pelagic  sargassum  community 
(Dooley,  1972)  and  are  carried  along  the  Florida 
Current  and  Gulf  Stream. 


Banded  rudderfish, 

Seriola  zonata  (Mitchill) 

Figure  3 

Literature 

Larvae  of  Seriola  zonata  have  not  been  previ- 
ously described.  Early  juveniles  of  the  banded 
stage  were  described  by  Nichols  (1946),  Ginsburg 
(1952),  and  Mather  (1958).  Lutken  (1880)  illus- 
trated an  unhanded  20-mm  juvenile. 

As  noted  earlier,  larvae  ofSeriola  dumerili  were 
described  by  Hildebrand  and  Cable  (1930)  and 
Sanzo  (1933).  Japanese  workers  have  described 
life  history  series  of  three  species  of  Seriola.  The 
most  detailed  study  of  development  from  eggs  to 
juveniles  was  made  on  Seriola  quinqueradiata 
[Uchida,  Dotu  et  al.  (1958),  Uchida  in  Uchida, 
Imai  et  al.  (1958),  Mitani  (1960),  and  Mito  (1961)]. 
Larvae  and  juveniles  of  two  other  Japanese 
species,  S.  aureovittata  and  S.  purpurascens  were 
covered  by  Uchida  in  Uchida,  Imai  et  al.  (1958). 

Distinguishing  Features 

Seriola  larvae  resemble  most  those  of  Elagatis 
bipinnulata  in  size,  body  structure,  and  pigmenta- 
tion. Unlike  £.  bipinnulata,  however,  there  is  no 
supraoccipital  crest;  the  spines  of  the  dorsal  fin  are 
of  unequal  length,  the  anterior  and  posterior  ones 
being  shorter;  and  the  preopercular  spines  have 
smooth  sides  until  the  transition  period  when  the 
longest  spine  develops  1  to  2  denticles.  The  larvae 
transform  at  about  13  mm.  They  are  deep-bodied 
and  robust.  The  head  is  massive  and  slightly  de- 
pressed, and  the  eyes  protrude  slightly  from  the 
orbit  at  the  dorsal  side. 

Early  larvae  of  Seriola  zonata  (3-7  mm)  are  dif- 
ferentiated from  those  of  other  species  of  Seriola 
by  the  presence  of  5  to  6  large  melanophores  on  the 
middorsal  line  at  the  base  of  the  dorsal  fin  (Figure 
3  B).  These  large  melanophores  which  are  apposed 
to  the  myomeres  stand  out  among  the  more 
numerous  and  smaller  pigment  spots  on  the  back 
and  sides.  In  older  larvae  these  melanophores  be- 
come embedded  in  the  muscles  and  covered  by 


FISHERY   BULLFTIN:  VOL    72.  NO.  2 

superficial  melanophores.  When  the  full  comple- 
ment of  dorsal  fin  rays  is  formed  at  about  8  mm, 
larvae  of  S.  zonata  are  distinct  in  having  35  to  40 
soft  rays  in  the  second  dorsal  fin,  the  highest  sec- 
ond dorsal  fin  ray  count  of  all  species  of  Seriola. 
All  dorsal  fin  rays  are  sharply  visible  even  in  un- 
stained specimens. 

The  first  interhemal  spine  of  the  first  ventral 
pterygiophore  is  only  slightly  enlarged  and  does 
not  press  against  the  first  hemal  spine. 

Morphology 

Maximum  body  depth  at  3.6  mm  is  30%  of  the 
standard  length.  It  increases  to  37%  at  initial 
notochord  flexion  and  does  not  change 
significantly  during  larval  and  transition  periods. 
In  early  juveniles,  the  body  depth  is  never  less 
than  30%  of  the  standard  length  (Table  4). 

Head  length  is  33%  of  standard  length  in  the 
smallest  larva  (3.6  mm)  and  attains  a  maximum  of 
43%  at  7.0  mm.  Thereafter,  head  length  decreases 
gradually,  with  an  average  of  35%  in  early 
juveniles  18.0  mm  in  length.  Depth  of  head  is  91% 
of  the  head  length  at  3.6  mm  and  attains  a  max- 
imum of  122%  at  5  mm.  Thereafter,  head  depth 
decreases  slightly  and  is  never  less  than  89%  of 
the  head  depth  throughout  the  larval  and  juvenile 
periods.  The  dorsal  profile  of  the  snout  is  slightly 
concave  at  3.6  mm  but  becomes  straight  at  about  5 
mm  and  then  convex  in  the  older  larvae  and 
juveniles. 

The  eyes  are  round  and  large,  and  the  orbit 
diameter  increases  in  relation  to  head  length.  Rel- 
ative orbit  diameter  ranges  from  28  to  36%  of  the 
head  length  in  larvae  and  transforming  specimens 
and  gradually  increases  in  early  juveniles.  A  low 
orbital  crest  with  a  weak  spine  is  present  in  the 
early  larvae  and  is  resorbed  at  metamorphosis. 

Marginal  and  lateral  surface  preopercular 
spines  are  present.  The  marginal  angle  spine 
which  is  the  longest  develops  1  or  2  denticles  on  its 
dorsal  side  in  transforming  larvae  and  early 
juveniles.  All  preopercular  spines  gradually 
diminish  in  size  and  become  overgrown  by  the 
expanding  preopercle. 

Scales  along  the  posterior  end  of  the  lateral  line 
in  front  of  the  caudal  peduncle  are  formed  at  20 
mm.  Subsequently,  the  scales  along  the  anterior 
portion  of  the  lateral  line  ossify,  followed  by  those 
on  the  head  and  sides  of  the  body. 

The  slender  gut  is  coiled  in  a  single  loop  in 
larvae  up  to  10  mm  long.  The  number  of  loops 


422 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 


Table  4— Measurements  (mm)  of  larvae  and  juveniles  of  Seriola  zonata. 
(Specimens  between  dashed  lines  are  undergoing  notochord  flexion.) 


Stan- 
dard 

Snout-to- 
anus 
distance 

Head 
length 

Head 
depth 

Body  depth 

at  base  of 

pectoral 

fin 

Snout 
length 

Orbit 
diameter 

Snout  to  fin  origin 

length 

Predorsal           Prepelvic 

Preanal 

3.6 
3.7 

2.1 
2.3 

1.2 
1.25 

1.1 
1.15 

1.1 
1.2 

0.35 
.36 

0.36 
.36 

- 

- 

4.7 

3.0 

16 

1.5 

1.5 

.42 

.42 

- 

- 

_ 

5.5 

3.5 

1.8 

2.1 

2.0 

.50 

.60 

2.5 

2.1 

3.6 

5.6 

3.5 

1.8 

2.2 

2.0 

.52 

.62 

2.5 

2.1 

3.7 

62 

4.0 

2.0 

2.3 

2.0 

.65 

.70 

2.9 

2.2 

4.0 

6.4 

3.9 

2.3 

23 

2.1 

.65 

.70 

2.9 

2.5 

4.0 

65 

4.0 

2.5 

2.5 

2.3 

.65 

.72 

3.0 

2.5 

4.2 

68 

4.5 

2.8 

2.6 

2.4 

.67 

.72 

3.4 

2.8 

4.6 

7.0 

4.6 

3.0 

2.8 

2.5 

.70 

.75 

3.4 

2.9 

4.8 

7.1 

4.7 

3.0 

3.0 

2.6 

.72 

.75 

3.5 

2.8 

5.0 

7.5 

4.8 

3.0 

3.0 

2.5 

.80 

.85 

3.8 

3.0 

5.0 

8.0 

5.2 

3.0 

2.8 

2.5 

.85 

.90 

3.8 

3.0 

5.3 

8.2 

5.2 

3.1 

3.1 

2.8 

.90 

1.0 

3.9 

3.2 

5.3 

8.4 

5.4 

3.2 

3.5 

3.2 

1.0 

1.1 

4.0 

3.5 

5.5 

9.1 

5.8 

3.5 

3.5 

3.2 

1.0 

1.2 

4.1 

3.9 

5.9 

9.5 

6.2 

3.5 

3.6 

3.2 

1.0 

1.2 

4.3 

3.9 

6.4 

9.8 

6.2 

4.0 

3.8 

3.5 

1.2 

1.3 

4.3 

4.1 

6.4 

MOO 

6.5 

4,0 

3.8 

3.5 

1.1 

1.3 

4.3 

4.1 

6.6 

'10.3 

6.6 

4.0 

3.8 

3.5 

1.1 

1.3 

4.5 

4.1 

6.8 

'10.8 

7.4 

4.2 

4.0 

3.6 

1.3 

1.5 

5.2 

4.4 

7.6 

'11.9 

8.4 

4.7 

4.8 

4.5 

1.5 

1.6 

5.8 

5.5 

8.6 

'12.0 

8.5 

4.9 

4.8 

4.5 

1.6 

1.6 

6.0 

56 

8.6 

'12.1 

8.5 

5.0 

4.6 

4.5 

1.6 

1.6 

5.9 

5.6 

8.6 

'12.5 

8.6 

5.0 

4.8 

4.5 

1.6 

1.6 

6.0 

5.2 

8.7 

'13.1 

8.8 

5.0 

4.8 

4.5 

1.4 

1.8 

6.1 

5.3 

8.3 

213.5 

9.2 

5.0 

4.8 

4.6 

1.5 

1.9 

6.1 

5.6 

9.5 

213.6 

9.2 

50 

4.6 

4.5 

1.4 

2.0 

6.2 

5.5 

10.0 

215.0 

9.8 

5.5 

5.0 

5.0 

1.4 

2.0 

6.0 

55 

10.2 

215.1 

10.0 

5.6 

5.0 

5.0 

1.5 

2.0 

6.3 

5.5 

10.5 

215.2 

10.0 

5,7 

5.1 

5.2 

1.5 

2.0 

6.4 

5.6 

10.6 

216.2 

10.5 

5,8 

5.2 

5.4 

1.6 

2.1 

7.5 

5.8 

11.0 

217.5 

10.5 

6,0 

5.5 

6.0 

1.5 

2.2 

7.5 

6.0 

11.0 

218.1 

no 

6,5 

5.8 

6.2 

1.7 

2.3 

7.5 

7.0 

11.0 

'Transforming, 

2Juveniles. 

increases  with  growth  and  at  15  mm  four  loops  are 
present.  Snout-to-anus  distance  increases  in  rela- 
tion to  standard  length.  It  is  58.39c  at  3.6  mm  and 
gradually  increases  to  70^^  at  transformation. 
Hypaxial  musculature  develops  at  6  mm  and  com- 
pletely surrounds  the  abdominal  cavity  except  at 
the  gut  opening  at  10  mm. 

There  are  24  myomeres — 10  preanal  plus  14 
postanal — throughout  the  larval  and  juvenile 
stages. 

Pigmentation 

Larval  pigmentation  consists  of  conspicuous 
melanophores  along  the  bases  of  the  dorsal  and 
anal  fins,  on  the  lateral  midline,  and  in  the 
peritoneum  lining  the  middorsal  wall  of  the  ab- 
dominal cavity.  In  a  freshly  preserved  9-mm  larva 
there  are  dense  concentrations  of  xanthophores  on 


the  head,  preopercle,  and  on  the  back  and  upper 
sides  of  the  body  while  iridiophores  are  profuse  on 
the  sides  of  the  body  below  the  lateral  midline.  In 
older  larvae,  the  melanophores  are  apparently  ac- 
tively expanding  and  contracting  as  most  larvae 
have  either  contracted  melanophores  and  are  pale 
looking,  or  are  dark  when  the  melanophores  are 
expanded.  Other  larvae  have  alternating  patches 
of  expanded  and  contracted  melanophores  form- 
ing false  bands  (Figure  3F-H).  In  early  juveniles 
(17  mm),  the  body  definitely  becomes  banded.  A 
bold  color  pattern  develops  including  a  distinct 
nuchal  bar  and  6  solid  bands  which  extend  to  the 
dorsal  and  anal  fins  (Figure  31).  In  a  young 
juvenile  23  mm  long,  the  lobes  of  the  unpigmented 
caudal  fin  have  a  brown  spot  developing  at  the 
tips.  Alcohol-preserved  metamorphic  larvae  and 
early  juveniles  have  chocolate-brown  bands  over  a 
silvery  background.   With  the  exception  of 


423 


FISHERY  BULLETIN;  VOL.  72.  NO.  2 


!->i?.--. -■■■■■ 


424 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 


o 

en 
g 
S 

ea 

CO 

S 
G 
<o 

m 


B 
E 

CO 


CO 

S 
S 


■5  ii 

^   CO 

o 


en 
E 
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«^   E 

a  "  s 

OS* 


425 


melanophores,  all  other  chromatophores  fade  on 
preservation  in  formaldehyde  solution. 

Fin  Development 

The  dorsal,  anal,  caudal,  and  pectoral  finfolds 
are  present  in  the  youngest  larva  (3.6  mm).  Dif- 
ferentiation of  the  fin  rays  occurs  in  the  following 
sequence:  1)  caudal,  2)  first  dorsal  and  anal,  3) 
second  dorsal  and  pectoral,  4)  ventral.  All  fins  are 
essentially  formed  at  9  mm  (Table  5). 

The  pectoral  fin  rays  ossify  at  6  mm  beginning 
with  the  most  dorsal  rays,  and  the  rest  ossify  ven- 
trally.  The  full  complement  of  19  to  20  rays  is 
formed  at  10  mm. 

The  pelvic  fin  rays  differentiate  at  7  mm,  and 
the  full  complement  of  5  rays  is  present  at  9  mm. 

The  dorsal  and  anal  fin  rays  ossify  anteropos- 
teriorly.  At  8  to  9  mm  the  full  number  of  8  spines  in 
the  first  dorsal  fin  and  1  spine  and  35  to  40  soft  rays 
in  the  second  dorsal  is  completed.  The  first  dorsal 
fin  becomes  arch-shaped  as  the  spines  increase  in 
height  and  remains  continuous  with  the  second 
dorsal  fin  until  in  early  juveniles  (15-17  mm)  a 
deep  notch  demarcates  the  2  fins.  The  anal  fin  rays 
begin  to  ossify  at  5  mm,  and  the  full  complement  of 
3  spines  and  19  to  22  soft  rays  is  completed  at  10 
mm. 

The  caudal  fin  begins  to  develop  at  4  to  5  mm  in 
a  manner  similar  to  that  occurring  in  Elagatis 
bipinnulata.  The  full  complement  of  9  dorsal  and 
8  ventral  principal  rays  is  present  at  7  to  8  mm, 
while  the  full  complement  of  10  to  11  dorsal  and 
of  9  to  10  ventral  secondary  rays  is  completed  at  9 
mm. 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

Distribution  and  Spawning 

Juveniles  of  Seriola  zonata  (12-23  mm)  have 
been  reported  to  be  regular  summer  visitors  in 
Cape  Cod  waters  which  appear  to  be  their  most 
northernly  record  (Mather,  1952).  Adults  have 
been  recorded  from  various  points  of  the  Atlantic 
coast  and  in  the  Gulf  of  Mexico  (Ginsburg,  1952). 

Larvae  and  early  juveniles  up  to  26  mm  were 
taken  in  all  months  except  in  February,  April, 
September,  and  December.  They  were  caught  with 
a  1-m  plankton  net  in  the  Gulf  Stream  off  Miami, 
with  dip  nets  at  the  pier  of  the  Southeast  Fisheries 
Center  in  Biscayne  Bay,  and  with  neuston  nets  in 
the  Gulf  of  Mexico,  Yucatan  Channel,  Straits  of 
Florida,  and  south  Atlantic  coast.  The  larvae  oc- 
curred in  1.4%  of  the  net  stations  and  constituted 
1.8%  of  the  larval  carangids  in  the  collection.  The 
occurrence  of  the  larvae  is  too  erratic  to  indicate 
whether  or  not  the  spawning  period  is  continuous 
over  12  mo  or  broken  into  two  parts,  winter-spring 
and  fall.  Spawning  occurred  mainly  in  offshore 
waters  in  the  eastern  Gulf  of  Mexico,  Yucatan 
Channel,  Santaren  Channel,  along  the  edge  of  the 
continental  shelf  in  the  Straits  of  Florida,  and  in 
the  Carolina  Bight  off  New  Brunswick,  Ga.  (Fig- 
ure 2).  The  planktonic  larvae  are  presumably  car- 
ried along  the  Florida  Current  and  Gulf  Stream 
and  reach  their  northern  limits  as  juveniles. 

Round  scad,  Decapterus  punctatus 
(Agassiz) 

Figure  4 
Literature 

The  early  growth  of  this  species  were  described 


Table  5. — Meristic  characters  of  cleared  and  stained  larvae  and  juveniles  ofSeriola  zonata. 


Primary  caudal 

Secondarv  caudal 

Left  pre- 

Left                 Left 

fin 

rays 

fin 

rays 

Gill  rakers, 

opercular 

Standard 

pectoral          p 
fin 

BlvIC 

fin 

left  first 
gill  arcfi 

margin 
spines 

length 

Dorsal  fin 

Anal  fin 

Dorsal 

Ve 

ntral 

Dorsal 

Ventral 

3.6 

_ 

4 

4.4 

- 

- 

- 

- 

4 

5 

_ 

_ 

_ 

4 

5.5 

IV 

5 

- 

- 

8 

7 

_ 

_ 

0  +  6 

5 

6.5 

VI 

22 

11 

8 

- 

9 

8 

- 

_ 

0  +  8 

6 

75 

VII 

30 

16 

10. 

,3 

9 

8 

1 

2 

0  +  11 

7 

8.4 

VIII 

1,  34 

19 

13 

,  4 

9 

8 

3 

3 

3+13 

7 

9.5 

VIII 

1,  36 

20 

17 

,  5 

9 

8 

5 

5 

4  +  15 

7 

10.3 

VIII 

1.  38 

1,  20 

18 

,5 

9 

8 

7 

8 

5  +  15 

7 

11.2 

VIII 

1,  39 

1.  21 

20 

,  5 

9 

8 

8 

8 

5+15 

7 

12.0 

VIII 

1,  36 

1,  22 

20 

.  5 

9 

8 

9 

8 

5  +  15 

5 

13.0 

VIII 

1,  37 

1,  20 

20 

.  5 

9 

8 

9 

9 

5+16 

3 

14.2 

VIII 

1,  36 

1.  19 

20 

,  5 

9 

8 

10 

9 

6  +  16 

4 

15.2 

VIII 

1,  38 

1.  20 

19 

,  5 

9 

8 

11 

10 

6  +  16 

4 

16.0 

VIII 

1,  40 

1,  21 

20 

,  5 

9 

8 

11 

10 

6  +  17 

4 

17.0 

VIM 

1,38 

1,  20 

20 

,  5 

9 

8 

11 

10 

8  +  18 

3 

426 


APRIETO:  EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 


by  Hildebrand  and  Cable  (1930)  who  also  studied 
the  abundance  and  distribution  of  the  young  up  to 
50  mm  taken  from  the  coastal  and  offshore  waters 
of  Beaufort,  N.C.  In  addition,  life  history  series 
were  described  for  two  species  of  Decapterus  from 
the  Indo-Pacific  region:  D.  russelli  by  Vij- 
ayaraghavan  (1958)  andD.  maruadsi  by  Shojima 
(1962).  The  latter  series  is  quite  similar  to  that  of 
D.  punctatus. 

Distinguishing  Features 

Larvae  of  D.  punctatus  are  decidedly  deep- 
bodied  although  the  adults  are  the  most  slender  of 
all  carangids.  The  head  has  a  supraoccipital  and 
an  orbital  crest  and  preopercular  spines.  During 
metamorphosis,  the  ultimate  rays  of  the  dorsal 
and  anal  fins  become  separated  and  modified  into 
finlets.  The  first  interhemal  spine  is  slightly  swol- 
len. Together  with  the  hemal  spine  of  the  first 
caudal  vertebra  to  which  it  is  closely  apposed  it 
forms  a  strong  brace  at  the  posterior  border  of  the 
abdominal  cavity.  There  are  25  vertebrae — 10 
trunk  plus  15  caudal.  D.  punctatus  is  one  of  the 
few  carangids  with  a  vertebral  count  of  25,  the 
usual  number  being  24;  this  is  a  useful  character 
for  separating  the  larvae  from  other  species  of 
Decapterus.  Berry  (1968)  used  the  scales,  scutes, 
and  lateral  line  spots  in  the  identification  of  the 
older  juveniles  from  90  mm  long.  These  characters 
are  not  yet  formed  in  the  larvae. 

Morphology 

Body  depth  decreases  relative  to  standard 
length  and  is  30.6  to  35.4%  during  the  entire  lar- 
val period  (Table  6).  In  transforming  larvae  and 
early  juveniles,  body  depth  decreased  to  28%.  The 
head  is  long  and  deep;  relative  head  length  in- 
creases throughout  the  larval  and  juvenile  stages. 
It  is  27%  in  the  smallest  larvae  (3.0  mm)  and 
attains  a  maximum  of  35%  in  the  larval  period.  In 
transforming  larvae  and  early  juveniles,  it  is 
never  less  than  31%  of  the  standard  length.  The 
head  is  deeper  than  long  in  the  early  larval  stages 
up  to  notochord  flexion  and  ranges  from  108.3  to 
113%.  Thereafter,  head  depth  decreases  gradually 
with  an  average  of  90%  but  is  never  less  than  80% 
of  the  head  length  in  the  early  juveniles.  A  supra- 
occipital  crest  is  present  during  the  larval  period 
but  is  resorbed  at  metamorphosis.  The  snout  is 
slightly  concave  in  the  youngest  larvae  (3.0  mm), 
but  becomes  straight  at  initial  notochord  flexion. 


In  older  and  transforming  larvae,  the  snout  de- 
velops a  convex  profile. 

The  eyes  are  large  and  round,  and  the  orbit 
diameter  increases  relative  to  head  length.  Eye 
index  ranges  from  30  to  46.1%  during  the  larval 
and  transition  periods  and  is  highest  at  notochord 
flexion.  A  low  orbital  crest  bearing  a  weak  spine  is 
present  above  the  eyes  in  larvae  3  to  7  mm  long.  In 
older  larvae,  the  crest  is  gradually  resorbed  and  is 
no  longer  visible  at  10  mm. 

Marginal  and  lateral  surface  spines  are  present 
on  the  preopercle.  They  increase  in  size  and 
number  during  the  larval  period  but  are  gradually 
resorbed  at  metamorphosis.  At  17  mm,  the  lateral 
surface  spines  are  gone  and  the  margin  spines  are 
reduced  to  fine  crenulations  on  the  preopercular 
margin. 

The  slender  gut  is  coiled  in  a  single  loop  in  the 
early  larvae.  A  second  loop  is  formed  at  transfor- 
mation and  a  third  is  added  in  the  early  juveniles. 
Snout-to-anus  distance  increases  relative  to  stan- 
dard length;  it  is  52.3  to  59.5%  of  the  standard 
length  during  the  entire  larval  and  transition 
periods  and  does  not  change  noticeably  during  the 
early  juvenile  stages.  Hypaxial  muscles  begin  to 
develop  around  the  gut  in  5-mm  larvae,  and  at  7 
mm,  the  abdominal  cavity  is  completely  enclosed 
except  at  the  anal  opening  of  the  gut. 

The  first  scales  to  ossify  are  those  at  the  post- 
erior region  of  the  lateral  line  in  juveniles  17  mm 
long.  Ossification  of  the  lateral  line  scales  pro- 
ceeds anteriad  and  the  full  complement  of  scales 
and  scutes  is  present  at  20  mm  when  the  body 
scales  are  formed. 

Pigmentation 

Chromatophores  are  slow  to  develop  in  the  lar- 
vae and  remain  sparse  until  the  early  juvenile 
stages.  There  are  a  few  melanophores  on  the  back 
of  the  head,  on  the  jaws,  and  infrequently  on  the 
snout  and  cheeks.  As  in  other  carangid  larvae, 
there  is  a  row  of  melanophores  on  each  side  of  the 
bases  of  the  dorsal  and  anal  fins,  along  the  lateral 
line  at  the  caudal  region,  and  on  the  dorsal  wall  of 
the  peritoneum.  Compared  to  those  of  Seriola 
zonata  and  Elagatis  bipinnulata,  the  larvae  of 
Decapterus  punctatus  are  pale.  Melanophores  are 
not  profusely  developed  until  metamorphosis,  and 
they  are  mostly  located  above  the  midline.  In  the 
early  juveniles,  iridiophores  spread  all  over  the 
body  but  are  most  dense  below  the  lateral  line, 
giving  the  fish  a  metallic  sheen. 


427 


/ 


FISHER'*    BULLETIN:  VOL.  12.  NO.  2 


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428 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CAR.ANG1D  FISHES 


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Fin  Development 

The  dorsal,  anal,  caudal,  and  pectoral  finfolds 
are  distinct  in  the  smallest  larvae  (3.0  mm),  but 
the  fin  rays  begin  to  ossify  at  4  to  5  mm  in  the 
following  sequence:  1)  caudal;  2)  dorsal,  anal,  and 
pectoral;  3)  ventral  (Table  7). 

The  pectoral  fin  rays  are  differentiated  at  5  mm, 
and  the  full  complement  of  19  to  21  rays  is  present 
at  11  mm. 

The  pelvic  fin  buds  are  present  at  4  to  5  mm,  but 
the  fin  rays  ossify  at  6  mm,  and  the  full  comple- 
ment of  1  spine  and  5  soft  rays  is  formed  at  7  mm. 

As  in  E.  bipinnulata  and  S.  zonata,  ossification 
of  the  dorsal  and  anal  fin  rays  proceed  anteropos- 
teriorly.  The  full  complement  of  8  spines  in  the 
first  dorsal  fin  and  of  1  spine  and  31  to  34  soft  rays 
in  the  second  dorsal  fin  is  present  at  10  mm.  At  this 
stage  also,  the  ultimate  fin  rays  gradually  sepa- 
rate from  the  dorsal  and  anal  fins  and  each 
modifies  into  a  much  branched  finlet.  The  anal  fin 
rays  start  to  ossify  at  5  mm,  and  the  full  comple- 
ment of  3  spines  and  27  to  31  rays  is  completed  at 
9  mm. 

The  pattern  of  caudal  fin  formation  is  generally 
similar  to  that  of  £■.  bipinnulata.  Caudal  fin  struc- 
tures initially  develop  at  4  mm,  and  all  17  principal 
rays  are  present  at  6  mm.  The  full  complement  of 
9  dorsal  and  9  ventral  secondary  rays  is  formed  at 
13  mm.  Unlike  E.  bipinnulata,  only  two  median 
epurals  are  normally  developed  as  the  center 
epural  is  markedly  reduced. 

Distribution  and  Spawning 

Adults  of  D.  punctatus  have  been  reported  from 
both  sides  of  the  Atlantic  from  Nova  Scotia  to 
Brazil  (Jordan  and  Evermann,  1896)  and  West 
Africa  (Fowler,  1936).  The  first  record  of  the  lar- 
vae was  reported  by  Hildebrand  and  Cable  (1930) 
in  Beaufort,  N.  C.  They  noted  that  spawning  oc- 
curred throughout  the  summer  or  from  May  to 
November  with  a  peak  from  July  to  September. 
Larvae  and  juveniles  2  to  50  mm  long  were  present 
in  inshore  as  well  as  offshore  waters,  possibly  ex- 
tending beyond  the  Gulf  Stream,  from  the  sur- 
face to  the  bottom  up  to  a  depth  of  20  fathoms.  In 
the  present  study,  larvae  and  juveniles  of  D. 
punctatus  were  taken  in  all  the  months  during 
the  routine  fish  larvae  sampling  in  the  Gulf 
Stream  off  Miami  and  in  numerous  net  stations 
in  the  Gulf  of  Mexico  and  the  south  Atlantic 
coast.  Spawning  occurs  in  pelagic  inshore  as  well 


429 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Table  6. — Measurements  (mm)  of  larvae  and  juveniles  of  Decapterus  punctatus. 
(Specimens  between  dashed  lines  are  undergoing  notochord  flexion.) 


Stan- 
dard 
length 


Snout-to- 
anus 
distance 


Head 
length 


Head 
depth 


Body  depth 

at  base  of 

pectoral 

fin 


Snout 
length 


Orbit 
diameter 


Snout  to  fin  origin 


Predorsal  Prepelvic 


Preanal 


3.0 
3.1 
3.5 
3.7 


1.7 
1.8 
2.0 
2.0 


1.0 
1.1 


0.9 

1.0 
1.1 
1.2 


1.0 
1.1 
1.2 
1.2 


0.26 
.30 
.37 
.40 


0.32 
.37 
.42 
.47 


4.0 
4.2 
4.8 
5.2 
5.5 
6.4 
6.5 
6.7 
7.1 
7.5 
7.8 


2.2 
2.5 
2.6 
3.0 
3.2 
3.7 
3.8 
3.9 
4.0 
4.1 
4.2 


1.2 
1.3 
1.5 
1.6 
1.8 
2.2 
2.2 
2.2 
2.2 
2.5 
2.5 


1.3 
1.5 
1.6 
1.8 
2.0 
2.1 
2.1 
2.2 
2.4 
2.5 
2.5 


1.2 
1.3 
1.6 
1.8 
1.9 
2.0 
2.0 
2.1 
2.2 
2.4 
2.5 


.45 
.47 
.50 
.55 
.57 
.62 
.62 
.65 
.67 
.72 
.75 


.52 
.60 
.65 
.70 
.75 
.82 
.82 
.80 
.85 
.90 
92 


2.8 
2.9 
2.8 
3.1 
3.2 
3.2 


2.2 
2.1 
2.0 
2.4 
2.3 
2.6 


3.8 
3.8 
3.7 
4.2 
4.2 
4.5 


8.0 

8.3 

8.6 

9.8 

10.0 

10.2 

10.5 

11.0 

11.2 

11.4 

'12.0 

M2.3 

'12.5 

'13.0 

'13.2 

'13.5 

'14.0 

214.4 

214.9 

215.2 

215.5 

216.0 

216.2 

216.5 

217.0 

217.5 

218.0 

218.5 

219.2 

2195 


4.2 
4.5 
4.5 
5.5 
5.8 
5.8 
6.2 
6.1 
6.2 
6.4 
6.9 
6.8 
7.0 
7.2 
7.4 
7.5 
8.0 
7.8 
8.0 
8.2 
8.6 
8.7 
8.8 
8.8 
9.5 
9.2 
9.5 
9.6 
10.0 
10.0 


2.7 
28 
3.0 
3.2 
3.5 
3.5 
3.5 
3.5 
3.5 
3.7 
4.0 
4.0 
4.2 
4.2 
4.2 
4.3 
4.4 
4.5 
4.8 
5.0 
5.2 
5.3 
5.6 
5.7 
5.7 
5.7 
6.0 
60 
6.1 
6.1 


2.6 
2.6 
2.6 
3.0 
3.0 
3.2 
3.2 
3.5 
3.5 
3.7 
3.8 
3.8 
4.0 
4.0 
4.0 
4.1 
4.5 
4.1 
4.2 
4.2 
4.1 
4.5 
4.6 
4.7 
5.0 
4.6 
5.0 
5.2 
5.4 
5.4 


2.6 
2.6 
2.7 
3.0 
3.0 
3.4 
3.2 
3.4 
3.5 
3.6 
3.7 
3.7 
3.8 
4.1 
4.1 
4.2 
4.3 
4.3 
4.3 
4.4 
4.5 
4.6 
4.6 
4.7 
4.8 
4.9 
5.2 
5.3 
5.5 
5.7 


.75 
,75 
.80 
.85 

1.0 

1.1 

1.1 

1.1 

1.2 

1.2 

1.2 


1.4 
1.5 
1.6 
1.5 
1.6 
1.7 
1.8 
1.9 
1.9 
1.8 
2.0 
1.9 


.95 
1.0 
1.0 
1.2 
1.1 
1.2 
1.25 
1.2 
1.2 
1.2 
1.3 
1.3 
1.3 
1.3 
1.4 
1.5 
1.6 
1.6 
1.6 
1.6 
1.6 
U 
1.7 
1.8 
1.9 
1.9 
2.0 
2.0 
2.0 
2.0 


3.2 
3.5 
3.2 
3.9 
4.5 
4.5 
4.6 
4.5 
4.6 
4.6 
4.8 
4.8 
5.0 
5.2 
5.4 
5.2 
5.8 
5.6 
5.9 
5.8 
5.9 
6.5 
6.4 
6.3 
7.0 
6.4 
7.0 
7.0 
7.0 
7.3 


2.6 
2.7 
2.6 
3.0 
4.0 
4.3 
4.0 
4.3 
4.0 
4.5 
4.5 
4.5 
4.8 
4.9 
4.7 
5.0 
5.8 
5.4 
6.0 
5.6 
5.5 
5.8 
5.9 
5.9 
6.0 
5.8 
6.3 
6.5 
6.8 
6.6 


4.3 
4.7 
4.6 
5.6 
6.2 
6.6 
6.3 
6.6 
6.4 
6.6 
6.8 
6.8 
7.2 
7.5 
7.6 
7.8 
8.5 
8.3 
8.6 
8.2 
8.3 
9.0 
9.0 
9.0 
9.8 
9.3 
10.0 
10.0 
11.3 
11.5 


'Transforming. 
2Juveniles. 

as  offshore  waters  and  along  the  edge  of  the  con- 
tinental shelf  (Figures  5,  6).  In  the  Gulf  of  Mex- 
ico, the  larvae  appear  to  have  their  center  of 
abundance  in  the  eastern  area.  They  have  the 
highest  frequency  of  occurrence  and  are  the  most 
abundant  among  the  larval  carangids  considered 

Figure  5. — Distribution  and  apparent  relative  abundance  of  the 
larvae  of  Decapterus  punctatus  in  the  Gulf  of  Mexico  and  the 
South  Atlantic  coast  of  the  United  States:  a  composite  record  of 
occurrences  at  stations  occupied  in  October  to  November  1970  by 
theJoiedeVivre  and  in  August,  October,  and  November  1971  by 
the  Dan  Braman  and  Oregon  II.  Open  circles  indicate  other 
stations  occupied. 


430 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 

Table  7. — Meristic  characters  of  cleared  and  stained  larvae  and  juveniles  ofDecapterus  punctatus. 


Standard 
length 


Dorsal  fin 


Anal  fin 


Left 

pectoral 

fin 


Left 

pelvic 

fin 


Primary  caudal 
fin  rays 

Dorsal  Ventral 


Secondary  caudal 
fin  rays 

Dorsal  Ventral 


Gill  rakers, 
left  first 
gill  arch 


Left  pre- 

opercular 

margin 

spines 


3.1 

— 

3.5 

— 

4.2 

— 

5.3 

V:  6 

6.6 

Vi;  1 

19 

7.6 

VII:  1 

20 

8.2 

VIII;  1 

25 

9.0 

VIII;  1 

30 

10.4 

VIII;  1 

31 

11.5 

VIII;  1 

23 

12.5 

VIII;  1 

34 

13.5 

VIII;  1 

32 

14.4 

VIII;  1 

32 

15.1 

VIII;  1 

33 

16.5 

VIII;  1 

32 

17.0    ■ 

VIII;  1 

31 

19.0 

VIII;  1 

34 

23.0 

VIII;  1 

32 

28.2 

VIII;  1 

31 

11;  6 

II;  I.  16 

II;  I,  18 

II;  I.  19 

I,  21 

11;  i.  24 

II;  I.  26 

II;  I,  31 

II;  I,  28 

II;  I,  27 

II;  I.  29 

II;  I,  27 

II;  I.  27 

II;  I,  27 

II;  I,  28 

II;  I,  28 


II 


— 

— 

— 

— 

— 

— 

— 

5 





4 

3 





0+   6 

6 
8 

3 

— 

6 

— 

— 

— 

0  +  12 

10 

10 

1,  5 

9 

8 

3 

2 

0  +  14 

11 

14 

1,3 

9 

8 

4 

4 

0  +  16 

12 

17 

1,  5 

9 

8 

5 

6 

0  +  17 

12 

18 

1.5 

9 

8 

7 

8 

0  +  17 

11 

17 

1,  5 

9 

8 

8 

8 

3  +  17 

11 

19 

1,5 

9 

8 

8 

8 

3  +  21 

11 

19 

1,5 

9 

8 

9 

9 

6  +  24 

10 

20 

1,  5 

9 

8 

9 

9 

6  +  25 

10 

20 

1,  5 

9 

8 

9 

9 

6  +  26 

9 

20 

1,  5 

9 

8 

9 

9 

6  +  25 

10 

19 

1,5 

9 

8 

9 

9 

6  +  25 

7 

20 

1,  5 

9 

8 

9 

9 

6  +  27 

5 

20 

1,  5 

9 

8 

9 

9 

6  +  28 

3 

21 

1,  5 

9 

8 

9 

9 

8  +  28 

2 

20 

1,  5 

9 

8 

9 

9 

9  +  28 

0 

Figure  6. — Distribution  and  apparent  relative  abundance  of  the 
larvae  ofDecapteruspunctatus  in  the  Gulf  of  Mexico:  a  compwsite 
record  of  occurrences  at  stations  occupied  from  May  to  August 
1972  by  the  Tursiops,  Dan  Braman,  and  Gerda. 

here.  They  occurred  in  18.5%  of  the  net  stations 
and  constituted  44.7%  of  the  larval  carangids 
collected. 

Lookdown,  Selene  vomer  (Linnaeus) 
Figure  7 

Literature 

Larvae  of  S.  vomer  are  previously  undescribed. 
Fowler  (1936)  illustrated  a  15-mm  juvenile  and 
Lutken  (1880)  a  28-mm  juvenile. 

Distinguishing  Features 

Larvae  of  S.  vomer  have  extremely  deep  and 


trenchant  bodies.  The  advanced  development  of 
the  dorsal  and  ventral  fins  is  perhaps  the  most 
notable  feature  of  their  development;  it  is  the  ear- 
liest observed  among  carangid  larvae.  The  second 
and  third  dorsal  spines  develop  into  long  filaments 
often  twice  the  length  of  the  body.  The  ventral  fins 
are  elongated,  often  extending  to  the  anal  fin.  The 
larvae  probably  attain  a  maximum  length  of  12 
mm  before  transformation.  The  biggest  larva  in 
the  series  in  9  mm  long  (Figure  7F)  and  the  next 
size,  13.5  mm,  (Figure  7G)  is  a  transforming  larva 
hatched  from  a  planktonic  egg  and  reared  in  an 
aquarium.  The  smallest  juvenile  is  23.9  mm  long 
and  has  attained  most  adult  features. 

As  in  most  larval  carangids,  there  is  a  bony  crest 
in  the  supraoccipital  bones,  two  rows  of  preopercu- 
lar  spines,  and  a  supraorbital  crest.  The  distance 
from  the  snout  to  the  occipitals  is  long  and  slopes 
into  an  abrupt  angle.  The  first  interhemal  spine  is 
much  enlarged  and  pressed  against  an  equally 
enlarged  hemal  spine. 

Morphology 

The  larvae  are  among  the  most  deep  bodied  of 
all  larval  carangids.  Relative  body  depth  in- 
creases during  the  larval  and  early  juvenile  pe- 
riods (Table  8).  It  is  32%  at  2.5  mm  and  increases 
steadily,  attaining  a  maximum  of  96%  at  23.9  mm. 
Thereafter,  body  depth  gradually  declines  but  is 
never  less  than  74%  of  the  body  length  in  the 
juveniles.  Simultaneous  with  the  deepening  of  the 
body  is  the  enlargement  of  the  first  interhemal 
and  hemal  spine  of  the  first  caudal  vertebra.  The 


431 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


432 


APRIETO:   EARLY  DEVELOPMENT  OE  EIVE  CARANGID  EISHES 


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two  spines  fuse  at  the  posterior  wall  of  the  abdomi- 
nal cavity  which  becomes  elongated  vertically. 
Consequently,  the  long  and  slender  gut  forms  ver- 
tical loops  following  the  shape  of  the  abdominal 
cavity.  The  gut  opening  is  pushed  anteriorly  and 
lies  adjacent  to  the  base  of  the  pelvic  fins.  Snout- 
to-anus  distance  decreases  relative  to  standard 
length.  It  is  56%  at  2.5  mm  and  declines  to  40%  at 
the  end  of  the  larval  period.  During  the  early 
juvenile  stages,  snout-to-anus  distance  had  an  av- 
erage of  38%. 

The  length  and  width  of  the  head  increases  rela- 
tive to  standard  length.  Head  length  is  31.0%  in 
the  smallest  larva  (2.5  mm)  and  does  not  increase 
substantially  until  the  juvenile  period  when  it 
attains  a  maximum  of  41.9%  at  23.9  mm.  To  ob- 
tain the  true  depth  of  the  head  and  not  the  body 
depth  at  the  head  region,  the  measurement  is 
taken  from  the  posterior  margin  of  the  preopercle 
from  the  dorsal  margin  of  the  head  to  the  articula- 
tion of  the  mandible  and  maxillary.  Head  depth  is 
100%  of  the  head  length  at  2.5  to  3.2  mm.  There- 
after, head  depth  exceeds  head  length.  During  the 
larval  period,  the  head  is  deepest  at  4.6  mm  when 
it  is  140%  of  the  head  length.  This  is,  however, 
exceeded  by  the  progressive  deepening  of  the  head 
during  the  transition  and  juvenile  stages  with  a 
maximum  of  182%  and  an  average  of  158%.  The 
dorsal  profile  of  the  snout  is  slightly  concave  in  the 
early  larval  period  (2.5-3.8  mm)  but  becomes 
straight  in  older  and  transforming  larvae.  The 
nasal,  frontal,  and  supraoccipital  bones  become 
markedly  elongated  and  slope  steeply,  giving  the 
head  an  almost  vertical  anterior  profile. 

The  eyes  are  round  and  large.  Relative  orbit 
diameter  increases  during  the  larval  and  juvenile 
development;  it  is  32%  at  2.5  mm  and  attains  a 
maximum  of  37%  at  notochord  flexion  with  an 
average  of  31%  during  the  larval  and  transition 
periods.  In  the  juveniles,  orbit  diameter  decreases 
to  a  range  of  20  to  27%. 

The  orbital  and  supraoccipital  crests  are  well 
marked  in  early  larval  stages  up  to  5  mm.  The 
crests  are  gradually  resorbed  and  are  vaguely  vis- 
ible at  metamorphosis.  Preopercular  marginal 
spines  consist  of  4  to  7  long  and  strong  spines  while 
the  lateral  surface  spines  are  smaller  and  limited 
to  the  lower  surface.  All  preopercular  spines  are 
resorbed  at  transformation.  Scales  are  absent. 

Pigmentation 

The  common  larval  pattern  of  pigmentation  in 

433 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Standard 
length 


Table  8. — Measurements  (mm)  of  larvae  and  juveniles  of  Selene  vomer. 
(Specimens  between  dashed  lines  are  undergoing  notochord  flexion.) 


Snout-to- 
anus 
distance 


Head 
length 


Head 
depth 


Body  depth 

at  base  of 

pectoral 

fin 


Snout 
length 


Orbit 
diameter 


Snout  to  fin  origin 


Predorsal       Prepelvic        Preanal 


2.5 

1.4 

0.78 

0.78 

0.80 

0.25 

0.25 

1.0 

0.7 

_ 

3.2 

1.7 

1.0 

1.0 

1.0 

.37 

32 

1.1 

1.2 

1.7 

3.5 

1.8 

1.1 

1.2 

1.3 

.37 

.35 

1.2 

1.0 

1.8 

3.8 

1.8 

1.2 

1.4 

1.5 

.42 

.42 

1.2 

1.35 

2.0 

4.0 

2.0 

1.2 

1.5 

1.5 

.47 

.37 

1.3 

1.2 

2.0 

4.3 

2.2 

1.5 

1.9 

1.9 

.52 

.50 

1.5 

1.6 

1.9 

4,4 

2.1 

1.5 

2.0 

2.1 

.55 

.50 

1.4 

1.6 

1.8 

4.5 

2.2 

1.5 

2.0 

2.0 

.52 

.45 

1.4 

1.5 

2.0 

4.6 

1.8 

1.5 

2.1 

2.1 

.55 

.42 

1.6 

1.6 

2.1 

48 

2.6 

1.7 

2.0 

2.1 

.55 

.45 

1.8 

1.7 

2.8 

5.0 

2.7 

1.7 

2.2 

2.2 

.52 

.47 

1.8 

1.9 

3.0 

5.3 

3.0 

1.7 

2.1 

2.3 

.55 

.45 

1.7 

2.0 

3.0 

5.5 

2.7 

2.0 

2.5 

2.9 

.62 

eo 

1,8 

1.8 

3.1 

6.1 

2.8 

2.0 

3.0 

3.2 

.87 

62 

2.0 

2.0 

3.0 

7.5 

3.6 

2.6 

3.5 

3.9 

.90 

.85 

2.4 

2.5 

4.0 

8.2 

4.5 

3.0 

3.8 

4.8 

1.2 

.87 

2.9 

3.0 

4.6 

'9.0 

3.6 

3.1 

5.2 

5.8 

1.3 

1.0 

2.9 

2.8 

5.0 

M3.5 

6.7 

5.2 

9.5 

6.2 

2.2 

1.7 

5.5 

5.5 

6.2 

^23. 9 

8.7 

10.0 

14.0 

23.0 

3.1 

2.5 

7.0 

8.0 

11.0 

227.5 

11.5 

10.0 

15.0 

24.5 

3.5 

26 

11,0 

8.0 

14.0 

^30.0 

12.0 

11.0 

17.0 

27.0 

5.0 

3,0 

14,0 

12.0 

14.0 

^34.0 

12.0 

13.5 

22.0 

31.0 

6.5 

3.0 

14.0 

13.0 

14.0 

^38.0 

14.0 

14.5 

200 

31.0 

5.0 

3.2 

15.5 

11.5 

16.0 

^42. 5 

14.0 

17.0 

28,0 

35.0 

5.5 

3.9 

17.0 

15.0 

14.0 

247.0 

16.0 

200 

30,0 

35,0 

80 

42 

16.0 

18.0 

17.0 

'Transfornning 
^Juveniles 


carangids,  including  melanophores  along  the 
bases  of  the  dorsal  and  anal  fins  and  along  the 
lateral-midline,  is  present  inS.  vomer.  In  the  early 
larvae  (2.5-5.0  mm),  a  few  melanophores  develop 
on  the  tips  of  the  jaws,  head,  sides  of  the  body, 
pelvic  fin,  dorsal  fin,  and  base  of  the  caudal  fin.  The 
earliest  patch  of  melanophores  is  formed  on  the 
lower  side  of  the  body  anterior  to  the  caudal 
peduncle.  In  older  larvae,  the  melanophores 
gradually  proliferate  all  over  the  body  and  form 
discrete  patches  which  develop  into  broad  spots  at 
transformation  and  in  the  juvenile  stages.  The 
heaviest  concentrations  of  pigment  cells  comprise 
those  lining  the  dorsal  wall  of  the  peritoneum. 
Reglarly  spaced  melanophores  similar  to  those  in 
Elagatis  bipinnulata  (Figure  IB-D)  are  present 
along  the  midventral  line  in  the  trunk  region. 


Fin  Development 

The  sequence  of  fin  formation  and  ossification  is 
as  follows:  1)  pelvic;  2)  first  dorsal;  3)  second  dor- 
sal, caudal,  and  anal;  and  4)  pectoral  (Table  9). 


The  pectoral  finbud  is  formed  at  2.5  mm  but  the 
rays  are  not  differentiated  until  the  larvae  are  5  to 
6  mm.  The  full  complement  of  18  to  21  is  formed 
at  9  mm. 

The  pelvic  fins  are  fully  formed  in  the  smallest 
larva  (2.5  mm).  They  steadily  increase  in  length 
and  at  metamorphosis  extend  beyond  the  origin  of 
the  anal  fin. 

The  first  3  dorsal  spines  are  ossified  at  2.5  mm. 
The  second  and  third  spines  progressively  in- 
crease in  length  throughout  the  larval  period, 
forming  extremely  long  filaments.  At  metamor- 
phosis, they  are  about  twice  the  length  of  the  body. 
The  full  complement  of  8  spines  in  the  first  dorsal 
fin  and  of  1  spine  and  20  to  22  soft  rays  in  the 
second  dorsal  fin  is  present  at  9  mm. 

Rudiments  of  the  anal  fin  are  discernible  at  3.2 
mm  and  the  rays  ossify  at  4  to  5  mm.  The  full 
complement  of  3  spines  and  16  to  18  soft  rays  is 
present  at  6  mm. 

The  development  and  structure  of  the  caudal  fin 
and  supporting  structures  are  similar  to  those  of 
E.  bipinnulata.  The  full  complement  of  17  princi- 
pal and  7  to  9  dorsal,  and  7-8  ventral  secondary 
caudal  rays  is  present  at  9  mm. 


434 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 

Table  9. — Meristic  characters  of  cleared  and  stained  larvae  and  juveniles  of  Selene  vomer  (Linnaeus). 


Standard 
length 

nal  fin 

Left 

pectoral 

fin 

Left 

pelvic 

fin 

Primary  caudal 
fin  rays 

Secondary 
fin  ray 

caudal 
s 

Gill  rakers, 
left  first 
gill  arch 

Left  pre- 
opercular 

Dorsal  fin                       A 

Dorsal 

Ventral 

Dorsal 

Ventral 

margin 
spines 

2.5 

III 

_ 



1,  5 





_ 

_ 





3.2 

V 

— 

— 

1,  5 

— 

— 

— 

— 

— 

— 

3.4 

V 

— 

— 

1,  5 

— 

— 

— 

— 

— 

— 

3.5 

VI 

— 

— 

1.  5 

— 

— 

— 

— 

— 

— 

4.0 

V;  3                            II 

— 

1,  5 

2 

3 

— 

— 

0+11 

1 

4.4 

VIII 

1,  10                       II 

,  10 

— 

1,  5 

5 

6 

— 

— 

0+11 

2 

4.9 

VIII 

15                       II 

1.  14 

— 

1,5 

7 

7 

— 

— 

0  +  16 

2 

5.2 

VIII 

18                        II 

,  1.  16 

— 

1,  5 

7 

8 

— 

— 

3  +  16 

2 

5.5 

VIII 

18                       II 

;  1.  17 

6 

1.  5 

7 

8 

— 

— 

3  +  18 

3 

6.1 

VIII 

19                        II 

;  1.  17 

10 

1.  5 

8 

8 

— 

— 

4  +  19 

2 

6.3 

VIII 

20                      1 

;  1,  16 

13 

1,  5 

8 

8 

3 

4 

5  +  20 

2 

7.6 

VIII 

21                        1 

;  1.  17 

17 

1,  5 

9 

8 

5 

4 

6  +  20 

2 

8.6 

VIII 

20                      1 

:  1.  17 

17 

1,  5 

9 

8 

6 

6 

6  +  20 

2 

9.0 

VIII 

20                      1 

;  1.  18 

18 

1,  5 

9 

8 

7 

8 

6  +  22 

1 

13.5 

VIII 

21                        1 

;  1.  18 

18 

1,  5 

9 

8 

8 

7 

6  +  23 

— 

23.9 

VIII 

21                        1 

;  1,  18 

20 

1,  5 

9 

8 

9 

8 

6  +  25 

— 

Distribution  and  Spawning 

Adults  of  Selene  vomer  have  been  recorded  on 
both  coasts  of  the  United  States,  from  Cape  Cod  to 
Brazil  and  from  Lower  California  to  Peru  (Jordan 
and  Evermann,  1896).  They  have  also  been  re- 
ported from  the  Gulf  of  Mexico  (Ginsburg,  1952), 
the  Bahamas  (Bohlke  and  Chaplin,  1968),  and 
West  Africa  (Fowler,  1936). 

Larval  and  early  juveniles  of  S.  vomer  were 
taken  in  all  months  except  in  June,  October,  and 
December.  The  monthly  occurrence  and  distribu- 
tion of  the  larvae  is  a  composite  of  the  records  of 
specimens  which  include  those  taken  from  the 
coastal  waters  of  the  eastern  tropical  Pacific  from 
Baja  California  to  Costa  Rica,  the  Gulf  of  Mexico, 
and  the  tropical  Atlantic  off  Brazil  and  Liberia 
(Aprieto,  1973).  In  the  Gulf  of  Mexico,  larvae  were 
abundant  mainly  in  the  northeastern  offshore 
waters  in  August  which  suggests  a  short  spawn- 
ing period  in  that  area  (Figure  2).  The  larvae  oc- 
curred in  2.2%  of  the  net  stations  and  constituted 
2.6%  of  the  larval  carangids  collected  in  the  Gulf 
of  Mexico  and  the  south  Atlantic  coast. 

Leatherjacket,  Oligoplites  saurus 
(Bloch  and  Schneider) 

Figure  8 
Literature 

Larvae  of  this  species  have  not  been  described 
previously. 

Distinguishing  Features 

Larvae  of  O.  saurus  resemble  those  ofElagatis 
bipinnulata  and  Seriola  zonata.  Further,  as  in 


E.  bipinnulata,  the  first  interhemal  spine  is  thick- 
ened and,  as  in-S.  zonata,  the  supraoccipital  crest 
is  lacking.  Larvae  of  O.  saurus  are  distinct  from 
those  of  the  two  species  mentioned  in  having  an 
orbital  crest  with  fine  serrations,  1  to  3  denticles 
which  appear  early  in  the  larval  period  on  the 
dorsal  side  of  the  longest  preopercular  spine,  and 
26  vertebrae — the  highest  vertebral  count  among 
carangids.  The  number  of  dorsal  spines  and  pec- 
toral fin  rays  formed  is  fewer  than  in  most  caran- 
gids, 5  to  6  and  15  to  17  respectively.  Larval  pig- 
mentation is  moderately  profuse  and,  as  in  most 
carangid  larvae,  conspicuous  melanophores  are 
present  along  the  bases  of  the  dorsal  and  anal  fins, 
on  the  lateral  midhne,  and  on  the  dorsal  wall  of 
the  abdominal  cavity.  The  larvae  transform  at  7  to 
10  mm. 

The  Embryo 

Two  preserved  eggs  of  O.  saurus  are  0.87  and 
0.88  mm  in  diameter.  They  have  ventral,  single  oil 
globules,  0.33  and  0.34  mm  in  diameter.  The  oil 
globule  consists  of  minute  oil  droplets  and  is  en- 
closed in  a  rather  tough,  pigmented  capsule.  The 
pigmented  yolk  is  bright  yellow  and  unseg- 
mented.  The  perivitelline  space  is  narrow  and  the 
egg  case  smooth.  The  embryos  are  well  developed 
and  have  stellate  melanophores  along  the  back 
and  upper  sides  of  the  body.  A  large  melanophore 
is  present  at  the  posteroventral  midline  (Figure 
8A). 

Morphology 

The  larvae  are  1.87  and  1.97  mm  at  hatching. 

435 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


436 


APRIETO;   EARL'l    DEVELOPMENT  OF  FIVE  CAR.ANG1D  FISHES 


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The  body  is  slender  but  appears  robust  at  the  an- 
terior end  in  view  of  the  distended  yolk  sac  (Figure 
8B).  The  head  is  well  marked  and  the  eye  buds  are 
discernible.  The  dorsal  finfold  originates  behind 
the  nape  and  is  continuous  with  the  anal  finfold  at 
the  tail  region.  At  the  first  day  of  hatching, 
the  yolk  sac  is  reduced  to  a  spherule,  the  eyes 
are  formed  but  unpigmented,  and  the  dorsal  and 
anal  finfolds  completely  surround  the  larva  except 
at  the  mouth.  More  and  bigger  melanophores  are 
formed  along  the  sides  and  back,  and  a  large 
ventral  melanophore  is  located  at  the  opening  of 
the  gut  (Figure  8C). 

Early  larvae  of  O.  saurus  are  slender  compared 
to  other  larval  carangids.  Body  depth  increases 
relative  to  standard  length  and  ranges  from  20  to 
26.9^f  during  the  larval  period  (Table  10).  It  in- 
creases to  a  maximum  of  32%  at  metamorphosis 
and  thereafter  declines  to  28  to  29%.  The  slender 
gut  is  straight  and  forms  a  single  loop  at  4  mm.  A 
second  loop  develops  at  metamorphosis,  and  a 
third  is  added  in  the  early  juvenile  period.  Snout- 
to-anus  distance  ranges  from  51  to  61%  during  the 
larval  period  and  decreases  slightly  in  subsequent 


437 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 
Table  10. — Measurements  (mm)  of  larvae  and  juveniles  of  Oligoplites  saurus. 
(Specimens  between  dashed  lines  are  undergoing  notochord  flexion;  W  -  wild,  L  -  laboratory  reared.) 


Specimen 
number 

Standard 
length 

Snout-to- 
anus 
distance 

Head 

Head 

Orbit 

Body  depth 

Snout  to  fin  origin 

length 

depth 

length 

diameter 

pectoral  fin 

Predorsal       Prepelvic        Preanal 

1(L) 

1.87 

_ 













2(L) 

1.95 

— 

— 

— 

— 

— 

— 

_                   _                   _ 

3(L) 

2.17 

1.25 

0.50 

0.45 

0.05 

0.10 

0.45 

~                   —                   — 

4(L) 

2.25 

1.3 

.51 

.50 

.07 

.10 

.50 

— -                   —                   

5(L) 

2.3 

1.3 

.57 

.54 

.09 

.20 

.60 

—                   —                   — 

6(L) 

2.5 

1.4 

.60 

.59 

.09 

.25 

.60 

—                   —                   — 

7(L) 

2.5 

1.5 

.60 

.60 

.12 

.25 

.50 

— 

— 

— 

8(1) 

2.6 

1.5 

.60 

.55 

.12 

.25 

.55 

— 

— 

— 

9(L) 

2.8 

1.6 

.67 

.65 

.12 

.30 

.60 

— 

— 

— 

10(L) 

4.1 

2.4 

1.1 

.95 

.25 

.40 

.87 

— 

— 

— 

11(W) 

4.3 

2.2 

1.3 

1.2 

.37 

.37 

1.0 

1.9 

— 

2.0 

12(W) 

4.9 

2.7 

1.4 

1,3 

.40 

.45 

1.3 

2.1 

— 

2.8 

13(L) 

5.2 

3.0 

15 

1.4 

.40 

.52 

1.4 

2.1 

— 

3.0 

14(1) 

5.9 

3.5 

1.8 

1.5 

.45 

.62 

1.4 

2.5 

— 

3,5 

15(L) 

7.2 

4.4 

2.6 

2.2 

.75 

.75 

2.2 

36 

3.2 

46 

16(W) 

8.7 

5.1 

3.0 

2.5 

.80 

.80 

2.4 

4.0 

3.6 

5,4 

17(W) 

10.4 

5.4 

3.3 

3.0 

.75 

1.1 

3.0 

4.7 

3.9 

5.7 

18(L) 

10.5 

5.8 

3.5 

2.9 

.90 

1.0 

3.4 

4.9 

3.7 

6,0 

19(W) 

10.5 

5.5 

3.5 

3.0 

1.0 

1.0 

3.0 

4.9 

3.7 

5.6 

20(W) 

11.0 

5.9 

3.6 

3.2 

1.0 

1.0 

3.3 

5.2 

3.8 

6,1 

21(W) 

15.0 

6.9 

4.4 

3.7 

1.3 

1.3 

4.1 

60 

4.8 

7,0 

22(W) 

16.0 

8.0 

4.5 

4.0 

1.2 

1.3 

4.5 

6.5 

5.0 

8.1 

23(L) 

18.5 

9.5 

5.3 

4.6 

1.3 

1.9 

5.3 

8.0 

6.0 

9.5 

24(L) 

21.0 

10.5 

60 

5.3 

1.5 

2.1 

6.1 

8,9 

6.0 

11.0 

stages.  Hypaxial  muscles  enclose  the  gut  at  4  mm, 
and  the  abdominal  cavity  is  completely  covered  at 
7.2  mm. 

As  in  most  carangid  larvae,  the  head  is  long  and 
deep.  Relative  head  length  ranges  from  23  to  36% 
of  standard  length  during  the  larval  and  juvenile 
periods.  Depth  of  head  ranges  from  82  to  100%  of 
the  head  length.  The  dorsal  profile  of  the  snout  is 
convex  except  for  a  slight  indentation  at  the  an- 
terior margin  of  the  forebrain.  The  eyes  are  round 
and  large;  eye  index  ranges  from  20  to  44%  during 
the  larval  and  early  juvenile  periods  and  is  high- 
est in  larvae  2  to  3  mm  long.  Pigmentation  de- 
velops on  the  second  day  of  hatching.  A  finely  ser- 
rated orbital  crest  is  present  in  larvae  from  4  mm 
long  and  is  gradually  resorbed  following 
metamorphosis.  Preopercular  spines  are  present 
but  only  the  marginal  ones  are  well  developed. 
One  to  three  denticles  occur  on  the  dorsal  side  of 
the  longest  marginal  spine. 

The  scales  and  lateral  line  are  not  yet  developed 
in  25-mm  juveniles,  the  oldest  of  the  laboratory- 
reared  specimens. 

Pigmentation 

Larval  pigmentation  is  well  developed  and 
progressively  increases  during  the  larval  and 
juvenile  stages.  Pigment  cells  are  more  abundant 


in  laboratory-reared  specimens  than  in  the  wild 
ones.  A  conspicuous  U-shaped,  unpigmented  area 
at  the  caudal  peduncle  persists  from  7.2  mm  up  to 
the  early  juveniles  20  mm  long  (Figure  8H-J). 
Throughout  the  larval  and  juvenile  stages  xanth- 
ophores  are  present  on  the  sides  of  the  body,  but 
they  readily  fade  on  preservation.  Melanophores 
form  at  the  base  of  the  dorsal  finfold  in  the  early 
larvae  but  disappear  when  the  fin  rays  are  dif- 
ferentiated. The  conspicuous  anal  pigment  spot  in 
the  embryo  and  newly  hatched  larvae  disappear  at 
the  third  day  of  hatching.  In  the  early  juveniles, 
pigmentation  develops  on  the  membrane  of  the 
dorsal  and  anal  fin  spines. 

Fin  Development 

The  dorsal,  anal,  and  caudal  finfolds  are  present 
at  hatching,  and  the  sequence  of  ossification  is  as 
follows:  1)  dorsal,  anal,  and  caudal;  2)  pectoral  and 
pelvic  (Table  11). 

The  pectoral  finfold  is  formed  a  day  after  hatch- 
ing. As  in  other  larvae  described  here,  the  pectoral 
fin  rays  begin  to  ossify  dorsally  and  the  rest  are 
added  ventrally.  The  full  complement  of  15  to  17 
rays  is  completed  at  10  mm. 

The  pelvic  fin  buds  appear  13  days  after  hatch- 
ing at  6  mm  and  the  rays  soon  become  differen- 
tiated. The  full  complement  of  1  spine  and  5  soft 
rays  is  present  at  10  mm. 


438 


APRIETO;  EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 

Table  11. — Meristic  characters  of  cleared  and  stained  larvae  and  juveniles  of  OUgoplites  saurus. 


Primary 

caudal 

Secondarv  caudal 

Lett  pre- 

Standard 

Lett 
pectoral 

Left 
pelvic 

fin 

rays 

fin 

rays 

Gill  rakers, 
left  first 

opercular 
margin 

length 

Dorsal  fin 

Ana 

fin 

fin 

fin 

Dorsal 

Ventral 

Dorsal 

Ventral 

gill  arch 

spines 

4,1 









— 

— 

— 

4 

4.3 

— 

— 

— 

— 

— 

— 

— 

— 

4 

4.9 

— 

— 

— 

— 

— 

— 

— 

— 

4 

5.9 

III 

8 

7 

— 

— 

3 

3 

— 

— 

0+4 

6 

7.2 

V 

18 

,  16 

7 

2 

9 

8 

1 

2 

0+10 

8 

8.7 

V 

1,  17 

.  17 

10 

1,  5 

9 

8 

— 

— 

0+9 

9 

10.4 

IV 

1,  20 

,  19 

13 

i,  5 

9 

8 

9 

9 

3  +  12 

12 

11.0 

V 

1.  20 

,  18 

14 

1,  5 

9 

8 

9 

9 

3+11 

9 

12.2 

V 

1.  21 

.  19 

14 

1,  5 

9 

8 

10 

9 

3  +  11 

10 

13.0 

V 

1.  19 

,  18 

14 

1,  5 

9 

8 

9 

9 

3  +  10 

9 

15.1 

V 

1,20 

,  19 

14 

1,  5 

9 

8 

9 

9 

5  +  11 

8 

15.2 

V 

1.  21 

.  19 

15 

1,  5 

9 

8 

9 

9 

5  +  11 

6 

16 

V 

1,21 

,  18 

16 

1,  5 

7 

9 

9 

9 

5  +  11 

5 

17 

V 

1,21 

,  20 

16 

1,  5 

9 

8 

9 

10 

5  +  12 

6 

18.5 

V 

1,  20 

,  20 

16 

1,  5 

9 

8 

9 

8 

5  +  13 

4 

19 

V 

1,20 

,  18 

15 

1.5 

9 

8 

10 

9 

5  +  13 

3 

21.0 

V 

1,  21 

,  18 

16 

1,  5 

9 

8 

9 

9 

5  +  13 

3 

The  dorsal  and  anal  fin  rays  differentiate  simul- 
taneously in  an  anteroposterior  direction.  Unlike 
previously  described  species,  in  which  either  the 
middle  or  anterior  spines  are  longer,  the  posterior 
spine  of  the  first  dorsal  fin  is  slightly  longer  than 
the  rest.  The  full  complement  of  6  spines  and  19  to 
21  rays  is  present  at  10  mm.  The  anal  fin  rays  of  3 
spines  and  18  to  20  soft  rays  are  also  complete  at 
10  mm. 

Caudal  fin  formation  is  similar  to  that  of  the 
other  species  described.  The  full  complement  of  9 
to  10  dorsal  and  8  to  10  ventral  principal  rays  and 
18  to  20  secondaries  is  present  at  10  mm. 

Distribution  and  Spawning 

Adults  of  O.  saurus  are  known  from  both  coasts 
of  Central  America  and  in  the  West  Indies  (Jordan 
and  Evermann,  1896).  They  also  occur  along  the 
Atlantic  coast  of  the  United  States  from  Mas- 
sachusetts to  Florida  and  in  the  Gulf  of  Mexico 
(Ginsburg,  1952).  The  wild  larvae  and  juveniles  in 
the  present  work  were  taken  from  Escambia  Bay, 
Fla.,  and  at  Sapelo  and  St.  Simons  Islands,  Ga.,  in 
May  and  July  by  means  of  channel  nets  and  beach 
seines.  The  laboratory-reared  larvae  were 
hatched  from  planktonic  eggs  collected  from  Bis- 
cayne  Bay.  Larvae  and  juveniles  were  not  col- 
lected in  any  of  the  net  stations  in  the  Gulf  of 
Mexico  and  the  south  Atlantic  coast.  Distribution 
of  the  young  in  these  regions  is  obscure,  and  abun- 
dance and  frequency  of  occurrence  in  relation  to 
the  other  larval  carangids  could  not  be  estab- 
lished. The  wild  larvae  obtained  were  too  few  to 
derive  conclusive  information,  but  apparently 
spawning  occurs  in  summer.  Unlike  the  other 


carangids  which  spawn  in  offshore  pelagic  waters, 
O.  saurus  spawns  in  inshore  and  shallow  waters. 
Further  investigation  is  necessary  to  establish 
with  certainty  the  spawning  period  and  sites  and 
the  distribution  of  the  young. 

Laboratory  Rearing 

Planktonic  eggs  of  O.  saurus  were  collected  in  a 
1-m,  505-;u  mesh  plankton  net  at  the  pier  of  the 
Rosenstiel  School  of  Marine  and  Atomospheric 
Science  on  15  July  1972,  at  9:00  A.M.,  EDT.  A 
total  of  75  eggs  was  sorted  from  the  plankton  and 
incubated  in  a  50-liter  glass  aquarium.  The 
aquarium  water  was  drawn  from  Biscayne  Bay 
through  the  School's  seawater  system.  It  was  oxy- 
genated and  circulated  with  compressed  air 
added  through  airstones  and  lighted  continuously 
by  two  cool,  white,  fluorescent  bulbs.  Temperature 
ranged  from  23.9"  to  28'C  and  salinity  from  32  to 
36  %o  during  the  experiment.  The  larvae  were  fed 
wild  plankton  collected  from  Biscayne  Bay  as  well 
as  nauplii  of  brine  shrimp  {Artemia  salina).  A 
detailed  description  of  the  rearing  technique  em- 
ployed is  given  in  Houde  and  Palko  (1970). 

The  eggs  began  hatching  in  the  afternoon  of  the 
day  of  collection  and  after  24  h  all  the  eggs  were 
presumed  hatched.  The  larvae  averaged  1.92  mm 
at  hatching,  were  5.2  mm  8  days  after  hatching, 
and  about  21  mm  at  34  days  (Figure  9).  Mortality 
in  the  first  18  days  included  2  eggs  and  16  larvae 
preserved  for  describing  larval  development.  Six 
young  juveniles  averaged  25  mm  after  45  days. 
Thereafter,  the  juveniles  failed  to  feed  and  all  but 
one  died  at  51  days  when  the  rearing  experiment 
was  terminated. 


439 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Ossification 

The  sequence  of  ossification  of  the  skull,  axial, 
and  appendicular  skeleton  is  generally  similar 
among  the  four  species  in  which  ossification  was 
observed  (Table  12).  Without  exception,  the  pre- 
maxillaries,  preopercular  spines,  and  cleithra  os- 
sify in  the  smallest  larvae  (2.5-3.8  mm).  Next  to 
ossify  at  4  to  5  mm  are  the  maxillaries,  dentaries, 
parasphenoid,  supraoccipital,  articulars,  frontals, 
angulars,  and  the  branchial  arches.  The  entire 
maxillary  arch  is  ossified  before  the  larvae  are  6 
mm  long.  Teeth  are  formed  along  the  entire  mar- 
gin of  the  premaxillaries  and  anterior  region  of 
the  dentaries  in  the  youngest  larvae  following  the 
ossification  of  these  elements.  It  is  apparent  that 
the  bones  related  to  feeding  ossify  early,  and  this 
is  consistent  with  the  need  of  the  larvae  for  food 
from  external  sources  following  the  absorption  of 
the  yolk. 

Seven  branchiostegal  rays  on  each  side  are  pre- 
sent in  3-mm  larvae.  Ossification  begins  with  the 
posterior  and  longer  rays  and  proceeds  anteriad. 
The  ceratohyal  and  epihyal  to  which  the  bran- 
chiostegal rays  are  attached  ossify  simulta- 
neously with  the  rays.  The  rest  of  the  hyoid  arch 
including  the  glassohyal,  urohyal,  and  hypohyal 
ossify  at  metamorphosis. 

Aside  from  the  quadrate  and  hyomandibular 
which  ossify  during  the  larval  period,  the  rest  of 
the  palatine  arch  is  not  calcified  until  metamor- 
phosis. 

The  branchial  arches  initially  ossify  in  larvae  4 
to  5  mm  long  and  all  arches  are  calcified  at  6  mm. 
The  first  branchial  arch  is  the  first  to  ossify  start- 
ing from  the  center  of  the  ceratobranchial  towards 


20.0 
18.0- 
16.0 


;i2.o 

c 

-•   10.0 


— I 1 1 1 1 1 1 1 1 1 1 1  I  I  I  I  I  '" 

0  2  4  6  8  10         12         It         16         18        20        22        24        26       28        30        32        34 

Dar*    Aflar    Halchlni 


Figure  9. — Growth  of  Oligoplites  saurus  larvae  reared  in  the 
laboratory  at  an  average  temperature  of  26.0°C. 


both  ends.  The  epibranchial  is  the  next  to  ossify 
beginning  from  near  the  angle  of  the  arch  out- 
ward. Ossification  of  the  other  arches  follows  in  a 
similar  sequence. 

The  gill  rakers  calcify  following  the  ossification 
of  the  elements  to  which  they  are  attached.  The 
number  of  gill  rakers  increase  as  growth  pro- 
gresses but  gill  rakers  are  slow  to  ossify,  and  the 
full  complement  usually  is  not  completed  until  the 
transition  and  early  juvenile  stages.  The  adult 
count  in  Seriola  zonata  is  fewer  than  is  formed  in 
the  juveniles  due  to  the  reduction  of  the  terminal 
gill  rakers  into  tubercles  in  the  ceratobranchial. 
Patches  of  fine  teeth  are  formed  on  the  superior 
pharyngeals  of  the  third  and  fourth  gill  arches 
while  the  fifth  and  shortest  gill  arch  has  teeth 
patches  for  most  of  its  length.  Pharyngeal  teeth 
ossify  in  larvae  6  to  8  mm  long. 

In  the  cranium,  the  parasphenoid,  frontals,  and 
supraoccipitals  ossify  in  the  youngest  larvae 
(2.5-3.8  mm).  Except  for  the  parietals  which  ossify 
in  the  midlarval  period,  the  rest  of  the  cranium  is 
not  ossified  until  the  late  larval  and  transition 
periods. 

The  cleithra,  postcleithra,  and  posttemporals 
are  ossified  in  the  early  and  midlarval  stages,  but 
the  rest  of  the  pectoral  girdle  calcifies  in  late  and 
transforming  larvae.  From  2  to  4  posttemporal 
spines  protrude  from  the  myotomes  during  the 
early  larval  period.  These  are  small  and  hardly 
visible  in  most  species  except  in  stained  speci- 
mens. These  spines  are  soon  overgrown  by  the 
developing  muscles. 

The  pelvic  girdle  calcifies  following  the 
ossification  of  the  pelvic  fins. 

Ossification  occurs  at  5  to  8  mm  in  the  vertebral 
column  and  proceeds  in  an  anteroposterior  direc- 
tion. The  neural  and  hemal  spines  ossify  ahead  of 
the  centra  of  their  respective  vertebrae.  The 
centra  ossify  at  their  anterior  margins  and 
ossification  proceeds  posteriorly.  This  pattern  of 
ossification  in  the  vertebrae  was  noted  in 
Trachurus  symmetricus  (Ahlstrom  and  Ball, 
1954). 

Ribs  similarly  ossify  in  an  anteroposterior  di- 
rection. The  pleural  ribs  are  the  first  to  ossify 
followed  by  the  epipleural  ribs.  All  trunk  verte- 
brae have  ossified  pleural  and  epipleural  ribs  in 
juveniles  15  to  17  mm  long  except  on  the  first  and 
second  in  which  pleural  ribs  are  lacking. 

Teeth  are  initially  uniserial  but  become  multi- 
serial  as  tooth  formation  progresses.  Following 


440 


APRIETO:   EARLY  DEVELOPMENT  OF  FIVE  CARANGID  FISHES 


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metamorphosis  2  to  3  irregular  rows  of  sharp  teeth 
are  present. 

ACKNOWLEDGMENTS 

The  author  wishes  to  thank  the  Miami  Labora- 
tory, Southeast  Fisheries  Center  of  the  National 
Marine  Fisheries  Service,  which  made  available 
the  working  space,  facilities,  materials,  and  funds. 
She  is  deeply  grateful  to  William  J.  Richards  for 
supervision  and  encouragement  and  to  Thomas 
W.  McKenney  for  the  many  helpful  discussions 
and  suggestions  on  larval  fish  work.  She  wishes  to 
express  her  appreciation  to  Elbert  H.  Ahlstrom  for 
reviewing  the  manuscript  and  for  his  valuable 
criticisms  and  suggestions,  and  also  wishes  to 
acknowledge  the  helpful  comments  from  Donald 
P.  de  Sylva,  Hilary  B.  Moore,  Charles  E.  Lane,  and 
Lowell  P.  Thomas.  She  is  grateful  to  Barbara 
Palko,  Edward  D.  Houde,  and  George  Miller  for 
carangid  larvae  given  to  her,  and  also  wishes  to 
thank  Thomas  Potthoff  for  information  on  stain- 
ing fish  larvae,  Alexander  Dragovich  for  transla- 
tion of  Russian  literature,  John  Wise  and  John 
Stimpson  for  assistance  in  computer  work,  and 
Elizabeth  Leonard  for  help  in  securing  much 
needed  literature. 

This  research  project  was  completed  while  the 
author  was  on  a  University  of  the  Philippines  Fac- 
ulty Fellowship  and  a  scholarship  grant  from  the 
International  Women's  Fishing  Association  of 
Palm  Beach,  Fla. 


LITERATURE  CITED 

Aboussouan,  a. 

1968.  Oeufs  et  larves  de  Teleosteen  de  I'Ouest  Africain  VI. 
Larves  de  Chloroscombrus  chrysurus  (Linne)  et  de 
Blepharis  crinitus  (Mitchill)  (Carangidae).  Bull.  Inst.  Fr. 
Afr.  Noire,  Ser.  A.  30(3):226-237. 
Ahlstrom,  E.  H. 

1948.  A  record  of  pilchard  eggs  and  larvae  collected  during 
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443 


SOME  EFFECTS  OF  DREDGING  ON  POPULATIONS 
OF  MACROBENTHIC  ORGANISMS 

Eugene  H.  Kaplan/  J.  R.  Welker,^  and  M.  Gayle  Kraus^ 

ABSTRACT 

Populations  of  epi-  and  infauna  were  studied  from  10  mo  before  to  11  mo  after  a  navigation  channel 
was  dredged  through  a  small,  shallow  lagoon.  A  new  sampler  which  jjenetrated  20-30  cm  into  the 
substratum  was  used. 

Current  velocities  and  sedimentation  patterns  were  changed  due  to  an  altered  distribution  of  tidal 
currents,  although  flushing  time  was  not  appreciably  altered. 

Values  of  certain  particulate  and  dissolved  nutrients  changed  after  dredging,  but  no  correlation 
was  observed  between  animal  populations  and  fluctuations  in  nutrients. 

Significant  reductions  in  standing  crop  figures  and  species  and  specimen  numbers  occurred  in  both 
the  bay  and  the  dredged  channel.  Mercenaria  mercenaria  populations  were  reduced,  but  there  was 
no  evidence  of  mass  mortality.  Recovery  of  biomass  in  the  channel  was  affected  by  sediment 
composition,  but  seasonal  and  sediment  type  variations  were  not  significant  in  the  bay  as  a  whole. 

Goose  Creek  had  a  high  predredging  epi-  and  infaunal  standing  crop  estimated  at  36.83  g/m^,  but 
the  number  of  organisms/m^  was  relatively  low,  indicating  a  preponderance  of  large  forms. 

Productivity  of  Goose  Creek  was  calculated  at  89.87  g/m^/yr  before  dredging  and  31.18  g/m*/yr  after 
dredging.  Productivity  figures  for  the  mixed  peripheral  marsh  were  calculated  and  the  annual  loss 
due  to  replacement  of  10.87  ha  of  marsh  by  spoil  areas  was  estimated  at  49,487  kg.  Altered 
land  usage  patterns  tended  to  fix  this  loss  on  a  permanent  basis. 

The  unusually  profound  effects  of  dredging  reported  for  Goose  Creek  are  attributed  to  its  small 
size  and  shallowness. 


In  1965,  Suffolk  County,  N.  Y.,  obtained  the 
services  of  a  consortium  of  universities  to  study 
the  characteristics  of  a  small  embayment  before 
and  after  a  channel  22.8  m  wide  x  2.1  m  deep  x 
1,037  m  long  was  dredged  from  the  narrow  inlet 
through  most  of  the  bay.  The  investigations  re- 
ported in  this  paper  are  confined  to  the  population 
dynamics  and  ecology  of  the  macrobenthic 
organisms.  Reference  will  be  made  to  the  other 
areas  of  investigation  only  as  they  affect  the 
macrobenthos. 

The  following  phenomena  will  be  considered  in 
relation  to  their  effects  on  epi-  and  infaunal 
population  dynamics: 

1.  Changes  in  the  hydrodynamics  of  Goose 
Creek  as  the  result  of  the  introduction  of  the  newly 
dredged  channel. 

2.  Changes  in  the  morphology  of  the  sediment 
effected  by  the  dredging  process. 


'Biology  Department,  Hofstra  University,  Hempstead,  NY 
11550. 

^Institute  of  Marine  Sciences,  Southampton  College,  South- 
ampton, NY  12837. 

^Zoology  Department,  University  of  Rhode  Island,  Kingston, 
RI  02881. 


3.  Changes  in  physical  and  chemical  char- 
acteristics of  the  water  associated  with  the  dredg- 
ing process. 

4.  Changes  in  populations  of  macrobenthic 
organisms  which  occurred  during  1966  and  1967. 

The  Study  Area 

Goose  Creek  is  a  small,  shallow  lagoon  located 
on  the  north  fork  of  Long  Island  in  the  town  of 
Southold,  N.  Y.  (lat.  41°03'00"N,  long.  72°25'23" 
W).  Its  dimensions  are  1,464  m  east-west  by  533  m 
north-south,  a  total  area  of  about  0.32  km^.  A 
channel  approximately  30.5  m  wide  at  the  east- 
ern end  opens  into  Southold  Bay,  thence  into 
Shelter  Island  Sound,  an  arm  of  Little  Peconic 
Bay  (see  Figure  1). 

The  mean  high  water  depth  before  dredging  was 
1.7  m,  but  much  of  the  bay  was  extremely  shallow 
and  at  low  water  it  was  impossible  to  navigate 
even  a  small  boat  in  the  western  half  of  the  bay. 
Mean  tidal  range  was  68.5  cm,  and  the  mean  depth 
at  mean  low  water  was  1.0  m. 

The  prevailing  wind  is  from  the  southwest  in 


Manuscript  accepted  September  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  2,  1974. 


445 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


72=  25' 


GOOSE    CREEK,  N.Y. 


0     100    200  300 
A1  e  f  e  r  s 


41°  03 


Figure  1. — Location  map  of  Goose  Creek,  N.Y. 


the  summer  months  and  from  the  northwest  in 
winter. 

There  are  four  "minor"  and  five  "major"  islands 
in  Goose  Creek,  the  largest  of  which  is  115.6  m  by 
42.4  m.  They  sustain  a  heavy  growth  of  Spartina 
alterniflora  with  dense  colonies  of  Modiolus 
demissus  and  Uca  pugnax. 

The  entrance  of  Goose  Creek  was  dredged  from 
a  mean  low  water  depth  of  0.8  m  to  a  minimum 
of  2.1  m  below  mean  low  water.  In  cross  section 
the  channel  was  changed  from  a  gentle  depres- 
sion to  a  steep-sided  U.  As  a  consequence  of  dredg- 
ing the  channel,  the  main  water  flow  was  shifted 
from  one  channel  to  another  and  current  velocities 
dropped  approximately  one-half,  except  in  the 
western  half  of  the  bay  where  previously  negli- 
gible velocities  increased. 


The  substratum  of  the  bay  consists  of  coarse 
gravel  and  sand  in  the  main  channel  before  it 
trifurcates  into  channels  A,  B,  and  C,  which  are 
characterized  by  sand  grading  into  fine  sand  and 
mud  in  areas  with  reduced  current  velocity.  The 
bottom  sediments  in  the  western  half  of  the  bay 
consist  of  thick  silt  over  gray  clay  mixed  with 
shell  and  sand. 

The  surrounding  upland  consists  of  Spartina 
marsh  edged  by  stands  ofPhragmites  communis. 
Before  dredging,  the  south  shore  was  almost 
completely  developed,  with  small  summer  homes 
along  the  shores.  The  north  and  west  shores  were 
undergoing  partial  development  with  year-round 
homes.  Five  years  after  the  dredging  (1972),  the 
area  was  almost  completely  developed,  much  of 
the  marsh  having  been  replaced  by  areas  filled 
for  homesites. 


446 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 


In  1966-1967  salinities  ranged  from  a  mean 
low  of  26.79  7cc  to  a  mean  high  of  28.34,^^0.  The 
pH  ranged  from  7  to  8.  The  dissolved  oxygen 
levels  varied  seasonally  and  from  station  to 
station  from  a  low  of  4.50  ml  02/liter  to  a  high 
of  9.95  ml  02/liter.  Readings  were  always  at 
saturation.  The  mean  temperature  range  was 
between  -1.0°C  and  26.18°C  over  the  2  years; 
the  bay  is  too  shallow  to  exhibit  a  pronounced 
thermocline.  Portions  of  the  surface  were  frozen 
solid  during  parts  of  the  months  of  February  and 
March,  1966,  and  January,  February,  and  March, 
1967. 

The  tidal  currents  were  relatively  rapid  in  the 
eastern  section  of  the  bay,  reaching  a  velocity 
of  56.7  cm/sec  at  station  1,  at  the  confluence  of 
the  three  channels,  but  they  rapidly  lost  velocity 
until  negligible  readings  were  recorded  in  most  of 
the  western  half  of  the  bay. 

Yearly  rainfall  (1967)  amounted  to  126.09  cm. 
Pollution  by  effluents  from  cesspools  along  the 
southern  periphery  of  the  bay  consisted  of  fecal 
material,  other  organic  material,  and  detergents 
as  indicated  by  coliform  bacteria  and  phosphate 
levels. 


Previous  Dredging  of  Goose  Creek 

Goose  Creek  was  chosen  for  this  investigation 
because  of  its  unspoiled  nature.  This  is  a  relative 
term,  however,  and  on  Long  Island,  with  its  high 
population  density,  it  is  unlikely  that  any  bay 
or  inlet  has  escaped  some  form  of  dredging 
operation. 

There  have  been  a  number  of  private  drag-line 
dredgings  in  Goose  Creek  reported  by  local 
residents.  The  earliest  incident  described  was  a 
dredging  operation  along  channel  A  in  1930;  a 
1904  map  of  the  region  reveals,  however,  that  the 
general  contours  of  the  bay  remained  unchanged. 

The  first  officially  recorded  dredging  in  the 
environs  of  Goose  Creek  performed  by  Suffolk 
County  occurred  in  November,  1959.  A  channel 
approximately  500  m  long  and  30  m  wide  was 
dredged  from  the  bridge  east  by  southeast  into 
Southold  Bay  as  an  aid  to  small  boat  navigation. 
The  depth  of  the  channel  was  increased  from 
approximately  0.5  m  to  3  m  mean  depth  below 
mean  low  water,  and  35,653  m^  of  spoil  were 
placed  along  the  southeast  shore  of  the  inlet, 
covering  20,920  m^  of  Spartina  marsh. 


Another  area,  smaller  in  size,  received  some 
spoil  from  this  dredging.  It  was  contiguous 
with  what  was  to  become  spoil  area  C. 

The  second  dredging  operation  began  on  27 
June  1967  and  ended  on  2  August  1967.  The 
effects  of  that  operation  are  the  subject  of  this 
investigation. 

A  channel  23  m  wide  by  825  m  long  was 
dredged  from  the  bridge  at  the  inlet  to  the  bay  in 
an  easterly  direction  along  Channel  B.  A  total  of 
57,383  m^  of  spoil  was  removed  and  placed  on 
spoil  areas  A,  B,  and  C.  Spoil  area  A  covered 
approximately  6,000  m^  of  Spartina  and  Phrag- 
mites  marsh  adjacent  to  a  previously  used  spoil 
area  of  approximately  26,000  m^  covered  to  a 
maximum  height  of  3  m  above  mean  low  water. 
Spoil  areas  B  and  C  in  the  southwest  corner  of 
Goose  Creek  covered  44,640  m^  and  23,250  m^ 
of  Spartina  marsh  respectively. 

A  third  dredging  took  place  from  22  December 
1967  to  12  April  1968.  A  15.25-m  wide  channel 
was  dredged  to  extend  the  previously  constructed 
channel  across  the  bay  to  the  cut  opening  into 
the  eastern  shore.  A  small  extension  to  an 
existing  channel  was  also  dredged  through  the 
center  of  Thyone  Cove.  The  combined  dimensions 
of  these  extensions  were  427  m  x  15.25  m  and 
8,508  m^  of  substratum  were  removed  and  placed 
on  spoil  area  B. 

During  the  spring  and  summer  of  1970,  drag- 
line operations  in  the  northwest  corner  of  Goose 
Creek  obliterated  13,950  m^  of  Spartina  marsh 
along  a  frontage  of  152  m  as  site  preparation  for 
a  housing  development.  This  was  part  of  the 
largest  portion  of  the  original  peripheral  marsh 
which  remained  after  the  dredging  operations 
of  1967-1968.  The  only  remaining  marsh  in  Goose 
Creek  at  the  time  of  this  writing  was  an  area 
approximately  16,000  m^  bordering  the  north- 
western edge  of  the  bay  (see  Figure  2). 

Estimates  of  the  areas  of  marsh  covered  by 
dredge  spoil  along  the  periphery  of  Goose  Creek 
can  be  seen  on  Table  1. 

An  estimate  of  the  remaining  marsh  in  Goose 
Creek  comes  to  43,826  m^  (islands)  plus  23,715  m^ 
(peripheral)  or  a  total  of  67,541  m^.  This  is  31.4% 
of  the  total  acreage  covered  by  marsh  in  1959. 
Excluding  the  islands,  only  10.7%  of  the  1959 
peripheral  marsh  remains.  Examination  of  a  map 
of  the  Goose  Creek  area  drawn  in  1904  reveals 
that  the  entire  periphery  of  the  bay  was  sur- 
rounded by  extensive  marshes.  Probably  less  than 


447 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Figure  2.— Aerial  photograph  of  Goose  Creek,  May  1972.  Note  straight  edge  of  northwest  shorehne  (light  area)  caused  by 
1970  private  dredge  and  landfill  operation.  Upper  embayment  is  Jockey  Creek.  Note  dredged  channels  in  both  bays  and 
virtually  complete  eradication  of  marsh  around  Jockey  Creek. 


1%  of  the  original  Goose  Creek  marsh  is  still 
present. 

METHODS  AND  MATERIALS 

In  order  to  determine  what  changes  occurred 
in  the  macrobenthic  population  in  Goose  Creek, 
23  stations  were  established  in  the  bay,  exclusive 
of  the  area  to  be  dredged  for  the  deepened 
channel.  Fifteen  additional  stations  were  located 
at  30  m  intervals  in  the  path  of  the  proposed 
channel. 

The  present  study  was  initiated  1  yr  before  the 
scheduled  dredging  operation.  Since  a  complete 
characterization  of  Goose  Creek  was  necessary 
before  the  onset  of  dredging,  it  was  deemed 


necessary  to  use  a  sampling  procedure  which 
could  cover  the  whole  of  Goose  Creek  once  every 
month.  As  the  western  half  of  the  bay  is  uniform  in 
bottom  composition,  being  composed  of  deep, 
gray-black  silt  over  muddy  gray  sand,  there  is 
little  need  to  sample  it  as  extensively  as  the 
eastern  half  of  the  bay,  which  is  characterized  by 
f'-equent  changes  in  sediment  type  caused  by 
variegated  current  flow  patterns  and  topographic 
variability.  Faunistic  distribution  was  found 
to  be  dependent  on  the  nature  of  the  sediment, 
whose  characteristics  were,  in  turn,  dependent  on 
the  erosion  and  deposition  rates  of  the  overlying 
tidal  currents.  Consequently,  it  was  decided  to 
divide  the  bay  into  zones  of  high,  medium,  and 
low  current  velocities,  sampling  each  region  by 


448 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 

Table  1. — Dimensions  of  known  dredging  operations  in  Goose  Creek. 


Area 

Amount 

Dredged  area 

Spoil  area 

covered 

of  spoil 

Navigation  channel 

Edge  of  Southold 

20,920m2 

35,653m3 

in  Southold  Bay  to 

Bay  on  either  side 

bridge. 

of  inlet  to  Goose 
Creek. 

June-August  1967 

Spoil  areas  A,  B, 

73,842m2 

57,383m3 

dredging  of  channel 

and  C. 

through  Goose  Creek. 

Dec.  1967-April 

Spoil  area  B. 

Included 

8,508m3 

1968  dredging  of 

above. 

spur  channel  to 

western  shore,  plus 

navigational  channel 

through  Thyone  Cove. 

Spring-summer, 

Northwest  edge 

ca.  13,950m2 

Unknown 

1970  private  drag- 

line operation  in  NW 

corner  of  Goose  Creek. 

Totals 

108,712m2 

101,544m3 

means  of  transects  across  the  zone.  In  addition, 
a  number  of  intertidal  stations  were  set  up,  and 
a  "characterization"  survey  was  embarked  on 
which  sampled  the  intertidal  area  2  m  from  shore 
and  the  sublittoral  6  m  from  shore  every  30  m 
around  the  periphery  of  the  bay.  Using  data  from 
the  preliminary  surveys,  sampling  stations  were 
established  as  representative  of  major  substratum 
categories  in  Goose  Creek.  The  advantages  of 
placing  greater  sampling  emphasis  on  certain 
areas  rather  than  randomly  sampling  or  using 
established  as  representative  of  major  substratum 
(1967),  Stickney  and  Stringer  (1957),  and  Lee 
(1944). 

Figure  3  indicates  the  positions  of  the  stations 
in  Goose  Creek. 

Each  station  was  sampled  with  a  "suction- 
corer"  (Kaplan,  Welker,  and  Kraus,  In  press-a) 
once  a  month  for  9  mo  preceding  dredging  and  11 
mo  after  dredging  terminated.  A  small  shallow- 
draft  vessel  was  propelled  to  the  stations  by  an 
outboard  motor.  Locations  were  fixed  by  tri- 
angulation. 

Once  the  vessel  was  located  over  a  station, 
"spuds"  consisting  of  7.62  cm  OD  galvanized  pipes 
were  lowered  fore  and  aft  to  keep  the  barge  from 
swinging  with  current  or  wind.  The  sampler 
consisted  of  a  chamber  36  cm  in  diameter  by  30 
cm  high  from  which  extended  a  hydraulic  hose 
leading  to  a  3  hp  pump  on  the  deck  of  the  barge. 
The  corer  was  then  lowered  through  a  hole  in 
the  center  of  the  deck  until  it  reached  the  bottom. 
The  pump  was  started  and  the  water  was  with- 
drawn from  the  coring  chamber.  The  evacuated 


chamber  had  negative  pressure  relative  to  the 
water  column  above  it;  this  pushed  it  into  the 
bottom.  In  practice  depth  of  penetration  varied, 
but  a  sample  was  not  considered  adequate 
unless  the  chamber  had  penetrated  to  a  mini- 
mum depth  of  20  cm.  After  maximum  penetra- 
tion the  chamber  was  inverted  by  means  of  a 
winch  and  the  sample  was  hauled  to  the  deck 
where  it  was  emptied  onto  a  60  cm  x  90  cm 
sieve  of  1 .4  mm  mesh  size  and  washed.  The  screen- 
ings were  placed  in  gallon  bottles  and  formalde- 
hyde was  added  to  a  concentration  of  10%. 


GOOSE    CREEKN.y. 


Figure  3. — Location  of  stations,  Goose  Creek.  Letters  in 
circles  represent  channel  stations;  letters  in  squares  repre- 
sent intertidal  stations;  letters  in  triangles  represent  spoil 
areas.  Shaded  extension  of  channel  represents  1968  dredging. 


449 


Holme  (1953)  and  Reish  ( 1959)  established  that 
1.5  mm  and  1.4  mm  mesh  sieves  recovered  90%  of 
the  biomass  from  their  samples,  respectively.  In 
view  of  the  importance  of  large  forms  in  the  Goose 
Creek  species  composition,  it  is  likely  that  the  10% 
potential  error  described  by  Reish  and  Holme  is 
a  conservative  estimate.  Since  the  purpose  of 
this  investigation  required  an  accurate  estimate 
of  total  standing  crop,  with  special  emphasis  on 
such  commercially  important  species  as  Mercen- 
aria  and  Mya,  no  attempt  was  made  to  separate 
the  "large"  and  "small"  forms  by  using  an  arbi- 
trary cut-off  point,  as  the  0.2  g  of  Sanders  (1956). 
Thirty-eight  stations  and  the  once-a-month 
sampling  schedule  produced  over  400  separate 
samples;  this  large  A^  helped  compensate  for 
statistical  inaccuracies  introduced  by  the  pres- 
ence of  large  forms. 

After  a  minimum  of  1  yr  of  storage  the  speci- 
mens were  identified,  weighed  (blotted  wet 
weight),  and  dried  at  40°C  until  uniform  dry 
weight  was  obtained.  Pelecypods  were  shelled,  but 
crustaceans  did  not  have  their  carapaces  re- 
moved, since  many  were  too  small  for  this 
procedure  to  be  performed  with  precision.  Instead 
the  major  weight  factor  of  the  shells,  the  car- 
bonates, was  substantially  removed  by  the  acidic 
action  of  the  unbuffered  formaldehyde.  The  use 
of  an  acidic  medium  to  remove  carbonates  was 
employed  by  Sanders  (1956),  Holme  (1953),  and 
others. 

The  data  were  expressed  as  number  of  organ- 
isms/wet weight/dry  weight  (biomass)  per  m^  of 
substratum,  including  all  animals  recovered, 
according  to  the  recommendation  of  Lee  (1944). 

RESULTS 

Hydrography  of  Goose  Creek 

The  hydrographic  data  recorded  below  were 
obtained  from  the  reports  of  Hair  (1968),  Fazio 
(1969),  and  Black  (pers.  comm.).  Salinity  was 
measured  by  a  portable  Beckman  salinometer 
(Model  RS  5-3),'*  dissolved  oxygen  and  tempera- 
ture readings  were  taken  with  a  portable  oxygen 
meter  (Electronic  Instruments  Ltd.  Model  15  A) 
and  pH  was  determined  with  a  portable  Orion 
Instruments  Specific  Ion  Meter  (Model  401).  Light 
penetration  was  measured  by  a  Secchi  disc. 


••Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


FISHERY  BULLETIN:   VOL.   72,  NO.  2 

Water  Temperature 

Average  daily  temperatures  ranged  from  25.5°C 
to  0.5"C  in  the  bay  in  1967-68.  The  lowest  indi- 
vidual reading  was  -1.5°C  on  11  January  1968 
and  the  highest  29.0°C  on  7  July  1967.  In  January, 
February,  and  March,  the  bay  was  often  covered 
by  ice. 

Salinity 

Maximum  salinity  values  occurred  in  mid- 
July  to  mid-October  with  a  1966-1968  high  of 
30. 12 /CO.  Low  salinities  occurred  from  mid- 
January  to  mid-April,  with  the  1966-68  low  of 
18.38  Vco  recorded  on  28  March  1968. 

Mean  1966-67  salinity  in  the  bay  proper  (ex- 
cluding the  relatively  less  saline  cut  extending 
from,  the  west  shore)  was  28.37 /^o . 

pH 

Average  daily  pH  in  Goose  Creek  ranged  from 
7.1  to  8.3  (excluding  the  somewhat  more  variable 
western  cut)  in  1967  and  7.7-8.2  in  1966.  The 
highest  individual  value  in  1967  was  8.6,  occur- 
ring during  a  phytoplankton  bloom  in  Thyone 
Cove,  on  27  July  1967.  The  highest  individual 
value  for  1966  was  9.0  during  a  dinoflagellate 
bloom. 

Light  Penetration 

Secchi  disc  readings  were  taken  at  weekly 
intervals  throughout  the  duration  of  the  study.  In 
the  bay  itself  the  photic  zone  usually  reached  to 
the  bottom,  since  the  total  water  column  was 
never  more  than  3.5  m.  Virtually  the  entire  bay 
could  be  considered  euphotic  except  during  the 
month  in  which  the  dredging  took  place,  July 
1967,  when  the  minimum  light  penetration  as 
recorded  by  the  Secchi  disc  was  0.4  m  (Fazio, 
1969).  It  appears,  then,  that  light  penetration 
values  were  not  substantially  affected  by  the 
introduction  of  suspended  materials  into  the 
water  as  the  result  of  dredging.  This  is  not 
surprising  in  view  of  the  shallow  nature  and 
relatively  rapid  flushing  time  of  the  region  of  the 
bay  most  severely  affected  by  the  dredging,  the 
eastern  half.  On  the  other  hand,  deposition  of  a 
canopy  of  flocculent  material  on  the  leaves  of  the 
Ruppia  and  the  thalli  of  the  Enteromorpha  was 
observed  during  and  after  the  dredging  process. 


450 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 


This  factor  almost  certainly  reduced  available 
light  to  the  plants  despite  the  relative  clarity  of 
the  water. 

Current  Velocity 

Readings  of  current  velocities  were  taken  on 
9  June  1967,  before  dredging,  and  on  19  July  1968, 
after  the  new  channel  was  completed.  Attempts 
were  made  to  match  the  tide  height  and  wind 
direction  and  velocity  on  both  occasions  so  as  to 
minimize  variables  related  to  natural  fluctuations 
of  water  level  and  current  velocity.  During  both 
readings  the  wind  was  from  the  southwest  and 
differences  in  wind  velocity  between  the  two  days 
were  not  greater  than  10  mph.  The  wind  velocity 
was  slightly  higher  during  the  post-dredging 
series  (7  mph  vs  15  mph)  as  was  the  tidal 
range  (70  cm  vs  73  cm).  These  factors  would  tend 
to  increase  the  velocity  of  the  flood  tide  rather 
than  decrease  it.  Since  current  velocities  de- 
creased, this  effect  cannot  be  attributed  to  the 
influences  of  wind  and/or  tide. 

The  bridge  readings  were  made  with  an  Ekman 
current  meter  at  20  min  intervals,  0.5  m  beneath 
the  surface  and  0.5  m  above  the  bottom  of  the 
channel.  The  meter  was  allowed  to  run  for  120 
sec  and  the  readings  were  converted  into  centi- 
meters per  second  according  to  the  standard 
formula. 

The  readings  in  the  channels  were  taken  with 
Price  meters  on  hand-held  rods.  The  meters  were 
set  at  0.5  m  above  the  bottom.  Maximum  depth 
of  water  at  any  station  was  approximately  1 .2  m  so 
that  lamination  or  stratification  according  to 
current  velocity  was  minimized.  Maximum  inter- 
vals between  readings  at  the  same  station  were 
less  than  30  min. 

The  data  consisted  of  the  number  of  revolu- 
tions of  the  wheel  during  a  70  sec  interval  con- 
verted into  centimeters  per  second  from  a  nomo- 
graph calibrated  to  each  meter.  One  replication 
of  each  measurement  was  taken  as  a  check  on 
the  accuracy  of  the  meters. 

Table  2  and  Figure  4b  compare  current  veloci- 
ties before  and  after  dredging.  Figure  4a  indicates 
the  current  velocity  sampling  stations. 

Maximum  current  velocity  before  dredging  was 
through  channel  A.  After  dredging,  the  most 
westerly  portion  of  channel  A  still  has  the  maxi- 
mum current  velocity,  but  approximately  100  m 
east  of  the  point  of  trifurcation  at  stations  4  and 


Table  2. — A  comparison  of  current  velocities  at  flood  tide  in 
Goose  Creek,  before  and  after  dredging. 


Before 

After 

Difference 

Station 

(cm/sec) 

(cm/sec) 

(cm/sec) 

1 

56.7 

25.8 

-30.9 

7 

41.4 

13.r 

-28.3 

6 

40.2 

7.2 

-33.0 

2 

55.2 

25.2 

-30.0 

'3 

43.9 

2.6 

-41.3 

4 

23.2 

13.1 

-10.1 

5 

17.2 

18.0 

+   0.8 

ID 

28.8 

NA 

NA 

2D 

38.4 

5.5 

-32.9 

3D 

12.1 

2.7 

-  9.4 

4D 

Neg  (0) 

5.5 

+   5.5 

50 

Neg  (0) 

4.8 

+   4.8 

Bridge 

92.0 

47.2 

2-44.8 

Bridge 

83.8 

39.6 

3-44.2 

'Station  3  was  a  sand  bar  with  a  thin,  rapid  flow.  The  water  was 
never  more  than  30  cm  deep  over  this  bar.  It  was  removed  by  the 
dredging  operation  and  replaced  by  a  2.1  m  deep  channel. 

^f^aximum  surface  velocity. 

^Maximum  bottom  velocity. 


GOOSE    CREEK,  N.y: 


Figure  4  a. — Map  of  current  velocity  sampling  stations. 


Figure  4  b. — Map  of  current  velocity  differences  before  (open 
arrows)  and  after  (solid  arrows)  dredging.  Each  millimeter 
represents  4  cm/sec  current  velocity. 


451 


7,  the  current  velocities  in  channels  A  and  B  were 
matched  at  13.1  cm/sec.  Thereafter,  the  post- 
dredging  velocity  in  channel  B  was  greater  than 
in  channel  A,  i.e.,  18.0  cm/sec  at  station  5  and 
7.2  cm/sec  at  station  6.  Thus,  maximum  flow  was 
changed  from  channel  A  to  channel  B  as  a  result 
of  the  dredging. 

Channel  B  was  converted  from  a  shallow,  wide 
passage  with  maximum  surface  area  in  contact 
with  the  current  (hence  maximum  friction  and 
impedance  of  water  flow)  to  a  deep  channel,  whose 
depths  at  mean  low  water  before  and  after 
dredging  were  0.4  m  and  2.1  m  at  the  entrance. 

The  substratum  of  channel  A  was  gravel  and 
sand  at  the  most  westerly  end,  changing  to  sand 
for  most  of  the  length  of  the  channel  as  it  passed 
islands  I  and  II,  after  which  it  gradually  became 
muddy  sand.  Near  Thyone  Cove  only  the  shoreline 
and  3  m  of  littoral  remained  muddy  sand;  below 
this  level  the  substratum  was  gray  sand  covered 
by  2  cm  of  silt. 

As  indicated  earlier,  channel  B  had  a  lower 
velocity  before  dredging  than  channel  A.  The 
transitional  area  was  compressed  in  channel  B; 
the  area  of  sand  at  the  westerly  end  merged 
rapidly  into  muddy  sand,  then  silt,  a  short 
distance  past  the  easterly  end  of  island  I. 

Channel  C,  both  pre-  and  postdredging,  was 
characterized  by  an  initial  high  velocity  (55.17 
cm/sec  at  station  2  and  38.40  cm/sec  at  station 
2D),  but  this  rapidly  dissipated  over  the  sand  flats 
and  eddies  north  of  islands  III  and  IV. 

Maximum  surface  and  bottom  velocity  was 
halved  after  dredging  at  the  inlet  to  the  bay.  This, 
of  course,  would  have  a  most  profound  influence 
on  transport  of  materials,  since  it  represented  a 
section  of  water  approximately  22  m  wide  by  2.8  m 
deep.  Since  the  original  mean  depth  of  the  channel 
was  approximately  1  m,  the  cross  section  of  the 
dredged  channel  was  approximately  three  times 
greater  than  the  original  channel,  increasing  its 
volume  commensurately. 

Isaac  (1965)  stated  that  current  velocities  of  0.6 
to  1.3  ft/sec  (18.29  to  39.62  cm/sec)  are  sufficient 
to  resuspend  bottom  deposits  with  1 .0  mm  particle 
diameter.  According  to  changes  in  current 
velocity  at  Goose  Creek,  the  deposition  of  such 
particles  would  have  taken  place  at  the  following 
stations  after  dredging,  although  not  before  dredg- 
ing: station  7  (41.4  to  13.1  cm/sec),  station  6  (40.2 
to  7.2  cm/sec),  station  3  (43.9  to  2.6  cm/sec), 
station  4  (23.2  to  13.1  cm/sec)  and  station  2D 
(38.4  to  5.5  cm/sec). 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

Mass  Movement  of  Water 

Hair  (1968)  calculated  the  volume  of  water 
moving  in  and  out  of  Goose  Creek  during  each 
phase  of  the  tidal  cycle.  Assuming  the  average 
depth  to  be  1.3  m  at  high  tide  with  a  tidal  range 
of0.8mandanareaof2.59  x  lO^m^,  he  calculated 
the  volume  of  the  bay  at  high  tide  to  be  3.88  x 
lO^m^.  At  low  tide  the  corresponding 
calculation  was  1.44  x  lO^m^.  The  volume  lost 
at  each  falling  tide  would  then  represent  approxi- 
mately 60%  of  the  volume  at  high  tide.  Fazio 
(1969)  recalculated  the  tidal  exchange  on  the 
basis  of  the  increased  volume  of  the  bay  caused 
by  the  construction  of  the  dredged  channel.  His 
volumes  were  7  x  lO^m^  at  high  tide  and  3.1  x 
lO^m^  at  low  tide.  This  represents  a  loss  of  66%  at 
each  ebb  and  is  considered  by  Fazio  as  a  corrobora- 
tion of  Hair's  calculations. 

Of  importance  in  any  consideration  of  the 
benthos  in  Goose  Creek  is  the  fact  that  during 
the  6  h  of  ebb  tide  roughly  60%  to  66%  of  the 
total  volume  of  water  in  Goose  Creek  (approxi- 
mately 2  X  lO^m^  before  dredging  and  4  x  lO^m^ 
after  dredging)  flowed  out  of  the  bay.  All  of  this 
water  passed  through  channels  A,  B,  and  C 
which,  at  a  maximum  value  of  23  m  wide  and 
3.0  m  deep  for  channel  B  and  30  m  x  1.5  m  for 
the  combined  channels  A  and  C,  represents  a  total 
cross-sectional  volume  of  114  m^  for  the  passage 
of  ca.  3.9  X  lO^m^  of  water.  The  relatively  small 
volume  of  channels  A,  B,  and  C  and  the  244  m 
channel  formed  by  their  confluence  and  flowing 
eastward  into  Southold  Bay  accounts  for  the 
rapid  current  velocity  in  the  eastern  half  of 
Goose  Creek. 

On  21  May  1966,  an  attempt  was  made  to 
determine  the  proportion  of  water  exchanged  in 
various  parts  of  the  bay.  Rhodamine  B  was 
released  into  the  easternmost  portion  of  Goose 
Creek  (near  the  bridge)  on  an  incoming  tide,  so 
that  the  average  dilution  was  approximately  27 
ppm  after  2  h  over  the  entire  surface  area  of 
the  bay.  Six  weeks  later  the  readings  on  the 
fiuorometer  revealed  values  of  the  order  of  1.7 
ppm  in  most  of  the  eastern  half  of  the  bay  while 
Thyone  Cove  and  the  western  shore  of  Goose 
Creek  had  readings  as  high  as  9.6  ppm  and  lows 
rarely  below  6.3  ppm. 

Figure  5  demonstrates  that  the  exchange  of 
water,  as  revealed  by  residues  of  Rhodamine 
B,  was  greater  in  the  eastern  half  of  the  bay,  with 
areas  of  Thyone  Cove  and  the  west  shore  having 


452 


KAPLAN,  WELKER.  and  KRAUS:  EFFECTS  OF  DREDGING 


maximum  values  for  the  dye  and,  therefore,  a 
comparatively  low  exchange  rate. 


Dissolved  Nutrients 

Fazio  (1969)  and  Hair  (1968)  studied  the  dis- 
tribution of  certain  nutrients  in  Goose  Creek 
before  and  after  the  dredging  operation.  The 
results  of  their  investigations  are  summarized 
in  Table  3  and  fluctuations  in  pre-  and  post- 
dredging  concentrations  of  chlorophyll  a,  silicate, 
dissolved  organic  phosphate,  and  nitrite  are 
depicted  in  Figure  6. 

Fazio  reported  that  there  were  significant 
changes  in  the  values  of  particulate  phosphorus, 
silicates,  and  chlorophyll  a  as  a  result  of  the 
dredging.  He  demonstrates  high  correlations 
between  particulate  phosphorus  and  chlorophyll 
a  {r  =  0.83),  but  is  unwilling  to  suggest  a  direct 
relationship  between  this  nutrient  and  phy- 
toplankton  productivity. 

Instead,  he  explains  the  congruent  increases  in 
particulate  phosphates  and  chlorophyll  a  as  either 
a  suspension  of  living  benthic  organisms  intro- 
duced into  the  water  by  the  disturbance  of  the 
sediment,  or  resuspension  of  detrital  material 
and/or  land  runoff.  Analysis  of  the  water  near 
a  leaking  spoil  area  revealed  great  amounts  of 
particulate  phosphorus  and  chlorophyll  a  were 
being  added  to  the  water  column. 

The  distribution  of  silicates  was  shown  to  be 
related  to  the  dredging  process  since  highest 
readings  were  associated  with  stations  in  the 
vicinity  of  the  dredge  pipe  and  spoil  areas;  these 
high  readings  shifted  down  the  bay  following  the 
movements  of  the  dredge.  There  was,  however,  a 
low  positive  correlation  between  silicates  and 
chlorophyll.  Coupling  high  concentrations  of 
chlorophyll  a  with  extreme  turbidity  and  very 
low  light  penetration  in  the  vicinity  of  the  dredge, 
Fazio  (1969)  concludes  that  the  chlorophyll  is  not 
necessarily  an  indicator  of  the  presence  of 
phytoplankton,  since  the  opacity  of  the  sediment- 
laden  water  would  prevent  photosynthesis  and 
limit  phytoplankton  production.  Instead,  he  sug- 
gests that  plant  detritus  in  the  spoil  runoff  is  the 
main  source  of  the  high  chlorophyll  a  readings 
and  that  phytoplankton  populations  might  be 
very  low. 

Examination  of  Figure  6  reveals  a  second  high 
in  chlorophyll  a  readings  in  December  1967- 


GOOSE    CREEK,  NY. 


Figure  5. — Rhodamine  B  residues  in  ppm  on  day  of  adminis- 
tration and  after  6  weeks.  Figures  in  parentheses  represent  the 
later  readings.  (Drawn  from  data  from  Black,  pers.  comm.) 

January  1968.  This  corresponds  with  a  second 
dredging  which  occurred  from  22  December  1967 
to  12  April  1968  in  the  western  quarter  of  the 
bay.  The  picture  is  very  much  like  that  of  the 
first  dredging.  A  similar  peak  chlorophyll  a  read- 
ing occurred  at  the  onset  of  dredging  followed  by 
a  sustained  high  yield  throughout  the  late 
winter  and  early  spring.  Mean  chlorophyll  a 
readings  for  the  months  of  December  1967  to  June 
1968  are  consistently  two  to  five  times  those  of 
the  comparable  1966-1967  period.  Resolution  of 
the  problem  of  whether  the  chlorophyll  readings 
represent  an  increase  in  phytoplankton  or  are 
artifacts  resulting  from  runoff  will  be  decided 
when  Cassin  publishes  his  analysis  of  the  phy- 
toplankton cycle  1967-1968. 

Table  3. — The  fluctuations  in  certain  dissolved  and  particulate 
nutrients  in  Goose  Creek,  1966-1968. 


Nutrients 


Mean  concentration 
1966  (Hair) 


Mean  concentration 
1967  (Fazio) 


Dissolved 

0.81  pg  at.  P/liter 

0.86  Aig  at.  P/llter 

inorganic 

phosphorus 

Nitrates 

2.8;i/g  at.  NOj-N/liter 

3.5 /ig  at.  NOa-N/liter 

Silicates 

July-Aug.  values 

July-Aug.  dredging 

betw/een  8  and  16 

period  values  between 

fig  at.  Si/liter 

30and35/:/gat.Si/liter. 
Variable  from  station 
to  station  according  to 
proximity  to  dredge. 

Particulate 

Mean  of  8  readings 

Mean  of  8  readings 

phosphorus 

6/16-7/18.  1966 

7/5-8/7,  1967 

4.94 /:ig  at.  P/liter 

18.30 /jg  at.  P/liter 

453 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


30 

25 

O20 


10 
5 


ASONDJ  f/MAAIJ 


^P 

Sl.l 

40 

•      * 

\    30 

V) 

^ 

0 

^    20 

Mn'^ 

10 

-^  H 

r^^Ay-lA^^ 

A        SON         OJ         FA1AA1J 


ON         OJ         f        M       A       M        J 


Figure  6. — Fluctuations  of  (from  top  to  bottom)  chlorophyll 
a,  silicates,  dissolved  inorganic  phosphates,  and  nitrites  in 
Goose  Creek,  1966-1968.  (Redrawn  from  Hair,  1968;  Fazio 
1969.)  Solid  line  represents  1966-1967  data;  dotted  line  repre- 
sents 1967-1968  data. 


In  general,  the  results  of  the  Goose  Creek 
nutrient  studies  are  similar  to  those  carried  on 
in  Chesapeake  Bay  by  Flemer  (1970)  and  Biggs 
(1968).  Particulate  phosphates,  silicates,  and 
chlorophyll  a  increased  significantly.  Concentra- 
tions of  nitrates,  nitrites,  and  dissolved  organic 
and  inorganic  phosphates  were  not  appreciably 
different  before  and  after  dredging. 

Copeland  and  Dickens  (1969)  report  that  in 
Maryland,  Texas,  and  South  Carolina  there  was 
an  initial  diminution  of  phytoplankton  produc- 
tivity due  to  shading  and  a  later  enhancement 
due  to  resuspension  of  nutrients  from  dredge  spoil. 
Flemer  (1970)  indicates  that  he  found  no  demon- 
strable effect  of  the  deposition  of  fine  sediments 
from  dredging  on  the  production  of  phytoplankton 
in  Chesapeake  Bay. 

There  is  no  evidence  that  the  release  of  nu- 
trients from  dredging  produces  an  effect  similar 
to  that  described  by  Raymont  (1947,  1949) 
where  the  addition  of  fertilizer  to  small,  enclosed 
embayments  raised  the  level  of  benthic  pro- 
ductivity up  to  300%  by  stimulating  production 
of  phytoplankton. 

Mechanical  Analysis  of  the  Sediment 

Sanders  (1956)  points  out  the  great  variability 
in  establishing  criteria  for  the  differentiation 
of  particles  constituting  the  sediment.  He  ex- 
pressed the  composition  of  the  sediment  in  terms 
of  the  proportion  of  the  particular  component 
which  was  either  most  predominant  or  most  rele- 
vant to  the  point  he  was  making  (e.g.,  Mulinia 
lateralis  is  either  absent  or  present  in  low  num- 
bers when  the  proportion  of  silt-clay  in  the  sample 
is  greater  than  40*7^).  In  the  present  study  the 
samples  were  sieved  and  the  lighter  fractions 
analyzed  by  pipetting.  Phi  values  were  calculated 
and  eight  fractions  recorded,  one  for  sand  (up  to 
a  maximum  phi  coefficient  of  4.0),  six  for  the 
various  fractions  of  silt  (phi  =  4.5-8.0)  and  one 
for  clay  (phi  =  9.0  and  beyond).  Data  are  recorded 
in  percent  sand,  silt,  and  clay  to  conform  with 
common  practice. 

Three  sets  of  sediment  samples  were  obtained 
during  the  course  of  the  study.  A  preliminary 
survey  was  performed  in  September  1966,  using  a 
1  m  Phleger  corer  at  each  of  the  permanent 
sampling  stations.  Figure  7  delineates  the  sedi- 
ment facies  distribution  compiled  during  this 
survey.  Also  found  on  this  map  are  the  stations 


454 


KAPLAN.  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 

for  the  second  survey  (triangles)  taken  just 
before  the  dredging  in  June  1967,  and  the  post- 
dredging  survey  (circles)  in  July  1968,  1  yr  after 
dredging. 

Table  4  reveals  that  1  yr  after  dredging,  sedi- 
ments in  those  stations  in  the  path  of  the  dredge 
(3,  10b,  11,  and  11a)  contained  less  sand  after 
dredging  in  the  previously  sandy,  high  current 
velocity  stations  (3,  10b)  and  more  sand  in  the 
previously  silty,  low  current  velocity  stations 
(11,  11a). 

Station  10a,  in  channel  A,  experienced  a  reduc- 
tion in  its  sand  proportion  and  an  increase  in  silt. 
This  conforms  to  the  hypothesis  that  the  lowered 
current  velocity  in  channel  A,  resulting  from  a 
shift  in  the  main  volume  of  water  transport  to 
channel  B,  would  favor  the  settling  of  lighter 
particles  in  the  post-dredging  period.  Similarly, 
station  5  in  channel  C  increased  in  its  silt  and 
clay  components. 

Stations  16  and  17  were  located  in  the  west- 
central  portion  of  the  bay,  south  of  the  channel. 
Both  stations  maintained  a  constant  proportion  of 
sand.  Station  17  exhibited  a  marked  increase  in 
silt  and  a  decrease  in  the  clay  facies. 

Stations  14  and  24  exhibited  an  increase  in 
sand  and  a  decrease  in  silt  and  clay.  Since  these 
stations  were  near  the  western  shore  in  an  area 
of  negligible  current  flow,  it  is  difficult  to  envision 
pronounced  sediment  transport  brought  about  by 
normal  tidal  flow,  even  with  the  slightly  enhanced 
exchange  rate  brought  about  by  the  deepening  of 
channel  B.  It  is  possible  that  spring  tides  and 
strong  easterly  winds  could  have  acted  syner- 
gistically  with  the  deepened  channel  to  bring 
about  this  effect. 


GOOSE    CRIEK    NY. 


Figure  7. — Sediment  facies  and  station  locations,  Goose  Creek. 
Triangles  represent  pre-dredging  stations,  circles  represent 
post-dredging  stations. 


The  foregoing  data  must  be  viewed  in  con- 
junction with  data  on  current  velocities,  wind- 
driven  currents,  etc.,  as  further  presumptive 
evidence  of  what  appear  to  be  permanent  changes 
in  the  sediment  transport  patterns  of  Goose 
Creek  brought  about  by  current  velocity  modifica- 
tions in  the  tidal  channels. 

The  Effects  of  Wind-Driven  Currents 
on  Sediment  Deposition 

The  importance  of  wind-driven  water  currents 
on  the  deposition  of  sediment  in  shallow-water 
estuarine  situations  has  been  emphasized  by 


Table  4.— Comparison  of  pre-  and  post-dredging  sediment  composition  at  selected  stations. 

Goose  Creek. 


Pre 

-dredging 

Post-dredg 

ng 

Station 

%Sand 

%Silt 

%Clay 

Station 

%Sand 

%Silt 

%Clay 

Comparison 

F6 
F7 
F8 

97 
97 

97 
97 
65 

3%  silt, 
3%  silt, 
3%  silt, 

clay 
clay 
clav 

3 

78 

14 

8 

Less  sand 

F4 
F5 

3%  silt, 
18 

clay 

17 

5 

30 

41 

29 

Less  sand 

E8 
D5 
D6 
C5 

B7 

97 
97 
97 
40 

44 

3%  silt 
3%  sill, 
3%  silt. 

26 

26 

clay 

clay 

clay 

34 

30 

7 

10b 
10a 
11a 
11 

70 
91 
72 
75 
74 

20 
8 
24 
17 
13 

10 
1 
4 
8 

13 

Less  sand 
Less  sand 
Less  sand 
More  sand 
More  sand 

B8 
B9 

48 
49 

28 

18 

24 
33 

16 

49 

29 

22 

No  change 

B11 

34 
24 
21 

34 
24 
39 

32 

1/ 

35 

54 

1 

More  silt 

A2 
A4 

52 
40 

14 

80 

17 

3 

More  sand 

A7 
A8 

37 
55 

44 
12 

19 
33 

24 

62 

28 

10 

More  sand 

455 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Table  5.- — Wind  velocity  recordings  at  or  above  15  mph  on 
days  when  there  were  two  or  more  such  recordings,  1967.' 


Wind 
direction 


Number  of  3-hourly 
recordings 


NE  (10°-80') 

E  (90°) 

SE  (100=- 170°) 

S  (180°) 

SW  (190-260=) 

W  (270=) 

NW  (280-350°) 

N  (360=) 


76 
2 

23 
2 

77 

10 
224 

29 


'Source:  Local  Cllmatologjcal  Data,  1967,  John  F.  Kennedy  Airpori. 
US.  Dep.  Commer.,  Environ.  Sci.  Serv.  Adm. -Environ,  Data  Serv. 
U.S.  Gov.  Print.  Off.,  Wash..  D.C. 


Biggs  (1968),  Hantzschel  (1939),  Hellier  and 
Kornicker  (1962),  and  others. 

In  a  shallow,  almost  completely  enclosed  em- 
bayment  like  Goose  Creek,  with  a  relatively  broad 
exposure  to  prevailing  winds,  the  effect  of  wind  on 
the  distribution  of  fine  sediments  becomes  accen- 
tuated. Biggs  (1968:481)  states  that  "strong  and 
persistent  winds  may  cause  high  suspended 
sediment  loads  .  .  ." 

The  wind  velocity  data  for  Kennedy  airport 
on  Long  Island  were  tabulated,  and  those  days 
with  two  or  more  recordings  of  winds  at  15  mph 
or  above  were  compared.  As  can  be  seen  from 
Table  5,  the  prevailing  winds  15  mph  and  above 
come  from  the  northwest  on  Long  Island.  Indi- 
vidual recordings  from  the  northwest  were  more 
than  ten  times  as  common  as  those  coming  from 
the  opposite  direction,  and  at  least  three  times 
more  common  than  winds  coming  from  any  other 
quarter. 

All  other  factors  being  equal,  one  would  expect 
that  the  difference  in  mean  wind  velocity  favoring 
the  northwesterly  prevailing  winds  would  result 
in  a  net  deposition  of  sediment  in  the  south- 
eastern region  of  the  bay.  Examination  of  Figure 
1  reveals  that  this  is  the  region  where  the  channel 
opens  to  Southold  Bay,  the  area  of  maximum  tidal 
current  velocity.  This  complex  interaction  of 
factors  would  probably  result  in  an  unusually 
high  suspended  sediment  load  in  the  incoming 
and  outgoing  tidal  currents  and  the  deposition 
of  light  particles  carried  by  incoming  tides  in  the 
southwestern  margins  of  the  bay. 

This  hypothesis  is  given  substance  by  three 
sets  of  data:  Hair  (1968)  and  Fazio  (1969)  demon- 
strate that  the  transport  of  nutrients  in  Goose 
Creek  was  strongly  influenced  by  wind-induced 


currents  both  before  and  after  dredging.  By  draw- 
ing isopleths  of  NO3  concentrations  and  relating 
them  to  wind  direction  and  velocity,  they  were 
able  to  show  that  nitrate  concentrations  were 
responsive  to  both  factors,  with  progressive 
diminutions  of  concentration  across  the  bay  in  the 
direction  of  the  wind  source  (see  Figures  8  and  9). 

Minimum  wind  velocity  required  to  induce 
clear-cut  distribution  of  particulate  constituents 
was  5  mph  according  to  Fazio.  He  also  showed 
that  a  wind  increase  from  13  to  20  mph  caused 
a  resuspension  of  bottom  material  affecting  con- 
centrations of  particulate  phosphorus,  chlorophyll 
a,  dissolved  inorganic  phosphate,  and  nitrate. 

Nuzzi  (1969)  shows  a  correlation  between  bac- 
terial count  and  wind  velocity  in  Goose  Creek. 
He  suggests  that  a  critical  wind  velocity  is 


GOOSE    CREEK    NY. 


WIND    DieEC  TION 


Figure  8. — Isopleths  of  NO3  concentration  in;ugat.  NOs-N/liter, 
wind  coming  from  the  northern  quarter.  (Redrawn  from  Hair, 
1968). 


456 


KAPLAN,  WELKER,  and  KRAUS;  EFFECTS  OF  DREDGING 


GOOSE    CREIKN.Y. 


Figure  9.— Isopleths  of  NO3  concentration  in  ug  at.  NOg-N/liter, 
wind  coming  from  the  southern  quarter.  (Redrawn  from  Hair, 
1968). 


GOOSf    CREEK    NY. 


Figure   10. — Depths  of  sediment  below  mean  low  water  in 
meters.  Data  taken  from  Suffolk  County  map  dated  4/5/67. 


necessary  to  overcome  the  inertia  of  the  sediment 
particles  as  well  as  associated  bacteria. 

Further  substantiation  of  the  hypothesis  that 
sediment  distribution  in  Goose  Creek  was  affected 
by  wind-driven  currents  can  be  obtained  from 
an  examination  of  Figure  10.  Depth  of  the  sedi- 
ment increases  in  a  north-south  direction,  irre- 
spective of  the  probable  contour  of  the  basin. 

Table  6  tabulates  the  number  of  3-hourly 
records  of  winds  at  or  above  15  mph  for  1967. 

Suspension  of  fine  sediments  during  dredging 
occurred  during  the  months  of  least  occurrence  of 
high  winds  (July- August).  The  absence  of  strong 
winds  would  tend  to  minimize  the  distribution  of 
suspended  sediment  but  it  also  prevents  the  re- 
moval of  the  canopy  of  flocculent  material 
observed  covering  the  Enteromorpha  and  Ruppia 
stipes  and  leaves  during  and  after  dredging. 

Flemer  et  al.  (1968)  suggest  that  late  fall  is 
the  season  which  would  be  most  desirable  for 
dredging,  since  benthic  animal  populations  are 
lowest  then.  On  the  other  hand,  the  months  of 
November  and  December  are  characterized  by 
frequent  windy  days  and  any  disturbance  of  the 
sediment  would  be  accentuated  by  wind-driven 
currents.  Saila,  Polgar,  and  Rogers  (1968) 
describe  summer  surface  and  bottom  current  pat- 
terns which  caused  maximum  harmful  effects  of 
dumped  dredged  sediment.  Such  factors  as  water 
depth,  contour  of  basin,  and  wind-  and  water- 
driven  currents  must  be  studied  further  to  deter- 
mine the  optimal  season  for  dredging. 


Mercenaria  Survey 

Mercenaria  mercenaria  is  exploited  commer- 
cially in  Goose  Creek  and  it  supports  a  substantial 
sport  fishery.  Both  before  and  after  dredging, 
from  two  to  four  commercial  clammers  regularly 
visited  the  creek.  In  1968,  less  than  a  year  after 
the  dredging,  two  clammers  were  interviewed 
regarding  changes  in  the  productivity  of  clams 
over  the  interval  of  the  dredging  operation.  They 
reported  that  there  was  no  substantial  difference 
in  the  size  of  their  catch  which,  according  to  the 
local  conservation  officer,  was  4-5  bushels  of  clams 
per  day. 

Apparently  there  was  no  mass  mortality  of 
clams  resulting  from  the  release  of  flocculent  and 
suspended  material  into  the  water  as  a  result 
of  dredging. 

Four  major  clam  producing  areas  of  the  bay 
were  sampled  before  and  after  dredging,  on  8 
July  1967  and  4  July  1968  (dredging  was  com- 
pleted on  2  August  1967  (see  Figure  11)). 

Table  6. — Number  of  days  of  at  least  two  recordings  of  winds 
over  15  mph  by  months  (recordings  taken  at  3  h  intervals),  1967. 


Number 

Number 

Month 

of  days 

Month 

of  days 

January 

7 

July 

1 

February 

13 

August 

1 

March 

9 

September 

13 

April 

17 

October 

5 

May 

18 

November 

13 

June 

10 

December 

11 

457 


FISHERY  BULLETIN;  VOL.  72,  NO.  2 


GOOSF    CREEK,  N.y. 


Figure  11. — Map  of  stations,  Mercenaria  study. 

A  3.35  m^  square  frame  was  placed  on  the  sub- 
stratum and  a  skin  diver  sampled  the  area  by 
hand,  removing  all  clams.  These  were  sorted  as  to 
size  in  the  following  categories:  up  to  1.90  cm; 
1.90-3.80  cm;  3.81-5.70  cm;  5.71-8.90  +cm. 

The  areas  sampled  were  channel  B  (destined 
to  be  the  region  of  the  newly  dredged  channel) 
and  the  three  major  clamming  areas  used  by  local 
residents.  Stations  7c  to  lie  were  30  m  apart 
running  east  to  west  down  channel  B.  Stations 
12c,  13c,  and  14c  were  located  on  the  north, 
west,  and  south  shores  of  the  bay  respectively. 

Each  station  in  channel  B  comprised  two 
sampling  areas,  one  1.5  m  from  shore  and  the 
other  in  midchannel  or  about  9  m  from  shore. 

Each  station  in  the  clam  beds  used  by  local 
residents  (stations  12c,  13c,  14c)  comprised  four 
sampling  areas  beginning  6  m  from  the  shore- 
line at  the  east  end  of  the  bed  and  progressing 
westerly  at  6-m  intervals.  The  total  area  sampled 
was  33.5  m^  in  the  channel  and  39.25  m^  on  the 
clam  beds  (total  72.75  m^). 

The  data  obtained  on  the  pre-  and  post-dredging 
surveys  are  compared  in  Table  7. 

Clams  in  Goose  Creek  not  directly  exposed  to 
mechanical  disturbance  by  the  dredge  (such  as 
clam  beds  at  stations  12c  and  13c)  were  able  to 
survive  the  dredging  process  itself,  even  though 
they  were  located  within  400  m  of  the  channel 
(see  Table  7).  The  considerable  reduction  in  the 
size  of  the  clam  populations  at  stations  12c  and 
13c  suggests  that  some  mortality-inducing  factor 
was  at  work. 


The  effects  of  the  mechanical  removal  of  the 
clams  by  the  dredge  are  obvious.  Whether  or  not 
finding  a  few  clams  in  the  post^dredging  survey  at 
stations  10c  and  lie  means  that  there  are  signs 
of  recovery  in  the  population  remains  to  be  seen. 

No  evaluation  of  the  long-term  effects  of 
changes  in  the  environment  has  been  attempted. 
These  include  processes  such  as  the  gradual  incur- 
sion of  silt  towards  the  mouth  of  the  bay  due  to 
lowered  current  velocity,  factors  affecting  pro- 
ductivity such  as  a  reduction  of  the  quantity  of 
organic  materials  introduced  into  the  water  as  the 
Spartina  marshes  were  covered  with  spoil,  and  an 
increase  in  pollutants  as  the  population  density  of 
humans  along  the  periphery  of  the  bay  increased. 

Changes  in  Land  Usage  Patterns 

At  the  inception  of  the  study  (1966)  most  of 
the  periphery  of  Goose  Creek  was  composed  of 
Spartina  and  Phragmites  marshes,  except  for  the 
south  shore  and  a  neck  of  land  on  the  southeastern 
corner  which  were  developed  with  summer  homes. 

On  a  map  of  the  area  drawn  in  1954,  41  homes 
are  recorded  bordering  the  bay.  The  total  number 
of  houses  within  300  m  of  the  bay  was  114.  At 
the  present  writing  most  of  the  previously 
undeveloped  north  shore  of  the  bay  is  undergoing 
intensive  development  of  houses  used  year  round. 

An  aerial  photograph  taken  in  1972  (Figure  2) 
revealed  223  houses  within  300  m  of  the  bay,  an 
increase  of  94%.  All  of  the  houses  along  the  shore 
of  Goose  Creek  were  built  on  spoil  taken  from 
public  or  private  dredging  operations.  All  homes 
have  cesspools. 

Smith  (pers.  comm.)  introduced  Rhodamine  B 
into  a  toilet  in  one  of  the  homes  bordering  Goose 
Creek.  In  four  weeks  detectable  quantities  were 
found  in  the  bay  waters.  Nuzzi  (1969)  speculates 
that  human  fecal  coliform  bacteria  (as  identified 
by  elevated  temperature  incubation)  were  re- 
leased into  Goose  Creek  from  the  septic  tanks  of 
the  surrounding  homes.  Maximum  coliform 
counts  in  his  1966-1968  study  were  918  MPN 
(most  probable  number)/100  ml. 

The  maximum  federal  permissible  level  for 
waters  from  which  shellfish  are  taken  is  a  median 
of  15  readings  not  exceeding  70  MPN/100  ml,  or 
10%  of  15  readings  above  230  MPN/100  ml 
(Houser,  1965).  Individual  readings  above  230 
MPN/100  ml  were  recorded  throughout  the  period 
December-March  1967,  at  one  station,  and  three 


458 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 

Table  7. — A  comparison  ofMercenaria  populations  in  four  selected  areas  of  Goose  Creek  before  and  after  dredging. 


Num 

bar  of  clams 

Befo 

re  dredging  (7/8/67) 

After 

dredging  (7/4/68) 

Station 

Inshore 

Mid-Chan 

nel 

Inshore 

Mid-Channel 

7C 

1.9  cm 
1.9-3.80  cm 

5 

8 

13 

1.9-3,80  cm 

9 
"9 

0 

0 

8C 

1.9  cm 
1.9-3.8  cm 
3.8-5.7  cm 

4 

18 
16 
38 

3.8-5.7  cm 

17 

0 

0 

9C 

1.9-3.8  cm 

3.8-5,7  cm 

31 

3 

34 

1  9-3.8  cm 

14 
14 

0 

0 

IOC 

1.9-3.8  cm 
3.8-5.7  cm 

2 
_5. 

7 

to  1.9  cm 
3.8-5.7  cm 
5,7-8.9  cm 

2 
9 
2 

13 

1.9-3.8  cm 

1 
T 

0 

11C 

1.9-3.8  cm 

2 

0.75-1,50  cm 
1.50-2.25  cm 

3 

-6 
9 

to  1.9  cm 

3 
3 

to  1.9  cm 

1 

T 

12C 

Station 

A 

Station 

B 

Station  A 

Station  B 

1.9-3.8  cm 

29 

to  1.9  cm 

12 

to  1.9  cm 

8 

to  1.9  cm 

8 

29 

1.9-3.8  cm 

11 
23 

1.9-3.8  cm 

7 
15 

1.9-3.8  cm 

3 

11 

Station 

C 

Station 

D 

Station  C 

Station  D 

to  1.9  cm 

16 

to  1.9  cm 

7 

to  1.9  cm 

5 

to  1.9  cm 

3 

1.9-3.8  cm 

14 

1.9-3.8  cm 

12 

1.9-3.8  cm 

1 

1.9-3.8  cm 

3 

3.8-5.7  cm 

30 

19 

3.8-5  7  cm 

1 

7 

T 

Average  numbe 

r  of  clams 

perm'  =  7.5 

Average  number 

of  clams 

jerm'  =  2.9 

13C 

Station 

A 

Station 

8 

Station  A 

Station  B 

5.71-8.9  cm 

27 
"27 

3.8-5.7  cm 
5.7-8.9  cm 

18 
10 
28 

0 

"o 

0 

"o 

Station 

C 

Station 

D 

Station  C 

Station  D 

1.9-3.8  cm 

22 

3.8-5.7  cm 

8 

1.9-3.8  cm 

3 

0 

5,7-8.9  cm 

9 
31 

5.7-8.9  cm 

n 

19 

3.8-5.7  cm 

1 
4 

0 

Average  numbe 

r  of  clams 

perm»  =  7.8 

Average  numbe 

rofclams 

perm' =  0.3 

14C 

Station 

A 

Station 

B 

Station  A 

Station  B 

5,71-8  9  cm 

44 
"44 

3.8-5.7  cm 
5.7-8  9  cm 

17 
20 
37 

na. 

na. 

Station 

C 

Station 

D 

Station  C 

Station  D 

1.9-3.8  cm 

24 

5,7-8.9  cm 

47 

na. 

na. 

3.8-5.7  cm 

6 

5  71-8.9  cm 

17 
47 

47 

Average  numbe 

rofclamsperm'  =  12.1 

Average  numbe 

r  of  clams 

perm'  =  na. 

times  at  another,  with  levels  of  542,  918,  and  348 
MPN/100  ml.  These  readings  appear  to  exceed 
the  10%  limit  mentioned  above  and  may  be  suf- 
ficient grounds  for  closing  the  bay  to  clamming. 
The  densities  of  presumptive  human  fecal  coli- 
forms  found  by  Nuzzi  correlated  with  increases 
in  human  population  size,  suggesting  that  the 
increase  in  number  of  homes  around  the  periphery 
of  the  bay  during  the  1968-1972  will  further 
increase  the  contamination  of  clams  beyond 
acceptable  sanitary  standards. 


ANALYSIS  OF  THE  EFFECTS  OF 

DREDGING  ON  MACROBENTHIC 

ANIMAL  POPULATIONS 

Dry  weights  from  263,  0.1  m^  samples  collected 
from  the  bottom  of  Goose  Creek  over  22  mo  were 
compared  by  means  of  analysis  of  variance.  In 
addition,  chi-square  analyses  were  performed  to 
determine  whether  or  not  significant  differences 
existed  between  pre-  and  post-dredging  popula- 
tions in  number  of  individuals  and  species.  All 


459 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Table  8. — Analyses  of  variance  of  pre-  and  post-dredging  dry  weights  and  between  stations,  in  the  bay 

and  dredged  channel. 


Sum 

Degrees  of 

Mean  squares 

Source 

of  squares 

freedom 

(variance) 

F  test 

Probability 

Stations  before  and 

after  dredging 

158.387 

1 

158  387 

10.623 

0005 

Variation  between 

stations 

492.212 

22 

22373 

1  501 

Less  than  0.05 

Interaction  of  pre- 

and  post-dredging 

and  stations 

311  698 

22 

14.168 

0.950 

Less  than  0.05 

STATIONS  2-25  PLUS 

A-J,  M  (CHANNEL) 

Stations  before  and 

after  dredging 

491.813 

1 

491.813 

37.211 

0001 

Variation  between 

stations 

691.024 

33 

20.940 

1.584 

Lessthan0.05 

Interaction  of  pre- 

and  post-dredging 

and  stations 

635.301 

33 

19252 

1.457 

Less  than  0.05 

STATIONS  A-J,  M 

(CHANNEL) 

Stations  before  and 

after  dredging 

341.885 

1 

341.885 

127  426 

0.001 

Variation  between 

stations 

163.579 

10 

16.358 

6.097 

0.001 

Interaction  of  pre- 

and  post-dredging 

and  stations 

133.872 

10 

13  387 

4990 

0001 

computations  were  performed  on  an  RCA 
SPECTRA  70/46  computer.^ 

Two-way  analyses  of  variance  were  performed 
on  dry  weights  of  the  samples  drawn  from  sta- 
tions 2-25;  2-25  plus  channel  stations  A-J,  M; 
and  channel  stations  A-J,  M  alone. 

Table  8  reveals  that  pre-  and  post-dredging 
biomass  varied  significantly  among  stations  2-25, 
among  all  stations,  and  between  each  channel 
station.  The  variances  in  biomass  between  sta- 
tions were  not  significant  in  the  bay  and  combina- 
tion of  bay  and  channel,  even  though  they 
represented  a  substantial  spectrum  of  substrata 
and  current  velocities.  Biomass  variances  were, 
however,  significant  in  the  channel  alone.  There 
was  also  no  significance  in  the  variances  of  the 
interaction  between  stations  and  dredging,  except 
in  the  channel. 

The  macrobenthic  biomass  in  Goose  Creek  had 
not  returned  to  its  pre-dredged  level  11  mo  after 
dredging. 

In  the  channel  substratum,  which  had  a 
virtually  linear  reduction  in  particle  size  and 
current  velocity  progressing  from  east  to  west, 
there  was  significance  in  both  station  to  station 


'The  authors  are  grateful  for  the  assistance  rendered  by  the 
Hofstra  University  academic  computing  facility,  Eugene  In- 
goglia.  Director;  John  Pizzeriella,  Programmer;  Claire  Gittel- 
man,  Statistician. 


variance  and  in  the  interaction  between  stations 
and  pre-  and  post-dredging  variances.  This 
demonstrates  a  systematic  difference  between 
stations,  as  well  as  a  significant  difference  from 
station  to  station  in  the  manner  in  which  the 
animal  populations  responded  to  the  dredging 
process. 

A  second  two-way  analysis  of  variance  was 
performed  on  all  three  sets  of  data  in  an  attempt 
to  determine  whether  or  not  the  variance  in  bio- 
mass was  a  function  of  sediment  type.  The 
sampling  stations  were  classified  according  to  the 
sediment  map  (Figure  7),  with  verification  pro- 
vided by  visual  analysis  of  samples  from  the 
suction  corer.  Table  9  lists  the  stations  according 
to  their  sediment  classification. 


Table  9. — Classification  of  the  Goose  Creek  sampling  stations 
according  to  sediment  type. 


Sediment  type 


stations 


Sand 

Muddy  sand 
Sandy  mud 
Mud-silt 
Intertidal 


2,  3,  4.  9,  10 
A,  B,  C.  D 
6,  7,  8.  24 
E,  F.  G 
11,  12,  18 
H,  I,  J 

14,15,16,17 
22,  23.  25,  K 
9A,  13,20.21 


460 


KAPLAN,  WELKER,  and  KRAUS:   EFFECTS  OF  DREDGING 


Table  10  summarizes  an  analysis  of  variance  of 
the  biomass  at  the  Goose  Creek  stations  according 
to  sediment  type.  Separate  analyses  were  per- 
formed on  the  data  for  stations  2-25;  2-25  plus 
channel  stations  A-J,  M;  and  channel  stations 
A-J,  M  alone. 

Significance  was  found  in  all  three  analyses 
only  among  dry  weights  before  and  after  dredging. 
There  was  no  significance  in  the  variances  among 
substratum  types,  nor  among  the  interactions 
of  substrata  and  pre-  and  post-dredging  bio- 
mass. There  was,  then,  no  systematic  effect  of 
particular  sediment  types  alone  on  the  rate  of 
recovery  of  the  in-  and  epifauna,  even  in  the 
channel. 

A  four- way  analysis  of  variance  was  performed 
to  examine  the  relationship  between  seasons  and 
variances  in  biomass  at  each  station,  without 
considering  pre-  and  post-dredging  effects.  Sta- 
tions 2-18  were  studied.  The  unrepresented 
stations  are  in  the  less  saline  western  half  of 
Goose  Creek  which  was  frozen  over  during  Jan- 


uary and  February  of  both  years.  There  were  no 
significant  differences  in  the  seasonal  variances 
among  stations,  indicating  that  seasonal  fluctua- 
tions in  biomass  were  not  factors  which  accounted 
for  the  differences  in  biomass,  heretofore  attrib- 
uted to  the  dredging  operation.  Table  11  sum- 
marizes the  statistics  for  the  analysis  of  variance 
according  to  seasons. 

Another  four- way  analysis  of  variance  was  per- 
formed to  examine  the  relationship  between 
seasonal  variances  and  substratum  type  for 
stations  2-25.  Again,  there  was  no  significance  in 
any  of  the  interactions,  indicating  that  variances 
in  biomass  are  not  a  function  of  season,  sediment 
type,  or  of  an  interaction  between  these  factors. 
This  analysis  is  summarized  in  Table  12. 

It  was  expected  that  the  channel  would  show 
substantial  effects  of  the  dredging  process,  since  it 
was  from  the  channel  that  massive  quantities  of 
substratum  were  removed.  The  sediment  and  its 
inhabitants  were  physically  removed  to  a  depth  of 
2  m.  What  is  of  greater  importance  is  the  evidence 


Table  10. — Analyses  of  variance  of  pre-  and  post-dredging  dry  weights  according  to  sediment  type  in  the  bay 

and  channel. 


Sum 

Degrees  of 

Mean  squares 

Source 

of  squares 

freedom 

(variance) 

F  test 

Probability 

STATIONS  2-25 

stations  before  and 

after  dredging 

107.634 

1 

107.634 

6.584 

0.025 

Sediment  types 

32.746 

4 

8.187 

0.501 

Less  than  0.05 

Interaction  of  stations 

and  sediment  types 

62.912 

4 

15.728 

0.962 

STATIONS  2-25  PLUS 

A-J,  M  (CHANNEL) 

Stations  before  and 

after  dredging 

206.841 

1 

206.841 

13.899 

0001 

Sediment  types 

42489 

4 

10.622 

0.714 

Less  tfian  0.05 

Interaction  of  stations 

and  sediment  types 

81.747 

4 

20.437 

1.373 

Less  tfian  0.05 

STATIONS  A-J,  M 

(CHANNEL) 

stations  before  and 

after  dredging 

160.146 

1 

160.146 

22.043 

0.001 

Sediment  types 

17.083 

3 

5.694 

0.784 

Lessthan0.05 

Interaction  of  stations 

and  sediment  types 

22.863 

3 

7.621 

1.049 

Less  than  0.05 

Table  11.- 

-Four-way  analysis  of 

variance  of  dry 

weights  according  to 

season,  stations  2-18. 

Sum 

Degrees  of 

Mean  squares 

Source 

of  squares 

freedom 

(variance) 

F  test 

Probability 

Seasonal 

variations 

10.653 

3 

3.551 

0.250 

Less  than  0.05 

stations 

224.442 

16 

14.028 

0.988 

Less  than  0.05 

Interaction 

between  seasons 

and  stations 

566.497 

48 

11.802 

0.831 

Less  than  0.05 

461 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 
Table  12. — Four-way  analysis  of  variance  of  dry  weights  according  to  season  and  sediment  type. 


Source 

Sum 
of  squares 

Degrees  of 
freedom 

t^ean  squares 

(variance) 

F  test 

Probability 

Seasons 

17.307 

3 

5.769 

0332 

Less  than  0  05 

Sediments 

18.002 

4 

4.500 

0259 

Less  than  0  05 

Interaction 

between  seasons 

and  sediments 

119  121 

12 

9.927 

0,572 

Lessthan0.05 

that  the  rest  of  Goose  Creek,  as  represented  by 
stations  2-25,  also  suffered  a  reduction  in  biomass 
from  which  recovery  was  not  evident  11  mo  after 
dredging. 

Further  evidence  of  the  reduction  in  biomass 
after  dredging  can  be  found  in  Table  13,  which  is 
a  comparison  of  dry  weights  at  stations  2-25  in 
-June  1967  and  1968,  1  mo  before  and  11  mo  after 
dredging.  Only  one  station  of  the  13  (station  11) 
for  which  comparative  data  exist  had  biomass  in 
excess  of  the  1967  levels.  The  significance  of  any 
individual  datum  is  not  great,  since  the  presence 
of  an  adult  clam  or  sea  cucumber  could  inor- 
dinately affect  a  particular  station.  The  general 
trend,  however,  is  clear;  12  out  of  13  stations 
have  substantial  reductions  in  biomass.  This 
reduction  cannot  be  attributed  to  mechanical 
removal  of  sediment  or  specimens,  and  is  attrib- 
uted to  the  dredging  process  itself. 

Chi-Square  Analysis  of  Number  of 
Species  and  Specimens 

Chi-square  analyses  were  performed  to  deter- 
mine whether  or  not  the  number  of  species  and 
individuals  in  the  post-dredging  series  differed 
significantly  from  the  pre-dredging  population. 
Data  were  further  analyzed  to  determine  if  sub- 
stratum and  seasonal  variations  affected  species 
diversity  and  numbers  of  individuals.  Table  14 
represents  the  chi-square  analysis  of  the  number 
of  species  before  and  after  dredging  for  the  whole 
bay  (minus  the  intertidal  stations),  the  bay  sta- 
tions plus  the  channel  stations,  and  the  channel 
stations  alone.  In  all  cases  the  chi-square  was 
significant,  indicating  that  species  number  was 
affected  by  dredging.  Since  chi-square  analysis  is 
limited  by  its  inability  to  discriminate  between 
sign  (-1-  or  -),  Table  15  tabulates  the  number  of 
species  found  at  stations  2-25  in  June  1967,  1  mo 
before  dredging,  and  in  June  1968.  A  reduction  in 


species  number  occurred  at  75%  of  the  stations 
after  dredging,  with  three  stations  or  18.7% 
exhibiting  small  increases  in  species  number. 

A  chi-square  analysis  was  performed  on  the 
number  of  species  according  to  sediment  type 
(e.g.,  sand,  muddy  sand,  mud-silt).  The  number  of 
species  altered  significantly  according  to  sub- 
stratum after  dredging,  both  in  the  bay  as  a  whole 
and  in  the  channel  (see  Table  16). 

Table  13. — A  comparison  of  dry  weights  from  stations  2-25, 
June  1967  and  June  1968  (in  g). 


Station 


2 

3 

4 

5 

6 

7 

3 

9 

9A 
10 
11 
12 
13 
14 
15 
16 
17 
18 
20 
21 
22 
23 
24 
25 


June  1967 

1,37 

1,80 

1.92 

0.63 

9.44 

4.81 

18.25 

0.55 

1.07 

0.30 

586 

0.00 

7.68 

8.77 

2.70 

1,41 

June  1968 


9,47 

16,13 

0  00 


0.92 
0,31 

1.04 


0.15 
0  83 

0,07 
1,64 
1.82 


000 
0,71 
0.41 
1.08 


0,01 
0,005 


Table  14.— Chi-square  analyses  of  the  number  of  species  before 
and  after  dredging  for  stations  2-12,  14-19,  22,  23;  stations 
2-12,  14-19,  22,  23  plus  channel  stations  A-J,  M,  and  stations 
A-J,  M  alone. 


Stations 

Chi-square 

Degrees  of 
freedom 

Level  of 
significance 

2-23 

32,763 

18 

0.025 

2-23,  plus  A-J, 
M 

55.366 

26 

0,005 

A-J,  M 

21,557 

7 

0.005 

462 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 


Table  15. — Number  of  species  found  at  stations  2-12,  14-19, 
22,  23  on  June  1967  and  June  1968. 


Station 

June  1967 

2 

22 

3 

16 

5 

19 

6 

11 

7 

25 

8 

19 

9 

21 

10 

26 

11 

9 

12 

3 

14 

0 

15 

11 

16 

10 

17 

5 

18 

5 

22 

9 

23 

1 

June  1968 


5 

5 

17 

3  (4/68) 

13 
13 

5 
5 

6 

4  (4/68) 
0 

3 
1 
7 
3 
1 


Table  16.— Chi-square  analysis  of  the  number  of  species  before 
and  after  dredging,  as  a  function  of  sediment  type.  Stations 
2-25;  2-25  and  A-J,  M;  channel  stations  A-J,  M. 


Stations 

Chi-square 

Degrees  of 
freedom 

Level  of 
significance 

2-25 

8.43 

3 

0.05 

2-25;  A-J. 
M 

21.41 

3 

0.005 

A-J.  M 

38.24 

3 

0005 

Table  17.— Chi-square  analyses  of  number  of  organisms  before 
and  after  dredging,  stations  2-21,  23;  2-21,  23  plus  A-J,  M; 
stations  A-J,  M  only. 


Stations 

Chi-square 

Degrees  of 
freedom 

Level  of 
significance 

2-25 

6.075,22 

20 

0.005 

2-25.  A-J. 
M 

6,364.59 

29 

0.005 

A-J,  M 

152,84 

8 

0005 

Table  18. — Chi-square  analysis  of  the  number  of  organisms 
before  and  after  dredging  as  a  function  of  sediment  type, 
stations  2-25;  2-25  plus  A-J,  M;  stations  A-J,  M. 


Degree  of 

Level  of 

Stations 

Chi-square 

freedom 

significance 

2-25 

2.051.59 

3 

0,005 

2-25.  A-J, 

M 

1,679.51 

3 

0005 

A-J.  M 

21,57 

3 

0005 

Similar  chi-square  analyses  were  performed 
using  number  of  individuals  at  all  stations.  Here 


results  were  even  more  positive.  For  example, 
the  pre-dredging  number  of  specimens  at  station 
2  was  6,682;  the  post-dredging  number  was  27. 
Five  out  of  30  stations,  or  16.6%,  showed  post- 
dredging  increases  in  population;  the  others 
experienced  drastic  decreases. 

Table  17  is  a  summary  of  the  chi-square 
analysis  of  the  number  of  individuals  before  and 
after  dredging.  The  difference  in  specimen  num- 
bers was  highly  significant  in  both  the  bay  as  a 
whole  and  in  the  channel. 

Chi-square  analyses  were  made  on  the  number 
of  specimens  before  and  after  dredging  as  a  func- 
tion of  sediment  type.  In  both  the  bay  as  a  whole 
and  the  channel  the  number  of  specimens  was 
significantly  different  (0.005)  in  the  post-dredging 
samples,  according  to  sediment  types  (Table  18). 

In  summary,  the  numbers  of  species  and 
organisms  differed  significantly  before  and  after 
dredging,  in  the  bay  as  a  whole,  as  well  as  in 
the  channel.  Additional  data  show  that  this 
difference  was  in  the  direction  of  a  post-dredging 
reduction  in  both  species  diversity  and  number  of 
individuals  found  at  each  station.  A  few  stations 
showed  apparent  recovery  by  June  1968,  11  mo 
after  dredging.  These  were  invariably  low-popula- 
tion stations  in  the  mud-silt  region  of  the  bay, 
where  a  few  influents  could  appreciably  change 
the  population  size.  Stations  2-11,  the  sand, 
muddy  sand,  sandy  mud  stations,  had  drastic 
reductions  in  both  parameters.  Table  19  provides 
further  substantiation  for  this  conclusion. 


Standing  Crop  Estimates 

A  total  of  137  species  was  taken  from  the  sedi- 
ment of  Goose  Creek  during  the  22  mo  of  the 
study.  Maximum  wet  weight  at  any  one  sta- 
tion was  2,581.4  g/m^,  with  a  corresponding  dry 
weight  of  355.6  g/m^.  Mean  dry  weight  before 
dredging  (excluding  the  channel)  was  36.8  g/m^ 
(49.6  g/m^  including  the  channel)  while  the  cor- 
responding weight  after  dredging  was  12.7  g/m^ 
(10.1  g/m^  including  the  channel),  a  loss  of 
63%  of  dry  weight.  The  loss,  including  the  channel, 
was  79%.  (Pfitzenmeyer,  1970,  reported  a  loss  of 
64%  in  his  spoil  deposition  area  and  72%  in 
the  channel.) 

The  mean  number  of  species  per  station  (sta- 
tions 2-24  minus  the  four  intertidal  stations)  was 
5.47  (54.7/m2)  before  dredging  and  4.02  (40.20/m2) 
after  dredging,  a  reduction  of  26%. 


463 


The  maximum  number  of  specimens  found  at 
any  one  station  was  3,521,  of  which  3,470  were 
the  gastropod,  Crepidula  fornicata  (station  2, 
October  1966).  The  mean  number  of  specimens 
before  dredging  for  stations  2-24  (minus  the  inter- 
tidal  stations)  was  120.14  (1201.4/m2),  ^^lile  the 
after-dredging  mean  was  25.63  (256.3/m2).  This 
constitutes  a  79%  reduction  in  the  number  of 
specimens  found  at  the  post-dredging  stations.^ 

Comparison  With  Other  Areas 

Direct  comparisons  between  the  standing 
crop  estimates  at  Goose  Creek  and  other  areas 
is  complicated  by  the  diverse  methods  of  obtaining 
these  estimates  used  by  workers  in  the  field. 
As  previously  indicated,  Holme  (1953)  and 
Sanders  (1956,  1958)  used  HCl  to  remove  the 
carbonates  from  the  carapaces  of  crustaceans 
and  both  removed  all  specimens  greater  than  0.2  g 
dry  weight  from  their  samples.  For  reasons  pre- 
viously mentioned,  it  is  important  in  this  investi- 
gation to  obtain  data  on  the  populations  of  the 
larger  forms  which  dominate  the  communities  of 
the  shallow,  estuarine  study  area  being  investi- 
gated. Variation  in  sieve  mesh  size  between 
studies  is  also  an  important  factor  accounting  for 
differences  in  infaunal  biomass  estimates,  but 
Sanders  (1956)  attempted  to  compare  numerical 
results  of  several  investigations  by  plotting  mesh 
size  against  the  log  of  the  number  of  animals 
per  square  meter.  The  lowest  estimates  were  those 
obtained  by  Holme  (1953)  from  the  English 
Channel  (160/m2)  and  Miyadi  (1940,   1941a, 
1941b)  from  Japanese  bays  (266-1, 290/m2). 
Sanders'  mean  number  of  animals  for  Long  Island 
Sound  was  16,443/m2,  although  63%  of  his  sta- 
tions had  fewer  than  8,500  animals/m^.  The  mean 
number  of  animals  at  Goose  Creek  (l,201.4/m2) 
is  considerably  lower  than  that  obtained  by 
Sanders,  but  it  is  unlikely  that  this  parameter 
is  the  most  useful  in  comparing  areas  since  his 
Ampelisca  and  Nepthys  incisa-Yoldia  limatula 
communities  contained  relatively  dense  popula- 
tions of  small  organisms,  while  at  Goose  Creek 
amphipods  and  protobranch  pelecypods  made 
up  a  very  small  proportion  of  the  biomass. 


FISHERY  BULLETIN: 

VOL. 

72,  NO.  2 

Table  19.— The  number  of  organisms 

found 

at  each  station 

before  and  afler  dredging,  stations  2-25 

,  A-J 

M. 

Station  number                       Before  dredging 

After  dredging 

2                                              6.682 

27 

3                                              1.499 

188 

5                                                466 

330 

6                                                266 

41 

7                                                566 

266 

8                                                   342 

95 

9                                                    153 

56 

9A                                                   92 

80 

10                                                505 

239 

11                                                    144 

49 

12                                                      47 

117 

13                                                        6 

5 

14                                                      73 

92 

15                                                 125 

100 

16                                                 192 

121 

17                                                    270 

79 

18                                                  66 

241 

20                                                 129 

809 

21                                                    124 

21 

22                                                    271 

38 

23                                                    102 

1 

24                                                   300 

325 

25                                                  65 

4 

A                                                       74 

35 

B                                                     708 

43 

C                                                     612 

208 

D                                                  262 

33 

E                                                    53 

23 

F                                                    54 

11 

G                                                    95 

26 

H                                                    64 

5 

1                                                      49 

1 

J                                                     51 

7 

M                                                   46 

0 

«The  data  for  the  means  of  the  stations  (per  0.1  m^  samples) 
were  provided  as  a  more  accurate  estimate  of  such  quantities 
as  species  number,  because  extrapolations  from  0.1  m^  to  1.0  m^ 
in  the  case  of  small  numbers  like  5.47  specimens/0.1  m^  seem 
to  introduce  an  inordinate  amount  of  potential  error. 


In  a  comparison  of  the  dry  weights  of  Long 
Island  Sound  with  other  areas,  Sanders  gives  a 
figure  for  the  mean  total  dry  weight  (including 
"large  animals")  of  54.627  g/m^.  This  corresponds 
to  a  dry  weight  of  only  "small  animals"  of  15.88 
g/m^,  a  figure  which  is  roughly  twice  as  great 
as  the  highest  mean  value  for  the  other  areas 
discussed.  Pfitzenmeyer  (1970)  performed  a  study 
closer  in  purpose  to  the  present  investigation  than 
those  described  by  Sanders.  His  pre-dredging 
mean  dry  weight  (including  large  forms)  was  0.90 
g/m^,  while  the  immediate  post-dredging  mean 
was  0.67  g/m2. 

Holme's  (1953)  mean  dry  weight  was  11.2  g/m^, 
including  "large"  animals. 

The  figure  obtained  by  Sanders  for  total  dry 
weight  are  in  good  agreement  with  those  com- 
puted for  the  present  study,  since  the  pre-dredging 
dry  weight  for  Goose  Creek  was  36.83  g/m^, 
while  the  Long  Island  Sound  figure  was  54.627 
g/m^.  The  substantial  variance  of  these  data  from 
those  of  Holme  (11.2  g/m^)  and  Pfitzenmeyer 
(0.90  g/m2)  has  been  accounted  for,  in  principle, 
by  Sanders  in  his  1956  paper. 


464 


KAPLAN,  WELKER,  and  KRAUS:   EFFECTS  OF  DREDGING 


For  data  reported  on  the  basis  of  the  0.2  g 
dry  weight  cut-off  point,  it  is  sufficient,  in  many 
cases,  to  add  the  factor  suggested  by  Holme  when 
he  points  out  that  64.4%  of  the  dry  weight  of  his 
samples  was  excluded  by  the  0.2  g  point,  in  order 
to  bring  the  data  to  comparable  levels. 

Factors  relevant  in  an  explanation  of  the 
relatively  high  standing  crop  in  Goose  Creek  are: 

1.  None  of  the  studies  referred  to  sampled  to  a 
depth  beyond  22  cm,  and  most  examined  only 
the  top  6-10  cm  of  sediment.  Deeper-dwelling, 
large  forms  were  excluded. 

2.  Virtually  all  of  the  investigations  previously 
referred  to  examined  relatively  large,  slow  cur- 
rent velocity,  deep  bodies  of  water  with  relatively 
unvarying  bottom  sediments,  such  as  Chesapeake 
Bay.  Often  the  populations  described  comprise 
mud-silt  or  silt-clay  communities,  such  as  the 
Ampelisca  community  described  by  Stickney  and 
Stringer  (1957).  It  is  well  known  that  this 
sediment  is  not  highly  productive  of  biomass 
since  most  organisms  are  relegated  to  the  upper 
few  centimeters  where  gaseous  exchange  is  most 
rapid  (cf  Raymont,  1950;  Sanders,  1956;  Holme, 
1953;  Pfitzenmeyer,  1970).  In  Goose  Creek  the 
high  current  velocity  over  a  substantial  portion  of 
the  bay  and  the  diversity  of  sediment  types  sup- 
ported sizeable  populations  of  large  organisms, 
such  as  the  3,470  C.  fornicata  found  in  one 
dredge  haul  at  station  2. 

3.  Phytoplankton  production  is  high.  Cassin 
(1968)  studied  the  phytoplankton  cycle  in  Goose 
Creek  during  the  year  before  dredging,  and  found 
a  mean  standing  crop  of  1.64  x  10^  cells/liter. 
This  was  lower  than  that  for  Long  Island  Sound 
(2.38  X  106  cells/liter;  Conover,  1952),  but 
considerably  higher  than  those  for  Block  Island 
Sound  and  Vineyard  Sound.  According  to  Riley 
(1955),  the  mean  standing  crop  of  phytoplankton 
in  the  English  Channel  is  one-quarter  that  of 
Long  Island  Sound;  while  Flemer  (1970)  makes  a 
primary  production  estimate  for  Upper  Chesa- 
peake Bay  at  one-fifth  of  that  estimated  by  Riley 
for  Long  Island  Sound.  Phytoplankton  population 
size  appears  to  vary  with  benthic  standing  crop 
in  the  studies  mentioned  above. 


Population  Dynamics  and  Distribution 
of  Organisms 

Most  of  the  dominant  and  subdominant  organ- 
isms found  in  the  channel  before  dredging  were 


present  in  greatly  reduced  numbers  after  dredg- 
ing (Kaplan,  Welker,  and  Kraus,  in  press-b). 
Three  species  of  mollusc  increased  in  numbers 
after  dredging.  Tellina  agilis  and  Lyonsia  hyalina 
increased  in  sandy  sediments  while  Mulinia 
lateralis  became  more  abundant  in  the  finer 
substrata.  Two  polychaetes,  Notomastus  later- 
iceus  and  Clymenella  torquata,  abundant  before 
dredging,  virtually  disappeared  afterwards. 
O'Connor  (1972)  noted  an  increase  in  popula- 
tions of  Mulinia  lateralis  and  Tellina  agilis  in 
his  study  of  Moriches  Bay.  He  suggests  that 
M.  lateralis  is  a  fast-growing,  short-lived  species 
that  is  more  successful  in  silt.  If  this  is  so,  it 
may  be  suited  as  an  indicator  organism  which 
would  rapidly  increase  in  numbers  in  areas  where 
dredged  channels  cause  decreased  current  veloc- 
ity and,  consequently,  invasion  of  sandy  areas 
by  softer  sediments. 

The  channel  data  were  not  duplicated  in  the 
bay  as  a  whole.  The  most  fundamental  difference 
between  the  two  areas  was  the  fact  that  the 
substratum  and  all  its  infauna  were  removed  in 
the  channel  study,  while  only  stations  2  and  3 
in  the  bay  study  were  directly  in  the  path  of  the 
dredge.  Consequently,  the  drastic  effects  of  the 
removal  of  the  habitat  were  limited,  and  the 
reduced  population  size  throughout  the  bay  must 
be  a  concomitant  of  other  long-term  variables, 
such  as  changes  in  current  velocity  and  anoxia 
resulting  from  siltation.  Stations  22,  23,  and  5 
were  particularly  susceptible  to  this  latter  in- 
fluence, being  near  spoil  areas.  Portions  of  Thyone 
Cove  were  inundated  when  the  spoil  gate  broke 
during  the  dredging  operation.  In  addition,  sta- 
tion 23  was  in  the  path  of  the  1968  dredging  of 
an  extension  of  the  navigation  channel  through 
Thyone  Cove. 

Most  stations,  even  those  in  the  farthest 
reaches  of  the  bay,  showed  reductions  in  benthic 
populations;  however,  no  station  was  farther  than 
500  m  from  the  dredge  at  some  time  during  the 
operation,  except  for  station  25.  Figure  12  depicts 
the  changes  in  population  densities  of  13  domi- 
nant and  subdominant  benthic  organisms  before 
and  after  dredging.  In  addition,  the  abscissa  of 
each  histogram  represents  the  sediment  type, 
from  the  gravel  of  station  2  to  the  silt  of  station  23. 

Clymenella  torquata,  the  nearly  ubiquitous 
bamboo  worm,  was  the  numerical  dominant  in 
the  sandy  substrata,  forming  dense  colonies. 
Notomastus  latericeus  shared  this  habitat,  though 
in  reduced  numbers.  Both  species  of  worm 


465 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


24 

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Figure  12. — Population  fluctuations  before  and  after  dredging, 
and  distribution  according  to  substratum,  of  13  dominant  and 
subdominant  epi-  and  infauna  of  Goose  Creek.  The  solid  line 
represents  pre-dredging;  the  dotted  line  post-dredging  popu- 
lation sizes. 


2     3    S    6    7 


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STATIONS 


SANDY     MUD 


N  0 
D  0 


SUBSTRATES 


466 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 


showed  substantial  reductions  in  density  in  the 
post-dredging  samples.  Spio  setosa,  another 
inhabitant  of  sandy  substrata,  seems  to  have 
maintained  its  population  size,  with  50%  of  the 
stations  recording  increases  in  the  number  of 
specimens.'^ 

Capitella  capitata  and  Polydora  ligni,  inhabi- 
tants of  sandy  mud,  also  decreased  in  number. 
Nereis  areonodacea  was  found  in  muddy  sand  in 
small  numbers,  whileNereis  succinea  was  present 
in  densities  up  to  42/in^  in  the  sandy  mud  and 
silt  stations,  which  were  also  frequented  by 
Mercenaria  mercenaria.  Modest  reductions  in  the 
Nereis  and  Mercenaria  populations  occurred  after 
dredging. 

Mya  arenaria  was  found  in  sand  and  muddy 
sand.  Certain  areas  experienced  drastic  reduc- 
tions in  the  densities  of  these  organisms,  but  since 
most  of  the  Mya  recorded  were  juveniles,  popula- 
tion fluctuations  independent  of  dredging  may 
have  been  an  important  factor.  Factors  favorable 
to  larval  settling  and  the  growth  of  juveniles 
may  have  been  unsuited  to  their  sustenance  as 
adults,  resulting  in  mass  mortality  of  juveniles  at 
critical  points  in  their  development. 

Of  the  epifauna,  Neopanope  texana  sayi  was 
found  in  greatest  abundance  in  the  high  current 
velocity,  stony  gravel  of  station  2.  It  was  also 
abundant  in  the  muddy  sand  of  station  8  and  the 
silt  of  stations  16,  18  and  22.  It  was  recovered  in 
five  of  the  samples  at  station  16  and  four  at  station 
18,  so  it  is  unlikely  that  the  presence  of  this  crab 
in  the  silt  regions  was  accidental.  Neopanope 
texana  sayi  experienced  a  reduction  in  population 
density  after  dredging. 

Crepidulafornicata  was  found  in  large  numbers 
(3,470  in  one  haul)  at  station  2  before  dredging,- 
but  since  this  station  was  in  the  channel,  it  was 
decimated  by  the  dredge  and  no  recovery  was 
noted  in  the  11  mo  period  after  dredging.  Crepi- 
dula  broods  its  young;  recovery  would  be  expected 
to  be  relatively  slow  in  a  decimated  area  as 
dispersal  is  not  accomplished  by  free-swimming 
larvae. 

Four  species  of  Caridean  shrimp  were  abundant 
on  the  silt  substratum  of  Goose  Creek.  These  were 


■'The  reader  should  be  cautioned  in  interpreting  the  fluctua- 
tions in  population  densities  on  these  graphs.  Although  each 
column  represents  six  pre-dredging  or  six  post-dredging 
samples,  the  distribution  of  organisms  was  so  patchy  that 
accumulating  the  data  and  recording  means  still  does  not 
compensate  for  possible  sampling  error  as  the  corer  penetrated 
a  worm  colony  one  month  and  sampled  a  relatively  sterile 
area  1  m  away  from  it  the  next.  Trends,  however,  are  apparent. 


Hippolyte  pleurancanthus ,  Crangon  septimspino- 
sus,  Palaemonetes  vulgaris,  and  P.  pugio.  Their 
numbers  fluctuated  seasonally  and  from  station  to 
station,  possibly  reflecting  sampling  error  in- 
herent in  using  the  cumbersome  corers  to  capture 
these  relatively  rapidly  moving  organisms.  There 
were  population  decreases  at  most  stations. 

The  snail,  Hydrobia  totteni,  was  most  common 
in  the  sandier  sediments,  especially  at  stations 
3  and  7  which  had  substantial  current  velocities. 
Its  post-dredging  density  was  considerably  re- 
duced from  pre-dredging  levels. 

Mulinia  lateralis  was  found  to  be  more  abun- 
dant in  the  channel  after  dredging  than  before. 
Too  few  were  encountered  in  the  bay  study 
to  corroborate  this  finding. 

The  polychaete  Maldanopsis  elongata  was 
found  only  at  station  11  in  virtually  all  samples, 
reaching  a  density  of  60/m2.  Its  population  size 
was  maintained  after  dredging. 

The  holothurian  Sclerodactyla  ( =  Thyone) 
hriaerius  was  common  in  the  silt  stations  12-22, 
reaching  a  density  of  QOIva^  in  the  deep  silt  of 
station  22.  The  mean  numbers  at  station  22  were 
33/m2  before  dredging  and  2lxn^  after 
dredging,  reflecting,  perhaps,  the  close  proximity 
of  this  station  to  the  spoil  gate  of  spoil  area  C. 
Sclerodactyla  briaerius  experienced  declines  at 
five  of  the  six  stations  at  which  it  was  recorded 
in  substantial  numbers. 

The  tunicate,  Molgula  manhattanensis ,  was 
common  on  the  Enterornorpha  which  covered  the 
silt  at  stations  22,  23,  and  24,  reaching  a  con- 
centration of  590/m2  in  December  1966  at  station 
23  and  declining  in  numbers  after  dredging  at 
all  three  stations. 

An  amphipod  community,  similar  to  those 
described  by  Stickney  and  Stringer  (1957)  and 
Rhoades  and  Young  (1970),  occurred  in  the  silt 
west  of  station  12.  The  most  abundant  species 
were  identified  as  Ampelisca  macrocephala  and  A. 
spinipes.  Maximum  abundance  recorded  for  sta- 
tions 16,  17,  and  18  was  310,  490,  and  190/m2, 
considerably  lower  than  the  level  of  10,000  m^ 
mentioned  by  Stickney  and  Stringer  for  Green- 
wich Bay.  The  1.4  mm  sieve  size  used  in  this 
study  contrasts  with  the  practice  used  by  Stickney 
and  Stringer  of  examining  the  fine  sediments 
completely,  using  no  sieve.  However,  it  seems 
unlikely  that  population  densities  would  be 
comparable,  since  there  was  no  massive  concen- 
tration of  amphipod  tubes  in  the  Goose  Creek 


467 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


samples.  The  amphipods  found  in  Goose  Creek 
were  limited  to  the  soft  sediments,  in  contrast 
to  Long  Island  Sound  and  Buzzards  Bay,  as 
reported  by  Sanders  (1956, 1958),  making  it  likely 
that  they  are  detritus  feeders.  No  pattern  was 
evident  between  pre-  and  post-dredging  popula- 
tion densities  of  amphipods. 

The Nepthys  incisa-Nucula  proxima  community 
of  Sanders  was  not  found  in  Goose  Creek  since 
both  species  were  not  abundant  enough  at  any 
one  station  to  be  considered  dominant.  Instead,  a 
Nereis  succinea-Mercenaria  mercenaria-Sclero- 
dactyla  briaerius  community  was  found,  with 
subdominants  including  Capitella  capitata  and 
the  caridean  shrimp  previously  mentioned  as 
epifaunal  subdominants. 

Clymenella  torquata  and  Mya  arenaria  can  be 
considered  the  dominant  sandy  sediment  assem- 
blage, with  Notomastus  latericeus  and  Hydrobia 
totteni  comprising  important  subdominant  popu- 
lations. 

Scoloplos  robustus,  S.  fragilis,  and  Neopanope 
texana  sayi  were  distributed  throughout  the 
sediment  types  in  Goose  Creek,  apparently  with- 
out specificity. 

There  was  no  evidence  that  the  dredging  process 
eradicated  any  species.  There  was,  however, 
evidence  of  two  cyclical  fluctuations  in  population 
density  which  occurred  naturally  and  were  super- 
imposed on  the  dredging  data.  Individual  Aequi- 
pecten  irradians  were  found  in  only  four  sampler 
hauls.  Much  of  the  shell  in  the  substratum  was 
contributed  to  by  this  species,  testifying  to  its 
former  abundance.  In  fact,  it  was  commercially 
harvested  from  Goose  Creek  in  previous  years. 
Its  absence  coincided  with  a  cyclical  low  in  its 
density  and  had  nothing  to  do  with  the  dredging. 
Similarly,  not  one  specimen  ofCallinectes  sapidus 
was  recorded  for  the  22  mo  of  the  study,  yet  in 
July  1970  large  numbers  of  these  crabs  were 
observed  in  Goose  Creek. 


Sanders'  mean  ratio  for  all  stations  in  his  Long 
Island  Sound  survey  was  2.44.  He  estimated  the 
total  productivity  of  "small  infauna"  in  the  sedi- 
ment of  Long  Island  Sound  at  21.49  g/m^.  In 
computing  his  estimate  he  did  not  consider 
epifauna  and  "large"  forms.  He  also  makes  the 
assumption  that  the  substratum  of  Long  Island 
Sound  is  comprised  of  80%  fine  sediments  and 
20%  coarse.  Goose  Creek  has  a  distribution 
closer  to  50%  of  each  type  of  sediment.  Correct- 
ing for  these  factors  would  tend  to  raise  the  total 
value  of  the  estimate,  even  though  the  biomass 
of  "short-lived"  species  is  a  practically  negligible 
component  of  the  Goose  Creek  samples,  a  factor 
which  could  lower  the  figure  to  2.1.  Because  of 
these  considerations,  and  because  of  the  con- 
tiguity of  the  two  study  areas,  Sanders'  figure 
of  2.44  was  adopted  for  Goose  Creek. 

Macrobenthic  animal  production  in  Goose 
Creek  before  dredging  is  estimated  at  89.87 
g/m^/yr,  using  the  factor  of  2.44.  If  Sanders  had 
used  his  standing  crop  figure  for  all  epi-  and  in- 
fauna from  Long  Island  Sound  (54.627  g/m^) 
in  a  similar  calculation,  his  estimate  would  be 
54.63  X  2.44=  133.30  g/m^/yr,  a  figure  in  essential 
agreement  with  the  ratios  of  the  standing  crop 
estimates  in  the  two  areas. 

The  after-dredging  productivity  figure  is  31.18 
g/m^/yr  for  a  loss  of  58.69  g/m^/yr.  This  means 
that  18,780  kg  of  animal  production  were  lost 
from  the  0.32  km^  of  bottom  in  Goose  Creek  during 
the  post-dredging  year.  This  corresponds  to  ap- 
proximately 58,700  kg/km^/yr  reduction  in  the 
productivity  of  the  bay,  out  of  a  total  productivity 
of  89,870  kg/km2/yr. 

Primary  productivity  of  the  extensive  Ruppia 
and  Enteromorpha  beds  was  not  estimated. 


An  Estimate  of  the  Productivity  of 
the  Marsh 


Productivity 

The  mean  pre-dredging  dry  weight  for  Goose 
Creek  was  36.83  g/m^  before  dredging  and  12.78 
g/m^  after  dredging,  a  decrease  of  63%.  Sanders 
(1956)  suggests  that  standing  crop  figures  for  in- 
fauna are  a  function  of  productivity  by  a  ratio 
of  2.1-5.0:1.  Taylor  and  Saloman  (1968)  used  a 
factor  of  4  in  their  calculations  of  infaunal 
productivity  in  highly  productive  turtle  grass 
beds. 


The  islands  in  Goose  Creek  are  represented  on 
a  1904  map  with  virtually  unaltered  boundaries. 
Their  natural  isolation  makes  it  unlikely  that 
they  have  ever  been  exploited  by  man.  The 
relative  abundance  of  "bank"  or  "mud"  oysters 
and  extensive  colonies  oi  Modiolus  and  Uca  give 
further  evidence  of  their  pristine  state. 

The  islands  evidently  have  been  created  by  the 
deposition  of  materials  at  the  confluence  of  chan- 
nels A,  B,  and  C.  They  are  covered  with  a 
uniform  growth  of  Spartina  alterniflora,  with 


468 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 


Salsola  kali  and  other  plants  growing  on  patches 
of  shghtly  higher  ground.  The  dominant  animal 
is  Modiolus  demissus  which  was  abundant  on  all 
four  major  islands,  averaging  19.58  specimens  per 
m^.  Colonies  of  fiddler  crabs,  predominantly  Uca 
pugnax,  were  found  on  islands  I  and  II. 

The  islands  are  little  more  than  hassocks  of 
Spartina.  At  low  tide  they  project  0.7  m  to  1  m 
above  the  water  surface;  at  high  tide  they  are  vir- 
tually inundated.  The  largest  of  the  islands, 
island  II,  was  115.59  m  x  42.39  m. 

The  islands  represent  the  most  unspoiled  aspect 
of  the  Goose  Creek  marsh.  For  that  reason,  they 
were  chosen  as  the  site  for  estimating  the 
productivity  of  the  Spartina  alterniflora  marsh 
along  the  periphery  of  Goose  Creek.  The  result- 
ing figure  will  be  higher  than  other  productivity 
estimates  because  it  does  not  represent  the 
Spartina  patens  and  Phragmites  communis 
marshes  which  are  both  transitory  and  strongly 
affected  by  man  in  the  Goose  Creek  area. 

Island  II,  the  most  southeasterly  of  the  islands, 
was  sampled  by  means  of  seven  stations  arranged 
at  15  m  intervals  and  staggered  so  that  both 
edges  and  the  center  of  the  islands  were  sampled 
at  least  twice  (Figure  13). 

A  1.83  m  X  1.83  m  frame  was  placed  on  the  area 
to  be  sampled  so  that  3.34  m^  were  delimited.  A 
team  of  four  collectors  was  stationed,  one  collector 
on  each  of  the  sides  of  the  sample  area,  to  prevent 
motile  forms  from  escaping.  All  surface-dwelling 
animals  were  removed  by  hand.  The  area  was  then 
spaded  to  a  depth  of  20  cm  to  remove  burrowing 
forms.  The  total  area  sampled  was  23.4  m^. 

Table  20  represents  the  animal  biomass  of  the 
stations  on  island  II.  Animals  making  up  the 
species  mix  were:  104  Uca  pugnax,  6  Uca  pugi- 
lator,  442  Modiolus  demissus,  28  Sesarma  reticu- 
latum,  1  Carcinus  maenus,  3  Littorina  littorea, 
and  one  unidentified  Nereid. 

The  total  wet  weight  of  the  macrofauna  taken 
from  the  seven  stations  is  2,327.01  g,  or  90.94 
g/m^.  The  corresponding  calculation  for  dry 
weight  is  20.21  g/m^.  The  ratio  of  dry  weight  to 
wet  weight  is  1:4.9. 

The  computations  for  estimating  primary  pro- 
ductivity of  the  marsh  were  taken  from  Udell  et 
al.  (1969)  from  their  study  of  the  Hempstead, 
Long  Island,  salt  marsh.  They  calculated  a  total 
minimal  estimate  (harvest  method)  of  annual 
production  of  3.68  tons  per  acre  of  tall  Spartina 


Figure  13. — The  distribution  of  stations  on  island  II. 


Table  20.— Biomass  of  animals  found  on  island  II,  Goose  Creek. 


Animals 

Wet  wt. 

Dry  wt. 

Dry-wet 

No. 

No. 

Station 

(g) 

(g) 

ratio 

specimens 

species 

1 

397.32 

78.52 

1/5 

62 

2 

2 

595.55 

108.90 

1/5 

109 

4 

3 

155.76 

28.47 

1/6 

39 

4 

4 

175.46 

34.19 

1/5 

47 

4 

5 

705.24 

156.86 

1/5 

157 

3 

6 

213.97 

41.90 

1/4 

96 

4 

7 

83.71 

16.43 

1/5 

29 

3 

Total 

2.327  01 

475.27 

alterniflora  and  2.55  tons  per  acre  of  the  mixed 
species  comprising  the  typical  Long  Island  marsh 
(tall  and  short  .S.  alterniflora,  S.  patens,  Distichlis 
spicata,  etc.).  These  weights  corresponded  to  a 
mean  dry  weight  of  827.2  g/m^  for  tall  S.  alterni- 
flora and  (by  extrapolation)  578  g/m^  for  the  mixed 
species.  Animal  production  taken  from  our  mid- 
August  study  is  20.21  g/m^,  dry  weight.  Sanders 
(1956)  suggests  that  standing  crop  figures  for 
infauna  are  a  function  of  productivity  by  a 
ratio  of  2.1-5:1.  Since  the  organisms  predomi- 
nating in  our  samples  are  predominantly  "long- 
lived,"  Sanders'  factor  of  2.1  was  applied.  Animal 
productivity  of  the  marsh  comes  to  42.4  g/m^/yr, 
by  this  calculation.  This  is  roughly  5%  of  the  tall 
S.  alterniflora  productivity  figure  or  7%  of  the 
overall  estimate.  The  total  animal  and  plant  pro- 
ductivity of  the  tall  S.  alterniflora  marsh  as  repre- 
sented by  island  II,  is  869.64  g/m^/yr.  Thus,  if  the 
dredged  channel  had  passed  through  island  II 
instead  of  skirting  it,  its  4,900  m^  of  marsh  or 
4,261.2  kg  (dry  weight)  of  animal  and  plant 
productivity  would  have  been  permanently 
obliterated. 

The  portion  of  the  Goose  Creek  marsh  inun- 
dated as  spoil  areas  has  been  estimated  at  108,712 
m^.  Using  Udell's  estimate  of  2.55  tons/acre 
(4,553.57  kg/ha),  the  total  primary  productivity 
of  the  marsh  which  became  the  spoil  areas  would 


469 


be  4,553.57  kg/ha   x    10.87  ha  or  49,497.31 
kg/yr. 

Animal  production  of  tall  S.  alterniflora  marsh 
has  been  estimated  to  be  5-7'7f  of  primary  pro- 
ductivity. Since  mixed  marsh  is  not  as  productive 
of  animals  as  tall  S.  alterniflora  marsh,  a  figure 
of  4%  of  the  mixed  marsh  primary  production 
seems  to  be  a  reasonable  estimate.  Annual  animal 
production  on  the  10.87  ha  of  inundated  mixed 
marsh  would  then  be  4%  of  49,497.31  kg  or 
1,979.89  kg. 

Virtually  the  entire  spoil  areas  have  been 
turned  into  homesites.  If  they  had  been  left  to 
produce  aPhragmites  communis  community,  only 
a  relatively  small  proportion  of  the  original 
productivity  would  have  been  locally  available 
on  a  trophic  level  (Johnson,  pers.  comm.). 

Since  approximately  45%  of  the  net  production 
of  a  salt  marsh  (Teal,  1962)  is  exported  outside 
the  area  of  its  source,  the  loss  of  this  productivity 
will  have  repercussions  beyond  Goose  Creek. 

The  estimates  given  herein  should  be  con- 
sidered conservative,  as  E.  P.  Odum  (1959) 
estimated  the  primary  productivity  of  tall  S. 
alterniflora  in  Georgia  salt  marshes  at  a  high 
of  14  tons/acre  and  Ryther  (1959)  gives  a  figure 
for  net  organic  production  of  Spartina  marsh  of 
9.0  g/m2/day. 

H.  T.  Odum  (1963)  indicates  that  Thalassia 
beds  in  Redfish  Bay,  Tex.,  recovered  in  the  areas 
not  directly  in  the  path  of  the  dredge  after  one 
year,  but  his  data  indicate  that  the  dredged  area 
and  an  area  0.25  mile  east  of  the  channel  had 
no  productivity  due  to  removal  of  the  substratum 
to  bedrock  in  one  case  and  "beds  covered  with 
30  cm  of  soft  silt"  in  the  other.  Virtually  all  of 
Goose  Creek  was  within  0.25  mile  of  the  dredge. 
Studies  of  large  embayments  tend  to  deemphasize 
dredging  effects  because  of  the  dissipation  of  the 
products  of  the  dredging  process  and  dilution 
factors.  Similarly,  regions  like  Chesapeake  and 
Redfish  Bays  have  relatively  extensive  bottom 
areas  and  circumferences  and  dredge  spoil  is 
either  deposited  back  in  the  basin  where  it  spreads 
to  form  a  relatively  shallow  homogeneous  layer 
often  virtually  indistinguishable  from  the  bottom 
(Biggs,  1968,  1970),  or  covers  a  relatively  small 
portion  of  the  bay  edge. 

The  effects  of  dredging  appear  to  be  accentuated 
as  the  size  of  the  embayment  decreases. 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

DISCUSSION 

The  Relationship  of  the  Substratum  to 
the  Distribution  of  Organisms 

Wilson  (1938,  1953),  Morgans  (1956),  Sanders 
(1958),  and  Sasaki  (1967)  related  larval  or  adult 
infaunal  population  densities  to  sediment  type. 
McNulty,  Work,  and  Moore  (1962)  and  Harrison, 
Lynch,  and  Altschaeffl  (1964)  fail  to  corroborate 
either  degree  of  sorting  or  median  grain  size  as 
definitive  factors  affecting  the  distribution  of 
deposit  or  filter  feeders.  It  appears  that  animal- 
sediment  relationships  are  variable  depending  on 
such  factors  as  sediment  type,  life  cycles  of  related 
fauna,  and  location. 

In  the  Goose  Creek  study  the  analysis  of 
variance  between  biomass  before  and  after 
dredging  as  a  function  of  sediment  type  revealed 
no  significant  interaction  between  productivity  of 
animal  biomass  and  sediment  type  in  the  bay  as 
a  whole.  In  the  channel,  however,  there  was  a 
positive  correlation  between  biomass  and  sta- 
tions. Since  the  stations  were  arranged  in  linear 
fashion  virtually  in  descending  order  of  particle 
size  and  in  the  direction  of  lowered  current 
velocity,  these  factors  appear  to  have  had  an 
influence  on  productivity. 

The  recovery  rate  of  the  macrobenthic  popula- 
tions varied  in  different  substrata  according  to 
a  chi-square  of  the  number  of  species  found  at 
the  stations  representing  different  sediment 
types.  Similarly,  the  number  of  species  was  sig- 
nificantly different  before  and  after  dredging,  as  a 
function  of  sediment  type. 

It  appears,  then,  that  productivity  in  terms  of 
animal  tissue  was  not  independently  influenced 
by  substratum  in  the  bay  as  a  whole,  but  there 
was  a  response  to  the  specific  conditions  in  the 
channel.  Recovery  of  species  and  specimen  num- 
bers appeared  to  be  affected  by  sediment  type  in 
both  channel  and  bay.  These  data  tend  to  sub- 
stantiate those  of  Sasaki  (1967). 

The  Relationship  of  Current  Velocity 

to  the  Characteristics  of  the  Sediment 

and  the  Distribution  of  Organisms 

In  a  shallow  bay  with  a  narrow  mouth  like 
Goose  Creek,  wind-driven  currents  probably  have 
a  disproportionately  large  effect  on  the  char- 
acteristics of  the  sediment.  Prevailing  winds  can 


470 


KAPLAN.  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 

cause  a  net  transport  of  materials  towards  the 
lee  shore.  Wind  storms  can  so  pile  up  water  at 
the  mouth  of  the  bay  that  flood  tide  current  veloci- 
ties would  be  considerably  above  the  normal 
range,  causing  erosion  of  the  banks  of  tidal 
channels  and  exaggerated  depositional  patterns, 
or  winds  can  depress  the  natural  flushing  action 
of  the  ebb  tide,  increasing  the  deposition  of  light 
particles.  A  number  of  the  aforementioned  factors 
have  not  been  considered  in  the  literature  in 
detail,  perhaps  because  most  investigations  are 
concerned  with  relatively  large  and  deep  bodies 
of  water.  However,  Biggs  (1968)  concludes  that 
most  of  the  suspended  material  in  Upper 
Chesapeake  Bay  came  from  the  bottom  and  had 
been  stirred  by  wind-waves  and  currents. 

Inman  ( 1949)  refers  to  three  basic  factors  in  the 
transportation  and  deposition  of  sediments: 
degree  of  bottom  roughness,  settling  velocity, 
and  threshold  velocity.  He  shows  that  as  current 
velocity  drops  in  a  downstream  direction,  particle 
size  also  decreases.  The  degree  of  sorting, 
however,  is  at  a  maximum  in  sediments  with  a 
median  diameter  near  the  grade  of  fine  sand 
(0.18  mm).  Threshold  velocity  for  grain  diameters 
less  than  0. 18  mm  increases  with  decreasing  grain 
size.  Since  the  threshold  velocity  is  much  greater 
than  the  setting  velocity  for  smaller  particles, 
suspended  particles  entering  a  bay  will,  when 
deposited,  have  a  tendency  to  remain  a  part  of  the 
substratum  rather  than  move  about  by  surface 
creep  or  resuspension.  On  the  basis  of  these 
characteristics  of  fine  sands,  Sanders  (1958) 
deduces  that  they  must  represent  a  very  stable 
environment.  He  also  emphasizes  the  role  of  clay 
as  an  efficient  binding  agent  for  organic  matter, 
thus  influencing  the  number  of  deposit  feeders 
present.  The  simple  clay-silt  proportion  governing 
the  population  size  of  Sanders'  deposit  feeders 
is  not  apparent  in  the  distribution  of  filter  feeders, 
where  more  complex  factors  are  at  work. 

McNulty  et  al.  (1962)  related  low  current  veloc- 
ity to  the  accumulation  of  a  detritus  layer  on  the 
sediment  surface  capable  of  supporting  large 
populations  of  detritus  feeders. 

Rhoads  and  Young  (1970)  suggest  that  biogenic 
reworking  lowers  critical  erosion  velocity  and 
increases  the  instability  of  the  substratum  as 
manifested  by  a  high  resuspension  rate  and  in- 
creased turbidity  close  to  the  silt-water  interface, 
placing  selective  pressure  on  suspension  feeders. 

In  the  present  investigation,  maxima  in  bio- 
mass  production  occurred  in  areas  of  coarse  and 


fine  sand  in  the  channel  (stations  B,  C,  and  H) 
with  current  velocities  of  the  order  of  56  cm/sec 
and  17  cm/sec,  before  dredging. 

In  the  bay  as  a  whole  14  of  113  individual 
dredge  hauls  yielded  dry  weights  above  80  g/m^. 
Since  the  distribution  of  organisms  was  so  patchy, 
these  extraordinarily  large  standing  crop  mea- 
sures are  perhaps  the  best  index  of  the  productiv- 
ity of  the  various  substrata.  The  highest  biomass 
was  recorded  for  station  2.  However,  this  con- 
sisted almost  exclusively  of  Crepidula  fornicata, 
an  epibenthic  gastropod  which  requires  the 
scouring  action  of  a  rapid  current  to  establish 
a  substratum  of  stones  upon  which  it  clings  with 
a  broad  foot.  Stations  7  and  9  had  high  and 
medium  current  velocities  (41.5  and  12  cm/sec) 
and  supported  extensive  colonies  of  the  poly- 
chaetes  Clymenella  torquata  and  Notomastus  la- 
tericeus,  as  well  as  large  pelecypods  (Mya,  Ensis, 
Mercenaria)  in  the  case  of  station  9.  Both  C 
torquata  and  A'^.  later iceus  are  deposit  feeders 
inhabiting  sandy  sediments. 

Stations  16,  17,  and  22  were  in  regions  of 
almost  negligible  current  velocity  which  were 
characterized  by  a  substratum  of  silt  over  fine 
gray  sand.  The  major  weight  contributors  at  sta- 
tions 16  and  17  were  Sclerodactyla  (Thyone)  and 
large  Mercenaria,  with  the  polychaetes,  Capitella 
capitata,  Polydora  ligni,  Scoloplos  robustus,  and 
S.  fragilis  making  important  contributions.  Poly- 
dora is  almost  exclusively  an  inhabitant  of  mud, 
while  the  other  worms  are  found  in  sandy  mud. 

All  of  the  above-mentioned  worms  are  deposit 
feeders  whereas  Sanders  groups  Mercenaria  and 
Sclerodactyla  together  as  suspension  feeders. 

Deposit-detritus  feeders  were  important  con- 
tributors to  the  biomass  in  Goose  Creek,  in  both 
the  sandy  and  muddy  habitats.  These  animals  are 
more  or  less  substratum-specific,  as  can  be  seen 
on  their  distribution  graphs  (Figure  12)  and  in 
Sanders'  data.  Changes  in  current  velocity  have  a 
profound  influence  on  the  nature  of  the  sub- 
stratum and,  consequently,  on  animal  distribu- 
tion. This  is  especially  true  in  the  regions  of  the 
sandier  sediments.  Stations  2,  7,  and  9  had 
reductions  from  50  to  75%  of  pre-dredging 
velocities.  In  the  western  portion  of  the  bay,  wind- 
driven  currents  are  the  predominant  means  of 
sediment  transport,  and,  although  some  changes 
in  the  mid-bay  region  could  be  expected  due  to 
increased  current  velocities,  these  would  not  have 
a  substantial  influence  on  the  soft  sediment  of 
the  western  half  of  the  bay. 


471 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


The  most  numerous  instances  of  high  infaunal 
standing-crop  production  were  in  areas  which  cor- 
respond to  the  general  classification  proposed  by 
Sanders  (1956),  of  a  relatively  high  silt-clay 
composition,  although  the  stations  with  the 
highest  animal  biomass  were  either  somewhat 
above  the  13-25'7c  silt-clay  level  reported  as  most 
highly  productive,  or  toward  the  lower  end  of 
the  spectrum.  Suspension  feeders,  with  the  excep- 
tion of  station  2,  were  not  the  dominant  forms  in 
the  sandy  sediments  of  Goose  Creek,  except  in  the 
littoral.  Instead,  deposit  feeding  polychaetes  were 
numerically  dominant  and  often  constituted  the 
major  weight  factor  in  the  biomass.  Further- 
more, if  Mercenaria  andSclerodactyla  are  grouped 
together  (Sanders,  1956),  the  biomass  of  suspen- 
sion feeders  predominates  in  high  silt-clay  regions. 
An  important  Ampelisca  community  was  not 
found. 

The  Effects  of  Dredging  on  the 
Substratum  and  Its  Fauna 

Three  major  categories  of  environmental  dis- 
turbance brought  about  by  dredging  are: 

1.  Immediate  effects,  during  and  directly  after 
the  dredging,  including  suffocation  of  benthic  ani- 
mals by  siltation;  flocculation  and  removal  from 
the  water  column  of  planktonic  organisms  (which 
affects  benthic  filter  feeders  by  removing  their 
source  of  food);  and  changes  in  water  chemistry, 
as  substances  are  released  from  the  substratum 
and  dissolved.  Large  quantities  of  bottom  mater- 
ials placed  in  suspension  by  the  dredging  process 
decrease  light  penetration,  change  the  propor- 
tion of  wavelengths  of  light  reaching  the  plants 
and  interfere  with  the  food-getting  processes  of 
filter  feeders  by  inundating  them  with  wrong  size 
or  nonnutritive  particles. 

On  the  other  hand,  the  release  of  nutrients  into 
the  water  profoundly  affects  the  composition  of 
the  plankton  by  favoring  the  growth  of  some 
species.  This  effect  could  be  beneficial  or  harmful 
depending  on  whether  or  not  the  plankton  bloom 
is  utilized  by  the  filter  feeders.  If  nannoplankton 
like  Nannochloris  and  Stichococcus,  which  have 
been  incriminated  in  mass  mortalities  of  Mer- 
cenaria, are  the  dominant  forms  in  the  bloom, 
selective  removal  of  certain  species  of  filter- 
feeders  could  be  expected. 

2.  Transitory  or  semipermanent  effects  such 
as  the  mechanical  removal  of  the  benthos  from  the 


dredged  area  and  a  change  in  the  nature  of  the 
substratum  by  the  deposition  of  spoil.  These 
changes  may  be  temporary,  as  the  dredged  area 
is  recolonized  or  tidal  currents  reestablish  the 
original  substratum  composition  by  scouring 
away  fine  particles  and  reestablishing  old  chan- 
nels, or  depositing  fine  sediment  over  exposed, 
sandy  areas. 

Recolonization  of  areas  denuded  of  organisms 
has  been  studied  under  either  artificially  induced 
conditions  or  as  the  result  of  major  disturbances 
such  as  oil  spillage.  Reestablishment  of  the 
original  fauna  is  estimated  to  take  at  least 
8  yr  in  the  intertidal  zone,  as  reported  by 
Castenholz  (1967)  and  by  North  (1967).  Clarke 
and  Neushul  ( 1967:47)  give  some  insight  into  the 
complexity  of  the  recolonization  process  when 
they  report:  "Apparently  a  barnacle  stage  had  to 
be  established  before  the  surface  of  the  rock  was 
suitable  for  the  larval  stages  ofMytilus  to  become 
established."  In  their  study  it  took  4  yr  for  the 
reestablishment  of  small  Mytilus  californianus 
colonies. 

In  the  aforementioned  works  the  environment 
was  not  fundamentally  changed  by  the  conditions 
leading  to  defaunation,  namely,  storms,  oil  spil- 
lage, or  artificial  removal  of  the  organisms  from 
the  substratum. 

If  a  rock  has  been  manually  denuded  of 
organisms,  natural  succession  can  begin  imme- 
diately. In  the  case  of  dredging,  however,  the 
substratum  may  remain  unstable  for  a  con- 
siderable time  and  final  recolonization  cannot 
begin  until  the  climax  substratum  is  reestab- 
lished. 

3.  Permanent  changes  in  the  ecology  brought 
about  by  dredging  occur  if  the  ambient  flow  of 
water  and  current  distribution  patterns  are  dis- 
rupted. One  of  the  results  of  dredging  was  the 
reapportionment  of  maximum  water  transport 
into  Goose  Creek  from  channel  A  to  channel  B. 
Furthermore,  the  current  velocity  in  all  three 
channels  dropped  because  of  the  enlarged  capacity 
of  the  dredged  channel  for  containing  water, 
since  it  was  approximately  three  times  deeper 
than  the  channel  it  replaced.  A  different  dis- 
tribution pattern  of  silt  and  other  fine  particles 
occurred  as  the  result  of  lowered  current  veloci- 
ties which  resulted  in  sediment  changes  in  a  sub- 
stantial portion  of  the  bay. 

Spoil  deposition  on  the  surrounding  marshes 
has  a  profound  effect  on  the  species  composition 


472 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 

and  productivity  of  an  estuarine  area.  Raising 
the  level  of  the  marsh  above  the  inundation  zone 
will  replace  the  highly  productive  Spartina 
community  with  the  less  biologically  useful 
Phragmites  communis.  Much  of  the  food  of  detritus 
feeders  comes  from  the  disintegrating  plant 
material  of  the  Spartina  marsh  and,  in  the  ab- 
sence or  depletion  of  this  food  source,  the  species 
mix  and/or  proportion  of  detritus  to  deposit  on 
filter  feeders  may  be  permanently  changed. 

Even  the  removal  of  shell  from  a  mud  bottom 
has  been  suggested  as  a  reason  for  the  exclusion 
of  certain  species  from  a  dredged  bay.  Barnard 
and  Reish  (1959)  suggest  that  the  amphipod, 
Metaceradocus  occidentalis  and  the  polychaete 
Scyphoproctus  oculatus  were  in  danger  of  losing 
their  habitat  as  the  upper  shell  and  rock  laden 
layers  of  the  mud  substratum  were  removed  by 
a  dredging  operation. 

The  distribution  or  removal  of  materials  during 
dredging  in  a  body  of  water  with  even  minimal 
flushing  action  results  in  immediate,  temporary, 
and  long-term  changes  in  its  ecology.  The  inter- 
action of  organisms  with  this  rapidly  changing 
environment  is  poorly  understood.  Estuarine 
organisms  are  noted  for  their  ability  to  withstand 
environmental  vicissitudes,  yet  this  adaptability 
may  be  overstressed  by  one  or  another  aspect 
of  the  dredging  process.  For  example,  Postma 
(1967:226)  refers  to  the  difference  in  the  distribu- 
tion patterns  of  dissolved  and  suspended  ma- 
terials. He  points  out  that  dissolved  materials 
have  a  net  transport  from  regions  of  high  con- 
centration to  regions  of  low  concentration,  causing 
a  rapid  dispersal  of  the  dissolved  matter  and  its 
consequent  removal  from  the  source  area:  "In 
the  case  of  suspended  matter  the  reverse  often 
occurs.  This  material  may  be  trapped  and  accumu- 
lated in  the  nearshore  environment."  Thus,  a 
benthic  organism  in  the  vicinity  of  a  dredging 
operation  can  be  subjected  to  a  short-term  rapid 
surge  of  dissolved  nutrients  in  its  environment, 
with  all  of  the  concomitant  interactions  this 
represents.  Superimposed  on  this  relatively  fleet- 
ing enrichment  of  the  water  would  be  the  longer- 
term  deposition  of  suspended  sediments.  The 
interaction  between  the  two,  such  as  the  adsorp- 
tion of  organic  compounds  on  suspended  clay 
particles  (e.g.  amino  acid  complexes  binding 
strongly  to  clays)  (Siegel,  1966),  the  effects  of 
flocculation,  etc.,  is  poorly  understood.  The  pre- 
sence of  the  dissolved  organic  compounds  lib- 
erated by  the  dredging  process  also  can  have 


beneficial  effects  on  the  benthic  organisms. 
Siegel  quotes  Stephens  and  Schinske  (1961)  who 
found  that  glucose,  glycine,  and  aspartic  acid 
can  serve  as  energy  sources  for  marine  inverte- 
brates. Organic  matter  may  also  supply  a  growth 
factor  such  as  vitamin  B12  or  may  inhibit  the 
growth  of  bacteria  by  its  antibiotic  effect  (Saz 
et  al.,  1963).  It  may  promote  growth  by  solu- 
bilizing  trace  metals,  thus  making  them  available 
(Johnston,  1964).  Udell  et  al.  (1969)  analyzed 
marsh  grasses  and  found  a  number  of  vitamins, 
including  vitamin  B12.  The  destruction  of  peri- 
pheral marsh  by  spoil  deposition  may  eliminate 
a  constant  source  of  vitamins  and  other  nu- 
trients made  available  by  the  disintegration  of 
the  Spartina. 

The  effects  of  the  dispersion  of  light  rays  in 
the  turbid  water  of  a  dredged  bay  is  also  in- 
completely understood.  It  is  unlikely  that  in- 
creased turbidity  can  destroy  benthic  flora 
through  light  deprivation  in  shallow  waters. 
Clendenning  (1958)  studied  the  relationship  be- 
tween photosynthesis  and  light  intensities  for 
Macrocystis  pyrifera  laminae.  Compensation 
(light  intensity  where  photosynthesis  balanced 
respiration)  occurred  at  15  foot  candles  using 
white  light.  First  evidences  of  saturation  occurred 
at  about  400  foot  candles  and  maximum  photo- 
synthetic  rates  occurred  at  1,600  foot  candles. 
Since  the  intensity  of  daylight  delivered  to  the 
water  surface  is  about  10,000  foot  candles,  it  is 
unlikely  that  the  light  values  would  so  depreciate 
in  shallow  water  as  to  seriously  impair  photo- 
synthesis. On  the  other  hand,  the  authors  ob- 
served a  colony  of  Ruppia  after  dredging  and  the 
leaves  were  covered  by  a  light  brown  flocculent 
material  which  had  been  deposited  from  the  water. 
Large  areas  of  Enteromorpha  and  Aghardiella 
showed  a  similar  canopy  of  fine  sediment.  It  is 
possible  that  the  deposition  of  opaque  material 
from  the  water  onto  leaves  and  stipes  in  areas 
of  negligible  current  velocity  might  pose  a  threat 
to  the  plants  by  inhibiting  photosynthetic  activity 
even  though  the  turbidity  of  the  overlying  water 
is  not  high  enough  to  reduce  adequate  light 
penetration. 

The  estuarine  environment  is  particularly  sus- 
ceptible to  particle  deposition.  Although  it  shares 
the  factor  of  close  proximity  to  the  source  of  the 
particulate  matter  with  open  beaches,  the  beaches 
have  a  longshore  drift  factor  which  tends  to 
distribute  particulate  matter.  It  is  well  known 
that  beach  sands  are  well  sorted.  Estuarine  areas, 


473 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


on  the  other  hand,  have  a  circulation  cycle  which 
favors  deposition.  Postma  (1967:229)  states:  "The 
estuarine  circulation  therefore  acts  as  a  'sediment 
trap'  in  which  water  flows  freely  seaward,  but 
particles  heavier  than  the  water  are  retained." 

Flemer  et  al.  (1968)  list  a  numher  of  factors 
associated  with  the  effects  of  dredging  on  animal 
survival  and  suggest  that  suspended  sediments 
probably  affect  many  sites  in  the  energy  flow 
sequence  of  the  benthic  community. 

Several  studies  have  been  made  on  the  effects 
of  siltation  on  the  survival  of  pelecypods. 

Loosanoff  and  Tommers  (1948),  Davis  (1960), 
Davis  and  Hidu  (1969),  and  Loosanoff  (1962) 
described  harmful  effects  of  heavy  sediment  loads 
on  eggs,  larval  development,  and  adult  pelecypods, 
while  Lunz  (1938),  Wilson  (1950),  Mackin  (1956), 
and  Dunnington  (1968)  showed  that  adult  oysters 
do  not  suffer  appreciable  physiological  damage 
unless  subjected  to  very  heavy  siltation  or  buried. 

Pfltzenmeyer  (1970)  described  the  effects  of 
dredging  and  spoil  deposition  in  Upper  Chesa- 
peake Bay.  The  dredging  process  did  not  cause 
major  topographical  or  stratigraphical  changes 
since  the  spoil  was  fundamentally  identical  with 
the  substratum  upon  which  it  was  deposited  and 
it  spread  out  to  form  a  thin  layer  over  the  bottom, 
undisturbed  by  strong  currents.  Species  mix  and 
biomass  were  markedly  reduced  immediately 
after  dredging,  but  recovered  to  original  levels 
after  18  mo. 

Of  interest  in  Pfitzenmeyer's  study  is  the  super- 
imposition  of  the  natural  cycles  of  certain  mol- 
luscs on  the  data  related  to  dredging.  The  pele- 
cypods Macoma  phenax  and  M.  balthica  were  in  a 
period  of  natural  decline  during  the  period  of  the 
study,  while  i?an^ia  cuneata  experienced  a  short- 
lived population  explosion,  reaching  a  density  of 
10,000  clams  per  m^.  One  year  after  the  study, 
the  Rangia  population  had  disappeared.  These 
rapid  and  extreme  fluctuations  in  the  population 
densities  of  organisms  profoundly  affected  bio- 
mass calculations  because  of  the  relatively  large 
size  of  the  pelecypods,  compared  with,  for  example, 
the  three  permanent  dominants,  two  of  which 
were  an  isopod  and  an  amphipod.  If  the  Rangia 
population  increase  had  not  compensated  for  de- 
creases in  the  Macoma  populations  during  the 
study,  it  is  possible  that  there  might  have  been 
significant  differences  in  the  results.  If  the  dredg- 
ing had  substantially  altered  the  substratum,  e.g., 
by  removing  the  silt  to  a  depth  sufficient  to 


expose  the  sand  underneath,  the  recovery  of  the 
populations  might  have  required  a  period  of 
substratum  stabilization  before  achievement  of 
normal  populations. 

Pearce  (1970)  studied  a  spoil  deposition  area 
of  the  New  York  Bight  known  as  the  "dead  sea." 
He  describes  the  benthic  environment  as  severely 
affected  by  the  deposition  of  large  quantities  of 
spoil.  He  found  contamination  by  heavy  metals, 
pesticides,  and  petroleum  derivatives.  The  central 
portion  of  the  spoil  area  contained  no  living 
macrofauna;  peripheral  areas  were  frequently 
barren  or  impoverished;  interstitial  waters  of  spoil 
sediments  had  extremely  high  coliform  counts. 

In  laboratory  experiments  where  the  crusta- 
ceans Homarus  americanus  and  Cancer  irroratus 
and  the  xiphosuran  Limulus  polyphemus  were 
exposed  to  sludge  and  spoil  sediments,  high 
mortalities,  and  pathological  conditions  were 
described. 

Pearce  concluded, ". . .  sewage  sludge  and  dredge 
spoil  deposits  are  incompatible  with  most  normal 
biological  phenomena,"  (p.  66).  He  blames  this 
condition  on: 

1)  adults  being  killed  by  toxins,  anoxia,  or 
inundation  by  solid  wastes; 

2)  interference  with  or  destruction  of  eggs  and 
larvae;  and, 

3)  active  avoidance  by  adult  and  larval 
organisms. 

A  number  of  reasons  suggest  themselves  to 
explain  why  the  results  of  Pfitzenmeyer's  and 
Pearce's  studies  are  so  diametrically  opposed. 
For  one,  Pearce's  study  area  was  one  of  constant 
spoil  deposition;  Pfitzenmeyer's  had  only  one  in- 
undation. Secondly,  Pfitzenmeyer  records  rela- 
tively normal  concentrations  of  oxygen  while 
Pearce  indicates  that  oxygen  concentrations  were 
frequently  2-3  ppm  lower  in  the  water  above  the 
spoil. 

Finally,  there  seems  to  be  a  very  high  degree  of 
contamination  of  the  dredged  sediments  with 
heavy  metals,  insecticides,  and  petroleum  frac- 
tions in  Pearce's  study,  which  is  absent  in  Pfitzen- 
meyer's. 

A  number  of  studies  was  performed  on  the 
effects  of  dredging  on  oyster  production.  Breuer 
(1962)  reported  major  changes  produced  by  dredg- 
ing spoil  deposition  in  South  Bay,  Tex.  Water 
circulation  was  impaired  by  reducing  the  size  of 
the  entrance.  Water  depth  decreased,  much  of  the 
oyster  population  was  silted  over  and  destroyed, 
and  high  local  turbidity  was  evident. 


474 


KAPLAN,  WELKER.  and  KRAUS:  EFFECTS  OF  DREDGING 


Mackin  (1961)  reviewed  the  literature  on  the 
biological  effects  of  dredging,  with  special  refer- 
ence to  oyster  survival.  Most  of  the  authors  he 
cited  found  that  oyster  mortality  was  caused  by 
direct  inundation  with  spoil  resulting  in  suffoca- 
tion. Beyond  the  area  of  deposition,  oysters  and 
fishes  were  unaffected. 

Mackin  found  that  at  low  current  velocities 
turbidity  is  not  an  important  factor  in  oyster 
mortality  at  levels  up  to  700  ppm.  Such  levels 
were  higher  than  those  found  beyond  250  ft  from 
the  outlets  of  the  three  types  of  dredges  studied. 
He  also  argues  that  oxygen  levels  are  not  appreci- 
ably decreased  under  conditions  normally  found 
on  oyster  beds. 

SUMMARY  AND  CONCLUSIONS 

The  results  of  the  present  study  differ  from 
those  reported  in  most  other  investigations  of  the 
effects  of  dredging  in  that  profound  changes  are 
reported  in  macrobenthic  animal  populations 
throughout  the  bay.  Abundant  evidence  is  avail- 
able concerning  long-term  depreciation  of  stand- 
ing crop  in  dredged  channels  (cf.  Taylor  and 
Saloman,  1968;  Odum,  1963;  Murawski,  1969; 
and  O'Connor,  1972),  but  these  reports  show 
limited  residual  effects  beyond  the  immediate 
region  of  the  channel  and/or  spoil  areas.  This 
difference  in  results  is  attributed  to  the  fact  that 
most  previous  studies  reported  on  the  creation  of 
channels  through  relatively  large  bodies  of  water 
such  as  Chesapeake  or  Boca  Ciega  Bays.  Spoil 
distribution  effects  and  changes  wrought  in  cur- 
rent velocity  and  sediment  deposition  are  mini- 
mized when  the  ratio  of  the  dredged  area  to  total 
bottom  area  and  contained  water  volume  is  large. 
Long  flushing  time  and  reduced  inlet  size  of  small 
estuarine  bays  exaggerates  the  hydrodynamic 
effects  of  channel  construction.  Wind-induced 
sediment  transport  and- the  effects  of  spoil  deposi- 
tion on  the  surrounding  peripheral  marshes  are 
factors  which  complicate  the  evaluation  of  the 
effects  of  dredging,  especially  in  small  bays. 

In  areas  of  high  human  population  density, 
combined  dredging-landfill  operations  have  be- 
come common  and  their  effects  have  been  felt 
primarily  in  the  small  shallow  bays  which  could 
provide  (if  dredged)  good  anchorages  for  pleasure 
boats  and  picturesque  settings  for  homes.  Yet 
these  small  bays,  edged  with  Spartina  marshes, 
are  primary  trophic  energy  sources  in  the  economy 


of  the  sea.  It  appears  that  further  long-term 
investigations  of  the  effects  of  dredging  on 
these  bays  is  warranted. 

A  summary  of  the  areas  of  investigation  and 
conclusions  follow: 

1.  The  dredging  process  caused  turbidity 
throughout  the  bay.  Light  penetration  was  re- 
duced to  0.4  m  during  dredging,  but  the  particu- 
late matter  released  was  rapidly  dissipated.  It  is 
unlikely  that  turbidity  affected  light  penetration 
enough  to  interfere  with  photosynthesis.  How- 
ever, a  canopy  of  flocculent  material  deposited 
on  the  plants  as  the  result  of  the  deposition  of 
suspended  bottom  material  may  have  interfered 
with  primary  productivity  in  the  low  current 
velocity  areas  of  the  bay. 

2.  Water  transport  patterns  were  greatly  modi- 
fied as  the  result  of  dredging.  Current  velocity 
in  the  eastern  half  of  the  bay  was  reduced 
approximately  50%,  while  small  increases  were 
noted  for  the  middle  portion  of  the  bay,  which 
previously  had  negligible  velocities. 

The  main  mass  movement  of  water  shifted 
from  channel  A  to  channel  B  as  the  result  of 
deepening  the  latter  channel. 

Dye  studies  revealed  that  flushing  time  of  the 
bay  as  a  whole  was  not  appreciably  changed. 

3.  Correlations  between  sediment  particle  size 
and  changes  in  current  velocity  suggested  that 
the  distribution  of  sediment  types  in  Goose  Creek 
would  be  permanently  changed  as  the  result  of 
modified  current  velocities. 

4.  Values  of  particulate  phosphorus,  silicates, 
and  chlorophyll  a  increased  substantially.  Dis- 
solved organic  phosphorus  and  nitrates  increased 
slightly  during  the  post-dredging  year. 

A  number  of  authors  have  reported  increases 
in  phytoplankton  and/or  benthic  productivity  as  a 
result  of  increased  nutrient  levels,  but  no  defini- 
tive correlation  could  be  observed  in  the  course 
of  this  study. 

5.  It  was  found  that  wind-driven  currents  af- 
fected the  distribution  of  nutrients  and  bacteria 
in  the  bay.  In  view  of  the  predominance  of  strong 
northwesterly  winds  over  the  year  and  the 
shallow,  slowly  moving  water  of  the  western 
half  of  Goose  Creek,  it  was  suggested  that  sedi- 
ment deposition  in  this  region  was  primarily  a 
function  of  wind-driven  currents.  The  assertion 
by  Flemer  (1968)  that  late  fall  is  the  best  season 
for  dredging  is  disputed  on  the  basis  of  a  high 


475 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


level  of  wind-influenced  sediment  distribution  at 
that  season. 

6.  Standing  crop  figures  for  the  commercially 
important  clam,  Mercenaria  mercenaria,  were 
reduced  in  the  bay  as  a  whole.  Some  areas, 
especially  those  in  the  path  of  the  dredge,  did 
not  recover  one  year  after  dredging. 

7.  Land  usage  patterns  were  drastically  altered 
during  the  study  as  well  as  in  the  previous  15  yr. 
Homes  within  300  m  of  the  bay  increased  by  94%. 

Rhodamine  B  placed  in  a  toilet  in  a  house 
along  the  periphery  of  the  bay  was  detected  in 
the  bay  water,  although  all  houses  have  septic 
tanks.  Maximum  coliform  counts  exceeded  pres- 
ent legal  standards  in  1968. 

8.  Significant  reductions  in  standing  crop 
figures  occurred  in  the  channel  and  the  bay  as  a 
whole.  Recovery  of  biomass  in  the  channel  was 
also  affected  by  sediment  composition  and  an 
interaction  between  the  sediment  and  the  dredg- 
ing process  itself 

The  effect  of  different  sediment  types  and 
seasonal  variances  on  the  biomass  is  shown  to  be 
not  significant,  negating  two  of  the  most  important 
variables  which  might  confuse  the  interpretation 
of  the  pre-and  post-dredging  data. 

Chi-square  analyses  were  done  on  number 
of  species  and  number  of  individuals  in  the  bay 
and  in  the  channel.  There  were  significant  reduc- 
tions in  both  parameters.  Recovery  of  species  and 
specimen  numbers  appeared  to  be  affected  by 
sediment  type. 

Drastic  reductions  in  biomass,  species  number, 
and  population  size  occurred  in  the  dredged 
channel  as  a  function  of  the  removal  of  the  sub- 
stratum and  its  in-  and  epifauna.  Recovery  had 
not  occurred  at  the  termination  of  this  study, 
11  mo  after  dredging. 

Of  perhaps  greater  significance  are  the  sub- 
stantial reductions  in  all  parameters  which  oc- 
cured  in  the  bay  as  a  whole,  with  only  a  few 
stations  showing  recovery  to  pre-dredging  levels. 
Only  one  of  the  stations  was  more  than  500  m 
from  the  dredged  channel  and  spoil  deposition 
areas. 

9.  Goose  Creek  had  a  relatively  high  in-  and 
epifaunal  standing  crop  estimated  at  36.83  g/m^ 
for  the  bay  as  a  whole,  including  large  forms. 
This  compares  to  Sanders'  (1956)  estimate  of 
54.627  g/m2  for  Long  Island  Sound,  but  is  much 
higher  than  the  standing  crop  levels  obtained 
for  Upper  Chesapeake  Bay  or  the  English 
Channel. 


The  number  of  organisms  per  m^  is  lower  for 
Goose  Creek  than  for  the  other  areas  reported 
on,  indicating  a  preponderance  of  large  forms. 

10.  Phytoplankton  production  in  Goose  Creek 
was  lower  than  that  of  Long  Island  Sound,  but 
far  higher  than  that  of  the  English  Channel  or 
Upper  Chesapeake  Bay.  There  were  three  maxima 
in  phytoplankton  production  in  Goose  Creek  in 
1966-1967. 

11.  The  removal  of  the  substratum  in  the 
channel  affected  the  population  dynamics  of  the 
infauna.  The  molluscs  Tellina  agilis,  Lyonsia 
hyalina,  and  Mulinia  lateralis,  while  insignificant 
components  of  the  standing  crop  both  before  and 
after  dredging,  increased  in  numbers  in  the  post- 
dredging  samples. 

Two  dominant  forms,  the  polychaetes  Cly- 
menella  torquata  and  Notomastus  latericeus, 
virtually  disappeared  after  dredging. 

In  the  bay  as  a  whole  there  appeared  to  be  no 
substantial  change  in  the  species  mix,  except 
for  the  removal  of  the  dense  population  of 
Crepidula  fornicata  (34,000/m2)  by  the  dredge 
near  the  confluence  of  the  three  channels.  No 
recovery  was  noted  for  this  species  after  11  mo  at 
that  station. 

In  general,  the  bay  sediments  exhibited  an  over- 
all reduction  in  epi-  and  infaunal  populations, 
which  did  not  approach  recovery  levels  11  mo 
after  dredging. 

The  Ampelisca  spinipes  and  Nepthys  incisa- 
Nucula  proxima  communities  described  by 
Stickney  and  Stringer  (1957)  and  Sanders  (1956, 
1958)  were  not  found  in  Goose  Creek,  being 
replaced  by  a  Clymenella  torquata-Mya  arenaria 
community  in  the  sandy  sediments,  and  a  Mer- 
cenaria mercenaria-Sclerodactyla  briaerius- 
Nereis  succinea  community  in  the  softer  sub- 
stratum. 

12.  Animal  productivity  for  Goose  Creek  was 
calculated  at  89.87  g/m^/yr  before  dredging  and 
31.18  g/m^/yr  after  dredging.  During  the  post- 
dredging  year,  18,780  kg  of  animal  production 
was  lost  from  the  0.32  km^  bottom  of  Goose  Creek. 

13.  The  productivity  of  island  II  was  considered 
representative  of  unspoiled  tall  Spartina  alterni- 
flora  marsh.  Animal  productivity  was  estimated 
at  42.44  g/m^/yr,  composed  almost  entirely  of 
Uca  pugnax,  Modiolus  demissus,  and  Sesarma 
reticulatum.  This  represented  5-7%  of  the  total 
productivity  figures  of  869.64  g/m^/yr.  The  gross 
estimate  for  mixed  peripheral  marsh  came  to 
4,553.57  kg/ha.  Using  this  figure  to  calculate  the 


476 


KAPLAN,  WELKER,  and  KRAUS:  EFFECTS  OF  DREDGING 


loss  of  productivity  represented  by  the  spoil 
areas  which  had  inundated  10.87  ha  of  marsh, 
49,497.31  kg  of  plant  matter  were  removed  from 
the  trophic  cycle  of  Goose  Creek  in  the  post- 
dredging  year. 

Replacement  by  houses  or  Phragmites  marsh 
would  tend  to  fix  this  loss  on  a  permanent  basis. 

In  summary,  reductions  in  the  productivity  of 
Goose  Creek  were  induced  by  the  dredging  pro- 
cess. Recovery  to  pre-dredging  levels  had  not 
occurred  11  mo  after  dredging.  Arguments  were 
proposed  which  suggested  that  changes  in  current 
velocity  and  the  concomitant  modifications  in 
substratum  type  represented  permanent  changes 
which  would  affect  the  future  productivity  of  the 
bay  by  changing  the  nature  of  the  habitat. 

Spoil  disposal  and  land  usage  changes  brought 
about  an  enhanced  land  value  of  the  disposal 
areas,  stimulating  the  development  of  the  peri- 
phery of  the  bay,  removing  or  depleting  the  marsh 
as  an  energy  source  available  to  the  aquatic 
environment.  These  changes  also  were  of  a  perma- 
nent nature. 

ACKNOWLEDGMENTS 

This  study  was  supported  in  part  by  a  grant 
from  Suffolk  County,  N.Y.  The  authors  are  grate- 
ful to  the  following  persons  for  assistance  in 
obtaining  samples:  John  Dinaro,  Paul  Laucher, 
Ed  Wainwright,  Pat  Langstone,  Paul  Salomans, 
and  Harry  White.  Edwin  J.  Sherrill,  Jr.,  designed 
the  vessel  and  saw  to  its  construction.  John 
Black  supplied  data  on  water  chemistry.  Walter 
Smith  originated  the  project. 

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1958.     Benthic  studies  in  Buzzards  Bay.     I.  Animal- 
sediment  relationships.     Limnol.  Oceanogr.  3:245-258. 
Sasaki,  R.  K. 

1967.  The  autecology  of  the  genus  Saxidomis  in  southern 
Humboldt  Bay,  California.  M.A.  Thesis,  Humboldt 
State  Coll.,  Areata,  Calif.,  43  p. 

Saz,  a.  K.,  S.  Watson,  S.  R.  Brown,  and  D.  L.  Lowery. 

1963.  Antimicrobial  activity  of  marine  waters.  I.  Macro- 
molecular  Nature  of  Antistaphylococcal  Factor.  Limnol. 
Oceanogr.  8:63-67. 

SlEGEL,  A. 

1966.  Equilibrium  binding  studies  of  zinc-glycine  com- 
plexes to  ion-exchange  resins  and  clays.  Geochim. 
Cosmochim  Acta.  30:757-768. 

1967.  A  new  approach  to  the  concentration  of  trace 
organics  in  seawater.  In  T.  A.  Olson  and  F.  J.  Burgess 
(editors).  Pollution  and  marine  ecology,  p.  235-256. 
John  Wiley  and  Sons,  N.Y. 

Stephens,  G.  C,  and  R.  A.  Schinske. 

1961.     Uptake  of  amino  acids  by  marine  invertebrates. 
Limnol.  Oceanogr.  6:175-181. 
Stickney,  a.  p.,  and  L.  D.  Stringer. 


1957.    A  study  of  the  invertebrate  bottom  fauna  of  Green- 
wich Bay,  R.I.  Ecology  38:111-122. 
Taylor,  J.  L.,  and  C.  H.  Saloman. 

1968.  Some  effects  of  hydraulic  dredging  and  coastal 
development  in  Boca  Ciega  Bay,  Florida.  U.S.  Fish 
Wild].  Serv.,  Fish.  Bull.  67:213-241. 

Teal,  J.  M. 

1962.     Energy  flow  in  the  salt  marsh  ecosystem  of 
Georgia.    Ecology  43:614-624. 
Townes,  H.  K.,  Jr. 

1939.     Ecological  studies  on  the  Long  Island  marine 

invertebrates  of  importance  as  fish  food  or  bait.  28th 

Annu.  Rep.,  1938,  State  N.Y.  Conserv.  Dep.,  14  (Suppl.): 

163-176. 

Udell,  H.  F.,  J.Zarudsky,T.  E.  Doheny,  andP.R.  Burkholder. 

1969.  Productivity  and  nutrient  values  of  plants  growing 
in  the  salt  marshes  of  the  Town  of  Hempstead,  Long 
Island.    Bull.  Torrey  Bot.  Club  96:42-51. 

Wilson,  D.  P. 

1938.  The  influence  of  the  substratum  on  the  meta- 
morphosis of  Notomastus  larvae.  J.  Mar.  Biol.  Assoc. 
U.K.  22:227-243. 
1953.  The  settlement  o{  Ophelia  bicornis  Savigny  larvae. 
The  1951  experiments.  J.  Mar.  Biol.  Assoc.  U.K. 
31:413-438. 
Wilson,  W.  B. 

1950.  The  effects  of  dredging  on  oysters  in  Capano  Bay, 
Texas.  Annu.  Rep.  Mar.  Lab.  Tex.  Game,  Fish  Oyster 
Comm.  1948-1949,  p.  1-50. 


Appendix  Table  I. — Faunal  list  for  Goose  Creek. 

Total  number  of  species  =  138. 


CNIDARIA— ANTHOZOA 

Haloclava  products^ 

Metndium  senile 

Sagartia  modesta'' 
PLATYHELMINTHES— TURBELLARIA 

Euplana  gracilus'' 
NEMERTINEA 

Amphiporus  caecus'' 

Carinoma  tremaphoros^ 

Cerebratulus  lacteus 

Zygeupolia  ru bens' 
ANNELIDA— POLYCHAETA 

Amphitnte  af finis'' 

A.  cirrata' 

A.  ornata' 

Arabella  iricolor 

Arenicola  cristata' 

Capitella  capitata 

Cirratulus  grandis 

Clymenella  mucosa'^ 

C.  torquata 

Dispio  uncinata 

Dnlonereis  longa 

Eteone  heteropoda'' 

E.  /acrea' 

E.  longa' 

Eumida  sanguinea 

Glycera  americana 

G.  dibranchiata 

Glycinde  sotitaria' 

Harmothoe  imbncata 

Lepidametria  commensalis'' 

Lumbrinens  tenuis 

Maldanopsis  elongata' 

Melinna  cristata 

Nephtys  picta 

Nereis  (Neanthes)  arenaceondonta' 

N.  (Hediste)  diversicolor' 

N.  (Neanthes)  succinea 


N.  (Neanthes)  virens' 
Notomastus  latericeus' 
Orbinia  omata' 
Pectinana  gouldii 
Phyllodoce  arenae' 
P.  groenlandica' 
Pista  cristata'' 
P  palmata 
Poly  dor  a  ligni' 
Prionspio  malmgreni'' 
Sabella  microphthalma' 
Scolecolepides  viridis' 
Scoloplos  fragilis 
S  robustus    - 
Spio  setosa 
Sthenelais  boa' 
Tharyx  acutus'' 
SIPUNCULOIDEA 

Golfingia  gouldi 
ARTHROPODA— CRUSTACEA 

Cirrjpedia 

Balanus  amphritrite  niveus' 

B.  balanoides 
Isopoda 
Chiridotea  almyra'' 

C.  caeca' 

Cyathura  polita  (  =  C.  carinata)' 

Amphipoda 

Ampelisca  macrocephala 

A.  abdita  {=Ampelisca  B.) 

A.  spinipes 

Gammarus  (=Carinogammarus)  mucronatus 

Microdeutopus  gryllotalpa 

Oecapoda 

Caridea 

Crangon  septemspinosus 

Hippolyte  pleuracanthus 
Palaemonetes  intermedius' 
P.  pugio 


P.  vulgaris 
Thallassinidea 

Callianassa  atlantica^ 

Upogebia  aftinis' 
Brachyura 

Neopanope  texana  sayi 

Ovalipes  ocellatus 

Pinnixa  chaetopterana' 

P.  cylindrica' 

P.  sayana 

Sesarma  reticulatum' 

Uca  pugilator 

U.  pugnax 
Anomura 

Pagurus  longicarpus 
MOLLUSCA 
Gastropoda 

Acteon  punctostriatus 

Alexia  myosotis' 

Bittium  alternatum 

Busy  con  carica^ 

B.  canaliculatum' 
Columbella  lunata'  ^ 

C.  translirata'  ^ 
Crepidula  fornicata 
Crepidula  plana' 
Eupleura  caudata 
Epitonium  multistriatum' 
Haminoea  solitaria 
Hydrobia  totteni' 
Littorina  littorea 

L.  obtusata 
L.  saxatilis 
Lunatia  heros 
Melampus  bidentatus' 
Melanella  oleacea' 
Nassarius  obsoletus 
N.  vibex' 
N.  trivittatus 


479 


FISHERY  BULLETIN:  VOL.   72,  NO.  2 


Odostomia  bisuturalis^ 
O.  seminuda 
Polinices  duplicatus 
Pyramidella  fusca''  ' 
Tornatina  canallculatum^ 
Triphora  nigrocincta''  ^ 
Urosalpinx  cinerea 

Pelecypoda 

Aequipecten  irradians 

Aligena  elevata^ 

Anadara  transversa' 

Anomia  simplex 

Clinocardium  cilialum  (=Cardium  islandicay 


Crassostrea  virginica' 
Cuminga  tellenoides'' 
Ensis  directus 
Gemma  gemma 
Laevicardium  mortoni'' 
Lyonsia  hyalma 
Macoma  balthica'' 
Mercenaria  mercenana 
Modiolus  demissus 
Mulmia  lateralis 
Mya  arenaria 
Nucula  proxima 
Pandora  gouldiana 
Petricola  pholadiformis 


Solemya  vellum'' 
Spisula  solidissima' 
Tagelus  plebeius'' 
Tellma  agilis 
Yoldia  limatula 

ECHINODERMATA— HOLOTHUROIDEA 
Leptosynapta  roseola^ 
Sclerodactyla  (  =  Thyone)  briareus 

CHORDATA-UROCHORDATA 
ASCIDIACEA 

Dendrodoa  ■arnea'' 
Molgula  manhattensis 
Styela  partita^ 


'Organisms  not  heretofore  reported  in  the  major  faunal  lists  of  Long 
Island  (Sanders.  1956;  Hechtel.  1968;  Townes.  1938. 

^Shells  only;  no  living  specimens  found 


480 


SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES, 
UROPHYCISCHUSS  AND  U.  TENUIS  (PISCES,  GADIDAE) 

IN  NEW  ENGLAND  12 


John  A.  Musick^ 


ABSTRACT 

The  seasonal  distribution  patterns  of  sibling  hakes,  Urophycis  chuss  and  U.  tenuis,  differ  from 
one  another  in  depth  and  geographic  area  and  within  each  species  by  life  history  stage. 

Urophycis  chuss  spawns  off  southern  New  England  in  depths  of  less  than  60  fm  and  probably 
at  temperatures  between  5°  and  10°C.  Two  major  spawning  concentrations  occur,  one  east  of  Block 
Island,  the  other  on  the  southwest  part  of  Georges  Bank.  Spawning  in  the  Gulf  of  Maine  probably 
occurs  inshore  at  depths  shoaler  than  30  fm.  After  spawning,  the  adult  fish  disperse  and  the  larger 
individuals  move  offshore  into  water  60  fm  or  deeper  where  the  mature  fish  remain  until  the 
following  spring.  Juvenile  U.  chuss  are  inquiline  within  sea  scallops,  Placopecten  magellanicus , 
until  they  outgrow  their  hosts  or  until  water  temperatures,  colder  than  about  4°C,  either  kill  the 
hake  or  force  them  to  seek  out  warmer  temperatures  in  deeper  water.  Immature  U.  chuss  remain 
in  the  vicinity  of  the  scallop  beds  if  water  temperatures  are  compatible  until  the  fish  are  in  their 
second  year  of  life.  During  that  autumn,  the  fish  migrate  inshore  to  within  30  fm  and  remain 
until  water  temperatures  drop  to  about  4°C,  at  which  time  they  move  to  warmer,  deeper  water 
along  the  offshore  shelf.  The  following  spring,  these  fish  migrate  inshore  with  the  older  adult  fish 
during  April  and  by  summer  are  mature  and  attain  the  typical  seasonal  behavior  of  adults.  Im- 
mature U.  tenuis  in  the  Gulf  of  Maine  occur  at  all  depths  but  tend  to  remain  in  shallower  water 
than  the  adults  during  the  winter.  Mature  U.  tenuis  migrate  inshore  in  the  northern  Gulf  of  Maine 
in  the  summer,  disperse  in  the  fall,  and  move  into  the  deepest  area  of  the  Gulf  in  winter.  Along 
the  eastern  edge  of  Georges  Bank  and  west  of  there,  both  immature  and  mature  U.  tenuis  are 
fish  of  the  continental  slope.  Both  stages  occur  over  the  shelf  in  small  numbers,  but  at  all  seasons 
the  highest  concentrations  are  found  deeper  than  100  fm.  The  distribution  patterns  of  these  two 
sibling  species  are  not  coincidental,  as  assumed  in  the  past.  Rather,  they  are  complementary. 
Urophycis  chuss  is  more  abundant  in  the  Mid-Atlantic  Bight,  whereas  U.  tenuis  is  more  abundant 
on  the  Scotian  shelf,  in  the  Gulf  of  St.  Lawrence,  and  on  the  Grand  Banks.  They  occur  together 
most  often  in  the  Gulf  of  Maine.  But  even  there,  U.  chuss  is  more  abundant  in  the  southwest  sector 
and  U.  tenuis  predominates  in  the  northern  part  and  in  the  Bay  of  Fundy. 


The  geographical  ranges  and  seasonal  movements 
of  the  red  hake,  Urophycis  chuss  (Walbaum), 
and  of  the  white  hake,  U.  tenuis  (Mitchill),  have 
not  been  defined  because  previous  workers  have 
had  difficulty  in  distinguishing  between  the  two 
species  (Musick,  1973).  The  purpose  of  the  present 
paper  is  to  examine  the  validity  of  published 
accounts  of  the  ranges  off/,  chuss  and  U.  tenuis; 
to  compare  the  seasonal  distribution  of  the  two 
species  with  regard  to  depth,  bottom  temperature, 
and  substrate  in  New  England  waters;  and  to 
determine  whether  the  patterns  of  seasonal  dis- 
tribution vary  among  juvenile,  immature,  and 
adult  stages  (these  stages  are  defined  below). 


'  Contribution  Number  562  of  the  Virginia  Institute  of 
Marine  Science. 

*  This  paper  contains  parts  of  a  Ph.D.  dissertation  submitted 
to  Harvard  University. 

'  Virginia  Institute  of  Marine  Science,  Gloucester  Point,  VA 
23062. 


Two  recent  faunal  works  treat  both  species 
together  and  give  the  northern  limit  of  distribu- 
tion of  U.  chuss  and  U.  tenuis  as  Labrador 
(Leim  and  Scott,  1966)  or  the  Grand  Banks  of 
Newfoundland  (Bigelow  and  Schroeder,  1953). 
However  neither  documentation  nor  voucher 
specimens  are  available  to  establish  the  presence 
of  U.  chuss  off  Labrador  or  on  the  Grand  Banks 
(as  there  are  for  U.  tenuis).  Kendall  (1909)  re- 
ported U.  tenuis  from  Labrador,  and  the  New- 
foundland Fisheries  Research  Commission  (1932, 
1933,  1934)  captured  U.  tenuis  along  the  south- 
western edge  of  the  Grand  Banks  during  warmer 
months  of  the  year.  Templeman  (1966)  reported 
that  all  Urophycis  taken  commercially  on  the 
Grand  Banks  have  been  U.  tenuis  (1966)  and 
that  he  had  never  seen  a  specimen  of  U.  chuss 
from  Newfoundland  waters  (pers.  comm.).  Jordan 
and  Evermann  (1898)  and  Breder  (1948)  gave  the 


Manuscnpt  accepted  September  1973. 
FISHERY  BULLETIN;  VOL.  72.  NO.  2.  1974. 


481 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


northern  limit  of  U.  chuss  as  the  Gulf  of  St. 
Lawrence,  apparently  on  the  basis  of  reports  of 
U.  chuss  (under  the  name  of  Phycis  americanus 
(Block  and  Schneider))  from  the  Gulf  of  St.  Law- 
rence by  H.  R.  Storer  ( 1850),  Fortin  (1863),  Knight 
(1866),  and  Gilpin  ( 1867).  These  authors,  however, 
had  followed  the  nomenclatural  usage  of  D.  H. 
Storer  (1839,  1846,  1858)  whose  descriptions  of 
Phycis  americanus  from  Massachusetts  obviously 
referred  to  U.  tenuis  because  of  the  large  size  of 
his  specimens  (Musick,  1973).  Similarly  all  other 
reports  off/,  chuss  from  the  Gulf  of  St.  Lawrence 
are  based  on  nomenclatural  errors  or  were  made 
by  workers  (Cox,  1905,  1921;  Cornish,  1907, 
1912;  Craigie,  1916,  1927;  Vladykov  and  Trem- 
blay,  1935;  Vladykov  and  McKenzie,  1935;  Mc- 
Kenzie,  1959;  and  Vladykov  and  McAllister,  1961) 
who  by  their  own  admission  or  by  the  species 
descriptions  they  published  had  shown  their  in- 
ability to  distinguish  between  U.  chuss  and  U. 
tenuis  (Musick,  1969). 

Urophycis  chuss  is  absent  from  or  very  rare  in 
the  Gulf  of  St.  Lawrence.  Several  thousand 
specimens  of  Urophycis  examined  at  Souris, 
Prince  Edward  Island,  in  August  1966  were  all 
U.  tenuis  (Musick,  1973).  Juvenile  and  post- 
larval  Urophycis  captured  in  the  Gulf  of  St. 
Lawrence  by  Fisheries  Research  Board  of  Canada 
personnel  from  St.  Andrews,  New  Brunswick, 
and  sent  to  me  for  identification  were  all  U. 
tenuis.  Several  hundred  Urophycis  examined  on  a 
cruise  of  the  RV  Prince  in  the  Northumberland 
Straits  and  Magdalen  shallows  in  September  1972 
were  all  U.  tenuis  (K.  Able,  pers.  comm.). 

The  Newfoundland  Fishery  Research  Commis- 
sion captured  one  U.  chuss  (a  pelagic  juvenile) 
and  many  U.  tenuis  (benthic  adults)  on  the 
Scotian  shelf  between  Sable  Island  and  Ban- 
quereau  Banks  (Newfoundland  Fisheries  Re- 
search Commission,  1932).  Similarly,  trawl  col- 
lections made  from  RV  Albatross  IV  on  the 
Scotian  shelf  in  March  1969  and  1970  and  Novem- 
ber 1969  (J.  McEachran,  pers.  comm.)  contained 
few  U.  chuss  and  many  U.  tenuis.  Trawl  col- 
lections made  from  RV  Cameron  between  Canso, 
Nova  Scotia,  and  Banquereau  Bank  in  August 
1970  and  1971  contained  very  few  U.  chuss  but 
many  U.  tenuis  (C.  Wenner  and  J.  McEachran, 
pers.  comms.).  To  my  knowledge  the  most  north- 
eastern locality  from  which  voucher  specimens 
of  U.  chuss  are  available  is  lat.  43°39'N,  long. 
59°26.5'W  (Virginia  Institute  of  Marine  Science 
lot  No.  01957)  collected  by  otter  trawl  from  RV 


Cameron,  14  July  1971,  at  a  depth  of  197  m. 
Both  U.  chuss  and  U.  tenuis  have  been  reported 
frequently  from  the  Gulf  of  Maine  and  the  Mid- 
Atlantic  Bight  as  far  south  as  Cape  Hatteras, 
N.C.  (Musick,  1969). 

Svetovidov  (1955)  classified  Phycis  borealis 
Saemundson  1913,  an  Icelandic  form,  as  a  junior 
synonym  off/,  tenuis.  Icelandic  specimens  exam- 
ined during  my  study  confirm  Svetovidov's  taxo- 
nomic  judgment  and  document  the  range  exten- 
sion of  the  species  to  Iceland.  Similarly  Bullis 
and  Thompson  (1965)  reported  U.  tenuis  from  the 
continental  slope  of  the  east  coast  of  Florida.  I 
examined  these  specimens  and  confirm  their 
identification  as  U.  tenuis. 

Fraser-Brunner  (1925)  reported  two  small  speci- 
mens of  U.  chuss  from  the  Irish  Atlantic  slope 
but  was  not  certain  of  their  identity:  "Two  small 
specimens  [25  and  55  mm  standard  length] 
apparently  referable  to  this  species  (U.  chuss) 
were  taken  in  the  tow  net  near  the  surface  .  .  .  ." 
Urophycis  chuss  of  this  size  were  considered  to  be 
unidentifiable  by  American  workers  such  as 
Bigelow  and  Welsh  (1925)  who  had  many  oppor- 
tunities to  examine  small  specimens.  It  is  probable 
that  Fraser-Brunner's  postlarvae  were  a  species 
of  Phycis,  not  Urophycis. 

The  known  ranges  of  the  two  species  can  now 
be  summarized:  U.  chuss  occurs  on  the  continental 
shelf  from  southern  Nova  Scotia  to  North  Carolina 
and  may  stray  to  the  Gulf  of  St.  Lawrence. 
Urophycis  tenuis  occurs  on  the  continental  shelf 
and  slope  from  Iceland,  Labrador,  and  the  Grand 
Banks  of  Newfoundland  to  the  coast  of  North 
Carolina,  straying  as  far  south  as  Florida  in  deep 
water. 

Sampling  Procedures 

Data  for  a  study  of  the  seasonal  distribution 
patterns  off/,  chuss  and  U.  tenuis  were  collected 
during  a  groundfish  survey  conducted  by  the 
National  Marine  Fisheries  Service  at  Woods 
Hole,  Mass.  The  survey  consisted  of  nine  seasonal 
cruises  by  RV  Albatross  IV  from  the  mouth  of 
the  Bay  of  Fundy  to  Hudson  Canyon.  Approxi- 
mately 1,800  fishing  stations  were  occupied,  and 
cruises  were  conducted  during  the  summer  and 
fall  in  1963,  1964,  and  1965  and  during  the 
winter  in  1964,  1965,  and  1966. 

The  survey  area  was  divided  into  42  sampling 
strata  according  to  depth  (Figure  1),  and  stations 
were  located  randomly  within  strata.  A  No.  36 


482 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


<i-^^^^^ 


'---^ 


Figure  1. — Sampling  strata  where  collections  were  made  during  the  RV  Albatross  IV 
groundfish  surveys.  (After  Grosslein,  1969.) 


Yankee  otter  trawl  with  a  cod-end  liner  (mesh 
diameter  one-half  inch  stretched)  was  towed  on 
the  bottom  for  one-half  hour  at  each  station. 
Towing  speed  was  approximately  3.5  knots.  The 
sampling  method  and  design  were  described  in 
detail  by  Grosslein  (1969).  Length  of  specimens 
reported  in  the  present  paper  is  total  length 
unless  noted  otherwise. 

Factors  Analyzed 

Life  History  Stages 

The  following  summary  of  the  life  histories  of 
U.  chuss  and  U.  tenuis  is  extracted  from  Musick 
(1969).  Urophycis  chuss  has  pelagic  eggs  and 
pelagic  larvae  that  descend  to  the  bottom  at  a 
length  of  about  35  to  40  mm.  The  young  then 
live  within  the  mantle  cavity  of  the  sea  scallop, 
Placopecten  magellanicus.  The  largest  U.  chuss 
thus  far  found  inside  Placopecten  have  been  130 
to  140  mm  long.  Urophycis  chuss  becomes 
mature  at  about  290  mm  in  length.  The  otter 
trawl  used  in  the  present  study  catches  no  eggs 
or  larvae  and  very  few  pelagic  juveniles;  there- 
fore, the  life  history  off/,  chuss  was  divided  into 
three  demersal  stages  defined  by  length:  juvenile, 
« 14  cm;  immature,  15-28  cm;  and  mature,  ^29  cm. 
Urophycis  tenuis  has  pelagic  eggs  and  pelagic 
larvae  which  migrate  to  the  bottom  at  a  length 
of  about  80  mm  (or  smaller  sizes  in  shallow 
harbors  and  estuaries).  Urophycis  tenuis  grows 
much  larger  than  U.  chuss  and  matures  at  about 


500  mm  in  length.  The  life  history  can  be 
divided  into  only  two  stages  by  length  in  the 
present  study  because  of  the  notable  lack  of 
young  fish  in  the  trawl  collections:  immature, 
9-50  cm;  and  mature,  2=51  cm.  The  biology  of  these 
species  does  not  change  abruptly  in  all  indi- 
viduals at  a  certain  size.  The  size  range  over 
which  major  biological  changes  occur  may  be  quite 
broad  in  populations  of  these  Urophycis,  but  most 
of  the  individuals  in  the  population  within  the 
size  ranges  cited  above  are  also  within  the  cor- 
responding ontogenetic  stage.  By  classifying  indi- 
viduals into  life  history  stage  by  size,  it  is  pos- 
sible to  use  length-frequency  data  to  determine 
whether  the  geographical  distribution  patterns 
of  species  change  during  ontogeny. 

Natural  Divisions  of  the  Study  Area 

The  survey  region  was  divided  into  two  natural 
subareas  according  to  topography  and  hydrog- 
raphy. The  southern  New  England  subarea 
includes  sampling  Strata  1  to  19,  i.e.,  the  southern 
parts  of  Georges  Bank,  Nantucket  Shoals,  and 
the  Mid-Atlantic  Bight  as  far  south  as  Hudson 
Canyon.  The  Gulf  of  Maine  subarea  includes 
sampling  Strata  20  to  40,  i.e.,  the  Gulf  of  Maine 
including  the  northern  edge  of  Georges  Bank  and 
Browns  Bank  (Figure  1). 

Topography 

The  southern  New  England  subarea  is  char- 
acterized by  a  broad,  shallow  continental  shelf 


483 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


that  slopes  gently  seaward  to  about  the  100- 
fathom  (fm)  isobath,  the  point  sometimes  desig- 
nated as  the  shoreward  limit  of  the  continental 
slope.  The  slope  itself  declines  much  more  steeply 
to  the  abyssal  plain  below.  The  distance  between 
the  100-  and  1,000-fm  isobaths  is  17  miles  off 
New  York  City,  16  miles  off  Martha's  Vineyard, 
and  no  more  than  20  miles  along  the  southern 
edge  of  Georges  Bank.  The  width  of  the  conti- 
nental shelf  "out  to"  the  100-fm  isobath  is  104 
miles  off  New  York  City  and  76  miles  off  Martha's 
Vineyard.  Most  of  the  southern  New  England 
subarea  is  contained  within  the  60-fm  isobath. 
The  Gulf  of  Maine  is  a  basin  of  irregular  relief 
within  the  continental  shelf,  surrounded  by  a 
shallow  sill  formed  by  Georges  Bank  on  the  south- 
east, Browns  Bank  on  the  east,  and  the  Seal 
Island  Banks  on  the  northeast.  The  sill  in  turn  is 
pierced  by  three  narrow  channels,  which  have 
been  named  according  to  their  locations:  the 
Great  South  Channel,  40  fm  maximum  depth; 
the  Eastern  Channel,  128  fm  maximum  depth; 
and  the  Northern  Channel,  65  fm  maximum 
depth.  Most  of  the  Gulf  of  Maine  is  deeper  than 
60  fm,  and  the  central  Gulf,  occupied  by  a  Y- 
shaped  trough,  is  deeper  than  100  fm.  The  topog- 
raphy of  the  Gulf  of  Maine  has  been  discussed 
in  detail  by  Bigelow  (1927). 

Temperature 

The  following  description  of  seasonal  thermal 
regimes  is  compiled  from  Bigelow  (1927,  1933) 
and  original  data  collected  during  the  Alba- 
tross IV  surveys.  The  southern  New  England 
subarea  has  extreme  seasonal  temperature 
changes  related  to  its  shallowness.  Bottom  tem- 
peratures reach  an  annual  minimum  in  late 
February  or  early  March,  and  are  lowest  in  the 
shoal  waters  close  to  shore  and  on  Georges  Bank 
and  highest  at  the  edge  of  the  continental  shelf 
(Figure  2).  Spring  warming  proceeds  most  rapidly 
in  the  shallowest  water.  By  early  summer, 
thermal  stratification  occurs  and  prevents  the 
bottom  water  from  warming  at  intermediate 
depths  (20  to  60  fm)  which  remain  at  4°  to  8°C 
(cooler  than  both  the  shoaler  depths  inshore  and 
the  deeper  slope  water  offshore)  (Figure  3). 

Bottom  temperatures  in  shallow  areas  attain 
the  annual  maximum  by  the  beginning  of  fall. 
However,  in  intermediate  depths  the  maximum 
is  not  reached  until  the  thermocline  is  broken 
down,  usually  during  October  or  November 


AVERAGE     WINTER    BOTTOM    TEMPERATURES    CO 
ALBATROSS     IV    GROUNDFISH    SURVEYS    64-1.65-284.66-1 


Figure  2. — Average  winter  bottom  temperatures  compiled 
from  RV  Albatross  IV  groundfish  surveys  64-1,  65-2,  65-4, 
and  66-1. 


(Figure  4).  Winter  cooling  proceeds  more  rapidly 
in  shoal  water  than  at  intermediate  depths. 
Depths  beyond  60  fm  under  the  influence  of  slope 
water  have  relatively  little  fluctuation  in  bottom 
temperatures  throughout  the  year. 

In  the  Gulf  of  Maine,  seasonal  thermal  changes 
on  the  bottom  are  most  pronounced  in  the  shoaler 
areas.  Also,  the  banks  on  the  Nova  Scotian  shelf 
are  generally  cooler  by  a  few  degrees  than  those 
to  the  west,  because  of  the  influence  of  the  cold 
coastal  current.  Bottom  temperatures  over  most  of 
the  Gulf  are  more  stable  than  those  off"  southern 
New  England,  because  the  deeper  Gulf  water  is 
made  up  in  part  of  warm  moderating  slope  water 
which  enters  by  way  of  the  Eastern  Channel. 

Procedures  of  Analysis 

Life  History  Stage  by  Sampling  Strata 

An  analysis  was  performed  to  determine  geo- 
graphical and  bathymetric  distribution  of  U. 
chiiss  and  U.  tenuis  by  life  history  stage  and 
season.  Taylor  (1953),  Moyle  and  Lound  (1960), 
and  Roessler  (1965)  demonstrated  that  fish  are  not 
randomly  distributed,  but  that  the  sampling 
distribution  of  the  number  of  individuals  of  a 
species  taken  per  sample  in  a  series  of  col- 
lections is  contagious  and  may  be  best  approxi- 
mated by  the  negative  binomial  distribution.  The 
natural  log  transformation  y  =  In  (x  +  1),  where 
jc  represents  the  number  of  individuals  of  a  species 
taken  at  each  station,  tends  to  "normalize"  the 
negative  binomial  distribution  and  substantially 


484 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


AVERAGE    SUMMER    BOTTOM    TEMPERATURES    <°C) 
ALBATROSS    IV    GflOUNDFISH    SURVEYS    63-5. 64-10. 65-10 


Figure  3. — Average  summer  bottom  temperatures  compiled 
from  RV  Albatross  IV  groundfish  surveys  63-5,  64-10,  65-10. 


reduces  correlation  between  the  mean  and  the 
variance  (Pereyra,  Heyamoto,  and  Simpson,  1967). 
An  index  of  numerical  abundance  of  U.  chuss 
and  U.  tenuis  was  computed  for  each  stratum 
by  applying  the  above  logarithmic  transformation 
to  each  catch  and  calculating  the  transformed 
mean  catch  per  stratum.  Catch  data  from  all 
3  yr  were  pooled  by  season  of  collection,  because 
U.  tenuis  did  not  occur  frequently  enough  or  in 
large  enough  numbers  to  allow  calculation  of 
reliable  estimates  of  mean  abundance  in  some 
strata  on  the  basis  of  single  cruises.  Thus  the 
analysis  estimates  average  seasonal  distribution 
for  a  3-yr  period  probably  with  little  distortion 
because  hydrographic  conditions  in  the  principal 
areas  of  hake  concentration  did  not  differ  drasti- 
cally among  the  3  yr. 


AVERAGE    FALL    BOTTOM    TEMPERATURES    (°C) 
ALBATROSS     IV    GROUNDFISH     SURVEYS    63-7,64-13,65-14 


Analysis  of  Temperature  and  Distribution 

The  mean  catch  per  tow  at  each  1°C  temperature 
interval  was  computed  by  species,  life  history 
stage,  subarea,  and  season.  A  few  temperature 
intervals  were  not  sufficiently  sampled  to  provide 
reliable  estimates  of  mean  abundance. 

RESULTS  AND  DISCUSSION 

Seasonal  Distribution  of  U.  chuss 

Juvenile  («14  cm)  U.  chuss  were  rarely  cap- 
tured during  summer  cruises  because  young-of- 
the-year  were  pelagic  and  unavailable  to  the 
trawl,  and  most  yearlings  had  grown  larger  than 
14  cm  and  were  classified  as  immature  fish 
(Figure  5).  In  the  fall  juvenile  U.  chuss  were 
most  abundant  off  southern  New  England  at 
depths  shoaler  than  60  fm  (Figure  6).  Their 
distribution  coincides  with  that  of  the  sea  scallop, 
Placopecten  magellanicus,  which  serves  as  a  host 
to  the  young  inquiline  U.  chuss  (Musick,  1969). 
The  shoreward  distribution  of  Placopecten  is 
limited  by  temperature  off  southern  New  Eng- 
land. Dickie  (1958)  found  the  upper  lethal  range 
to  be  20°  to  23.5°C,  temperatures  which  occur 
normally  in  the  summer  in  the  shallow  bays 
and  sounds  of  southern  New  England.  In  the  cooler 
Gulf  of  Maine,  Placopecten  are  most  abundant  in 
inshore  areas  shoaler  than  30  fm  and  occur  com- 
monly in  shallow  bays  (Dow  and  Baird,  1960; 
Bourne,  1964).  Thus  in  the  Gulf  of  Maine,  the 


SUMMER 
<  14  cm.  Total  length 


0 

□  <-0.24 

□  0.25-0.99 


Figure  4. — Average  fall  bottom  temperatures  compiled  from 
RV  Albatross  IV  groundfish  surveys  63-7,  64-13,  and  65-14. 


Figure  5. — Distribution  and  abundance  of  juvenile  Urophycis 
chuss  during  the  summer.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


485 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


FALL 
<  14  cm  Total  tength 


Figure  6. — Distribution  and  abundance  of  juvenile  Urophycis 
chuss  during  the  fall.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


Placopecten  habitat  (the  U.  chuss  nursery)  was 
not  sampled  because  no  strata  were  shallower 
than  30  fm;  consequently  estimates  of  juvenile 
hake  abundance  were  low. 

Juvenile  U.  chuss  appear  to  avoid  water  colder 
than  4^  (Figure  7).  In  winter  (Figure  8),  abun- 
dance of  juvenile  U.  chuss  increased  in  the  Gulf 
of  Maine  probably  because  the  temperature  on  the 
inshore  Placopecten  beds  had  dropped  below  4°C, 
prompting  the  young  U.  chuss  to  migrate  into 
deeper  water  where  they  became  available  to  our 
sampling  gear.  Juvenile  U.  chuss  were  absent  in 
winter  from  the  shoaler  Georges  Bank  strata 
where  bottom  temperatures  were  below  4°C.  The 
winter  temperature  histogram  for  the  Gulf  of 
Maine  shows  juvenile  U.  chuss  to  be  fairly  abun- 
dant at  3°C  (Figure  7).  This  apparent  contradic- 
tion to  the  rest  of  the  data  is  attributable  to  a 
single  large  trawl  catch  at  3X.  The  winter  distri- 
bution pattern  of  juvenile  U.  chuss  off  southern 
New  England  was  similar  to  the  fall  pattern 
(Figure  8).  Abundance  values  were  lower,  prob- 
ably because  of  natural  mortality  and  growth 
of  some  juveniles  beyond  14  cm  in  length. 

During  the  summer,  immature  (15  to  28  cm) 
U.  chuss  were  abundant  from  the  southern  part 
of  Georges  Bank  throughout  the  southern  New 
England  area  at  depths  of  60  fm  or  less.  Almost 
no  immature  fish  were  taken  at  depths  of  100 
fm  or  more  off  southern  New  England  (Figure  9). 
Fish  were  most  abundant  at  depths  of  30  fm  or 
less  between  Martha's  Vineyard  and  Long  Island 
(Stratum  5).  In  the  Gulf  of  Maine,  the  heaviest 


»^'r  I 


GULF     OF     MAINE 

FALL 


WINTERc^ 


J  «    5   6    7    8  9   10  II    12  13  14  3  4  5    6    7  8   9  (0  II  12  U  K  15  2    3  4  5  6    7 


SOUTHERN     NEW     ENGLAND 


a 


I .,., 


3 

L 


3|r-lM292^22  4   I      I 


5... 


I 


4    5   6    7    8   9   10  II   12    13  14  15  16  4    5    6    7    8   9    lO  U  l2   13  l4  l5 

TEMPERATURE     (°C  ) 


lier^s 


234567    69   10  I 


Figure  7. — Seasonal  catch  per  tow  of  juvenile  Urophycis 
chuss  taken  off  southern  New  England  and  the  Gulf  of  Maine. 
Abundance  data  are  stratified  by  temperature  intervals  of  one 
degree  (C).  The  total  number  of  individuals  captured  during 
each  season  =  n.  The  number  of  stations  occupied  at  each 
temperature  is  indicated  above  each  respective  histogram  bar. 

concentrations  of  fish  were  found  in  the  Great 
South  Channel  (Stratum  23).  Moderate  numbers 
were  taken  in  the  deeper  strata  to  the  north  of 
the  channel  area  and  in  shoal  water  on  Georges 
Bank. 


WINTER 
<  14  cm  Total  length 


Figure  8. — Distribution  and  abundance  of  juvenile  Urophycis 
chuss  during  the  winter.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


486 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


'j. 

.o'' 

U.chuss 

SUMMER 

15-28  on.  Totol  length 

>i^ 

^/^ 

^Hb^       8' jV^ 

ij^ 

^^5\ 

^K/Ny.t,<J<J 

^^^^TN 

a)  '^Tlf^^'^ 

■^  yimlm  \ 

\ 

Hi  0 

\j?l^ 

^^ 

□   <-0.24 

^^'^^--T'"^""""— i—^ 

kJ 

Q  0.25-0.99 

^'iwV 

Ikd 

■   1.00-2.49 

^*I^^«^ 

-J 

■   >2.S0 

^*^"i.£iu^ 

i°- 

'o. 

*> 

Figure  9. — Distribution  and  abundance  of  immature  Urophy- 
cis  chuss  during  the  summer.  Abundance  in  each  sampling 
stratum  is  indicated  on  a  log  scale. 

The  fall  distribution  pattern  off  southern  New 
England  (Figure  10)  suggests  a  movement  inshore 
which  is  further  substantiated  by  an  increase  of 
U.  chuss  in  the  inshore  industrial  fisheries  land- 
ings in  October  and  November  (Edwards  and  Lux, 
1958;  Edwards,  1958a,  1958b;  Edwards  and  Law- 
day,  1960).  Edwards  (pers.  comm.)  has  noted  that 
this  fall  fishery  off  southern  New  England  landed 
mostly  small  hake.  Also  reports  by  Smith  (1898) 
for  Woods  Hole;  Latham  (1917)  for  Orient,  Long 
Island;  Breder  (1922)  for  Sandy  Hook  Bay;  and 
Hildebrand  and  Schroeder  (1928)  for  the  New 
Jersey  coast  and  New  York  Bay  document  an 
immigration  of  U.  chuss  in  these  inshore  areas 
in  the  fall  with  an  emigration  in  the  winter. 


In  the  Gulf  of  Maine,  immature  U.  chuss  were 
moderately  abundant  in  the  fall  around  the  entire 
perimeter  in  strata  shoaler  than  60  fm. 

The  winter  distribution  of  immature  U.  chuss 
was  essentially  limited  to  those  strata  deeper  than 
30  fm  off  Long  Island,  60  fm  off  Nantucket,  and 
100  fm  along  the  southern  edge  of  Georges  Bank 
(Figure  11).  In  the  Gulf  of  Maine  immature  U. 
chuss  were  moderately  abundant  in  strata  deeper 
than  60  fm.  Concentrations  occurred  between 
60  and  100  fm  along  the  northern  edge  of  Georges 
Bank  and  off  Massachusetts  Bay  and  Jeffries 
Ledge  (Stratum  27).  The  only  strata  shoaler  than 
60  fm  with  moderate  values  of  abundance  were 
26  and  40,  located  in  the  southwestern  part  of  the 
Gulf  where  temperatures  were  warmer  than  to  the 
north  and  east. 

Immature  U.  chuss  were  taken  during  three 
seasons  within  the  entire  temperature  range 
with  the  exception  of  the  highest  intervals  (15°  to 
16°C),  which  were  inadequately  sampled  (Figure 
12).  Most  immature  fish  were  taken  between  5° 
and  13°C.  As  with  the  juveniles,  immature  U. 
chuss  were  absent  from  the  shallow  parts  of 
Georges  Bank  during  the  winter  and  they  may 
avoid  water  colder  than  4°C.  Edwards  (1965) 
noted  that  in  the  late  fall  most  U.  chuss  had 
migrated  from  the  inshore  industrial  fishing 
grounds  when  the  water  temperature  dropped 
to  5°C. 

Adult  U.  chuss  migrate  inshore  in  the  spring 
of  the  year.  Smith  (1898)  reported  U.  chuss  to  be 
abundant  at  Woods  Hole  in  May  or  June  but  rare 


FALL 
15-28  cm.  Total  length 


Figure  10. — Distribution  and  abundance  of  immature  Urophy- 
cis  chuss  during  the  fall.  Abundance  in  each  sampling 
stratum  is  indicated  on  a  log  scale. 


^r 


WINTER 
15-28  cm  Totol  length 


Figure  11. — Distribution  and  abundance  of  immature  Uro- 
phychis  chuss  during  the  winter.  Abundance  in  each  sampling 
stratum  is  indicated  on  a  log  scale. 


487 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


in  the  summer.  Latham  (1917)  reported  U.  chuss 
from  Orient,  Long  Island,  in  the  spring  but  not 
summer.  Breder  ( 1922)  noted  U.  chuss  from  Sandy 
Hook  Bay  in  the  spring;  and  Hildebrand  and 
Schroeder  (1928)  reported  that  off  New  Jersey 
and  New  York  U.  chuss  appeared  in  April,  dis- 
tended with  spawn,  that  they  remained  close 
inshore  for  a  short  period,  were  caught  2  to  6 
miles  off  until  late  May,  and  in  July  were 
abundant  offshore  on  Cholera  Bank.  Edwards 
and  Lawday  (1960)  reported  that  U.  chuss  were 
abundant  in  the  industrial  fish  landings  in  April 
and  May  from  the  shallow  inshore  fishing  grounds 
off  No  Man's  Land,  Mass.,  and  Point  Judith,  R.L 
The  fish  dispersed  in  June  and  July  and  were 
less  available  to  the  fishery. 

After  they  migrate  inshore  in  the  spring, 
southern  New  England  U.  chuss  migrate  offshore 
in  the  summer  to  spawn.  Mature  U.  chuss  were 
heavily  concentrated  during  the  summer  (Figure 
13)  in  the  strata  shoaler  than  60  fm  off  Block 
Island  and  on  the  southwest  part  of  Georges  Bank. 


GULF    OF     MAINE 


sxjmmeb 

0  =  309 


FALL 


WINTER 


78 


pj 

4 

1 

I  5  e  7  e  9  to  II  12  [3  14  c  e 


4  5  6   7  a  9  10  II  12  13  14  15 

TEMPERATURE       (°C  ) 


25456789  10  I 


Figure  12. — Seasonal  catch  per  tow  of  immature  Urophycis 
chuss  taken  off  southern  New  England  and  the  Gulf  of 
Maine.  Abundance  data  are  stratified  by  temperature  intervals 
of  one  degree  (C).  The  total  number  of  individuals  captured 
during  each  season  =  n.  The  number  of  stations  occupied  at 
each  temperature  is  indicated  above  each  respective  histo- 
gram bar. 


'J. 

-1°" 

U  chuss 

SUMMER 

K?-S-^ 

>  29  cm  Total  length 

'--t>^ 

V,  i^ti. 

V    > 

"^ 

WiM^ 

i-'X 

111 

^~-  fi- 

Iffl  0                              \\ 

^^fe^ 

s^ 

0 

n   5-0.24                           ^ 

^^^)^^^^^ 

^                 NX 

yJltttk 

7 

□  0.25-0.99 

"v^^^H 

-                      > 

ij      WitlUk 

/ 

■  1.00-2.49 

^^^5^- 

__y^ 

i^-^ 

■   >2.S0 

^=^^ 

—^ 

•v°° 

'o. 

*?■ 

Figure  13. — Distribution  and  abundance  of  mature  Urophycis 
chuss  during  the  summer.  Abundance  in  each  sampling  stra- 
tum is  indicated  on  a  log  scale. 

These  concentrations  were  probably  spawning 
aggregations  because  ripe  fish  were  taken  quite 
frequently  during  the  survey  (Musick,  1969). 
Also  Domanevsky  and  Nozdvin  (1963)  reported 
spawning  aggregations  of  U.  chuss  offshore  on 
Georges  Bank  in  July  and  August.  Although  a 
small  number  oft/,  chuss  remain  in  the  southern 
New  England  sounds  during  the  summer  (Ed- 
wards and  Lawday,  1960),  these  are  probably 
immature  fish  because  spawning  does  not  occur 
there.  Wheatland  (1956)  found  no  U.  chuss  eggs 
or  larvae  in  Long  Island  Sound,  and  Merriman 
and  Sclar  ( 1952)  took  no  eggs  but  captured  larvae 
in  Block  Island  Sound,  an  area  less  land-locked 
and  more  adjacent  to  deep  water  than  the  previous 
one. 

U.  chuss  emigration  from  shallow  southern 
New  England  waters  to  offshore  spawning 
grounds  is  probably  correlated  with  temperature. 
Figure  14  shows  that  U.  chuss  were  not  abundant 
within  adequately  sampled  temperature  intervals 
higher  than  12°C.  Riley  ( 1956)  noted  that  temper- 
atures exceeded  12°C  over  most  of  Long  Island 
Sound  during  June  and  increased  until  October 
when  temperatures  were  in  excess  of  20°C.  Ed- 
wards, Livingstone,  and  Hamer  (1962)  reported 
that  during  the  summer  off  southern  New  Eng- 
land U.  chuss  were  most  abundant  at  about  9°C, 
and  Edwards  (1965)  showed  that  U.  chuss  mi- 
grated offshore  when  the  bottom  temperature 
reached  about  10°C  in  the  early  summer. 

In  the  Gulf  of  Maine  U.  chuss  became  avail- 
able to  the  shallow  water  trawl  fishery  off 
Gloucester  and  Ipswich,  Mass.,  in  April  or  May 


488 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


GULF    OF    MAINE 


SUMMER 
n-  709 


,^^. 


WINTER 
n:976 


25 


3   4   5  6    7  a  9  '0' I  12  13  14  3  4  5  6  7  8  9  10  M  I2  13  14  15  2    J  4  5  6  7 


SOUTHERN    NEW    ENGLAND 


j  t*^ 


^ 


4   5  6  7  8    9  <0  I)  [2  13  14  15  16 


4    S   6  7   a   9  O  II   12  1314   15 

TEMPERATURE      (°C) 


nil 


S456789I0I 


Figure  14. — Seasonal  catch  per  tow  of  mature  Urophycis 
chuss  off  southern  New  England  and  the  Gulf  of  Maine. 
Abundance  data  are  stratified  by  temperature  intervals  of  one 
degree  (C).  The  total  number  of  individuals  captured  during 
each  season  =  n.  The  number  of  stations  occupied  at  each 
temperature  is  indicated  above  each  respective  histogram  bar. 

(Edwards,  1958a;  Edwards  and  Lawday,  1960) 
and  increased  in  abundance  until  August.  Thus 
mature  U.  chuss  are  abundant  in  the  summer  at 
depths  less  than  30  fm.  The  Albatross  IV  survey 
data  (Figure  13)  which  show  highest  values  of 
abundance  in  strata  60  fm  and  deeper  are 
probably  not  indicative  of  the  true  summer  dis- 
tribution off/,  chuss.  Both  the  industrial  fishery 
and  region  of  greatest  abundance  in  the  Albatross 
IV  survey  are  in  the  southwestern  section  of  the 
Gulf,  but  the  fishery  and  survey  data  were  taken 
at  different  depths.  Additional  evidence  that  U. 
chuss  congregate  in  the  summer  at  depths  less 
than  30  fm  comes  from  Bigelow  and  Schroeder 
(1953).  They  noted  that  U.  chuss  spawns  in  the 
Gulf  in  the  summer  and  that  most  eggs  and  larvae 
have  been  collected  close  to  shore.  Water  tem- 
peratures inshore  are  comparable  to  those  that 
occur  in  known  offshore  spawning  areas  of  U. 
chuss  off  southern  New  England  (5°-10°C).  Similar 
temperatures  also  occur  in  deeper  waters  of  the 
Gulf,  but  young  U.  chuss  spawned  in  such  areas 
would  have  little  chance  of  finding  Placopecten 
for  shelter  after  descending  because  Placopecten 
is  restricted  to  shoal  areas  of  the  Gulf  (Dow  and 
Baird,  1960).  Therefore,  there  may  be  selection 


for  inshore  spawning  in  the  Gulf  of  Maine. 

During  the  fall  (Figure  15),  mature  U.  chuss 
were  dispersed  over  the  entire  survey  area,  but 
the  original  data  (Musick,  1969)  show  that  most 
individuals  longer  than  32  cm  had  moved  into 
water  deeper  than  60  fm.  The  winter  distribution 
pattern  of  mature  U.  chuss  (Figure  16)  shows  that 
a  very  strong  offshore  movement  occurred  in  water 
deeper  than  60  fm,  in  the  Gulf  of  Maine,  and  off 
southern  New  England.  The  fish  were  most 
heavily  concentrated  along  the  edge  of  the  conti- 
nental slope  from  the  southwest  part  of  Georges 
Bank  to  Hudson  Canyon.  Edwards  et  al.  (1962) 
reported  U.  chuss  to  be  most  abundant  in  winter 
between  100  and  250  fm  in  their  study  area  south 
of  Nantucket.  In  addition,  Edwards  et  al.  (1962) 
found  that  U.  chuss  were  "most  abundant  where 
the  water  temperature  was  between  47°F  (8.3°C) 
and  50°F  (10.0°C),"  values  which  are  within  the 
range  which  adult  hake  were  most  abundant  in 
the  present  study  (5-12°C). 

Juvenile  and  immature  U.  chuss  occurred  with- 
in a  narrower  temperature  range  than  the  adults. 
However,  the  latter  were  more  concentrated 
within  relatively  narrow  temperature  limits. 
This  implies  that  although  adults  may  tolerate 
a  wider  range,  they  may  prefer  a  narrower  range 
than  young  fish  do  or,  at  least,  are  more  mobile 
and  can  undertake  longer  and  faster  seasonal 
migrations,  thus  remaining  within  relatively  nar- 
rower temperature  limits  throughout  the  year. 
Such  behavior  might  allow  the  fish  to  maintain 
an  optimal  thermal  environment  for  gonadal 
development,  spawning,  and  feeding  during 
various  times  of  the  year. 


Figure  15. — Distribution  and  abundance  of  mature  Urophycis 
chuss  during  the  fall.  Abundance  in  each  sampling  stratum  is 
indicated  on  a  log  scale. 


489 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Figure  16. — Distribution  and  abundance  of  mature  Urophycis 
chuss  during  the  winter.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


U  tenuis 


SUMMER 
9-50  cm  Total  lengtti 


0 

□  <-0.24 

□  0.25-0.99 
■   1.00-2.49 


Figure  17. — Distribution  and  abundance  of  immature  Urophy- 
cis tenuis  during  the  summer.  Abundance  in  each  sampling 
stratum  is  indicated  on  a  log  scale. 


Seasonal  Distribution  of  U.  tenuis 

During  summer  (Figure  11 ),  immatur ell.  tenuis 
were  rare  or  absent  over  most  of  the  southern 
New  England  area.  Moderate  numbers  were 
taken  in  the  strata  deeper  than  100  fm  off 
Nantucket  and  the  southern  part  of  Georges  Bank 
and  the  strata  deeper  than  60  fm  along  the 
eastern  part  of  Georges  Bank.  In  the  Gulf  of 
Maine,  immature  U.  tenuis  were  taken  in  mod- 
erate numbers  in  the  Great  South  Channel 
(Stratum  23)  and  in  the  northern  part  of  the 
Gulf.  The  highest  abundance  value  was  in 
Stratum  39  off  the  northern  Maine  coast. 

In  the  fall,  immature  U.  tenuis  were  most 
abundant  in  the  northern  and  eastern  parts  of 
the  Gulf  (Figure  18),  and  moderately  abundant 
in  the  deep  central  Gulf,  the  Great  South  Chan- 
nel, and  on  the  middle  and  northern  edge  of 
Georges  Bank.  Immature  U.  tenuis  were  also 
abundant  in  the  stratum  deeper  than  100  fm 
at  the  eastern  edge  of  Georges  Bank  and  mod- 
erately abundant  in  strata  deeper  than  60  fm  to 
the  south  and  west  off  southern  New  England. 
Only  one  stratum  south  of  Georges  Bank  less 
than  60  fm  deep  (Stratum  2)  had  moderate 
numbers  of  U.  tenuis.  This  stratum  includes  the 
inshore  extension  of  Hudson  Canyon. 

In  the  Gulf  of  Maine  during  the  winter  (Figure 
19),  immature  U.  tenuis  were  most  abundant  in 
the  deeper  northern  strata  (Strata  36  and  38) 
and  along  the  northern  edge  of  Georges  Bank. 
Immature  U.  tenuis  were  absent  or  rare  in  areas 
less  than  60  fm  off  southern  New  England  but 


were  fairly  abundant  in  some  strata  deeper  than 
100  fm. 

Indices  of  abundance  of  U.  tenuis  by  tempera- 
ture interval  were  less  reliable  than  those  of 
U.  chuss  because  U.  tenuis  was  much  less 
abundant,  particularly  off  southern  New  Eng- 
land. Single  large  tows  often  lowered  the  preci- 
sion of  mean  catch  estimates  because  of  the 
relatively  small  total  number  of  U.  tenuis  col- 
lected. Consequently,  for  some  seasons  only  tem- 
perature ranges  can  be  discussed.  In  the  southern 
New  England  area,  immature  U.  tenuis  were 
taken  from  4°  to  14°C  in  the  summer.  Only  one 
station  was  made  at  15^C  and  at  16°C.  Although 
U.  tenuis  was  not  taken  there,  the  sampling 


U  tenuis 


FALL 
9-50  cm  Total  length 


Figure  18. — Distribution  and  abundance  of  immature  Urophy- 
cis tenuis  during  the  fall.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


490 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


intensity  does  not  give  a  true  indication  of  its 
presence  or  absence.  During  the  fall,  immature 
U.  tenuis  occurred  over  the  entire  temperature 
range,  4°  to  IS^'C.  In  the  winter,  they  were  taken 
from  3°  to  10°C.  In  the  Gulf  of  Maine  in  the  sum- 
mer, immature  U.  tenuis  occurred  from  4°  to  9°C 
and  the  highest  mean  catch  was  at  8°C.  The  fish 
were  absent  at  3°C  and  from  10°  to  14°C;  how- 
ever, these  temperature  intervals  were  not  ade- 
quately sampled.  In  the  fall,  immature  U.  tenuis 
occurred  from  3°  to  11°C  and  the  highest  mean 
abundance  was  at  9°C.  The  fish  were  absent 
from  12''  to  15°C  but  the  sampling  intensity  at 
these  temperatures  was  inadequate.  In  the  winter, 
only  a  few  fish  were  taken  at  2°C  and  3°C  and 
mean  catches  increased  from  4°  to  7°C.  Im- 
mature U.  tenuis  were  taken  over  an  annual 
range  of  2°  to  15°C  but  were  most  abundant  be- 
tween 4°  and  10°C  (Figure  20). 

During  the  summer  (Figure  21),  mature  U. 
tenuis  were  rare  or  absent  off  southern  New  Eng- 
land except  in  two  strata  deeper  than  100  fm. 
They  were  moderately  abundant  in  the  Gulf  of 
Maine  and  heavily  concentrated  in  Stratum  39 
along  the  northern  coast  of  Maine.  In  the  fall 
(Figure  22),  off  southern  New  England,  mature 
U.  tenuis  were  moderately  abundant  in  all  strata 
deeper  than  100  fm,  in  two  strata  from  60  to  99  fm 
deep,  and  in  only  one  stratum  from  30  to  59  fm 
deep.  They  were  rare  or  absent  in  all  other  south- 
ern New  England  strata.  Mature  U.  tenuis  were 
mo^lerately  abundant  in  the  Gulf  of  Maine.  The 
highest  values  of  abundance  are  in  Strata  27  and 
28,  between  60  and  100  fm. 


SUMMER 
n:  35r 


GULF      OF     MAINE 


FALL 


/\ 


3  4    5   6  7    8  9   10  II   l2  i3 


SOUTHERN    NEW     ENGLAND 


WINTER 
n:634 


^^4£r 


a 


f^ 


5   6    7   a   9  10  II    12  II  14  15  16 


kq.^764i& 


1 


4    5  6  7    8   9  to  II    t2  13  14  15  2    3    4    5  6  7   8    9  10  II 

TEMPERATURE        l°C) 


Figure  20. — Seasonal  catch  per  tow  of  immature  Urophycis 
tenuis  off  southern  New  England  and  the  Gulf  of  Maine. 
Abundance  data  are  stratified  by  temperature  intervals  of  one 
degree  (C).  The  total  number  of  individuals  captured  during 
each  season  =  n.  The  number  of  stations  occupied  at  each 
temperature  is  indicated  above  each  respective  histogram  bar. 


During  the  winter  off  southern  New  England 
(Figure  23),  mature  U.  tenuis  were  rare  or  absent 
in  all  strata  shoaler  than  100  fm  except  Stratum 
7,  which  was  60  to  99  fm  deep.  Mature  U.  tenuis 
were  moderately  abundant  there  and  in  all  strata 
deeper  than  100  fm.  In  the  Gulf  of  Maine, 
mature  U.  tenuis  were  absent  from  all  strata 


WINTER 
9-50  cm  Totol  length 


Ho 

n   5-0.24 
n  0.25-0.99 
■   100-2.49 


Figure  19. — Distribution  and  abundance  of  immature  Uro- 
phycis tenuis  during  the  winter.  Abundance  in  each  sampling 
stratum  is  indicated  on  a  log  scale. 


SUMMER 
>5I  cm  Totol  length 


11  0 

□  <-0.24 

□  0.25-0.99 
■   >250 


Figure  21. — Distribution  and  abundance  of  mature  Urophycis 
tenuis  during  the  summer.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


491 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


FALL 
>5(  cm-Tolol  length 


'^^-iush.^ 


0 

□   <-0.24 
[~1  025-0.99 
■  1.00-2.49 


Figure  22.— Distribution  and  abundance  of  mature  Urophycis 
tenuis  during  the  fall.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 

shoaler  than  60  fm.  They  were  moderately  abun- 
dant in  most  deeper  strata  and  most  abundant  in 
Strata  28  and  36,  which  were  deeper  than  100  fm. 
Catches  of  adult  U.  tenuis  off  southern  New 
England  were  very  small.  Consequently,  tem- 
perature-abundance estimates  (Figure  24)  are  not 
reliable.  Adult  U.  tenuis  occurred  from  6°  to  12°C 
in  the  summer,  from  4°  to  13°C  in  the  fall,  and 
from  4"  to  10°C  in  the  winter.  Adult  U.  tenuis 
were  taken  in  the  Gulf  of  Maine  from  4°  to  9°C 
in  the  summer  (Figure  24).  The  highest  mean 
catch  was  at  8°C.  During  the  fall,  the  range  of 
occurrence  was  3"  to  11°C,  the  highest  mean  catch 
occurring  at  9°C,  and  in  the  winter  the  range  was 
2°  to  7°C,  the  highest  mean  catch  occurring  at  7°C. 


WINTER 
>5I  cm  Totol  length 


Figure  23. — Distribution  and  abundance  of  mature  Urophycis 
tenuis  during  the  winter.  Abundance  in  each  sampling  stratum 
is  indicated  on  a  log  scale. 


GULF     OF      MAINE 

FALL 

n=350 

n 

6l,»478l 

^ 

/^»^ 


3    4    ^     G    7    e    9     10  II    12    13  14  3    4    5    6     7    B  9    10   II    ■£   l3   14  1%  2    3    4    S    G    7 


SOUTHERN      NEW     ENGLAND 


32 


iir^^23Z^iZ. 


% 


4    5    6     7    8    9    lOII    12    13  14  15  16  4     5    6     7   8   9    lO    1 1  (2    H    14  (5 

TEMPERATURE    (°C  ) 


Figure  24. — Seasonal  catch  per  tow  of  mature  Urophycis 
tenuis  off  southern  New  England  and  the  Gulf  of  Maine. 
Abundance  data  are  stratified  by  temperature  intervals  of  one 
degree  (C).  The  total  number  of  individuals  captured  during 
each  season  =  n.  The  number  of  stations  occupied  at  each 
temperature  is  indicated  above  each  respective  histogram  bar. 


Annually,  adult  U.  tenuis  were  taken  from  2°  to 
13°C  but  were  most  abundant  between  5°  and  9°C. 
Adult  U.  tenuis  appear  to  occupy  a  more  restricted 
temperature  range  than  immature  U.  tenuis. 
Also,  adult  U.  tenuis  occupy  a  narrower  and  lower 
temperature  range  than  adult  U.  chuss. 

U.  tenuis  may  be  more  abundant  off  southern 
New  England  than  the  survey  data  indicate. 
Edwards  et  al.  (1962)  and  Schroeder  (1955)  fre- 
quently captured  U.  tenuis  along  the  continental 
slope  off  southern  New  England  at  greater  depths 
than  those  sampled  during  the  Albatross  IV  sur- 
vey and  recent  research  (Musick,  unpublished 
data)  indicates  that  U.  tenuis  is  a  common  mem- 
ber of  the  continental  slope  fish  fauna  of  Virginia. 

Distribution  of  Urophycis  chuss  and 
U.  tenuis  with  Substrate 

U.  chuss  and  U.  tennuis  are  absent  or  rarely, 
occur  on  rock,  shell,  or  gravel  bottoms.  Both 
"prefer"  sand  or  mud.  Few  or  no  Urophycis  oc- 
curred in  Strata  24,  32,  and  33  during  any  season. 


492 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


These  strata  are  dominated  by  rock  or  gravel 
bottoms  (Fritz,  1965,  Plate  B).  Storer  (1858), 
Goode  (1884),  Hildebrand  and  Schroeder  (1928), 
and  Bigelow  and  Schroeder  (1939)  noted  the 
association  of  U.  chuss,  U.  tenuis,  or  both  with 
mud  bottoms.  Bigelow  and  Welsh  (1925)  reported 
that  both  species  dwelled  over  soft  bottoms  (silt, 
sand,  or  mud)  but  that  the  U.  tenuis  was  more 
strictly  a  "mud  fish"  than  the  U.  chuss.  The  Alba- 
tross IV  data  appear  to  agree  with  the  last  state- 
ment, because  the  regions  where  U.  tenuis 
occurred  most  commonly  are  dominated  by  muddy 
or  silty  substrates — the  northeastern  Gulf  of 
Maine,  the  central  basins  of  the  Gulf,  and  along 
the  continental  slope  on  Georges  Bank  and  south- 
west. However,  these  areas  are  also  cooler  during 
the  summer,  and  the  correlation  between  U. 
tenuis  abundance  and  mud  bottoms  (rather  than 
sand)  may  be  an  artifact.  Urophycis  chuss  were 
abundant  over  mud  or  sand  or  both  depending  on 
season,  because  the  deeper  strata  were  covered 
with  muddy  substrates  whereas  the  shallower 
strata  in  the  southwest  Gulf  of  Maine  and  off 
southern  New  England  were  covered  with  sand 
(Fritz,  1965,  Plate  B). 


ACKNOWLEDGMENTS 

Thanks  are  due  to  R.  L.  Edwards  and  M.  D. 
Grosslein  of  the  National  Marine  Fisheries  Ser- 
vice (NMFS)  Laboratory,  Woods  Hole,  Mass.,  for 
providing  ship  time,  research  space,  and  scientific 
direction  during  the  course  of  my  study.  A.  C. 
Kohler  of  the  Fisheries  Research  Board  of  Canada 
Laboratory,  St.  Andrews,  New  Brunswick,  pro- 
vided me  with  specimens  from  the  Gulf  of  St. 
Lawrence.  G.  Jonsson  of  the  Hafrannsoknastof- 
nunin  Marine  Research  Institute,  Reykjavik,  sent 
me  material  from  Iceland  and  D.  M.  Cohen  of  the 
NMFS  Systematics  Laboratory,  Smithsonian  In- 
stitution, allowed  me  to  examine  hake  from 
Florida.  Also,  I  wish  to  thank  my  students  at  the 
Virginia  Institute  of  Marine  Science — J.  D. 
McEachran,  K.  Able,  and  C.  Wenner — for  col- 
lecting data  for  me  on  Urophycis  while  pursuing 
their  own  research  at  sea,  and  to  G.  W.  Mead 
formerly  of  the  Museum  of  Comparative  Zoology, 
Harvard  University,  for  thoroughly  editing  the 
early  drafts  of  the  dissertation  from  which  parts 
of  the  present  paper  have  been  extracted.  My 
research  was  supported  in  part  by  National 
Science  Foundation  grants  G-19727  and  GB-3167 


to  the  Harvard  Committee  on  Evolutionary 
Biology  (Principal  Investigator,  Reed  C.  Rollins) 
and  a  Grant-in-Aid  from  the  Sigma  Xi  -  RESA 
Committee. 


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1939.     Notes  on  the  fauna  above  mud  bottoms  in  deep 
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Breder,  C.  M.,  Jr. 

1922.     The  fishes  of  Sandy  Hook  Bay.     Zoologica  (N.Y.) 

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1905.    Extension  ofthe  list  ofNew  Brunswick  fishes.    Proc. 

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1918-1920:109-114. 
Craigie,  E.  H. 

1916.    The  life-history  ofthe  hake  (Urophycis  chuss  Gill) 

as  determined  from  its  scales.     Contrib.  Can.  Biol. 

1914-1915:87-94. 
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pollock,  the  winter  flounder,  and  the  smelt,  and  on  the 

weights  of  the  liver  and  gonads  in  the  hake  and  in  the 

pollock.    Trans.  R.  Soc.  Can.,  Ser.  3,  21:153-173. 
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1958.    Effects  of  high  temperature  on  survival  of  the  giant 

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1963.    Silver  and  red  hakes.  In  Reproduction  offish  stocks. 

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493 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


Dow,  R.  L.,  AND  F.  T.  Baird,  Jr. 

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1958a.     Gloucester's  trawl  fishery  for  industrial  fish. 

Commer.  Fish.  Rev.  20(8):10-15. 
1958b.    Species  composition  of  industrial  trawl  landings  in 

New  England,   1957.     U.S.  Fish  Wildl.  Serv.,  Spec. 

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1965.     Relation  of  temperature  to  fish  abundance  and 

distribution  in  the  southern  New  England  area.     Int. 

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Edwards,  R.  L.,  and  L.  Lawday. 

1960.  Species  composition  of  industrial  trawl-fish  landings 
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Edwards,  R.  L.,  R.  Livingstone,  Jr.,  and  P.  E.  Hamer. 

1962.    Winter  water  temperatures  and  an  annotated  list  of 

fishes— Nantucket  shoals  to  Cape  Hatteras.  Albatross  III 

Cruise  no.  126.     U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep 

Fish.  397,  31  p. 

Edwards,  R.  L.,  and  F.  E.  Lux. 

1958.    New  England's  industrial  fishery.    Commer.  Fish. 
Rev.  20(5):  1-6. 

FORTIN,  P. 

1863.  List  of  the  cetacea,  fishes,  Crustacea  and  mollusca 
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of  St.  Lawrence,  etc.  Annu.  Rep.  of  Pierre  Fortin,  Esq., 
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Fraser-Brunner,  a. 

1925.     New  or  rare  fishes  from  the  Irish  Atlantic  slope. 
Proc.  R.  Irish  Acad.  43:319-326. 
Fritz,  R.  L. 

1965.     Autumn  distribution  of  groundfish  species  in  the 
Gulf  of  Maine  and  adjacent  waters,  1955-1961.     Ser. 
Atlas  Mar.  Environ.  Folio  10,  1  p. 
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1867.     On  the  food  fishes  of  Nova  Scotia,  No.  5,  the  cod 
family.     Proc.  Trans.  N.  S.  Inst.  Nat.  Sci.  2(1):101-111. 
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1884.     Natural  history  of  useful  aquatic  animals.  Part 
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Grosslein,  M.  D. 

1969.  Groundfish  survey  program  of  BCF  Woods  Hole. 
Commer.  Fish.  Rev.  31(8-9):22-30. 

Hildebrand,  S.  F.,  and  W.  C.  Schroeder. 

1928.     Fishes  of  Chesapeake  Bay.     Bull.  U.S.  Bur.  Fish. 
43(1),  366  p. 
Jordan,  D.  S.,  and  B.  W.  Evermann. 

1898.    The  fishes  of  North  and  Middle  America.  Part  III. 
U.S.  Natl.  Mus.  Bull.  47:2183-3136. 
Kendall,  W.  C. 

1909.     The  fishes  of  Labrador.  Proc.  Portland  Soc.  Nat. 
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1866.  Descriptive  catalogue  of  the  fishes  of  Nova  Scotia. 
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Latham,  R. 

1917.     Migration  notes  of  fishes,  1916,  from  Orient,  Long 
Island.  Copeia  41:17-23. 
Leim,  a.  H.,  and  W.  B.  Scott. 

1966.     Fishes  of  the  Atlantic  coast  of  Canada.  Fish  Res. 
Board  Can.,  Bull.  155,  485  p. 
McKenzie,  R.  a. 

1959.  Marine  and  freshwater  fishes  of  the  Miramichi 
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Merriman,  D.,  and  R.  C.  Sclar. 

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Sound.  Bull.  Bingham  Oceanogr.  Collect.,  Yale  Univ. 

13(3):165-219. 
Moyle,  J.  B.,  and  R.  Lound. 

1960.  Confidence  limits  associated  with  means  and 
medians  of  series  of  net  catches.  Trans.  Am.  Fish.  Soc. 
89:53-58. 

MusicK,  J.  A. 

1969.    The  comparative  biology  of  two  American  Atlantic 

hakes,  Urophycis  chuss  and  U.  tenuis  (Pisces,  Gadidae). 

Ph.D.  thesis.  Harvard  Univ.,  Cambridge,  Mass.,  150  p. 
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1932.  First  list  of  fishes  in  the  Newfoundland  fishing 
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1933.  Second  list  of  fishes  in  the  Newfoundland  fishing 
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1934.  Third  list  of  fishes  in  the  Newfoundland  fishing 
area.  1933.  Newfoundland  Fish.  Res.  Comm.,  Annu. 
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Pereyra,  W.  T.,  H.  Heyamoto,  and  R.  R.  Simpson. 

1967.    Relative  catching  efficiency  of  a  70-foot  semiballoon 
shrimp  trawl  and  94-foot  eastern  fish  trawl.  U.S.  Fish. 
Wildl.  Serv.,  Fish.  Ind.  Res.  4(1):49-71. 
Riley,  G.  A. 

1956.     Oceanography  of  Long  Island  Sound,  1952-1954. 
II.  Physical  oceanography.  Bull.  Bingham  Oceanogr. 
Collect.,  Yale  Univ.  15:15-46. 
Roessler,  M. 

1965.  An  analysis  of  the  variability  of  fish  populations 
taken  by  otter  trawl  in  Biscayne  Bay,  Florida.  Trans. 
Am.  Fish.  Soc.  94:311-318. 

Schroeder,  W.  C. 

1955.    Report  on  the  results  of  exploratory  otter-trawling 

along  the  continental  shelf  and  slope  between  Nova 

Scotia  and  Virginia  during  the  summers  of  1952  and 

1953.  Pap.  Mar.  Biol.  Oceanogr.,  Deep-Sea  Res.,  suppl. 

to  Vol.  3,  p.  358-372. 
Smith,  H.  M. 

1898.     The  fishes  found  in  the  vicinity  of  Woods  Hole. 

Bull.  U.S.  Fish  Comm.  17:85-111. 
Storer,  D.  H. 

1839.     A  report  on  the  fishes  of  Massachusetts.  Boston 

J.  Nat.  Hist.  2:289-570. 
1846.     A  synopsis  of  the  fishes  of  North  America.  Mem. 

Am.  Acad.  Arts  Sci.,  New  Ser.  2:253-550. 
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494 


MUSICK:  SEASONAL  DISTRIBUTION  OF  SIBLING  HAKES 


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1850.  Observations  on  the  fishes  of  Nova  Scotia  and 
Labrador,  with  descriptions  of  new  species.  Boston  J.  Nat. 
Hist.  6(l):247-270. 

SVETOVIDOV,  A.  N. 

1955.     Notes  on  Phycis  borealis  Saemundsson  (Pisces, 

Gadidae).  Tr.  Zool.  Inst.  Acad.  Nauk.  SSRF  17:346-348. 

(Engl,  transl.,  [U.S.]   Bur.  Commer.  Fish.,  Ichthyol. 

Lab.,  Wash.,  D.C.,  1961,  6  p.) 
Taylor,  C.  C. 

1953.     Nature  of  variability  in  trawl  catches.  U.S.  Fish 

Wildl.  Serv.,  Fish.  Bull.  54:145-166. 
Templeman,  W. 

1966.    Marine  resources  of  Newfoundland.  Fish.  Res.  Board 

Can.,  Bull.  154,  170  p. 


Vladykov,  V.  D.,  AND  D.  E.  McAllister. 

1961.  Preliminary  list  of  marine  fishes  of  Quebec.  Nat. 
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Vladykov,  V.  D.,  and  R.  A.  McKenzie. 

1935.  The  marine  fishes  of  Nova  Scotia.  Proc.  N.S.  Inst. 
Sci.  19:17-113. 

Vladykov,  V.  D.,  and  J.  L.  Tremblay. 

1935.  Liste  des  poissons  recuellis  jjendant  I'ete  1934  par 
la  Station  Biologique  due  St.  Laurent,  dans  la  region 
de  Trois-Pistoles,  P.Q.  Nat.  Can.  62:77-82. 

Wheatland,  S.  B. 

1956.  Oceanography  of  Long  Island  Sound,  1952-1954. 
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Oceanogr.  Collect.,  Yale  Univ.  15:234-314. 


495 


DEVELOPMENT  OF  EGGS  AND  LARVAE  OF 
CARANX  MATE  (CARANGIDAE)i 

John  M.  Miller  and  Barbara  Y.  Sumida^ 

ABSTRACT 

The  development  of  eggs  and  larvae  of  omaka  (Caranx  mate)  is  described  from  approximately 
2  h  after  fertilization  to  day  36  after  hatching.  The  pelagic,  spherical  eggs  (700-740  /i  diameter) 
had  a  single  oil  droplet  and  hatched  after  about  26  h  incubation  at  24.5°C.  The  average 
growth  rate  in  culture  was  0.44  mm/day;  feeding  began  four  days  after  hatching.  Fin  develop- 
ment and  ossification  of  omaka  occurred  at  smaller  sizes,  but  in  the  same  sequence  as  jack 
mackerel  (Trachurus  symmetricus)  off  California.  Of  the  body  proportions  measured,  body 
depth  was  most  useful  in  separating  omaka  from  at  least  two  other  species  of  carangid  larvae. 
The  pigment  pattern  was  also  of  diagnostic  value.  Reared  larvae  were  indistinguishable 
from  similar-sized  field  specimens. 


Omaka  {Caranx  mate)  is  one  of  the  most  abundant 
carangids  in  the  Hawaiian  Islands.  The  species 
is  rather  widespread  throughout  the  Indo-Pacific, 
reaching  the  eastern  coast  of  Africa.  In  Hawaii, 
the  preferred  habitats  are  estuaries,  bays,  and 
harbors  with  relatively  long  water  residence 
times.  Kuthalingham  ( 1959)  described  the  feeding 
habits  of  omaka  near  Madras,  India.  The  growth 
rate  of  captive  adult  omaka  was  reported  by 
Watarai  (1973). 

Omaka  have  a  protracted  spawning  period  in 
Hawaii;  the  eggs  can  be  taken  with  fair  regu- 
larity from  March  through  September  from  the 
surface  waters  of  Kaneohe  Bay,  Oahu.  Little  else 
is  known  of  the  spawning  habits.  However,  a  bi- 
weekly year-round  fish-egg  survey  in  Kaneohe 
Bay  indicated  three  spawning  peaks:  one  in  April 
and  May,  another  in  September  and  October, 
and  a  third,  smaller,  peak  in  July  (Watson  and 
Leis,  1973).^  During  these  peaks  omaka  eggs  were 
by  far  the  most  abundant  of  any,  occasionally 
exceeding  concentrations  of  10/m^  in  the  surface 
waters  of  south  Kaneohe  Bay.  Larval  densities, 
on  the  other  hand,  were  found  to  be  much  lower 
than  these  egg  densities,  rarely  reaching  0.1/m^ 
(Watson  and  Leis,  see  footnote  3).  As  is  char- 
acteristic of  many  carangids,  young  are  frequently 


'Hawaii  Institute  of  Marine  Biology  Contribution  No.  427. 

^Hawaii  Institute  of  Marine  Biology,  University  of  Hawaii, 
Coconut  Island— P.O.  Box  1346,  Kaneohe,  HI  96744. 

^Watson,  W.,  and  J.  M.  Leis.  1973,  Ichthyoplankton  in 
Kaneohe  Bay:  A  one-year  study  of  the  fish  eggs  and  larvae. 
Unpubl.  manuscr. 


seen  under  medusae.  Large  larvae  and  juveniles 
are  similarly  attracted  to  floating  raffia,  and  have 
been  collected  in  this  manner.  Adult  omaka  do 
not  appear  to  make  the  off'shore  spawning  move- 
ments characteristic  of  many  of  the  resident  fish 
species  in  Kaneohe  Bay. 

MATERIALS  AND  METHODS 

Larvae  used  for  description  came  from  two 
sources:  reared  specimens  and  field  specimens. 
Reared  larvae  of  known  age  were  the  primary 
source  of  material;  field  specimens  were  used 
mainly  to  verify  observations  and  conclusions 
based  on  the  former.  Over  the  past  2  yr  omaka 
larvae  have  been  taken  in  numerous  plankton 
tows.  Each  time  that  comparisons  were  made 
between  similar-sized  field  and  reared  specimens, 
the  larvae  were  indistinguishable. 

Larvae  were  obtained  from  two  cultures  (called 
Series  A)  begun  in  February  1971.  One  of  these 
(Al)  supplied  larvae  through  day  5  (Table  1). 
This  culture  was  terminated  on  day  6,  when  high 
mortality  (of  unknown  cause)  was  experienced. 
Although  the  sizes  of  these  larvae  are  included 
in  the  growth  rate  curve  (Figure  4),  they  were 
not  used  in  the  description  of  developmental 
stages.  The  second  (A2)  was  maintained  for  36 
days  during  which  post  yolk  sac  specimens  (day 
6  and  older)  were  taken  for  description. 

Two  other  cultures  (Series  B)  were  begun  in 
May  1972  to  provide  eggs  and  yolk-sac  larvae. 
The  first,  begun  1  May,  was  to  determine  the 
approximate  rate  of  development  and  design  a 


Manuscript  accepted  September  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  2.  1974. 


497 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Table  1. — Caranx  mate- 

-reared  larvae,  22  February-31  March 

1971. 

Age 

No  larvae 

Date 

(day) 

picked 

standard  length(mm) 

Feb.  22  (eggs 

tched) 

mean 

range 

collected  &  ha 

SERIES  A 

A1 
Feb.  23 

1 

8 

1.36 

1.16-1.55 

Feb.  24 

2 

10 

2.18 

1.47-2.50 

Feb.  25 

3 

10 

2.46 

2  13-2.58 

Feb.  26 

4 

5 

2.59 

2.55-2.68 

Feb.  27 

5 

5 

2.57 

2.35-2.84 

>42 

Feb.  28 

6 

10 

3.05 

2.94-3.19 

Mar.     1 

7 

10 

3.24 

2.77-3.39 

Mar.    2 

8 

10 

3.46 

3.31-3.75 

Mar.    4 

10 

10 

3.97 

3.50-4.41 

Mar.    6 

12 

10 

4.47 

3.48-533 

Mar.    8 

14 

10 

5.17 

4.28-5.75 

Mar.  10 

16 

10 

6.21 

5.83-7.00 

Mar.  12 

18 

10 

7.43 

5.58-842 

Mar.  14 

20 

10 

8.27 

7.25-8.88 

Mar.  16 

22 

10 

9.50 

8.13-1063 

Mar.  18 

24 

10 

10.41 

888-1200 

Mar.  20 

26 

10 

10.89 

8.63-11.75 

Mar.  22 

28 

10 

11.42 

9.38-12.75 

Mar.  24 

30 

10 

12.46 

10.63-14.95 

Mar.  27 

33 

10 

13.83 

11.50-17.25 

Mar.  30 

36 

5 

16.62 

14.28-18.00 

Mar.  31  (Term 

nated — no  larvae  remaining) 

sampling  schedule.  The  second,  begun  5  May, 
provided  most  of  the  specimens  used  in  the 
description,  although  certain  additional  measure- 
ments (e.g.,  size  at  hatching)  were  made  on 
specimens  from  the  first  culture. 

Series  A  Cultures 

One  thousand  eggs  were  pipetted  from  the 
washed  plankton  of  a  surface  tow  with  a  505  /j 
mesh  meter  net  in  south  Kaneohe  Bay,  Oahu, 
on  22  February  1971.  These  eggs  were  placed 
in  a  78-liter  fiberglass  and  glass  aquarium 
which  had  been  filled  with  triple  CUNO^  filtered 
(5 /J  effective  pore  size)  bay  water.  The  water  was 
previously  exposed  to  long-wave  ultraviolet  light 
for  1  min.  Penicillin  (to  a  concentration  of  50 
mg/liter)  and  Polymixin  B  (to  a  concentration 
of  8  mg/liter)  were  added  before  introduction  of 
the  eggs.  These  antibiotics  have  been  shown  to 
substantially  reduce  bacterial  counts  in  cultures 
and  materially  increase  hatching  success  of 
omaka  eggs  (Struhsaker,  Hashimoto,  Girard, 
Prior,  and  Cooney,  1973).  A  Chlorella  sp.  culture 
was  added  initially  to  an  approximate  cell  count 
of  10  X  10"  cells/ml. 


■•Reference  to  trade  names  does  not  imply  endorsement 
by  the  National  Marine  Fisheries  Service,  NOAA. 


Salinity,  oxygen,  and  temperature  in  the  tank 
were  usually  measured  daily.  Salinity  remained 
nearly  constant  throughout  the  experiment  at 
35 /CO,  the  value  in  the  bay  at  the  time  of 
collection.  Oxygen  values  ranged  from  6.1  to  9.5 
mg/liter  during  the  subsequent  36  days.  The 
maximum  range  of  temperature  in  the  tank  was 
21.5  to  25.9°C,  with  a  36-day  mean  of  24.5°C. 
The  bay  surface  temperature  at  the  time  of 
collection  was  24.4°C. 

The  tank  was  continuously  illuminated  by  two 
40  watt  fluorescent  "daylight"  bulbs.  The  light 
intensity  at  the  surface  of  the  water  was  approxi- 
mately 6.5  X  10^  flux.  The  tank  was  aerated  with 
a  single  airstone,  with  airflow  adjusted  to  produce 
a  slow  single  stream  of  bubbles. 

Food  was  added  daily  from  the  third  day 
after  hatching.  Through  day  11  the  food  was  the 
75-150  Ai  fraction  of  wild  zooplankton  attracted 
to  a  night  light  suspended  in  the  bay.  On  day 
12  the  addition  of  wild  plankton  was  replaced 
with  additions  ofArtemia  nauplii.  Wild  plankton 
and  Artemia  were  added  each  time  to  a  concen- 
tration in  the  tank  of  5/ml  and  1/ml,  respectively. 
No  doubt  the  culture  tank  supported  other 
(unknown)  populations  of  plankters  and  micro- 
organisms. 

Usually  ten  larvae  were  captured  by  dipping  or 
pipetting  at  about  two-day  intervals  from  hatch- 
ing (the  day  after  introduction  of  the  eggs) 
until  36  days  after  that  time  (Table  1).  No 
attempt  was  made  to  select  particular  sized 
larvae. 

Series  B  Cultures 


Larvae  reared  for  yolk-sac-stage  description 
were  hatched  from  eggs  taken  from  Kaneohe 
Bay  on  5  May  1972.  At  the  time  of  collection 
(midafternoon),  eggs  were  found  in  both  late 
middle  stage  and  early  stage,  i.e.,  from  two 
spawnings.  Only  the  latter  (in  blastodisc  stage) 
were  selected  for  culture.  (The  exact  time  of 
fertilization  is  unknown;  hence  the  duration  of  the 
early  stage  was  estimated.)  Extrapolating  from 
the  subsequent  rate  of  development,  we  estimate 
the  eggs  had  been  fertilized  for  about  2  h 
before  capture. 

Two  hundred  eggs  were  placed  in  each  of  four 
4-liter  beakers  of  unfiltered  seawater  obtained 
about  two  miles  offshore  from  Kaneohe  Bay. 
This  "offshore"  water  contained  less  plankton 


498 


MILLER  and  SUMIDA:  DEVELOPMENT  OF  CARANX  MATE 


and,  in  general,  was  of  higher  quality  than  that 
found  in  the  bay  used  in  the  Series  A  cultures. 
Salinity  was  always  about  35  Vco . 

Water  temperature  in  the  beakers  during 
the  experiment  ranged  from  23.5  to  24.4°C.  Bay 
surface  temperature  at  the  time  of  collection 
was  25°C.  No  food  or  algae  was  added  to  these 
cultures.  Erythromycin  gluceptate  was  added  to 
a  concentration  of  9  mg/liter  before  intro- 
duction of  the  eggs.  The  beakers  were  con- 
tinuously illuminated  with  fluorescent  lights. 

Eggs  and  larvae  were  pipetted  from  these 
cultures,  which  were  terminated  on  the  sixth  day 
after  hatching.  Larvae  were  immobilized  in  a 
refrigerator  (ca.  lO^C)  before  preservation  in  2.5% 
buffered  formaldehyde.  This  practice  resulted  in 
fewer  distorted  and  curled  larvae  than  did  placing 
them  directly  in  preservative. 

All  measurements  and  counts  were  made  with 
a  microscope  equipped  with  an  ocular  micrometer. 
At  the  usual  magnification  (50  x)  the  precision 
of  measurement  is  ±  0.02  mm.  Illustrations  are 
camera  lucida  drawings,  subsequently  inked,  by 
B.  Sumida.  Owing  to  rapid  loss  of  certain 
pigments  after  preservation,  a  size  series  of  larvae 
was  microphotographed  with  color  film  for  sub- 
sequent reference. 

Illustrations  of  early  larvae  (day  6  and  younger) 
show  pigment  patterns  observed  in  live  larvae. 
Pigment  patterns  retained  after  preservation  are 
so  noted  in  the  text.  Pigments  stabilized  in 
older  larvae  so  that  differences  between  live  and 
dead  larvae  became  much  less  pronounced  with 
age.  Illustrations  of  these  larger  larvae  (day  8 
and  older)  were  made  from  preserved  specimens. 


DEFINITIONS,  MERISTICS  AND 
MORPHOMETRICS 

Body  depth     At  insertion  of  pectoral  fin.  (Prior 

to  pectoral  bud  formation,  taken  through 

shoulder.) 
Dorsum     Region  dorsal  to  medial  horizontal 

line  through  body. 
Eye  diameter     Horizontal  diameter  of  orbit. 
Head  length     Tip  of  snout  to  posterior  margin 

of  operculum. 
Larva     Larva  after  yolk  absorption  completed 

and  prior  to  metamorphosis  when  scales  and 

lateral  line  develop.  (All  of  our  specimens  were 

larvae  based  on  this  definition.) 


Lateral  line  streak  Dashed  line  of  pigment  along 
the  lateral  midline  of  body. 

Snout  to  anus  length  Tip  of  snout  to  vertical 
from  anus. 

Standard  length  (SL)  Prior  to  notochord  flexion 
and  formation  of  hypural  bones,  SL  taken  from 
snout  to  tip  of  notochord.  Thereafter,  taken 
to  posterior  margin  of  hypural  plate.  SL  = 
mean  standard  length.  Deviations  from  means 
are  standard  deviations.  All  length  measure- 
ments were  made  on  preserved  specimens, 
except  where  noted. 

Ventrum  Region  ventral  to  medial  horizontal 
line  through  body  exclusive  of  abdominal  area; 
generally  area  inclusive  of  hypomeres. 

Yolk  sac  larva  Larva  from  hatching  to  approxi- 
mately the  third  day  when  yolk  absorption 
was  nearly  complete. 

DEVELOPMENT  OF  THE  EGG 

Because  the  development  of  the  omaka  egg 
proceeds  rapidly  in  discrete  stages,  we  have 
chosen  to  summarize  it  as  follows: 
Early  stage 

Blastodisc  stage  to  blastopore  closure  (fertiliza- 
tion to  blastopore  closure)  (Figure  lA). 
Egg  size: 

(diameter)  Live:   722  ±  19  m. 
Preserved:  722  ±  19  m- 


Figure  1A.— Ventral  view  of  early  stage  egg  oi  Caranx  mate. 
BP  =  blastopore. 


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FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Figure  IB. — Early  middle  stage  egg.  Ventral  view  of  embryo. 

The  omaka  egg  is  pelagic,  clear,  and  spherical 
with  a  single  oil  droplet  at  the  vegetative 
pole.  At  the  time  of  collection  the  eggs  were 
in  the  early  blastodisc  stage. 
Oil  globule: 
Diameter  in  live  egg:   190-200  ^. 
Diameter  in  preserved  egg:   176-192  /j. 
Positioned  at  the  vegetative  pole,  the  oil 
globule  was  almost  centered  on  the  polar  axis 
of  the  developing  blastodisc  (Figure   lA) 


Figure  ID. — Dorsal  view  of  advanced  middle  stage  egg.  Pigment 
on  oil  globule  omitted. 

and  later  between  the  head  and  tail  bud  of  the 
early  embryo.  At  the  time  of  blastopore 
closure,  the  oil  globule  was  situated  slightly 
off-center  and  closer  to  the  tail  end  of  the 
developing  embryo.  The  blastopore  closed 
between  the  oil  globule  and  the  tail  end  of 
the  embryo. 
Perivitelline  space: 
Size  range:  26  ±  4  /j. 


Figure  IC. — Ventro-lateral  view  of  advanced  middle  stage  egg, 
showing  oil  globule  pigmentation. 


Figure  IE. — Lateral  view  of  early  late-stage  egg. 


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MILLER  and  SUMIDA:  DEVELOPMENT  OF  CARANX  MATE 


The  perivitelline  space  was  not  evident  in  the 
early  blastoderm  stages  but  developed  as  the 
egg  advanced. 

Yolk: 
(diameter)  660±  23  m. 

The  segmentation  of  the  yolk  was  apparent 
in  the  form  of  irregular  polygons  across  the 
egg  diameter  in  the  early  stage  eggs  (not 
illustrated).  This  pattern  was  lost  with 
preservation  of  the  eggs  in  2.5%  formalde- 
hyde, whereupon  the  yolk  took  on  a  "bubbly" 
irregular  appearance. 

Embryo  development: 

The  optic  vesicles  were  evident  on  the  young 
embryo  before  blastopore  closure  of  the  egg 
(not  illustrated).  Initiation  of  somite  develop- 
ment in  the  anterior  end  of  the  embryo  was 
also  observed  before  closure  of  the  blasto- 
pore. Kupffer's  vesicle  was  conspicuous  at 
the  tip  of  the  rudimentary  tail  bud. 

Pigmentation: 

No  pigmentation  was  present  in  the  egg  or 
embryo  during  this  stage. 

Duration  of  early  stage: 

11-12  h  subsequent  to  capture.  Estimated 
total  time — 14  h. 


Middle  stage 

Following  blastopore  closure  to  separation  of  the 

tail  bud  from  the  yolk  (Figure  IB). 

Noteworthy  events: 

Advanced  development  of  the  embryo  and 
pigmentation  patterns.  Egg  size,  width  of 
perivitelline  space,  etc.,  same  as  above. 

Oil  globule: 

The  oil  globule  remained  nearly  centered 
between  the  developing  head  and  tail  of  the 
embryo.  The  underside  of  the  oil  globule 
(closest  to  the  embryo)  appeared  heavily 
pigmented  during  the  latter  part  of  the 
middle  stage  owing  to  melanophores  which 
had  migrated  from  the  surrounding  yolk 
surface  (Figure  IC). 

Yolk  pigmentation: 

In  the  early  middle  stage,  numerous  small 
melanophores  were  observed  overlying  the 
anterior  surface  of  the  yolk  surrounding  the 
oil  globule  (Figure  IB).  Most  of  these  melano- 
phores migrated  during  the  middle  stage  and 
aggregated  on  the  underside  of  the  oil 
globule. 


Embryo  pigmentation: 

Small,  faintly  pigmented  melanophores  first 
appeared  along  the  lines  separating  the 
developing  somites  and  spread  laterally 
covering  the  dorso-lateral  region  of  the  body. 
A  conspicuous  patch  of  pigment  was  notice- 
able at  the  anterior  and  posterior  margins 
of  the  optic  vesicles,  and  a  small  cluster  of 
melanophores  in  the  area  of  the  snout.  Later 
in  this  stage,  larger  melanophores  appeared 
in  an  irregular  line  along  the  medial  dorsal 
surface  of  the  body  (Figure  ID). 

Somite  development: 

By  the  end  of  the  middle  stage,  21  well- 
defined  myomeres  could  be  counted.  Kupffer's 
vesicle  was  still  evident  in  the  middle  stage. 

Duration  of  the  middle  stage: 
11-12  h  at24.5°C. 

Late  stage 

Tail  bud  completion  to  hatching  of  larva  (Figure 

IE). 

Oil  globule: 

When  the  advanced  embryo  had  coiled  around 
the  yolk,  the  oil  globule  shifted  in  position 
and  became  situated  closer  to  the  head  rather 
than  maintaining  a  median  position  under 
the  embryo.  Pigmentation  became  more 
abundant,  extending  over  the  hemisphere  of 
the  underside  in  contrast  to  the  small,  dense 
cluster  in  the  middle  stage.  Virtually  no 
pigment  remained  on  the  surrounding  yolk. 

Embryo  pigmentation: 

Dense  pigmentation  remained  on  the  dorso- 
lateral surfaces  of  the  body.  Melanophores 
appeared  over  the  top  of  the  head  in  addition 
to  those  on  the  snout  and  along  the  anterior 
and  posterior  margins  of  the  eye.  A  band  of 
small  melanophores  developed  around  the 
body  near  the  tail  region.  There  also  appeared 
a  ring  of  melanophores  on  the  yolk  surface 
posterior  to  the  tip  of  the  tail  bud.  This  was 
subsequently  lost  in  the  final  span  of  the  late 
stage  when  fin  fold  formation  was  com- 
pleted and  tail  flexure  occurred.  Kupffer's 
vesicle  was  observed  in  the  early  part  of  the 
late  stage  but  was  subsequently  lost. 

Somite  development: 

The  adult  complement  of  24  somites  was 
attained  in  the  late  stage  embryo. 

Duration  of  late  stage: 
0.5-1  h  at  24.5°C. 


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FISHERY   BULLETIN:  VOL.  72.  NO. 


YOLK  SAC  LARVAE 

The  newly  hatched  omaka  larvae  measured 
1.32  mm  to  1.70  mm  SL  live,  with  a  mean  of 
1.46  ±  0.12  mm  for  47  larvae.  Following  preser- 
vation in  2.5%  formaldehyde,  a  different  group 
often  larvae  ranged  from  0.87  mm  to  1.03  mm 
with  a  mean  of  0.98  ±  0.05  mm.  The  difference 
between  means  (0.48  mm)  indicates  a  shrinkage 
of  33%. 

Pigmentation 

Live  Larvae  at  Hatching 

Newly  hatched  omaka  larvae  resembled  ad- 
vanced embryos  in  pigmentation  pattern.  Melano- 
phore  pigment  was  heaviest  on  the  dorso-lateral 
surfaces  of  the  body  with  melanophores  usually 
forming  a  loop  posterior  to  the  head.  Additional 
small  clusters  of  melanophores  were  observed  on 
the  top  of  the  head  and  at  the  anterior  and 
posterior  margins  of  the  eye  vesicles.  A  broad 
band  of  small  melanophores  encircled  the  body 
about  6  myomeres  posterior  to  the  anal  papilla. 
Ventral  body  pigment  was  not  apparent  in  the 
newly  hatched  larvae  but  was  found  in  older  yolk 
sac  larvae,  perhaps  due  to  the  migration  of  some 
dorso-lateral  melanophores  and  those  in  the  band 
region  (see  Orton,  1953).  Dendritic  melanophores 
(Figure  2A)  lined  the  posterior  margin  of  the  yolk 
sac.  The  oil  globule  displayed  heavier  pigmenta- 
tion than  in  the  late  egg  stage,  with  melanophores 
present  on  both  its  anterior  and  posterior  surfaces. 

Preserved  Larvae  at  Hatching 

The  remaining  pigmentation  following  preser- 
vation in  2.5%  formaldehyde  for  at  least  24  h 
were  the  melanophores  on  the  head  and  dorso- 
lateral region  of  the  body.  The  band  of  pigment 
around  the  body  posterior  to  the  anal  papilla 
was  lost  except  for  a  few  scattered  melanophores. 
The  yolk  sac  and  oil  globule  had  contracted  and 
obscured  any  pigment  which  may  have  remained. 

Live  Larvae  One  to  Three  Days  Old 

The  pigmentation  pattern  of  the  yolk  sac  larvae 
changed  markedly  during  the  first  few  days  after 
hatching.  Owing  to  the  rapid  change,  larvae 
(preserved)  at  any  time  exhibited  various  stages 


of  pigment  development.  Therefore  the  descrip- 
tions presented  are  "average"  patterns  observed. 
Had  the  larvae  come  from  simultaneously  fer- 
tilized eggs,  the  differences  would  probably  have 
been  less  pronounced.  As  the  pigment  pattern 
stabilized  with  age,  variations  among  larvae 
were  correspondingly  reduced. 

There  was  a  loss  of  lateral  pigmentation 
coinciding  with  a  coalescense  of  the  small  dorsal 
melanophores  to  form  fewer,  large  melanophores 
on  the  dorsal  edge  of  the  body,  and  also  with  the 
appearance  of  pigment  on  the  ventral  edge  of  the 
hypomeres.  These  cjianges  were  apparent  in  most 
of  the  day-old  larvae. 

By  the  end  of  the  second  day,  the  larvae  pos- 
sessed discrete  melanophores  on  the  dorsal  and 
ventral  edges  of  the  body  in  a  single  discon- 
tinuous line.  The  dorsal  body  melanophores 
showed  branches  or  "dendrites"  which  projected 
up  into  the  fin  fold.  These  were  most  pro- 
nounced in  the  region  of  the  dorsal  fin  opposite 
the  divergence  of  the  posterior  end  of  the  gut 
from  the  body.  A  network  of  dendritic  melano- 
phores developed  about  midway  along  the  dorsal 
and  ventral  fin  folds  (Figure  2B).  These  networks 
were  gradually  lost  within  the  next  five  days  of 
growth. 

Also  evident  on  the  second  day  was  the  cluster  of 
melanophores  on  the  top  of  the  head  and  over  the 
snout  region  (present  in  the  advanced  embryo). 
The  first  indication  of  eye  pigmentation  appeared 
with  faintly  pigmented  melanophores  over  the 
iris,  but  concentrated  along  its  posterior  margin. 

The  caudal  region  usually  possessed  a  single 
minute  melanophore  dorsal  and  two  or  three 
ventral  to  the  end  of  the  notochord  (Figure  2A). 
The  dorsal  melanophore  was  lost  in  the  older 
larvae,  but  the  ventral  melanophores  persisted 
and  were  situated  over  the  early  caudal  actino- 
trichia  at  about  the  sixth  day. 

Three-day-old  larvae  were  similar  in  pigmen- 
tation to  the  two-day-old  larvae  except  in  their 
heavier  eye  pigmentation  and  fewer  melano- 
phores on  the  dorsal  body  edge. 


Preserved  Larvae  One  to  Three  Days  Old 

Following  preservation  in  2.5%  formaldehyde 
for  48  h,  virtually  all  pigmentation,  except  for 
the  dorsal  and  ventral  body,  eye,  and  head 
melanophores,  were  lost.  In  a  few  specimens, 


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MILLER  and  SUMIDA:  DEVELOPMENT  OF  CARANX  MATE 


Figure  2A. — Yolk  sac  larva,  Caranx  mate,  just  after  hatching,  1.62  mm  SL. 


Figure  2B. — Three-day  old  larva,  Caranx  mate,  2.26  mm  SL. 


Figure  2C. — Six-day  old  larva,  Caranx  mate,  3.06  mm  SL. 


Figure  2D. — Twelve-day  old  larva,  Caranx  mate,  3.96  ram  SL. 


503 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


faint  traces  of  the  fin  fold  and  oil  globule 
pigment  could  be  distinguished. 


Morphological  Development  of  Yolk 
Sac  Larvae 

Omaka  larvae  hatch  in  a  relatively  undif- 
ferentiated state,  the  only  conspicuous  structures 
being  the  large  yolk  sac,  the  unpigmented  eyes, 
otic  vesicles,  and  heart.  The  oil  globule,  positioned 
forward  of  the  head  at  the  extreme  anterior 
margin  of  the  yolk  sac,  is  characteristic  of 
carangids  (Ahlstrom  and  Ball,  1954).  Ten  hours 
after  hatching  (1.80  mm  SL),  the  larvae  had 
developed  a  narrow,  straight  gut  tube  (it  became 
convoluted  on  the  fifth  day)  terminating  at  the 
anal  papilla  and  urinary  bladder  (Figure  2B). 
The  gradual  yolk  resorption  resulted  in  the  oil 
globule's  shifting  its  position  posteriad  while 
remaining  at  the  anterior  margin  of  the  sac.  The 
oil  globule  lay  just  ventral  to  the  head  at  10  h. 

Pectoral  buds  appeared  in  the  larvae  by  the 
end  of  the  second  day  and  the  jaw  buds  by  the 
third  day.  After  three  days  most  of  the  yolk 
had  been  absorbed,  and  the  oil  globule  had 
diminished  in  size  to  a  small,  barely  noticeable 
spherical  body.  The  end  of  the  third  day  was  thus 
selected  as  the  termination  of  the  yolk  sac  stage 
of  the  larvae. 

By  the  fourth  day,  the  eyes  were  completely 
pigmented,  the  mouth  was  open  and  the  broad, 
membranous  pectoral  fins  were  functional.  The 
small  collapsed  yolk  sac  containing  the  now 
minute  oil  globule  was  still  evident  ventral  to  the 
anterior  portion  of  the  abdominal  cavity. 

LARVAE 

Pigmentation 

Head  Pigmentation 

Following  yolk  absorption  (in  three-to  four- 
day-old  larvae),  head  pigmentation  was  present 
in  the  following  areas:  (1)  the  median  dorsal 
surface  of  the  midbrain  (optic  lobes)  consisting 
of  one  or  two  small  melanophores;  (2)  the  floor 
of  the  otic  vesicle  with  two  or  three  expanded 
melanophores  which  remained  visible  until 
obscured  by  the  overgrowth  of  tissue  in  older 
larvae  at  about  day  10  (Figure  2C);  (3)  along 


the  dorsal  margin  of  the  opercle  which  exhibited 
a  few  faintly  pigmented  melanophores;  (4)  on  the  I 
lower  jaw  with  a  melanophore  situated  at  the  tip  , 
of  the  lower  jaw  and  another  at  the  angular  I 
bone,  with  most  of  the  larvae  having  a  melano-  ' 
phore  midway  between  these  two. 

As  the  larvae  grew,  the  density  of  head  pig-  j 
mentation  increased — particularly  over  the  mid- 
and  forebrain  region  and  on  the  jaws.  The 
number  of  melanophores  increased  on  the  postero- 
lateral half  of  the  midbrain  lobe  while  a  ring 
of  melanophores  concurrently  outlined  the  mar- 
gin of  the  midbrain  capsule.  Larvae  of 
approximately  3.5  mm  (day  8-not  illustrated) 
exhibited  a  cluster  of  expanded  melanophores 
over  the  midbrain  which  gradually  extended 
antero-ventrally  to  the  forebrain  and  snout 
region.  Pigmentation  on  the  surface  of  the  head 
had  intensified  in  the  older  larvae,  with  the  cap 
over  the  midbrain  being  especially  conspicuous. 

By  the  tenth  day  (4.0  mm  SL),  most  larvae 
possessed  a  melanophore  at  the  tip  of  the  upper 
jaw  in  addition  to  those  on  the  lower  jaw; 
pigmentation  subsequently  increased  over  the 
premaxillary,  maxillary,  and  dentary  region 
as  the  larvae  advanced.  Melanophores  located  on 
the  jaws  were  smaller  and  more  punctate  than 
those  on  the  top  of  the  head  and  along  the 
operculum. 

Pigmentation  on  the  membrane  overlying  the 
branchiostegal  rays  and  along  the  gular  region 
developed  in  eight-  to  ten-day-old  larvae  (3.5- 
4.0  mm  SL)  (Figure  2D).  The  most  anterior 
branchiostegal  rays  were  initially  pigmented  with 
pigmentation  proceeding  distad  until  the  full 
complement  of  seven  rays  was  pigmented. 
Pigmentation  of  each  ray  also  proceeded  distad 
resulting  in  larvae  of  20  to  22  days  (8.3-9.5 
mm  SL)  possessing  as  many  as  two  or  three 
melanophores  over  the  basal  end  of  each  branchi- 
ostegal ray  (Figure  3A).  This  pigmentation  was 
barely  discernible  in  larvae  of  26  days  (10.9 
mm  SL)  and  eventually  lost  altogether  in  larvae 
of  28  days  (11.4  mm  SL).  Melanophores  along 
the  median  gular  region  similarly  increased  in 
density,  forming  an  almost  continuous  dotted 
line  of  contracted  melanophores  posterior  to  the 
isthmus  in  larvae  of  14  days  (5.2  mm  SL). 
Additional  melanophores  formed  along  this  line 
but  pigmentation  in  this  region  gradually  dis- 
appeared, like  the  branchiostegal  pigmentation, 
in  the  advanced  larvae. 


504 


MILLER  and  SUMIDA:   DEVELOPMENT  OF  CARANX  MATE 


Figure  3A. — Eighteen-day  old  larva,  Caranx  mate,  7.67  mm  SL. 


Figure  3B. — Thirty-three-day  old  larva,  Caranx  mate,  12.60  mm  SL. 


The  operculum  was  never  heavily  pigmented, 
although  melanophores  formed  along  the  region 
between  the  preopercular  spines  of  larvae  from 
day  8  to  16  (3.5-6.2  mm  SL),  as  the  spines  were 
being  resorbed.  In  addition  there  were  several 
melanophores  scattered  over  the  upper  region  of 
the  operculum  posterior  to  the  eye. 

Body  Pigmentation 

ABDOMINAL  REGION.— The  abdominal 
region  of  the  omaka  larvae  following  yolk  absorp- 
tion as  used  here  refers  to  the  peritoneal  cavity 
with  its  overlying  tissue.  At  six  days  (3.0  mm 
SL)  the  one  or  two  faintly  pigmented  melano- 
phores could  be  seen  immediately  ventral  to  the 
base  of  the  pectoral  fin.  These  melanophores 
persisted  until  the  larvae  were  14  days  old 
(5.2  mm  SL)  (Figure  2C,  D).  A  few  melanophores 
were  scattered  over  the  abdominal  wall  in  the 
early  larvae  with  increasing  numbers  being 
formed  in  older  larvae. 

The  spherical  gas  bladder  was  apparent  by  the 
sixth  day  (3.0  mm  SL)  with  its  dorsal  cap  of 
embedded  pigmentation.  The  gas  bladder  was 


gradually  depressed  into  an  elliptical  shape  by 
day  10  (4.0  mm  SL)  and  its  pigment  largely 
obscured  with  the  increasing  growth  of  muscula- 
ture dorsally. 

A  line  of  melanophores  developed  by  day  6 
(3.0  mm  SL)  (Figure  2C)  extending  along  the 
dorsal  wall  of  the  abdominal  cavity  from  the 
gas  bladder  to  the  terminus  of  the  gut  where  it 
converged  with  the  ventral  line  of  melanophores 
along  the  edge  of  the  hypomeres  (see  section  on 
ventrum  pigmentation).  This  pigmentation  in- 
creased in  density  through  day  8  (not  illustrated) 
until  it  was  obscured  by  the  growth  of  overlying 
tissue  by  day  12  (Figure  2D).  This  pigmentation 
had  a  diffused  appearance  owing  to  its  internal, 
dorsal  position,  but  consisted  of  discrete  melano- 
phores. 

Also  evident  in  six-day-old  larvae  was  peri- 
toneal pigmentation  along  the  ventral  edge  of  the 
abdominal  cavity,  including  a  small  precleithral 
cluster  of  melanophores,  a  larger  cluster  just 
ventral  to  the  liver  (where  the  pelvic  bud  sub- 
sequently appeared),  and  a  row  of  melanophores 
extending  from  the  ventral  surface  of  the  stomach 
to  the  anus.  These  pigments  gradually  diminished 


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FISHERY  BULLETIN:  VOL.  72.  NO.  2 


and  were  obscured  or  lost  in  larvae  of  about 
26  days  (10.9  mm  SL). 

DORSUM. — Dorsum  pigmentation  of  the  post 
yolk  sac  larvae  of  four  days  of  age  (2.6  mm  SL) 
consisted  of  a  single  line  of  9  to  13  large,  stellate 
melanophores  extending  posteriad  from  the  base 
of  the  hindbrain  to  the  17th  to  19th  myomere 
along  the  dorsal  edge  of  the  body  (Figure  2C). 
At  ten  days  (4.0  mm  SL),  numerous  small 
melanophores  had  formed  ventro-laterally,  inter- 
spersed along  the  prominent  line  of  melanophores 
of  the  dorsal  edge.  The  appearance  of  these 
lateral  melanophores  coincided  with  the  appear- 
ance of  dorsal  and  anal  fin  anlagen  (which  were 
visible  as  opaque  thickenings  in  the  fin  fold). 

By  day  12  (Figure  2D)  (4.5  mm  SL)  the  dorsal 
melanophores  had  become  smaller  and  more 
numerous,  bordering  each  side  of  the  ventral 
margin  of  the  dorsal  fin  anlage.  The  formerly 
conspicuous  single  row  of  large  melanophores 
on  the  edge  of  the  dorsum  was  now  lost,  having 
been  replaced  by  these  smaller  dorsal  melano- 
phores in  a  double  row  along  the  base  of  the  fin 
anlage  and  continuing  in  a  single  row  posteriorly. 

Larvae  of  15  to  16  days  of  age  (5.2-6.2  mm 
SL)  showed  increased  lateral  spreading  of  pigmen- 
tation. By  18  days  (7.4  mm  SL)  (Figure  3A), 
melanophores  had  formed  along  the  more  pos- 
terior two-thirds  epaxial  myoseptal  lines,  which 
became  more  pronounced  in  20-day-old  larvae 
(8.3  mm  SL).  This  epaxial  myoseptal  pigmenta- 
tion pattern  was  gradually  obscured  by  the 
increasing  density  of  pigmentation  over  the  entire 
area  of  the  dorsum  beginning  in  22-day-old  larvae 
(9.5  mm  SL). 

The  caudal  peduncle  remained  sparsely  pig- 
mented both  dorsally  and  ventrally  throughout 
development.  (The  pigment  along  the  base  of  the 
caudal  fin  is  described  in  the  section  on  fin 
pigmentation.) 

VENTRUM. — The  pigmentation  changes  of  the 
ventrum  from  the  four-day-old  larvae  followed  a 
similar  pattern  to  that  of  the  dorsum  with  a  few 
exceptions.  The  larvae  of  four  to  eight  days  of 
age  exhibited  a  single  line  of  12  to  26  small 
melanophores  along  the  ventral  edge  of  the  body 
from  the  anus  to  the  23rd  or  24th  myomere.  These 
ventral  melanophores  were  smaller  and  extended 
more  posteriad  than  those  aligned  along  the 
dorsal  edge  of  the  body  until  fin  formation  was 
well  initiated.  In  addition,  two  to  four  minute 


punctate  melanophores  appeared  on  the  ventral 
tip  of  the  notochord  (which  subsequently  migrated 
ventrally  to  become  situated  along  the  proximal 
edges  of  the  caudal  actinotrichia  discussed  in  the 
section  on  fin  pigmentation). 

With  the  first  appearance  of  the  anal  fin 
anlage  in  ten-day-old  specimens,  faint  melano- 
phores formed  dorsolaterally  over  the  ventrum, 
followed  by  the  appearance  of  a  double  line  of 
melanophores  along  the  base  of  the  anal  fin 
anlage  in  12-day-old  larvae  (4.5  mm  SL)  from 
the  previously  single  line  as  it  occurred  along  the 
base  of  the  dorsal  anlage.  From  day  14  to  16 
(5.2-6.2  mm  SL),  melanophores  formed  a  con- 
spicuous pattern  along  the  hypaxial  myoseptal 
lines,  with  others  scattered  in  the  surrounding 
region  (Figure  3A,  B).  These  latter  were  most 
concentrated  over  the  ventral  one-third  of  the 
hypomeres.  The  hypaxial  myoseptal  pigment 
pattern  remained  visible  in  the  largest  larvae 
(18.0  mm)  in  contrast  to  that  on  the  dorsum 
and  remained  as  a  major  distinguishing  char- 
acteristic. 

"LATERAL  LINE  STREAK".— The  "lateral 
line  streak"  refers  to  the  dashed  line  of  pigmen- 
tation along  the  lateral  midline  of  the  body  as 
described  for  several  other  carangid  larvae  (see 
Ahlstrom  and  Ball,  1954;  and  Kramer,  1960). 
It  appeared  in  the  six-day  (Figure  2C)  omaka 
larvae  (3.0  mm  SL)  with  two  or  three  elongate 
melanophores  arising  near  the  vertical  of  the 
anterior  portion  of  the  hindgut,  with  as  many  as 
13  melanophores  having  formed  in  eight-day-old 
(3.5  mm  SL)  larvae.  Indeed,  body  pigmentation 
of  the  larvae  at  this  age  was  characterized  by 
three  lines:  along  the  dorsal  and  ventral  edges 
of  the  body,  and  the  lateral  line  streak. 

Although  it  was  largely  obscured  by  the  over- 
growth of  tissue  and  heavier  lateral  pigmentation, 
the  streak  was  still  noticeable  in  the  36-day-old 
larvae  (16.6  mm  SL).  It  provided  a  sharp  line 
of  demarcation  between  the  heavily  pigmented 
dorsum  and  the  more  sparsely  pigmented  ven- 
trum in  the  older  larvae  (Figure  3B). 

Fin  Pigmentation 

CAUDAL. — Prior  to  notochord  flexion,  a  few 
small  melanophores  were  present  along  the  distal 
margin  of  the  early  hypural  plate  (Figure  2D). 
In  addition,  a  line  of  minute  melanophores  had 
formed  along  the  ventral  margin  of  the  caudal 


506 


MILLER  and  SUMIDA:  DEVELOPMENT  OF  CARANX  MATE 

fin  fold,  but  was  lost  in  older  larvae  (ca.  7.5 
mm  SL). 

Following  flexion  of  the  notochord  (ca.  6.0  mm 
SL),  melanophores  were  still  evident  along  the 
posterior  margin  of  the  hypural  bones  and  along 
the  dorsal  and  ventral  margins  of  the  fin  mem- 
brane in  the  caudal  peduncle  region,  with  addi- 
tional caudal  fin  pigment  developing  distally 
between  the  rays.  The  density  of  melanophores 
increased  in  the  older  larvae,  generally  forming 
in  one  or  two  rows  between  the  rays. 


PECTORAL.— Larvae  of  ca.  6.0  mm  SL  had 
minute  melanophores  scattered  along  the  distal 
margin  of  the  pectoral  fin,  but  pigmentation 
remained  sparse  compared  to  that  of  the  caudal, 
dorsal,  and  anal  fins.  By  8.5  mm,  the  pigmentation 
had  increased  to  rows  of  three  to  five  melano- 
phores interspersed  between  the  more  dorsal  rays, 
with  this  pigmentation  spreading  ventrad  as  the 
larvae  grew. 

DORSAL  AND  ANAL.— Pigmentation  of  the 
dorsal  fin  fold  was  described  earlier.  In  the  early 
larvae  up  to  ca.  3.0  mm,  there  were  dendritic 
melanophores  lining  the  edge  of  the  preanal 
fin  fold  which  were  lost  in  larvae  by  4.5  mm. 

The  pattern  of  pigment  development  was 
similar  for  both  fins,  although  that  on  the  anal 
was  formed  earlier.  This  was  consistent  with  the 
apparent  earlier  formation  of  the  anal  fin.  By 
6.0  mm,  larvae  displayed  the  beginning  of  a  row 
of  melanophores  along  the  distal  margin  of  the 
anal  pterygiophores  (Figure  3A).  Initially  each  of 
these  melanophores  was  situated  between  ad- 
jacent pterygiophores  in  the  anterior  portion  of 
the  fin;  more  developed  posteriad  in  older  larvae. 
The  entire  length  of  the  proximal  margin  of  the 
anal  fin  had  this  pigment  by  8.0  mm,  but  the 
dorsal  fin  margin  showed  no  evidence  of  it  until 
ca.  7.0  mm.  Approximately  three-fourths  of  the 
anterior  portion  of  the  dorsal  fin  margin  was 
pigmented  at  10.0  mm. 

Rows  of  two  to  four  melanophores  were  evident 
along  the  distal  region  of  the  fin  membrane 
between  the  anteriormost  anal  fin  rays  at  ca. 
6.0  mm.  The  fin  pigmentation  process  proceeded 
posteriad,  with  the  melanophore  number  increas- 
ing to  as  many  as  14  in  double  rows  between 
rays  in  larvae  of  ca.  10.5  mm. 

Larvae  of  ca.  8.5  mm  showed  melanophores 
forming  distally  on  the  fin  membrane  surrounding 


the  dorsal  spines  and  between  the  first  few  dorsal 
rays.  Subsequently,  the  fin  pigment  developed 
posteriad  as  in  the  anal  fin;  and  the  density  of 
melanophores  on  the  dorsal  fin  membrane  was 
similar  to  that  of  the  anal  fin  by  11.3  mm. 

PELVIC  (VENTRAL).— Like  the  pectoral  fin, 
each  pelvic  fin  was  sparsely  pigmented.  Two  or 
three  melanophores  were  observed  on  the  small, 
rayless  fin  on  larvae  of  ca.  6.0  mm.  By  ca.  7.6 
mm,  two  or  three  rows  of  a  few  small,  incon- 
spicuous melanophores  had  formed  between  the 
rudimentary  fin  rays  (Figure  3A). 

Fin  Development 

The  omaka  larvae  hatched  with  no  developed 
fins  but  a  broad,  flat  fin  fold.  The  subsequent 
formation  of  fins  (first  development  of  lepido- 
trichia)  followed  a  sequential  pattern  much  like 
that  described  for  Trachurus  symmetricus  (Ahl- 
strom  and  Ball,  1954),  viz.  caudal,  pectoral,  anal 
and  soft  dorsal,  spiny  dorsal,  and  pelvic  (ventral) 
in  that  order. 

The  stage  of  omaka  fin  development  par- 
ticularly, appeared  to  us  to  be  more  dependent 
on  size  attained  than  age.  Smaller,  older  larvae 
were  found  to  have  not  yet  completed  certain 
stages,  while  some  precocious  (larger)  larvae  had. 
Owing  to  rapid  development  of  larvae,  larger 
samples  at  more  frequent  time  intervals  would  be 
required  to  test  a  hypothesis  of  size  versus  age 
dependence  of  developmental  events. 

Caudal 

Caudal  actinotrichia  could  be  observed  in 
larvae  as  small  as  2.2  mm  in  the  form  of  faint 
lines  projecting  distally  from  the  area  around  the 
tip  of  the  notochord.  True  rays  (lepidotrichia) 
were  first  evident  in  larvae  ca.  3.4  mm  (day  7) 
and  became  more  prominent  in  4.0  mm  larvae  as 
ventrally  projecting  incipient  rays  from  the 
presumptive  hypural  plate  below  the  tip  of  the 
notochord.  These  rays  were  well-defined  in  larvae 
of  ca.  4.5  mm  (day  12),  when  notochord  flexion 
was  initiated.  At  this  time  as  many  as  15  rays 
of  the  total  17  principal  caudal  rays  could  be 
observed  still  projecting  obliquely  from  the 
developing  unossified  hypural  bones  lying  ventral 
to  the  notochordal  tip.  Notochord  flexion  and  the 
formation  of  the  17  principal  caudal  rays  (nine 


507 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


above  the  midline  of  the  hypural  plate,  eight 
below)  were  completed  in  larvae  by  6.0  mm  (day 
16).  (Secondary  rays  were  added  anteriad  along 
the  dorsal  and  ventral  margins  of  the  caudal 
peduncle  with  as  many  as  nine  formed  on  each 
edge  in  the  largest  larvae.) 

The  rounded  caudal  fin  fold  was  confluent  with 
the  dorsal  and  anal  fin  folds  in  the  young  larvae, 
but  an  indentation  of  the  fin  fold  occurred  in  the 
region  of  the  future  caudal  peduncle  in  the  older 
larvae.  The  caudal  fin  was  separated  from  the 
dorsal  and  anal  fin  membranes  in  larvae  between 
5.3  mm  and  6.0  mm  (day  14-16).  At  this  stage 
of  development  the  caudal  fin  possessed  a  straight 
margin,  rather  than  rounded,  along  its  posterior 
edge  and  subsequently  attained  a  bilobate  shape 
in  larvae  of  ca.  10.5  mm  (day  24). 

Pectoral 

The  pectoral  fin  developed  early  during  the  yolk 
sac  stage  (see  earlier  sections).  However,  rays  did 
not  form  until  the  larvae  were  ca.  5.4  mm  (day  14) 
when  six  or  more  rays  could  be  counted  in  the 
upper  region  of  the  fin.  Addition  of  rays  pro- 
ceeded ventrally  with  the  rays  decreasing  in 
length  ventrally  to  give  the  pectoral  fin  an  obovate 
shape  in  the  older  larvae  compared  to  the  earlier, 
more  rounded,  membranous  larval  fin. 

The  adult  complement  of  21  to  22  rays  was 
attained  in  larvae  of  9.3  mm.  A  short,  inconspicu- 
ous spine  at  the  extreme  dorsal  margin  of  the 
pectoral  was  evident  upon  close  examination  of 
our  cleared  and  stained  specimens  of  minimal 
length  8.4  mm  and  larger  cleared  and  stained 
juveniles  from  our  field-collected  samples. 

Anal 

Formation  of  the  anal  fin  was  first  evidenced 
by  the  appearance  of  the  anal  anlage  in  larvae 
as  small  as  3.75  mm.  (See  section  on  ventrum 
pigmentation.)  Following  the  formation  of  the 
dorsal  and  anal  anlagen,  it  appeared  that  the 
separation  of  the  fin  fold  into  dorsal,  anal,  and 
caudal  sections  coincided  with  the  development 
of  incipient  rays  and  first  few  spines  of  the  dorsal 
and  anal  fins  in  larvae  from  5.4  mm  to  5.5 
mm  (day  14). 

One  anal  spine  formed  concurrently  with  six 
or  more  incipient  rays  in  larvae  of  5.4  mm  or 
larger;  the  two  remaining  spines  developed 


anteriad  to  the  first  formed  spine  in  larvae 
between  7.0  and  9.0  mm  which  had  at  least  15 
rays  formed  posteriorly. 

Generally  by  9.0  mm,  the  two  most  anterior 
anal  spines  had  separated  from  the  third  which 
remained  associated  with  the  soft  rays.  However,, 
a  well-defined  separation  of  the  fin  membrane  did 
not  occur  until  the  larvae  were  16.0-17.0  mm  in 
length.  The  adult  complement  of  II-I,  17-19  for 
the  anal  fin  was  completed  in  larvae  by  9.0  mm, 
although  three  smaller  specimens  (8.13,  8.63  and 
8.88  mm  SL)  had  complete  anal  fins. 

An  inconspicuous  flap  of  tissue  could  be 
observed  developing  over  the  bases  of  the  spines 
and  first  few  rays  of  the  anal  fin  in  most  of 
the  larvae  by  11  mm.  The  flap  was  not  completely 
formed  along  the  basal  margin  of  the  anal  fin 
in  our  largest  larva  (18  mm)  but  had  covered 
only  about  three-fourths  of  the  length  of  the 
fin  base.  This  was  the  precursor  to  the  flap  of 
tissue  which  overlies  the  entire  length  of  the 
dorsal  and  anal  fin  bases  in  adult  omaka. 


Dorsal 

The  dorsal  anlage  appeared  at  approximately 
the  same  size  as  the  anal  anlage.  Development  of 
the  soft  dorsal  occurred  prior  to  formation  of  the 
spiny  dorsal.  There  was  no  clear  difference  in 
the  rate  of  development  of  the  soft  dorsal  fin 
and  anal  fin  in  contrast  to  the  jack  mackerel 
(Ahlstrom  and  Ball,  1954). 

Distal  pterygiophores  of  the  soft  rays  were 
evident  in  larvae  of  5.0  to  5.4  mm,  with  incipient 
rays  becoming  differentiated  in  5.55  mm  (and 
larger)  larvae.  Subsequent  fin  development  was 
rapid.  Four  to  six  spines  had  developed  with  as 
many  as  16  rays  in  larvae  of  5.8-6.0  mm.  Spines 
were  added  anteriad  and  rays  posteriad.  Most  of 
the  larvae  of  7.3  to  8.0  mm  length  had  attained 
a  dorsal  fin  complement  of  IX-20  to  IX-22.  In 
larvae  larger  than  9.0  mm,  the  ninth  spine  had 
separated  from  the  preceding  eight  to  separate 
the  two  dorsal  fins.  The  fourth  dorsal  spine 
remained  the  longest  in  the  larger  larvae,  with 
the  others  progressively  decreasing  in  length. 
Larvae  from  9.0  to  18.0  mm  possessed  the  adult 
fin  complement  of  VIII-I,  20-23. 

By  9.25  mm,  only  cleared  and  stained  specimens, 
showed  a  small,  embedded,  forwardly  projecting 
spine  arising  from  the  pterygiophore  of  the  first 
external  spine.  We  did  not  count  this  spine 


508 


MILLER  and  SUMIDA:   DEVELOPMENT  OF  CARANX  MATE 


separately  in  the  fin  complement,  although  some 
investigators  have  apparently  done  so  in  pre- 
senting spiny  dorsal  meristics  for  C.  mate  as 
I+Vm+I  (e.g.,  Smith,  1965;  Munro,  1967).  The 
spine  is  apparent  only  upon  dissection  of  juveniles 
and  adults  of  the  omaka. 

A  narrow  flap  of  tissue  had  begun  to  form  over 
the  basal  edge  margin  of  the  anterior  three  to 
four  dorsal  spines  in  larvae  of  10  mm.  It 
appeared  slightly  earlier  than  that  for  the  anal 
fin.  Like  the  flap  over  the  anal  fin  base,  the  dorsal 
flap  had  only  developed  along  three-fourths  of 
the  length  of  the  dorsal  fin  base  in  our  largest 
reared  larva  (18  mm). 

Pelvic  (Ventral) 

The  inconspicuous  pelvic  fin  bud  appeared  in 
larvae  of  4.4  to  5.7  mm,  except  for  two  specimens 
of  3.64  and  3.96  mm  which  had  already  formed 
the  fin  buds.  These  appeared  as  small  pro- 
tuberances just  ventral  to  the  liver  and  gradually 
differentiated  into  a  larval  fin  in  6.0  mm  larvae. 
Two  or  three  rays  had  formed  in  larvae  by  6.2 
mm,  and  the  adult  complement  of  I,  5  was  com- 
pleted in  larvae  of  7.7  mm. 

OSSIFICATION 

Eighteen  larvae,  one  of  each  age  group  sampled 
and  representative  of  the  size  range  in  the  sample, 
were  cleared  and  stained  with  alizarin  following 
the  technique  described  by  Hollister  (1934). 
(Three  7-day-old  larvae  were  cleared  and  stained 
to  further  define  the  sequence  of  tooth  formation 
on  the  upper  jaw. )  The  specimens  were  cleared  and 
stained  primarily  to  confirm  the  meristics  taken 
and  developmental  descriptions  presented  earlier 
on  unstained  material. 

In  order  to  determine  the  limits  of  precision 
for  our  statements  derived  from  these  cleared 
and  stained  larvae  about  size  of  first  structural 
development,  length  differences  among  our 
relatively  few  specimens  were  measured.  They 
ranged  from  0.1  to  0.2  mm  for  2.9-3.5-mm  speci- 
mens, 0.5  mm  for  specimens  3.5-4.6  mm,  and 
about  1  mm  for  larger  specimens. 

Ahlstrom  and  Ball  (1954)  present  a  thorough 
discussion  of  the  ossification  sequence  for  the 
carangid,  T.  symmetricus  (jack  mackerel).  Our 
cleared  and  stained  specimens  showed  exactly  the 
same  sequence,  but  ossification  (defined  as  taking 


up  alizarin)  of  each  bone  began  in  smaller  omaka 
larvae  than  jack  mackerel  (Ahlstrom  and  Ball, 
1954).  Likewise,  most  of  these  bones  had  com- 
pleted ossification  at  a  smaller  size  in  omaka. 

The  cleithrum,  upper  and  lower  jaw  bones,  and 
preopercular  spines  were  already  ossified  in  our 
2.94  mm  larva.  Minute  teeth  (ca.  4  on  the  upper 
jaw)  had  begun  staining  in  the  larva  of  3.35  mm 
with  numerous  small  teeth  filling  in  the  single 
row  in  larger  larvae.  Teeth  on  the  lower  jaw 
first  appeared  in  the  9.25  mm  larve.  Five  branchi- 
ostegal  rays  were  stained  in  the  larva  of  3.50  mm, 
with  all  seven  branchiostegal  rays  on  each  side 
of  the  base  of  the  operculum  being  stained  in  the 
4.58  mm  larva.  Gill  arches  were  ossified  or 
stained  in  the  4.09  mm  specimen,  and  gill  rakers 
began  staining  in  the. 5.42  mm  larva.  Meristics 
for  ossification  of  fin  elements  are  presented  in 
Table  2. 

All  neural  and  haemal  spines  and  centra  of  the 
24  vertebrae  (10  abdominal  vertebrae,  14  caudal 
vertebrae)  had  completed  ossification  in  the  6.25 
mm  larva.  The  initial  vertebral  ossification, 
indicated  by  the  stain  in  the  neural  spines  of  the 
first  few  abdominal  vertebrae  and  in  the  haemal 
spines  of  the  caudal  vertebrae,  was  present  in 
the  4.09  mm  larva. 

Preopercular  spines  of  the  omaka  larvae  were 
formed  along  two  rows  as  in  the  jack  mackerel 
(Ahlstrom  and  Ball,  1954),  viz.  the  posterior  edge 
of  the  preoperculum  and  the  "preopercular  crest" 
just  anterior  to  the  preopercular  edge  (as  defined 
by  Ahlstrom  and  Ball,  1954).  Those  spines 
situated  along  the  preopercular  crest  were  fewer 
and  smaller  than  those  along  the  edge  of  the 
preoperculum.  During  the  larval  development 
of  omaka,  the  number  of  spines  along  the 

Table  2. — Meristics  of  cleared  and  stained  Caranx  mate 
larvae.  Larvae  smaller  than  4.58  mm  are  omitted  owing  to  lack 
of  ossification  of  these  fin  elements. 


SL 

Age 

Caudal 

Dorsal 

Dorsal 

(mm) 

(days) 

(principal) 

Pectoral 

Anal 

(second) 

(first) 

Ventral 

4.58 

12 

7  +  8 

5.42 

14 

8  +  7 

6 

1.6 

9 

6.25 

16 

9  +  8 

11 

11,13 

17 

VII 

3 

7.67 

18 

9  +  8 

18 

111.17 

1,21 

VIII 

1,5 

8.38 

20 

9  +  8 

20         1 

1-1,18 

1,21 

VIII 

1,5 

9.25 

22 

9  +  8 

21         1 

1-1,17 

1,22 

VIII 

1,5 

9.88 

24 

9  +  8 

22         1 

1-1,17 

1,21 

VIII 

1,5 

10.88 

26 

9  +  8 

1,20         1 

1-1,18 

1,22 

VIII 

1,5 

11.63 

28 

9  +  8 

1,20         1 

1-1,19 

1,22 

VIII 

1,5 

12.38 

30 

9  +  8 

1,20         1 

1-1,17 

1,21 

VIII 

1,5 

13.50 

33 

9  +  8 

1.21         1 

-1,19 

1,23 

VIII 

1,5 

17.00 

36 

9  +  8 

1,21         1 

-1,18 

1,22 

VIII 

1,5 

509 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


ascending  arm  of  the  preoperculum  increased 
from  two  (2.9-3.5  mm  larvae)  to  as  many  as 
six  (7.0-9.0  mm  larvae)  and  from  two  to  seven 
along  the  anteriorly  projecting  descending  arm. 
The  apical  spine  of  the  preoperculum  remained 
slightly  larger  and  broader-based  than  the  others 
as  in  the  jack  mackerel  (Ahlstrom  and  Ball, 
1954),  but  was  still  smaller  and  less  prominent 
than  in  our  other  common  carangid  larva, 
Gnathanodon  speciosus  (unpublished  data),  and 
provides  one  characteristic  for  separating  the  two 
species. 

The  omaka  larvae  showed  no  serrated  dorsal 
crest  at  the  back  of  the  head  which  was  evident 
in  the  jack  mackerel  (Ahlstrom  and  Ball,  1954). 
It  is  considered  to  be  a  rather  common  feature 
of  carangid  larvae  (Berry  1959,  McKenney, 
Alexander,  and  Voss  1958,  Okiyama  1970,  Sho- 
jima  1962)  and  is  present  in  several  of  our 
unidentified  species  of  carangid  larvae. 

GROWTH 

The  growth  rate  and  description  of  changes  in 
body  form  are  based  mainly  on  specimens  reared 
from  eggs  taken  in  surface  tows  from  Kaneohe 
Bay  on  22  February  1971  (Table  1).  At  that  time 
the  bay  surface  temperature  was  24.4°C.  Rearing 
tank  temperatures  ranged  from  22.1°  to  25.9°C, 
with  a  mean  of  24.5°C,  so  the  thermal  environ- 
ments were  similar.  As  stated  in  the  methods 
section,  the  salinity  and  oxygen  level  in  the  tank 
remained  similar  to  those  in  the  bay  throughout 
the  experiment.  Without  data  on  the  quantity 
and  quality  of  food  for  any  given  time  of  the 
rearing  period,  however,  it  is  impossible  to  assess 
the  reality  of  the  growth  rate.  The  general  shape 
of  the  curve  (a  nearly  straight  line)  and  the 
absence  of  any  mass  mortality  suggests  that  the 
rearing  environment  was  at  least  adequate 
throughout  the  experiment.  The  absence  of 
prolonged  lags  in  growth  suggest  the  absence  of 
periods  of  major  stress. 

The  growth  curve  (Figure  4)  is  composed  of  at 
least  three  segments  of  differing  slope:  from 
hatching  through  day  2;  day  3  through  day  5;  and 
from  day  6  onward.  The  inflection  in  the  curve 
at  day  2-3  coincides  with  the  near  final  absorp- 
tion of  yolk,  and  perhaps  more  important,  the 
development  of  a  functional  mouth.  No  major 
structural  change  occurs  at  day  6  which  might  be 
linked  to  that  inflection.  Among  four  rearing 


o 

z 


z 


Y^-0  3016  ♦0.4362  X 

r.  0.9929 

n.16 


16  20 

TIME  (DAYS) 


28 


32 


Figure  4. — Growth  rate  oiCaranx  mate  in  culture.  Regression 
based  on  mean  length  after  day  6.  n  =  16. 

trials,  the  change  in  length  from  hatching  to  day  6 
(ca.  2.5  mm)  was  extremely  variable.  In  two  of 
the  trials,  larvae  increased  in  length  through 
day  3,  then  shrank.  It  appears  that  the  vari- 
ability in  early  omaka  growth  rate  might  be 
linked  to  the  success  of  larvae  in  obtaining  their 
first  exogenous  energy  (Thomas  Cooney,  pers. 
comm. — M.A.  thesis  research).  Owing  to  this 
variability,  the  statistical  description  of  the 
growth  rate  of  larvae  through  day  5  is  of  little 
value.  Interpolation  between  mean  (preserved) 
size  at  hatching  (1.03  mm)  and  mean  size  of  day  6 
(3.05  mm)  yields  an  estimate  growth  of  0.35 
mm/day. 

The  relationship  chosen  to  express  larval 
growth  beyond  day  6  was  the  linear  regression: 
SL  (in  mm)  =  -0.3016  +  0.4362  (age  in  days) 
(Figure  4),  as  determined  from  153  preserved 
specimens.  A  slightly  better  fit  would  have  been 
obtained  with  a  more  complex  function,  but  the 
improvement  in  the  curve  would  be  slight. 

The  greatest  departures  from  linear  growth 
occurred  at  day  14  and  day  28  (SL  =  5.2  mm  and 
11.4  mm,  respectively).  No  major  morphological 
developments  occurred  at  these  sizes,  so  the 
causes  (if  the  departures  are  real)  are  not  known. 
The  generally  poorer  fit  of  the  data  to  the  curve 
at  the  largest  sizes  is  probably  attributable  to 
sampling.  As  the  vagility  of  larvae  increases  with 
size,  the  probability  increases  that  the  smaller 


510 


MILLER  and  SUMIDA:   DEVELOPMENT  OF  CARANX  MATE 


larvae  in  a  tank  are  selected  for  preservation. 
This  effect  is  apparent  from  the  larger  (than 
predicted  from  the  curve)  mean  size  of  the  five 
fish  on  day  36,  which  were  the  last  specimens 
in  the  tank  when  it  was  emptied. 

One  source  of  error  in  relating  early  growth 
rates  of  larvae  to  those  of  larger  larvae  is  their 
shrinkage  upon  preservation.  Five  groups  of  ten 
live  larvae  (one  to  five  days  old),  ranging  in  mean 
standard  length  from  2.46  to  2.85  mm,  ranged  in 
length  from  2.13  to  2.55  mm  24  h  after  preserva- 
tion. Shrinkage  was  also  observed  to  begin  within 
seconds  after  death  when  larvae  died  while  being 
observed  microscopically.  This  latter  observa- 
tion suggests  that  shrinkage  was  not  entirely  due 
to  the  effects  of  formaldehyde  on  body  proteins. 
The  percent  shrinkage  was  not  correlated  in  a 
simple  way  with  size.  Although,  presumably, 
this  percentage  decreases  with  increased  size  of 
larvae,  the  shrinkage  values,  which  ranged  from 
8  to  22'7f  in  the  five  groups,  can  introduce 
significant  error  into  estimates  of  early  larval 
growth.  Newly  hatched  larvae  shrank  as  much  as 
30%  when  they  died. 

Farris  (1959)  described  two  growth  stanzas  of 
the  jack  mackerel,  viz.  (A)  from  hatch  to  day  3 
and  (B)  from  day  3  to  7.  If  these  corres- 
pond to  our  first  two  segments,  then  the  second 
segment  (day  3-7)  of  growth  in  omaka  is  twice 
that  of  jack  mackerel  (0.195  mm/day  compared  to 
0.10  mm/day).  Alternatively,  comparing  growth 
from  hatching  to  yolk  absorption — day  3  in 
omaka,  day  6  in  jack  mackerel — yields  a  similar 
difference,  0.48  and  0.26  mm/day,  respectively. 
The  comparisons  suggest  that  effects  of  starva- 
tion may  occur  prior  to  complete  yolk  absorption. 
Farris'  growth  rates  for  segment  B  (on  starved 
fish)  may  be  underestimates.  Lasker,  Feder, 
Theilacker,  and  May  (1970)  found  that  larvae 
may  begin  to  feed  before  complete  yolk  absorp- 
tion. Comparisons  need  to  be  made  between 
starved  and  fed  yolk-sac  larvae  of  the  same 
species  reared  in  the  same  physical  environment 
before  a  definitive  answer  can  be  reached. 


BODY  PROPORTIONS 

As  Marr  (1955)  pointed  out,  expression  of 
relationships  between  body  dimensions  as  ratios 
contributes  nothing  more  than  plots  of  the 
original  measurements,  so  the  latter  were  used. 
Relationships  between  standard  length  and 


1)  head  length,  2)  eye  diameter,  3)  snout  to  anus 
length,  and  4)  body  depth  at  pectoral  fin  were 
all  adequately  described  by  an  equation  of  the 
form:  Y  =  a  +  6(SL).  All  of  the  data  used  in 
the  regressions  are  from  one  series  of  reared 
omaka  larvae  (Table  1).  The  ratios  all  adequately 
describe  specimens  captured  in  the  field. 

In  the  following  discussions  of  these  relation- 
ships, comparisons  are  made  between  the  omaka 
and  jack  mackerel  (T.  symmetricus),  described 
by  Ahlstrom  and  Ball  (1954).  The  latter  is  the 
only  carangid  larva  for  which  these  kinds  of  data 
are  published.  With  similar  data  for  other 
carangid  species,  these  may  prove  useful  in  a 
key  to  carangid  larvae. 

Head  Length 

Head  length  was  related  to  standard  length 
according  to  the  equation:  HL  =  -0.2796  +  0.3477 
(SL  in  mm)  (Figure  5).  Unlike  T.  symmetricus 
(Ahlstrom  and  Ball,  1954),  there  was  no  inflection 
in  the  curve  at  ca.  4  mm.  The  slope  of  the  regres- 
sion line  for  omaka  (0.3477)  is  not  very  different 
than  that  for  the  jack  mackerel  (0.378),  so  this 
ratio  would  not  be  very  useful  by  itself  in  dis- 
tinguishing the  two  species.  Ahlstrom  and  Ball 
( 1954)  did  find  a  different  slope  (0.556)  in  the  jack 
mackerel  larvae  smaller  than  4.2  mm,  but  several 
of  our  smaller  larvae  would  fit  either  regression. 

Eye  Diameter 

The  relationship  between  eye  diameter  and 


STANDARD  LENGTH    (MM) 


Figure  5. — Relationship  between  standard  length  and  head 
length  ofCaranx  mate  larvae. 


511 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


S        15 


Y>  -0  1089*0  1366  X 

'.09928 

n.l9l 


.^■^ 


STANOASD  LENGTH        (MM) 


Snout-to-Anus  Length 

The  snout-to-anus  length  increased  0.5347  mm 
for  each  millimeter  increment  in  standard  length 
throughout  larval  development  (Figure  7).  As 
might  be  expected  from  the  body  depth  differences 
between  omaka  and  jack  mackerel,  the  ratio 
between  snout-to-anus  length  and  standard 
length  of  omaka  is  slightly  smaller  than  that 
for  the  jack  mackerel  (0.581),  the  latter  being 
a  more  elongate  larva.  Again,  however,  the 
difference  is  probably  too  small  to  be  useful 
in  separating  the  species. 


Figure  6. — Relationship  between  standard  length  and  eye 
diameter  ofCarartx  mate  larvae. 


standard  length  was  described  by  a  straight  line 
of  the  equation:  ED  =  -0.1089  +  0.1266  (SL  in 
mm)  (Figure  6).  Omaka  larvae  have  almost  the 
same  (proportional)  eye  size  as  T.  symmetricus 
(0.127),  reported  by  Ahlstrom  and  Ball  (1954). 
Therefore,  this  ratio  is  not  useful. as  a  dis- 
tinguishing characteristic. 

The  omaka  eye  was  somewhat  ovoid  with  the 
blunt  end  anterior.  The  posterior,  more  acute, 
end  of  the  eye  became  more  angled  up  to  day  4, 
then  the  trend  was  reversed  so  the  juvenile 
round  eye  shape  was  reached  by  day  20  (SL  = 
8.27).  The  "squarish  distortion"  reported  for  T. 
symmetricus  (Ahlstrom  and  Ball,  1954)  did  not 
occur  in  omaka. 


Body  Depth  at  Pectoral  Insertion 

The  relationship  between  the  body  depth  and 
standard  length  remained  constant  throughout 
larval  development  (Figure  8).  No  inflection  was 
evident  in  the  omaka,  as  was  reported  for  T. 
symmetricus  by  Ahlstrom  and  Ball,  1954  (larvae 
smaller  than  4.2  mm).  The  slopes  of  the  regres- 
sion lines  (0.425  for  omaka  and  0.278  for  jack 
mackerel  larvae)  are  different  enough  to  be  used 
to  distinguish  these  species  over  4  mm;  omaka 
larvae  are  considerably  deeper-bodied.  The  other 
common  carangid  in  Kaneohe  Bay,  G.  speciosus, 
has  a  still  deeper-bodied  larva  (our  unpublished 
data);  so  this  ratio  appears  the  most  useful  of 
the  four  discussed  to  distinguish  at  least  these 
three  species. 


•  0  1223.0  5347  X 
■  09972 


_1 1 l_ 


STANDARD    LfNGTH        (MM) 


6  3 


Y.  -0  S583  *OA24bx 

f  .0  9953 

n.l9) 


S  10 


STANDARD  LENGTH        (MM) 


Figure  7. — Relationship  between  standard  length  and  snout- 
to-anus  length  ofCaranx  mate  larvae. 


Figure  8. — Relationship  between  standard  length  and  body 
depth  oCCaranx  mate  larvae. 


512 


MILLER  and  SUMIDA:  DEVELOPMENT  OF  CARANX  MATE 

SUMMARY 

1.  Omaka  eggs  were  pelagic  and  spherical 
with  a  single  oil  droplet  and  segmented  yolk. 
The  diameter  was  about  700-740  fi. 

2.  Egg  development  occurred  in  three  distin- 
guishable stages:  early — fertilization  to  blasto- 
pore closure;  middle — to  tail  flexure;  and  late — 
to  hatching.  Respective  duration  times  at  24.5°C 
were  11-12  hours,  11-12  hours,  and  0.5-1  hour. 

3.  Yolk  sac  larvae  hatched  at  a  length  of  1.3- 
1.7  mm  with  the  oil  globule  positioned  forward 
in  the  yolk  sac. 

4.  By  the  fourth  day  (SL  =  2.6  mm),  the 
eyes  were  pigmented,  the  yolk  and  oil  globule 
absorbed,  and  the  mouth  functional. 

5.  Fin  development  (first  appearance  of  lepido- 
trichia)  occurred  in  the  order:  caudal  (3.4  mm); 
pectoral  (5.4  mm);  anal  and  soft  dorsal  (5.4-5.5 
mm);  spiny  dorsal  (5.8  mm);  and  pelvic  (6.2  mm). 

6.  Unlike  many  carangid  larvae,  omaka  did 
not  develop  a  serrated  crest  behind  the  head. 

7.  Values  for  ratios  of  body  proportions  to 
standard  length  were:  head  length,  0.3477;  eye 
diameter,  0.1266;  snout-to-anus  length,  0.5347; 
body  depth,  0.4246.  Only  the  body  depth/SL 
ratio  was  useful  in  separating  omaka  from  jack 
mackerel  and  certain  other  Hawaiian  carangid 
larvae. 

8.  The  growth  of  our  cultured  omaka  after 
day  6  was  adequately  described  by  a  straight  line 
with  slope  0.44.  Before  day  6,  growth  was  ex- 
tremely variable,  averaging  about  0.35  mm/day. 

9.  Of  primary  use  in  separating  omaka  from 
jack  mackerel  larvae  (the  only  other  similarly 
described  carangid  larva)  were  pigment  pattern, 
the  absence  of  a  serrated  dorsal  ridge  behind  the 
head,  and  the  difference  in  the  ratios  of  body  depth 
to  standard  length. 

10.  Significant  decreases  in  size  (up  to  33%) 
and  pigmentation  of  larvae  occurred  upon  preser- 
vation. Both  of  these  effects  decreased  with  age 
of  larvae. 

11.  Although  based  on  larvae  reared  in  the 
laboratory,  our  data  relating  growth  and  develop- 
ment to  time  would  be  expected  to  simulate  those 
from  natural  tropical  habitats,  especially  the  data 
for  fish  eggs  and  early  larva. 

ACKNOWLEDGMENTS 

Throughout  the  paper  reference  is  made  to  the 


excellent  paper  by  Ahlstrom  and  Ball  (1954), 
describing  the  eggs  and  larvae  of  the  jack 
mackerel  (T.  symmetricus).  The  authors  acknowl- 
edge a  debt  to  Ahlstrom  and  Ball  for  their 
example.  Many  of  their  descriptive  techniques 
were  used  by  us,  and,  in  our  opinion,  should 
be  considered  a  standard  for  all  larval  fish 
descriptions.  Larval  fish  taxonomy  suffers  greatly 
from  dissimilarities  among  descriptive  tech- 
niques. Thanks  are  also  extended  to  David 
Hashimoto,  Senior  Technician  at  the  Hawaii 
Institute  of  Marine  Biology,  for  rearing  the 
larvae.  This  research  was,  in  part,  supported  by 
University  of  Hawaii  Sea  Grant  No.  GH-93. 
(UNIHI-SEAGRANT-JC-74-02.) 


LITERATURE  CITED 


Ahlstrom,  E.  H.,  and  O.  P.  Ball. 
\     1954.     Description  of  eggs  and  larvae  of  jack  mackerel 
{Trachurus  symmetricus)  and  distribution  and  abun- 
dance of  larvae  in  1950  and  1951.     U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  56:209-245. 

Berry.  F. H. 

1959.  Young  jack  crevalles  (Caranx  species)  off  the  south- 
eastern Atlantic  coast  of  the  United  States.  U.S.  Fish 
Wildl.  Serv.,  Fish.  Bull.  59:417-535. 

Farris,  D.  a. 

1959.  A  change  in  the  early  growth  rates  of  four  larval 
marine  fishes.    Limnol.  Oceanogr.  4(l):29-36. 

Hollister,  G. 

1934.    Clearing  and  dyeing  fish  for  bone  study.    Zoologica 
12:89-101. 
Kramer,  D. 

1960.  Development  of  eggs  and  larvae  of  Pacific  mackerel 
and  distribution  and  abundance  of  larvae,  1952-56.  U.S. 
Fish  Wildl.  Serv.,  Fish.  Bull.  60:393-438. 

Kuthalingham,  M.  D.  K. 

1959.     A  contribution  to  the  life  histories  and  feeding 

habits  of  horse-mackerels,  Mega/aspis  cordyla  (Linn)  and 

Caranx  mate  (Curv  and  Val)  and  notes  on  the  effect  of 

absence  of  light  on  the  development  and  feeding  habits 

of  larvae  and  post  larvae  oiMegalaspis  cordyla.  J.  Madras 

Univ.,  B.  29(2):79-96. 

Lasker,  R.,  H.  M.  Feder,  G.  H.  Theilacker,  and  R.  C.  May. 

1970.    Feeding,  growth,  and  survival  ofEngraulis  mordax 

larvae  reared  in  the  laboratory.     Mar.  Biol.  5:345-353. 

Marr,  J.  C. 

1955.    The  use  of  morphometric  data  in  systematic,  racial 
and  relative  growth  studies  in  fishes.    Copeia  1955:23-31. 
McKenney,  T.  W.,  E.  C.  Alexander,  and  G.  L.  Voss. 

1958.     Early  development  and  larval  distribution  of  the 
carangid  fish,  Caranx  crysos  (Mitchill).     Bull.  Mar.  Sci. 
GulfCaribb.  8:167-200. 
MUNRO,  I.  S.  R. 

1967.  The  fishes  of  New  Guinea.  Victor  C.  N.  Blight, 
Sydney,  New  South  Wales,  650  p.,  78  pis. 


513 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 


Okiyama,  M. 

1970.     Studies  on  the  early  life  history  of  the  rainbow 
runner,  Elagatis  hipinnulatus  (Quoy  &  Gaimard)  in  the 
Indo-Pacific  Ocean.     Bull.  Far  Seas  Fish.  Res.  Lab. 
(Shimizu)  3:167-186. 
Orton,  G.  L. 

1953.    Development  and  migration  of  pigment  cells  in  some 
teleost  fishes.    J.  Morphol.  93:69-99. 
Shojima,  Y. 

1962.  On  the  postlarvae  and  juveniles  of  carangid  fishes 
collected  together  with  the  jelly-fishes.  (In  Jap.,  Engl, 
summ.]     Bull.  Seikai  Reg.  Fish.  Res.  Lab.  27:47-58. 


Smith,  J.  L.  B. 

1965.  The  sea  fishes  of  Southern  Africa.  Cape  and 
Transvaal  Printers  Ltd.,  Capetown,  580  p..   Ill  pis. 

Struhsaker,  J.  W.,  D.  Y.  Hashimoto,  S.  M.  Girard,  F.  T.  Prior, 
and  T.  D.  Cooney. 

1973.  Effect  of  antibiotics  on  survival  of  carangid  fish 
larvae  (Caranx  mate),  reared  in  the  laboratory.  Aqua- 
culture  2(l):53-88. 

Watarai,  L.  T. 

1973.  Growth  rate  of  a  carangid  fish,  the  omaka  Caranx 
mate,  in  Hawaii.     Trans.  Am.  Fish.  See.  102:617-620. 


514 


FOOD  HABITS  OF  GEORGIA  ESTUARINE  FISHES 

I.     FOUR  SPECIES  OF  FLOUNDERS 

(PLEURONECTIFORMES:  BOTHIDAE) 

Robert  R.  Stickney/  Gary  L.  Taylor/  and  Richard  W.  Heard  III^ 

ABSTRACT 

The  food  habits  of  four  species  of  bothid  flounders  from  Georgia  coastal  waters  were  examined  by 
means  of  stomach  content  analyses.  Ocellated  flounders,  Ancylopsetta  quadrocellata  (Gill);  bay 
whiff,  Citharichthys  spilopterus  (Giinther);  and  windowpane,  Scophthalmus  aquosus  (Mitchill) 
fed  heavily  on  the  mysid  shrimp,  Neomysis  americana,  without  regard  to  season  of  the  year  or 
location  within  the  estuary.  The  food  habits  of  both  A.  quadrocellata  and  C.  spilopterus  changed 
to  some  extent  as  the  fish  became  larger.  Organisms  larger  than  N.  americana  dominated  the 
stomach  contents  of  A.  quadrocellata  larger  than  150  mm  standard  length  and  C.  spilopterus 
larger  than  125  mm.  S.  aquosus,  in  the  size  range  examined,  fed  almost  exclusively  on  A^.  americana. 
Fringed  flounder,  Etropus  crossotus  (Jordan  and  Gilbert)  primarily  consurried  the  calanoid 
copepod,  Pseudodiaptomus  coronatus,  during  the  spring,  summer,  and  fall  and  diversified  their 
food  habits  during  the  winter.  P.  coronatus  dominated  the  stomach  contents  both  in  the  rivers 
and  sounds  of  Georgia  estuarine  waters  and  was  the  dominant  organism  in  fishes  of  all  sizes  up 
to  100  mm  when  polychaete  annelids  became  important.  The  food  of  E.  crossotus  did  not  appear 
to  vary  with  time  of  day;  however,  E.  crossotus  did  not  actively  feed  at  night.  The  difference  in 
food  habits  between  E.  crossotus  and  the  other  three  bothid  species  appears  to  be  associated  with 
the  relative  size  of  the  mouth. 


Pleuronectiform  fishes  of  the  family  Bothidae  are 
common  in  the  estuarine  waters  of  the  southeast- 
ern United  States.  Otter  trawl  samples  taken 
within  the  sounds  and  rivers  of  Georgia  indicate 
that  fishes  of  the  family  Sciaenidae  are  the  most 
common,  with  bothids  being  among  the  next 
most  common  species.  Summer  flounder,  Para- 
lichthys  dentatus  and  southern  flounder,  P.  letho- 
stigma,  are  common,  but  are  not  present  in  com- 
mercially exploitable  quantities.  P.  albigutta 
has  also  been  reported  from  Georgia  waters,  but 
appears  to  be  relatively  rare  (Dahlberg  and 
Odum,  1970).  Ocellated  flounder,  Ancylopsetta 
quadrocellata,  while  not  commercially  valuable, 
is  occasionally  caught  by  sport  fishermen. 

Bothid  flounders  are  generally  associated  with 
the  bottom,  either  lying  on  the  surface  of  the 
substrate  or  buried  to  a  greater  or  lesser  extent 
in  the  sediments.  The  feeding  behavior  of  floun- 
ders under  various  conditions  (both  in  nature  and 
in  culture)  has  been  described  (Steven,   1930; 


'  Skidaway  Institute  of  Oceanography,  P.O.  Box  13687, 
Savannah,  GA  31406. 

^  Gulf  Coast  Research  Laboratory,  P.O.  Box  AG,  Ocean 
Springs,  MS  39564. 


011a,  Wicklund,  and  Wilk,  1969;  de  Groot,  1970; 
011a,  Samet,  and  Studholme,  1972;  Stickney, 
White,  and  Miller,  1973),  but  little  information  on 
the  selective  food  habits  of  bothids  is  presently 
available.  The  food  habits  of  Paralichthys  sp. 
have  been  examined  by  Darnell  (1958)  in  the 
Gulf  of  Mexico  and  by  Poole  (1964)  in  New 
England  waters.  A  limited  amount  of  additional 
information  on  P.  albigutta  is  also  available 
from  samples  taken  off  the  southwestern  coast 
of  Florida  (Topp  and  Hoff,  1972).  Examination 
of  the  stomachs  from  a  few  specimens  of  A. 
quadrocellata  and  Etropus  crossotus,  fringed 
flounder,  demonstrated  that  both  feed  on  crusta- 
ceans in  Florida  waters  (Topp  and  Hoflf,  1972) 
with  E.  crossotus  also  utilizing  polychaetes  and 
chaetognaths  for  food  (Reid,  1954;  Topp  and 
Hoff,  1972).  Fourteen  species  of  bothid  flounders 
were  examined  by  de  Groot  (1971)  who  found 
that  they  divided  into  three  groups  by  food 
preference:  fish  feeders,  crustacean  feeders,  and 
polychaete-mollusc  feeders. 

The  food  habits  of  bothid  flounders  along  the 
Georgia  coast  have  not  been  previously  elabor- 
ated. For  purposes  of  the  present  study,  four 


Manuscript  accepted  September  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO. 


1974. 


515 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


species  were  selected  which  seasonally  account 
for  the  majority  of  bothids  captured  by  otter 
trawling  and  were  thus  judged  to  be  important 
in  the  energy  flow  through  the  Georgia  estuarine 
ecosystem.  The  four  species  chosen  were  A. 
quadrocellata;  bay  whiff,  Citharichthys  spilop- 
terus;  E.  crossotus\  and  windowpane,  Scophthal- 
mus  aquosus.  Other  important  Pleuronectiform 
fishes  of  the  Georgia  coast  include  P.  dentatus, 
P.  lethostigma,  Trinectes  maculatus,  and  Sym- 
phurus  plagiusa. 

MATERIALS  AND  METHODS 

The  coastal  region  of  Georgia  consists  of  a 
system  of  barrier  islands  separated  by  sounds 
from  which  a  network  of  rivers  and  tidal  creeks 
emanate.  The  tide  range  (reaching  nearly  3  m 
on  spring  tides)  coupled  with  the  low  relief  of 
the  barrier  islands  and  coastal  plain  results  in 
extensive  areas  of  intertidal  marshlands.  The 
marshes  are  dominated  by  Spartina  alterniflora. 

Flounders  were  collected  by  otter  trawl  and 
cast  net  from  Wassaw  Sound,  Ossabaw  Sound, 
St.  Catherines  Sound,  and  Sapelo  Sound,  and  from 
various  locations  in  rivers  above  the  sound  limits 
(Figure  1).  Most  of  the  fish  utilized  in  this  study 
were  captured  during  1971  and  1972  by  personnel 
from  the  Savannah  Science  Museum  and  Skid- 
away  Institute  of  Oceanography.  Others  were 
donated  from  collections  made  by  workers  at  the 
University  of  Georgia  Marine  Institute  during 
1968.  Whole  fish  were  preserved  in  10%  Formalin^ 
after  capture. 

Location,  date  of  capture,  and  standard  length 
were  recorded  for  each  specimen  used  in  the  study. 
The  stomachs  were  removed,  and  their  contents 
examined  under  a  dissecting  microscope.  Or- 
ganisms found  within  the  stomachs  were  identi- 
fied to  species  when  possible  and  counted.  Para- 
sitic nematodes  and  trematodes  were  found  in 
many  stomachs  but  were  excluded  from  the  food 
habit  data. 

In  many  instances  identifications  of  food  or- 
ganisms were  made  from  pieces  of  animals  found 
within  stomachs.  In  most  cases  these  pieces  pro- 
vided enough  material  for  specific  identification, 
but  in  those  cases  where  decomposition  made 
identification  to  species  impossible,  the  material 
was  identified  to  the  class  or  family  level.  Few 


^  Reference  to  trade  names  does  not  imply  endorsement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


cases  were  found  in  which  the  stomachs  contained 
completely  unidentifiable  organic  material. 
Emphasis  was  placed  on  correctly  enumerating 
the  organisms  found  in  stomachs.  Neither  bio- 
mass  nor  volumetric  displacement  data  were 
obtained.  Since  food  items  were  often  identified 
from  parts  of  an  individual  (the  remainder  having 
been  either  digested  or  not  actually  ingested), 
it  was  felt  that  any  estimate  of  biomass  would 
have  little  significance. 

Many  stomachs  contained  pieces  of  polychaete 
annelids  which  had  apparently  been  nipped  off 
by  the  fish  in  their  feeding  activities.  Since  it 
was  not  possible  to  reconstruct  these  fragments 
into  whole  animals,  heads  were  counted.  Counts 
based  on  fragments  of  organisms  cannot  be  con- 
sidered completely  accurate;  however,  such  food 
organisms  often  accounted  for  a  relatively  small 
fraction  of  the  total  stomach  contents.  The  or- 
ganisms which  made  up  the  numerical  bulk  of 
the  food  were  usually  in  good  condition,  facilitat- 
ing exact  counting. 

One  of  the  more  important  organisms  found, 
Neomysis  americana,  has  not  been  reported  from 
as  far  south  as  Georgia  by  many  previous  authors, 
although  it  has  been  reported  from  the  stomachs 
of  two  species  of  Gadidae,  Urophycis  regius  and 
U.  floridanus  (Sikora,  Heard,  and  Dahlberg,  1972). 
The  reported  range  oiN.  americana  is  from  the 
Gulf  of  St.  Lawrence  to  Virginia  (Tattersall, 
1951;  Wigley  and  Burns,  1971).  This  range  was 
extended  to  near  the  northern  South  Carolina 
border  by  Williams  (1972)  who  also  reported  that 
N.  americana  was  common  in  North  Carolina. 
The  range  is  presently  again  being  extended  by 
A.  B.  Williams  (pers.  commun.)  who  has  examined 
and  verified  examples  of  A^.  americana  from  our 
collections. 


RESULTS  AND  DISCUSSION 

Overall  Evaluation 

Data  summarizing  the  food  of  each  of  the  four 
bothid  species  are  presented  in  Table  1.  Organ- 
isms are  excluded  which  were  not  present  in  at 
least  V7c  of  the  stomachs  examined  in  any  of 
the  four  species  of  fish  or  which  did  not  account 
for  1%  or  more  of  the  total  food  organisms  found 
in  the  stomachs  of  one  or  more  of  the  species  of 
fish.  A  complete  list  of  food  organisms  recovered 
is  presented  in  the  Appendix. 


516 


STICKNEY,  TAYLOR,  and  HEARD:   FOOD  HABITS  OF  FOUR  FLOUNDERS 


GEORGIA 


Location  of 

River   Sampling   Stations 


Savannah  River 


Wassaw  Sound 


GEORGIA 


Ossabaw  Sound 


BRUNSWICK  i 


Catherines  Sound 


Sapelo  Sound 


Doboy  Sound 
'^<^~^AItamaha  Sound 


ATLANTIC 


OCEAN 


St.  Simons  Sound 


Andrew  Sound 


Cumberland  Sound 


i 


Figure  1. — Sampling  area  along  the  coast  of  Georgia  indicating  the  sounds  and  river  locations  from  which  fish 

samples  were  obtained. 


517 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


The  food  habits  of  E.  crossotus  are  distinct 
from  those  of  the  other  three  species  (Table  1). 
Pseudodiaptomus  coronatus  dominated  the  stom- 
ach contents  of  E.  crossotus  but  accounted  for 
only  an  insignificant  fraction  of  the  stomach 
contents  of  A.  quadrocellata ,  C.  spilopterus,  and 
S.  aquosus.  The  stomach  contents  of  each  of  the 
latter  three  species  were  dominated  by  Neomysis 
americana. 

Of  secondary  importance  in  the  stomachs  of 
E.  crossotus  were  polychaete  annelids,  especially 
the  spionid,  Paraprionospio  pinnata.  The  im- 
portance of  Pa.  pinnata  is  extended  if  the  assump- 
tion is  made  that  most  of  the  animals  listed  under 
Spionidae  (Table  1)  were,  in  fact.  Pa.  pinnata 
in  a  state  of  decomposition,  making  specific 
identification  impossible. 

No  fish  remains  were  found  in  any  of  the 
stomachs  ofE.  crossotus  examined,  although  they 
were  found  in  A.  quadrocellata,  C.  spilopterus, 
andS.  aquosus.  The  difference  in  primary  feeding 
habits  between  E.  crossotus  and  the  other  three 
species  of  bothids  appears  to  be  a  reflection  of 


relative  mouth  size  (Figure  2).  E.  crossotus  has 
a  very  small  mouth  relative  to  head  length  (mouth 
averages  about  6  into  head),  whereas,  A.  quadro- 
cellata, C.  spilopterus,  and  S.  aquosus  all  have 
relatively  larger  mouths  in  proportion  to  head 
length  (mouth  averages  3  to  4  into  head).  The 
small  mouth  of  E.  crossotus  correlates  with  its 
selectivity  for  small  organisms  (such  as  Ps. 
coronatus,  which  range  {vom  1  to  1.5  mm  in  length) 
and  those  of  small  diameter  (such  asPa.  pinnata). 
While  the  remaining  three  fish  species  appear  to 
favor  A^.  americana  as  a  primary  food  organism, 
the  diversity  of  sizes  or  organisms  available  to 
them  appears  greater.  A'^.  americana  ranged  from 
6  to  12  mm  in  length  in  our  collections.  This 
organism  was  not  completely  excluded  from  the 
food  of  £■.  crossotus  (Figure  3)  but  was  fed  upon 
only  to  a  limited  extent. 

Table  1  presents  the  food  habit  data  collected 
for  each  species  without  regard  to  season  of  the 
year,  location  in  the  estuary,  or  size  of  the  fish 
under  investigation.  In  order  to  more  critically 
evaluate  the  data  collected  on  each  species,  a 


Cithorichthys      spilopterus 


Ancylopsetta    quadrocellata 


Scophthalmus    aquosus 


Etropus      crossotus 


I   cm 


Figure  2. — Line  drawings  of  the  four  species  of  Bothidae  discussed  depicting  the  differences  in  mouth  size  relative  to  body  length. 

518 


STICKNEY,  TAYLOR,  and  HEARD:  FOOD  HABITS  OF  FOUR  FLOUNDERS 

Table  1. — Occurrence  of  organisms  appearing  in  1%  or  more  of  the  stomachs  examined,  or  representing  1%  or  more  of  the  total 
number  of  food  organisms  recovered  from  the  stomachs  of  one  or  more  of  the  four  species  of  Bothidae  under  investigation.* 


Etropus 

crossotus 

Citharichthys  spilopterus 
Percentage    Percentage  of 

Ancylopsetta 

quadrocellata 

Scophthain 
Percentage 

lus  aquosus 

Percentage 

Percentage  of 

Percentage 

Percentage  of 

Percentage  of 

occurrence 

total  number 

occurrence 

total  number 

occurrence 

total  number 

occurrence 

total  number 

Food  organisms 

in  stomachs 

of  organisms 

in  stomachs 

of  organisms 

in  stomachs 

of  organisms 

in  stomachs 

of  organisms 

Ectoprocta: 

Bugula  nentina 

0.2 

<0.1 

0.0 

0,0 

0,0 

0,0 

1.0 

0.1 

Polychaeta: 

Diopatra  cuprea 

1.7 

0.3 

0.0 

0,0 

0,0 

0,0 

1.0 

0.1 

Nereis  succinea 

4.0 

0.2 

0.0 

0,0 

0,5 

0,1 

1.0 

0.1 

Nereidae 

1.0 

0.1 

0,0 

0,0 

0,0 

0.0 

0.0 

0.0 

Parapnonospio  pinnata 

29.5 

2.9 

0.5 

0.2 

00 

0.0 

0.0 

0.0 

Spionidae 

15.9 

2.6 

0.5 

<0,1 

0,9 

0.2 

0.0 

0.0 

Asabellides  oculata 

3.3 

0.4 

0-0 

0.0 

0,0 

0.0 

0.0 

0.0 

Sabella  microphthalma 

1.0 

0.1 

0.0 

0.0 

0-0 

0.0 

0.0 

0.0 

Unidentified  remains 

1.7 

0.1 

0.0 

00 

0,5 

0.1 

0.0 

0.0 

Mollusca: 

Pelecypod  siphons 

1.9 

0.1 

0.0 

0.0 

00 

0.0 

0.0 

0.0 

Decapoda — Reptantia 

Pmnixa  sp. 

2.4 

0.1 

0.0 

0,0 

3,2 

0.5 

0.0 

0.0 

Portunid  megalops  and  zoea 

2.6 

0.2 

7,1 

0,9 

0,0 

0.0 

0.0 

0.0 

Portunus  spinimanus 

0.0 

0.0 

0,5 

<0,1 

1.4 

0.3 

0.0 

0.0 

Portunus  gibbesii 

0.0 

0.0 

0.0 

0,0 

1.4 

0.4 

0.0 

0.0 

Neopanope  sayi 

0.0 

0.0 

0.0 

0,0 

3.7 

1.0 

0.0 

0.0 

Hexapanopeus  angustifrons 

0.0 

0.0 

0,0 

0,0 

1,8 

0.5 

0.0 

0.0 

Cancer  irroratus 

0.0 

0.0 

0,0 

0,0 

1,4 

0.4 

0.0 

0.0 

Portunid  postlarvae 

0.2 

<0.1 

1,4 

0,1 

2.8 

0.8 

0.0 

0.0 

Calltnectes  sapidus 

0.0 

0.0 

4.3 

06 

0.5 

0.1 

0.0 

0.0 

Decapoda— Natantia: 

Acetes  americanus  carolinae 

0.2 

<0.1 

0.0 

0,0 

0.0 

0.0 

1.0 

0.1 

Palaemonetes  pugio 

1.4 

0.1 

16.2 

28 

0.9 

0.5 

1.0 

0.1 

Trachypenaeus  constrictus 

1.0 

0.1 

35.7 

10,4 

7,8 

5.3 

0.0 

0.0 

Penclimenes  longicaudatus 

00 

0.0 

1.4 

0,1 

0,0 

0.0 

0.0 

0.0 

Ogyrides  limicola 

5.2 

0.3 

10.5 

3,3 

0.0 

0,0 

0.0 

0.0 

Stomatopoda: 

Squilla  empusa 

0.0 

0.0 

15.2 

2,0 

5,5 

1.0 

1.0 

0.1 

Amphipoda: 

Ampelisca  vadorum 

3.8 

0.6 

1,0 

0,1 

1,4 

0.3 

1.0 

0.1 

Corophium  tuberculatum 

2.6 

0.2 

0,0 

0,0 

0,9 

0.1 

1.0 

0.1 

Unciola  serrata 

0.2 

<0.1 

0.0 

0,0 

3.7 

4.6 

1.9 

0.1 

Batea  cattiarinensis 

0.5 

<0.1 

0.0 

0.0 

0.5 

0.1 

2.9 

0.2 

Monoculodes  edwardsl 

7.4 

0.6 

1.0 

0,1 

0,5 

0.1 

1.0 

0.1 

Erichttionius  brasiliensis 

0.2 

0.1 

0,0 

0,0 

0.5 

0.1 

2.9 

0.1 

Caprella  equilibra 

0.0 

0.0 

0,0 

0,0 

0,0 

0.0 

1.0 

0.1 

Gammarus  palustris 

0.0 

0.0 

0,0 

0,0 

0.0 

0.0 

1.0 

0.1 

Microprotopus  ranei 

0.2 

<0.1 

0,0 

0,0 

0.0 

0.0 

1.0 

0.1 

Listnella  barnardi 

2.1 

0.1 

1.0 

0.1 

0.9 

0.1 

0.0 

0.0 

Copepoda; 

Pseudodiaptomus  coronatus 

34.2 

84.6 

1,4 

0.8 

0,5 

0.8 

1.9 

0.5 

calanoid  copepod  remains 

0.5 

0.1 

1,0 

0.2 

0,9 

0-1 

3.8 

1.0 

Cumacea: 

Leucon  americanus 

6.9 

0.5 

0.5 

<0.1 

0,0 

0,0 

0.0 

0.0 

Mancocuma  altera 

2.1 

0.2 

0,0 

00 

0,0 

0.0 

4.8 

0.2 

Oxyurostylis  smith! 

7.4 

1.4 

0.0 

0.0 

0,5 

0.1 

3.8 

0.3 

Mysldacea: 

Neomysis  americana 

19.0 

3.1 

65.7 

72.1 

51.6 

81.0 

59.0 

96.3 

Isopoda: 

Edotea  montosa 

5.7 

0.4. 

00 

0-0 

0,5 

0.1 

0.0 

0.0 

Osteichthyes: 
Symphurus  plagiusa 
Anchoa  mitctiilli 
Cynoscion  sp. 
Sciaenidae  remains 
Gobiidae  remains 
Unidentified  remains 


0.0 

0.0 

4,8 

0.5 

1,4 

0.2 

0.0 

0.0 

0.0 

0.0 

1,0 

0-1 

0,9 

0.3 

0.0 

0.0 

0.0 

0.0 

1,9 

0,2 

00 

0.0 

0.0 

0.0 

0.0 

0.0 

16.7 

2,8 

0.0 

0,0 

0.0 

0.0 

0.0 

0.0 

4.3 

0,5 

0,0 

0.0 

0.0 

0.0 

0.0 

0.0 

11.4 

1,1 

1,8 

0,3 

1.0 

0.1 

Others 


0.0 


0.0 


0,0 


0,7 


0,0 


0,5 


0.0 


0.0 


Empty  stomachs 


26,5 


7,6 


309 


35.2 


'The  total  number  of  stomachs  analyzed  for  each  species  were:  E.  crossotus.  421 :  C,  spilopterus.  210;  A.  quadrocellata.  217:  and  S,  aquosus.  105, 
The  total  number  of  organisms  obtained  from  the  stomachs  of  fishes  examined  were:  E.  crossotus,  8,734;  C,  spilopterus.  2,442;  A.  quadrocellata, 
1,490;  S  aquosus.  2,209, 


519 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


SPRING 

SUMMER 

FALL 

WINTER 

RIVERS 
SOUNDS 

<4I 

41-50 
51-  60 
61-70 
71-80 
81-90 
91-100 
>I00 

Pseudodioplomus     coronatus 

Poiychoeto 

Crustaceo 
Mdiusca 

N=I55 

z 
o 

Pseudodloptomus    coronatus 

P 

C 

N  =128 

< 

Pseudodioptomus    coronatus 

P, 
C 

N  =  89 

</) 

Ps 

Paroprionospio 
pinnata 

Neomysis 
omericono 

Asobellides        P, 
oculata 

M  a 
c 

N  =49 

> 

H 
-I 

Pseudodioptomus  coronatus 

P     c 

N=7I 

< 

o 
o 

Pseudodlaptomus   coronatus 

P 

C  SM 

N  =  350 

_l 

Pseudodioptomus      coronatus 

"      'u 

N  =  I2 

'e 

F 

Pseudodioptomus     coronotus 

P, 

c 

N  =  40 

X 

Pseudodioptomus    coronatus 

pac 

N  =  45 

1- 
(S> 

Pseudodioptomus    coronatus 

P 

c 

N=57 

y 

Pseudodioptomus  coronatus 

N 

P 

caM 

N=87 

o 

IE 
< 

Pseudodioptomus    coronatus 

'  a  c 

N  «95 

Q 

Z 

Pseudodioptomus    coronotus 

P 

cau 

N=56 

1- 

Pseudodioptomus 
coronotus 

Polychoetes 

c 

N  =  29 

1            1            1            1 

1           1           1           1           1 

0      10     20     30    40     50     60    70     80    90    100 

CUMULATIVE      PERCENTAGE 

Figure  3. — Histogram  illustrating  the  feeding  habits  of Etropus 
crossotus  by  season  of  the  year,  locality,  and  standard  length. 
(N  =  number  of  stomachs  analyzed  for  each  bar,  P  =  Poly- 
chaetes,  C  =  Crustacea  other  than  those  sjjecifically  identified 
in  the  bar,  Ps  =  Pseudodiaptomus  coronatus,  M  =  moUusca, 
and  N  =  Neomysis  americana.) 

series  of  figures  was  prepared  which  take  these 
parameters  into  consideration  (Figures  3-8). 


year.  This  change  in  food  habits  does  not  appear 
to  reflect  a  reduction  in  the  availability  of  Ps. 
coronatus.  Plankton  samples  taken  in  conjunction 
with  this  and  other  studies  have  demonstrated 
thatPs.  coronatus  is  present  during  the  winter  in 
numbers  often  exceeding  those  of  other  seasons  of 
the  year.  The  change  in  food  habits  may  reflect  an 
increased  availability  of  Pa.  pinnata  rather  than 
a  decrease  in  the  availability  of  Ps.  coronatus. 
The  increased  availability  of  Pa.  pinnata  may 
have  been  a  function  of  an  increase  in  absolute 
numbers  of  the  polychaetes  or  may  have  been  due 
to  a  change  in  the  behavior  patterns  of  the  preda- 
tor, prey  or  both.  Studies  of  benthos  associated 
with  stations  in  Ossabaw  Sound,  from  which 
many  of  the  fishes  were  collected,  indicate  that 
Pa.  pinnata  is  the  dominant  benthic  infaunal  form 
throughout  the  year  on  mud  substrates  and  exhib- 
its widely  fluctuating  standing  crop  levels  (Stick- 
ney  and  Perlmutter,  unpubl.  data). 

The  possibility  that  the  shift  in  food  habits  in 
winter  may  have  been  a  function  of  the  size  of 
the  fishes  occurring  in  the  estuaries  during  that 
season  was  considered.  Animals  in  the  larger 
size  ranges  did  not  dominate  the  winter  samples 
but  were  generally  present  during  the  spring 
(Figure  4).  Fish  in  the  smallest  groups  were  pre- 
sent most  often  in  the  summer  when  Ps.  coronatus 
were  highly  dominant  in  the  stomachs.  Suitable 
numbers  of  £■.  crossotus  were  present  throughout 


Etropus  crossotus 

The  food  habits  ofE.  crossotus  related  to  season 
of  the  year,  locality  within  the  estuary  (rivers  as 
opposed  to  sounds),  and  standard  length  are  pre- 
sented in  Figure  3  indicating  the  percentage  of 
total  numbers  of  food  organisms  contributed  by 
each  taxa.  E.  crossotus  was  most  abundant  during 
the  spring  and  summer  months  (March  through 
August).  Ps.  coronatus  was  the  dominant  organ- 
ism in  the  stomachs  of  E.  crossotus  during  the 
spring,  summer,  and  fall.  During  the  winter, 
Ps.  coronatus  was  displaced  to  a  large  extent  by 
the  spionid  polychaete  Pa.  pinnata  and  by  N. 
americana.  Whereas  Table  1  indicated  that  Pa. 
pinnata  was  of  general  importance  especially  in 
terms  of  frequency  of  occurrence  in  the  stomachs. 
Figure  3  indicates  that  this  organism  was  more 
important  during  the  winter  (December  through 
February)  than  during  any  other  season  of  the 


4! 
41-50 
51-60 
61-70 
71-80 

81-  90 
91-100 

100 

Summer 

E 

F 

Sp 

Summer 

Foil 

X 

Summer 

Fall 

Winter 

H 
O 

Spring 

Summer 

Foil 

Winter 

LlI 

_l 

Spring 

Su 

Fall 

Winter 

Q 

Spring 

Su 

Fall 

Winter 

ir 

< 

Sprmg 

S 

Fall 

Winter 

< 

Spring 

Su 

Fall 

Winter 

(n 

1             1            1             1            1             1             1             1            1             1 

0       10      20      30      40     50      60     70     80     90     100 

CUMULATIVE      PERCENTAGE 


Figure  4. — Histogram  of  percentage  of  stomachs  examined 
during  spring  (March  through  May),  summer  (June  through 
August),  fall  (September  through  November),  and  winter 
(December  through  February)  for  Etropus  crossotus  of  various 
standard  length  groups. 


520 


STICKNEY,  TAYLOR,  and  HEARD:  FOOD  HABITS  OF  FOUR  FLOUNDERS 


each  season  of  the  year  to  provide  rehability  to 
the  data  (Figure  4). 

The  food  habits  of  E.  crossotus  were  similar  in 
both  the  rivers  and  sounds  of  Georgia.  There  were 
some  alterations  in  food  habits  associated  with 
increased  standard  length,  however.  While  Ps. 
coronatus  was  present  in  a  greater  percentage  in 
the  stomachs  ofE.  crossotus  of  all  sizes  than  any 
other  food  organism,  polychaetes  increased  in 
importance  in  fishes  longer  than  100  mm.  The 
appearance  of  polychaetes  in  stomachs  of  larger 
E.  crossotus  may  be  a  function  of  the  increase 
in  mouth  size  during  growth. 

Virtually  all  of  the  copepods  found  in  the 
stomachs  of  E.  crossotus  were  Ps.  coronatus. 
Plankton  samples  taken  by  us  during  the  course 
of  this  study  verified  that  the  copepod  population 
in  Georgia  coastal  waters  is  dominated  by 
Ps.  coronatus. 

During  October  1972,  a  series  of  bihourly 
trawls  over  a  24-h  period  was  obtained  in  Ossa- 
baw  Sound.  Each  trawl  was  of  10-min  duration 
and  covered  the  same  bottom.  A  total  of  121 
E.  crossotus  were  captured  in  the  12  samples, 
and  their  stomachs  were  analyzed.  Data  from 
these  fish  were  excluded  from  Figure  3  but  are 
included  in  Figure  5. 


UJ 


0800 
1000 

1200 
1400 

1600 
1800 

2000 
2  200 

2400 

0200 
0400 

0600 


Pseudodioptomus 
coronatus 


Porapnonospio         Neomysis  r 

pinna  To  amer  icana 


Pseudodiaptomus     coronatus 


Pseudodioptomus     coronatus 


Pseudodioptomus    coronatus 


Pseudodiaptomus    coronatus 


Leucon    p  r 
amer.  .       ' 


Pseudodioptomus    cornotus 


Pseudodioptomus   coronatus 


pac^ 


Pseudodiaptomus  coronatus 


Pseudodiaptomus    coronotus 


Pseudodiaptomus   coronotus       (  5  of  6    stomachs  empty) 


N  =  2 
N  =  13 

N  =  8 
N  =  II 

N  =18 
N  =  7 

N  =  17 
N  =12 

N  =  II 

N  =  1 
N  =  6 

N  =  15 


_L. 


0       10      20      30    40      50     60     70     80      90     100 
CUMULATIVE      PERCENTAGE 

Figure  5. — Histogram  illustrating  the  feeding  habits  of 
Etropus  crossotus  at  2-h  intervals  for  24  h.  (N  =  number 
of  stomachs  analyzed  for  each  bar,  C  =  Crustacea  other  than 
those  specifically  identified  in  the  bar,  P  =  polychaetes,  and 
Leucon  amer.  .  .  =  Leucon  americanus.) 


P.  coronatus  was  the  numerically  dominant 
organism  in  the  stomachs  with  the  exceptions  of 
samples  taken  at  0200,  0600,  and  0800  h.  At 
0200  and  0600  h  none  of  the  stomachs  examined 
(16)  contained  food.  At  0800  h  only  two  E. 
crossotus  were  obtained,  and  a  variety  of  food 
organisms  were  identified,  with  Ps.  coronatus 
most  abundant.  The  0400  h  sample  contained  six 
E.  crossotus  of  which  only  one  contained  food 
(100%  Ps.  coronatus). 

Based  on  this  limited  information,  it  appears 
that£.  crossotus  feeds  mainly  during  the  daylight 
hours  with  unchanging  food  habits  throughout 
the  day.  This  observation  correlates  with  the 
findings  of  de  Groot  (1971)  which  indicate  that 
bothids  are  visual  feeders. 


Ancylopsetta  quadrocellata 

The  food  habits  of  A.  quadrocellata  at  different 
seasons  of  the  year,  location  within  the  estuary, 
and  standard  length  are  presented  in  Figure  6. 
The  preponderance  of  the  animals  were  captured 
during  the  spring,  reflecting  the  seasonal  avail- 
ability of  this  fish  in  Georgia  estuarine  waters. 

N.  americana  was  the  dominant  food  organism 
throughout  the  year.  Trachypenaeus  constrictus 
became  important  during  the  summer  and  fall. 
Neopanope  sayi  was  present  in  significant  quan- 
tities during  the  winter. 

While  the  food  habits  of  A.  quadrocellata  cap- 
tured in  rivers  were  nearly  identical  to  those  cap- 
tured in  sounds,  there  were  some  differences  in 
food  habits  with  size  of  the  fish.  A^^.  americana 
exceeded  50%  of  the  total  number  of  organisms 
found  in  the  stomachs  of  fishes  of  less  than  150 
mm.  Fish  remains  were  found  in  the  stomachs  of 
fishes  longer  than  75  mm,  although  fish  were 
never  the  dominant  food  organism.  T.  constrictus 
first  became  important  as  food  in  A.  quadrocellata 
longer  than  100  mm  and  was  the  dominant  or- 
ganism in  fishes  from  150  to  174  mm.  Fishes 
longer  than  175  mm  fed  on  a  variety  of  organisms. 
These  data  indicate  that  the  diversity  of  foods 
increases  with  the  size  of  the  predator.  The  rela- 
tively large  mouth  of  A.  quadrocellata  compared 
to  that  ofE.  crossotus  may  account  for  some  of 
this  variability  in  food  habits  with  size  (Figure  2). 

Ps.  coronatus,  the  dominant  organism  in  the 
stomachs  of  E.  crossotus,  was  virtually  absent 
from  the  stomachs  of  A.  quadrocellata  longer  than 


521 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


O 
V) 
< 

UJ 


< 
u 
o 


E 
E 

X 

I- 
o 

z 

UJ 

_l 

d 

I- 


SPRING 

SUMMER 

FALL 

WINTER 

RIVERS 
SOUNDS 

25-49 
50-74 

75-99 
100-124 
125-149 
150-174 

175-199 


Neomys'S  (mericona 


Neomysis  amenc 


Trochypeneus 
ccnstrtctus 


Neomysis  amerlcono 


Trachypeneus 
consir  ictus 


Nsomysis  omthcoKi 


Neopanope 
•oyi 


U    P,C,       N  =  I66 
N  =  7 
N  =37 

7 


Squilla 
•P 


[]     N 


Neomysis    omencana 


Fa  C         N  = 


Neomysis  americona 


27 

F,  p  a  c        N  =  190 


Neomysis   omencona 


u|     N  = 


Neomysis  americona 


Neomysis  am«ricana 


Neomysis  amsncono 


Neomysis  omericono 


constncrus  pugio 


Trochypeneus    constnctus 


N   sayi 


Neopanope        3 
soyi 


Co       Po     Fish  P  a  C 


3 
N  =  58 

N=88 

N=29 

N=4 

N«I4 

N^ll 


0       10     20      30    40      50     60     70     80     90    100 

CUMULATIVE      PERCENTAGE 

Figure  6.— Histogram  illustrating  the  feeding  habits  of 
Ancylopsetta  quadrocellata  by  season  of  the  year,  locality, 
and  standard  length.  (N  =  number  of  stomachs  analyzed  for 
each  bar,  U  =  Unciola  serrata,  P  =  polychaetes,  C  =  Crus- 
tacea other  than  those  specifically  identified  in  the  bar, 
F  =  fish  remains,  Ps  =  Pseudodiaptomus  coronatus,  and 
T.  constrictus  =  Trachypenaeus  constrictus,  P.  pugio  = 
Palaemonetes  pugio,  N  =  Neomysis  americana,  S  =  Squilla 
sp.,  H  =  Hexapanopeus  augustifrons,  Ca  =  Cancer  ir- 
roratus,  and  Po  =  Portunus  gibbesii. 


50  mm.  This  may  also  relate  to  mouth  size  dif- 
ferences between  the  species.  Studies  with  Para- 
lichthys  lethostigma  and  P.  dentatus  reared  in  the 
laboratory  on  brine  shrimp,  Artemia  salina, 
indicate  that  once  the  flounders  reach  sufficient 
size  (in  this  case  about  25  mm),  they  have  diffi- 
culty retaining  ingested  A.  salina  nauplii  (Stick- 
ney  and  White,  unpubl.  data).  The  nauplii  tend 
to  be  flushed  through  the  gills  and  out  the  oper- 
culums. While  the  fish  are  still  able  to  hunt 
the  A.  salina  by  sight,  they  do  not  seem  to  ingest 
a  great  number  of  nauplii.  The  relative  mouth 
sizes  of  P.  lethostigma  and  P.  dentatus  are  simi- 
lar to  those  of  A.  quadrocellata,  C.  spilopterus, 
and  S.  aquosus. 

Citharichthys  spilopterus 

The  food  habits  of  C.  spilopterus  in  relation  to 
season  of  the  year,  location,  and  size  are  docu- 


mented in  Figure  7.  The  majority  of  the  fish 
examined  were  captured  during  the  summer  (June 
through  August).  No  fish  were  captured  during 
the  winter  months  (December  through  February). 
N.  americana  was  the  dominant  species  occurring 
in  the  stomachs  of  C.  spilopterus  during  each  of 
the  three  seasons  for  which  data  are  available. 
A  greater  proportion  of  T.  constrictus  occurred 
in  fishes  captured  in  sounds  than  in  those  taken 
from  rivers.  The  percentage  of  A^.  americana  and 
fish  remains  in  the  stomachs  of  C.  spilopterus 
from  the  two  localities  were  nearly  identical. 

Food  habit  patterns  relative  to  standard  length 
of  C.  spilopterus  were  similar  to  those  observed  in 
A.  quadrocellata.  N.  americana  became  less  impor- 
tant as  food  with  increasing  size  in  C.  spilop- 
terus. T.  constrictus  became  the  dominant  organ- 
ism in  C.  spilopterus  of  125  mm  and  above.  N. 
americana  was  absent  in  the  stomachs  of  fishes 
longer  than  125  mm. 

Fish  less  than  50  mm  were  not  obtained  in  the 
trawls.  It  is  possible  that  all  sizes  of  C.  spilop- 
terus do  not  occur  in  Georgia  estuarine  waters 
but  merely  that  they  migrate  through  the  south- 
eastern Atlantic  coast  during  certain  seasons  of 
the  year.  Specimens  longer  than  140  mm  were 
not  taken.  The  seasonal  distribution  observed 
agrees  with  that  determined  by  Dahlberg  and 
Odum  (1970). 


o 

CO 

< 

UJ 
ID 


< 

o 


SPRING 
SUMMER 

FALL 

RIVERS 
SOUNDS 


Neomysis    omencona 


Neomysis    omencona 


Neomysis    omencona 


1   N=4 
N=I83 
N=23 


Neomysis    omericono 


Neomysis      omencano 


D" 


N=69 
141 


50-74 

75-99 

100-124 

125-149 

Neomysis    americana 

T 

F 

CrustGceo 

X 

1- 

UJ  E 
_J^ 

Neomysis      omencano 

T 

F 

pac 

Neomysis     omencona 

T     constrictus      F 

Ish 

c 

d 

1- 

Trachypeneus    constrictus 

"Pp 

u»o  S 

(/) 

1       1       1       1    _i 1 i 1 

N=52 

N=II7 
N=37 

N  =  4 


0      10       20      30      40     50      60      70      80     90     100 

CUMULATIVE       PERCENTAGE 

Figure  7.— Histogram  illustrating  the  feeding  habits  of 
Citharichthys  spilopterus  by  season  of  the  year,  locality, 
and  standard  length.  (N  =  number  of  stomachs  analyzed  foi" 
each  bar,  T  =  Trachypeneus  constrictus,  F  =  fish  remains, 
C  =  Crustacea  other  than  those  specifically  identified  in  the 
bar,  P  =  Palaemonetes  pugio,  and  S  =  Squilla  empusa.) 


522 


STICKNEY,  TAYLOR,  and  HEARD:  FOOD  HABITS  OF  FOUR  FLOUNDERS 


Scophthalmus  aquosus 

S.  aquosus  were  present  in  Georiga  coastal 
waters  primarily  during  the  spring  (March 
through  May).  Few  specimens  were  captured  dur- 
ing the  remainder  of  the  year  (Figure  8).  S. 
aquosus  fed  nearly  exclusively  on  N.  americana 
during  all  seasons  and  in  all  locations.  Several 
species  of  Crustacea,  fish  remains,  and  an  ectoproct 
made  up  the  remainder  of  the  food  organisms 
found  in  the  stomachs  of  S.  aquosus  (Table  1). 

There  was  no  change  in  food  habits  with  size 
as  found  in  A.  quadrocellata  and  C.  spilopterus, 
even  though  S.  aquosus  longer  than  150  mm 
were  captured.  There  were  few  animals  in  the 
size  ranges  above  74  mm,  however,  and  the 
presumed  food  habits  may  reflect  a  lack  of 
samples.  Most  of  the  fish  captured  were  rather 
small.  The  relative  abundance  of  small  fish 
compared  with  the  larger  sizes  is  probably  a  good 
indication  of  their  relative  abundance  in  nature. 


CONCLUSIONS 

The  four  bothid  fish  species  examined  during 
this  study  are  all  relatively  small  fishes  which  feed 
on  a  variety  of  organisms.  All  appear  to  be  totally 
carnivorous,  since  no  plant  material  was  re- 
covered from  the  stomachs.  Because  of  the  pre- 
dominance of  certain  organisms  within  the  stom- 
achs and  the  lack  of  detritus  and  sand  so  common 
in  animals  which  indiscriminately  browse  off 
the  sediments,  they  appear  to  be  selective  feeders. 
This  selectivity  apparently  relates  to  the  ability 
of  bothids  to  feed  by  sight  (de  Groot,  1971). 

E.  crossotus  was  found  to  feed  heavily  on  Ps. 
coronatus ,  and  secondarily  on  spionid  polychaetes, 
especially  Pa.  pinnata.  The  small  mouth  relative 
to  body  size  of  £■.  crossotus  may  play  an  impor- 
tant role  in  the  food  habits  of  this  species.  By 
the  same  token,  the  larger  mouths  of  the  other 
species  may  prohibit  them  from  feeding  on  small 
food  items. 

A.  quadrocellata,  C.  spilopterus,  andS.  aquosus 
fed  heavily  on  A^.  americana,  however,  A.  quadro- 
cellata and  C  spilopterus  adjusted  their  food 
habits,  becoming  more  diversified  and  utilizing 
T.  constrictus  as  a  primary  food  organism  as  they 
grew  larger.  The  food  habits  of  S.  aquosus 
did  not  change  with  increasing  size  within  the 
range  of  sizes  examined.  The  relatively  larger 
mouths  of  these  three  species  seem  important  in 


SPRING 

Z 

O  SUMMER 

^         FALL 

WINTER 


t     RIVERS 


g   SOUNDS 


25-49 
E     50-74 

X     75-99 

I- 


100-124 


LlI 


in 


125-149 


150  -  174 


Neomysis  americana 


Neomysis  americana 


Neomysis  omericana 


Neomysis  americana 


c      N=95 
N=2 
N  =  7 
N  =  l 


Neomysis   amencano 


J[\     N  =  24 


Neomysis   americana 


Fsc-         N=86 


Neomysis  americana 


Neomysis  americana 


Neomysis  americana 


C  - 


Neomysis  omencano 


Neomysis   americana 


Neomysis  amencano 


c  -       N  =  ll 

N  =75 

N=  12 

N  =  5 

N  =  3 

N  =  4 


c- 


0       10      20     30      40    50     60     70     80     90     100 
CUMULATIVE       PERCENTAGE 

Figure  8. — Histogram  illustrating  the  feeding  habits  of 
Scophthalmus  aquosus  by  season  of  the  year,  locality,  and 
standard  length.  (N  =  number  of  stomachs  analyzed  for  each 
bar,  F  =  fish  remains,  and  C  =  Crustacea  other  than 
Neomysis  americana. ) 

allowing  them  to  consume  food  organisms  of 
larger  sizes  than  those  eaten  by  E.  crossotus.  The 
three  fishes  with  the  larger  mouths  fed  to  some 
extent  on  other  species  of  fishes,  whereas  no  fish 
remains  were  found  inthe  stomachs  ofE.  crossotus. 


ACKNOWLEDGMENTS 

The  authors  are  grateful  to  Walter  Sikora  for 
providing  specimens  from  the  area  in  the  vicinity 
of  Sapelo  Island,  Ga.,  and  to  the  Savannah  Science 
Museum  for  allowing  us  access  to  some  of  their 
specimens  from  Wassaw  and  Ossabaw  Sounds. 
This  study  was  supported  in  part  by  the  IDOE 
Office  of  the  National  Science  Foundation  (GX- 
33615).  Ship  support  was  provided  by  NSF  Grant 
GD37558  (Office  of  Oceanographic  Facilities  and 
Support). 

LITERATURE  CITED 

Dahlberg,  M.  D.,  and  E.  P.  Odum. 

1970.    Annual  cycles  of  species  occurrence,  abundance,  and 


523 


diversity  in  Georgia  estuarine  fish  populations.     Am. 
Midi.  Nat.  83:382-392. 
Darnell,  R.  M. 

1958.  Food  habits  of  fishes  and  larger  invertebrates  of 
Lake  Pontchartrain,  Louisiana,  an  estuarine  community. 
Publ.  Inst.  Mar.  Sci.,  Univ.  Tex.  5:343-416. 

DE  GrOOT,  S.  J. 

1970.  Some  notes  on  an  ambivalent  behaviour  of  the 
Greenland  halibut  Reinhardtius  hippoglossoides 
(Walb.)  Pisces:  Pleuronectiformes.  J.  Fish  Biol.  2:275- 
279. 

1971.  On  the  interrelationships  between  morphology  of 
the  alimentary  tract,  food  and  feeding  behaviour  in 
flatfishes  (Pisces:  Pleuronectiformes).  Neth.  J.  Sea 
Res.  5:121-196. 

Olla,  B.  L.,  C.  E.  Samet,  and  A.  L.  Studholme. 

1972.  Activity  and  feeding  behavior  of  the  summer 
flounder  {Paralichthys  dentatus)  under  controlled  labora- 
tory conditions.    Fish.  Bull.,  U.S.  70:1127-1136. 

Olla,  B.  L.,  R.  Wicklund,  and  S.  Wilk. 

1969.     Behavior  of  winter  flounder  in  a  natural  habitat. 
Trans.  Am.  Fish.  Soc.  98:717-720. 
Poole,  J.  C. 

1964.     Feeding  habits  of  the  summer  flounder  in  Great 
South  Bay.    N.Y.  Fish  Game  J.  11:28-34. 
Reid,  G.  K.,  Jr. 

1954.     An  ecological  study  of  the  Gulf  of  Mexico  fishes, 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 

in  the  vicinity  of  Cedar  Key,  Florida.     Bull.  Mar.  Sci. 
Gulf  Caribb.  4:1-94. 
SiKORA,  W.  B.,  R.  W.  Heard,  and  M.  D.  Dahlberg. 

1972.  The  occurrence  and  food  habits  of  two  species  of 
hake,  Urophycis  regius  and  U.  flcridanus  in  Georgia 
estuaries.    Trans.  Am.  Fish.  Soc.  101:513-525. 

Steven,  G.  A. 

1930.     Bottom  fauna  and  the  food  of  fishes.     J.  Mar. 
Biol.  Assoc.  U.K.  16:677-698. 
Stickney,  R.  R.,  D.  B.  White,  and  D.  Miller. 

1973.  Observations  of  fin  use  in  relation  to  feeding  and 
resting  behavior  in  flatfishes  (Pleuronectiformes).  Copeia 
1973:154-156. 

Tattersall,  W.  M. 

1951.     A  review  of  the  Mysidacea  of  the  United  States 
National  Museum.     Bull.  U.S.  Natl.  Mus.  201,  292  p. 
Topp,  R.  W.,  and  F.  H.  Hoff,  Jr. 

1972.  Memoirs  of  the  Hourglass  Cruises.  Flatfishes 
(Pleuronectiformes).  Fla.  Dep.  Nat.  Resour.,  Mar.  Res. 
Lab.  4(2):1-135. 

WiGLEY,  R.  L.,  AND  B.  R.  BURNS. 

1971.  Distribution  and  biology  of  mysids  (Crustacea, 
Mysidacea)  from  the  Atlantic  coast  of  the  United  States 
in  the  NMFS  Woods  Hole  collection.  Fish.  Bull.,  U.S. 
69:717-746. 

Williams,  A.  B. 

1972.  A  ten-year  study  of  meroplankton  in  North  Carolina 
estuaries:  mysid  shrimps.    Chesapeake  Sci.  13:254-262. 


524 


STICKNEY,  TAYLOR,  and  HEARD:  FOOD  HABITS  OF  FOUR  FLOUNDERS 

APPENDIX 

List  of  organisms  found  in  stomachs  of  Bothidae  from  Georgia  estuarine  waters 


Rhynchocoela 

Cerebratulus  sp. 
Ectoprocta 

Bugula  neritina  (Linnaeus) 
Polychaeta 

Diopatra  cuprea  (Bosc) 

Paraprionospio  pinnata  (Ehlers) 

Nereis  succinea  (Frey  and  Leuckart) 

Sabellaria  vulgaris  Verrill 

Sabella  microphthalma  Verrill 

Asabellides  oculata  Webster 

Clymenella  torquata  Leidy 

Spionidae 

Nereidae 
Mollusca 

Gastropod  remains 

Pelecypod  siphons 

Pelecypod  postlarvae 
Crustacea 

Amphipoda' 
Ampelisca  uadorum  Mills 
Ampelisca  sp. 

Listriella  barnardi  (Wigley) 
Corophium  tuberculatum  Shoemaker 
Unciola  serrata  Shoemaker 
Batea  catharinensis  Muller 
Melita  appendiculata  (Say) 
Melita  nitida  Smith 
Monoculodes  edwardsi  Holmes 
Erichthonius  brasiliensis  Dana 
Paracaprella  tenuis  Mayer 
Microprotopus  ranei  Wigley 
Corophium  simile  Shoemaker 
Cerapus  tubularis  Say 
Lembos  websteri  Bate 
Gammarus  palustris  Bousfield 
Caprella  equilibra  Say 
Corophium  lacustre  Vanhoffen 

Copepoda 
Pseudodiaptomus  coronatus  Williams 
Labidocera  aestiva  Wheeler 
Calanoid  copepoda 

Cumacea 
Leucon  americanus  Zimmer 
Oxyurostylis  smithi  Caiman 
Mancocuma  altera  Zimmer 


Mysidacea 

Neomysis  americana  (S.  I.  Smith) 
Ostracoda  (unidentified) 
Isopoda 

Edotea  montosa  Stimpson 

Stomatopoda 
Squilla  empusa  Say 
Squilla  neglecta  Gibbes 

Decapoda  (Natantia) 
Acetes  americanus  carolinae  Hansen 
Penaeus  setiferus  (Linnaeus) 
Trachypenaeus  constrictus  (Stimpson) 
Palaemonetes  pugio  Holthuis 
Palaemonetes  vulgaris  (Say) 
Ogyrides  limicola  Williams 
Periclimenes  longicaudatus  (Stimpson) 
Latreutes  parvulus  (Stimpson) 
Alpheus  normanni  Kingsley 
Caridean  larvae 

Decapoda  (Reptantia) 
Pagurus  pollicaris  Say 
Pagurus  sp. 

Callinectes  sapidus  Rathbun 
Portunus  spinimanus  Latreille 
Portunus  gibbesii  (Stimpson) 
Callinectes  similis  Williams 
Cancer  irroratus  Say 

Hexapanopeus  angustifrons  (Benedict  and  Rathbun) 
Neopanope  sayi  (Smith) 
Pinnixa  sp. 

Persephona  punctata  aquilonaris  Rathbun 
Megalops  and  zoea 
Portunid  postlarvae 

Osteichthyes 
Prionotus  sp. 

Symphurus  plagiusa  (Linnaeus) 
Synodus  foetens  (Linnaeus) 
Bairdiella  chrysura  (Lacepede) 
Anchoa  mitchilli  (Valenciennes) 
Etropus  crossotus  Jordan  and  Gilbert 
Fundulus  heteroclitus  (Linnaeus) 
Menidia  sp. 
Cynoscion  sp. 
Bothid  postlarvae 
Fish  remains 


525 


DISTRIBUTION  OF  SIPHONOPHORES  IN  THE  REGIONS 
ADJACENT  TO  THE  SUEZ  AND  PANAMA  CANALS 


Angeles  Alvarino^ 


ABSTRACT 

These  studies  are  based  on  the  material  collected  by  Israeli  cruises  in  the  eastern  Mediterranean 
and  the  Red  Sea  (Gulf  of  Elat),  and  by  Scripps  Institution  of  Oceanography  Expeditions  in  the 
Caribbean  and  the  Pacific  regions  adjacent  to  the  Panama  Canal.  Published  information  on  the 
distribution  of  siphonophores  in  those  areas  and  in  adjacent  regions  is  included.  Distributional 
tables  and  maps  are  also  included. 

The  eastern  Mediterranean  collections  encompass  21  species  of  siphonophores.  Most  of  these 
species  have  been  previously  recorded  in  the  western  Mediterranean.  Eudoxia  russelli  (eudoxid 
of  Chelophyes  appendiculata),  Sulculeolaria  angusta,  and  S.  chuni  have  not  been  previously 
observed  in  any  Mediterranean  region.  New  records  for  the  eastern  Mediterrranean  are:  Ch. 
contorta,  Diphyes  bojani.  D.  dispar.  Lensia  campanella,  L.  meteori,  L.  subtilis,  S.  quadrivalvis, 
S.  turgida.  Rosacea  plicata,  Physophora  hydrostatica ,  and  Apolemia  uvaria.  Few  sjjecies  previously 
observed  in  the  Mediterranean  were  not  present  in  the  collections  here  analyzed. 

Fifteen  species  of  siphonophores  appeared  in  the  material  from  the  Gulf  of  Elat.  New  records 
for  the  Red  Sea  are  Ch.  appendiculata,  E.  russelli,  Diphyopsis  mitra.  The  other  species 
present  iCh.  contorta,  Diphyes  dispar,  L.  subtilis,  S.  chuni,  S.  quadrivalvis,  Abylopsis 
eschscholtzi,  A.  tetragona,  Enneagonum  hyalinum,  Cordagalma  cordiformis,  Agalma 
elegans,  and  A.  okeni)  have  been  previously  observed  in  the  Red  Sea. 

New  records  at  both  sides  of  the  Suez  Canal  which  could  be  considered  indicative  of 
migration  along  this  waterway  are:  Ch.  appendiculata  (Mediterranean  to  the  Red  Sea),  and 
S.  chuni  (Red  Sea  to  the  Mediterranean).  However,  the  species  are  cosmopolitan  in  distribution, 
and  the  source  of  the  populations  in  the  regions  adjacent  to  the  Suez  Canal  may  be  in  the 
adjacent  oceanic  regions. 

Thirty  species  of  siphonophores  were  observed  in  the  Caribbean  and  Pacific  regions  adjacent 
to  the  Panama  Canal.  Most  of  the  species  are  new  records  for  those  regions.  Twenty  one  more 
species,  not  present  in  the  collections  here  analyzed,  had  been  previously  recorded  at  either  or  in 
both  the  Caribbean,  Gulf  of  Mexico  and/or  in  regions  of  the  Pacific  adjacent  to  the  area  surveyed. 

Particular  attention  is  devoted  to  the  distribution  of  closely  related  pairs  of  allopatric  species, 
Muggiaea  atlantica-M.  kochi,  and  Ch.  appendiculata-Ch.  contorta.  Muggiaea  kochi  (neritic  species) 
and  Ch.  appendiculata  inhabit  the  Caribbean,  Gulf  of  Mexico  and  adjacent  regions  of  the 
western  tropical  Atlantic.  Muggiaea  atlantica  (neritic  species)  and  Ch.  contorta  inhabit  the 
Pacific  regions  off  Mexico  and  Central  America.  However,  few  specimens  of  Ch.  contorta 
and  M.  atlantica  were  also  observed  in  the  Caribbean  at  locations  near  the  opening  of  the  Panama 
Canal,  and  specimens  of  Ch.  appendiculata  and  M.  kochi  occurred  at  locations  in  the  Pacific  close 
to  the  Panama  Canal.  This  distributional  incidence  may  suggest  that  migration  or  artificial 
transport  is  taking  place  via  the  Panama  Canal.  It  is  also  indicated  that  few  specimens  of 
L.  challengeri  (Indo-Pacific  species)  were  observed  near  the  opening  of  the  Panama  Canal  in 
the  Caribbean, 


New  data  have  been  published  on  the  siphono- 
phores of  the  regions  adjacent  to  the  Suez  Canal 
(eastern  Mediterranean  and  the  Red  Sea),  as  well 
as  for  the  regions  adjacent  to  the  Panama  Canal 
(western  Caribbean  and  the  Central  American 
Pacific).  Bigelow  and  Sears  (1937)  included  data 
on  the  distribution  of  the  siphonophores  in  the 
eastern  Mediterranean,  and  Lakkis  ( 1971)  on  the 


'Southwest  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  P.  O.  Box  271,  La  Jolla,  CA  92037. 


Manuscript  accepted  September  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO.  2.  1974. 


Lebanese  region.  Schneider  (1898),  Totton  (1954), 
and  Halim  (1969)  presented  information  on  the 
siphonophores  of  the  Red  Sea.  Bigelow  (1911) 
analyzed  the  siphonophores  of  the  eastern  tropical 
Pacific,  which  included  few  locations  in  the 
regions  here  surveyed;  Alvariho  (1968,  1972) 
studied  the  siphonophores  of  the  tropico-equa- 
torial  oceanic  regions,  and  Alvarino  (1971) 
covered  the  Central  American  Pacific  including 
also  a  compilation  of  distributional  data  for  the 
world  oceans. 


527 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


The  present  work  constitutes  a  more  detailed 
survey  on  the  siphonophores  of  the  regions  ad- 
jacent to  the  above  mentioned  interoceanic  canals. 
These  studies  are  based  on  the  Siphonophorae 
material  (65  plankton  samples)  collected  by  Israel 
in  the  eastern  Mediterranean  during  1967,  1968, 
1969,  and  18  plankton  samples  (Red  Sea,  1969, 
1970)  corresponding  to  two  locations  in  the  Gulf 
of  Elat;  and  the  64  plankton  samples  from  Scripps 
Institution  of  Oceanography  Expeditions  (La 
Creuse  1962,  Bonacca  1963,  Thomas  Washing- 
ton 1969)  in  the  Caribbean  and  Pacific  regions 
adjacent  to  the  Panama  Canal.  The  Scripps 
Institution  collections  covered  larger  regions  than 
the  area  in  which  the  present  studies  are  con- 
centrated, and  the  total  collections  of  the 
mentioned  expeditions  have  been  analyzed  and 
the  results  included  in  Alvariiio  (1968,  1971, 
1972). 

The  present  studies  chiefly  concern  with  the 
distribution  and  some  ecological  aspects  of  the 
siphonophores.  The  subject  is  treated  under  two 
parts:  1)  distribution  of  siphonophores  in  the 
eastern  Mediterranean  and  the  Red  Sea,  and 
2)  the  siphonophores  of  the  western  part  of  the 
Caribbean  and  the  Central  American  Pacific. 

The  pattern  of  distribution  of  the  species  is 
presented.  Tables  with  the  distribution  of  the 
species  include  also  references  on  previous  records 
for  the  regions. 

Maximum  density  for  most  of  the  species  off 
Israel  and  around  Cyprus  can  be  attributed  to 
the  high  productivity  of  the  region  (Lakkis, 
1971). 

The  present  study  also  indicates  the  Red  Sea 
includes  fewer  species  than  the  Indian  Ocean. 
This  factor  may  be  related  to  the  high  salinity 
and  temperature  of  the  Red  Sea,  as  well  as  to 
the  shallowness  of  the  sill  at  Bab  el  Mandeb. 

The  incidence  of  both  polygastric  and  eudoxid 
forms  in  most  of  the  samples  shows  breeding 
is  taking  place  in  those  regions,  and  that  repro- 
duction may  be  an  uninterrupted  process  along 
the  year. 

A  large  number  of  species  of  siphonophores  are 
truly  cosmopolitan,  inhabiting  the  Arctic,  Antarc- 
tic, Indian,  Pacific,  and  Atlantic  Oceans,  whereas 
other  species  inhabit  only  the  Atlantic,  Pacific, 
and  Indian  Oceans  (Alvariho,  1971),  and  some 
others  are  restricted  to  the  Indian  Ocean,  adjacent 
waters  and  the  southeastern  Asiatic  regions, 
while  few  are  restricted  to  either  the  Atlantic 
or  the  Indo-Pacific  regions. 


Owing  to  the  above  mentioned  biogeographic 
considerations,  particular  emphasis  in  the  dis- 
tribution of  the  species  should  be  dedicated  to 
the  pairs  of  closely  related  species  allopatric 
in  distribution.  The  pairs  to  be  considered  corres- 
pond to  the  Panamanian  region:  Chelophyes 
appendiculata-Ch.  contorta  (respectively  related 
to  cold-temperate,  and  warm  waters),  Muggiaea 
atlantica-M.  kochi  (inhabiting  respectively  the 
neritic  temperate  and  neritic  warm  waters),  and 
Lensia  challengeri-L.  fowleri  (respectively  Indo- 
Pacific  and  Atlantic  species). 

The  evidence  of  a  two  way  migration  "via"  the 
Panama  Canal,  as  shown  by  the  distribution  pre- 
sented by  several  species  at  the  regions  adjacent 
to  the  entrance  to  the  Panama  Canal,  could  be 
active,  by  progression  of  the  population  along  the 
waterway,  or  passively  transported  in  the  ballast 
waters  or  the  waters  used  in  the  cooling  system 
of  ships.  Therefore,  migrations  could  be  also 
greatly  intensified  or  enhanced  by  passive 
transport  along  the  canal. 


METHODS 

The  plankton  samples  here  analyzed  were  not 
collected  in  uniform  manner.  The  plankton 
collections  from  the  eastern  Mediterranean  and 
the  Gulf  of  Elat  were  obtained  with  a  standard 
plankton  net  of  the  Villefranche  type,  as  designed 
and  described  by  Working  Party  No.  2  (1968). 
The  net  has  a  mouth  internal  diameter  of  57  cm, 
a  total  length  of  261  cm,  and  200-^(  mesh.  Vertical, 
oblique,  and  horizontal  tows  were  taken.  The 
vertical  and  oblique  hauls  in  the  eastern  Mediter- 
ranean and  the  Gulf  of  Elat  reached  from  200  m 
to  the  surface,  and  the  horizontal  tows  were 
obtained  at  various  depths  in  the  upper  200  m  at 
a  speed  of  2-3  knots  during  10  min. 

The  material  from  the  Scripps  Institution  col- 
lections corresponds  to  1-m  net  oblique  hauls 
taken  from  about  140  m  to  the  surface,  and  at 
less  than  100  m  or  less  than  50  m  in  shallow 
waters;  and  the  V2-m  net  oblique  tows  were 
obtained  from  about  150  m  to  the  surface  and  the 
horizontal  hauls  at  various  depths  between  50 
and  0  m. 

Each  total  plankton  sample  was  analyzed  for 
siphonophores,  and  the  number  of  specimens 
determined  for  both  polygastric  and  eudoxid 
forms.  However,  owing  to  the  diversity  of  the 
collecting  methods  used,  and  the  time  span 


528 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 


covered  by  the  collections,  quantitative  data  are 
not  considered,  and  only  qualitative  data  are 
included  in  the  presentation  of  the  results. 

DISTRIBUTION  OF 

SIPHONOPHORES  IN  THE 

EASTERN  MEDITERRANEAN 

AND  THE  RED  SEA 

Twenty-one  species  of  siphonophores  were 
observed  in  the  eastern  Mediterranean  collec- 
tions, and  fifteen  species  in  the  Gulf  of  Elat  (Red 
Sea)  collections. 

Eudoxia  russelli  (eudoxid  of  Ch.  appendicu- 
lata),  Sulculeolaria  angusta,  and  S.  chuni  are 
new  records  for  the  Mediterranean. 

Chelophyes  contorta,  Diphyes  bojani,  D. 
dispar,  Lensia  campanella,  L.  meteori,  L. 
subtilis,  Sulculeolaria  quadrivalvis,  S.  tur- 
gida.  Rosacea  plicata,  and  Apolemia  uuaria 
are  first  records  for  the  eastern  Mediterranean. 
These  species  have  been  previously  observed  in 
the  western  Mediterranean.  The  only  previous 
records  of  Ch.  contorta  for  the  Mediterranean 
correspond  to  the  Alboran  Sea  (Alvarino,  1957). 
Therefore,  the  presence  of  the  species  in  the 
Levant  Mediterranean  basin  could  be  considered 
a  tracer  of  Atlantic  waters.  All  the  Mediter- 
ranean species  are  also  found  in  the  Atlantic. 
Some  of  the  species  have  permanently  established 
populations  in  the  Mediterranean,  while  others 
may  be  only  remains  of  the  Atlantic  flow. 

Most  of  the  species  previously  found  in  the 
eastern  Mediterranean  (Bigelow  and  Sears,  1937; 
Lakkis,  1971)  were  also  observed  in  the  collec- 
tions here  analyzed. 

Some  species  previously  found  in  the  western 
Mediterranean  (M.  atlantica,  L.  fowleri,  Clau- 
sophyes  ovata,  Ceratocymha  sagittata, 
Vogtia  pentacantha,  V.  spinosa,  Praya  cymbi- 
formis,  Amphicaryon  acaule,  Anthophysa 
rosea,  Rhizophysa  filiformis,  Cordagalma 
cordiformis,  Athoribya  rosacea,  and  Nanomia 
cara)  have  not  been  observed  in  the  eastern 
Mediterranean  (Alvariiio,  1971;  Lakkis,  1971) 
(Table  1). 

The  most  abundant  species  in  both  distribu- 
tional coverage  of  the  surveyed  region  and  in 
number  of  species,  Ch.  appendiculata,  D. 
dispar,  Hippopodius  hippopus,  Bassia  bas- 
sensis   were  found  along  the  years,  and  in 


December  appeared  scattered  or  absent  (Figures 
1,  2,  6,  8).  Eudoxoides  spiralis,  S.  turgida, 
S.  quadrivalvis ,  and  S.  angusta  followed  in 
decreasing  order  of  abundance  in  both  space 
covered  and  number  of  individuals  (Figures  3,  5). 
These  species  appeared  abundantly  off  Israel, 
Lebanon,  Syria  and  around  Cyprus.  Sulculeolaria 
angusta  and  S.  turgida  were  also  found  in  the 
Cretan  region. 

Species  with  few  scattered  records  are,  E. 
russelli  (north  of  Cyprus),  C/i.  contorta  (off  Israel 
and  between  Syria  and  Cyprus),  D.  bojani,  M. 
kochi,  L.  campanella,  L.  multicristata,  L.  subtilis, 
S.  chuni,  A.  tetragona,  R.  plicata,  A.  uvaria, 
Agalma  elegans,  and  Physophora  hydrostatica 
(spread  along  the  Levant  basin).  (Figures  1-8.) 

It  is  worthy  of  notice  that  the  maximum  density 
for  most  of  the  species  of  siphonophores  appeared 
at  the  easternmost  part  of  the  Mediterranean 
Sea,  off  Israel  and  around  Cyprus,  which  can  be 
attributed  to  the  high  productivity  of  the  region 
(Lakkis,  1971). 

The  species  scattered  along  the  eastern  Mediter- 
ranean, not  previously  observed  in  this  sea,  could 
be  considered  tracers  of  Atlantic  waters  (Oren, 

1971). 

The  presence  of  L.  multicristata  (a  meso- 
planktonic  species)  off  Tira,  Israel,  could  be  an 
indicator  of  upwelling. 

It  is  well  established  that  the  fauna  of  the 
eastern  Mediterranean  is  an  impoverished  fauna 
from  that  of  the  western  basin.  Many  species 
do  not  reach  the  Levant  Mediterranean  basin, 
and  only  appear  accidentally  there,  and  few  be- 
come established  in  the  area.  Por  (1971)  con- 
sidered that  "The  colder  areas  of  the  Aegean  Sea 
probably  constitute  an  environment  in  which  the 
Atlantic  fauna  is  much  better  represented  and 
better  fitted  to  withstand  the  competition  of  the 
tropic  immigrants." 

Siphonophorae  fauna  of  the  Red  Sea  is  poorer 
than  that  of  the  Indian  Ocean,  both  in  number 
of  species  and  in  the  density  of  the  respective 
populations.  The  Gulf  of  Elat  may  also  include 
fewer  species  than  the  main  Red  Sea  basin.  The 
Gulf  of  Elat  collections  correspond  to  the  winter 
months.  Some  of  the  species  observed  in  the  Gulf 
of  Elat  constitute  new  records  for  the  Red  Sea 
(Ch.  appendiculata,  E.  russelli,  and  Diphyop- 
sis  mitra).  Por  (1971)  stated  that  siphonophores 
and  other  holoplanktonic  groups  have  not  been 
found  in  the  Suez  Canal  waters. 


529 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


•TV 

29* 

_          r 

30* 

35' 

*^  ^  ^^^^^r 

*     » 

•M — ^^ 

^ 

.^^^^      + 

;;^*S^ 

r d 

I0S"        ^^        + 

38* 

. « 

r-^^ 

+ 

_^^L^ 

4- 

— 4-^y -1- ^ 

+ 

+     ■ 

+ 

■ 

fl 

+ 

+ 

+•        ^™ 

^^ 

4.^H 

.+..T'^« 

3E 


1 39* 


Ch    appendiculata 


E     russelli 


Ch     contorta 


A,B 


^  A,B 


13  A,B 


1 


35* 


Figure   1. — Distribution  of  Chelophyes  appendiculata,  Eudoxia  russelli,  and  Chelophyes 
contorta  in  the  regions  adjacent  to  the  Suez  Canal. 


D.     mitra 


Figure  2. — Distribution  of  Diphyes  bojani,  Diphyes  dispar,  and  Diphyopsis  mitra  in  the 

regions  adjacent  to  the  Suez  Canal. 


530 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 

zv 


Figure  3. — Distribution  of  Muggiaea  kochi,  Eudoxoides  spiralis,  and  Lensia  campanella 

in  the  regions  adjacent  to  the  Suez  Canal. 


38* 

25* 

f 

+ 

"7^ 

30* 

■r 

1' 

+ 

39* 

^1 

+ 

+ 

+ 

k 

gj 

1 

4^^^^^| 

L.   meteori 

m 

30* 

L    multicristata 
L     subtilis 

tiilill    A.B 

1 

1 

^^^H  ^^^^^^^^^Ly*^^^^^^^^! 

L.    subtiloides 

1 

2a« 

n  A,B 

30* 

1 

35* 

39* 


30* 


Figure  4. — Distribution  of  Lensia  meteori,  Lensia  multicristata,  Lensia  subtilis,  and  Lensia 
subtiloides  in  the  regions  adjacent  to  the  Suez  Canal. 


531 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Figure  5. — Distribution  of  Sulculeolaria  angusta,  Sulculeolaria  chuni,  Sulculeolaria  quadrival- 
vis,  and  Sulculeolaria  turgida  in  the  regions  adjacent  to  the  Suez  Canal. 


A.  eschscholtzi 
A  tetragona 

B.  bassensis 
E.  hyalinum 


□  A,B 


25 


Figure  6. — Distribution  of  Abylopsis  eschscholtzi.  Abylopsis  tetragona,  Bassia   bassensis, 
and  Enneagonum  hyalinum  in  the  regions  adjacent  to  the  Suez  Canal. 


532 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 

29* 


9»*  — 


30' 


30* 


39* 


f 

IK 

+ 

■r 

+ 

+ 

^H 

+ 

+ 

+ 

k 

1 

K^^^J^^H 

R    plicata 

^ 

i 

A.   uvaria 

n 

■ 

1 

K^^Hj^H 

C.    cordiformis 

□   B 

■ 

1 

K^K^I 

Ath.  rosacea 

1 

29* 

n  B 

1 

30* 

1 

^ 1  ^B 

39* 

39* 


Figure  7. — Distribution  of  Rosacea  plicata,  Apolemia  uvaria,  Cordagalma  cordiformis ,  and 
Athoribya  rosacea  in  the  regions  adjacent  to  the  Suez  Canal. 


Figure   8. — Distribution  of  Hippopodius  hippopus,  Agalma  elegans,  Agalma  okeni,  and 
Physophora  hydrostatica  in  the  regions  adjacent  to  the  Suez  Canal. 


533 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Other  new  records  for  the  Gulf  of  Elat  are 
Diphyes  dispar, L.  subtilis,  L.  subtiloides,  S.  chuni, 
S.  quadrivalvis,  A.  eschscholtzi ,  A.  tetragona,  E. 
hyalinum,  C.  cordiformis,  A.  rosacea,  A.  elegans, 
and  A.  okeni.  These  species,  except  CA.  contorta, 
were  only  previously  observed  in  either  the 
central  and  the  southern  Red  Sea  or  both  (Figures 
1,  2,  4-8).  Ch.  contorta  was  previously  observed  in 
the  Gulf  of  Elat  (Furnestin,  1958). 

The  depth  of  the  sill  at  Bab  el  Mandeb  does  not 
exceed  100  m  (Halim,  1969)  and  consequently 
meso  and  bathypelagic  species  are  extensively 
excluded  from  the  Red  Sea.  Halim  considered 
the  scarcity  of  species  in  the  Red  Sea  as  due 
to  the  "excluding  action  of  the  deep  outflow  over 
the  sill  at  the  southern  entrance  of  the  Red  Sea 
on  the  deep  water  species;  and  .  .  .  the  effect 
of  the  high  (21.5°-22°C)  minimum  tempera- 
ture of  the  Red  Sea  deep  water  in  inhibiting 
many  species.  .  .  ."  He  also  considers  excluding 
features  the  "high  salinity  (40.5-41.0''/oo)  and  the 
very  low  oxygen  content  (below  1  ml/1  in  summer 
and  2  ml/1  at  the  end  of  the  winter)  below 
sill  depth." 

Similar  interpretation  could  be  applied  for  the 
paucity  of  the  Mediterranean  siphonophores  as 
compared  with  the  Atlantic,  because  of  the  sill  at 
Gibraltar. 

Thorson  (1971)  stated  that  "the  physical- 
chemical  conditions  for  the  animals  to  pass  the 
Canal  have  improved  enormously  although 
there  are  still  obstacles  for  the  migration  of  many 
species." 

Seasonal  variations  in  occurrence,  abundance 
and  in  the  distributional  pattern  presented  by  the 
species  of  siphonophores  in  both  the  Levant 
Mediterranean  basin  and  the  Gulf  of  Elat  are  to 
be  expected.  The  various  populations  may  show 
changes  in  both  location  and  time  of  year.  These 
changes  may  be  due  to  the  characteristics  of  the 
flow  through  the  Strait  of  Gibraltar,  and  Bab  el 
Mandeb  respectively,  and  the  characteristics  of 
the  circulation  in  the  Mediterranean  and  the 
Arabian  Sea,  as  well  as  the  aspects  of  the  vertical 
migration  (Halim,  1969),  and  the  ontogeny  of  the 
population. 

Most  of  the  siphonophores,  except  for  a  few 
species  as  explained  above,  present  a  wide 
almost  cosmopolitan  distribution  (Alvariho, 
1971).  However,  species  abundant  in  the  western 
Mediterranean  and  the  Atlantic  reaching  the 
easternmost  Mediterranean  region  could  be  con- 


sidered "indicators"  or  tracers  of  the  Atlantic 
waters.  This  could  be  similarly  applied  to  some 
Indo-Pacific  or  Indian  Ocean  species  reaching 
the  Red  Sea. 

SIPHONOPHORES  OF 

THE  WESTERN  CARIBBEAN  AND 

THE  CENTRAL  AMERICAN  PACIFIC 

The  pairs  of  closely  related  species  allopatric  in 
distribution,  Ch.  appendiculata-Ch.  contorta, 
M.  atlantica-M.  kochi,  and  L.  challengeri- 
L.  fowleri  deserve  special  attention. 

Chelophyes  appendiculata  inhabits  the 
temperate  oceanic  regions,  and  appears  scattered 
along  the  tropico-equatorial  realm,  while  Ch. 
contorta  presents  a  distribution  restricted  to 
the  tropico-equatorial  regions  (Alvariho,  1971). 

Muggiaea  atlantica  inhabits  the  neritic  tem- 
perate eastern  Pacific,  Transition  region  (band 
between  the  Subarctic  and  Central  Pacific), 
the  Japanese  neritic  waters  and  the  neritic 
regions  of  the  temperate  Atlantic.  Muggiaea 
kochi  occupies  the  neritic  tropico-equatorial 
Atlantic  and  the  eastern  equatorial  Pacific  (Al- 
variho, 1971). 

Lensia  challengeri  is  an  Indo-Pacific  species, 
and  L.  fowleri  is  most  probably  restricted  to  the 
Atlantic  waters  (Alvariho,  1971). 

However,  Ch.  appendiculata,  M.  kochi,  and 
L.  fowleri  appear  widely  distributed  in  the  Carib- 
bean region  annex  to  the  Panama  Canal  and  in 
adjacent  regions  of  the  Caribbean,  Gulf  of  Mexico, 
and  western  tropical  Atlantic.  Ch.  contorta, 
M.  atlantica,  and  L.  challengeri  appear  in  the 
Central  American  Pacific  region.  Few  specimens 
of  Ch.  appendiculata  and  M.  kochi  were 
observed  at  locations  near  the  opening  of  the 
Panama  Canal  in  the  Pacific,  and  few  specimens 
of  Ch.  contorta,  M.  atlantica,  and  L.  chal- 
lengeri occurred  at  locations  near  the  opening 
of  the  Panama  Canal  in  the  Caribbean.  These 
observations  suggest  the  Caribbean  and  the 
Pacific  populations  may  be  able  to  migrate  or 
survive  artificial  transport  via  the  Panama  Canal 
(Figures  9-11,  Table  2). 

The  species  of  siphonophores  appearing  abun- 
dantly distributed  in  the  surveyed  region  in  both 
the  Caribbean  and  the  Central  American  Pacific 
are  Diphyes  bojani,  D.  dispar,  Diphyopsis  mitra, 
and  A.  eschscholtzi.  Diphyes  bojani  occurred  at 
all  Caribbean  stations,  except  for  the  close  to 


534 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 


Figure  9. — Distribution  of  Chelophyes  appendiculata  and  Chelophyes  contorta  in  the  regions 

adjacent  to  the  Panama  Canal. 


84" 


81* 


78° 


^^■1 

R 

I 

1 

^^H 

%. 

H^^^^H 

^       "" 

B   ^^^^^^^^^^^ 

1    ^ 

■^^                   X 

^ 

» 

flj^H 

^^^§\                   X 

^H 

X  x^^H 

^^ 

H 

X               X      J 

X 

X 

X 

x"        igSW 

X 

^^|| 

^^Hm.  atlantica 

^  1 

1 

1 

I 

^Bm.    kochi 

■ 

f^  - 

-  6* 


75* 


Figure   10. — Distribution  of  Muggiaea  atlantica  and  Muggiaea  kochi  in  the  regions  adjacent 

to  the  Panama  Canal. 


535 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

75° 


Figure   11. — Distribution  of  Lensia  challengeri  and  Lensia  fowleri  in  the  regions  adjacent 

to  the  Panama  Canal. 


shore  locations  off  Huani,  Nicaragua,  off  Puerto 
Colombia  and  Cartagena  de  Indias,  and  east  to 
the  entrance  of  the  Panama  Canal.  In  the  Pacific 
region  it  was  only  missing  at  the  northernmost 
station  in  the  Gulf  of  Panama,  south  of  Peninsula 
de  Azuero,  south  of  Coiba  Island,  off  Gulf  of 
Nicoya,  and  ofFPunta  Arenas  and  Punta  Guiones 
(Costa  Rica)  (Figure  12). 

Diphyes  dispar  and  Diphyopsis  mitra 
appeared  abundantly  distributed  in  the  Pacific 
region,  and  only  in  two  locations  in  the  Carib- 
bean. Diphyes  dispar  was  present  off  Colombia 
and  off  Laguna  Perlas  (Nicaragua),  and  Diphyop- 
sis mitra  at  two  locations  a  few  miles  north 
of  Panama  (Figures  12,  13). 

Abylopsis  eschscholtzi  was  only  absent  at  a 
few  stations  in  the  Caribbean  and  in  the  Central 
American  Pacific  (Figure  14). 

Species  scattered  distributed  in  both  the  Carib- 
bean and  the  Pacific  regions  were  Eudoxoides 
spiralis,  A.  tetragona,  S.  chuni,  A.  okeni,  and 
E.  hyalinum.  Eudoxides  spiralis  was  present  only 
at  five  Caribbean  locations,  which  include  two 
stations  off  Nicaragua  and  three  off  the  entrance 
to  the  Panama  Canal,  and  in  the  Pacific  appeared 
at  two  stations  southeast  of  Peninsula  de  Azuero 


and  at  two  offshore  stations  west  of  Costa  Rica 
(Figure  13). 

Abylopsis  tetragona  appeared  off  Colombia 
and  near  the  entrance  of  the  Panama  Canal  in 
the  Caribbean,  and  south  of  the  Azuero  Peninsula, 
south  of  Coiba  Island,  west  of  Nicoya  Peninsula, 
and  at  one  offshore  station  west  of  Costa  Rica  in 
the  Pacific  (Figure  14). 

Sulculeolaria  chuni  was  observed  at  three 
locations  over  the  deepest  part  of  the  western 
Caribbean,  and  in  the  Gulf  of  Panama,  south  of 
Nicoya  Peninsula,  and  at  two  offshore  stations 
west  of  Costa  Rica  in  the  Pacific  (Figure  16). 

Agalma  okeni  was  found  once  in  the  Caribbean 
region  (off  Costa  de  Mosquitos,  Nicaragua),  and 
in  the  Pacific  regions  appeared  from  the  Azuero 
Peninsula  to  Coiba  Island,  south  of  Costa  Rica 
and  west  of  Nicoya  Peninsula  (Figure  19). 

Enneagonum  hyalinum  was  only  observed  at 
the  western  Caribbean,  and  at  several  locations  in 
the  Pacific  extending  northwestwards  from  Coiba 
Island  (Figure  17). 

Species  scattered  distributed  in  the  surveyed 
region  of  the  Central  American  Pacific  were,  S. 
quadrivalvis,  S.  turgida,  B.  bassensis,  and  H. 
hippopus  (Figures  16-18). 


536 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 


Figure  12. — Distribution  of  Diphyes  bojani  and  Diphyes  dispar  in  the  regions  adjacent  to 

the  Panama  Canal. 


6*  - 


-  12° 


-  6* 


84* 


78* 


75* 


Figure  13. — Distribution  of  Diphyopsis  mitra  and  Eudoxoides  spiralis  in  the  regions  adjacent 

to  the  Panama  Canal. 


537 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Figure   14. — Distribution  of  Abylopsis  eschscholtzi  and  Abylopsis  tetragona   in  the  regions 

adjacent  to  the  Panama  CanaL 


Figure  15. — Distribution  of  Lens ia  cossack,  Lensia  hotspur,  and  Lensia  subtilis  in  the  regions 

a4jacent  to  the  Panama  CanaL 


538 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 


6*  - 


Figure   16. — Distribution  of  Sulculeolaria  chuni,  Sulculeolaria  monoica,  Sulculeolaria  quadri- 
valvis,  and  Sulculeolaria  turgida  in  the  regions  adjacent  to  the  Panama  Canal. 


Figure   17. — Distribution  of  Abyla  haeckeli,  Abyla  schmidti,  Bassia  bassensis,  Ceratocymba 
dentata,  and  Enneagonum  hyalinum  in  the  regions  adjacent  to  the  Panama  Canal. 


539 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

75° 


Figure   18. — Distribution  of  Hippopodius  hippopus,  Athoribya  rosacea,  and  Amphicaryon 
acaule  in  the  regions  adjacent  to  the  Panama  Canal. 


Figure   19. — Distribution  of  Agalma  okeni,  Stephanomia  bijuga,  and  Melophysa  melo  in  the 

regions  adjacent  to  the  Panama  Canal. 


540 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 

Table  1. — Siphonophores  of  the  regions  adjacent  to  the  Suez  Canal. 


Species 


Eastern 
Mediterranean 


Red  Sea 


Species 


Eastern 
Mediterranean 


Red  Sea 


Chelophyes  appendiculata 


(Diphyes  dispar) 


Eschscholtz.  1829 

32=20'N-34=51'E 

Gulf  of  Elat: 

32=45'N-34=57'E 

29=30'N-34'55'E 

33=03'N-34=55'E 

29=25'N-34=50'E 

35=05'N-35=00'E 

33=00'N-35=00E 

32=55'N-34=34E 

35=35'N-35=26'E 

34=50'N-28=55'E 

35=55'N-28=37'E 

36=30'N-28=13'E 

36=31 ■N-27=27'E 

35=14'N-26=33'E 

33=25'N-30=20'E 

33=10'N-33=50'E 

31=31 'N-34=28E 

32=23'N-34=37'E 

34=37'N-32=20E 

32=30'N-33=21'E 

31=42'N-34=28'E 

32=46'N-34=53E 

32=50'N-34=50'E 

33=25'N-33=14'E 

32=01 'N-33=25'E 

33'25'N-25=15'E 

34=47'N-25=10'E 

35=11'N-22=15'E 

35=35'N-21=50'E 

35=57'N-22=15'E 

34=10'N-34=29'E 

35=57'N-32=23'E 

34=35'N-33=35'E 

35=05'N-34=38  E 

35=50'N-31  =  15'E 

32=43'N-34=38'E 

32=10'N-32=50'E 

32=07'N-33=24'E 

31=42'N-33=00'E 

35=55'N-28=33'E 

Eudoxia  russelli 

Totton,  1932 

35=57'N-32=23'E 

Gulf  of  Elat: 

29=30'N-34=55'E 

29=25'N-34=50'E 

Chelophyes  contorts 

•* 

*  + 

(Lens  &  Riemsdijk. 

32=45'N-34=57'E 

Gulf  of  Elat: 

1908) 

35=05'N-35=00'E 
32=23'N-34=37'E 
32=50'N-34=51'E 
32=01  ■N-33=25'E 
32=43'N-34=38'E 

29'25'N-34=50'E 

Diphyes  bojani 
(Escfischoltz.  1829) 


36=31 'N-27=27'E 
33=25'N-30=20'E 


Diphyes  chamissonis 

+ 

Huxley.  1859 

Diphyes  dispar 

•*   . 

+ 

Chamisso  & 

34=50'N-32=47'E 

Gulf  of  Elat: 

Eysenhardt,  1821 

35=05'N-35=00'E 
33=00' N-35=00'E 
32=46'N-34=53'E 
32=55'N-34=34'E 
35=35'N-35=26'E 
35=05'N-34=05'E 
34=50 ■N-28= 55 'E 
35=55'N-28=37'E 
36=30'N-28'13'E 
36=31  ■N-27=27'E 
35=14'N-26=33'E 
33=25'N-30=20E 
31=31 ■N-34=28'E 
32=23'N-34=37'E 
34=37'N-32=20'E 
32=30'N-33=21'E 
31=42'f^-34=28'E 

29=30'N-34=55'E 

Diphyopsis  mitra 

Huxley,  1859 
Muggiaea  atlantica 

Cunningfiam,  1892 
Muggiaea  kochi 

Will.  1844 
Eudoxoides  spiralis 

Bigelow,  1911 


Clausophyes  ovata 

Keferstein  &  Ehlers.  1861 
Sphaeronectes  spp. 
Lensia  campanella 

Moser,  1925 


Lensia  conoidea 

Keferstein  &  Ehlers.  1861 
Lensia  fowleri  Bigelow,  1911 
Lensia  hotspur  Totton,  1954 
Lensia  meteon  Leioup.  1934 


Lensia  multicristata 

Moser,  1925 
Lensia  subtilis  Chun,  1886 


33=25 
32=01 
34=47 
35=35 
35=57' 
32=20 
31=37 
31=44 
32'=45 
32=50 
35=57' 
34=35' 
35=05' 
33=50' 
32=43' 
32=10' 
32=07' 
35=00 
35=55 


N-33' 
N-33' 
N-25 
N-21' 
N-22' 
N-34' 
N-34' 
N-34' 
N-34' 
N-34' 
N-32' 
N-33' 
N-34= 
N-3r 
N-34' 
N-32' 
N-33' 
N-35' 
N-28' 


14'E 
25'E 
10'E 
50 'E 
15'E 
51'E 
32'E 
26'E 
49'E 
50'E 
23E 


35' 

38' 

15' 

38 'I 

'50'l 

24'l 

OO'E 

33'E 


33°03'N-34°55'E 


35'=05' 
31=31' 
34=37' 
32=50' 
34=35' 
34=10' 
35=57' 
34=35' 
35=05' 
33=50' 
32=43' 
32=10' 
32=07' 
31=42' 


N-35= 
N-34= 
N-32= 
N-34= 
N-29= 
N-34= 
N-32= 
N-33= 
N-34= 
N-31  = 
N-34= 
N-32= 
N-33= 
N-33= 


OO'E 
28'E 
20'E 
51'E 
40'E 
29'E 
23'E 
35'E 
38  E 
15'E 
48'E 
50'E 
24'E 
OO'E 


32=43'N-34=38E 
32=10'N-32=50'E 
32=07'N-33=27'E 


34=35'N-33=35'E 
33=50'N-31  =  15'E 

32°45'N-34°49'E 


Gulf  of  Elat: 
29=30'N-34=55'E 

-I- 


+ 
+ 
+ 


34=35'N-29''40'E 

Gulf  of  Elat: 

32'10'N-32'50'E 

29°30'N-34=55'E 

32=07 'N-33=24'E 

29=25'N-34=50'E 

Lensia  subtiloides 

•  •• 

-t- 

Lens  &  Riemsdijk,  1908 

Gulf  of  Elat: 
29°30'N-34°55'E 

Sulculeolaria  angusta 

Totton.  1954 

35=05'N-35=00'E 
32=55'N-34=34'E 
32=46'N-34=53'E 
37=17'N-22=47'E 
35=11'N-22=15'E 
34=35'N-29=40'E 
32°07'N-33=24'E 
35=00'N-35=00'E 

Sulculeolaria  biloba 

Sars.  1846 

541 


FISHERY  BULLETIN;  VOL.  72,  NO.  2 


Table  1 


ontinued. 


Species 


Eastern 
Medjterranean 


Red  Sea 


Species 


Eastern 
Mediterranean 


Red  Sea 


Sulculeolaria  chuni 
Lens  &  Riemsdijk.  1908 


Sulculeolaria  quadrivalvis 
Blainville,  1834 


Sulculeolaria  turgida 
(Gegenbauer,  1854) 


Abylopsis  eschscholtzi 
Huxley,  1859 

Abylopsis  tetragona 
Otto,  1823 


Bassia  bassensis 
Quoy  &  Gaimard.  1834 


Ceratocymba  sagittata 
Quoy  &  Gaimard.  1827 

Enneagonum  hyalinum 
Quoy  &  Gaimard.  1827 

Hippopodius  hippopus 
Forskal,  1776 


32=10N-32'50E 
32'07N-33'24'E 
32=45'N-34°49'E 

32'21N-34=48'E 
32=55'N-34'34'E 
35'57N-32'23'E 
34'35N-33'35'E 
35°05N-34  38E 
33'50N-3ri5'E 


32=45 
35'35 
34'47 
35°35 
35=57 
34=35 
34=10 
35=57 
34=35' 
35=05 
33=50' 
32=43' 
32=10' 
35=00 


N-34 

N-35 

N-25 

N-21 

N-22 

N-29 

N-34 

N-32 

N-33' 

N-34' 

N-3r 

N-34' 

N-32= 

N-35' 


49'E 
26  E 
10'E 
50'E 
15'E 
40'E 
29'E 
23'E 
35'E 
38'E 
15'E 
38'E 
50'E 
OO'E 


33=25'N-30=20'E 
35=05'N-34=38'E 
32=10'N-32=50'E 


33=03 'N• 
33=25'N■ 
31=31 'N- 
32=23'N 
32=30  N 
35=1 1  N- 
35°57'N- 
34=35'N- 
34=10'N- 
32=46'N- 
35=57'N- 
34=35'N- 
35=05'N- 
33=50'N- 
32=43  N- 
32=10'N- 
32=07 'N■ 
31°42'N■ 
3r37'N- 
35=55'N- 


34=55'E 
30=20'E 
34=28  E 
34=37'E 
33=21 'E 
22=15'E 
22=15'E 
29=40'E 
34=29 'E 
34=53'E 
32=  23'E 
33=35'E 
34= 38'E 
31  =  15'E 
34=48 'E 
32=50'E 
33=24'E 
33=00'E 
34=32'E 
28=33  E 


Gulf  of  Elat: 
29=30  N-34=55'E 


Gulf  of  Elat: 

29'30'N-34=55'E 

29=25'N-34=50'E 


(Hippopodius  hippopus) 


Gulf  of  Elat: 

29=25'N-34=50'E 

+ 

Gulf  of  Elat: 

29=30'N-34=55'E 

29=25'N-34=50'E 

+ 


Vogtia  glabra  Bigelow,  1918 
Vogtia  pentacantha 

Kolliker.  1853 
Vogtia  spinosa 

Keferstein  &  Efilers,  1861 
Praya  cymbilormis 

Cfiiaje,  1841 
Rosacea  plicata 

Quoy  &  Gaimard.  1827 
Amphicaryon  acaule 

Cfiun,  1888 
Amphicaryon  ernesti 

Totton,  1954 
Anthophysa  rosea 

Brandt,  1835 
Apolemia  uvaria 

Lesueur,  1811 
Rhizophysa  filiformis 

Forskal,  1775 
Cordagalma  cordiformis 

Totton,  1932 
Athoribya  rosacea 

(Forskal,  1775) 
Agalma  elegans  Sars.  1846 


Agalma  okeni 

•• 

Eschscholtz,  1825 

+ 
Gu 

If  of  Elat; 

'Stephanomia  bijuga 

29=25'N-34=50'E 

(Cfiiaje.  1841-42) 

•  •* 

+ 

Stephanomia  rubra 

32=21 'N-34=48'E 

Vogt.  1852 

35=39 'N-26'34'E 

Nanomia  cara  Agassiz,  1865 

35=05'N-35=00'E 

Physophora  hydrostatica 

32°23'N-34°37'E 

Forskal,  1775 

32=55'N-34=34'E 

35=35'N-35=26'E 

35=05'N-34=05'E 

34=50'N-28=55'E 

Forskalia  edwardsi 

35=55'N-28'37'E 

Kolliker,  1853 

36=31' 

32=46' 

33=25' 

32=01 

34=47 

33=25 

37=17 

35=11' 

35=35 

35=57' 

34=35' 

34=10' 

32=50 

32=20 

31=37 

31=42 

31=44 

32=45 

34=35 

35=05 

33=50 

32=43 

32=10 

32=07 

31=42 

35=00 

35=55 


N-27' 
N-34' 
N-33 
N-33 
N-25 
N-25 
N-22 
N-22= 
N-21  = 
N-22= 
N-29= 
N-34= 
N-34' 
N-34' 
N-34' 
N-34' 
N-34' 
N-34' 
N-33' 
N-34' 
N-31' 
N-34' 
N-32' 
N-33' 
N-33 
N-35' 
N-28' 


27E 

53'E 
14'E 
25'E 
10'E 
15'E 
47'E 
15'E 
50'E 
15'E 
40'E 
29'E 
50'E 
51  E 
32'E 
28'E 
26 'E 
49'E 
35'E 
38'E 
15'E 
38'E 
50'E 
24'E 
OO'E 
OO'E 
33'E 


32=10'N-32=50'E 


36=31 'N-27=27'E 


35=55'N-28=33'E 


35°57'N-22°45'E 
34=35 'N-29=40'E 
35=50'N-3r  15'E 
3r42'N-33=00'E 


+ 
+ 
+ 


29=25'N-34=50'E 

+ 

29=25'N-34=50'E 

+ 

Gulf  of  Elat: 

29=30'N-34=55'E 

29=25'N-34=50'E 

+ 

Gulf  of  Elat: 

29=30 'N-34=55'E 

29=25'N-34=50'E 

+ 


Previously  observed  (see  Alvarirto.  1971:  Lakkis.  1971). 
•    Previously  observed  in  tfie  Red  Sea  (Alvarirto.  1971  compilation  of  distributional  data). 
'Previously  observed  in  the  western  (Mediterranean  (see  Alvarirto,  1971). 


542 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 

Table  2. — Siphonophores  of  the  regions  adjacent  to  the  Panama  Canal. 


Caribbean  Sea 

Central 

Eastern 

Species 

region 

American  Pacific 

Species 

Mediterranean 

Red  Sea 

Chelophyes  appendiculata 

{Diphyopsis  mitra) 

07=12'N-79'54'W 

ir07N-74'47'W 

08=41 ■N-79=31W 

07=02N-79=57W 

10M9'N-75=38'W 

08=48 'N-79=30W 

06'40'N-79=59'W 

09^46N-79'20W 

08=00N-79=43W 

06=55N-80=50W 

09'37'N-79^39'W 

07=18N-82=25'W 

09'27N-7y48W 

07=30'N-83=54'W 

14'19'N-83  09'W 

07=39'N-84=46'W 

13=56N-82  59W 

07=57'N-85=49'W 

13°38N-82'38W 

08=48'N-85=57'W 

13=12  N-82'25W 

09=07N-84=58'W 

12'=3rN-8r52'W 

09=32N-85=10'W 

12=11  N-8138'W 

09=51 'N-85=43'W 

10=04'N-80  22'W 

Muggiaea  atlantica 

•  • 

Chelophyes  contorta 

•• 

09=28N-84=2rW 

09=38 'N-85=44'W 

09=27N-79=48W 

07=30'N-79=54W 

09=46'N-79=20'W 

08=41  ■N-79=3rW 

09'25N-79=57'W 

08  46'N-84=irW 
09=13'N-84=45W 

09  28N-85=15'W 
09=39'N-85=4rW 
07=12'N-79=54W 
07=02'N-79=57W 
06=55'N-80=50'W 
07=12'N-81=48W 
07=18'N-82=25'W 
07=27N-83=04'W 
07=30N-83=54W 
0739'N-84=46'W 
07=51  ■N-85=49'W 
08=48'N-85=17W 
09=07'N-84=58'W 
09=23'N-84=52W 

09=27'N-79=48'W 

07=30'N-79=54'W 
08=10N-82=13W 
08=10'N-82=15'W 
08=10N-82=16W 
09=13N-84=45W 
09=28'N-85=15'W 
09=39'N-85=4rW 
08=48'N-79=30W 
07=12'N-79=54'W 
07=02'N-79=57'W 
06=55N-80=50W 
09=07N-84=58'W 
09=23N-84=52'W 
09=39  ■N-84=44W 
09=32N-85=10W 
09=51 'N-85=43'W 

09=51  ■N-85=43W 

Muggiaea  l<ochi 

•• 

Dimophyes  arctica 

** 

*" 

11=07'N-74=47'W 

08°41  'N-79°31  'W 

(Chun,  1897) 

10=19N-75=38W 

Diphyes  bojani 

•* 

** 

09=46N-79=20W 

09=46N-46=20'W 

07=30'N-79=54'W 

09=37'N-79=39W 

09=27'N-79=47'W 

08=10'N-82=13'W 

09=28N-79=46W 

09'27N-79'38W 

08=10N-82=15'W 

09=27'N-79=47'W 

13=56'N-82=59'W 

08=10N-82=16'W 

14=19'N-83  09W 

13=38N-82=38W 

08=46N-84=irW 

14=07'N-83=0rW 

13'12N-82  25'W 

09=13'N-84=45W 

13=56'N-82=59'W 

12=31  ■N-81=52'W 

09=28'N-85=15W 

13=38'N-82=38W 

12=11'N-8r38'W 

09  39N-85=41'W 

10=04N-80=22'W 

ir27'N-8ri5'W 

07=27'N-83=04'W 

09=25'N-79=57'W 

10=44N-80=45'W 

07=30N-83=54'W 

Eudoxoides  spiralis 

** 

•• 

10'04'N-80=22'W 

07=39'N-84=46'W 

09=37'N-79=39'W 

07=12'N-79=54'W 

07=57'N-85=49'W 

09=28N-79=46'W 

07=02'N-79=57'W 

08=48'N-85'17'W 

13=38'N-82=38'W 

07=39'N-84=46'W 

09=07N-84=58W 

12=31'N-81=52'W 

07=57'N-85=49'W 

09=23N-84=52W 

10=04'N-80=22W 

Diphyes  dispar 

•  '* 

Lensia  campanella 

'" 

** 

10=19'N-75=38'W 

09=38'N-85=44'W 

Lensia  challengeri 

*• 

08=46N-84=11'W 

08=48'N-79=30'W 

Totton,  1954 

10=04'N-80=22'W 

06=40'N-79=59'W 

09=13'N-84=45'W 

08=00N-79=43W 

07=30'N-83=54'W 

09=28N-85=15'W 

06=40N-79=59W 

07=39'N-84=46'W 

09=39'N-85=4rW 

06=55N-80=50'W 

07=57N-85=49'W 

12=31  ■N-81=52W 

07=12'N-81=48W 

Lensia  conoidea 

** 

07=27'N-83=04'W 

Lensia  cossacl<  Totton,  1941 

•  • 

*' 

07=30'N-83'54'W 

06=55'N-80=50'W 

07=39'N-84=36W 

Lensia  fowleri 

•• 

07=57N-85=49'W 

14'19'N-83'09'W 

08=48'N-85=17W 

Lensia  hotspur 

•• 

*• 

09=07'N-84=58'W 

10'04'N-80^22'W 

09=51 'N-85=43'W 

09=23N-84=52W 

Lensia  lelouveteau 

•' 

09=39'N-84=44'W 

Totton,  1941 

09=32'N-85=10W 

Lensia  meteori 

*• 

09=51  ■N-85=43'W 

Lensia  multicristata 

•* 

Diphyopsis  mitra 

** 

** 

Lensia  reticulata 

** 

10°44'N-80=45'W 

07=30'N-79=54'W 

Totton,  1954 

10=04N-80=22W 

08=46N-84=11W 
09=13'N-84=45'W 

Lensia  subtilis 

10=04N-80=22'W 

09=28N-85=15W 

Sulculeolaria  bigelowi 

*' 

09'39'N-85=41'W 

(Sears.  1950) 

08'00'N-79=43'W 

Sulculeolaria  biloba 

** 

** 

543 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Table  2. — Continued. 


Eastern 

Eastern 

1 

Species 

Mediterranean 

Red  Sea 

Species 

Mediterranean 

Red  Sea 

I 

Sulculeolaria  chuni 

.. 

.. 

(Ceratocymba  dentata) 

07'39'N-84=46W 

12°31'N-8r52W 

08'00N-79'13W 

09'07N-84'58W 

ir27'N-8ri5'W 

07'30'N-83'54W 

Ceratocymba  leuckarti 

•* 

1 

10'=44'N-80'45W 

07  57N-85  49'W 

Huxley.  1859 

09'23N-84  52W 

Ceratocymba  sagittata 

•• 

Sulculeolaria  monoica 

•  • 

*' 

Enneagonum  hyalinum 

•• 

•  ** 

Chun,  1888 

07  30N-83'54W 

12'1VN-8r38'W 

07'18'N-82'25'W 

Sulculeolaria  quadrivalvis 

•  • 

08'46N-84=irW 
09=28N-85'15W 
08'48N-85'17W 
09'07N-84'58W 
09'23N-84=52'W 

08  46'N-84'11'W 
07'39N-84=46'W 
07'57N-85=49'W 
09"07'N-84=58'W 
09=23'N-84=52'W 
09'32'N-85=10'W 

Sulculeolaria  turgida 

08'=00N-79'43'W 
07'30'N-83'54'W 
07=57'N-85'49'W 
09'23'N-84=52W 

Hippopodius  hippopus 

•  • 

0r30'N-79'54'W 
07M2'N-79'54'W 
07'02'N-79°57'W 
06^42'N-79'59'W 

Abyla  carina  Haeckel,  1888 

•  • 

07M8'N-82'25'W 

Abyla  haeckeli 

•    •• 

•    •• 

07  57'N-85'49'W 

Lens  &  RIemsdijk.  1908 

12°31'N-8r52'W 

09°51'N-85°43'W 

08=48'N-85'17W 

Abyla  schmidt  Sears.  1953 

09^51 'N-85°43'W 

09'07N-84'58'W 
09'23'N-84°52W 

Abylopsis  eschscholtzi 

•    •• 

•  •' 

09'32N-85'10W 

10'46'N-79'20'W 

07'30'N-79=54'W 

09''51'N-85°43'W 

14^19'N-83'09'W 

08=46N-84'irw 

Vogtia  glabra 

•• 

14'07'N-83'01'W 

09'28N-85=15W 

Vogtia  pentacantha 

*• 

13^12'N-82°25'W 

09'39'N-83'09'W 

Vogtia  spmosa 

•• 

12'31'N-8r52'W 

07'12'N-97'54'W 

Rosacea  plicata 

•• 

10'44N-80'45'W 

07°02'N-79°57'W 

Nectopyramis  natans 

•• 

10'04N-80'22'W 

06^40N-79'59'W 

Bigelow,  1911 

09'25'N-79'57'W 

06=55'N-80'50'W 

Amphicaryon  acaule 

•• 

■ 

07M8'N-82'25'W 

10'04N-80^22'W 

09^51  'N-85'=43'W 

07'27'N-83'04'W 

Amphicaryon  ernesti 

•* 

07°30'N-83'54'W 

Rhizophysa  filiformis 

** 

07°39'N-84'46'W 

Alhoribya  rosacea 

07^27 'N-83°04'W 

07"57'N-85'49'W 

Agalma  elegans 

•• 

08°48'N-85'17W 

Agalma  okeni 

" 

•  •• 

09°07N-84'58W 

13'12N-82'25W 

06=55 'N-80'=50'W 

09^51  ■N-85^43'W 

07'=12'N-8r48'W 

Abylopsis  tetragona 

•    •• 

07'39'N-84'46'W 

ir07'N-74"47'W 

09=38'N-85  44'W 

09=07'N-84'58'W 

10^19'N-75=38'W 

07=02'N-79'57'W 

09'32N-85'10W 

09'37'N-79'39'W 

07^57'N-85'49W 

09-51  ■N-85=43'W 

09°25'N-79=57'W 

09"51'N-85'43'W 

Stephanomia  bijuga 

** 

** 

Bassia  bassensis 

07°02'N-79°57'W 

14"19'N-83=09'W 

09°32'N-85'10'W 
09=51  ■N-85'43'W 

07=57'N-85'49'W 

Stephanomia  rubra 

•• 

09=23'N-84'52W 

Physophora  hydrostatica 

•  * 

09°51'N-85'=43'W 

Ceratocymba  dentata 

.  .. 

Melophysa  melo 

* 

Bigelow,  1918 

07"30'N-83°54'W 

Quoy  &  Gaimard.  1827 

07=57'N-85=49'W 

"Previously  observed. 
"Previously  observed  in  adjacent  regions  of  the  Caribbean  Sea  and/or  the  Gulf  of  Mexico,  and  adjacent  regions  of  the  Pacific  Ocean  (see 
Alvarirto,  1971  compilation  of  distributional  data). 


Species  present  at  few  locations  in  the  surveyed 
region  of  the  Caribbean  and  Pacific  were,  L.  hot- 
spur, Abyla  haeckeli,  and  A.  acaule.  Lensia 
hotspur  and  A.  acaule  were  only  found  at  one 
location  to  the  north  off  the  entrance  of  the 
Panama  Canal  in  the  Caribbean,  and  west 
of  the  Peninsula  de  Nicoya  in  the  Pacific  (Fig- 
ures 15,  18).  Abyla  haeckeli  was  observed  once 
off  Costa  de  Mosquitos,  Caribbean  Sea,  and  at 
one  location  off  Punta  Guiones  in  the  Pacific 
(Figure  17). 


Species  present  once  or  at  few  locations  in 
the  Pacific  region  were,  L.  cossack,  S.  monoica, 
Abyla  schmidti,  C.  dentata,  Melophysa  melo, 
A.  rosacea,  and  Stephanomia  bijuga  (Figures 
15-19). 

Lensia  subtilis  and  L.  fowleri  were  found  only 
once  each,  respectively  at  few  miles  north  of  the 
entrance  to  the  Panama  Canal,  and  off  Huani 
in  the  Caribbean  (Figures  11,  15). 

The  information  presented  here  should  be 
considered  only  as  a  basis  for  future  and  more 


544 


ALVARINO:  DISTRIBUTION  OF  SIPHONOPHORES 


detailed  sets  of  investigations  to  enlighten  further 
the  distribution  and  the  characteristics  of  the 
populations  of  siphonophores,  their  fluctuations  in 
time  and  locations,  concurrently  with  the  hydro- 
graphic,  ecological  characteristics  and  other 
variants. 

The  author  regrets  that  the  pertinent  hydro- 
graphic  data  obtained  concurrently  with  the 
zooplankton  collections  were  not  available  in  time 
to  be  included  in  the  discussion  of  results. 

ACKNOWLEDGMENTS 

I  am  deeply  indebted  to  B.  Kimor,  O.  H.  Oren, 
and  F.  D.  Por,  for  providing  me  with  the  valuable 
Israeli  collections  of  siphonophores  from  the 
eastern  Mediterranean  and  the  Gulf  of  Elat,  and 
from  their  encouragement  to  complete  this  piece 
of  work.  This  paper  was  presented  at  the  XVII 
International  Zoological  Congress,  Symposium  on 
Biological  Effects  of  Interoceanic  Canals,  Monte 
Carlo,  24-30  September  1972. 

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545 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

Schneider,  K.  C.  Totton,  A.  K. 

1898.     Mitteilungen    iiber    Siphonophoren    III.    Sys-  1954.     Siphonophora  of  the  Indian  Ocean  together  with 

tematische  und  andere  Bemerkungen.     Zool.  Anz.  systematic  and  biological  notes  on  related  specimens 

21:51-200.  from  other  oceans.     Discovery  Rep.  27:1-162. 

Working  Party  No.  2. 

Thorson,  G.  1968.     Smaller  mesozooplankton.    /n  J.  H.  Fraser  (editor), 

1971.     Animal  migrations  through  the  Suez  Canal  in  the  Standardization  of  zooplankton  sampling  methods  at 

past  recent  years  and  the  future.  (A  preliminary  report.)  sea,  p.  153-159.     UNESCO  Monogr.  Oceanogr.  Methodol. 

Vie  Milieu  21:841-846.  2,  Zooplankton  sampling. 


I 


546 


THREE  NEW  SPECIES  OF  THE  GENUS  MONOGNATHUS  AND 
THE  LEPTOCEPHALI  OF  THE  ORDER  SACCOPHARYNGIFORMES 

Solomon  N.  Raju* 

ABSTRACT 

Three  new  species  of  the  genus  Monognathus — M.  isaacsi,  M.  ahlstromi,  and  M.  Jesse — are 
described  from  the  Pacific  Ocean,  bringing  the  number  of  the  species  to  six.  M.  isaacsi  differs 
from  the  other  species  in  having  a  relatively  large  head  and  dark  brown  pigmentation  on 
the  whole  body.  M.  ahlstromi  has  a  characteristic  paddle-shaped  caudal  fin,  and  M.  jesse  has 
a  lanceolate  caudal  fin.  A  key  to  the  six  species  and  their  distribution  in  the  Pacific  and 
Atlantic  are  given.  Leptocephali  of  Monognathus  sp.  are  identified  and  described  for  the  first 
time.  The  status  and  relationships  of  the  Monognathidae  are  discussed. 

Metamorphic  forms  oi Saccopharynx  and  Eurypharynx  are  described.  The  identity  of  Leptocephalus 
latissimus  to  Saccopharynx  and  ofL.  pseudolatissimus  to  Eurypharynx  is  confirmed.  An  unknown 
leptocephalus  closely  resembling  that  of  Cyema  is  described,  and  the  possibility  of  a  new  genus 
in  the  Cyemidae  is  suggested.  Relationships  of  the  Cyemidae  to  the  Nemichthyidae  are  refuted, 
and  relationships  of  the  Cyemidae  to  the  Saccopharyngiformes  are  supported. 


The  deepsea  gulpers  of  the  order  Saccopharyngi- 
formes (Monognathidae,  Saccopharyngidae,  and 
Eurypharyngidae)  are  among  the  most  curious 
and  extremely  modified  bathypelgic  fishes,  and 
very  little  is  known  about  them.  Bohlke  (1966) 
reviewed  the  literature  on  the  attempts  to  relate 
them  to  diverse  groups  of  fishes. 

I  describe  three  new  species  of  Monognathus 
{M.  isaacsi,  M.  ahlstromi.  and  M.  jesse)  and  four 
metamorphic  stages  of  Monognathus  sp.  A  key 
to  the  six  known  species  of  the  genus  Monogna- 
thus is  given.  This  is  the  first  record  of  the  family 
from  the  southern,  central,  and  eastern  Pacific. 
The  three  species  of  Monognathus  described  by 
Bertin  (1934,  1938)  from  the  Atlantic  and  Indo- 
Pacific  regions  are  only  juveniles.  The  lack  of 
adult  monognathids  even  led  Bohlke  (1966)  to 
suspect  that  the  then  known  monognathids  might 
be  postlarval  saccopharyngids.  The  specimen 
named  as  M.  isaacsi  is  in  a  more  advanced 
stage  than  any  of  the  other  specimens  of  the  six 
species.  Many  of  its  features  clearly  indicate  that 
this  family  is  distinct  from  the  Saccopharyngidae. 
A  leptocephalus  stage  in  the  life  history  of  Mono- 
gnathus is  reported  for  the  first  time.  Information 
on  the  ethmoid  tooth,  food,  and  distribution  of 
Monognathus  is  given.  The  status  and  relation- 
ships of  the  family  Monognathidae  to  the  Sac- 
copharyngiformes are  discussed. 


'Simpson  College,  San  Francisco,  CA  94134. 


Two  metamorphic  forms,  one  belonging  to 
Saccopharynx  and  the  other  to  Eurypharynx,  are 
described,  and  Leptocephalus  latissimus  Schmidt 
1912  is  assigned  to  Saccopharynx  and  L.  pseu- 
dolatissimus Bertin  1934  to  Eurypharynx. 

An  unknown  leptocephalus  closely  resembling 
that  of  Cyema  is  described  from  the  North  Pacific, 
and  the  possibility  of  a  new  genus  in  the  Cyemidae 
is  suggested.  The  relationship  of  the  Cyemidae  to 
the  Nemichthyidae  is  questioned,  and  its  relation- 
ship to  the  Saccopharyngiformes  is  supported. 

MATERIALS  AND  METHODS 

The  account  is  based  on  the  study  of  one  fully 
transformed  juvenile,  two  early  juveniles,  and 
four  metamorphic  forms  of  the  genus  Monogna- 
thus collected  from  the  central  and  eastern  North 
Pacific  during  the  Tethys  (1960),  CalCOFI  (1962), 
and  Scan  (1969)  expeditions.  One  specimen  of 
Leptocephalus  latissimus  was  obtained  from  the 
San  Diego  Trough  (1950)  and  its  metamorphic 
form  off  Baja  California.  A  metamorphic  form  of 
Eurypharynx  pelecanoides  was  collected  from  the 
central  North  Pacific  during  the  Styx  expedition 
(1968).  All  the  specimens  were  collected  by  the 
10-foot  Isaacs-Kidd  midwater  trawl  (IKMT).  Total 
length  and  body  depth  were  measured  with  dial 
calipers,  and  measurements  of  head,  snout,  and 
eye  were  taken  by  ocular  micrometer  following 
the  methods  of  Castle  (1963).  Some  specimens 


Manuscript  accepted  August  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  2,  1974. 


547 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


were  dissected.  Drawings  were  made  with  the  aid 
of  a  projector  and  camera  lucida.  All  the  holotypes 
are  presently  housed  in  the  Marine  Vertebrates 
Collection  of  the  Scripps  Institution  of  Ocean- 
ography. 

Names:  The  new  species  of  the  genus  Mo/zo^na- 
thus  are  named  for  John  D.  Isaacs  of  the  Scripps 
Institution  of  Oceanography  (SIO),  La  Jolla; 
Elbert  H.  Ahlstrom  of  the  Southwest  Fisheries 
Center,  National  Marine  Fisheries  Service,  La 
Jolla;  and  Jesse  N.  Raju,  wife  of  the  author  (noun 
in  apposition). 

KEY  TO  THE  SPECIES  OF 
THE  GENUS  MONOGNATHUS 

la.  Pectoral  fin  present  2 

lb.  Pectoral  fin  absent  3 

2a.  Head  large,  about  13.3  in  total 

length,  caudal  fin  normal  M.  isaacsi 

2b.  Head  small,  about  9  in  total 

length,  caudal  fin  lanceolate  M.jesse 

3a.  Caudal  fin  normal,  vertebrae  long  4 

3b.  Caudal  fin  either  whiplike  or 

paddle  shaped,  vertebrae  short  5 

4a.  Vertebrae  94,  teeth  in  mandible  8, 

adipose  region  of  dorsal  fin  with 

48-63  rays  M.jesperseni 

4b.  Vertebrae  88,  teeth  in  mandible  12, 

adipose  region  of  dorsal  fin  with 

36-48  rays  M.  hruuni 

5a.  Caudal  fin  whiplike,  dorsal 

commences  on  myotome  3,  two 

ethmoid  teeth  M.  taningi 

5b.  Caudal  fin  compressed,  paddle 

shaped,  dorsal  commences  on 

myotome  13,  one  median  ethmoid 

tooth  M.  ahlstromi 

MONOGNATHUS  ISAACSI  SP.  N. 

Figures  ID,  I;  20 

Holotype:  SIO  69-353,  western  North  Pacific, 
32^02. 3'N-32'=07.9'N,  156^07. 0'E- 156^06. 7'E, 
depth  of  capture  0-950  m,  IKMT,  1(56  mm), 
2  June  1969. 

Description:  Body  elongate,  compressed  except 
at  head.  Trunk  clearly  marked  from  tail,  2.9 
in  total  length.  Maximum  depth  at  middle  of 


body,  10.3  in  total  length.  Head  large,  7.6  in 
total  length.  Snout  moderately  long,  2.4  in  head. 
Olfactory  organ  rudimentary,  a  short  curved 
tube  open  at  both  ends.  Eyes  tubular,  small, 
18.7  in  head.  Upper  jaw  soft,  maxilla  not 
recognizable,  no  upper  teeth.  Skin  inside  of 
mouth  dusted  with  melanophores.  Median  eth- 
moid tooth  projects  below  level  of  lips,  visible 
from  side.  Lower  jaw  slightly  longer  than  upper 
jaw,  with  four  small  teeth.  Mouth  large,  gape 
reaching  far  behind  eye.  Postorbital  distance  1.7 
in  head.  No  branchiostegals  recognizable.  Gill 
opening  small,  ventrolateral.  About  75  myotomes 
could  be  counted  and  another  25-30  are  estimated 
for  a  total  of  about  100.  Tail  blunt  at  tip. 
Stomach  bulging,  extending  beyond  trunk  as  a 
sac.  Dorsal  fin  high,  originating  behind  gill  open- 
ings, with  80  unsegmented  rays.  Predorsal  dis- 
tance 3.7  in  total  length.  Anal  fin  high,  originat- 
ing behind  vent,  with  52  unsegmented  rays. 
Preanal  distance  1.5  in  total  length.  Pectoral 
fins  small,  rays  not  distinct. 

Pigmentation:     Uniformly  dark  brown. 

Remarks:  This  is  the  first  known  specimen  of 
the  Monognathidae  with  complete  body  pigmenta- 
tion. The  absence  of  an  upper  jaw  and  the 
presence  of  an  ethmoid  fang  indicate  that  M. 
isaacsi  is  properly  referable  to  the  Monogna- 
thidae. Of  all  the  members  of  the  Saccopharyngi- 
formes  so  far  known,  this  species  represents  the 
most  generalized  form  except  for  the  reduced 
eye,  presence  of  the  enlarged  ethmoid  fang,  and 
absence  of  the  upper  jaw.  The  shape  of  the  body, 
the  head  with  its  long  snout  and  large  mouth, 
the  nature  of  the  median  fins,  and  the  presence  of 
pectoral  and  absence  of  ventral  fins  are  typical 
of  eels.  In  Eurypharynx  and  Saccopharynx  the 
mouth  is  enlarged  and  the  suspensorium  highly 
modified,  and  in  Saccopharynx  the  tail  is  whip- 
like. The  snout  in  these  genera  is  reduced  whereas 
it  is  long  in  M.  isaacsi. 

The  meristic  and  morphometric  characters  of 
the  three  species  described  by  Bertin  (1938)  and 
the  three  new  species  described  in  this  account 
are  given  in  Table  1.  The  relative  lengths  of  the 
head,  cranium,  snout,  and  predorsal  distance  are 
the  highest  in  M.  isaacsi.  The  head  is  depressed. 
The  teeth  in  the  lower  jaw  are  different  in  shape 
and  fewer  in  number  than  in  other  species.  The 
median  ethmoid  tooth  is  long  and  projects  into 


548 


RAJU:  THE  GENUS  MONOGNATHUS 


Figure  1.— A-C,  metamorphic  stages  ofMonognathus  sp.:  A,  42  mm  TL;  B,  48  mm  TL  and  G,  its  head;  C,  42.2  mm  TL  and  H,  its  head.  D. 
M.  isaacsi  and  I,  its  head;  E,  M.  ahlstromi;  F,  M.jesse.  Am,  adductor  mandibulae;  Dp,  depressor;  Et,  ethmoid  tooth;  Eg,  ethmoid  gland; 
Ey,  eye;  Gl,  gills;  Go,  gill  opening;  Gn,  gonad;  In,  intestine;  Lr,  liver;  Of,  olfactory  organ;  Pf,  pectoral  fin;  Sp,  suspensorium;  St,  stomach. 


549 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Figure  2. — A-E,  Monognathus  ahlstromi:  A,  head;  B,  lower  jaw;  C,  midbody;  D,  vertebrae  and  myotomes;  E,  tail.  F-N,  M.jesse:  F, 
ethmoid  tooth;  G,  head,  H,  lower  jaw;  I,  midbody;  J,  vertebrae  of  myotomes;  K,  gill  arch;  L,  ethmoid  gland  and  tooth;  M,  tail;  N,  dorsal 
view  of  urostyle.  O,  caudal  fin  of  M.  isaacsi.  P,  gut  and  Q,  tail  of  metamorphic^Mryp/iarynjc.  R,  portion  of  the  ovary  of  and  S,  ovary  of  adult 
Eurypharynx.  Am,  adductor  mandibulae;  Ca,  caudal  organ;  Dp,  depressor;  Et,  ethmoid  tooth;  Eg,  ethmoid  gland;  Ey,  eye;  Gl,  gills;  Go, 
gill  opening;  In,  intestine,  Lr,  liver;  Oe,  esophagus;  Of,  olfactory  organ;  Pf,  pectoral  fin;  Sp,  suspensorium;  St,  stomach;  Ur,  urostyle. 


550 


RAJU:  THE  GENUS  MONOGNATHUS 

Table  1. — Morphometric  and  meristic  characters  of  the  species  of  the  genusMonognathus . 


Item 

taningi 

bruuni 

jesperseni 

ahlstromi 

jesse 

isaacsi 

Total  length  (mm) 

56 

80 

109 

48.5 

63 

56 

Percentage  of 

total  length: 

Depth 

3.9 

5.9 

4.6 

9 

8 

9.6 

Predorsal  distance 

7.7 

'   35 

13.8 

13.2 

11.9 

19.5 

Preanal  distance 

25 

38.7 

35.8 

27.6 

25.4 

34.0 

Head 

8 

10 

9.1 

10.7 

9 

13.3 

Cranium 

5 

3.9 

3.2 

4.3 

4.9 

7.9 

Percentage  of 

head  length: 

Snout 

— 

— 

— 

19 

21.4 

41.3 

Eye 

— 

— 

— 

5.5 

8.9 

5.2 

Suspensorium 

70 

56.2 

65 

63 

57 

— 

Mandible 

122 

75 

85 

83 

89 

84 

Number  of  vertebrae 

or  myotomes 

95(23) 

88(26) 

94(25) 

113(31) 

104(26) 

115(24) 

Dorsal  fin  rays 

120 

74 

97 

90 

80 

80 

Anal  fin  rays 

60 

42 

97 

60 

54 

52 

Teeth  in  mandible 

8 

12 

8 

9 

16 

4 

Predorsal  myotomes 

3 

12 

11 

13 

11 

— 

Preanal  myotomes 

24 

30 

29 

32 

27 

— 

'The  predorsal  distance  given  by  Bertin  is  obviously  wrong  as  the  dorsal  originates  on  myotome  12. 


the  mouth,  but  it  does  not  do  so  in  other  species. 
There  is  a  small  pectoral  fin.  The  vertebrae  are 
weakly  ossified,  not  distinct  in  radiographs,  but 
about  75  myotomes  could  be  counted,  and  about 
30-35  more  are  estimated  on  the  basis  of  the  size 
of  the  myotomes.  Differences  of  this  magnitude 
could  well  indicate  generic  separation,  but  I  hesi- 
tate to  introduce  new  genera  in  this  poorly 
known  group. 

MONOGNATHUS  AHLSTROMI  SP.  N. 

Figures  IE;  2A-E 

Holotype:  SIO  63-405,  eastern  North  Pacific, 
34'=57.0'N,  129^19.0'W,  0-2,000  m,  IKMT,  1(48.5 
mm),  29  Mar.  1962. 

Description:  Body  compressed  except  at  head, 
very  delicate,  covered  with  loose  semitransparent 
skin.  Preanal  region  3.6  in  total  length,  very  deep 
due  to  voluminous  stomach.  Tail  (postanal  region) 
very  narrow,  1.3  in  total  length,  tapering 
gradually  to  a  point.  Maximum  depth  before  anus, 
11.0  in  total  length  (may  vary  according  to  quan- 
tity of  contents  of  stomach).  Head  deep,  large, 
9.0  in  total  length;  cranium  very  small  and  weak. 
Snout  small,  5.4  in  head,  membranous.  Olfactory 
organ  reduced,  a  small  curved  tube  open  at  both 
ends.  Eye  rudimentary,  oval,  vertical  length 
18.0  in  head,  lens  round,  extremely  small.  Gape 
of  mouth  reaching  far  beyond  eye.  Region  of  upper 
jaw  membranous,  devoid  of  teeth,  no  maxilla 


distinguishable.  Ethmoid  tooth  short,  hollow,  tip 
sharp  and  bifid,  and  does  not  project  into 
mouth  as  in  M.  isaacsi;  it  appears  as  though  it  is 
lodged  in  a  sheath  and  comes  out  of  the  sheath 
through  an  opening  on  the  membranous  palate 
only  when  pressed.  Ethmoid  glands  paired,  oval 
(0.8  mm  X  0.4  mm)  on  either  side  of  tooth.  Lower 
jaw  long,  9.7  in  total  length,  tip  armed  with  three 
sharp  closely  packed  teeth  followed  by  series  of  six 
pointed,  equally  spaced,  triangular  teeth.  Oper- 
cular bones  and  branchiostegals  absent.  Gills 
four,  covered  by  delicate  transparent  membrane. 
Gill  filaments  short,  foliaceous.  Gill  openings 
ventrolateral,  moderate  in  size.  Pectoral  fin 
absent.  Myotomes  28  +  85  =  113,  W-shaped. 
Esophagus  short,  followed  by  thickened  girdle- 
like region.  Stomach  large,  bulging  with  opening 
just  posterior  to  anus.  This  opening  of  the  stomach 
appears  to  be  a  structural  feature  and  not  a 
wound  associated  with  capture.  Intestine  a 
narrow  straight  tube  on  right  side  of  body, 
opening  to  exterior  on  right  side.  Liver  small  and 
lobular.  Dorsal  fin  originating  on  myotome  14, 
moderately  high,  90  unsegmented  rays.  Caudal 
fin  represented  by  an  enlarged,  paddlelike  struc- 
ture without  fin  rays.  Vertebral  centra  short. 

Pigmentation:  No  trace  of  any  larval  mid- 
lateral  pigmentation.  A  few  dendritic  melano- 
phores  on  snout  and  lower  jaw.  Dendritic  mel- 
anophores  around  esophageal  and  liver  region 
inside  body  and  on  body  wall  in  stomach  and  anal 


551 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


regions.  Dendritic,  deep  pigmentation  at  base  of 
dorsal  fin  on  myotomes  14-20  and  50-57,  and  on 
anal  fin  on  myotomes  32-51. 

Remarks:  This  species  differs  from  all  the 
three  species  ofMonognathus  described  by  Bertin 
(1938)  and  from  M.  jesse  described  in  this 
account  in  having  a  high  myotome  count  of  113. 
The  structure  of  the  caudal  fin  also  is  different. 
In  M.  bruuni  and  M.  jesperseni  the  urostyle  is 
produced  into  a  needlelike  structure  forming  a 
false  caudal  fin  along  with  the  dorsal  and  anal 
fin  rays.  In  M.  taningi  the  urostyle  is  produced 
into  a  very  long,  whiplike  structure.  The  urostyle 
in  this  species  is  spinelike,  surrounded  by  a  large 
paddle-shaped,  compressed  structure.  The  eth- 
moid tooth  is  small  and  does  not  project  into  the 
mouth.  If  Bertin's  ( 1938)  observations  are  correct, 
this  species  differs  from  the  above  three  species 
also  in  having  four  gills  as  only  one  gill  was 
figured  in  his  drawings.  There  is  a  series  of  three 
closely  packed  teeth  at  the  tip  of  the  lower  jaw, 
and  such  a  series  is  not  seen  in  the  forms  described 
by  Bertin. 


curved,  tip  armed  by  5  closely  packed  large  teeth 
followed  by  11  teeth  of  characteristic  shape.  No 
opercular  bones  or  branchiostegals  recognizable. 
Gills  four,  small,  but  proportionally  larger  than 
those  of  M.  ahlstromi.  First  gill  slit  smallest, 
second  and  third  largest,  last  gill  slit  slightly 
larger  than  first.  Gill  filaments  short  and  folia- 
ceous,  alternately  on  either  side.  First  three  gills 
holobranchs,  fourth  a  hemibranch.  All  gills 
covered  by  membranous  operculum.  Gill  opening 
vertical,  moderate  in  size,  in  front  of  pectoral 
fin.  Myotomes  W-shaped,  26  -h  78  =  104. 
Vertebrae  heavy,  shorter  in  length  in  trunk 
region,  slender  and  elongate  in  tail  region. 
Esophagus  short  with  opaque  girdlelike  region. 
Stomach  voluminous,  recurved  at  end.  Intestine 
a  straight  tube,  shorter  than  stomach,  situated  on 
right  side  of  stomach.  Liver  lobular.  Pancreas  and 
heart  lost  due  to  damage.  Dorsal  fin  originates 
on  myotome  11,  relatively  high,  with  80  unseg- 
mented  rays.  Anal  fin  originates  on  myotome  30, 
with  54  unsegmented  rays.  Urostyle  depressed, 
lanceolate,  with  middorsal  ridge.  Pectoral  fin 
small,  triangular,  rays  indistinct. 


MONOGNATHUS  JESSE  SP.  N. 

Figures  IF;  2F-N 

Holotype:  SIO  60-245,  central  North  Pacific, 
12^07. l'N-12^23.8'N,  148^35. l'W-148=18.0'W, 
0-2,100  m,  IKMT,  1(63  mm),  9-10  July  1960. 


Description:  Body  compressed  except  at  head. 
Preanal  region  deep  due  to  voluminous  stomach, 
preanal  region  3.9  in  total  length.  Postanal  region 
3.6  in  total  length,  tapering  to  point.  Body  covered 
with  loose  semitransparent  skin.  Maximum  depth 
at  middle  of  preanal  region,  12.6  in  total  length. 
Head  deep,  large,  8.7  in  total  length.  Snout  blunt, 
membranous,  small,  4.7  in  head.  Olfactory  organ  a 
slightly  curved  short  tube,  open  at  both  ends. 
Eye  rudimentary,  11.2  in  head,  oval,  lens 
extremely  small.  Gape  of  mouth  reaching  beyond 
eye.  Upper  jaw  degenerate,  membranous,  unsuit- 
able to  serve  as  jaw,  no  maxilla  recognizable,  no 
teeth.  Median  ethmoid  tooth  large,  pointed,  tip 
calcified  and  bifid,  surrounded  and  hidden  by  soft 
tissue.  Ethmoid  glands  paired  oval  bodies,  one 
on  either  side  of  tooth.  Lower  jaw  long,  slightly 


Pigmentation:  Brown  chromatophores  on 
snout,  tip  of  lower  jaw,  at  angle  of  mouth. 
Dendritic  brown  chromatophores  on  head,  pre- 
dorsal  region,  gill  membrane,  lateral  side  of  body 
as  far  back  as  anal  region.  Three  deeply  seated 
melanophore  patches  (seen  only  if  cleared  in 
glycerine)  at  base  of  dorsal  fin  inside  myotomes, 
one  long  patch  on  myotomes  5-22,  second  on  myo- 
tomes 40-43,  and  third  on  myotomes  58-62.  Anal 
fin  has  similar  large  patch  on  myotomes  30-39. 


Remarks:  This  species  differs  basically  from 
the  three  species  described  by  Bertin  (1938)  and 
from  M.  ahlstromi  in  the  presence  of  a  small 
pectoral  fin,  structure  of  the  urostyle,  myotome 
number,  dentition  of  the  lower  jaw,  relatively 
longer  tail,  and  fin  ray  counts.  Bertin  (1938) 
gave  no  account  of  the  pigmentation  of  his  speci- 
mens, hence  it  is  not  possible  to  compare  pig- 
mentation. The  pigmentation  in  this  specimen 
differs  from  that  of  M.  ahlstromi  in  the  follow- 
ing respects.  There  is  additional  pigmentation 
on  the  head,  angle  of  the  lower  jaw,  and  gill  mem- 
brane, more  profuse  pigmentation  on  the  lateral 
side  of  the  body  and  predorsal  region,  and  three 
patches  at  the  base  of  the  dorsal  fin. 


552 


RAJU:  THE  GENUS  MONOGNATHUS 


METAMORPHIC  FORMS  OF 
MONOGNATHUS  SP. 

Figure  lA,  B,  C,  G,  H 

SIO  60-241,  central  North  Pacific,  7"25.5'N- 
7^55.0'N,  144^29.0'W-144=35.0'W,  depth  of  cap- 
ture 0-2,100  m,  IKMT,  1(42.2  mm),  7  July  1960. 
SIO  60-276,  central  North  Pacific,  24=28. 9'N- 
24=36.9'N,  147=55. 5'W-147=27.0'W,  0-3,000  m, 
IKMT,  1(48  mm),  7-8  Aug.  1960.  SIO  60-275, 
central  North  Pacific,  23=23. 4'N-23=40.0'N, 
15r04.0'W-150=38.8'W,  0-3,000  m,  IKMT,  1(58 
mm),  6  Aug.  1960.  SIO  60-283,  eastern  North 
Pacific,  28=13. 0'N-28=19.1'N,  135=21. 8'W- 
134=54.1'W,  0-3,000  m,  IKMT,  1(50  mm),  12  Aug. 
1960. 

Description  (Figure  IB,  G):  Total  length  48 
mm,  body  elongate,  compressed,  and  transparent. 
Depth  12.0  in  total  length,  maximum  depth  at 
middle  of  body.  Head  long.  Cranium  weak, 
triangular,  10.7  in  total  length.  Snout  slightly 
blunt.  Olfactory  organ  rudimentary,  a  small 
curved  tube  open  at  both  ends.  Eyes  lost  due  to 
damage.  Upper  jaw  membranous,  without  teeth. 
Ethmoid  tooth  long,  projecting  into  mouth.  Eth- 
moid gland  paired,  well  developed.  Lower  jaw  8.6 
in  total  length.  Suspensorium  24.0  in  total  length. 
Adductor  mandibulae  well  developed.  Gills,  liver, 
and  part  of  gut  damaged  and  lost.  Posterior 
region  of  gut  projects  out  of  body  outline.  Opis- 
thonephros  a  coiled  tube  extending  behind  vent 
(not  shown  in  figure).  Ovaries  tubular,  elongate, 
with  few  ova  (250-300).  Dorsal  originates  on  myo- , 
tome  32  and  anal  on  myotome  30.  Myotomes  W- 
shaped,  30  +83  =  113.  Midlateral  brown, 
chromatophore  patches  conspicuous,  one  on  left 
and  four  on  right  side.  Brown  chromatophores  on 
tip  of  upper  and  lower  jaws,  at  base  of  dorsal  fin 
rays  on  myotomes  50-60,  and  anal  fin  rays  on 
myotomes  31-49.  Juvenile  pigmentation  appears 
on  body  as  minute,  uniformly  scattered  brown 
chromatophores  (not  shown  in  figure). 

Changes  during  metamorphosis:  Most  of  the 
morphological  changes  undergone  are  similar  to 
those  observed  in  the  metamorphosis  of  the  eels. 
In  the  smallest  specimen  (42  mm.  Figure  lA) 
the  body  is  deeper,  and  the  lower  jaw  and 
suspensorium  are  relatively  shorter.  A  median 
ethmoid  tooth  is  not  yet  formed.  In  later  stages 


(48  mm,  50  mm,  42.2  mm;  A,  B,  C  of  Figure 
1,  respectively)  there  is  a  slight  decrease  in  the 
length  and  depth  of  the  body,  and  increase  in  the 
length  of  the  head,  snout,  lower  jaw,  and 
suspensorium.  A  median  ethmoid  tooth  is  formed 
with  its  associated  gland.  Larval  midlateral  pig- 
mentation begins  to  fade  with  the  gradual 
development  of  juvenile  pigmentation.  The  dorsal 
and  anal  fins  move  slightly  forward.  Two  speci- 
mens have  developed  a  pair  of  tubular  ovaries 
containing  about  250-300  spherical  ova  0.06  mm 
in  diameter  (not  shown  in  figure).  An  interesting 
aspect  of  the  metamorphosis  of  monognathids  is 
the  degenerative  changes  that  take  place  in  the 
head,  olfactory  organ,  and  eye.  The  bones  of  the 
head  become  very  weak  and  membranous.  The 
eye  and  the  olfactory  organs  are  reduced  to  minute 
structures.  A  median  ethmoid  tooth  with  a  pair 
of  glands  develops.  The  wide  W-shaped  myotomes 
become  narrower  with  the  decrease  in  the  depth 
of  the  body,  and  in  the  larval  condition  they  may 
approach  a  V-shape  as  in  Cyema  and  L.  latis- 
simus  and  L.  pseudolatissimus. 

Remarks:  The  four  metamorphic  stages  de- 
scribed above  are  assigned  to  Monognathus 
sp.  on  the  basis  of  the  characteristic  median 
ethmoid  tooth  and  the  absence  of  an  upper  jaw. 
These  stages  share  some  features  with  M.  isaasci 
such  as  general  shape  of  the  body,  large  head, 
projecting  ethmoid  tooth,  myotome  number,  and 
structure  of  the  tail.  ButM.  isaacsi  has  a  pectoral 
fin  which  is  not  seen  in  the  metamorphic  forms. 
Assignment  to  the  species  is  not  possible  at  this 
time. 

The  leptocephali  of  monognathids  are  not 
identified  as  yet.  But  the  features  of  metamorphic 
forms  (Table  2)  indicate  that  they  are  small 
(40-60  mm),  elongate  larvae  with  a  series  of  five 
splanchnic,  unequally  placed,  midlateral  melano- 
phores  with  pigmentation  on  the  gut,  and  with 
about  100-120  wide  V-shaped  myotomes. 


GENERAL  REMARKS 

Upper  jaw:  The  name  Monognathidae  was 
given  to  these  fishes  by  Bertin  (1937a),  who 
assumed  that  only  one  jaw  (lower  jaw)  was  pres- 
ent. But  Tchernavin  (1947b)  pointed  out  that 
there  is  no  evidence  that  a  palatopterygoid 
cartilage  is  absent  in  the  Monognathidae.  As  all 


553 


FISHER1    BLLLETIN:  VOL.  72.  NO.  2 
Table  2. — Number  and  position  of  midlateral  melanophores  in  five  metamorphic  monognathids  and  Pacific  leptocephalus. 


Metamorphic  monogna- 
thids and 

Pacific  leptocephalus 


42-mm  specimen 


48-mm  specimen 


58-mm  specimen 


50-mm  specimen 


42.2-mm  specimen 


Pacific  leptocephalus 


Total  number 
myotomes 


31  ^80=  111 


30  +  83=113 


30  +  75  -  1 1 5 


31  -.-82  =  113 


24  +81  =  105 


56  +  46  =  102 


Left  side 
melanophores 


Right  side 
melanophores 


Total  number 

melanophores 

(pre  +  postanal) 


2  +  3  =  5 


1+4  =  5 


1+4  =  5 


2  +  3  =  5 


2  +  3  =  5 


4  +-  1  =  5 


Distribution  of  chromatophores 

on  myotomes 

R  =  Right.  L  =  Left 


(15-16)R,  (29-30)L.  (44-45)R, 
(59-60)R.  (67-68)L 

(15-16)R.  (32-33)R,  (45-46)L, 
(57-58)R.  (67-68)R 

(12-13)L,  (31-32)R,  (46-48)R, 
(56-58)R.  (70-71)L 

(15-16)L,  (28-29)L.  (44-45)R. 
(55-56)R, (67-68)L 

(9-10)R,  (27-28)L,  (43-44)L, 
(55-56)L,  {67-68)L 

(13-14)L,  (25-26)L,  (40-41)L, 
(50-51)L,  (59-60)R 


other  known  leptocephali  possess  a  maxilla  with 
larval  teeth  until  metamorphosis,  monognathid 
leptocephali  also  possibly  have  a  maxilla  bearing 
larval  teeth.  Leptocephali  of  eels  characteris- 
tically lose  their  larval  teeth  during  metamorpho- 
sis, and  the  adult  teeth  develop  after  meta- 
morphosis. Hence  it  is  possible  that  monognathid 
leptocephali  might  have  possessed  the  maxilla 
with  its  larval  teeth  which  might  have  been  lost 
during  metamorphosis.  Due  to  the  extreme 
degenerative  changes  and  deossification  of  the 
skull  the  maxilla  might  have  lost  its  identity 
and  the  adult  set  of  teeth  failed  to  develop. 

Median  ethmoid  tooth:  The  median  ethmoid 
tooth  is  a  structure  unique  to  the  Monognathidae, 
and  its  function  is  not  known.  It  develops  during 
metamorphosis  and  persists  in  the  adult.  It  is 
larger  in  M.  isaacsi  than  in  other  species.  It  is 
hollow  and  slightly  curved  with  a  minute  opening 
at  its  sharp  tip.  There  is  a  pair  of  glandular 
masses,  one  on  each  side  of  the  tooth.  The  ethmoid 
tooth  with  its  gland  closely  resembles  the  fangs 
of  a  poisonous  snake  and  probably  serves  a 
similar  function. 

Gills:  Only  one  gill  arch  is  present  in  the 
monognathids  according  to  Bertin  (1937a).  But  a 
close  examination  of  M.  ahlstromi  and  M.  Jesse 
showed  four  distinct  gill  arches  bearing  short 
foliaceous  gill  filaments  arranged  alternately  as 
in  Eurypharynx.  The  gills  and  gill  openings  are 
very  small  as  are  those  of  Eurypharynx  and 
Saccopharynx. 


Pectoral  fin:  The  pectoral  fin  is  absent  in 
the  three  species  described  by  Bertin  (1937a) 
and  in  M.  ahlstromi.  There  is  a  small  fleshy 
pectoral  fin  in  M.  isaacsi  and  M.  Jesse. 

Caudal  organ:  A  caudal  organ,  whose  func- 
tion is  much  disputed,  is  present  at  the  tip  of  the 
tail  in  Eurypharynx  and  Saccopharynx.  Although 
a  typical  caudal  organ  is  not  present  in  any  of 
the  known  species  of  the  monognathids,  the 
caudal  fin  is  modified  either  into  a  filamentous 
structure  as  in  M.  taningi,  or  into  a  flattened 
structure  as  in  M.  ahlstromi  and  M.  Jesse,  or 
is  relatively  unmodified  as  in  M.  isaacsi. 

Food:  Fish  eggs  with  a  sculptured  egg 
membrane,  fish  larvae,  and  copepods  were  found 
in  the  mouth  and  pharynx  of  the  metamorphic 
forms,  but  they  might  have  been  taken  accident- 
ally while  in  the  net. 

Distribution  (Figure  3):  This  family  has 
previously  been  known  only  from  the  Atlantic  off 
the  coast  of  North  Africa  and  from  the  western 
Pacific  (Bertin,  1938).  This  study  shows  that  it  is 
widely  distributed  in  the  whole  tropical  and  sub- 
tropical belt  of  the  Pacific,  and  it  is  likely  that 
the  family  may  also  be  found  in  the  tropical 
Indian  Ocean. 

RELATIONSHIPS 

Bertin  (1937a,  1938)  erected  the  family  Mono- 
gnathidae based  on  his  study  of  four  juveniles. 


554 


RAJU:  THE  GENUS  MONOGNATHUS 

W   U  laningi,  O  M  jisp»r$»ni,     ^Ht  bruuni. 


▲  iW 


ttaocsi , 


I  H  ohistromi,      D  M  j§ss» 


FIGURE  3.— Distribution  of  the  six 
species  of  the  genus  Monognathus. 


One  of  the  four  specimens  had  been  earlier 
described  by  Roule  (1934)  as  a  semilarva  of  the 
Lyomeri.  According  to  Bertin  the  family  Monog- 
nathidae  consists  of  a  single  genus,  Monognathus , 
with  three  species,  none  of  which  was  designated 
as  the  genotype.  Myers  (1940)  recognized  two 
genera,  Monognathus  (genotype  M.  taningi 
Bertin)  and P has matostoma  (new  genus;  genotype 
M.jesperseni  Bertin),  on  the  basis  of  the  number 
of  ethmoid  teeth,  position  of  the  dorsal  fin  origin, 
and  nature  of  the  vertebrae  and  caudal  fin. 
Bbhlke  (1966)  accepted  Phasmatostoma  as  a 
separate  genus  of  the  Monognathidae.  As  already 
pointed  out,  M.  isaacsi  may  well  represent  a  third 
genus  of  the  family  Monognathidae  as  the  dif- 
ferences between  M.  isaacsi  and  M.  taningi  are 
even  more  pronounced  than  those  between  M. 
taningi  and  M.  jesperseni  or  M.  bruuni,  which 
are  separated  as  Phasmatostoma.  M.  ahlstromi 
and  M.  jesse  may  also  turn  out  to  be  new  genera 
as  the  caudal  fin,  which  is  a  conservative  struc- 
ture in  fishes,  varies  greatly  in  the  two  fishes. 
However,  I  would  restrain  myself  to  introduce 
new  genera  till  a  detailed  study  of  many  adult 
and  larval  specimens  is  undertaken,  as  the  stud- 
ies on  these  fishes  are  based  only  on  very  few 
specimens  (1-2  in  number),  and  even  these  are 
only  juvenile  and  metamorphic  forms. 

Tchernavin  (1947a)  stated  that  there  is  no  evi- 
dence that  the  Monognathidae  are  related  to  the 
Saccopharyngiformes.  His  arguments  were  based 


on  some  of  the  observations  of  Bertin  such  as  the 
absence  of  pectoral  fin,  presence  of  only  one  gill 
arch,  and  other  osteological  characters.  Green- 
wood et  al.  (1966)  and  Bohlke  (1966)  considered 
monognathids  to  be  related  to  the  Saccopharyngi- 
formes. The  general  features  of  M.  isaacsi — such 
as  the  elongated  suspensorium,  presence  of  small 
gill  openings  and  four  small  gill  arches,  alter- 
nating arrangement  of  gill  filaments  on  the  arch 
as  in  Eurypharynx,  voluminous  stomach,  oc- 
currence of  leptocephalus  stage  in  the  life  his- 
tory, the  presence  of  the  pectoral  fin,  and  the 
modified  caudal  fin — indicate  that  the  Monogna- 
thidae are  related  to  the  Saccopharyngiformes, 
more  closely  to  the  Saccopharyngidae  than  to  the 
Eurypharyngidae. 

LEPTOCEPHALUS  LATISSIMUS 
SCHMIDT  1912 

Figure  4C 

Leptocephalus  latus  Schmidt  1909.  SIO  66-353, 
San  Diego  Trough,  32^40'N,  117=35'W,  480- 
366  mwo,  Tucker  net,  1(30  mm),  23  Aug.  1950. 
LACM,  6525-16,  Santa  Catalina  Basin, 
33n8'27"N-33"24'40"N,  118M4'00"W-118°51' 
35"W,  0-213  mwo,  IKMT,  1(39  mm),  22  Aug. 
1963.  LACM,  9830-10,  No  Name  Basin,  32" 
01'30"N-32"04'00"N,  117"59'00"W-117=56'00" 
W,  600  mwo,  IKMT,  1(40  mm),  28  July  1967. 


555 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 


556 


RAJU:  THE  GENUS  MONOGNATHUS 

Description:  Specimen  described  (SIO  66-353): 
Body  deep,  compressed  except  at  head,  total 
length  30  mm.  Maximum  depth  in  middle  of 
body,  3.8  in  total  length.  Posterior  end  of  body 
attenuate,  caudal  organ  not  yet  developed.  Head 
short,  7.5  in  total  length.  Skull  membranous  and 
transparent.  Snout  short,  4.0  in  head.  Olfactory 
organ  rudimentary.  Eyes  round,  dark  brown,  5.7 
in  head.  Upper  jaw  soft,  maxilla  indistinct.  Lower 
jaw  partly  damaged.  Teeth  six  in  upper  jaw,  five 
in  lower  jav/.  Gill  opening  small,  four  gill  arches. 
Pectoral  fin  small,  thick.  Esophagus  a  narrow 
tube,  reaching  middle  of  body.  Stomach  rudi- 
mentary. Intestine  short,  swollen,  looped.  Liver 
a  small  ventral  lobe.  Pancreas  rectangular, 
dorsal  to  gut.  Opisthonephros  a  short  tube. 
Myotomes  45  +  125  =  170. 

Pigmentation:  Minute  dark  brown  chromato- 
phores  on  swollen  part  of  intestine. 

LEPTOCEPHALUS  PSEUDOLATIS- 
SIMUS  BERTIN  1934 

Figure  4D 

Leptocephalus  gastrostomi  bairdii  Lea  1912. 
Leptocephalus  pseudolatissimus  Bertin  1934. 
Material  examined:  SIO  56-127,  Marshall  Islands 
vicinity,  western  Pacific,  1(32  mm). 

Description:  Body  deep,  compressed  except  at 
head,  posterior  end  tapering.  Maximum  depth  in 
the  middle  of  body,  4.0  in  total  length.  Head 
large,  very  deep,  7.6  in  total  length.  Skull  bones 
transparent  and  membranous.  Teeth  in  both  jaws 
lost  due  to  damage.  Gill  opening  small,  gill 
arches  five  in  number.  Pectoral  rudimentary. 
Esophagus  a  narrow  tube.  Stomach  small.  Liver 
a  small  ventral  lobe.  Pancreas  rectangular.  Opis- 
thonephros a  short  tube.  Myotomes  38  +  65  =  103. 

Pigmentation:  Dense  brown  pigmentation  in 
the  form  of  small  patches  on  the  swollen  part 
of  the  intestine. 


Figure  4. — A,  leptocephalus  of  Cyema  atrum;  B,  unknown 
Pacific  leptocephalus;  Bl,  head  of  unknown  Pacific  leptoce- 
phalus; C,  Leptocephalus  latissimus;  D,  Leptocephalus  pseudo- 
latissimus; E,  leptocephalus  of  Nemichthys  scolopaceus.  Gb, 
gall  bladder;  Gl,  gills;  Go,  gill  opening;  In,  intestine;  Lr, 
liver;  Op,  opisthonephros;  Pf,  pectoral  fin;  Sp,  suspensorium; 
'  St,  stomach;  Th,  thyroid  gland?;  Pn,  pancreas. 


Remarks:  Leptocephalus  latissimus  and  L. 
pseudolatissimus  resemble  each  other  in  many 
characters  except  for  the  differences  in  myotomal 
count,  number  of  gill  arches,  length  and  number  of 
intestinal  loops,  and  pigmentation.  L.  latissimus 
has  a  higher  myotomal  count  ranging  from  170  to 
250  and  four  gill  arches  whereas  L.  pseudolatis- 
simus has  103-125  myotomes,  five  gill  arches,  a 
short  intestinal  loop,  and  more  pigmentation  on 
the  loop. 

Murray  and  Hjort  (1912)  discovered  the  lep- 
tocephalus stage  in  the  life  history  of  Sacco- 
pharyngiformes.  The  larva  was  later  described 
by  Lea  (1913),  who  named  it  Leptocephalus  gas- 
trostomi bairdii  (Gastrostomus  bairdii  =  Eury- 
pharynx  pelecanoides)  and  suggested  that  L. 
latissimus  Schmidt  (1909,  1912)  was  a  larva  of 
another  saccopharyngiform.  Bertin  (1938)  de- 
scribed a  series  of  four  saccopharyngiforms  and 
assigned  both  L.  latissimus  and  L.  pseudolatis- 
simus to  Saccopharynx  on  the  basis  of  the  nature 
of  suspensorium  and  myotomal  counts.  The  lowest 
myotomal  count  in  his  larvae  was  115,  and  since 
the  highest  vertebral  count  of  Eurypharynx 
known  to  him  at  that  time  was  110,  he  assigned 
the  larvae  to  Saccopharynx  as  the  number 
exceeded  the  highest  vertebral  count  of  Eury- 
pharynx. It  is  now  known  that  the  vertebral 
count  of  £.  pelecanoides  ranges  from  103  to  125 
(Orton,  1963).  Tchernavin  (1947a)  disputed 
Bertin's  allocation  of  larvae  of  Saccopharynx  on 
the  basis  of  myotomal  count  and  suggested  that 
the  low  count  forms  might  belong  to  Eurypharynx 
and  the  high  count  forms  to  Saccopharynx.  Orton 
(1963)  and  Bohlke  (1966)  also  suggested  the 
identity  ofL.  pseudolatissimus  with  Eurypharynx 
on  the  basis  of  vertebral  counts  (97-125). 

METAMORPHIC  FORM  OF 
SACCOPHARYNX 

(Not  illustrated) 

LACM  9579-36,  30^00'00"N-29^30'21"N, 
118°40'59"W-118°29'18"W,  2,910  mwo,  IKMT, 
1(80  mm),  30  Aug.  1966. 

Description:  Body  elongate,  posterior  region 
whiplike.  Head  large,  depressed,  14.3  in  total 
length.  Snout  small,  4.7  in  head.  Olfactory  organ 
small,  two  nostrils  placed  closely  one  above  the 
other  in  front  of  eye.  Eye  small,  7.0  in  head. 


557 


Jaws  unusually  long,  with  minute  recurved  teeth 
on  both  jaws.  Gills  plumose.  Esophagus  short, 
thin,  no  girdlelike  region.  Stomach  well  de- 
veloped, empty,  white.  Intestine  long,  thick 
walled,  empty,  posterior  end  with  series  of  12 
melanophores  on  dorsal  side  till  vent.  Posterior 
end  of  intestine  of  metamorphic  Eurypharynx  also 
has  similar  series  of  five  melanophores  on  dorsal 
side.  Liver  elongate,  pale  yellow.  Gall  bladder 
oval,  thin,  transparent.  About  40  preanal  and 
110  postanal  myotomes  can  be  counted.  Myotomes 
in  whiplike  portion  of  tail  are  not  distinct.  Tip 
of  tail  (caudal  organ)  enlarged  into  bulblike  struc- 
ture. Median  fin  delicate,  low.  Pectoral  fins 
large,  fleshy. 

Pigmentation:  Microscopic  brown  dotlike  ju- 
venile pigmentation  scattered  sparsely  all  over 
body,  but  dense  on  snout  and  jaws.  Larval  pig- 
mentation before  vent  as  a  row  of  linear  patches. 
Tip  of  tail  unpigmented. 


METAMORPHIC  FORM  OF 
EURYPHARYNX  PELECANOIDES 

Figure  2P,  Q 

SIO  68-451,  central  North  Pacific,  Hess  Sea- 
mount,  17°59.0'N,  174°24.1"W,  0-1,250  m,  IKMT, 
1(39  mm),  31  Aug.-l  Sept.  1968. 

Description:  Body  elongate,  compressed  ex- 
cept at  head.  Depth  8.0  in  total  length,  maximum 
depth  near  middle  of  body,  posterior  half  tapering 
gradually  to  whiplike  tail  with  rudimentary 
caudal  organ  (Figure  2Q).  Head  small,  broad, 
depressed,  badly  damaged.  Snout  very  short, 
blunt.  Eyes  large,  round,  black.  Olfactory  organ 
rudimentary.  Upper  jaw  cartilaginous,  maxilla 
toothless,  its  boundary  not  clear.  Lower  jaw  lost 
due  to  damage.  Gills  extremely  small,  five  holo- 
branchs,  six  gill  slits,  white  in  color,  gills  of  both 
sides  placed  very  close  together,  gill  filaments 
very  small,  gill  arches  very  soft,  and  do  not  appear 
to  have  any  bony  or  cartilaginous  elements. 
Esophagus  short,  slightly  bulged,  brown,  followed 
by  rudimentary  stomach  (Figure  2P).  Stomach 
bulged,  muscular,  with  brown  pigment.  Liver  lost 
due  to  damage.  Intestine  short,  continued  as 
rectum  with  five  black  dendritic  chromatophores 
on  dorsal  side.  Opisthonephros  lost  due  to  damage. 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 

Myotomes  about  105.  Dorsal  and  anal  fins 
damaged. 

Pigmentation:  Body  covered  uniformly  with 
dark  brown  juvenile  pigmentation.  Tip  of  tail 
white  except  for  black  caudal  organ. 

Ovary  of  adult  (Figure  2R,S):  Examination  of 
the  ovary  of  one  large  specimen  of  E.  pelecanoides 
(600  mm,  vertebrae  31  +  87  =  118)  in  the 
Scripps  Institution  of  Oceanography  (group  25, 
H. 52. 376)  gives  the  following  information.  Ovary 
large,  oval,  paired,  brown  in  isopropyl  alochol, 
two  ovaries  of  same  size,  62.2  mm  in  length, 
29  mm  in  breadth,  oval  in  shape,  maximum  thick- 
ness in  center  10  mm,  weight  of  two  ovaries 
18.4  g,  about  33,000  ova  in  both  ovaries,  eggs 
arranged  in  single  layer  which  is  folded  into 
laminae  of  double  layers.  Thus,  each  ovary  is  a 
long  sheet  of  ova.  Ova  embedded  in  sheet  of 
jellylike  mass  divided  into  hexagonal  meshes, 
each  mesh  enclosing  single  ovum.  Ova  well 
developed,  round,  average  diameter  0.9  mm, 
yellow,  containing  4  or  5  yellow  oil  globules  of 
varying  sizes,  diameter  of  largest  oil  globule 
0.15  mm. 

Remarks:  The  two  metamorphic  forms  L. 
latissimus  and  L.  pseudolatissimus  were  badly 
damaged  and  distorted,  making  it  very  difficult 
for  illustration.  But  characters  such  as  pigmenta- 
tion and  the  caudal  organ  provided  some  informa- 
tion on  their  identity  to  the  adults. 

The  metamorphic  specimen  of  L.  pseudolatissi- 
mus has  juvenile  pigmentation,  and  the  caudal 
organ  is  well  developed  and  is  more  advanced 
than  the  larvae  described  before.  The  myotomal 
count,  the  number  of  gill  arches,  the  position 
and  structure  of  the  caudal  organ,  the  juvenile 
pigmentation,  and  other  characters  clearly  estab- 
lish the  identity  of  L.  pseudolatissimus  as  the 
larva  of  the  deepsea  gulper  Eurypharynx  pele- 
canoides. 

The  higher  myotomal  count  of  L.  latissimus 
certainly  indicates  its  identity  vjWhSaccopharynx, 
as  suggested  by  Tchernavin  ( 1947a).  Orton  ( 1963), 
in  discussing  the  relationship  of  L.  latissimus, 
pointed  out  its  possible  identity  as  the  larva  of 
Saccopharynx  but  also  warned  that  the  then 
unknown  monognathid  larva  might  be  a  possible 
candidate  forL.  latissimus.  The  characters  of  the 
metamorphic  monognathid  and  saccopharyngid 


558 


RAJU    THE  GENUS  MONOGNATHUS 


larvae  described  in  this  account  help  to  identify 
L.  latissimus  as  the  larva  of  Saccopharynx. 
Bohlke  (1966)  pointed  out  that  the  similarities 
between  saccopharyngids  and  monognathids 
might  warrant  consideration  of  monognathids  as 
postlarval  saccopharyngids.  The  characters  of  the 
metamorphic  Saccopharynx  and  M.  isaacsi  do  not 
support  his  contention.  The  ethmoid  tooth  persists 
into  the  fully  transformed  stage  in  monognathids 
(M.  isaacsi),  but  it  is  absent  in  the  metamorphic 
Saccopharynx.  A  girdlelike  region  is  present  on 
the  esophagus,  and  the  liver  is  a  short  lobe  in 
monognathids,  whereas  no  girdlelike  region  is 
present;  the  liver  is  elongate,  and  the  tail  is 
extremely  attenuate  and  whiplike  in  meta- 
morphic Saccopharynx. 

A  new  type  of  saccopharyngiform  larva  has 
been  recently  studied  (Castle  and  Raju,  unpub- 
lished data),  and  the  details  will  be  published 
elsewhere.  This  larva  (myotomes  62  +  43  =  105) 
resembles  L.  latissimus  and  L.  pseudolatissimus 
in  the  shape  of  the  body,  myotomes,  and  other 
features,  but  differs  from  them  in  having  a  large 
eye,  absence  of  long  needlelike  teeth  in  the  upper 
jaw,  and  the  structure  of  the  intestine.  At  present, 
it  is  not  possible  to  assign  the  larva  to  any  of  the 
known  families  of  the  Saccopharyngiformes. 


UNKNOWN  PACIFIC 
LEPTOCEPHALUS 

Figure  4B 

Holotype:  SIO  70-118,  24°33'S,  154°55'W- 
154^56'W,  IKMT,  1(40  mm),  4  Oct.  1969. 

Description:  Body  elongate,  compressed  ex- 
cept at  head,  tapering  toward  both  ends  of  body. 
Maximum  depth  in  middle  of  body,  3.2  in  total 
length.  Head  long,  3.6  in  total  length.  Snout  long, 
about  4.0  in  head.  Olfactory  organ  small,  an 
elongate  cup,  nostrils  not  formed.  Eye  fairly  large, 
13.7  in  head,  round,  black,  surrounded  by  a  trans- 
parent area.  Upper  jaw  elongate,  maxilla  distinct, 
dentition  1  +  11.  Lower  jaw  elongate,  slightly 
projecting  beyond  upper  jaw,  dentition  1  +  7. 
Suspensorium  long.  Gill  opening  wide.  Opercular 
elements  present,  cartilaginous.  Gills  very  small, 
four.  Branchiostegals  absent.  Myotomes  wide, 
V-shaped,  56  +  46  =  102,  muscle  fibers  very 
broad.  Dorsal  fin  origin  on  myotome  38,  fin  rays 
not  formed,  predorsal  distance  2.0  in  total  length. 


Anal  fin  rays  not  formed.  Pectoral  fin  small, 
behind  gills.  Esophagus  a  straight  tube.  Stomach 
a  rudimentary,  fingerlike  process  at  myotomes 
17-19.  Intestine  long,  muscular,  thrown  into  three 
loops  of  increasing  depth  posteriorly  opening  to 
exterior  at  myotome  56.  Liver  small.  Gall  bladder 
and  stomach  enclosed  by  liver.  Pancreas  a  small, 
thick  lobe.  Opisthonephros  tubular,  wavy,  open- 
ing behind  vent.  First  and  last  blood  vessels  to 
viscera  at  myotomes  8  and  48,  respectively. 

Pigmentation:  A  thick  black  patch  at  tip  of 
lower  jaw,  a  small  black  patch  at  tip  of  upper 
jaw  on  ventral  side.  Sparse  black  pigment 
along  midline  of  snout  and  olfactory  region,  a 
series  of  midlateral  patches,  one  each  on  myo- 
tomes 13,  25,  40,  50,  59,  the  last  patch  on  right 
side  and  the  rest  on  left,  two  stellate  melano- 
phores  on  dorsal  finfold,  and  a  series  of  five  on 
heart,  liver,  and  intestinal  loops  on  ventral  side. 

Remarks:  This  is  the  first  report  of  this  type 
of  larva  from  the  Pacific.  It  appears  that  there  is 
only  one  record  of  a  similar  larva,  L.  holti,  from 
the  North  Atlantic  off  the  coast  of  northern  Spain 
(Schmidt,  1909).  L.  holti  resembles  this  larva  in 
most  characters  such  as  the  shape  of  the  body, 
head,  and  snout,  in  dentition,  myotomes,  gut, 
liver,  and  pigmentation.  The  preanal  and  total 
myotomal  counts  (67  +  45  =  125  +  ca)  ofL.  holti 
are  higher  than  the  myotomal  counts  of  this  larva, 
which  undoubtedly  belongs  to  a  different  but 
closely  related  species. 

Schmidt  did  not  allocate  L.  holti  to  its  adult, 
but  simply  suggested  that  it  may  belong  to  some 
southern  warm-water  eel.  Although  it  is  difficult 
to  establish  the  identity  of  the  larva  conclusively 
in  the  absence  of  successive  metamorphic  and 
juvenile  stages,  certain  morphological  and  ana- 
tomical characters  of  the  larva  are  closer  to  the 
larval  features  of  Cyema,  saccopharyngids,  and 
monognathids,  and  a  comparison  of  its  characters 
is  made  with  their  larval  features. 

Comparison  with  Cyema:  This  larva  has 
striking  resemblances  to  that  of  Cyema  in  the 
following  features:  The  shape  and  the  size  of  the 
body  are  similar  although  less  deep;  the  head  is 
elongate;  the  teeth  are  similar  in  shape;  the  eye 
is  larger  and  circular;  the  myotomes  are  V-shaped; 
the  intestine  is  thrown  into  loops;  the  gill  open- 
ing and  gills  are  small.  But  the  larva  differs  from 


559 


Cyema  in  the  following  respects:  Cyema  has  five 
intestinal  loops  (four  in  early  stages)  which  are 
more  compact  and  deeper  whereas  this  larva  has 
only  three  shallow  intestinal  loops;  the  liver  in 
Cyema  is  small,  laminar,  and  situated  at  myo- 
tome 6  whereas  in  this  larva  the  liver  is  a  very 
thick  lobe  at  myotome  17;  the  pancreas  in  Cyema 
is  a  large  and  thin  film  of  tissue  extending  along 
all  the  intestinal  loops  except  the  last  and  does 
not  form  a  bulge  with  the  liver  whereas  it  is  a 
thick  lobe  forming  a  bulge  with  the  liver  in  this 
larva;  the  position  of  the  gills  in  Cyema  is  more 
anterior  than  in  this  larva;  the  body  depth  in  this 
larva  is  less  than  that  oi  Cyema;  the  pigmenta- 
tion on  the  myotomes  in  Cyema  is  scattered  all 
over  the  body  whereas  it  is  limited  to  a  series  of 
five  midlateral  melanophore  patches  in  this  larva. 
But  the  basic  characteristics  of  the  larva  are  so 
strikingly  similar  to  those  of  the  larva  of  Cyema, 
I  am  compelled  to  relate  it  to  an  unknown  species 
of  the  family  Cyemidae.  If  the  larva  is  a  cyemid 
larva,  it  will  probably  belong  to  a  new  genus 
other  than  Cyema  as  the  differences  between  the 
larva  of  Cyema  atrum  and  this  larva  appear  to  be 
at  generic  level. 

Comparison  with  saccopharyngid  and  eury- 
pharyngid  larvae:  In  all  three  kinds  of  lepto- 
cephali  the  size  and  shape  are  approximately 
similar,  the  myotomes  are  V-shaped,  the  suspen- 
sorium  is  elongated,  the  gills  are  small  and  more 
posterior  in  position,  the  liver  is  a  thick  lobe,  the 
pancreas  is  a  thick  lobe  forming  a  bulge  with  the 
liver,  the  intestine  is  looped,  and  the  opisthone- 
phros  and  the  last  blood  vessel  are  on  the  last 
intestinal  loop.  However,  this  larva  differs  from 
saccopharyngid  and  eurypharyngid  larvae  in  the 
shape  of  the  head  and  the  nature  of  the  teeth, 
in  having  more  intestinal  loops  and  a  longer 
intestine,  and  in  the  presence  of  a  midlateral 
series  of  pigmentation  spots. 

Comparison  with  metamorphic  monognathids: 
This  larva  resembles  the  metamorphic  forms  in 
myotome  shape,  the  elongate  snout,  the  total 
number  of  myotomes  and  the  midlateral  melano- 
phores  (Table  2),  the  structure  and  position  of 
the  melanophores  in  relation  to  mytome  number, 
and  the  pigmentation  at  the  tip  of  the  jaws. 
But  this  larva  has  a  well-developed  eye  whereas 
the  metamorphic  forms  have  rudimentary  eyes. 
But  degeneration  of  the  eye  may  take  place  during 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 

metamorphosis  as  in  Cyema,  which  has  a 
degenerate  eye  in  the  adult  and  a  very  large 
eye  in  the  larva.  The  gills,  liver,  and  intestine 
are  lost  due  to  damage  in  the  42-mm  and  48-mm 
metamorphic  specimens,  and  a  comparison  of 
these  structures  cannot  be  made.  A  pectoral  fin 
is  absent  in  metamorphic  forms  whereas  this 
larva  has  a  pectoral  fin.  The  position  of  the  vent 
is  more  anterior  in  the  metamorphic  forms  than 
in  Monognathus ,  which  may  be  attributed  again 
to  metamorphosis.  The  deep  pigmentation  at  the 
base  of  the  median  fins,  which  increases  progres- 
sively in  later  stages,  is  obviously  juvenile 
pigmentation.  Although  the  midlateral  pigmen- 
tation, myotome  number  and  shape,  and  other 
characters  agree  with  those  of  metamorphic  forms 
of  Monognathus ,  the  differences  preclude  a  close 
relationship. 


AFFINITIES  OF 

SACCOPHARYNGOIDEI  WITHIN 

THE  ANGUILLIFORMES 

The  Saccopharyngiformes  have  not  been  suc- 
cessfully related  to  any  family  within  the  Anguil- 
liformes.  In  the  most  recent  classification  of  the 
teleostean  fishes  (Greenwood  et  al.,  1966),  the 
group  is  placed  next  to  Aoteidae  and  Cyemidae 
as  a  suborder  (Saccopharyngoidei)  of  the  order 
Anguilliformes.  The  family  Cyemidae  has  been 
traditionally  regarded  as  related  to  nemichthyid 
eels  because  of  the  superficial  resemblances  of  the 
beak.  I  suggest  that  the  Cyemidae  be  considered 
as  related  to  the  Saccopharyngiformes  and  not 
to  the  Nemichthyidae  for  the  following  reasons. 

The  adults  of  Cyema  differ  from  the  nemich- 
thyids  in  morphological  and  osteological  char- 
acters. All  the  nemichthyid  eels  are  extremely 
elongate,  but  Cyema  is  very  short.  The  adult 
Cyema  has  a  small  degenerate  eye  and  a  large 
stomach  (about  one-fourth  of  the  total  length 
excluding  the  beak),  as  in  the  Saccopharyngi- 
formes, whereas  the  nemichthyids  have  large 
eyes. 

The  differences  in  their  larvae  are  even  more 
basic.  The  larvae  of  Nemichthys  scolopaceus 
Richardson,  1848  (Bertin,  1937b)  and  other 
nemichthyids  (Beebe  and  Crane,  1936,  1937a, 
1937b)  are  also  elongate  and  become  extremely 
attenuate  during  growth  and  metamorphosis,  but 
the  larva  of  Cyema  has  a  short   and  deep  body. 


560 


RAJU:  THE  GENUS  MONOGNATHUS 


The  myotomes  of  the  nemichthyid  larvae  are 
W-shaped  whereas  those  ofCyema  are  V-shaped. 
The  intestine  is  looped  in  Cyema  whereas  it  is 
straight  in  the  nemichthyid  larvae.  On  the  other 
hand,  the  larva  of  Cyema  closely  resembles  those 
of  the  Saccopharyngiformes  in  the  size  and  shape 
of  the  body,  myotome  shape,  looped  intestine, 
position  of  the  vent,  and  elongate  suspensorium. 
Bertin  (1937b)  has  pointed  out  some  of  the  larval 
and  osteological  resemblances  between  the 
Cyemidae  and  the  Saccopharyngiformes  and  at- 
tributed the  similarities  of  the  beak  of  the 
Cyemidae  and  Nemichthyidae  to  convergent 
evolution  as  the  beak  in  Nemichthys  is  mainly 
formed  by  the  elongation  of  the  vomer,  but  in 
Cyema  by  the  two  maxillaries. 

The  four  families — Cyemidae,  Monognathidae, 
Saccopharyngidae,  and  Eurypharyngidae — share 
some  basic  characters  such  as  short,  deep  bodied 
larvae  with  V-shaped  myotomes,  looped  gut, 
elongated  suspensorium,  and  a  degenerate  eye  in 
the  adult  condition.  The  striking  similarities  of 
these  larvae  and  their  differences  with  the 
larva  of  Nemichthys  are  shown  in  Table  3  and 
Figure  4.  The  gross  differences  in  the  adults 
of  the  four  families  are  probably  due  to  the 
drastic  changes  undergone  during  metamorphosis 
and  other  causes.  At  present,  I  can  only  point  out 
the  similarities  of  the  Cyemidae  to  the  Sac- 
copharyngiformes. Further  studies  may  provide 
information  to  help  include  or  exclude  the 
Cyemidae  in  the  Saccopharyngiformes. 

ACKNOWLEDGMENTS 

I  thank  Richard  H.  Rosenblatt  of  the  Scripps 


Institution  of  Oceanography  and  Elbert  H. 
Ahlstrom  of  the  National  Marine  Fisheries  Serv- 
ice, La  Jolla,  for  critically  reading  the  manu- 
script. Joseph  F.  Copp  checked  the  station  data. 
I  am  especially  grateful  to  John  D.  Isaacs  for  his 
encouragement  and  for  the  award  of  a  postdoctoral 
fellowship  from  his  research  funds  during  the 
tenure  of  this  work.  I  thank  the  authorities  of 
Simpson  College  for  the  assistance  given  in 
finalizing  this  paper.  This  paper  is  a  contribution 
of  the  Scripps  Institution  of  Oceanography. 

LITERATURE  CITED 

Beebe,  W.,  and  J.  Crane. 

1936.     Deep-sea  fishes  of  the  Bermuda  Oceanographic 

Expeditions.  Family  Serrivomeridae.  Part  I:  Genus 

Serrivomer.     Zoologica  (N.Y.)  20:53-102. 
1937a.     Deep-sea  fishes  of  the  Bermuda  Oceanographic 

Expeditions.   Family  Serrivomeridae.  Part  II:   Genus 

Platuronides.     Zoologica  (N.Y.)  22:331-348. 
1937b.     Deep-sea  fishes  of  the  Bermuda  Oceanographic 

Expeditions.  Family  Nemichthyidae.     Zoologica  (N.Y.) 

22:349-383. 
Bertin,  L. 

1934.     Les  poissons  apodes  appartenant  au  sous-ordre  des 

Lyomeres.     Dana  Rep.  Carlsberg  Found.  3,  55  p. 
1937a.     Un  nouveau  genre  de  poissons  apodes  caracterise 

par  I'absence  de  machoire  superieure.     Bull.  Soc.  Zool. 

Fr.  61:533-540. 
1937b.     Les  poissons  abyssaux  du  genre  Cyema  Giinther 

(anatomie,  embryologie,  bionomie).     Dana  Rep.  Carls- 
berg Found.  10,  30  p. 
1938.     Formes  nouvelles  et  formes  larvaires  de  poissons 

apodes  appartenant  au  sous-ordre  des  Lyomeres.     Dana 

Rep.  Carlsberg  Found.  15,  26  p. 
Bohlke,  J.  E. 

1966.     Order  Lyomeri,  Deep-sea  gulpers.    In  Fishes  of  the 

western  North  Atlantic.     Part  Five,  p.  603-628.     Mem. 

Sears  Found.  Mar.  Res.  1. 


Table  3. — Comparison  of  larval  characters. 


Characters 

Cyema  atrum 

Pacific 
leptocephalus 

Leptocephalus 
la  t  is  Sim  us 

L.  pseudo- 
latissimus 

Nemichthys 
scolopaceus 

Size  of 
body  (mm) 

Small 
(20-60) 

Small 
(35-40) 

Small 
(20-40) 

Small 
(20-40) 

Large 
(over  100) 

Shape  of 
body 

Oval 

Oval 

Oval 

Oval 

Ribbonlike 

Myotomes 

V-shaped 
(obtuse  angle) 

V-shaped 
(obtuse  angle) 

V-shaped 
(obtuse  angle) 

V-shaped 
(obtuse  angle) 

W-shaped 

Intestme 

Looped 

Looped 

Looped 

Looped 

Straight 

Position  of 
vent 

About 

three-fourths 
from  head 

About 

three-fourths 
from  head 

About  one-half 
from  head 

About  one-half 
from  head 

Subterminal 

Liver 

Short  lobe 

Short  lobe 

Short  lobe 

Short  lobe 

Elongate 

Pancreas 

Very  large 

Large  lobe 

Large  lobe 

Large  lobe 

Small  and 
elongate 

Suspensorium 

Elongate 

Elongate 

Elongate 

Elongate 

Small 

561 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 


Castle,  P.  H.  J. 

1963.     Anguillid  Leptocephali  in  the  Southwest  Pacific. 
Zool.  Publ.  Victoria  Univ.  Wellington  34:1-14. 
Greenwood,  P.  H.,  D.  E.  Rosen,  S.  H.  Weitzman,  and 
G.  S.  Myers. 

1966.     Phyletic  studies  of  teleostean  fishes,  with  a  pro- 
visional classification  of  living  forms.     Bull.  Am.  Mus. 
Nat.  Hist.  131:339-455. 
Lea,  E. 

1913.     Muraenoid   larvae.     Rep.   Sci.  Results  "Michael 
Sars"  North  Atl.  Deep-sea  Exped.,  1910.  Bergen  Mus., 
Bergen,  1933  ed.  3(l):l-48. 
Murray,  J.,  and  J.  Hjort. 

1912.  The  depths  of  the  ocean.  A  general  account  of  the 
modern  science  of  oceanography  based  largely  on  the 
scientific  researches  of  the  Norwegian  steamer  Michael 
Sars  in  the  North  Atlantic.  Macmillan  and  Co.,  Lond., 
821  p. 
Myers,  G.  S. 

1940.     A  note  on  Monognathus.     Copeia  1940:141. 


Orton,  G.  L. 

1963.     Notes  on  larval  anatomy  of  fishes  of  the  order 

Lyomeri.     Copeia  1963:6-15. 
Roule,  L. 

1934.     Les  poissons  et  le  monde  vivant  des  eaus.     Paris, 

7:242-243. 
Schmidt,  E.  J. 

1909.     On  the  occurrence  of  leptocephali  (larval  murae- 

noids)  in  the  Atlantic  W.  of  Europe.     Medd.  Komm. 

Havunders.,  Ser.  Fiskeri  3(6):1-19. 
1912.     Contributions  to  the  biology  of  some  North  Atlantic 

species  of  eels.     Vidensk.  Medd.  Dan.  Naturhist.  Foren. 

Kbh.  64:39-51. 
Tchernavin,  V.  V. 

1947a.     Six  specimens  of  Lyomeri  in  the  British  museum 

(with  notes  on  the  skeleton  of  Lyomeri).     J.  Linn.  Soc. 

Lond.  Zool.  41:287-350. 
1947b.     Further  notes  on  the  structure  of  the  bony 

fishes  of  the  order  Lyomeri  (Eurypharynx).     J.  Linn. 

Soc.  Lond.  Zool.  41:377-393. 


562 


OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION  IN  YOUNG 
TUNAS,  GENUS  THUNNUS  (PISCES,  SCOMBRIDAE),  FROM  THE 

ATLANTIC  OCEAN' 


Thomas  Potthoff^ 


ABSTRACT 


The  development  and  variability  of  osteological  and  meristic  features  obtained  from  427 
juvenile  Thunnus  from  8  to  117  mm  SL  are  described.  The  juveniles  of  T.  atlanticus,  T. 
thynnus,  and  T.  alalunga  can  be  identified.  Thunnus  obesus  cannot  be  separated  from  T.  albacares , 
but  both  are  separable  as  the  "Thunnus  spp.  complex"  from  the  other  three  species.  Identification 
methods  are  discussed  with  emphasis  on  the  features  of  the  axial  skeleton,  number  of  gillrakers 
over  the  ceratobranchial  bone,  pterygiophore  pattern  under  the  second  dorsal  fin,  and  the  shape 
of  the  lateral  line. 


This  paper  describes  the  development  of  osteo- 
logical features  and  their  variability  for  the  iden- 
tification of  juvenile  Thunnus  from  8  to  100  mm 
standard  length  (SL).  To  date,  this  has  not  been 
attempted  in  an  orderly  and  systematic  fashion 
for  the  species  in  the  Atlantic  Ocean,  mainly 
because  all  juveniles  have  the  same  general 
external  appearance  as  T.  atlanticus  shown  in 
Figure  1.  Nevertheless,  some  species  have  been 
previously  identified  by  using  mostly  external 
characters:  Sella  (1924),  Schaefer  and  Marr 
(1948),  Wade  (1950,  1951),  Mead  (1951),  Padoa 
(1956),  Jones  (1960),  Matsumoto  (1961),  Marchal 
(1963a,  b),  and  Yabe,  Ueyanagi,  and  Watanabe 
(1966).  The  identifications  were  probably  correct, 
although  other  species  of  juvenile  Thunnus 
could  fit  these  same  descriptions.  Scaccini  (1961) 
published  on  a  series  of  juvenile  Thunnus  from 
the  Mediterranean  and  stated  that  they  were 
T.  thynnus,  but  he  did  not  reveal  how  he  arrived 
at  his  identifications.  Ueyanagi  (1967)  mentioned 
the  occurrence  of  small  T.  alalunga  in  the  North 
and  South  Atlantic  Oceans,  but  he  gave  no  identi- 
fication methods.  Klawe  and  Shimada  (1959)  and 
Klawe  (1961)  examined  juvenile  Thunnus  ma- 
terial, using  external  and  osteological  characters, 
but  they  had  doubts  as  to  the  correctness  of  their 
identifications.  Watson  and  Mather  (1961)  used 
the  soft  X-ray  method  to  distinguish  between  the 
species.  One  of  their  major  characters  was  the 


vertebral  position  of  the  first  ventrally  directed 
parapophysis.  I  found'  this  character  to  be  of 
limited  value,  because  the  vertebral  position  of 
the  first  parapophyses  changes  with  growth. 
Potthoff  and  Richards  (1970)  used  osteological 
characters  to  identify  two  species  of  juvenile 
Thunnus  from  bird  stomachs,  and  Juarez  (1972) 
described  larvae  of  T.  atlanticus,  also  on  the 
basis  of  osteological  methods.  Other  researchers 
have  used  adult  osteological  characters  on  speci- 
mens larger  than  100  mm  (Yabe  et  al.,  1958; 
Nakamura  and  Kikawa,  1966). 

I  was  not  entirely  successful  in  separating  all 
species.  Using  osteological  characters,  T.  alba- 
cares and  T.  obesus  were  not  separable  from  each 
other  as  juveniles  (from  8  mm  to  about  100  mm 
SL),  but  together  they  can  be  separated  from  the 
other  three  Thunnus  species  in  the  Atlantic 
Ocean.  Thus,  I  have  lumped  them  together  as  the 
"Thunnus  spp.  complex." 

Adult  characters  from  the  works  of  Kishinouye 
(1923),  Frade  (1932),  Godsil  and  Byers  (1944), 
de  Sylva  (1955),  Watson  (1964),  Nakamura 
(1965),  and  Gibbs  and  Collette  (1967)  formed  the 
basis  for  my  study.  At  first  I  identified  the  largest 
fish  in  my  collection  and  then  worked  down  to 
the  smaller  sizes,  noting  changes  that  occurred. 


METHODS 


'Contribution  No.  229,  Southeast  Fisheries  Center,  National 
Marine  Fisheries  Service,  NOAA,  Miami,  Fla. 

^Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Miami,  FL  33149. 


Manuscript  accepted  October  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO. 


1974. 


The  specimens  used  in  this  study  were  first 
measured  with  dial  calipers  or  calibrated  ocular 
micrometers  and  the  standard  length  (SL)  from 


563 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Figure  1. — Thunnus  atlanticus,  85  mm  SL.  Specimen  was  cleared  and  stained  later  for  species  determination. 


the  anterior  tip  of  the  upper  jaw  to  the  posterior 
edge  of  the  hypural  plate  was  taken.  After 
determining  length  measurement  the  right  oper- 
cular plates  were  removed  and  the  specimens  were 
then  cleared  and  stained  (Taylor,  1967).  All  counts 
were  made  on  cleared  and  stained  material  that 
was  preserved  in  100%  glycerin,  using  a  binocular 
microscope  with  100  x  magnification.  On  a  few 
of  the  larger  specimens  25  x  magnification  was 
used.  Counts  on  the  gill  arches,  fins,  and  vertebral 
column  were  made  on  the  right  side  of  the  speci- 
men, except  for  the  pectoral  finrays  and  lateral 
line  scales,  which  were  counted  on  both  sides.  The 
side  with  the  higher  count  was  used  for  tabula- 
tion. Small  gillrakers  and  finrays  that  were  just 
beginning  to  appear  in  their  first  stage  of  develop- 
ment were  always  included  in  the  counts. 
Structures  such  as  the  pterygiophores,  neural 
and  haemal  spines,  zygapophyses,  etc.,  were 
always  counted,  although  in  smaller  specimens 
some  of  these  structures  were  very  small  and 
showed  very  weak  ossification.  The  hypural 
complex  (parhypural,  hypural  plates,  and  ural 
centrum)  was  considered  as  the  last  vertebra. 
Iwas  unable  to  make  every  count  on  all  of  the 
specimens  because  of  damage  or  their  develop- 
mental stage.  For  these  reasons,  the  number  of 
specimens  used  for  the  various  counts  may  vary. 
The  osteological  terms  used  in  this  paper  are 
mainly  from  Eaton  (1945)  and  Gibbs  and  Collette 
(1967).  The  terms  transforming  and  juvenile  are 
defined  for  scombrid  fishes  as  follows:  specimens 
of  the  transforming  stage  can  be  identified  with 
the  aid  of  larval  pigment  characters  but  have 
attained  most  adult  gross  anatomical  features, 


such  as  number  of  vertebrae  and  median  fins; 
juveniles  attain  the  juvenile  pigmentation  which 
obliterates  the  larval  pigmentation.  The  transi- 
tion from  larval  to  transforming  to  juvenile  stages 
is  gradual  in  scombrids  and  allows  for  individual 
subjective  judgment.  In  my  opinion,  the  larval 
stage  for  Thunnus  lasts  to  about  9  mm  SL,  the 
transforming  stage  to  about  13  mm  SL,  and  the 
juvenile  stage  to  sexual  maturity. 

MATERIAL 

Most  of  the  Thunnus  used  in  this  study  were 
collected  with  a  dip  net,  using  a  strong  light  at 
night.  A  few  were  collected  by  plankton  nets  and 
some  were  taken  from  fish  or  bird  stomachs.  The 
numbers  and  standard  lengths  of  all  specimens 
examined  for  this  study  are  shown  in  Figure  2. 
Their  numbers  and  size  ranges  for  general  capture 
areas  are  shown  in  Table  1. 

VERTEBRAL  COLUMN 

Number  of  Vertebrae 

(Figures  3  to  6;  Tables  2,  13) 

The  species  of  Thunnus  usually  have  39  verte- 
brae, including  the  hypural  plate:  18  precaudal 
and  21  caudal  vertebrae  for  all  species  except  the 
western  Atlantic  T.  atlanticus,  which  usually  has 
19  and  20,  respectively.  In  juveniles  the  centra 
in  the  anterior  two-thirds  of  the  vertebral  column 
are  already  ossified  at  8  mm  SL,  but  are  still  de- 
veloping in  the  posterior  third.  About  9  mm  SL, 
ossification  of  all  centra  is  completed.  Pleural  ribs 


564 


POTTHOFF:  OSTEOLOGICAL   DEVELOPMENT  AND  VARIATION   IN   YOUNG  TUNAS 


start  on  the  3rd  precaudal  vertebrae  attached 
to  the  parapophyses  and  to  the  tips  of  the  haemal 
arches.  Caudal  vertebrae  lack  pleural  ribs  and 
their  haemal  arches  continue  as  one  haemal 
spine.  In  transforming  specimens,  it  is  sometimes 
difficult  to  distinguish  pleural  ribs  from  haemal 
spines,  but  one  can  use  the  first  large  anal 
pterygiophore  as  a  demarkation  point  because  it  is 


always  found  in  the  interhaemal  space  anterior 
to  the  first  haemal  spine. 

Knowledge  of  the  variability  of  precaudal  and 
caudal  arrangement  and  number  of  vertebrae  is 
important  in  the  identification  of  specimens,  par- 
ticularly in  the  8-  to  14-mm-SL  size  range  where 
fewer  characters  are  available.  However,  great 
differences  in  vertebral  variability  exist  from 


THUNNUS   ATLANTICU8 


n=io« 

J5- 

r    1 

10- 

THUNNUS    OBESUS    AND/OR    THUNNUS   ALBACARES 

Z 

UJ 

S 

n=4l 

u   15- 

«   <5-| 

t 

UJ 

S 

O 

o 

UJ 

g'o- 

&'»- 

i 

» 

z 

E 

5- 

£     5- 

3 

3 

Z 

1        I— 

— 1    r-1 

0 

5 

10     15     20     25     30     35     40     45     50     55     60    65     70     75     (0     as 

0 

5      10     15     20    25     30    35     40    45 

4 

9 

14 

19 

24 

29 

34 

39 

44 

49 

54 

59 

64 

69 

74     79     (4 

90 

4 

9 

14 

19 

24 

29 

34 

39    44     49 

STANDARD    LENGTH   (mm) 


STANDARD    LENGTH  (mm) 


S 

u 


UJ     20' 


THUNNUS    AIALUN6A 
n:119 


Z  15- 


5      10     15     20     25     30     35     40    45     50     55     60     65      70     75     SC     as     90 


19     24     29     34     39     44     49     54     59     64     69 
STANDARD    LENGTH  (mm) 


74     79     a4     89     94 


THUNNUS  THYNNU8 
n:1S9 


I  I   I   I 


15     20     25     30     35     40    45     50     55     60    65      70     75  aO  aS  90  95  100  105   110  115 

I         ,        I         I        I        I         I        I        I        I         I         I         I         I  I        I  )        I        t        I        )  I 

14      19     24     29     34    39     44     49     54     59     64     69      74     79  a4  a9  94  99  104  109  114  120 

STANDARD    LENGTH  (mm) 


Figure  2. — Length  distribution  by  species  of  all  specimens  examined  for  this  study. 


565 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


Table  1. — Capture  areas,  species,  number,  size  range,  and  mean  standard 
length  for  specimens  studied. 


Size  range 

Mean 

Area 

Species 

No. 

SL  (mm) 

SL(mm) 

Northeast  Pacific  Ocean 

Thunnus  spp. 

23 

14-31 

19 

Northwest  Atlantic  Ocean 

7.  thynnus 

14 

8-71 

32 

Northwest  Atlantic  Ocean 

J.  alalunga 

1 

9 

Northwest  Atlantic  Ocean 

T.  atlanticus 

35 

9-71 

34 

Northwest  Atlantic  Ocean 

Thunnus  spp 

4 

18-33 

27 

Gulf  of  Mexico 

T.  thynnus 

15 

17-115 

45 

Gulf  of  Mexico 

T.  atlanticus 

65 

8-87 

23 

Gulf  of  Mexico 

Thunnus  spp 

1 

32 

Caribbean  Sea 

T.  alalunga 

9 

15-22 

19 

Caribbean  Sea 

T.  atlanticus 

7 

8-85 

35 

Mid-North  Atlantic  Ocean 

T.  alalunga 

1 

18 

Equatorial  East  Atlantic  Ocean 

Thunnus  spp. 

11 

8-47 

17 

Mediterranean  Sea 

T.  thynnus 

78 

14-117 

33 

Mediterranean  Sea 

T.  alalunga 

102 

9-91 

23 

Unknown 

T  thynnus 

52 

13-44 

23 

Unknown 

T.  alalunga 

6 

16-41 

24 

Unknown 

T.  atlanticus 

1 

11 

Unknown 

Thunnus  spp. 

2 

16.20 

various  reports,  probably  because  of  insufficient 
sample  size  and  population  differences.  I  have 
found  variability  in  precaudal  and  caudal 
arrangement,  as  well  as  in  total  vertebrae.  Verte- 
bral numbers  ranged  from  38  to  40,  and  total 
variability  from  the  normal  counts  of  18  +  21  =  39 
and  19  +  20  =  39  ranged  from  1.97c  for  T.  atlanti- 
cus to  14.69c  {or  Thunnus  spp.  Frade  (1932)  found 
13.6%  variability  for  T.  thynnus  compared  to  my 
5.1%,  and  he  reported  eight  specimens  with  38, 
six  with  40,  and  one  with  41  vertebrae.  Gibbs 
and  Collette  (1967)  doubted  Frade's  (1932)  high 
counts  of  40  and  41  vertebrae,  but  they  confirmed 
Godsil  and  Byers'  (1944)  specimen  of  T.  thynnus 
with  38  vertebrae.  Otherwise,  they  report  no 


variability  in  vertebral  numbers  from  more  than 
200  skeletons,  except  for  three  abnormalities 
where  two  adjacent  centra  were  fused.  I  found  one 
such  "fusion  abnormality"  in  a  T.  thynnus  with 
16  +  22  =  38  from  more  than  400  Thunnus 
specimens  examined. 

First  Ventrally  Directed  Parapophysis 

(Figure  3) 

Ventrally  directed  parapophyses  are  already 
present  on  the  anterior  centra  in  the  smallest 
(8  mm  SL)  specimens.  There  are  two  parapophy- 
ses per  centrum.  Posteriorly,  these  two  structures 
become  larger  and  finally  join  to  form  the  haemal 


DORSAL     FIN     PTERYGIOPHORE 


NEURAL     SPINE 


HAEMAL      PREZYQAPOPHY8I8  /  ^ANAL    FIN     PTERYGIOPHORE 

1ST    HAEMAL     SPINE 

Figure  3. — Relationship  of  the  axial  skeleton  to  the  fin  supports  and  fins  in  Thunnus  thynnus,  24  mm  SL. 


566 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION   IN  YOUNG  TUNAS 


Figure  4. — Relationship  of  the  axial  skeleton  to  the  fin  supports  and  fins  in  Thunnus  alalunga,  22  mm  SL. 


arches.  The  first  (anteriormost)  ventrally  directed 
parapophysis  occurred  on  the  8th  or  9th  vertebra 
on  specimens  10  mm  SL  and  smaller.  In  fish 
larger  than  10  mm  SL  the  first  ventrally  directed 
parapophysis  occurred  on  the  6th,  7th,  or  8th 
vertebra.  I  could  not  determine  specific  dif- 
ferences in  the  position  of  the  first  ventrally 
directed  parapophysis.  Differences  reported  by 
Watson  and  Mather  (1961),  Watson  (1964),  and 
Gibbs  and  Collette  (1967)  occur  only  in  specimens 
larger  than  80  mm  SL.  In  juveniles  less  than  80 
mm  SL,  the  first  ventrally  directed  parapophysis 
is  one  to  three  vertebrae  anterior  to  the  adult 
position.  As  the  fish  grow,  some  of  the  anterior- 
most  parapophyses  move  to  a  lateral  position  on 
the  centra. 

First  Closed  Haemal  Arch 
(Tables  3,  13) 

The  closed  haemal  arches  are  formed  quite ' 
early.  Even  the  smallest  (8  mm  SL)  specimens  of 

Table  2. — Precaudal  and  caudal  arrangement  of  the  vertebrae 
and  total  vertebral  number  in  juveniles  oi  Thunnus. 


Thunnus 

Item 

7.  thynnus 

7.  alalunga 

7.  atlanticus 

spp. 

Total  variability 

from  mode  (%) 

5.1 

3.4 

1.9 

146 

Precaudal.  caudal. 

and  total  number 

of  vertebrae 

16  +  22  =  38 

1 

18  +  20  =  38 

2 

19  +  19  =  38 

1 

17  +  22  =  39 

1 

5 

18  +  21  =  39 

149 

114 

1 

35 

19  +  20  =  39 

2 

4 

105 

18  +  22  =  40 

1 

19  +  21  =  40 

1 

1 

Thunnus  that  I  examined  had  their  first  anterior- 
most  closed  haemal  arch  on  the  diagnostic  verte- 
bra. The  arch  is  formed  by  the  fusion  of  the  distal 
ends  of  the  elongated  two  parapophyses  on  each 
centrum.  At  times  it  is  difficult  to  determine 
whether  the  parapophyses  have  actually  fused  or 
are  only  lying  close  together.  Care  should  be  taken 
to  determine  this  fact.  The  position  of  the  first 
closed  haemal  arch  is  a  character  of  some  value, 
since  it  forms  at  very  small  sizes.  Posteriorly, 
the  arches  become  more  elongated  in  a  dorso- 
ventral  direction,  forming  spines  at  their  distal 
points  (Figures  3  to  6).  The  vertebral  position  of 
the  first  closed  haemal  arch  separates  the  species 
of  the  genus  Thunnus  into  two  groups.  In  T. 
thynnus  and  T.  alalunga  the  first  arch  occurs 
on  the  10th  vertebra;  in  T.  atlanticus  and 
Thunnus  spp.  it  occurs  on  the  11th.  The  variability 
of  this  character  ranges  from  17c  to  12%  for  the 
various  species.  Thunnus  alalunga  is  the  most 
conservative  for  this  character,  and  T.  thynnus 
is  the  most  variable. 


First  Ventrally  Directed  Haemal 
Postzygapophysis 

(Figures  3  to  7;  Tables  3,  13) 

The  haemal  postzygapophyses  begin  to  develop 
a  little  later  than  the  parapophyses.  In  12-  to 
15-mm-SL  fish,  they  first  appear  as  tiny  bony 
projections  on  the  ventral  posterior  edge  of  the 
centrum.  They  develop  anteriorly  and  posteriorly 
from  the  center  of  the  vertebral  column.  At  about 
13  to  16  mm  SL,  the  position  of  the  first  haemal 
postzygapophysis  becomes  a  diagnostic  character. 
A  100  X   magnification  should  be  used  in  the 


567 


FISHERY   BULLETIN:  VOL.  12.  NO. 


smaller  specimens.  The  species  of  Th annus  can 
be  separated  into  two  groups  by  the  vertebral 
position  of  the  first  haemal  postzygapophyses. 
Thunnus  thynnus  and  Thunnus  spp.  have  the  first 
haemal  postzygapophyses  most  often  on  the  7th 
vertebra;  T.  alalunga  and  T.  atlanticus  on  the  8th. 
Thunnus  thynnus,  T.  atlanticus,  and  Thunnus 
spp.  develop  the  haemal  postzygapophyses  on 
their  respective  diagnostic  vertebrae  at  about  13 
to  14  mm  SL;  T.  alalunga  develops  them  at 
about  15  to  16  mm  SL. 

I  examined  seven  prepared  skeletons  from 
young  adults  for  all  species  from  400  to  700  mm 
SL  and  found  that  the  position  of  the  first 
ventrally  directed  haemal  postzygapophyses 
was  one  vertebra  posterior  to  those  of  juveniles. 
I  attribute  this  difference  between  juveniles  and 
adults  to  the  lateral  movement  of  the  structures 
during  growth  and  also  to  differential  growth 
between  the  centrum  and  the  haemal  postzyga- 
pophyses. The  elongate  haemal  postzygapophyses 
that  characterize  the  adult  T.  atlanticus,  i.e., 
the  longest  haemal  postzygapophysis  is  equal  to 
or  longer  than  the  centrum  (Gibbs  and  Collette, 
1967),  develop  only  gradually  in  juveniles  of  that 
species,  and  no  specimens  below  80  mm  SL  can 
be  separated  on  the  basis  of  this  character.  The 
same  is  true  for  adult  T.  albacares,  which 
approach  the  condition  of  T.  atlanticus.  I  was 
unable  to  follow  this  through  on  juveniles  in  the 
Thunnus  spp.  complex  because  I  lacked  speci- 
mens in  the  larger  sizes.  All  my  Thunnus  spp. 
specimens  had  haemal  postzygapophyses  no 
larger  than  those  of  all  the  other  species  in  their 
comparable  size  groups. 


Haemal  Prezygapophyses 

(Figures  3  to  7;  Table  3) 

The  haemal  prezygapophyses  develop  almost  at 
the  same  time  as  the  haemal  postzygapophyses, 
but  later  than  the  parapophyses.  They  first 
show  up  as  minute  bony  projections  on  the  two 
anterior  parts  of  the  haemal  arches  near  the 
centra  in  about  10-  to  13-mm-SL  fish.  Develop- 
ment, in  order  of  appearance,  proceeds  from  the 
anterior  to  the  posterior  vertebrae  and  varies 
slightly  with  species  and  size.  Young  T.  atlanticus 
develop  them  at  10  mm  SL,  the  remaining  species 
between  12  and  13  mm  SL.  High  magnification 
(lOOx)  should  be  used  on  specimens  that  just 
develop  this  structure.  Most  specimens  of  T. 
thynnus  and  T.  alalunga  have  their  first  haemal 
prezygapophyses  under  the  15th  or  16th  verte- 
bra, T.  atlanticus  under  the  16th  and  17th,  and 
Thunnus  spp.  under  the  14th.  There  is  however 
considerable  overlap  with  apparent  bimodal 
tendencies  for  the  various  species. 

In  small  juvenile  Thunnus,  all  haemal  prezyga- 
pophyses arise  from  the  haemal  arches.  Only  in 
specimens  larger  than  80  mm  SL  are  the  haemal 
prezygapophyses  on  the  centra  and  then  only 
posterior  from  about  the  30th  vertebra.  In  adult 
Thunnus  the  haemal  prezygapophyses  arise  from 
the  centra  posterior  from  about  the  25th  vertebra 
(Gibbs  and  Collette,  1967). 

The  position  of  the  anterior  haemal  prezy- 
gapophyses on  the  haemal  arches  or  centra  varies 
for  the  species  of  the  adults  of  Thunnus.  Adult 
T.  alalunga  have  their  more  anterior  haemal 


Figure  5. — Relationship  of  the  axial  skeleton  to  the  fin  supports  and  fins  in  Thunnus  atlanticus,  23  mm  SL. 


568 


POTTHOFF:   OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION   IN   YOUNG  TUNAS 


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FISHERY  BULLETIN:  VOL.  72,  NO.   2 


Figure  6. — Relationship  of  the  axial  skeleton  to  the  fin  supports  and  fins  in  Thunnus  spp.,  31  mm  SL. 


VERTEBRA 


HAEMAL     PREZYGAPOPHYSIS 


r.  alalunga 


MAL     POSTZYGAPOPHYSIS 
HAEMAL     SPINE 


r.  atlanticus 


L  thynnus 


T.  spp. 


Figure  7. — Shape  of  the  first  haemal  spine  for  juveniles  of  the  Thunnus  species.  From  left  to  right:  T.  alalunga   17, 
34,  61,  91  mm  SL;  T.  atlanticus  18,  34,  64,  85  mm  SL;  T.  thynnus  17,  33,  65,  100  mm  SL;  Thunnus  spp.  16,  33,  47  mm  SL. 


570 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION  IN  YOUNG  TUNAS 


prezygapophyses  on  the  centra,  T.  thynnus  and 
T.  obesus  have  them  near  the  centra  but  on  the 
haemal  arches,  and  T.  albacares  and  T.  atlanticus 
have  them  well  ventrad  of  the  centra  on  the 
haemal  arches  (Gibbs  and  Collette,  1967).  In 
juveniles  below  50  mm  SL,  this  specific  difference 
for  the  adults  is  not  apparent  because  the  more 
anterior  haemal  prezygapophyses  arise  at  about 
the  same  position  on  the  anterior  parts  of  the 
haemal  arches  for  all  species.  In  specimens 
larger  than  50  mm  SL,  the  differences  between 
the  species  can  be  gradually  perceived  with 
increased  size. 

In  my  collection  not  even  the  largest  juvenile 
T.  alalunga  (91  mm  SL)  had  its  anterior  haemal 
prezygapophyses  on  the  centra;  instead,  they  were 
close  to  the  centra  on  the  haemal  arches  as  in 
T.  thynnus.  The  largest  juvenile  T.  atlanticus 
(87  mm  SL)  had  the  anterior  haemal  prezyga- 
pophyses well  ventrad  on  the  haemal  arches. 
Consequently,  large  juveniles  of  T.  alalunga  and 
T.  thynnus  cannot  be  separated  by  the  position 
of  their  anterior  haemal  prezygapophyses,  but 
large  juvenile  T.  atlanticus  can  be  separated 
from  T.  alalunga  and  T.  thynnus  because  the  shift 
of  the  more  anterior  haemal  prezygapophyses  to 
ventrad  is  accomplished  at  a  smaller  size  in 
T.  atlanticus  than  the  shift  dorsad  to  the  edge 
of  the  centra  in  T.  alalunga.  Lack  of  larger 
Thunnus  spp.  specimens  prevents  their  separa- 
tion by  this  character.  I  am  certain  that  large 
juveniles  (>100  mm  SL)  of  the  Thunnus  spp. 
complex  could  be  separated  to  the  species  on  the 
basis  of  the  position  of  the  anterior  haemal 
prezygapophyses  since  differences  have  been 
observed  on  adult  T.  albacares  and  T.  obesus  as 
mentioned  above. 

Ventrolateral  Foramina 

(Figures  3  to  6;  Table  3) 

The  ventrolateral  foramina  are  the  last  gross 
anatomical  feature  to  develop  on  the  vertebral 
column.  They  begin  to  form  as  projecting  bony 
bridges  from  the  anterior  edges  of  the  haemal 
postzygapophyses  to  the  posterior  edges  of  the 
haemal  arches  in  specimens  from  19  to  22  mm 
SL.  On  rare  occasions  17-mm-SL  fish  may  show 
beginning  development  of  the  structure.  The  very 
first  developing  ventrolateral  foramen  can  be 
located  beneath  any  vertebra  from  the  27th  to 
30th,  but  it  is  most  often  found  beneath  the  28th. 
During  growth,  new  structures  are  added  beneath 


the  centra,  anterior  and  posterior  to  the  first 
foramen.  All  of  the  ventrolateral  foramina  are 
developed  at  about  25  mm  SL,  generally  from  the 
22nd  to  the  36th  vertebra.  There  is  considerable 
overlap  for  all  the  species  with  some  modal 
separation  for  specimens  greater  than  25  mm  SL 
in  the  vei-tebral  position  of  the  first  ventrolateral 
foramen.  The  ventrolateral  foramina  can  be  found 
posteriorly  to  the  36th  vertebra  on  all  25-  to 
35-mm-SL  specimens  of  all  species.  After  35  mm 
SL,  some  posterior  openings  are  gradually  filled 
in  by  ossification.  Juvenile  T.  thynnus  from  71  to 
117  mm  SL  had  the  last  ventrolateral  foramen 
on  the  32nd  and  33rd  vertebra,  T.  alalunga  from 
54  to  91  mm  SL  on  the  31st,  and  T.  atlanticus 
from  52  to  87  mm  SL  on  the  29th  or  30th. 
My  largest  Thunnus  spp.  specimen  (47  mm  SL) 
had  the  last  ventrolateral  foramen  on  the  34th 
vertebra.  In  adult  Thunnus  the  last  foramen  is 
found  on  the  29th  to  30th  vertebra  according  to 
my  own  examination  of  seven  skeletons  of  adults 
(400  to  700  mm  SL).  Gibbs  and  Collette  (1967) 
found  it  on  the  29th  to  33rd  vertebra. 

All  species  of  Thunnus  have  initially  circular 
or  nearly  circular  shaped  openings,  which 
gradually  decrease  in  diameter  posteriorly.  Ju- 
veniles larger  than  60  mm  SL  lose  the  circular 
shape  on  the  anteriormost  foramina,  acquiring  a 
more  triangular  or  oval  shape.  Specific  dif- 
ferences in  the  size  and  shape  of  the  anterior 
openings  are  not  distinct  for  juveniles  as  they 
are  for  adults  (Gibbs  and  Collette,  1967). 


First  Haemal  Spine 

(Figure  7) 

The  first  haemal  spine  is  located  on  the  haemal 
arch  of  the  first  caudal  vertebra.  It  is  a  consider- 
ably elongated  process.  Anterior  to  this  process, 
in  close  proximity,  are  the  first  two  anal  pterygio- 
phores  (Figures  3  to  6).  The  preceding  haemal 
processes  on  the  haemal  arches  of  the  precaudal 
vertebrae  are  shorter  than  the  first  haemal  spine 
and  also  have  at  their  tips  flattened  parapophy- 
ses  for  rib  articulation.  Yabe  et  al.  (1958), 
Matsumoto  (1963),  and  Yoshida  (1965)  reported 
on  the  flattening  of  the  first  haemal  spine  in  T. 
alalunga  and  stated  that  this  character  may  be 
unique  to  the  species.  I  believe  that  this  is  true 
for  the  adults  but  not  for  the  juveniles  because 
in  all  Thunnus  species  the  first  haemal  spine 
goes  through  a  variety  of  flattened  shapes  during 


571 


FISHER\    BULLETIN:  VOL.  72.  NO. 


its  ontogeny.  In  addition,  there  is  great  indi- 
vidual variability  in  the  shape  of  the  first  haemal 
spine  within  each  species.  Nevertheless,  T. 
alalunga  exhibits  the  greatest  flattening  of  the 
first  haemal  spine  during  its  ontogeny  and  Thun- 
nus spp.  the  least.  Thunnus  thynnus  and  T. 
atlanticus  generally  show  less  flattening  than  T. 
alalunga  but  more  than  Thunnus  spp. 

In  T.  alalunga  the  first  haemal  spine  begins  to 
flatten  a  little  at  21  mm  SL.  Flattening  continues 
to  increase  to  about  35  mm  SL.  From  this  size  on 
changes  in  shape  occur,  but  the  degree  of  flatten- 
ing remains  essentially  the  same.  Thunnus 
atlanticus  does  not  show  any  flattening  before 
60  mm  SL  and  T.  thynnus  not  before  30  mm  SL. 
Thunnus  spp.  showed  slight  flattening  at  47  mm 
SL. 

As  the  shape  of  the  first  haemal  spine  is  a  char- 
acter of  degree  and  cannot  be  accurately  assessed, 
I  suggest  that  only  persons  familiar  with  the 
Atlantic  species  of  Thunnus  juveniles  in  all 
sizes  use  this  character. 


Table  4. — Variability  of  spine  and  ray  counts  of  the  dorsal 
and  anal  fins  in  the  various  species  for  juveniles  of  Thunnus. 


Species 

Spines, 
first  dorsal  fin 

Number  of 
specimens 

Variability 

from  mode 

% 

13 

14         15 

16 

7.  thynnus 
7.  alalunga 
T.  atlanticus 

1 
2 

144          1 

112          1 

97          1 

1 

147 
113 
100 

2 

^ 

3 

Thunnus  spp. 

— 

37        — 

— 

37 

0 

Species 

Rays,  second  dorsal 
fin  and  finlets 

Number  of 
specimens 

Variability 
from  mode 

% 

22 

23 

24 

7.  thynnus 
7.  alalunga 
7.  atlanticus 
Thunnus  spp. 

4 

4 

134 

104 

89 

30 

4 
4 

1 

142 

108 

94 

30 

6 
4 
5 
0 

Species 

Rays, 
anal  fin  and  finlets 

Number  of 
specimens 

Variability 

from  mode 

% 

20 

21       22      23 

24 

7.  thynnus 
7,  alalunga 
7.  atlanticus 
Thunnus  spp. 

1 

5      127      6 

2      101       5 

85          6     — 

1        28       1 

2 

140 

108 

92 

30 

9 
6 
8 

7 

FINS  AND  FIN  SUPPORTS 

First  Dorsal  Fin 

(Table  4) 

All  species  develop  the  full  complement  of 
spines  in  the  first  dorsal  fin  before  8  mm  SL.  Four- 
teen spines  were  regularly  counted  in  the  first 
dorsal,  even  in  the  smallest  specimens  (8  mm  SL). 
The  count  of  14  spines  is  remarkably  constant  for 
juveniles  with  a  variability  of  0%  to  3%  for  the 
various  species.  This  remarkably  constant  count 
of  14  can  serve  as  a  generic  character  to  separate 
juveniles  of  the  genus  Thunnus  from  other 
scombrid  genera  in  the  Atlantic  Ocean  such  as 
Euthynnus  (15-16),  Katsuwonus  (15-16),  and 
Auxis  (10-12)  (Potthoff  and  Richards,  1970); 
Scomberomorus  (15-19)  (W.  J.  Richards,  pers. 
comm.)3;  Scomber  (9-13)  (Matsui,  1967);  Acan- 
thocybium  (24-26)  (Rivas,  1951);  Sarda  (20-22); 
and  Orcynopsis  (13)  (Collette  and  Chao,  1973).^ 
There  is  conflict  between  the  consistency  of  first 
dorsal  fin  counts  in  juveniles  and  greater  varia- 
tion of  counts  in  adults  (Frade,  1931;  Rivas,  1951; 


^Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Miami,  FL  33149. 

"Collette,  B.  B.,  and  L.  N,  Chao.  1973.  Systematics  and 
anatomy  of  the  bonitos  (Sarda  and  their  relatives).  Unpublished 
manuscript. 


BuUis  and  Mather,  1956;  Gibbs  and  Collette, 
1967).  In  some  adults  the  posteriormost  spines 
become  embedded  in  the  dorsal  groove  and  sur- 
rounding tissue  and  are  consequently  overlooked. 
The  first  dorsal  fin  can  be  easily  separated 
from  the  second  dorsal  fin  because  the  last  spine 
of  the  first  dorsal  is  always  shorter  than  the  first 
element  in  the  second  dorsal  (Figures  3  to  6),  and 
the  spacing  between  spines  of  the  first  dorsal  fin 
is  greater  than  that  between  rays  of  the  second 
dorsal.  The  space  between  the  last  spine  of  the 
first  dorsal  and  the  first  element  of  the  second 
dorsal  is  wider  than  the  following  spaces  between 
the  rays  of  the  second  dorsal.  This  diff'erence  in 
spacing  is  due  to  the  shape,  structure,  and 
spacing  of  pterygiophores,  which  support  the 
visible  elements  of  the  fins. 


Second  Dorsal  Fin  and  Finlets 

(Table  4) 

Eight-mm  SL  larvae  of  all  species  have  already 
acquired  the  full  complement  of  rays  in  the  second 
dorsal  fin,  but  lack  two  or  three  of  the  posterior- 
most  finlets.  By  11  to  13  mm  SL  all  finlets 
are  developed.  Thunnus  atlanticus  develops  its 
second  dorsal  rays  and  finlets  to  a  full  comple- 
ment at  a  slightly  smaller  size,  usually  by  10 


572 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION   IN   YOUNG  TUNAS 


to  12  mm  SL.  A  total  count  of  23  rays  was 
obtained  most  of  the  time  for  the  second  dorsal 
fin  and  finlets  of  all  the  species  (Frade,  1931; 
Bullis  and  Mather,  1956;  Gibbs  and  Collette, 
1967).  Although  the  variability  was  greater 
than  that  for  the  first  spinous  dorsal  fin,  it  did 
not  exceed  6%  in  the  second  dorsal  fin.  I  included 
the  dorsal  finlet  counts  with  ray  counts  of  the 
second  dorsal  fin  because  in  larvae  and  juveniles 
ofThunnus,  and  perhaps  with  all  other  scombrid 
genera,  it  is  impossible  to  determine  precisely  the 
break  between  the  last  posterior  second  dorsal 
fin  softray  and  the  first  anterior  dorsal  finlet  even 
in  cleared  and  stained  specimens.  Figures  3  to 
6  show  this  gradual  intergradation  from  softrays 
to  finlets.  The  last  ray  of  the  second  dorsal  fin 
can  be  separated  from  the  first  finlet  by  their 
pterygiophore  structure  in  specimens  larger  than 
50  mm  SL.  Finlet  pterygiophores  have  two  clearly 
visible  bony  parts  from  a  lateral  view  and  second 
dorsal  fin  pterygiophores  have  only  one  clearly 
visible  part.  Figures  3  to  6  show  specimens  that 
have  not  yet  developed  the  two  clearly  visible 
parts  in  their  finlet  pterygiophores. 


wide  ranges  narrow  in  the  25  to  29  mm  SL  size 
groups  where  adult  counts  of  more  than  30  rays 
are  attained  (Frade,  1931;  Bullis  and  Mather, 
1956;  Gibbs  and  Collette,  1967).  The  rays  in  the 
pectoral  fins  were  counted  on  both  sides  for  each 
specimen.  The  side  that  yielded  the  highest  value 
was  taken  for  tabulation.  In  34%  of  all  specimens 
counted  there  was  no  difference  in  counts  between 
the  two  pectoral  fins;  in  47%  of  the  specimens,  a 
difference  of  one  ray  was  noted;  11%  of  the  speci- 
mens had  a  difference  of  two  rays;  6%  had  a  three 
ray  difference;  and  2%  differed  by  four  rays.  Only 
one  specimen  differed  by  five  rays.  At  8  mm  SL, 
8  to  12  rays  were  developed  on  the  dorsal  side 
of  the  finfold.  Development  of  rays  proceeded 
progressively  ventrad  until  the  finfold  was 
completely  occupied  with  rays.  At  20  mm  SL, 
very  few  juveniles  have  the  adult  count  of  more 
than  30  rays.  At  23  mm  SL,  about  one-half  of 
the  specimens  have  adult  counts,  and  at  27  mm 
SL  all  have  adult  counts.  Adults  and  all  juveniles 
>27  mm  SL  have  more  than  30  pectoral  fin 
rays,  usually  31  to  34,  sometimes  35,  rarely  36 
or  37.  My  data  are  corroborated  by  Schaefer 
and  Marr  (1948)  and  Mead  (1951). 


Anal  Fin  and  Finlets 

(Tables  4,  13) 

The  anal  fin  develops  similarly  to  the  second 
dorsal  fin.  At  8  mm  SL,  all  rays  in  the  anal  fin 
are  present  with  three  or  four  of  the  posteriormost 
finlets  lacking.  By  11  to  12  mm  SL  all  finlets 
are  developed.  Thunnus  atlanticus  typically  has 
21  anal  elements  (rays  plus  finlets),  and  the 
remainder  of  the  species  have  22  (Frade,  1931; 
Bullis  and  Mather,  1956;  Gibbs  and  Collette, 
1967).  Variability  for  this  character  ranges  from 
6%  to  9%.  The  counts  of  the  anal  finlets  were 
included  in  the  anal  ray  counts  for  the  same 
reasons  given  previously  for  the  second  soft 
dorsal  fin. 

Pectoral  Fins 

(Table  5) 

Development  of  rays  in  the  pectoral  finfold  had 
already  started  in  my  smallest  (8  mm  SL)  speci- 
mens. The  increase  in  number  of  pectoral  rays  and 
their  sequence  of  development  was  similar  for  all 
the  species.  Wide  ranges  in  number  of  pectoral 
'fin  rays  were  common  for  equal  size  groups.  These 


Pelvic  Fins 

All  the  fin  elements  of  the  pelvic  fins  were 
visible  in  my  smallest  (8  mm  SL)  specimens  of 
Thunnus.  A  count  of  six  fin  elements  was  obtained 
for  each  fin  throughout  the  size  range  sampled.  I 
could  not  be  certain  if  the  first  element  was  a  spine 
but  all  have  1,5  as  adults. 

Table  5. — Range  of  variation  in  pectoral  fin  ray  counts  for 
selected  sizes  in  juveniles  ofThunnus  of  all  the  species  combined. 


Range  of  variation. 

l^ost  frequent 

Size 

number  of 

number  of 

mm  SL 

pectoral  fin  rays 

pectoral  fin  rays 

8 

8-12 



9 

10-19 

10,14 

10 

9-24 

— 

11 

13-23 

18 

12 

16-20 

17 

13 

15-24 

18,19,21 

14 

18-25 

23 

19 

26-31 

27,28 

20 

26-32 

27,29 

21 

28-31 

29,30 

22 

28-31 

29,30 

23 

28-33 

29,31,32 

24 

29-35 

31 

25 

29-34 

31,32 

26 

29-33 

32 

27 

31-34 

31,32 

28 

32-33 

32 

573 


FISHERY   BULLETIN:  VOL.  72.  NO.  2 


Caudal  Fin 

(Table  6) 

At  8  mm  SL,  a  total  of  27  to  31  rays  is 
developed  on  the  caudal  fin.  If  the  total  was  an 
even  number  then  an  equal  number  of  rays  was 
found  dorsad  and  ventrad  to  the  midline.  If  it  was 
an  uneven  number  then  the  dorsal  side  of  the 
caudal  fin  always  carried  one  more  ray.  As  the 
larvae  grow,  additional  procurrent  rays  are  added 
equally  on  the  caudal  fin  to  the  dorsal  and  ventral 
side.  The  last  rays  to  develop  are  the  anterior- 
most.  There  is  a  difference  in  caudal  ray  develop- 
ment between  T.  thynnus  and  the  other  species. 
Thunnus  thynnus  usually  has  fewer  caudal 
rays  than  the  other  species  at  all  sizes,  par- 
ticularly from  14  to  22  mm  SL.  At  17  mm  SL, 
few  T.  thynnus  have  the  maximum  caudal  counts 
of  more  than  48  rays.  At  23  mm  SL,  about  one- 
half  of  the  T.  thynnus  specimens  had  maximum 
counts  and  only  after  about  35  mm  SL  did  all 
but  two  specimens  have  maximum  caudal  counts. 
Collectively,  the  remaining  species  differ  from 
T.  thynnus  in  that,  at  15  mm  SL,  a  few  speci- 
mens had  already  acquired  the  maximum  comple- 
ment of  caudal  rays.  At  18  mm  SL,  one-half 
of  the  specimens  had  maximum  counts,  and  all 
but  one  specimen  had  the  maximum  counts  at 
24  mm  SL.  I  noted  three  exceptions  to  the  above 
statements:  one  34-mm-SL  T.  atlanticus  had  48 


rays  and  two  T.  thynnus  had  47  and  44  rays 
at  40  and  50  mm  SL,  respectively.  From  my  data 
I  believe  that  all  Thunnus  juveniles  >24  mm  SL 
have  a  maximum  of  more  than  48  caudal  rays, 
usually  49  to  51,  rarely  52.  I  also  believe  the 
maximum  juvenile  counts  represent  the  adult 
complement  of  caudal  rays,  although  I  did  not 
examine  any  adult  fish.  Frade  (1931)  found  46 
caudal  rays  as  the  most  frequent  number  for  adult 
T.  thynnus.  The  difference  is  likely  due  to  dif- 
ficulty in  counting  the  anteriormost  rays  on 
adults.  For  this  study,  I  did  not  attempt  a  detailed 
examination  of  the  principal  caudal  rays  or  of  the 
hypural  complex.  A  study  of  the  ontogeny  of  the 
caudal  skeleton  in  T.  atlanticus  will  be  published 
in  the  future. 

Dorsal  and  Anal  Fin  Supports 

(Figures  8  to  10;  Tables  7,  13) 

The  spines,  rays,  and  finlets  of  the  dorsal  and 
anal  fins  are  supported  within  the  body  by  ptery- 
giophores.  The  pterygiophores  are  made  up  of 
two  or  three  bony  parts  referred  to  as  radials. 
Spines  and  rays  have  a  proximal  and  a  distal 
radial;  finlets  have  an  additional  middle  radial. 
The  distal  radials  of  the  posterior  rays  of  the 
second  dorsal  fin  and  finlets  and  of  the  anal  fin 
and  finlets  cannot  be  seen  from  a  lateral  view 
because  they  are  hidden  by  the  bifurcate  bases  of 


Table  6. — Range  of  variation  in  total  caudal  fin  ray  counts  for  selected  sizes 
and  species  groups  of  juveniles  of  Thunnus. 


Range  of  variation,  number 

Most  frequent  number 

of 

of  total  caudal  fin 

rays 

total  caudal  fin  rays 

Size 

T.  alalunga,  T.  atlanticus 

T.  alalunga,  T.  atlanticus, 

mm  SL 

Thunnus  spp. 

T.  thynnus 

Thunnus  spp.             T. 

thynnus 

8 

27-31 







9 

32-40 

— 

33,37 

— 

10 

34-43 

— 

— 

— 

11 

39-46 

— 

— 

— 

12 

41-43 

— 

— 

— 

13 

42-45 

— 

45 

— 

14 

45-47 

41 

45 

— 

15 

44-49 

43 

47 

— 

16 

45-49 

46-47 

46,47,48 

47 

17 

46-49 

45-49 

47,48,49 

47 

18 

47-50 

47 

48,49 

47 

19 

48-51 

46-49 

49 

47 

20 

47-51 

47-48 

49 

47 

21 

47-51 

47-49 

49,50 

47,48 

22 

49-51 

47-49 

49 

47 

23 

47-51 

48-50 

50 

49 

24 

48-51 

47-49 

50,51 

49 

25 

49-51 

47-50 

51 

49 

26 

50-52 

49-51 

50 

50 

27 

48-50 

48-49 

50 

49 

574 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION  IN  YOUNG  TUNAS 


RAY 


INLET 


-*^IIIODLE     RADIAL 
PROXIMAL    RADIAL 


PROXIMAL    RADIAL 


Figure  8. — Schematic  representation  of  the  relationship  between  vertebrae,  pterygiophores,  and 
fin  elements  in  juveniles  of  Thunnus  (lateral  view).  A.  Anterior  portion  of  first  dorsal  fin, 
pterygiophores,  and  vertebrae;  B.  Last  spine  of  first  dorsal  fin,  anterior  portion  of  second  dorsal 
fin,  pterygiophores,  and  vertebrae;  C.  Last  ray  of  second  dorsal  fin,  anterior  finlets,  pterygiophores, 
and  vertebrae;  D.  Anterior  portion  of  anal  fin,  pterygiophores,  and  vertebrae. 


the  fin  elements.  Generally,  all  species  of  Thun- 
nus have  37  dorsal  fin  elements  (XIV- 15-8)  but 
only  36  pterygiophores;  the  first  pterygiophore 
supports  the  first  two  spines.  In  actuality,  the  first 
pterygiophore  is  serially  associated  with  the 
second  spine  but  has  captured  and  fused  to  it 
the  distal  radial  of  the  first  spine  (Figure  8A). 
The  proximal  radial  of  the  first  spine  has  been 
lost.  The  first  spine  is  therefore  only  secondarily 
associated  with  the  first  pterygiophore.  Pos- 
teriorly, each  fin  element  is  serially  associated 
with  a  pterygiophore,  but  each  fin  element  also 
rests  atop  the  adjacent  posterior  pterygiophore 
in  a  secondary  association  (Figure  8).  Thus,  two 
pterygiophore  fin  element  associations  exist.  The 
serial  association  is  most  often  overlooked.  The 
last  fin  element  (finlet)  in  the  dorsal  fin  assembly 
is  serially  associated  with  its  pterygiophore.  It 
also  rests  in  a  secondary  association  on  a  very 
small  bone,  which  I  assume  to  be  a  reduced 
proximal  radial  of  a  lost  finlet  without  its  serial 
middle  and  distal  radials.  The  distal  radials  of 
the  spinous  dorsal  that,  to  me,  resemble  the  horns 


of  a  moose  (Kramer  (1960)  uses  the  term 
"alate"),  form  in  part  and  rigidly  support  the 
dorsal  groove  and  become  smaller  in  size  in  a 
posterior  direction.  The  distal  radials  are  still 
present  in  the  second  dorsal  fin,  although  their 
semblance  to  moose  horns  has  disappeared  ("non- 
alate").  They  decrease  in  size  posteriorly  (Figure 
8B)  until  they  disappear  from  the  lateral  view  at 
about  the  9th  ray.  Dissection  of  posterior  fin 
rays  and  finlets  revealed  the  presence  of  the  distal 
elements  between  the  bifurcate  bases  of  the  rays 
or  finlets  (Figure  9B,  C).  Spines,  on  the  other 
hand,  do  not  have  bifurcate  bases  (Figure  9A). 
Instead,  the  distal  radials  are  located  anterior  to 
the  base  of  the  spine. 

The  anal  fin  and  finlet  pterygiophores  are 
structurally  similar  to  the  pterygiophores  of  the 
second  dorsal  fin  and  finlets  with  one  exception: 
The  first  anal  pterygiophore  in  Thunnus  is 
derived  from  two  cartilaginous  parts  which  fuse 
at  about  8  mm  SL.  It  has  two  anal  fin  elements 
in  serial  association  and  one  in  secondary  (Figure 
8D).  Thus,  all  Atlantic  species  of  Thunnus, 


575 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


except  T.  atlanticus,  have  22  anal  fin  elements 
(15-7)  but  only  20  pterygiophores.  Thunnus 
atlanticus  has  21  fin  elements  (14-7)  but  only 
19  pterygiophores.  As  in  the  second  dorsal  fin, 
all  the  anal  fin  rays  and  finlets  have  a  bifurcate 
base  that  contains  a  small  distal  radial  (Figure 
9B,  C).  The  last  anal  finlet,  as  well  as  the  last 
dorsal  finlet,  is  serially  associated  with  a  pterygio- 
phore  but  has  a  secondary  association  with  a  small 
bone  that  I  assume  to  be  a  greatly  reduced 
proximal  radial  of  a  lost  finlet. 

Pterygiophore  development  is  more  or  less 
synchronous  with  fin  spine  and  ray  development. 
My  smallest  8-mm-SL  Thunnus  specimens  lacked 
about  two  to  four  posteriormost  pterygiophores 
dorsally  and  ventrally  (see  earlier  fin  sections).  At 
13  mm  SL,  all  specimens  had  acquired  a  full  count 
of  pterygiophores.  Thunnus  atlanticus  has  a  full 
count  at  the  slightly  smaller  size  of  11  to  12 
mm  SL.  In  the  very  small  sizes  of  8  to  11  mm 
SL,  the  pterygiophores  cannot  be  differentiated 
into  proximal,  middle,  and  distal  radials.  At  about 
11  mm  SL,  differentiation  first  begins  under  the 
anteriormost  section  of  the  first  dorsal  fin.  A  few 
of  the  distal  radials  begin  to  separate  from  the 
main  mass  of  the  pterygiophores  in  tiny  nonalate 
blocks.  The  separation  and  development  sequence 
is  in  a  posterior  direction.  At  20  to  35  mm  SL,  all 
the  distal  radials  are  separated  under  the  first 
dorsal  fin,  are  well  ossified,  and  gradually  assume 
an  alate  shape. 

The  middle  radials  under  the  finlets  (usually 
eight  dorsal  and  seven  ventral)  begin  to  separate 
and  ossify  over  a  great  size  range.  Some  speci- 
mens showed  no  separation  at  30  mm  SL,  whereas 
others  showed  some  separation  and  ossification  as 
small  as  22  mm  SL.  The  middle  radials  of  the 
finlet  pterygiophores  separate  and  develop  in  an 
anterior  direction.  First  to  develop  are  the 
posterior  middle  radials  of  the  last  finlets.  Most 
specimens  had  all  their  ventral  middle  radials 
developed  by  40  mm  SL,  but  a  few  still  lacked 
the  first  (e.g.,  anteriormost)  dorsal  middle  radial. 
By  60  mm  SL,  all  specimens  had  their  eight 
dorsal  middle  radials  developed. 

In  juvenile  Thunnus  it  is  difficult  to  determine, 
externally,  the  exact  number  of  finlets  because  of 
the  gradual  intergradation  from  fin  ray  to  finlet. 
A  finlet  can  now  be  precisely  defined  as  having 
a  middle  radial  serially  associated  with  it.  I  think 
that  at  50  mm  SL  one  can,  with  some  certainty, 
count  middle  radials  to  determine  finlet  number. 
Caution  is  warranted,  however,  because  a  few 


o 


t=::\ 


Figure  9. — Schematic  representation  of  the  relationship 
between  fin  elements  and  distal  radials  (anterior  view)  in 
juveniles  of  Thunnus.  A.  First  dorsal  fin  spine  and  distal 
radial  near  base;  B.  Second  dorsal  fin  ray  and  distal  radial 
within  bifurcate  base;  C.  Finlet  and  distal  radial  within 
bifurcate  base. 


specimens  may  still  lack  the  first  (e.g.,  anterior- 
most)  dorsal  middle  radial.  Table  7  has  been 
compiled  from  my  specimens  above  40  mm  SL. 
There  was  not  enough  material  available  in  the 
larger  sizes  to  assess  variability  and  specific 
differences  in  the  number  of  middle  finlet  radials. 
The  most  common  combination  of  middle  dorsal 
and  ventral  radials  is  8/7.  Variability  from  this 
combination  seems  to  be  low  in  T.  atlanticus  and 
T.  alalunga  and  high  in  T.  thynnus. 

Most  of  the  interneural  and  interhaemal  spaces 
bounded  by  the  neural  and  haemal  spines  are 
occupied  by  one  or  more  pterygiophores  in 
Thunnus  (Figures  3  to  6).  The  association  of 
pterygiophores  with  the  interneural  and  inter- 
haemal spaces  is  limited  to  smaller  juveniles.  By 
100  mm  SL,  the  anteriormost  pterygiophores 
under  the  first  dorsal  fin  are  already  situated 
above  the  neural  spines  and  do  not  insert  into 
any  interneural  spaces.  As  the  juveniles  grow, 
more  pterygiophores  lose  their  association  with 
their  respective  interneural  spaces.  I  did  not 
examine  specimens  larger  than  117  mm  SL  and 
cannot  say  if  all  pterygiophores,  dorsally  and 
ventrally,  pull  away  by  the  time  the  fish  become 
adults.  For  the  identification  of  juveniles,  how- 
ever, the  serially  associated  pterygiophores  of  the 
second  dorsal  fin  can  be  used  successfully  in 


576 


POTTHOFF:   OSTEOLOGICAL   DEVELOPMENT  AND  VARIATION    IN   ^  OUNG  TUNAS 


Table  7. — Number  of  dorsal  and  ventral  middle  radials  of  the 
finlets  in  three  species  of  juveniles  ofThunnus  (41-117  mm  SL). 


Middle 

radials 

Dorsal 

7 

8 

9 

8 

9 

n 

Species 

Ventral 

7 

7 

7 

8 

8 

T.  atlanticus 

1 

14 

_ 

1 

16 

T.  alalunga 

2 

5 

— 

— 

— 

7 

T.  thynnus 

~ 

9 

2 

6 

2 

19 

separating  T.  thynnus  from  T.  alalunga  and  T. 
alalunga  from  the  Thunnus  spp.  complex.  All  of 
my  T.  alalunga  specimens  (n  =  116)  had  their 
first  three  second  dorsal  interneural  spaces 
occupied  with  only  one  pterygiophore  (Figure  10, 
Table  13).  The  following  five  spaces  were  filled 
with  two  and  one  with  three  pterygiophores,  and 
the  last  posteriormost  second  dorsal  interneural 
space  again  had  only  one  pterygiophore.  This 
pattern  of  pterygiophore  insertions  under  the 
second  dorsal  fin  is  most  characteristic  of  T. 
alalunga,  but  may  occur  in  the  other  species  to  a 
lesser  degree.  Figure  10  and  Table  13  also  show 
the  percentages  of  occurrence  for  the  second  dorsal 
pterygiophore  insertion  sequences  which  are  most 
characteristic  for  that  species.  Ninety-five  percent 
of  my  148  T.  thynnus  specimens  had  their  first 
two  second  dorsal  interneural  spaces  occupied 
with  only  one  pterygiophore.  The  following  five 
spaces  were  filled  with  two  and  one  with  three 
pterygiophores,  and  the  last  two  posteriormost 
second  dorsal  interneural  spaces  had  only  one 
pterygiophore.  The  remaining  5%  of  my  T.  thyn- 
nus specimens  had  the  identical  T.  alalunga 


second  dorsal  pterygiophore  insertion  sequence. 
Ninety-eight  percent  of  my  41  Thunnus  spp. 
specimens  resembled  T.  thynnus  and  2%  T. 
alalunga.  Thunnus  atlanticus  was  the  most 
variable  in  the  second  dorsal  pterygiophore  inser- 
tion sequence;  A&7c  of  my  92  specimens  resembled 
T.  alalunga,  19*^  resembled  T.  thynnus,  and  35% 
had  six  interneural  spaces  occupied  with  two 
pterygiophores  but  did  not  have  a  space  with  three 
pterygiophores  (Table  13). 

Counting  from  anterior,  the  first  12  occupied 
interneural  spaces  associate  in  Thunnus  with  the 
first  dorsal  fin.  The  diagnostic  second  dorsal 
interneural  spaces  are  the  13th  through  the  21st. 
Following,  in  the  22nd  to  30th  spaces  are  the 
finlet  pterygiophores  (Figure  10).  The  interneural 
spaces  occupied  by  three  or  zero  pterygiophores  for 
the  second  dorsal  fin  and  finlets  are  depicted  in 
Figure  10  on  the  basis  of  where  they  most  often 
occurred,  but  they  could  vary  as  much  as  two 
spaces  in  an  anterior  or  posterior  direction.  The 
percentages  in  Figure  10  refer  only  to  the  arrange- 
ment under  the  second  dorsal  fin. 

The  distribution  of  pterygiophores  under  the 
anal  fin  (Figure  10,  Table  13)  present  too  much 
variability  to  be  useful  for  species  separation, 
except  perhaps  in  Thunnus  spp.  and  T.  atlanti- 
cus. The  first  five  anteriormost  interhaemal 
spaces  are  occupied  by  two  or  three  pterygio- 
phores in  T.  thynnus  and  T.  alalunga.  The  6th  and 
7th  spaces,  which  complete  the  anal  fin  associa- 
tion, always  have  only  one  pterygiophore.  The 
anal  finlet  pterygiophores  insert  into  the  8th  to 
14th  spaces,  one  to  a  space.  The  last  or  14th 
interhaemal  space  that  is  occupied  by  the  last  or 


NUMBER  OF  DORSAL  PTERYGIOPHORES 


1*t  Dorsal    Fin 


2nd  Dorsal    Fin 


Dorsal   Finlet 


T.   ATLAKTICUS 

46% 

JHUKHUS     SPP. 

98% 

T.    THYItllUS 

95% 

T.    ALALUHSA 

100% 

Vertebrae 
r    ALALUHSA 
T.    THYItllUS 
THUMMUS    SPP. 
T.    ATLAMTICUS 


10 


12 


13 


14 


15 


16 


17 


18 


66% 
84% 
78% 
61% 


19 


20 


21 


22 


23 


24 


25 


26 


27 


28 


29 


30 


31 


N 

46 

40 
140 
116 


32  33  34 


74 

116 

31 

SS 


Anal  Fin 


Anal   Finlets 


NUMBER    OF    ANAL    PTERYGIOPHORES 

Figure  10. — Representative  arrangement  of  pterygiophores  in  relation  to  the  fins  and  vertebrae  for  the  juvenile  Thunnus 
species.  Percentages  and  number  of  specimens  (N)  are  for  the  occurrence  of  the  commonest  arrangement  under  the  second 
dorsal  fin  only;  other  arrangements  given  in  Table  12.  Modified  after  Matsui  (1967). 


577 


FISHERY   BULLETIN;  VOL.  72.  NO.  2 


posteriormost  pterygiophore  is  directlj'  opposite 
the  last  or  30th  interneural  space  that  is  occupied 
by  the  pterygiophore  of  the  last  dorsal  finlet. 
Thunnus  spp.  and  T.  atlanticus  deviate  from  this 
pattern.  In  TS'^  oimy  AOThunnus  spp.  specimens, 
only  the  first  four  interhaemal  spaces  were 
occupied  by  more  than  one  pterygiophore,  the  5th 
through  7th  spaces  had  only  one.  Thunnus 
atlanticus  differed  by  having  only  six  interhaemal 
spaces  available  for  the  anal  fin.  Thus,  61%  of 
a  total  of  89  fish  had  their  first  five  spaces 
occupied  with  more  than  one  pterygiophore  and 
the  6th  space  with  one. 


BONES  AND  RAKERS  OF  THE  FIRST 
GILL  ARCH 

(Figures  11,  12) 

In  Thunnus  the  gillrakers  develop  within  the 
epithelium  that  overlies  the  three  bones  of  the 
first  gill  arch  and  their  connective  cartilage.  In 
its  first  stage  of  development,  the  raker  can  be 
observed  on  cleared  and  stained  preparations, 
under  100  x  power,  as  a  tiny  speck  of  weakly 
stained  material  within  the  translucent  epithe- 
lium. As  the  speck  grows  it  gradually  assumes 
the  triangular  shape  of  a  raker.  The  tip  of  the 
raker  will  finally  break  through  the  epithelium, 
and  its  broad  base  remain  anchored  in  the  tissue 
close  to  the  bone.  Ankylosed  rakers  were  not 
observed  on  the  bones  of  the  first  gill  arch,  even 
in  the  larger  specimens.  As  the  epithelium  is 
opaque  in  preserved  specimens,  gillraker  counts 


for  smaller  juveniles  should  be  made  only  on 
cleared  and  stained  material  for  accuracy.  Mead 
(1951)  noted  that  no  gillrakers  could  be  seen  in 
fish  smaller  than  15  mm.  I  believe  that  he 
referred  to  untreated  specimens,  because  in  my 
collection  all  species  of  Thunnus  had  six  or 
seven  rakers  at  their  smallest  size  (8  mm  SL). 

The  ceratobranchial  bone  of  all  species  has  six 
to  seven  rakers  at  8  mm  SL.  Development  and 
acquisition  of  rakers  over  the  ceratobranchial 
proceeds  distally  from  the  angle  towards  the 
hypobranchial  bone.  The  raker  in  the  angle  is 
always  included  in  the  ceratobranchial  count.  It 
develops  at  about  8  mm  SL. 

At  14  mm  SL  some  specimens  of  all  the  species 
develop  a  raker  on  the  epibranchial  bone  next 
to  the  angle.  One  exception  was  noted:  an  11-mm- 
SL  T.  atlanticus  with  one  raker  on  the  epi- 
branchial. Additional  rakers  over  the  epibran- 
chial bone  develop  distally  from  the  angle. 

The  last  bone  of  the  gill  arch  to  acquire  rakers 
is  the  hypobranchial.  The  size  of  the  juveniles 
when  this  occurs  depends  on  the  size  at  which  the 
ceratobranchial  becomes  entirely  occupied  with 
rakers.  In  the  hypobranchial  count  I  have  in- 
cluded the  rakers  (usually  one,  sometimes  two) 
found  over  the  cerato-hypobranchial  cartilage. 

The  first  rakers  to  appear  are  usually  located 
over  the  cartilage  but  are  considered  hypo- 
branchial rakers.  Occasionally  rakers  appear  over 
the  hypobranchial  bone  leaving  the  cartilage 
empty.  Thunnus  atlanticus  has  the  lowest  adult 
gillraker  counts  and  completes  its  entire  cerato- 
branchial complement  at  the  smallest  size  (9-15 


CARTILAGE 


EPIBRANCHIAL 


CARTILAGE 
HYPOBRANCHIAL 


r  alalunga 
(26.0  mm  SL) 


T.  atlanticus 
(27.1mm  SL) 


T.  thynnus 
(25.6  mm  SL) 


Figure  11. — First  right  gill  arches  of  juveniles  of  three  Thunnus  species. 


578 


POTTHOFF:  OSTEOLOGICAL   DEVELOPMENT  AND  VARIATION   IN   YOUNG  TUNAS 


EPIBRANCHIAL 


CERATOBRANCHIAL 


HYPOBRANCHIAL 


TOTAL    GILL    ARCH 


r.  iTLAMTICUS 

T.  iLALUHe* 

T.  THYHIIUS 

T.  ATLAMTICUS 

T.  ALALUM6A 

T.  THYKKUS 

T.  AILAMTICUS 

T.  ALALUKSA 

T.  THYHMUS 

T.  ATLAMTICUS 

T.  ALALUHBA 

T.  THYMHUS 


? 

I 1- 


I 1- 


—I 1 — I — I 1— I — I — r— I — I — I      I      I      I      I      I — I— I 

10     15    20    25    30    35    40    45     50    55    60    65    70    75    80    85    90  95 
STANDARD    LENGTH,  MM 

Figure  12. — Representative  scheme  of  gillraker  development  with  increase  in  size  over  the  three 
bones  of  the  first  gill  arch  for  juveniles  of  three  Thunnus  species.  Dotted  line:  developmental 
stage,  one  or  more  rakers  present;  dashed  line:  adult  gillraker  complement  present  in  some 
specimens;  solid  line:  adult  gillraker  complement  present  in  all  specimens;  question  mark: 
assumed,  no  data  available. 


mm  SL)  of  the  Atlantic  species.  Therefore,  some 
juvenile  T.  atlanticus  have  their  first  raker  over 
the  hypobranchial  at  16  mm  SL,  and  all  have  at 
least  one  raker  over  the  hypobranchial  at  20  mm 
SL.  Some  T.  alalunga  and  Thunnus  spp.  juve- 
niles have  their  first  raker  over  the  hypobranchial 
at  18  mm  SL,  and  all  have  at  least  one  raker  over 
the  hypobranchial  at  22  mm  SL.  Thunnus 
thynnus  has  the  highest  adult  gillraker  counts 
and  adds  its  first  rakers  to  the  hypobranchial 
at  the  largest  size  of  all  the  species;  they  begin 
to  appear  on  some  of  the  21-mm-SL  specimens 
from  the  western  Atlantic  and  on  some  of  the 
23-mm-SL  specimens  from  the  Mediterranean. 
Not  until  28  mm  SL  do  all  T.  thynnus  have  at  least 
one  raker  over  the  hypobranchial. 

Summarizing  the  data  from  Tables  8  to  11,  one 
can  conclude  that: 

1.  The  species  differ  in  size  at  which  they 
attain  the  maximum  gill  raker  counts  on  each 
bone  of  the  first  gill  arch. 

2.  Each  species  differs  from  the  others  in  maxi- 
mum number  of  rakers  that  it  can  have  on  some 
or  all  of  the  three  bones  of  the  first  gill  arch. 

3.  All  species  of  Thunnus  first  attain  the  maxi- 
mum complement  of  rakers  over  the  cerato- 
branchial  bone. 

4.  The  range  of  the  maximum  number  of  rakers 


over  the  ceratobranchial  bone  shows  the  greatest 
interspecific  difference. 

Thunnus  atlanticus  (Table  8;  Figures  11, 12).  The 
maximum  gillraker  count  over  the  epibranchial 
bone  of  7  to  9  rakers  was  first  present  in 
specimens  of  58  mm  SL.  The  diagnostic  maxi- 
mum count  of  11  to  13  rakers  over  the  cerato- 
branchial bone  was  first  present  in  a  9-mm-SL 
specimen,  but  it  was  not  until  15  mm  SL  that 
all  specimens  had  the  diagnostic  count.  Maxi- 
mum counts  over  the  hypobranchial  bone  (in- 
cluding the  cerato-hypobranchial  cartilage)  of 
4  to  6  rakers  were  first  observed  on  21-mm-SL 
specimens,  but  not  before  26  mm  SL  did  all 
juveniles  attain  the  maximum  count.  The  maxi- 
mum total  count  for  the  first  gill  arch  of  23 
to  27  rakers  was  first  observed  in  a  43-mm- 
SL  specimen  and  all  specimens  larger  than  52 
mm  SL  had  maximum  total  counts.  The  maxi- 
mum total  count  is  attained  in  some  specimens 
at  a  smaller  size  than  the  maximum  epi- 
branchial count.  This  discrepancy  is  explained 
by  the  range  in  number  of  rakers  over  the 
ceratobranchial  and  hypobranchial  bone.  Gibbs 
and  Collette  (1967)  give  19  to  25  rakers  as  the 
total  number  over  the  first  arch  for  T.  atlanti- 
cus. Because  all  specimens  larger  than  34  mm 
SL  had  more  than  20  gillrakers,  I  believe  that 


579 


FISHERY   BULLETIN:  VOL.  72,  NO.  2 

Table  8. — Distribution  of  gillrakers  over  the  branchial  bones  of  the  first  gill  arch  for  various  size  groups  in  Thunnus  atlanticus 

juveniles,  n  =104. 

(Total  gillraker  counts  for  western  Atlantic  adults  from  Gibbs  and  Collette,  1967,  Table  2*.) 


N 


SL 
(mm) 


0      1 


Epibi'anchlal 


Ceratobranchial 


10     11      12     13 


Hypobranchial 


7 

5-9 

7 

14 

10-14 

12 

2 

19 

15-19 

8 

8 

3 

23 

20-24 

6 

16 

10 

25-29 

1 

7 

12 

30-34 

3 

1 

35-39 

6 

40-44 

2 

2 

50-54 

2 

55-59 

2 

60-64 

2 

65-69 

1 

70-74 

1 

80-84 

2 

85-89 

7 

5-9 

14 

10-14 

19 

15-19 

23 

20-24 

10 

25-29 

12 

30-34 

1 

35-39 

6 

40-44 

2 

50-54 

2 

55-59 

2 

60-64 

2 

65-69 

1 

70-74 

1 

80-84 

2 

85-89 

•120 

>300 

6      7 


1      — 


Total  gillraker  coun 


9      10     11     12     13     14     15     16     17     If 


1 

3 

15 

20 

8 

10 

1 

6 

2 

1 
2 

1 
1 


7 

14 

4 


8       1 

8       4 

1 

—  5 
2 
1 
1 

1  — 
1 
1 

1       1 


9     20     21      22     23     24     25     26    27 


1       2       5 


3     —      1 


—  1 

—  1 


1       7      29     59    21 


T.  atlanticus  may  actually  not  fully  develop 
or  may  lose  some  rakers  during  its  later  life. 
Potthoff  and  Richards  (1970)  already  mentioned 
this  possibility. 
Thunnus  alalunga  (Table  9;  Figures  11,  12).  The 
maximum  gillraker  count  over  the  epibranchial 
bone  of  7  to  8  rakers  was  first  obtained  in  a 
61-mm-SL  specimen.  Most  likely,  however, 
maximum  counts  over  the  epibranchial  would 
first  show  in  the  55-  to  59-mm-SL  size  range, 
but  the  lack  of  specimens  for  those  sizes  pre- 
cludes a  definite  statement.  Bullis  and  Mather 
(1956)  counted  7  to  9  rakers  on  four  adult 
specimens.  The  diagnostic  maximum  count  of 
14  to  16  rakers  over  the  ceratobranchial  bone 
was  first  present  in  a  few  17-mm-SL  specimens. 
At  20  mm  SL,  all  specimens  had  the  diagnostic 
maximum  count.  This  count  overlaps  with  the 
Thunnus  spp.  complex.  Maximum  counts  over 


the  hypobranchial  bone  (including  the  cerato- 
hypobranchial  cartilage)  of  5  to  6  rakers  were 
first  observed  on  a  34-mm-SL  specimen;  all 
specimens  larger  than  35  mm  SL  had  the  maxi- 
mum count.  The  maximum  total  count  for  the 
first  gill  arch  of  27  to  29  rakers  is  attained 
at  53  mm  SL.  Gibbs  and  Collette  (1967)  give 
25  to  31  rakers  as  the  total  number  over  the 
first  gill  arch  for  adult  T.  alalunga  from  the 
western  Atlantic.  Our  difference  is  due  to  my 
smaller  sample  size  and  population  variance. 
Thunnus  thynnus  (Table  10;  Figures  11,  12).  The 
maximum  total  gillraker  count  over  the  epi- 
branchial bone  of  12  to  13  rakers  was  first 
present  in  one  79-mm-.SL  specimen.  Because  I 
lack  data  in  the  larger  size  ranges,  I  can  only 
estimate  that  all  T.  thynnus  have  a  full  epi- 
branchial after  they  have  reached  90  mm  SL. 
The  diagnostic  maximum  counts  of  17  to  20 


580 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION   IN  YOUNG  TUNAS 


rakers  over  the  ceratobranchial  bone  were 
first  observed  in  17-mm-SL  specimens  from  the 
western  Atlantic.  It  was  not  until  23  mm  SL 
that  all  specimens,  including  the  Mediter- 
ranean samples,  had  the  diagnostic  maximum 
count.  Maximum  counts  over  the  hypobranchial 
bone  (including  the  hypo-ceratobranchial  carti- 
lage) of  7  to  9  rakers  were  first  observed  on  a 
34-mm-SL  specimen  from  the  western  Atlantic, 
but  not  before  45  mm  SL  did  all  juveniles, 
including  the  Mediterranean  samples,  attain 
the  maximum  count.  One  exception  was  noted 
at  71  mm  SL  with  6  hypobranchial  rakers. 
The  maximum  total  count  for  the  first  gill  arch 
of  36  to  41  rakers  was  first  observed  in  a  62-mm- 
SL  specimen;  all  juveniles  in  the  90-  to  94-mm- 
SL  size  range  will  probably  have  the  maximum 
total  count.  As  in  T.  atlanticus,  the  maximum 
total  gill  arch  count  is  reached  in  some  T. 
thynnus  specimens  at  a  smaller  size  than  the 
maximum  epibranchial  count.  This  discrepancy 


is  again  explained  by  the  range  in  number  of 
rakers  over  the  ceratobranchial  and  hypo- 
branchial bone.  Gibbs  and  Collette  (1967)  give 
34  to  43  rakers  as  the  total  number  over  the 
first  arch  for  the  western  Atlantic  T.  thynnus 
thynnus.  Our  difference  is  due  to  my  smaller 
sample  size  and  population  variance. 
Thunnus  spp.  (Table  11).  Juvenile  T.  albacares 
and  T.  obesus  could  not  be  separated  and  were 
grouped  together  under  Thunnus  spp.  Lack  of 
enough  specimens  in  a  proper  size  range  pre- 
vented me  from  making  observations  on  gill- 
raker  ontogeny.  There  is  considerable  over- 
lap between  the  Thunnus  spp.  complex  and 
T.  alalunga  in  number  of  rakers  and  their 
development  over  the  three  bones  of  the  first 
arch.  The  maximum  counts  of  14  to  16  rakers 
over  the  ceratobranchial  bone  are  identical  for 
Thunnus  spp.  and  T.  alalunga.  At  15  mm  SL, 
one  Thunnus  spp.  specimen  had  the  maximum 
ceratobranchial  count  and  at  20  mm  SL  all 


Table  9. — Distribution  of  gillrakers  over  the  branchial  bones  of  the  first  gill  arch  for  various  size  groups  in  Thunnus  alalunga 

juveniles,  n  =  118. 

(Total  gillraker  counts  for  western  Atlantic  adults  from  Gibbs  and  Collette,  1967,  Table  2*.) 


Epibranchiai 


Ceratobranchial 


Hypobranchial 


N 

(mm) 

0 

1 

2 

3 

4 

5 

6 

7 

8 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

0 

1 

2 

3 

4 

5 

6 

3 

5-9 

3 

1 

1 

1 

3 

13 

10-14 

10 

3 

2 

— 

— 

— 

5 

2 

3 

1 

13 

50 

15-19 

5 

28 

11 

6 

13 

8 

11 

17 

1 

38 

11 

1 

25 

20-24 

1 

6 

18 

8 

16 

1 

2 

9 

6 

7 

1 

11 

25-29 

1 

6 

4 

2 

8 

1 

2 

5 

3 

1 

4 

30-34 

2 

2 

2 

2 

1 

2 

1 

5 

35-39 

1 

4 

1 

3 

1 

5 

1 

40-44 

1 

1 

1 

1 

45-49 

1 

1 

1 

2 

50-54 

2 

* 

2 

2 

1 

60-64 

1 

1 

1 

1 

80-84 

1 

1 

1 

1 

90-94 

1 

1 

1 

Total  gillraker  count 


6       7       8       9      10     11     12     13     14     15     16     17     18     19     20     21     22     23    24     25     26    27    28     29     30    31 


3 

5-9 

13 

10-14 

50 

15-19 

25 

20-24 

11 

25-29 

4 

30-34 

5 

35-39 

1 

40-44 

1 

45-49 

2 

50-54 

1 

60-64 

1 

80-84 

1 

90-94 

•55 

>700 

1    —   —    1    —    1 

2      5       2      2      2 

2      12     7      4      11      4      8       1        1 

12       5       5        8       3       1 

12       4       12       1 

1      —      2     —      1 

2  2  1 
1 
1 


1       1      10    20    15     6      2 


581 


FISHERY  BULLETIN;  VOL.  72.  NO. 


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582 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION  IN  YOUNG  TUNAS 


specimens  had  it.  Therefore,  the  juveniles  of  the 
Thunnus  spp.  complex  can  only  be  separated 
from  T.  alalunga  by  the  vertebral  position  of  the 
first  haemal  arch,  by  the  shape  of  the  first 
haemal  spine,  by  the  vertebral  position  of  the 
first  ventral  postzygapophysis,  and  by  the 
pterygiophore  pattern  of  the  second  dorsal  and, 
perhaps,  anal  fins.  However,  caution  should  be 
used  in  applying  any  separating  character  be- 
cause of  variability.  Percentages  for  variabili- 
ties can  be  found  in  the  respective  tables. 

LATERAL  LINE  SCALES 

(Figure  13,  Table  12) 

All  species  develop  the  first  lateral  line  scale  at 
16  to  18  mm  SL.  The  scale  originates  near  the 
dorso-posterior  edge  of  the  pectoral  girdle.  It  is 
rectangular  in  shape,  with  strong  ossifications  on 
the  dorsal  and  ventral  sides.  These  strong  ossifica- 
tions develop  into  two  plates  that  project  ver- 
tically to  the  base  of  the  scale.  As  growth  proceeds, 
more  scales  are  added  posteriorly,  forming  a  dis- 
tinct broken  line,  which  at  first  slopes  ventrad 
then  dorsad  and  levels  off  in  a  posterior  direction. 
At  about  60  mm  SL,  lateral  line  scales  cannot 
be  counted  because  the  scales  fuse  to  form  a  con- 
tinuous line.  Fusion  of  the  scales  occurs  first 


on  the  anterior  portion  of  the  lateral  line  and 
proceeds  posteriorly. 

Sella  (1924)  and  Watson  and  Mather  (1961) 
noted  specific  differences  in  the  shape  of  the 
lateral  line.  I  have  examined  this  character  in 
detail  and  found  that  T.  thynnus  can  be  separated 
from  all  the  other  Thunnus  species.  Eighty-one 
T.  thynnus  from  a  total  of  159  were  undamaged 
and  large  enough  to  show  the  lateral  line  contour. 
In  all  81  specimens  the  first  three  scales  formed 
a  posteriorly  descending  straight  line,  whereas 
the  following  scales  formed  a  posteriorly  ascend- 
ing line  at  an  angle  approximately  90""  to  the  first 
line.  At  the  8th  or  9th  scale  the  line  curved 
in  a  posterior  direction,  parallel  to  the  body  axis. 
At  19  mm  SL,  some  T.  thynnus  can  be  separated 
on  the  basis  of  the  lateral  line  contour  because 
at  this  size  some  have  acquired  four  scales.  The 
4th  scale  in  T.  thynnus  is  always  aligned  at  a 
90°  angle  to  the  preceding  three.  At  22  mm  SL, 
all  T.  thynnus  have  acquired  four  or  more  scales 
and  are  therefore  totally  separable  from  the  other 
species. 

In  the  remaining  species  a  descent  and  ascent  in 
the  lateral  line  is  also  present,  but  it  forms  a 
smooth  curve  instead  of  a  right  angle.  In  all 
specimens  (29  T.  alalunga,  46  T.  atlanticus,  and 
14  Thunnus  spp.)  the  last  scale  to  descend 


Table  11. — Distribution  of  gillrakers  over  the  branchial  bones  of  the  first  gill  arch  for  various  size  groups  in  Thunnus  spp. 

juveniles,  n  =  40. 
(Total  gillraker  counts  for  western  Atlantic  adults  from  Gibbs  and  Collette,  1967,  Table  2*.) 


SL 

(mm) 

Epibranch 

al 

N 

0 

1 

2 

3 

4 

5 

6 

7 

6 

5-9 

6 

6 

10-14 

3 

3 

12 

15-19 

9 

3 

8 

20-24 

3 

4 

1 

2 

25-29 

2 

> 

4 

30-34 

1 

2 

1 

1 

35-39 

1 

1 

45-49 

1 

Ceratobranchlal 


Hypobranchial 


6      7 


9     10    11     12    13     14    15    16 


1      — 


2     — 


Total  gillraker  count 


7      8      9     10    11     12    13    14    15    16    17    18    19   20    21     22    23    24    25    26    27    28    29    30    31     32    33 


6 

5-9 

6 

10-14 

12 

15-19 

8 

20-24 

2 

25-29 

4 

30-34 

1 

35-39 

1 

45-49 

127 

>600  7.  albacares 

•55 

>600  r  obesus 

1      —      4 


2 

1 

2 

3 

4 

1 

1 

1 

1 

— 

1 

3 

1 

1 

6    11     33    37    30 
13     15     17      4 


583 


FISHERY   BULLETIN:  VOL.  11.  NO.  2 
Table  12. — Number  of  lateral  line  scales  for  selected  sizes  of  juveniles  ofThunnus. 


Thunnus  alalunga 

Thunnus 

thynnus 

SL 

(mm) 

0 

1 

2 

3 

4       5       6       7       8       9 

10 

11 

12 

13 

0 

1 

2 

3 

4 

5 

6 

7 

8       9 

10 

11 

12 

13 

16 

2 

17 

4 

2 

2 

3 

18 

2 

1 

1 

1 

1 

1 

1 

19 

2 

2 

— 

— 

5 

3 

1 

20 

1 

4 

—    —     —      2 

2 

5 

1 

1 

21 

2 

1 

1 

4 

1 

22 

2      1       2 

— 

1 

1 

— 

3 

— 

1 

23 

1 

1 

4 

— 

—      1 

— 

1 

— 

1 

Thunnus  atlanticus 

Thunnus  spp. 

0 

1 

2 

3 

4       5       6       7       8       9 

10 

11 

12 

13 

0 

1 

2 

3 

4 

5 

6 

7 

8       9 

10 

11 

12 

13 

16 

1 

1 

17 

1 

— 

2 

18 

1 

1 

1 

1 

1 

19 

1 

1 

1 

2 

20 

1 

1      —      1 

1 

1 

1 

21 

1      _    _    _    _      1 

1 

1 

1 

22 

1      — 

1 

— 

— 

1 

23 

1 

1 

4 

posteriorly  is  the  4th  or  5th,  never  the  3rd  as 
in  T.  thynnus.  If  the  Hnes  of  the  curve  that  show 
descent  and  ascent  were  to  subtend  an  angle,  it 
would  be  larger  than  90^.  Some  specimens  of  these 
species  have  also  acquired  four  or  more  scales 
by  19  mm  SL.  They  can  be  distinguished  from 
T.  thynnus  by  their  4th  scale  that  stays  in  line 
on  a  descent  with  the  3rd.  At  21  mm  SL,  all 
specimens  have  four  or  more  scales.  Slight  dif- 
ferences in  the  curvature  of  the  lateral  line  were 
noted  between  T.  alalunga,  T.  atlanticus,  and 
Thunnus  spp.,  but  these  differences  were  not 
distinct  enough  for  separating  the  species. 

IDENTIFICATION 

(Table  13) 

The  generic  external  characters  of  transforming 
and  juvenile  Thunnus  have  been  adequately  docu- 
mented by  a  number  of  workers  as  pointed  out  in 
the  introduction.  Richards  and  PotthofF(in  press) 
concluded  that  if  accurate  identifications  to 
species  are  necessary,  the  only  choice  is  to  use 
osteological  characters,  even  though  this  involves 
the  time-consuming  task  of  clearing  and  staining. 

Only  three  characters  are  available  to  separate 
the  species  from  8  to  14  mm  SL:  the  number  of 
precaudal  and  caudal  vertebrae,  vertebral  posi- 
tion of  the  first  closed  haemal  arch,  and  the 
pterygiophore  pattern  under  the  second  dorsal 
fin.  Assuming  a  specimen  is  not  a  variant  in 


any  of  the  three  characters,  it  can  be  identified 
as  follows: 


Character 

Number  precaudal  +  caudal 

vertebrae 
First  closed  haemal  arch 


Pterygiophore  pattern 


Species  separated 

T.  atlanticus  from  T.  thynnus, 

T.  alalunga,  Thunnus  spp. 
T.  atlanticus  +  Thunnus  spp. 

from  T.  thynnus  +  T. 

alalunga 
T.  alalunga  from  T.  thynnus  + 

Thunnus  spp. 


Although  the  vertebrae  are  not  yet  developed 
posteriorly  at  8  mm  SL,  they  nevertheless  can  be 
counted  by  noting  chondrified  neural  and  haemal 
spines  which  are  present  above  and  below  the 
notochord.  Care  should  be  taken  not  to  count 
the  parhypural  bone  as  a  haemal  spine.  The 
parhypural  belongs  to  the  hypural  plate  but 
resembles  a  haemal  spine  during  early  develop- 
ment. The  position  of  the  first  closed  haemal  arch 
is  difficult  to  determine  in  small  specimens  but 
it  can  be  done  with  diligence  and  patience.  The 
pterygiophores  may  not  be  entirely  ossified  at 
8  mm  SL,  but  they  are  present  as  chondrified 
struts.  Varying  the  substage  light,  by  moving  the 
mirror  below  the  microscope,  will  bring  them 
into  view. 

The  vertebral  position  of  the  first  haemal  post- 
zygapophysis  becomes  available  as  a  character  on 
specimens  from  15  to  20  mm  SL.  In  this  size 
range,  only  T.  atlanticus  acquires  the  diagnostic 


584 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION  IN  YOUNG  TUNAS 


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FISHERY  BULLETIN:  VOL.  72.  NO.  2 


PECTORAL     GIRDLE 


LATERAL      LINE 


T.  alalunga 


71  atlantlcus 


specific  ranges  do  not  overlap  except  for  T.  ala- 
lunga with  the  Thunnus  spp.  complex.  Thus, 
the  ceratobranchial  count,  if  available,  should 
take  precedence  over  the  vertebral  count.  The 
first  haemal  postzygapophysis  may  be  very  small 
and  high  magnification  should  be  used  when  view- 
ing this  character. 

All  characters  listed  in  Table  13  are  available 
for  identification  on  specimens  past  21  to  23  mm 
SL.  The  following  features  can  be  used  to 
identify  a  specimen: 


T.  thynnus 


T.  spp. 


Figure  13. — Outline  of  the  lateral  line  for  juveniles  of  the 
Thunnus  species.  Each  pair  of  dashes  in  the  lateral  line 
represents  one  scale. 


count  of  gillrakers  over  the  ceratobranchial.  The 
juveniles  can  be  identified  as  follows: 


Character 

Number  precaudal  +  caudal 

vertebrae 
Ceratobranchial  filled  with 

11-12  rakers 
First  closed  haemal  arch 


Pterygiophore  pattern 

First  haemal  postzygapophysis 


Species  separated 

T.  atlanticus  from  T.  thynnus, 
T.  alalunga,  Thunnus  spp. 


T.  atlanticus  +  Thunnus  spp. 
from  T.  thynnus  +  T.  ala- 
lunga 

T.  alalunga  fromT.  thynnus  + 
Thunnus  spp. 

T.  alalunga  +  T.  atlanticus 
from  T.  thynnus  +  Thunnus 
spp. 


Juveniles  in  this  size  range  are  easier  to  identify 
for  two  reasons.  First,  they  are  further  advanced 
in  development,  they  stain  better,  and  the  charac- 
ters are  more  readily  discernible.  Second,  the 
availability  of  two  additional  characters  permit 
cross-checking  so  that  it  is  possible  to  identify 
"one  character"  variants.  For  example,  a  specimen 
with  18  +  21  vertebrae  and  the  ceratobranchial 
filled  with  12  gillrakers  is  a  vertebral  variant 
of  T.  atlanticus.  Although  gill  rakers  over  the 
ceratobranchial  bone  can  vary  over  a  range. 


Character 

Number  precaudal  +  caudal 
vertebrae 

Gillraker  number  over  cerato- 
branchial 

First  closed  haemal  arch 


Pterygiophore  pattern 

First  haemal  postzygapophysis 

Shape  lateral  line 


Species  separated 

T.  atlanticus  from  T.  thynnus, 
T.  alalunga,  Thunnus  spp. 

All  species  separable  except 
T.  alalunga  from  Thunnus 
spp. 

T.  atlanticus  +  Thunnus  spp. 
from  T.  thynnus  +  T.  ala- 
lunga 

T.  alalunga  fromT.  thynnus  + 
Thunnus  spp. 

T.  alalunga  +  T.  atlanticus 
fromT".  thynnus  +  Thunnus 
spp. 

T.  thynnus  from  T.  alalunga, 
T.  atlanticus,  Thunnus  spp. 


It  is  not  difficult  to  identify  specimens  larger 
than  21  mm  SL.  Sufficient  characters  are  avail- 
able and  bones  are  well  ossified  and  stained.  How- 
ever, variability  should  be  taken  into  account  and 
characters  with  the  least  variability  should  be 
relied  upon  the  most.  The  number  of  gillrakers 
over  the  ceratobranchial  bone  and  the  shape  of 
the  lateral  line  should  take  precedence  over  the 
other  characters.  I  have  never  observed  the  range 
for  the  number  of  ceratobranchial  rakers  in  one 
species  overlap  with  that  of  another,  except  T. 
alalunga  with  Thunnus  spp.,  and  I  have  never 
seen  a  T.  thynnus  with  a  smoothly  curved  lateral 
line. 


ACKNOWLEDGMENTS 

I  express  my  sincere  thanks  to  Frank  J.  Mather 
III  of  the  Woods  Hole  Oceanographic  Institution 
for  providing  the  Mediterranean  specimens;  to  the 
staff  of  the  Florida  Department  of  Natural 
Resources  Marine  Research  Laboratory  in  St. 
Petersburg  and  Donald  P.  de  Sylva  of  the  Rosen- 


586 


POTTHOFF:  OSTEOLOGICAL  DEVELOPMENT  AND  VARIATION   IN  YOUNG  TUNAS 

stiel  School  of  Marine  and  Atmospheric  Science 
for  the  western  Atlantic  specimens;  and  to  Robert 
H.  Gibbs,  Jr.  of  the  Smithsonian  Institution  for 
the  Pacific  specimens.  I  thank  WilUam  J.  Richards 
of  the  National  Marine  Fisheries  Service  (NMFS), 
Southeast  Fisheries  Center,  Miami  Laboratory, 
who  helped  me  through  all  phases  of  research 
and  manuscript  preparation  with  his  valuable 
advice  and  criticism.  I  am  grateful  to  Bruce  B. 
Collette  of  the  NMFS  Systematics  Laboratory  and 
Elbert  H.  Ahlstrom  of  the  NMFS  Southwest 
Fisheries  Center  for  their  critical  review  of  the 
manuscript.  Finally,  I  thank  Grady  W.  Reinert, 
Gabrielle  Ranallo,  and  Claire  R.  Ulanoff  of  the 
NMFS  Southeast  Fisheries  Center  for  preparing 
the  illustrations. 


LITERATURE  CITED 

BuLus,  H.  R.,  Jr.,  and  F.  J.  Mather  III. 

1956.     Tunas  of  the  genus  Thunnus  of  the  northern  Carib- 
bean.    Am.  Mus.  Novit.  1765,  12  p. 
DE  Sylva,  D.  p. 

1955.     The  osteology  and  phylogenetic  relationships  of  the 
blackfin  tuna,  Thunnus  atlanticus  (Lesson).     Bull.  Mar. 
Sci.  Gulf  Caribb.  5:1-41. 
Eaton,  T.  H.,  Jr. 

1945.     Skeletal  supports  of  the  median  fins  of  fishes.     J. 
Morph.  76:193-212. 
Frade,  F. 

1931.  Sur  le  nombre  de  rayons  des  nageoires  et  de  pin- 
nules branchiales  chez  le  thon  rouge  Atlantique.  Bull. 
Soc.  Port.  Sci.  Nat.  11:139-144. 

1932.  Sur  les  caracteres  osteologiques  a  utiliser  pour  la 
determination  des  thonides  de  I'Atlantique  oriental  et 
de  la  Mediterranee.  Rapp.  P.-V.  Reun.  Comm.  Int. 
Explor.  Sci.  Mer  Mediterr.  7:79-90. 

Gibbs,  R.  H.,  Jr.,  and  B.  B.  Collette. 

1967.     Comparative  anatomy  and  systematics  of  the  tunas, 
genus  Thunnus.   U.S.  Fish  Wildl.  Serv.,  Fish.  Bull. 
66:65-130. 
GoDsiL,  H.  C,  AND  R.  D.  Byers. 

1944.     A  systematic  study  of  the  Pacific  tunas.     Calif  Div. 
Fish  Game  Fish  Bull.  60,  131  p. 
Jones,  S. 

1960.     Notes  on  eggs,  larvae  and  juveniles  of  fishes  from 
Indian  waters.  III.  Katsuwonus  pelamis  (Linnaeus)  and 
IV.  Neothunnus  macropterus  (Temminck  and  Schlegel). 
Indian  J.  Fish.  6:360-373. 
JuArez,  M. 

1972.  Las  formas  larvarias  del  Thunnus  atlanticus 
(Larval  forms  of  Thunnus  atlanticus).  Mar  Pesca  78: 
26-29.  (Translated  by  L.  Dupart  and  W.  Klawe,  1972, 
Inter-Am.  Trop.  Tuna  Comm.,  La  Jolla,  Calif.,  5  p.) 

KiSHINOUYE,  K. 

1923.  Contributions  to  the  comparative  study  of  the  so- 
called  scombroid  fishes.  J.  Coll.  Agric.  Imp.  Univ. 
Tokyo  8:293-475. 


Klawe,  W.  L. 

1961.     Young  scombroids  from  the  waters  between  Cape 

Hatteras  and  Bahama  Islands.     Bull.  Mar.  Sci.  Gulf 

Caribb.  11:150-157. 
Klawe,  W.  L.,  and  B.  M.  Shimada. 

1959.  Young  scombrid  fishes  from  the  Gulf  of  Mexico. 
Bull.  Mar.  Sci.  Gulf  Caribb.  9:100-115. 

Kramer,  D. 

1960.  Development  of  eggs  and  larvae  of  Pacific  mackerel 
and  distribution  and  abundance  of  larvae  1952-56.  U.S. 
Fish  Wildl.  Serv.,  Fish.  Bull.  60:393-438. 

Marchal,  E. 

1963a.  Description  des  stades  post-larvaires  et  juveniles 
de  Neothunnus  albacora  (Lowe)  de  I'Atlantique  tropico- 
oriental.  FAO  (Food  Agric.  Organ.  U.N.)  Fish.  Rep. 
6:1797-1811. 
1963b.  Description  des  stades  post-larvaires  et  juveniles 
de  quatre  especes  de  Scombridae  de  I'Atlantique  tropico- 
oriental.  Mem.  Inst.  Fr.  Afr,  Noire  68:201-240. 
Matsui,  T. 

1967.     Review  of  the  mackerel  generaScomfter  andRastrel- 
liger  with  description  of  a  new  species  of  Rastrelliger. 
Copeia  1967:71-83. 
Matsumoto,  W.  M. 

1961.     Collection  and  descriptions  of  juvenile  tunas  from 

the  central  Pacific.     Deep-Sea  Res.  8:279-286. 
1963.     Unique  shape  of  the  first  elongate  haemal  spine  of 
albacore,  Thunnus  alalunga  (Bonnaterre).     Copeia  1963: 
460-462. 
Mead,  G.  W. 

1951.     Postlarval  A^eofAunnus  macropterus,  Auxis  thazard, 
and  Euthynnus  lineatus  from  the  Pacific  coast  of  Cen- 
tral America.     U.S.  Fish  Wildl.  Serv.,  Fish.  Bull.  52: 
121-127. 
Nakamura,  I. 

1965.  Relationships  of  fishes  referable  to  the  subfamily 
Thunninae  on  the  basis  of  the  axial  skeleton.  Bull. 
Misaki  Mar.  Biol.  Inst.  8:7-38. 

Nakamura,  I.,  and  S.  Kikawa. 

1966.  Infra-central  grooves  of  tunas  with  special  reference 
to  the  identification  of  young  tunas  found  in  the  stomachs 
of  large  predators.  Rep.  Nankai  Reg.  Fish.  Res.  Lab. 
23:55-66. 

Padoa,  E. 

1956.  Monografia:  Uova,  larve  e  stadi  giovanili  di  Teleos- 
tei  (Eggs,  larvae  and  juvenile  stages  of  the  Scombri- 
formes  (in  part)  of  the  Gulf  of  Naples).  [In  Ital.] 
Fauna  Flora  Golfo  Napoli  38:471-521.  [Translated  by  J.  P. 
Wise  and  G.  M.  Ranallo,  1967,  Transl.  No.  12  of  the 
Trop.  Atl.  Biol.  Lab.,  49  p.;  avail,  at  Bur.  Commer. 
Fish,  (now  Natl.  Mar.  Fish.  Serv.),  Miami,  Fla.] 

POTTHOFF,  T.,  and  W.  J.  RiCHARDS. 

1970.    Juvenile  bluefin  tuna,  Thunnus  thynnus  (Linnaeus), 
and  other  scombrids  taken  by  terns  in  the  Dry  Tortugas, 
Florida.     Bull.  Mar.  Sci.  20:389-413. 
Richards,  W.  J.,  and  T.  Potthoff. 

In  press.  Analysis  of  taxonomic  characters  of  young  scom- 
brid fishes,  genus  Thunnus.  In  J.  H.  S.  Blaxter  (editor). 
The  Early  Life  History  of  Fish.  Proceedings  of  a  Sym- 
posium held  in  Scotland  in  1973.  Springer,  Heidelberg. 
RiVAS,  L.  R. 

1951.  A  preliminary  review  of  the  western  North 
Atlantic  fishes  of  the  family  Scombridae.  Bull.  Mar.  Sci. 
Gulf  Caribb.  1:209-230. 


587 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


SCACCINI,  A. 

1961.  Les  premiers  stades  juveniles  du  thon  rouge 
{Thunnus  thynnus).  Rapp.  P.-V.  Reun.  Comm.  Int. 
Explor.  Sci.  Mer  Mediterr.  16:351-352. 

SCHAEFER,  M.  B.,  AND  J.  C.  MaRR. 

1948.     Spawning  of  yellowfin  tuna  (Neothunnus  macrop- 
terus)  and  skipjack  (Katsuwonus  pelamis)  in  the  Pacific 
Ocean  ofFCentral  America,  with  descriptions  of  juveniles. 
U.S.  Fish  Wildl.  Serv.,  Fish.  Bull.  51:187-196. 
Sella,  M. 

1924.  Caratteri  differenziali  dei  giovani  stadi  di  Orcynus 
thunnus  Ltkn.,  O.  alalonga  B.\&so,Auxis  bisus  Bp.  Atti 
Accad.  Naz.  Lincei  Rene.  33  (3)  (l):300-305.  (Engl, 
transl.  by  F.  J.  S.  Lara;  9  p.,  typescript  in  files  of  Natl. 
Mar.  Fish.  Serv.,  n.d.). 

Taylor,  W.  R. 

1967.  An  enzyme  method  of  clearing  and  staining  small 
vertebrates.     Proc.  U.S.  Natl.  Mas.  122(3596)  17  p. 

Ueyanagi,  S. 

1967.     On  the  spawning  grounds  of  tunas  (margurorui  no 
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60:15-20.     (Engl,  transl.  by  Fish.  Res.  Board  Can., 
Biol.  Stn.,  St.  Andrews,  N.B.,  Transl.  Ser.  1100,  14  p.) 
Wade,  C.  B. 

1950.  Juvenile  forms  of  Neothunnus  macropterus,  Katsu- 
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seas.     U.S.  Fish  Wildl.  Serv.,  Fish.  Bull.  51:395-404. 


1951.     Larvae  of  tuna  and  tuna-like  fishes  from  Philippine 
waters.     U.S.  Fish  Wildl.  Serv.,  Fish.  Bull.  51:445-485. 
Watson,  M.  E. 

1964.  Tunas  (genus  Thunnus)  of  the  western  North 
Atlantic.  Part  L  Key  to  the  species  of  Thunnus  based 
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Watson,  M.  E.,  and  F.  J.  Mather  III. 

1961.  Species  identification  of  juvenile  tunas  (genus 
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Serv.,  Spec.  Sci.  Rep.  Fish.  415. 

Yabe,  H.,  S.  Ueyanagi,  S.  Kikawa,  and  H.  Watanabe. 

1958.  Young  tuna  found  in  the  stomach  contents.  Rep. 
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Yabe,  H.,  S.  Ueyanagi,  and  H.  Watanabe. 

1966.  Studies  on  the  early  life  history  of  bluefin  tuna 
Thunnus  thynnus  and  on  the  larva  of  the  southern 
bluefin  tuna  T.  maccoyii.  Rep.  Nankai  Reg.  Fish.  Res. 
Lab.  23:95-129. 

YOSHIDA,  H.  O. 

1965.  New  Pacific  records  of  juvenile  albacore,  Thunnus 
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Sci.  19:442-450. 


i 


588 


A  NEW  MODEL  OF  OCEAN  MIGRATIONS  OF 
BRISTOL  BAY  SOCKEYE  SALMON 

Robert  R.  French  and  Richard  G.  Bakkala' 


ABSTRACT 

A  model  is  presented  that  describes  the  ocean  migrations  of  Bristol  Bay  sockeye  salmon  from 
the  time  the  fish  leave  the  estuary  until  they  return  as  adults.  Bristol  Bay  sockeye  salmon 
inhabit  extensive  areas  of  the  ocean  during  various  stages  of  their  life  at  sea,  ranging  across 
most  of  the  North  Pacific  Ocean  from  about  long.  140°W  to  near  long.  167'E  and  from  near 
lat.  46'N  to  lat.  58^N  in  the  central  Bering  Sea.  Initially,  their  migration  route  takes  the  young 
juveniles  from  the  eastern  Bering  Sea  through  the  central  and  eastern  Aleutian  Islands  passes 
to  south  of  lat.  50^N  where  in  late  winter  they  become  broadly  distributed  across  the  North 
Pacific  Ocean.  In  June  the  immature  fish  start  a  northward  movement  and  in  summer  occupy 
waters  from  lat.  50'N  to  the  Aleutian  Islands  and  over  an  east-west  area  from  long.  160^W  to 
170'E;  part  of  the  population  moves  north  into  the  Bering  Sea.  The  following  winter  the  sockeye 
separate  into  immature  and  maturing  components.  Those  that  will  mature  remain  in  waters 
north  of  lat.  SCN  from  whence  they  will  migrate  back  to  Bristol  Bay  in  the  spring  with  the 
major  proportion  entering  the  Bering  Sea  through  passes  east  of  long.  175°W.  The  immature  fish 
that  will  remain  at  sea  another  year  move  south  of  lat.  50°N  in  the  winter  and  early  spring, 
then  essentially  repeat  the  migration  they  had  made  the  previous  summer.  These  fish  as  maturing 
fish  the  following  winter  and  spring  follow  the  same  migration  route  as  the  earlier  maturing  group. 
No  direct  relationship  was  found  between  the  distribution  and  migration  of  the  sockeye  and 
defined  oceanographic  features  of  the  Subarctic  Region  of  the  North  Pacific  Ocean. 


A  model  of  the  complete  ocean  migrations  of  sock- 
eye salmon,  Oncorhynchus  nerka,  from  Bristol 
Bay,  Alaska,  was  originally  developed  by  Royce, 
Smith,  and  Hartt  (1968).  Their  model  suggested 
that  Bristol  Bay  sockeye  during  their  life  at  sea 
make  two  or  three  circuits  of  an  elongated  east- 
west  course  extending  from  about  long.  165°E  to 
140°W  in  the  North  Pacific  Ocean  and  Bering  Sea. 
These  migrations  were  thought  to  be  associated 
with  major  currents  of  this  region — the  Alaskan 
Stream  and  Subarctic  Current. 

Since  formulation  of  the  model  by  Royce  et  al. 
(1968),  Bakkala  (1971)  studied  the  distribution 
and  abundance  of  immature  sockeye  salmon  in 
relation  to  ocean  currents  and  other  features  of 
the  Subarctic  Region  and  suggested  certain  refine- 
ments to  the  earlier  model.  New  information 
available  through  continued  offshore  studies  com- 
bined with  a  review  of  existing  tagging  data  has 
led  us  to  propose  a  new  model  of  migration  of 


'Northwest  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  2725  Montlake  Boulevard  East,  Seattle,  WA 
98112. 


Manuscript  accepted  October  1973. 
FISHERY  BULLETIN;  VOL.  72,  NO.  2,  1974. 


Bristol  Bay  sockeye  to  supplement  that  proposed 
by  Royce  et  al.  (1968). 

Studies  of  the  oceanic  distribution  of  Pacific 
salmon  have  shown  sockeye  salmon  from  Bristol 
Bay,  Alaska,  to  be  widely  distributed  in  the 
North  Pacific  Ocean  and  Bering  Sea.  Tagging 
experiments  have  shown  that  Bristol  Bay  sockeye 
salmon  range  from  about  long.  140°W,  approxi- 
mately 111  km  from  the  coast  of  southeastern 
Alaska,  to  near  long.  167°E,  approximately  463. 
km  from  the  coast  of  Kamchatka,  an  east-west 
distance  of  about  3,700  km.  From  south  to  north, 
Bristol  Bay  sockeye  have  been  identified  near 
lat.  46°N  in  the  northeastern  Pacific  Ocean  to  near 
lat.  58°N  in  the  central  Bering  Sea.  Notwith- 
standing their  broad  distribution  and  dynamic 
movements,  the  basic  distribution  and  seasonal 
migrations  of  the  sockeye  are  known. 

In  this  report  we  examine  data  from  tagging 
experiments  and  salmon  catches  in  relation  to 
environmental  features  to  describe  the  distribu- 
tion and  migration  of  Bristol  Bay  sockeye  salmon 
from  the  time  they  leave  the  estuary  until  they 
return  as  maturing  fish.  Following  these  discus- 
sions, a  model  of  migrations  for  Bristol  Bay 
sockeye  salmon  is  presented. 


589 


A 


{ 


LIMITS  OF  AREA  OCCUPIED   BY  MATURING  WESTERN  ALASKAN   SOCKEYE     AS  DETERMINED  BY  COASTAL  TAG    REIURNS   AND  BY  PARASITES 

POSSIBLE    EXTENSION    OF   AREA  OCCUPIED  BY   MATURING   WESTERN  ALASKAN    SOCKEYE    AS  DETERMINED    BY  MORPHOLOGICAL  AND    SCALE    STUDIES 

LIMITS   OF  AREA  OCCUPIED  BY  MATURING    KAMCHATKAN    SOCKEYE    AS    DETERMINED  BY  COASTAL   TAG    RETURNS  AND  BY  PARASITES 

POSSIBLE    EXTENSION    OF  AREA   OCCUPIED  DY   MATURING    KAMCHATKAN  SOCKEYE    AS  DETERMINED  DY    HIGH  SEAS  TAG  RETURNS  AND   MORPHOLOGICAL  AND  SCALE  STUD)! 

AREA  OF    OVERLAP 


V 


LIMITS  OF  AREA  OCCUPIED  BY  IMMATURE   WESTERN   ALASKAN  SOCKEYE  AS   DETERMINED  BY  COASTAL  TAG   RETURNS  AND  BY  PARASITES 
LIMITS  OF  AREA  OCCUPIED  BY  IMMATURE    KAMCHATKAN    SOCKEYE    AS    DETERMINED  BY  COASTAL  TAG    RETURNS    AND    BY  PARASITES 
POSSIBLE    EXTENSION    OF    AREA  OCCUPIED    BY   IMMATURE    KAMCHATKAN    SOCKEYE    AS  DETERMINED    BY  OTHER   INDIRECT   MEANS    ISEE    TEXT) 
AREA  OF  OVERLAP 


i5)(r 


lelo- 


Jfc 


m^ 


'^. 


^^ 


-^■^^v- 


FiGURE  1. — Range  and  area  of  overlap  for  maturing  (a)  and  immature  (b)  sockeye  salmon  from  Asia  and  North  America 

(Figures  74  and  76  of  Margolis  et  al.,  1966). 


REVIEW  OF  DISTRIBUTION  OF 

BRISTOL  BAY  SOCKEYE  SALMON 

AS  DETERMINED  BY 

COASTAL  TAG  RETURNS 

Numerous  researchers,  through  tagging  experi- 
ments, morphometric  studies,  scale  studies,  and 
analysis  of  parasites,  have  defined  certain  aspects 
of  the  distribution  of  Bristol  Bay  sockeye  salmon 
(defined  as  those  sockeye  originating  in  the  east- 
ern Bering  Sea  from  Unimak  Island  northward 
to  the  Kuskokwim  River).  From  a  comprehensive 
review  and  updating  of  these  studies,  Margolis 
et  al.  (1966)  defined  the  limits  of  oceanic  dis- 
tribution of  maturing  and  immature  western 
Alaska  sockeye  salmon  (Figure  1).  Examination  of 


recent  summaries  of  tag  returns^  for  1956-69 
(Figures  2  and  3)  corroborates  the  general  distri- 
bution pattern  of  sockeye  salmon  stocks  from 
western  Alaska,  from  other  North  American 
regions,  and  from  Asia  as  described  by  Margolis 
et  al.  The  tag  returns  show,  however,  an  extension 
in  the  range  of  western  Alaska  immature  sockeye 
salmon  to  west  of  long.  170°E  (see  Figure  3). 
Maturing  Bristol  Bay  sockeye  salmon,  which 
had  been  tagged  at  sea  primarily  during  April, 
May,  and  June,  are  shown  to  be  distributed 


^Aro,  K.  v.,  J.  Arthur  Thomson,  and  Dorothy  P.  Giovando. 
1971.  Summaries  of  salmon  tag  recoveries  in  North  Pacific 
coastal  and  high  seas  areas  from  salmon  tagging  in  INPFC 
statistical  Eireas  in  the  North  Pacific  Ocean  by  Canada,  Japan, 
and  the  United  States,  1956  to  1969.  Fish.  Res.  Board  Can., 
Manuscr.  Rep.  1148,  641  p.  (Unpubl.) 


590 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


..'■'•■■ -Cv 


;38-, 


■   ,    29      ;28      ;-_    .  .  „.. 


Total  Number 
of    Returns 


Proportion  of  Returns  from: 

[48(553 — W****"""  Alaska 

Other    N   American 

areas 

Asia 


T 


Figure  2. — Tagging  locations  (2°  x  5°  areas)  for  maturing  sockeye  salmon  recovered  in  western  Alaska,  other  North  American 
areas,  and  Asia,  1956-69.  The  proportion  of  returns  to  these  major  land  areas  from  each  2°  x  5°  area  of  the  ocean  are  shown 
diagrammatically  by  having  each  2°  x  5°  rectangle  represent  100%.  Small  percentage  returns  could  not  be  accurately 
illustrated,  and  in  some  instances  percentages  are  exaggerated  to  show  presence. 


across  most  of  the  North  Pacific  Ocean  and  in  the 
central  and  eastern  Bering  Sea  south  of  lat. 
60°N  (Figure  2). 

These  tagging  data  also  illustrate  areas  where 
Bristol  Bay  sockeye  predominate  as  well  as  areas 
where  they  overlap  with  other  stocks.  Although 
tagging  effort  varied  between  some  years  and 
was  far  from  uniform  in  various  parts  of  the 
ocean,  the  return  showed  Bristol  Bay  sockeye 
predominating  in  the  spring  from  about  long. 
155°W  to  170°E.  Their  main  area  of  overlap  with 
other  North  American  stocks  was  from  about  long. 
140°  to  160°W.  With  Asian  sockeye,  their  main 
area  of  overlap  was  between  long.  165°  and  175°E. 

Tag  returns  from  immature  sockeye  salmon 
tagged  primarily  in  the  summer  (late  June 
through  August)  have  been  too  few  to  portray 
their  oceanic  distribution  in  detail  (Figure  3). 
The  small  numbers  of  tag  returns  are  due  to  the 
poor  survival  associated  with  tagging  small  im- 
mature fish  and  the  lack  of  widespread  tagging 
throughout  the  oceanic  areas  inhabited  by  the 
fish.  For  limited  data,  the  results  show  overlap 
of  Bristol  Bay  sockeye  with  other  North  American 


stocks  between  about  long.  145°W  and  175°E. 
Bristol  Bay  immatures  predominate  south  of  the 
Aleutian  Islands.  Total  returns  of  tagged  fish  for 
all  years  indicate  that  in  the  area  immediately 
south  of  Adak  Island,  approximately  10%  of  the 
tag  returns  were  from  other  North  American 
areas.  Very  few  tag  returns  were  reported  from 
Asian  streams.  The  returns  suggest  some  overlap 
of  immature  fish  of  Asian  origin  with  Bristol 
Bay  fish  south  of  the  central  and  western  Aleu- 
tian Islands,  but  they  do  not  indicate  areas  where 
Asian  sockeye  predominate. 

Recent  studies  by  the  National  Marine  Fisheries 
Service  (NMFS)  have  been  directed  toward  under- 
standing the  influence  of  the  oceanic  environ- 
ment on  distribution  and  migration  of  salmon  at 
sea.  These  studies,  primarily  concerned  with 
Bristol  Bay  sockeye  salmon,  should  disclose  the 
causes  of  change  in  distribution  and  movements 
of  the  Bristol  Bay  stock.  They  should  also  lead 
to  improved  forecasts  of  run  sizes  and  predictions 
of  the  effect  of  the  Japanese  high-seas  fishery  on 
salmon  stocks  of  the  United  States.  Results  of 
these  investigations  and  conclusions  drawn  from 


591 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


coastal  tag  returns  have  provided  information  for 
describing  the  migrations  of  sockeye  salmon 
through  most  of  their  life  at  sea. 

DISTRIBUTION  AND  MIGRATION 

OF  BRISTOL  BAY  SOCKEYE 

SALMON  INFERRED  FROM 

HIGH-SEAS  CATCHES 

The  apparent  relative  abundance  of  sockeye 
salmon  taken  in  gill  nets,  purse  seines,  and  long- 
lines  from  synoptic  sampling  over  periods  of  time 
and  large  areas  of  the  ocean  furnish  much 
information  on  movements  and  distribution  offish. 
This  information  coupled  with  the  age  composi- 
tion of  the  catches  and  tagging  data  provides 
important  links  for  formulating  migration  pat- 
terns of  the  stock. 

First  Year  at  Sea 

Juveniles  Age  .0  (July-December)^ 

Juvenile  salmon,  age  .0  fish  after  leaving  the 
rivers  of  Bristol  Bay,  move  southwest  along  the 
north  side  of  the  Alaska  Peninsula  throughout 
summer,  but  substantial  numbers  remain  in  the 
eastern  Bering  Sea  until  sometime  after  the 
middle  of  September  (Hartt  et  al.,  1967;  Hartt, 
Dell,  and  Smith,  1969;  Straty  and  Jaenicke, 
1969'*).  Sampling  with  purse  seines  indicates  that 
the  juveniles  do  not  make  a  rapid  directional 
migration  at  this  stage  of  life  but  disperse  slowly 
toward  the  southwest  as  they  move  back  and 
forth  with  the  tides.  By  mid-September  the  juve- 
niles are  still  present  in  large  numbers  east  of 
long.  165°W  extending  at  least  167  km  offshore. 
The  length  of  time  that  the  juveniles  spend  in 
the  eastern  Bering  Sea  and  their  restricted  dis- 
tribution are  probably  due  to  the  local  abundance 
and  availability  of  food.  During  this  period  of 
late  summer,  growth  is  rapid  as  the  fish,  averag- 
ing 17  to  18  cm  long,  feed  on  the  abundant 
supply  of  zooplankton  and  larval  fish  (Hartt  et  al., 
1967). 

The  migration  routes  of  the  juvenile  sockeye 


^Age  designation  used  are  those  suggested  by  Koo  (1962). 
The  numeral  preceding  the  dot  indicates  number  of  winters 
in  fresh  water;  the  numeral  following  the  dot  indicates  number 
of  winters  at  sea. 

■•Straty,  R.  R.,  and  H.  W.  Jaenicke.  1969.  Estuarine  ecology 
of  sockeye  salmon  in  Bristol  Bay.  Bur.  Commer.  Fish.  Biol. 
Lab.,  Auke  Bay,  Alaska.  (Unpubl.  manuscr.) 


as  they  leave  the  eastern  Bering  Sea  is  unknown 
due  to  lack  of  sampling  in  fall  and  early  winter. 

Immatures  Age  .1  (January-June) 

The  small  sockeye  were  next  taken  as  age  .1 
fish  (an  additional  year  is  added  on  1  January 
regardless  of  state  of  annulus  formation)  in  winter 
catches  in  the  North  Pacific  Ocean  at  various 
locations;  a  few  specimens  have  been  taken  in 
the  south-central  Bering  Sea.  Bakkala  (1971) 
has  summarized  winter  gill-net  catches  of  age  .1 
fish  for  1962-67  by  research  vessels  of  the  North- 
west Fisheries  Center,  NMFS.  To  his  data  we 
have  added  catches  made  in  the  winters  of  1969 
and  1970  (Figure  4).^  These  data  illustrate  that 
main  catches  of  age  .1  sockeye  were  made  near 
lat.  46°30'N  in  the  central  North  Pacific  and 
between  lat.  48°  and  51°N  in  the  northeastern 
Pacific  from  long.  165°  to  155°W.  A  good  catch 
was  also  made  near  lat.  50°N  at  175°  and  170°W. 
Relatively  small  numbers  offish  were  taken  in 
the  Bering  Sea  during  sampling  in  late  January 
and  early  February  1963  and  near  long.  170°E 
in  February  1965.  (Stations  shown  on  long.  170°E 
represent  stations  fished  as  far  west  as  long. 
167°18'E.) 

There  were  no  tagging  data  to  indicate  area  of 
origin  of  the  age  .1  fish  taken  in  the  winter.  We 
can  surmise  their  origin,  however,  on  the  basis 
of  the  freshwater  age  composition  of  catches,  at 
least  for  some  years.  The  largest  catches  of  age  .1 
fish  occurred  in  1965  (10  and  16  March)  near 
lat.  46°30'N  between  long.  175°E  and  180°.  CPUE 
(see  footnote  5  for  definition  of  catch  per  unit 
effort)  of  16  and  13  were  the  largest  made  during 
the  years  of  winter  sampling.  Most  of  these  fish 
(78%  of  the  catch)  were  age  2.1  (a  salmon  of  age 
2.1  has  spent  two  winters  in  fresh  water  after 
hatching  and  one  winter  in  the  ocean).  Later 
in  the  year  in  the  samples  taken  south  of  Adak 
Island  (where  tag  returns  indicate  that  Bristol 
Bay  fish  predominate) ,  the  2 . 1  age-group  made  up 
approximately  75%  of  the  catch  of  age  .1  fish. 
One  year  later  this  same  group,  now  age  2.2  fish, 
made  up  about  70%  of  the  mature  age  .2  fish 
in  the  1966  run  to  Bristol  Bay.  That  same  year 
the  age  composition  of  the  mature  Asian  sockeye 


sin  this  and  other  figures  the  catch  per  unit  of  effort 
(CPUE)  of  gill  nets  is  the  value  of  the  sums  of  the  average 
catch  per  shackle  of  each  mesh  size.  A  shackle  is  approxi- 
mately 91.5  m  long. 


592 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


Figure  3. — Tagging  locations  (2°  x  5°  areas)  for  immature  sockeye  salmon  recovered  in  western  Alaska,  other  North  American  areas, 
and  Asia,  1956-69.  The  proportion  of  returns  to  these  major  land  areas  from  each  2°  x  5°  area  of  the  ocean  are  shown  diagrammatically 
by  having  each  2°  x  5°  rectangle  represent  100%  .  Small  percentage  returns  could  not  be  accurately  illustrated,  and  in  some  instances 
percentages  are  exaggerated  to  show  presence. 


I60°E 


170° 


leo" 


ITO'W 


160° 


150° 


140° 


60*  N 


60°N 


Figure  4.— Distribution  of  age  .1  sockeye  salmon  in  February  and  March    1962-70,  with  the  exception  of  1964,  1966,  and  1968. 

593 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Table  1.— Proportion  of  age  2.1  sockeye  salmon  in  samples 
from  the  northeastern  Pacific  and  south  of  Adak  Island  in  1962, 
1967,  and  1969  and  of  age  2.2  sockeye  in  the  following  year's 
Bristol  Bay  run. 


Area  and  time  of  sampling 

Year 

Northeastern  Pacific 
winter  (aqe  2.1) 

Adak  Island 
summer 
(age  2.1) 

Bristol  Bay  in 
following  year 

155=W 

162  W         165°W 

(age  2.2) 

35 
53 
60 

Percent 

34               — 
—               83 

1962 
1967 
1969 

53 
43 
79 

50 

37 
90 

was  estimated  to  be  about  24%  age  2.2  fish  (Fredin 
and  Worlund).*'  On  the  basis  of  age  composition, 
therefore,  we  can  surmise  that  most  of  the  small 
fish  taken  near  lat.  46°30'N  in  the  central  Aleu- 
tian area  were  of  Bristol  Bay  origin  and  that  this 
is  one  area  occupied  by  Bristol  Bay  fish  in  winter. 
In  the  northeastern  Pacific  Ocean,  good  catches 
of  age  .1  sockeye  salmon  were  made  in  the  winters 
of  1962,  1967,  and  1969.  The  proportions  of  age 
2.1  fish  in  these  catches  are  shown  in  Table  1. 
Also  shown  are  the  proportions  of  age  2.1  fish 
in  the  catches  made  the  following  summer  south 
of  Adak  Island  (where  Bristol  Bay  fish  tradi- 
tionally predominate  as  shown  by  tag  returns) 
and  the  proportions  of  age  2.2  fish  in  the  following 
year's  run  to  Bristol  Bay. 

Catches  in  1969  probably  best  illustrate  the 
presence  of  Bristol  Bay  fish  in  the  area  during  the 
winter  season.  Progeny  of  the  record-size  spawn- 
ing run  to  Bristol  Bay  in  1965  were  expected 
to  be  abundant  and  predominate  among  samples 
of  immature  fish  at  sea  in  1969  and  as  age  2.2 
maturing  fish  in  returns  to  Bristol  Bay  in  1970. 
The  1969  winter  sampling  along  ISS^'W  resulted 
in  relatively  large  catches  of  age  .  1  sockeye  salmon 
in  January  which  were  composed  of  approximately 
60%  age  2.1  fish  (73%  in  areas  of  largest  catches 
near  lat.  49'  and  50'N)  as  would  be  expected 
if  they  originated  from  Bristol  Bay.  The  few  age  .1 
sockeye  taken  in  more  northern  waters  along  this 
longitude  (near  lat.  52'  to  55°N)  were  mainly  age 
1.1  fish  (82% );  they  possibly  originated  from  North 
American  coastal  areas  eastward  of  Bristol  Bay. 
The  1969  samples  of  age  .1  sockeye  salmon  taken 


sPredin,  R.  A.,  and  D.  Worlund.  Catches  of  sockeye  salmon 
of  Bristol  Bay  origin  by  the  Japanese  mothership  salmon 
fishery,  1956-70.  Natl.  Oceanic  Atmos.  Admin.,  Natl.  Mar. 
Fish.  Serv.,  Northwest  Fish.  Cent.,  Seattle,  Wash.  (Unpubl. 


manuscr.) 


along  long.  165°W  had  an  even  higher  proportion 
of  age  2.1  fish  (83%)  than  samples  taken  along 
long.  155''W  and  compared  more  closely  to  the  age 
composition  of  samples  south  of  Adak  Island  in 
the  summer  (79%  age  2.1)  and  to  the  age  compo- 
sition of  maturing  fish  returning  to  Bristol  Bay 
rivers  in  1970  (90%  age  2.2). 

The  1967  winter  sampling  produced  catches  of 
age  .1  sockeye  salmon  along  long.  162'W  which 
were  also  similar  in  age  composition  (34%  age 
2.1  fish)  to  that  of  maturing  fish  returning  to 
Bristol  Bay  in  1968  (37%  age  2.2).  Sampling  along 
long.  155'W  in  1967  showed  a  somewhat  dif- 
ferent proportion  of  age  2.1  fish  (53%)  from  that 
along  long.  162'W.  In  1962  the  proportion  of 
age  2.1  fish  along  long.  155'W  also  differed 
substantially  from  that  of  maturing  fish  in  Bristol 
Bay  in  1963  (35%  age  2.1  along  long.  155° W  in 
winter  1962  and  50%  2.2  fish  in  Bristol  Bay 
in  1963). 

From  the  above  relations,  we  surmise  that 
sockeye  salmon  originating  from  Bristol  Bay 
reach  the  northeastern  Pacific  Ocean  by  January 
and  February  of  their  first  year  at  sea.  It  appears 
from  age  comparisons  that  they  probably  pre- 
dominate eastward  to  about  long.  160'W  and 
possibly  to  long.  155'W  in  years  of  high  abun- 
dance such  as  in  1969.  Their  range  may  extend 
even  farther  to  the  east.  Catch  data  thus  demon- 
strate that  Bristol  Bay  sockeye  become  widely 
distributed  across  the  North  Pacific  Ocean  in  their 
first  winter  at  sea  and  probably  extend  from  near 
long.  175'E  to  at  least  155"W. 

Catch  data  also  indicated  possible  routes  used 
by  the  young  fish  to  move  from  the  Bering  Sea 
into  the  North  Pacific  Ocean.  Sampling  near 
long.  170°E  in  the  winter  of  1965  resulted  in  a 
catch  of  a  single  age  .1  sockeye  salmon  whereas, 
as  previously  shown,  large  catches  were  made 
between  long.  175'E  and  180".  The  lack  of  age 
.1  fish  along  long.  170'E  and  the  evidence  from 
age  composition  that  fish  from  175'E  to  180°  were 
of  Bristol  Bay  origin  suggest  that  the  waters 
near  long.  170'E  may  represent  an  area  separat- 
ing Asian  and  Bristol  Bay  sockeye  in  winter.  Most 
Asian  sockeye  salmon  are  assumed  to  be  located 
west  of  long.  170°E.  Inasmuch  as  catches  of  age  .1 
fish  were  made  in  the  central  North  Pacific 
Ocean  from  the  Aleutian  Islands  to  near  lat.  45'N, 
it  is  likely  that  one  route  of  the  young  fish 
from  the  Bering  Sea  is  through  central  Aleutian 
Islands  passes.  In  sampling  on  long.  165°,  160°, 
and  155° W,  we  caught  few  age    .1  sockeye  north 


594 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


of  about  lat.  51^N  compared  to  catches  south  of 
this  latitude.  It  appears,  therefore,  that  the  young 
salmon  migrate  through  passes  between  long. 
169°W  and  179^E  (the  area  bordered  by  Umnak 
Island  on  the  east  and  Amchitka  Island  on  the 
west)  and  then  move  eastward.  A  possible  path- 
way from  the  Bering  Sea  to  the  North  Pacific  may 
be  Amchitka  Pass  where  a  branch  of  the  Alaskan 
Stream  in  September  flows  northward  into  the 
Bering  Sea  (Favorite  and  Ingraham,  1972). 

Depending  on  routes  followed,  the  migration 
from  the  eastern  Bering  Sea  to  the  central  North 
Pacific  near  lat.  46''N  or  south  of  the  Alaska 
Peninsula  between  lat.  48^  and  Sl'^N  would 
require  migrations  of  from  about  700  to  1,000 
miles  (1,300-1,850  km)  and  travel  rates  of  at 
least  8  to  10  miles  (14.8-18.5  km)  per  day.  This 
rate  is  entirely  reasonable  for  it  has  been  esti- 
mated that  juvenile  salmon  travel  about  10  miles 
(18.5  km)  per  day  in  the  Gulf  of  Alaska  (Royce 
et  al.,  1968). 

Salmon  research  cruises  have  also  included 
oceanographic  studies  which  have  defined  major 
oceanographic  features  of  the  Subarctic  North 
Pacific  (McAlister  et  al.,  1970).  These  are  perma- 
nent features  of  the  Subarctic  Region  and  are 
defined  by  surface  and  subsurface  characteristics 
(generally  between  100  and  400  m).  Salmon 
catches  have  been  related  to  these  features  in 
an  attempt  to  determine  their  influence  on  distri- 


bution and  movements  of  salmon.  Bakkala  (1971) 
related  winter  catches  of  age  .1  sockeye  salmon 
in  1962,  1963,  1965,  and  1967  to  the  major  water 
masses  and  indicated  that  the  salmon  were  usu- 
ally associated  with  the  Oyashio  Extension  Area 
(Figure  5). 

Catches  in  winter  1969  and  1970,  however, 
show  that  the  age  .1  fish  were  not  always 
associated  with  this  water.  The  eastward-moving 
water  between  the  Ridge  and  Transition  Areas 
was  previously  separated  into  Oyashio  and  Sub- 
arctic Current  Areas,  but  more  recent  termi- 
nology combines  the  two  areas  into  a  single 
feature  called  the  Western  Subarctic  Intrusion 
(Favorite,  Ingraham,  and  Fisk,  1972).  In  Figure  6 
are  shown  four  years  of  winter  catch  data  and 
associated  oceanic  features  in  the  northeastern 
Pacific.  In  1962  and  1967,  age  .1  fish  were 
associated  with  the  Western  Subarctic  Intrusion. 
In  1969  and  1970,  this  water  mass  shifted 
northward  (in  1970  it  formed  only  a  relatively 
narrow  tongue  stretching  east  of  long.  160'' W)  but 
was  not  accompanied  by  a  corresponding  shift  in 
distribution  of  the  age  .1  sockeye  salmon.  These 
fish  remained  at  much  the  same  latitudes  as  in 
the  earlier  years,  and  their  winter  distribution 
was  not  affected  by  changes  in  location  of  the 
specific  water  mass.  Because  this  particular  water 
mass  is  defined  by  weak  eastward  flow  and 
temperature  conditions  between  200  and  400  m,  it 


I70°E 


180 


I70°W 


I60°W 


I50°W 


Figure  5. — Distribution  of  age  .1  sockeye  salmon  in  the  winters  of  1962,  1963,  1965,  and  1967 
in  relation  to  oceanographic  features  of  the  Subarctic  Region  of  the  North  Pacific  Ocean. 


595 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


ecN 


SS'N 


SCN 


45°^ 


40°N 


I65°W 


155°  W 


55''W 


Figure  6. — Distribution  of  age  .1  sockeye  salmon  from  winter  catches  in  the  northeastern  Pacific  Ocean  in  relation  to 

defined  oceanographic  features. 


is  possible  that  other  surface  conditions  may  have 
greater  bearing  on  the  distribution  and  move- 
ments of  salmon. 

Examination  of  surface  water  temperatures  in 
relation  to  winter  catches  of  age  .1  sockeye 
(Figure  5)  revealed  that  the  largest  catches 
were  in  the  temperature  range  of  3.5°  to  about 
5.5°C.  The  young  fish  were  not  generally  taken  in 
the  extremes  of  cold  or  warm  surface  waters. 
This  was  clearly  illustrated  in  1965  by  sampling 
near  long.  170°E.  Only  a  single  age  .1  sockeye 
was  taken  between  long.  165^  and  170°E  in  surface 
water  temperatures  of  l.S'^C.  No  fish  were  caught 
at  other  stations  where  surface  temperatures 
ranged  from  l.G''  to  2.4°C.  Areas  in  the  Bering 
Sea,  where  age  .  1  sockeye  were  caught,  generally 
had  surface  temperatures  of  S^C  or  more.  The 
low  surface  water  temperatures  or  the  subsequent 
reduction  in  abundance  of  food  forms  may  cause 
age  .1  sockeye  to  move  out  of  the  Bering  Sea 
and  seek  warmer  water  in  the  North  Pacific 
Ocean.  The  highest  water  temperature  at  which 
age    .1  fish  were  taken  was  G.S'C. 

By  April  and  May  the  age  .1  sockeye  salmon 
reach  their  southernmost  limits  of  distribution 
(Figure  7).  Japanese  research  vessels  caught 
relatively  large  numbers  of  age  .1  sockeye  in 
gill  nets  from  lat.  44°  to  46°N  along  long.  175°W 
illustrating  their  occurrence  south  of  the  central 


Aleutian  Islands.  Samples  taken  in  1969  were 
composed  of  about  70%  age  2.1  fish,  which  was 
comparable  to  the  age  composition  of  age  .1 
sockeye  salmon  taken  south  of  Adak  Island  that 
same  summer  in  purse  seines  by  the  Fisheries 
Research  Institute  (79%  age  2.1). 

A  few  age  .1  sockeye  salmon  were  taken  in 
early  May  1968  by  a  Japanese  research  vessel 
along  long.  175°E  (Figure  7).  The  small  sample 
of  readable  scales  (10  fish)  was  50%  age  2.1, 
40%  age  3.1,  and  10%  age  1.1.  This  was  quite 
unlike  the  age  composition  of  age  .1  sockeye 
caught  south  of  Adak  Island  during  summer  1968 
by  the  Fisheries  Research  Institute  (71%  age  1.1 
fish),  indicating  that  the  immature  sockeye  along 
long.  175°E  in  early  May  might  have  been  Asian 
fish. 

In  the  northeastern  Pacific,  sampling  with  gill 
nets  along  long.  165°W  in  the  spring  of  1969 
resulted  in  small  catches  of  age  .1  fish  as 
far  south  as  lat.  46°N,  the  limit  of  sampling. 
Longline  fishing  surveys  provided  some  data  on 
the  distribution  of  age  .1  sockeye  salmon  to  the 
east  of  long.  165°W. 

During  1964,  1965,  and  1966,  longline  surveys 
by  the  Fisheries  Research  Institute  (FRI)  were 
made  in  the  northeastern  Pacific  including  the 
Gulf  of  Alaska  to  obtain  salmon  for  tagging. 
Although  longline  gear  is  not  considered  as 


596 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


■c-^. 


^.V*""' 


APRIL- MAY 


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■  J 


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'M 


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o 


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cS* 


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■'V'-St',    _| 


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60°N 


50°  N 


^ 


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sfl 


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JUNE 


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SCN 


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1^ 


lecE  i/CE  180'  i70"w  leo'w  iscw  i40''w  lao-w 

Figure  7. — Distribution  of  age  .1  sockeye  salmon  in  the  spring  (data  from  1956-61  and  1966-70). 


I20°W 


efficient  for  age  .1  salmon  as  for  older  age -groups, 
some  age  .1  fish  were  taken,  and  these  catches 
at  least  reflected  the  presence  of  the  immature 
fish.  In  April  and  May  (Figure  8)  age  .1  sock- 
eye  salmon  were  primarily  found  south  of  lat. 
52°  to  about  46°N  and  extended  eastward  to  about 
140°W. 

Most  of  the  age  .1  sockeye  salmon  caught  by 
FRI  during  the  3  yr  of  longline  surveys  were 
taken  in  1964.  These  fish  in  the  area  of  the  largest 
catches  (long.  160°  to  145°W,  south  of  lat.  52°N) 
were  mainly  age  2.1  fish  (75%),  the  age-group 


which  predominated  among  samples  taken  in  the 
central  Aleutian  Islands  area  during  the  summer 
and  which  were  likely  of  Bristol  Bay  origin,  and 
fish  which  made  up  part  of  the  record  run  of 
age  2.2  sockeye  to  Bristol  Bay  in  1965.  Thus  it 
appears  that  Bristol  Bay  stocks  in  April  and  May 
could  extend  eastward  in  the  northeastern  Pacific 
at  least  as  far  as  long.  145°W. 

By  June  the  age  .1  sockeye  have  started  a 
northward  movement  along  a  broad  east-west 
front  and  in  late  June  have  even  reached  the 
central  portions  of  the  Bering  Sea  (Figure  7). 


597 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


-^ 


'''~t> 


^W 


7*^1 

3^ 


;ii 


2 
19 


36 


15 


-i__^       .  APRIL-MAY 


60*N 


W 


2^-. 


50'N 


-ckx 


JUNE 


60''n 


140°  W 


I30*W 


50  N 


I20°W 


Figure  8. — Catches  of  age  .1  sockeye  salmon  in  the  northeastern 
Pacific  (in  numbers  offish)  with  longline  gear,  1964-66.  Data 
are  total  catches  not  weighted  for  effort. 


Longline  sampling  also  indicated  northward 
movement  of  the  age  .1  sockeye  in  the  north- 
eastern Pacific  (Figure  8).  The  sample  of  11  fish 
caught  south  of  Kodiak  Island  near  long.  ISO'^W 
and  lat.  54''N  were  all  taken  in  1964  and  were 
all  age  2.1  fish;  possibly  these  results  indicate 
the  presence  of  Bristol  Bay  immature  stocks  in 
this  area  in  June. 

Second  Year  at  Sea 
Immatures  Age     .1  (July-December) 

In  the  summer,  July-September,  the  distribu- 
tion and  migration  of  immature  sockeye  salmon 
south  of  the  Aleutian  Islands  has  been  well 
documented  (Hartt,  1962,  1966;  French,  1964; 
French,  Craddock,  Bakkala,  Dunn,  and  Thorson, 
1967;  Royce  et  al.,  1968;  Bakkala,  1971;  Roths- 
child et  al.,  1971). 

An  example  of  the  distribution  in  late  July 
is  shown  in  Figure  9.  This  typifies  the  distribu- 
tion of  immature  sockeye  salmon  south  of  the 
Aleutians  in  July  and  August;  the  relative  abun- 


dance of  immatures  is  usually  highest  in  late 
July  or  early  August  and  at  lower  levels  in  early 
July  and  late  August. 

It  has  also  been  demonstrated  that  Bristol  Bay 
stocks  predominate  south  of  the  central  Aleutian 
Islands  by  coastal  tag  returns  1  or  2  yr  later 
and  by  the  relation  between  age  composition  and 
abundance  at  sea  and  by  the  age  composition 
and  abundance  in  the  Bristol  Bay  run  1  yr  later 
(Ossiander,  1965;  Rogers,  1970).  Based  on  the 
limited  tag  returns  from  other  areas  south  of  the 
Aleutians  and  on  the  abundance  of  immatures  in 
these  waters,  we  surmise  that  Bristol  Bay  sockeye 
salmon  predominate  south  of  the  entire  Aleutian 
Islands  chain. 

Considerable  evidence  has  been  produced  which 
indicates  that  migration  of  immature  sockeye 
south  of  the  Aleutian  Islands  in  summer  is 
predominantly  westward  (Hartt,  1962,  1966; 
Larkins,  1964;  Dunn,  1969);  tagging  studies  have 
indicated  that  this  westward  migration  for  some 
fish  is  rapid  and  extensive  (Royce  et  al.,  1968). 
This  evidence  implies  that  the  total  population  of 
Bristol  Bay  immature  sockeye  salmon  shifts  to  the 
west  or  northwest  during  the  summer.  Royce 
et  al.  (1968)  describe  this  migration  as  ".  .  .  they 
migrate  westward  south  of  the  Aleutian 
Islands  in  a  more  or  less  continuous  band,  from 
late  June  through  mid-September."  This  ap- 
parent movement  further  implies  that  the  east- 
ward extent  of  the  Bristol  Bay  population  may 
also  shift  to  the  west  through  the  summer.  We 
have  not  found  evidence,  however,  that  waters 
to  the  south  of  the  eastern  Aleutian  Islands  and 
Alaska  Peninsula  become  devoid  of  Bristol  Bay 
fish  during  the  summer.  Rather,  it  appears  that 
the  Bristol  Bay  population  of  immatures  main- 


^    p 


Figure  9. — Distribution  of  immature  sockeye  salmon,  21-31 
July  (from  Bakkala,  Figure  12,  1971). 


598 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 
180°  ITCW  I60°W 


1 

Ad 

1                    1                    1 
CRUISE    TRACK 

CRUISE    TRACK 

JULY    l-IO 
11-20 

1 
=1 

21-31 

1 

1 

AUGUST    l-IO 

1 

1 

1 1  -  20 

1 

1 

21-31 

=1 
,   ,  ,  ,  1  ,  ,  ,  ,  1  ,  ,  ,  ,  1 

1 

SEPTEMBER  l-IO 

1 

.  I  I  .  1  1  1  1  J  1  1  1  1  1  1 

55°  N 


50°N 


0  50        100        150  0  50         100       150 

RELATIVE      ABUNDANCE 

Figure  10. — Relative  abundance  of  age  .1  sockeye  salmon  along 
cruise  tracks  fished  in  summer  1963. 


tains  a  broad  east-west  distribution  throughout 
the  summer.  Definition  of  the  eastward  limit  of 
this  distribution  is  complicated  by  the  inter- 
mingling of  Bristol  Bay  and  other  North 
American  stocks  of  immature  sockeye  salmon  in 
the  northeastern  Pacific.  Some  evidence  of  the 
eastward  range  of  Bristol  Bay  fish  is  provided  by 
the  age  composition  of  age  .1  fish  sampled 
between  long.  176"  and  158"W  in  1963  and  1966. 
In  1963  systematic  sampling  along  long.  176''  and 
162"W  from  July  to  early  September  (Figure 
10)  showed  that  age  composition  of  age  .1 
fish  was  very  similar  for  the  two  areas  as  shown 
in  Table  2.  Sockeye  salmon  in  the  following  year's 
Bristol  Bay  run  was  composed  of  approximately 
66%  age  1.2  fish  and  34*!^  age  2.2  fish  or  very  simi- 
lar to  the  dominant  ages  of  age  1.1  and  2.1  fish, 
noted  in  each  area  the  previous  summer.  This 
suggests  that  in  the  summer  of  1963,  Bristol 
Bay  sockeye  were  distributed  as  far  east  as  long. 
162''W  throughout  the  summer. 


Table  2. — Freshwater  age  composition  of  age  .1  sockeye  salmon 
from  samples  along  long.  162°W  and  176°W  in  summer  1963. 


Sampling 

Age-group 

area 

0  1 

1  1 

2  1 

3.1 

4.1 

176°W 
162°W 

0.7 

1.3 

65.2 
67.9 

31.9 
27.7 

23 

3.1 

0.03 
0 

The  age  composition  for  the  three  lines  fished 
in  1966  (Figure  11)  varied  considerably  as 
illustrated  in  Table  3.  Substantial  differences 
were  shown  between  samples  at  long.  176''W 
and  samples  to  the  east.  The  FRI  purse  seine 
samples  south  of  Adak  Island  were  approximately 
33%  age  1.1  and  67%  age  2.1  fish — very  similar 
to  the  age  composition  observed  from  gillnetting 
in  this  area.  The  following  year's  run  to  Bristol 
Bay,  however,  was  composed  of  about  17%  age 
1.2  fish  and  83%  age  2.2  fish  (Rogers,  1970).  This 
indicates  that  Bristol  Bay  sockeye  (or  age-groups 
within  the  Bristol  Bay  stock)  were  distributed 
differently  in  1966  compared  to  1963.  Other  pos- 
sibilities were  that  non-Bristol  Bay  fish  made  up 
a  higher  proportion  of  the  catches  in  1966  or 
that  there  were  differential  maturity  schedules 
for  the  two  major  age-groups. 

Although  age  composition  of  the  samples  did  not 
clearly  demonstrate  the  predominance  of  Bristol 
Bay  sockeye  in  the  northeastern  Pacific  in  1966, 
it  seems  likely  that  a  large  proportion  of  the  fish 
taken  in  this  area  as  well  as  south  of  the 
Aleutian  Islands  generally  were  of  Bristol  Bay 
origin.  This  assumption  is  based  on  the 
relative  high  abundance  of  sockeye  shown  by 
catches  south  of  the  Alaska  Peninsula  and 
Aleutian  Islands,  in  view  of  the  relative  size  of  the 
Bristol  Bay  stock  compared  to  other  North 
American  stocks  and  the  evidence  from  tagging 
studies  on  immatures  (see  Figure  3). 


180° 

— r- 


I70°W 


I60°W 


"1 r 


.^^- 


,^/' 


X 


JUNE  21-31 

JULY   I  -10 

I  1-20 

21-31 

AUGUST   l-IO 

I  1-20 

AUGUST  21 -31 


n 


CRUISE    TRACK 


I  I  I  I  I  1   I  I  I  I 


CRUISE  TRACK 


I 


CRUISE  TRACK 


55°N 


50°N 


I  I  t  I  I  I  I  I  I 


0     50    100   0    50    100  0    50    100 

RELATIVE   ABUNDANCE 

Figure  11. — Relative  abundance  of  age  .1  sockeye  salmon  along 
cruise  track  fished  in  summer  1966. 


599 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


z:^^ 


\ 


V/ 


Y\^ 


.=3= 


M-i-i 
0  12 
CPUE 


0      12 
CPUE 


Figure   12. — Distribution  and  abundance  of  age  .1   sockeye  salmon  in  July   1967,   1968, 
1969  as  shown  by  catches  of  Japanese  research  vessels. 


and 


Table  3. — Freshwater  age  composition  of  age  .1  sockeye  salmon 
from  samples  along  long.  158°W,  167°W,  and  176°W  in  summer 
1966. 


Sampling 

Age-group 

area 

0.1 

1,1 

2.1 

3.1 

4.1 

pQrcQnt 

176°W 
167°W 
158°W 

0.1 
0.6 
0 

29.6 
52.7 
68.1 

68.5 
43.7 
29.5 

1.8 
3.0 
2.4 

0 
0 
0.16 

Further  evidence  that  a  considerable  proportion 
of  the  Bristol  Bay  immature  sockeye  salmon 
remain  in  the  northeastern  Pacific  Ocean  through 
the  summer  is  indicated  by  catch  data  from 
research  vessels  fishing  simultaneously  along 
various  longitudes  in  July  and  August  (Bak- 
kala,  1971).  These  data  (Figures  10  and  11) 
showing  peaks  in  relative  abundance  followed  by 
a  decline  in  abundance  in  two  or  three  areas  at 
similar  time  periods  indicated  that  the  major 
proportion  of  immatures  from  the  eastern  areas 
did  not  migrate  westward  and  move  through  the 
area  south  of  the  central  Aleutian  Islands  at  a 
later  time  period. 

Royce  et  al.  (1968)  suggested  that  many  age 


.1  sockeye  salmon  from  Bristol  Bay  migrate  north- 
ward into  the  Bering  Sea  in  late  summer.  The 
fact  that  some  Bristol  Bay  sockeye  occupy  waters 
of  the  western  Bering  Sea  has  been  established 
by  the  recapture  of  5  sockeye  in  Bristol  Bay 
tagged  as  immatures  in  the  Bering  Sea  west  of 
180".  Recent  catch  data  indicate  that  the  abun- 
dance of  Bristol  Bay  immatures  in  the  Bering 
Sea  varies  depending  upon  the  abundance  of  the 
stock  and  perhaps  on  other  factors.  Machidori 
(1970)'  reported  on  catches  of  age  .1  sockeye 
salmon  in  the  Bering  Sea  during  research  cruises 
in  1967,  1968,  and  1969.  His  data  are  shown  in 
Figures  12,  13,  and  14  as  converted  from  tans 
(one  tan  of  gill  net  is  50  m  long)  to  CPUE  in 
equivalent  shackles  of  gear.  Although  fishing 
effort  was  not  equal  in  all  areas  in  July, 
August,  and  September,  the  data  suggested  lack  of 
substantial  numbers  of  salmon  in  the  Bering  Sea 
east  of  long.  175''E  in  July,  but  show  large 
catches  in  August  indicating  a  movement  of 


''Machidori,  S.  1970.  On  summer  distribution  of  immature 
sockeye  salmon  in  the  northwestern  North  Pacific  and  its 
adjacent  waters.  [In  Japanese]  Fish.  Agency  Jap.,  Tokyo 
(Int.  North  Pac.  Fish.  Comm.  Doc.  1311),  59  p.  (Transl.,  15  p.) 


600 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


160° 

170°                                                     180° 

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e 

160° 

Longitude  170°  East  from  Greenwich          180° 

Figure   13. — Distribution  and  abundance  of  age  .1  sockeye  salmon  in  August  1967,   1968,  and 
1969  as  shown  by  catches  of  Japanese  research  vessels. 


immatures  into  the  Bering  Sea  in  August.  In  1969 
catches  were  much  larger  in  August  from  long. 
172=30'  to  177'30'E  than  in  1967  or  1968, 
suggesting  the  presence  of  large  numbers  of  age 
.1  fish  that  were  progeny  of  the  1965  record  run 
to  Bristol  Bay.  Evidence  from  age  composition  of 
these  catches  (mainly  age  2.1  fish)  also  indicated 
that  they  were  predominantly  Bristol  Bay  fish 
as  originally  suggested  by  Machidori.  The  location 
of  these  fish  in  the  central  and  western  Bering 
Sea  indicates  that  routes  of  travel  from  the  North 
Pacific  to  the  Bering  Sea  were  through  passes 
west  of  Adak  Island.  Large  numbers  of  age  .1 
fish,  probably  of  Asian  origin,  were  taken  in  the 
Bering  Sea  west  of  long.  175''E  in  September 
(Figure  14),  but  sampling  did  not  extend  far 
enough  eastward  to  determine  if  Bristol  Bay  fish 
still  remained  in  the  Bering  Sea. 

From  the  above  analysis  we  conclude  that  some 
proportion  of  the  age     .1  fish  from  Bristol  Bay 


inhabit  the  central  and  western  Bering  Sea  in 
August  and  that  their  abundance  in  the  Bering 
Sea  varies  with  the  abundance  of  the  total  stock. 
Although  some  of  the  Bristol  Bay  immatures 
move  north  into  the  western  Bering  Sea,  the  large 
numbers  of  immatures  remaining  south  of  the 
Aleutians  indicate  that  many  of  the  Bristol 
Bay  sockeye  remain  in  the  North  Pacific  Ocean 
and  maintain  a  broad  east-west  distribution 
throughout  the  summer.  At  the  time  large  catches 
of  age  .1  sockeye  were  taken  in  the  Bering  Sea 
— from  12  to  30  August  1969 — large  catches  were 
also  being  made  south  of  Adak  Island  from  1  to 
15  August  (French,  Bakkala,  Dunn,  and 
Sutherland,  1971).  Catches  by  Japanese  and 
United  States  research  vessels  in  August  1970 
better  illustrate  this  point  (Figure  15).  The  rela- 
tive abundance  of  age  .1  sockeye  was  generally 
higher  throughout  the  area  south  of  the  Aleutian 
Islands  than  it  was  at  stations  fished  in  the  Bering 


601 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


180' 


CPUE 


1967      1968       1969 
CPUE         □  ■  E2 

NO  CATCH      o  •  e 


T>Attu 

^=1 


\6i 


^50' 


I I I I 

0    4    8   12 
CPUE 


E-tiiE 


160° 


Longitude  170"  East  from  Greenwich 


180' 


Figure  14. — Distribution  and  abundance  of  age  .1  sockeye  salmon  in  September  1967,  1968,  and 
1969  as  shown  by  catches  of  Japanese  research  vessels. 

Sea;  the  CPUE  averaged  about  four  times  higher 
in  the  North  Pacific  than  in  the  Bering  Sea 
(sets  with  no  catch  were  disregarded). 

Further  evidence  offish  remaining  in  the  North 
Pacific  Ocean  is  provided  by  tag  recoveries  in 
1964,  as  reported  by  Bakkala  (1971).  His 
summary  of  FRI  tagging  experiments  (Figures 
16  and  17)  shows  that  immature  sockeye,  mainly 
age  .1  (129)  but  including  16  age  .2  fish,  wei-e 
recaptured  in  the  North  Pacific  from  1  to  43  days 
after  tagging.  Recovery  locations  indicated  that 
direction  of  movement  from  the  tagging  site  was 
diverse  and  that  recaptures  were  made  to  the 
south,  southwest,  west,  and  north.  Four  immature 
sockeye  salmon  were  recaptured  in  the  Bering 
Sea  near  lat.  60°N,  apparent  further  evidence  of 
movement  of  some  Bristol  Bay  immatures  into  the 
western  Bering  Sea. 

Because  tag  recoveries  were  dependent  on  the 
!?.„„„„  ic     r.  t   u  *  J    u     J  r         1       1  location  and  effort  of  the  Japanese  mothership 

riGURE  15. — Distribution  and  abundance  of  age  .1  sockeye  ^  ^ 

salmon  in  August  1970  as  shown  by  catches  of  United         Aeet,  the  degree  of  movement  to  certain  areas,  as 
States  and  Japanese  research  vessels.  illustrated  in  Figure  16,  may  not  have  been 


■.icr 

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602 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 

leo'E  iro-E  180°  i70°w  i60°w  isooyv 


50°N 


''h::^ 


55°N  — 


50°  N 


60°N 


55°N 


50°N 


60°N 


55°N 


50°N 


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TAGGING    AREA 


RECOVERED      I  -  9    DAYS 
AF-TER     TAGGING 


RECOVERED    10-  19    DAYS 
AFTER     TAGGING 


RECOVERED    20-29   DAYS 
AFTER       TAGGING 


RECOVERED    30-43  DAYS 
AFTER      TAGGING 


50°  N 


55°N 


50°N 


60°  N 


55°N 


50°N 


60°N 


55°N 


50°N 


Figure  16. — Recovery  locations  for  immature  sockeye  salmon  tagged  near  Adak  Island  from  16  June 
to  24  July  1964  and  recovered  in  the  North  Pacific  Ocean  from  12  July  to  9  August  1964  (data 
from  Fisheries  Research  Institute,  1964). 


accurately  reflected.  Effort  was  concentrated 
south  of  the  Aleutian  Islands  (near,  west,  and 
southwest  of  the  release  location)  and  in  the 
Bering  Sea  near  lat.  60^N  (Figure  17).  Movement 
of  tagged  fish  to  the  east  could  not  be  detected, 
and  movement  north  and  northwest  in  the  area 
between  the  Aleutian  Islands  and  lat.  58^N  would 
have  a  low  probability  of  being  detected  compared 


to  movement  in  the  North  Pacific  Ocean.  A  sub- 
stantial portion  of  the  recoveries  occurred  in  the 
North  Pacific  Ocean  over  an  extended  period; 
36%  of  the  recoveries  were  taken  10  to  19  days 
after  tagging,  19%  20  to  29  days  after  tagging, 
and  4%  30  or  more  days  after  tagging.  These 
recoveries  indicated  that  substantial  numbers  of 
the  releases  remained  in  the  North  Pacific  Ocean. 


603 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


162°E    165°E 


170°E 


17  5°W 


170°W 


160,702 
0.12 


50° 


45°- 


5,267 
0 


1,837 
0 


93,962 
0 


12,923 
0 


24,295 
0.41 


25,362 
0 


25,889 


30,902 
0.32 


162,525 
0.43 


228,440 
0 


977 
,     0 


122,646 
3.02 


159,557 
0.50 


11,494 
0 


394,944 
2.03 


40,728 
0.74 


vliji^' 


UPPER  NUMBER  — NUMBER   OF   TANS  FISHED 

LOWER  NUMBER-  TAG  RECOVERIES  PER  10,000  TANS  FISHED 


60° 


55° 


50° 


-45° 


162°E    165°E 


170°E 


175°E 


180° 


175°W 


170°W 


Figure  17. — Fishing  effort  and  tag  recoveries  per  unit  of  effort 
by  the  Japanese  mothership  fleet  in  2°  by  5°  areas  and  for  the 
period  of  21  July  to  10  August  (data  from  Fisheries  Agency 
of  Japan,  1966  and  Fisheries  Research  Institute,  1964). 


There  is  some  doubt  about  the  true  proportion  of 
immature  sockeye  salmon  remaining  in  the  North 
Pacific  Ocean  in  comparison  to  those  moving  to 
the  Bering  Sea.  The  rates  of  return  from  the  high- 
seas  fleet  was  3.5%  of  age  .1  fish  and  5.1%  of 
age  .2  fish,  rather  low  rates  considering  the  total 
fishing  effort,  although  the  small  age  .1  fish 
even  with  tags  affixed  may  not  be  vulnerable  to 
the  fishery  with  its  large-mesh  gill  nets.  By  way 
of  comparison  tag  returns  of  8.9%  were  made  on 
the  high  seas  of  maturing  fish  from  tagging 
experiments  in  the  central  and  western  Aleutian 
Islands  area  in  1960  (Hartt,  1966). 

Because  of  the  dynamic  nature  of  the  ocean 
migration  of  salmon  (the  rate  of  travel  of  those 
recovered  in  1964  ranged  from  2  to  50  nautical 
miles  per  day  and  averaged  17  nautical  miles  per 
day),  it  is  possible  that  the  fish  recovered  in  the 
North  Pacific  Ocean  after  an  extended  period  had 
migrated  extensively  and  reentered  the  fishing 
area  south  of  the  Aleutian  Islands.  We  do  not 
know  if  the  immature  salmon  make  such  a  migra- 
tion in  the  summer.  It  is  known,  however,  that 


immature  sockeye  salmon  become  more  widely 
distributed  in  the  Bering  Sea  in  August  compared 
to  their  distribution  in  July  (see  Machidori,  foot- 
note 7),  a  pattern  which  might  argue  against  the 
possibility  of  a  return  migration  to  the  North 
Pacific  Ocean  in  July  or  even  by  early  August. 

In  relation  to  oceanographic  features,  the  age  .1 
fish  in  summer  were  found  primarily  in  the  Ridge 
Area  water  south  of  the  Alaska  Peninsula  and 
eastern  Aleutian  Islands  but  were  located  in  both 
the  Ridge  Area  and  the  Alaskan  Stream  south 
of  the  central  and  western  Aleutian  Islands  (Bak- 
kala,  1971).  Ridge  Area  waters  in  summer  were 
also  found  to  have  greater  concentrations  of  food 
organisms  than  other  water  areas  of  the  Subarctic 
Pacific  Region  (McAlister  et  al.,  1969,  1970). 

In  summary,  the  evidence  from  distribution 
studies  indicates  that  movements  of  Bristol  Bay 
immatures  in  June  are  northward  from  areas  they 
occupy  in  spring  to  waters  they  occupy  in 
summer — generally  between  lat.  50''N  and  the 
Aleutian  Islands  and  Alaska  Peninsula.  The 
majority  of  Bristol  Bay  fish  appears  to  remain 
in  these  waters  through  the  summer,  but  some 
smaller  proportion  continues  northward  or  north- 
westward into  the  Bering  Sea.  Thus,  the  distribu- 
tion of  immatures  is  seen  to  shift  northward 
from  spring  to  summer  but  not  extensively  on  an 
east-west  plane. 

Conflicting  with  this  hypothesis  of  summer 
distribution  is  other  evidence  which  has  indicated 
that  migrations  in  the  North  Pacific  are  pre- 
dominantly and  continuously  westward  through- 
out the  summer  (Royce  et  al.,  1968),  implying 
that  the  population  of  Bristol  Bay  immatures  is 
displaced  to  the  west  during  the  summer  and 
leaves  waters  of  the  northeastern  Pacific  Ocean. 
Direct  evidence  of  immature  sockeye  salmon 
migrating  long  distances  across  the  North  Pacific 
from  the  northeast  Pacific  is  provided  by  tag 
recoveries  on  the  high  seas  of  age  .2  immature 
fish.  Three  immature  sockeye  salmon  were  tagged 
in  the  northeast  Pacific  near  long.  145^W  in  May 
and  recovered  in  the  central  Aleutian  Islands  area 
in  July  and  August  of  the  same  year.  Similarly, 
two  immature  sockeye  tagged  south  of  Unalaska 
Island  in  late  June  were  recovered  in  the  western 
Aleutian  Islands  area,  one  near  171°E  in  late 
July  and  one  near  173°E  in  early  August  of  the 
same  year.  Such  long  migrations  across  the  North 
Pacific  have  not  been  demonstrated  by  the  age 
.1  fish.  The  apparent  contradiction  of  the  two  lines 
of  evidence  cannot  satisfactorily  be  resolved  at 


604 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


present.  It  may  be  that  the  Bristol  Bay  popula- 
tion of  immatures  actually  shifts  to  the  west  in 
the  summer  but  to  a  limited  degree,  or  the 
movements  of  the  fish  are  not  constant  from  year 
to  year.  Our  inability  to  readily  identify  stocks  of 
sockeye  at  sea  and  the  limited  sampling  make 
such  movements  difficult  to  detect.  Another  possi- 
bility is  that  migrations  are  not  as  directional  as 
some  evidence  would  imply  but  rather  more 
variable;  a  yet  undetected  recirculation  (or 
eastward  movement)  of  immatures  may  also  be 
occurring  to  maintain  a  broad  east-west  distri- 
bution of  immatures  throughout  the  summer. 

Information  on  the  distribution  and  movements 
of  age  .1  fish  in  the  fall  and  early  winter  is 
limited.  The  only  catch  data  available  are  from 
south  of  the  western  Aleutian  Islands  (Figure  18). 
Age  .1  fish  were  still  abundant  in  this  area  in 
October  and  November.  It  is  unknown  whether 
these  sockeye  had  remained  in  the  North  Pacific 
Ocean  through  the  summer  and  fall  or  were,  at 
least  in  part,  fish  that  had  returned  from  the 
Bering  Sea. 

Immature  and  Maturing  Age  .2  (January -June) 

During  their  second  winter  at  sea,  the  sockeye 
(now  age  .2  fish)  either  remain  in  the  northern 
part  of  the  North  Pacific  Ocean  or  move  into 
southern  areas  depending  on  their  maturation 
schedule  (if  they  mature  as  age  .2  fish  the  follow- 
ing summer  or  not).  Generally  most  age  .2 
sockeye  mature;  the  percentage  maturing  has 
been  estimated  as  ranging  from  60  to  80% 
each  year  (Royce  et  al.,  1968).  Separation  of  the 
immature  age  .2  fish  is  evident  at  least  by  mid- 
winter. Catch  data  from  winter  cruises  show  a 
partial  separation  of  the  two  groups  of  age  .2 
sockeye  in  most  areas  fished  (Figures  19  and  20). 
This  may  represent  the  period  when  the  immature 
component  of  the  age  .2  group  are  in  the  process 
of  separating  from  the  maturing  group  by  moving 
south,  leaving  the  matures  in  the  more  northerly 
waters. 

By  spring,  separation  of  immature  and  matur- 
ing age  .2  sockeye  is  much  more  pronounced 
(French,  Bakkala,  Osako,  and  Ito,  1971).  It  was 
shown  that  in  the  northeastern  Pacific  Ocean  im- 
mature sockeye  were  not  taken  north  of  about 
lat.  49""  in  April  and  only  appeared  in  catches 
in  this  area  in  late  May  and  June.  Maturing 
sockeye,  however,  were  taken  throughout  the  area 
from  lat.  49""  to  54''N.  In  the  western  and  central 


Aleutian  area  along  long.  ITS^E  and  175^W,  im- 
matures were  primarily  south  of  lat.  48^N,  and 
matures  were  caught  mainly  north  of  this 
latitude  in  May. 

On  the  basis  of  the  winter  and  spring  catch 
data,  we  surmise  that  in  winter,  age  .2  immature 
sockeye  start  migrating  to  southern  waters  and  by 
spring  become  well  separated  from  the  maturing 
fish.  Maturing  sockeye  tend  to  remain  in 
northern  waters  throughout  the  winter  and 
spring.  They  are  found  primarily  in  Ridge  Area 
water  and  waters  of  the  Western  Subarctic 
Intrusion  Area  (Bakkala  and  French,  1971). 

Most  of  the  maturing  Bristol  Bay  population 
probably  shifts  eastward  in  Ridge  or  Western 
Subarctic  Intrusion  Area  waters  during  the  fall 
or  winter.  Evidence  of  eastward  movement  is 
provided  by  comparing  results  of  sampling  south 
of  Adak  Island  in  summer  1969  with  those  from 
south  of  the  Aleutians  in  spring  1970  (Figure  21). 
On  the  basis  of  age  composition,  magnitude  of 
catches,  and  historical  tagging  data  from  this 
area,  we  conclude  that  the  large  numbers  of  sock- 
eye taken  near  long.  176^W  in  July  and  August 
were  primarily  Bristol  Bay  fish;  some  of  these 
sockeye  undoubtedly  moved  even  farther  west, 
and  others  were  probably  already  to  the  west  of 
Adak  Island.  In  spring  1970,  sampling  demon- 
strated that  most  maturing  sockeye  were  east  of 
long.  175^W  indicating  that  many  of  the  fish 
located  west  of  long.  175°W  in  the  previous 
summer  had  returned  east  of  long.  175''W  by 
spring. 

The  location  of  concentrations  of  Bristol  Bay 
sockeye  in  spring  (which  is  influenced  by  the 
extent  of  their  eastward  movement  in  fall  or 
winter)  determines  the  main  migration  routes 
taken  to  reach  Bristol  Bay;  probably  the  largest 
part  of  the  population  is  located  east  of  long. 
175^W,  and  the  main  migration  is  through  passes 
east  of  long.  175°W.  This  conclusion  was  also 
indicated  by  Kondo  et  al.  (1965).  (We  do  not  know 
the  relative  abundance  or  distribution  of  Bristol 
Bay  sockeye  that  may  be  in  the  Bering  Sea  in 
late  winter  or  early  spring  prior  to  the  time  of 
migration.)  The  intrusion  of  the  Western  Sub- 
arctic Gyre  or  northward  shift  of  the  Western 
Subarctic  Current  may  affect  the  westward  dis- 
tribution of  Bristol  Bay  sockeye  or  the  eastward 
distribution  of  Asian  sockeye  in  some  years.  For 
example,  the  percentage  of  Bristol  Bay  fish  in 
catches  by  the  Japanese  mothership  fleet  in  the 
area  where  Asian  and  Bristol  Bay  sockeye  salmon 


605 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


60' 


170  E 


lecT 


55' 


50" 


40 


SEPTEMBER-OCTOBER     1964 


^ 


,--*- 


OYASHIO    EXTENSION 

AREA 

SUBARCTIC 

CURRENT   AREA 


I70*E 


180 


OCTOBER-NOVEMBER      1965 


^V 


LEGEND 

CPUE 

o  - 

0 

•  - 

<I.O 

•  - 

1  0-« 

9 

•  ' 

5.0-9 

9 

•  - 

10  0- 

9  9 

AGE 

J    ON 

LEFT  — 

AGE 

2  ON 

RIGHT 

ALASK-A^         :  ^*^ 

TREAM     AREA 
RIDGE       SREA 


OYASh  10 
EXTENSION 


AREA 


oo 
oo 


^SUBARCTIC     CURRENT     AREA 
TRANSITION       AREA 


5  5" 


Figure  18. — Distribution  of  immature  sockeye  salmon  in  the  fall  in  relation  to  oceanographic 
features  of  the  Subarctic  Region  of  the  North  Pacific  Ocean  (from  Bakkala,  Figure  48,  1971). 


Figure  19. — Distribution  of  immature  age  .2  sockeye  salmon  in  winter  (data  from  1962-70  with 

the  exception  of  1964,  1966,  and  1968). 


intermingle  (long.  170°  to  175°E,  lat.  46°  to  52°N) 
was  estimated  to  be  5.8%  in  1967  and  49.4% 
in  1968  (Fredin  and  Worlund^).  In  spring  1967, 
cold  water  (2°C)  from  the  Western  Subarctic 
Domain  intruded  well  east  of  long.  170°E  at  lat. 
47°N,  whereas  in  1968  the  cold  water  was  farther 
west  than  in  1967  (French  et  al.,  1971).  This 
change  in  the  environment  may  have  limited  the 


westward  distribution  of  Bristol  Bay  fish  and  in 
turn  the  catch  of  Bristol  Bay  sockeye  by  the 
Japanese  in  1967. 

Tagging  data  indicate  that  salmon  west  of  long. 
170°W  in  April  and  May  will  pass  through 
Aleutian  Islands  passes  west  of  Adak  Island; 
fish  east  of  long.  170''W  will  pass  through  Aleu- 
tian passes  east  of  long.   175''W.  In  Figure  22, 


606 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


Figure  20. — Distribution  of  maturing  age  .2  sockeye  salmon  in  winter  (data  from  1962-70  with 

the  exception  of  1964,  1966,  and  1968). 


Figure  21. — Fishing  stations  and  relative  abundance  of  immature  sockeye  salmon  during  summer 
1969  near  Adak  Island  (shown  above  station  line)  and  maturing  sockeye  salmon  in  spring  1970 
(shown  below  stations). 


recoveries  of  tagged  salmon  by  the  mother- 
ship  fishery  (which  were  made  only  west  of  long. 
ITS'^W)  show  a  marked  decline  in  recoveries  for 
tagging  locations  east  of  long.  175°W.  For  tagging 
locations  east  of  long.  170°W,  recoveries  were 
almost  all  from  Bristol  Bay  and  only  a  very 
few  recoveries  were  made  in  the  mothership 


fishery.  Thus,  primary  routes  to  Bristol  Bay  for 
the  salmon  located  east  of  long.  170^W  must  have 
been  through  Aleutian  Islands  passes  east  of  long. 
175°W  (primarily  Amukta  Pass). 

Routes  of  maturing  sockeye  salmon  moving 
eastward  in  the  Bering  Sea  may  be  variable 
and  over  a  broad  front.  Largest  catches  by  the 


607 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Japanese  mothership  fleet  between  long.  180°  and 
ITS^W  in  the  Bering  Sea  in  June  occur  from  the 
Aleutian  Islands  to  lat.  SS^N,  and  fairly  good 
catches  may  extend  to  lat.  58^N  (Peterson,  1971). 
U.S.  research  vessels  have  made  large  catches  of 
maturing  sockeye  salmon  in  June  near  the 
Pribilof  Islands — which  indicate  migrations  far 
north  of  the  Aleutian  Islands.  The  entry  of  most 
sockeye  into  Bristol  Bay,  however,  is  apparently 
off  the  southern  coast  of  the  bay.  Gill-net 
sampling  near  Bristol  Bay,  before  the  fishing 
season,  between  long.  165^  and  160^W  indicated 
that  the  largest  concentration  of  sockeye  salmon 
was  about  40  miles  (74  km)  from  the  Alaska 
Peninsula  (French,  Craddock,  and  Dunn,  1967). 
Paulus  (1968)^  reported  the  largest  catches  in  this 
area  to  be  from  40  to  60  miles  (74  to  111  km) 
offshore. 

Third  Year  at  Sea 

Most  age  .2  sockeye  that  do  not  mature  after 
their  second  year  at  sea  remain  an  additional  year 
in  the  ocean  and  then  return  to  Bristol  Bay  to 
spawn  as  age  .3  fish.  A  few  fish  will  stay  at 
sea  still  another  year  to  return  as  age  .4  fish. 


*Paulus,  R.  D.  1968.  Bristol  Bay  intermediate  high  seas 
inshore  test  fishing  program.  Project  AFC-6-2,  1968  field 
season.  Alaska  Dep.  Fish  Game,  Annu.  Tech.  Rep.  Anadro- 
mous  Fish  Proj.,  61  p. 


but  they  make  up  a  very  small  percentage  of  the 
Bristol  Bay  run.  From  1960  to  1965  the  estimated 
number  of  age  .4  fish  in  the  spawning  run  ranged 
from  2,300  fish  to  25,600  fish  or  from  0.01%  to 
0.22%  of  the  total  run. 

Immatures  Age  .2  (July-December) 

The  immature  age  .2  sockeye  were  shown  to 
move  south  and  separate  from  the  concentrations 
of  maturing  fish  of  age  .2  in  the  winter.  In  the 
winter  and  spring,  they  become  intermixed  with 
the  newly  arrived  age  .1  immatures.  In  the 
summer,  they  probably  repeat  the  migration  they 
made  the  previous  summer  as  age  .1  fish  since 
age  .2  immatures  are  intermixed  with  age  .1 
fish  in  all  areas  sampled.  Machidori  (see  foot- 
note 7)  shows  the  immature  age  .2  sockeye  in  the 
Bering  Sea  in  the  same  general  areas  as  the  age 
.1  sockeye. 

Maturing  Age  .3  (January-June) 

The  maturing  age  .3  sockeye,  in  the  winter,  are 
generally  distributed  in  northern  areas  of  the 
North  Pacific  Ocean,  and  in  January  and 
February  they  were  also  found  in  the  Bering  Sea 
(Figure  23).  In  these  areas,  the  distribution  of 
age  .3  fish  overlaps  considerably  with  that  of 


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Figure  22. — Tagging  location  for  maturing  sockeye  salmon  tagged  in  the  North  Pacific  Ocean 
in  April,  May,  and  June  1956-67  and  recaptured  in  Bristol  Bay  or  the  Japanese  mothership  fishery. 
Percentage  recovery  for  each  5^  of  longitude  is  shown  below. 


608 


Figure  23. — Distribution  of  age  .3  sockeye  salmon  in  winter  (data  from  1962-70  with  the  exception 

of  1964,  1966,  and  1968). 


maturing  age  .2  fish  but  is  somewhat  north  of 
the  latter  group.  We  do  not  know  if  these  fish 
remain  in  the  Bering  Sea  throughout  winter  and 
early  spring. 

By  spring,  the  age  .3  sockeye  are  distributed 
across  the  North  Pacific  Ocean  primarily  in  the 
Ridge  Area  and  the  northern  part  of  the  Western 
Subarctic  Intrusion  Area  waters.  Their  move- 
ments toward  Bristol  Bay  in  late  spring  are 
assumed  to  be  similar  to  those  described  for  age 
.2  sockeye. 


INFLUENCE  OF  WATER  AREAS 

AND  CURRENTS  ON 

SALMON  MIGRATIONS 

In  the  previous  sections  we  have  inferred  from 
various  research  results  the  migrations  of  Bristol 
Bay  sockeye  salmon  from  the  time  they  leave  the 
estuary  until  they  return  as  maturing  fish.  We 
have  also  shown  their  distribution  in  relation  to 
water  masses  which  can  be  summarized  as 
follows:  After  leaving  the  Bering  Sea,  possibly 
in  Alaskan  Stream  Area  water  extruding  through 
Aleutian  Islands  passes,  (Favorite  and  Ingraham, 
1972),  the  young  salmon  move  southward  in 
winter  through  the  Alaskan  Stream  and  Ridge 
Areas  into  the  Western  Subarctic  Intrusion  Area 
waters.  In  spring  they  usually  are  in  Transition 
waters.  In  early  summer  they  move  northward 


(a  reversal  of  the  winter  movement)  through  the 
Western  Subarctic  Intrusion  Area  to  Ridge  and 
Alaskan  Stream  Area  waters.  Some  components 
of  the  population  move  into  central  and  northern 
parts  of  the  Bering  Sea.  The  salmon  that  will 
mature  the  following  spring  remain  in  northern 
waters,  the  Ridge  Area  primarily,  over  the  winter 
and  spring  until  they  commence  the  spawning 
migration.  Immature  age  .2  fish  repeat  the 
southward  movement  they  made  a  year  earlier 
and  join  the  new  group  of  age  .1  fish.  The  matures, 
in  late  spring,  migrate  from  the  Ridge  Area  and 
the  northern  part  of  the  Western  Subarctic 
Intrusion  Area  waters  through  the  Alaskan 
Stream  and  into  the  Bering  Sea  through  various 
passes  of  the  Aleutian  Islands. 

The  influence  of  these  water  masses  on  distri- 
bution and  migrations  of  sockeye  salmon  is  not 
evident  from  our  observations.  As  demonstrated, 
sockeye  salmon  in  all  life  history  stages  appear 
to  move  readily  in  and  out  of  the  various  water 
masses.  Although  salmon  at  certain  life  history 
stages  appeared  to  associate  with  certain  water 
masses  in  some  years,  a  shift  in  location  of  water 
masses  in  other  years  was  not  accompanied  by 
a  corresponding  shift  in  salmon  distribution. 
Examples  of  this  were  shown  in  Figure  6;  in 
1962  and  1967,  immatures  were  mainly  found 
near  or  south  of  lat.  50^N  and  in  the  Western 
Subarctic  Intrusion  Area;  but  in  1970  when  this 
oceanographic  feature  was  located  north  of  50^N, 
most  immatures  were  in  the  same  general  location 


609 


(near  or  south  of  lat.  50^N)  but  were  now  mainly 
in  the  Transition  Area.  Bakkala  (1971)  noted  a 
similar  situation  in  the  summer;  immatures  were 
usually  found  in  the  Ridge  Area  south  of  the 
eastern  Aleutian  Islands  and  Alaska  Peninsula, 
but  when  the  Alaskan  Stream  extended  farther 
offshore,  the  geographical  distribution  of  salmon 
was  unchanged  and  the  immature  salmon  were  in 
both  the  Alaskan  Stream  and  Ridge  Areas.  His 
data  also  demonstrated  that  whereas  immatures 
south  of  the  eastern  Aleutian  Islands  and  Alaska 
Peninsula  were  found  mainly  in  the  Ridge  Area, 
those  south  of  the  central  Aleutian  Islands  were 
most  abundant  in  the  Alaskan  Stream.  The 
Alaskan  Stream  was  previously  thought  to  be  the 
major  route  of  westward  migration  for  salmon,  but 
westward  migration  occurred  in  the  Ridge  Area 
as  well.  The  Subarctic  Current,  a  term  used  to 
describe  the  faster  moving  waters  near  the 
boundary  of  the  Western  Subarctic  Intrusion  and 
Transition  Areas,  was  also  hypothesized  to  be  a 
route  of  eastward  movement  by  maturing  sockeye 
salmon  in  fall  and  winter,  but  most  maturing 
fish  are  far  north  of  this  current  and  probably 
move  east  in  Ridge  Area  waters. 

In  summary,  it  could  not  be  demonstrated  that 
defined  oceanographic  features  of  the  North 
Pacific  Ocean  had  any  direct  influence  on  the 
north-south  movements  and  distribution  of 
sockeye  salmon.  Their  movements  and  distribu- 
tion may  be  governed  by  other  environmental 
conditions  such  as  water  temperature  or  food 
abundance. 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 

Research  vessel  catch  data  and  the  variable 
numbers  of  Bristol  Bay  sockeye  available  to  the 
Japanese  mothership  fishery  indicate  that  matur- 
ing Bristol  Bay  sockeye  make  eastward  migra- 
tions in  the  North  Pacific  Ocean  in  the  fall  or 
winter  and  that  the  proportion  of  Bristol  Bay 
fish  making  this  migration  or  the  extent  of  these 
migrations  vary  between  some  years.  This  is  per- 
haps influenced  by  the  interaction  of  the  Alaskan 
and  Western  Subarctic  Gyres  and  possibly  by  the 
recirculation  of  Alaskan  Stream  waters.  Matur- 
ing Bristol  Bay  sockeye  are  found  mainly  in  the 
Alaskan  Gyre  in  spring,  and  if  the  westward 
extent  of  this  gyre  is  limited  by  the  strength 
of  the  Western  Subarctic  Gyre,  the  westward  dis- 
tribution of  maturing  sockeye  may  also  be 
limited.  (See  Figure  24  for  the  location  of  the 
two  gyres.)  We  have  no  direct  evidence  to  support 
this  possibility. 


MODEL  OF  MIGRATION  OF  BRISTOL 
BAY  SOCKEYE  SALMON 


From  the  accumulated  knowledge  of  distribu- 
tion and  migration  of  Bristol  Bay  sockeye  salmon, 
we  have  diagrammed  a  model  of  their  movements 
from  the  time  they  leave  the  estuary  until 
they  return.  The  model  differs  from  that  given 
by  Royce  et  al.  (1968),  but  the  two  models  are 
in  agreement  in  regard  to  the  major  areas  in 
which  the  salmon  are  found. 


I70°E 


Figure  24. — Schematic  diagram  of  surface  circulation  in  the  Subarctic  North  Pacific  to  illustrate 
the  general  location  of  the  Alaskan  and  Western  Subarctic  Gyres  (from  Dodimead,  Favorite,  and 
Hirano,  Figure  109,  1963). 


610 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 
A 


1st  YEAR  AT  SEA    (  JULY-  MAY) 
AGE    0    TO   AGE     1 


''    -  --^P-- 


\\x 


180° 


JV.vx.vV^- 


2nd   YEAR  AT   SEA 

(JUNE-SEPTEMBER) 

IMMATURE    AGE  .1 


/ 
n 


\ 


V        V    |.^^'_       ^ 


55°  N 


55° 


OCTOBER  -MAY 
IMMATURE    AGE  .1  TO   AGE  .2 


^^■•°"   /^^ 


3rd  YEAR  AT  SEA  (JUNE-SEPTEMBER) 
IMMATURE  AGE  .2      Migrotion  continued  as  in  EftF 


OCTOBER -MAY 
MATURING    AGE     I    TO  AGE    2 


1 70^  1 80° 


f\' 


I70°W^  160°  >50' 


3fd  YEAR  AT  SEA     (JUNE-JULY) 
MATURING    AGE   .2 


55° 


50° 


45° 


Figure  25. — Model  of  migration  of  Bristol  Bay  sockeye  salmon. 


The  new  model  calls  attention  to  changes  in 
migration  or  distribution  patterns  from  year  to 
year — which  could  affect  indices  of  abundance 
that  are  based  on  data  from  only  one  area  or  time 
period. 

A  graphical  illustration  of  the  model  appears 
in  Figure  25,  and  a  brief  narrative  account  follows. 

First  Year  at  Sea 

Juveniles  Age  .0  (July-December) 

Juveniles,  age  .0  fish,  after  leaving  the  rivers 
of  Bristol  Bay,  move  southwest  along  the  north 


side  of  the  Alaska  Peninsula,  and  by  mid- 
September  many  still  remain  east  of  long.  leS'^W 
and  within  90  miles  (167  km)  of  shore.  In  late 
fall  or  early  winter  the  juveniles  move  south- 
westward  along  the  Aleutian  Islands  and  then 
proceed  south  through  various  passes,  most  likely 
between  long.  179'E  and  169°W.  The  migration 
out  of  the  Bering  Sea  may  be  motivated  by  lowered 
surface  water  temperatures  and  reduced  food 
supplies — ^juveniles  generally  are  not  found  in 
surface  waters  with  temperatures  less  than  3^C. 
Principal  routes  of  migration  may  be  through 
Aleutian  Islands  passes  where  the  Alaskan 
Stream  branches  into  the  Bering  Sea. 


611 


FISHERY  BULLETIN:  VOL.  72.  NO.  2 


Immatures  Age  .1  (January-May) 

The  immatures  (age  .1  on  1  January),  after 
reaching  the  North  Pacific  Ocean,  move  south- 
ward through  the  Alaskan  Stream  and  Ridge  Area 
and  by  midwinter  become  located  primarily  south 
of  lat.  SO'^N  in  Western  Subarctic  Instrusion  or 
Transition  Area  waters.  There  is  no  evidence  that 
the  young  fish  follow  major  currents  during  the 
southward  movement;  they  move  southward  over 
a  broad  east-west  area.  The  young  immatures  are 
probably  in  search  of  food  sources  and  favorable 
water  temperatures  (3.5-6.0^C)  that  prevail  in 
more  southern  waters. 

In  early  spring  the  immatures  shift  somewhat 
farther  south  and  become  more  sharply  separated 
from  the  matures  (sockeye  salmon  from  an  earlier 
brood  year).  By  April  and  May  the  immature 
age  .1  fish  have  reached  their  so.uthern  limit  of 
migration  over  a  broad  area  from  about  long. 
n5^E  to  145''W  and  are  found  from  about  lat. 
45°  to  50°N  in  Transition  and  Western  Sub- 
arctic Intrusion  waters — an  area  of  favorable 
water  temperatures,  4.5-6.0°C,  and  food  sources. 

Second  Year  at  Sea 

Immatures  Age  .1  (June-September) 

In  June  the  immatures  start  a  return  north- 
ward movement  over  a  broad  east-west  area. 
This  movement  may  be  related  to  the  increase  in 
surface  water  temperatures  and  subsequent 
zooplankton  blooms  from  south  to  north. 

By  July,  the  age  .1  fish  have  moved  north 
from  areas  occupied  in  the  spring  and  are  mainly 
located  north  of  lat.  SO^'N  in  the  Alaskan  Stream 
and  Ridge  Areas.  These  waters  in  summer  have 
more  abundant  food  than  other  water  areas  of 
the  Subarctic  Pacific  Region,  which  probably 
accounts  for  the  distribution  of  sockeye  on  the 
north-south  plane.  On  an  east-west  plane,  the 
immature  sockeye  are  distributed  over  a  wide 
area,  from  about  long.  170°E  to  about  160^W. 
Most  of  the  fish  are  moving  in  a  westerly  direc- 
tion during  the  summer,  but  recirculation  of  im- 
matures or  limited  westerly  movement  maintains 
the  wide  east-west  distribution  through  the 
summer.  Some  elements  of  the  population  move 
north  into  the  Bering  Sea  in  summer  and  become 
distributed  in  the  central  Bering  Sea  to  at  least 
lat.  60°N.  The  majority  of  the  population  remains 
south  of  the  Aleutian  Islands. 

612 


The  continuity  of  the  Alaskan  Stream  and 
Alaskan  Gyre  or  the  eastward  intrusion  of  the 
Western  Subarctic  Gyre  are  oceanic  features  that 
may  influence  the  western  limits  of  distribution 
of  Bristol  Bay  immature  sockeye. 

Separation  of  Immature  and  Maturing  Sockeye 
(October-May) 

In  January  and  February  of  this  period  (the 
sockeye  now  become  age  .2  fish),  they  separate 
into  immature  and  maturing  components.  The 
immature  group  will  remain  at  sea  a  third 
year  before  maturing  and  will  follow  a  somewhat 
different  migration  pattern  (as  shown  in  Figure 
25  C)  than  the  maturing  group  (Figure  25  E). 
The  remaining  period  at  sea  for  the  immature 
group  will  be  discussed  following  the  description 
of  movements  of  the  maturing  fish. 

Maturing  Age  .1  to  Age  .2  (October-May) 

The  age  .1  sockeye  which  will  mature  the  fol- 
lowing spring  remain  in  the  more  northerly 
waters  of  the  North  Pacific  Ocean  (primarily  north 
of  lat.  50''N  in  the  Alaskan  Stream  and  Ridge 
Areas)  throughout  fall,  winter,  and  spring  until 
they  begin  their  inshore  migration.  The  extensive 
east-west  distribution  of  sockeye  (which  was 
noted  previously)  is  maintained.  Evidence  of  vary- 
ing catch  rates  of  Bristol  Bay  sockeye  by  the 
Japanese  mothership  fishery  west  of  long.  175''W 
(rates  have  varied  between  years  from  2.2  to  35.2% 
of  the  total  run)  suggests  that  the  distribution  of 
maturing  sockeye  shifts  to  the  east  in  fall  and 
winter  and  that  the  magnitude  and  extent  of  this 
movement  governs  the  availability  of  sockeye  to 
the  Japanese  fishing  fleet. 

During  this  period,  the  maturing  sockeye 
salmon  are  associated  with  the  Alaskan  Gyre — 
primarily  the  Ridge  Area,  but  they  are  also 
found  in  the  Western  Subarctic  Intrusion  and 
Transition  Areas,  depending  upon  the  location  of 
these  oceanic  features. 

The  areas  from  which  the  maturing  Bristol 
Bay  fish  initiate  their  inshore  migration  essen- 
tially have  been  established  by  April  as  a  result 
of  previous  migrations.  At  that  time  their  routes 
of  inshore  migration  (and  the  proportion  of  the 
population  available  to  the  Japanese  mothership 
fishery)  have  been  determined,  and  variations  in 
oceanographic  features  are  assumed  to  have  little 
effect  on  these  inshore  routes  of  migration. 


FRENCH  and  BAKKALA:  NEW  MODEL  OF  OCEAN  MIGRATIONS 


Maturing  Age  .2  (June-July) 

In  June  the  spawning  migration  toward  Bristol 
Bay  is  northward  through  Alaskan  Stream  waters 
and  through  various  Aleutian  Islands  passes  into 
the  Bering  Sea.  Maturing  age  .2  fish  move 
eastward  over  a  broad  south-north  area  extend- 
ing from  the  Aleutian  Islands  to  about  lat.  58°N. 
As  they  approach  Bristol  Bay  the  schools  of  fish 
become  more  concentrated,  and  their  main  route 
of  migration  is  about  40-60  miles  (74-111  km) 
from  the  north  side  of  the  Alaska  Peninsula. 

Third  Year  at  Sea 

The  fish  that  remain  immature  through  their 
second  year  at  sea  separate  from  the  maturing 
component  in  midwinter  and  move  into  more 
southern  waters  of  the  North  Pacific  (Figure 
25  C).  Here  they  are  joined  by  the  new  group  of 
age  .1  fish;  the  two  age  groups  repeat  the  migra- 
tions already  described  and  shown  in  Figures 
25  D,  E,  and  F. 

ACKNOWLEDGMENTS 

We  are  indebted  to  the  Oceanographic  Unit 
(F.  Favorite,  Program  Leader)  of  the  Northwest 
Fisheries  Center  (NWFC),  National  Marine 
Fisheries  Service,  NOAA,  for  definition  of  oceano- 
graphic features  and  stimulating  discussions  on 
the  oceanography  of  the  Subarctic  Pacific  Region. 
The  Stock  Identification  and  Aging  Unit  of  the 
NWFC  (R.  Major,  Program  Leader)  provided  all 
salmon  age  readings  from  scale  samples  obtained 
during  the  various  research  cruises.  W.  Royce, 
L.  Smith,  and  A.  Hartt  of  the  Fisheries  Research 
Institute,  University  of  Washington,  authors  of  a 
paper  on  the  ocean  migrations  of  Bristol  Bay 
sockeye  (Royce  et  al.,  1968),  kindly  read  the 
manuscript  and,  although  they  view  the  migra- 
tions somewhat  differently  than  the  present 
authors,  offered  many  useful  suggestions  that 
were  incorporated  into  the  paper. 


LITERATURE  CITED 

Bakkala,  R.  G. 

1971.  Distribution  and  migration  of  immature  sockeye 
salmon  taken  by  U.S.  research  vessels  with  gillnets  in 
offshore  waters,  1956-67.  Int.  North  Pac.  Fish.  Comm., 
Bull.  27:1-70. 


Bakkala,  R.,  and  R.  French. 

1971.  U.S.  &  Japan  continue  cooperative  research  in 
North  Pacific  (1970-71).  Commer.  Fish.  Rev.  33(9): 
41-52. 

DoDiMEAD,  A.  J.,  F.  Favorite,  and  T.  Hirano. 

1963.  Salmon  of  the  North  Pacific  Ocean — Part  II.  Review 
of  oceanography  of  the  Subarctic  Pacific  Region.  Int. 
North  Pac.  Fish.  Comm.,  Bull.  13,  195  p. 

Dunn,  J.  R. 

1969.  Direction  of  movement  of  salmon  in  the  North 
Pacific  Ocean,  Bering  Sea,  and  Gulf  of  Alaska  as  indi- 
cated by  surface  gillnet  catches,  1962-65.  Int.  North  Pac. 
Fish.  Comm.,  Bull.  26:27-55. 

Favorite,  F.,  and  W.  J.  Ingraham,  Jr. 

1972.  Influence  of  Bowers  Ridge  on  circulation  in  Bering 
Sea  and  influence  of  Amchitka  Branch,  Alaskan  Stream, 
on  migration  paths  of  sockeye  salmon.  In  A.  Y.  Taken- 
outi  (chief  editor),  Biological  oceanography  of  the 
northern  North  Pacific  Ocean,  dedicated  to  Sigeru  Motoda, 
p.  13-29.     Idemitsu  Shoten,  Tokyo,  Japan. 

Favorite,  F.,  W.  J.  Ingraham,  Jr.,  and  D.  M.  Fisk. 

1972.     Oceanography.     Int.  North  Pac.  Fish.  Comm., 
Annu.  Rep.  1970:90-98. 
Fisheries  Agency  of  Japan. 

1966.  Report  on  research  by  Japan  for  the  International 
North  Pacific  Fisheries  Commission  during  the  year 
1964.  Int.  North  Pac.  Fish.  Comm.,  Annu.  Rep.  1964: 
48-79. 

Fisheries  Research  Institute. 

1964.  Tag  returns— 1964 — United  States  high  seas  tag- 
ging. Univ.  Wash.,  Coll.  Fish.,  Fis.  Res.  Inst.  Circ.  263, 
20  p. 

French,  R. 

1964.     Salmon  distribution  and  abundance  on  the  high 
seas — summer  season — 1963.     Int.  North  Pac.  Fish. 
Comm.,  Annu.  Rep.  1963:121-131. 
French,  R.,  R.  Bakkala,  J.  Dunn,  and  D.  Sutherland. 

1971.     Ocean  distribution,  abundance,  and  migration  of 
salmon.     Int.  North  Pac.  Fish.  Comm.,  Annu.  Rep. 
1969:89-102. 
French,  R.  R.,  R.  G.  Bakkala,  M.  Osako,  and  J.  Ito. 

1971.     Distribution  of  salmon  and  related  oceanographic 

features  in  the  North  Pacific  Ocean,  spring   1968. 

U.S.  Dep.  Commer.,  NOAA  Tech.  Rep.  NMFS  SSRF-625, 

22  p. 

French,  R.,  D.  Craddock,  R.  Bakkala,  J.  Dunn,  and  K. 

Thorson. 

1967.  Ocean  distribution,  abundance,  and  migrations  of 
salmon.  Int.  North  Pac.  Fish.  Comm.,  Annu.  Rep. 
1966:78-89. 

French,  R.  R.,  D.  R.  Craddock,  and  J.  R.  Dunn. 

1967.     Distribution  and  abundance  of  salmon.     Int.  North 
Pac.  Fish.  Comm.,  Annu.  Rep.  1965:82-94. 
Hartt,  A.  C. 

1962.  Movement  of  salmon  in  the  North  Pacific  Ocean 
and  Bering  Sea  as  determined  by  tagging,  1956-1958. 
Int.  North  Pac.  Fish.  Comm.,  Bull.  6,  157  p. 
1966.  Migrations  of  salmon  in  the  North  Pacific  Ocean 
and  Bering  Sea  as  determined  by  seining  and  tagging, 
1959-1960.  Int.  North  Pac.  Fish.  Comm.,  Bull.  19, 
141  p. 
Hartt,  A.  C,  M.  B.  Dell,  and  L.  S.  Smith. 

1969.  Tagging  and  sampling.  Int.  North  Pac.  Fish. 
Comm.,  Annu.  Rep.  1967:78-85. 


613 


FISHERY  BULLETIN:  VOL.  72,  NO.  2 


Hartt,  a.  C,  L.  S.  Smith,  M.  B.  Dell,  and  R.  V.  Kilambi. 
1967.     Tagging  and  sampling.     Int.   North   Pac.   Fish. 
Comm.,  Annu.  Rep.  1966:73-78. 
KoNDO,  H.,  Y.  HiRANO,  N.  Nakayama,  and  M,  Miyake. 

1965.     Offshore  distribution  and  migration  of  Pacific 
salmon  (genus  Oncorhynchus)  based  on  tagging  studies 
(1958-i96i>.     Int.  North  Pac.  Fish.  Comm..  Bull.  17. 
213  p. 
Koo,  T.  S.  Y. 

1962.     Age  designation  in  salmon.    /;?  T.  S.  Y.  Koo  (editor), 
Studies  of  Alaska  red  salmon,  p.  37-48.     Univ.  Wash. 
Publ.  Fish.,  New  Ser.  1. 
Larkins,  H.  a. 

1964.     Direction  of  movement  of  salmon  in  the  North 
Pacific  Ocean,  Bering  Sea  and  Gulf  of  Alaska  as 
indicated  by  surface  gillnet  catches,  1961.     Int.  North 
Pac.  Fish.  Comm.,  Bull.  14:49-58. 
McAlister,  W.  B.,  W.  J.  Ingraham,  Jr.,  D.  Day,  and 
J.  Larrance. 

1969.  Oceanography.     Int.   North  Pac.  Fish.  Comm., 
Annu.  Rep.  1967:97-107. 

1970.  Oceanography.     Int.   North  Pac.  Fish.   Comm., 
Annu.  Rep.  1968:90-101. 


Margolis,  L.,  F.  C.  Cleaver,  Y.  Fukuda,  and  H.  Godfrey. 
1966.     Salmon  of  the  North  Pacific  Ocean— Part  VI.  Sock- 
eye  salmon  in  offshore  waters.     Int.  North  Pac.  Fish. 
Comm.,  Bull.  20,  70  p. 

OsSIANDER,  F.  J.  (EDITOR). 

1965.     Bristol  Bay  red  salmon  forecast  of  run  for  1965. 
Alaska  Dep.  Fish  Game,  Inf  Leaf!.  59,  22  p. 
Peterson,  A.  E. 

1971.     Statistics  of  Japanese  mothership  salmon  fishery. 
Int.  North  Pac.  Fish.  Comm.,  Annu.  Rep.  1969:119-125. 
Rogers,  D.  E. 

1970.  Forecast  of  the  sockeye  salmon  run  to  Bristol  Bay 
in  1970,  based  on  purse  seine  catches  of  immature 
sockeye  salmon  south  of  Adak.  Univ.  Wash.  Coll.  Fish., 
Fish.  Res.  Inst.  Circ.  70-3,  21  p. 

Rothschild,  B.  J.,  A.  C.  Hartt,  D.  E.  Rogers,  and  M.  B.  Dell. 

1971.  Tagging  and  sampling.  Int.  North  Pac.  Fish.  Comm., 
Annu.  Rep.  1969:67-89. 

RoYCE,  W.  F.,  L.  S.  Smith,  and  A.  C.  Hartt. 

1968.  Models  of  oceanic  migrations  of  Pacific  salmon  and 
comments  on  guidance  mechanisms.  U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  66:441-462. 


614 


NOTES 


MIGRANT  GRAY  WHALES  WITH  CALVES 

AND  SEXUAL  BEHAVIOR  OF 

GRAY  WHALES  IN  THE  MONTEREY  AREA 

OF  CENTRAL  CALIFORNIA,  1967-73 

This  paper  presents  evidence  modifying  two  state- 
ments in  the  monographic  study  of  the  gray  whale, 
Eschrichtius  robustus ,  by  Rice  and  Wolman 
(1971): 

1.  "The  route  taken  by  females  with  calves 
during  the  spring  [northward]  migration  is 
unknown  [page  14]."  They  arrived  at  this 
conclusion  after  being  able  to  cite  only  three 
records  of  cows  with  calves  over  a  10-yr 
survey  period  inshore  and  offshore,  at  San 
Francisco  and  on  aerial  censuses  from  San 
Francisco,  Cahf.,  to  Cape  Flattery,  Wash. 

2.  "Non-pregnant  adult  females  regularly  ovu- 
late in  late  November  and  early  December  . .  . 
while  still  north  of  central  California  on  the 
southward  migration  [page  61]."  and 
"Almost  all  of  the  adult  females  (except  those 
carrying  near-term  fetuses)  taken  during 
southward  migration  [end  of  page  73]  prob- 
ably had  already  conceived,  although  none 
was  visibly  pregnant.  .  .  .  The  mean  concep- 
tion date  calculated  from  the  fetal  growth 
curve  ...  is  5  December.  .  .  .  The  calculated 
conception  dates  fall  between  27  November 
and  13  December,  except  for  one  on  22  De- 
cember and  one  on  5  January  [pages  73-74]." 

Whales  with  Calves  on  Northward  Migration 

The  known  breeding  grounds  of  the  north- 
eastern Pacific  Ocean  population  of  gray  whales 
were  described  in  detail  by  Gilmore  (1960).  Rice 
and  Wolman  (1971)  reviewed  in  their  monograph 
the  seasonal  migratory  cycle  of  this  species. 
Leatherwood  (1973)^  reported  23  observations  of 
northbound  females  with  calves  sighted  during 
aerial  censusing  from  1969  to  1972,  off  southern 
California.  The  majority  were  "well  inshore." 


'Leatherwood,  J.  S.  1973.  Aerial  observations  of  migrating 
gray  whales,  Eschrichtius  robustus,  off  southern  California 
(1969-1972).  California  Gray  Whale  Workshop,  21-22  Aug. 
1972.  (Unpubl.  manuscr.) 


At  1400  h  on  12  May  1967,  at  Point  Lobos 
State  Reserve  near  Carmel,  Calif.,  a  group  of  six 
or  seven  killer  whales,  Orcinus  orca,  attacked  a 
gray  whale  and  its  6-m  calf,  killing  the  latter 
as  it  took  refuge  in  beds  of  giant  kelp,  Macro- 
cystis  pyrifera,  (Baldridge,  1972).  This  was  con- 
sidered to  be  the  same  group  of  killer  whales 
that  unsuccessfully  attacked  two  adult  gray 
whales  and  a  calf  just  outside  the  surf  at  Moss 
Landing,  Monterey  County  on  2  May  1967  (More- 
john,  1968). 

At  1350  h  on  27  March  1970,  at  Lucia, 
Monterey  County,  70  km  south  of  Carmel, 
together  with  W.  B.  Gladfelter,  I  observed  an 
adult  and  calf,  with  a  second  adult  in  close 
attendance.  All  were  resting  at  the  surface  in 
open  water  on  a  day  of  remarkable  calm.  One 
adult  frequently  rolled  on  its  side,  raising  a  flipper 
and  half  of  the  tail  flukes  above  the  surface.  The 
distance  from  the  point  of  observation  was  too 
great  to  confirm  whether  or  not  the  calf  nursed. 
They  remained  in  the  same  location  for  30  min  and 
were  still  there  when  observation  was  terminated. 

From  0715  to  0800  h  on  16  April  1970,  two 
adults  accompanied  by  their  calves  with  an 
estimated  length  of  6-7  m  remained  in  a  sheltered 
cove  at  Hopkins  Marine  Station  in  Pacific  Grove, 
Monterey  County,  where  the  water  depth  is  12  m. 
Both  calves  appeared  to  nurse  when  the  adults 
rolled  on  their  longitudinal  axes,  each  with  a 
flipper  and  half  fluke  raised.  Although  the  calves 
were  mottled  in  pigmentation,  no  barnacle  in- 
crustations could  be  seen  on  the  dorsal  areas. 
Upon  completion  of  the  nursing  behavior  the 
adults,  very  closely  accompanied  by  their  calves, 
swam  off  on  a  course  following  the  shore  of 
Monterey  Bay.  Northbound  whales  unaccom- 
panied by  calves  for  the  most  part  follow  a  direct 
course  from  the  vicinity  of  Point  Pinos,  Monterey 
County,  toward  Davenport,  Santa  Cruz  County, 
48  km  to  the  north. 

At  0900  h  on  15  May  1971,  at  Julia  Pfeiffer 
Burns  State  Park,  40  km  south  of  Carmel, 
Judson  E.  Vandevere  and  I  observed  two  adults, 
one  very  closely  accompanied  by  a  half-grown 
calf.  They  swam  steadily  north  very  close  to, 
and  in  some  instances  through,  the  outer  edges 
of  the  kelp  beds. 


615 


At  1200  h  on  3  May  1973,  at  Hopkins  Marine 
Station  in  Pacific  Grove,  an  adult  and  calf,  closely 
attended  by  two  more  adults,  the  four  in  very 
close  formation  and  almost  touching,  followed  a 
course  identical  with  that  of  the  animals  seen 
on  16  April  1970.  They  did  not  appear  to  stop 
and  nurse  although  there  was  much  splashing  and 
rolling  on  their  sides  as  they  proceeded. 

In  addition  to  these  observations,  L.  G.  Ingles 
(1965:329)  recorded  an  instance  of  nursing 
behavior  observed  "early  one  April  a  few  miles 
south  of  Carmel."  P.  Sund  of  the  National 
Marine  Fisheries  Service  reported  (pers.commun.) 
that  on  23  January  1973,  during  aerial  census- 
ing  of  southbound  gray  whales,  he  observed  an 
adult  with  a  small  nursing  calf  just  north  of 
Pt.  Sur,  Monterey  County.  This  is  the  first 
instance  which  has  come  to  the  attention  of  this 
author,  of  a  calf  born  north  of  San  Diego,  Calif. 

Hubbs  (1959)  in  describing  the  northwar  mi- 
gration off  southern  California  stated  "the  cows 
with  calves  seem  to  take  a  more  offshore  path." 
With  the  possible  exception  of  the  1970  record,  my 
own  observations  suggest  that  females  accom- 
panied by  calves  keep  very  close  to  shore,  often 
moving  through  the  outer  fringes  of  the  exten- 
sive beds  of  giant  kelps.  In  all  of  these  observa- 
tions the  very  close  proximity  of  calves  to 
females  when  swimming  was  apparent.  J.  S. 
Leatherwood  (pers.  commun.)  indicated  that  his 
aerial  observations  showed  the  calves  "all  nearly 
touching  the  mother." 

Sexual  Behavior  of  Courting  and 
Possibly  of  Mating  Pairs  and  Trios 

Published  reports  of  sexual  activity  in  gray 
whales  outside  the  known  calving  areas  in  west- 
ern Mexico  were  reviewed  by  Rice  and  Wolman 
(1971:97).  They  are  of  a  fragmentary  nature  and 
include  a  single  observation  in  Humboldt  County 
in  northern  California  (Houck,  1962)  and  several 
summer  reports  of  courtship  behavior  and  ap- 
parent copulation  from  the  Bering  Sea  (Tomilin, 
1937;  Sauer,  1963;  Fay,  1963).  In  addition,  Gil- 
more  (1960:12)  stated  that  gray  whales  "occasion- 
ally calve  and  more  often  mate  in  waters  off  San 
Diego."  The  species  bred  in  large  numbers  in  San 
Diego  Bay  until  the  1870's  (Gilmore,  1960). 

It  would  therefore  seem  worthwhile  to  indicate 
that  such  activity  is  not  unknown  in  the  Monterey 
Bay  area  of  central  California.  It  has  been 
observed  during  both  the  southbound  and  the 


return  migration  (See  Table  1). 

In  all  cases  the  attention  of  the  observer  was 
first  drawn  to  these  whales  by  behavior  unlike 
that  of  the  normal  activity  of  migrating  whales. 
The  whales  remained  in  one  particular  place  for 
long  periods  and  frequently  exposed  flukes  and 
flippers  in  a  manner  not  typically  seen  in  actively 
migrating  individuals. 

Because  Sauer  ( 1963)  provides  the  only  detailed 
published  description  of  courtship  behavior  in  this 
species,  I  have  used  the  same  terminology  in 
the  present  account.  After  cessation  of  migratory 
swimming,  the  whales  remained  for  the  most 
part  within  a  very  small  area,  with  one  individual, 
thought  to  be  the  9 ,  proceeding  to  swim  almost 
imperceptibly,  with  an  "exaggerated  arching" 
(Sauer's  phrase)  out  of  the  water  of  the  back  and 
caudal  area.  This  was  repeated  several  times,  fol- 
lowing which  the  S  appeared  to  maneuver  to  get 
beneath  the  9 ,  by  rolling  on  his  side  with  one 
flipper  and  half  of  the  fluke  raised  vertically 
above  the  water  surface.  After  one  or  more 
attempts  in  this  manner,  the  "2  rolled  around  the 
longitudinal  axis"  (Sauer's  phrase)  and  in 
apparent  genital  contact  the  whales  proceeded  to 
"swim  in  line"  (Sauer's  phrase)  for  periods  of  up 
to  30  s.  In  this  position  the  left  flipper  of  the  <5 
and  the  right  flipper  of  the  S ,  together  with  the 
left  half  of  the  male's  flukes  and  the  right  half 
of  that  of  the  female  were  raised  above  the  surface 
as  the  two  whales  moved  very  slowly  forward. 

The  ?  in  the  initial  stages,  and  prior  to  rolling 
around  the  longitudinal  axis,  often  raised  her  head 
from  the  water  at  a  35"  angle.  The  swimming  in 
line  sometimes  began  or  ended  with  both  animals 
apparently  in  genital  contact  vertically  in  the 
water  column,  both  with  their  heads  raised  above 
the  water  surface  and  some  3 — 4  m  apart. 

The  fact  that  this  was  copulatory  behavior  of 
considerable  intensity  was  apparent  from  the 
erect  penis  of  the  male,  which  was  clearly  visible 
on  many  occasions.  When  the  2  failed  to  roll  on 
her  side,  the  S  then  appeared  at  the  surface  ven- 
tral side  uppermost  with  penis  erect  in  an  approxi- 
mate semicircle.  Gilmore  (1954)  illustrates  this 
posture.  On  one  occasion  (28  January  1971)  while 
the  6  swam  in  this  way,  the  penis  was  seen  to  be 
extruded  and  withdrawn.  The  sequence  of  events 
leading  to  copulation  was  repeated  as  many  as 
three  times  within  a  2-h  period. 

It  is  of  interest  to  note  that  on  six  of  the  eight 
occasions  on  which  courtship  behavior  was  ob- 
served, there  were  three  whales  involved.  The 


616 


Table  1. — Sexual  behavior,  indicating  date,  water  depth,  locality,  migration  direction  and  remarks. 


Date 

time 
water  depth 


Location' 


Direction 

of 
nnigration 


Remarks 


27  Jan.  1968 

300  m  off  Lover  s 

1520-1720  h 

Point,  Pacific  Grove 

18  m 

27  Mar.  1970 

850  m  offshore  at 

1230-1300 h 

Lucia.  70  km  south 

40  m 

of  Carmel 

28  Jan.  1971 

400  m  off  Hopkins 

1445-1600  h 

Marine  Station. 

32  m 

Pacific  Grove 

3  Feb.  1971 

400  m  off  Cannery 

0700-1200  h 

Row.  Monterey 

30  m 

18  Mar    1972 

near  Point  PInos. 

0925-1000  ti 

Pacific  Grove 

30  m 

21  Mar.  1972 

400  m  ncwth  of 

1230-1430  h    . 

Point  Pinos, 

40  m 

Pacific  Grove 

24  Mar.  1972 

1  km  north  of 

1700  h 

Lovers  Point, 

40  m 

Pacific  Grove 

4  Apr    1972 

Close  to  Point  Pinos 

1800-1830  h 

Pacific  Grove 

20  m 

south 


north 


south 


south 


north 


north 


north 


north 


2  whales  attempting  copulation  (see  text  for  description) 


3  whales  lay  at  the  surface  and  rolled  on  their  sides  Water  surface 
much  agitated  and  2  animals  seen  to  surface  with  heads  vertically 
thrust  from  the  water  as  far  as  the  eye,  in  close  enough  contact  to 
be  attempting  copulation.  No  penis  observed  0.5  km  away  another 
pair  behaving  similarly.  Water  exceptionally  calm. 

3  whales  made  repeated  attempts  at  copulation  (see  text  for 
description). 


2  whales  repeatedly  attempted  copulation. 


3  courting  whales  observed  by  Margot  Nelson.  Erect  penis  of  S 
clearly  seen  during  attempted  copulation 


3  courting  whales.  Still  in  progress  when  observation  terminated 
(see  text  for  description) 


3  courting  whales  observed.  Too  far  off  for  details  to  be  observed, 
although  behavior  pattern  similarto  that  observed  on  other  occasions. 


3  courting  whales  Behavior  similar  to  that  observed  on  other  occa- 
sions, although  no  penis  observed.  For  whole  period  of  observation 
3-4  California  sea  lions  Zaiophus  calilornianus  cavorted  around  the 
whale  trio,  about  their  heads,  moving  under  and  over  the  whales, 
often  "porpoising."  On  occasion  the  sea  lions  would  remain  vertically 
in  the  water,  heads  down  beneath  the  surface,  presumably  observing 
the  whales,  while  their  hind  flippers  protruded  from  the  surface. 


'All  locations  in  Monterey  County,  Calif. 


third  whale  was  always  in  very  close  attendance 
and  apparently  in  bodily  contact  with  the  pair 
attempting  mating.  Gilmore  (1960:16;  1968:12) 
observed  such  trios  in  Mexican  waters  and  specu- 
lated that  the  third  whale  was  another  <J .  "With 
half  of  the  females  unavailable  each  winter  Tor 
mating',  there  are  two  eligible  males  for  each 
female."  He  described  the  apparent  lack  of  aggres- 
sion between  SS,  and  this  appeared  to  be  so  in  the 
present  observations.  Walker  (1971:403)  believed 
the  second  male  in  such  trios  helps  to  stabilize 
the  mating  pair.  More  detailed  aerial  observation 
will  be  needed  to  clarify  the  role  of  the  second 
male. 

In  comparing  the  Monterey  observations  with 
Sauer's  detailed  Bering  Sea  account,  the  following 
differences  were  noted: 

1.  His  observations  appear  to  have  involved 
pairs  rather  than  trios,  although  Fay  (1963)  re- 
ported three  whales  involved  in  "courtship  play" 
some  30  km  from  the  site  of  Sauer's  observations. 


2.  Sauer  does  not  mention  seeing  the  penis  dis- 
played. 

3.  Sauer's  animals  repeatedly  swam  in  circles 
50-200  m  in  diameter.  Such  circling  was  not  dis- 
cernible in  Monterey,  where  the  activity  took 
place  in  the  open  sea  rather  than  within  the  con- 
fines of  a  small  bay. 

4.  His  description  of  the  female  initiating  and 
achieving  copulation  (Sauer,  1963:166)  by  means 
of  a  "touch  display"  could  not  be  verified  in  Mon- 
terey, where  the  observers'  viewpoint  was  usually 
only  7-8  m  above  the  water  surface  and  the  whales 
from  300  to  600  m  distant.  Sauer  (1963:159)  also 
described  the  whales  as  sensitive  to  his  silhouette 
on  the  cliffs  above  and  liable  to  break  off  courtship 
activity.  This  contrasts  with  behavior  in  Mon- 
terey, where  courting  pairs  and  trios  were  seen  on 
three  occasions  to  be  approached  by  powered  boats 
to  within  a  few  meters  without  apparent  interrup- 
tion of  their  activity.  No  "post-copulatory  shake" 
was  observed  among  the  Monterey  animals. 


617 


Acknowledgments 

I  would  like  to  thank  M.  Nelson,  J.  E.  Vande- 
vere,  and  H.  L.  Wilhelm  who  in  some  cases  ini- 
tially located  the  whales  described  and  Kenneth 
S.  Norris  for  reading  and  commenting  upon  the 
manuscript. 

Literature  Cited 

Baldridge,  a. 

1972.     Killer  whales  attack  and  eat  a  gray  whale.     J. 
Mammal.  53:898-900. 
Fay,  F.  H. 

1963.  Unusual  behavior  of  gray  whales  in  summer.  Psy- 
chol. Forsch.  27:175-176. 

GiLMORE,  R.  M. 

1954.    The  return  of  the  gray  whale.    Sci.  Am.  192(1):62- 

67. 
1960.     A  census  of  the  California  gray  whale.     U.S.  Fish 

Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish.  342,  30  p. 
1968.    The  gray  whale.    Oceans  Mag.  l(l):9-20. 
HOUCK,  W.  J. 

1962.  Possible  mating  of  grey  whales  on  the  northern 
California  coast.     Murrelet  43:54. 

HuBBS,  G.  L. 

1959.     Natural  history  of  the  grey  whale.  Proc.  XVth  Int. 
Congr.  Zool.,  p.  313-316. 
Ingles,  L.  G. 

1965.     Mammals  of  the  Pacific  States;  California,  Oregon 
and  Washington.  Stanford  Univ.  Press,  Stanford,  506  p. 
MOREJOHN,  G.  V. 

1968.    A  killer  whale — gray  whale  encounter.    J.  Mammal. 
49:327-328. 
Rice,  D.  W.,  and  A.  A.  Wolman. 

1971.     The  life  history  and  ecology  of  the  gray  whale 
{Eschrichtius  robustus).    Am.  Soc.  Mammal.,  Spec.  Publ. 
3,  142  p. 
Sauer,  E.  G.  F. 

1963.  Courtship  and  copulation  of  the  gray  whale  in  the 
Bering  Sea  at  St.  Lawrence  Island,  Alaska.  Psychol. 
Forsch.  27:157-174. 

Tomilin,  a.  G. 

1937.    Kity  Dal'nego  Vostoka  (The  whales  of  the  Far  East). 
[Engl,  summ.]     Uch.  Zap.  Mosk.  Gos.  Univ.,  Ser.  Biol. 
Nauk  13:119-167. 
Walker,  T.  J. 

1971.  The  California  gray  whale  comes  back.  Natl.  Geogr. 
Mag.  139:394-415. 


Alan  Baldridge 


Hopkins  Marine  Station  of 
Stanford  University 
Pacific  Grove,  CA  93950 


NET  FILTERING  EFFICIENCY 

OF  A  3-METER 

ISAACS-KIDD  MIDWATER  TRAWL 


The  errors  associated  with  quantitative  sampling 
of  open  ocean  populations  of  zooplankton  and 
epipelagic  nekton  have  received  considerable 
attention.  Net  selectivity,  net  sampling  efficiency, 
and  patchiness  have  been  examined  by  Barkley 
(1964),  Murphy  and  Clutter  (1972),  and  Wiebe 
and  Holland  (1968),  respectively.  Studies  of  the 
error  caused  by  avoidance  have  been  summarized 
by  Clutter  and  Anraku  (1968)  and  further 
advanced  by  Barkley  (1972).  Aron  and  Collard 
(1969)  have  reported  on  the  effects  of  net  speed 
on  catch.  Extrusion  of  organisms  through  the  net, 
the  degree  of  mesh  retention,  and  the  effects  of 
net  clogging  have  been  summarized  by  Vannucci 
(1968),  and  a  review  of  filtration  problems  has 
been  presented  by  Tranter  and  Smith  (1968). 

Somewhat  less  effort  has  been  directed  toward 
problems  encountered  in  sampling  the  mid- 
water  fish  fauna.  Harrison  (1967)  reported  on  the 
reliability  of  trawl  data,  the  bias  that  may  result 
from  using  various  types  of  gear,  and  the  prob- 
lems associated  with  sampling  mesopelagic  fishes. 
These  fishes  are  commonly  sampled  with  an 
Isaacs-Kidd  Midwater  Trawl  (IKMT)  (Isaacs  and 
Kidd,  1953)  and  results  of  such  sampling,  which 
include  considerations  of  net  performance,  have 
been  reported  by  Pearcy  and  Laurs  (1966),  Gibbs 
et  al.  (1971),  Friedl  (1971),  Backus  (1972)  Krue- 
ger  and  Bond  (1972),  and  others. 

Net  performance  is  critically  dependent  on  the 
filtering  efficiency  of  the  net.  Filtering  efficiency 
is  a  measure  of  the  total  volume  of  water  fil- 
tered by  the  net  and  enables  a  better  quantitative 
estimate  to  be  made  of  the  actual  population 
density  of  organisms  sampled.  Pearcy  and  Laurs 
(1966)  reported  a  filtering  efficiency  of  85%  for 
a  2-m  IKMT.  To  the  authors'  knowledge,  no 
comparable  figure  has  been  published  for  the 
3-m  IKMT.  This  paper  investigates  the  efficiency 
of  this  larger  net. 

Methods 

In  conjunction  with  studies  of  macroplankton 
and  midwater  fishes  of  an  area  off  Bermuda 
called  Ocean  Acre  (Brooks,  1972),  experiments 
were  conducted  in  January  1973  to  determine 
the  net  filtering  efficiency  of  a  3-m  IKMT. 


618 


Although  the  design  and  shape  of  the  2-  and  3-m 
IKMTs  in  general  use  are  similar,  it  is  obvious 
from  the  literature  that  net  construction  may  vary 
considerably.  The  size  of  the  mesh  and  the  thread 
of  the  outer  net  may  differ  widely,  as  may  the 
pattern  of  a  graded  mesh.  Liner  mesh  size,  type, 
and  placement  within  the  outer  net,  as  well  as 
size,  shape,  and  mesh  of  the  cod  end  of  the  net, 
may  also  differ.  As  shown  in  Table  1,  the  cross- 
sectional  area  of  the  net  mouth  may  also  vary. 

Since  the  influence  of  such  factors  on  the  filter- 
ing efficiency  of  a  given  net  can  be  considerable, 
the  net  used  in  the  present  experiment  is 
described  in  detail.  Dimensions  and  material 
specifications  are  shown  in  Table  2.  The  net  was 
made  of  No.  21  thread  nylon  and  has  outer  walls 
of  6.36-cm  stretch  mesh.  The  entire  inner  surface 
of  the  net  was  lined  with  No.  42  thread  knotless 
nylon  having  a  0.95-cm  stretch  mesh,  which  was 
sewn  to  the  outer  walls  of  the  net  at  every  foot. 

The  aft  tube  of  the  IKMT  was  fitted  with  four 
rings  made  of  0.95-cm-diameter  stainless  steel 
rod  spaced  as  follows:  one  0.81-m-diameter  ring  at 
the  aft  end  of  the  funnel,  one  1-m-diameter  ring 
at  the  aft  end  of  the  tube,  and  two  0.66-m-diameter 
rings  in  the  aft  tube  centered  between  the  other 
rings.  The  mouth  of  the  net  was  hung  on  1.59-cm- 
diameter  Polydac^  net  rope  with  four  legs  extend- 
ing 0.61  m  and  the  center  bosom  leg  extending 
0.41  m.  Riblines,  composed  of  0.95-cm-diameter 
nylon  rope,  were  rigged  down  each  of  the  five 
seams  from  the  mouth  opening  to  the  cod  end. 
A  standard  1-m  conical  nylon  plankton  net  (1-m 
mouth  diameter  tapering  to  19  cm  over  its  length 
of  3  m)  of  No.  00  mesh  (0.752-mm  aperture)  was 
attached  to  the  aft  end  of  the  main  body  of  the 
IKMT.  Dimensions  of  the  IKMT  mouth  are  shown 
in  Figure  1;  cross-sectional  area  was  7.08  m^, 
and  principal  dimensions  of  bridle  and  paravane 
were  as  specified  for  the  3-m  IKMT  in  Aron  ( 1962). 

Table  1. — Mouth  area  of  Isaacs-Kidd  midwater  trawl. 


Table  2. — Dimensions  and  material  specifications  of  10-foot 
IKMT  net  used  for  filtering-efficiency  studies. 


Reference 

2-m  IKMT  (m2) 

3-mlKMT(m2) 

King  and  Iversen  (1962)' 
Aron  (1962) 

Pearcy  and  Laurs  (1966) 
Fnedl  (1971) 

3.21 

2.89 
2.94 

819 
7.44 

768 

'Calculated  from  dimensions 

given  in  Figures  7 

and  9. 

respectively. 

Item 


Dimension 


Mesh  size 

Forward  section 

Intermediate  section 

Cod  end 
Cross-section  area 

Mouth 

Intermediate  section 
Forward  end 
Mid  section 
Aft  end 

Cod  end 
Filtering  area 

Forward  section 

Intermediate  section 

Cod  end 


'0.95 

Dm 

'0.95 

cm 

0.75  mm 

7.08 

m2 

052 

m2 

0.34 

m2 

0.79 

m2 

0.79 

m2 

52.39 

m2 

12.12 

m2 

2.27 

m2 

'Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


'Knotless  nylon  liner — stretched  mesh  size 

When  the  net  is  in  regular  use,  a  Mark  III  ( 15-cm- 
diameter)  GM  discrete-depth  plankton  sampler 
(DDPS)  (Aron  et  al.,  1964)  is  attached  to  the  aft 
end  of  the  1-m  plankton  net. 

Estimates  of  the  filtering  efficiency  of  the  3-m 
IKMT  described  here  were  obtained  by  two  dif- 
ferent methods.  In  the  first  method,  a  calibrated 
TSK  (Tsurumi-Seiki  Kosakusho)  flowmeter  was 
mounted  in  the  net  mouth  as  shown  in  Figure  1. 
The  meter  (A)  was  tautly  suspended  by  0.32-cm 
steel  cable  (B)  inside  a  1-m-diameter  ring  of  1.9- 
cm-diameter  brass  rod  (C).  The  1-m  ring,  in  turn, 
was  suspended  in  the  net  mouth  by  three  legs  of 
0.95-cm-diameter  shock  cord  (D).  Each  leg  of  the 
shock  cord  was  tensioned  so  that  the  ring  and 
suspended  flowmeter  were  positioned  in  the  ap- 
proximate center  of  the  net  mouth  and  maintained 
at  right  angles  to  the  water  flow  during  net 
towing.  During  the  tows,  the  shock  cord  stretched, 
positioning  the  ring  and  flowmeter  about  1  m 
inside  the  net  mouth.  It  is  assumed  that  the  water 
flow  at  the  center  of  the  net  mouth  was  represen- 
tative of  the  average  flow  through  the  entrance. 
A  second  TSK  meter  of  identical  design  and 
calibration  characteristics  was  mounted  on  the 
spreader  bar  outside  the  net.  The  difference  in  the 
number  of  revolutions  registered  by  the  two 
meters  was  used  in  arriving  at  the  estimate  of 
filtering  efficiency.  The  four-bladed  impeller  of 
each  meter  was  restrained  from  turning  until 
after  the  net  was  launched  and  in  its  towing 
position. 

In  the  second  method  used  to  determine  filtering 
efficiency,  a  Clarke-Bumpus  (C-B)  plankton 
sampler  (Clarke  and  Bumpus,  1950),  with  shutter 


619 


2.286  m 


o 
CO 


Figure   1. 


A-METER 
B- STEEL  CABLE 
C-BRASS  ROD 
D- SHOCK  CORD 


-Diagrammatic   view  of  3-m  IKMT  mouth  with 
mounted  flowmeter. 


and  net  removed,  was  suspended  in  the  IKMT 
mouth.  This  sampler  had  been  calibrated  by 
carefully  controlled  tows  over  distances  of  2  and 
6  nautical  miles  before  being  installed  in  the 
IKMT.  Start  and  end  positions  for  each  tow  were 
determined  by  radar,  LORAN,  and  shore  fixes. 

The  three  legs  of  shock  cord  used  in  the  pre- 
vious trial  were  attached  directly  to  the  frame  of 
the  C-B  sampler  so  that  the  flowmeter  could 
pivot  freely  within  its  frame.  During  launch  and 
again  as  soon  as  the  flowmeter  cleared  the  water 
during  retrieval,  the  flowmeter  automatically 
pivoted,  causing  the  axis  of  the  impeller  to  lie 
perpendicular  to  the  direction  of  the  tow;  i.e.,  the 
meter  did  not  register.  The  impeller  blade  housing 
protected  the  blades  from  winds,  thus  preventing 
rapid  spinning  of  the  impeller  and  erroneous  flow 
readings.  As  soon  as  the  net  was  lowered  and  in 
towing  position,  proper  aspect  of  the  impeller  axis 
(parallel  to  the  flow)  was  maintained  by  water 
pressure  acting  on  the  stabilizing  fins  attached  to 
the  impeller  blade  housing. 

Two  net  tows  were  carried  out  using  this 
apparatus,  with  the  shock  cord  again  stretching  to 
place   the   C-B  sampler  just  inside  the   net 


mouth.  Start  and  end  positions  were  obtained,  as 
during  the  calibration  runs,  by  radar,  LORAN, 
and  shore  fixes.  Previously  determined  calibra- 
tion information  allowed  calculation  of  the 
number  of  revolutions  that  would  have  resulted 
if  the  sampler  had  been  towed  by  itself  over  the 
same  known  distances  covered  during  the  two 
tows. 

All  net  tows  were  made  at  ship  speeds  ranging 
between  3  and  4.5  knots  over  distances  of  6  and 
10.75  nautical  miles.  The  direction  of  the  tows  was 
approximately  perpendicular  to  the  prevailing 
current  flow.  Very  little  biological  material  was 
captured  during  these  net  tests,  hence  clogging 
was  considered  a  negligible  factor. 

Results  and  Discussion 

The  two  methods  used  to  determine  filtering 
efficiency  yielded  similar  results  (Figure  2).  For 
method  1,  the  total  number  of  revolutions  (N') 
registered  by  the  meter  in  the  net  mouth  is 
plotted  against  the  number  of  revolutions  (N) 
registered  by  the  meter  on  the  spreader  bar  for  the 
two  net  lowerings.  These  results  are  shown  as 
squares.  For  method  2,  the  number  of  revolu- 
tions (N')  registered  by  the  calibrated  C-B  meter 

n    INDICATES  NUMBER  OF  REVOLUTIONS  REGISTERED  BY 
THE  METER  ON  THE  SPREADER  BAR  (N)  PLOHED  AGAINST 
NUMBER  OF  REVOLUTIONS  REGISTERED  BY  THE  METER  IN 
THE  NET  MOUTH  (N'l  FOR  TWO  NET  LOWERINGS  (METHOD  1). 

A  INDICATES  NUMBER  OF  REVOLUTIONS  EQUIVALENT  TO 
THE  DISTANCE  TOWED  (N)  PLOTTED  AGAINST  NUMBER  OF 
REVOLUTIONS  REGISTERED  BY  CALIBRATED  C-B  IN  THE 
NET  MOUTH  (N')  (METHOD  2). 


100 

CO 

O 

X  80 

CO 

Z 

g 
5  60 

6 
> 


EFFICIENCY=92%         ^t-. 


120 


N  (REVOLUTIONS)  x  lO" 
Figure  2.— Filtering  efficiency  of  3-m  IKMT. 


620 


in  the  net  mouth  is  plotted  against  the  number 
of  revolutions  (N)  obtained  in  the  calibration 
distance  tow.  These  data  are  shown  as  triangles. 
A  linear  regression  analysis  performed  on  the 
data  points  produced  the  regression  line  shown  in 
Figure  2.  The  slope  of  the  line  (regression  coef- 
ficient) was  taken  as  a  measure  of  the  filtering 
efficiency  of  the  3-m  IKMT  and  had  a  value  of 
92%.  Although  the  filtering  efficiency  determined 
by  this  study  applies  to  the  specific  net  described 
in  this  note,  it  can  probably  serve  as  a  guide  to 
the  filtering  efficiency  of  most  3-m  IKMTs  and 
enable  a  better  quantitative  estimate  to  be  made 
of  the  actual  population  density  of  organisms 
sampled. 

Acknowledgments 

We  wish  to  thank  George  Botseas  for  computer 
calculations  and  graphs.  This  task  was  sponsored 
by  Naval  Ships  Systems  Command,  Code  302-4, 
under  Subproject  Number  SF  52552004. 

Literature  Cited 

Aron,  W. 

1962.     Some  aspects  of  sampling  the  macroplankton. 
Rapp.  P.-V.  Reun.,  Cons.  Perm.  Int.  Explor.  Merl53:29- 
38. 
Aron,  W.,  and  S.  Collard. 

1969.     A  study  of  the  influence  of  net  speed  on  catch. 
Limnol.  Oceanogr.  14:242-249. 
Aron,  W.,  N.  Raxter,  R.  Noel,  and  W.  Andrews. 

1964.     A  description  of  a  discrete-depth  plankton  sampler 
with  some  notes  on  the  towing  behavior  of  a  6-foot 
Isaacs-Kidd  Mid-water.  Trawl  and  a  one-meter  ring  net. 
Limnol.  Oceanogr.  9:324-333. 
Backus,  R.  H. 

1972.     Midwater  fish  distribution  and  sound-scattering 
levels  in  the  North  Atlantic  Ocean  (U).     U.S.  Navy  J. 
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Barkley,  R.  a. 

1964.     The  theoretical  effectiveness  of  towed-net  samplers 
as  related  to  sampler  size  and  to  swimming  speed  of 
organisms.     J.  Cons.  29:146-157. 
1972.     Selectivity  of  towed-net  samplers.     Fish.  Bull.,  U.S. 
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Brooks,  A.  L. 

1972.     Ocean  Acre;  Dimensions  and  characteristics  of  the 
sampling  site  and  adjacent  areas.     NUSC  (Nav.  Under- 
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Clarke,  G.  L.,  and  D.  F.  Bumpus. 

1950.     The  plankton  sampler — An  instrument  for  quanti- 
tative plankton   investigations.     Limnol.   Oceanogr. 
Spec.  Publ.  No.  5.,  Revised  1950. 
Clutter,  R.  I.,  and  M.  Anraku. 

1968.  Avoidance  of  samplers.  In  D.  J.  Tranter  (editor), 
Part  I,  Reviews  on  zooplankton  sampling  methods, 
p.  57-76.  UNESCO  Monogr.  Oceanogr.  Methodol.  2, 
Zooplankton  sampling. 


Friedl,  W.  a. 

1971.     The  relative  sampling  performance  of  6-  and  10-foot 
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1971.  Biological  studies  of  the  Bermuda  Ocean  Acre. 
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Harrisson,  C.  M.  H. 

1967.  On  methods  for  sampling  mesopelagic  fishes.  In 
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Isaacs,  J.  D.,  and  L.  W.  Kidd. 

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King,  J.  E.,  and  R,  T.  B.  Iversen. 

1962.     Midwater  trawljng  for  forage  organisms  in  the 
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Krueger,  W.  H.,  and  G.  W.  Bond. 

1972.  Biological  studies  of  the  Bermuda  Ocean  Acre.  IIL 
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Murphy,  G.  I.,  and  R.  I.  Clutter. 

1972.     Sampling  anchovy  larvae  with  a  plankton  purse 
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1966.     Vertical  migration  and  distribution  of  mesopelagic 
fishes  off  Oregon.     Deep-Sea  Res.  13:153-165. 
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1968.  Filtration  performance.  In  D.  J.  Tranter  (editor), 
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Vannucci,  M. 

1968.     Loss  of  organisms  through  the  meshes.    In  D.  J. 
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Wiebe,  p.  H.,  and  W.  R.  Holland. 

1968.  Plankton  patchiness:  Effects  on  repeated  net  tows. 
Limnol.  Oceanogr.  13:315-321. 


New  London  Laboratory 

Naval  Underwater  Systems  Center 

New  London,  CT  06320 


New  London  Laboratory 

Naval  Underwater  Systems  Center 

New  London.  CT  06320 

On  exchange  from 
R.A.N.  Research  Laboratory 
Garden  Island,  N.S.W.  2000 
Australia 


A.  L.  Brooks 
C.  L.  Brown,  Jr. 


P.  H.  Scully-Power 


621 


AMERICAN  LOBSTERS  TAGGED 
BY  MAINE  COMMERCIAL  FISHERMEN, 

1957-59 


In  1957  at  the  suggestion  of  C.  Owen  Smith, 
then  editor  of  the  "Maine  Coast  Fisherman," 
several  commercial  lobster  fishermen  volunteered 
to  tag  illegal  American  lobster,  Homarus  ameri- 
canus,  with  tags  furnished  by  the  Maine  Depart- 
ment of  Sea  and  Shore  Fisheries.  The  purpose 
of  the  tagging  was  to  obtain  additional  informa- 
tion on  the  migratory  behavior  of  lobsters. 

Between  April  1957  when  the  first  lobster  was 
tagged  and  October  1959  when  the  last  of  the 
recaptures  was  reported,  162  lobsters  ranging 
from  78  to  200  mm  in  carapace  length  (CD 
were  tagged  and  released  under  this  cooperative 
program.  No  legal  lobsters  were  tagged.  The 
lobsters  consisted  of  four  illegal  classifications: 
1)  those  with  extruded  eggs,  2)  those  less  than  the 
legal  minimum  size,  3)  those  larger  than  the  legal 
maximum  size,  and  4)  those  which  had  had  a 
V-shaped  notch  cut  into  the  telson  to  signify 
successful  motherhood.  Seventy-three  were 
tagged  in  Penobscot  Bay  (72  in  1957  and  1  in 
1958)  and  89  in  Sheepscot  Bay  (all  in  1958). 

The  small  number  of  lobsters  involved  does  not 
permit  definitive  conclusions  regarding  their 
behavior.  The  evidence  furnished  by  the  results 
does  not  agree  with  tagging  reports  before  and 
since  (Harriman  1952,'  Cooper  1970)  of  an  area 
which  apparently  is  more  isolated  and  the  lobster 
population  more  static. 

Of  the  lobsters  tagged,  75  or  46%  were  127  mm 
or  larger  in  carapace  length.  Only  23  or  14%  of 
the  total  tagged  were  recaptured  (2  were  recap- 
tured twice),  14  were  recaptured  after  more  than 
1  mo  of  freedom,  and  the  remaining  9  were 
recaptured  within  1  mo.  Although  only  18  or  24% 
of  large  lobsters  (127-200  mm)  were  recaptured, 
they  represented  78%  of  all  lobsters  recovered 
(Table  1).  Four  or  22%  of  large  lobsters  recap- 
tured, all  from  Penobscot  Bay,  traveled  75  or 
more  nautical  miles  from  the  point  of  release  to 
the  place  of  recovery  (Table  2,  Figure  1).  In 
addition,  one  V-notched  female  of  111  mm  CL 
tagged  near  Tom  Rock,  Sheepscot  Bay,  was  re- 


Cope  Porpoise 


0^ 


N,H.      UCapeAnn^         ^^, 
>*  Gloucester 

X  Race  Point 


w  Nouset  Light 


•      LOCATION   OF  RELEASE 
X     POINT  OF  RECOVERY 


'Harriman,  D.  M.  1952.  Progress  report  on  Monhegan 
tagging — 1951-1952.  Maine  Dep.  Sea  Shore  Fish.,  Augusta. 
(Unpubl.  Rep.) 


Figure  1. — Location  of  release  and  point  of  recovery  of  the 
five  major  wandering  lobsters. 


captured  7  mo  later  near  Race  Point  Light  off 
Provincetown,  Mass. 

The  four  from  Penobscot  Bay  included  a  large 
female  tagged  near  Little  Green  Island  and 
recaptured  near  Timber  Island,  Cape  Porpoise, 
2  mo  later;  another  large,  sexually  unidentified 
lobster  also  tagged  near  Little  Green  Island  in 
April  1957  and  recaptured  near  Gloucester,  Mass., 
14  mo  later;  and  a  133-mm  CL  male  tagged  12 
September  1957,  near  Little  Green  Island  and 
recaptured  19  March  1959,  near  Cape  Ann  Light, 
Mass.  The  longest  migration  was  from  Penobscot 
Bay  to  Nauset  Light,  Mass.,  an  estimated  straight- 
line  distance  of  138  nautical  miles  (250  km)  made 
in  13  mo  by  a  lobster  greater  than  127  mm  CL 
and  of  unidentified  sex. 

Of  the  five  major  wandering  lobsters,  four 
exceeded  the  Maine  maximum  legal  size  of  127 
mm,  suggesting  that  large  mature  lobsters  are 
more  prone  to  major  migration  than  are  smaller 
lobsters. 

Before  they  were  recaptured,  6%  of  the  68 
Penobscot  Bay  tagged  lobsters  between  127 
and  151  mm  CL  traveled  between  75  and  138 
nautical  miles  from  the  release  area.  This  com- 
pares with  an  average  7%  recovery  of  all  sizes 
reported  by  Cooper  and  Uzmann  (1971)  of  their 
tagging  from  April  1968  to  June  1969. 

One  79-mm  CL  female,  the  smallest  lobster 
recaptured,  traveled  less  than  6  nautical  miles 
(10.9  km)  in  9  mo.  All  other  recaptures  were 
lobsters  90  mm  or  larger.  One  of  these  traveled 


622 


Table  1. — Tagging  and  recovery  data.' 


Carapace 
Length  (mm) 


Tagged  lobsters 

Total 

Recovered  1 

obsters 

Penobsco 

t  Bay 
Unk 

Sheepscot  Bay 
M        F      Unk 

Penobsc 

Dt  Bay 
Unk 

Shee 

pscot  Bay 

F 

M         F 

M 

F 

Total 

1          3 

40       25 

1 

3 

3 
31 

14 
39 

2 

4 
71 

15 
72 

1 
10 

5 

2 

2 
3 

1 

17 
2 
3 

41        29 

3 

34 

53 

2 

162 

11 

5 

2 

5 

23 

178-200 

127-151 

102-126 

78-101 


Total 


'M  =  male.  F  =  female,  Unk  =  not  determined. 


Table  2. — Information  on  the  five  major  wandering  lobsters. 


Approximate  distance 
traveled 


Tagging 
site 


Sex' 


Carapace 
length! 
(mm) 


Tagging 
date 


Recapture 
site 


Recapture 
date 


Elapsed 
time 
(mo) 


Nautical 
miles 


km 


Little 
Green  Isl. 
Penobscot 
Bay,  Me. 

Little 
Green  Isl. 

Little 
Green  Isl. 

Little 
Green  Isl. 

Tom  Rock 
Stieepscot 
Bay.  Me. 


Unk 


Unk 


>127 


>127 


>127 


133 


111 


4/57 


5/10/57 


4/57 


9/12/57 


11/4/58 


Nauset 
Light,  Mass. 

5/26/58 

Cape  Porpoise 
Maine 

7/16/57 

Gloucester 
Mass. 

6/5/58 

Cape  Ann 
Mass, 

3/19/59 

Race  Point 
Light,  Mass. 

6/5/59 

13 


14 


18 


138 


75 


113 


113 


113 


250 


136 


205 


205 


205 


'Unk  =  not  determined,  F  =  female,  M  =  male. 


8  nautical  miles  (14.5  km);  the  remainder  less 
than  4  nautical  miles  (7.3  km).  Movements 
appeared  to  be  random  in  contrast  to  the  south- 
westerly trend  of  the  major  migrants. 

Preliminary  conclusions  resulting  from  this 
study  are  supported  by  the  frequent  comments  of 
Massachusetts  lobster  fishermen  who  profess 
appreciation  for  Maine's  maximum  size  limit 
which  permits  lobsters,  telson  V  notched  in 
Maine,  to  migrate  to  Massachusetts  where  they 
are  legal. 


Literature  Cited 

Cooper,  R.  A. 

1970.  Retention  of  marks  and  their  effects  on  growth, 
behavior,  and  migrations  of  the  American  lobster, 
Homarusamericanus.     Trans.  Am.  Fish.  Soc.  99:409-417. 

Cooper,  R.  A.,  and  J.  R.  Uzmann. 

1971.  Migrations  and  growth  of  deep-sea  lobsters,  Homar- 
us  americanus.     Science  (Wash.,  D.C.)  171:288-290. 

Robert  L.  Dow 

State  of  Maine 

Department  of  Marine  Resources 

Augusta,  ME  04330 


623 


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'  Contents-continued) 


ALVARINO,  ANGELES.  Distribution  of  siphonophores  in  the  regions  adjacent  to 
the  Suez  and  Panama  Canals 527 

RAJU,  SOLOMON  N.  Three  new  species  of  the  genus  Mofwgnatkus  and  the  lepto- 
cephali  of  the  order  Saccopharyngi formes 547 

POTTHOFFi  THOMAS.  Osteological  development  and  variation  in  young  tunas, 
genus  Thunnus  (Pisces,  Scombridae),  from  the  Atlantic  Ocean 563, 

FRENCH,  ROBERT  R.,  and  RICHARD  G.  BAKKALA.  A  new  model  of  ocean  mi- 
grations of  Bristol  Bay  sockeye  salmon 589 

Notes 

BALDRIDGE,  ALAN.  Migrant  gray  whales  with  calves  and  sexual  behavior  of 
gray  whales  in  the  Monterey  area  of  central  California,  1967-73 615 

BROOKS,  a:  L.,  C.  L.  BROWN,  JR.,  and  P.  H.  SCULLY-POWER.  Net  filter- 
ing efficiency  of  a  3-meter  Isaacs-Kidd  midwater  trawl 618 

DOW,  ROBERT  L.  American  lobsters  tagged,  by  Maine  commercial  fishermen. 
1957-59 622 


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Fishery  Bulletin 

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^^ATES  O^  ^ 


r-lnrine  Bioiogioal  laborati,:; , 

LIBRARY 


AUG  1  9  1974  ' 

Vol.  72,  No.  3  I      1:^/4  July  1974 

EVANS,  DALE  R.,  and  STANLE>)fv'©oBlCPi:affecMsf  oil  on  marine  ecosystems: 

A  review  for  administratOrs.aad4X)licy..makers. .«-.^^^,,^ 625 

JOHNSON,  MARTIN  W.  On  the  dispersal  of  lobster  larvae  into  the  East  Pacific 

Barrier  (Decapoda,  Palinuridea) 639 

PORTER,  RUSSELL  G.  Reproductive  cycle  of  the  soft-shell  clam,  Mja  arenaria,  at 

Skagit  Bay,  Washington 648 

SEIDEL,  WILBUR  R.,  and  EDWARD  F.  KLIMA.  In*  situ  experiments  with  coastal 

pelagic  fishes  to  establish  design  criteria  for  electrical  fish  harvesting  systems  657 
ROSENTHAL,  RICHARD  J.,  WILLIAM  D.  CLARKE,  and  PAUL  K.  DAYTON. 

Ecology  and  natural  history  of  a  stand  of  giant  kelp,  Macrocystis  pyrifera,  off 

Del  Mar,  California   670 

WILLIAMS,  AUSTIN  B.  The  swimming  crabs  of  the  germs  Callinecfes  (Decapoda: 

Portunidae) ■ 685 

JOHNSON,  ALLYN  G.,  FRED  M.  UTTER,  and  HAROLD  0.  HODGINS.  Elec- 

trophoretic  comparison  of  five  species  of  pandalid  shrimp  from  the  northeastern 

Pacific  Ocean   799 

HAYNES,  EVAN  B.  Distribution  and  relative  abundance  of  larvae  of  king  crab, 

Paralithodes  camtschatica,  in  the  southeastern  Bering  Sea,  1969-70 804 

FAHAY,  MICHAEL  P.  Occurrence  of  silver  hake,  Merluccius  bilinearis,  eggs  and 

larvae  along  the  middle  Atlantic  continental  shelf  during  1966 813 

WILLIAMS,  AUSTIN  B.,  THOMAS  E.  BOWMAN,  and  DAVID  M.  DAMKAER. 

Distribution,  variation,  and  supplemental  description  of  the  opossum  shrimp, 

Neomysis  americana  (Crustacea:  Mysidacea)    835 

Notes 

BAKUN,  ANDREW,  DOUGLAS  R.McLAIN,  and  FRANK  V.  MAYO.  The  mean 
annual  cycle  of  coastal  upwelling  off  western  North  America  as  observed  from 
surface  measurements 843 

SMITH,  VEGA  J.,  JAMES  S.  LIN,  and  HAROLD  S.  OLCOTT.  The  residual  lipids 
of  fish  protein  concentrates 845 

LENARZ,  WILLIAM  H.  Length- weight  relations  for  five  eastern  tropical  Atlantic 

scombrids 848 


(Continued  on  back  cover) 
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Dr.  John  R.  Hunter 

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Mr.  Alonzo  T.  Pruter 

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Dr.  Theodore  R.  Rice 

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Fishery  Bulletin 

CONTENTS 
Vol.  72,  No.  3  July  1974 

EVANS,  DALE  R.,  and  STANLEY  D.  RICE.  Effects  of  oil  on  marine  ecosystems: 

A  review  for  administrators  and  policy  makers 625 

JOHNSON,  MARTIN  W.  On  the  dispersal  of  lobster  larvae  into  the  East  Pacific 

Barrier  (Decapoda,  Palinuridea) 639 

PORTER,  RUSSELL  G.  Reproductive  cycle  of  the  soft-shell  clam,  Mya  arenaria,  at 

Skagit  Bay,  Washington 648 

SEIDEL,  WILBUR  R.,  and  EDWARD  F.  KLIMA.  In  situ  experiments  with  coastal 

pelagic  fishes  to  establish  design  criteria  for  electrical  fish  harvesting  systems  657 
ROSENTHAL,  RICHARD  J.,  WILLIAM  D.  CLARKE,  and  PAUL  K.  DAYTON. 

Ecology  and  natural  history  of  a  stand  of  giant  kelp,  Macrocystis  pyrifera,  off 

Del  Mar,  Cahfornia   670 

WILLIAMS,  AUSTIN  B.  The  swimming  crabs  of  the  genus  Callinectes  (Decapoda: 

Portunidae) 685 

JOHNSON,  ALLYN  G.,  FRED  M.  UTTER,  and  HAROLD  O.  HODGINS.  Elec- 

trophoretic  comparison  of  five  species  of  pandalid  shrimp  from  the  northeastern 

Pacific  Ocean   799 

HAYNES,  EVAN  B.  Distribution  and  relative  abundance  of  larvae  of  king  crab, 

Paralithodes  camtschatica,  in  the  southeastern  Bering  Sea,  1969-70 804 

FAHAY,  MICHAEL  P.  Occurrence  of  silver  hake,  Merluccius  hilinearis,  eggs  and 

larvae  along  the  middle  Atlantic  continental  shelf  during  1966 813 

WILLIAMS,  AUSTIN  B.,  THOMAS  E.  BOWMAN,  and  DAVID  M.  DAMKAER. 

Distribution,  variation,  and  supplemental  description  of  the  opossum  shrimp, 

Neomysis  americana  (Crustacea:  Mysidacea)    835 

Notes 

BAKUN,  ANDREW,  DOUGLAS  R.  McLAIN,  and  FRANK  V.  MAYO.  The  mean 
annual  cycle  of  coastal  upwelling  off  western  North  America  as  observed  from 
surface  measurements 843 

SMITH,  VEGA  J.,  JAMES  S.  LIN,  and  HAROLD  S.  OLCOTT.  The  residual  lipids 

of  fish  protein  concentrates 845 

LENARZ,  WILLIAM  H.  Length-weight  relations  for  five  eastern  tropical  Atlantic 

scombrids 848 

(Continued  on  next  page) 
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KLIMA,  EDWARD  F.  Electrical  threshold  response  of  some  Gulf  of  Mexico  fishes  .  851 
DURKIN,  JOSEPH  T.,  and  DAVID  A.  MISITANO.  Occurrence  of  a  ratfish  in  the 

Columbia  River  estuary   854 

MISITANO,  DAVID  A.,  and  CARL  W.  SIMS.  Unusual  occurrence  of  an  eastern 

banded  killifish  in  the  lower  Columbia  River - 855 

SHERMAN,  KENNETH.  In  Memoriam:  Robert  Louis  Dryfoos,  1939-1974 856 


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EFFECTS  OF  OIL  ON  MARINE  ECOSYSTEMS: 
A  REVIEW  FOR  ADMINISTRATORS  AND  POLICY  MAKERS 

Dale  R.  Evans^  and  Stanley  D.  Rice^ 


ABSTRACT 

A  broad  selection  of  recent  literature  on  the  effects  of  oil  on  marine  ecosystems  is  reviewed.  The  focus  is  on 
studies  on  crude  oil,  and  the  results  are  discussed  with  the  purpose  of  providing  a  summary  of  findings  that 
will  be  a  useful  reference  for  administrators  and  policy  makers  involved  in  decisions  concerning  petroleum 
developments  and  related  activities.  The  characteristics  of  crude  oil  and  factors  modifying  its  impact  on  the 
marine  environment  are  discussed.  Most  research  on  the  toxicity  of  oil  has  dealt  with  acute  effects  and  data 
on  long-term  impacts  at  the  community  level  are  inconclusive.  It  is  concluded  that  chronic  low-level 
pollution  is  potentially  more  damaging  to  ecosystems  than  isolated  catastrophic  spills.  Decision  makers  are 
forced  to  rely  on  interpretative  judgments  rather  than  conclusive  data. 


Much  of  the  material  in  this  report  was  gathered 
as  background  material  for  use  in  preparing  the 
marine  section  of  the  final  environmental  impact 
statement  on  the  proposed  trans-Alaska  pipeline 
system  (U.S.  Department  of  the  Interior,  1972). 
Some  of  the  statements  are  essentially  unchanged 
from  the  way  they  were  presented  in  the  appendix 
to  volume  IV  of  the  impact  statement.  The  impact 
statement  made  it  clear  that  not  enough  data  are 
available  to  analyze  conclusively  all  of  the  poten- 
tial environmental  impacts  of  operation  of  the 
pipeline  marine  terminal  facilities  at  Port  Valdez, 
Alaska,  and  the  transshipment  of  crude  oil  by 
tankers  to  west  coast  ports.  A  conclusion  that  can 
be  drawn,  however,  and  a  message  of  the  impact 
statement,  is  that  oil  poses  a  significant  hazard  to 
marine  ecosystems,  and  a  good  deal  of  intensive 
research  is  necessary  if  these  hazards  are  to  be 
quantified  and  fully  understood. 

Research  on  oil  pollution  published  since  the 
impact  statement  on  the  pipeline  was  issued  re- 
veals that  scant  progress  has  been  made,  particu- 
larly with  regard  to  the  effects  of  chronic  low-level 
oil  pollution.  Current  and  projected  demands  for 
energy  in  the  United  States  are  prompting  accel- 
erated development  of  offshore  petroleum  re- 
serves, expanded  oil  tanker  traffic,  and  proposals 
for  construction  of  deepwater  port  facilities  to 
handle  the  increasing  number  of  supertankers. 
These  developments  will  not  wait  for  conclusive 


'Alaska  Region,  National  Marine  Fisheries  Service,  NOAA, 
Juneau,  AK  99801. 

^Auke  Bay  Fisheries  Laboratory,  National  Marine  Fisheries 
Service,  NOAA,  Auke  Bay,  AK  99821. 


answers  to  questions  on  oil  pollution.  Recognizing 
this,  we  feel  it  is  important  that  public  adminis- 
trators and  policy  makers  be  made  aware  of  the 
inferences  and  trends  evident  in  the  research 
findings  to  date.  These  findings  present  a  persua- 
sive case  that  decisions  regarding  the  handling  of 
crude  oil  and  petroleum  products  should  be  con- 
servative and  in  favor  of  protecting  the  natural 
environment.  While  this  report  is  by  no  means  a 
complete  review  of  the  literature,  it  is  sufficient  to 
illustrate  the  potential  danger  of  oil  pollution  to 
marine  ecosystems  and  provide  some  guidance  for 
policy  decisions. 

History  is  replete  with  examples  of  man's 
scientific  and  technological  advances  carrying 
him  into  situations  he  did  not  fully  comprehend 
and  with  consequences  he  could  not  evaluate. 
Bella  ( 1970)  noted  that  "our  ability  to  change  this 
world  is  going  to  increase  faster  than  our  ability  to 
predict  what  that  change  is  going  to  be."  He  con- 
cludes that  our  management  procedures  must  rec- 
ognize the  degree  of  ignorance  we  have  about  this 
world  in  which  we  live. 

Pollution  of  the  ocean  by  oil  is  a  worldwide  prob- 
lem of  growing  concern  to  many  nations.  Spills 
like  the  Torrey  Canyon,  ih.e  Arrow,  the  Santa  Bar- 
bara Channel  blowout,  and  other  spectacular  in- 
cidents have  helped  stimulate  international  or- 
ganizations of  governments  and  industry  to  react 
to  the  problem.  Viewed  pragmatically,  interna- 
tional response  has  been  at  least  as  adequate  as 
domestic  programs.  Predicting  the  impact  of  an  oil 
spill  on  the  environment  requires  an  understand- 
ing of  the  complex  interactions  involved.  What 


Manuscript  accepted  November  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3.  1974. 


625 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


appears  to  be  universally  lacking  is  the  difficult 
research  leading  to  an  understanding  of  chronic 
and  sublethal  effects  of  oil  at  the  biological  com- 
munity level.  The  following  discussion  outlines 
these  complexities  and  points  out  how  they  make 
most  generalizations  invalid  and  the  extrapola- 
tion of  most  data  dangerous. 

DESCRIPTION  OF  OIL 

Crude  oil  is  a  complex  mixture  of  many  different 
specific  hydrocarbons  and  a  variety  of  compounds 
containing  sulfur,  oxygen,  nitrogen,  and  some 
trace  metals.  Hydrocarbons  make  up  the  bulk  of 
crude  oil  and  can  roughly  be  placed  into  one  of 
three  classes:  paraffinic,  naphthenic,  and  aromat- 
ic. From  one  area  to  another,  crude  oils  vary  in 
their  composition  and  in  density,  volatility,  and 
solubility.  Their  relative  toxicity  will  vary  (Ott- 
way,  1971)  but  is  roughly  proportional  to  their 
aromatic  content. 

Paraffinic  (or  aliphatic)  hydrocarbons  are 
straight  or  branched  carbon  chains  and  are  satu- 
rated (thus  no  carbon-carbon  double  bonds)  with 
hydrogen  or  other  groups.  These  hydrocarbons  are 
the  least  toxic,  although  they  may  have  an 
anesthetic  or  narcotic  effect  if  concentrations  are 
great  enough. 

Naphthenic  compounds  (cycloparaffins)  contain 
at  least  one  ring  structure  that  is  saturated.  With 
this  base,  more  rings  or  chains  may  be  attached  to 
form  a  variety  of  complex  molecules. 

Aromatic  hydrocarbons  also  contain  a  ringed 
structure,  but  the  ring  is  unsaturated  with  hy- 
drogen and  contains  carbon-carbon  double  bonds 
(benzene  ring).  The  simplest  aromatic  is  benzene, 
which  is  very  toxic  and  relatively  water  soluble  in 
comparison  to  most  hydrocarbons  found  in  crude 
oil.  Benzene  and  other  low-boiling  aromatics  are 
the  most  toxic  petroleum  fractions.  High-boiling 
aromatics  act  as  slower  poisons  than  low-boiling 
aromatics,  but  they  are  equally  severe  in  their 
effect.  In  addition,  some  are  known  to  induce 
cancer;  3,4-benzpyrene,  1,2-benzanthracene,  and 
some  alkylbenzanthracenes  have  been  isolated 
from  crude  oil,  and  their  carcinogenic  effects  on 
animals  and  man  have  been  demonstrated 
(Blumer,  1970).^ 


^Blumer,  M.  1970.  Scientific  aspects  of  the  oil  spill  problem. 
Presented  at  NATO  Conference,  Brussels,  6  Nov.  1970,  21  p., 
Woods  Hole  Oceanogr.  Inst.,  Woods  Hole,  Mass. 


Olefinic  hydrocarbons  (paraffinlike  but  unsatu- 
rated and  containing  reactive  carbon-carbon  dou- 
ble bonds)  are  not  generally  found  in  crude  oils  but 
are  plentiful  in  certain  gasolines  and  other  refined 
products.  The  fate  of  olefins  in  the  marine  envi- 
ronment is  poorly  understood,  but  this  class  of 
compounds  may  be  quite  reactive  under  certain 
conditions  and  may  combine  readily  with  hy- 
drogen, oxygen,  chlorine,  sulfur,  and  other  ele- 
ments to  produce  toxic  substances.  Once  incorpo- 
rated into  organisms,  olefins  may  remain  intact 
for  surprisingly  long  times  (Blumer,  1967).  The 
full  range  of  olefinic  hydrocarbons  probably  inter- 
feres with  the  reception  of  chemical  messengers, 
or  odors,  in  the  sea  by  certain  marine  organisms 
(Blumer,  1970,  see  footnote  3). 

When  crude  oil  is  processed  ("cracked"),  olefins 
and  other  compounds  for  gasoline  and  fuel  oils 
may  be  formed  or  separated.  Fuel  oils,  commonly 
involved  in  spills,  are  rated  from  1  to  6.  Those 
rated  1  are  the  lightest,  most  volatile,  and  most 
toxic  and  have  the  greatest  aromatic  concentra- 
tions; those  rated  6  are  the  least  volatile,  least 
soluble,  and  least  toxic  and  are  asphaltic  (tarlike). 

Hydrocarbons  are  not  foreign  to  the  marine  en- 
vironment; normal  paraffins  are  synthesized  by 
most,  if  not  all,  living  organisms.  Blumer,  Guil- 
lard,  and  Chase  (1971)  characterized  the  natural 
hydrocarbon  content  of  22  species  of  phytoplank- 
ton  and  cited  literature  for  zooplankton.  There  are 
certain  characteristic  differences,  however,  be- 
tween hydrocarbons  native  to  organisms  and  the 
hydrocarbons  in  petroleum,  particularly  in  the  rel- 
ative distribution  of  the  various  hydrocarbons. 
Crude  oils  and  certain  petroleum  products  are 
complex  mixtures  that  contain  molecules  of  dif- 
ferent sizes  in  ratios  not  found  in  any  one  species  of 
organism.  Certain  specific  paraffins,  and  some 
naphthenic  and  aromatic  compounds,  are  rarely 
found  in  organisms  not  exposed  to  oil  pollution. 
These  characteristic  differences  have  been  the 
basis  for  several  scientific  papers  (Blumer,  Souza, 
and  Sass,  1970;  Ehrhardt,  1972;  Clark  and  Finley, 
1973;  and  others). 

FACTORS  INFLUENCING 
THE  IMPACT  OF  OIL 

The  impact  of  oil  on  the  marine  environment  is 
governed  by  several  factors — physical,  chemical, 
and  biological — in  addition  to  the  inherent  com- 
plexity of  crude  oil  and  refined  products.  The  be- 
havior, effects,  and  fate  of  an  oil  spill  involve  all  of 


626 


EVANS  and  RICE:  EFFECTS  OF  OIL  ON  ECOSYSTEMS 


these  factors;  and  because  they  are  interdepen- 
dent, the  reliabihty  of  our  predictions  concerning 
the  impact  of  a  spill  is  limited  by  our  knowledge  of 
the  least  understood  variable. 

Straughan  (1972)  noted  our  general  inability  to 
predict  the  environmental  impact  of  a  spill  be- 
cause of  the  complexity  of  the  matter,  and 
identified  several  factors  that  govern  biological 
damage  caused  by  a  spill:  1)  type  of  oil  spilled,  2) 
dose  of  oil,  3)  physiography  of  the  area  of  the  spill, 
4)  weather  conditions  at  the  time  of  the  spill,  5) 
biota  of  the  area,  6)  season  of  the  spill,  7)  previous 
exposure  of  the  area  to  oil,  8)  exposure  to  other 
pollutants,  and  9)  treatment  of  the  spill.  Several  of 
these  factors  are  touched  upon  below. 


Natural  Physical  Processes 
Affecting  Oil  in  the  Water  Column 

Once  oil  is  spilled,  it  is  dissipated  by  evapora- 
tion, dissolution,  and  mixing  or  dilution  in  the 
water  column.  The  natural  processes  are  speeded 
by  wind  action  and  by  waves  and  currents  that 
increase  spreading  and  vertical  mixing.  Various 
fractions  respond  differently  to  these  processes, 
and  the  weathered  residue  behaves  differently 
than  the  material  originally  spilled.  A  contami- 
nated bay  may  be  flushed  by  freshets,  tidal  action, 
or  longshore  currents.  Some  oil  sinks  directly  to 
the  bottom,  especially  in  fresh  water,  where  some 
oil  fractions  have  densities  approaching  that  of 
fresh  water,  and  in  water  with  high  sediment 
loads.  Certain  fractions  may  undergo  autoxida- 
tion. 

Conover  (1971)  reported  that  sedimentation  of 
fecal-bound  oil  that  had  been  ingested  by  zoo- 
plankton  may  have  accounted  for  up  to  20%  of  the 
spilled  oil  entering  the  water  column  at 
Chedabucto  Bay,  Nova  Scotia.  Oil  can  also  be  re- 
moved from  the  water  column  by  absorption 
within  organisms  and  accumulation  within  the 
food  chain.  Suspended  sediments  carried  by  runoff 
from  a  major  flood  entered  the  Santa  Barbara 
Channel  area  immediately  before  and  after  the 
well  blowout  (Kolpack,  1971).  Kolpack  noted  that 
adsorption  of  oil  on  the  flocculated  suspended  par- 
ticles followed  by  decomposition  was  a  major  fac- 
tor in  carrying  much  of  the  oil  to  the  sea  floor. 
Kinney  et  al.  (1970)  reported,  however,  that  in 
Cook  Inlet,  Alaska,  glacial  silt  from  the  inlet  had 
no  apparent  effect  on  the  emulsion  properties  or 


the  sinking  of  the  type  of  crude  oil  found  in  that 
area. 

Forrester  (1971)  noted  the  extensive  distribu- 
tion of  oil  particles  stirred  into  the  water  by  wave 
action  after  a  bunker  C  oil  spill  in  Chedabucto 
Bay.  Oil  particles  were  found  to  a  depth  of  80  m 
inside  the  bay  and  to  depths  of  45  m  at  a  distance  of 
65  km  outside  the  bay.  Near-surface  distribution 
of  particles  extended  250  km  southwest  along 
Nova  Scotia  in  a  band  extending  up  to  25  km 
offshore.  Berridge,  Thew,  and  Loriston-Clark 
(1969)  indicated  that  the  stabilization  of  emul- 
sions like  those  observed  at  Chedabucto  Bay  and 
elsewhere  was  caused  by  complex  chemical  com- 
ponents in  the  nonvolatile  residues  and  not  by 
bacterial  activity,  marine  organisms,  or  sus- 
pended solid  matter. 

Environmental  Differences 

The  fate  and  effects  of  oil  spilled  in  the  marine 
environment  are  difficult  to  generalize  because 
several  types  of  environments  may  be  involved. 
Some  extreme  comparisons  are  tropics  versus  arc- 
tic, open  ocean  versus  estuaries,  and  the  differ- 
ences between  the  intertidal  and  subtidal  zones. 

Within  these  environments  are  several  diverse 
physical  conditions  such  as  temperature,  salinity, 
oxygen,  and  nutrient  concentrations,  as  well  as 
biological  differences  such  as  species  composition, 
diversity  and  density,  and  community  metabolic 
rate.  The  prediction  or  assessment  of  pollution 
effects  on  the  basis  of  observations  extrapolated 
from  one  environment  to  another  is  seldom  sup- 
ported by  adequate  data.  Unfortunately,  however, 
few  data  on  pollution  effects  exist  for  most  areas 
and  species,  which  has  led  to  the  use  of  informa- 
tion from  areas  that  may  be  dissimilar  in  critical 
respects. 

There  are  arguments  as  to  which  environment 
is  the  most  stable  and  capable  of  withstanding 
attacks  by  additional  pollution  stresses.  Copeland 
(1970),  discussing  the  response  of  ecological  sys- 
tems to  stress,  suggested  the  principle  that 
".  .  .those  systems  already  subjected  to  energy- 
requiring  stresses  are  more  likely  to  resist  the 
changes  than  those  (such  as  tropical  systems) 
adapted  to  relatively  constant  environments."  He 
concluded  that  estuarine  ecosystems  composed  of 
organisms  capable  of  wide  adaptations  and 
generalizations,  such  as  north  temperate  systems, 
would  be  relatively  unaffected  by  the  same  mag- 
nitude of  disturbance  that  would  drastically  alter 


627 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


a  tropical  system.  Odum  (1970)  noted,  however, 
that  many  estuarine  species  are  living  near  the 
limit  of  their  tolerance  range  and  that  any  altera- 
tion in  the  environment,  such  as  additional  stress- 
es caused  by  low  levels  of  pollution,  could  exclude 
these  animals  permanently  from  the  estuary. 

All  healthy  balanced  ecosystems  are  generally 
functioning  at  or  near  some  critical  tolerance 
limit.  In  an  ecosystem  with  a  variable  environ- 
ment, such  as  a  north  temperate  estuary,  re- 
sponses to  additional  stress  might  not  always  be 
the  same.  For  example,  even  though  factors  sur- 
rounding an  oil  pollution  incident  might  be  out- 
wardly similar  in  most  respects  to  another  spill  in 
a  comparable  area,  the  biological  impacts  may 
differ.  The  ability  of  the  local  community  to  absorb 
the  additional  stress  will  be  influenced  by  the 
coincidence  of  seasonal  variability  of  natural 
stresses,  the  differences  in  vulnerability  of  stages 
in  an  organism's  life  cycle,  and  many  other 
dynamic  features  of  the  ecosystem. 

Biological  Differences 

The  effects  of  oil  pollution  on  many  different 
organisms  in  various  habitats  may  vary  from  no 
effect  to  responses  of  avoidance  and  decreased  ac- 
tivity, to  nonadaptive  responses  of  panic  and 
physiological  stress.  What  kills  one  species  may 
have  little  or  no  effect  on  another.  Affected  or- 
ganisms vary  from  single  cells,  to  sedentary 
clams,  to  highly  mobile  predators,  each  of  which 
has  different  behavioral  and  physiological  in- 
teractions with  the  environment. 

Just  as  different  species  are  affected  differently, 
so  may  individuals  within  a  species  be  affected 
differently.  In  particular,  different  life  stages  such 
as  eggs,  hatched  larvae,  and  newly  molted  indi- 
viduals may  have  different  sensitivity  to  the  same 
level  of  pollution.  Mironov  (1968),  for  example, 
reported  that  prelarval  stages  of  barnacle, 
Balanus  sp.,  were  100  times  more  sensitive  to  oil 
pollution  than  the  adult  form.  This  contrasts  with 
the  relative  lack  of  sensitivity  to  crude  oil  by  pink 
salmon  eggs  and  sac  fry,  which  were  10  times 
more  tolerant  than  older  fry  (Stanley  D.  Rice  and 
Adam  Moles,  Auke  Bay  Fisheries  Laboratory,  Na- 
tional Marine  Fisheries  Service  (NMFS),  NOAA, 
Auke  Bay,  AK  99821,  pers.  commun.). 

Renzoni  (1973)  conducted  a  series  of  experi- 
ments on  the  toxicity  of  several  crude  oils  and 
petroleum  products  to  the  sperm,  eggs,  and  larvae 
of  the  oysters  Crassostrea  angulata  and  C.  gigas 
and  the  mussel  Mytilus  galloprovincialis.   He 


found  a  relatively  high  degree  of  tolerance  by  eggs 
and  larvae  but  reported  that  the  fertilizing  capac- 
ity of  sperm  was  markedly  affected  by  similar 
exposures. 

Biodegradation 

Quantitative  data  describing  the  biodegrada- 
tion of  various  components  of  crude  oil,  especially 
in  arctic  and  subarctic  areas,  are  limited. 

ZoBell  ( 1973a)  briefly  reviewed  the  current  un- 
derstanding of  microbial  degradation  of  oil,  in- 
cluding interactions,  limiting  factors,  problems, 
and  perspectives.  Ahearn  (1973)  stated  that  re- 
search on  microbial  utilization  of  hydrocarbons 
for  treatment  of  oily  pollutants  in  the  environ- 
ment, though  more  intensive  in  recent  times,  is 
still  in  an  early  stage  of  development.  It  is  known 
that  microorganisms  can  degrade  much  of  a 
crude  oil,  particularly  the  less  toxic  paraffinic 
compounds.  No  single  species  can  degrade  all  the 
compounds,  but  many  different  species  together 
can  metabolize  a  large  number  of  the  compounds, 
if  not  all.  The  rate  of  microbial  degradation, 
which  is  principally  aerobic,  decreases  with  a 
decrease  in  temperature.  Large  quantities  of 
oxygen  are  needed.  It  has  been  estimated,  for 
instance,  that  complete  oxidation  of  1  gallon  of 
crude  oil  would  require  all  of  the  dissolved 
oxygen  in  320,000  gallons  of  water.  This  com- 
parison may  be  unrealistic  because  most  oil  is  at 
the  surface  of  water  in  contact  with  air  and  only 
the  outer  surfaces  of  oil  can  be  attacked  at  any 
one  time.  It  is  reasonable  to  assume,  however, 
that  an  oxygen-deficient  environment  may  well 
occur  under  some  oil  slicks  and  in  oil-contam- 
inated sediments. 

Glaeser  and  Vance  (1971)  studied  the  behavior 
of  Prudhoe  Bay  crude  oil  in  controlled  spills  in  the 
Chukchi  Sea  but  were  not  able  to  isolate  any  mi- 
croorganisms which  could  degrade  hydrocarbons 
at  the  ambient  temperatures  of  the  Arctic,  al- 
though some  emulsification  of  the  crude  oil  was 
observed.  However,  ZoBell  and  Agosti  (1972)  col- 
lected oil-oxidizing  bacteria  near  natural  oil  seeps 
from  the  Alaska  North  Slope  and  observed  oxida- 
tion rates  of  mineral  oil  at  -1°C  and  above.  They 
noted  that  the  solid  surfaces  of  the  ice  crystals 
appeared  to  facilitate  bacterial  growth,  because 
the  rate  at  -1°C  was  substantial  and  near  the 
4°C  rate. 

The  apparent  contradiction  between  the  studies 
is  probably  best  explained  by  ZoBell's  (1973b)  con- 
tinued observations  with  North  Slope  bacteria.  He 


628 


EVANS  and  RICE:  EFFECTS  OF  OIL  ON  ECOSYSTEMS 


found  that  the  nine  different  crude  oils  were  not 
degraded  as  rapidly  as  purified  mineral  oil. 
Glaeser  and  Vance's  studies  were  with  microor- 
ganisms from  the  surface  water  of  the  Chukchi 
where  small  numbers  of  bacteria  may  have  been 
present.  Furthermore,  the  observations  of 
Straughan  (1971),  who  noted  the  apparent  lack  of 
biological  damage  by  the  Santa  Barbara  blowout, 
may  apply  here.  She  discussed  the  possibility  that 
the  fauna  had  an  unusually  high  tolerance  for  oil, 
probably  because  of  adaptation  from  chronic  low- 
level  oil  exposures  from  local  natural  seepages. 
The  observations  of  ZoBell  and  Agosti  (1972)  on 
the  oxidation  rates  of  oil  at  —  1°C  may  be  an  exam- 
ple of  similar  adaptive  response  by  the  North 
Slope  bacteria  collected  near  natural  seeps.  These 
oxidation  rates  and  other  adaptive  responses 
might  not  occur  from  organisms  that  have  not 
been  preacclimated  to  chronic  low-level  exposures 
of  oil  and  may  explain  why  Glaeser  and  Vance 
obtained  reports  of  negligible  oxidation  rates  at 
0°C  from  microorganisms  from  surface  water  of 
the  Chukchi  Sea.  Robertson  et  al.  (1973)  esti- 
mated hydrocarbon-oxidizing  bacteria  popula- 
tions were  in  the  order  of  1/ml  in  Cook  Inlet  and 
Port  Valdez,  but  less  in  the  Arctic  Ocean.  Num- 
bers decreased  with  salinity  in  Cook  Inlet  and 
with  depth  in  Port  Valdez. 

ZoBell  (1963)  reported  that  oil  is  readily  ad- 
sorbed by  clay  and  silt  and  suggests  that  although 
adsorption  of  oil  by  solids  renders  the  oil  more 
susceptible  to  autobial  and  microbial  oxidation, 
almost  no  bacterial  decomposition  occurs  after 
burial  in  the  bottom  sediments,  probably  because 
the  environment  is  anaerobic.  Blumer  and  Sass 
(1972)  found  that  some  paraffmic  hydrocarbons 
remained  in  bottom  sediments  2  yr  after  the  West 
Falmouth  oil  spill  and  aromatic  hydrocarbons 
were  prominent,  which  suggests  that  these  more 
toxic  compounds  are  utilized  by  bacteria  to  a 
minimum  degree. 

Oil  in  Sediments 

The  effect  of  oil  in  sediments  is  poorly  under- 
stood, although  several  authors  have  quantitated 
oil  concentrations  and  noted  its  persistence.  Scar- 
ratt  and  Zitko  (1972)  observed  little  diminution  of 
bunker  C  oil  concentration  from  soft  sediments  26 
mo  after  the  wreck  of  the  tanker  Arrow.  The  oil 
reached  maximum  concentrations  in  coarse  sedi- 
ments 1  yr  after  the  spill,  but  the  concentrations 
reduced  thereafter.  Chemical  degradation  can 


occur  but  is  normally  restricted  to  the  surface 
layer  of  the  bottom  penetrated  by  ultraviolet  light. 
Blumer  and  Sass  ( 1972)  noted  that  "The  preserva- 
tion of  hydrocarbons  in  marine  sediments  for 
geologically  long  time  spans  is  one  of  the  accepted 
key  facts  in  current  thought  on  petroleum  forma- 
tion." However,  in  spite  of  the  stability  of  hy- 
drocarbons in  marine  sediments,  there  are  charac- 
teristic differences  between  the  hydrocarbons  in 
polluted  and  unpolluted  areas.  Tissier  and  Oudin 
(1973)  found  that  hydrocarbons  in  polluted  sedi- 
ments differed  from  those  of  unpolluted  sediments 
by  having  lower  percentages  of  heavy  compo- 
nents, by  not  having  an  odd  carbon  dominance  in 
the  n-alkanes,  and  by  having  polycyclic  aromatic 
hydrocarbons  with  alkyl  chains. 

Oil  residues  were  observed  on  sandy  beaches  by 
ZoBell  (1963)  and  in  marshes  and  in  sediments  of 
the  deepest  area  (15.3  m)  near  the  West  Falmouth 
spill  by  Blumer,  Sass,  Souza,  Sanders,  Grassle, 
and  Hampson  (1970).^  About  2  wk  after  fuel  oil 
was  spilled  at  Resolute  Bay,  Northwest  Territory, 
in  August  1970,  casual  sampling  revealed  that  oil 
penetrated  into  beach  material  to  a  depth  of  about 
3  inches  (7.6  cm)  (Barber,  1971).  Oil  may  be  buried 
and  stay  intact  for  a  considerable  time,  even  at  the 
higher  temperature  of  the  California  coast 
(ZoBell,  1963).  During  laboratory  experiments, 
Johnston  (1970)  determined  oil  decay  rates  in 
sand  columns  contaminated  with  various  concen- 
trations of  oil.  Ten  percent  of  the  oil  was  oxidized 
over  a  period  of  several  months;  the  remaining 
90%  decayed  much  slower. 

The  West  Falmouth  spill  provided  a  unique  op- 
portunity for  a  study  of  the  immediate  and  long- 
term  effects  of  an  oil  spill  on  an  area  where  the 
previously  existing  environmental  base  was  well 
known  (Blumer,  Sanders,  Grassle,  and  Hampson, 
1971).  One  effect  of  the  oil  was  to  reduce  the  cohe- 
sion of  bottom  sediments  of  tidal  marshes  and  the 
estuary  by  killing  the  benthic  plants  and  animals 
(Blumer,  Sass,  Souza,  Sanders,  Grassle,  and 
Hampson,  1970,  see  footnote  4).  The  resulting  ero- 
sion spread  hydrocarbons  to  new  areas,  where  the 
process  was  repeated.  Because  of  the  stability  and 
persistence  of  the  hydrocarbons  in  marine  bottom 
sediments,  Blumer,  Souza,  and  Sass  (1970)  noted 
that  hydrocarbons  may  be  returned  to  the  bio- 
sphere by  organisms  living  and  feeding  in  the  sed- 
iments. This  redistribution  of  hydrocarbons  can  be 


■'Blumer.  M.,  J.  Sass,  G.  Souza,  H.  Sanders,  F.  Grassle,  and  G. 
Hampson.  1970.  The  West  Falmouth  oil  spill.  Unpubl.  manuscr. 
Woods  Hole  Oceanogr.  Inst.,  Ref.  No.  70-44,  32  p. 


629 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


the  source  of  a  chronic  pollution  problem  near  that 
spill. 

It  is  quite  possible  that  normal  functions  of  sed- 
iments will  be  disrupted  when  contaminated  by 
oil.  Changes  in  the  sediments  that  are  subtle  and 
difficult  to  detect,  such  as  decreased  nutrient  re- 
cycling and  community  metabolism,  could  result 
in  the  loss  of  significant  contributions  to  the  pro- 
ductivity and  stability  of  an  area.  Although  oil  in 
sediments  has  been  monitored  and  measured  after 
several  spills,  other  aspects  of  the  oil-sediment 
relation  have  yet  to  be  studied. 

BIOLOGICAL  EFFECTS  OF 
OIL  POLLUTION 

Blumer  (1970,  see  footnote  3)  summarizes  the 
potential  damage  to  organisms  from  pollution  by 
crude  oil  and  oil  fractions  as  follows: 

1.  Direct  kill  of  organisms  through  coating  and 
asphyxiation. 

2.  Direct  kill  through  contact  poisoning  of  or- 
ganisms. 

3.  Direct  kill  through  exposure  to  the  water- 
soluble  toxic  components  of  oil  at  some  distance  in 
space  and  time  from  the  accident. 

4.  Destruction  of  the  generally  more  sensitive 
juvenile  forms  of  organisms. 

5.  Destruction  of  the  food  sources  of  higher 
species. 

6.  Incorporation  of  sublethal  amounts  of  oil  and 
oil  products  into  organisms  (resulting  in  reduced 
resistance  to  infection  and  other  stresses — the 
principal  cause  of  death  in  birds  surviving  im- 
mediate exposure  to  oil). 

7.  Incorporation  of  carcinogenic  and  potentially 
mutagenic  chemicals  into  marine  organisms. 

8.  Low-level  effects  that  may  interrupt  any  of 
numerous  events  (such  as  prey  location,  predator 
avoidance,  mate  location  or  other  sexual  stimuli, 
and  homing  behavior)  necessary  for  the  propaga- 
tion of  marine  species  and  for  the  survival  of  those 
species  higher  in  the  marine  food  web. 

Some  of  the  potential  effects  described  by 
Blumer  may  be  obvious,  such  as  the  direct  deaths 
from  acute  exposures.  Less  obvious  indirect 
deaths  may  occur  from  effects  at  either  the  indi- 
vidual or  population  level.  Individual  organisms 
subjected  to  sublethal  exposures  may  undergo  an 
"ecological  death"  if  they  are  less  capable  of  ad- 
justing to  and  responding  to  natural  changes 
(stresses)  in  their  physical  and  biological  envi- 
ronments. For  example,  postmolt  Tanner  (snow) 


crab,  Chionoecetes  bairdi,  lost  legs  during  short 
exposures  to  crude  oil  (Karinen  and  Rice,  in 
press).  Even  though  the  crabs  lived  through  the 
exposure,  they  probably  could  not  have  survived 
in  the  natural  environment  because  some  of  them 
lost  as  many  as  seven  legs,  including  both  chelae. 
Moreover,  crabs  or  other  adversely  but  suble- 
thally  affected  organisms  would  be  more  likely 
to  be  eliminated  by  natural  selection. 

Effects  from  chronic  exposure  may  be  adverse  to 
a  population  over  a  period  of  time  if  exposed  but 
normal-appearing  adults  have  their  ability  to  re- 
produce seriously  impaired.  This  loss  may  be  due 
to  physiological  changes  such  as  reduced  fecun- 
dity and  delayed  ovary  development  or  to  im- 
paired behavioral  mechanisms  which  could  pre- 
vent mate  location  and  identification  or  homing 
and  timing  of  spawning.  Although  the  effects  at 
this  level  might  not  result  in  death  of  the  adult, 
they  could  induce  a  trend  of  decreasing  numbers 
that  might  eventually  eliminate  the  population  or 
race. 

Hydrocarbons  in  the  Marine  Food  Web 

Blumer  (1967,  1969)  and  Blumer,  Guillard,  and 
Chase  (1971)  studied  the  fate  of  organic  com- 
pounds in  the  marine  food  web.  They  found  that 
certain  hydrocarbons,  even  highly  unsaturated 
ones,  are  stable  once  they  are  incorporated  into  a 
particular  marine  organism  and  that  they  may 
pass  through  many  members  of  the  marine  food 
web  without  alteration  and  may  actually  be  con- 
centrated in  tissue.  Most  hydrocarbons  are  lipid 
soluble  and  thus  may  accumulate  in  food  webs  to 
the  point  where  toxic  levels  are  reached.  This 
pathway  is  illustrated  by  the  well-documented 
chlorinated  hydrocarbon  group  of  pesticides. 

The  entrance  of  oil-derived  hydrocarbons  into 
marine  food  webs  has  been  observed  several  times 
at  several  trophic  levels.  Conover  (1971)  reported 
that  l(X7f  of  the  bunker  C  oil  in  the  water  column 
after  the  Chedabucto  Bay  spill  was  combined  with 
zooplankton  and  that  their  feces  contained  up  to 
1%  oil.  Mironov  (1968)  also  noted  the  ability  of 
some  zooplankters  to  accumulate  hydrocarbons. 
The  incorporation  of  hydrocarbons  into  the  food 
web  at  these  primary  levels  assures  exposure  at 
all  higher  trophic  levels. 

Blumer,  Souza,  and  Sass  (1970)  and  Ehrhardt 
( 1972 )  reported  pollution-derived  hydrocarbons  in 
shellfish.  Uptake  and  retention  of  labeled  hy- 
drocarbons of  several  classes  by  a  marine  mussel, 


630 


EVANS  and  RICE:  EFFECTS  OF  OIL  ON  ECOSYSTEMS 


Mytilus  edulis.  was  noted  by  Lee,  Sauerheber,  and 
Benson  ( 1972 ).  Smith  ( 1968)  reported  the  presence 
of  oil  and  benzene-ring  compounds  in  the  feces  of 
limpets  browsing  on  an  oily  deposit,  and  in  top 
shells,  Monodonta,  and  limpets, Pa te//a,  living  on 
oiled  rocks.  He  reported  that  analysis  of  the  gut 
indicated  "the  proportion  of  oil  in  material  in- 
gested by  these  animals  was  estimated  as  about 
20-30  percent  in  Patella  and  5-50  percent  in 
Monodonta ." 

Organisms  at  the  highest  trophic  levels  may  be 
affected  directly  by  the  oil  itself  or  indirectly  by 
hydrocarbons  that  have  reached  them  through  the 
food  web.  Horn,  Teal,  and  Backus  (1970)  found 
large  amounts  of  tar  in  the  stomachs  of  three 
saury,  Scomberesox  saurus,  from  a  sample  often 
in  the  Mediterranean  Sea  near  Gibraltar.  Al- 
though saury  are  generally  considered  to  be  car- 
nivorous, the  occurrence  of  tar  and  also  of  "vege- 
table debris"  in  one  of  the  stomachs  examined  by 
Horn  et  al.  ( 1970)  suggests  that  the  species  is  not  a 
vei-y  discriminate  feeder.  Although  all  ingested  oil 
was  obviously  not  incorporated  into  the  tissues 
(some  oil  was  found  in  feces),  such  feeding  be- 
havior does  describe  a  pathway  for  hydrocarbons 
to  be  directly  taken  up  into  the  tissues  of  the  or- 
ganism. Thus,  oil  ingested,  absorbed,  and  even 
adsorbed  may  enter  the  food  chain  when  contami- 
nated organisms  are  eaten. 

Carcinogenicity 

Some  doubt  may  remain  as  to  the  direct  car- 
cinogenicity to  man  of  crude  oil  and  crude  oil  res- 
idues in  marine  organisms  (Blumer,  1969),  but 
evidence  pointing  toward  this  is  accumulating 
(Blumer,  1970,  see  footnote  3;  1972).  A  literature 
search  and  evaluation  conducted  for  the  U.S. 
Coast  Guard  by  Battelle  Memorial  Institute 
(1967)  noted  that  shellfish,  although  alive,  may 
have  been  unfit  for  consumption  because  of  the 
carcinogenic  hydrocarbon  3, 4-benzpyrene  in  their 
bodies.  Oysters  that  were  heavily  polluted  and 
contaminated  with  ship  fuel  oil  were  reported  to 
contain  3, 4-benzpyrene.  The  Battelle  review  also 
reported  that  barnacles  attached  to  creosoted 
poles  contained  the  same  carcinogenic  hydrocar- 
bon (3, 4-benzpyrene).  Sarcomas  were  elicited 
when  extracts  from  the  barnacles  were  injected 
into  mice.  The  endem.ic  occurrence  of  papillary 
tumors  around  the  rectal  opening  of  soft-shell 
clam,  Mya  arenario ,  was  reported,  but  the  author 
(Battelle  Memorial  Institute,  1967)  did  not  feel 


these  were  due  to  oil  pollution,  even  though  the 
clams  were  taken  from  waters  adjacent  to  areas 
highly  polluted  by  ship  fuel  oil.  Hyperplasia  in 
reproductive  cells  of  a  bryozoan  in  response  to  coal 
tar  derivatives  was  observed  by  Powell,  Sayce, 
and  Tufts  (1970).  They  noted  that  similar  abnor- 
malities may  also  have  occurred  in  coastal  faunas 
exposed  to  spills  such  as  the  Torrey  Canyon  and 
the  Santa  Barbara  blowout.  However,  most  obser- 
vations on  these  spills  were  concerned  with  gross 
mortality  and  may  not  have  detected  the  sublethal 
effects. 

ZoBell  (1971)  reported  the  natural  synthesis 
and  metabolism  of  carcinogenic  hydrocarbons  by 
several  marine  organisms.  Thus,  oil  pollution  is 
certainly  not  the  only  source  for  carcinogenic  hy- 
drocarbon introduction  into  marine  food  webs. 
Suess  (1972)  recognized  that  carcinogens  were  in 
seafoods  but  concluded  that  they  would  probably 
not  be  dangerous  unless  the  foods  contained  an 
excess  amount  of  polynuclear  aromatic  hydrocar- 
bon carcinogens.  Carcinogenesis  from  oil- 
contaminated  marine  organisms  has  not  been 
proved,  but  Ehrhardt  (1972)  expressed  a  need  for 
carcinogenic  testing  of  hydrocarbon  fractions  ex- 
tracted from  marine  organisms  contaminated  by 
exposure  to  oil. 

Observed  Toxic  Effects 

A  study  of  the  available  information  on  poten- 
tial toxic  effects  of  oil  pollution  reveals  more  un- 
knowns than  proven  conclusions.  Only  a  decade 
ago,  ZoBell  ( 1963)  reviewed  the  literature  on  the 
effects  of  oil  on  bacteria  and  higher  organisms  and 
concluded  that  oil  pollution  had  no  great  adverse 
impact  on  fishery  resources  in  general.  He  did 
point  out,  however,  a  few  reports  of  toxic  effects, 
tainting  of  flesh,  and  damage  to  vessels  and 
fishing  gear. 

The  quantity  of  literature  on  effects  of  oil  spills 
has  increased  since  the  Torrey  Canyon  incident  of 
1967.  Most  of  the  recent  work  has  depended  on 
onsite  visual  surveys  after  occurrence  of  an  oil 
spill  rather  than  on  experiments  and  detailed 
study.  The  surveys  have  been  limited  mostly  to 
the  effects  of  oil  and  of  cleaning  or  dispersing 
agents  on  primarily  adult  intertidal  organisms 
and  populations.  These  observations  on  a  restrict- 
ed segment  of  the  affected  ecosystem  include  only  a 
few  of  the  factors  that  influence  the  total  impact  of 
oil.  Wilson,  Cowell,  and  Beynon  (1973)  noted  that 
the  absence  of  results  from  studies  at  the  commu- 


631 


nity  level  make  the  interpretation,  extrapolation, 
and  use  of  many  observations  very  difficult. 
Further,  the  differences  between  various  crude 
oils  and  between  the  hundreds  of  petroleum  prod- 
ucts in  their  physical  and  biological  effects  must 
always  be  kept  in  mind.  Comparative  data  gener- 
ally are  far  too  few  to  permit  attaching  any  rela- 
tive significance  to  production  area  or  product 
formulation  in  this  review. 

Field  Investigations 

The  utility  of  many  "after-the-fact"  studies  is 
limited  because  of  the  lack  of  knowledge  of  prespill 
conditions.  Data  are  often  collected  without 
proper  controls  for  comparison,  and  knowledge  of 
natural  local  fluctuations  and  species  composition 
of  animal  populations  is  usually  quite  limited.  For 
these  reasons  conclusions  about  the  impact  of  a 
particular  spill  may  vary. 

Ehrsam  (1972)  reported  substantial  immediate 
kills  of  marine  life  from  a  fuel  oil  spill  at 
Anacortes,  Wash.,  and  concluded  that  if  larval  and 
juvenile  forms  of  certain  organisms  were  killed, 
the  full  impact  of  the  spill  may  not  be  known  for 
some  time.  Katz  (1972)  observed  intertidal  tran- 
sects of  the  same  affected  area  and  concluded  that 
the  effects  were  minor  and  long-term  effects  would 
be  unlikely.  Webber  (1972)  pointed  out,  however, 
that  these  after-the-fact  studies  observed  only  a 
small  wedge  of  the  total  biota.  Knowledge  of  sub- 
tidal  and  benthic  organisms  as  well  as  larvae  and 
juveniles  was  lacking. 

Other  large  spills  have  been  studied  in  greater 
detail  and  have  contributed  significantly  to  our 
understanding  of  the  gross  effects  of  oil.  Yet,  they 
have  been  unable  to  answer  many  important 
questions  on  the  effect  of  pollutant  hydrocarbons 
in  the  marine  environment,  and  generalizations 
learned  from  one  spill  may  not  apply  to  another 
because  each  is  different. 

Field  observations  of  behavior  and  effects  of  oil 
in  Arctic  ice  environments  are  few.  The  U.S. 
Coast  Guard  investigations  in  the  Arctic  have 
primarily  been  directed  toward  gaining  knowl- 
edge to  improve  cleanup  methods  (Glaeser  and 
Vance,  1971;  McMinn  and  Golden,  1973).  Camp- 
bell and  Martin  (1973)  discussed  possible  large- 
scale  movements  and  persistence  of  oil  spilled  in 
the  Beaufort  Sea.  They  suggested  that  the  surface 
waters  of  the  Arctic  Ocean  and  the  winter  waters 
of  Chedabucto  Bay,  Nova  Scotia,  might  be  com- 
parable, particularly  with  regard  to  the  physical 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

behavior  of  oil.  Chedabucto  Bay  is  the  site  of  the 
grounding  of  the  tanker  Arrow  in  February  1970 
with  2.8  million  gallons  of  bunker  C  oil  aboard. 
Campbell  and  Martin  (1973)  found  that  highly 
stable  oil-water  emulsions  formed  to  a  depth  of  50 
m  throughout  Chedabucto  Bay.  They  described 
conditions  by  which  oil  reaching  the  edge  of  the 
pack  ice  could  be  distributed  under  the  ice. 

Thomas  ( 1973)  also  suggested  that  results  of  the 
studies  at  Chedabucto  Bay  might  in  some  respects 
be  applicable  to  spills  in  the  Arctic.  He  observed 
remobilization  of  oil  from  beneath  the  weathered 
surface  of  deposits  during  the  summers  following 
the  Arrow  spill  and  the  subsequent  re-oiling  of 
some  intertidal  areas,  adding  a  chronic  pollution 
aspect  to  the  spill.  Extensive  mortalities  of  soft- 
shell  clams  and  salt  marsh  cord  grass,  Spartina 
alterniflora ,  resulted  where  this  occurred.  In  other 
areas,  clams  were  visibly  contaminated  with  oil 
and  clam  fishing  was  closed,  at  least  through  the 
summer  of  1972  (Thomas,  1973). 

When  the  Torrey  Canyon  broke  up  near  the 
southwest  coast  of  England  in  1967,  15  million 
gallons  of  Kuwait  crude  oil  with  a  high  aromatic 
content  were  released.  Efforts  to  cope  with  this 
first  super  disaster  depended  principally  upon  2 
million  gallons  of  toxic  dispersant,  which  probably 
caused  more  damage  than  the  oil,  most  of  which 
had  weathered  at  sea  for  a  week  or  more  before 
reaching  the  shores.  Many  techniques  for  oil  con- 
tainment and  control  on  the  seas  were  attempted 
during  the  time  oil  leaked  from  the  tanker;  the 
fact  that  they  all  failed  reveals  the  inadequacies  of 
our  technology  and  preparedness  for  such 
emergencies. 

Extensive  investigations  of  the  West  Falmouth 
spill  by  Blumer  and  his  associates  at  Woods  Hole 
provide  one  of  the  best  documentaries  of  an  oil 
spill.  A  total  of  185,000  gallons  of  no.  2  fuel  oil 
(41%  aromatic  content)  were  spilled  in  1969  from  a 
ruptured  barge.  Intertidal  and  subtidal  benthic 
organisms  of  all  phyla  were  killed  during  the  first 
few  days  (Blumer  and  Sass,  1972).  Blumer,  Souza, 
and  Sass  (1970)  showed  that  the  uptake  of  fuel  oil 
hydrocarbons  by  shellfish  left  them  unfit  for 
human  consumption.  Later,  Blumer  and  Sass 
(1972)  reported  the  continued  persistence  of  fuel 
oil  hydrocarbons  in  the  sediments  after  2  yr.  Al- 
though there  had  been  some  degradation,  the  boil- 
ing range  and  composition  of  the  hydrocarbon 
mixture  was  basically  unchanged. 

The  1969  Santa  Barbara  blowout  released  an 
estimated  5,000  barrels  of  crude  oil  per  day  ini- 


632 


EVANS  and  RICE:  EFFECTS  OF  OIL  ON  ECOSYSTEMS 


tially  (Foster,  Charters,  and  Neushul,  1971),  yet 
biological  damage  was  not  reported  widespread 
and  the  area  has  started  to  recover.  Foster, 
Neushul,  and  Zingmark  (1971)  observed  that 
much  of  the  damage  to  intertidal  areas  corres- 
ponded to  sand  movement,  probably  from  storm 
damage.  Cimberg,  Mann,  and  Straughan  (1973) 
concluded  that  the  blowout  had  less  effect  on  in- 
tertidal marine  organisms  than  did  sand  move- 
ment and  substrate  stability.  Straughan  (1971), 
reporting  on  investigations  at  Santa  Barbara, 
noted  factors  unique  to  that  accident:  1)  the  long 
history  of  natural  oil  seepage  in  the  Santa  Bar- 
bara Channel  and  2)  the  unusually  heavy  winter 
runoff  at  the  time  of  the  spill,  which  reduced 
salinities,  increased  sedimentation,  and  possibly 
increased  pesticides  in  the  channel.  R.  L.  Kolpack 
(pers.  commun.  cited  by  Kanter,  Straughan,  and 
Jessee  (1971))  noted  that  Santa  Barbara  crude  oil 
is  relatively  insoluble  in  seawater  and  contains  a 
very  low  percentage  of  the  toxic  aromatic  com- 
pounds. Thus,  information  gathered  on  the  effect 
of  the  Santa  Barbara  spill  or  any  other  is  of  limited 
utility  in  predicting  the  ecological  effects  of  crude 
oil  spills  or  of  other  oils  in  other  areas. 

Several  studies  have  provided  encouraging  re- 
ports of  varying  degrees  of  recovery  after  some  of 
the  recent  larger  spills.  Investigations  about  11/2 
yr  after  the  Torrey  Canyon  spill  revealed  that  at 
least  the  affected  shoreline  areas  were  recoloniz- 
ing  and  recovering,  although  recovery  was  not  yet 
complete  at  that  time  (Spooner,  1969).  The  areas 
affected  by  the  1969  Santa  Barbara  blowout  were 
recently  reported  to  be  recovering  (Cimberg  et  al., 
1973),  as  was  a  reef  affected  by  bunker  C  oil  spilled 
from  a  tanker  collision  in  San  Francisco  Bay  in 
January  1971  (Chan,  1973). 

Too  few  of  the  controlled  field  investigations 
have  been  designed  to  bridge  the  gap  between  field 
surveys  after  spills  and  simulative  laboratory  ex- 
periments. Perkins  (1970)  exposed  periwinkles 
and  other  intertidal  organisms  to  the  oil  disper- 
sant  BP1002  in  the  laboratory  and  then  released 
marked  individuals  in  the  natural  environment. 
After  recapture  of  the  individuals  exposed,  he 
found  that  survival  from  doses  as  low  as  one 
three-thousandth  of  the  24  h  LCso^  was  lower 
than  among  the  recaptured  controls.  Crapp 
(1971a)  conducted  field  experiments  by  applying 
crude  oil  and  oil  emulsifiers  to  the  intertidal  zone. 


^24  h  LCso  equals  that  dose  of  toxicant  that  resulted  in  50% 
survival  after  24-h  exposure. 


Physical  damage  by  the  oil  was  observed,  but  tox- 
icity damage  was  not  great  because  the  oil  had 
previously  been  exposed  to  air;  in  contrast,  the 
oil-emulsifier  mixtures  were  toxic.  Baker  (1970) 
applied  a  crude  oil  to  salt-marsh  plots  at  different 
times  of  the  year  and  monitored  the  effects  on 
plants.  Summer  applications  of  oil  severely  af- 
fected annuals  but  not  perennials. 

Laboratory  Studies 

Experiments  in  the  laboratory  also  do  not  pro- 
vide all  the  answers  about  how  an  oil  spill  will 
affect  a  marine  organism  or  its  environment. 
Laboratory  research  has  demonstrated  the  toxic- 
ity of  various  crude  oils  and  petroleum  products  on 
several  forms  of  marine  life.  Much  of  this  research 
has  focused  on  the  planktonic  life  history  stages  of 
pelagic  and  benthic  animals.  Many  of  these  plank- 
tonic larvae  are  phototactic  at  their  earliest  stages 
and  concentrate  in  the  surface  layer  of  the  sea. 
This  community  of  the  surface  5  cm,  the  neuston, 
is  the  first  affected  by  most  oil  entering  the  water. 
Thus,  many  organisms  are  most  sensitive  to  oil 
pollution  at  the  time  of  their  greatest  likelihood  of 
exposure. 

Studies  by  Mironov  (1968)  on  the  development 
of  fertilized  eggs  of  the  plaice.  Rhombus 
macoticus ,  showed  extreme  sensitivity  of  the  eggs 
to  the  influence  of  the  oil  products  in  seawater.  He 
noted  that  injury  to  the  eggs  occurred  at  concen- 
trations of  lO'^o  lO'^ml/liter  (0.1  to  0.01  ppm).  In 
these  concentrations  of  oil  products,  40  to  100%  of 
the  hatched  prelarvae  showed  some  signs  of  de- 
generation during  development  and  perished. 
Mironov  (1969a)  also  demonstrated  that  0.001  ml 
of  crude  oil  per  liter  was  toxic  to  the  eggs  of  an- 
chovy, scorpionfish,  and  sea  parrots  from  the 
Black  Sea. 

Newly  set  spat  of  Elinius  modestus,  an  Aus- 
tralian barnacle  introduced  to  Europe,  were  tol- 
erant of  100  ppm  crude  oil  but  showed  reduced 
cirral  activity  and  retarded  shell  growth  (Corner, 
Southward,  and  Southward,  1968).  Adults  of  this 
species  also  showed  reduced  activity  at  100  ppm 
(Corner  et  al.,  1968). 

Mironov  (1969b)  tested  crude  oil  on  several 
copepods  and  a  cladoceran,  and  found  that  0.001 
ml/liter  accelerated  death  in  all  forms  and  that 
0.1  ml/liter  caused  death  in  less  than  1  day.  Acar- 
tia  and  Calanus  died  at  0.01  ml/liter  oil  in  sea- 
water in  72  to  96  h  (Mironov,  1968).  Larvae  of 
crab  and  shrimp  died  at  1  ppm  (Mironov,  1969c). 

Little  is  known  of  the  mechanisms  of  various 


633 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


toxic  effects.  Damage  to  cell  membranes  and  the 
cellular  contents  of  planktonic  larvae  may  occur. 
Goldacre  (1968)  demonstrated  such  cytological 
damage  and  death  to  the  freshwater  protozoan, 
Amoeba  proteus,  exposed  to  crude  oil  fractions. 
Brocksen  and  Bailey  (1973)  measured  increased 
respiratory  response  of  striped  bass  and  chinook 
salmon  to  sublethal  concentrations  of  benzene. 
The  fish  recovered  to  normal  activity  when  they 
returned  to  noncontaminated  water  for  several 
days.  Rice  and  Short  were  unable  to  demonstrate 
changes  in  the  enzyme  activity  of  cholinesterase 
or  Na-K  stimulated  ATPase  in  juvenile  pink 
salmon,  Oncorhynchus  gorbuscha,  after  in  vivo 
and  in  vitro  exposures  to  Prudhoe  Bay  crude  oil 
(Stanley  D.  Rice  and  Jeffrey  Short,  Auke  Bay 
Fisheries  Laboratory,  NMFS,  NOAA,  Auke  Bay, 
AK  99821,  pers.  commun.).  This  is  somewhat 
surprising  because  various  hydrocarbon  pesti- 
cides have  been  shown  to  affect  both  enzymes. 

Cellular  membranes  of  phytoplankton  are  also 
damaged  by  the  penetration  of  hydrocarbon 
molecules:  the  cellular  contents  are  extruded,  and 
oil  penetrates  into  the  cell.  Detergents  adminis- 
tered in  a  concentrated  solution  also  penetrate  the 
plant  cells  and  cause  the  dissolution  of  cellular 
membranes  and  the  extrusion  of  cellular  fluid 
(Ruivo,  1972).  The  effects  of  oils  on  plant  respira- 
tion are  variable,  but  an  increase  of  respiration  is 
frequently  observed,  probably  because  of  an  alter- 
ation of  the  mitochondria.  This  could  result  in  an 
uncoupling  of  the  oxidative  phosphorylation  en- 
zymes from  the  electron  transport  enyzmes,  and 
the  energy  release  would  be  lost  as  heat. 

All  marine  animals  ultimately  depend  on  the 
photosynthetic  activity  of  phytoplankton  and 
algae  for  the  production  of  biomass.  Baker 
(1971),  reviewing  the  literature,  noted  that 
weathered  Torrey  Canyon  oil  had  no  apparent  ef- 
fect on  the  photosynthetic  activity  of  green  algae. 
He  did  find,  however,  that  green  algae  treated 
with  fresh  crude  oil  died  and  that  photosynthesis 
in  kelp,  Macrocystis  sp.,  was  reduced  when  the 
kelp  was  exposed  to  various  petroleum  products. 
Kauss  et  al.  (1973)  determined  the  effects  of  crude 
oil  on  several  species  of  freshwater  algae  in  both 
field  and  laboratory  experiments.  In  their  field 
studies,  response  of  the  algae  to  a  spill  varied  from 
suppression  of  growth  to  its  stimulation.  In  their 
laboratory  studies,  they  noted  depressed  photo- 
synthetic rates  in  one  algal  species  after  it  had 
been  exposed  to  aqueous  crude  oil  and  other 
selected  aromatics. 


Growth  of  phytoplankton  from  axenic  cultures 
and  mixed  cultures  of  natural  populations  was 
inhibited  by  water-soluble  extracts  from  no.  2  fuel 
oil  in  a  laboratory  study  by  Nuzzi  (1973).  Mironov 
and  Lanskaya  (1968)  demonstrated  that  marine 
phytoplankton  vary  several  orders  of  magnitude 
in  sensitivity  to  crude  oils  and  kerosene  in  oil 
concentrations  ranging  from  0.1  to  1,090  ppm.  Of 
the  20  species  tested,  a  diatom,  Ditylum 
brightwellii ,  was  the  most  sensitive.  The  wide  var- 
iation in  susceptibility  may  account  for  the  state- 
ments in  other  reviews  of  low  toxicity  of  crude  oils 
to  phytoplankton  (F0yn,  1965;  Nelson-Smith, 
1970)  and  supports  the  premise  that  biological 
response  will  differ  among  species. 

Sublethal  and  Chronic  Effects 
of  Oil  Pollution 

While  data  are  scarce  in  some  of  the  areas  previ- 
ously discussed,  information  on  the  ecological  ef- 
fects of  chronic  sublethal  oil  pollution  is  essen- 
tially nonexistent.  Observing  these  effects  is 
difficult  because  they  are  not  dramatic  and  may 
pass  unnoticed  by  the  casual  observer.  A  full  de- 
scription would  require  observations  extending 
over  a  long  period  of  time. 

Lewis  (1972),  commenting  on  approaches  to  the 
study  of  chronic  pollution,  contends  ".  .  .  that 
without  a  massive  expansion  of  ecological  and  re- 
productive data  by  simultaneous  multidisciplin- 
ary  studies  not  only  will  we  be  unable  to  detect 
the  significant  long-term  changes,  but  we  will 
even  remain  unaware  of  the  most  suitable  or  im- 
portant species  and  methods  to  build  into  a 
monitoring  program." 

A  few  studies  concerning  sublethal  effects  on 
organisms  have  appeared  in  the  literature.  Wells 
(1972)  reported  deaths  of  lobster  larvae  to  expos- 
ures of  0.1  ml  of  Venezuelan  crude  oil  per  liter, 
while  larvae  exposed  to  0.01  ml/liter  had  poor 
survival  rates  and  were  unable  to  molt  to  the 
fourth  stage.  Decreased  limb  (cirral)  activity  of 
marine  larvae  exposed  to  oil  has  been  reported 
(Smith,  1968).  Kuhnhold  (1972),  while  observing 
toxic  effects  of  crude  oils  to  eggs  of  cod  and  to 
larvae  of  cod,  plaice,  and  herring  noted  that  the 
larvae  exposed  to  oil-contaminated  water  were 
unable  to  avoid  well-defined  milky  clouds  of  toxic 
oil  dispersions.  Blanton  and  Robinson  (1973)  ob- 
served damage  to  the  gills  of  specimens  of  seven 
species  offish  that  had  apparently  been  exposed  to 
an  oil  spill  off  the  Louisiana  coast. 


634 


EVANS  and  RICE:  EFFECTS  OF  OIL  ON  ECOSYSTEMS 

Crapp  (1971b)  observed  that  fucoid  algae  re- 
placed barnacle  and  limpet  populations  near  an 
outfall  where  the  effluent  contained  about  20-25 
ppm  oil  from  treated  ballast  water  of  tankers  un- 
loading at  Milford  Haven.  Although  the  relative 
oil  content  was  low,  the  cumulative  volume  dis- 
charged was  large  (20,000  gallons  of  oil  per  year), 
a  situation  similar  to  that  which  may  occur  at  Port 
Valdez,  Alaska,  when  the  trans-Alaska  pipeline  is 
completed. 

Blumer  (1972)  discussed  how  low-level  chronic 
effects  of  oil  may  damage  marine  organisms  be- 
cause of  their  dependence  on  natural  organic 
chemical  clues  for  a  variety  of  functions.  Salmon 
and  other  fishes  utilize  organic  chemical  clues  in 
migrations;  predators  are  attracted  to  prey  by  or- 
ganic compounds  at  the  parts-per-billion  level 
(Whittle  and  Blumer,  1970);  and  other  organisms 
may  use  chemical  clues  for  predator  avoidance, 
selection  of  habitat,  and  sex  attraction.  Blumer 

(1972)  discussed  the  fears  that  oil  pollution  may 
interfere  with  these  fundamental  biological  pro- 
cesses by  masking  or  blocking,  or  by  mimicking 
natural  stimuli  (resulting  in  false  responses).  He 
cited  literature  discussing  the  attraction  of  lob- 
sters to  kerosene  and  to  purified  hydrocarbon  frac- 
tions derived  from  kerosene  and  noted  that  many 
dead  lobsters  were  washed  ashore  after  the  West 
Falmouth  spill.  Blumer's  fears  about  interference 
with  chemoreception  are  further  substantiated  by 
the  observations  of  Takahashi  and  Kittredge 

(1973)  on  crab  behavior.  Crabs,  Pachygrapsus 
crassipes,  exposed  to  water-soluble  extracts  of 
crude  oil  failed  to  exhibit  feeding  behavior  or  mat- 
ing behavior  responses  when  given  appropriate 
chemical  stimuli.  Inhibition  of  chemoreception  of 
some  motile  marine  bacteria  by  a  crude  oil  and 
several  other  hydrocarbons  has  been  demon- 
strated by  Walsh  and  Mitchell  (1973). 

Rice  (1973)  performed  laboratory  tests  of  avoid- 
ance of  pink  salmon  fry  to  Prudhoe  Bay  crude  oil 
and  observed  avoidance  of  oil  at  concentrations  as 
low  as  1.6  mg/liter.  He  concluded  that  salmon  fry 
had  the  capability  of  detecting  sublethal  concen- 
trations of  oil  and  that  they  might  avoid  areas 
contaminated  with  sublethal  levels  of  oil,  which 
would  result  in  confused  and  nonadaptive  migra- 
tory behavior.  The  effect  of  chronic  low-level  pollu- 
tion in  areas  such  as  Port  Valdez,  the  terminus  of 
the  trans- Alaska  oil  pipeline,  could  be  as  severe  as 
the  total  loss  of  all  salmon  runs  in  the  local  area 
because  of  altered  behavioral  responses  to  sub- 
lethal oil  pollution. 


CONCLUSIONS 

Although  crude  oil  generally  should  be  consid- 
ered toxic  to  marine  organisms  and  harmful  to 
their  environment,  most  ecosystems  can  tolerate 
some  pollution  because  oil  can  be  dissipated  or 
removed  by  processes  like  evaporation,  autoxida- 
tion,  dilution,  and  biodegradation.  However,  each 
organism  and  environment  has  a  limit  to  how 
much  oil  can  be  absorbed  and  metabolized.  Cat- 
astrophic spills  are  obviously  pollution  at  a  level 
that  ecosystems  cannot  tolerate  without  damage. 
However,  if  the  spills  are  not  continued,  the  oil 
will  slowly  be  removed  and  recovery  of  the  area,  at 
least  to  some  degree,  will  likely  occur.  There  is 
some  evidence  for  recovery  of  some  affected  indi- 
viduals. 

Assessments  of  the  impact  of  oil  pollution  can- 
not depend  solely  on  evaluation  of  immediate  kills 
of  organisms  from  acute  exposures.  Chronic  low- 
level  oil  pollution  can  cause  subtle  changes  in 
organisms  and  is  potentially  more  dangerous  to 
the  ecosystem  than  dramatic  catastrophic  spills. 
For  this  reason,  the  effects  of  chronic  pollution 
warrant  intensive  study  so  that  they  will  not  be 
underestimated.  The  cumulative  impact  of 
"ecological  death"  of  individuals  which  have  im- 
paired functions  may  be  quite  significant,  yet 
difficult  to  assess  because  the  death  is  not  tied 
directly  to  an  acute  oil  exposure.  Equally  as 
dangerous  is  the  potential  impact  on  populations 
where  reproductive  processes,  adversely  affected 
through  physiological  or  behavioral  mechanisms, 
result  in  fewer  progeny.  Chronic  pollution  may 
eliminate  a  species  from  an  area  entirely,  and  once 
eliminated  that  species  may  remain  suppressed 
and  may  not  repopulate  the  area  because  of  con- 
tinuing pollution  or  because  its  niche  has  been 
filled  by  a  more  tolerant,  possibly  less  desirable, 
species. 

The  adverse  effects  of  oil  on  animal  populations 
has  been  of  wide  concern  when  stocks  of  special 
interest,  such  as  those  providing  the  basis  of  a 
sport  or  commercial  fishery,  have  been  involved.  It 
should  be  remembered  that  changes  in  popula- 
tions of  lesser  apparent  significance  will  also 
cause  changes  in  the  community  because  each 
species  population  interacts  with  and  is  dependent 
on  the  rest  of  the  community. 

The  foregoing  review  of  information  does  little 
to  simplify  or  ease  the  problems  of  policy  makers 
concerned  with  marine  production  and  transpor- 
tation of  oil  and  petroleum  products.  The  weight  of 


635 


the  evidence  leaves  little  doubt  that  oil  poses  a 
serious  hazard  to  living  marine  resources,  that 
spills  and  chronic  pollution  have  happened  and 
will  continue  to  occur,  and  that  the  interests  of  the 
marine  environment  are  best  preserved  if  marine 
transportation  of  oil  and  petroleum  products  is 
minimized.  The  continuing  need  for  new  sources 
and  increased  amounts  of  energy,  however,  limits 
many  of  the  conservative  and  prudent  alterna- 
tives to  these  hazards.  Until  research  has  provided 
conclusive  data,  policy  makers  must  continue  to 
rely  on  these  interpretative  judgments  for  much 
of  their  guidance  in  making  decisions  that  can 
profoundly  affect  the  well  being  of  marine 
ecosystems. 

ACKNOWLEDGMENTS 

We  received  much  counsel  in  the  preparation  of 
the  report  from  Jack  E.  Bailey,  Theodore  R.  Mer- 
rell,  Jr.,  Richard  T.  Myren,  and  Bruce  L.  Wing, 
biologists  of  the  Auke  Bay  Fisheries  Laboratory, 
NMFS,  NOAA;  and  Robert  C.  Clark,  Jr.,  of  the 
Northwest  Fisheries  Center,  NMFS,  NOAA,  Seat- 
tle, Wash. 

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1973.  Microbial-facilitated  degradation  of  oil:,  a  prospec- 
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Baker,  J.  M. 

1970.  The  effects  of  oils  on  plants.  Environ.  Pollut.  1:27-44. 

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Barber,  F.  G. 

1971.  An  oiled  arctic  shore.  Arctic  24:229. 
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Perkins,  E.  J. 

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1973.  Influence  of  crude  oil,  derivatives  and  dispersants  on 
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1973.  Toxicity  and  avoidance  tests  with  Prudhoe  Bay  oil 
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638 


ON  THE  DISPERSAL  OF  LOBSTER  LARVAE  INTO 
THE  EAST  PACIFIC  BARRIER  (DECAPODA,  PALINURIDEA) 

Martin  W.  Johnson  ^ 

ABSTRACT 

The  seaward  drift  of  phyllosoma  larvae  of  lobsters  occurring  along  the  coast  and  adjacent  islands  of  the 
eastern  tropical  Pacific  Ocean  was  studied  from  plankton  collections  made  jointly  by  the  Scripps 
Institution  of  Oceanography,  Tuna  Oceanography  Research  Program,  and  the  National  Marine 
Fisheries  Service,  La  JoUa,  Calif. 

Numerous  samples  taken  with  trawl  and  plankton  nets  were  made  across  the  Equatorial  current 
system  in  two  areas:  lat.  15°N-5°S,  long.  115°-125°W,  and  lat.  5°N-15°S,  long.  95°-115°W.  Many  late 
developmental  stages  of  Panulirus  penicillatus  and  P.  gracilis  and  a  fev/  Scyllarides  astori  were  found, 
all  apparently  having  drifted  mainly  with  the  South  Equatorial  Current  over  a  distance  of  1,800  to 
2,000  or  more  nautical  miles  from  their  likely  origin,  the  Galapagos  Islands  or  the  coast  of  Central 
America.  A  few  larvae  were  found  in  the  North  Equatorial  Countercurrent.  This  is  at  times  a  possible 
route  for  return  to  the  adult  habitat,  but  it  is  doubtful  that  any  of  the  larvae  that  have  drifted  to  the 
most  western  survey  area  will  be  returned  by  countercurrents  in  time  for  metamorphosis  or  that  they 
can  successfully  negotiate  the  remainder  of  the  expanse  of  the  East  Pacific  Barrier  to  reach  the 
mid-Pacific  islands. 


The  present  report  is  essentially  a  follow-up  of 
a  previous  survey  in  which  a  large  plankton 
collection  made  by  the  multiship  eastern  tropi- 
cal pacific  (EASTROPAC)  Project  in  1967-68 
was  used  in  part  to  ascertain  the  systematics 
and  geographic  distribution  of  the  pelagic  phyl- 
losoma larvae  of  all  of  the  spiny  lobsters 
(Palinuridae)  and  slipper  lobsters  (Scyllaridae) 
known  to  inhabit  the  west  coast  and  offshore  is- 
lands of  Central  America,  Colombia,  and 
Ecuador  (Johnson,  1971).  In  that  survey  an  ex- 
tensive area  was  covered  along  the  coast  and 
seaward  both  north  and  south  of  the  Equator  to 
about  long.  126°W.  It  therefore  forms  the  basic 
groundwork  drawn  upon  in  the  present  report 
dealing  with  the  phyllosoma  larvae  taken  dur- 
ing a  more  restricted  offshore  survey  within  the 
same  area  by  the  Scripps  Tuna  Oceanography 
Research  Program  (STOR)  in  cooperation  with 
the  National  Marine  Fisheries  Service  at  La 
Jolla,  Calif.,  and  Honolulu,  Hawaii.  This 
offshore  "skipjack  survey"  was  designed  and  ini- 
tiated in  1970  to  study  the  migrations  of  young 
skipjack  tuna,  Katsuwonus  pelamis,  in  the  east- 
ern tropical  Pacific  Ocean  (Williams,  1971,  1972). 
A  comprehensive  review  of  the  current  system 
and  water  masses  so  important  to  pelagic  larvae 
of  the  area  is  given  by  Wyrtki  (1967). 
From  Point  Conception  southward  to  the  Gulf 

'Scripps  Institution  ofOceanography,  University  of  California 
at  San  Diego,  La  Jolla,  CA  92037. 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


of  Guayaquil,  Ecuador  a  total  of  four  species  of 
palinurid  and  two  species  of  scyllarid  lobsters 
occur.  In  the  present  survey  only  the  larvae  of 
Panulir us  penicillatus  (Olivier,  ISll) ,  P .  gracilis 
(Streets,  1871),  P.  inflatus  (Bouvier,  1895),  and 
Scyllarides  astori  Holthuis,  1960  were  found  as 
expatriate  larvae  from  the  coast  or  coastal  is- 
lands. Panulirus  interruptus  (Randall,  1840)  oc- 
curs off  the  coast  of  southern  and  Baja  Califor- 
nia, too  far  north  for  its  larvae  to  be  expected  to 
enter  into  the  current  system  covered  here  ex- 
cept as  rare  stragglers  in  the  North  Equatorial 
Current.  Evibacus  princeps  Smith,  1869  (the 
second  scyllarid)  although  common  to  the  east- 
ern tropical  Pacific,  apparently  has  a  larval 
period  too  short  to  be  carried  far  from  the  coast 
(Johnson,  1971).  The  larvae  of  P.  gracilis  and  P. 
inflatus  are  difficult  to  separate  specifically  if 
the  fourth  pereiopods  have  been  lost.  However, 
adults  of  only  P.  gracilis  occur  in  the  southern 
range  including  the  Galapagos  Islands  and  all 
but  two  larvae  could  be  referred  to  that  species. 
The  larvae  of  Jasus  frontalis  (H.  Milne  Ed- 
wards, 1837)  and  Scyllarus  delfini  (Bouvier, 
1909),  the  two  lobsters  found  in  the  Juan  Fer- 
nandez Islands  off  Chile,  were  not  found  in  the 
equatorial  currents  or  in  the  Peru  Current  to 
lat.  24°S  during  the  EASTROPAC  survey  and 
none  were  taken  in  the  present  survey. 

The  duration  of  the  phyllosoma  larval  period 
as  derived  from  studies  of  different  species  in 


639 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


nature  indicate  about  8  to  11  mo  for  palinurids 
(Johnson,  1960;  Lazarus,  1967;  Chittleborough 
and  Thomas,  1969).  In  some  scyllarids  shorter 
periods  are  indicated  (Saisho,  1962;  Robertson, 
1968),  but  in  others,  including  Scyllarides 
astori,  a  length  comparable  to  that  of  palinurids 
is  suggested  by  the  wide  dispersal  of  the  larvae. 
These  long  drifting  periods  provide  ample 
time  for  far  and  wide  dispersal.  Coincident  with 
this,  the  number  of  larvae  caught  in  a  plankton 
tow  is  always  small  especially  for  the  later 
stages  and  this  precludes  close  statistical 
analysis  for  short  surveys.  But  the  presence  of 
even  small  numbers  of  larvae  when  scattered 
over  a  large  area  or  period  of  time  are 
significant  in  indicating  major  outlines  of  the 
type  of  drift  and  dispersal  by  currents  from 
adult  spawning  areas. 

PROCEDURE 

In  view  of  the  scarcity  of  larvae  and  the  pres- 
ence of  only  later  developmental  stages  VI-XI 
(the  final  phyllosoma  stage)  in  far  offshore  wa- 
ters, the  collections  most  generally  useful  were 
those  from  nets  filtering  large  quantities  of 
water:  a  15  x  15  m  mid-water  trawl  with  a 
section  of  3-mm  bar  mesh  and  towed  obliquely 
in  steps  from  100  to  0  m  or  from  30  to  0  m  for 
about  1  h  30  min;  and  a  Blackburn  micronekton 
net  5.8  m  long  constructed  of  nylon  with  mesh 
apertures  of  about  5.5  x  2.5  mm,  and  cod  end  of 
no.  56  XXX  grit  gauze.  This  net  attached  to  a  5 
X  5  foot  (1.52  X  1.52  m)  frame  was  towed  about 
60  min  obliquely  from  200  to  0  m.  Samples 
were  also  analyzed  from  tows  taken  with  a  5-m 
long  "neuston"  net  constructed  of  nylon  with 
mesh  apertures  of  about  0.65  mm,  and  cod  end 
of  no.  56  grit  gauze.  This  net  was  attached  to  a 
1-m  ring  bent  to  form  a  narrow  opening  and 
buoyed  to  tow  at  the  immediate  surface  for 
15  min.  For  David  Starr  Jordan  cruise  65, 
analyses  were  also  made  of  all  samples  taken 
with  a  similar  net  attached  to  a  regular  1-m 
ring  towed  obliquely  from  200  to  0  m  for  20-25 
min  simultaneously  with  the  neuston  net. 

RESULTS 

David  Starr  Jordan  Cruise  57 

and  Townsend  Cromivell  Cruise  51 

5  N0V.-2I  Dec.  1970 

In  Figure   1  is  shown  the  station  pattern 

640 


I5°N 


10' 


.i)_ 


o 

■(•f  A«  A» 


NORTH  EQUATORIAL  CURRENT 


•  •  •!     O 


EQUATORIAL    COUNTERCURRENT 


>  l--h--  ^ 


'^S.  astori  post  larva 
0^:__.O ! 


SOUTH  EQUATORIAL  CURRENT 


S'S 


II5°W 


JORDAN  57  and   CROMWELL  51 
Stations  with  available 
plankton  samples: 

•  Jordan  5'x  5'  net 

A       "       midwater  trawl 

n       "       neuston  net 

O  Cromwell  5x5'  net 

A  "         midwater  trawl 

/  ptiyllosoma  larvae  taken 

Figure  I.— RV  Townsend  Cromwell  cruise  51  and  RV  David 
Starr  Jordan  cruise  57  station  pattern  in  unit  areas  1-6.  Neuston 
net  tows  are  shown  only  where  larvae  were  taken. 

where  net  tows,  positive  or  negative  for  phyl- 
losoma larvae,  were  taken  by  the  trawl  or  the  5 
X  5  foot  net.  The  stations  occupied  fall  into 
more  or  less  distinct  unit  areas  as  designed  for 
the  tuna  study  to  correlate  with  the  prevailing 
major  elements  of  the  Equatorial  Current  Sys- 
tem. 

The  number  and  stages  of  larvae  caught  in 
the  various  nets  are  given  in  Table  1  for  each  of 


JOHNSON:  DISPERSAL  OF  LOBSTER  LARVAE 


the  unit  areas.  Because  of  the  scarcity  of  speci- 
mens, no  attempt  is  made  to  give  figures  based 
on  unit  volume  of  water  filtered. 

In  unit  area  1,  52%  of  27  tows  (other  than  with 
the  neuston  or  1-m  net)  yielded  a  total  of  87  larvae 
in  this  8°  square  area  in  the  South  Equatorial 
Current.  Nine  neuston  net  tows  caught  no  larvae. 

The  three  stations  below  4°S  were  negative 
and  approach  or  fall  into  a  large  expanse  of 
water  that  yielded  no  larvae  during  the  EAS- 
TROPAC  cruises  (Johnson,  1971,  Chart  12). 

Unit  area  2  also  in  the  South  Equatorial  Cur- 
rent was  less  well  sampled,  but  36%  of  11  tows 
with  the  trawl  and  5x5  foot  net  yielded  a 
total  of  35  phyllosoma  larvae  and  one  scyllarid 
postlarva  (nesto).  The  five  neuston  tows  were 
negative. 

The  large  number  of  larvae  caught  by  the 
trawl  in  unit  areas  1  and  2  when  compared 
with  the  more  northern  unit  areas  is  striking  in 
indicating  the  tendency  of  the  South  Equatorial 
Current  to  retain  its  load  of  phyllosoma  larvae 
in  their  long  drift  from  the  adult  area. 

In  unit  area  3  overlapping  into  the  North 
Equatorial  Countercurrent,  which  was  well  de- 
veloped at  the  time  (Williams,  1971),  20%  of  15 


tows  with  the  trawl  and  5x5  foot  net  were 
successful  but  yielded  only  seven  larvae  in 
these  nets.  However  five  additional  larvae  were 
caught  in  2  of  11  neuston  tows. 

Unit  area  4  comprises  only  a  2°  square  area 
within  the  North  Equatorial  Countercurrent. 
Here  two  of  three  trawls  and  one  of  nine  5x5 
foot  net  tows  yielded  3  and  1  larvae  respectively 
while  the  neuston  net  caught  a  total  of  10  lar- 
vae in  two  of  eight  tows.  The  successful  neuston 
tows  in  this  area  and  in  unit  area  3  were  taken 
during  evening  or  nighttime  tows. 

Unit  areas  5  and  6  provided  no  phyllosomas 
although  both  areas  were  comparatively  well 
sampled. 

The  relatively  large  number  of  larvae  taken 
during  these  two  cruises  compared  with  the  fol- 
lowing cruises  reflects  more  intensive  sampling, 
especially  with  the  trawl,  but  a  seasonality  in 
release  of  larvae  in  the  adult  area  may  also 
have  contributed. 

David  Starr  Jordan  Cruise  60 
6  Mar.- 11  Apr.  1971 

The  stations  occupied  for  plankton  were  more 
scattered  and  very  few  larvae  were  caught, 


Table  1. — David  Starr  Jordan  cruise  57  andTownsend  Cromwell  cruise  51.  Types  of  gear, 
total  number  of  tows  taken  (the  successful  number  of  which  is  shown  in  parenthesis)  and 
the  number  nf  larval  species  caught  with  different  gear  in  unit  areas  1-6. 


Unit  areas 

No.  of  tows 

Successful  no. 

Species  taken  and 

Phyllosoma  stages 

Total  larvae 

in  parentheses 

type  of  gear 

VII 

VIII        IX         X 

XI 

in  unit  area 

1 

5'  X  5',  14(3) 
Trawl,  13  (11) 
Neuston,  9  (0) 

P 
P. 
P. 
S. 

gracilis,  5'  x  5' 
gracilis,  trawl 
penicillatus,  trawl 
astori.  trawl 

1 
1 

1 
11 

1 

18 
7 
3 

2 

16         16 
4           6 

87 

2 

5'  X  5',  8  (1) 
Trawl,  3  (3) 
Neuston,  5  (0) 

P. 
P. 
P. 
S. 
S. 

gracilis.  5'  x  5' 
gracilis,  trawl 
penicillatus,  trawl 
astori.  5'    ■  5' 
astori.  trawl 

1 
2 
1 

1 

10 
1 

1 
11 

1 

1 
6 

35  +  1  nesto 

3 

5'  X  5',  13  (2) 
Trawl,  2  (1) 
Neuston,  11  (2) 

P. 
P. 
P. 
P 

gracilis.  5'  x  5' 
gracilis,  trawl 
gracilis,  neuston 
penicillatus,  trawl 

1 
1 

1 

2 

3 

1 

1 
1 

1 

12 

4 

5'  X  5'.  9  (1) 
Trawl,  3  (2) 
Neuston,  8  (2) 

P 
P 
P 
P 

gracilis.  5'  x  5' 
gracilis,  trawl 
gracilis,  neuston 
penicillatus,  trawl 

1 
1 

4 

1 
5 

1 

1 

14 

5 

5'  X  5',  13(0) 
Trawl,  8  (0) 
Neuston,  1 1  (0) 

none 

0 

6 

5'  X  5',  8  (0) 
Trawl,  5  (0) 
Neuston,  8  (0) 

none 

0 

641 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


hence  the  data  on  larval  distribution,  species, 
and  stages  taken  are  entered  directly  on  the 
chart  (Figure  2).  The  successful  tows  indicate  at 
least  a  presence  of  larvae  in  all  of  the  major 
currents  traversed.  The  North  Equatorial  Cur- 
rent at  this  time  showed  a  few  stage  VII  P. 
penicillatus  with  Clipperton  Island  a  likely 
source  of  origin. 


IS'N 


10' 


SOS 


< 

NORTH  EQUATORIAL 
CURRENT 


<r 


~l 1 1 r 

p.p.  I M  ~\ 


•   □ 


D 


D' 


TRANSITION        ZONE 


EQUATORIAL 
COUNTERCURRENT 


•  □  .D 
*—P.g.  i,X 


D' 


D 


Ck^- 


D 


•a 


/?/£3.l,3mi;2,IX- 


SOUTH  EQUATORIAL 


CURRENT 


•fg'x'? 


n~ 


^/P.  i,x 


<- 


•  D 


P.g.\,ll.- 


□  . 


125°  120°  IISOW 

JORDAN  60 

Stations   with  available 
plankton  samples: 

•   5'x5'  net  * 

A   nnidwater  trawl 

n  neuston  net 

Pp.  Ponulirus  penicillatus 

P.g.  Ponulirus  gracilis 

nunnber  of  phyllosomo 
larvae  taken  (Arabic  No.) 

stage  of  phyllosoma 
larvae  token  (Romon  No.) 

Figure  2. — RV  David  Starr  Jordan  cruise  60  station  pattern  with 
number  and  stage  (Roman  numeral)  of  phyllosoma  larvae  taken  at 
station  indicated. 


David  Starr  Jordan  Cruise  65 
24  Aug.-30  Sept.  1971 

As  shown  in  Figure  3,  this  cruise  covered  an 
area  much  nearer  the  Galapagos  Islands,  from 
which  most  of  the  phyllosomas  taken  probably 
originated.  It  also  extended  less  to  the  north 
and  farther  to  the  south.  The  data  will  again  be 
presented  here  by  unit  areas  (2°  squares). 

Unit  1  falls  below  lat.  11°S  and  yielded  no 
larvae  in  a  total  of  eight  tows  (Table  2).  It  is 
probable  that  the  area  is  within  the  influence  of 
the  northern  boundary  of  the  western  extension 
of  the  Peru  Current  which  as  already  men- 
tioned had  few  or  no  phyllosomas  during  the 
EASTROPAC  cruises. 

In  unit  2  within  the  South  Equatorial  Cur- 
rent, a  total  of  16  tows  with  the  various  nets 
yielded  19  larvae,  mainly  by  the  trawl. 

Units  3  and  4  although  within  the  South 
Equatorial  Current  had  only  two  and  four  lar- 
vae respectively  in  a  total  of  18  mixed  tows. 

Unit  5  directly  west  of  the  Galapagos  was  the 
most  productive  of  larvae  where  five  of  eight 
neuston  hauls  yielded  a  total  of  33  specimens. 

Unit  6,  still  within  the  South  Equatorial  Cur- 
rent, was  less  productive  of  larvae  although 
three  of  eight  neuston  net  tows  took  five  larvae. 

A  total  of  35  tows  taken  with  the  1-m  net 
simultaneously  with  the  neuston  net  during  the 
cruise  yielded  no  larvae  whatever  (see  Discus- 
sion). 

David  Starr  Jordan  Cruise  77 
8  Jan.-17  Feb.  1973 

Figure  4  depicts  the  station  pattern  across 
the  current  system.  As  in  cruise  60  there  were 
so  few  phyllosoma  larvae  that  it  will  suffice  to 
record  the  data  relative  to  these  directly  on  the 
chart.  There  were  a  few  scattered  palinurid  lar- 
vae in  the  North  Equatorial  Current.  The 
nearest  likely  source  of  these  being  Clipperton 
Island.  A  few  also  occurred  in  the  northern  part 
of  the  South  Equatorial  Current.  That  these 
probably  came  from  the  Galapagos  Islands  is 
indicated  by  the  accompanying  larvae  of  Scyl- 
larides  astori,  the  adult  of  which  is  relatively 
rare  except  in  that  area. 

Of  special  interest  however  is  the  occurrence 
of  a  single,  late  stage  Parribacus  sp.  phyllosoma 
in  this  group  of  stations.  No  adult  species  of 
this  genus  has  been  reported  from  the  west 


642 


JOHNSON:  DISPERSAL  OF  LOBSTER  LARVAE 


S'N 


Figure  3. — RW  David  Starr  Jordan  cruise  65  sta- 
tion pattern  in  unit  areas  1-6;  1-m  net  tow  also  made 
at  neuston  stations. 


10° 


I4''S 


-   <r 


n 


D  I 


I 


I 


J* 

I     • 


;2 


100° 


•n°^ 


JORDAN  65 

Stations  with  ovailable 
plankton  samples: 

•  5'x5'  net 

A  midwater   trawl 

n  neuston  net 

/  ptiyllosoma  larvae  token 


SOUTH  EQUATORIAL  CURRENT 

< 


SOUTH  EQUATORIAL  CURRENT 


PERU  COASTAL  CURRENT 


95° 


90° 


87°W 


coast  of  the  Americas.  Hence  one  is  forced  to 
conclude  that  it  most  likely  had  drifted  from  is- 
lands to  the  southwest  where  the  genus  is 
known  to  occur.  It  should  be  mentioned  here 
also  that  a  late  larva  of  this  genus  was  taken  at 
lat.  14°13.6'S,  long.  126°00'W  near  the  southern 
limit  of  the  most  distant  offshore  stations  of 
EASTROPAC.  Nothing  is  known  regarding  the 
duration  of  the  entire  floating  period  of  this 
genus. 

Saisho  (1962)  included  Pam6acus  antarcticus 
in  his  generalization  stating  that  the  free- 
swimming  life  of  scyllarids  is  shorter  than  for 
palinurids.  This  was  based  on  laboratory 
studies  of  only  the  first  three  larval  stages. 
However,  if  the  present  observations  of  the  two 
late,  but  not  yet  the  last,  stage  is  characteristic 
of  the  genus  they  suggest  that,  like  Scyllarides 
astori,  the  free-swimming  life  is  not  ab- 
breviated. 


DISCUSSION 

This  survey  is  of  special  interest  in  substan- 
tiating the  earlier  findings  of  the  EASTROPAC 
survey  relative  to  the  far  offshore  drift  of 
planktonic  stages  of  lobster  larvae  in  the 
Equatorial  Current  System.  As  in  the  earlier 
survey,  only  species  known  to  occur  in  the  east 
tropical  area  were  found  with  one  exception 
(Parribacus  sp.)  referred  to  above. 

Assuming  that  the  Galapagos  Islands  are  the 
main  source  of  the  larvae  encountered,  it  is  evi- 
dent that  the  westward  transport  with  the 
South  Equatorial  Current  involves  at  least  a 
distance  of  about  1,800  nautical  miles.  In 
Townsend  Cromwell  cruise  51  larvae  of  each  of 
the  prevailing  species  Panulirus  penicillatus,  P. 
gracilis,  and  S.  astori  were  netted  in  trawl  tows 
at  the  western-most  stations  at  long. 
121°32'-121°54'W  between  lat.  02°45'N  and 


643 


FISHERY  BULLETIN:  VOL.  72.  NO.  ? 


Table  2. — David  Starr  Jordan  cruise  65.  Types  of  gear,  total  number  of  tows  taken  (the 
successful  number  of  which  is  shown  in  parenthesis)  and  the  number  of  larval  species 
caught  with  different  gear  in  unit  areas  1-6. 


Unit  areas 

No.  of  tows 

Successful  no. 

Species  taken  and 

Phyllosoma  stages 

Total  larvae 

in  parentfieses 

type  of  gear 

VI 

VII       VIII        IX 

X 

in  unit  area 

5'  X  5',  4  (0) 
Trawl.  1  (0) 
Neuston,  3  (0) 

none 

2 

5'  X  5',  7(1) 
Trawl.  2  (2) 
Neuston.  7  (1) 

P.  gracilis,  neuston 
P.  penicillatus.  5'  x  5' 
P.  penicillatus,  trawl 
S.  astori,  trawl 

1 

5 

1 

3 

5'  X  5'.  4  (0) 

Neuston.  2  (1) 

P.  gracilis,  neuston 

2 

4 

5'  X  5',  3(0) 
Trawl,  2  (2) 
Neuston,  7  (0) 

P.  gracilis,  trawl 

5 

5'  X  5',  6  (1) 

Neuston,  8  (5) 

P.  gracilis,  neuston            6 
P.  penicillatus,  5'   -5' 

14 

1 

6 

5'  X  5'.  4  (0) 
Neuston,  8  (3) 

P,  gracilis,  neuston            2 

North  of  unit  6 
Isolated  Stn   229 

P.  gracilis,  5'    ■   5' 

10 


19 


34 


02°57'S.  During  the  EASTROPAC  survey  only 
P.  penicillatus  was  found  at  the  western-most 
stations  at  about  long.  126°W  near  the  equator, 
a  distance  of  about  2,000  nautical  miles.  These 
P.  penicillatus  larvae  might  conceivably  have 
drifted  eastward  from  the  oceanic  islands  of  the 
south  Pacific  where  the  adult  is  known  to  occur. 
But  no  other  species  common  to  the  mid-Pacific 
islands  has  ever  been  found  in  any  part  of  the 
eastern  tropical  Pacific  survey  areas  except  for 
the  two  specimens  of  Parribacus  sp.  mentioned 
previously.  Obviously  one  sees  here  the  working 
of  the  East  Pacific  Barrier  towards  maintaining 
a  specific  separation  of  west  American  and 
Indo-Pacific  lobster  faunas.  Panulirus 
penicillatus,  which  occurs  all  the  way  through 
the  Pacific  and  Indian  Oceans  to  the  Red  Sea,  is 
unique  among  lobsters  in  having  successfully 
overcome  this  barrier  to  become  established  on 
offshore  islands,  but  appears  to  have  found  ad- 
ditional barriers  that  prevent  establishment  on 
the  coast  of  the  mainland.  George  (1969)  inter- 
prets this  as  a  failure  to  compete  successfully 
with  the  east  Pacific  mainland  species  that 
have  evolved  there  by  natural  selection.  The 
absence  of  P.  penicillatus  in  the  coastal  envi- 


ronment may  result  largely  fiom  elimination  of 
the  larvae  by  an  admixture  of  inimical  coastal 
water  as  they  approach  the  coast.  This  supposi- 
tion is  suggested  by  the  fact  that  no  larvae  of 
this  species  have  thus  far  been  found  at  stations 
near  the  coast  despite  their  capability  of  wide 
dispersal  offshore. 

Other  Crustacea  with  relatively  shorter 
planktonic  lives  appear  also  to  have  migrated 
eastward  across  the  East  Pacific  Barrier  (Chace, 
1962;  Garth,  1966). 

The  countercurrents  within  the  Equatorial 
Current  System  provide  possible  routes  for  re- 
turn of  east  Pacific  species  that  have  either  for- 
tuitously or  through  instinctive  behavior  shifted 
into  countercurrents,  possibly  through  habits  of 
diurnal  migrations,  and  that  have  not  drifted 
westward  to  a  point  of  no  return  determined  by 
requirements  inherent  in  their  life  cycle. 

To  evaluate  how  effective  these  return  routes 
may  be  needs  further  study  based  on  plankton 
collections  designed  to  elucidate  the  vertical  dis- 
tribution of  the  larvae  and  the  diurnal  migrations 
that  they  undergo  in  relation  to  light,  etc.,  and  to 
the  depths  of  prevailing  countercurrents  in  rela- 
tion to  adjacent  currents.  In  this  connection  it  is 


644 


JOHNSON:  DISPERSAL  OF  LOBSTER  LARVAE 


useful  to  examine  the  results  of  certain  neuston 
and  1-m  net  tows,  especially  those  taken  during 
David  Starr  Jordan  cruise  65  where  28.5%  of  35 
neuston  tows  yielded  one  or  more  larvae,  and  two 
tows  contained  eight  and  nine  larvae  respectively. 
All  but  two  of  the  neuston  tows  that  were  positive 
for  larvae  were  taken  during  dusk  or  darkness. 
The  1-m  net  tows  taken  simultaneously  from  200 
to  0  m  yielded  no  larvae  in  either  the  nighttime  or 
daytime  tows.  This  discrepancy  is  rather  surpris- 
ing and  the  cause  is  not  clear.  But  it  may  indicate 
that  larvae  are  so  scarce  and  widely  dispersed 
vertically  at  depth  that  the  1-m  net  does  not  filter 
enough  water  to  be  effective  at  depth  and  its  pas- 
sage through  the  immediate  surface  layer  is  very 
brief,  whereas  the  neuston  net,  although  filtering 
less  water,  caught  larvae  because  of  their  active 
concentration  in  a  very  narrow  horizon  at  the  very 
surface  during  conditions  of  reduced  light.  Other 
observations  in  the  field  (Chittleborough  and 
Thomas,  1969)  and  in  laboratory  experiments 
(Ritz,  1972)  demonstrate  this  behavioral  response 
of  phyllosoma  leading  to  a  migration  into  surface 
layers  at  night. 

In  David  Starr  Jordan  cruises  57  and  60  the 
trawl  and  neuston  tows  show  that  larvae  do  get 
into  the  North  Equatorial  Countercurrent  (Fig- 
ures 1  and  2).  This  is  an  expected  correlation 
with  the  physical  studies  of  the  countercurrent 
which  indicate  that  some  variable  transverse 
circulation  does  occur  across  the  current  such 
that  water  is  drawn  in  at  the  surface  along  the 
southern  boundary  and  a  loss  occurs  across  the 
northern  boundary  (Wyrtki,  1967).  The 
Equatorial  Undercurrent  at  the  Equator,  is 
another  possible  route  for  return  to  the 
Galapagos  and  surrounding  area. 

Williams  (1972),  in  presenting  a  hypothetical 
model  of  an  eastward  passive  migration  of  skip- 
jack tuna  from  the  central  Pacific  spawning 
area  in  recruitment  of  the  fisheries  in  the  east- 
ern Pacific,  has  reviewed  hydrographic  details 
relative  especially  to  the  position,  speed,  and 
seasonal  interruptions  of  the  North  Equatorial 
Countercurrent.  The  seasonal  fluctuations  of 
this  current  could  aid  or  retard  the  passive 
migration  of  tuna  larvae  and  juveniles  from  the 
spawning  grounds  depending  upon  the  degree  of 
coordination  with  the  season  of  spawning.  Much 
of  this  transport  mechanism  might  apply  also  to 
the  return  of  the  long-lived  lobster  larvae.  But 
it  is  not  known  if  there  is  a  significant  season- 
ahty  in  the  release  of  the  larvae  in  the  adult 


habitat  that  might  fortuitously  correlate  with 
the  North  Equatorial  Countercurrent  and  thus 
enhance  the  likelihood  of  return  of  larvae  that 
have  drifted  to  the  west.  Data  from  EAS- 
TROPAC  suggest  a  very  long  breeding  season 
for  the  tropical  species  as  judged  by  the  persis- 
tent occurrence  of  early  larval  stages  (III-IV)  in 


I5°N 


10° A-  - 


s-s 


Till 

1 

1           1          1 

- 

<x 

V 

"       NORTH   EQUATORIAL 
CURRENT 

•— 

-f?g.\,im 

- 

<. 

•         • 

• 

_--- 

/°^.I,VIII,^       A* 

• 

TRANSITION 
ZONE 

_ 

> 

-'' 

_ 

•                -* 

EQUATORIAL 
_      COUNTERCURRENT 

• 
• 

- 

^ 

• 

— *•- 

'- 

*v 

V 

•^ 

-'S.a.\,X 

Pp.\,IK- 

-*  tl» 

jf—ep.l,IK;\,X 

- 

• 

^Parribacus  sp. 
I{56mm) 

- 

SOUTH  EQUATORIAL 

CURRENT 

~               ^ 

• 

< 

- 

^ 

•  • 
•    • 

^ 

• 

• 

• 

1           1          1          1 

1 

1            1           1 

125° 


IIS^W 


120° 

JORDAN  77 

Stations  with  available 
plankton  sannples: 

•    5'x5'  net 

A   midwater  trawl 

D  neuston  net 

Rp.  Panu/irus  penicillatus 

Pg.         "       gracilis 

So.  Scyllorides  astori 
number  of  ptiyllosomo 
larvae  taken  (Arabic  No.) 
stage  of  phyllosoma 
larvae  taken  (Romon  No.) 


Figure  4.— RV  David  Starr  Jordan  cruise  77  station  pattern  with 
number  and  stage  (Roman  numeral)  of  piiyllosoma  larvae  taken  at 
station  indicated.  Neuston  net  tow  is  shown  where  larva  was  taken. 


645 


FISHERY   BULLETIN:  VOL.  72.  NO.  3 


the  more  coastal  waters.  Larvae  that  have 
shifted  into  the  countercurrents  from  the  South 
Equatorial  Current  in  the  eastern  part  of  its 
course  may  well  be  returned  in  time  for 
metamorphosis  near  the  coast  or  at  offshore  is- 
lands. It  seems  probable,  however,  that  safe  re- 
turn from  the  area  of  the  more  westward  sta- 
tions surveyed  is  doubtful  in  view  of  the  great 
distance  covered  and  the  expected  attrition 
through  predation,  etc.  Assuming,  as  before, 
that  the  larvae  occurring  below  about  lat.  10°N 
near  long.  120°W,  originated  in  the  Galapagos 
Islands  area  and  allowing  an  average  of  20 
nautical  miles  per  day  westward  flow  of  the 
South  Equatorial  Current  it  would  require  3  mo 
sustained  drift  to  cover  the  1,800  nautical  miles 
involved.  If  shifted  promptly  at  this  point  into 
the  North  Equatorial  Countercurrent  with  an 
average  speed  of  15  nautical  miles  per  day 
another  4  mo  of  sustained  transport  would  be 
required  to  reach  an  adult  area  suitable  for 
metamorphosis.  It  should  be  noted,  however, 
that  only  larval  stages  VII  to  XI  (final  stage) 
were  taken  at  the  more  distant  stations  on  all 
skipjack  cruises  except  David  Starr  Jordan 
cruise  65,  the  one  nearest  to  the  Galapagos  Is- 
lands. This  would  indicate  that  even  the 
youngest  larvae  taken  near  long.  120°W  were 
probably  older  than  3  mo  and  the  likelihood  of 
much  additional  delay  in  returning  by  way  of 
countercurrents  militate  against  a  safe  return 
unless  metamorphosis  can  be  delayed  pending 
encountering  conditions  favorable  to  metamor- 
phosis and  assumption  of  the  benthic  habit.  Re- 
cruitment must  depend  mainly  on  larvae  that 
have  been  retained  relatively  near  the  coast  by 
coastwise  currents,  eddies,  and  backwashes. 

None  of  the  east  Pacific  larvae  taken  in  the 
far  offshore  areas  show  any  tendency  to  gigan- 
tism such  as  was  believed  to  occur  in  some 
Crustacea  when  settlement  has  been  postponed 
(Bruce,  1970). 

To  what  extent  metamorphosis  of  the  phyl- 
losoma  larvae  to  the  postlarval  stage  may  take 
place  in  the  far  offshore  waters  is  not  known. 
No  palinurid  postlarvae  were  found  in  any  of 
the  cruises.  However,  a  single  specimen  of  Scyl- 
larides  astori  postlarva  (known  as  a  nesto)  was 
taken  in  a  trawl  at  lat.  OriT'N,  long.  120°06'W 
during  Townsend  Cromwell  cruise  51  (Johnson, 
in  press). 

The  chances  of  the  larvae  continuing  to  float 
successfully   westward   all    the   way   to   the 


mid-Pacific  islands  is  unlikely  and  the  absence 
of  the  species,  except  for  P.  penicillatus ,  in  these 
islands  substantiates  this  supposition  and 
clearly  manifests  the  East  Pacific  Barrier  func- 
tioning against  westward  migration  of  the  east 
Pacific  species. 

ACKNOWLEDGMENTS 

The  plankton  collections  and  field  data  were 
kindly  supplied  to  me  by  the  coordinators  of  the 
Skipjack  Cruises,  involving  the  Institute  of 
Marine  Resources  at  Scripps  Institution  of 
Oceanography  (SIO)  and  the  National  Marine 
Fisheries  Service  (NMFS),  Southwest  Fisheries 
Center,  La  Jolla,  Calif.  The  laboratory  work 
was  supported  by  the  Marine  Life  Research 
Program,  the  SIO  part  of  the  California 
Cooperative  Oceanic  Fisheries  Investigation 
sponsored  by  the  Research  Committee  of  the 
State  of  California.  Thanks  are  extended  to 
Mizuki  Tsuchiya  of  SIO  for  discussions  pertain- 
ing to  the  hydrography  and  to  Mary  Farrel  of 
NMFS  for  aid  in  sorting  some  of  the  samples. 

LITERATURE  CITED 


Bruce,  A.  J. 

1970.  On  the  identity  of  Periclimenes  pusillus  Rathbun, 
1906.  (Decapoda,  Pontoniinae).  Crustaceana  19:306-310. 

Chace,  F.  a.,  Jr. 

1962.  The  non-brachyuran  decapod  crustaceans  of  Clip- 
perton  Island.  Proc.  U.S.  Natl.  Mus.  113:605-635. 
Chittleborough,  R.  G.,  and  L.  R.  Thomas. 

1969.  Larval  ecology  of  the  western  Australian  crajrfish, 
with  notes  upon  other  panulirid  larvae  from  the  east- 
ern Indian  Ocean.  Aust.  J.   Mar.  Freshwater  Res. 
20:199-223. 
Garth,  J.  S. 

1966.  On  the  oceanic  transport  of  crab  larval  stages.  In 
Proceedings  of  the  Symposium  on  Crustacea,  Part  1,  p. 
443-448.  Mar.  Biol.  Assoc.  India,  Symp.  Ser.  2. 
George,  R.  W. 

1969.  Natural  distribution  and  speciation  of  Marine  ani- 
mals. J.  R.  Soc.  West.  Aust.  52(2):33-40. 
Johnson,  M.  W. 

1960.  Production  and  distribution  of  larvae  of  the  spiny 
lobster,  Panulirus  interruptus  (Randall)  with  records 
on  P.  gracilis  Streets.  Bull.  Scripps  Inst.  Oceanogr., 
Univ.  Calif  7:413-461. 

1971.  The  palinurid  and  scyllarid  lobster  larvae  of  the 
tropical  eastern  Pacific  and  their  distribution  as  re- 
lated to  the  prevailing  hydrography.  Bull.  Scripps  Inst. 
Oceanogr.,  Univ.  Calif  19:1-36. 

In  press.   The  postlarvae  of  Scyllarides  astori   and 
Evibacus  princeps   of  the   Eastern  Tropical   Pacific 
(Crustacea,  Decapoda,  Scyllaridae).  Crustaceana. 


646 


JOHNSON:  DISPERSAL  OF  LOBSTER  LARVAE 

Lazarus,  B.  I. 

1967.  The  occurence  of  phyllosomata  off  the  Cape  with 
particular  reference  to  Jasus  lalandii.  S.  Afr.  Div.  Sea 
Fish.,  Invest.  Rep.  63,  38  p. 

RiTZ,  D.  A. 

1972.  Behavioral  response  to  light  of  the  newly  hatched 
phyllosoma  larvae  of  Panulirus  longipes  cygnus  George 
(Crustacea:  Decapoda:  Palinuridae).  J.  Exp.  Mar.  Biol. 
Ecol.  10:105-114. 

Robertson,  P.  B. 

1968.  The  complete  larval  development  of  the  sand  lobster, 
Scyllarus  americanus  (Smith),  (Decapoda,  Scyllaridae)  in 
the  laboratory,  with  notes  on  larvae  from  the  plankton. 
Bull.  Mar.  Sci.  18:294-342. 


Saisho,  T. 

1962.  Notes  on  the  early  development  of  a  scyllarid  lobster, 
Parribacus  antarcticus  (Lund).  Mem.  Fac.  Fish. 
Kogoshima  Univ.  11(2):174-178. 

Williams,  F. 

1971.  Current  skipjack  oceanography  cruises  in  eastern 
tropical  Pacific  Ocean.  Commer.  Fish.  Rev.  33(2):29-38. 

1972.  Consideration  of  three  proposed  models  of  the  migra- 
tion of  young  skipjack  tuna  (Katsuwonus  pelamis)  into  the 
eastern  Pacific  Ocean.  Fish.  Bull.,  U.S.  70:741-762. 

Wyrtki,  K. 

1967.  Circulation  and  water  masses  in  the  eastern  equator- 
ial Pacific  Ocean.  Int.  J.  Oceanol.  Limnol.  1:117-147. 


647 


REPRODUCTIVE  CYCLE  OF  THE  SOFT-SHELL  CLAM, 
MY  A  ARENARIA,  AT  SKAGIT  BAY,  WASHINGTON 


Russell  G.  Porte r^ 


ABSTRACT 

The  annual  reproductive  cycle  of  the  soft-shell  clam,  Mya  arenaria  L.,  was  studied  at  Skagit  Bay  in 
northern  Puget  Sound.  Wash.  Spawning  occurred  from  late  May  to  early  September  in  both  1971  and 
1972  with  peak  spawning  in  July  and  June  respectively.  Small  clams  (less  than  60  mm  in  length)  had  a 
spawning  peak  that  coincided  with  other  size  classes  although  the  spawning  period  was  shorter  in 
duration.  The  single  yearly  spawning  period  at  Skagit  Bay  corresponds  with  east  coast  populations  in 
Canada  and  Maine. 


The  soft^ shell  clam,  Mya  arenaria  L.,  is  found  on 
virtually  all  coastlines  in  the  northern  hemi- 
sphere (Hanks,  1963)  and  is  still  extending  its 
range  as  evidenced  by  its  recent  movement  into 
the  Black  Sea  (Zambriborshch,  Marchenko,  and 
Telegin,  1968;  Ivanov,  1969).  On  the  North 
American  continent,  it  is  native  to  the  east  coast 
from  which  it  reportedly  was  accidentally  intro- 
duced into  San  Francisco  Bay,  Calif.,  about  1874 
(Fitch,  1953).  However,  there  is  some  evidence 
from  Indian  middens  that  the  soft^shell  clam  is 
also  native  to  the  west  coast  (Craig,  1927).  Its 
range  on  the  west  coast  presently  extends  from 
California  to  Alaska  (Morris,  1966). 

The  reproductive  cycle  of  the  softr-shell  clam 
has  been  described  from  a  variety  of  locations  on 
the  east  coast,  but  no  data  have  been  presented 
for  west  coast  populations  except  for  one  brief 
note  from  Oregon  (Edmondson,  1920).  The  first 
detailed  study  on  the  histology  of  the  gonad  of 
Mya  arenaria  was  conducted  by  Coe  and  Turner 
(1938)  in  New  England.  They  found  that  spawn- 
ing occurred  in  the  summer.  At  Martha's  Vine- 
yard in  Massachusetts  spawning  was  found  to 
occur  over  a  6-mo  period  from  spring  through 
early  fall  (Deevey,  1948).  In  northern  Mas- 
sachusetts, spawning  occurs  in  late  summer  and 
early  fall  (Ropes  and  Stickney,  1965),  while  in 
New  Jersey,  spawning  takes  place  in  the  spring 
(Belding,  1930;  Nelson  and  Perkins,  1931).  Two 
spawnings  per  year  (spring  and  fall)  have  been 
reported  for  the  Chesapeake  Bay  in  Maryland 
(Pfitzenmeyer,  1962,  1965)  and  for  Narragansett 
Bay,  R.I.  (Landers,  1954).  Ropes  and  Stickney 


(1965)  have  tabulated  the  results  of  most  east 
coast  studies  for  easy  comparison. 

This  paper  describes  the  annual  reproductive 
cycle  for  a  soft^shell  clam  population  from  Puget 
Sound,  Wash.  Skagit  Bay  was  selected  as  the 
study  area  since  it  has  a  potential  for  commercial 
operations,  a  commercial  soft-shell  clam  fishery 
is  in  the  beginning  stages,  and  it  appears  to  be 
the  area  with  the  greatest  abundance  of 
soft-shell  clams  in  Puget  Sound. 

DESCRIPTION  OF  AREA 

Skagit  Bay,  Wash.,  is  located  in  northern  Puget 
Sound  60  miles  north  of  Seattle.  The  Skagit  River, 
which  has  an  average  discharge  of  16,560  ft^/s 
(U.S.  Department  of  Interior,  1971:190),^  empties 
into  the  end  of  the  bay  via  the  South  Fork  and  at 
the  northern  entrance  of  the  bay  via  the  North 
Fork.  The  northern  side  of  the  bay  is  made  up  of  a 
large  broad  mud  flat  approximately  13  square 
miles  in  area.  The  study  area  was  located  on  the 
mud  flat  off  Fir  Island  between  Hall  Slough  and 
Browns  Slough. 

The  mean  tide  range  at  Skagit  Bay  is  6.5  feet, 
and  the  diurnal  range  10  feet.  The  soft^shell  clam 
beds  are  located  at  a  tidal  level  of  approximately 
+  3.5  feet. 

Water  temperatures  and  salinities  in  the  vicini- 
ty of  Skagit  Bay  may  vary  widely  on  both  an 
annual  and  a  diurnal  basis  due  to  river  discharge 
and  tidal  effects.  During  1971,  surface  tempera- 
tures at  Strawberry  Point  varied  from  4.79°  to 
15.68°C,  while  salinities  ranged  from  2.54  to 
24.53/^0.  The  maximum  recorded  daily  variation 


'Washington  Cooperative  Fishery  Unit.  University  of  Washing- 
ton, Seattle.  WA  9819.S. 


Manuscript  accepted  December  197.'?. 
FISHERY  BULLETIN:  VOL.  72.  NO.  y.  1974 

648 


^Thirty-year  period — maximum  recorded  flow:  144,000  ff/s, 
minimum  recorded  flow:  2,740  ft^/s. 


PORTER:   REPRODUCTIVE  CYCLE  OF  MYA  ARENARIA 

in  surface  water  temperature  at  Strawberry  Point 
was  4°C. 

METHODS  AND  MATERIALS 

The  study  began  in  November  1970  and  was 
completed  in  November  1972.  Samples  were  col- 
lected once  a  month  from  November  thru  Feb- 
ruary and  twice  a  month  from  April  thru  October 
in  1971  and  March  thru  October  in  1972.  The 
bimonthly  samples  were  taken  at  2-wk  intervals: 
generally  during  the  first  and  third  weeks  of  the 
month.  No  sample  was  collected  in  January  1971 
because  river  flooding  prevented  access  to  the 
study  area.  Each  sample  consisted  of  50  clams 
which  was  separated  from  a  larger  random  sample 
to  represent  five  size  classes:  clams  less  than  60 
mm  in  length,  those  in  the  60-,  70-,  and  80-mm 
length  ranges,  and  those  larger  than  90  mm.  As 
far  as  possible  the  50  clams  selected  for  each  sam- 
ple were  equally  distributed  between  the  five  size 
classes.  The  samples  taken  during  the  first  3  mo  of 
the  study  consisted  of  only  10,  10,  and  15  clams 
respectively.  A  total  of  1,785  clams  were  collected 
which  ranged  from  22  to  105.5  mm  in  length.  Of 
this  total  2.6%  were  immature,  leaving  a  total  of 
1,739  mature  clams  that  were  utilized  in  the 
analysis  of  the  reproductive  cycle. 

The  samples  were  returned  to  the  laboratory 
where  they  were  measured  and  weighed  and  the 
gonadal  mass  removed  and  preserved  in 
Davidson's  acetic  acid  fixative  (Shaw  and  Battle, 
1957).  In  smaller  clams  the  entire  visceral  mass 
was  preserved  and  sectioned;  for  larger  clams  a 
cube  of  gonadal  tissue  was  removed  from  the 
mid-lateral  portion  of  the  visceral  mass.  Usually 
dissection  and  preservation  were  accomplished 
the  day  of  collection.  Clams  not  dissected  until  the 
following  day  were  held  in  a  refrigerated  saltwa- 
ter system  overnight. 

Slides  were  prepared  by  standard  histological 
techniques:  tissues  were  dehydrated  in  alcohol, 
cleared  in  xylene,  embedded  in  paraffin,  sectioned 
at  5-8  microns,  and  stained  with  Mayer's 
hematoxylin  and  alcoholic  eosin  (Galigher  and 
Kozloff,  1971). 

The  number  of  gonadal  stages  used  to  describe 
bivalve  reproductive  cycles  varies  widely.  Lam- 
mens  (1967)  distinguished  11  stages  and  meas- 
ured the  nuclear-cytoplasmic  ratio.  Previous  in- 
vestigations on  Mya  reproductive  biology  gener- 
ally have  recognized  five  phases  of  development 
(Shaw,  1962,  1965;  Ropes  and  Stickney,  1965); 
therefore  the  following  five  phases  were  used:  in- 


active, active,  ripe,  spawning,  and  spent.  These 
five  phases  were  distinguished  by  the  following 
characteristics. 

Males 

Inactive  (Figure  la) 

During  this  phase  the  alveoli  are  filled  with 
follicle  cells  which  contain  the  typical  male  type 
inclusions  as  described  by  Coe  and  Turner  ( 1938). 
Primary  spermatocytes  may  be  visible  along  the 
alveolar  wall,  but  are  not  abundant. 

Active  (Figure  Ib-d) 

This  phase  is  typified  by  the  proliferation  and 
maturing  of  the  spermatocytes.  In  staging  the 
slides,  an  early  active,  middle  active,  and  late 
active  stage  were  identified.  The  early  active  stage 
(Figure  lb)  is  characterized  by  the  proliferation  of 
primary  spermatocytes  at  the  basal  membrane  of 
the  alveoli  and  the  appearance  of  some  sper- 
matids. The  middle  active  stage  (Figure  Ic)  is 
characterized  by  the  disappearance  of  the  follicle 
cells  and  the  migration  of  spermatids  toward  the 
center  of  the  alveoli  where  they  begin  aligning  in 
radial  columns.  The  late  active  stage  (Figure  Id)  is 
characterized  by  the  greatly  increased  number  of 
radially  aligned  spermatids  and  the  formation  of  a 
central  lumen  in  the  alveoli. 

Ripe  (Figure  le) 

In  the  ripe  male  clam,  the  sperm  are  distinctly 
bunched  in  radial  columns  around  the  alveoli  with 
their  tails,  which  stain  pink  with  eosin,  projecting 
into  the  central  lumen. 

Spawning  (Figures  If  and  2a) 

When  spawning  commences  a  single  row  of  fol- 
licle cells  form  at  the  alveolar  membrane  (Figure 
If).  These  follicle  cells  contain  the  typical  inclu- 
sions of  the  male,  and  the  number  of  rows  in- 
creases as  spawning  proceeds  (Figure  2a). 

Spent  (Figure  2b) 

In  the  spent  clam  most  all  sperm  have  been 
discharged,  but  a  few  may  remain.  The  alveoli  are 
almost  completely  filled  with  follicle  cells. 

Females 

Inactive  (Figure  2c) 

In  the  inactive  phase  the  alveoli  are  filled  with 
follicle  cells  which  contain  the  distinctive  female 

649 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  1. — Gonadal  stages  of  the  soft-shell  clam,  Mya  arenaria,  at  Skagit  Bay,  Wash,  a)  Inactive  male  (160x),  22  Sept.  1972. 
Follicle  cells  with  inclusions  fill  the  alveoli,  b)  Early  active  male  ( 160  x ),  17  Feb.  1972.  Proliferation  of  the  primary  spermatocytes 
is  visible  along  the  basal  membrane  of  the  alveoli,  c)  Active  male  (250x),  30  Apr.  1971.  Spermatids  begin  aligning  in  radial 
columns  toward  the  central  lumen  of  the  alveoli.  A  few  sperm  balls  are  visible  near  the  periphery  of  the  alveolus,  d)  Late  active 
male  ( 250  X),  14  May  1971.  e)  Ripe  male  (250  x),  llJune  1971.  The  sperm  are  aligned  in  radial  columns,  their  tails  projecting  into 
the  central  lumen,  f)  Early  spawning  male  (250  x),  1  June  1972.  A  single  row  of  follicle  cells  containing  inclusions  forms  at  the 
basal  membrane  of  the  alveoli. 


650 


PORTER:  REPRODUCTIVE  CYCLE  OF  MYA  ARENARIA 


i;^). 


••  •. 


'*.->*■ 
.*•*-. 


f". 


^':'  W' .  -^..^ 


4 

* 


rx 


^  .^< 


[O 


tkt/ 


Figure  2. — Gonadal  stages  of  the  soft-shell  clam,  Mya  arenaria ,  at  Skagit  Bay,  Wash,  a)  Spawning  male  (100  x ),  6  Aug.  1971.  The 
follicle  cells  reappear  as  spawning  progresses,  b)  Spent  male  ( 100  x ),  8  Sept.  1972.  c)  Inactive  female  (100  x ),  12  Oct.  197 1 .  Follicle 
cells  containing  the  typical  female  inclusions  fill  the  alveoli,  d)  Early  active  female  (145  x ),  3  Mar.  1972.  The  primary  ovocytes 
begin  enlarging  forming  stalked  ovocytes,  e)  Active  female  (136x),  8  May  1972.  The  follicle  cells  and  their  inclusions  have 
disappeared,  f)  Late  active  female  (240  x),  14  June  1972.  The  nucleolus  and  amphinucleolus  of  the  ova  have  appeared,  but  most 
ova  are  still  attached  to  the  basal  membrane  of  the  alveoli. 


651 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


type  inclusions  (Coe  and  Turner,  1938).  A  few 
primary  ovocytes  are  visible  along  the  alveolar 
membrane. 

Active  (Figure  2d-f) 

As  in  the  male,  three  stages  were  identified  for 
this  phase:  early,  middle,  and  late  active.  The 
early  active  stage  (Figure  2d)  is  characterized  by 
the  proliferation  of  primary  ovocytes  and  their 
elongation  producing  stalks  which  protrude  to- 
ward the  center  of  the  alveolus  between  the  follicle 
cells.  In  the  middle  active  stage  (Figure  2e)  the 
follicle  cells  and  their  inclusions  have  disappeared 
leaving  a  central  lumen  in  each  alveolus.  An  in- 
creasing number  of  stalked  ovocytes  attached  to 
the  alveolar  wall  protrude  into  this  lumen.  In  the 
late  active  stage  ( Figure  2f)  the  ovocytes  are  begin- 
ning to  become  spherical  with  slender  stalks, 
and  in  many  the  nucleolus  and  amphinucleolus 
are  readily  visible. 

Ripe  (Figure  3a,  b) 

In  the  ripe  phase  a  majority  of  the  ova  are  free  of 
the  alveolar  wall  and  have  taken  on  spherical 
shape  (Figure  3a).  In  some  individuals  the  ova  are 
quite  abundant,  and  almost  all  will  be  free  of  the 
alveolar  wall  (Figure  3b). 

Spawning  (Figure  3c) 

The  spawning  phase  is  characterized  by  the 
emptying  of  the  alveoli  of  ripe  ova,  leaving  behind 
a  few  ovocytes  that  are  still  attached  to  the  alveo- 
lar wall. 

Spent  (Figure  3d) 

In  the  spent  clam  the  alveoli  are  empty,  and 
follicle  cells  begin  to  fill  in  the  alveoli  from  the 
basal  membrane  inward.  Inclusions  reappear 
with  the  follicle  cells,  and  some  of  the  primary 
ovocytes  are  visible. 

Iminature 

The  immature  gonad  (Figure  3e)  has  a  much 
smaller  number  of  alveoli  which  are  filled  with 
follicle  cells  devoid  of  any  inclusions. 

Each  clam  was  identified  as  to  sex  and  staged  in 
accordance  with  the  above  phases.  The  percentage 
of  clams  in  each  phase  was  then  calculated.  For 
the  purposes  of  analyzing  the  reproductive  cycle 
(Figure  4),  the  three  stages  of  the  active  phase: 
early,  middle,  and  late  were  combined  under  the 
single  term  active  phase.  In  addition,  mean 
monthly  percentages  were  utilized  in  analyzing 


the  reproductive  cycle  (Figure  4)  for  those  months 
during  which  two  samples  were  collected. 

In  the  presentation  of  results,  the  terms  1971 
and  1972  reproductive  cycle  refer  to  the  cycle 
whose  spawning  phase  occurred  during  that  re- 
spective calendar  year.  However,  the  reproductive 
cycle  as  a  whole  does  not  necessarily  coincide  with, 
nor  is  it  restricted  to,  a  particular  calendar  year. 
The  reproductive  cycle  was  assumed  to  begin  with 
the  active  phase  and  end  with  the  inactive  phase. 

RESULTS 

The  histological  examinations  revealed  a  single 
yearly  spawning  period  which  occurred  from  late 
May  to  early  September.  This  was  true  for  both 
sexes  and  for  both  the  1971  and  the  1972  reproduc- 
tive cycles  although  the  period  of  peak  spawning 
varied  slightly  (Figure  4).  The  sex  ratio  of  the 
1,739  clams  utihzed  in  the  analysis  of  the  repro- 
ductive cycle  was  48%  males  (837)  and  52% 
females  (902). 

1971  Reproductive  Cycle 

During  the  1971  reproductive  cycle  (Figure  4) 
clams  in  the  active  phase  were  encountered  from 
February  through  July  for  males  and  February 
through  June  for  females.  Active  clams  were  un- 
doubtedly first  present  in  January  although  no 
samples  were  collected  that  month.  Individuals  in 
the  early  active  stage  (Figures  lb  and  2d)  first 
appeared  in  February  for  both  sexes,  while  those 
in  the  middle  active  stage  (Figures  Ic  and  2e)  first 
appeared  in  March  and  the  late  active  stage  (Fig- 
ures Id  and  2f)  in  early  April. 

Ripe  clams  of  both  sexes  were  first  observed  in 
late  April.  Ripe  males  (35%)  were  most  abundant 
in  May  and  ripe  females  (47% )  in  June. 

Clams  in  a  spawning  condition  were  first  en- 
countered in  the  later  part  of  May,  peaked  in 
July,  and  were  last  observed  in  the  early  Septem- 
ber sample.  During  July  75%  of  the  males  and 
55%  of  the  females  were  in  a  spawning  condition. 

Spent  clams  were  present  from  July  to  October 
with  the  highest  percentage  occuring  in  August 
when  38%  of  the  males  and  65%  of  the  females 
were  in  this  phase. 

There  was  no  observed  difference  in  reproduc- 
tive cycle  with  size  class,  except  for  clams  under  60 
mm  in  length.  In  general  the  period  of  peak 
spawning  for  those  clams  was  the  same  as  other 
size  classes,  but  the  duration  of  the  spawning 
period  was  shorter.  It  began  about  1  mo  later  than 
other  size  classes  and  ended  a  month  earlier. 


652 


PORTER:  REPRODUCTIVE  CYCLE  OF  MYA  ARENARIA 


•-«v    *♦'*•■• 


■>■  -  ^Q  y  '.■'■•'■■I .'* .'  '.        ■••'■■■  . 


_  <5^ 


"\ 


«« •.».  • 


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t 


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.    %0* 


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Figure  3. — Gonadal  stages  of  the  soft-shell  clam,  Mya  arenaria ,  at  Skagit  Bay,  Wash,  a)  Ripe  female  (180x),  14  June  1972.  The 
ova  are  now  free  of  the  alveolar  wall  and  have  taken  on  a  spherical  shape,  b)  Ripe  female  ( 145  x ),  14  June  1972.  c)  Spawning  female 
(180x),  1  June  1972.  d)  Spent  female  (lOOx),  24  Aug.  1972.  The  ova  have  been  discharged,  and  follicle  cells  with  inclusions  are 
forming  along  the  basal  membrane  of  the  alveoli,  e)  Immature  clam  ( 160  x),  24  Aug.  1972.  Follicle  cells  devoid  of  inclusions,  but 
containing  the  small  black  follicular  nucleii,  fill  the  alveoli.  From  an  individual  38.4  mm  in  length,  f)  Hermaphrodite  (40  x )  in  a 
spawning  condition  (14  June  1972). 


653 


D 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

SPAWNING  LIU       SPENT 


MALE 


1-       60 

z 

uj 
O 

cc 

Ui 

a      40- 


H 


i:^ 


FEMALE 


I 


I 


i 


I 


NOV       DEC 
1970 


FEB       MAR       APR      MAY        JUN       JUL        AUG       SEP       OCT        NOV       DEC    I    JAN        FEB      MAR       APR       MAY        JUN       JUL        AUG        SEP        OCT       NOV 

1971  I  1972 


Figure  4. — Male  and  female  reproductive  cycles  of  the  soft-shell  clam,  Mya  arenaria,  during  1971  and  1972  from  Skagit  Bay,  Wash. 
The  length  of  each  shaded  area  represents  the  percentage  frequency  of  clams  in  each  reproductive  phase.  A  total  of  1,739  clams  (48% 
males  and  52%  females)  were  examined  during  the  2-yr  study.  y 


The  smallest  mature  male  clam  examined  dur- 
ing the  1971  reproductive  cycle  was  22.9  mm  in 
length,  and  the  smallest  female  31.0  mm.  Both 
were  taken  in  the  September  sample  and  were  in 
the  inactive  phase.  The  largest  immature  clam 
was  collected  in  late  May  and  was  45.2  mm  in 
length. 

1972  Reproductive  Cycle 

The  1972  reproductive  cycle  (Figure  4)  was 
similar  to  1971  with  the  exception  that  the  cycle  as 
a  whole  began  earlier  and  the  active  phase  was  of 
longer  duration.  Active  female  clams  first  ap- 
peared in  November  1971  and  active  males  in 
December  1971.  The  active  phase  lasted  until  May 
1972.  During  the  period  from  February  until  April 
the  majority  of  all  clams  sampled  of  both  sexes 
were  in  the  active  phase. 

Ripe  male  clams  first  appeared  in  April  and  ripe 
females  in  May.  Ripe  clams  of  both  sexes,  78%  of 
the  males  and  49%  of  the  females,  were  most 
abundant  in  May. 

Spawning  commenced  in  late  May  and  peaked 


in  June  for  both  males  (86%)  and  females  (65%) 
and  then  continued  at  a  diminished  rate  until 
September. 

Spent  clams  of  both  sexes  were  present  from 
June  through  October.  They  were  most  abundant 
in  September  when  45%  of  the  males  and  72%  of 
the  females  were  in  the  spent  phase. 

Inactive  male  clams  first  appeared  in  July 
(10%),  while  inactive  females  first  appeared  in 
September  (13%).  The  highest  percentage  of  inac- 
tive clams  occurred  in  October  with  79%  of  the 
males  and  70%  of  the  females  in  the  inactive 
phase. 

As  in  1971,  the  spawning  cycle  for  most  of  the 
clams  under  60  mm  in  length  commenced  about  1 
mo  later  than  the  normal  cycle  and  ended  1  mo 
earlier.  The  smallest  mature  clam  collected  was  a 
36.3-mm  spawning  male  obtained  in  July.  The 
smallest  mature  female  was  38.9  mm  in  length 
and  was  in  the  active  phase  in  March.  The  largest 
.immature  clam  was  51.5  mm  in  length  and  was 
collected  in  March. 

In  1971  spawning  was  quite  complete  in  both 


654 


PORTER:  REPRODUCTIVE  CYCLE  OF  MYA  ARENARIA 

sexes,  while  in  1972  many  of  the  females  failed  to 
spawn  completely  although  the  discharge  of  male 
sex  products  seemed  complete. 

DISCUSSION 

The  gonadal  inclusions  of  male  and  female 
soft-shell  clams  are  distinctive.  Coe  and  Turner 
( 1938)  state  that  the  origin  of  these  inclusions  is 
partly  from  cytoplasmic  activity  of  follicle  cells 
and  partly  from  cyto  lysis  of  gametes.  The  fact  that 
all  immature  clams  in  the  process  of  sexual  dif- 
ferentiation were  found  to  be  developing  inclu- 
sions characteristic  of  their  sex  seems  to  verify 
cytoplasmic  activity  of  the  follicle  cells  as  one 
origin  of  these  inclusions.  In  older  male  clams,  the 
method  of  formation  of  the  multinucleated  cells 
first  described  by  Coe  and  Turner  ( 1938)  as  pycno- 
tic  nucleii  and  later  by  Shaw  ( 1965)  as  sperm  balls, 
needs  further  study.  If  the  unspawned  sperm  are 
retained  by  the  male  clam  as  sperm  balls  as  re- 
ported by  Shaw  (1965)  and  as  my  observations 
indicate  (Figure  Ic),  then  perhaps  cytoplasmic  ac- 
tivity of  the  follicle  cells  is  the  major  method  by 
which  the  inclusions  are  formed.  In  female  clams 
the  exact  relationship  between  cytolysis  of  un- 
spawned ova  and  the  formation  of  inclusions  is  not 
known.  The  single  row  of  follicle  cells  which  form 
almost  immediately  at  the  basal  membrane  of  the 
alveoli  in  spent  female  clams  already  contain  a 
number  of  inclusions  (Figure  3d)  before  any  of  the 
unspent  ova  have  undergone  cytolysis.  The  origin 
and  function  of  gonadal  inclusions  in  both  sexes 
requires  further  investigation. 

The  gametogenic  cycle  of  the  soft-shell  clam  at 
Skagit  Bay  is  identical  to  that  reported  for  clams 
from  the  east  coast  (Coe  and  Turner,  1938;  Shaw, 
1962,  1965;  Pfitzenmeyer,  1965;  Ropes  and  Stick- 
ney,  1965).  The  single  spawning  cycle  per  year, 
from  late  May  to  early  September,  is  similar  to 
that  described  for  studies  in  eastern  Canada  (Staf- 
ford, 1912;  Battle,  1932;  Sullivan,  1948)  and  the 
New  England  area  (Welch,  1953  ;  Ropes  and 
Stickney,  1965). 

The  slight  variations  noted  between  the  spawn- 
ing cycles  of  1971  and  1972  and  the  incomplete 
spawning  of  females  in  1972  cannot  be  explained 
at  present. 

Few  hermaphroditic  Mya  are  reported  from 


^Welch,  W.  R.  1953.  Seasonal  abundance  of  bivalve  larvae  in 
Robinhood  Cove.  Maine.  Fourth  Annual  Conference  on  Clam 
Research,  U.S.  Fish  and  Wildlife  Service.  Clam  Investigations, 
Boothbay  Harbor,  Maine,  p.  4-6. 


other  areas  (Coe  and  Turner,  1938;  Shaw,  1965).  A 
single  hermaphroditic  specimen  was  collected  at 
Skagit  Bay  (Figure  3f). 

ACKNOWLEDGMENTS 

I  wish  to  extend  my  thanks  to  the  Washington 
Cooperative  Fishery  Unit  for  providing  transpor- 
tation and  equipment  for  the  study.  Also,  to 
Preston  E.  Porter  for  his  dutiful  help  with  field 
collections  and  to  the  Department  of  Ocean- 
ography, University  of  Washington  for  provid- 
ing environmental  data. 

LITERATURE  CITED 

Battle,  H.  I. 

1932.  Rhythmic  sexual  maturity  and  spawning  of  certain 
bivalve  moUusks.  Contrib.  Can.  Biol.  Fish.,  New  Ser. 
7:255-276. 
Belding,  D.  L. 

1930.  The  soft-shelled  clam  fishery  of  Massachusetts.  Mass. 
Dep.  Conserv.,  Div.  Fish  Game,  Mar.  Fish.  Serv.  1,  65  p. 

Coe,  W.  R.,  and  H.  J.  Turner. 

1938.   Development  of  the  gonads  and  gametes  in  the  soft- 
shell  clam  (Mya  arenaria).  J.  Morphol.  62:91-111. 
Craig,  E.  L. 

1927.  Some  mollusks  and  other  invertebrates  from  the 
northwest.  Univ.  Colo.  Stud.  16(l):63-74. 
Deevey,  C.  B. 

1948.  The  zooplankton  of  Tisburry  Great  Pond.  Bull.  Bing- 
ham Oceanogr.  Collect.  Yale  Univ.  12(1):  1-44. 
Edmondson,  C.  H. 

1920.  Edible  mollusca  of  the  Oregon  coast.  Occas.  Pap. 
Bernice  Pauahi  Bishop  Mus.  7(9):77-201. 
Fitch,  J.  E. 

1953.  Common  marine  bivalves  of  California.  Calif.  Dep. 
Fish  Game,  Fish  Bull.  90,  102  p. 

Galigher,  a.  E.,  and  E.  N.  Kozloff. 

1971.  Essentials  of  practical  microtechnique.  2d  ed.  Lea 
and  Febiger,  Phila.,  531  p. 
Hanks,  R.  W. 

1963.  The  sofl-shell  clam.  U.S.  Fish  Wildl.  Serv.,  Circ.  162, 
16  p. 
Ivanov,  a.  I. 

1969.  Immigration  of  Mya  arenaria  L.  to  the  Black  Sea,  its 
distribution  and  quantity.   [In  Russ.,  Engl,  summ.] 
Okeanologiya  9:341-347. 
Lammens,  J.  J. 

1967.  Growth  and  reproduction  in  a  tidal  flat  population  of 
Macoma  balthica  (L.)  Neth.  J.  Sea  Res.  3:315-382. 
Landers,  W.  S. 

1954.  Seasonal  abundance  of  clam  larvae  in  Rhode  Island 
waters,  1950-1952.  U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep. 
Fish.  117,  29  p. 

Morris,  P.  A. 

1966.  A  field  guide  to  shells  of  the  Pacific  coast  and  Hawaii 
including  shells  of  the  Gulf  of  California.  2d 
ed.  Houghton  Mifflin  Co.,  Boston,  297  p. 

Nelson,  T.  C,  and  E.  B.  Perkins. 

1931.  Annual  report  of  the  department  of  biology  July  1, 


655 


1929  -  June  30,   1930.   N.J.  Agric.  Exp.  Stn.  Bull. 

522:1-47. 
Pfitzenmeyer,  H.  T. 

1962.  Periods  of  spawning  and  setting  of  the  soft-shelled 

clam,  Myaarenaria,  at  Solomons,  Maryland.  Chesapeake 

Sci.  3:114-120. 
1965.  Annual  cycle  of  gametongenesis  of  the  soft-shell 

clam,  M.va  arenaria,  at  Solomons,  Maryland.  Chesapeake 

Sci.  6:52-59. 
Ropes,  J.  W.,  and  A.  P.  Stickney. 

1965.   Reproductive   cycle   of  Mya   arenaria   in   New 

England.  Biol.  Bull.  (Woods  Hole)  128:315-327. 
Shaw,  W.  N. 

1962.  Seasonal  gonadal  changes  in  female  soft-shell  clams, 

Mya  arenaria,  in  the  Tred  Avon  River,  Maryland.   Proc. 

Natl.  Shellfish.  Assoc.  53:121-132. 
1965.  Seasonal  gonadal  cycle  of  the  male  soft-shell  clam, 

Mya  arenaria,  in  Maryland.  U.S.  Fish.  Wildl.  Serv.,  Spec. 

Sci.  Rep.  Fish.  508,  5  p. 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

Shaw,  B.  L.,  and  H.  I.  Battle. 

1957.  The  gross  and  microscopic  anatomy  of  the  digestive 
tract  of  the  oyster  Crassostrea  virginica  (Gmelin).  Can.  J. 
1  ■s'''Zoora6:325-347. 
Stafford,  J. 

1912.  On  the  recognition  of  bivalve  larvae  in  plankton 
collections.  Contrib.  Can.  Biol.  Fish.  1906-1910:221-242. 
Sullivan,  C.  M. 

1948.  Bivalve  larvae  of  Malpeque  Bay,  P.E.I.  Fish.  Res. 
Board  Can.,  Bull.  77,  36  p. 
U.S.  Department  of  the  Interior. 

1971.  Water  resources  data  for  Washington,  1970.  Part  1. 
Surface  water  records.  U.S.  Dep.  Inter.,  Geol.  Surv., 
448  p. 

Zambriborshch,  F.  S.,  A.  S.  Marchenko,  and  O.  N.  Telegin. 

1968.   New  findings  and  distribution  of  Afya  arenaria  L.  in 

the  northwest  part  of  the  Black  Sea.  [In  Russ.]  Gidrobiol. 

Zh.  4(6):48-51.  Engl,  abstr.  in  Biol.  Abstr.  50:8638,  Abstr. 

89709. 


656 


IN  SITU  EXPERIMENTS  WITH  COASTAL  PELAGIC  FISHES 
TO  ESTABLISH  DESIGN  CRITERIA  FOR  ELECTRICAL  FISH 

HARVESTING  SYSTEMS^ 

WiLBER  R.  Seidel^  and  Edward  F.  Klima^ 

ABSTRACT 

In  situ  experiments  to  test  the  efficacy  of  a  scale  electrical  harvesting  system  were  conducted  off 
Panama  City,  Fla.  with  both  captured  and  wild  coastal  pelagic  fishes.  Six  species  of  fish  were 
exposed  to  preselected  combinations  of  pulse  rate,  pulse  width,  and  voltage  by  either  attracting 
wild  fish  or  placing  captured  fish  between  electrodes.  Both  captured  and  wild  fish  could  be 
effectively  controlled  with  a  minimum  field  strength  of  15  V/m,  20  to  35  pulses/s,  and  a  pulse  width 
of  more  than  0.5  ms.  Voltage,  pulse  width,  and  pulse  rate  were  equally  important  for  controlling  the 
species  tested.  Based  on  these  results,  resistance  measurements  were  calculated  and  a  potential 
netless  harvesting  system  specified  which  would  require  a  minimum  energy  output  of  120  kVA 
dissipated  into  an  electrode  configuration  10  x  5  x  5  m  with  a  load  resistance  of  0.01558  ohms. 
The  basic  design  specifications  for  a  prototype  pulse  generator  are  provided  for  netless  fish 
harvesting  applications  and  mid- water  trawling. 


Commercial  fishing  for  the  small,  fast-swimming 
fish  schools  characterizing  much  of  the  pelagic 
fishery  resource  in  the  Gulf  of  Mexico  has  been 
hampered  due  to  a  lack  in  harvesting  technology 
(Bulhs  and  Thompson,  1970).  The  Southeast 
Fisheries  Center,  Pascagoula  Laboratory,  Na- 
tional Marine  Fisheries  Service  has  been  engaged 
in  the  design  and  development  of  an  electrical 
harvesting  system  capable  of  economically  exploit- 
ing this  resource.  Results  from  laboratory  experi- 
ments (Klima,  1972)  provided  design  criteria  for 
a  12-kVA  (kilovolt  ampere)  pulse  generator  which 
was  used  to  field  test  and  validate  the  electrical 
control  parameters  and  to  provide  design  criteria 
for  a  pulse  generator  capable  of  commercially 
harvesting  marine  fishes  from  the  Gulf  of  Mexico. 
This  paper  describes  the  results  of  the  electrical 
in  situ  experiments  using  captured  and  wild  fish. 
Fishing  with  electricity  was  first  used  in  fresh 
water  during  the  latter  part  of  the  19th  century  by 
Ishan  Baggs,  who  was  granted  a  British  patent  in 
1863.  Electrical  fishing  remained  in  obscurity 
until  after  World  War  I,  when  McMillan  (1928) 


'Contribution  No.  249,  Southeast  Fisheries  Center,  Pas- 
cagoula Laboratory,  National  Marine  Fisheries  Service. 

^Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  P.O.  Drawer  1207,  Pascagoula,  MS  39567. 

^Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Pascagoula;  present  address:  Plans  and  Policy 
Development  Staff,  National  Marine  Fisheries  Service,  NOAA, 
Washington,  DC  20235. 


began  to  use  electricity  to  systematically  guide 
and  lead  fish.  The  use  of  electrical  fishing  in  the 
sea  has  lagged  considerably  behind  that  in  fresh 
water  because  of  the  high  conductivity  of  salt 
water,  which  results  in  extremely  low  load 
resistance  and  therefore  very  high  current  and 
power  requirements  for  generation  of  significant 
field  strengths.  Kreutzer  (1964)  showed  pulsed 
direct  current  could  be  utilized  economically  to 
harvest  fish  in  the  sea  provided  that  the  field 
voltage  gradient  and  shape,  duration,  and  rate  of 
impulses  are  suitable.  Electrical  stimulation 
produces  either  fright,  taxis,  tetanus,  or  even- 
tually death,  depending  upon  the  electrical  field 
pulse  characteristics  (Viber,  1967;  Halsband, 
1967;  Lamarque,  1967). 

The  reaction  to  various  combinations  of  char- 
acteristics varies  with  species,  fish  size,  and 
probably  other  factors  (Riedel,  1952;  Collins, 
Volz,  and  Trefethen,  1954;  Bary,  1956;  Higman, 
1956;  Monan  and  Engstrom,  1963;  Kessler,  1965; 
Halsband,  1967;  Klima,  1968);  hence,  a  combina- 
tion of  electrical  factors  which  will  induce 
electrotaxis  in  one  species  may  induce  a  fright 
response  or  no  response  in  another.  As  a  result, 
it  is  critical  to  know  the  combination  of  electrical 
field  characteristics  which  will  produce  the  de- 
sired reaction  for  each  species  of  interest. 

Success  of  electrical  fishing  equipment  depends 
upon  use  of  optimum  electrical  combinations  for 


Manuscript  accepted  November  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


657 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


inducing  fright,  taxis,  or  even  tetanus.  These 
various  responses  have  successfully  been  used  to 
commercially  harvest  marine  animals.  The  prin- 
cipal applications  include  an  electrical  fish  pump 
for  hardening  menhaden  in  a  purse  seine 
(Kreutzer,  1964),  an  electrical  fish  trawl  (McRae 
and  French,  1965),  and  an  electrical  shrimp  trawl 
(Klima,  1968;  Seidel,  1969). 

MATERIALS  AND  METHODS 

Test  Procedure 

Field  experiments  were  performed  in  the  near- 
shore  waters  off  Panama  City,  Fla.  The  test 
equipment  used  in  evaluating  fish  response  to  an 
electrical  field  consisted  of  a  deck-mounted  pulse 
generator  and  an  electrode  array  deployed  in  the 
water  alongside  the  vessel.  Salinity  and  tempera- 
ture ranged  from  29.5  to  33.8%oand  28.0° 
to  29.6°C,  respectively. 

Two  separate  groups  of  experimental  animals 
were  used  in  the  experiments  and  are  referred  to 
as  captured  fish  and  wild  fish,  respectively.  The 
first  group  consisted  of  393  Spanish  sardines, 
Sardinella  anchovia  Valenciennes;  397  round 
scad,  Decapterus  punctatus  (Agassiz);  390  scaled 
sardines,  Harengula  pensacolae  Goode  and  Bean; 
228  Atlantic  thread  herring,  Opisthonema  og- 
linum  (Lesueur);  and  37  Atlantic  bumper,  Chloro- 
scombrus  chrysurus  (Linneaeus).  They  were 
attracted  by  lights  at  night  and  caught  with  a 
5-m  lift  net  in  the  northern  Gulf  of  Mexico  and 
held  in  a  tank  of  circulated  seawater.  Prior  to 
testing,  each  fish  was  inspected  for  damage,  and 
only  fish  in  good  condition  were  used.  Each  fish 
was  exposed  to  a  preselected  combination  of  pulse 
rates,  voltage,  and  pulse  widths  by  carefully 
dropping  them  into  the  electrical  field  facing 
toward  and  within  1  m  of  the  negative  electrode. 

The  second  group  (wild  fish)  was  not  handled  by 
the  investigators  but  rather  was  attracted  by 
lights  at  night  to  an  area  between  the  electrodes 
positioned  next  to  the  boat.  When  five  or  more  fish 
were  between  the  electrodes,  they  were  exposed  to 
preselected  combinations  of  pulse  rates,  pulse 
widths,  and  voltage.  Visual  observations  were 
used  to  estimate  species  composition,  approximate 
size,  and  responses. 

To  evaluate  the  in  situ  effectiveness  of  the  pulse 
characteristics  tested,  we  measured  the  percent  of 
fish  which  escaped  from  the  electrical  field  and  the 


percent  which  swam  the  length  of  the  field  to  the 
positive  electrode.  The  captured  fish  were  intro- 
duced into  the  field 'in  such  a  way  that  they 
were  forced  to  turn  180°  in  order  to  swim  to  the 
anode,  whereas  the  wild  fish  schools  were  ran- 
domly oriented.  Fish  not  electrically  stimulated 
when  placed  between  the  electrodes  exhibited 
immediate  escape  movement  toward  the  cathode, 
the  side,  or  down,  but  usually  did  not  escape 
by  swimming  toward  the  anode  since  they  were 
dropped  into  the  electrode  array  facing  the 
cathode.  Test  fish  would  occasionally  mill  between 
the  electrodes  for  several  seconds  before  slowly 
moving  away  and  to  the  side.  Wild  fish  not 
electrically  stimulated  would  mill  between  the 
electrodes.  Consequently,  the  reactions  of  the 
electrically  stimulated  fish  were  evaluated  in 
terms  of  electrotaxis  or  a  positive  response  by 
their  directed  behavior  to  the  anode.  We  con- 
sidered swimming  to  the  anode  a  positive  response. 
All  other  responses  were  designated  negative. 

Description  of  Test  Equipment 

The  pulse  generator  providing  electrical  energy 
to  the  electrode  array  had  an  output  capability 
of  12  kVA  at  a  pulse  rate  of  50  pulses/s  with  a 
peak  output  voltage  of  approximately  150  V  at  a 
pulse  width  of  0.8  ms  (millisecond).  The  pulse 
rate  could  be  varied  from  4  to  55  pulses/s,  and 
three  different  output  widths  were  available  with 
the  unit;  0.3,  0.5,  and  0.8  ms  measured  at  the 
10%  power  points.  Pulse  rise  time  was  around 
0.05  ms  with  a  sloped  decay.  The  pulse  generator 
output  was  designed  to  operate  into  load  resistance 
of  either  0.05  or  0.2  ohm,  since  the  operational 
array  resistance  could  not  be  predicted  for  all 
variations  in  field  conditions.  At  these  loads,  the 
output  pulse  was  relatively  smooth  and  undis- 
torted,  exhibiting  only  slight  imperfections  in  the 
decay  portion  of  the  waveform.  The  waveform  was 
distorted  with  other  array  resistances  (Figure  1). 

In  Figure  ID,  both  the  output  pulse  and  the 
recharging  compensating  pulse  are  shown. ^  The 
compensating  pulse  is  an  important  feature  of 
the  pulse  generator  and  is  designed  to  significantly 
reduce  both  electrode  electrolysis  and  electrolysis 
of  any  incidental  metal  within  the  electrical  field, 
such  as  a  ship's  hull.  Essentially,  the  same 


^Kreutzer,  Patent  No.  3,363,353;  16  January  1968. 


658 


SEIDEL  and  KLIMA:  CRITERIA  FOR  ELECTRICAL  HARVESTING 


« 
• 

f\ 

r                • 

k  A  •  A-4-4  •  ■  A  •  a 

' 

•                      4 

i 

4             • 

^  w  ^  ^r^^    ^   T    w    »   1 

4m, 

•             .*.,*— Ml 

1 

N^ 

^«»----*                           *             «          "T^^^^SfeMBBBH^^ 

c 

*                                           1 

'                                           1 

Figure  1. — Pulse  generator  output  pulse  matched  into  the  load  resistance  A  -  low,  B  - 

compensating  pulse  are  shown  in  D. 


high,  C  -  correctly;  the  output  pulse  and 


amount  of  electrical  energy  is  contained  within 
the  envelope  of  the  compensating  pulse  as  is 
within  the  main  pulse  except  the  compensating 
pulse  is  of  an  opposite  polarity.  The  compensating 
pulse  has  no  effect  on  fish  reaction,  since  its 
amplitude  is  many  times  less  than  the  main  pulse 
and  is  below  the  threshold  level  of  the  fish. 

The  electrode  array  and  pulse  generator  were 
designed  to  effectively  energize  a  minimum 
volume  of  water  at  least  2  m  in  cross  section 
and  4  m  long,  and  provide  a  selection  of  minimum 
electrical  field  concentration  from  15  to  30  V/m. 
Each  electrode  of  the  array  consisted  of  a  copper 
tube  frame  with  copper  strips  arranged  in  a  grid 
pattern.  The  strips  of  copper  were  15.2  cm  wide 
(6  inches)  with  square  grid  openings  of  45.7  cm 
(18  inches)  between  strips.  It  has  been  experi- 
mentally demonstrated  that  the  surface  of  an 
electrode  can  be  reduced  to  approximately  10% 
of  the  total  area  and  the  surface  will  function 


electrically  as  if  it  were  a  solid  plate  (C.  Kreutzer,'* 
pers.  commun.).  Our  electrode  design  reduced  the 
conducting  surface  of  the  electrode  to  approxi- 
mately 53%  of  the  total  area.  Therefore,  this  grid 
technique  was  utilized  to  allow  the  fish  to  be  led 
to  and  pass  through  the  anode  for  easier  evalua- 
tion of  their  response.  The  cable  connecting  the 
electrode  array  to  the  pulse  generator  was  a  12-m 
length  of  1/0  coaxial  conducting  cable  and  repre- 
sented a  total  resistance  of  approximately  0.01 
ohm,  or  a  total  power  loss  of  20%  in  an  overall 
array  resistance  of  0.05  ohm.  Coaxial  cable  was 
utilized  to  eliminate  pulse  distortion  and  losses 
caused  by  inductance  in  parallel  conductors. 

Field  strengths  listed  in  volts  per  meter  are 
averages  based  on  measured  electrode-to-elec- 
trode values  and  separation  distance  between 
electrodes  rather  than  an  in  situ  field  strength 


"Smith  Research  and  Development  Company,  Lewes,  Del. 


659 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


measurement,  because  the  density  of  an  electrical 
field  in  seawater  is  not  uniform.  For  ease  of 
measurement,  the  electrode-to-electrode  voltage 
was  measured  at  the  output  of  the  pulse  generator 
and  did  not  take  into  account  cable  and  connection 
losses.  Also,  due  to  the  hookup  restriction  in  the 
research  vessel's  instrumentation  room,  short 
lengths  of  parallel  conductors  were  utilized, 
resulting  in  a  409^  total  cable  loss.  Therefore  the 
true  electrode-to-electrode  voltages  and  average 
field  strengths  are  related  to  measured  values  as 
follows: 

A.  150  V  =  90  V  electrode  to  electrode  =  22.5 

V/m. 

B.  120  V  =  72  V  electrode  to  electrode  =  18.0 

V/m. 

C.  90  V  =  54  V  electrode  to  electrode  =  13.5 

V/m. 

D.  60  V  =  36  V  electrode  to  electrode  =    9.0 

V/m. 
The  configuration  of  the  electrical  field  at  a  pulse 
generator  output  of  120  V  along  with  actual 
measured  field  strengths  (expressed  as  voltage 
drops  measured  across  10  cm)  at  various  posi- 
tions within  the  field  are  shown  in  Figure  2A. 
The  measurements  are  fairly  close  in  value  but 


not  exact.  The  pickup  probe  was  attached  to  a  long 
pole  and  the  measurements  taken  from  the  side  of 
the  RV  George  M.  Bowers.  Because  of  water 
current  and  boat  movement,  it  was  difficult  to 
hold  the  probe  parallel  to  the  electric  field  in 
exactly  each  position  shown. 

Laboratory  tests  indicated  a  field  strength  of 
about  15  V/m  was  required  to  properly  produce 
electrotaxis  in  fish  10  cm  long.  Field  strengths 
throughout  the  volume  of  water  within  the 
electrode  envelope  could  be  maintained  equal  to  or 
greater  than  the  15  V/m  requirement. 

Based  on  initial  field  tests,  the  general  zones  of 
fish  response  produced  by  the  electrode  array  are 
1)  effective  control,  2)  possible  control,  depending 
on  fish  size  and  its  orientation,  and  3)  fright  zone 
(Figure  2B).  The  zone  of  control  also  extends  to 
the  back  side  of  the  positive  electrode. 

RESULTS 
Captured  Fish 

Voltage,  pulse  width,  and  rate  are  equally  im- 
portant for  controlling  the  species  tested  (Figures 
3-5,  Table  1).  Comparison  between  the  pulse 
widths  indicates  that  a  higher  percentage  of 
experimental  animals  were  controlled  at  the 
wider  pulse  widths  (0.8  ms).  The  lower  and  inter- 
mediate stimulation  voltages  (60  and  90  V)  were 
not  as  effective  in  controlling  the  animals  as  the 
higher  voltage  (120  V).  Furthermore,  the  com- 
bination of  0.8  ms  pulse  width  with  120  V  appeared 
to  be  adequate  for  inducing  electrotaxis  at  the 
widest  range  of  pulse  rates  (20  to  35/s). 

The  ideal  pulse  rates  for  inducing  electrotaxis 
varied  for  each  species.  Spanish  sardines  and 
scaled  sardines  were  under  good  control  at  20 
to  35  pulses/s  and  round  scad  at  25  to  35 


PUISE      WIDTH      MS 


B  FRIGHT   ZONE 

...f  ;^»ii  CON  I  «oi  ioi,, 


Figure  2. — A.  Field  strength  configuration  at  72  V  electrode 
to  electrode.  B.  General  zones  of  fish  response. 


Figure  3. — Percent  positive  response  of  scaled  sardines  to 
various  combinations  of  voltage,  pulse  rate,  and  pulse  width. 


660 


SEIDEL  and   KLIMA:  CRITERIA  FOR  ELECTRICAL  HARVESTING 


Figure  4. — Percent  positive  response  of  Spanish  sardines  to 
various  combinations  of  voltage,  pulse  rate,  and  pulse  width. 


PUISE        WIDTH       MS 


IS  3S  3S 


S  3S  35 


PUISE       RATE 


Figure  5. — Percent  positive  response  of  round  scad  to  various 
combinations  of  voltage,  pulse  rate,  and  pulse  width. 

Table  1. ^Percent  of  thread  herring  and  bumpers  at  various 
stimulation  parameters.  Each  observation  consisted  of  15 
individuals  except  where  noted. 


Pulse 

rate 

Voltage  and 
pulse  width 

Thread  he 

rring 

Bumper 

15 

25 

35 

25 

60  V:  0.5  ms 

56 

53 

'50 

90  V: 

0.3  ms 

20 

67 

0.5  ms 

261 

63 

80 

0.8  ms 

100 

85 

120  V: 

0.3  ms 

27 

47 

0.8  ms 

41 

67 

75 

150  V;  0.3  ms 

33 

53 

73 

'7  individuals. 
^31  individuals. 


pulses/s.  Based  on  the  limited  data  for  thread 
herring  and  bumper,  the  best  pulse  rates  were 
25  to  35  pulses/s. 

A  factorial  analysis  was  used  to  determine  the 
most  effective  combination  of  pulse  rate,  width, 
and  voltage  for  controlling  Spanish  sardines, 
scaled  sardines,  and  round  scad  (Table  2).  This 
analysis  demonstrates  that  selection  of  the  proper 
level  of  voltage,  pulse  width,  and  pulse  rate  are 
clearly  important  for  controlling  these  species. 


Another  important  aspect  may  be  the  interactions 
between  the  three  main  effects,  although  the 
meaning  behind  this  significance  is  uncertain.  It 
can  be  seen  from  Table  2  that  these  interactions 
vary  between  species.  Interdependence  was 
observed  for  all  tested  electrical  combinations  in 
scaled  sardines  and  Spanish  sardines.  Surpris- 
ingly, this  was  not  observed  for  the  round  scad. 
Voltage  and  pulse  rate  interact  for  scaled  sardines 
and  round  scad. 

General  observations  for  the  first  (captured) 
group  of  fish  indicated  if  the  electrical  combina- 
tion was  not  adequate,  these  fish  would  immedi- 
ately escape  to  the  side  or  towards  the  cathode. 
However,  at  times  when  the  pulse  width  was  0.3 
ms,  thread  herring  would  elicit  a  jump  and  skip  on 
the  surface  of  the  water  and  dart  out  of  the  field. 
This  escape  behavior  was  never  observed  at  the 
wider  pulse  widths.  Controlled  fish  would  swim  to 
the  anode  and  circle  between  the  plates  of  the 
electrode  from  the  inside  of  the  field  to  the  back 
of  the  field  and  back  again  in  a  circular  swimming 
motion,  and  were  held  until  the  power  was  turned 
off. 

The  most  effective  electrical  combinations  for 
each  species  are  listed  in  Table  3.  We  felt  that 
if  70%  or  more  of  the  experimental  group  re- 
sponded positively,  the  combination  was  effective. 
Output  voltages  of  60  V  or  less  were  ineffective 
for  controlling  fish  regardless  of  the  pulse  rate  or 
pulse  width.  Effective  fish  control  required  an 
output  voltage  of  at  least  90  V  with  a  pulse  rate 
of  25  or  more,  and  except  for  bumper  the  pulse 
width  had  to  be  0.8  ms.  An  overall  effective 
electrical  combination  was  120  V  at  25  to  35 
pulses/s  at  0.5  to  0.8  ms,  and  90  V  at  25  to  35 
pulses/s  at  0.8  ms. 

Wild  Fish 

The  second  group  of  fish  was  attracted  into 
the  electrode  configuration  by  a  surface  night- 
light  positioned  above  the  electrodes  and  then 
stimulated.  Usually  we  were  successful  in  attract- 
ing sufficient  quantities  offish  to  evaluate  a  spe- 
cific combination  of  electrical  parameters.  How- 
ever, their  exact  position  between  the  electrodes 
was  never  the  same,  especially  when  a  large  school 
of  30  to  50  fish  were  positioned  between  the  elec- 
trodes. We  only  used  electrical  field  characteris- 
tics which  appeared  to  be  successful  during  our 
daytime  experiments  with  individual  captured 


661 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


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Table  3. — Effective  electrical  combinations  based  on  a  mini- 
mum of  70%  eliciting  a  positive  response  (Group  1  fish). 


Pulse 

Pulse 

Species 

Volts 

rates 

width 

Spanish  sardine 

90 

25-35 

0.8 

120 

20-35 

0.8 

Round  scad 

90 

25-35 

0.8 

120 

25 

0.5 

120 

25-35 

0.8 

Scaled  sardine 

90 

25-35 

0.8 

120 

25 

0.5 

120 

20-35 

0.8 

Thread  herring 

90 

25-35 

0.8 

Bumper 

90 

25 

0.5 

120 

25 

0.5 

fish.  The  wild  fish  were  only  exposed  to  a  pulse 
width  of  0.5  ms,  as  the  time  between  tests  did 
not  permit  a  change  in  pulse  width.  Since  this 
pulse  width  provided  satisfactory  results,  we  felt 
that  either  0.5  or  0.8  ms  would  be  satisfactory, 
as  indicated  from  our  captured  fish  experiments. 
Visual  observations  indicated  that  the  larger 
fish  (>10  cm)  reacted  more  quickly  and  swam  to 
and  from  the  anode  before  the  smaller  fish 
(<10  cm)  did.  Table  4  provides  details  and  sum- 
maries of  our  nighttime  observations  with  wild 
fish.  In  general,  Spanish  sardines  and  round  scad 
were  controlled  adequately  at  120  V  and  a  pulse 
rate  of  25  to  35  pulses/s  at  a  pulse  width  of 
0.5  ms.  When  large  schools  were  attracted 
between  the  electrodes,  it  was  not  always  pos- 
sible to  control  all  of  the  animals.  Our  visual 
observations  indicated  that  fish  in  the  fringe  area 
would  escape  since  the  voltage  gradient  was  insuf- 
ficient to  control  fish  in  the  fringe  areas.  The 
number  offish  escaping  probably  varied  with  their 
position  in  the  electrical  field  and  their  size, 
since  smaller  fish  require  higher  voltage  gradi- 
ents for  control  than  large  fish.  At  35  pulses/s 
and  120  V,  we  were  able  to  pull  or  force  fish  into 
the  electrode  array  from  the  back  side  of  the  posi- 
tive electrode.  Positive  reactions  were  elicited  in 
all  species  at  the  prime  voltage  of  120  and  pulse 
rates  between  25  and  35.  The  results  from  the 
wild  fish  experiment  conclusively  demonstrate 
that  coastal  pelagic  fish  of  the  species  tested  can 
be  controlled  and  led  with  combinations  of 
120  V,  25  to  35  pulses/s,  and  a  pulse  width  of  0.5  ms. 

DISCUSSION 

Effective  electrical  combinations  for  controlling 
coastal  pelagic  species  determined  during  our  field 
experiments  compared  favorably  with  the  param- 
eters determined  by  Klima  (1970)  in  labora- 


662 


SEIDEL  and   KLIMA:  CRITERIA  FOR  ELECTRICAL  HARVESTING 


Table  4. — Responses  of  wild  fish  attracted  to  electrode  configuration  at  preselected  electrical  combinations  (pulse  width  — 

0.5  millisecond). 


Species 

Approximate 
school  size 

Volts 

Pulse 
rate 

Reactions 

Spanish  sardine,  round  scad 
and  bumper 

10-15 

120 

25 

Positive;  pulled  into  anode  and  held 

Spanish  sardine,  round  scad 
and  bumper 

10-15 

120 

35 

Positive;  pulled  into  anode  and  held. 

Spanish  sardine  and  round 

Positive  50  to  90%  led  to  anode  and  held;  only  fish  in 

scad 

30-50 

120 

35 

fringe  area  escaped. 

Thread  herring  and  bumper 

5-8 

120 

35 

Positive;  led  to  anode. 

Spanish  sardine 

10 

90 

15 

3  had  positive  response. 

Spanish  sardine  and  round 
scad 

10 

100 

50 

Turn  fish  to  anode— all  escaped. 

Spanish  sardine  and  round 
scad 

10 

100 

25 

Turn  fish  to  anode — all  escaped. 

Round  scad 

20-40 

120 

35 

Positive  and  held  at  electrode. 

Blue  runner.  Caranx  crysos 
Blue  runner 

15 
10 

120 

120 

25 

35 

Positive  and  held  at  anode. 
Positive  and  held  at  anode. 

Blue  runner 

30 

120 

35 

20-25  positive  response  and  held  at  anode. 

tory  studies.  The  range  of  pulse  widths  was 
slightly  narrower  in  the  field  than  in  the  labora- 
tory where  the  experiment  tank  maintained  a  uni- 
form field,  test  animals  could  not  escape,  and  in 
which  narrow  pulse  widths  were  not  possible. 
Since  wide  pulse  widths  require  more  electrical 
energy,  it  is  desirable  to  select  the  narrowest 
pulse  width  possible  which  will  allow  proper  con- 
trol of  the  species.  This  in  situ  investigation 
clearly  demonstrates  that  pulse  widths  between 
0.5  and  0.8  ms  can  be  effectively  employed  in  open 
water  situations  in  conjunction  with  proper  field 
strengths  and  pulse  rates.  Our  results  demon- 
strate that  the  effective  control  of  the  fishes  tested 
requires  no  less  than  15  V/m  at  pulse  widths  of  0.5 
ms  or  greater  and  pulse  rates  ranging  between 
20  and  35/s.  A  pulse  width  of  0.3  ms  was  com- 
pletely ineffective  within  the  proper  field  strength 
and  pulse  rate  range  used  in  our  experiment.  - 

A  review  of  the  field  test  data  suggests  an 
additional  parameter,  minimum  pulse  control 
power  for  a  specific  pulse  width  and  field  strength, 
should  be  determined  during  future  field  experi- 
ments. Obviously  a  minimum  output  voltage  and 
current  is  necessary  to  maintain  the  established 
15  V/m  in  any  particular  electrode  configuration 
and  resulting  load  resistance.  However,  once  the 
minimum  power  to  maintain  15  V/m  is  reached,  if 
future  research  can  establish  that  a  pulse  enve- 
lope of  minimum  total  power  within  a  minimum 
and  maximum  set  of  values  for  pulse  rate  and 
pulse  width  is  the  important  criterion  for  proper 
fish  control,  much  greater  latitude  would  be  pos- 
sible in  designing  a  pulse  generator  for  a  par- 
ticular fishing  system.  This  would  permit  a 
designer  to  better  select  pulse  rate,  pulse  width, 
and  maximum  values  for  voltage  and  current 


to  provide  better  equipment  reliability  and  pos- 
sibly cheaper  construction. 

The  power  required  to  control  fish  is  presented 
in  the  following  discussion  based  on  the  param- 
eters of  pulse  width,  pulse  rate,  and  field  strength 
which  we  used  as  criteria  during  the  field  tests. 
Power  for  each  pulse  {Pp  )  is  described  as: 

Pp    ^Ve    Xl    X  P^,  (1) 

where    Ve     =  electrode  voltage 

/        =  current  at  load  resistance  in 

amperes 
P„,     =  pulse  width,  milliseconds. 

The  total  load  resistance  equaled  0.05  ohm  with 
an  electrode-to-electrode  resistance  of  0.033  ohm 
and  a  cable  loss  of  0.017  ohm.  Slight  daily 
variations  of  0.006  ohm  were  noted  in  electrode- 
to-electrode  resistance  due  to  small  changes  in 
salinity  and  temperature.  For  computations,  we 
rounded  the  resistance  values  slightly  and  the 
electrode-to-electrode  voltage  was  established  as 
60%  of  the  output  voltage.  The  current  (/)  and 
electrode-to-el"ctrode  voltage  (Vg  )  at  selected 
output  voltages  using  an  array  resistance  of  0.03 
ohm  and  a  loss  resistance  of  0.02  ohm  were: 


Output 
voltage 

150 

120 

90 


Ve 

90 

72 
54 


I 

3,000 
2,400 
1,800 


The  total  power  (kW)  delivered  into  the  electrode 
array  after  cable  losses  can  be  computed  as  follows; 


663 


FISHERY  BULLETIN:  VOL.   72,  NO.  3 


Pt    =Ve    Xl   ^  Pu     X  Pr  (2) 

where  Pr    =  pulse  rate,  pulses  per  second 

Pt    =  total  power  in  kilovolt  ampere. 

Using  the  above  values,  the  total  power  for 
effective  electrical  control  values  used  was: 


Ve 


Pt 


54 

25 

0.8 

1.94 

72 

25 

0.5 

2.16 

72 

25 

0.8 

2.77 

90 

35 

0.3 

2.84 

The  preceding  results  suggest  there  is  a 
minimum  requirement  of  total  power  (Pi)  to 
properly  control  the  fish  which  would  be  a 
constant  regardless  of  the  specific  combinations  of 
pulse  width,  pulse  rate,  and  field  strengths.  Once 
the  effective  field  strength  of  15  V/m  is  exceeded, 
it  appears  that  different  minimum  values  of 
pulse  rate  and  pulse  width  can  be  obtained  to 
produce  equally  effective  fish  response.  Unfor- 
tunately, there  are  too  few  data  points  to  support 
this  conclusion.  To  properly  substantiate  such  a 
hypothesis,  we  would  have  to  determine  either  a 
minimum  pulse  width  for  a  constant  electrode 
voltage  at  each  pulse  rate  or  a  minimum  pulse 
rate  for  a  constant  electrode  voltage  at  each 
pulse  width.  Without  this,  we  cannot  definitely 
state  that  a  parameter  of  total  power  (Pt)  can 
be  used  as  a  control  specification  rather  than 
various  combinations  of  electrode  voltage,  pulse 
width,  and  pulse  rate.  Many  more  tests  would  be 
needed  to  substantiate  the  hypothesis,  although 
this  approach  would  be  advantageous  from  a 
designer's  standpoint. 

120-kVA  Pulse  Generator  Design 

The  primary  objective  in  the  design  of  our 
pulse  generator  was  to  produce  a  system  which, 
based  on  the  results  of  the  12-kVA  pulse  genera- 
tor electrical  fish  control  experiments,  would 
provide  the  capability  for  prototype  development 
and  effective  harvest  of  fish  in  several  modes 
of  system  operation.  The  output  power  of  the 
pulse  generator  and  pulse  control  characteristics 
were  established  to  satisfy  requirements  for  auto- 
matic fish  harvesting  without  nets  (Klima,  1970), 
electrical  mid-water  and  bottom  trawling  for  fish, 
and  to  provide  the  potential  for  prototype  develop- 


ment of  possible  future  applications  such  as  fish 
barriers,  electrical  aquaculture  cages,  or  other 
such  applications. 

Netless  Fish  Harvesting  Mode 

The  initial  reason  for  our  development  efforts 
in  the  field  of  electrical  fishing  was  to  eventually 
achieve  the  automatic  fish  harvesting  system. 
Since  this  application  imposed  the  most  serious 
power  demands,  the  design  specifics  were  estab- 
lished around  that  set  of  conditions  and  results 
of  this  study  were  used  to  calculate  the  power 
requirements  for  a  netless  fishing  system.  Allow- 
ances were  made,  however,  for  application  of  the 
system  to  other  electrical  control  applications. 
One,  a  mid-water  trawl  mode,  is  described  later 
in  the  paper. 

Use  of  lights  at  night  concentrate  fish  (Wick- 
ham,  1971)  in  a  volume  of  water  which  can  then 
be  electrified.  The  minimum  volume  of  water 
within  a  light  field  which  needs  to  be  effectively 
covered  electrically  to  produce  commercial  quan- 
tities of  fish  would  be  5  m  in  cross  section  and 
10  m  in  length.  An  equation  for  resistance  of 
seawater  between  the  electrodes  is: 


R     = 


PL 


(3) 


where   L 
A 

P 


=  distance  between  electrodes  in 
meters 

=  surface  area  of  the  electrodes  in 
square  meters 

=  resistivity  of  seawater  in  ohm- 
meters. 


According  to  this  equation  the  load  resistance  of 
two  parallel  plates  is: 


R 


0.213  X  10 
25 


=  0.0852  ohm 


where  p    at  30%o  and  24°C  =  0.213  ohm-m. 

However,  this  formula  only  describes  the  resis- 
tance of  the  volume  of  water  between  two 
electrodes  as  if  the  electrode  array  was  a  finite 
conductor.  In  actual  practice,  a  significant  spread- 
ing of  the  electrical  field  occurs  in  seawater.  If  the 
size  of  an  electrode  is  small  in  comparison  to  the 


664 


SEIDEL  and  KLIMA:   CRITERIA  FOR  ELECTRICAL  HARVESTING 


separation  distance,  the  configuration  of  the 
electrode  in  the  array  is  the  principal  factor  in 
determining  the  resistance  value,  as  would  be  the 
case  with  small  balls  or  cables  for  electrodes.  For 
our  situation,  the  size  of  the  electrodes  and 
separation  distance  are  equally  important.  Since 
the  load  resistance  of  the  array  in  seawater  is 
extremely  low,  the  resistance  value  used  to  calcu- 
late power  requirements  becomes  extremely 
important.  A  small  error  in  the  resistance  could 
result  in  a  large  miscalculation  of  the  necessary 
power  requirements.  For  this  reason  we  took  great 
care  in  computing  resistance  accurately.  Resis- 
tance measurements  for  this  situation  can  be 
calculated  by  two  methods  referred  to  as  Kreutzer 
and  empirical  technique.  Kreutzer  developed  a 
formula  for  calculating  spread  resistance  for  one 
electrode: 


R. 


Ko  a +Tx  0.02) 


(4) 


where  Rs     = 


T 

A 


=  spread  resistance  of  one  electrode, 

including  field  fringing 
=  a  constant  at  a  specific  salinity 
=  temperature  in  centigrade 
=  area,  square  meters. 


(C.  Kreutzer,  pers.  commun.)  The  constant  K^, 
varies  with  different  salinity  values  and  must  be 
recalculated  for  each  new  salinity.  It  can  be  ob- 
tained by  solving  fori^,,  in  Equation  (4)  which  re- 
quires knowledge  of  resistance,  surface  area,  and 
temperature.  Once  the  value  of /Co  is  determined 
for  a  specific  salinity.  Equation  (4)  can  be  used  to 
calculate  Rs  for  varying  electrode  surface  areas. 
Because  the  value  of  K^,  varies  with  different 
salinity  and  is  difficult  to  determine  since  in  situ 
resistance  measurements  are  required,  we 
decided  to  establish  an  empirical  ratio  which  com- 
pares the  theoretical  calculated  resistance  from 
Equation  (3)  to  an  actual  measured  electrode 
resistance.  The  calculated  resistance  according  to 
Equation  (3),  using  the  2  x  2  x  4  m  electrodes 
of  one  test  was: 


0.189x4 
R  = =  0.189ohm 


with  a  salinity  of  32.9%o  and  a  temperature  of 
28.7°C  (p  =  0.189  ohm-m).  The  measured  resis- 


tance was  actually  0.039  ohm.  An  index  of  dif- 
ference between  the  calculated  and  measured 
resistance  provides  a  ratio  of  4.85.  The  ratio  of 
calculated  to  measured  resistance  ranged  from 
4.85  to  5.2  throughout  the  study  period,  with  the 
measured  resistance  of  the  electrode  array  vary- 
ing from  0.035  to  0.04  ohm.  Hence,  a  midrange 
value  of  5.0  seems  the  most  practical  and  resis- 
tance value  one-fifth  of  the  Equation  (3)  calculated 
value  is  used  to  compute  total  spread  resistance 
as  shown  in  the  following  equation: 


Rt  = 


PL 
5A 


(5) 


where  R, 


=  total  spread  resistance  including 
both  electrodes. 


As  a  cross-check  to  Equation  (5)  we  also  computed 
the  spread  resistance  from  Equation  (4)  using  a 
value  of  K  „  derived  from  the  sample  test.  The 
measured  resistance  of  the  electrode  array  in  sea- 
water  was  0.039  ohm.  Since  each  electrode  con- 
tributes one-half  the  resistance,  the  spread  resis- 
tance for  Equation  (4)  is  0.0195  ohm.  In  addi- 
tion, since  both  sides  of  each  electrode  in  our 
tests  were  exposed,  the  surface  area  for 
the  equation  is  twice  that  of  one  side.  Using 
these  values,  K^  is  determined  to  be: 


0.0195  = 


K^a  +  28.7  X  0.02) 


\|   2(2)2 
where  Ko    =  0.035  ohm-m. 

For  a  5  X  5  X  10  m  electrode  array  using 
Equations  (4)  and  (5),  the  following  load  resis- 
tances are  determined  at  28.7°C  and  32.9  'oo: 

Equation  (4) 

0.189  X  10 
Ri      =  =  0.01512  ohm, 

5(5)2 

Equation  (5) 

0.035(1  +  28.7x0.02) 


ii<j 


where  R  t 
Rt 


n]  2(5)2 


0.00779, 


2Rs  =  2(0.00779)  =  0.01558, 
2i?,  since  Rs  is  the  resistance  of 
one  electrode. 


665 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


As  can  be  seen,  the  value  for  the  load  resistance 
of  a  5-square  meter  by  10-m  array  compares 
favorably  when  determined  by  the  two  different 
equations.  The  higher  value  of  0.01558  ohm  was 
used  in  making  power  calculations  since  any 
electrode  array  will  have  some  additional  resis- 
tance due  to  connection  losses. 

Results  from  our  field  study  thus  provided  the 
following  set  of  basic  design  specifics  for  our  proto- 
type pulse  generator  for  use  with  attracting  lights 
in  a  netless  fish  harvesting  application: 

1.  Minimum  field  strength-  15  V/m. 

2.  Pulse  rate  -  20-35  pulses/s. 

3.  Pulse  width-  >0.5  ms. 

4.  Array  size  -  5  x  5  x  10  m. 

5.  Load  resistance  of  array-  0.01558  ohm. 

Using  these  specifications,  we  determined  the 
output  capability  of  the  pulse  generator  which 
would  satisfy  our  requirements  by  the  following 
equation: 

P  =  VI  X  fl  (6) 

where  P  =  power,  watts 

V  =  output  voltage,  volts 

/  =  current,  amperes 

f  =  pulse  rate,  pulses  per  second 

I  =  pulse  length  or  width,  seconds. 

To  insure  an  adequate  field  strength  throughout 
our  electrode  array,  we  chose  a  value  of  20  V/m 
for  the  power  calculations.  We  also  selected  a 
maximum  pulse  rate  of  50/s  and  pulse  widths  of 
0.5,  0.75,  and  1.0  ms  to  give  the  pulse  generator 
more  versatility.  Using  Equation  (6),  the  power 
requirement  is: 

V    =  20  X  10  =  200  V  for  10-m  array 


V 


I      =- 


200 


Rt        0.01558 


=  12,837  A, 


and  at  50  pulses/s  and  0.75  ms  pulse  width 

P     =(200)(12,837)(50)(0.75  X  10-=^) 
P    =  96,278  W. 

In  an  applied  system,  a  cable  and  connection 
loss  will  be  experienced.  Because  of  the  very  low 
load  resistances  of  seawater,  a  25*^  cable  loss  can 


easily  be  expected.  Rounding  off  our  requirement 
to  90  kVA  and  after  allowing  for  a  25%  loss,  we 
need  a  pulse  generator  of  120-kVA  output  to 
satisfy  the  system  requirements  we  established. 
As  a  crosscheck  of  the  above  designed  system, 
the  following  formula  (Kreutzer,  1964)  is  used  to 
calculate  the  effective  fish  control  range  of  one 
electrode: 


R 


I  X  L  X  P 
G  X  2  xn 


where  R 
I 
L 

9 
G 


=  effective  range,  meters 

=  current  into  the  water,  amperes 

=  length  of  fish,  meters 

=  water  resistivity,  ohm-meter 

=  body  voltage  of  fish. 


To  determine  the  effective  range  of  20  V/m,  a 
value  of  1  m  is  used  for  the  fish  length,  fish  body 
voltage  is  20  V,  and  the  resistivity  is  again  0.189 
ohm-m. 

Allowing  a  25%  cable  loss  requires  a  total  input 
voltage  of  267  V  at  a  total  load  resistance  of 
0.0208  ohm,  and  the  current  in  the  water  is  found 
to  be: 


/      = 


V 


267 


12,837  A. 


R        0.0208 
Using  these  values,  range  (R)  is  found  to  be: 


R    = 


R 


(12,837  X  1  X  0.189 

20  X  2  X  3.14 
4.40  m. 


Since  this  value  is  computed  for  one  electrode, 
the  20  V/m  range  of  two  electrodes  will  be  8.8 
m.  In  actual  practice,  however,  the  range  of  two 
electrodes  paired  together  is  greater  than  twice 
the  reach  of  one,  and  we  can  supply  a  5  x  5  x  10 
m  array  with  20  V/m.  At  our  minimum  specifica- 
tion of  15  V/m,  the  calculated  reach  of  one 
electrode  is  5.08  m. 

Since  the  configuration  of  the  electrode  array 
determines  array  resistance,  various  combina- 
tions of  electrode  size  and  separation  distance  can 
change  the  pulse  voltage  and  current  require- 
ments. For  this  reason,  a  certain  degree  of  flexi- 
bility was  designed  into  the  netless  fish  harvest- 
ing mode  of  the  pulse  generator.  The  system  is 


666 


SEIDEL  and  KLIMA:  CRITERIA  FOR  ELECTRICAL  HARVESTING 


capable  of  delivering  up  to  1,000  V  to  an 
electrode  array.  However,  at  this  voltage,  the 
array  shape  has  to  be  changed  to  produce  a  much 
higher  load  resistance  to  maintain  the  current  at 
a  value  which  is  within  the  120-kVA  rating  of 
the  system  and  the  current  and  voltage  carrying 
capability  of  various  components  in  the  unit.  For 
instance,  at  1,000  V  the  electrode  array  has  to 
have  a  total  resistance  of  0.3  ohm. 

Mid- Water  Trawling  Mode 

The  pulse  generator  was  also  designed  for  appli- 
cation to  electrical  trawling.  This  use  of  the  sys- 
tem requires  a  significantly  different  configura- 
tion than  in  netless  harvesting.  Since  the  pulse 
generator  components  are  far  too  large  to  con- 
sider underwater  mounting  of  the  system  on  a 
trawl,  it  was  necessary  to  design  the  unit  for 
operation  through  a  long  power  cable.  The  cable 
transmits  the  pulsed  power  from  the  vessel  to  the 
trawl.  A  cable  length  of  2,200  feet  (670.1  m)  was 
chosen  to  allow  trawling  to  depths  of  100  fm 
(fathoms)  (182.9  m)  with  a  cable  to  depth  ratio 
of  at  least  3:1.  The  length  of  the  cable  is  impor- 
tant because  as  it  gets  longer  its  direct  current 
resistance  increases  and  therefore  either  the  cable 
losses  become  greater  or  the  size  of  the  conductors 
has  to  be  increased  to  prevent  excessive  losses. 
Since  a  large  power  loss  is  not  acceptable,  con- 
ductor size  and  the  resulting  cable  diameter 
eventually  become  too  large  and  are  limiting 
factors  in  the  total  length  and  therefore  the  power 
then  can  be  transmitted  down  the  cable. 

The  operation  of  a  pulse  generator  into  a  long 
cable  requires  careful  design  in  order  to  work. 
First,  the  impedences  of  the  pulse  generator, 
cable,  and  electrode  array  have  to  be  properly 
matched  through  step-up  and  step-down  trans- 
formers to  accomplish  transmission  of  the  pulse 
down  the  cable.  Unless  impedences  are  properly 
matched,  the  pulse  will  become  very  distorted  or 
can  be  totally  lost  in  the  cable.  Another  serious 
limiting  factor  in  the  operation  of  a  pulse 
generator  through  a  long  cable  for  trawling  is  the 
underwater  transformers  which  match  the  power 
supply  cable  to  the  electrode  array.  The  delivery  of 
significant  levels  of  power,  such  as  120  kVA, 
through  a  single  transformer  would  require  a 
transformer  that  is  quite  large  and  would  weigh 
several  hundred  pounds  to  handle  the  pulse 
current  into  an  array  with  a  load  resistance  of 
0.05  ohm. 


Our  first  intended  application  of  the  pulse 
generator  in  a  trawling  mode  was  with  a  mid- 
water  trawl.  The  standard  mid- water  trawl  being 
used  at  the  Pascagoula  Laboratory  was  a  net  that 
opened  approximately  9  x  9  m  under  water.  In 
actual  field  measurements,  it  has  been  found  that 
the  net  generally  opens  between  7.5  and  9.0  m  in 
height.  Therefore  we  required  the  pulse  generator 
to  accomplish  effective  electrical  trawling  on  a 
vertical  opening  of  7.5  to  9.0  m  and  a  horizontal 
opening  of  approximately  9.0  m.  In  the  mid- water 
trawl  application  we  expect  the  electricity  to 
provide  a  combination  of  fright,  leading,  and  some 
tetanus  to  aid  in  harvesting  of  fish.  Past  experi- 
ments at  the  Pascagoula  Laboratory  demon- 
strated that  fish  generally  accumulate  in  the 
mouth  and  forward  body  of  the  trawl.  Therefore 
an  electrical  field  applied  periodically  should  force 
the  fish  back  into  the  cod  end. 

Because  of  component  ratings,  loading  of  under- 
water transformers,  and  design  restrictions,  a 
power  of  80  kVA  was  chosen  as  the  maximum 
which  could  be  supplied  to  our  electrode  array  in 
a  mid-water  trawling  mode.  Since  the  application 
of  80  kVA  through  a  single  transformer  is  difficult 
under  water,  we  chose  four  electrode  pairs  and 
four  underwater  transformers  matched  to  each 
electrode  pair  to  cover  the  9.0  x  9.0  m  net.  It  was 
found  that  a  reasonable  electrode  size  could  be 
used  which  would  provide  a  load  resistance  of  0.2 
ohm  for  each  pair  and  deliver  20  kVA  from  each 
transformer.  This  meant  that  by  connecting  the 
electrode  pairs  in  parallel,  each  transformer 
would  carry  one  fourth  the  current  which  would  be 
required  of  a  single  transformer  at  the  same  total 
output.  In  addition,  the  four  parallel  electrode 
pairs  would  represent  a  total  load  resistance  of 
0.05  ohm  which  could  easily  be  matched  to  the 
other  impedences  of  the  system. 

Within  the  impedence  matching  requirements 
of  the  pulse  generator,  cable,  and  electrode 
array,  and  using  the  maximum  output  voltage  of 
2,500  V  that  the  unit  is  capable  of  supplying  in 
this  mode,  450  V  can  be  supplied  to  each  elec- 
trode pair  through  the  matching  transformers. 
The  surface  area  of  each  electrode  pair  must  be 
adjusted  to  provide  a  resistance  value  of  0.2  ohm. 
Therefore,  the  pulse  current  of  this  condition  is: 


V       450 

/      =  —  = =  2,250  A. 

R        0.2 


667 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Using  Equation  (7)  at  15  V/m,  the  range  of  an 
electrode  is: 


R 


[2,250  X  1  X  0.189 
15  X  2  X  3.14 


R    =  2.13  m. 

However,  to  accomplish  at  least  a  fright 
reaction  required  10  V/m  or  less,  depending  on  fish 
size.  We  feel  that  a  fright  reaction,  although  not  as 
effective  as  positive  control  offish,  will  accomplish 
disorientation  and  therefore  harvest  of  some  fish 
in  an  electrical  trawling  mode.  Since  the  tem- 
perature of  below-surface  water  will  be  colder, 
we  can  use  higher  resistivities  than  0.189  in 
calculations  as  shown  in  the  following  calculation 
for  field  reach  at  100  fm  water  depth.  In  addition, 
Kreutzer's  Equation  (7)  states  that  the  factor 
in  the  denominator  goes  from  2  to  4  as  the 
electrodes  are  placed  in  mid-water.  Using  these 
values,  we  calculate  the  maximum  variation  of 
values  from  the  surface  to  100  fm  in  the  10 
V/m  range  of  one  electrode  to  be: 

Surface: 
Salinity  32.9%o,  temperature  28.7°C, 
p  =  0.189 


R    = 


2,250  X  1  X  0.189 
10  X  2  X  3.14 


R     =  2.60  m. 
100  fm: 

Sahnity 30 °/oo, temperature  10°C,  P=   0.3 


R    = 


/2,250  X  1  X  0.3 
10   X   4   X   3.14 


R     =  2.32  m. 

Again,  the  range  of  two  electrodes  is  found  to  be 
greater  than  twice  the  range  of  one  electrode.  In 
addition,  since  each  electrode  pair  based  on  their 
required  size  for  0.2  ohm,  will  be  separated 
by  about  1.22  m,  field  strength  adding  will  occur. 
Therefore,  the  effective  range  of  an  electrode  pair 
is  significantly  more  than  twice  the  range  of  one 
electrode.  By  installing  one  polarity  electrode  on 
the  headrope  and  the  opposite  on  the  footrope,  we 
should  be  able  to  cover  a  9  x  9  m  area  with 


the  weakest  part  of  the  field  having  at  least 
enough  strength  to  frighten  fish.  We  can  also  use 
pulse  rates  higher  than  35/s,  which  will  immobi- 
lize fish  more  rapidly.  In  addition,  it  must  be 
remembered  that  at  distances  closer  to  the 
electrodes,  the  field  strength  increases  and 
reaches  values  which  will  effectively  lead  or  stun 
the  fish.  Because  the  size  of  each  electrode  is 
relatively  small,  current  densities  capable  of  stun- 
ning fish  will  be  found  at  some  minimum  distance 
from  the  electrodes.  This  is  not  desirable  for 
leading  fish  in  a  netless  harvesting  application 
and  is  avoided  by  using  large  electrodes,  but  it  is 
very  desirable  in  a  trawling  mode  where  the 
electrodes  are  inside  the  body  of  the  net. 

ACKNOWLEDGMENTS 

We  are  grateful  to  Harvey  R.  Bullis,  Jr.  for 
his  support  and  continual  encouragement  of  this 
project.  Conradin  Kreutzer  was  of  invaluable 
assistance  with  his  expert  advice,  technical 
knowledge  of  physics  and  electricity,  and  design 
experience  in  constructing  the  pulse  generator 
and  experimental  hardware. 

LITERATURE  CITED 

Bary,  B.  M. 

1956.     The  effect  of  electric  fields  on  marine  fishes.     Scotl. 

Home  Dep.  1,  32  p. 

Bullis,  H.  R.,  Jr.,  and  J.  R.  Thompson. 

1970.  Bureau  of  Commercial  Fisheries  Exploratory  Fish- 
ing and  Gear  Research  Base,  Pascagoula,  Mississippi, 
July  1,  1967  to  June  30,  1969.  U.S.  Fish  Wildl.  Serv., 
Circ.  351,  29  p. 

Collins,  G.  B.,  C.  D.  Volz,  and  P.  S.  Trefethen. 

1954.  Mortality  of  salmon  fingerlings  exposed  to 
pulsating  direct  current.  U.S.  Fish  Wildl.  Serv.,  Fish 
Bull.  56:61-81. 

Halsband,  E. 

1967.  Basic  principles  of  electric  fishing.  In  R.  Vibert 
(editor),  Fishing  with  electricity- Its  applications  to 
biology  and  management,  p.  57-64.  Fishing  News  (Books) 
Ltd.,  Lond. 

Higman,  J.  B. 

1956.     The  behavior  of  pink  grooved  shrimp,  Penaeus 
duorarum  Burkenroad,  in  a  direct  current  electrical  field. 
Fla.  State  Board  Conserv.,  Tech.  Ser.  16,  23  p. 
Kessler,  D.  W. 

1965.     Electrical  threshold  responses  of  pink  shrimp 
Penaeus  duorarum,  Burkenroad.     Bull.  Mar.  Sci. 
15:885-895. 
Klima,  E.  F. 

1968.  Shrimp-behavior  studies  underlying  the  develop- 
ment of  the  electric  shrimp-trawl  system.  U.S.  Fish. 
Wildl.  Serv.,  Fish.  Ind.  Res.  4:165-181. 


668 


SEIDEL  and  KLIMA:  CRITERIA  FOR  ELECTRICAL  HARVESTING 


1970.  Development  of  an  advanced  high  seas  fishery  and 
processing  system.     Mar.  Technol.  Soc.  J.  4(5):80-87. 

1972.     Voltage  and  pulse  rates  for  inducing  electrotaxis  in 
twelve  coastal  pelagic  and  bottom  fishes.     J.  Fish.  Res. 
Board  Can.  29:1605-1614. 
Kreutzer,  C.  O. 

1964.  Utilization  of  fish  reactions  to  electricity  in  sea 
fishing.  In  Modern  fishing  gear  of  the  world,  Vol.  2,  p. 
545-550.    Fishing  News  (Books)  Ltd.,  Lond. 

Lamarque,  p. 

1967.   Electrophysiology  of  fish  subject  to  the  action  of  an 
electric  field. /n  R.  Vibert  (editor).  Fishing  with  electricity 
-Its  applications  to  biology  and  management,  p.  65-100. 
Fishing  News  (Books)  Ltd.,  Lond. 
McMillan,  F.  O. 

1928.     Electric  fish  screen.  U.S.  Bur.  Fish.,  Bull.  44:97-128. 
McRae,  E.  D.,  Jr.,  and  L.  E.  French,  Jr. 

1965.  An  exp)eriment  in  electrical  fishing  with  an  electric 
field  used  as  an  adjunct  to  an  otter-trawl  net.  Commer. 
Fish.  Rev.  27(6):1-11. 

MoNAN,  G.  E.,  AND  D.  E.  Engstrom. 

1963.  Development  of  a  mathematical  relationship  be- 


tween electric-field  parameters  and  the  electrical  charac- 
teristics of  fish.  U.S.  Fish  Wildl.  Serv.,  Fish  Bull. 
63:123-136. 

Reidel,  D. 

1952.  Concerning  the  influence  of  electric  current  on  the 
sexual  products  of  fish  with  special  emphasis  on  electro- 
fishing.  Inst.  Fisch.  Dtsch.  Akad.  Lanwirt.-Wiss.  Berl., 
p.  53. 

Seidel,  W.  R. 

1969.  Design,  construction,  and  field  testing  of  the  BCF 
electric  shrimp-trawl  system.  U.S.  Fish  Wildl.  Serv., 
Fish.  Ind.  Res.  4:213-231. 

Vibert,  R. 

1967.  Part  I  -  general  report  of  the  working  party  on  the 
applications  of  electricity  to  inland  fishery  biology  and 
management. /n  R.  Vibert  (editor).  Fishing  with  electric- 
ity- Its  applications  to  biology  and  management,  p.  3-51. 
Fishing  News  (Books)  Ltd.,  Lond. 

WiCKHAM,  D.  A. 

1971.  Nightlighting — a  harvesting  strategy  for  under- 
utilized coastal  pelagic  schoolfishes.  Proc.  Gulf  Caribb. 
Fish.  Inst.,  23  Annu.  Sess.,  p.  84-90. 


669 


ECOLOGY  AND  NATURAL  HISTORY  OF  A  STAND  OF 

GIANT  KELP,  MACROCYSTIS  PYRIFERA, 

OFF  DEL  MAR,  CALIFORNIA 

Richard  J.  Rosenthal,^  William  D.  Clarke,^  and  Paul  K.  Dayton^ 

ABSTRACT 

The  assemblage  of  plants  and  animals  living  within  a  stand  of  Macrocystis  pyrifera  off  the  coast 
of  southern  California  was  studied  from  July  1967  through  February  1973.  Macrocystis  is  a  perennial 
kelp,  with  some  individuals  living  as  long  as  7  yr;  however,  the  average  life  span  in  this  bed  was 
approximately  3  to  4  yr.  Physical  disturbances  associated  with  storms  were  the  major  mortality 
causes  of  adult  Macrocystis  in  this  area.  Once  detached,  these  plants  drift  through  the  bed  and 
become  entangled  with  other  plants  which  results  in  extensive  mortality.  The  fact  that  germination 
was  greatest  after  the  surface  canopy  was  thinned  by  natural  attrition  and  commercial  harvesting 
suggests  that  light  is  a  critical  factor  influencing  the  recruitment  o{  Macrocystis.  There  was  little 
indication  to  show  that  sea  urchin  grazing  contributed  to  kelp  mortality. 

Faunal  species  identified  included  38  fish  species  and  98  invertebrate  species.  Of  these,  14  species 
of  macroinvertebrates  were  chosen  for  more  intensive  study  as  they  represented  common  or  char- 
acteristic species  in  the  kelp  bed.  Patterns  of  distribution  and  abundance  were  recorded  during 
the  study  period.  Most  species  had  aggregated  distribution  patterns  and  the  populations  of  most 
remained  reasonably  constant  over  4.25  yr.  Styela  montereyensis  (ascidian)  fluctuated  annually 
and  the  Muricea  californica  (octocoral)  population  slowly  decreased  during  this  time.  Conversely, 
Diopatra  ornata  (polychaete)  displayed  a  numerical  increase,  such  that  in  August  1972  it  was  the 
most  abundant  macroinvertebrate  in  the  Del  Mar  kelp  bed.  A  qualitative  food  web  is  presented 
based  on  limited  trophic  information. 


Many  large  kelp  stands  historically  have  either 
undergone  dramatic  oscillations  in  areal  cover  and 
standing  crop  or  completely  disappeared  (see 
North,  1971,  for  history  and  data).  Nearshore 
kelp  stands  are  found  in  many  scattered  locations 
along  the  mainland  of  California  and  fringe  most 
of  the  state's  offshore  islands;  in  southern  Cali- 
fornia kelps  are  often  conspicuous  when  the 
dominant  plant,  Macrocystis  pyrifera  (Linnaeus) 
C.  Agardh,  forms  a  floating  canopy  or  bed  along 
the  sea  surface.  This  kelp  community  contains 
many  plant  and  animal  species  which  contribute 
aesthetic  as  well  as  diverse  recreational  and  com- 
mercial resources.  The  loss  and  deterioration  of 
these  stands  is  correlated  with  many  man-caused 
perturbations  and  natural  events  such  as  reduced 
water  quality,  the  over-harvest  of  numerous  im- 
portant component  animal  populations,  and  fluc- 
tuations in  seawater  temperature. 


'Scripps  Institution  of  Oceanography,  University  of  California 
at  San  Diego,  La  Jolla,  CA  92037;  present  address:  Dames  and 
Moore,  711  "H"  Street,  Suite  500,  Anchorage,  AK  99501. 

^Westinghouse  Ocean  Research  Laboratory,  Annapolis,  MD 
21404.  Deceased. 

'Scripps  Institution  of  Oceanography,  University  of  California 
at  San  Diego,  La  Jolla,  CA  92037. 


There  is  widespread  concern  regarding  effects 
of  increasing  human  perturbations  to  these  near- 
shore  kelp  communities  which  include  increas- 
ing recreational  and  commercial  usage  as  well  as 
many  projected  sewer  and  thermal  outfalls  into  or 
in  the  proximity  of  kelp  beds.  Despite  this  concern, 
there  is  little  information  regarding  natural 
temporal  variation  of  populations  inhabiting 
these  assemblages.  Furthermore,  natural  history 
data  such  as  food  web  interactions  critical  to  a 
functional  understanding  of  this  community  are 
in  a  very  rudimentary  state.  This  information  is 
obviously  vital  to  the  proper  management  of 
this  resource. 

The  objectives  of  this  paper  are  to:  1)  describe 
patterns  of  distribution  and  abundance,  2)  record 
long  term  population  fluxes,  and  3)  note  food  web 
and  other  natural  history  observations  of  con- 
spicuous members  of  a  relatively  undisturbed  kelp 
association.  Such  data  are  essential  to  the  growth 
of  a  functional  understanding  of  this  community. 

The  study  site  (Figure  1)  was  located  in  a  bed 
oi  Macrocystis  pyrifera  about  1  km  offshore  from 
Del  Mar,  Calif,  (lat.  32°57'N,  long.  117°16'W). 
The  majority  of  the  observations  were  made  at 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


670 


ROSENTHAL,  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GIANT  KELP 


50m  T 


100 


ISOm 


0^  50 

TRANSECT  LINES  AND  FIXED 

QUADRATS  WITHIN  STUDY  AREA 

Figure  1. — Location  of  the  subtidal  study  area  off  Del  Mar, 
Calif.  The  drawing  shows  the  layout  of  the  transect  lines  and 
the  position  of  each  fixed  quadrat. 

depths  between  14  and  20  m  in  the  most  seaward 
Macrocystis  stand  directly  off  8th  Street  in  Del 
Mar.  These  continuing  studies  were  begun  in 
June  1967. 

Within  the  perimeter  of  the  study  area  the  sub- 
stratum is  composed  primarily  of  sedimentary 
mudstones  and  siltstones,  coarse  sand,  and  silt. 
The  sea  floor  is  somewhat  flat  in  appearance, 
although  low  (<1.5  m)  consolidated  mounds  and 
shallow  ledges  break  up  the  overall  visual 
uniformity  of  the  bottom. 

The  monthly  mean  surface  water  temperatures 
recorded  off  the  pier  at  Scripps  Institution  of 
Oceanography,  approximately  24  km  south  of  the 
study  site,  varied  from  a  minimum  of  10.1°C  to  a 
maximum  of  24.6°C  between  June  1967  and 
December  1971  (Scripps  Institution  of  Oceanog- 
raphy, 1968-1971).  The  annual  mean  temperature 
during  this  same  period  was  16.3°C.  Since  the 
water  column  in  this  area  is  thermally  stratified, 
it  is  essential  to  consider  bottom  temperatures 


as  well.  To  this  end,  70  bottom  temperatures  were 
recorded  at  a  depth  of  17  m  in  which  the  mean 
temperature  was  13.0°C  with  the  minimum  re- 
corded temperature  being  10.5°C,  and  the  maxi- 
mum being  16.0°C. 

A  great  deal  of  water  movement  is  typical  to 
this  environment  (Inman  and  Brush,  1973)  and 
water  transparency  or  underwater  visibility  is 
greatly  affected  by  the  resulting  sediment  dis- 
turbance. Over  the  5.7-yr  study,  the  underwater 
visibility  ranged  from  0  to  20  m,  the  average 
visibility  being  about  3  to  4  m.  However,  on  many 
dives  the  underwater  visibility  was  so  reduced 
that  it  was  impossible  to  see  along  the  bottom  in 
the  vicinity  of  the  kelp  bed. 

METHODS 

The  study  was  initiated  in  June  1967  after 
several  months  of  exploratory  observations.  All  of 
the  in  situ  observations  were  made  while  scuba 
diving  and  more  than  300  h  were  spent  under- 
water in  this  location.  Most  observations  were 
made  during  daylight  hours,  however  about  5  h 
were  spent  in  this  location  between  2000  and  2200 
h.  The  observations  reported  in  this  paper  span 
more  than  5  yr,  from  June  1967  through  February 
1973. 

Initially  a  100-m  transect  consisting  of  20  brass 
stakes  (75  cm  in  height)  was  placed  along  the  sea 
floor  in  June  1967.  One  stake  was  placed  every 
5  m,  and  the  entire  array  was  perpendicular  to  the 
shoreline.  During  July  1967  the  position  of  each 
attached  Macrocj's^/s  plant  growing  within  1  m  on 
either  side  of  the  100-m  transect  was  recorded. 
The  condition  (i.e.,  number  of  living  stipes,  ap- 
pearance of  the  holdfast,  etc.)  of  each  plant  was 
noted  at  various  times  from  the  beginning  of  the 
study  until  the  plant  disappeared.  Also,  juvenile 
Macrocystis  were  recorded  as  they  appeared  along 
the  2  m  X  100  m  strip. 

In  the  fall  of  1967,  the  main  transect  was 
extended  50  m  shoreward,  and  during  March  1968 
three  additional  lines  running  parallel  to  the 
coastline  were  added  (Figure  1).  Sectioned  25-m 
polypropylene  lines  (0.60  cm  in  diameter)  were 
staked  into  the  bottom  alongside  of  the  brass 
stakes.  The  lines  were  sectioned  so  that  fouling  or 
detachment  of  any  part  would  not  necessitate 
replacement  of  the  entire  transect.  All  lines  were 
marked  at  meter  intervals  with  tape,  and  the 
brass  stakes  were  numbered  with  line  and  plastic 


671 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


tags.  This  marking  system  made  it  possible  to 
sample  any  point  on  the  transect  and  return  to  the 
same  position  even  during  days  of  marginal 
underwater  visibility. 

The  entire  transect  area  was  stratified  into  six 
2  X  50  m  areas.  Two  sample  points  were  randomly 
selected  per  stratum;  at  each  of  these  12  locations 
a  4-m2  quadrat  was  placed  in  September  1968. 
Each  quadrat  consisted  of  polypropylene  line, 
arranged  in  a  square  2  m  on  a  side,  and  held  in 
place  at  each  corner  with  galvanized  spikes.  Two 
additional  4-m2  quadrats  (no.  13  and  14)  were 
added  in  August  1969,  but  in  this  case  the  loca- 
tions were  selected  by  the  presence  of  juvenile 
Macrocystis  in  this  part  of  the  kelp  bed.  The  latter 
two  quadrats  were  not  included  in  the  evaluation 
of  density  or  aggregation. 

During  September  1968  a  drawing  or  map  of 
each  fixed  quadrat  was  made  underwater  on  a 
sheet  of  plastic  recording  natural  history  infor- 
mation and  the  position  of  each  individual  macro- 
organism.  A  brass  meter  square  quadrat  divided 
into  0.25-m2  sections  was  used  while  mapping 
the  quadrats  in  order  to  reduce  the  visual  area 
being  examined.  Quadrats  were  examined  at 
irregular  intervals  (i.e.  monthly,  bimonthly,  or 
quarterly)  by  the  same  observer. 

Data  regarding  density,  frequency  of  occur- 
rence, and  distribution  patterns  were  calculated 
from  observations  in  the  12  4-m^  fixed  quadrats 
and  from  48  1-m^  quadrats  placed  at  randomly 
chosen  points  along  the  transects.  All  quadrat 
analyses  are  from  observations  taken  in  August 
1972.  The  distribution  patterns  of  the  conspicuous 
species  were  analyzed  with  the  index  of  disper- 
sion, variance/mean  x  (number  of  observations 
-1),  described  by  Greig-Smith  (1964).  If  the  var- 
iance to  mean  ratio  is  significantly  less  than  1.0, 
the  distribution  is  considered  even,  while  an 
index  significantly  greater  than  1.0  indicates  an 
aggregated  pattern  of  distribution.  Significance 
is  tested  in  a  Chi  square  table  with  n  -  \  degrees 
of  freedom.  Lack  of  significance  indicates  a  ran- 
dom distribution.  Since  the  results  of  most  such 
indices  depend  upon  quadrat  size,  we  compared 
independently  the  A-xn^  quadrats  and  the  l-m^ 
quadrats.  The  only  differences  in  the  two  analyses 
of  pattern  were  minor  and  involved  slight  loss 
of  significance  in  three  of  the  4-m^  quadrat 
analyses;  in  each  case  this  was  a  result  of  small 
numbers  of  individuals  in  the  12  larger  samples. 
The  results  of  the  pattern  analysis  are  given  in 
Table  5  and  are  based  on  the  48  l-m^  quadrats. 


THE  ALGAL  ASSOCIATION 

The  floristic  components  of  southern  California 
kelp  beds  have  been  described  by  Limbaugh 
(1955);  Dawson,  Neushul,  and  Wildman  (1960); 
North  (1971);  and  Neushul  (1971).  Many  of  the 
mainland  and  insular  kelp  stands  that  we  have 
surveyed  in  southern  California  appeared  dis- 
similar with  respect  to  the  algal  species  present 
or  their  relative  abundances.  Therefore  a  gen- 
eralized list  of  the  algae  known  to  inhabit  these 
kelp  communities  is  inadequate  when  describing 
a  particular  stand  or  comparing  two  or  more 
kelp  stands  (Dawson,  Neushul,  and  Wildman, 
1960).  The  one  characteristic  of  all  mainland 
southern  California  beds  appear  to  share  is  the 
overall  domination  of  Macrocystis,  in  terms  of 
both  biomass  (McFarland  and  Prescott,  1959) 
and  apparent  competition  for  the  available  light. 
The  kelp  bed  at  Del  Mar  is  two  layered,  with  the 
floating  portion  o{  Macrocystis  suspended  over  an 
algal  turf  composed  primarily  of  encrusting  coral- 
lines. There  is  also  a  thinly  scattered  under- 
growth of  Pterygophora  californica,  Laminaria 
farlowi,  and  Rhody me nia  pad fica.  These  species 
are  taller  than  the  corallines,  but  they  occur  so 
sparsely  in  this  area  that  they  cannot  be  con- 
sidered a  separate  canopy.  The  algal  association 
at  Del  Mar  consisted  of  only  a  few  species  of 
attached  macroalgae  (Table  1);  most  of  these 
plants  were  found  along  the  margins  of  the 
Macrocystis  bed. 

Table  1. — The  attached  macroalgae  found  in  the  Del  Mar 

kelp  bed. 

Bossiella  orbigniana  (Decaisne)  Silva 

Corallina  officinalis  var.  cfiilensis  (Harvey)  Kutzing 

Cystoseira  osmundacea  (Turner)  C.  Agardh 

Desmarestia  munda  Setchell  and  Gardner 

Desmarestia  tabacoides  Okamura 

Laminaria  farlowii  Setchell 

Litfiopliyllum  sp. 

Litfiothamnium  sp. 

fi/lacrocystis  pyrifera  (Linnaeus)  C.  Agardh 

Pterygophora  californica  Ruprecht 

Rhodymenia  arborescens  Dawson 

Rhodymenia  pacifica  Kylln 

Tiffaniella  snyderae  Farlow 


OBSERVATIONS  ON 
MACROCYSTIS  PYRIFERA 

The  giant  kelp  was  the  most  abundant  and 
conspicuous  species  of  brown  algae  within  the 
study  area.  It  is  perennial  and  usually  grows 
attached  to  solid  substratum  anchored  into  place 


672 


ROSENTHAL,  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GLANT  KELP 


by  the  holdfast.  In  July  1967,  35  attached  Macro- 
cystis  plants  which  contributed  fronds  to  the  sur- 
face canopy  were  recorded  along  the  2  x  100  m 
transect  band  (Figure  2).  For  convenience  we 
have  arbitrarily  lumped  all  plants  with  fronds 
(stipe  and  blade)  reaching  the  sea  surface  into  a 
category  as  canopy  adults.  With  the  passage  of 
time,  the  number  of  adult  Macrocystis  growing 
within  this  100-m  transect  band  was  gradually 
reduced  from  35  plants  to  a  single  survivor  in 
June  1970.  In  addition  to  the  plants  along  this 
part  of  the  transect  we  followed  14  adult  Macro- 
cystis that  grew  along  the  50-m  shoreward  exten- 
sion of  the  transect  (Figure  3).  This  shallower 
portion  of  the  kelp  bed  displayed  a  similar  reduc- 
tion in  the  number  of  adult  Macrocystis.  In  April 
1968,  14  plants  were  recorded  along  this  2  x  50  m 
belt,  however  by  April  1970  the  last  survivor  had 
disappeared. 

The  dramatic  fluctuations  in  the  number  of 
adult  Macrocystis  within  this  kelp  stand  can  be 
detected  from  both  in  situ  counts  and  kelp  har- 


FiGURE  2. — Occurrence  of  adult  Macrocystis  pyrifera  in  the 
2  m  X  100  m  transect  (0-100  m). 


3 


1968 


1969  1970 

TIME 


vesting  records  over  the  past  32  yr  (Figure  4). 
North  (1971)  stated  "that  beds  five  and  six,  lying 
between  Del  Mar  and  Oceanside,  California  have 
often  fluctuated  in  this  manner.  These  beds 
actually  consist  of  approximately  eight  major 
kelp  areas  along  about  15  km  of  coastline.  They 
flourish  and  disappear  more  or  less  in  unison, 
typically  but  not  invariably  with  a  four  year 
period." 

The  general  pattern  for  the  Del  Mar  Macro- 
cystis population  seemed  to  be  gradual  attrition 
of  the  adult  plants  with  little  or  no  replacement 
over  a  3-yr  period,  followed  by  recruitment  after 
most  of  the  adult  plants  had  disappeared.  With 
the  addition  of  40  young  adult  Macrocystis  along 
the  100-m  transect  (Figure  2)  during  the  summer 
of  1971  the  study  area  again  supported  a  density 
of  kelp  plants  similar  to  July  1967. 


I970_ 
STUDY    PERIOD 


YEAR 


Figure  3. — Occurrence  of  adult  Macrocystis  pyrifera  in  the 
2  m  X  50  m  transect  (100-150  m). 


Figure  4. — Relative  kelp  harvest  from  bed  number  5  I  Del 
Mar).  After  North  (1971)  and  Kelco  Company. 


Causes  of  Plant  Mortality 

Severe  grazing  of  Macrocystis  by  sea  urchins, 
as  described  by  Leighton  (1971)  off  southern 
California,  has  not  been  observed  within  this 
kelp  stand.  The  two  conspicuous  sea  urchins  in 
this  area,  Strongylocentrotus  franciscanus  and 
S.  purpuratus  were  usually  observed  on  consoli- 
dated sedimentary  mounds,  under  rocks,  or 
within  ledges.  During  both  daylight  and  noc- 
turnal hours  the  sea  urchins  remained  in  these 
locations,  and  in  most  instances  their  feeding 
was  restricted  to  detritus  and  detached  pieces 
of  drift  algae.  However,  S.  purpuratus  was  occa- 
sionally noted  within  the  deteriorating  holdfasts 
of  aging  Macrocystis.  In  general,  it  appeared  that 
there  was  enough  drift  algae  for  the  sea  urchin 
population  to  make  foraging  unnecessary,  and  we 
gathered  no  evidence  that  the  urchins  were 
exerting  much  grazing  pressure  on  Macrocystis. 


673 


FISHERY  BULLETIN;  VOL.  72.  NO.  3 


Fish  damage  to  Macrocystis  was  minimal  in 
mature  plants.  Most  of  the  grazing  by  fishes  was 
directed  towards  juvenile  plants.  Quast  (1968b, 
1971)  investigated  the  stomach  contents  of  fishes 
collected  at  Del  Mar  and  found  Macrocystis  frag- 
ments in  the  stomachs  of  the  labrid  Oxyjulis 
californica,  the  kyphosid  Medialuna  californien- 
sis  and  the  embiotocid  Phanerodon  furcatus.  He 
also  found  macroalgae  as  a  predominant  item  in 
terms  of  frequency  and  volume  in  the  stomachs 
of  Girella  nigricans.  During  daylight  hours  in 
this  area  O.  californica,  Embiotoca  jacksoni ,  and 
G.  nigricans  were  observed  biting  off  portions  of 
adult  and/or  juvenile  Macrocj'sft's.  Some  of  the  fish 
grazing  may  have  been  directed  at  the  inverte- 
brates associated  with  the  algae,  but  for  what- 
ever reason,  the  plants  were  damaged  by  these 
feeding  activities. 

Most  adult  Macrocystis  attrition  recorded  over 
the  5.7  yr  was  caused  by  detachment  of  the 
holdfast  and  thereby  elimination  of  the  entire 
plant.  Plants  with  weakened  or  decaying  hold- 
fasts were  particularly  vulnerable  to  physical 


stress.  Three  factors  probably  accounted  for  most 
of  the  plant  mortality  in  this  location:  1)  storms 
and  strong  surge,  2)  entanglement  of  drifting 
plants  with  attached  Macrocystis,  and  3)  kelp 
harvesting.  Many  of  the  kelp  stands  in  San 
Diego  County  have  been  greatly  thinned  or 
almost  torn  away  by  the  effects  of  storms  (Brandt, 
1923;  ZoBell,  1971).  Brandt  (1923)  reported  that 
the  La  Jolla  and  Pt.  Loma  kelp  beds  were 
reduced  nearly  40%  in  area  by  storms  in  the 
late  winter  and  early  spring  of  1915.  When 
Macrocystis  plants  become  detached  they  drift 
along  in  the  water  column,  often  becoming  en- 
tangled with  other  kelps  (Figure  5).  Drifting  or 
dislodged  plants  thus  present  a  potential  source 
of  mortality  for  attached  Macrocystis.  The  stipes, 
blades,  and  holdfasts  of  entangled  plants  become 
so  entwined  that  separation  becomes  almost  im- 
possible. We  have  observed  as  many  as  18  adult 
Macrocystis  entwined  in  one  cluster  near  the 
transect.  In  almost  every  case  the  entanglement 
resulted  in  the  mortality  of  the  attached  plant. 
This  is  a  partial  explanation  why  Macrocystis 


Figure  5. — A  detached  Macrocystis  drifting  through  the  kelp  bed. 


674 


ROSENTHAL.  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GIANT  KELP 


growing  along  the  transect  were  frequently  re- 
moved in  clumps  of  two  or  three  plants  at  a  time 
(Table  2). 

The  effect  of  harvesting  on  individual  plants 
is  still  inconclusive.  ZoBell  (1971)  concluded  from 
observations  of  drift  seaweeds  on  San  Diego 
beaches  that  there  is  no  consistent  relationship 
between  kelp  harvesting  operations  and  the 
amount  of  seaweed  on  beaches.  However,  at  Del 
Mar  we  found  adult  Macrocystis  pulled  free  of 
the  substratum  following  harvesting.  On  6  Jan- 
uary 1969,  10  marked  plants  were  growing 
along  the  100-m  transect  (Figure  2)  and  4  plants 
remained  in  the  50-m  extension  (Figure  3).  The 
seas  were  calm  and  there  were  no  loose  or  drift- 
ing Macrocystis  observed  along  the  entire  tran- 
sect. The  kelp  bed  was  harvested  on  7-8  Jan- 
uary 1969.  Returning  to  the  study  area  on  9 
January  1969  we  found  unattached  Macrocystis 
which  were  either  drifting  in  the  water  column 
or  entangled  with  other  attached  Macrocystis. 
Two  of  the  marked  plants  on  the  100-m  transect 
were  detached  from  the  substratum,  and  one 
plant  from  the  50-m  extension  was  missing. 
Also,  one  adult  Macrocystis  from  fixed  quadrat 
number  1  was  removed.  These  detached  plants 
probably  caused  additional  mortalities  by  en- 
tangling with  other  plants  in  the  kelp  bed.  In 
summary,  strong  water  movement,  plant  en- 
tanglement, and  harvesting  probably  act  in  a 
synergistic  manner  on  attached  Macrocystis. 


Germination,  Recruitment, 
and  Survivorship 

Macrocystis  undergoes  a  life  cycle  that  alter- 
nates between  an  asexual  macroscopic  stage 
termed  the  sporophyte,  and  a  sexual  microscopic 
gametophyte  stage  (Brandt,  1923;  Neushul  and 
Haxo,  1963).  Because  of  the  difficulties  inherent 
in  microscopic  investigation  underwater  we  re- 
corded recruitment  only  when  the  young  sporo- 
phytes  became  visible.  Although  Macrocystis 
spores  and  gametophytes  were  probably  present 
at  different  times  of  the  year  (Neushul,  1959; 
North,  1964),  we  were  primarily  concerned  with 
the  plants  when  they  visually  became  part  of 
the  epibenthic  community.  A  few  young  plants 
(<1  m  in  height)  were  observed  in  the  study  area 
during  the  early  summer  of  1967,  however  by 
the  fall  of  that  same  year  all  of  these  juvenile 
sporophytes  had  disappeared.  For  the  next  23  mo, 
no  Macrocystis  recruits  were  observed  in  the 
vicinity  of  the  transect.  During  this  time  the  over- 
lying canopy  was  expanding  to  a  point  when,  in 
December  1968,  it  covered  approximately  90% 
of  the  150-m  transect  line.  Thus,  insufficient 
light  penetration  resulting  from  shading  by  adult 
plants  and  water  turbidity  may  have  been  key 
reasons  for  the  absence  of  juvenile  Macrocystis 
during  1967  and  1968.  However,  the  bed  was 
harvested  in  January  1969,  which  apparently 
reduced  the  surface  canopy  to  about  15%  cover 


Table  2. — Stipe  counts  of  individually  tagged  plants  through  study  period.  Plant  number  1  survived  with  7-8  stipes  until 
August  1972.  "G"  means  that  the  plant  was  completely  gone  and  "O"  signifies  that  there  were  no  stipes  but  that  the  holdfast 
was  still  attached.  Note  the  tendency  for  groups  of  plants  to  disappear  together;  in  each  case  this  resulted  from  mutual 
entanglement. 


ite 

Plant  number 

Dc 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

July 

1967 

18 

34 

20 

30 

22 

36 

18 

16 

53 

9 

34 

20 

30 

54 

28 

11 

55 

97 

90 



30 

— 

71 

25 

30 

41 

74 

— 

58 

22 

Sept 

.  1967 

21 

38 

20 

12 

22 

44 

13 

2 

54 

7 

27 

15 

40 

60 

30 

14 

67 

108 

98 

53 

37 

34 

64 

27 

58 

40 

93 

80 

53 

24 

Dec. 

1967 

22 

34 

26 

G 

0 

43 

13 

0 

57 

0 

22 

6 

30 

56 

32 

6 

67 

96 

86 

62 

42 

41 

58 

22 

52 

39 

80 

81 

68 

0 

Jan. 

1968 

28 

38 

0 

64 

17 

64 

23 

6 

37 

72 

35 

6 

75 

88 

106 

0 

48 

45 

63 

23 

52 

34 

71 

72 

68 

Apr. 

1968 

32 

31 

16 

60 

27 

G 

32 

G 

30 

4 

67 

63 

102 

46 

44 

G 

22 

42 

35 

74 

60 

G 

May 

1968 

34 

28 

10 

63 

28 

35 

31 

G 

73 

82 

115 

42 

53 

22 

52 

34 

78 

62 

June  1968 

29 

22 

10 

49 

25 

36 

35 

81 

84 

123 

42 

52 

22 

46 

31 

75 

57 

Aug 

1968 

25 

17 

11 

58 

30 

34 

34 

70 

64 

116 

43 

40 

22 

44 

37 

77 

54 

Sept 

.  1968 

30 

14 

9 

47 

30 

32 

38 

80 

70 

114 

42 

39 

24 

50 

36 

87 

64 

Nov. 

1968 

29 

11 

G 

G 

29 

23 

42 

93 

27 

114 

43 

43 

26 

G 

G 

92 

62 

Jan. 

1969 

23 

12 

24 

22 

40 

— 

G 

127 

43 

40 

24 

G 

65 

Mar. 

1969 

27 

6 

14 

15 

24 

65 

108 

50 

G 

G 

G 

July 

1969 

23 

G 

1 

17 

22 

G 

77 

130 

51 

Sept 

1969 

22 

14 

27 

66 

126 

54 

Oct. 

1969 

21 

13 

30 

G 

90 

50 

Jan 

1970 

25 

G 

23 

G 

G 

Apr. 

1970 

20 

34 

June  1970 

12 

G 

675 


FISHERY  BUI  I.ETIN:  VOL.  72,  NO.  3 


along  the  150-m  transect.  In  addition  to  the  har- 
vesting effect,  the  kelp  bed  was  aging  and  the 
canopy  was  being  reduced  through  the  natural 
attrition  of  older  plants.  More  areas  of  the  bed 
were  gradually  opened  to  receive  increased  light 
penetration. 

The  first  visible  germination  of  Macrocystis 
sporophytes  occurred  during  August-September 
1969,  when  plants  approximately  1  to  3  cm  in 
height  appeared  on  or  near  the  survey  lines. 
Although  juvenile  plants  were  found  in  scattered 
locations  throughout  the  kelp  bed,  the  most  dense 
concentrations  appeared  around  the  shoreward 
(eastern)  end  of  the  transect,  from  about  100  m 
to  150  m  (Figure  1).  Only  two  adult  plants  re- 
mained within  this  2  x  50  m  band  transect  during 
the  summer  of  1969  (Figure  3);  therefore,  shading 
of  the  underlying  sea  floor  was  probably  minimal. 
Also,  this  shoreward  edge  of  the  bed  is  approxi- 
mately 5  m  shallower  than  the  seaward  portion 
and  there  may  have  been  more  ambient  light  in 
this  part  of  the  kelp  bed.  Juvenile  sporophyte 
density  ranged  from  0  to  32  plants/m^  within 
the  fixed  quadrats.  Macrocystis  recruitment  was 
especially  pronounced  in  the  100-  to  150-m  area 
on  the  transect.  For  this  reason  two  additional 
4-m2  quadrats  (no.  13  and  14)  were  added  in  this 
location  when  the  first  sporophytes  appeared  in 
August  1969.  In  September  1969,  a  total  of  387 
single-bladed  Macrocystis  were  counted  within 
the  fixed  quadrats  (Figure  6).  After  the  first 
month  only  156  plants  survived,  and  by  June 
1970  the  young  sporophj^te  population  was  re- 
duced to  only  5  survivors. 

Most  of  the  juvenile  plant  mortality  was  be- 
lieved to  be  caused  by  plant  entanglement,  fish 


grazing,  physical  scouring,  and/or  actual  burial 
of  the  plants  by  moving  sand.  Many  of  the  young 
sporophytes  were  damaged,  primarily  in  the 
region  of  the  apical  tip.  These  plants  were  in- 
spected for  invertebrate  grazers,  but  none  were 
found.  It  seems  likely  that  the  grazers  were 
positioned  in  the  water  column  because  most  of 
the  grazing  was  located  around  the  terminal  ends 
of  each  blade.  On  two  occasions  the  labrid  Oxy- 
julis  californica  and  the  embiotocid  Embiotoca 
jacksoni  were  seen  nibbling  on  juvenile  Macro- 
cystis. However,  because  of  marginal  underwater 
visibility  in  this  area,  it  was  generally  not 
possible  to  observe  the  grazing  activities  of  fishes 
directly. 

Physical  scouring  and  burial  is  another  cause 
of  juvenile  plant  mortality.  For  example,  one 
group  of  young  plants  (n  =  36)  growing  within  a 
shallow  depression  along  the  sea  floor  became 
completely  covered  with  sand  during  the  late  fall 
of  1969  and  never  reappeared.  The  stipes  of 
Macrocystis  are  quite  sensitive  to  being  enclosed 
or  covered  (North,  1971),  and  apparently  the 
young  plants  can  not  tolerate  burial  for  any 
length  of  time.  In  kelp  beds  such  as  Del  Mar, 
the  juvenile  Macrocystis  appear  to  be  highly 
vulnerable  to  this  physical  phenomenon. 

The  five  surviving  Macrocystis  plants  that  grew 
within  the  fixed  quadrats  continued  to  mature 
and  eventually  the  stipes  reached  the  sea  surface. 
One  plant  perished  in  September  1972;  however, 
the  other  four  were  still  present  within  the 
quadrats  in  December  1972,  3  yr  and  3  mo  after 
germination. 


Plant  Longevity 


IOOOt 
500- 


A 


100^ 

so: 


(I9S9) 


\ 


(1970) 


(1971) 
AGE    IN    MONTHS 


'1   ' 
28 


40 


Figure  6. — Survivorship  curve  of  individual  Macrocystis  which 
were  observed  to  recruit  in  September  1969. 


At  the  present  time  there  is  little  information 
available  in  the  literature  on  the  life  span  of 
Macrocystis  because  most  of  the  data  have  been 
collected  on  the  longevity  of  individual  fronds. 
The  maximum  life  span  of  a  Macrocystis  frond 
was  found  to  be  about  6  mo  (Brandt,  1923;  Cribb, 
1954;  North,  1961).  North  (1968)  reported  that 
3  yr  were  required  to  totally  eliminate  tagged 
mature  plants  within  a  stand  of  kelp  off  La  Jolla, 
Calif.  Most  of  the  plants  were  very  large  at  the 
beginning  of  the  study,  "so  they  probably  were  at 
least  5  years  of  age  when  they  vanished,  or  quite 
Hkely  older."  (North,  1968:224). 

Of  the  49  adult  Macrocystis  plants  originally 
marked  along  the  Del  Mar  transect  no  survivors 


676 


ROSENTHAL.  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GIANT  KELP 


persisted  in  August  1972.  The  oldest  surviving 
plant  lived  until  July  1972,  an  elapsed  time  of 
5  yr.  During  July  1967  this  plant  (number  1)  had 
18  living  stipes  (Table  2).  The  number  of  stipes 
growing  from  this  plant  reached  a  maximum  of 
34  during  May  1968;  thereafter,  the  number  of 
stipes  slowly  decreased.  Based  on  data  derived 
from  the  fixed  quadrats,  a  Macrocystis  plant 
growing  in  this  bed  with  18  stipes  is  at  least 

2  yr  old.  Therefore,  by  July  1972  plant  number 
1  was  probably  at  least  7  yr  of  age.  In  addition, 
three  other  tagged  plants  were  believed  to  be 
more  than  5  yr  of  age  at  the  time  of  their  dis- 
lodgement,  and  four  of  the  Macrocystis  that  grew 
up  within  the  fixed  quadrats  were  still  alive  after 

3  yr  and  3  mo  (Figure  6). 

Counting  the  number  of  living  stipes  on 
selected  Macrocystis  plants  does  not  necessarily 
indicate  the  age  of  a  kelp  bed  or  ages  of  plants 
within  the  bed.  For  example,  the  number  of  stipes 
found  on  individual  plants  at  Del  Mar  usually 
fluctuated  with  the  season  and  the  condition  of 
the  plant  (Table  2).  Most  of  the  adult  Macro- 
cystis displayed  a  period  during  which  each  plant 
maintained  a  maximum  number  of  stipes,  fol- 
lowed by  a  gradual  decline  in  the  total  number 
of  stipes.  At  some  point  in  the  life  of  a  Del  Mar 
Macrocystis  the  plant  no  longer  appears  to  be  able 
to  actively  support  a  peak  number  of  stipes. 

FAUNAL  ASSOCIATION 

Components  of  the  Epifauna 

Within  the  study  area  38  species  of  fishes  were 
sighted  (Table  3),  and  98  species  of  epibenthic 
invertebrates  have  been  identified  (Table  4). 
Many  of  the  macroinvertebrates  listed  in  the 
table  were  rarely  observed,  but  39  were  seen  on 
over  half  of  the  dives.  A  number  of  these  species 
were  numerically  uncommon  in  this  area,  while 
other  animals  were  infrequently  seen  because  of 
differences  in  activity  periods.  For  example,  the 
gastropod  Cypraea  spadicea  was  rarely  observed 
in  exposed  positions  during  daylight  hours,  but 
was  one  of  the  most  abundant  mollusks  during 
the  three  nocturnal  surveys  made  in  this  loca- 
tion. Of  the  38  species  of  fish  which  we  recorded, 
20  species  were  collected  in  1958  by  Quast  (1968a). 

Epibenthic  Invertebrates 

Invertebrates  considered  in  this  study  consisted 


Table  3. — A  list  of  fishes  observed  in  the  kelp  bed  by  Quast 
( 1968a)  and  during  this  study.  +  +  signifies  those  species  seen 
in  both  studies;  —  signifies  those  species  seen  in  our  study, 
but  not  reported  by  Quast  (1968a). 


Anisotremus  davidsoni  (Steindachner) 

Alherinops  alfinls  (Ayers) 

Brachylstius  Irenatus  Gill 

Chromis  punctipinnis  (Cooper) 

Coryphopterus  nicholsi  (Bean) 

Embiotoca  jacksoni  Agasslz 

Engraulis  mordax  GIrard 

Girella  nigricans  (Ayres) 

Gymnothorax  mordax  (Ayres) 

Halichoeres  semicinctus  (Ayres) 

Heterostichus  rostratus  GIrard 

Hyperprosopon  argenteum  Gibbons 

l-lypsurus  caryi  (Agasslz) 

Leiocottus  hirundo  GIrard 

Medialuna  calilorniensis  (Steindachner) 

Oxyjulis  californica  Giinther 

Oxylebius  pictus  Gill 

Paralabrax  clathratus  (GIrard) 

Paralabrax  maculatofasciatus  (Steindachner) 

Paralabrax  nebulifer  (GIrard) 

Paralichthys  californicus  (Ayres) 

Phanerodon  lurcatus  GIrard 

Pimelometopon  pulchrum  (Ayres) 

Pleuronichthys  coenosus  GIrard 

Pneumatophorus  diego  (Ayres) 

Rhacochilus  toxotes  Agasslz 

Rhacochilus  vacca  (GIrard) 

Scorpaena  guttata  Girard 

Scorpaenichthys  marmoratus  (Ayres) 

Sebastes  atrovirens  (Jordan  and  Gilbert) 

Sebastes  auriculatus  GIrard 

Sebastes  chrysomelas  (Jordan  and  Gilbert) 

Sebastes  rastrelliger  (Jordan  and  Gilbert) 

Sebastes  serriceps  (Jordan  and  Gilbert) 

Seriola  dorsalis  (Gill) 

Sphyraena  argentea  Girard 

Torpedo  californica  (Ayres) 

Urolophus  halleri  (Cooper) 


+  + 
+  + 
+  + 

+  + 
+  + 
+  + 


+  + 
+  + 
+  + 
+  + 
+  + 
+  + 


+  + 
+  + 
+  + 

+  + 
+  + 
+  + 


of  those  species  living  along  the  sea  floor  that 
could  be  counted  without  disturbing  the  under- 
lying substratum.  Visually  and  numerically  con- 
spicuous macroinvertebrates  were  selected  for 
study  after  data  were  collected  on  presence  of 
species  and  their  relative  abundance  in  1967. 
Of  the  98  invertebrate  species  seen,  only  14 
species  appeared  to  comprise  the  "characteristic" 
assemblage  of  epibenthic  invertebrates  in  this 
kelp  bed  (Table  5).  Characteristic  epifauna  were 
those  "species  that  were  always  seen  and  that 
dominated  the  habitat,  both  numerically  and  in 
terms  of  their  demand  and  impact  on  it."  (Fager, 
1968).  Table  5  lists  the  frequency  of  occurrence, 
numerical  density,  pattern  of  distribution,  and 
habit  of  each  of  the  14  species.  Because  of  the 
importance  of  natural  history  information  to  an 
eventual  synthesis  of  the  organization  of  the  kelp 
community,  the  following  observations  are  pre- 
sented for  the  14  species.  The  species  are  dis- 
cussed in  order  of  their  relative  abundance. 

The  most  abundant  and  frequently  encountered 
epifaunal  invertebrate  in  the  study  site  during 


677 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


Table  4. — Epifaunal  invertebrates  collected  within  the  perimeter  of  the  study  area. 


Porifera 

Leucilla  (=  Rhabdodermilla)  nuttingii  Urban 

Leucosolenia  sp. 

Tethya  aurantia  (Pallas) 

Verongia  thiona  de  Laubenfels 

Cliona  celata  Grant 
Cnidaria 

Aglaophenia  spp. 

Corynactis  californica  Carlgren 

Epiactis  prolifera  Verrill 

Pachycerianthus  sp. 

Tubulana  sp. 

Balanophyllia  elegans  Verrill 

Paracyathus  stearnsi  Verrill 

Lophogorgia  chilensis  (Verrill) 

Muricea  californica  (Aurivillius) 

Muricea  truticosa  (Verrill) 

Tealia  coriacea  (Cuvier) 

Harenactis  attenuata  Torrey 

Parazoanthus  lucificum  Cutress  and  Peguegnat 

Serlularia  sp. 

Plumularia  sp. 

Anthopleura  elegantissima  (Brandt) 
Annelida 

Diopatra  ornata  Moore 

Salmacina  Iribanchiata  (Moore) 

Phyllochaetopterus  prolifica  Potts 

Eudistylia  polymorpha  Johnson 

Dexiospira  spirillum  (Linnaeus) 

Spirobranchus  spinosus  Moore 
Arthropoda 

Paguristes  ulreyi  Schmitt 

Loxorhynchus  grandis  Stimpson 

Taliepus  nuttallii  Randall 

Synalpheus  spp. 

Alpheus  dentipes  Guerin 

Panulirus  interruptus  (Randall) 

Betaeus  harfordi  (Kingsley) 

Cancer  anthonyi  Rathbun 


Arthropoda — Continued 
Hippolysmata  californica  Stimpson 
Parapleustes  oculatus  Barnard 
Balanus  tintinnabulum  Pilsbry 
Balanus  pacificus  Pilsbry 
Pachycheles  rudis  Stimpson 
Idothea  resecata  (Stimpson) 
Acanthomysis  sculpta  (Tattersall) 
Lophopanopeus  frontalis  (Rathbun) 
Ampithoe  humeralis  Stimpson 

Mollusca 
Kelletia  kelletii  (Forbes) 
Mitra  idae  Melville 
Bursa  californica  (Hinds) 
Conus  californicus  Hinds 
Norrisia  norrisi  (Sowerby) 
Astraea  undosa  (Wood) 
Trivia  californiana  (Gray) 
t^egatliura  crenulata  Sowerby 
Cypraea  spadicea  Swainson 
Haliotis  rufescens  Swainson 
Haliotis  corrugata  Wood 
Shaskyus  (=  Jaton)  festivus  Hinds 
Simnia  vidlen  Sowerby 
fjlaxweilia  gemma  (Sowerby) 
Crassispira  semiinflata  (Grant  and  Gale) 
Acteon  punctocaelatus  (Carpenter) 
Mitrella  carinata  (Hinds) 
Crepidula  adunca  Sowerby 
Anisodoris  nobilis  (MacFarland) 
Glossodoris  californiensis  (Bergh) 
Dendrodoris  fulva  (MacFarland) 
Cadlina  llavomaculata  MacFarland 
Flabellinopsis  iodinea  (Cooper) 
Hinnites  multirugosus  (Gale) 
Platyodon  cancellatus  (Conrad) 
Parapholas  californica  (Conrad) 
Adula  (=  Botula)  falcata  (Gould) 
Litliophaga  plumula  (Hanley) 


Mollusca — Continued 
Leptopecten  latiauratus  (Conrad) 
Lima  fiemphilli  Henlem  and  Strong 
Saxidomus  nuttalli  Conrad 
Octopus  bimaculatus  Verrill 
Penitella  penita  (Conrad) 
Chaeceia  ovoidea  (Gould) 

Bryozoa 
Diaperoecia  californica  (d'Orbigny) 
Membranipora  membranacea  (Linnaeus) 
f/lembranipora  serrilamella  Osburn 
Bugula  neritina  (Linnaeus) 
Antropora  tincta  Osborn 
Thalamoporella  californica  (Levinson) 

Echmodermata 
Dermasterias  imbricata  (Grube) 
Astropecten  armatus  Gray 
Astrometis  sertulifera  (Xantus) 
Henricia  leviuscula  (Stimpson) 
Patiria  miniata  (Brandt) 
Pisaster  brevispinus  (Stimpson) 
Pisaster  giganteus  (Stimpson) 
Ophioplocus  esmarki  Lyman 
Opiiiothrix  spiculata  Le  Conte 
Parastichopus  parvimensis  (Clark) 
Eupentacta  quinquesemita  (Selenka) 
Amphipholis  sp. 

Ophioderma  panamensis  Lutken 
Ophiopteris  papulosa  (Lyman) 
Strongylocentrotus  franciscanus 

(A.  Agassiz) 
Strongylocentrotus  purpuratus 
(Stimpson) 

Chordata 
Styela  montereyensis  (Dall) 
Polyclinum  planum  (Ritter  and  Forsyth) 
Pyura  tiaustor  (Stimpson) 
Eudistoma  diaptianes  Ritter  and  Forsyth 


Table  5. — The  conspicuous  macroinvertebrates  in  the  Del  Mar  kelp  bed. 


Species 


Distribution 

Habit 

Frequency' 

Density^ 

pattern 

Probability" 

Sessile 

87/96 

12.95 

Aggregated 

P<0.001 

Sessile 

79/96 

340 

Aggregated 

P<0.001 

Sessile 

67/96 

253 

Aggregated 

P<0.001 

Motile 

35/96 

062 

Aggregated 

0.001<P<0.01 

Sessile 

22/96 

0.47 

Aggregated 

P<0.001 

Motile 

9/96 

0.39 

Aggregated 

P<0.001 

Sessile 

18/96 

0.27 

Aggregated 

0  05>P>0.02 

Motile 

2/96 

0.16 

Aggregated 

P<0.001 

Sessile 

11/96 

0.16 

Aggregated 

0.001<P<0.01 

Sessile 

10/96 

0.14 

Random^ 

0.05<P<0.10 

Motile 

12/96 

0.13 

Aggregated 

0.05>P>0.025 

Sessile 

4/96 

0.04 

Random^ 

0.70>P>0.50 

Motile 

2/96 

0.03 

Aggregated 

0.001<P<.01 

Motile 

3/96 

0,01 

Random^ 

0.30<P<0.50 

Diopatra  ornata 
Styela  montereyensis 
l^uricea  californica 
Kelletia  kelletii 
Parapholas  californica 
Paguristes  ulreyi 
Muricea  fruticosa 
Strongylocentrotus  franciscanus 
Tealia  coriacea 
Tethya  aurantia 
Astrometis  sertulifera 
Lophogorgia  chilensis 
Strongylocentrotus  purpuratus 
Pisaster  giganteus 


'  Occurrence  in  96  l-m^  quadrats. 
2  Per  m2. 


^  n  is  small  —  index  of  dispersion  inadequate. 
"  Probability  of  a  random  distribution. 


August  1972  was  the  tubicolous  polychaete 
Diopatra  ornata  (Table  5).  Diopatra  was  seen 
along  the  transect  during  the  early  years  of 
the  study  (1967-68)  however,  it  was  not  until  the 
summer  of  1971  that  the  species  was  considered 
to  be  common.  During  August  1972,  Diopatra 
occurred  in  all  12  of  the  fixed  quadrats,  and 
quadrat  number  7,  which  contained  only  a  few 


individuals  in  1968,  had  many  clumps  of  Dio- 
patra tubes.  The  tubes  covered  an  estimated 
25-30'7f  of  the  total  area  (4  m^)  in  the  quadrat. 
Unpublished  work  of  Ray  Emerson  (pers.  com- 
mun.)"*  demonstrates  that  approximately  90% 


''Emerson,  R.  In  preparation.  Reproductive  biology  and  popu- 
lation dynamics  of  the  polychaete  Diopatra  ornata.  Ph.D. 
thesis,  Univ.  of  Southern  Calif. 


678 


ROSENTHAL.  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GIANT  KELP 


of  Diopatra  tubes  represent  living  worms. 
Emerson  considers  Diopatra  a  selective  but 
omnivorous  deposit  feeder.  We  have  seen  frag- 
ments of  Macrocystis  attached  to  its  tube  ap- 
parently serving  a  dual  function  of  camouflage 
and  food  reserve.  The  gastropod  Kelletia  kelletii 
and  the  sea  star  Pisaster  giganteus  were  the  only 
invertebrates  seen  eating  Diopatra  in  this  area. 
Kelletia  was  frequently  observed  penetrating 
either  the  sides  or  opening  of  the  Diopatra 
tube  with  an  extensible  proboscis,  and  Pisaster 
was  found  with  its  stomach  everted  into  the 
opening  of  the  tube. 

The  solitary  ascidian  Styela  montereyensis 
usually  grows  attached  to  rocks,  shells,  and 
Macrocystis  holdfasts.  Styela  was  found  to  live 
approximately  12  to  20  mo;  however,  one  indi- 
vidual lived  for  more  than  30  mo.  Usually  there 
is  a  heavy  recruitment  in  the  late  summer  and 
heavy  mortality  late  the  next  spring  (Figure  7). 
The  fall  Styela  population  remained  reasonably 
constant  over  4  yr  (1968-72),  despite  the  fluctua- 
tions in  the  population  during  a  calendar  year. 
A  major  cause  of  mortality  in  the  fixed  quadrats 
was  sediment  movement  and  strong  water 
motion  that  either  buried  or  detached  the  ascid- 
ians  from  the  substratum.  Three  predators  of 
Styela  were  observed:  Pisaster  giganteus  and 
Kelletia  kelletii  frequently  were  seen  feeding  on 
Styela.  On  five  occasions  these  two  species  were 
encountered  feeding  simultaneously  on  the  same 
Styela  (Rosenthal,  1971).  In  addition,  we  found 
the  sea  star  Astrometis  sertulifera  eating  Styela 
in  this  location. 

The  gorgonian  Muricea  californica  was  the  most 


visually  conspicuous  and  the  third  most  abundant 
(2.53/m2)  macroinvertebrate  in  the  assemblage 
(Table  5).  It  is  a  colonial  animal  usually  found 
growing  erect  from  solid  substratum.  Muricea 
californica  recruits  become  visible  to  the  unaided 
eye  when  the  colony  is  approximately  1  cm  high; 
at  this  stage  they  appear  to  be  at  least  several 
months  old  (Grigg,  1970).  A  decline  in  the  M. 
californica  population  was  recorded  during  the 
time  period  of  this  study.  A  total  of  192  indi- 
vidual colonies  were  living  within  the  48-m^ 
area  in  September  1968,  but  by  December  1972 
the  population  had  declined  to  119  colonies. 
During  this  time  interval  there  were  147  mor- 
talities and  74  recruitments  recorded  in  the 
fixed  quadrats  (Figure  8).  Grigg  (1970)  found  a 
similar  decrease  in  the  M.  californica  population 
off  Del  Mar  in  which  he  recorded  a  relatively 
heavy  mortality  with  no  replacement  or  recruit- 
ment during  a  1-yr  period  of  observation  in  1968. 
There  are  several  physical  factors  contributing 
to  the  mortality  of  M.  californica  in  this  area. 
Scouring,  holdfast  detachment,  and  burial  by 
sand  are  important  examples.  Grigg  (1970)  felt 
that  two-thirds  of  the  mortality  recorded  at  Del 
Mar  during  1968  resulted  from  physical  abrasion 
by  suspended  particles,  and  one-third  from  colony 
detachment.  Occasionally,  M.  californica  growing 
either  between  the  holdfasts  of  adult  Macrocj's^is 
or  in  close  proximity  to  an  established  plant 
died  when  the  plant  became  detached  and  drifted 
away.  In  such  cases  the  M.  californica  were 
entangled  and  pulled  from  the  sea  floor  or  were 


5     80 


Figure  7. — Styela  montereyensis  in  the  12  fixed  quadrats 

(48  m^). 


Figure  8. — Muricea  californica  in  the  12  fixed  quadrats 

(48  m2). 


679 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


killed  by  increased  scouring  and  sediment  burial 
in  the  absence  of  the  large  Macrocystis  holdfast. 

The  Kellet's  v^f\\e\^,  Kelletia  kelletii,  is  usually 
found  on  rocky  substrata  or  in  sand  areas  adja- 
cent to  more  solid  substratum.  During  August 
1972  we  observed  a  mean  density  of  0.62/m2  in 
the  combined  samples  (Table  5).  On  other  occa- 
sions the  density  along  the  transect  ranged  from 
0.42  to  0.75/m2.  Movement  off  Del  Mar  is  appar- 
ently not  random,  for  individual  snails  were 
often  found  in  aggregated  patterns  of  distribu- 
tion. Such  aggregations  may  reflect  feeding  and 
reproductive  behavior.  For  example,  during  the 
height  of  the  April-May  spawning  period  (Rosen- 
thal, 1970),  mixed  aggregations  of  both  male  and 
female  Kelletia  were  repeatedly  encountered.  A 
few  of  these  spawning  aggregations  contained 
between  200  and  300  individuals;  however,  the 
average  spawning  cluster  was  about  15  to  20 
snails. 

Kelletia  is  basically  a  carnivorous  scavenger; 
however  it  does  feed  on  live  sedentary  poly- 
chaetes  and  solitary  ascidians.  It  has  been 
observed  eating  22  species  of  invertebrates  and  3 
species  of  dead  or  moribund  fish  in  the  subtidal 
waters  off  San  Diego  County  (Rosenthal,  1971). 

Predators  of  Kelletia  include  the  asteroids 
Pisaster  giganteus,  P.  brevispinus,  and  Astrometis 
sertulifera,  and  the  cephalopod  Octopz/s  bimacula- 
tus  (Rosenthal,  1971).  Few  other  predators  are 
known,  although  Limbaugh  (1955)  reported  find- 
ing juvenile  Kelletia  in  the  stomachs  of  pile 
perch,  Rhacochilus  vacca. 

Parapholas  californica ,  a  bivalve  clam,  was  the 
most  conspicuous  terrigenous  borer  off  Del  Mar. 
It  primarily  bores  into  sedimentary  rocks  con- 
sisting of  consolidated  mudstones  and  siltstones. 
Within  the  12  fixed  quadrats  the  Parapholas 
population  density  was  0.54/m2.  During  the  moni- 
toring period  there  were  two  recruitments  and 
three  mortalities  recorded  in  these  quadrats. 
Pisaster  giganteus  and  P.  brevispinus  occasionally 
prey  upon  Parapholas  in  this  location,  as  they 
do  in  other  nearshore  areas  off  San  Diego  County 
(Rosenthal,  1971).  Predation  by  sea  stars  often 
has  the  additional  effect  of  breaking  the  sub- 
stratum surrounding  the  clam. 

Paguristes  ulreyi  is  a  relatively  large,  pubescent 
hermit  crab.  Almost  all  were  found  in  discarded 
Kelletia  shells;  however,  a  few  crabs  were  also 
seen  in  the  shells  of  Bursa  californica.  Paguristes 
was  seen  throughout  the  study  area,  although  its 


most  frequent  habitat  appeared  to  be  the  silt- 
stone  ledges  and  consolidated  sedimentary 
mounds  located  towards  the  seaward  edge  of  the 
bed.  Each  year  large  aggregations  (to  220/m2) 
of  Paguristes  were  observed  in  this  area  from 
August  through  October,  the  crabs  often  being 
stacked  several  layers  thick.  Paguristes  is  a 
scavenger  (Pequegnat,  1964),  a  conclusion  sup- 
ported by  our  observations  of  it  feeding  upon 
dead  invertebrates  and  pieces  of  detached  algae. 
Octopus  bimaculatus  was  the  only  known  preda- 
tor of  Paguristes  in  this  location.  On  two  occa- 
sions, O.  bimaculatus  was  observed  moving  shells 
inhabited  by  Paguristes  and  one  individual  was 
encountered  while  feeding  on  a  Paguristes. 

Muricea  fruticosa  is  similar  in  appearance  to 
M.  californica,  but  is  usually  bushier  with  a 
rusty-brown  coenenchymal  layer  and  white 
polyps.  Both  species  of  Muricea  were  observed 
growing  on  similar  or  identical  substrata.  The 
mean  of  0.27  colonies/m^  in  this  area  (Table  5) 
is  in  agreement  with  the  estimate  of  0.25  colo- 
nies/m^  of  Grigg  (1970).  The  M.  fruticosa  popula- 
tion was  almost  balanced  with  respect  to  mor- 
tality and  recruitment.  Fourteen  M.  fruticosa 
were  recorded  in  the  fixed  quadrats  during  Sep- 
tember 1968,  and  13  individual  colonies  were 
found  in  these  same  quadrats  during  December 
1972,  but  during  this  period  17  mortalities  and 
16  recruitments  were  noted.  No  predators  of 
M.  fruticosa  were  observed  in  the  study  area, 
and  causes  of  mortality  are  believed  to  be  similar 
to  those  reported  for  M.  californica. 

Tealia  coriacea  is  a  solitary,  medium  sized 
(4  to  7  cm)  sea  anemone.  It  attaches  to  solid 
substratum  and  usually  the  column  is  partially 
buried  or  enclosed  by  sediment.  Two  mortalities 
and  three  recruitments  were  recorded  in  the  fixed 
quadrats.  One  Tealia  was  eaten  by  a  leather 
star,  Dermasterias  imbricata,  and  the  other  died 
from  an  unknown  cause.  Dermasterias  has  been 
reported  to  eat  Tealia  spp.  and  other  sea  anemones 
in  the  Pacific  Northwest  (Mauzey,  Birkeland, 
and  Dayton,  1968),  and  may  on  occasion  be  an 
important  source  of  mortality  in  California  kelp 
beds. 

The  largest  and  most  conspicuous  sea  urchin 
seen  off  Del  Mar  was  Strongylocentrotus  fran- 
ciscanus.  Individual  test  diameters  ranged  from 
5.5  to  18.2  cm.  Most  of  these  animals  inhabited 
the  sedimentary  mounds  and  boulders  located 
towards  the  seaward  edges  of  the  kelp  stand. 


680 


ROSENTHAL.  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GL'SiNT  KELP 


The  trophic  role  displayed  by  S.  franciscanus 
in  southern  California  kelp  communities  has  been 
adequately  described  (Limbaugh,  1955;  Leighton, 
1971;  North,  1971).  Strongylocentrotus  francis- 
canus is  important  because  it  often  overexploits 
its  algal  resources  in  areas  of  high  sea  urchin 
density.  Despite  the  fact  that  this  species  is 
highly  motile,  foraging  movements  on  attached 
kelps  were  not  witnessed  in  this  kelp  bed.  The 
S.  franciscanus  population  appeared  to  be  sus- 
tained by  snagging  detached  pieces  of  macro- 
algae  that  drifted  along  the  sea  floor.  The  only 
predator  we  observed  feeding  upon  live  S.  fran- 
ciscanus in  this  area  was  the  labrid  Pimelome- 
topon  pulchrum. 

Tethya  aurantia,  a  hemispherical  shaped 
sponge,  attains  a  circumference  of  at  least  25  cm 
and  is  usually  found  attached  to  rocks  and  con- 
solidated sediments.  There  were  two  mortalities 
and  three  recruitments  recorded  in  the  fixed 
quadrats.  One  mortality  was  attributed  to  sedi- 
ment burial,  and  Dermasterias  imbricata  was 
observed  feeding  on  Tethya  in  the  vicinity  of  the 
transect.  Rosenthal  and  Chess  (1972)  reported 
Dermasterias  to  be  a  predator  of  Tethya  in  the 
sublittoral  zone  off  Pt.  Loma,  Calif. 

Astrometis  sertulifera  was  the  most  abundant 
(O.lS/m^)  sea  star  encountered  off  Del  Mar  (Table 
5).  This  estimate  of  abundance  is  probably  con- 
servative because  Astrometis  is  relatively  small 
(4  to  6  cm  in  radius)  and  individuals  are  some- 
what cryptic  in  habit.  The  most  frequent  habitat 
of  Astrometis  off  Del  Mar  was  the  undersides 
of  rocks  and  the  interstices  of  Macrocystis  hold- 
fasts. It  appears  to  be  ideally  suited  for  preying 
upon  the  assemblage  of  organisms  found  associ- 
ated with  the  holdfasts  of  Macrocystis.  Astro- 
metis  was  observed  eating  juvenile  Kelletia  kel- 
letii  (gastropod),  Conus  californica  (gastropod), 
Mitrella  sp.  (gastropod),  Styela  montereyensis 
(ascidian)  and  juvenile  Strongylocentrotus  pur- 
puratus  (echinoid)  in  this  study.  Leighton  (1971) 
mentioned  that  Astrometis  feeds  heavily  on  juve- 
nile sea  urchins  off  southern  California.  No  pred- 
ators of  Astrometis  were  observed  in  the  study 
area;  however,  Rosenthal  and  Chess  (1972)  found 
that  4%  of  437  feeding  Dermasterias  were  eating 
Astrometis. 

The  gorgonian  Lophogorgia  chilensis  is  one  of 
the  most  exquisite  macroinvertebrates  in  this 
region.  It  usually  grows  in  an  upright  manner 
attached  to  solid  substratum.  A  few  small  colonies 


were  found  growing  attached  to  Muricea  cali- 
fornica. Lophogorgia  was  not  nearly  as  abundant 
as  M.  californica  or  M.  fruticosa;  the  mean  den- 
sity during  August  1972  was  0.04/m2  (Table  5). 
There  was  one  mortality  and  one  recruitment 
recorded  in  the  48-m2  quadrat  area  during  1968- 
72.  No  predators  of  Lophogorgia  were  observed 
in  this  kelp  bed  and  causes  of  colony  mortality 
are  probably  similar  to  those  of  Muricea 
spp. 

The  purple  sea  urchin,  Strongylocentrotus 
purpuratus ,  ranged  in  size  from  15  to  68  mm,  with 
a  median  size  of  42  mm  (n  =  82).  In  contrast 
to  the  low  density  in  this  location  (O.OS/m^),  other 
kelp  stands  off  southern  California  have  been 
found  to  contain  as  many  as  77  S.  purpuratus /yd^ 
(Leighton,  1971).  The  most  frequent  habitat  of 
S.  purpuratus  off  Del  Mar  was  the  undersides 
of  rocks;  however,  individuals  were  also  found 
on  consolidated  mounds  and  siltstone  ledges.  A 
few  individuals  were  noted  within  the  holdfasts 
of  adult  Macrocystis;  however,  we  believe  the 
incidence  of  holdfast  infestation  is  low  in  com- 
parison to  other  San  Diego  County  kelp  beds. 
Strongylocentrotus  purpuratus  is  a  herbivore 
well  known  to  overexploit  its  algal  resources 
(Leighton,  1971;  North,  1971).  In  the  Del  Mar 
area  most  of  the  purple  sea  urchins  were  observed 
eating  detritus  and  drift  algae;  rarely  were  the 
attached  macroalgae  grazed  upon. 

Dermasterias  imbricata  (Rosenthal  and  Chess, 
1972),  Astrometis  sertulifera  (Leighton,  1971; 
pers.  observation),  and  Pi?nelometopon  pulchrum 
(Limbaugh,  1955;  pers.  observation)  are  three 
known  S.  purpuratus  predators  which  inhabited 
the  study  area. 

Pisaster  giganteus  is  one  of  the  most  abundant 
and  widely  distributed  sea  stars  found  off  southern 
California.  Although  visually  conspicuous  at  Del 
Mar,  Pisaster  was  not  nearly  as  abundant 
(O.Ol/m^)  as  it  was  in  some  of  the  other  kelp  beds 
(i.e.  Pt.  Loma,  La  Jolla,  Catalina  Island)  we 
surveyed  between  1968  and  1972.  The  diet  of 
Pisaster  has  been  partially  quantified  (Rosenthal, 
1971).  Although  it  was  occasionally  observed 
scavenging,  it  primarily  feeds  on  live  animals 
which,  in  this  area,  include  Astraea  undosa 
(gastropod),  Conus  californicus  (gastropod),  Kel- 
letia kelletii  (gastropod),  Botula  falcata  (pelecy- 
pod),  Hinnites  multirugosus  (pelecypod),  Litho- 
phaga  plumula  (pelecypod),  Parapholas  cali- 
fornica (pelecypod), Pennitella penita  (pelecypod). 


681 


Diopatra  ornata  (polychaete),  and  Styela  mon- 
tereyensis  (ascidian). 

DISCUSSION 

During  the  years  of  this  study  (1967-73)  there 
was  a  pronounced  oscillation  in  the  number  of 
adult  Macrocystis  in  the  study  area.  Partially 
concurrent  with  these  in  situ  observations  has 
been  a  fluctuation  in  the  amount  of  kelp  har- 
vested in  this  area  since  1940  (Figure  4).  The 
disappearance  or  detachment  of  adult  Macroc^'s^ts 
along  the  transect  was  usually  related  to  physical 
stress  from  an  increase  in  water  motion  and/or 
entanglement  with  detached,  drifting  kelp  plants. 
Storms,  particularly  during  the  months  of  October 
through  April,  seem  to  be  the  major  cause  of 
plant  mortality  in  this  bed.  For  example,  during 
a  2-mo  period  (December-February  1973),  46% 
of  the  adult  Macrocystis  were  lost  along  the  tran- 
sect (Figure  2).  There  is  historical  evidence  of 
severe  storm  mortality  as  Brandt  (1923)  reported 
the  La  Jolla  and  Pt.  Loma  kelp  beds  were  severely 
diminished  in  area  by  storms  in  1888-89  and  1915. 
Doty  (1971)  also  reports  that  storms  have  impor- 
tant effects  on  the  standing  crop  of  algae 
in  Hawaii. 

Another  cause  of  plant  attrition  was  commer- 
cial harvesting.  Four  tagged  Macrocystis  repre- 
senting 21%  of  the  marked  plants  in  the  study 
area  were  detached  from  the  substratum  during 
a  kelp  harvesting  operation  in  January  1969. 
However,  this  rate  of  mortality  could  be  higher 
than  the  harvesting  attrition  rate  in  other  beds 
because  of  the  relatively  unstable  substratum  of 
the  north  San  Diego  County  kelp  beds.  Certainly 
a  preharvest  consideration  should  be  given  to  the 
actual  cutting  technique  best  suited  to  each 
individual  stand  of  kelp. 

The  vulnerability  of  adult  Macrocystis  to  en- 
tanglement and  detachment  would  appear  to 
result  in  the  development  of  a  multiage  class 
kelp  bed  in  which  there  are  patches  of  cohorts 
or  plants  of  the  same  age  class.  That  is,  the 
drifting  and  entanglement  is  rather  localized  and 
results  in  distinct  patches  of  the  canopy  being 
cleared.  Thus,  germination  and  recruitment  take 
place  not  only  around  the  periphery  of  the  bed, 
but  also  within  central  portions.  This  spatial 
heterogeneity  of  different  aged  Macrocystis  may 
add  stability  to  a  particular  kelp  bed  as  mature, 
perhaps  more  secure  plants  are  growing  adjacent 


FISHERY  BULLETIN:  VOL.  72.  NO   3 

to  both  young  and  senile  plants.  During  February 
1972,  it  was  estimated  that  the  Del  Mar  bed  was 
composed  of  at  least  four  age  classes  of  Macro- 
cystis. 

The  paucity  of  juvenile  Macrocystis  sporo- 
phjd;es  during  the  first  23  mo  of  the  study  was 
believed  to  be  related  to  the  establishment  of  a 
well-developed  adult  canopy,  turbidity  of  the 
water  column,  and  the  relatively  unstable  sub- 
stratum. These  factors  are  interrelated  since  they 
contribute  to  the  absorption  and  scattering  of  the 
available  light  necessary  for  germination  and 
sporophyte  development.  A  layer  of  fine  sediment 
(silt)  remained  along  the  bottom  during  the  entire 
study  period,  and  this  silt  was  usually  suspended 
by  increased  water  motion.  The  Los  Penasquitos 
salt  marsh  located  approximately  2  km  south- 
east of  the  study  site  could  be  a  source  of  much 
silt.  Whatever  the  source,  this  sediment  layer 
seems  to  be  a  general  feature  of  most  north 
San  Diego  County  kelp  beds,  and  as  it  contrib- 
utes to  a  reduction  in  the  submarine  light  and 
physically  scours  the  substratum,  it  probably  has 
a  strong  negative  effect  on  Macrocystis  recruit- 
ment. Despite  these  limiting  factors,  young 
Macrocystis  sporophytes  appeared  in  the  Del  Mar 
bed  during  August  1969.  The  reduction  of  the  kelp 
canopy  from  natural  attrition  and  harvesting 
probably  paved  the  way  for  the  late  summer 
germination  and  recruitment.  Following  recruit- 
ment of  these  young  plants  there  continued  to  be 
a  strong  attrition  as  only  4  of  the  original  387 
sporophytes  growing  within  the  fixed  quadrats 
survived  the  3.25  yr  (to  December  1972). 

Many  of  the  same  physical  parameters  that 
influence  the  Macrocystis  population  at  Del  Mar 
appear  to  effect  the  distribution,  frequency  of 
occurrence,  and  abundance  of  the  fauna.  Quast 
( 1968a)  determined  from  three  flsh  collection  sites 
off  Del  Mar,  Bathtub  Rock  (San  Diego  County), 
and  Papalote  Bay,  Baja  California  that  Del  Mar 
was  lowest  in  fish  species  diversity,  despite  the 
fact  that  it  covered  the  greatest  area.  He  con- 
cluded that  the  differences  between  the  three 
areas  were  due  to  differences  in  the  amount  of 
shifting  sediment  and  the  durability  of  the  rocky 
substratum.  Furthermore,  he  found  a  positive 
correlation  between  the  degree  of  bottom  relief 
and  the  abundance  and  species  diversity  of  fish. 

The  epibenthic  invertebrates  are  similarily 
affected  by  the  physical  characteristics  of  the 
habitat.  The  aggregated  distribution  patterns  of 


682 


ROSENTHAL.  CLARKE,  and  DAYTON:  ECOLOGY  OF  A  STAND  OF  GLANT  KELP 


such  sessile  species  as  Muricea  californica,  Styela 
montereyensis ,  and  Parapholas  californica  (Table 
5)  probably  reflect  physical  heterogeneity  within 
the  Del  Mar  study  site.  The  aggregated  distribu- 
tion patterns  of  motile  species  (Kelletia  kelletii, 
Paguristes  ulreyi,  and  Strongylocentrotus  francis- 
canus)  are  probably  related  to  aspects  of  their 
foraging  and/or  reproductive  behavior  as  well  as 
to  the  physical  heterogeneity  of  the  habitat. 

The  species  composition  of  the  epifauna  was 
reasonably  constant,  however,  the  abundances  of 
some  species  has  undergone  change  during  the 
5.7  yr.  The  most  pronounced  population  change 
occurred  with  the  tube  dwelling  polychaete  Dio- 
patra  ornata.  Although  this  species  was  recorded 
within  the  study  area  during  1967-68,  it  was 
somewhat  rare  and  individuals  were  not  noted 
within  the  12  fixed  quadrats  until  1971.  By 
August  1972  however,  Diopatra  was  the  most 
abundant  and  most  frequently  encountered 
macroinvertebrate  in  the  Del  Mar  kelp  bed  (Table 
5).  Reasons  for  the  Diopatra  population  increase 
are  unknown  at  this  time. 

During  the  same  time  period  the  Muricea 
californica  population  decreased  from  192  to  119 
colonies  during  4.25  yr  (Figure  8),  despite  con- 
siderable recruitment  of  small  identifiable 
colonies.  In  contrast  to  the  decline  in  the  M. 
californica  population  at  Del  Mar,  Grigg  (1970) 
studied  a  population  of  M.  californica  off  La 
Jolla  which  was  relatively  stable  with  respect  to 
mortality  and  recruitment.  Differences  between 
these  two  sea  fan  populations  were  believed  to 
be  due  to  the  physical  characteristics  of  each 
habitat  (Grigg,  1970). 

The  Styela  montereyensis  population  had  a 
reasonably  predictable  seasonal  oscillation, 
usually  reaching  a  peak  during  the  late  summer 
and  fall  (Figure  7).  The  maximum  annual  popu- 
lation ranged  from  81  to  153  individuals.  The 
average  life  span  of  S.  montereyensis  is  shorter 
(12  to  20  mo)  than  some  of  the  other  members 
of  this  community  such  as  Muricea  californica, 
which  is  thought  to  reach  at  least  50  yr  of  age 
(Grigg,  1970).  Three  species:  Pisaster  giganteus, 
Astrometis  sertulifera,  and  Kelletia  kelletii  feed 
upon  Styela  in  this  area;  however,  natural  preda- 
tion  is  slight  in  proportion  to  the  heavy  mor- 
tality caused  by  strong  water  motion  and  sedi- 
ment burial.  Other  Del  Mar  invertebrate  popu- 
lations were  somewhat  more  constant.  For 
example,  the  Muricea  fruticosa  population  re- 


mained relatively  constant  over  the  monitoring 
period  (changing  from  a  total  of  14  to  13), 
despite  17  mortalities  and  16  recruitments  re- 
corded in  the  fixed  quadrats. 

There  is  sufficient  evidence  of  trophic  inter- 
action to  present  a  very  qualitative  food  web 
(Figure  9).  Two  of  the  predators,  Pisaster  gigan- 
teus and  Astrometis  sertulifera  feed  upon  living 
members  of  the  community;  the  diet  of  the  former 
species  is  probably  better  understood  (Rosenthal, 
1971),  because  it  is  seen  more  often.  While  both 
asteroid  species  attack  a  variety  of  prey,  mollusks 
appear  to  be  the  major  food  items  off  Del  Mar. 
In  addition,  Dermasterias  imbricata,  Pisaster 
brevispinus,  Octopus  bimaculatus,  and  Pimelo- 
metopon  pulchrum  have  been  added  to  this  food 
web.  We  have  only  qualitative  data  on  the  diets 
of  these  four  species.  Two  other  carnivores, 
Kelletia  kelletii  and  Paguristes  ulreyi,  generally 
feed  upon  moribund  or  decaying  animal  matter, 
but  they  occasionally  eat  live  organisms  (Rosen- 
thal, 1971).  The  rest  of  the  generalized  food  web 
represents  lower  trophic  levels. 

The  biotic  components  and  temporal  popula- 
tion changes  recorded  off  Del  Mar  should  not  be 
interpreted  as  "characteristic"  of  all  southern 
California  kelp  beds.  Although  the  Del  Mar  bed 
closely  resembles  kelp  stands  off  northern  San 
Diego  and  Orange  Counties,  it  appears  to  be  dif- 
ferent from  those  at  La  Jolla  and  Pt.  Loma. 


FILTER       I  Slytlo 
FEEDERS  I  "WlJ'Wi'S 


PRODUCERS-    I    Mocrocriii 
MACRO  ALGAE  I    W"'"° 


Figure  9. — A  qualitative  food  web  that  depicts  trophic  inter- 
action in  the  Del  Mar  kelp  bed. 


ACKNOWLEDGMENTS 

The  authors  are  indebted  to  B.  Allen,  R.  Bower, 
J.  Chess,  R.  Grigg,  R.  Fritzsche,  E.  Habecker, 
T.  Rosenthal,  and  T.  Tutschulte  for  their  diving 
help  in  this  project.  R.  Grigg  provided  many 


683 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


helpful  suggestions  on  underwater  sampling. 
C.  Barilotti,  J.  Chess,  V.  Currie,  L.  Dayton, 
R.  Fay,  R.  McPeak,  M.  Neushul,  and  W.  North 
helped  in  the  preparation  of  this  manuscript. 
Special  thanks  go  to  R.  Gaul  for  his  backing 
of  this  project.  This  study  was  initially  (1967-70) 
supported  by  the  Westinghouse  Ocean  Research 
Laboratory  and  is  currently  (1971-73)  supported 
by  the  University  of  California  Sea  Grant  GH- 
112  and  an  NSF  grant  #  GA-30877. 

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1954.  Macrocystis  pyrifera  (L.)  Ag.  in  Tasmanian  waters. 
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Dawson,  E.  Y.,  M.  Neushul,  and  R.  D.  Wildman. 

1960.    Seaweeds  associated  with  kelp  beds  along  southern 
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1968.     A  sand-bottom  epifaunal  community  of  inverte- 
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1964.    Quantitative  plant  ecology.    2d.  ed.    Butterworths, 
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QUAST,  J.  C. 

1968a.  Estimates  of  the  populations  and  the  standing  crop 
of  fishes.    Calif.  Dep.  Fish  Game,  Fish  Bull.  139:57-79. 

1968b.  Observations  on  the  food  of  the  kelp-bed  fishes. 
Calif.  Dep.  Fish  Game,  Fish  Bull.  139:109-142. 

1971.     Fish  fauna  of  the  rocky  inshore  zone.    In  W.  J. 
North  (editor).  The  biology  of  giant  kelp  beds  (Macro- 
cystis) in  California.  Nova  Hedwigia  Z.  Kryptogamenkd. 
Suppl.  32,  p.  481-507. 
Rosenthal,  R.  J. 

1970.  Observations  on  the  reproductive  biology  of  the 
Kellet's  whelk,  Kelletia  kelletii  (Gastropoda:  Nep- 
tuneidae).    Veliger  12:319-324. 

1971.  Trophic  interaction  between  the  sea  star  Pisaster 
giganteus  and  the  gastropod  Kelletia  kelletii.  Fish. 
Bull.,  U.S.  69:669-679. 

Rosenthal,  R.  J.,  and  J.  R.  Chess. 

1972.  A  predator-prey  relationship  between  the  leather 
star,  Dermasterias  imbricata  and  the  purple  urchin, 
Strongylocentrotus  purpuratus.  Fish.  Bull.,  U.S. 
70:205-216. 

ScRipps  Institution  of  Oceanography. 

1968.  Surface  water  temperatures  at  shore  stations. 
United  States  West  Coast.  1967,    SIO  Ref.  68-22,  26  p. 

1968.  Surface  water  temperatures  at  shore  stations 
(United  States  West  Coast).    SIO  Ref  69-14. 

1969.  Surface  water  temperatures  at  shore  stations 
(United  States  West  Coast).    SIO  Ref.  70-26. 

1970.  Surface  water  temperatures  at  shore  stations 
(United  States  West  Coast).    SIO  Ref  71-23. 

1971.  Surface  water  temperatures  at  shore  stations 
(United  States  West  Coast).    SIO  Ref.  72-62. 

ZoBell,  C.  E. 

1971.  Drift  seaweeds  on  San  Diego  County  ueaches.  In 
W.  J.  North  (editor).  The  biology  of  giant  kelp  beds 
(Macrocystis)  in  California.  Nova  Hedwigia  Z.  Krypto- 
gamenkd. Suppl.  32,  p.  269-314. 


684 


THE  SWIMMING  CRABS  OF  THE  GENUS  CALLINECTES 

(DECAPODA:  PORTUNIDAE) 


Austin  B.  Williams^ 


ABSTRACT 


The  genus  Callinectes  and  its  14  species  are  reevaluated.  Keys  to  identification,  descriptions  of  species, 
ranges  of  variation  for  selected  characters,  larval  distribution,  and  the  fossil  record  as  well  as  problems 
in  identification  are  discussed.  Confined  almost  exclusively  to  shallow  coastal  waters,  the  genus  has 
apparently  radiated  both  northward  and  southward  from  a  center  in  the  Atlantic  Neotropical  coastal 
region  as  well  as  into  the  eastern  tropical  Pacific  through  continuous  connections  prior  to  elevation  of 
the  Panamanian  isthmus  in  the  Pliocene  epoch  and  along  tropical  West  Africa.  Eleven  species  occur  in 
the  Atlantic,  three  in  the  Pacific.  Callinectes  marginatus  spans  the  eastern  and  western  tropical 
Atlantic.  Callinectes  sapidus.  with  the  broadest  latitudinal  distribution  among  all  the  species  (Nova 
Scotia  to  Argentina),  has  also  been  introduced  in  Europe.  All  species  show  close  similarity  and  great 
individual  variation.  Both  migration  and  genetic  continuity  appear  to  be  assisted  by  transport  of 
larvae  in  currents.  Distributional  patterns  parallel  those  of  many  organisms,  especially  members  of 
the  decapod  crustacean  genus  Penaeus  which  occupy  similar  habitats. 


The  blue  crab,  Callinectes  sapidus  Rathbun,  a  sta- 
ple commodity  in  fisheries  of  eastern  and  southern 
United  States,  is  almost  a  commonplace  object  of 
fisheries  and  marine  biological  research,  but  its 
taxonomic  status  has  been  questionable  for  a  long 
time.  Other  members  of  the  genus  also  have  ques- 
tionable taxonomic  status,  and  they  are  difficult  to 
identify.  In  a  time  when  expanding  interest  in 
species  easily  exploitable  for  food  has  generated 
new  research,  we  can  benefit  from  a  fresh  look  at 
the  component  species  of  this  important  genus  in 
order  that  major  areas  of  study  such  as  fisheries 
biology,  ecology,  zoogeography,  embryology,  and 
physiology  can  proceed  on  a  stable  nomenclatural 
basis.  The  purposes  of  this  paper  are  to:  11 
synonymize  nomenclature,  2)  characterize  the 
species,  3)  discuss  variation  in  morphology,  4) 
provide  illustrations  and  keys  to  identification,  5) 
delineate  geographic  distribution  of  species,  6) 
provide  remarks  on  ecological  associations,  7)  con- 
tribute to  resolution  of  the  fossil  record,  and  8) 
document  evidence  and  provide  a  list  of  identified 
specimens  in  major  museums  of  the  world. 

HISTORY 

Crabs  of  the  genus  Callinectes  have  an  anec- 
dotal record  dating  from  early  explorations  of  the 
Western  Hemisphere.  Perhaps  the  earliest  listing 
among  natural  assets  in  the  New  World  is  Thomas 
Hariot's  (1588)  mention  of  "Sea  crabbes,  such  as 


'Systematics  Laboratory,  National  Marine  Fisheries  Service, 
NOAA,  U.S.  National  Museum,  Washington,  DC  20560. 


we  have  in  England."  A  similar  record  is 
Marcgrave's  account  in  1648  (Lemos  de  Castro, 
1962)  of  a  South  American  Callinectes  [=  danae 
Smith  (1869)],  one  of  the  common  portunids  used 
for  food.  D.  P.  de  Vries  in  1655  (Holthuis,  1958) 
referred  to  the  eating  qualities  of  blue  crabs  in  the 
New  York  area  and  likened  the  white  and  orange 
color  of  their  chelipeds  [females]  to  colors  of  the 
House  of  Orange.  Lawson  (1714),  recounting  his 
years  among  the  Indians  in  the  Carolinas,  may 
have  initiated  the  tale  of  raccoons  fishing  for  crabs 
in  marshes  with  their  tails,  but  more  factually  he 
wrote  [undoubtedly  of  the  blue  crab,  C  sapidus 
Rathbun  (1896)],  "the  smaller  flat  Crabs  I  look 
upon  to  be  the  sweetest  of  all  Species  .  .  .  the 
Breadth  of  a  lusty  Man's  Hand  ....  These  are 
inumerable,  all  over  the  salts  of  Carolina  .  .  . 
taken  not  only  to  eat,  but  are  the  best  Bait  for  all 
sorts  of  Fish,  that  live  in  the  Salt-Water." 

Holthuis  (1959)  thought  that  de  Geer  (1778) 
probably  represented  Callinectes  bocourti  A. 
Milne  Edwards  (1879)  under  the  name  "Crab  de 
I'ocean"  when  he  described  a  swimming  crab  from 
Surinam  in  general  terms  as  Cancer  pelagicus. 
Ordway  (1863)  considered  de  Geer's  species 
synonymous  with  Lupa  sayi  Gibbes  (1850),  and 
Rathbun  (1896:350)  stated  "Figures  8,  9  and  11 
correctly  represent  neither  of  these  species,  nor 
are  they  applicable  to  any  species  of  Callinectes, 
while,  on  the  other  hand,  Figure  10  shows  the 
narrow  abdomen  characteristic  of  that  genus." 
Since  C.  bocourti  is  the  commonest  portunid  in 
Surinam,  abundant  enough  to  be  marketed,  and 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


685 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


certain  of  de  Geer's  figures  can  be  interpreted  as 
Callinectes,  Holthuis's  conclusion  seems  reason- 
able. 

Bosc  (1802)  gave  a  thumbnail  natural  history 
sketch  for  C.  sapidus  in  South  Carolina  comparing 
crudely  in  its  accuracy  with  some  modern  ac- 
counts, but  he  used  the  name  Portunus  hastatus 
along  with  a  description  taken  from  J.  C.  Fab- 
ricius  which  applied  to  a  European  species. 

Thomas  Say  (1817)  was  the  first  naturalist  to 
give  a  description  of  the  common  blue  crab  of  the 
eastern  United  States,  calling  it  Lupa  hastata,  in 
what  he  intended  as  a  redescription  of  Lupa  has- 
tata (Linn.),  a  species  known  from  the  Mediterra- 
nean (Rathbun,  1896). 

A  few  years  later  Latreille  ( 1825)  gave  the  name 
Portunus  diacantha  to  the  common  blue  crab  of 
eastern  United  States  accompanied  by  a  poor  de- 
scription that  applied  to  more  than  one  species. 
Say  and  Latreille,  plus  perhaps  De  Kay  (1844) 
who  published  a  description  and  beautifully  col- 
ored plate  of  what  he  called  Lupa  dicantha  [  = 
C.  sapidus]  from  New  York,  account  for  the  main 
early  treatments  of  Callinectes  by  naturalists. 

Search  of  newspaper  and  popular  journal  files 
could  yield  a  harvest  of  fact  and  fiction  about  these 
crabs  culminating  perhaps  in  accounts  of  the  "crab 
derbies"  held  in  recent  years  to  promote  market- 
ing in  crab  producing  states  of  the  eastern  sea- 
board of  the  United  States.  Crab  stories  abound 
and  crab  fishing  techniques  are  similar  in  all 
countries  where  Callinectes  occurs.  It  is  not  sur- 
prising, therefore,  that  this  profusion  has  carried 
over  into  the  scientific  literature  where  scholars 
have  bequeathed  a  complex  nomenclature  in 
numerous  contributions. 

Scholarly  systematic  work  on  the  whole  genus 
was  last  presented  by  Rathbun  in  1896  as  a  gen- 
eral revision  and  amended  in  1897.  There  is  no 
need  to  clutter  the  text  here  by  recalling  the 
parade  of  specific  epithets  employed  in  the  game  of 
taxonomic  musical  chairs  played  by  a  succession 
of  authors.  Each  built  on  the  foundation  of  previ- 
ous work,  usually  as  collections  substantially  in- 
creased in  museums,  but  many  minor  papers  were 
reports  on  expeditions  extending  the  bounds  of 
known  geographic  ranges  for  certain  species.  De- 
tails of  these  histories  may  be  followed  in  the 
synonymies,  but  the  principal  studies  should  be 
placed  in  perspective  as  an  introduction,  and  in 
reviewing  them  I  repeat  part  of  Rathbun's  (1896) 
review. 

William  Stimpson  (1860)  created  the  genus CaZ- 


linectes  to  contain  portunids  in  which  the  males 
have  a  T-shaped  abdomen  and  the  merus  of  the 
outer  maxillipeds  is  short,  sharply  prominent,  and 
curved  outward  at  its  antero-external  angle. 
He  regarded  as  one  species  "the  common  Amer- 
ican Lupa  diacantha  (Latreille)"  in  his  new 
genus,  and  doubtfully  distinguished  a  second, 
L.  (=  Callinectes)  bellicosa,  which  he  had  de- 
scribed (1859)  from  the  Gulf  of  California.  We  now 
know  that  the  second  of  Stimpson's  generic 
characters  is  nearly  valueless  because  other  por- 
tunids have  similar  third  maxillipeds,  but  the 
narrow  sixth  segment  of  the  T-shaped  abdomen  of 
males  holds  and  is  reinforced  by  absence  of  an 
internal  spine  on  the  carpus  of  the  chelipeds  in 
Callinectes. 

The  limited  view  of  the  genus  held  by  Stimpson 
was  soon  broadened  by  Ordway  ( 1863)  who  recog- 
nized nine  species  distinguished  in  part  by  struc- 
ture of  the  male  first  pleopods.  Ordway  restricted 
the  name diacanthus  to  a  Brazilian  form  described 
by  Dana  (1852)  which  we  now  know  as  C.  danae. 
The  common  blue  crab  of  the  eastern  United 
States  was  given  Say's  (1817)  name  hastatus, 
Stimpson's  bellicosus  retained,  and  six  new 
species  named.  Ordway's  study  of  crustaceans  was 
diverted  by  the  Civil  War,  and  he  remained  in 
military  life  until  his  death  in  1897.  Poor  com- 
munication may  have  led  to  Ordway's  confusion  in 
nomenclature,  but  his  concept  of  species  based  on 
material  then  available  was  remarkably  clear. 

Latreille's  (lS2b)  diacantha,  though  valid,  was 
never  widely  recognized  because  of  its  poor 
definition.  Various  "diacanthas"  were  employed 
for  139  yr  finally  ending  in  official  suppression  of 
Latreille's  ill-starred  name  in  1964  for  purposes  of 
nomenclatural  stability.  Smith  (1869)  substituted 
C.  danae  for  Dana's  Brazilian  C.  diacantha. 

Then  followed  an  interval  dominated  by  A. 
Milne  Edwards's  revision  of  the  Portunidae  ( 1861 ) 
and  his  review  of  the  Crustacea  of  Mexico  ( 1879). 
Milne  Edwards  at  first  did  not  recognize  Cal- 
linectes as  a  distinct  genus  but  later  accepted  it. 
He  conservatively  viewed  Callinectes  species  as 
"varieties"  of  diacanthus  (adding  five  new  ones  to 
Ordway's  nine  in  1879),  and  the  influence  of  his 
ideas  pervaded  the  field  for  a  long  time,  leading 
eventually  to  Rathbun's  revisionary  papers. 
Milne  Edwards's  reasoning  was  not  without  merit 
for  the  genus  is  close  to  other  portunids.  Indeed,  its 
validity  as  a  distinct  unit  was  again  challenged  for 
a  time  by  Stephenson  and  Campbell  (1959)  and 
Stephenson  (1962)  during  reassessment  of 


686 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Indo-Pacific  Portunidae,  but  later  left  intact 
(Stephenson,  Williams,  and  Lance,  1968). 

In  1896  Rathbun  recognized  the  following  num- 
bers of  species:  western  Atlantic,  six  species  and 
one  subspecies  (Rathbun  never  treated  the  nomi- 
nal subspecies  as  anything  but  a  full  species); 
eastern  Pacific,  four  species;  eastern  Atlantic  off 
Africa,  one  species  and  one  subspecies.  The  list 
was  almost  immediately  altered  (1897)  by  name 
recombinations,  elevation  of  subspecies,  descrip- 
tion of  a  new  species,  and  extension  of  known 
geographic  ranges.  This  brought  the  numbers  to: 
western  Atlantic,  six  species  and  one  subspecies; 
eastern  Pacific,  four  species;  eastern  Atlantic  off 
Africa,  four  species.  There  the  inventory  rested 
until  1921  when  Rathbun  revised  the  African 
species,  reducing  them  to  three  but  noting  a  doubt- 
ful subspecies  reported  from  Europe  (Bouvier, 
1901)  greatly  resembling  C.  sapidus  of  the  United 
States.  In  1930  Rathbun  published  the  third  of  a 
four-volume  work  that  serves  as  the  standard  ref- 
erence on  American  crabs.  In  this  she  reduced  the 
recognized  species  in  the  eastern  Pacific  by  one. 
Collaterally  she  treated  fossil  members  of  the 
genus,  describing  three  new  species  from  the 
Oligocene  and  Miocene  of  Middle  America 
(1919b),  and  two  more  species  from  similar  ages  in 
North  America  (1935).  One  of  these  from  the 
Miocene  (=?)  of  Virginia  and  Florida  was  consid- 
ered identical  with  living  C.  sapidus. 

By  1930  the  genus  seemed  stabilized,  but  Rath- 
bun herself  had  introduced  confusion  in  1907  by 
describing  a  juvenile  Portunus  from  the  South 
Pacific  as  Callinectes  alexandri.  This  error  bore 
fruit  years  later  in  helping  to  generate  doubt  con- 
cerning validity  of  the  genus  (Stephenson  and 
Campbell,  1959).  During  the  same  year  that 
Rathbun's  cancroid  treatise  appeared,  Contreras 
( 1930)  described  two  new  species  in  a  little  known 
paper,  one  from  the  Gulf  of  California  and  another 
from  the  Gulf  of  Mexico.  Capart  (1951)  and  Monod 
(1956)  both  supported  Rathbun's  analysis  of  West 
African  forms,  and  in  shedding  more  light  on  the 
introduction  of  C.  sapidus  into  European  waters 
(first  noticed  in  1901)  erased  Rathbun's  doubts 
about  a  poorly  documented  subspecies  from  that 
area.  They  also  pointed  out  difficulties  in  identify- 
ing some  specimens.  The  introduction  of  C. 
sapidus,  documented  by  numerous  authors,  was 
reviewed  by  Holthuis  (1961,  1969).  Following  pe- 
tition of  Holthuis  (1962),  the  International  Com- 
mission (1964),  to  avoid  confusion  in  nomencla- 
ture of  such  a  well-known  species,  made  Cal- 


linectes sapidus  Rathbun  the  type  species  of  the 
genus  and  suppressed  the  long  dormant  Portunus 
diacantha  Latreille,  1825.  Garth  and  Stephenson 
(1966)  confirmed  Rathbun's  interpretation  of  the 
eastern  Pacific  Callinectes,  and  Williams  (1966) 
described  a  new  species  from  the  Carolinian  Prov- 
ince of  North  America. 

Such  was  the  status  of  the  species  problem  when 
the  present  study  was  undertaken.  Numerous  au- 
thors had  expressed  difficulty  in  making 
identifications,  especially  of  juvenile  material. 
Geographic  limits  for  species  seemed  ill  defined. 
Few  attempts  to  analyze  large  series  systemati- 
cally had  been  attempted,  but  results  of  work  in 
fisheries  management  indicated  that  populations 
within  species  might  be  distinct.  Mindful  of  this 
and  aware  of  series  of  specimens  in  museums,  a 
review  of  the  group  seemed  profitable.  Simultane- 
ously, Taissoun  (1969,  1972)  began  study  of  Cal- 
linectes in  Venezuela  finding  a  form  endemic  to 
Lake  Maracaibo.  It  is  likely  that  new  approaches 
such  as  ecological  and  larval  studies  may  continue 
to  elucidate  variation  in  the  genus. 

CHARACTERS    OF    SYSTEMATIC 

VALUE 

The  gross  features  of  morphology  having 
greatest  usefulness  in  distinguishing  species  of 
Callinectes  are  (Figures  1,  2):  viewing  dorsally,  1) 
the  number,  shape,  and  arrangement  of  frontal 
teeth,  2)  shape  of  the  metagastric  area,  3)  shape 
and  curvature  of  the  anterolateral  teeth  and  the 
lateral  spine,  4)  granulation  of  the  dorsal  surface; 
viewing  ventrally,  shape  of  male  and  mature 
female  abdomen.  Shape  of  the  chelipeds  is  also 
useful,  as  are  the  colors  in  fresh  specimens.  In 
addition  to  gross  features,  male  first  pleopods 
(Figures  18-21)  are  diagnostic,  and  shapes  of 
female  gonopores  (Figures  22-23)  are  aids  to 
identification. 

Body  proportions. — Proportions  of  the  body  in 
both  sexes  change  with  growth  until  a  charac- 
teristically male  or  female  form  develops.  The 
carapace  of  males  becomes  relatively  broader  than 
that  of  females,  with  lateral  spines  accentuated; 
in  especially  large  individuals  of  some  species  the 
metagastric  region  tends  to  be  somewhat  sunken 
at  its  side  and  rear  margins.  Females  have  a  dor- 
sally  tumid  appearance,  with  the  carapace  more 
uniformly  inflated  and  granulated  and  relatively 
not  so  broad  nor  with  lateral  spines  so  accentuated 


687 


as  in  males.  Body  heights  are  alike  in  the  two 
sexes. 

Spines. — All  spiniform  characters,  poorly  de- 
veloped and  rounded  at  the  apices  in  juveniles, 
gradually  assume  conformation  characteristic  of 
the  species  as  growth  progresses. 

Chelipeds. — All  species  in  the  genus  have  the 
hands  of  the  chelipeds  (Figures  3-17)  modified 
into  a  major  chela  (crusher,  usually  on  right  side) 
and  a  minor  chela  (cutter,  usually  on  left  side) — 
heterochelic  and  heterodont  (Schafer,  1954; 
Stevcic,  1971).  Loss  of  the  major  chela  induces 
a  well-known  reversal  at  the  next  molt  with  the 
new  hand  becoming  a  minor  chela.  A  few  indi- 
viduals have  two  minors,  but  almost  none  exhibit 
two  major  chelae.  Size  and  strength  of  the  major 
hand  vary  a  good  deal,  each  species  having  a  some- 
times ill  defined  but  characteristic  shape.  In  all, 
especially  among  males,  the  dactyl  of  the  major 
chela  has  a  strongly  developed  proximal  tooth 
which  closes  against  a  molariform  complex  on  the 
propodus  (Schafer,  1954).  A  decurved  lower  mar- 
gin near  the  base  of  the  propodal  finger  opposite 
the  proximal  crushing  apparatus  on  opposed  edges 
of  the  fingers  accompanies  development  of  the 
complex,  and  in  huge  males  of  some  species  is  a 
prominent  feature.  Teeth  distal  to  the  molariform 
complex  of  the  major  chela  are  more  sectorial  in 
structure,  but  not  so  sharp  as  those  on  the  minor 
hand.  Sectorial  teeth  of  both  hands  tend  to  be 
arranged  in  triads,  a  large  central  tooth  flanked  by 
smaller  ones,  but  there  is  much  variation.  In  old 
individuals  no  longer  molting  or  molting  infre- 
quently, the  proximal  crusher  teeth  become  worn, 
occasionally  almost  obliterated.  Size  and  wear 
vary  with  species  and  are  undoubtedly  associated 
with  feeding  habits.  Callinectes  sapidus,  for  ex- 
ample, is  known  to  feed  on  the  American  oyster, 
Crassostrea  uirginica,  and  other  mollusks.  Other 
species  of  Callinectes  probably  have  similar  feed- 
ing habits,  but  these  are  not  well  documented. 

Secondary  sexual  structures. — Immature 
females  have  a  triangular  abdomen  (Figure  2) 
with  most  segments  indistinguishably  fused,  but 
at  the  terminal  maturation  molt  (Churchill,  1919) 
all  segments  become  free.  The  abdomen  of  mature 
females  has  a  variable  but  roughly  characteristic 
shape  in  each  species.  Distal  portions  of  the  abdo- 
men in  immature  males  also  have  a  developing 
shape  which  becomes  characteristic  of  the  species 
in  adults. 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

Primary  sexual  structures. — The  copulatory  ap- 
paratus of  male  Callinectes  has  been  recognized  as 
a  good  separator  of  species  since  the  time  of  Ord- 
way  (1863),  but  until  recently  no  one  used  fine 
structure  of  these  organs  as  serious  aid  to 
identification.  Snodgrass  (1936)  and  Cronin 
(1947)  both  described  the  external  male  sexual 
apparatus,  and  I  here  adopt  Snodgrass's  term 
"first  gonopod"  for  the  first  male  pleopod.  The  first 
gonopod  is  essentially  a  narrow  flat  plate  rolled 
longitudinally  into  a  cylinder  that  may  be  vari- 
ously curved  and  twisted,  terminating  in  a  tip 
varying  from  nearly  tubular  to  a  simply  flared 
trough.  First  gonopods  of  each  species  have 
characteristic  shapes,  but  there  is  individual  vari- 
ation reinforced  by  age,  molt  stage,  wear,  and 
irregularity  in  preservation.  The  distal  portion  of 
each  first  gonopod  is  armed  with  retrogressive  ar- 
ticulated spinules,  exceedingly  tiny  and  rather 
unevenly  distributed  in  one  set  of  species  having, 
short  first  gonopods — C.  gladiator  Benedict 
(1893),  marginatus  A.  Milne  Edwards  (1861),  or- 
natus  Ordway  (1863),  andsimilis  Williams  (1966) 
(Figures  18a-d,  20a-d),  as  well  as  in  a  second  set 
with  relatively  longer  first  gonopods — C.  arcu- 
atus  Ordway  (1863),  danae,  and  exasperatus  (Ger- 
staecker,  1856)  (Figures  18e-g,  20  e-i),  but  larger 
and  arranged  in  longitudinal  bands  among  species 
with  long  curved  first  gonopods  in  a  third  set — 
C.  bellicosus,  bocourti,  latimanus  Rathbun  (1897), 
maracaiboensis  Taissoun  (1972),  rathbunae 
Contreras  (1930),  sapidus,  and  toxotes  Ordway 
(1863)  (Figures  18h-j,  19,  20j-p,  21).  In  the  last 
group,  the  spinules  are  irregular  in  size  show- 
ing evidence  of  breakage  and  replacement  during 
growth.  Moreover,  first  gonopods  of  certain  species 
bear  slender  setae.  In  C  arcuatus  and  danae,  with 
first  gonopods  of  moderate  length,  the  setae  are 
subterminal  (Figure  20e-h)  but  in  others  with 
longer  first  gonopods  [C.  bellicosus,  latimanus, 
maracaiboensis,  rathbunae,  sapidus,  and  toxotes 
(Figures  20j-p,  21)]  they  are  arranged  along  the 
shaft  at  levels  between  the  fifth  to  seventh 
thoracic  sternites  in  a  single  sternomesial  row 
following  the  twist  of  the  appendage.  The  setae  are 
relatively  largest  in  bellicosus  (Figure  20j,  k). 

Structure  of  the  female  gonopores  covered  by 
the  abdomen  and  located  near  the  midline  on  the 
sixth  thoracic  somite  (Snodgrass,  1936)  is  less  use- 
ful as  a  specific  character  than  that  of  the  male 
first  gonopod,  but  even  here  there  are  some  con- 
formational types.  Each  gonopore  leads  via  a 
spermathecal  duct  (vagina)  to  a  spermatheca 


688 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLIXECTES 

which  in  turn  is  connected  to  oviduct  and  ovary, 
but  it  is  the  gonopore  alone  that  shows  crude 
structural  specificity.  Hartnoll  ( 1968)  showed  that 
the  gonopore  of  portunids  is  an  uncovered  struc- 
ture often  rounded  laterally  and  pointed  mesially, 
whose  margin  is  the  "rigid  integument  of  the  ster- 
num, while  the  lumen  is  normally  blocked  by 
bulges  of  the  flexible  integument  which  comprises 
the  lining  of  the  vagina."  In  the  set  of  species 
having  males  with  long  first  gonopods,  the  gono- 
pores  of  females  are  paraboloid  in  outline  (Figures 
22i-l,  23a-c).  Parallels  with  the  other  two  sets  of 
male  gonopod  types  are  less  pronounced.  Of  the 
intermediate  second  set,  female  C.  arcuatus  and 
danae  have  asymmetrically  ovoid  gonopores  (Fig- 
ure 22e,  f);  exasperatus  has  an  elongate  sinuous 
gonopore  with  shelflike  overgrowth  on  the 
cephalic  border  (Figure  22g),  and  hellicosus  fits 
into  this  group  (Figure  22h).  Females  correspond- 
ing to  the  set  of  males  with  short  first  gonopods 


have  gonopores  varying  from  broadly  open 
paraboloid  in  C.  ornatus  (Figure  22d)  to  increas- 
ingly narrowed  openings  in  C.  gladiator  and  mar- 
ginatus  (Figure  22b,  c),  culminating  in  the  narrow 
transverse  slit  of  C.  similis  (Figure  22a). 

MEASUREMENTS 

The  foregoing  discussion  shows  that  measure- 
ments must  be  taken  from  adults  if  they  are  to 
have  systematic  usefulness  because  the  young  are 
proportionally  different  from  adults  as  well  as 
being  incomplete  for  secondary  sexual  characters. 
Some  species  are  larger  than  others  and  certain 
proportions  are  considered  useful  in  keys  for 
identification  (Rathbun,  1930;  Garth  and 
Stephenson,  1966).  Certain  populations  within 
species  may  deviate  from  the  "typical."  Initially  I 
thought  that  analysis  of  morphometric  characters 
might  help  to  define  differences  among  species  as 
well  as  among  populations  within  species. 


Figure  1 . — Mature  male  Callinectes  sapidus  from  North  Carolina  in  dorsal  view  ( x  1 ).  Measured  features  indicated  by  numbered  lines: 
1,  length;  2,  width  to  base  of  lateral  spines;  3,  width  including  lateral  spines;  dimensions  of  metagastric  area  —  a,  anterior  width,  b, 
length,  c,  posterior  width.  Other  features  included  in  descriptions:  (carapace)  F,  frontal  teeth;  O,  outer  orbital  tooth;  AL,  anterolateral 
teeth;  LS,  lateral  spine;  PL,  posterolateral  margin;  EP,  epibranchial  line;  ES,  epistomial  spine;  MB,  mesobranchial  area;  CA,  cardiac 
area;  BL,  branchial  lobe;  (cheliped)  M,  merus;  C,  carpus;  P,  propodus;  D,  dactyl. 


689 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Measurements  taken  included  18  characters  for 
mature  males,  21  for  mature  females  (Figures  1, 
2).  These  characters  comprise  two  sets,  one  as- 
sociated with  the  carapace  or  general  body  form, 
and  another  with  sexual  characters.  Measure- 
ments for  both  sexes  included: 

1.  Length  of  carapace  including  epistomial 
spine. 

2*  Length  of  carapace  excluding  epistomial 
spine. 

3.*  Width  of  carapace  including  lateral 
spines. 

4*  Width  of  carapace  at  base  of  notch  be- 
tween lateral  spine  and  preceding  an- 
terolateral tooth. 

5.*  Width  between  tips  of  outer  orbital 
spines  (first  anterolateral  teeth). 


6.  Width  between  tips  of  suborbital  spines. 

7.  Width  between  tips  of  lateral  interorbit- 
al  spines. 

8.*  Maximum  height  of  body. 

9.*  Anterior  width  of  metagastric  area. 

Posterior  width  of  metagastric  area. 

Length  of  metagastric  area. 

Angular  (lateral)  length  of  metagastric 

area. 


10.* 
11.* 
12.* 


Measurements  of  elements  in  the  T-shaped 
male  abdomen  included: 


13. 
14. 
15. 
16. 

17.* 
18.* 


Greatest  width  of  fused  segments  3-5. 
Median  length  of  fused  segments  3-5. 
Median  length  of  narrow  segment  6. 
Narrowest  width  of  narrow  segment  6. 
Length  of  telson. 
Width  of  telson. 


Figure  2. — Composite  ventral  view  of  thoracic  sternites  (roman  numerals),  abdomen  (arabic  numerals),  and  telson  (T)  in  situ,  a, 
mature  male;  b,  mature  female;  c,  immature  female.  Measurements:  lengths  in  midline,  widths  maximal  for  structure. 


690 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  3. — Callinectes  marginatus  (A.  Milne  Edwards):  a,  chelae  in  frontal  view;  c,  abdomen  and  sternal  area,  male,  USNM  72351, 
Salt  River  Bay,  St.  Croix,  V.I.;  b,  carapace;  d,  abdomen  and  sternal  area,  female,  USNM  73285,  W  end  San  Juan  Island  near  Ft.  San 
Geronimo,  P.R.;  a  x  1;  b  x  1.5;  c  x  1.4;  d  x  1.7. 


691 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  4. — Callinectes  similis  Williams:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male;  d,  abdomen  and 
sternal  area,  female;  paratypes,  UNC-IMS  1556,  Beaufort  Inlet,  Carteret  County,  N.C.;  a  x  1;  b  x  1.4;  c  x  1.2;  d  x  1.3. 


692 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  5. — Callinectes  gladiator  Benedict:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male;  d,  abdomen 

and  sternal  area,  female,  USNM  120940,  Nigeria;  a  x  0.9;  b  x  1.4;  c,  d  x  1.6. 


693 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  6. — Callinectes  ornatus  Ordway:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male,  48401,  Punta  [= 
Cabo]  Cajon,  Cuba;  d,  abdomen  and  sternal  area,  female,  7584,  Curasao;  a  x  1;  b,  d  x  1.3;  c  x  1.5. 


694 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  7. — Callinectes  danae  Smith:  a,  chelae  in  frontal  view,  male,  USNM  60983,  Sao  Francisco,  Niteroi,  Brazil;  b,  carapace;  d, 
abdomen  and  sternal  area,  female,  USNM  48400,  Los  Arroyos,  Cuba;  c,  abdomen  and  sternal  area,  male,  UNC-IMS  2128,  Bahia  de 
Mayagiiez,  P.R.;  a,  c  x  1;  b  x  1.4;  d  x  1.5. 


695 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  8. — Callinectes  arcuatus  Ordway:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male,  USNM  33417,  Isla 
Magdalena,  Baja  California,  Mexico;  d,  abdomen  and  sternal  area,  female,  USNM  15431,  Estero  de  los  Algodones,  SE  Guaymas, 
Sonora,  Mexico;  a  x  1;  b,  c  x  1.2;  d  x  1.4. 


696 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  9. — Callinectes  exasperatus  (Gerstaecker):  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male, 
USNM  19428,  Vitoria,  Estado  Espirito  Santo,  Brazil;  d,  abdomen  and  sternal  area,  female,  USNM  24467,  Puerto  Real,  P.R.;  a  x 
0.8;  b  X  1.1;  c  X  1;  d  X  1.4. 


697 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  10. — Callinectes  bellicosus  (Stimpson):  a,  chelae  in  frontal  view;  d,  abdomen  and  sternal  area,  female,  USNM  60010,  Pt. 
Abreojos,  Bahia  Ballenas,  Baja  California,  Mexico;  b,  carapace;  c,  abdomen  and  sternal  area,  male,  USNM  15436,  La  Paz  Harbor, 
Baja  California,  Mexico;  a,  c,  d  x  1;  b  x  1.1. 


698 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  11. — Callinectes  toxotes  Ordway:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male;  d,  abdomen 
and  sternal  area,  female,  USNM  18507,  Acapulco,  Guerrero,  Mexico;  a  x  1.1;  b  x  0.8;  c,  d  x  1. 


699 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  12. — Callinectes  hocourti  A.  Milne  Edwards:  a,  chelae  in  frontal  view,  male,  USNM  72354,  Fairplain  stream  above  bridge, 
St.  Croix,  V.I.;  b,  carapace;  d,  abdomen  and  sternal  area,  female,  USNM  18235,  Sabanilla,  Colombia;  c,  abdomen  and  sternal 
area,  male,  USNM  18233,  Sao  Luis,  Estado  Maranhao,  Brazil;  a,  c  x  1;  b  x  1.2;  d  x  1.4. 


700 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  13. — Callinectes  rathbunae  Contreras:  a,  chelae  in  frontal  view;  b,  carapace;  d,  abdomen  and  sternal  area,  female;  c, 
abdomen  and  sternal  area,  male,  USNM  122922,  Laguna  de  Alvarado,  Veracruz,  Mexico;  a,  b  x  1;  c,  d  x  1.1. 


701 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  14. — Callinectes  maracaiboensis  Taissoun:  a,  chelae  in  frontal  view,  male,  USNM  143392,  Lago  de  Maracaibo;  b,  carapace, 
male,  USNM  143393,  Puerto  Caballo,  Maracaibo;  c,  abdomen  and  sternal  area,  male;  d,  abdomen  and  sternal  area,  female,  USNM 
139621,  Lago  de  Maracaibo,  Venezuela;  a  x  0.95;  b  x  0.85;  c,  d  x  1. 


702 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  15. — Callinectes  latimanus  Rathbun:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area,  male;  d,  abdomen 
and  sternal  area,  female,  USNM  54310,  Banana,  Zaire  [=  Belgian  Congo]  a  x  0.8;  b,  c  x  1;  d  x  1.9. 


703 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  16. — Callinectes  sapidus  Rathbun,  forma  typica:  a,  chelae  in  frontal  view,  male,  UNC-IMS  2136,  5  km  S  Lajas,  P.R.;  b, 
carapace,  male,  UNC-IMS  741,  North  River,  Carteret  County,  N.C.;  c,  abdomen  and  sternal  area,  male,  USNM  92452,  Wye  River, 
Md.;  d,  abdomen  and  sternal  area,  female,  USNM  30567,  Cameron,  La.;  a  x  0.8;  b  x  1.3;  c  x  0.6;  d  x  0.85. 


704 


WILLIAMS;  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  17. — Callinectes  sapidus  Rathbun,  forma  acutidens:  a,  chelae  in  frontal  view;  b,  carapace;  c,  abdomen  and  sternal  area, 
male,  USNM  18630,  Rio  Escondido,  Nicaragua;  d,  abdomen  and  sternal  area,  female,  USNM  99848,  Roca  Arroyo  Balizas  [=  Arroyo 
de  Valizes?],  Uruguay;  a  x  0.9;  b,  c  x  1;  d  x  1.1. 


705 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  18. — Male,  first  gonopods 
in  situ  with  abdomen  removed; 
portions  of  thoracic  sternites 
IV-VIII:  a,  Callinectes  mar- 
ginatus  (A.  Milne  Edwards), 
USNM  72351,  Salt  River  Bay,  St. 
Croix,  V.I.;  b,  C.  similis  Williams, 
paratype,  UNC-IMS  1556, 
Beaufort  Inlet,  Carteret  County, 
N.C.;  c,  C.  gladiator  Benedict, 
Cote  du  Dahomey,  6°19'N, 
2°24'E;  d,  C.  ornatus  Ordway, 
USNM  48401,  Punta  (=  Cabo] 
Cajon,  Cuba;  e,  C.  danae  Smith, 
USNM  60983,  Sao  Francisco, 
Niteroi,  Estado  de  Rio  de  Janeiro, 
Brazil;  f,  C.  arcuatus  Ordway, 
USNM  33417,  Isla  Magdalena, 
Baja  California,  Mexico;  g,  C  ex- 
asperatus  (Gerstaecker),  UNM- 
IMS  2137,  Bahia  Fosforescente, 
P.R.;  h,  C.  bellicosus  (Stimpson), 
USNM  15436,  La  Paz  Harbor, 
Baja  California,  Mexico;  i,  C.  tox- 
otes  Ordway,  USNM  18507, 
Acapulco,  Guerrero,  Mexico;  j,  C. 
bocourti  A.  Milne  Edwards, 
USNM  72354,  Fairplain  stream 
above  bridge,  St.  Croix,  V.I. 
Scales  =  1  cm;  a-f  have  higher 
magnification. 


706 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  19. — Male,  first  gonopods  in  situ  with  abdomen  removed;  portions  of  thoracic  sternites  IV- VIII;  a,  Callinectes  rathbunae 
Contreras,  USNM  122922,  Laguna  de  Alvarado,  Veracruz,  Mexico;  b,  C.  maracaiboensis  Taissoun,  Lago  de  Maracaibo,  Venezuela;  c, 
C.  latimanus  Rathbun,  Plage  de  Pointe  Noire,  Congo;  d,  C.  sapidus  Rathbun,  USNM  92452,  Wye  River,  Chesapeake  Bay,  Md.  Scales 
=  1  cm;  d  has  lower  magnification. 


707 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


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FISHERY  BULLETIN:  VOL.   72,  NO.  3 


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Figure  22. — Female,  left  gonopore  and  portions  of  thoracic  sternites  IV- VII:  a,  Callinectes  similis  Williams,  paratype,  UNC-IMS 
1556,  Beaufort  inlet,  Carteret  County,  N.C.;  b,  C.  marginatus  (A.  Milne  Edwards),  USNM  73285,  W  end  San  Juan  I.  near  Ft. 
Geronimo,  P.R.;  c,  C.  gladiator  Benedict,  Coast  of  Cameroon,  3°32'N,  9°35'E;  d,  C.  ornatus  Ordway,  USNM  7584,  Curasao;  e,  C. 
danae  Smith,  USNM  60983,  Sao  Francisco,  Niteroi,  Estado  de  Rio  de  Janeiro,  Brazil;  f,  C.  arcuatus  Ordway,  USNM  15431,  Estero  de 
los  Algodones  near  Guaymas,  Sonora,  Mexico;  g,  C.  exasperatus  (Gerstaecker),  USNM  24467,  Puerto  Real,  P.R.;  h,  C.  bellicosus 
(Stimpson),  USNM  60010,  Pt.  Abreojos,  Bahia  Ballenas,  Baja  California,  Mexico;  i,  C.  toxotes  Ordway,  USNM  18507,  Acapulco, 
Guerrero,  Mexico;  j,  C.  bocourti  A.  Milne  Edwards,  USNM  18235,  Sabanilla,  Colombia;  k,  C.  rathbunae  Contreras,  USNM  122922, 
Laguna  de  Alvarado,  Veracruz,  Mexico;  1,  C.  maracaiboensis  Taissoun,  paratype,  USNM  139621,  Lago  de  Maracaibo,  Venezuela. 
Scales  =  1  mm. 


710 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


g 


?'>/^ 

=*!.*•. 
'^3''-' 


^ 


711 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


P: 


^'X 


T-' 


t<AW«ii.i.-rji.i^VifcS;i;C«iifvlo;-. 


a 


b  _ 


Figure  23. — Female,  left  gonopore  and  portion  of  thoracic  sternites  IV- VII:  a.,Callinectes  latimanus  Rathbun,  Plage  de  Pointe  Noire, 
Congo;  b,  C.  sapidus  Rathbun,  typical  form,  USNM  30567,  Cameron,  La.;  c,  C.  sapidus  Rathbun,  acutidens  form,  USNM  99848,  Roca 
Arroyo  Balizas  [=  Arroyo  de  Valizes?],  Uruguay.  Scales  =  1  mm. 


Measurements  of  elements  in  the  broad  apron- 
shaped  abdomen  of  sexually  mature  females  in- 
cluded: 


13. 

14. 
15. 
16. 
17. 
18. 
19. 

20* 
21* 


Greatest  width  of  segment  2. 

Greatest  width  of  segment  3. 

Greatest  width  of  segment  5. 

Median  length  of  segment  5. 

Greatest  width  of  segment  6. 

Median  length  of  segment  6. 

Median  length  of  segment  3  (proximal 

edge)  to  tip  of  telson. 

Length  of  telson. 

Width  of  telson. 


Analysis  of  selected  nonsexual  characters . — 
Study  showed  that  some  of  these  measurements 
were  more  valuable  than  others  at  the  specific 
level  and  11  (marked  with  asterisks),  generally 
considered  useful  in  verbal  description,  were 
chosen  for  cluster  analysis.  Unfortunately,  they 
neither  clustered  as  species  nor  as  species  groups 
when  analyzed.  Results  indicated  that  specific 
morphological  differences  in  this  genus  are  based 
on  characters  other  than,  or  in  addition  to,  those 
measured  and  analyzed  in  this  test.  Measure- 


ments therefore  were  judged  to  have  limited  value 
in  identification. 

This  finding  is  supported  strongly  by  evidence 
other  than  results  of  the  attempt  at  cluster 
analysis.  Female  Callinectes  attain  sexual  matur- 
ity in  a  terminal  metamorphic  molt.  Males  attain 
an  adult  conformation  at  sexual  maturity  but  may 
continue  to  molt  at  reduced  frequency.  Van  Engel 
(1958)  and  others  have  shown  that  C.  sapidus 
females  molt  18  to  20  times  in  attaining  maturity, 
males  18  or  19  before  becoming  mature  and  3  or  4 
times  beyond  that  stage.  The  range  of  variation  in 
number  of  molts  may  be  much  greater  than  this, 
for  both  dwarf  and  giant  sexually  mature  indi- 
viduals are  known.  Allometric  changes  accen- 
tuated at  the  two  ends  of  this  continuum  attest  to 
wide  variability  in  form.  Estevez  (1972)  em- 
phasized variability  in  C.  arcuatus  and  C.  toxotes. 
Tables  1  and  2  show  means,  standard  devia- 
tion, and  sample  size  for  selected  characters  from 
adult  male  and  female  Callinectes  species.  For 
almost  all  species  the  coefficient  of  variation 
( V  =  lOOs/x )  IS  high  for  all  characters  shown,  an 
indication  that  morphometrically  there  is  great 
variation  in  the  group.  Simpson,  Roe,  and  Lewon- 
tin  ( 1960:91 )  stated  that  V  values  greater  than  10 


712 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  24. — Respective  geographic  distributions  of  Callinectes  arcuatus  Ordway,  C.  danae  Smith,  C.  gladiator  Benedict,  and  C. 
similis  Williams  in  the  Atlantic  and  eastern  Pacific  oceans  based  on  specimens  studied  and  verified  published  records. 


indicate  that  a  sample  is  not  reasonably  unified. 
Throughout  the  genus  great  variation  in  mor- 
phometry of  the  body  makes  keys  for  identification 
involving  proportions  almost  impossible  to  devise 
unless  qualified  by  exceptions. 

From  a  different  viewpoint,  Stephenson  et  al. 
(1968)  applied  methods  of  numerical  analysis  to 
44  species  and  putative  subspecies  of  Portunus 
(mainly  from  America,  but  certain  Indo-Pacific 
species  for  comparison),  Callinectes,  Arenaeus, 
and  Scylla,  relying  on  presence  or  absence  of  57 
characters  to  build  up  a  data  matrix  from  which 
character  assessments  could  be  made.  The  method 
nicely  demonstrates  that  Callinectes  is  a  very 
homogeneous  group,  but  the  internal  relation- 
ships implied  do  not  correspond  harmoniously 
with  classical  interpretation.  This  is  not  a  matter 
of  conflict,  but  simply  one  of  judgment,  the  method 
seeming  to  be  limited  by  interpretation  of  charac- 


ter states,  weighting  being  one  serious  problem 
and  choice  of  characters  another.  Were  the 
analysis  run  with  different  emphases,  results 
might  reflect  those  to  some  extent. 

LARVAL  DEVELOPMENT 

Among  Callinectes  species,  larval  development 
of  only  C.  sapidus  and  C.  similis  has  been  deter- 
mined by  hatching  eggs  and  rearing  in  the 
laboratory.  Costlow,  Rees,  and  Bookhout  (1959) 
and  Costlow  and  Bookhout  (1959)  described  seven 
zoeal  stages,  atypically  an  eighth,  and  a  megalopa 
for  C.  sapidus.  Larvae  and  megalopae  of  the  two 
species  are  apparently  almost  identical,  the  stages 
being  similar  to  those  of  other  portunids  (Costlow 
and  Bookhout,  pers.  commun.).  Importantly,  the 
megalopae  of  Callinectes  lack  an  internal  carpal 
spine  on  the  chelipeds  whereas  megalopae  of  Por- 
tunus have  a  well-developed  spine  on  this  member 


713 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


':■'''  I  I 


I  I  '  I  '  '  I  ft- 


Figure  25. — Geographic  distribution  of  Callinectes  ornatus  Ordway  in  the  western  Atlantic  Ocean  based  on  specimens  studied  and 

verified  pubHshed  records. 


714 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Figure  26. — Respective  geographic  distributions  of  Callinectes  exasperatus  (Gerstaecker)  and  C.  sapidus  Rathbun  in  the  western 
Atlantic  Ocean  with  introductions  to  the  eastern  Atlantic  and  Mediterranean  Sea,  based  on  specimens  studied  and  verified  published 
records. 


(Williams,  1971),  showing  one  of  the  generic  dis- 
tinctions at  an  early  phase  of  development. 

Costlow  ( 1965,  1967)  followed  the  early  work  on 
larvae  with  a  series  of  experimental  studies  show- 
ing that  development  of  C.  sapidus  is  subject  to 
variation  both  in  staging  and  duration.  Total  de- 
velopment time  of  C.  sapidus  from  hatching  of  egg 
to  transformation  of  the  megalopa  to  first  crab 
stage  has  varied  from  31  to  69  days  in  the  labora- 
tory in  various  combinations  of  salinity  and  tem- 
perature, but  duration  of  individual  stages  is  vari- 
able even  in  a  single  salinity-temperature  combi- 
nation. The  stages  are  constant  enough,  however, 
that  Van  Engel  ( 1958),  Cargo  (1960),  Nichols  and 
Keney  (1963),  Pinschmidt  (1964),  Tagatz  (1968), 
More  (1969),  and  Williams  (1971)  were  able  to 
identify  zoeae  or  megalopae  from  nearshore 
oceanic  and  estuarine  plankton.  In  nature  as  in 
experiments,  development  time  may  be  extended 


by  environmental  conditions.  Megalopae  have 
been  found  throughout  the  year  in  North  Carolina 
estuaries. 

FOSSIL  RECORD 

Hard  parts  of  portunids  most  abundant  as  fossils 
in  Tertiary  formations  in  eastern  North  and  Mid- 
dle America  are  portions  of  the  chelipeds,  usually 
the  dactyls  and  portions  of  the  propodi.  Some  de- 
posits contain  remains  of  carapaces  and/or  sterna, 
occasionally  almost  whole  exoskeletons  of  crabs, 
but  any  of  the  remains  are  scarce.  It  was  largely  on 
the  basis  of  cheliped  fragments  that  Rathbun 
(1919a,  b,  1926,  1935)  listed  and  described  Cal- 
linectes species  from  formations  attributed  to  ages 
as  old  as  the  Oligocene.  Withers  ( 1924)  described  a 
fragment  of  chela  from  the  Eocene  of  Jamaica  as 
Callinectes,  and  Blake  (1953)  added  information 


715 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  27. — Respective  geographic  distributions  of  Callinectes  bellicosus  Stimpson,  C  bocourti  A.  Milne  Edwards,  C.  latimanus 
Rathbun,  C.  marginatus  (A.  Milne  Edwards),  C.  maracaiboensis  Taissoun,  C.  rathbunae  Contreras,  and  C.  toxotes  Ordway  in  the 
Atlantic  and  eastern  Pacific  oceans  based  on  specimens  studied  and  verified  published  records. 


on  remains  from  the  Quarternary.  Williams 
(1965)  uncritically  accepted  determinations  for 
Atlantic  and  Gulf  Coastal  Plain  records  from  the 
Miocene  to  Recent,  but  study  of  this  material,  even 
though  its  interpretation  is  beyond  the  scope  of  the 
present  paper,  leads  to  an  attitude  of  restraint. 
The  characters  by  which  Callinectes  is  distin- 
guished from  other  portunid  genera,  shape  of  male 
abdomen  and  lack  of  an  internal  carpal  spine  on 
the  chelipeds,  are  rarely  evident  in  the  fossil  ma- 
terial, the  only  undoubted  specimens  (treated  in 
species  accounts  below)  coming  mainly  from  Pleis- 
tocene and  a  few  Miocene  horizons.  All  others 
studied  lack  characters  for  positive  first  order 
identification  and  therefore  their  determinations 
rest  on  secondary  features  such  as  shape  of  the 
chelae  or  other  nondiagnostic  parts  of  the  body. 
Although  the  numerous  cheliped  fragments  most 
resemble  these  parts  in  living  species  of  Cal- 


linectes, they  also  resemble  those  of  Ovalipes  and 
certain  Portunus,  especially  the  large  P.  pelagi- 
cus  and  P.  sanguinolentus  distributed  widely  in 
the  Indo-Pacific  region  today  (Stephenson,  1962), 
as  well  as  the  robust  Arenaeus  cribrarius  and  A. 
mexicana,  respectively  from  Atlantic  and  Pacific 
shores  of  the  Western  Hemisphere  (Rathbun, 
1930).  A  single  propodal  finger  of  a  form  attrib- 
uted to  P.  sayi  reported  from  the  Miocene  of 
Florida  (Rathbun,  1935)  greatly  resembles  other 
remains  attributed  to  Callinectes.  Margins  of 
warmer  seas  of  early  and  mid  Tertiary  (Ekman, 
1953;  Hazel,  1971)  could  have  favored  such  forms 
or  others  like  contemporary  Scj-Z/a  of  Indo-Pacific 
waters,  fossil  representatives  of  which  were  de- 
scribed [-?]  by  Rathbun  (1919b,  1935)  from  the 
Miocene  of  Florida,  Dominican  Republic,  and 
Mexico.  Judging  by  ecological  requirements  of 
living  species,  Callinectes  would  have  been  well 


716 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


adapted  to  such  an  environment,  but  fossil  evi- 
dence for  its  existence  in  the  Paleocene  remains 
indirect. 

There  are  constant  structural  differences  be- 
tween the  early  fossil  series  and  modern  Cal- 
linectes.  The  palms  of  chelae  of  C.  jamaicensis 
Withers,  1924  (Eocene),  C.  alabamensis  Rathbun, 
1935  (01igocene),C.  dedivis  Rathbun,  1919a  (low- 
er Miocene),  and  C.  reticulatus  Rathbun,  1919a 
(Oligocene-lower  Miocene)  are  short  and  faceted 
more  like  Callinectes  than  other  living  genera  of 
portunids,  but  they  are  relatively  thinner  than  in 
living  members  of  the  genus.  The  fingers  in  these 
early  forms  have  length-width  proportions  and 
tooth  arrangements  that  resemble  modern  C. 
sapidus,  but  the  tooth  rows  are  relatively  nar- 
rower proximally  on  propodal  fingers  and  less  in- 
clined toward  development  of  a  molariform  crush- 
ing surface.  Of  the  four  external  facets  on  the 
palm,  the  upper  mesial  one  in  the  fossil  series  is 
always  inclined  downward  toward  the  inner  sur- 
face in  major  chelae  whereas  in  modern  Cal- 
linectes species  it  is  nearly  horizontal  in  the  major 
chela  and  noticeably  inclined  downward  only  in 
the  minor  one;  moreover,  the  third  or  dorsolateral 
facet  is  relatively  wider  in  living  Callinectes 
species  than  in  any  of  the  early  fossils.  Compres- 
sion and  erosion  may  have  altered  relief  but  not 
uniform  angle  of  inclination  of  facets  in  the  fos- 
sils. Generally,  fossils  older  than  early-mid  Mio- 
cene attributed  to  Callinectes  have  less  powerful 
chelae  than  living  species  and  these  differences  in 
structure  seem  significant  enough  to  warrant 
generic  separation  of  the  two  series  when  more 
material  comes  to  light. 

MODERN  DISTRIBUTION 

Confined  almost  exclusively  to  shallow,  often 
brackish  coastal  waters  as  adults,  the  genus  Cal- 
linectes is  represented  by  six  species  distributed 
(Figures  24-27)  around  the  Caribbean  Sea  and 
southward  to  southern  Brazil:  C  marginatus,  or- 
natus,  danae,  exasperatus,  bocourti,  and  sapidus. 
A  seventh  species,  C  maracaiboensis ,  is  localized 
in  estuaries  of  Venezuela.  One  of  these  species,  C 
marginatus,  bridges  the  Atlantic,  ranging  with  C 
gladiator  and  C.  latimanus  from  Mauritania  to 
Angola  in  West  Africa.  It  also  reaches  the  Cape 
Verde  Islands.  Only  three  species  occur  in  the  Gulf 
of  Mexico,  exclusive  of  the  southeastern  part  off 
Florida:  C  rathbunae,  an  isolated  relative  of  C. 
bocourti  in  the  western  Gulf,  C  similis,  an  essen- 


tially Carolinian  form  ranging  northward  along 
the  coast,  and  C.  sapidus,  which  ranges  far 
beyond,  occasionally  to  the  Maritime  Provinces  of 
Canada.  In  the  eastern  Pacific,  disregarding  dis- 
tant island  occurrences,  C.  arcuatus  is  distributed 
from  extreme  southern  California  to  Peru,  shar- 
ing its  range  with  C.  bellicosus  in  the  region  of 
Baja  California  and  with  C.  toxotes  from  there 
south. 

If  one  relies  on  structure  of  male  first  gonopods 
alone  for  estimation  of  morphological  similarity, 
the  following  zoogeographical  associations 
emerge.  The  set  of  species  with  short  first 
gonopods  (C  marginatus,  gladiator,  ornatus,  and 
similis)  has  separate  eastern  and  western  Atlan- 
tic components,  and  one  member  on  both  sides  of 
the  tropical  Atlantic.  The  second  set  with  longer 
first  gonopods  (C.  arcuatus,  bellicosus,  danae,  and 
exasperatus)  occurs  in  the  tropical  western  Atlan- 
tic and  eastern  Pacific.  The  third  set  with  quite 
long  first  gonopods  (C  toxotes,  bocourti,  rath- 
bunae, maracaiboensis,  latimanus,  and  sapidus) 
has  representatives  in  all  regions.  Distributions  of 
all  species  fit  patterns  accepted  by  Ekman 
(1953:30,  ff.)  as  representative  of  many  along  the 
tropical-subtropical  Atlantic  and  east  Pacific 
coasts,  but  one,  C.  sapidus,  has  a  latitudinal  range 
that  seems  to  exceed  this  pattern.  In  this  species, 
development  of  a  northern  and  southern  form  may 
be  in  progress. 

The  amphi-Atlantic  distribution  of  C.  mar- 
ginatus, records  of  C  exasperatus,  marginatus, 
ornatus,  and  sapidus  from  Bermuda,  C.  arcuatus 
from  the  Galapagos  Islands,  C.  toxotes  from  Juan 
Fernandez,  as  well  as  less  removed  northern  mar- 
ginal records  for  essentially  southern  species 
along  the  North  American  continent  (C.  bocourti 
in  southern  Florida  and  Mississippi;  C.  mar- 
ginatus in  North  Carolina;  C.  similis  in  New  Jer- 
sey; C  sapidus  in  Nova  Scotia)  all  point  to  exten- 
sions of  range  by  larval  transport  in  currents 
(Verrill,  1908b;  Garth,  1966).  Investigators  work- 
ing with  larval  stages  (reviewed  in  Williams, 
1971)  suggest  that  larvae  and  megalopae  can 
move  considerable  distances;  zoeae  have  been 
found  off  St.  Johns  River,  Fla.,  at  stations  up  to 
160  km,  and  megalopae  in  the  same  area  up  to  128 
km  from  shore.  In  Chesapeake  Bay  and  Pamlico 
Sound,  N.C.,  megalopae  have  been  found  170  and 
100  km  respectively  from  presumed  points  of 
entry  to  the  estuarine  systems.  Most  of  this  off- 
and-onshore  movement  of  larval  stages  appears  to 
be  a  homeostatic  developmental  feature  in  the  life 


717 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


histories  of  the  species.  Among  spiny  lobsters, 
whose  larvae  are  seemingly  better  fitted  for  tem- 
porary pelagic  existence  than  crab  larvae  because 
of  leaflike  shape,  up  to  6  mo  or  greater  duration  of 
larval  life  occurs  (Lewis,  1951;  Austin,  1972). 
Phyllosomas  of  some  spiny  lobsters  are  rarely 
found  beyond  the  latitudinal  geographic  limits  of 
the  coastal  adult  population.  George  and  Main 
( 1967)  attributed  this  result  to  behavioral  re- 
sponses of  the  larvae,  vertical  migration,  etc., 
within  prevailing  current  systems  which  act  to 
preserve  integrity  of  distribution,  but  Austin 
(1972)  held  open  the  idea  of  long  distance  trans- 
port over  considerable  lengths  of  time.  Some  dis- 
persal of  larvae  at  the  fringes  of  less  pelagic  Cal- 
linectes  populations  obviously  occurs,  but  the 
wanderers  are  at  a  competitive  disadvantage  in 
establishing  temporary  range  extensions. 
Nevertheless,  larval  dispersal  of  Callinectes 
coupled  with  movement  of  adults,  judged  to  be 
minor  except  within  an  estuarine  system  (Fischler 
and  Walburg,  1962;  Tagatz,  1968),  seems  to  assure 
genetic  continuity  over  broad  areas. 

If  one  accepts  the  tenet  that  the  center  of  evolu- 
tion for  a  group  contains  the  largest  number  of 
species,  Neotropical  Atlantic  American  shores 
seem  to  be  the  primary  center  in  which  the  genus 
Callinectes  developed  and  from  which  it  radiated. 
Fossil  evidence  indicates  that  this  radiation  took 
place  in  the  Tertiary,  a  period  of  time  in  which 
land-water  relationships  of  that  region  diverged 
widely  from  their  positional  and  areal  extent 
today  (Woodring,  1966,  1971).  Olsson  (1972)  re- 
garded the  Miocene  as  the  time  when  Panama- 
nian molluscan  biotas  related  to  those  of  today 
evolved  under  conditions  of  general  subsidence 
and  when  parts  of  present  day  Central  America 
were  reduced  to  an  archipelago  of  large  islands 
separated  by  straits  between  the  Caribbean  and 
east  Pacific.  Ekman  ( 1953),  Fell  ( 1967),  and  others 
regarded  the  marine  fauna  that  evolved  in  this 
region  as  an  impoverished  western  outpost  of  the 
Tethyan  fauna,  related  most  closely  to  that  of  the 
eastern  Atlantic  and  southern  Europe.  Though 
the  tropical  Atlantic  and  neighboring  east  Pacific 
regions  both  shared  in  the  radiation  of  Cal- 
linectes, the  conservatism  of  this  offshoot  contrasts 
remarkably  with  the  far  richer  divergence  of  its 
parent  stock.  Stephenson  (1962)  considered  the 
Indo-Pacific,  with  175  living  species,  as  the  ger- 
minal center  for  the  Portunidae.  It  seems  reason- 
able to  view  Callinectes  as  a  portunid  group  evolv- 
ing at  the  geographic  limits  of  the  family, 


specializing  in  occupation  of  estuaries,  and  paral- 
leling in  many  ways  the  heavy- bodied  Indo- 
Pacific  Scy//a  serrata  (Stephenson,  1962). 

If  Callinectes  evolved  mainly  in  the  Caribbean 
faunal  province,  the  present  distribution  of 
species  in  essentially  three  isolated  centers  raises 
questions  concerning  dispersal.  Separation  of  the 
east  Pacific  from  the  Caribbean  by  elevation  of  the 
Panamanian  isthmus  near  the  close  of  the  Ter- 
tiary understandably  isolated  certain  elements  of 
the  genus  and  may  have  promoted  further  radia- 
tion, but  close  relationship  of  species  in  the  two 
areas  is  emphasized  by  an  obvious  geminate  pair 
— danae-arcuatus — similar  in  a  number  of  mor- 
phological features,  which  occurs  today  on  east 
and  west  coasts  of  Middle  and  South  America. 
Separation  of  the  east  and  west  Atlantic  frag- 
ments of  the  genus  is  harder  to  resolve  because 
not  only  does  one  species  bridge  this  gap,  but  two 
species  groups  (short  and  long  first  gonopods)  are 
represented  on  both  sides  of  the  ocean,  seemingly 
specialized  along  the  same  general  lines.  Which  is 
the  ancestral  stock?  Were  pelagic  larvae  the 
mechanism  of  transport,  as  Fell  (1967)  proposed 
for  analogous  but  cold-tolerant  echinoderms, 
perhaps  aided  by  island  stepping  stones  in  the  mid 
Atlantic?  (Fell  rejected  continental  drift  as  a 
plausible  explanation  for  transport,  an  idea  more 
acceptable  today  than  it  was  in  1967,  but  involv- 
ing a  time  span  greater  than  concerned  here 
[McKenzie,  1972].)  Length  of  life  of  the  larvae  of 
most  species  of  Callinectes  under  pelagic  condi- 
tions remains  unknown.  West  Africa  is  upstream 
from  the  Western  Hemisphere  in  prevailing 
equatorial  surface  currents.  It  seems  unlikely  that 
the  larvae  could  move  counter  to  this  current  from 
a  center  in  the  west  or  survive  the  much  longer 
(and  today,  colder)  northern  transit  from  the  West 
Indies  via  the  Gulf  Stream  beyond  Bermuda  to  the 
Azores,  Canaries,  and  finally  to  west  Africa.  So  far 
as  known,  all  Callinectes  utilize  estuaries  during 
part  of  their  lives.  Populations  on  small  islands 
may  be  nonbreeding,  transitory  implants,  or  un- 
successful breeders.  Means  and  paths  of  long- 
distance transport,  and  effectiveness  of  transients 
in  colonization,  among  these  forms  will  remain 
unknown  until  more  data  are  collected. 

Finally,  the  clustering  of  species  by  numerical 
methods  employed  by  Stephenson  et  al.  (1968) 
does  not  reflect  the  three  groups  suggested  by  first 
gonopod  types,  but  it  does  support  classical  in- 
terpretation setting  C  marginatus  and  perhaps  C. 
gladiator  aside  as  the  most  peripheral  morpholog- 


718 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


ically.  It  suggests  that  the  three  west  American 
species,  C.  arcuatus,  bellicosus,  and  tcxotes  differ 
appreciably  from  each  other  and  that  they  arose 
from  eastern  American  ancestors.  It  also  supports 
the  idea  that  most  of  the  postulated  "central" 
species  occur  in  the  Atlantic  and  that  "it  is  con- 
ceivable that  the  group  originated  from  an  eastern 
American  ancestor."  Beyond  this  the  results  are 
less  compatible  with  conclusions  reached  here,  but 
the  analysis  was  done  without  including  C  similis 
which  may  be  a  linking  form  that  would  have 
changed  the  interpretation. 

SPECIES  ACCOUNTS 

In  the  species  accounts  that  follow,  the 
synonymies  include  only  citations  of  works  that 
primarily  are  concerned  with  descriptive,  tax- 
onomic,  or  zoogeographic  information.  The  reason 
for  this  limitation  is  that  commercially  valuable 
species  often  have  a  voluminous  literature.  All 
inclusive  synonymies  for  them  become  so  un- 
wieldy that  the  real  purpose — taxonomic  history 
of  the  species — becomes  obscured.  The  descrip- 
tions also  are  limited  because  full  descriptions  are 
elsewhere  in  the  literature. 

Two  features  included  in  the  descriptions  need 
clarification.  The  term  "metagastric  area"  is  em- 
ployed for  the  central  trapezoidal  area  of  the 
carapace  in  the  sense  Chace  and  Hobbs  (1969) 
used  it  rather  than  the  term  "intramedial  area" 
employed  by  others  (cf.  Rathbun,  1930;  Williams, 
1966).  Strictly  speaking,  this  region  of  the 
carapace  includes  the  undifferentiated  metagas- 
tric (over  90%)  and  at  least  part  of  the  shortened 
urogastric  (less  than  10% )  areas,  but  for  all  practi- 
cal purposes  the  first  term  is  sufficiently  explicit. 
The  number  of  anterolateral  teeth  in  Callinectes  is 
nine  (Rathbun,  1930),  but  the  first  of  the  series  is 
also  known  as  the  outer  orbital  tooth  and  the  last 
as  the  lateral  spine.  This  partition  of  the  series  is 
observed  here.  The  first  and  last  teeth  are  always 
named  and  the  small  teeth  are  numbered. 

Abbreviations  adopted  for  institutions  loaning 
study  material  are:  AHF,  Allan  Hancock  Founda- 
tion, University  of  Southern  California;  AMNH, 
American  Museum  of  Natural  History,  New  York; 
ANSP,  Academy  of  Natural  Sciences  of  Philadel- 
phia; BMNH,  British  Museum  (Natural  History), 
London;  MCZ,  Museum  of  Comparative  Zoology, 
Harvard;  MNB,  Museu  Nacional,  Rio  de  Janeiro; 
MNHNP,  Museum  National  d'Histoire  Naturelle, 
Paris;  RMNH,  Rijksmuseum  van  Natuurlijke 


Historie,  Leiden;  SADZ-B,  Secretaria  da  Agricul- 
tura,  Departamento  Zoologia,  Sao  Paulo;  UNC- 
IMS,  University  of  North  Carolina,  Institute  of 
Marine  Sciences,  Morehead  City;  USNM,  Na- 
tional Museum  of  Natural  History,  Washington, 
D.C.;  YPM,  Peabody  Museum  of  Natural  History, 
Yale  University,  New  Haven,  Conn. 

Supplementary  literature  records  are  occur- 
rences not  represented  by  specimens  studied,  but 
accepted  on  basis  of  supporting  data. 

GENUS  CALLINECTES  STIMPSON, 

1860 

Callinectes  Stimpson,  1860,  p.  220  [92].-  Rathbun, 
1896,  p.  349  (revision).-  1921,  p.  394  (review  of 
African  species).-  1930,  p.  98  (review  of  West- 
ern Hemisphere  species).-  not  Chen,  1933,  p.  95 
(=Portunus?).-  Monod,  1956,  p.  204  (review  of 
African  species).-  Garth  and  Stephenson,  1966, 
^         p.  42  (review  of  eastern  Pacific  species). 

Description. — Portunid  crabs  lacking  an  inter- 
nal spine  on  carpus  of  chelipeds.  Abdomen  of 
males  broad  proximally,  narrow  distally,  roughly 
T-shaped;  first  segment  broad,  almost  hidden;  sec- 
ond segment  broad,  slightly  overlapping  coxae  of 
fifth  pereopods  at  each  side;  third-fifth  segments 
fused  and  tapering  sinuously  from  broad  third  to 
distally  narrow  fifth;  sixth  segment  elongate  and 
narrow;  telson  ovate  with  acute  tip.  Abdomen  of 
females  exhibiting  two  forms:  immature  females 
with  abdomen  triangular  from  fourth  segment  to 
tip  of  telson,  segments  fused;  mature  females  with 
abdomen  broadly  ovate  (excluding  telson),  seg- 
ments freely  articulated;  first  segment  almost 
hidden;  second  and  third  segments  slightly  over- 
lapping coxae  of  fifth  pereopods  at  each  side;  fifth 
and  sixth  segments  with  greatest  sagittal  length; 
sixth  segment  narrowing  distally  in  irregular 
broad  arc  to  articulate  with  triangular  telson.  Ab- 
domen and  telson  of  both  sexes  reaching  an- 
teriorly beyond  suture  between  thoracic  sternites 
IV  and  V. 

Type  species. — Callinectes  sapidus  Rathbun, 
1896,  by  designation  of  International  Commission 
of  Zoological  Nomenclature  (1964:336). 

Gender. — Masculine. 

Number  of  species. — Fourteen,  which  may  be 
distinguished  by  the  following  keys. 


719 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

KEY  TO  SPECIES  OF  CALLINECTES  (EXCLUDING  JUVENILES) 

Figures  3-17 

1.  Front  with  two  prominent,  broad  based,  triangular  teeth  between  inner  orbitals;  each 

with  or  without  rudimentary  submesial  tooth  on  mesial  slope  (Atlantic;  Western 

Hemisphere,  introduced  in  Europe) sapidus. 

1'.  Front  with  four  teeth  between  inner  orbitals,  or  two  prominent  lobulate  or  narrowly 
triangular  teeth  separated  by  a  nearly  plane  space  often  bearing  a  pair  of  rudimentary 
submesial  teeth 2 

2.  Submesial  pair  of  frontal  teeth  well  developed  and  more  than  half  as  long  as  lateral  pair 

(measuring  from  base  of  lateral  notch  between  teeth) 3 

2'.  Frontal  teeth  decidedly  unequal  in  size,  submesial  pair  no  more  than  half  as  long  as 

lateral  pair  (measuring  from  base  of  lateral  notch  between  teeth),  or  vestigial  ....  8 

3.  Four  frontal  teeth  reaching  nearly  common  level 4 

3'.  Submesial  frontal  teeth  definitely  falling  short  of  lateral  pair 7 

4.  Four  frontal  teeth  lobulate,  not  triangular  (Pacific;  Baja  California-Juan  Fernandez)        toxotes. 
4'.  One  or  both  pairs  of  frontal  teeth  triangular 5 

5.  Four  frontal  teeth  with  rather  rounded  tips,  lateral  pair  more  broadly  triangular  than 

submesial  pair  and  with  mesial  side  having  more  oblique  slope  than  lateral  side  . .  6 

5'.  Four  frontal  teeth  acute,  lateral  pair  usually  broader  than  submesial  pair  (Atlantic; 

Mexican  Gulf  coast) .  .  rathbunae. 

6.  Anterolateral  teeth  trending  forward,  their  anterior  margins  shorter  than  posterior; 

vestiges  of  reddish  color  usually  persisting  in  preserved  specimens  (except  long- 
preserved  ones);  distal  border  of  sixth  abdominal  segment  in  mature  females  broadly 

triangular  (Atlantic;  Caribbean-South  America) bocourti. 

6'.  Anterolateral  teeth  directed  outward,  their  tips  acuminate  and  margins  shouldered  at 
least  in  anterior  portion  of  row;  vestiges  of  greenish  color  usually  persisting  in 
preserved  specimens  (except  in  long-preserved  ones);  distal  border  of  sixth  abdominal 
segment  in  mature  females  semiellipsoid  (Atlantic;  Venezuelan  estuaries)  .  .  .  maracaiboensis. 

7.  Granules  on  ridges  and  crests  of  chelae  coarse  and  well  separated  (Atlantic;  Caribbean- 

South  America)  exasperatus. 

T.  Granules  on  ridges  and  crests  of  chelae  moderate  to  fine  and  closely  crowded,  often  worn 

smooth  in  adults  (Atlantic;  West  Africa)  latimanus. 

8.  Carapace  remarkably  smooth,  lines  of  granules  visible  but  barely  perceptible  to  touch 

(except  epibranchial  line  variably  prominent)   9 

8'.  Carapace  not  so  smooth,  scattered  granules  and  lines  of  granules  quite  evident  to  sight 

and  touch 10 

9.  Submesial  pair  of  frontal  teeth  vestigial  (Pacific;  Baja  California  and  Golfo  de  California)   bellicosus. 
9'.  Submesial  pair  of  frontal  teeth  small  but  definitely  formed  (Atlantic;  United  States-Gulf 

of  Mexico)   similis. 

10.  Carapace  coarsely  granulated;  all  anterolateral  teeth  except  first  two  curved  forward, 

without  shoulders  (Atlantic;  Bermuda-Florida-South  America- West  Africa)  ....  marginatus. 
10'.  Carapace  finely  granulated;  only  last  or  last  two  anterolateral  teeth  curved  forward, 

remainder  with  shoulders 11 

11.  Submesial  pair  of  frontal  teeth  absent  or  vestigial  (Atlantic;  Bermuda-North  America- 

South  America)  ornatus. 

11'.  Submesial  pair  of  frontal  teeth  never  vestigial,  but  no  more  than  half  length  of  lateral 

pair 12 

12.  Lateral  spine  almost  always  less  than  three  times  length  of  preceding  anterolateral 

tooth;  tips  of  anterolateral  teeth  forming  a  decided  arc;  males  with  distal  portion  of 

first  gonopods  almost  straight 13 

720 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 

12'.  Lateral  spine  almost  always  three  or  more  times  length  of  preceding  anterolateral  tooth; 

at  least  second  to  fifth  anterolateral  teeth  with  tips  in  a  nearly  straight  line;  males 

with  distal  portion  of  first  gonopods  S-curved  (Atlantic;  West  Africa) gladiator. 

13.   First  gonopods  of  mature  males  with  subterminal  dorsal  setae  never  more  than  four  in 

number,  often  inconspicuous  or  missing  (Atlantic;  Caribbean-South  America) danae. 

13'.  First  gonopods  of  mature  males  with  subterminal  dorsal  row  of  setae  numbering  more 

than  four  (Pacific;  Southern  California-Peru;  Galapagos  Islands) arcuatus. 

KEY  TO  MATURE  OR  NEARLY  MATURE  MALE  CALLINECTES  BASED 

PRIMARILY  ON  FIRST  GONOPODS 

Figures  18-21 

1.  Tips  of  gonopods  falling  well  short  of  suture  between  thoracic  sternite  VI  and  mesially 

expanded  sternite  VII    2 

1'.  Gonopods  reaching  to,  almost  to,  or  beyond  suture  between  thoracic  sternite  VI  and 

mesially  expanded  sternite  VII 5 

2.  Gonopods  well  separated  from  each  other,  never  touching  or  crossed 3 

2'.  Gonopods  overlapping  each  other,  often  crossed   4 

3.  Gonopods  slender  distally,  nearly  straight,  tips  bent  slightly  mesad  (Atlantic;  United 

States-Gulf  of  Mexico) similis. 

3' .  Gonopods  fairly  stout  distally,  angled  toward  midline,  then  abruptly  bent  forward  in  a 
short  slender  terminal  extension  (Atlantic;  Bermuda-Florida-South  America-West 
Africa)    marginatus. 

4.  Tips  of  gonopods  lanceolate,  continuing  in  line  with  shaft,  portion  proximal  to  tip  armed 

with  short  backward  pointing  spines  quite  visible  at  low  magnification  (Atlantic; 

Bermuda-North  America-South  America)   ornatus. 

4'.  Tips  of  gonopods  not  lanceolate,  curved  mesad,  spines  on  S-curved  shank  exceedingly 

small  at  low  magnification  (Atlantic;  West  Africa) gladiator. 

5.  Tips  of  gonopods  curved  abruptly  mesad  (Atlantic;  Caribbean- South  America)  ....   exasperatus. 
5'.  Tips  of  gonopods  not  curved  abruptly  mesad   6 

6.  Slender  portion  of  gonopods  almost  straight,  minutely  spined  (under  magnification),  tips 

almost  always  bent  ventrolaterally,  never  extending  beyond  abdominal  locking 

tubercle  on  thoracic  sternite  V 7 

6'.  Slender  portion  of  gonopods  definitely  curved  or  sinuous,  variously  spined,  tips  never 

bent  ventrolaterally 8 

7.  Gonopods  with  subterminal  dorsal  setae  never  more  than  four  in  number,  often  incon- 

spicuous or  missing  (Atlantic;  Caribbean- South  America) danae. 

T .  Gonopods  with  subterminal  dorsal  row  of  setae  numbering  more  than  four  (Pacific; 

Southern  California-Peru;  Galapagos  Islands ) arcuatus. 

8.  Tips  of  gonopods  reaching  well  beyond  abdominal  locking  tubercle  on  thoracic  sternite  V  9 
8'.  Tips  of  gonopods  not  reaching  beyond  abdotninal  locking  tubercle  on  thoracic  sternite  V 

(Pacific;  Baja  California  and  Golfo  de  California)   bellicosus 

9.  Slender  portion  of  gonopods  with  spinules  small  under  magnification  and  most  dense 

near  middle,  absent  near  tip  (Pacific;  Baja  California-Juan  Fernandez) toxotes. 

9'.  Slender  portion  of  gonopods  with  spinules  readily  visible  at  low  magnification  and 

distributed  to  tip 10 

10.  Gonopodal  spines  arranged  in  a  broad  dorsolateral  band 11 

10'.  Gonopodal  spines  arranged  in  a  single,  rather  uneven  dorsolateral  row  (a  few  tiny  spines 

lying  outside  row)  (Atlantic;  Western  Hemisphere,  introduced  in  Europe)    sapidus. 

11.  Tips  of  all  frontal  teeth  reaching  same  level   12 

11'.  Submesial  pair  of  frontal  teeth  definitely  shorter  than  lateral  pair  (Atlantic;  West  Africa)  latimanus. 

721 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

12.  Four  frontal  teeth  with  rather  rounded  tips,  lateral  pair  more  broadly  triangular  and 

with  mesial  side  having  more  oblique  slope  than  lateral  side 13 

12'.  Four  frontal  teeth  acute,  lateral  pair  usually  broader  than  submesial  pair  (Atlantic; 

Mexican  Gulf  coast)   rathbunae. 

13.  Anterolateral  teeth  trending  forward,  their  anterior  margins  shorter  than  posterior; 

vestiges  of  reddish  color  usually  persisting  in  preserved  specimens  (except  long- 
preserved  ones);  (Atlantic;  Caribbean-South  America) bocourti. 

13'.  Anterolateral  teeth  directed  outward  their  tips  acuminate  and  margins  shouldered  at 
least  in  anterior  portion  of  row;  vestiges  of  greenish  color  usually  persisting  in 
preserved  specimens  (except  in  long-preserved  ones);  (Atlantic;  Venezuelan 
estuaries) maracaiboensis. 


CALLINECTES  MARGINATUS 
(A.  MILNE  EDWARDS) 

Figures  3,  18a,  20a,  22b,  27 

Neptunus  marginatus  A.  Milne  Edwards,  1861,  p. 
318,  pi.  30,  fig.  2  (syntypes:  3  9  dry,  MNHNP 
895-lS,  895-2S,  896,  Gabon). 

Callinectes  larvatus  Ordway,  1863,  p.  573  [8]  (syn- 
types: 1  (5,  MCZ  5147,  Tortugas,  Fla.,  USA;  3 
^,  1 9,  MCZ  No.  5151,  Key  West,  Fla.,  USA;  3 
5  MCZ  5152,  Bahamas;  lS,l  juv  9  [not  5] 
MCZ  5155,  Jeremie,  Haiti).-  Smith,  1869,  p 
9.-  A.  Milne  Edwards,  1879,  p.  225  (var.  of  C 
diacanthus). -Ra.thhwn,  1896,  p.  358,  pi.  18 
pi.  24,  fig.  5;  pi.  25,  fig.  4;  pi.  26,  fig.  4;  pi.  27 
fig.  4.-  Rankin,  1898,  p.  232.-  Young,  1900,  p 
188  (var.  of  C.  diacanthus) .-  Doflein,  1904 
p.  99. 

Neptunus  diacanthus.-  Brocchi,  1875,  pi.  16,  fig. 
76  [?].-  de  Man,  1883,  p.  150.-  Pfeffer,  1890, 
p.  5,  pi.  1,  figs.  5,  6. 

Callinectes  africanus  A.  Milne  Edwards,  1879,  p. 
229  (var.  of  C.  diacanthus)  (syntypes: 
MNHNP,  Cape  Verde  Islands,  not  found  in 
1968).-  A.  Milne  Edwards  and  Bouvier, 
1900,  p.  71  (var.  of  C.  diacanthus)  (not  pi. 
4,  fig.  5  =  C  sapidus). 

Callinectes  larvatus  var.  africanus?   Benedict, 

1893,  p.  537. 

Neptunus  (Callinectes)  diacanthus.-  Ortmann, 

1894,  p.  77  (part;  specimen  b,  Cuba). 
Callinectes  marginatus.-  Rathbun,  1897,  p.  149.- 

1900a,  p.  291.-  1900b,  p.  142.-  1901,  p.  48.- 
1921,  p.  395,  text-fig.  2,  pi.  19,  fig.  1;  pi.  20, 
fig.  1.-  1930,  p.  123,  figs.  15e,  16d,  17d,  18c, 
pi.  53.-  1933,  p.  49.-  1936,  p.  383.-  de  Man, 
1900,  p.  41,  pi.  1,  fig.  5  (juv  9,  not  (J).-  Nobili, 
1906,  p.  305.-  Gruvel,  1912,  p.  3,  6,  pi.  2,  fig. 
1.-  Balss,  1921,  p.  58.-  Odhner,  1923,  p.  21.- 


Boone,  1927,  p.  32.-  Contreras,  1930,  p.  235, 
fig.  6.-  Vilela,  1949,  p.  59.-  Capart,  1951,  p. 
134,  fig.  48.-  Chace,  1956,  p.  154.-  Chace  and 
Hobbs,  1969,  p.  131,  fig.  37d.-  Monod,  1956, 
p.  208,  figs.  238, 239.-  Rossignol,  1957,  p.  82.- 
Guinot  and  Ribeiro,  1962,  p.  48.-  Forest  and 
Guinot,  1966,  p.  65.-  Taissoun,  1973,  p.  39, 
figs.  4A,  5B,  photo  7. 

Callinectes  diacanthus.-  Young,  1900,  p.  186 
(part). 

Callinectes  marginatus  var.  larvatus.-  Verrill, 
1908a,  p.  368,  text-fig.  22b,  pi.  18,  fig.  1. 

Description. — Carapace  (Figure  3)  bearing  four 
frontal  teeth,  submesial  pair  no  more  than  half 
length  of  lateral  pair.  Central  trapezoidal 
(metagastric)  area  short,  anterior  width  about  2.4 
times  length,  posterior  width  about  1.5  times 
length.  Anterolateral  margins  arched  slightly; 
anterolateral  teeth  exclusive  of  outer  orbital  and 
lateral  spine  without  shoulders,  usually  trending 
forward  and  anterior  margins  of  all  except  first 
two  concave,  last  two  teeth  spiniform.  Lateral 
spine  moderately  long  and  slender.  Surface 
coarsely  granulate  anterior  to  prominent  epibran- 
chial  line  and  over  mesobranchial  regions,  more 
finely  and  closely  granulate  on  proto-  and 
mesogastric  areas,  prominent  branchial  lobes, 
and  especially  on  cardiac  lobes;  posterior  and 
posterolateral  margins  smooth. 

Chelipeds  with  smoothly  granulate  prominent 
ridges  on  propodi  and  reduced  ones  on  carpi; 
fingers  compressed  but  broadened  dorsoventrally 
producing  a  pointed  spatulate  shape;  major  chela 
with  usual  enlarged  proximal  tooth  on  dactyl  op- 
posing propodal  molariform  complex,  propodus 
often  with  decurved  lower  margin. 

Male  abdomen  and  telson  narrow,  reaching 
slightly  beyond  suture  between  sternites  IV  and 
V;  telson  about  1.8  times  longer  than  wide;  sixth 


722 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


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724 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


segment  nearly  parallel  sided  but  somewhat 
broadened  proximally.  Mature  female  abdomen 
and  telson  reaching  same  level  as  in  male,  length 
slightly  exceeding  width  (1.05  times);  sixth  seg- 
ment longer  than  fifth.  First  gonopods  of  male 
(Figures  18a,  20a)  short,  reaching  about  mid- 
length  of  sternite  VII,  approximating  each  other 
or  occasionally  overlapping  at  level  of  sharp  distal 
curve,  distal  portion  abruptly  curved  laterad,  ta- 
pered to  a  rather  sharp  point,  twisted  one-fourth 
turn  on  axis  and,  except  for  membranous  spout- 
like tip,  armed  with  minute  scattered  retrogres- 
sive spinules  tending  to  arrangement  in  rows,  a 
few  spinules  proximal  to  flexure.  Gonopores  of 
female  (Figure  22b)  ovate  with  apex  on  long  axis 
directed  anteromesad,  aperture  of  each  with  mar- 
gin irregularly  rounded  and  sinuous  except  on 
mesial  side  where  it  slopes  from  surface  laterad 
under  superior  anterior  border. 

Size  of  carapace  in  mm. — Largest  male:  lengt* 
67,  width  at  base  of  lateral  spines  118,  including 
lateral  spines  142.  Largest  female:  length  49, 
width  at  base  of  lateral  spines  82,  including  lat- 
eral spines  95.  Mature  size  of  females  varies  con- 
siderably, the  smallest  examined  having  a 
carapace  length  of  33  and  width  including  lateral 
spines  of  70.  Summary  of  selected  measurements 
is  given  in  Tables  1  and  2. 

Color. — Carapace  brown  with  areas  of  bluish 
black.  Chelae  brown  above;  fingers  dark  on  exter- 
nal face  except  for  tips  and  proximal  portion,  in- 
ternal face  dark  in  distal  two-thirds;  dark  color  of 
fingers  retained  in  preservation  (in  part  from 
Rathbun,  1930,  and  pers.  commun.  from  Charles 
A.  Johnson).  Milne  Edwards  and  Bouvier  (1900) 
gave  essentially  the  same  impression,  charac- 
terizing the  entire  carapace,  abdomen,  external 
face  of  chelipeds,  posterior  legs,  some  areas  of  the 
walking  legs  with  their  marginal  hairs  as 
greenish  brown  and  other  parts  of  the  appendages 
as  a  beautiful  blue,  but  there  is  some  confusion 
here  because  the  colored  plate  accompanying  this 
description  (Plate  4,  Figure  5)  represents  C. 
sapidus.  Rossignol  (1957)  described  the  carapace 
as  marbled,  and  recently  preserved  material  in 
alcohol  sometimes  does  give  an  impression  of  mot- 
tled gray  and  white  on  the  carapace. 

Variation. — The  carapace  in  C.  marginatus 
shows  a  number  of  individual  variations.  The 
small  anterolateral  teeth  generally  trend  forward, 


but  there  is  enough  individual  departure  from  this 
pattern  to  cause  confusion.  Teeth  in  the  mesial 
part  of  the  row  trend  forward  more  than  those  in 
the  lateral  part,  the  first  three  often  being  rounded 
while  the  last  four  are  pointed.  Small  anterolat- 
eral teeth  on  syntype  females  in  MNHNP  do  not 
definitely  trend  forward,  and  those  on  the  syntype 
of  C.  larvatus  (MCZ  5155)  are  well  separated,  with 
apices  directed  outward  rather  than  hooked  for- 
ward. There  are  differences,  too,  in  width  of  the 
anterolateral  teeth,  a  suggestion  of  narrower 
teeth  in  Brazil  than  in  Florida,  and  broad  teeth  on 
some  African  material.  Occasionally  there  is  some 
iridescence  along  the  anterolateral  border,  and 
often  hairiness  along  the  lower  anterolateral  bor- 
der. 

The  inner  orbital  fissures  are  usually  tightly 
closed,  sometimes  with  a  slight  notch  on  the  orbit- 
al border,  but  open  in  some  African  and  Dutch 
West  Indies  (Aruba)  material. 

The  anterolateral  slopes  have  an  arching  con- 
cavity proximal  to  the  bases  of  the  anterolateral 
teeth  and  extending  transversely  behind  the  or- 
bitofrontal  region  that  is  more  pronounced  than 
in  other  species  of  the  genus.  This  is  especially 
evident  in  mature  females.  The  abdomen  of  imma- 
ture males  is  flush  with  the  sternum  and  rela- 
tively wider  than  in  adults  in  which  it  is  somewhat 
recessed.  Among  mature  males,  calcification  is 
weak  in  the  articulation  between  the  fifth  and 
sixth  abdominal  segments  allowing  definite 
flexure  in  this  joint,  but  transverse  ridges  ("stops") 
on  external  exposed  edges  of  the  joint  prevent 
doubling  backward.  The  calcification  pattern  is 
well  demonstrated  in  two  mature  males  in  USNM 
4172  from  Dominican  Republic.  Abdominal  seg- 
ment 6  is  constricted  at  mid-length  in  some  males. 
The  abdomen  of  adult  females  resembles  that  of 
C  ornatus. 

Sexual  differences  include  a  more  tumid  ap- 
pearing body  among  females  than  males,  an  effect 
resulting  partly  from  less  produced  lateral  spines, 
as  well  as  granulations  on  the  carapace  that  are 
relatively  more  prominent  than  on  males. 
Granules  on  the  carapace  sometimes  are  very 
coarse  in  front  of  the  epibranchial  line,  but  seldom 
as  coarse  behind  as  in  front  of  this  line.  Incon- 
spicuous spination  on  the  male  first  gonopods  in 
specimens  from  the  Canal  Zone  of  Panama,  Hon- 
duras, Colombia,  and  Venezuela  is  not  so  strong 
nor  dense  as  that  in  males  from  Florida  where 
there  is  a  suggestion  that  the  scattered  spines  are 
in  rows  proximal  to  the  distal  bend;  spination 


725 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


seems  entirely  lacking  in  some  Brazilian  mater- 
ial. 

This  is  the  species  that  should  be  named 
"latimanus"  because  broad,  spatulate,  often 
strongly  asymmetrical  chelae  occur  on  both 
juveniles  and  adults.  The  chelipeds  often  seem 
heavy  for  the  size  of  the  animal  bearing  them,  but 
pronounced  asymmetry  is  not  universally  present. 
Some  individuals  have  both  chelae  basically  alike 
except  for  size,  and  in  almost  all  except  juveniles 
the  ventral  side  of  the  propodus  (especially  the 
major)  is  decurved  in  a  wide  sweep  giving  em- 
phasis to  the  "spatulate"  character.  The  proximal 
tooth  on  the  dactyl  of  the  major  chela  may  be 
moderate  but  is  often  large  in  size  and  worn  as 
shown  in  Figure  3a.  Some  juveniles  with  worn 
chelae  have  a  gape  between  fingers  of  the  minor  as 
well  as  major  chela  along  with  development  of  a 
strong  proximal  tooth  on  the  dactyls.  Although 
similarity  in  chelae  may  indicate  regeneration, 
there  is  no  evidence  that  replacement  has  occur- 
red. 

Habitat. — Meager  data  recorded  with  speci- 
mens suggests  that  this  species  lives  in  a  variety  of 
shallow  littoral  environments  probably  seldom 
exceeding  15  m  (rarely  to  25  m  [?])  and  usually 
in  much  shallower  water  from  intertidal  pools  to  3 
m  deep.  Most  specimens  have  been  collected  by 
hand,  seine,  dip  net,  etc.,  from  sand  and  mud  flats, 
algae  and  grass  flats,  sandy  beaches,  rocky  pools, 
eroded  coral  bases,  oyster  bars,  shallows  at  edge  of 
mangroves,  and  at  the  surface  under  lights  at 
night.  A  number  of  authors  (Milne  Edwards  and 
Bouvier,  1900;  Monod,  1956;  Rossignol,  1957; 
Forest  and  Guinot,  1966;  Coelho,  1967a,  b,  1970) 
have  noted  that  C.  marginatus  is  a  coastal  species 
limited  to  depths  of  a  few  meters,  often  in  brackish 
water,  but  rather  rare  and  never  as  abundant  as 
other  species  of  Callinectes.  Capart  (1951)  found 
it  on  shallow  mud  bottoms  in  salinities  varying 
from  7.43-14.85^0  at  the  surface  to  19.29-32. 56%^ 
in  5-m  depths  and  in  a  bottom  temperature  range 
of  22.5°  to  27.42°C;  he  never  found  it  in  the  ocean. 
Buchanan  (1958)  similarly  found  it  in  5.5-14-m 
depths  in  a  temperature  range  of  27°  to  30°C  off 
Accra,  Ghana,  in  what  he  termed  the  inshore  fine 
sand  community.  Chace  (1956)  recorded  it  in 
27.5°C  water  oflF  Los  Roques,  Venezuela. 

Spawning . — Both  the  museum  material  studied 
and  records  in  literature  yield  only  fragmentary 
evidence  on  spawning.  Ovigerous  females  are  re- 


corded from  December  to  July  in  various  parts  of 
the  geographic  range  on  both  sides  of  the  Atlantic. 
Specifically  the  records  are:  Congo  and  St. 
Thomas,  December;  St.  Thomas,  January;  Gren- 
adines and  Cuba,  March;  Haiti,  April;  Jamaica 
and  Senegal,  May;  Colombia,  Curagao  and  Sao 
Tome  (Forest  and  Guinot,  1966),  June;  Florida 
and  Puerto  Rico,  July. 

Distribution. — Off  southern  Florida  through 
Caribbean  Sea  to  south  central  Brazil  off  Estado 
de  Sao  Paulo;  Bermuda  and  Cape  Verde  Islands; 
Senegal  to  central  Angola  (Figure  27).  A  recent 
record  from  North  Carolina  is  regarded  as  a  tem- 
porary range  extension. 

Economic  importance. — Gravel  (1912),  describ- 
ing fisheries  for  C.  latimanus  along  the  Gulf  of 
Guinea,  noted  that  C.  marginatus  is  also  caught 
all  along  the  coast  from  Senegal  to  the  Congo 
under  a  variety  of  local  names. 

Remarks. — The  populations  on  each  side  of  the 
Atlantic  seem  indistinguishable  by  means  of  ex- 
ternal morphological  characters.  Different  names 
applied  to  the  populations  on  each  side  reflect  the 
discontinuity  of  early  collections,  Verrill  (1908a) 
for  instance  considering  laruatus  the  American 
and  africanus  the  African  variety,  but  with  the 
progress  of  exploration  and  inventory  it  is  evident 
that  the  whole  is  a  genetic  continuum  with  minor 
local  variations  already  pointed  out.  Most  modern 
workers  (Capart,  1951;  Monod,  1956)  accept  this 
idea  although  deploring  the  difficulty  in  identify- 
ing juveniles. 

Verrill  (1908b)  early  recognized  the  significance 
of  larval  transport  in  oceanic  currents,  applying  it 
to  populations  of  C.  marginatus  in  Bermuda  that 
have  their  origin  in  the  West  Indies.  It  is  tempting 
to  make  the  generalization  that  this  species  in  its 
moderate  size,  short,  simply  ornamented  male 
first  gonopods,  and  amphi-Atlantic  pattern  of 
geographic  distribution  possibly  represents  an 
unspecialized  and  primitive  member  of  the  genus, 
but  such  ideas  are  qualified  by  the  specialization 
of  chelae  seemingly  well  adapted  by  their  dor- 
soventrally  broadened  but  rather  thin  fingers  for 
reaching  into  crevices,  perhaps  into  mollusk 
shells  after  they  are  cracked.  In  short,  generalized 
structure  is  hard  to  assess. 

Some  specimens  show  evidence  of  massive  foul- 
ing by  the  barnacle  Chelonibia.  A  male  (dry)  from 
Brazil  (BMNH  48.86)  measuring  89  mm  between 


726 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


tips  of  lateral  spines  bears  the  basal  disc  of  a  bar- 
nacle measuring  24.9  x  26.2  mm,  or  an  oval  area 
covering  all  of  the  metagastric  and  a  portion  of  the 
right  branchial  lobe  forward  to  the  base  of  the 
frontal  margin  and  edge  of  the  right  orbit.  A  sec- 
ond and  still  intact  barnacle  covers  all  of  the  left 
mesobranchial  region  (11.7  x  13.0  mm). 

Material. — Total.  242  lots,  615  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  (31091,  4172,  24445,  24446,  24447,  24448, 
24449,  24450,  24454,  43905,  62684,  54255  not 
found;  32514  =  C.  ornatus,  33103  =  C.  similis, 
61364  =  C.  danae)  and  MCZ. 

USNM.  99  lots,  282  specimens,  including  the 
following  not  cited  above: 

UNITED  STATES 

Florida:  80624,  Lake  Worth,  1945,  1  <J,  A.  H. 
Verrill.  113458,  Pigeon  Key,  Monroe  Co.,  7  Aug. 
1965,  1  S,  R.  B.  Manning.  123063,  Bahi.i  Honda 
Key,  Monroe  Co.,  14  June  1964,  2  S,  2  juv,  Foster 
and  Kaill,  No.  64-11-1.  71635,  Key  West,  1934, 

1  S,  H.  H.  Darby.  76972,  Key  West,  no  date,  5  c^,  1  9 
(ov),  C.  J.  Maynard.  123075,  Key  West,  no  date,  3 
c?,  2  2,  U.S.  Bur.  Fish.  The  following  from  Dry 
Tortugas— 62156,  25  July  1928,  (juv)  2  9,  A.  S. 
Pearse.  76968,  Fort  Jefferson,  Aug.  1930,  1  6,  W. 
L.  Schmitt.  62155,  Loggerhead  Key,  6  Aug.  1928, 

2  3  (juv),  A.  S.  Pearse.  76967  and  76970,  Long  Key, 
25  June  1931,  1  S,  5  juv,  W.  L.  Schmitt.  76969, 
Long  Key-Bush  Key,  18  June  1932,  1  S,  W.  L. 
Schmitt.  71636,  Bush  Key,  4  Aug.  1934,  1  9,  H.  H. 
Darby.  71655,  Sarasota  Bay,  summer  1930,  1  juv, 
W.  W.  Wallis. 

BAHAMAS 

101130,  Bimini  Bay,  27  Nov.  1951,  1  S  (juv),  F. 
Frieders. 

CUBA 

99977,  E  Xanadu,  Hicacos  Pen.,  Matanzas 
Prov.,  24-27  Jan.  1957,  1  carapace,  W.  L.  Schmitt. 

JAMAICA 

123060,  N  shore,  18°24.5'N,  77°07'W,  20  May 
1965, 1  9  (ov),  Oregon  Stn.  5405. 123062,  Kingston 
Harbor,  17  May  1965,  1  9,  B.  B.  Collette. 

HAITI 

65859,  He  a  Vache,  29  Apr.  1930, 1  9  (ov),  W.  M. 
Parish.  81481, 1,  opposite  Bayeaux,  23  June  1941, 
1  c5,  H.  H.  Bartlett. 


DOMINICAN  REPUBLIC 

62828,  near  Montecristi,  winter  1928-29,  1 
chela,  H.  W.  Kreiger. 

PUERTO  RICO 

73282,  off  Fort  San  Geronimo,  San  Juan,  30 
Apr.  1937, 3  6,  W.  L.  Schmitt.  73285,  near  Fort  San 
Geronimo,  W  end  San  Juan  I.,  27  Mar.  1937,  1  9, 
W.  L.  Schmitt. 

VIRGIN  ISLANDS 

St.  Croix:  72351  and  72359,  Salt  River  Bay, 
1935-36,  2  c^,  H.  A.  Beatty.  73284,  Christiansted,  9 
Apr.  1937,  1  6\  W.  L.  Schmitt.  76964  and  76965, 
Envy  Bay,  no  date,  1  d",  2  5,  H.  A.  Beatty.  Prickly 
Pear  I.  123070,  Vixen  Pt.,  Gorda  Sound,  15  Apr. 
1956,  1  9  (juv),  Nicholson,  Schmitt,  and  Chace. 

BARBUDA 

123069,  near  Oyster  Pond  Landing,  6  Apr.  1956, 
1  c?,  Schmitt,  Chace,  Nicholson,  and  Jackson. 

ANTIGUA 

123068,  Tank  Bay,  English  Harbor,  3  Apr.  1956, 
3  6,  Schmitt,  Chace,  Nicholson,  and  Jackson. 

GUADELOUPE 

123067,  between  Monroux  and  Rat  Is.,  Pointe  a 
Pitre,  30-31  Mar.  1956,  21  S,  5  9, 13  juv,  Chace  and 
Nicholson. 

ST.  LUCIA 

123066,  shore  of  bay  outside  Marigot  Lagoon,  21 
Mar.  1956,  1  6,  Chace,  Nicholson,  and  crew. 

GRENADINES 

123064,  Tyrrell  Bay,  Carriacou  I.,  15  Mar.  1956, 
3  9  (ov),  Schmitt  and  Nicholson.  123065,  Tyrrell 
Bay,  Carriacou  I.,  16  Mar.  1956,  1  9,  D.  V.  Nichol- 
son. 

MEXICO 

Quintana  Roo:  123072,  Cozumel  I.,  near  light- 
house at  Punta  Molas,  9  Apr.  1960, 5  6,  Rehder  and 
Bousfield.  123071,  Bahia  del  Espiritu  Santo,  north 
shore  near  Lawrence  Pt.,  6  Apr.  1960, 1  S,  Rehder, 
Daiber,  and  Haynes.  123073,  Pt.  Santa  Maria 
[20°19'N,  86°59'W],  22  Apr.  1960,  1  S,  Schmitt 
and  Rehder. 


HONDURAS 

78107,  Utila  I.,  Sept.  1938,  1  <^,  L.  Mouquin. 


727 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


COLOMBIA 

123061,  Isla  de  San  Andres,  5  June  1964,  1  9 
(ov),  B.  A.  Rohr. 

PANAMA 

61427,  Margarita  I.  [09°23'N,  79°53'W],  June 
1924,  1  9,  E.  Deichmann. 

BRAZIL 

Bahia:  123074,  Plataforma,  1875-77,  1  <?,  1  9 
(ov),  Hartt  Exped.  Rio  de  Janeiro:  123076,  Sao 
Francisco,  25  Aug.  1925,  1  6,  W.  L.  Schmitt. 

ZAIRE 

54255,  Banana,  mouth  of  Congo  River,  July- 
Aug.  1915,  1  9,  H.  Lang. 

AHF.  7  lots,  12  specimens. 

UNITED  STATES 

Florida:  Key  Largo  S  Gordons  Landing  at  Rock 
Harbor,  19  Sept.  1950,  2  S,  1  9,  Stn.  LM52.  Hawk 
Channel,  Plantation  Key,  3  mi  S  Tavernier 
bridge,  25  May  1949,  1  9,  A126-49,  Stn.  LM20-49. 
Hav^^k  Channel  off  Lower  Matecumbe  Key,  9  June 
1949,  2  6,  1  9,  A140-49,  Stn.  LM34-49.  Hawk 
Channel,  Lower  Matecumbe  Key,  23  Sept.  1950,  2 
9,  Stn.  LM57.  Long  Key,  Florida  Bay,  10  June 
1949,  A141-49,  Stn.  LM35-49. 

TOBAGO 

Bucco  Bay,  11°10'42"N,  60°48'07"W,  20  Apr. 
1939,  1  6,  Velero  III,  Stn.  A40-39. 

TRINIDAD 

Port  of  Spain,  10°38'12"N,  61°32'08"W,  18  Apr. 
1939,  1  9,  Velero  III,  Stn.  A37-39. 

AMNH.  30  lots,  81  specimens. 

UNITED  STATES 

Florida:  Lake  Worth,  July  and  Aug.  1945,  1  <J 
(juv),  W.  G.  Van  Name.  9789,  Lake  Worth,  June 
1945, 1  <?,  A.  H.  Verrill.  2290,  Key  Largo,  no  date,  1 
6,  C.  W.  Beebe. 

BAHAMAS 

11222,  North  Bimini,  June  1939,  7  S,  W.  Beebe 
Bermuda  Exped.  1 1288  and  11289,  Bimini,  5  Sept. 
1947,  2  6,  J.  C.  Armstrong.  9343,  Nassau,  Mar. 
1930,  1  S,  R.  W.  Miner.  3297,  no  date,  1  S,  col. 
unknown.  11290,  Dicks  Point,  New  Providence, 
1946-47, 1  o,  H.  Dodge.  11297,  Octagon  Point,  New 


Providence;  1946-47,  1  9,  H.  Dodge.  2252,  Andros, 
no  date,  3  S,  B.  E.  Dahlgren  and  H.  Mueller.  959, 
Andros,  Apr.  1908,  7  S,  1  9,  B.  E.  Dahlgren  and  H. 
Miieller. 

CUBA 

3158,  6  mi  SW  Cienfuegos,  off  Cayo  Carenas 
[22°05'N,  80°28'W],  18  June  1918,  1  6,  B.  Brown. 
3165,  Cayo  Cristo  [23°03'N,  80°00'W],  4  mi  N 
Isabela,  2-3  July  1918,  1  9,  B.  Brown. 

HAITI 

11219,  Bizoton  Reef  [18°32'N,  72°23'W],  4  Mar. 
1927,  1  (?,  2  9,  W.  Beebe  Exped. 

PUERTO  RICO 

2671,  near  San  Antonio  Bridge,  San  Juan,  10 
July  1914,  1  c?,  1  9,  R.  W.  Miner.  2674,  Landing 
place  in  Candado  Bay,  San  Juan,  9  July  1914,  1  9, 
R.  W.  Miner.  2682,  San  Juan  Harbor,  21  July 
1914, 1  9  (ov),  R.  W.  Miner.  2672,  rocks  at  entrance 
of  Condado  Bay,  San  Juan,  14  July  1914, 1  9,  R.  W. 
Miner. 

ZAIRE 

3455,  no  date,  1  S  (dry),  H.  Lang  and  J.  Chapin. 
3272  and  3329,  Banana,  Aug.  1915,  4  <?,  5  9,  H. 
Lang  and  J.  Chapin.  3340,  Banana,  no  date,  6  S,5 
9,  H.  Lang  and  J.  Chapin.  3428,  Manuba,  Banana, 
July  1915,  2  6,  H.  Lang  and  J.  Chapin.  3476, 
Banana,  July  1915,  1  9  (juv),  H.  Lang  and  J.  Cha- 
pin. 

ANGOLA 

3443,  Luanda,  23  Sept.  1915, 1  9,  H.  Lang  and  J. 
Chapin.  5895  [Angola  ?],  1925,  6  ^,  2  9  (1  ov), 
Vernay  Angola  Exped.  5901,  [Angola  ?],  1925,  3  cJ, 
Vernay  Angola  Exped.  5884,  Lobito  Bay,  Apr. 
1925,  1  9,  H.  Lang  and  R.  Boulton.  5882,  Lobito 
Bay,  May  1925,  7  juv  (frags.),  H.  Lang  and  R. 
Boulton. 

ANSP.  4  lots,  4  specimens. 

UNITED  STATES 

Florida:  3569,  Manatee  R.  [Manatee  Co.],  no 
date,  1  S,  S.  Ashmead. 

VIRGIN  ISLANDS 

St.  Croix:  3485,  no  date,  1  9  (dry),  R.  E.  Friffith. 

ST.  MARTINS 

1316,  no  date,  1  S,  Van  Rijgersma. 


728 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


[ST.  BARTHELEMY] 
621,  Bartholemew  I.,  no  date,  1  o,  A.  Goes. 

BMNH.  10  lots,  18  specimens. 

UNITED  STATES 

Florida:  1938.3.19.21,  Dry  Tortugas,  2  6,  Col- 
man  and  Tandy. 

JAMAICA 

1960.8.25.1,  Portland  Bight,  18  May  1956,  1  9 
(ov),  H.  M.  S.  Vidal. 

MEXICO 

65.29,  2  S,  (dry),  vi/9. 

BRAZIL 

48.86,  1  6,  (dry),  vi/6/7.  Pernambuco,  unreg.  1  S, 
D.  Wilson  Barker. 

GAMBIA  * 

Unreg.,  Gunjur  beach,  13  Nov.  1950,  1  <i  (juv), 
M.  H.  Routh.  1952.9.9.21/22,  1  mi  N  Gunjur,  3 
Mar.  1951, 1  2,  and  Rock  pool  N  end  Gunjur  beach, 
11  Dec.  1950,  1  juv,  M.  H.  Routh. 

SIERRA  LEONE 

1920.9.21.1/5,  Murray  Town,  2  c?,  3  9,  W.  P. 
Lowe. 

FERNANDO  P60 

53.1,  1  6  (dry),  vi/9,  Cuming. 

ANGOLA 

1911.2.28.14/15,  Luanda,  1  <^,  1  9,  W.  P.  Lowe. 

MCZ.  27  lots,  71  specimens. 

UNITED  STATES 

Florida:  5208,  July  1859,  1  9  (ov),  Capt.  Wood- 
bury. 5148,  13  Feb.  1861,  2  c<\  Capt.  Woodbury. 
8747,  no  date,  1  6,  Maynard.  5149,  Key  West,  Feb. 
1859,  1  S,  T.  Lyman.  5150,  Key  West,  no  date,  2  i, 
C.  E.  Faxon.  5209,  Fort  Jefferson,  Tortugas,  no 
date,  2  c?  (part  of  Ordway's  material). 

BAHAMAS 

8665,  E  Great  Abaco  I.,  1904,  1  9,  Allen,  Brant, 
and  Barbour.  11672,  Alicetown,  North  Bimini, 
May  1941,  1  i,  1  juv,  R.  W.  Foster  and  J.  Hunting- 
ton. 8635  and  8646,  Mangrove  Cay,  Andros  I.,  1 
Aug.  1904,  1  6,  1  juv,  O.  Bryant.  9425,  Simms, 
Long  I.,  7  July  1936,  1  6,  Harvard  Bahama  Exped. 


10359,  Salt  Pond  canal,  1.5  mi  SE  Matthew  Town, 
Great  Inagua  I.,  24  June  1938,  1  S,  R.  A.  McLean 
and  B.  Shreve. 

CUBA 

2893,  Bahia  Honda,  1877-78,  2  juv,  Blake 
Exped. 

HAITI 

5156,  near  Jeremie,  no  date,  1  6,  D.  F.  Weinland. 

DOMINICAN  REPUBLIC 

9841,  Santa  Barbara  de  Samana,  Aug.  1937, 1  9, 
W.  J.  Clench. 

VIRGIN  ISLANDS 

St.  Thomas:  5153  and  8864,  Dec.  1871,  20  6, 109 
(2  ov),  Hassler  Exped. 

TOBAGO 

9917,  Pigeon  Point,  17-18  Aug.  1937, 2  ^(juv),  E. 
Deichmann. 

CAPE  VERDE  ISLANDS 

6530.  La  Praia,  July  1883, 1  %Talisman  Exped. 

MNB.  4  lots,  8  specimens. 

BRAZIL 

Ceara:  333,  Fortaleza,  Praia  de  Mucuripe,  1945, 
1  9,  A.  Carvalho.  Pernambuco:  55,  [no  other  data], 
3  ^,  2  9.  331,  Recife,  Praia  do  Pina,  Sept.  1944,  1  6. 
330,  Recife,  Praia  do  Pina,  Aug.  1944,  1  6. 

MNHNP.  13  lots,  18  specimens. 

GUADELOUPE 

No  date,  2  S,  (dry),  M.  Beaupertuis. 

CAPE  VERDE  ISLANDS 

La  Praia,  July  1883,  1  6,  Talisman,  41-42.  No 
date,  1  <?,  M.  Barboradu  Bocage  587-66.  No  date,  1 
9,  M.  Bouvier. 

SENEGAL 
Beach  at  Dakar,  May  1895, 1  9  (ov),  M.  Chaper. 

GUINEA 

Fotoba,  Isles  des  Guinee,  [6  mi  W  Conakry], 
9-10  Mar.  1947,  2  6,  1  9,  Inst.  d'Afrique  Noire. 

SAO  TOME 

Golfe  de  Guinee,  1956,  1  9,  Calypso  Stn.  T  28. 
Golfe  de  Guinee,  1956,  1  9  (ov),  Calypso  Stn.  T  9. 


729 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


GABON 

Types,  3  5  (dry).  3  juv,  M.  Duparquet  181.63 
(dry). 

CONGO 

1892-94,  2  9,  Dybowski. 

RMNH,  38  lots,  105  +  specimens. 

UNITED  STATES 

Florida:  23268,  Bear  Cut,  Key  Biscayne,  1  Jan. 
1965,  2  S  (juv),  J.  A.  Cabreru  and  L.  B.  Holthuis. 
18719,  Bear  Cut,  Key  Biscayne,  1-9  Sept.  1963,  1 
<?,  L.  B.  Holthuis.  15003,  Tortugas,  July  1925,  1  <? 
(juv),  H.  Boschma. 

BAHAMAS 

6911  and  11859,  Nassau,  New  Providence  I., 
1887, 1  cJ,  1  2,  A.  de  Haas.  1860,  Bahama  Is.,  1887, 
many  adults,  A.  de  Haas. 

VIRGIN  ISLANDS 

15009,  St.  Croix,  Krause  Lagoon,  15  June  1955, 
2  juv,  P.  W.  Hummelinck. 

ST.  MARTIN 

11861,  coast  near  Philipsburg,  16-17  Feb.  1957, 
1  6,  4  juv,  L.  B.  Holthuis.  11866,  Freshwater  pond 
W  of  Philipsburg.  17  Feb.  1957,  6  ^,  2  9,  9juv,  L.  B. 
Holthuis.  Unnumbered,  mouth  freshwater  pond 
W  of  Philipsburg,  17  and  20  Feb.  1957,  dry 
carapace,  L.  B.  Holthuis.  10720,  Great  Bay,  7  June 
1950, 1  rf,  T.  W.  Hummelinck.  8121,  Great  Bay,  Ft. 
Blanche,  26  June  1949,  1  juv,  T.  W.  Hummelinck. 
11864,  Oyster  pond  on  E  coast,  22  Feb.  1957, 1  <?,  1 
9,  L.  B.  Holthuis.  1128,  NE  shore  Great  Bay,  16 
May  1949,  2  9,  P.  W.  Hummelinck. 

GUADELOUPE 

23423,  Grande  Anse  by  bridge.  La  Desirade,  23 
Jan.  1964,  1  6,  P.  W.  Hummelinck. 

ARUBA 

11863,  Lagoon  W  Savaneta,  19  Mar.  1957, 2  S,  L. 
B.  Holthuis.  15008,  Lagoon  NW  Savaneta,  21 
Mar.  1957,  cJ  juv,  L.  B.  Holthuis.  557, 1881-1882,  6 
S,  3  9,  A.  J.  van  Koolwijk.  11862,  1883,  1  9,  K. 
Martin.  1872,  July  1883,  3  <?,  1  9  (juv),  de  Haas. 
2273,  June  1920,  1  6  (juv).  Prof.  col. 

CURACAO 

15006,  Santa  Cruz  Baai,  13  Nov.  1956, 1  9  O'uv), 
L.  B.  Holthuis.  15004,  Piscadera  Baai,  14  Nov. 


1957,  2  9  O'uv),  L.  B.  Holthuis.  11865,  Piscadera 
Baai,  11-13  Feb.  1957,  2  ^,  1  9,  L.  B.  Holthuis. 
23422,  SE  part  Piscadera  Baai,  25  Oct.  1963,  1  <^, 
P.  W.  Hummelinck.  23401,  S  part  Piscadera  Baai, 
25  Oct.  1963,  1  9,  P.  W.  Hummelinck.  11860, 
Mouth  of  Piscadera  Baai,  19  Dec.  1956,  1  9,  2  juv, 
L.  B.  Holthuis.  23459,  Mouth  of  Piscadera  Baai,  14 
Dec.  1963,  1  9  (paper  shell),  P.  W.  Hummelinck. 
15015,  Mouth  of  Spanish  Water  near  Nieuwpoort, 
Santa  Barbara  beach,  25  Nov.  1956,  1  <?,  L.  B. 
Holthuis.  15005,  Mouth  of  Spanish  Water  near 
Nieuwpoort,  Santa  Barbara  beach,  8-13  Nov. 
1957,  1  c^,  4  juv,  L.  B.  Holthuis.  18644,  Boca 
Grandi,  St.  Jean,  6  Feb.  1955,  2  S,  J.  S.  Zaneveld. 
15007,  S  shore  St.  Joris  Baai  near  Choloma,  3  Jan. 
1957,  2  S,  1  9,  1  juv,  L.  B.  Holthuis.  18646,  back 
part  Playa  Grandi,  Boca  Wacao,  30  Jan.  1955, 1  S, 
juv,  J.  S.  Zaneveld.  15010,  Spanish  Water  near 
Jan  Zoutvat,  18  Nov.  1956, 1  ^,  juv,  L.  B.  Holthuis. 
Unnumbered,  reefwater,  June  1920,  1  9  (ov?), 
Boeke. 

BONAIRE 

Lagoon,  27  Mar.  1955,  dry  carapace,  mature,  J. 
S.  Zaneveld  and  R.  W.  Hummelinck.  11867, 
Lagoon  on  E  coast,  10  Mar.  1957,  3  cJ,  1  9,  4  juv,  L. 
B.  Holthuis. 

NIGERIA 

Lagos  Harbor,  23  May  1964,  1  carapace  (dry), 
Pillsbury  Stn.  1. 

SADZ-B.  7  lots,  11  specimens. 

UNITED  STATES 
Florida:  878,  Key  West,  1885, 1  S,  Smithsonian. 

BRAZIL 

Ceara:  3231,  Fortaleza,  Praia  de  Iracema,  21 
Jan.  1964,  3  S,  A.  L.  Castro.  Bahia:  3215,  Ilha 
Madre  de  Deus  [12°44'S,  38°37'W],  1932,  1  6, 
Oliviera  Pinto.  1731,  Ilha  Madre  de  Deus,  Jan. 
1933, 1  S,  Pinto  e  Camarao.  3224,  Ilheus,  1919, 3  S, 
E.  Garbe.  Rio  de  Janeiro:  Unnumbered,  Angra  dos 
Reis,  Praia  Mombaca,  1  9.  Sao  Paulo:  890,  Sao 
Sebastiao,  1915,  1  6,  E.  Garbe. 

UNC-IMS.  4  lots,  6  specimens. 

UNITED  STATES 

North  Carolina:  Back  Sound  off  mouth  of  Taylor 
Creek,  Carteret  Co.,  20  Nov.  1971, 1  9,  C.  A.  John- 
son III. 


730 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


CONGO 

2740,  Pte.  Indienne,  env.  de  Point-Noire,  12 
May  1964,  1  6,  1  9,  A.  Stauch.  2741,  Pte.  de 
Tchitembc,  31  Dec.  1963, 1  9  (ov),  A.  Stauch.  2742, 
W  de  Pointe-Noire,  1  c?,  1  9,  A.  Crosnier. 

Supplementary  literature  records. —  Bermuda 
(Verrill,  1908a);  Veracruz,  Mexico  (Contreras, 
1930);  Aruba  (de  Man,  1883);  Los  Roques  and  La 
Orchila,  Venezuela  (Chace,  1956);  Barra  das  Jan- 
gadas,  S  of  Recife,  Brazil  (Coelho,  1966);  near  Rio 
de  Janeiro,  Brazil  (Oliveira,  1956);  Ilha  da  Sao 
Sebastiao,  Brazil  (Luederwaldt,  1929);  Port 
Etienne,  Mauritania,  and  Apam,  [Ghana],  plus  a 
long  list  of  localities  duplicated  in  material  ex- 
amined and  other  literature  (Monod,  1956);  Cape 
Verde  Islands  (2  localities),  and  Angola  (3 
localities)  (Guinot  and  Ribeiro,  1962);  Bissau,  Por- 
tuguese Guinea  (Osorio,  1887,  1888,  1898);  Gold 
Coast  (Buchanan,  1958);  Sao  Tome  (Forest  and 
Guinot,  1966);  Pointe  Noire,  Congo  (Rossignol, 
1962). 

CALLINECTES  SIMILIS  WILLIAMS 
Lesser  Blue  Crab 

Figures  4,  18b,  20c,  22a,  24 

Callinectes  ornatus.-  Ordway,  1863,  p.  572  (part, 
the  Texas  specimen).-  Rathbun,  1896,  p.  356 
(part).-  1930,  p.  114  (part).-  Hay  and  Shore, 
1918,  p.  433,  pi.  34,  fig.  2.-  Contreras,  1930, 
p.  231  (part),  fig.  4  (?).-  Pounds,  1961,  p.  42, 
pi.  7,  fig.  2c.-  Wilhams,  1965,  p.  172,  fig.  152. 

Callinectes  danae.-  Rathbun,  1930,  p.  118  (part).- 
Pounds,  1961,  p.  42,  pi.  7,  fig.  2b. 

Callinectes  similis  Williams,  1966,  p.  87,  figs.  3, 
4E,  F  (type:  5,  USNM  113341,  2-3  mi  off 
beach  between  St.  Johns  River  jetties  and 
Jacksonville  Beach,  Fla.). 

Description. — Carapace  (Figure  4)  with  four 
frontal  teeth,  submesial  pair  small  but  definitely 
formed.  Central  trapezoidal  (metagastric)  area 
short  and  wide,  anterior  width  about  2.75  times 
length,  posterior  width  about  1.6-1.7  times  length. 
Anterolateral  margins  broadly  arched;  anterolat- 
eral teeth  exclusive  of  outer  orbital  and  lateral 
spine  short  and  broad,  tips  of  first  five  nearly  rec- 
tangular, sixth  and  especially  seventh  acuminate; 
first  five  teeth  with  anterior  margins  shorter  than 
posterior  and  separated  by  narrow  based  rounded 


notches.  Lateral  spine  strong,  slender,  and  curved 
forward.  Surface  of  carapace  even,  lightly  and 
quite  uniformly  granulate  except  smooth  along 
posterolateral  and  posterior  slopes,  and  nearly 
smooth  along  anterolateral  and  anterior  margins, 
especially  between  teeth  and  along  orbits;  smooth 
areas  with  tendency  to  iridescence. 

Chelipeds  with  very  fine  granulations  on  ridges; 
carpus  bearing  two  obsolescent  granulate  ridges 
and  suggestion  of  others,  inferior  lateral  ridge 
terminating  anteriorly  in  a  low  tooth  occasionally 
followed  by  a  low  flattened  eminence;  chelae 
strong,  not  greatly  dissimilar  in  size. 

Male  telson  longer  than  wide;  sixth  segment  of 
abdomen  slightly  sinuous  sided  but  broader  at  all 
levels  than  telson,  proximal  half  slightly  con- 
stricted laterally  and  less  indurated  than  other 
parts,  flush  with  sternum  in  retracted  position. 
Mature  female  telson  slightly  wider  than  long. 
First  gonopods  of  male  (Figures  18b,  20c)  reaching 
anteriorly  two-thirds  length  of  sternite  VII,  or 
beyond;  distal  portion  slender,  extending  straight 
to  tips  curved  slightly  mesad,  armed  with  scat- 
tered minute  retrogressive  spinules,  most  dense 
distally  and  laterally  and  largest  distally.  Gono- 
pores  of  female  (Figure  22a)  narrowly  ellipsoid 
with  long  axis  in  transverse  plane;  aperture  of 
each  with  simple  rounded  borders  except  at  mesial 
end  where  it  slopes  from  surface  laterad  under 
superior  anterior  margin. 

Size  of  carapace  in  mm. — Largest  male:  length 
55,  width  at  base  of  lateral  spines  97,  including 
lateral  spines  122.  Largest  female:  length  45, 
width  at  base  of  lateral  spines  76,  including  lateral 
spines  95.  Summary  of  selected  measurements  is 
given  in  Tables  1  and  2.  Franks  et  al.  (1972)  re- 
ported an  individual  with  carapace  width  of  171. 

Color. — Adult  male:  "Carapace  green  dorsally, 
irregular  areas  of  iridescence  at  bases  of,  and  be- 
tween, anterolateral  teeth,  and  on  posterior  and 
posterolateral  borders.  Chelipeds  and  portions  of 
legs  similar  in  color  or  more  tannish  green  dor- 
sally,  with  iridescent  areas  on  outer  and  upper 
edges  of  carpus  and  hands;  chelae  white  on  outer 
face,  blue  to  fuchsia  on  inner  surface,  with  fuchsia 
on  tips  of  fingers  and  teeth  of  opposed  edges.  Lat- 
eral spines  and  some  anterolateral  teeth,  as  well 
as  spines  on  chelipeds,  white  tipped.  Walking  legs 
grading  from  fuchsia  distally  through  violet  blue 
to  light  blue  mottled  with  white  proximally, 


731 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


pubescence  on  legs  beige.  Swimming  legs  variably 
mottled  with  white;  all  legs  with  stellate  fuchsia 
markings  at  articulations.  Underparts  white  and 
blue."  (Williams,  1965). 

Ovigerous  female:  "Similar  to  male  except  with 
more  violet  blue  on  inner  surface  of  chelae;  fingers 
either  with  white  teeth  or  fuchsia  colored  teeth. 
Legs  with  dactyls  reddish  orange  grading  a- 
bruptly  to  blue  on  propodi,  pubescence  brown  to 
beige.  Abdomen  with  iridescent  areas."  (Williams, 
1965). 

Carapace  of  juveniles  sometimes  with  a  macu- 
late light  olive  pattern. 

Variation. — Borders  of  the  metagastric  area  are 
somewhat  more  deeply  defined  on  young  indi- 
viduals than  adults,  and  the  shape  of  this  area 
tends  toward  that  in  C.  danae  (USNM  123015, 
Mississippi)  in  the  young.  Differentiation  of  the 
major  and  minor  chelae  resembles  that  in  other 
members  of  the  genus  although  the  two  chelae  on 
most  individuals  tend  to  be  similar  sized.  In  some 
specimens  the  major  chela  has  a  strong  proximal 
tooth  on  the  dactyl. 

Habitat. — Franks  et  al.  (1972)  gave  a  good 
summary  of  habitat  for  this  species.  In  Mississippi 
they  caught  it  year  round  in  trawl  samples  from  9- 
to  92-m  depths  at  temperatures  ranging  from 
13.2°  to  29.0°C  and  in  salinities  ranging  from  24.9 
to  37.4 /{o,  but  it  was  most  abundant  in  37-m 
depths  and  showed  a  slight  preference  for  29.0  to 
31.9  /CO  salinities.  The  same  environment  exists  in 
northeastern  Florida  where  Tagatz  (1967)  found 
the  species  most  abundant  in  the  ocean  near  shore 
and  in  the  lower  25  miles  of  St.  Johns  River, 
mainly  in  salinities  greater  than  15 ao;  also  in 
North  Carolina  it  is  seldom  found  in  estuaries 
beyond  lower  limits  of  15 ao  salinity.  In  all  areas 
studied  the  species  is  associated  with  C.  sapidus, 
often  in  large  numbers,  but  it  is  usually  culled  out 
of  commercial  catches  because  of  its  small  size 
(Lunz,  1958;  Pounds,  1961;  Williams,  1966; 
Franks  et  al.,  1972). 

Spawning. — Published  data  on  spawning  in 
Texas  and  South  and  North  Carolina  summarized 
by  Williams  (1966)  suggested  a  spring  and  fall 
spawning  season  for  C.  similis,  and  Tagatz  (1967) 
found  this  true  for  northeastern  Florida  as  well 
where  females  spawn  in  the  ocean  from  March  to 
July,  peaking  in  May  when  75%  of  them  are 
ovigerous,  and  again  from  October  to  November. 


Ovigerous  females  in  the  collection  of  the  USNM 
indicate  that  these  limits  are  somewhat  broader 
elsewhere  and  may  be  correlated  with  tempera- 
ture, for  there  are  representatives  from  Louisiana 
and  Texas  in  February  and  Campeche  Banks  in 
December. 

Distribution. — Off  Delaware  Bay  to  Key  West, 
Fla.;  northwestern  Florida  around  Gulf  of  Mexico 
to  off  Campeche,  Yucatan  (Figure  24). 

Remarks. — Small-  to  medium-sized  juveniles 
are  extremely  difficult  to  identify  in  parts  of  the 
range  where  C.  danae  and  C.  ornatus  also  occur 
(southern  Florida). 

The  few  specimens  from  off  Delaware  Bay  are 
all  juveniles,  suggesting  that  northern  limits  for 
this  species,  as  for  many  others  from  the  Carolin- 
ian Province,  vary  seasonally  and  are  extended 
northward  during  favorable  warm  years. 

Among  unusual  specimens  seen,  a  female  taken 
off  Cape  San  Bias,  Fla.  (USNM  101429)  with 
carapace  measuring  37  mm  long  x  64  mm  wide, 
exclusive  of  lateral  spines,  bears  dorsally  the 
largest  Chelonibia  seen  fouling  the  species.  The 
barnacle  measures  18.5  x  21.3  mm  at  base  x  18.3 
mm  height  of  sidewall.  An  immature  female  crab 
taken  off  Timbalier  Bay,  La.  (USNM  123026)  has 
that  part  of  the  front  bearing  frontal  teeth  pro- 
duced forward. 

Closely  resembling  C.  danae  and  C.  ornatus,  C. 
similis  seems  to  be  the  Carolinian  member  of  the 
complex.  Callinectes  similis  has  the  smoothest 
and  most  uniformly  granulated  carapace  among 
the  three,  and  the  shortest,  broadest  anterolateral 
teeth.  These  teeth  are  not  equilaterally  triangu- 
lar, having  shorter  anterior  than  posterior  bor- 
ders, and  are  more  directed  forward  in  the  anterior 
portion  than  in  the  remainder  of  the  row.  Central 
teeth  in  the  row  have  the  anterior  border  extend- 
ing almost  straight  laterad.  The  carapace  of  ma- 
ture females  has  very  little  sculpture  and  remark- 
ably uniform  granulation  overall.  Granulations 
on  the  ridges  of  the  chelipeds  are  among  the  finest 
of  any  species  of  Callinectes.  Because  of  simplicity 
in  structure  of  the  male  first  gonopods,  the  rela- 
tively broad  male  abdomen  and  relatively 
generalized  structure  of  the  chelae  and  frontal 
teeth,  it  is  tempting  to  regard  this  species  as  one  of 
the  most  primitive  or  unspecialized  members  of 
the  genus  and  I  have  arranged  it  so  in  the  order  of 
presentation,  knowing  full  well  that  such  evi- 
dence is  highly  subjective. 


732 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Material. — Total:  117  lots,  354  specimens. 

USNM.  104  lots,  329  specimens,  including  the 
following  listed  in  Rathbun  (1930)  as  C.  danae 
(20115,  22817),  C.  marginatus  (33103),  and  C. 
ornatus  (8863,  62460,  58366,  3185,  51029,  61428, 
21631). 

UNITED  STATES 

New  Jersey:  62674,  Cape  May,  8  Sept.  1928,  1  $ 
(juv),  H.  G.  Richards.  64257,  near  Brandywine 
Lightship,  Delaware  Bay,  29  July  1930,  1  S  (juv), 
H.  G.  Richards.  77009,  off  New  England  Creek, 
Delaware  Bay,  25  Aug.  1931,  1  2  (juv),  H.  G. 
Richards. 

Delaware:  77008,  off  Slaughter  Creek,  4  Aug. 
1931,  1  juv,  H.  G.  Richards. 

North  Carohna:  123058,  Beaufort,  reed.  19  Nov. 
1959,  1  9  (ov),  J.  D.  Costlow,  reared  larvae. 
123059,  Beaufort  Harbor,  Aug.  1946,  1  S,  D.  H.  B. 
Ulmer.  * 

South  Carolina:  97699,  N  Edisto  R.,  22  Apr. 

1953,  1  6,  7  9,  G.  R.  Lunz.  123012,  S  Creek  near 
entrance  into  N  Edisto  R.,  31  May  1966,  1  c5  (juv), 
J.  C.  McCain.  123011,  off  mouth  N  Edisto  R.,  31 
May  1966,  1  9,  J.  C.  McCain. 

Georgia:  123054,  Jointer  R.  [near  Jekyll  I.],  17 
Mar.  1932,  2  9,  W.  W.  Anderson. 

Florida:  123034,  [off  mouth  St.  Johns  R.], 
30°26.5'N,  81°23'W,  17  Apr.  1940,  9  <?,  9  9  (6  juv). 
Pelican  Stn.  215-1.  123047,  [off  mouth  St.  Johns 
R.]  30°26'N,  81°20.5'W,  17  Apr.  1940,  1  <?,  1  9, 
Pelican  Stn.  215-2. 113345,  off  St.  Johns  R.  jetties, 
14  Aug.  1962,  8  c?,  6  9,  M.  E.  Tagatz  and  G.  P. 
Frymire.  113341,  113342,  113343,  113344,  2-3  mj 
off  beach  between  St.  Johns  R.  jetties  and  Jack- 
sonville Beach,  18  June  1962,  8  <^,  9  9,  A.  B.  Wil- 
liams et  al.  123014,  [off  Jacksonville  Beach] 
30°21'N,  81°20.5'W,  19  Nov.  1963,  2  6,  2  9,  Silver 
Bay  Stn.  5381.  123101,  [off  St.  Augustine] 
29°54.5'N,  10°10'W,  9  Feb.  1965,  2  9,  Oregon  Stn. 
5234.  123018,  [off  SE  St.  Johns  Co.]  29°28.5'N, 
81°04.5'W,  28  Mar.  1940,  2  S,  Pelican  Stn.  202-6. 
99917,  Matanzas  R.  at  Crescent  Beach,  1  Dec. 

1954,  1  6,  D.  K.  Caldwell.  123017,  [N  Daytona 
Beach]  29°18.5'N,  81°01.5'W,  6  Apr.  1940,  1  9, 
Pelican  Stn.  212-3.  123046,  [off  Daytona  Beach] 
29°14.5'N,  80°59.5'W,  6  Apr.  1940,  1  c?,  1  9  (ov). 
Pelican  Stn.  212-2.  123020,  [off  Daytona  Beach] 
29°07.5'N,  80°55'W,  5  Apr.  1940,  5  o,  2  9,  Pelican 
Stn.  211-5.  123021,  [off  Daytona  Beach]  29°11'N, 
80°43'W,  19  Jan.  1940,  1  9,  Pelican  Stn.  172-3. 
123008,  123009,  Ponce  de  Leon  Inlet,  Volusia  Co., 
13  Apr.  1946,  2  S  (juv),  DePalma  and  Strickland. 


123045,  [off  New  Smyrna]  29°00'N,  80°47.5'W,  19 
Jan.  1940,  1  6,  Pelican  Stn.  171-7.  101686,  NE  off 
Cape  Canaveral,  29°15'N,  80°13'W,  1  June  1957, 2 
9  (1  ov).  Combat  Stn.  334.  123016,  [off  Cape 
Canaveral]  28°24'N,  80°32.5"W,  4  Apr.  1940,  1  S, 
Pelican  Stn.  207-3.  123022,  [SE  Cape  Canaveral] 
28°23'N,  80°27.5'W,  18  Jan.  1940,  1  S,  Pelican 
Stn.  169-2.  99902,  Sewall  Point,  Martin  Co.,  27 
Feb.  1955,  2  juv,  D.  K.  Caldwell  et  al.  113460, 
Bear  Cut  Key,  Biscayne  side  Miami,  17  Aug. 
1965,  1  5,  1  9  (juv),  R.  B.  Manning.  77103,  Coral 
Gables,  7  July  1932,  1  i,  J.  F.  W.  Pearson.  76984, 
Key  West,  26  May  1918,  1  <5  (ov),  3  juv.,  D.  R.  C. 
76980,  Key  West,  no  date,  2  9,  C.  H.  Maynard. 
123103,  mud  cove  2  mi  from  tip  of  Alligator  Har- 
bor, Franklin  Co.,  27  Oct.  1967,  4  5,  5  9,  C.  Swift 
and  J.  Rudloe.  101429,  off  Cape  San  Bias, 
29°16'N,  85°08'W,  15  July  1957,  1  9  (ov),  Oregon 
Stn.  1755.  123102,  St.  Andrews  Bay  Shipyard 
area.  Bay  Co.,  18  Aug.  1967,  1  5,  L.  Abele  and  C. 
Swift.  99914,  Choctawhatchee  Channel, 
Okaloosa  Co.,  no  date,  1  9,  K.  Caldwell.  99896, 
Intracoastal  Waterway  3.5  mi  E  Interarity  Point, 
Pensacola,15Aug.l953,lc;,F.  Berry  and  A.  Mead. 

Alabama:  92425,  3b°15.5'N,  88°10'W,  22  June 
1951, 3  <?,  1  9, 1  juv.,  H.  M.  Hefley, Oregon  Stn.  387. 

Mississippi:  123015,  inside  Petit  Bois  Island, 
Mississippi  Sound,  20  Apr.  1967,  27  J,  10  9,  George 
M.  Bowers  Stn.  4.  123010,  off  N  side  Little  Deer 
Island,  Ocean  Springs,  1  Sept.  1965,  3  juv,  J.  C. 
McCain. 

Louisiana:  123040,  28°22.5'N,  91°44.5'W,  12 
July  1938, 1  6,Pelican  Stn.  84-1. 123057,  28°31'N, 
91°09'W,  13  July  1938,  3  oM  9  (juv) ,  Pelican  Stn. 
86-4. 123029, 28°38'N,  9r05'W,  18  Mar.  1938, 1  S, 
Pelican  Stn.  31.  123019,  28°39.5'N,  91°06'W,  11 
Nov.  1938,  1  ci',  2  9  (1  juv).  Pelican  Stn.  90-2. 
123039,  28°40'N,  90°51.5'W,  10  July  1938,  1  S 
Huv),  Pelican  Stn.  80-7.  123035,  28°41.5'N, 
91°10'W,  11  Nov.  1938,  2  <?,  2  9(1  juv), Pelican  Stn. 
90-3.  123050,  28°42'N,  92°15.5'W,  13  Nov.  1938, 4 
cj,  4  9,  Pelican  Stn.  93-6.  101428,  28°46'N, 
90°47'W,  6  Mar.  1957,  7  9  (ov),  Oregon  Stn.  1749. 
123033,  28°46.5'N,  91°18.5'W,  11  Nov.  1938,  1  <?, 
Pelican  Stn.  90-5.  123037,  28°48'N,  89°51'W,  13 
May  1938,  3  9(2  ov).  Pelican  Stn.  69-6.  123048, 
28°49'N,  91°23'W,  11  Nov.  1938,  3  <?,  1  9,  Pelican 
Stn.  90-6.  92350,  28°50'N,  89°33'W,  7  May  1951, 1 
S,  Oregon  Stn.  342.  91432,  28°53.3'N,  89°36.5'W, 
13  Sept.  1950,  1  9  (juv),  Oregon  Stn.  107.  123038, 
25  mi  S  Grand  Isle,  28°55'N,  90°02'W,  17  Feb. 
1938,  1  3,  Pelican  Stn.  22.  123041,  28°55'N, 
92°15.5'W,  13  Nov.  1938,  3  S,  Pelican  Stn.  93-3. 

733 


123025,  28°55.5'N,  89°59'W,  10  Nov.  1938,  2  9(1 
ov),  Pelican  Stn.  87-7.  123028,  28°56'N,  91°52'W, 
29  Mar.  1938,  1  6,  2  9,  Pelican  Stn.  37.  123056, 
28°56.5'N,  91°50'W,  llJuly  1938,  2  S,  2  9, Pelican 
Stn.  82-5.  91939,  28°57'N,  89°36'W,  14  Sept.  1950, 
1  9,  Oregon  Stn.  110.  123036,  28°57'N,  89°43'W, 

10  Nov.  1938,4  9(1  ov), Pelican  Stn.  87-4.  123024, 
28°58'N,  89°28.5'W,  10  Nov.  1938,  1  6,  Pelican 
Stn.  87-1.  123026,  28°58'N,  90°17'W,  10  July 
1938, 1  9 (jxiv), Pelican  Stn.  79-7. 123023,  28°59'N, 
92^5. 5'W,  13  Nov.  1938, 16,29  (juv), Pelican  Stn. 
93-2.  123049,  28°59.5'N,  91°44.5'W,  12  Nov.  1938, 

1  S,  Pelican  Stn.  91-4.  64148,  off  Breton  Island, 
Nov.  1930,  1  <?,  Stewart  Springer.  91954,  29°22'N, 
88^49'W,  24  Sept.  1950,  3  6,  Oregon  Stn.  132. 
123027,  29°01.5'N,  89°33'W,  8  July  1939,  15,19, 
Pelican  Stn.  77-2.  91433,  29°12'N,  88°50'W,  12 
Sept.  1950,  1  6,  Oregon  Stn.  103.  123055,  3-6  mi 
ESE  SW  Pass,  16  Feb.  1934, 1  9  (ov),  T.  C.  P.,  M.  J. 
Lindner,  and  W.  W.  Anderson. 

Texas:  123030,  29°00'N,  94°38.5'W,  21  Jan. 
1939,  1  9,  Pelican  Stn.  104-5.  123031,  29°10.5'N, 
94^50.5' W,  3  May  1938,  5  o,  2  9, Pelican  Stn.  56-5. 
123005,  Galveston,  11  Aug.  1940,  4  c?,  1  9,  from  J. 
L.  Baughman.  123006,  Galveston,  7  July  1940, 1  S, 

2  9(juv),fromJ.L.  Baughman.  123007,  Galveston, 

11  Aug.  1940,  9  cj,  2  9  (1  soft),  from  J.  L.  Baugh- 
man. 80662,  Galveston,  no  date,  5  ti,  4  9,  J.  L. 
Baughman.  123013,  17  mi  S,  7  mi  E  Alvin,  Bra- 
zoria Co.,  28  July  1952,  1  9  (juv),  S.  Alvin.  22817, 
Alligator  Head,  Matagorda  Bay,  no  date,  1  cJ(dry), 
from  J.  D.  Mitchell.  123051,  27°59'N,  95°20.5'W, 
22  Jan.  1939,  1  9,  Pelican  Stn.  107-3.  123032, 
28°20.5'N,  96°13'W,  2  May  1938, 1  9  duv), Pelican 
Stn.  54-2.  101678,  28°20'N,  94°97'W,  25  Sept. 
1957,  2  9,  Silver  Bay  Stn.  187.  123044,  27°40'N, 
96°34'W,  22  Apr.  1938,  1  <?,  2  9  (ov),  Pelican  Stn. 
42.  123043,  27°51'N,  96°55.5'W,  2  May  1938,  3  S, 
2  9(1  ov).  Pelican  Stn.  53-1.  80663,  Port  Aransas 
Pass,  5  June  1941,  1  9,  G.  Gunter.  80664,  Port 
Aransas  Pass,  no  date,  10  S,  11  9,  G.  Gunter. 
123042,  26°48.5'N,  96°40'W,  4  Feb.  1939,  1  9  (ov), 
Pelican  Stn.  115-3.  123052,  26°05'N,  97°05'W, 
5  Feb.  1939,  1  9  (juv),  Pelican  Stn.  118-4. 

MEXICO 

Tamaulipas:  94452,  24°12'N,  97°17'W,  13  Oct. 
1952,  1  9,  Oregon  Stn.  662.  123053,  off  Soto  la 
Marina,  140  mi  S  Rio  Grande  R.,  15  Mar  1947, 
Pelican.  Campeche  Bank:  94453,  19°54.1'N, 
91°43'W,  10  Dec.  1952,  1  9  (ov),  Oregon  Stn.  719. 
94454,  20°12'N,  9r40'W,  11  Dec.  1952,  2  <5,  1  9 
(ov),  Oregon  Stn.  720. 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

AHF.  4  lots,  13  specimens. 

UNITED  STATES 

Florida:  Choctawhatchee  Bay  entrance  W  end 
Destin  bridge  [Okaloosa  Co.],  19  June  1949,  6  (?,  4 
9,  LM42-49. 

Louisiana:  Breton  Sound,  Mississippi  Delta,  21 
Oct.  1951,  1  S,  R.  H.  Parker. 

Texas:  1.25  mi  off  Mustang  Island,  31  Aug. 
1951, 1  9,  E.  Puffer,  J498.  Off  Padre  Island,  9  June 
1956,  1  9,  R.  H.  Parker,  J482. 

AMNH.  3  lots,  4  specimens. 

UNITED  STATES 

Florida:  11298,  Lake  Worth,  July  and  Aug. 
1945,  1  9,  W.  G.  Van  Name  and  A.  H.  Verrill. 

Texas:  2755,  Galveston,  no  date,  2  6  (juv),  col. 
unknown. 

BAHAMAS 
2445,  Nassau,  1899,  1  S,  R.  P.  W. 

BMNH.  1  lot,  1  specimen. 

UNITED  STATES 

Texas:  11.1.1946,  1  9,  Baughman. 

MCZ.  4  lots,  5  specimens. 

UNITED  STATES 

North  Carolina:  1 1352, 2  mi  SE  Roanoke  Island, 
19  Dec.  1940,  1  6  (juv),  R.  Foster. 

Florida:  5207,  1859,  2  6,  G.  Wurdemann.  5129, 
Cape  Florida  (S  end  Biscayne  Bay),  no  date,  1  <? 
(juv),  G.  Wurdemann. 

Texas:  5134,  13  Feb.  1861,  1  6,  G.  Wurdemann. 

RMNH.  1  lot,  2  specimens. 

UNITED  STATES 

Mississippi:  17825, 29°38.5'N,  88°30'W,  21  Aug. 
1962,  1  6,  1  9,  Oregon  Stn.  3713. 

UNC-IMS.  7  lots,  74  specimens  +  many  un- 
catalogued. 

UNITED  STATES 

North  Carolina:  1556,  (Paratypes),  off  Beaufort 
Inlet,  Carteret  County,  31  Oct.  1962,  5  6,49  (2  ov), 
E.  Bayer,  from  Ensign. 

Florida:  2140,  Clapboard  Creek,  trib.  of  St. 
Johns  River,  7  June  1964,  7  juv,  col.  unknown. 


734 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


2237,  Sisters  Creek  at  Fort  George  River?,  Duval 
County,  2  6,  2  9,  G.  P.  Frymire  and  G.  C.  Williams. 
2138,  Mouth  of  Sisters  Creek  off  St.  Johns  River, 
M.  E.  Tagatz  and  G.  P.  Frymire.  1995  (Paratypes), 
off  St.  Johns  River  jetties,  5  <J,  4  9,  3  juv,  M.  E. 
Tagatz  and  G.  P.  Frymire.  1990  (Paratypes),  2  to  3 
mi  off  beach  between  St.  Johns  River  jetties  and 
Jacksonville  Beach,  17  cJ,  16  2  (10  ov),  8  juv,  G.  P. 
Frymire,  M.  E.  Tagatz,  and  G.  C.  Williams. 

Texas:  2139,  Galveston  Bay,  June  1964, 1  <?,  col. 
unknown. 

Supplementary  literature  records. — Laguna 
Madre  de  Tamaulipas  (as  danae,  Hildebrand, 

1957). 

CALLINECTES  GLADIATOR 
BENEDICT 

Marine  Blue  Swimming  Crab 
Figures  5,  18c,  20b,  22c,  24 

Lupa  smythiana  Leach  (nomen  nudum)  in  White, 
1847,  p.  27. 

Callinectes  tumidus  var. gladiator  Benedict,  1893, 
p.  537  (type:  6,  USNM  14879,  Baya  River, 
Elmina,  Ashanti  [Ghana]). 

Callinectes  tumidus  gladiator.-  Rathbun,  1896,  p. 
360. 

Callinectes  gladiator.-  Rathbun,  1897,  p.  150.- 
1900a,  p.  291.- 1921,  p.  397,  fig.  3;  pi.  19,  fig. 
2.-  Balss,  1921,  p.  58.-  Monod,  1927,  p.  606.- 
1956,  p.  205,  figs.  236-237.-  Irvine,  1932,  p. 
15,  fig.  9.-  1947,  p.  298,  fig.  203.-  Vilela, 
1949,  p.  58,  fig.  6.-  Capart,  1951,  p.  130,  fig. 
46.-  Rossignol,  1957,  p.  82.-  1962,  p.  116.- 
Guinot  and  Ribeiro,  1962,  p.  48.-  Crosnier, 
1964,  p.  32.-  Forest  and  Guinot,  1966,  p.  64. 

Description. — Carapace  (Figure  5)  bearing  four 
frontal  teeth,  submesial  pair  almost  never  more 
than  half  length  of  lateral  pair.  Metagastric  area 
short,  anterior  width  about  2.5  times  length,  pos- 
terior width  about  1.5  times  length.  Anterolateral 
margins  arched  slightly;  teeth,  exclusive  of  outer 
orbital  and  lateral  spine,  with  tendency  to  ar- 
rangement in  a  3-2-2  pattern;  proximal  three 
narrow-acute  and  separated  by  narrow  sinuses; 
middle  two  broader,  acuminate,  and  more  widely 
separated;  lateral  two  spiniform  and  trending 
forward.  Lateral  spine  usually  long  and  slender. 
Surface  finely  or  moderately  and  evenly  granulate 


except  for  variably  smooth  portions  at  periphery, 
especially  on  posterior  and  posterolateral  slopes. 
Tendency  toward  ridging  or  heaping  of  granules 
on  branchial  and  cardiac  lobes.  Epibranchial  line 
prominent  and  nearly  uninterrupted. 

Chelipeds  with  propodus  sharply  ridged,  ridges 
granulated;  carpus  often  with  granulated  ridges 
evident  dorsally;  major  chela  with  strong  tooth  at 
base  of  dactyl. 

Male  abdomen  and  telson  narrow,  reaching 
slightly  beyond  suture  between  thoracic  sternites 
IV  and  V;  telson  about  1.6  times  longer  than  wide; 
sixth  segment  constricted  at  midlength,  sides 
markedly  divergent  proximally.  Mature  female 
abdomen  and  telson  reaching  same  level  as  in 
male,  telson  a  bit  wider  than  long,  sixth  segment 
slightly  shorter  than  fifth.  First  gonopods  of  male 
(Figures  18c,  20b)  reaching  slightly  beyond  mid- 
length  of  thoracic  sternite  VII;  curved  sigmoidally 
in  distal  half,  overlapping,  divergent  except  at 
extreme  tip  and  twisted  mesioventrally  on  axis; 
armed  distally  with  minute  retrogressive 
spinules,  scattered  or  occasionally  arranged  in 
rows.  Gonopores  of  female  (Figure  22c)  irregularly 
lunate  with  superior  limb  of  each  directed  an- 
teromesad;  aperture  of  each  with  rounded  margin 
becoming  lowest  mesially  where  it  slopes  from 
near  surface  level  laterad  under  posteriorly 
arched  anterior  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
48,  width  at  base  of  lateral  spines  92,  including 
lateral  spines  117.  Largest  female:  length  60, 
width  at  base  of  lateral  spine  108,  including  lat- 
eral spines  138.  Summary  of  selected  measure- 
ments is  given  in  Tables  1  and  2. 

This  species  shows  considerable  variability  in 
size  but  is,  on  the  whole,  the  smallest  in  the  genus. 
Females  are  often  quite  delicate,  maturing  at  sizes 
as  small  as  a  length  of  23,  width  at  base  of  lateral 
spines  41,  and  width  including  lateral  spines  of  54. 
Irvine  (1947)  noted  that  large  individuals  mea- 
sure 6  inches  or  more  (155  mm)  across  the  cara- 
pace. 

Color. — Uniform  gray-green  or  gray-blue  with 
spot  of  blue  on  palm  and  proximal  internal  part  of 
fingers  of  chela  (Rossignol,  1962).  Beautiful  mot- 
tled carapace  with  bright  blue  legs,  called  the 
marine  or  deep  sea  blue  swimming  crab  (Irvine, 
1932,  1947).  Preserved  specimens  often  have  an 
oval  dark  mahogany  colored  spot,  variable  in  size, 
on  the  gastric  and  metagastric  areas. 


735 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Variations. — In  some  ways  C.  gladiator 
resembles  the  "acutidens"  form  of  C.  sapidus, 
surpassing  it  in  development  of  even  more  acute, 
slender  spination,  and  showing  variable  ridging 
or  cresting  of  granulations  on  branchial  lobes  and 
mesobranchial  regions  as  well  as  formation  of  a 
transverse  ridge  of  granules  on  each  cardiac  lobe. 
The  peaking  of  granules  is  apparent  at  quite  small 
size.  In  addition,  these  lobes  and  regions  are  often 
prominent  and  thrown  into  somewhat  angular 
planes  bordering  the  contrastingly  sunken 
metagastric  area.  The  second  abdominal  segment 
terminates  laterally  in  a  spine  usually  sharper 
and  more  prominent  than  in  other  species  of  the 
genus,  especially  in  young  or  freshly  molted  indi- 
viduals. 

The  lateral  spines  of  most  individuals  are  rela- 
tively the  longest  among  species  in  the  genus. 
Anterolateral  teeth  may  be  bilaterally  asymmet- 
rical in  number.  Tips  of  the  teeth  may  lie  in  a 
nearly  straight  line  providing  relatively  flat  an- 
terolateral arcs.  All  older  individuals  have  a 
rounded  notch  between  the  first  two  anterolateral 
teeth.  The  lower  side  of  each  anterolateral  margin 
becomes  hairy  at  an  early  age. 

Openness  of  the  inner  orbital  fissure  is  random, 
bearing  no  relationship  to  age  or  width  of 
carapace.  When  the  fissure  is  closed,  a  V-shaped 
notch  usually  remains  open  on  the  orbital  margin. 

First  gonopods  of  males  are  not  completely 
S-shaped  and  not  overlapping  in  juveniles;  in  a 
few  males  they  extend  to  the  level  of  a  suture 
between  thoracic  sternites  VI  and  VII.  The  first 
gonopods  may  be  unnaturally  splayed  in  pre- 
served specimens.  Abdominal  segment  6  is  often 
poorly  calcified  at  midlength  in  males. 

Distribution. — West  Africa  from  Bale  de  Saint- 
Jean,  19°27'N,  16°22'W,  Mauritania,  to  Baia  do 
Lobito,  Angola  (Figure  24). 

Habitat. — Longhurst  (1958)  provided  an  excel- 
lent ecological  summary  of  the  West  African 
marine  benthos  primarily  in  and  off"  the  Sierra 
Leone  River,  but  elsewhere  as  well.  He  found  that 
in  shelf  regions  under  the  influence  of  tropical 
shelf  water  a  characteristic  fauna  was  revealed  by 
otter  trawls  in  each  sector  investigated;  the  most 
important  species  were  the  swimming  crabs  C. 
gladiator  and  Portunus  validus  Herklots  which 
occur  in  most  hauls  together  with  Penaeus 
duorarum  notialis  Burkenroad,  P.  kerathurus 
(Forsskdl),  Parapenaeus  longirostris   (Lucas), 


Panulirus  rissonii  (Desmarest),  and  Sepia 
officinalis  Linn.  Off  the  Sulima  River  [  =  Moa 
River,  Sierra  Leone]  occurrence  of  this  fauna  cor- 
responded with  the  inshore  Cynoscion  fauna  of 
demersal  fish,  with  the  thermocline  as  its  lower 
limit.  In  samples,  this  fauna  extended  from 
Senegal  to  the  Bight  of  Biafra,  the  genera  Cal- 
linectes,  Portunus,  and  Panulirus  occurring  in  a 
high  proportion  of  hauls  from  shallowest  to  50  m. 
Irvine  (1947),  Rossignol  (1962),  and  Crosnier 
(1964)  essentially  said  the  same,  that  this  coastal 
marine  species  lives  on  the  bottom  from  shore  to 
depths  of  30  m  on  sand,  sandy  mud,  or  gravel, 
sometimes  with  a  mixture  of  shell  fragments 
(Sourie,  1954a)  in  warm  water. 

Both  Monod  (1927)  and  Rossignol  (1957)  re- 
marked on  the  small  size  and  abundance  as  well  as 
the  rapidity  and  aggressiveness  with  which  C. 
gladiator  moves,  the  latter  saying  that  it  often 
rests  three-fourths  buried  in  a  predatory  position 
with  only  antennae  and  pincers  exposed.  In  addi- 
tion to  trawl  hauls,  the  crab  is  captured  in  nets 
allowed  to  hang  a  few  feet  from  the  bottom  (Irvine, 
1947)  and  at  the  surface  with  dip  nets  under  lights 
at  night. 

Though  found  in  estuaries  to  some  extent,  these 
accounts  imply  that  C.  gladiator  is  much  like  C. 
similis  of  the  western  Atlantic  in  ecological  as- 
sociation and  behavior,  and  less  estuarine  than  C. 
latimanus. 

Spawning. — Museum  records  provide  only  an 
outline  of  spawning  that  may  go  on  all  year.  Rec- 
ords of  ovigerous  females  are:  December,  Angola; 
January,  Guinea,  Liberia,  and  Cameroon;  Feb- 
ruary, Cameroon;  March,  Sierra  Leone,  Congo; 
April,  Ghana;  May,  Senegal,  Sierra  Leone,  and 
Nigeria;  June,  Sao  Tome;  October,  Congo. 

Economic  importance . — No  direct  statements  of 
economic  importance  are  made  in  literature.  Ir- 
vine (1947)  reported  the  flesh  and  eggs  edible  and 
of  good  quality. 

Remarks. — Aside  from  taxonomic  accounts  and 
faunal  lists,  there  is  less  published  information  on 
C.  gladiator  than  most  Callinectes.  Like  others, 
larger  or  older  specimens  often  bear  one  or  more 
barnacles  of  the  genus  Chelonibia  on  the  carapace. 
Teeth  of  fingers  on  the  major  chelae  are  often 
worn,  and  the  major  hands  often  seem  dispropor- 
tionately large  for  the  size  of  the  animal.  One 
ovigerous  female  in  the  BMNH  (unregistered) 


736 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


from  Victory  Bay,  Cameroon,  has  two  major 
chelae. 

The  holotype  is  an  immature  male  somewhat 
the  worse  for  wear.  The  left  chela  is  present  but 
dismembered  from  the  body,  as  are  other  legs  or 
parts  of  legs  and  the  abdomen.  The  left  lateral 
spine  is  broken  about  halfway  along  its  length, 
and  only  the  left  first  gonopod  remains. 

Figures  provided  by  Irvine  (9  and  13,  1932;  202 
and  203,  1947)  are  difficult  to  assign  to  synonymy 
with  confidence,  and  both  Capart  (1951)  and 
Monod  (1956)  had  trouble  with  them.  Figures  13 
and  202  could  represent  either  C.  gladiator  or 
marginatus,  but  9  and  203  are  labelled  as  C. 
gladiator,  yet  internal  carpal  spines  on  the  latter 
indicate  a  species  oiPortunus.  Since  the  features 
are  sketchy,  it  is  best  to  accept  the  author's  desig- 
nation with  allowance  for  error. 

The  specimen  named  by  Leach  (in  Wfeite,  1847) 
is  an  immature  female  with  prominently  ridged 
areas  on  the  carapace  and  straight  lateral  spines 
typical  of  C.  gladiator.  There  is  a  small  mature 
female  in  this  same  collection. 

Material. — Total:  80  lots,  412  specimens. 


226.  123094,  Lagos,  23  May  1964, 18  6,  22  9, 1  juv, 
Pillsbury  Stn.  2.  120939,  Lagos,  10  May  1965,  4  S, 
6  9,  Pillsbury  Stn.  229.  120940,  04°06'N,  05°58'E 
to  04°02'N,  06°04'E,  14  May  1965,  9  6,  11  9,  1  juv, 
Pillsbury  Stn.  250.  120941,  04°04'N,  06°18'E,  14 
May  1965,  1  9,  1  juv,  Pillsbury  Stn.  252. 

FERNANDO  p60 

120942,  03°35'N,  08°48'E,  15  May  1965,  1  juv, 
Pillsbury  Stn.  258. 

ZAIRE 

54251,  Banana,  mouth  of  Congo  River,  Aug. 
1915,  1  <?,  1  9,  H.  Lang.  54252,  Banana,  mouth  of 
Congo  River,  no  date,  1  3,  H.  Lang. 

AMNH.  4  lots,  7  specimens. 

ZAIRE 

3403  and  3470,  Banana,  Aug.  1915,  3  <J,  1  9,  H. 
Lang  and  J.  Chapin. 

ANGOLA 

3385  and  3463,  Santo  Antonio  do  Zaire,  Aug. 
1915,  2  <?,  1  9,  H.  Lang  and  J.  Chapin. 


USNM.  18  lots,  95  specimens. 

SENEGAL 

21384,  Dakar,  3  May  1892,  1  3,  O.  F.  Cook. 
119469,  Dakar  Harbor,  25-26  July  1964,  2  cJ,  2  9, 
Geronimo. 


BMNH.  19  lots,  64  specimens. 

GAMBIA 

1927.1.27.1,  Cape  St.  Mary,  1  <?,  T.  R.  Hayes,  Sir 
C.  H.  Armitage.  1952.9.9.19/20,  1  mi  N  Gunjur  on 
coast,  1  (5,  1  9,  M.  H.  Routh. 


LIBERIA 

20670,  Mouth  of  Mesurado,  Monrovia,  no  date,  1 
9  juv,  O.  F.  Cook.  87395,  Farmington  River  at 
Snafu  Docks,  Nov.  1946,  3  c?,  1  9,  H.  A.  Beatty. 
97861  and  97862,  off  St.  Paul  River  mouth,  Mon- 
rovia, 6  Jan.  1953,  2  9  (ov),  G.  C.  Miller.  97863,  off 
St.  Paul  River  mouth,  Monrovia,  4  Mar  1953,  1  d, 
G.  C.  Miller. 


IVORY  COAST 

120937, 05°02.5'N,  03°49.5'W,  30  May  1964, 2  9, 
Pillsbury. 

GHANA 

14879,  Baya  River,  Elmina,  Ashantee,  1889, 16  , 
W.  H.  Brown,  Jr.,  (Type). 

NIGERIA 

120938,  Lagos,  9  May  1965,  1  6,  Pillsbury  Stn. 


SIERRA  LEONE 

1955.10.7.35,  Rokel  estuary  [NE  Freetown],  1  9 
juv,  T.  S.  Jones.  1957.5.26.76/78,  Banana  I.,  2  <J,  2 
9,  A.  R.  Longhurst.  1922.0.13.1/5,  Sherbro  I.,  5  <J,  5 
9  (juv),  C.  H.  Allan. 

GHANA 

1931.5.21.1,  Accra,  1  6,  F.  R.  Irvine.  Two  unreg. 
lots,  Accra,  2  <J,  3  9  (1  ov),  F.  R.  Irvine. 

NIGERIA 

1966.10.17.3/4, 1  6, 1  9,Ejike.  1938.8.15.47/48,5 
juv,  A.  G.  Taylor. 

CAMEROON 

1967.11.4.1/2,  Ambas  Bay  [4°N,  9°10'E],  Feb. 
1966,  2  S,  T.  S.  Jones.  1962.2.1.24/27,  Victoria 
Bay,  4  d,  1  9,  J.  T.  Swarbrick.  Unreg.,  Victoria  Bay, 
16  9  (3  ov),  J.  T.  Swarbrick.  Unreg.,  Cameroon 
coast.  Mar.  1962,  1  S,  1  9,  R.  C.  Ward. 


737 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


WEST  AFRICA 

Unreg.,  22, 1 9 .  Dry  coll.  vi/9, 1  $,  Congo  Exped., 
I.  Cranch.  Unreg.,  l5,  Lupa  smythiana  Leach 
MS,  Neptunus  sanguinolentus  in  White  Cata- 
logue, 1847,  J.  Cranch. 

MNHNP.  11  lots,  27  specimens. 

SENEGAL 

Rufisque,  11  and  13  May  1947,  2  S,  T.  Monod. 
M'bour,  1948,  1  9,  Dekeyser-Villiers.  Off  M'bour- 
N'gaparou,  May  1949, 2  9  (ov),  G.  Treca,  Cremoux. 

SIERRA  LEONE 

Gulf  of  Guinea,  07°20'15"N,  12°39'W,  1956,  1  9 
(juv).  Calypso  Stn.  11. 

IVORY  COAST. 

Off  Abidjan,  05°16'12"N,  04°0'20"W,  1956, 9juv, 
Calypso  Stn.  20. 

CAMEROON 

Longji  (Kribi)?,  30  May  1956,  1  6,  Calypso  Stn. 
34.  Mouth  of  the  Kienke,  Kribi,  1  2,  T.  Monod. 
Souelaba,  1932,  3  S  (juv),  T.  Monod. 

SAO  TOME 

Gulf  of  Guinea,  1956, 1  9  (ov),  Calypso  Stn.  T27. 
3  <J,  3  juv.  Calypso  Stn.  T9. 

RMNH.  13  lots,  95  specimens. 

LIBERIA 

1871,  Grand  Cape  Mount,  1881,  1  <J,  2  9,  J. 
Biittikofer  and  J.  A.  Sala. 

NIGERIA 

24186,  Gulf  of  Guinea,  03°45'N,  08°03'E, 
03°45'N,  08°02'E,  14  May  1965,  1  9,  Pillshury 
Stn.  256.  23520,  off  Nigeria,  04°03'N,  06°03'E, 
04°04'N,  06°04'E,  14  May  1965,  3  <?,  5  9  (1  ov), 
Pillsbury  Stn.  251.  20597,  Lagos  Harbor,  23  May 
1964,  juv  5  S,  14  9,  Pillsbury  Stn.  2.  23519,  Lagos 
Harbor,  10  May  1965,  1  cJ,  2  9,  Pillsbury  Stn.  228. 
15532,  Port  Harcourt,  Niger  Delta,  May-Aug. 
1960,  4  (?,  H.  J.  G.  Beets. 

FERNANDO  P60 

24185,  03°45'N,  08°48'E,  15  May  1965, 1  <J(juv), 
Pillsbury  Stn.  257. 

CAMEROON 
21572,  Kribi,  9  Aug.  1964,  30+  (juv),  B.  de 

738 


Wilde-Duyfies.  21149,  Kribi,  9  Mar.  1964, 11  c5, 4  9, 
B.deWilde-Duyfies.21178,Doula,  lOFeb.  1964, 1 
<J,  B.  de  Wilde-Duyfies. 

GABON 

14995,  Port  Gentil,  1  juv,  J.  H.  Logeman 

CONGO 

374,  1880,  19,2  juv,  T.  Kamerman. 

ANGOLA 

1876,  Musserra,  1882,  1  <?,  1  9,  T.  Kamerman. 

UNC-IMS.  15  lots,  125  specimens. 

TOGO 

2717, 06°06'30"N,  01°37'30"E,  16  Oct.  1963, 1  9, 
A.  Crosnier. 

DAHOMEY 

2718, 06°19'N,  02°24'E,  20  July  1964, 1 .?,  2  9,  A. 
Crosnier. 

CAMEROON 

2719,  03°55'N,  09°00'E,  5  Jan.  1963,  3  9  (2  ov), 
A.  Crosnier.  2720,  03°32'N,  09°35'E,  24  Aug. 
1963,  5  <J,  5  9,  A.  Crosnier. 

GABON 

2721,  Baie  de  Corisco,  near  Libreville,  3  July 
1960,  1  S. 

CONGO 

2722,  off  Pointe-Noire,  Mar.  1962,  4  <J,  1  9  (ov), 
A.  Crosnier.  2723,  Beach  and  Bay  at  Pointe-Noire, 
Oct.  1963, 6  (J,  10  9(5  ov),  A.  Crosnier.  2724, 3  June 
1964, 2  c^,  A.  Stauch.  2725,  27  May  1964,  juy29  c?(l 
adult),  13  9,  A.  Stauch.  2727,  Nov.  1962,  9  S,  12  9, 
A.  Crosnier.  2728,  26  June  1964,  1  <?,  1  9,  A. 
Stauch.  2729,  27  May  1964,  2  6,  A.  Stauch.  2730, 
July  1963,  2  9,  A.  Crosnier.  2731,  Estuaire  de  la 
Songolo,  near  Pointe-Noire,  1  9,  A.  Stauch. 

ANGOLA 

2732,  off  Cabinda,  Dec.  1962,  6  <?,  8  9  (1  ov),  A. 
Crosnier. 

Supplementary  literature  records. — Baie  de 
Saint-Jean  [19°27'N,  16°22'W],  Mauritania; 
Hann,  Goree,  M'bour,  and  Joal,  all  S  of  Dakar, 
Senegal;  Baixos  das  Galinhas,  Ilha  de  Bissau,  Por- 
tuguese Guinea;  lies  de  Los,  1  and  3  mi  W  and  NW 
Tamara,  near  Cap  Matakong,  all  near  Conakry, 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


•Guinea;  Grand  Lahou,  Ivory  Coast  (Monod,  1956); 
Gold  Coast  shelf  (Longhurst,  1958);  Fernando  Poo 
(Crosnier,  1964);  7°20'N,  12°39'W,  Sierra  Leone; 
lagoon  at  Abidjan,  Ivory  Coast;  Kribi,  Cameroon; 
Morro  Peixe,  Sao  Tome  (Forest  and  Guinot,  1966); 
Cabinda,  Luanda,  and  Baia  do  Lobito,  Angola 
(Guinot  and  Ribeiro,  1962). 

CALLINECTES  ORNATUS  ORDWAY 

Figures  6,  18d,  20d,  22d,  25 

Callinectes  ornatus  Ordway,  1863,  p.  571  (syn- 
types:  labelled  "types,"  2  2,  MCZ  5120, 
Charleston,  South  Carolina;  1  <5,  2  9,  MCZ 
5128,  Charleston,  South  Carolina;  S  [dry], 
MCZ  5137,  Gonaives,  Haiti;  i,  MCZ  5136, 
Cumana,  Venezuela;  those  from  Tortiigas 
and  Bahamas  not  found).-.  Smith,  1869,  p.  8.- 
Rathbun,  1896,  p.  356  (part),  pi.  15;  pi.  24, 
fig.  3;  pi.  25,  fig.  2;  pi.  26,  fig.  2;  pi.  27,  fig.  2.- 
1898,  p.  596.-  1901,  p.  48.-  1930,  p.  114 
(part),  text-figs.  15b,  16a,  17a,  18b,  pi.  50.- 
1933,  p.  48,  fig.  40.-  Young,  1900,  p.  188  (var. 
of  C  diacanthus) .-  Verrill,  1908a,  p.  366, 
text-figs.  22c,  23b;  pi.  17,  fig.  1;  pi.  21,  fig.  3.- 
Boone,  1927,  p.  32.-  Contreras,  1930,  p.  232 
(part),  fig.  4.-  Chace,  1940,  p.  33.-  1956,  p. 
154.-  Chace  and  Hobbs,  1969,  p.  132,  fig. 
37e.-  Balss,  1957,  p.  1692  (part).-  Holthuis, 
1959,  p.  200.-  Guinot-Dumortier,  1960,  p. 
514,  figs.  13a,  b.-  WiUiams,  1965,  p.  172 
(part).-  1966,  p.  84,  figs.  lA,  B,  4A,  B.-  Tais- 
soun,  1969,  p.  69,  fig.  25A-D,  photo  9.- 1973, 
p.  22,  figs.  4D,  5A,  photo  1. 

Callinectes  diacanthus.-  A.  Milne  Edwards,  1879, 
p.  225  (var.  ofC.  diacanthus).-  Young,  1900, 
p.  186  (part). 

Neptunus  (Callinectes)  diacanthus.-  Ortmann, 
1894,  p.  77  (part;  specimens  c,  k,  n^,  West 
Indies;  d,  e,  Brazil). 

Callinectes  acutidens .-  Boschi,  1964,  p.  45,  pi.  2, 
figs,  e,  f,  g;  pi.  12,  figs.  1,  2. 

TCallinectes  humphreyi  Jones,  1968,  p.  187. 

Description. — Carapace  (Figure  6)  with  lateral 
pair  of  frontal  teeth  prominent  but  submesial  pair 
small,  often  almost  completely  rudimentary. 
Metagastric  area  of  adults  not  deeply  sculptured, 
anterior  width  about  2.8-2.9  times  length,  pos- 
terior width  about  1.75  times  length.  Antero- 
lateral margins  broadly  arched,  teeth  exclusive 
of  outer  orbital  and  lateral  spine  progressively 


more  acuminate  laterad;  first  five  teeth  with 
posterior  margins  longer  than  anterior  margins, 
shouldered,  distinctly  separated  by  narrow-based, 
rounded  notches;  last  two  teeth  with  margins  ap- 
proximately equal  in  length,  separating  notches 
broad,  next  to  last  tooth  distinctly  more  acumi- 
nate than  spiniform  last  one.  Lateral  spine  trend- 
ing forward.  Surface  of  carapace  with  granula- 
tions most  prominent  on  anterior  half  and  on 
mesobranchial  regions,  granulations  smaller  and 
more  closely  crowded  on  meso-metagastric  and 
cardiac  regions,  nearly  smooth  along  posterolat- 
eral and  posterior  borders. 

Chelipeds  with  smoothly  granulated  ridges  on 
chelae,  carpus  almost  smooth  dorsally,  inferior 
lateral  ridge  terminating  in  a  low  tooth  occasion- 
ally followed  by  an  inconspicuous  eminence. 
Major  chela  usually  with  strong  basal  tooth  on 
dactyl  and,  especially  in  adult  males,  lower  mar- 
gin of  propodal  finger  often  decurved  near  base. 

Male  abdomen  and  telson  reaching  beyond  su- 
ture between  thoracic  sternites  IV  and  V,  usually 
with  distal  portions  recessed  below  plane  of  ster- 
num in  retracted  position;  telson  slightly  longer 
than  broad  with  somewhat  inflated  sides;  sixth 
segment  of  abdomen  relatively  narrow,  sides 
slightly  constricted,  not  parallel.  Mature  female 
abdomen  and  telson  reaching  as  far  forward  as  in 
male,  telson  as  broad  as  long.  First  gonopods  of 
male  (Figures  18d,  20d)  reaching  almost  to  suture 
between  thoracic  sternites  VI  and  VII,  overlap- 
ping each  other  completely  near  base  but  diverg- 
ing distally  and  tapering  to  usually  lanceolate 
membranous  tip;  armed  subterminally  with  short 
retrogressive  spinules  quite  visible  at  low 
magnification,  somewhat  more  numerous  and 
longer  distally  than  proximally  with  tendency  to 
arrangement  in  rows  near  tip  on  ventral  and  me- 
sial margin.  Gonopores  of  females  (Figure  22d)  ir- 
regularly ovate  with  apex  on  long  axis  directed 
anteromesad;  aperture  of  each  irregularly  and 
broadly  lunate,  sloping  from  surface  on  mesial 
side  under  rounded  crenate  anterior  border  and 
rounded  eminence  on  posterior  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
60,  width  at  base  of  lateral  spines  105,  including 
lateral  spines  130.  Two  largest  females:  length  58, 
width  at  base  of  lateral  spines  84,  including  lat- 
eral spines  107 — length  69,  width  at  base  of  lat- 
eral spines  83,  including  lateral  spines  99.  These 
two  females  demonstrate  variability  in  mature 
form  that  is  characteristic  of  all  species  in  the 

739 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


genus.  Summary  of  selected  measurements  is 
given  in  Tables  1  and  2. 

Color. — Adult  males  with  carapace  dull  olive  to 
dark  brown,  usually  with  a  large,  ill-defined, 
roundish  spot  of  orange  or  orange-red  on  each  side 
posteriorly;  lateral  spines  and  anterolateral  teeth 
maroon,  light  blue  or  whitish,  white  tipped.  Eye- 
stalks  purple.  Chelipeds  proximally  similar  to 
carapace,  spotted  with  blue  or  soft  purple  and  with 
spines  paler,  joints  red;  inner  surface  of  palm 
white,  but  with  a  large  bright  red  patch  bordered 
with  purple;  fingers  mostly  purple,  tipped  with 
red.  Walking  legs  bright  blue  above,  with  a  band 
of  scarlet  at  each  joint  and  a  patch  of  paler  blue  or 
green  on  posterior  and  lower  side  of  each  article; 
dactyls  red  or  violet.  Swimming  legs  similar  in 
color,  but  with  red  articular  bands  wider,  a  patch 
of  orange  or  yellow  on  each  article;  dactyl  with 
proximal  blue  band  separated  from  distal  scarlet 
band  by  an  orange  band.  Abdomen  light  blue  pos- 
teriorly. Females  similar  to  males  except  upper 
surface  of  chela  more  violet;  fingers  with  white  or 
fuschia  colored  teeth. 

Many  individuals  less  brilliantly  colored, 
juveniles  often  dull  or  plain  olive-yellow  to 
greenish  above.  Some  males  more  melanistic,  ex- 
hibiting shades  of  dark  brown  and  purple  with 
accents  of  yellow  and  brownish  red.  Albinistic  (or 
light  hued)  forms  not  uncommon  (Verrill,  1908a 
as  condensed  in  Williams,  1966;  Taissoun,  1969). 

Variation. — A  close  relative  of  C.  danae  andC. 
similis  (shape  of  carapace,  metagastric  area,  and 
reduced  submesial  frontal  teeth),  C.  ornatus  is 
perhaps  most  often  confused  with  C.  danae 
because  of  their  broad  sympatric  geographic 
ranges.  Callinectes  ornatus  has  the  most  obsoles- 
cent submesial  frontal  teeth  of  the  three  species, 
they  being  entirely  absent  in  many  individuals 
but  developed  somewhat  in  others.  Within  a  single 
lot  of  equal-sized  specimens  both  extremes  may  be 
seen  (USNM  48401,  Cuba;  18227,  Jamaica)  and 
keys  to  identification  based  on  this  character 
alone  are  of  limited  usefulness.  The  lateral  pair  of 
frontal  teeth  may  have  either  rounded  or  quite 
sharp  tips  in  the  same  lot  of  specimens  (USNM 
48401).  Both  types  of  variation  in  frontal  teeth 
may  be  seen  anywhere  in  the  geographic  range. 

The  anterolateral  teeth  are  more  acuminate, 
forward  pointing,  and  longer  than  in  C.  similis. 
Brazilian  and  some  Guianian  juveniles  in  samples 
have  erect  anterolaterals,  relatively  longer  for 


their  width,  and  more  cleanly  separated  than 
teeth  on  those  from  Florida,  whereas  adult  speci- 
mens from  Brazil  (also  North  Carolina  and  some 
from  Bermuda  and  Jamaica)  tend  to  have  nar- 
rower sharper  anterolateral  teeth  than  those  from 
Venezuela,  Curagao,  Cuba,  and  especially 
Florida.  A  line  of  iridescent  patches  occurs  along 
the  bases  of  anterolateral  teeth  in  some  individu- 
als. One  specimen  from  Trinidad  (BMNH)  has 
coalesced  third  and  fourth  teeth  on  the  right  side. 

Major  chelae  may  be  broad,  even  on  moderate 
sized  juveniles  (Florida). 

The  abdomen  of  males  usually  is  recessed,  but 
may  be  flush  with  the  sternum  as  in  immature 
male  C.  similis  and  C.  danae,  but  is  never  as  broad 
as  in  C.  similis. 

First  gonopods  of  males  usually  extend  forward 
to  the  anterior  one-fourth  of  thoracic  sternite  VII, 
but  may  reach  beyond  the  suture  between 
thoracic  sternites  VI  and  VII  among  individuals  in 
the  same  lot.  Usually  overlapping  at  the  base,  at 
least  one  specimen  was  seen  in  which  no  gonopod 
overlap  occurred.  The  lanceolate  tip  is  not  always 
well  developed  in  juveniles,  and  the  membranous 
extreme  tip  tends  to  be  longer  in  Brazilian  (and 
North  Carolinian)  material  than  through  most  of 
the  range. 

Distribution. — Bermuda;  North  and  South 
Carolina  through  southern  Florida;  northwestern 
Yucatan  to  Estado  de  Sao  Paulo,  Brazil  (Figure 

25). 

Habitat. — Essentially  a  tropical  species  found 
mainly  on  sandy  or  muddy  bottom  from  shore  to 
about  75  m,  the  young  have  also  been  collected  on 
shell  and  sponge  bottoms.  Occurrence  in  bays  and 
river  mouths  (Holthuis,  1959;  Rouse,  1970;  in  ad- 
dition to  collection  data  presented  here),  as  well  as 
entrapment  in  fresh  water  (Brues,  1927),  indicate 
tolerance  of  a  broad  range  of  salinity  (recordings  of 
0-50  %o  in  temperatures  ranging  from  18°  to  31°C); 
nevertheless,  most  collections  have  come  from 
waters  of  relatively  high  salinity.  Taissoun  (1969) 
reported  occurrence  in  a  temperature  of  9°C,  but 
this  is  perhaps  a  reference  to  C.  similis  which 
occurs  in  colder  water. 

Spawning. — The  spawning  season  probably  ex- 
tends year  round.  Museum  collections  studied  in- 
clude ovigerous  females  as  follows:  January, 
Puerto  Rico;  April,  Guyana,  Estado  de  Rio  de 
Janeiro,  Brazil;  May,  Estado  de  Sao  Paulo,  Brazil; 


740 


WILLIAMS:  CRABS  OF  THE  GEhTUS  CALLINECTES 


July,  Estado  de  Rio  de  Janeiro,  Brazil;  August, 
Trinidad,  Guyana,  Surinam;  September,  Ven- 
ezuela, the  Guianas;  December,  St.  Thomas,  Es- 
tado de  Rio  de  Janeiro,  Brazil.  Taissoun  (1969) 
reported  ovigerous  females  from  the  Golfo  de  Ven- 
ezuela in  January  and  May.  Undated  collections 
are  recorded  from  southern  Florida,  Margarita  Is- 
land, Venezuela,  and  Estado  de  Sao  Paulo,  Brazil. 

Remarks. — It  is  difficult  to  distinguish  some 
juveniles,  immature  males,  and  adult  females  of 
C.  ornatus  from  C  danae  and  C.  similis.  Helpful 
distinguishing  comparisons  are  the  following: 
males  have  a  narrower  abdomen  than  C.  danae; 
mature  females  have  a  smaller  abdomen  than  C. 
danae;  identification  of  small-  to  moderate-sized 
juveniles  is  often  a  matter  of  judgment  based  on 
shape  of  anterolateral  teeth,  length  of  obsolescent 
submesial  frontal  teeth,  and  wid^  of  the  metagas- 
tric  area. 

Width  of  the  metagastric  area  approaches  that 
of  C.  similis  in  some  individuals  and  is  a  good 
separating  character  from  C.  danae  for  juveniles 
in  regions  where  no  confusion  with  C.  similis  can 
occur.  Borders  of  this  area  are  more  prominently 
defined  than  in  C  similis,  but  become  indistinct 
with  age;  in  that  condition  they  approach  the 
smoothness  of  young  C.  similis.  Callinectes  or- 
natus apparently  shows  less  variation  than  C. 
danae. 

Callinectes  humphreyi  Jones,  1968,  was  based 
on  an  albinistic  immature  female  from  Barbados 
(carapace  length  29,  total  width  60  mm).  Though 
its  status  must  remain  an  enigma  because  the 
type  was  lost  through  accident  in  1969  (dried 
specimen  destroyed  by  a  bloodhound  pup;  Jones, 
pers.  commun.)  and  no  illustration  was  furnished 
with  the  description,  it  was  characterized  as, 
"nearest  to  C.  ornatus,  from  which  it  may  be  im- 
mediately distinguished  by  its  very  different 
coloring  ....  C.  humphreyi  is  pure  white,  except 
for  a  band  of  intense  violet-purple  on  the  inner 
surface  of  each  cheliped,  which  fades  to  light  red  in 
dried  specimens.  C.  humphreyi  is  also  distin- 
guished by  its  smaller  size,  the  deeper,  more  con- 
spicuous sinuses  between  the  anterolateral  teeth, 
the  relatively  longer  intramedial  area  and  the 
distinctly  triangular  shape  of  the  abdomen."  The 
form  was  found  to  be  quite  common  along  the 
southwestern  coast  of  the  island  where  it  was  usu- 
ally seen  quite  near  shore  at  low  tide,  the  white 
color  camouflaging  the  animals  well  on  the  area's 
sandy  bottom.  In  view  of  the  obvious  similarity  to 


C.  ornatus,  endemic  occurrence,  and  coloration 
falling  within  the  range  recognized  by  Verrill 
(1908a),  it  seems  likely  that  this  is  a  color  variant 
of C.  ornatus. 

Williams.(1966),  in  restricting  C.  ornatus,  noted 
that  syntypes  from  Charleston,  S.C.  were  from  a 
locality  representing  an  apparent  extreme  north- 
ern limit  of  geographic  range.  At  that  time  no 
other  specimens  were  known  from  the  Carolinas, 
although  the  species  is  abundant  in  southern 
Florida.  Other  material  from  northeastern 
Florida  as  well  as  North  Carolina  is  now  avail- 
able. There  is  little  doubt  that  these  northern  rec- 
ords still  represent  peripheral  localities,  as  do 
those  from  southwestern  Florida  between  Char- 
lotte Harbor  and  Tampa  Bay.  Records  for  C  or- 
natus in  New  Jersey  (Chace  and  Hobbs,  1969; 
Taissoun,  1969)  represent  C.  similis,  the  Carolin- 
ian congener  of  C.  ornatus.  Collections  from 
Bermuda  are  large,  and  it  was  primarily  on  the 
basis  of  these  that  Verrill  (1908b)  postulated  drift 
of  larvae  in  oceanic  currents  as  island  colonizers 
for  the  genus. 

Locality  data  for  specimens  30-6  and  30-8  in 
MNHNP  (M.  Fontaines)  from  "Chili"  identified  as 
Neptunus  diacanthus  Latr.  (identified  as  C  or- 
natus by  Rathbun,  1896)  are  in  error. 

Material. — Total:  351  lots, 1,260+  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  and  MCZ  (listings  from  New  Jersey,  North 
Carolina,  South  Carolina,  Louisiana,  and  Texas  = 
C.  similis). 

USNM.  161  lots,  646  specimens,  including  the 
following  not  cited  above: 

BERMUDA 

65644,  Hungry  Bay,  Apr.  1928,  1  S,  E.  Deich- 
mann. 

UNITED  STATES 

North  Carolina:  77013,  Sea  Buoy,  Beaufort,  10 
Oct.  1935,  1  c^,  1  9,  J.  S.  Outsell. 

Florida:  122995,  28°21.5'N,  80°33.5'W,  4  Apr. 
1940, 1  6, Pelican  Stn.  207-1. 122987,  shoreline,  W 
side  Norris  Cut,  N  end  Virginia  Key,  Miami,  23 
Aug.  1966,  1  9  (juv),  col.  unknown.  76989,  Coral 
Gables,  no  date,  1  2, 1  juv,  J.  F.  W.  Pearson.  76966, 
Coral  Gables,  no  date,  1  2  (parasitized),  J.  F.  W. 
Pearson.  122994,  Biscayne  Bay,  5  Sept.  1938,  5  6, 5 
2,  USFWS  Launch  58.  113459,  Pigeon  Key,  Mon- 
roe Co.,  7  Aug.  1965,  6  <?,  4  2  (parasitized),  R.  B. 
Manning.  122988,  beach  area  and  tidal  flats  SW 

741 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


end  Bahia  Honda  Key,  Monroe  Co.,  14  JUne  1964, 
2  9  (juv),  Foster  and  Kaill.  The  following  from  Key 
West— 45805,  no  date,  1  6,  H.  Hemphill.  71638, 
1934, 1  9,  H.  H.  Darby.  76992,  no  date,  6  d,  5  9,  col. 
unknown.  76988,  front  of  Biol.  Stn.,  31  Oct.  1922,  7 
juv,  USBF,  S.  and  F.  76987,  no  date,  1  S,  USBF. 
76986,  front  of  Biol.  Stn.,  25  Nov.  1922,  1  9  (juv), 
USBF,  F.  and  S.  76985,  Little  Salt  Pond  Key,  7 
Nov.  1922,  1  <?,  1  9,  (juv),  USBF.  76983,  26  Feb. 
1919, 1  <?,  1  9  (juv),  USBF,  H.  and  S.  76982,  no  date, 

2  c?,  1  9  (juv),  USBF.  76981,  Marquesas  Keys,  no 
date,  4  cJ,  2  9,  A.  S.  Pearse.  122997,  Marquesas 
Keys,  11  Aug.  1931, 8  juv,  A.  S.  Pearse.  The  follow- 
ing from  Dry  Tortugas— 76976,  5  Aug.  1930,  1  9 
(juv),  W.  L.  Schmitt.  76977,  Long  Beach,  7  Aug. 
1930,  1  c?,  1  9  (juv),  W.  L.  Schmitt.  76978,  Long 
Key,  25  June  1931, 1  S,  W.  L.  Schmitt.  76995,  from 
Long  Key  to  Bush  Key,  5  Aug.  1930,  1  .5,  2  9  ( 1  ov), 
W.  L.  Schmitt.  77011,  Long  Key,  25  June  1931, 1  S, 
1  juv,  W.  L.  Schmitt.  76997,  Long  Key,  Aug.  1930, 

3  <?,  1  9,  W.  L.  Schmitt.  77012,  Long  Key,  24  June 
1932,  3  juv,  W.  L.  Schmitt.  76979,  Fort  Jefferson 
moat,  26  June  1931,  1  c^,  1  9  (juvs),  A.  S.  Pearse. 
71637,  Bush  Key,  4  Aug.  1934,  1  cJ,  1  9,  H.  H. 
Darby.  113009,  Charlotte  Harbor,  30  July  1964,  4 
9  (juv),  from  C.  H.  Saloman,  USFWS,  Stn.  X-9A. 
113010,  Charlotte  Harbor,  27  Jan.  1964,  1  <?,  2  9 
O'uv),  C.  H.  Saloman,  USFWS,  Stn.  X-9A.  122989, 
oyster  bed.  Cape  Haze  Marine  Lab.,  Sarasota,  21 
July  1965,  1  c?  (juv),  R.  Cressey.  113007,  Tampa 
Bay,  9  Oct.  1964,  1  6  (juv),  from  C.  H.  Saloman, 
USFWS,  Stn.  B-13.  113008,  Tampa  Bay,  16  Sept. 
1964, 1 9  (juv),  from  C.  H.  Saloman,  USFWS,  Stn. 
B-13. 

Unknown  locality  "South  Atlantic  and  Gulf 
Coasts  of  the  United  States":  2157,  no  date,  3  c5, 2  9, 
col.  unknown. 

BAHAMAS 

88653,  Bimini,  13  Nov.  1948,  2  9  (juv),  A.  S. 
Pearse.  88654,  Bimini,  Nov.  1948,  19  (juv),  A.  S. 
Pearse.  122990,  Clifton  Bay,  Lyford  Cay,  Nassau, 
14  Aug.  1961,  U  ,  2  9  (juv),  W.  L.  Schmitt.  Un- 
catalogued.  Great  Inagua  Island  just  N  Matthew- 
town,  20  Jan.  1968,  l6  ,  Gosner.  76994,  no  date,  1 
5,  Owen  Bryant.  122991,  British  West  Indies,  no 
date,  1(? ,  l9  (juv),  R.  Robbins. 

CUBA 

73306,  Bahia  de  la  Habana,  11  May  1937,  2$, 
5  9,  W.  L.  Schmitt.  76481,  Siguanea  Bay, 
12  Apr.  1937,  1  S  ,  (juv),  Paul  Bartsch.  76485  and 
76493,  Isla  de  Pinos,  opposite  Siguanea  I.,  11  Apr. 


1937,  50  juv,  Paul  Bartsch,  R113  and  R114.  76492, 
Isla  de  Pinos,  opposite  Siguanea  I.,  11  Apr.  1937,  2 
S  ,  Paul  Bartsch,  R115  and  116. 

JAMAICA 

122976, 17°53'N,  77°48'W,  18  May  1965, 2  <j ,  1 9 , 
Oregon  Stn.  5396.  73287,  Jamaica  or  Cienfuegos, 
Cuba,  4  May  1937,  1  2 ,  W.  L.  Schmitt,  Stn.  76. 

DOMINICAN  REPUBLIC 

122996,  Bahia  de  Calderas,  1  9  (juv),  through  I. 
B.  de  Calventi  and  S.  Jakowska,  10  July  1967. 

PUERTO  RICO 

73286,  San  Juan,  27  Apr.  1937,  U  ,  1  9,  W.  L. 
Schmitt.  122999,  off  Fort  San  Geronimo,  San 
Juan,  30  Apr.  1937,  1  c5,  W.  L.  Schmitt. 

VIRGIN  ISLANDS 

St.  Thomas:  2457,  no  date,  1  s  (dry),  A.  H.  Riise. 
St.  Croix:  73288,  Christiansted,  7  Apr.  1937,  1  9 
(juv),  W.  L.  Schmitt,  Stn.  31.  73289,  same,  9  Apr. 
1937,  1  s  ,  Stn.  34.  76470,  Christiansted  Harbor, 
Dec.  1937, 1 9 ,  H.  A.  Beatty,  No.  214.  Prickly  Pear 
Island:  122981,  Vixen  Point,  Gorda  Sound,  15  Apr. 
1956,  2  <J  ,  Nicholson,  Schmitt,  and  Chace,  Stn. 
111-56,  Freelance. 

BARBUDA 

122982,  Oyster  Pond  Landing,  lagoon  side,  25 
Apr.  1959,  6  (i,  3  9  (immat),  W.  L.  Schmitt,  et  al., 
Stn.  92-59.  122980,  near  Oyster  Pond  Landing, 
W  shore  lagoon,  6  Apr.  1956,  4  <5 ,  6  9  (immat), 
Schmitt,  Chace,  Nicholson,  and  Jackson,  Stn. 
85-86,  Freelance.  122978,  6  Apr.  1956,  1$  ,  Stn. 
88-56,  Freelance. 

GUADELOUPE 

122977,  Pointe  a  Pitre,  between  Monroux  and 
Rat  Is.,  30-31  Mar.  1956,  10  (juv),  Chace  and 
Nicholson,  Stn.  68-56,  Freelance. 

ST.  LUCIA 

122979,  Marigot  Lagoon,  shore  of  bay  outside, 
21  Mar.  1956,  1<S ,  Schmitt,  Chace,  Nicholson,  and 
crew,  Stn.  38-56,  Freelance. 

BARBADOS 

76993,  1918,  1  9,  Barbados-Antigua  Exped. 

MEXICO 

Yucatan:  12992,  ocean  beach  at  Progreso,  400 
yd  W  steamship  wharf,  30  Mar.  1936,  1  <5 ,  M.  B. 


742 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 

Trautman.  12993,  same,  600  yd  W  steamship 
wharf,  8  <?  (6  juv),  1  9  (juv),  Trautman,  Patton, 
and  Costello. 

Quintana  Roo:  122984,  Bahia  de  la  Ascension, 
about  1/3  mi  W  Allen  Pt.  light,  13  Apr.  1960, 15,39 
(juv),  Daiber  and  Rehder,  Stn.  66-60,  Blue  Goose. 
122983,  Bahia  de  la  Ascension,  shore  in  front 
Allen  Pt.  light,  13  Apr.  1960,  1  5  ,  2  9  (1 
parasitized),  6  juv,  Daiber,  Stn.  65-60, 5/we  Goose. 
122986,  Bahia  del  Espiritu  Santo,  N  shore,  5  Apr. 
1960,  23,29  (juv),  Bousfield,  Stn.  37-60,  Blue 
Goose.  122985,  Bahia  del  Espiritu  Santo,  N  shore 
near  Lawrence  Pt.,  6  Apr.  1960,  1  9  (juv),  Rehder, 
Daiber,  and  Haynes,  Stn.  42-60,  Blue  Goose. 


BRITISH  HONDURAS 

76990,  Behze,  Sergeants  Caye,  no  date,  2  9  (juv), 
P.  W.  Shufeldt. 

♦ 
VENEZUELA 

101824,  Estado  Falcon,  Bahia  de  Amuay, 
Peninsula  de  Paraguana,  May  1957,  1  9,  F.  A. 
Aldrich.  122965,  SE  Trinidad  and  off  Orinoco 
Delta,  09°55'N,  60°53'W,  26  Aug.  1958,  39(1  ov,  1 
juv),  Oregon  Stn.  2208. 122966,  09°32'N,  60°24'W, 
20  Sept.  1958,  4  3,59(3  ov),  Oregon  Stn.  2348. 

GUYANA 

122970,  08°30'N,  58°56'W,  28  Aug.  1958,  1  9, 
Oregon  Stn.  2228.  122969,  08°20'N,  58°30'W,  29 
Aug.  1958,  4  9  (2  ov),  Oregon  Stn.  2234.  122975, 
06°54'N,  57°47'W,  25  Mar.  1963,  1  6  ,  Oregon  Stn. 
4306. 

SURINAM 

103177,  06°15'N,  55°54'W,  6  June  1957,  1  S, 
Coquette  Stn.  182.  103178,  06°22'N,  55°03.5'W,  4 
June  1957,  37  juv.  Coquette  Stn.  157.  103179, 
06°22'N,  55°06' W,  11  May  1957, 1 S ,  Coquette  Stn. 
1. 103180, 06°23'N,  55°05.5'W,  11  May  1957, 1 5 , 1 
9  (juv).  Coquette  Stn.  2.  103181,  06°28'N, 
54°57.5'W,  11  May  1957,  1  S  (juv),  Coquette  Stn. 
20.  122968,  06°26'N,  54°20'W,  15  Sept.  1958,  Is, 
Oregon  Stn.  2327.  103454,  07°12'N,  57°22'W,  18 
Sept.  1958,  1  9  (ov),  Oregon  Stn.  2339.  122967,  off 
the  Guianas,  1958,  1  9  (ov)  Oregon. 

FRENCH  GUIANA 

122971,  05°56'N,  52°20'W,  11  Sept.  1958,  1  9 
(ov),  Oregon  Stn.  2307.  122972,  off  Cayenne, 
05°30'N,  52°10'W,  12  Sept.  1958,  1  9  (ov),  Oregon 
Stn.  2310. 


BRAZIL 

122973,  off  N  mouth  Amazon  R.,  02°29'N, 
48°58"W,  14  Nov.  1957,  2  3,(1  juv),  Oregon  Stn. 
2058.  122974,  off  Ceara,  02°23'S,  40°31'W,  12 
Mar.  1963,  1  9,  Oregon  Stn.  4250.  72313,  Villa 
Bella,  Sao  Sebastiao,  18  Sept.  1925,  3  carapaces 
(dry),  W.  L.  Schmitt.  122998,  Barro,  Santos,  12 
Sept.  1925,  5  3,  1  9,  W.  L.  Schmitt. 

AHF.  13  lots,  26  specimens. 

UNITED  STATES 

Florida:  Hillsboro  Inlet,  Sept.  1943,  1  3,  2  9, 
(immat),  E.  R.  T.  Hillsboro  Inlet,  15  May  1945, 1 3  , 
2  9,  J.  S.  Garth,  No.  8-45.  Pompano  Beach,  Sept. 
1944, 1 9  (juv),  E.  R.  J.  Hawk  Channel,  Key  Largo 
North,  7  June  1949, 1  9  (juv),  Stn.  LM32-49.  Same, 
29-31  May  1949,  3  3,39  (immat),  Stn.  LM25,  LM- 
27.  Key  Largo,  Florida  Bay,  0.8  km  SW  "My  Place" 
near  Hamper  Pt.,  23  May  1949,  2  parasitized  ap- 
parent 99,  Stn.  LM18-49.  Hawk  Channel,  Planta- 
tion Key  near  Tavernier  Creek,  26  May  1949,  1 3 
(juv),  Stn.  LM21-49.  Lower  Matecumbe  Key, 
Hawk  Channel,  5.3  km  SW  Indian  Key  Draw- 
bridge, 23  Sept.  1950,  1  9  (juv),  Stn.  LM-57.  Hawk 
Channel,  Grassy  Key,  E  coast  1.6  km  S  "Seaside 
Cabins,"  24  May  1949,  Stn.  LM19-49.  Margo  Is- 
land near  channel  S  Big  Marco  Pass,  14  June 
1949,  1  3  (juv),  Stn.  LM39-49. 

CURACAO 

Schottegat,  Santa  Anna  Harbor,  12°07'03"N, 
68°55'34"W,  23  Apr.  1939,  2  9  ,  Velero  III  Stn. 
A47-39. 

VENEZUELA 

Isla  Cubagua,  10°48'48"N,  64°13'30"W,  30  Apr. 
1939,  2  3,1  frag.,  Velero  III  Stn.  A30-39.  Isla 
Cubagua,  10°49'25"N,  64°16'W,  15  Apr.  1939,  19 
(juv),  Velero  III  Stn.  A28-39. 

AMNH.  26  lots,  73+  specimens. 

BERMUDA 

11252,  2  Sept.  1932,  1  9  O'uv),  W.  Beebe  Ber- 
muda Exped.  1 1223, 1939,  6  3,29,  (juv),  W.  Beebe 
Bermuda  Exped.  295,  no  date,  1  3 ,  W.  M.  Rankin. 

11220,  1939,  1  3,  W.  Beebe  Bermuda  Exped. 
11250,  1930,  1  9  (juv),  W.  Beebe  Bermuda  Exped. 
11225,  1929,   1  3,  W.  Beebe  Bermuda  Exped. 

11221,  29  Apr.  1937,  1  9,  W.  Beebe  Bermuda 
Exped. 


743 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


UNITED  ST  ATI  S 

Florida:  6684,  Indian  River,  Nov.  1920, 2  S  (juv), 
Prince.  10367,  Late  Worth,  July  and  Aug.  1945,  3 
S  (1  dry),  1  5  (juv),  W.  G.  Van  Name  and  A.  H. 
Verrill. 

BAHAMAS 

11222,  North  Bimini,  June  1939,  1  $  (juv),  W. 
Beebe  Bermuda  Exped.  11291,  Bimini,  5  Sept. 
1947,  1$,J.  C.Armstrong.  11292,  Bimini,  12  (ov), 
J.  C.  Armstrong.  11634,  Bimini,  14  June  1953, 12, 
W.  D.  Clarke.  11296,  Bimini,  21  Oct.  1947,  3  <5,  2  2, 
J.  C.  Armstrong.  Nassau  and  Andros  Islands, 
Mar.-Apr.  1930,  IS  (juv),  Bacon-Miner  Exped.  and 
International  Exped.  to  Andros  I.  10368,  Andros 
I.,  1926,  1  quart  juv  and  immat,  R.  A.  Miner. 

HAITI 

1949-1950,  2  c? ,  2  2  (1  juv),  A.  Curtiss.  11219, 
Bizoton  Reef  [NW  Port  au  Prince] ,  4  Mar.  1927, 2  S 
(1  juv),  W.  Beebe  Exped. 

DOMINICAN  REPUBLIC 

8641,  W  shore  north  half  of  El  Cayo  [Barahona 
Harbor],  7  July  1932,  Is,  l9  (juv),  J.  C.  Arm- 
strong. 9395,  southern  part  La  Piedra  Prieta  Reef, 
Barahona  Harbor,  16  July  1932,  1  2  (juv),  J.  C. 
Armstrong. 

PUERTO  RICO 

2945,  Bahia  de  Guanica,  Ensenada,  14  June 
1915,  3  juv,  R.  W.  Miner  and  H.  Mueller.  2999, 
yard  at  Miramar,  Santurce  Barrio,  San  Juan,  14 
July  1914,  1  juv,  R.  W.  Miner  and  L.  Estrada. 

ANSP.  3  lots,  8  specimens. 

UNITED  STATES 

4897,  Lake  Worth  Inlet,  Fla.,  no  date,  1  S 
(immat),  4  2  (immat),  H.  A.  Pilsbry. 

BAHAMAS 

3489,  New  Providence  Island,  no  date,  1  <j ,  1  2, 
H.  C.  Wood,  Jr. 

HAITI 

5422,  Port  au  Prince,  1950,  1  6  (dry),  A.  Curtis. 

BMNH.  11  lots,  18  specimens. 

UNITED  STATES 

Florida:  1966.12.5.558/559,  coast  of  Everglades 
Park,  1  <5 ,  12,  Univ.  Miami  Inst.  Mar.  Sci.  61.44, 


south  coast  of  United  States,  2  S,  3  juv  (dry),  vi/9, 
W.  Stimpson. 

CARIBBEAN  SEA 

1955.10.6.98/99,  Stn.  28  (44),  1  5,  1  2  (juv), 
Oxford  Univ.  Cayman  Exped. 

ANTIGUA 

1967.4.4.136,  1  2  (juv),  F.  H.  Mansell,  H.  M.  S. 
Dorsetshire.  1928.12.1.57,  1 ,5,  W.  R.  Forrest. 

BARBADOS 

1963.5.16.33,  1  2,  H.  M.  S.  Frobisher,  15  Feb. 
1933. 

TRINIDAD 

1962.12.12.2,  Mayaro-Point  Radix,  Stn.  1125,  1 
5,  D.  W.  Richardson.  Unregistered,  San  Fernanda, 
1  2,  N.  Boutakoff. 

GUYANA 

1958.11.12.27/28,  07°39'N,  57°44'W  to  07°47'N, 
57°32'W,  23-24  Apr.  1958,  1  <J,  1  2  (ov),  Trawler 
Cape  St.  Mary. 

BRAZIL 

50.32,  1  2  (dry),  vi/6. 

MCZ.  32  lots,  106  specimens. 

BERMUDA 

8377,  July  1903,  2  juv,  O.  Bryant.  8459,  Sinky 
Bay,  30  May  1916,  1  <5,  Bermuda  Biol.  Stn.  8460, 
Fairyland  Bay  in  eelgrass,  14  Feb.  1916, 1 ,5 ,  W.  J. 
Crozier.  8890,  1  5,  reed,  from  E.  L.  Mark,  19  Oct. 
1920.  8891,  Tom  Woods  Bay,  25  Apr.  1916,  1^,22 
(juv),  E.  L.  Mark.  8892,  Sinky  Bay,  11  Apr.  1916, 1 
(?  (immat),  E.  L.  Mark.  9203,  Richardsons  Inlet,  S 
side  St.  George  Island,  June  1936,  5  (J ,  6  2  (immat), 
F.  A.  Chace,  Jr.  9256,  Vaughns  or  Whites  Bay,  St. 
Davids  Island,  18  June  1936, 4  $  (juv),  F.  A.  Chace, 
Jr.  9447,  July  1936,  2  juv,  L.  H.  Kleinholtz. 

UNITED  STATES 

South  Carolina:  5210,  Charleston,  no  date,  2  2 
labelled  "Types,"  col.  unknown. 

Florida:  8749,  1  2  (ov),  Maynard.  5130,  Key 
West,  no  date,  1  2,  C.  E.  Faxon.  1134,  Tortugas,  1  2 
(juv).  Holder,  reed.  8  June  1960.  8748,  July  1859, 4 
5,  2  2  (juv),  Woodbury.  5131,  Tortugas,  3  5,  1  2, 
Woodbury,  reed,  from  Smithson.  Inst.,  13  Feb. 
1861.  5206,  Fort  Jefferson,  Tortugas,  3  $,  part  of 
Ordway's  material. 


744 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


BAHAMAS 

9481,  N  entrance  Hawksbill  Creek,  Grand 
Bahama  Island,  8  Apr.  1936.  1  5,  W.  J.  Clench. 
11673,  Alicetown,  North  Bimini,  May  1941, 1  9,  R. 
W.  Foster  and  J.  Huntington.  9488,  Governors 
Harbor,  Eleuthera  Island,  2  May  1936,  1  3 ,  W.  J. 
Clench.  9426,  Simms,  Long  Island,  7  July  1936, 1 5 
(juv),  Harvard-Bahama  Exped. 

MNB.  4  lots,  17  specimens. 

BRAZIL 

Pernambuco:  331,  Praia  do  Pina,  Recife,  Sept. 
1944,  3  9  (juv),  col.  unknown. 

Rio  de  Janeiro:  49,  no  other  data,  1  (5.  82,  Rio 
Guanabara,  no  other  data,  2  <?,  9  $  (3  juv).  Praia  do 
Fundao,  Baia  de  Guanabara,  Dec.  1951,  2  <j,  N. 
Santos. 

MNHNP.  9  lots,  16  specimens. 

UNITED  STATES 

Florida:  Tortugas,  4  <J,  from  MCZ. 


Holthuis.  18717,  1-9  Sept.  1963,  2$,  1  juv,  L.  B. 
Holthuis.  23377,  Pigeon  Key,  W  Marathon,  30 
Jan.  1965,  Ic?,  L.  B.  Holthuis  and  J.  A.  Cabrera. 
4920,  Tortugas,  July  1925,  juv,  H.  Boschma. 
15632,  Marco  Beach  S  of  Marco,  12  Sept.  1960, 1 5 , 
beached  after  hurricane  Donna,  L.  B.  Holthuis. 

BAHAMAS 

2853,  Nassau,  New  Providence,  1887,  2  3 , 1  2,  A. 
de  Haas.  1870,  Bahama  Islands,  no  date,  1  5  ,  12, 
Dr.  de  Haas. 

ST.  MARTINS 

23457,  freshwater  pond,  3  Oct.  1963,  2  2  (juv),  P. 
W.  Hummelinck.  14997,  Great  Bay,  23  June  1955, 
2  juv,  P.  W.  Hummelinck.  11870,  Oyster  Pond,  E 
coast,  22  Feb.  1957,  4  juv,  L.  B.  Holthuis.  11872, 
coast  near  Philipsburg,  16- 17  Feb.  1957,  1  9,  2  juv, 
L.  B.  Holthuis.  Simsons  Bay,  washed  ashore  on 
beach,  19  Feb.  1957,  1  carapace  (dry),  L.  B.  Hol- 
thuis. 11873,  freshwater  pond  W  Philipsburg,  17 
Feb.  1957,  3  <? ,  1  9,  1  juv,  L.  B.  Holthuis.  11875, 
Simsons  Bay,  23  Feb.  1957,  20  juv,  L.  B.  Holthuis. 


FRENCH  GUIANA 

Stn.  354, 23  m,  mud,  12  Aug.  1957, 2^,1  9, juv,  J. 
Durand,  ORSTOM  II.  Stn.  413,  48  m,  dead  shells- 
rocks,  24  July  1958, 1  juv,  J.  Durand,  ORSTOM  II. 
lies  du  Salut,  July  1957,  2  <J ,  1  9,  J.  Durand,  ORS- 
TOM II. 

Following  are  a  series  of  dry  specimens  with  poor 
or  questionable  locality  data  that  were  also  de- 
termined by  M.  J.  Rathbun  in  1896. 

Guadeloupe:  IS,  1  9,  M.  Beaupertuis.  Chili:  1  <5 , 
30-6,  1 9 ,  30-8,  M.  Fontaines.  Cote  de  Amerique,  1 
$,  30-19. 

RMNH.  60  lots,  200+  specimens. 

UNITED  STATES 

Florida:  Bear  Cut,  N  point  Key  Biscayne, 
Miami,  15802,  15  Sept.  1960,  juv.  15803,  4  Sept. 
1960,  juv.  15804,  14  Sept.  1960,  juv.  15805,  15 
Sept.  1960,  juv.  18718,  2-9  Sept.  1963,  1  juv. 
23385,  6  Dec.  1964,  1  9  (parasitized).  24372,  22 
Nov.  1964,  juv.  23366,  1  Jan.  1965,  juv 
(parasitized).  23415,  9  Jan.  1965,  1  3,  juv.  23418, 
Jan.  1965,  1  6,  juv.  24371,  1  Jan.  1965,  juv.  24373, 
10  Jan.  1965,  juv.  23430,  9  Jan.  1965,  juv 
(parasitized).  23421,  1  Feb.  1965,  1  S  and  juv 
(parasitized),  all  by  J.  A.  Cabrera  and  L.  B.  Hol- 
thuis. 23271,  16  Jan.  1965,  2  9  (parasitized),  L.  B. 


VENEZUELA 

10721,  Margarita  Island?,  possibly  Caracus 
Bay,  Curasao,  1955,  2  9(1  ov),  P.  W.  Hummelinck. 
1868,  coast,  no  date,  IS  (juv),  T.  Buitendijk. 

ARUBA 

2372,  Vaardenbaai  (?),  1  June  1905,  1  <?,  Prof. 
Boeke.  Pova  Beach,  NW  coast  of  island,  27  Apr. 
1955,  3  c5  (dry),  J.  S.  Zaneveld  and  P.  W.  Hum- 
melinck. 1307,  1883,  1  <?,  K.  Martin.  2261,  lagoon, 
3  July  1905,  1  S  (juv).  Prof.  Boeke.  1867,  June 
1883, 1  9  (juv),  A.  J.  V.  Koolwijk.  1869,  July  1883, 1 
3  (juv).  Dr.  de  Haas. 

CURACAO 

St.  Kruis  Baai,  7  Oct.  1948,  2  juv,  P.  W.  Hum- 
melinck. 23351,  NW  part  Piscadera  Baai,  25  Nov. 
1963,  5  juv,  P.  W.  Hummelinck.  Piscadera  Baai, 
16  Mar.  1957,  1  carapace  (beached,  dry),  L.  B. 
Holthuis.  23393,  S  part  Piscadera  Baai,  15  Oct 
1963,  19,  col.  unknown.  11874,  Piscadera  Baai, 
fish  trap,  11-14  Feb.  1957,  1  <;,  1  9,  L.  B.  Holthuis. 
3272,  Schottegat,  10  Feb.  1939,  5+  3,  2  9,  H.  W.  C. 
Cossee.  2234,  reefwater  (lagoon),  2  m,  26  July 
1905,  1  5  (juv),  Prof.  Boeke. 

BONAIRE 

NE  coast  of  Cay,  1  Sept.  1948,  2  6,  P.  W.  Hum- 
melinck. 


745 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


GUYANA 

22510,  06°54'N,  57°47'W,  25  Mar.  1963,  2  5, 
Oregon  Stn.  4306. 

SURINAM 

22518,  06°16'N,  55°56'W,  19  Feb.  1963,  25,29 
(juv),  Oregon  Stn.  4171.  21154,  off  coast  between 
mouths  of  Suriname  and  Coppename  Rivers, 
25-27  Aug.  1964,  1  2  {ov),i\iY,  Coquette.  11869,  10 
mi  N  mouth  of  Suriname  R.,  6-9  May  1957,  juv  and 
subadult.  Coquette.  14999,  mouth  Suriname  R. 
near  Resolutie,  22  Dec.  1942, 1  juv,  D.  C.  Geijskes. 
14996,  near  lightship  Suriname  Rivier,  3  May 
1957,  1  juv.  Coquette.  18672,  20  mi  E  Hghtship 
Suriname  Rivier,  20  Feb.  1963,  1  S ,  Coquette. 
11871,  20  mi  from  coast,  NNW  mouth  Marowdjne 
R.,  8-12  Apr.  1957,  1  3    (juv).  Coquette. 

FRENCH  GUIANA 

11868,  06°00'N,  53°29'W,  29  May  1957,  2  3 ,  juv, 
Coquette.  14998,  05°56'N,  53°17'W,  21  May  1957, 
1  juv.  Coquette. 

BRAZIL 

Sao  Paulo:  21587,  Ribeira  Beach,  Ubatuba,  18 
July  1962,  1  <? ,  L.  Forneris.  21694,  Enseada  Pal- 
mas,  Anchieta  I.,  Ubatuba,  28  Feb.  1962, 1  <5  (juv), 
L.  Forneris.  21695,  Pedra  Andorinha,  Ubatuba,  22 
Jan.  1963,  1  juv,  L.  Forneris.  17536,  Santos,  12 
Sept.  1960, 3  juv,  L.  R.  Tommasi.  17537,  Santos,  20 
Apr.  1961,  1  $,  (juv),  L.  R.  Tommasi. 

SADZ-B.  27  lots,  125  specimens. 

UNITED  STATES 

Florida:  1466,  Key  West,  1883,  2  subadult 
carapaces  (dry),  Jordan. 

BRAZIL 

Rio  de  Janeiro:  1728,  Atafona,  1964,  2<? ,  1  2,  N. 
Meneses.  1959,  Praia  do  Forma,  Cabo  Frio,  July 
1957,  1  <5  (juv),  Luiz  Tommazi.  3255,  Praia  do 
Forte,  Cabo  Frio,  Jan.  1964,  1  2,  S.  J.  Rand,  N. 
Papanen,  S.  Tocchetreu,  and  S.  Tacla.  2336,  Ilha 
Grande,  Dec.  1965,  12  (ow),  Emilia  Stn.  14.  3084, 
Ilha  Grande,  30  July  1966,  1  2  (ov),  Emilia  Stn. 
c-288.  2335,  Ilha  Grande,  no  date,  1  2,  Stn.  12. 
3226,  S  side  Ilha  Grande,  43  m,  mud,  17.8°C,  26 
Apr.  1968,  2  2(1  ov),  Hydrographic  Stn.  283.  3247, 
25  m,  dredge,  11  Nov.  1956,  1  <j.  Corvette So/imoes 
Stn.  99/56.  3249,  Ilha  Grande,  Aug.  1960,  2  S  , 
Emilia  Stn.  1.  3261,  3228,  Enseada  das  Estrelas, 
Ilha  Grande,  18  July  1966,  27  5,  5  2,  16  juv,  G. 


Melo.  3237,  Enseada  das  Estrelas,  Ilha  Grande,  26 
Feb.  1966,  22  3,  5  2,  col.  unknown.  2339,  Enseada 
das  Estrelas,  Ilha  Grande,  26  July  1966, 1  <? ,  1 2 ,  G. 
Melo.  3082,  Angra  dos  Reis,  Ilha  dos  Conqueiros, 
21  Apr.  1966,  U,  G.  Melo. 

Sao  Paulo:  3217,  Ubatuba,  1905,  1  <?,  E.  Garbe. 
3259,  Ubatuba,  1905,  1  2  (juv),  E.  Garbe.  1745, 
Ilha  Bela,  Sao  Sebastiao,  Mar.  1962,  1  3 , 1  2  (juv), 
P.  E.  Vanzolini.  3227,  Sao  Sebastiao,  1895  [?],  1  2 
O'uv),  H.  Britski.  348,  Ilha  Sao  Sebastiao,  1915, 
8  5,  2  2  (1  ov),  Bicego.  1740,  Praia  Grande,  Sao 
Sebastiao,  Feb.  1962,  2  6  (juv),  H.  Britski.  2109, 
Santos,  1959,  15,  12,  Servico  Especial  Pesca. 
1673,  Ilha  da  Moela  [near  Santos  off  Guaruja],  18 
May  1962,  3  5,22(1  ov),  C.  Jesus.  1671,  Baia  do 
Guaruja,  22  May  1962,  1  5,  1  2,  C.  Jesus.  Praia 
Grande,  Sao  Vincente,  4  Aug.  1954,  Is,  1  2,  L. 
Travassas,  E.  Dente,  and  Werner.  2064,  unknown 
locality,  July  1959,  2  5,2  2,  Emilia  (first  trip). 

YPM.  5  lots,  25+  specimens 

BERMUDA 

3850,  1901,  1  2  (juv),  A.  E.  Verrill  and  party. 

6397,  April  1901,  5  5,  4  2 ,  A.  E.  Verrill  and  party. 

6398,  1901,  45  ,  A.  E.  Verrill  and  party.  6392, 
1901,  1  5,  Bermuda  Biol.  Stn.  6394,  1901,  several 
juv,  A.  E.  Verrill  and  party. 

Supplementary  literature  records. — Southern 
Florida  (Rouse,  1970);  Isla  de  Pinos,  Cuba  (Boone, 
1927). 

CALLINECTES  DANAE  SMITH 

Figures  7,  ISe,  20e-f,  22e,  24 

Lupa  dicantha.-  Dana,  1852,  p.  272,  (type:  I5, 

dry,  USNM  2371,  Rio  de  Janeiro,  Brazil).- 

1855,  pi.  16,  fig.  7a-c. 
Callinectes  diacanthus.-  Ordway,  1863,  p.  575 

[10].-  A.  Milne  Edwards,  1879,  p.  226  (var. 

of  C.  diacanthus).-  Young,  1900,  p.   186 

(part). 
INeptunus  diacanthus.-  Heller,  1868,  p.  26.- 

Doflein,  1899,  p.  186  (part,  the  Colombia 

and  Brazil  specimens). 
Callinectes  Danae  Smith,  1869,  p.  7  (syntj^jes:  l5  , 

12,  MCZ  5143;  15,  12,  YPM  824,  Recife 

[==Pernambuco,  Estado  de  Pernambuco], 

Brazil,  C.  F.  Hartt).  (Type  locality  restricted 

by  Rathbun,  1930.) 
?Lupa  (Neptunus)  diacantha.-  von  Martens,  1872, 


746 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


p.  92,  (part,  the  Rio  de  Janeiro  specimens). 

Callinectes  danae.-  Rathbun,  1896,  p.  357,  pi.  16; 
pi.  24,  fig.  4;  pi.  25,  fig.  3;  pi.  26,  fig.  3;  pi. 
27,  fig.  3.-  1898,  p.  596.-  1901,  p.  48.-  1930, 
p.  118  (part),  text-figs.  15d,  16d,  17b,  18d, 
pi.  51.-  1933,  p.  49.-  Verrill,  1908a,  p.  370, 
fig.  22e  (not  22d).-  Chace,  1940,  p.  33.- 
Chace  and  Hobbs,  1969,  p.  130,  fig.  37b.- 
Holthuis,  1959,  p.  201.-  Lemos  de  Castro, 
1962,  p.  39,  pi.  2,  fig.  9.-  Williams,  1966,  p. 
86,  fig.  2A-D,  4C,  D.-  Jones,  1968,  p.  187.- 
Taissoun,  1969,  p.  75,  fig.  28A-D,  photo 
10.-  1973,  p.  33,  figs.  4B,  5D,  photo  4. 

Callinectes.-  Kretz  and  Biicherl,  1940,  p.  173,  un- 
numbered col.  pi.,  figs.  1-22. 

Description.  —  Carapace  (Figure  7)  beting  four 
frontal  teeth,  submesial  pair  no  more  than  half 
length  of  lateral  pair.  Metagastric  area  of  adults 
with  anterior  width  about  2-2.5  times  length, 
posterior  width  about  1.5  times  length.  Anterolat- 
eral margins  somewhat  arched,  teeth  exclusive  of 
outer  orbital  and  lateral  spine  varying  from  often 
convex  sided  with  subacute  tips  at  orbital  end  of 
row  to  sharper  and  more  spiniform  laterally,  each 
with  anterior  margin  shorter  than  posterior  and 
separated  from  contiguous  ones  by  narrow-based 
rounded  notches.  Surface  of  carapace  rather 
evenly  and  smoothly  granulate,  except  granules 
more  widely  spaced  on  epibranchial  region  and 
near  anterolateral  border,  most  crowded  on  gas- 
tric, mesobranchial,  and  cardiac  regions;  nearly 
smooth  along  frontoorbital,  posterolateral,  and 
posterior  borders. 

Chelipeds  with  granulate  ridges,  upper  surface 
of  carpus  bearing  slightly  developed  interrupted 
ridges  trending  longitudinally  with  axis  of  limb, 
ridges  bearing  obsolescent  granules  often  better 
developed  in  males  than  in  females,  inferior  lat- 
eral ridge  terminating  in  a  strong  lateral  spine  or 
tooth  often  followed  by  a  strong  eminence.  Male 
abdomen  and  telson  reaching  beyond  suture  be- 
tween thoracic  sternites  IV  and  V;  telson  triangu- 
lar, longer  than  broad  with  somewhat  inflated 
sides;  sixth  segment  of  abdomen  with  sides  nearly 
straight,  diverging  proximally,  poorly  calcified 
proximally  except  for  variably  indurated  basal 
portion  often  connected  to  distal  part  by  a  narrow 
central  column.  Mature  female  abdomen  and  tel- 
son reaching  as  far  forward  as  in  male,  sixth  seg- 
ment shorter  than  fifth,  telson  triangular  with 
slightly  inflated  sides.  First  gonopods  of  male 


(Figures  18e,  20e,  f)  reaching  beyond  midpoint  of 
thoracic  sternite  VI,  overlapping  each  other  near 
base,  or  adjacent,  and  tapering  to  narrow  mem- 
branous tips  usually  bent  ventrolaterally;  armed 
with  scattered  but  mainly  dorsal  minute  spinules 
and  two  to  four  subterminal  sternomesial  exceed- 
ingly slender  elongate  spinules.  Gonopores  of 
females  (Figure  22e)  broadly  and  irregularly 
ovate  with  apex  on  long  axis  directed  an- 
teromesad,  aperture  of  each  broadly  open  mesi- 
ally,  narrowing  laterally,  and  sloping  from  sur- 
face on  mesial  side  under  curved  and  rounded 
superior  border  and  a  rounded  prominence  on 
posterolateral  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
58,  width  at  base  of  lateral  spines  104,  including 
lateral  spines  139.  Largest  female:  length  48, 
width  at  base  of  lateral  spines  84,  including  lat- 
eral spines  108.  Summary  of  selected  measure- 
ments is  given  in  Tables  1  and  2. 

Color. — Live  males  from  Cubatao  River  near 
Santos,  Sao  Paulo,  Brazil:  Carapace  olive,  becom- 
ing indigo  on  edges  of  lateral  spines  and  outer 
anterolateral  teeth  in  some  individuals,  more  uni- 
formly olive  in  others;  teeth  and  spines  on  chelae 
white  tipped;  a  white  patch  in  deepest  part  of  de- 
pression above  third  walking  leg.  Cheliped  with 
upper  surface  of  palm,  dactyl,  part  of  carpus,  and 
spined  edge  of  merus  indigo  to  purple,  and  same 
color  in  splashes  on  inside  of  flngers,  distally  on 
merus  and  laterally  on  carpus.  Flat  outer  dorsal 
surface  of  palm  and  upper  surface  of  merus  reticu- 
late blue  and  olive  (but  many  crabs  predominantly 
olive  on  this  part).  Walking  and  swimming  legs 
predominantly  china  blue  to  azure  blue,  grading 
to  greenish  and  olive  in  darker  parts.  Lower  edge 
of  chelae  grading  from  purple  to  china  blue  or 
azure  individually.  Chelipeds  with  inner  face  of 
palm,  outer  face  of  palm  and  fingers,  lower  face  of 
merus,  as  well  as  meri  of  remaining  legs  and  ven- 
tral surface  of  cephalothorax,  white. 

Described  above  is  a  colorful  male  which  should 
be  called  the  "purple  crab"  if  C  sapidus  is  called 
a  "blue  crab."  Some  individuals  are  duller  and 
some  have  a  reticulate  pinkish-blue  cast  on  the 
upper  surface  of  chelipeds. 

Color  notes  by  Kretz  and  Biicherl  (1940)  and 
Taissoun  (1969)  emphasized  the  distal  intense 
purple  coloration  of  legs  and  a  grayish-blue 
carapace  on  adult  males. 


747 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Variation. — Individual  variation  of  first 
gonopods  outlined  by  Williams  (1966)  can  be 
elaborated  here.  The  first  gonopods  of  males  vary 
somewhat  in  length,  being  either  a  little  longer  or 
shorter  than  as  described  above  (long  in  southern, 
short  in  northern  parts  of  the  range).  Males  from 
Rio  de  Janeiro,  Brazil,  southward  tend  to  have 
first  gonopods  reaching  near  or  beyond  the  suture 
between  thoracic  sternites  V  and  VI,  as  do  some 
specimens  examined  from  St.  Lucia  in  the  Wind- 
ward Islands,  but  some  south  Brazilian  specimens 
have  shorter  first  gonopods.  Males  from  north  of 
Rio  de  Janeiro,  northeastern  South  America,  and 
the  West  Indies  tend  to  have  first  gonopods  reach- 
ing from  near  the  middle  of  thoracic  sternite  VI  to 
the  suture  between  thoracic  sternites  VI  and  VII. 
The  ill  defined  shortening  trend  is  accentuated  in 
Cuban,  Honduran,  and  a  single  lot  of  Floridian 
material,  reaching  extreme  shortness  in  the 
Panamanian  region  of  the  Caribbean,  especially 
in  USNM  lot  43931  in  which  male  gonopods  ex- 
tend only  to  the  suture  between  thoracic  sternites 
VII  and  VIII.  But  in  these  areas,  too,  there  is 
enough  variation  that  groupings  are  hard  to 
define. 

The  lower  margin  of  the  major  chela  is  often 
decurved  opposite  the  molar  complex  of  the  pro- 
podus  and  strongly  developed  proximal  tooth  of 
the  dactyl. 

Distribution. — Bermuda;  southern  Florida  and 
eastern  side  of  Yucatan  Peninsula  to  Estado  de 
Santa  Catarina,  Brazil  (Figure  24). 

Habitat. — Callinectes  danae  is  a  common 
species  in  Brazil  where  it  occurs  from  muddy  es- 
tuaries in  mangroves  and  algae  covered  broken 
shell  bottoms,  to  beaches  and  open  ocean  depths  of 
75  m.  Specific  limits  of  salinity  tolerated  are  not 
well  documented,  but  ranges  indicated  are  from 
fresh  to  full  sea  water,  and  perhaps  to  hypersaline 
lagoons. 

Kretz  and  Biicherl  ( 1940)  gave  no  specific  desig- 
nation to  species  of  Callinectes  studied,  but  they 
gave  (p.  173)  a  fairly  clear  description  of  the  first 
gonopods  of  C.  danae,  and  their  figures,  especially 
2  and  14,  indicate  this  species.  Callinectes  danae  is 
the  most  abundant  member  of  the  genus  along 
beaches  from  Santos  to  Rio  de  Janeiro  where  they 
worked. 

Park  (1969)  found  C.  danae  only  on  or  adjacent 
to  the  ocean  side  of  islands  in  Biscayne  Bay,  usu- 
ally on  wave  beaten  shores.  He  reported  it  absent 
from  the  Florida  Keys. 


Spawning. — The  spawning  season  probably  ex- 
tends year  round.  Museum  collections  studied  in- 
clude ovigerous  females  as  follows:  January, 
Surinam;  February,  Rio  de  Janeiro;  March, 
Puerto  Rico,  Haiti,  Panama;  May,  Haiti,  Estado  de 
Sao  Paulo,  Brazil;  June,  Estado  de  Sao  Paulo, 
Brazil;  July,  Colombia,  Rio  de  Janeiro;  August, 
Estados  de  Rio  de  Janeiro  and  Santa  Catarina, 
Brazil;  November,  Curagao,  St.  Lucia.  Undated 
collections  are  from  Estados  de  Bahia,  Rio  de 
Janeiro,  Sao  Paulo,  and  Santa  Catarina,  Brazil. 
Taissoun  (1969)  reported  an  abundance  of  oviger- 
ous females  from  May  to  July  in  the  Golfo  de 
Venezuela,  implying  an  even  longer  spawning 
season. 

Economic  importance. — Literature  available 
does  not  deal  with  commercial  exploitation  of  this 
species  except  that  incidental  reports  of  purchase 
in  markets  and  capture  on  fishing  vessels  imply 
fairly  general  usage. 

Vendors  along  roads  NW  of  Santos,  Estado  de 
Sao  Paulo,  Brazil,  near  mangrove  swamps  sell  the 
crabs  alive,  displaying  bunches  of  a  dozen  or  so 
each  suspended  on  strings  to  which  the  crabs  cling 
by  the  chelae  when  they  are  out  of  water. 

Remarks. — Closest  structurally  to  C.  arcuatus, 
its  Pacific  counterpart  (shape  of  carapace, 
metagastric  region,  male  first  gonopods,  and  fron- 
tal teeth),  C  danae  also  shows  similarity  to  C. 
marginatus.  The  metagastric  area  is  much  alike 
in  all  three  species.  In  C.  marginatus  the  well 
separated  anterolateral  teeth  trend  forward,  and 
the  portion  of  carapace  anterior  to  the  epibran- 
chial  line  is  coarsely  granulate.  In  both  C.  ar- 
cuatus and  C.  danae,  although  anterior  borders  of 
the  anterolateral  teeth  are  shorter  than  posterior 
borders,  the  teeth  point  outward  rather  than 
sweep  forward.  Callinectes  danae  is  quite 
smoothly  granulate  over  most  of  the  carapace;  C. 
arcuatus  is  much  the  same  but  shows  more  sculp- 
tured relief.  Among  males  of  the  three,  C.  mar- 
ginatus has  much  the  slenderest  abdomen  for  its 
length.  The  telson  of  C.  danae  males  is  relatively 
longer  than  in  C.  arcuatus. 

Width  of  the  sixth  abdominal  segment  in  adult 
female  C.  danae  is  relatively  greater  than  in  adult 
female  C.  ornatus,  a  character  valued  by  Rathbun 
(1930)  but  one  that  requires  practice  to  assess. 
Williams  (1966)  misnumbered  the  sixth  abdomi- 
nal segment  as  the  fifth  in  discussing  this  charac- 
ter. 


748 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Specimens  of  C.  danae  reported  from  Chile  in 
literature  must  be  regarded  as  of  uncertain  origin, 
either  mistakenly  identified  with  this  Atlantic 
species  by  early  naturalists  unfamiliar  with  simi- 
lar Pacific  forms,  or  carried  from  the  Atlantic  to 
Pacific  sides  of  South  America  by  sea  captains  or 
collectors  who  recorded  destination  of  voyages  as 
country  of  origin  rather  than  source  of  collection 
(Garth,  1957).  Locality  data  for  USNM  20270  (1 
3),  and  MNHNP  30.3,  30.2,  30.10,  30.11,  3  [?], 
S31  (dry,  5  <5 ,  1  2 )  listed  as  "Chili,"  and  30.20  (1  5  , 
dry)  as  "Amerique"  [labelled  as  Neptunus 
diacanthus],  col.  Fontaines,  are  erroneous  or  in- 
complete. Corrected  identifications  were  also 
made  by  Rathbun  in  1896. 

A  carapace  and  abdomen  of  an  immature  male 
from  the  Pleistocene  of  Maryland  (Wailes  Bluff: 
Bed  1)  reported  as  Callinectes  ornttus  by  Blake 
(1953)  is  probably  C.  danae.  Shape  of  the  abdomen 
is  nearer  to  C.  danae  or  C.  similis  than  C.  ornatus, 
and  the  metagastric  area  in  both  proportions  and 
granulation  is  most  like  the  average  condition  for 
modern  C.  danae,  next  nearest  to  C  sapidus,  and 
not  like  C.  ornatus. 


PUERTO  RICO 

24421,  Palo  Seco,  Bahia  de  San  Juan,  13  Jan. 
1899,  juv  2  5 ,  1  5  ,  Fish  Hawk.  123004,  Bahia  de 
San  Juan,  29  Mar.  1937, 1  ?,  W.  L.  Schmitt.  73280, 
Boca  de  Cangrejos,  7  mi  E  San  Juan,  31  Mar.  1937, 
1  2  (ov),  W.  L.  Schmitt. 

VIRGIN  ISLANDS 

St.  Croix:  77101,  Rust-op-Twist,  on  sea  coast,  no 
date,  1 S  ,  2  juv,  H.  A.  Beatty .  72833,  St.  Croix,  Salt 
River,  no  date,  8  juv,  H.  A.  Beatty. 

ST.  LUCIA 

22044,  Port  Castries,  29  Nov.  1887,  5$  ,  65, 
Albatross. 

MEXICO 

Quintana  Roo:  123002,  Bahia  del  Espiritu 
Santo,  N  shore,  5  Apr.  1960, 1  S  (parasitized),  E.  L. 
Bousfield. 

HONDURAS 

78099,  Utila  I.,  25  mi  off  coast,  Sept.  1938,  Is, 
Louis  Mouquin. 


Material.— Total.  202  lots,  782 -H  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  (24427,  24428,  24429,  22044,  not  found; 
20115,  22817  =  C.  similis;  60984  =  C.  ornatus;  Is, 
1  9  40591  =  C.  marginatus)  and  MCZ  (4278  not 
found). 

USNM.  86  lots,  310+  specimens,  including  the 
following  not  cited  above: 

UNITED  STATES 

Florida:  77087,  Long  Key,  Tortugas,  5  Aug. 
1930,  1  S  juv,  W.  Bullington.  [?]  Uncatalogued, 
Pompano  Beach,  Sept.  1943,  l5  ,  E.  R.  Tinkham. 

CUBA 

123003,  Bahia  del  a  Habana,  11  May  1937,  2  6  , 
W.  L.  Schmitt.  99862,  Plava  Baracoa,  16  Nov. 
1954,  16  juv,  K.  K.  Caldwell  et  al.  99916,  Playa 
Baracoa,  Fisheries  Lab.,  16  Nov.  1954,  1  2,  H.  H. 
Hobbs,  Jr.  99937,  E  Xanadu,  Hicacos  Pen., 
Matanzas  Prov.,  24-27  Jan.  1957,  1  3  ,  W.  L. 
Schmitt. 

JAMAICA 

42854,  Montego  Bay,  20  July  1910,  IS  juv,  C.  B. 
Wilson.  46246,  Montego  Bay,  12  Nov.  1910,  IS  ,  A. 
E.  Andrews.  61364,  4  Feb.  1928,  2  2  juv,  C.  R. 
Orcutt. 


PANAMA 

59283,  1912,  2  6,22,4  juv.  Meek  and  Hilde- 
brand.  59344,  no  date,  1  2,  Meek  and  Hilde- 
brand.  77089,  Fox  Bay,  Colon,  23  Feb.  1935,  2  5 
juv,  S.  F.  Hildebrand.  89575,  Galeta  Pt.,  Ft. 
Randolph,  C.  Z.,  1949,  2  2,1  juv,  V.  Walters. 

COLOMBIA 

105034,  Golfo  del  Darien,  7°56.8'N,  76°47'W  to 
7°56.5'N,  76°47'W,  8  Feb.  1960,  1  2  juv,  Atlantis. 

VENEZUELA 

Falcon:  101825,  Bahia  de  Amuay,  Peninsula  de 
Paraguana,  May  1957,  1  S  ,  F.  A.  Aldrich. 
Miranda:  89645,  Tacarigua  de  la  Laguna,  1  Mar. 
1949,  1  s  ,  Soc.  Cienc.  Nat.  La  Salle,  Stn.  C-4. 
Sucre:  Gulf  of  Paria,  10°29'N,  62°30'W,  24  Oct. 
1963,  1  S  ,  Oregon  Stn.  4495.  Delta  Amacuro: 
123001,  off  Orinoco  Delta,  09°39'N,  60°49'W, 
26-27  Aug.  1958,  19,  Oregon  Stn.  2211. 

BRAZIL 

40590,  1875-77,  1  2  juv,  Hartt.  Rio  de  Janeiro: 
77086,  Sao  Francisco,  25  Aug.  1925, 1  <5 , 2  2  juv,  W. 
L.  Schmitt.  77107,  Porto  da  Inhauma,  May  1935, 
11  6,  12  2,  Doris  Cochran.  Parana:  77095,  77096, 
Paranagua,  3  Oct.  1925, 46,1  2  juv,  W.  L.  Schmitt. 


749 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


AHF.  3  lots,  3  specimens. 

CURACAO 

Schottegat,  Santa  Anna  Harbor,  23  Apr.  1939, 1 
S,VeleroIII  Stn.  A47-39. 

TRINIDAD 

West  Manzanilla,  10°30'N,  61°02'W,  18  Apr. 
1939, 1  ? ,  VeleroIII  Stn.  A36-39.  Port  of  Spain,  18 
Apr.  1939,  1  S  ,  Velero  III  Stn.  A37-39. 

AMNH.  13  lots,  57  specimens. 

HAITI 

11219,  Bizoton  Reef,  4  Mar.  1927,  19  (ov),  W. 
Beebe  Exped.  11224,  21  May  1927,  2  9  (ov),  W. 
Beebe.  11242,  1927,  1  9  ,  W.  Beebe.  Unreg. 
1949-50,  15  ,  A.  Curtiss. 

SANTO  DOMINGO 

9393,  NW  corner  Bahia  de  Neiba,  Bahia  de 
Barahona,  6  July  1933,  23  juv,  J.  C.  Armstrong. 
9394,  N  half  of  El  Cay,  Bahia  de  Barahona,  7  July 
1933,  16  ,J.  C.  Armstrong. 

PUERTO  RICO 

2681,  Ensenada,  17  June  1915, 1 9,  R.  W.  Miner. 
2695,  Ensenada,  June  1915,  2  9,  Mayer.  2665,  San 
Juan,  Palo  Seco  Pt.,  18  July  1914,  7  <? ,  5  9,  R.  W. 
Miner.  2899,  San  Juan,  17  July  1914,  1  5 ,  R.  W. 
Miner.  2687,  San  Juan,  1  Aug.  1914,  local  boys. 
2680,  Id.  S  Catano  R.  mouth  Cano  de  San  Fer- 
nando, San  Juan,  11  July  1914,  1  5,  1  9,  R.  W. 
Miner  and  J.  T.  N.. 

PANAMA 

11241,  Bahia  de  Colon,  no  date,  46,5  9,  Arc- 
turus  Exped. 

ANSP.  2  lots,  3  specimens. 

UNITED  STATES 

3394,  America,  no  date,  1  <5 , 1  9,  E.  Wilson  and  I. 
Lea    [listed  in  catalogue  as  N.  America]. 

CUBA 

4697,  Cojimar  near  La  Habana,  10  July  1940,  1 
5,  R.  A.  McLean. 

BMNH.  13  lots,  20  specimens. 

BARBADOS 

72.28,  no  date,  2  6  juv,  F.  G.  Beckford. 


WEST  INDIES 
43.7,  no  date,  1  9  (dry)  vi/9. 

TRINIDAD 

1962.12.12.1,  Tapora  Point,  1  6,  D.  W.  Richard- 
son, Stn.  1123.  Unreg.,  San  Fernando,  2  6  ,  N. 
Boutakoff  1962,  Tapora  Point,  9  Feb.  1962,  1  S 
juv,  D.  W.  Richardson,  Stn.  1121/3. 

BRAZIL 

919b,  2  S  (dry)  vi/6/7,  C.  Stewart.  919a,  1  6  (dry) 
vi/7,  C.  Stewart.  Pernambuco:  80.37,  juv.  1  6,  1 
9,  W.  Forbes.  Bahia:  unreg.,  1  $  (dry)  vi/6.  Rio  de 
Janeiro:  1952.3.6.12, 1948, 1 6  ,  P.  Drach.  74.20, 3  9 
(2  ov),  A.  Fry.  50.32,  Rio  de  J.  market,  2  6,  juv  (dry) 
vi/6/7,  Rothesay. 

MCZ.  10  lots,  102  specimens  including  the  fol- 
lowing not  cited  above. 

CUBA 

10886,  Cienfuegos,  29  Mar.- 1  Apr.  1939,  36  ,2  9, 
Harvard-Havana  A ^/an^js  Exped. 

COLOMBIA 

5135,  Cartagena,  no  date,  1  6  juv,  A.  Schott. 

TRINIDAD 

9975,  Otheite,  9  mi  N  La  Brea,  22  Aug.  1937,  1 
6, 19, 2 juv,  E.  Deichmann.  9958,  Caroni Swamp, 8 
Aug.  1937,  16  ,  39  ,  E.  Deichmann. 

BRAZIL 

Rio  de  Janeiro:  5145,  no  date,  61  specimens. 
Thayer  Exped.  5146,  reed.  1  Dec.  1863,  46  ,  G.  N. 
Davis.  Sao  Paulo:  5142,  Santos,  no  date,  4  6,19 
juv,  Coutinho,  Thayer  Exped. 

MNB.  7  lots,  44  specimens. 

BRAZIL 

Pernambuco:  60,  no  date,  24  6  ,  5  9  Rio  de 
Janeiro:  65,  Rio-Guanabara,  2  6  .  Unnumbered, 
Praia  do  Fundao,  Baia  de  Guanabara,  Dec.  1951, 1 
5,  N.  Santos.  51,  Rio-Guanabara,  56  ,  39  .  260, 
Recreio  dos  Bandeirantes-Guanabara,  24  May 
1953, 1  6 ,  N.  Santos.  Sao  Paulo:  54,  Santos,  1 9  (ov). 
Santa  Catarina:  53,  Sao  Francisco  do  Sul,  no  date, 
16  ,  19,  L.  Jualberti. 

MNHNP.  3  lots,  6  specimens. 

BRITISH  HONDURAS 

Belize,  1  6  (dry),  date,  col.  unknown. 


750 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


BRAZIL 

30-21,  1  $  (dry),  date,  col.  unknown.  Santa 
Catarina,  1875,  1  <5 ,  1  2  (ov),  Vignes  1129.  202.64, 
Desterro  [=  Florianopolis],  1  <J  (dry),M.  Miiller. 

ARGENTINA  [?] 

Suitree  [?],  1922,  3  ^  (dry),  from  Museo  de  His- 
toria,  Nat.,  Buenos  Aires.  Incomplete  data  or  er- 
roneous localities:  6.5  ,  1  ?  (dry)  from  "Chile"  and 
"Amerique"  by  M.  Fontaines  and  col.  unknown. 
(No.  30.3,  30.2,  30.10,  30.11,  30  [?],  30.20,  and 
S31). 


SURINAM 

11848,  near  lightship  Suriname  Rivier,  12-13 
Jan.  1953,  19  (ov),  H.  W.  Lijding. 

BRAZIL 

Cat.  a,  no  date,  2  S  (dry).  375,  Bahia,  1909,  5  juv 
S  and  2 ,  J.  A.  Bierens  de  Haan. 

ATLANTIC  OCEAN 

1859,  1 S  juv,  R.  Conradsen. 

SADZ-B.  43  lots,  186+  specimens. 


RMNH.  21  lots,  49+  specimens. 

ST.  MARTIN 

Great  Bay,  7  June  1955, 1  <? ,  P.  W.  Htimmelinck. 
10716,  freshwater  pond,  27  July  1955,  1$  ,  P.  W. 
Hummehnck.  1 1850  and  1112,  freshwater  pond  W 
Philipsburg,  17  Feb.  1957,  2 2,  juv,  L.  B.  Holthuis. 

MARTINIQUE 

3273,  Fort  de  France,  6  Feb.  1939,  1  2,  H.  W.  C. 
Cossee. 

PANAMA 

Canal  Zone,  Bahia  de  Limon,  N  Limon  Point,  5 
July  1966,  6  juv,  Pillsbury  Stn.  322. 

COLOMBIA 

23518,  Golfo  de  Uraba,  08°0.1'N,  76°50.3'W  to 
08°1.2'N,  76°47.7'W,  12  July  1966, 3 <5 ,  2  2  (1  ov),  2 
juv,  Pillsbury  Stn.  357. 

NETHERLANDS  ANTILLES 

Aruba:  15040,  Lagoon  NW  Savaneta,  21  Mar. 
1957,  2  juv,  L.  B.  Holthuis. 

Curasao:  St.  Kruis  Baai,  7  Oct.  1940, 1  carapace, 
P.  W.  Hummelinck.  15038,  within  St.  Martha 
Baai,  near  St.  Nicolaas,  3  Nov.  1957,  1  juv,  L.  B. 
Holthuis.  11852,  Piscadera  Baai,  11  Feb.  1957, 2  S , 
12 ,  L.  B.  Holthuis.  15039,  Piscadera  Baai,  mudflat 
behind  mangroves,  Caraibisch  Mar.  Biol.  Inst.,  24 
Jan.  1957,  12  juv,  L.  B.  Holthuis.  10717,  Caracas 
Baai,  Nov.  1954,  1  2  (ov),  J.  S.  Zaneveld.  11849, 
Waaigat,  Willemstad,  30  Jan.  1957,  3  <? ,  3  2,  L.  B. 
Holthuis.  11851,  South  shore  St.  Joris  Baai  at 
Choloma,  3  Jan.  1957,  3c5  ,  1  2 ,  L.  B.  Holthuis. 

TRINIDAD 

23368,  and  unnumbered,  Diego  Martin  River, 
1965-66,  25  ,  H.  O.  von  Hagen. 


BRAZIL 

Bahia:  2098,  Ilha  de  Itaparica,  July  1959,  1  S  , 
Tagea  Bjornberg.  350,  June  1896,  1  5  ,  1  2,  Bicego. 
3225,  Ilheus,  1919,  45  ,  1  2,  E.  Garbe.  1725,  Ilha 
Madre  de  Deus,  1932,  1  6  ,  Oliviera  Pinto.  Rio  de 
Janeiro:  401,  Sao  Joao  da  Barra,  1911,  2  5  ,' E. 
Garbe.  3239,  Atafona,  12  July  1963,  55  ,  6  2,  N. 
Meneses.  3213,  Atafona,  lagoon,  3  5,  62,  N. 
Meneses.  1730,  S.  J.  Barra,  1963, 15  ,  N.  Meneses. 
3232,  Macae,  24  Oct.  1942,  1  5,  A.  Castro  and  J. 
Feio.  370,  Rio  de  Janeiro,  1898,  l5  ,  Bicego.  3252, 
Ilha  Grande,  17  May  1966, 1 2  juv.  3256,  Angra  dos 
Reis,  27  July  1966,  juv.  3257,  Praia  do  Baia,  Angra 
dos  Reis,  20  May  1966,  1  2 ,  G.  Melo.  3258,  Praia 
Grande,  Angra  dos  Reis,  18  May  1966,  15  ,  G. 
Melo.  1734,  Angra  dos  Reis,  1945, 15,12, 1  juv,  L. 
T.  Filho.  3083,  Ilha  Grande,  14  May  1966,  1  2  , 
Emilia.  3238,  Enseada  das  Estrelas,  Ilha  Grande, 
26  Feb.  1966,  13  5  ,  10  2  (2  ov).  3260  and  3229, 
Enseada  das  Estrelas,  Ilha  Grande,  18  July  1966, 
26  5,24  2  (8ov),  G.  Melo.  3248,  [ofTRiodeJ.?],  11 
Nov.  1956,  1  5  ,  Corvette  Solimoes,  Stn.  99/56. 

Sao  Paulo:  891,  Sao  Sebastiao,  1915,  3  5  ,  4  2 ,  E. 
Garbe.  1724,  Sao  Sebastiao,  no  date,  25  ,  2  2,  P.  E. 
Vanzolini.  1741,  Praia  Grande,  Sao  Sebastiao, 
Feb.  1962,  1  2  ,  H.  Britski.  2108,  Sao  Sebastiao, 
July  1959,  2  5 ,  H.  R.  Costa.  1737,  3253,  Estrada 
Caraquatatoba,  Sao  Sebastiao,  no  date,  15,22,1 
carapace.  3251,  Parol  da  Moela,  Aug.  1965,  12  , 
Inst.  Pesca  Santos.  1662,  Parol  da  Moela,  Mar. 
1964,  4  2(1  ov),  Inst.  Pesca  Santos.  522,  Piassa- 
quera,  Jan.  1914,  large  left  merus  of  chela.  398, 
Piassaquera,  Sept.  1910,  3  5,32.  359,  Piassa- 
quera,  June  1903,  52  (2  ov),  Luederwaldt.  1813, 
Santos,  11  Sept.  1962,  2  5,  6  2,  G.  Melo.  1732, 
Santos,  no  date,  2  2 ,  E.  Rabello.  1735,  Porto  Novo, 
Santos,  Nov.  1947,  2  5,  L.  Damico.  1403,  Itanhaen, 
May  1926, 1 5 ,  R.  Spitz.  1407,  Itanhaen,  May  1927, 
15,12  (ov),  R.  Spitz.  1302,  Itanhaen,  July  1935, 1 


751 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


$,  R.  Spitz.  3236,  Praia  da  Trincheira,  Cananeia, 
27  June  1964,  6  <5,  Cory  and  Isauro. 

Santa  Catarina:  665,  Itaja,  1900,  3  S  ,  Lueder- 
waldt.  3235,  Praia  de  Itapema,  Itapema,  July 
1965,  1<J  ,  Dep.  Zool.  Exped.  3244,  27°15'S, 
48°47'W,  70-75  m,  sand-shell,  21  Aug.  1966,  3  .J ,  2 
2  (1  ov),  M.  Iwai.  Rio  Grande  do  Sul:  3233,  Praia  de 
Torres,  5  Oct.  1964,  2  <? ,  J.  Bertoletti.  3250,  Praia 
na  desembocadure,  Rio  Tramandai,  8  Apr.  1965,  2 
5  juv,  R.  P.  Leal. 

YPM.  1  lot,  2  specimens. 

BRAZIL 

824,  Pernambuco,  1867,  1  5  ,  1  2 ,  C.  F.  Hartt. 

Supplementary  literature  records.-Bermuda 
(Verrill,  1908a);  Florida  (Futch,  1965;  Park, 
1969);  Golfo  de  Venezuela  and  Estr.  de  Mara- 
caibo,  Venezuela  (Taissoun,  1969);  Curasao 
(Nobili,  1897);  Barbados  (Jones,  1968);  Barra  das 
Jangadas  [S  Recife],  and  estuaries,  Pernambuco, 
Brazil  (Coelho,  1966,  1970,  1971);  Ilha  de  Sao 
Sebastiao  and  ocean  beaches,  Estado  de  Sao  Paulo, 
Brazil  (Luederwaldt,  1929;  Lavallard,  1960). 

CALLINECTES  ARCUATUS  ORDWAY 

Figures  8,  ISf,  20g-h,  22f,  24 


Callinectes  arcuatus  Ordway,  1863,  p.  578  [13] 
(type:  3,  USNM  61833,  Cape  San  Lucas 
[Baja  Cahfornia]).-  A.  Milne  Edwards,  1879, 
p.  228  (var.  of  C.  diacanthus) .-  Rathbun, 
1896,  p.  362,  pi.  20;  pi.  23, , fig.  1;  pi.  24,  fig.  8; 
pi.  25,  fig.  7;  pi.  26,  fig.  7;  pi.  27,  fig.  7.-  1898, 
p.  596.-  1910,  p.  537,  577,  pi.  56.-  1930,  p. 
121,  text-figs.  15h,  16h,  17f,  18g,  pi.  52.- 
Young,  1900,  p.  190  (var.  of  C.  diacanthus) .- 
Nobili,  1901,  p.  31.-  Boone,  1929,  p.  564 
text-fig.  3.-  Contreras,  1930,  p.  233,  text-fig 
5.-  Garth,  1948,  p.  35.- 1957,  p.  36.-  1961b,  p 
141.-  Garth  and  Stephenson,  1966,  p.  43,  pi 
5,  fig.  A;  pi.  8,  fig.  A;  pi.  10,  fig.  A;  pi.  12,  fig 
D.-  Buitendijk,  1950,  p.  275.-  Bott,  1955,  p 
56. 

Callinectes  pleuriticus  Ordway,  1863,  p.  578  [14] 
(syntypes:  2  J,  1  2,  MCZ  4701;  <?,  MCZ  987; 
Panama,  A.  Agassiz).-  A.  Milne  Edwards, 
1879,  p.  228  (var.  of  C.  diacanthus).-  Young, 
1900,  p.  190  (var.  of  C.  diacanthus). 

Callinectes  sp.  Smith,  1871,  p.  91.-  Lockington, 
1876,  p.  107  [13]. 


?Neptunus  diacanthus  Brocchi,  1875,  p.  54,  pi.  16, 
fig.  82.-  Cano,  1889,  p.  90,  99, 100, 102,  211.- 
Doflein,  1899,  pi.  186  (part;  the  Ecuador 
specimen). 

Callinectes  nitidus  A.  Milne  Edwards,  1879,  p. 
228,  explan.  pi.  41  (var.  of  C  diacanthus) 
(syntype:  6,  USNM  20269,  Tanesco  [  = 
Tahuesco,  14°01'13"N,  91°07'03"W]  Gua- 
temala, on  the  borders  of  the  Esteros).- 
Young,  1900,  p.  190  (var.  of  C.  diacanthus). 

Callinectes  diacanthus.-  A.  Milne  Edwards,  1879, 
pi.  41  [var.  nitidus]. 

Callinectes  dubia  Kingsley,  1879,  p.  156  (type:  <j, 
MCZ  5178,  Gulf  of  Fonseca,  west  coast  of 
Nicaragua,  J.  A.  McNeil).-  Young,  1900, 
p.  191. 

?Neptunus  (Callinectes)  diacanthus  Ortmann, 
1894,  p.  77  (part;  the  S.  Chile  specimen). 

Callinectes  diacanthus.-  Young,  1900,  p.  186 
(part). 

Description. — Inflated  carapace  (Figure  8)  bear- 
ing four  triangular  frontal  teeth,  submesial  pair 
no  more  than  half  length  of  lateral  pair.  Metagas- 
tric  area  of  adults  with  anterior  width  about  2.5 
times  length,  posterior  width  between  1.3  and  1.5 
times  length.  Anterolateral  margins  arched,  teeth 
exclusive  of  outer  orbital  and  lateral  spine  well 
separated  and  varying  from  convex-sided  with 
subacute  tips  at  orbital  end  of  row  to  sharper  and 
more  spiniform  laterally,  each  with  anterior  mar- 
gin shorter  than  posterior.  Surface  of  carapace 
with  granulation  fairly  uniform,  most  crowded  on 
gastric,  mesobranchial,  and  cardiac  regions,  more 
scattered  near  anterolateral  margins,  and  smooth 
along  frontoorbital,  posterolateral,  and  posterior 
borders.  Epibranchial  line  prominent,  interrupted 
slightly  at  corner  of  mesogastric  area. 

Chelipeds  with  sharply  granulate  ridges  on 
propodus,  basal  portion  of  dactyl,  and  exposed  sur- 
faces of  carpus.  Dactyl  of  major  chela  with  large 
basal  tooth  closing  against  molariform  complex  at 
base  of  propodal  finger,  lower  margin  of  propodal 
finger  often  decurved  near  base  in  adults. 

Male  abdomen  and  telson  reaching  beyond  su- 
ture between  thoracic  sternites  IV  and  V;  telson 
triangular,  longer  than  broad;  sixth  segment  of 
abdomen  with  sides  nearly  straight  distally,  di- 
verging proximally ,  segment  poorly  calcified  prox- 
imally  except  for  triangular  basal  portion  con- 
nected to  distal  half  by  a  narrow  (sometimes  obso- 
lescent) central  indurated  column.  Mature  female 
abdomen  and  telson  reaching  as  far  forward  as  in 


752 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


male,  last  two  segments  nearly  equal  in  length, 
telson  triangular  with  slightly  inflated  sides, 
apices  acute.  First  gonopods  of  male  (Figures  18f, 
20g,  h)  reaching  about  to  abdominal  locking 
tubercles  on  fifth  sternite,  often  partially  overlap- 
ping near  base,  tapering  to  narrowly  flared  tips 
bent  ventrolaterally  and  opening  mesioventrally, 
armed  with  scattered  minute  spinules  sternally 
and  laterally  and  with  a  subterminal  sternome- 
sial  row  of  elongate  slender  spinules.  Gonopores  of 
females  (Figure  22f)  elliptical  with  long  axis  in 
transverse  plane,  sinuous  aperture  of  each  with 
rounded  margins  except  mesial  side  sloping  from 
surface  under  overhanging  anterior  and  inferior 
bulbous  posterolateral  border. 

I? 
Size  of  carapace  in  mm. — Largest  male:  length 

54,  width  at  base  of  lateral  spines  93,  including 
lateral  spines  123.  Largest  female:  length  55, 
width  at  base  of  lateral  spines  96,  including  lat- 
eral spines  114.  Summary  of  selected  measure- 
ments is  given  in  Tables  1  and  2.  Estevez  (1972) 
judged  females  to  attain  sexual  maturity  at  a 
length  of  28-34  mm,  but  smaller  ones  are  known 
(see  Spawning). 

Color. — Male:  "Carapace  dull  olive  gray-green. 
Chelipeds  olive  green  dorsally,  whitish  ventrally, 
washed  with  bluish-violet  and  chelae  tipped  with 
pale  yellow-brown.  Legs  turquoise  washed  with 
olive;  hairs  straw  gold;  swimming  legs  olive  green 
with  suggestion  of  turquoise,  paddles  washed  with 
black;  hairs  straw;  tubercles  at  leg  joints  golden 
orange;  eyes  straw  with  brownish  streaks;  under- 
parts  pure  white"  (Garth,  1961b;  Garth  and 
Stephenson,  1966). 

Female:  Carapace  generally  blue,  central  por- 
tion blue  violet;  anterolateral  portions  deep 
purplish- vinaceous.  Chelipeds  with  base  of  merus 
olive,  inner  portion  of  hands  blue- violet,  remain- 
der purplish  but  varied,  fingers  barred  with  pur- 
ple, propodal  fingers  usually  white  tipped.  Re- 
maining legs  Italian  blue,  hairs  olive,  swimming 
legs  with  articulations  and  margins  narrowly  vio- 
let, paddles  sometimes  turquoise.  Abdomen  violet, 
joints  and  sternum  white  (Garth,  1961b). 

Variations. — Lateral  spines  in  C.  arcuatus  vary 
considerably,  some  being  relatively  no  longer 
than  in  C.  exasperatus.  Inner  orbital  fissures  are 
open  in  some  individuals.  Chelipeds  often  have 
smooth  ridges  rather  than  granulate  ones,  and  the 
propodal  molariform  complex  of  the  major  chela  is 


often  worn.  The  proximal  portion  of  abdominal 
segment  6  may  be  almost  completely  uncalcified 
in  males. 

Variations  in  C.  arcuatus  are  often  those  as- 
sociated with  proportional  growth  changes.  These 
are  pronounced  enough  to  make  identification 
difficult,  especially  among  juveniles.  Callinectes 
pleuriticus  and  C.  dubia  were  based  on  immature 
C.  arcuatus.  The  mesogastric  area  grows  rela- 
tively broader  with  the  maturing  carapace.  Adult 
females  have  a  more  arched  carapace  than  the 
immature,  and  seemingly  more  females  than 
males  have  a  hairy  growth  under  the  anterolat- 
eral border.  First  gonopods  of  juvenile  males  are 
short;  those  of  adult  males  range  in  length  from 
short,  with  tips  terminating  at  level  of  the  suture 
between  thoracic  sternites  VI  and  VII,  to  long, 
terminating  near  the  suture  between  thoracic 
sternites  IV  and  V.  The  tips  of  these  appendages 
usually  curve  ventrolaterally  but  may  curve  ven- 
trally, mesially,  or  asymmetrically,  and  the  slen- 
der distal  portions  occasionally  are  sinuous  rather 
than  straight.  Subterminal  dorsal  spinules  may 
be  worn  off  of  first  gonopods. 

An  ovigerous  female  from  Panama  (AHF,  Stn. 
111-33)  has  seven  anterolateral  teeth  on  the  left 
side. 

Distribution. — Los  Angeles  Harbor,  Calif.,  to 
Mollenda,  Peru;  Galapagos  Islands  (Figure  24). 
The  record  from  southern  Peru  is  an  immature 
male.  A  record  from  the  Galapagos  Islands  in 
April  1941,  is  a  soft  mature  male,  and  two  other 
records  in  February  1964,  are  an  immature  male 
and  female. 

Habitat. — Garth  and  Stephenson  (1966)  sum- 
marized habitat  as  sand  or  mud  bottom,  oyster 
beds,  lagoons,  estuaries,  channels  among  man- 
groves, or  river  mouths.  Recorded  depth  range  is 
shoreline  to  27.5  m,  with  many  occurrences  lim- 
ited to  shallows  less  than  1  or  2  m  along  shore, 
but  Estevez  (1972)  reported  common  occurrence  in 
Colombia  on  sand  or  sand-mud  bottom,  preferen- 
tially between  10  and  20  m  in  salinities  22%o  or 
higher.  Estevez  found  the  diet  included  mainly 
crustaceans,  bivalves,  fishes,  inorganic  remains, 
gastropods,  and  cephalopods  in  order  of  prece- 
dence (330  stomachs  examined). 

Spawning. — The  spawning  season  extends  year 
round.  Museum  records  include  ovigerous  females 
as  follows:  January,  Costa  Rica;  March,  Oaxaca, 


753 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Mexico,  Panama;  April,  between  San  Felipe  and 
mouth  of  Colorado  River,  Mexico,  Peru;  May  and 
June,  Sinaloa,  Mexico;  July,  Panama;  August, 
Jalisco,  Mexico;  September,  Guerrero,  Mexico; 
November,  Sonora  and  Jalisco,  Mexico;  De- 
cember, Sonora,  Mexico.  A  female  from  near  the 
mouth  of  the  Colorado  River  (AHF,  Golfo  de 
California,  6-9  April  1947,  Stn.  H47-53)  is  the 
smallest  egg  bearer  seen  in  this  species,  the 
carapace  having  a  length  of  23,  and  width  at  base 
of  lateral  spines  39,  or  including  lateral  spines  of 
52  mm.  Month  of  collection  is  unknown  for  an 
ovigerous  female  from  Anaheim  Slough,  Calif.,  in 
1928.  Estevez  (1972)  considered  ovigerous  females 
rare. 

Remarks. — The  cognate  species C.  arcuatus  and 
C.  danae  are  so  similar  that  differentiation  is 
difficult  except  on  grounds  of  male  first  gonopod 
morphology  or  geographic  distribution.  In  gen- 
eral, C.  arcuatus  is  the  more  robust  species,  hav- 
ing a  tumid  carapace  emphasized  in  the  arched 
anterolateral  border  and  inflated  branchial  re- 
gions. Anterolateral  teeth  stand  up  from  the  sur- 
face, as  if  each  is  reinforced  with  an  axial  rib 
extending  from  the  borders  of  the  anterolateral 
area,  but  almost  never  are  shoulders  developed  on 
their  margins,  whereas  in  C.  danae  there  is  less 
prominent  central  reinforcement  in  the  teeth  but 
a  tendency  to  development  of  shoulders.  Such  dif- 
ferences are  inconsistent. 

Distribution  of  C.  arcuatus  along  the  Pacific 
side  of  Baja  California  parallels,  but  is  more  ex- 
tensive than,  that  of  C.  bellicosus.  In  this  region, 
marine  climate  that  is  transitional  between  trop- 
ical and  dominant  temperate  extends  from  Punta 
Entrada  (Bahia  Magdalena)  to  Point  Conception 
north  of  Santa  Barbara  Channel  (Garth,  1961a). 
Here  temperate  and  tropical  faunas  mingle,  but 
tropical  elements  thin  out  in  the  north  surviving 
only  in  protected  areas  or  in  favorable  years. 
Records  of  C.  arcuatus  along  this  outer  coast  are 
less  numerous  than  in  the  Golfo  de  California  and 
southward,  but  occurrence  of  an  ovigerous  female 
at  Anaheim  Slough,  Calif.,  indicates  enough 
tolerance  of  temperate  conditions  to  develop 
breeding  populations,  at  least  in  favorable  years. 
Callinectes  arcuatus  shows  adaptation  to  a 
broader  spectrum  of  marine  climates  than  C. 
bellicosus  in  its  much  more  extensive  distribu- 
tion from  temperate  southern  California,  through 
the  essentially  insular  oceanic  province  at  the  tip 
of  Baja  California  and  tropical  eastern  Pacific,  to 


temperate  fringes  of  the  Humboldt  Current  along 
Peru. 

Callinectes  arcuatus  is  questionably  listed  from 
the  Caribbean  side  of  Colombia  at  Turbo  on  the 
Golfo  de  Uraba  in  MCZ  lot  9666.  I  agree  with  the 
cataloger  that  this  must  be  an  erroneous  locality 
for  the  collection. 

A  collection  of  C.  arcuatus  from  Estero  de  los 
Algodones,  SE  of  Guaymas,  Sonora,  Mexico 
(USNM  15431)  contains  a  large  female  which  has 
a  broken  male  first  gonopod  inserted  in  the  left 
genital  opening.  The  gonopod  fragment  is  14  mm 
long,  completely  inserted,  and  is  that  of  a  male  C. 
arcuatus. 

Brocchi's  (1875)  discussion  of  male  gonopods  in 
Callinectes  is  a  puzzle  because  there  is  no  sure  way 
to  know  which  species  he  studied;  neither  his  de- 
scriptions nor  figures  are  accurate  enough  to  allow 
certainty  in  forming  synonymy.  This  would  be  of 
no  real  concern  were  it  not  for  the  relationship  of 
his  work  to  that  of  Milne  Edwards  (1879).  Brocchi 
studied  material  obtained  from  Milne  Edwards, 
and  both  considered  gonopod  structure  of  males  to 
be  among  the  diagnostic  characters  for  species  or 
"varieties"  of  Callinectes.  Reasonable  assessment 
of  Brocchi's  material  rests  on  the  geographic 
source  of  material  then  available,  his  discussion, 
and  its  probable  influence  on  Milne  Edwards's 
thinking.  The  evidence  is  present  in  both  papers. 
Summarizing:  species  with  short  first  gonopods 
came  from  the  Antilles,  coast  of  America,  and 
Chile;  those  with  long  ones  came  from  Cayenne 
and  Guatemala.  Chile  must  be  regarded  as  an 
erroneous  locality  for  species  in  this  genus  (Garth, 
1957). 

Milne  Edwards  (1879)  described  C  cayennensis 
(=  C.  bocourti)  with  long  first  gonopods  from 
Cayenne  and  remarked  on  likeness  of  the  male 
gonopods  to  those  of  C.  hastatus.  Brocchi  (1875) 
may  have  worked  with  C  bocourti  from  Cayenne 
but  more  likely  with  C.  hastatus  (=  C  sapidus) 
itself,  for  he  remarked  on  its  broad,  strong  frontal 
teeth  and  designated  it  as  the  hastata  of  Ordway 
(plate  16,  Figure  81). 

By  designation  "very  long,"  Brocchi  indicated 
that  his  illustration  of  male  first  gonopods  from 
Guatemalan  material  (plate  16,  Figure  82)  must 
refer  to  C  arcuatus,  a  species  regarded  as  having 
nearly  straight  gonopods  (Milne  Edwards,  1879). 

Species  with  short  male  first  gonopods  from 
provenances  listed  by  Brocchi  (1875)  and  de- 
scribed in  more  detail  by  Milne  Edwards  (1879) 
were:  Antilles,  C.  ornatus  and  larvatus   (=  C. 


754 


WILLIAMS:  CRABS  OF  THE  GENUS  CALUNECTES 


marginatus);  coast  of  America,  the  same  species; 
Chile,  species  undetermined  by  either  Brocchi  or 
Milne  Edwards  because  of  fragmentary  informa- 
tion. Brocchi's  illustration  of  a  strongly  curved 
gonopod  (plate  16,  Figure  76)  seems  closest  to 
C.  marginatus.  Figure  78  depicting  a  short  and 
straight  gonopod  seems  closest  to  C.  ornatus  as 
does  the  undesignated  Figure  79.  Figure  77, 
though  clearly  called  "short,"  resembles  that  of 
C  bellicosus  in  sinuosity.  Milne  Edwards  (1879), 
making  no  mention  of  "long"  or  "short"  gonopods 
for  this  species,  was  impressed  with  the  double 
curvature,  but  listed  C.  bellicosus  only  from  Cabo 
de  San  Lucas,  Baja  California.  We  must  regard 
Figure  77  as  possibly  an  illustration  of  C.  mar- 
ginatus because  it  seems  closest  to  that  species 
from  geographic  origins  listed. 

Following  is  an  outline  summary  of  first 
gonopod  characters  as  understood  by  Milne  Ed- 
wards (1879). 

ATLANTIC 

hastatus  [=  sapidus]:  long,  reaching  to  near  end  of 

abdomen;  Nantucket  to  Mobile,  perhaps  on 

coast  of  Brazil, 
ornatus."  short  and  straight;  Charleston-Cumana, 

including  Tortugas,  Bahamas,  also  Santa 

Catarina,  Brazil. 
larvatus  [=  marginatus]:  very  short  and  curved; 

coast  of  Florida,  Key  West,  Tortugas, 

Bahamas,  Haiti,  Veracruz,  Mexico. 
tumidus  [=  exasperatus]:  long  but  moderate  and 

distinctly  hooked,  approaches  Aasta^j/s;  Key 

West,  Fla.,  Haiti. 
bocourti:  long,  to  end  of  abdomen  as  in  hastatus; 

Honduras. 
cayennensis  [=  bocourti]:  long  and  reach  end  of 

abdomen  as  in  hastatus;  Guyana. 
danae:    long   and   straight;    Rio   de   Janeiro 

(diacanthus) . 

PACIFIC 

toxotes:  very  long,  end  of  abdomen;  Cabo  de  San 
Lucas. 

robustus  [=  toxotes]:  very  long  as  above;  Colombia. 

bellicosus:  "the  verges  reach  almost  the  middle  of 
the  penultimate  article,  they  are  incurved 
strongly  and  outward  near  the  extremity, 
then  inward  similarly  and  finally  the  point 
is  directed  externally"  [sinuous].  Golfo  de 
California;  Cabo  de  San  Lucas. 

arcuatus:  long  and  straight,  reserahXes diacanthus 


of  Rio  de  Janeiro;  but  more  slender;  Cabo  de 

San  Lucas. 
pleuriticus   [=  arcuatus]:  long  and  straight; 

Panama. 
nitidus  [=  arcuatus]:  slender,  straight  and  long; 

Guatemala,  Tanesco. 

In  addition,  those  from  Chile  resemble  the 
Guatemalan  forms. 

Material. — Total:  199  lots,  655  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  [correction,  USNM  62050  =  62051]  and 
MCZ;  Garth  and  Stephenson  (1966)  from  AHF 
and  USNM. 

USNM.  76  lots,  316  specimens,  including  the 
following  not  cited  above: 

MEXICO 

Baja  California:  64119,  Isla  San  Lucas,  15  Jan. 
1930, 1  d  juv,  M.  Valerio.  Sonora:  111769,  Golfo  de 
Calif.?  no  date,  1  6,  T.  H.  Bullock,  Stn.  W53-289. 

Nayarit:  123089,  Estero  de  San  Bias,  7.5  mi  by 
road  NNE  San  Bias,  14  Feb.  1955,  juv  6  S,  2  9, 
Miller  and  Greenbank,  M55-18.  123090,  slough  at 
N  end  Laguna  de  Mexaltitan,  28  Mar.  1955,  1  S 
juv.  Miller  and  Greenbank,  M55-74. 

GUATEMALA 

20269,  Tanesco  [=  Tahuesco,  14°01'13"N, 
91°07'33"W]  on  the  borders  of  the  Esteros,  1  <? 
(dry).  123088,  Iztapa,  5  Apr.  1950,  1  S. 

NICARAGUA 
77085,  El  Realejo,  no  date,  1  S  juv,  Kingsley. 

COSTA  RICA 

61034,  Puntarenas,  Mar.  1927,  1  S  (dry),  M. 
Valerio.  76137,  San  Lucas  [—  Isla  San  Lucas],  15 
Feb.  1931,  2  juv,  M.  Valerio.  76685,  Golfo  Dulce,  2 
Feb.  1933,  1  9  (dry),  M.  Valerio. 

PANAMA 

77090,  Balboa,  C.Z.,  4  Feb.  1937, 1  <?  juv,  1  9,  S . 
F.  Hildebrand.  77094,  Drydock,  Balboa,  C.Z.,  8 
Feb.  1937, 1  $,  S.  F.  Hildebrand.  76917,  Miraflores 
Locks,  C.  Z.,  no  date,  2  juv,  S.  F.  Hildebrand. 
77081,  Farfan  Beach,  C.  Z.,  23  Feb.  1937,  1  6  juv, 
S.  F.  Hildebrand.  77082,  Venado  Beach,  26  Feb. 
1937,  1  S  juv,  S.  F.  Hildebrand.  77083,  Puerto 
Pilon,  2  Mar.  1937,  1  9  juv,  S.  F.  Hildebrand. 
77093,  Taboga  I.,  8  Feb.  1937,  1  juv,  H.  C.  Clark. 
82134,  Miraflores  Locks  (Lower  Chamber),  4  juv, 


755 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


S.  F.  Hildebrand.  82135,  Dry  Dock,  Balboa,  C.Z., 
18  Mar.  1937,  1  6  juv,  S.  F.  Hildebrand.  82136, 
Miraflores  Locks  (Lower  Chamber),  C.Z.,  26  and  29 
Mar.  1937,  1  juv,  S.  F.  Hildebrand.  111779,  Rio 
Anton,  Golfo  de  Panama,  2  Apr.  1957,  2  <?,  W.  L. 
Klawe.  119846,  Punta  Paitilla,  24  Feb.  1964,  1  S, 
R.  Dutary.  123091,  Bahia  Pinas,  near  mouth  of 
estuary  at  Santa  Dorotea,  07°34.5'N,  78°11.5'W, 
9  Sept.  1961,  7  juv,  Argosy  Stn.  10.  123092, 
Bahia  Pinas,  shallow  end  along  crescent  beach  to 
E  end  at  Santa  Dorotea,  9  Sept.  1961,  3  juv, 
Argosy  Stn.  9. 

COLOMBIA 

68552,  Tumaco,  no  date,  2  S. 

ECUADOR 

123093,  Esmeraldas,  in  harbor  and  fish  market, 
0°57.5'N,  79°42.5'W,  25  Sept.  1961,  1  6,  Argosy 
Stn.  41.  70990,  Salada,  Guayaquil,  1  and  2  Oct. 
1926,  1  <? ,  W.  L.  Schmitt.  97899,  Manta,  Prov. 
Manabi,  0°56'30"S,  80°44'W,  Aug.  1949, 1  S  (dry), 
T.  Mena.  97930,  supra  cit.,  1  9  (dry). 

PERU 

76574,  Paita,  8  Oct.  1926,  1  <?,  W.  L.  Schmitt. 
Uncatalogued,  Negritos,  Apr.  1941,  1  (J,  1  9,  H.  E. 
and  D.  L.  Frizzell  (160/433). 

GALAPAGOS  ISLANDS 

111676,  Conway  Bay,  15  Apr.  1941,  1  6,  W.  L. 
Schmitt. 

AHF.  66  lots,  221  specimens,  including  the  fol- 
lowing not  cited  above: 

MEXICO 

Sonora:  Guaymas,  tidal  flats  N  of  Motel  Tular, 
22  June  1966,  2  <?,  1  9,  R.  Reimer  and  A.  Alvarez, 
Stn.  2a. 

Sinaloa:  Topolobampo,  25  June  1966, 1  S,l9,  R. 
Reimer  and  A.  Alvarez,  Stn.  4g. 

Jalisco:  Bahia  Chamela,  North  Lagoon,  17  Nov. 
1937,  1  c5,  3  9  (2  ov),Zaca  No.  37,142. 

Guerrero:  Acapulco  Beach,  26-28  Nov.  1937, 1  9, 
Zaca-NYZS  37,277. 

EL  SALVADOR 

Golfo  de  Fonseca,  La  Union,  27  Dec.  1937,  1  9, 
Zaca  Stn.  199,  D-8  to  D-16,  5-6  fm. 

HONDURAS 

Golfo  de  Fonseca,  Cutuco  and  Potosi  Light?  20 
Dec.  1937,  4  <^,  6  9,  3  juv,  Zaca  No.  37,666. 


NICARAGUA 

Corinto,  29  Dec.  1937,  1  juv, Zaca  Stn.  200,  D-7, 
3.6  m.  Corinto,  Castenones  Lagoon  and  mid- 
harbor,  6  Jan.  1938,  4  <?,  4  9,  Zaca  NYZS  3814. 
Corinto,  7  Jan.  1938,  juv  1  cj ,  1  9 ,  Zaca  200,  D-20 
to  D-26,  2.7-11.9  m. 

COSTA  RICA 

Port  Parker  [=  Golfo  Elena],  13  Jan.  1938, 1  cJ,  3 
9  ( 1  ov),  4  juv, Zaca  No.  3859.  Golfo  Elena,  22  Jan. 
1938,  2  6  juv,  Zaca  Stn.  203,  D-9,  2.7-7.3  m. 
Puerto  Culebra,  26  Jan.  1938,  8  5,39,2  juv,  Zaca 
NYZS  38,115.  Mata  de  Limon,  30  July  1964,  2  S , 
J.  Mohr.  Piedra  Blanca  [=  Bahia  Carrillo], 
6  Feb.  1938,  2^,29,  Zaca  No.  38,195.  Golfo  de 
Nicoya,  Isla  Cedro,  12  Feb.  1938,  1  S,Zaca  NYZS 
38,302.  Golfo  Dulce,  Golfito,  5  Mar.  1938,  1  S  , 
19,  4  juv,  Zaca  No.  38,472.  Golfo  Dulce,  Golfito, 
9  Mar.  1938,  1  9  juv,  Zaca  218,  NYZS  38,596. 
Supra  cit.,  juv  1<5  ,  5  9,  Zaca  218,  D-4,  D-5,  D-8, 
11  m. 

PANAMA 

Bella  Vista,  Panama  City,  1944,  5  <?,  2  juv, 
Zaca.  Balboa,  C.Z.  1940,  2  cJ,  1  9,  5  juv,  Zaca. 
Balboa,  C.Z.,  Apr.  1938,  3  <?,  2  9,  8  juv  Bahia 
Honda,  16  Mar.  1938,  3  6  juv,  Zaca  No.  38,701. 
Bahia  Honda,  19  Mar.  1938,  1  d",  Zaca  NYZS 
38,734. 

ECUADOR 

Puerto  Bolivar,  Apr.  1944,  1  cf  juv,  Zaca. 

AMNH.  9  lots,  11  specimens. 

MEXICO 

Baja  California:  5527,  San  Jose  del  Cabo,  21 
Mar.  1911,  1  6,  Albatross.  Sinaloa:  7228,  off"  To- 
polobampo, 17  Nov.  1935, 1  9,  Templeton-Crocker 
Exped. 

PANAMA 

5405,  5408,  5419,  5434,  Punta  Paitilla,  26  Mar. 
1926,  2  <?,  1  9,  2  juv,  W.  G.  Van  Name.  5406, 
between  Punta  Paitilla  and  Panama  Viejo,  29 
Mar.  1926, 1  S,  W.  G.  Van  Name.  10568,  Santelmo 
Bay  [=  Ensenada  Santelmo],  Isla  del  Rey, 
Archipielago  de  las  Perlas,  15  Feb.  1941,  1  S, 
Askoy  Exped. 

PERU 

Uncatalogued,  Mollendo,  3  Dec.  1934,  1  c^  juv. 

BMNH.  4  lots,  8  specimens. 


756 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


COSTA  RICA 

1892.6.7.14,  Rio  Punta  Mala,  1  S,  H.  Pittier. 

PANAMA 

67.77,  2  S,  J.  C.  Dow. 

COLOMBIA 

1925.4.27.8/9,  Tumaco,  1  <?,  1  2  juv,  R.  H. 
Thomas. 

PERU 

1890.10.7.103/105,  Santa  Lucia,  2  <?,  1  2,  Stalz- 
man  collection,  Warsaw  Mus. 

MCZ.  14  lots,  36  specimens,  including  the  fol- 
lowing not  cited  above: 

MEXICO 

Baja  California:  5181,  Cabo  de  San  Lucas,  no 
date,  1  S,  J.  Xantus.  Guerrero:  5180,  Acapulco,  no 
date,  1  (?,  1  2,  Hassler  Exped. 

NICARAGUA 

5178,  Golfo  de  Fonseca,  May  1869,  1  $,  J.  A. 
McNiel. 

HONDURAS 

5179,  Golfo  de  Fonseca,  reed.  Nov.  1885,  5  juv,  J. 
A.  McNiel. 

PANAMA 

987, 15  Mar.  1869, 1  S,  A.  Agassiz.  4701, 15  Mar. 
1860,  2  J,  1  2,  A.  Agassiz.  4702,  July  1872,  1  6, 
Hassler  Exped.  4703,  reed.  13  Feb.  1861,  2  S,  J. 
Rowell.  5175,  Mar.  1860, 3  c?,  2  2,  A.  Agassiz.  5176, 
reed.  10  June  1862,  2  c5, 1  2,  C.  F.  Davis.  5177, 4  <5, 3 
2,  Hassler  Exped.  8376,  12  Mar.  1891,  1  2  juv, 
Albatross  Exped.  9669,  no  date,  3  S,  Maack. 

COLOMBIA 

9666,  Turbo?,  no  date,  1  S,  Maack,  Darien 
Exped.  [Error?]. 

MNB.  1  lot,  4  specimens. 

PANAMA 

Bahia  Honda,  10  Mar.  1933,  2  cJ,  2  2,  Vetera  HI, 
Stn.  111-33. 

MNHNP.  1  lot,  6  specimens. 

GUATEMALA 

445a,  445d,  Tanesco  [=  Tahuesco,  14°01'13"N, 
91°07'33"W],  3  ^,  3  2  (1  ov)  (dry),  Exp.  du Mexique. 


RMNH.  18  lots,  27  specimens. 

MEXICO 

Sonora:  7535,  Guaymas,  20  May,  1945,  1  S,  M. 
Cardenas.  7529,  Guaymas,  25  July  1946,  1  2  juv, 
M.  Cardenas.  7536,  Yavaros,  Bahia  de  Sta. 
Barbara,  29  Nov.  1944,  1  c^,  1  2  (ov),  M.  Cardenas. 

7532,  coast  of,  23  Nov.  and  1  Dec.  1944, 1^,12  (ov), 
M.  Cardenas.  Canjeme  [?],  22  Nov.  1944,  1  2(ov), 
M.  Cardenas. 

Sinaloa:  7528,  Ahome,  1  June  1945,  1  2,  M. 
Cardenas.  7537,  Topolobampo,  21  June  1945,  1  2 
(ov),  M.  Cardenas.  7531,  Macapule  [Bahia  de 
Navachiste],  22-23  Apr.  1948,  1  S,  M.  Cardenas. 

7533,  Macapule,  7  May  1946,  2  2,  M.  Cardenas. 
Colima:  7534,  Manzanillo,  13  Jan.  1943, 1  <?,  1  2, 

F.  Bonet. 

EL  SALVADOR 

9839,  W  of  Bocana  Rio  Lempa  at  Isla  Tasajera, 
San  Vicente,  19  Mar.  1953,  1  <S,  2  juv,  M.  Boese- 
man.  9840,  coast  at  El  Cuco,  San  Miguel,  19  Apr. 
1953,  2  juv,  M.  Boeseman. 

PANAMA 

23516,  Panama  Canal,  C.Z.,  8°59.5'N, 
79°30.5'W,  Strand,  Laagwater,  30  Apr.  1967,  1  3, 
Pillshury  Stn.  482.  23517,  Golfo  de  Panama, 
8°14.3'N,  78°25.2'W-8°14.3'N,  78°25.5'W,  7  May 
1967,  Pillsbury  Stn.  547. 

ECUADOR 

1  S,  Frank,  Cat-a. 

PERU 

23402,  Puerto  Pizarro,  dept.  Tumbes,  Apr.  1966, 
1  2  (ov),  1  juv,  H.  O.  van  Hagen.  23433,  Paracas 
bight  S  of  Pisco,  13  Apr.  1966,  2  S,  H.  O.  van 
Hagen.  2699, 1  S  from  Museo  de  Hist.  Nat.,  Lima. 

Supplementary  literature  records. — Bahia  de 
Santa  Elena,  Ecuador  (Nobili,  1901);  a  resume  of 
records  in  Peru  (Solar,  Blancas,  and  Mayta,  1970); 
along  Pacific  coast  of  Colombia  (Estevez,  1972). 

CALLINECTES  EXASPERATUS 
(GERSTAECKER) 

Figures  9,  18g,  20i,  22g,  26 

Lupea  exasperata  Gerstaecker,  1856,  p.  129  (type: 
6,  Berlin  Mus.  2104  [dry],  Puerto  Cabello, 
Venezuela,  Appun ). 

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FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Callinectes  tumidus  Ordway,  1863,  p.  574  [9]  (syn- 
types:  2  S,  MCZ  5159,  Key  West,  Fla.,  J.  E. 
Mills;  1  mature  9,  MCZ  5162,  Haiti,  A. 
Hilchenbach).-  A.  Milne  Edwards,  1879, 
p.  226  (var.  of  C.  diacanthus).-  Rath- 
bun,  1896,  p.  359,  pi.  18;  pi.  24,  fig.  6;  pi.  25, 
fig.  5;  pi.  26,  fig.  5;  pi.  27,  fig.  6.-  Rankin, 
1898,  p.  232.-  Young,  1900,  p.  189  (var.  of  C. 
diacanthus). 

ILupa  (Neptunus)  diacantha.-  von  Martens,  1872, 
p.  92  (part,  the  Puerto  Cabello,  Venezuela, 
specimens). 

Neptunus  (Callinectes)  diacanthus.-  Ortmann, 
1894,  p.  77  (part,  specimen  n,  Haiti). 

Callinectes  exasperatus .-  Rathbun,  1897,  p.  150.- 
1901,  p.  49.-  1930,  p.  130,  text-figs.  15f,  16f, 
17e,  18e,  pi.  56.-  1933,  p.  49.-  Contreras, 
1930,  p.  236,  fig.  7.-  Chace,  1940,  p.  33.- 
1956,  p.  154,  unnumbered  fig.-  Chace  and 
Hobbs,  1969,  p.  131,  fig.  37c.-  Taissoun, 
1969,  p.  81,  fig.  31A-D,  photo  11.- 1973,  p.  37, 
figs.  4C,  5C,  photo  6. 

Callinectes  diacanthus.-  Young,  1900,  p.  186 
(part). 

Description  .—Ca.va.p3iCe  (Figure  9)  bearing  four 
well  developed  frontal  teeth,  submesial  pair  nar- 
rower and  slightly  shorter  than  lateral  pair. 
Metagastric  area  with  posterior  width  1.2-1.3 
times  length,  anterior  width  2.3-2.5  times  length. 
Anterolateral  margins  strongly  arched  with  an- 
terolateral teeth  exclusive  of  outer  orbital  and 
lateral  spine  usually  but  not  always  curved  for- 
ward; teeth  progressively  broader  laterally  with 
fifth  tooth  often  largest.  Lateral  spine  stout,  usu- 
ally less  than  twice  length  of  preceding  tooth.  Sur- 
face of  carapace  conspicuously  granulate  with 
densest  concentrations  on  central  eminences, 
coarsest  and  most  widely  spaced  granules  in  front 
of  epibranchial  line  separated  by  smooth  surfaces. 
Central  sulci  on  carapace  definite  but  not  deep; 
epibranchial  line  rather  flatly  arched,  slightly 
sinuous. 

Chelipeds  robust,  ridges  and  crests  of  all  articles 
coarsely  granulate;  fingers  of  major  chela  strong 
but  not  markedly  gaping. 

Male  abdomen  and  telson  reaching  along  pos- 
terior quarter  of  thoracic  sternite  IV;  telson  lan- 
ceolate with  sinuous  inflated  sides,  length  1.5 
times  basal  width;  basal  portion  of  fused  segments 
3-4-5  truncate  laterally.  Mature  female  abdomen 
and  telson  reaching  about  same  level  as  in  male; 
telson  triangular  with  inflated  sides,  length  1.2 


times  basal  width;  fifth  segment  longer  than  sixth. 
First  gonopods  of  male  (Figures  18g,  20i)  reaching 
slightly  beyond  suture  between  thoracic  sternites 
VI  and  VII,  sinuously  curved,  overlapping  in  prox- 
imal half  along  midline  then  diverging  distally, 
twisting  on  axis  near  tip  and  bending  abruptly 
mesad;  armed  distally  with  scattered  minute 
spinules,  tip  slightly  broadened  and  opening  pos- 
teromesially.  Gonopores  of  female  (Figure  22g) 
broadly  and  somewhat  asymmetrically  ovate  in 
outline  with  orientation  of  long  axis  mainly  in 
frontal  plane  but  with  apex  directed  anteromesad; 
aperture  of  each  laterally  elongate  and  sinuous, 
sloping  from  broadest  area  at  surface  on  mesial 
side  to  narrower  and  deeper  portion  under 
rounded  overhanging  anterior  border  with  promi- 
nent central  projection  and  posterior  border  with 
elongate  posterolateral  eminence. 

Size  of  carapace  in  mm. — Largest  male:  length 
67,  width  at  base  of  lateral  spines  114,  including 
lateral  spines  129.  Largest  female:  length  59, 
width  at  base  of  lateral  spines  101,  including  lat- 
eral spines  124.  Summary  of  selected  measure- 
ments is  given  in  Tables  1  and  2. 

Color. — Carapace  of  adult  male  purplish  red, 
more  accented  on  proto-,  meso-,  and  metagastric 
areas  and  at  base  of  lateral  spines  and  anterolat- 
eral teeth;  branchial  region  and  anterolateral 
teeth  obscure  maroon.  Dorsal  surface  of  all  legs 
purplish  red  with  intense  orange  red  on  articula- 
tions; inferior  portion  of  merus,  carpus,  and 
fingers  of  chelipeds  intense  violet;  internal  and 
external  portion  of  chelae  as  well  as  entire  ventral 
portion  of  animal  white  with  tints  of  soft  purple 
(Taissoun,  1969). 

Variation. — There  is  notable  variation  in  an- 
terolateral tooth  pattern;  the  fifth,  sometimes  de- 
scribed as  largest  (Rathbun,  1930)  may  be  ex- 
ceeded by  the  fourth,  sixth,  or  a  combination  of 
both,  or  there  may  be  asymmetrical  size  and  tooth 
number  differences. 

Distribution. — Bermuda;  Veracruz,  Mexico; 
southern  Florida  to  Estado  de  Santa  Catarina, 
Brazil  (Figure  26).  Reason  for  lack  of  collections 
from  the  Guianas  and  northern  Brazil  is  un- 
known. 

Habitat. — This  species  lives  primarily  in  shoal 
marine,  estuarine,  and  perhaps  fresh  water,  espe- 


758 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


cially  in  association  with  mangroves  and  around 
river  mouths  from  water's  edge  to  recorded  depths 
of  about  7.5  m  (Rankin,  1900;  Coelho,  1967b,  1970; 
Chace  and  Hobbs,  1969;  Taissoun,  1969). 

Spawning. — Few  dated  collections  contain 
ovigerous  females:  March,  Puerto  Rico  and 
Guadeloupe;  April,  Barbuda  and  Panama;  May, 
Jamaica;  June,  West  Indies;  August,  Estado  de 
Santa  Catarina,  Brazil.  Other  undated  collections 
in  museums  are  from  Bermuda,  southern  Florida, 
Estados  de  Pernambuco  and  Sao  Paulo,  Brazil. 

Remarks . — Callinectes  exasperatus  has  a 
number  of  distinctive  features.  It  has  the  roughest 
appearing  carapace  and  chelipeds  of  any  species  in 
the  genus  because  the  granulations  are  coarser 
and  sharper  than  in  others.  The  median  episto- 
mial  tooth  is  more  widely  separated  from  the  front 
than  among  the  congeners,  perhaps  a  function  of 
the  vaulted  carapace  which  contributes  to  deep- 
bodied  form.  Similar  to  C.  bocourti  in  structure  of 
frontal  teeth,  C  exasperatus  has  less  prominent 
cardiac  lobes  and  sulci  bounding  the  metagastric 
area.  The  lateral  spines  are  relatively  shorter 
than  among  other  species  of  the  genus.  A  blunt 
anteromesial  eminence  on  the  carpus  is  pro- 
nounced. Narrowest  width  of  the  male  abdomen  is 
in  the  distal  third  of  the  sixth  segment,  the  nar- 
rowed portion  becoming  increasingly  distal  with 
age  together  with  progressive  crossing  of  the 
pleopods. 

Dahl  (1954)  worked  at  Canango  Beach,  Ven- 
ezuela, at  or  near  the  type-locality  for  C.  exas- 
peratus and  published  a  photograph  of  the  beach 
at  Puerto  Caballo  together  with  a  short  descrip- 
tion of  the  area,  saying  that  the  tidal  difference  is 
small  and  wave  exposure  very  great  on  the  rather 
steeply  sloping  beach. 

Locality  data  for  specimen  303-7  in  MNHNP 
(M.  Fontaines)  from  "Chili"  identified  as  Nep- 
tunus  diacanthus  Latr.  (=  C.  exasperatus)  is  an 
error. 

Material. — Total:  97  lots,  372  specimens. 
Specimens  listed  in  Rathbun  (1930)  from 
USNM  (24463,  24464, 18631  not  found)  and  MCZ. 

USNM.  38  lots,  282  specimens,  including  the 
following  not  cited  above: 

UNITED  STATES 

Florida:  77125,  E  of  Bush  Key,  Tortugas,  29 


July  1931, 1  <?,  Pearse.  80665,  Key  West,  no  date,  1 
6,  U.S.  Bur.  Fish. 

CUBA 

77127,  Bahia  Honda  [Pinar  del  Rio,  WSW 
Habana],  1  June  1893,  Univ.  Iowa. 

JAMAICA 

123077,  Kingston  Harbor,  17  May  1965, 1 9  (ov), 
B.  B.  Collette. 

HAITI 

71232,  Muertos  I.,  Seven  Brothers  group,  Feb. 
1929,  1  6,  Poole  and  Perrygo. 

PUERTO  RICO 

61563,  Cataho  [San  Juan  Harbor],  4  Jan.  1899, 

1  (J,  Fish  Hawk.  73281,  Bahia  de  San  Juan,  29 
Mar.  1937,  1  6,  W.  L.  Schmitt.  123084,  Boca  de 
Cangrejos,  7  mi  E  San  Juan,  31  Mar.  1937,  1  c?, 

2  9(1  ov),  W.  L.  Schmitt. 

VIRGIN  ISLANDS 

71639,  St.  Croix,  no  date,  1  6,  H.  A.  Beatty. 
72353,  St.  Croix,  1935-36, 2  6,  H.  A.  Beatty.  76466, 
St.  Croix,  no  date,  1  9,  H.  A.  Beatty. 

BARBUDA 

123079,  west  shore  of  lagoon  near  Oyster  Pond 
Landing,  6  Apr.  1956,  1  9  (ov),  Schmitt,  Chace, 
Nicholson,  and  Jackson,  Stn.  85-56,  Freelance. 

GUADELOUPE 

123080,  between  Monroux  and  Rat  Is.,  Pointe  a 
Pitre,  30-31  Mar.  1956,  3  o,  2  9  (1  ov),  Chace  and 
Nicholson,  Stn.  68-56,  Free/ance. 

GRENADINES 

123078,  Tyrrell  Bay,  Carriacou  I.,  16  Mar.  1956, 
2  <?,  D.  V.  Nicholson,  Stn.  11 -56,  Freelance. 

MEXICO 

Quintana  Roo:  78391,  Bahia  de  la  Ascension,  28 
Mar.  1939, 1 6  ,  Ralph  EUiott.  123082,  N  end  Bahia 
de  la  Ascension,  15  Apr.  1960,  3  S ,  19,  Daiber 
and  Schmitt.  123083,  Bahia  de  la  Ascension 
behind  Pta.  Allen,  16  Apr.  1960,  1 S  ,  Daiber  and 
Haynes.  123081,  Bahia  del  Espiritu  Santo,  near 
Pta.  Lawrence,  6  Apr.  1960,  1 9  ,  Rehder,  Daiber 
and  Haynes. 

VENEZUELA 

95713,  Gran  Roque,  Los  Roques  Is.,  7  Sept.  1950, 
1  S,  F.  H.  Weibezahn. 


759 


AHF.  3  lots,  4  specimens. 

UNITED  STATES 

Florida:  Key  Largo,  North  Hawk  Channel, 
29-31  May  1949,  2  6,  Stn.  LM  25,  27.  Hawk  Chan- 
nel, Plantation  Key,  3  mi  S  Tavernier  Bridge,  25 
May  1949,  1  6,  Stn.  LM20-49. 

TRINIDAD 

Purchased  from  fisherman  near  Port  of  Spain, 
17  Apr.  1939,  1  9. 

AMNH.  4  lots,  4  specimens. 

BERMUDA 

11223,  1939,  1  9  (ov),  W.  Beebe,  Bermuda 
Exped. 

BAHAMAS 

2286,  Andros,  1908,  1  9,  B.  E.  Dahlgren  and  H. 
Mueller. 

PUERTO  RICO 

2673,  San  Juan,  entrance  of  Bahia  de  Condado, 
14  July  1914,  1  9,  R.  W.  Miner.  2661,  July-Aug. 
1914,  1  S  (dry),  R.  W.  Miner. 

ANSP.  1  lot,  1  specimen. 

BRAZIL 

3514,  no  date,  1  9  (dry),  T.  B.  Wilson. 

BMNH.  7  lots,  12  specimens. 

UNITED  STATES 

Florida:  1938.3.19.22,  Dry  Tortugas,  1  S,  Col- 
man  and  Tandy. 

BRITISH  HONDURAS 

1967.7.1.49/50,  Long  Cay  Island,  23/10/1941,  1 
S,  1  9,  I.  Sanderson. 

CAYMAN  ISLANDS 

1955.10.6.59,  Stn.  33,  1  c ,  Oxford  Univ.  Exped. 

JAMAICA 

vi/8,  no  date,  2  6\  2  9  (dry).  Banks. 

BRAZIL 

80.37,  Pernambuco,  no  date,  2  <J,  W.  Forbes. 
61-44,  vi/7,  Rio  de  Janeiro,  no  date,  1  S  (dry),  U.S. 
Explor.  Exped.  919/C,  vi/7,  no  date,  1  6  (dry),  C. 
Stewart  Banks. 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 

MCZ.  14  lots,  26  specimens. 

UNITED  STATES 

Florida:  5160,  Key  West,  no  date,  1  <S  (juv),  1  9 
(ov),  J.  E.  Mills. 

BAHAMAS 

Bimini:  11671,  Alicetown,  May  1941,  1  S,  R.  W. 
Foster  and  J.  Huntington.  11692,  Nixons  Har- 
bour, May  1941,  1  6,  R.  W.  Foster  and  J.  Hunting- 
ton. 10360,  Great  Inagua  I.,  Salt  pond  canal  iy2  mi 
SE  Matthew  Town,  24  June  1938,  1  <J,  1  9,  R.  H. 
McLean  and  B.  Shreve. 

CUBA 

10889,  Bahia  de  Siguanea,  Isla  de  Pinos,  14  Feb. 
1938,  1  6,  1  juv,  Harvard-Havana  Exped. 

BRAZIL 

5167,  Santos,  Estado  de  Sao  Paulo,  no  date, 
1  9  (ov),  Coutinho,  Thayer  Exped. 

MNB.  6  lots,  9  specimens. 

BRAZIL 

56,  Pernambuco,  no  date,  1  d*,  2  9  (ov).  58,  Rio 
Guanabara,  no  date,  1  6.  52,  Rio  Guanabara,  no 
date,  2  S.  1380,  Baia  de  Guanabara,  1948,  1  6,  P. 
Drach.  Estado  de  Santa  Catarina:  59,  Sao  Fran- 
cisco do  Sul,  1901  (?),  1  9,  L.  Gralberto.  499,  no 
data,  2  9. 

MNHNP.  2  lots,  2  specimens. 

QUESTIONABLE  LOCALITIES 

Suitree(?),  1922,  1  S,  from  Museo  de  Historia 
Natural,  Buenos  Aires.  Chili(?),  303-7,  no  date,  1  9 
(dry),  M.  Fontaines. 

RMNH.  17  lots,  26  specimens. 

UNITED  STATES 

Florida:  15631,  Key  Biscayne,  Miami,  14  Sept. 
1960,  1  6,  R.  B.  Manning  and  L.  B.  Holthuis. 

WEST  INDIES 

2326,  June  1920,  1  9  (ov),  J.  Boeke. 

ST.  MARTIN 

11879,  Baie  Orient,  23  Feb.  1957,  1  S,  L.  B. 
Holthuis. 

ARUBA 

15044,  1882-1883,  2  6  (juv),  A.  J.  van  Koolwijk. 


760 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


CURACAO 

St.  Kruis  Baai,  7  Oct.  1948,  1  carapace  (dry),  P. 
W.  Hummelinck.  15056,  shore  of  Piscadera  Baai 
near  Raphael,  13  Nov.  1956,  1  (juv),  L.  B.  Hol- 
thuis.  11877,  Piscadera  Baai,  27-28  Dec.  1956, 
1  d,  2  9,  3  juv,  L.  B.  Holthuis.  Schottegat  at 
Pasanggrahan,  22  Aug.  1948,  1  9  (dry),  P.  W. 
Hummehnck.  South  shore  St.  Joris  Baai  near 
Choloma,  3  Jan.  1957,  1  9  (dry),  L.  B.  Holthuis. 
1 1878,  South  shore  St.  Joris  Baai  near  Choloma,  3 
Jan.  1957,  1  c?,  1  9,  L.  B.  Holthuis. 

BONAIRE 

11880,  lake  on  E  coast,  10  Mar.  1957, 1  ^,  1  9,  L. 
B.  Holthuis.  11876,  lake  on  E  coast,  6  Mar.  1957, 1 
$,  L.  B.  Holthuis.  Paloe  Lechi,  6  Apr.  1955,  1 
carapace  (dry),  Zaneveld. 

TRINIDAD 

23413,  Cocorite,  25  Aug.  1965, 1  S,  1  9,  H.  O.  von 
Hagen. 

VENEZUELA 

10719,  Isla  de  Margarita,  Feb.  1955,  1  6,  J.  S. 
Zaneveld.  23396,  Punta  Mangle,  Isla  de  Mar- 
garita, 11  Jan.  1964,  1  &,  P.  W.  Hummelinck. 

BRAZIL 

4873,  Bahia,  1909,  1  $,  J.  A.  Bierens  de  Haan, 
Zool.  Lab.  Utrecht. 

SADZ-B.  5  lots,  6  specimens. 

BRAZIL 

Bahia;  3223,  Ilheus,  1919,  1  ^  ,  1  9,  E. 
Garbe.  3214,  Ilha  Madre  de  Deus,  Jan.  1933, 
1  cJ.  Rio  de  Janeiro:  3242,  Atafona,  12  July 
1963,  2  juv,  N.  Meneses.  3246,  Atafona,  no  date, 
1  (J,  N.  Meneses.  Santa  Catarina:  3245,  27°15'S, 
48°47'W,  near  Florianopolis,  21  Aug.  1966, 
1  9  (ov),  M.  Iwai. 

UNC-IMS.  1  lot,  3  specimens. 

PUERTO  RICO 

2137,  Mangrove  channels  behind  Bahia  Fos- 
forescente,  2  May  1967, 2  (5, 1  9,  D.  R.  Torres  and  P. 
R.  Ramos. 

Supplementary  literature  records. — Southern 
Florida,  Futch  (1965);  Biscayne  Bay,  Fla.  (Park, 
1969);  Veracruz,  Ver.,  Mexico  (Contreras,  1930); 
Jamaica  (White,  1847);  Golfo  de  Venezuela  (Tais- 


soun,  1969);  Gran  Roque,  Venezuela  (Chace, 
1956);  Jangadas,  south  of  Recife,  and  other 
localities  in  Pernambuco,  Brazil  (Coelho,  1966, 
1967b);  Texas  ?  (tentatively  identified  specimen 
not  available  for  confirmation.  Pounds,  1961). 

CALLINECTES  BELLICOSUS 
(STIMPSON) 

Figures  10,  18h,  20j-k,  22h,  27 

Lupa  bellicosa  (Sloat,  MS)  Stimpson,  1859,  p.  57 
[11]  (type  locality:  Guaymas,  Gulf  of 
California,  C.  P.  Stone,  types  not  extant).- 
?  Lockington,  1876,  p.  105  [11]. 

Callinectes  bellicosus  Ordway,  1863,  p.  577  [12].- 
Streets  and  Kingsley,  1878,  p.  107.-  A.  Milne 
Edwards,  1879,  p.  227  (var.  of  C. 
diacanthus ).-  Rathbun,  1896,  p.  365,  pi.  22; 
pi.  24,  fig.  10;  pi.  25,  fig.  8;  pi.  26,  fig.  8.- 1898, 
p.  596.-  1926,  p.  75  [Signal  Hill 
Pleistocene].-  1930,  p.  112,  text-figs.  15k, 
16i,  17g,  20,  pi.  49.-  Holmes,  1900,  p.  73.- 
Young,  1900,  p.  190  (var.  ofC.  diacanthus).- 
Schmitt,  1921,  p.  236,  text-fig.  140.- 
Meredith,  1939,  p.  108  [figure].-  Steinbeck 
and  Ricketts,  1941,  p.  468,  pi.  14,  fig.  2.- 
Buitendijk,  1950,  p.  275.-  Garth  and 
Stephenson,  1966,  p.  47,  pi.  5,  fig.  B;  pi.  8,  fig. 
B;  pi.  10,  fig.  B;  pi.  12,  fig.  B.-  ?  Contreras, 
1930,  p.  240,  text-fig.  11. 

Callinectes  diacanthus.-  Young,  1900,  p.  186 
(part). 

Callinectes  ochoterenai  Contreras,  1930,  p.  229, 
text-figs.  2,  3A-C  (type  localities:  LaPaz, 
Baja  California,  and  Punta  Arena, 
Guaymas,  Sonora  [Mexico]). 

Description. — Carapace  (Figure  10)  with  two 
slender  frontal  teeth  separated  by  a  space  often 
bearing  a  rudimentary  submesial  pair  of  teeth; 
median  epistomial  spine  below  front  prominent 
and  slightly  exceeding  frontal  teeth.  Metagastric 
area  with  lateral  sulci  fairly  deep  but  anterior  and 
posterior  margins  obsolescent,  posterior  width 
greater  than  length.  Inner  orbital  fissure  usually 
open.  Anterolateral  margins  broadly  arched, 
teeth  exclusive  of  outer  orbital  and  lateral  spine 
relatively  short  and  concave  sided  with  acuminate 
tips  directed  outward  more  than  forward;  lateral 
spines  short,  about  twice  length  of  preceding 
tooth,  longer  in  juveniles.  Surface  finely  granulate 
and  remarkably  smooth  except  on  anterolateral 


761 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


region  where  granules  are  more  widely  spaced; 
sulci  and  lines  of  granules  more  prominent  on 
young  than  on  adults. 

Chelipeds  with  prominent  and  sharply  tubercu- 
late  or  spiniform  ridge  on  outer  surface  of  prop- 
odus,  other  ridges  lower  and  nearly  smooth. 

Male  abdomen  and  telson  reaching  a  bit  beyond 
suture  between  thoracic  sternites  IV  and  V;  telson 
triangular,  longer  than  broad,  sixth  segment 
slightly  constricted  in  proximal  half.  Mature 
female  abdomen  and  telson  reaching  about  same 
level  as  male,  telson  with  inflated  sides  longer 
than  wide,  segments  5  and  6  almost  equal  in 
length.  First  gonopods  of  male  (Figures  18h,  20j, 
k)  reaching  to  midlength  of  thoracic  sternite  VI 
with  tips  slightly  inclined  mesad  toward  each 
other,  not  overlapping  but  thrown  into  sinuous 
curves,  twisting  on  axis  at  level  of  suture  between 
thoracic  sternites  VI  and  VII  and  armed  at  this 
level  with  a  crowded  lateral  band  of  assorted 
short,  rather  blunt,  retrogressive  spinules  becom- 
ing less  numerous  and  more  slender  proximal  and 
distal  to  this  level,  longer  distally  and  shorter 
proximally;  a  subterminal  row  of  rather  promi- 
nent well  separated  exceedingly  slender  setae  on 
sternomesial  aspect.  Gonopores  of  female  (Figure 
22h)  asymmetrically  ovate  in  outline  with  orien- 
tation of  long  axis  mainly  in  frontal  plane  but  with 
apex  directed  anteromesad;  aperture  of  each  lat- 
erally elongate  and  sloping  from  broadest  area  at 
surface  on  mesial  side  to  narrower  deeper  portion 
under  uniformly  rounded  borders  on  remaining 
sides. 

Size  of  carapace  in  mm. — Largest  male:  length 
76,  width  at  base  of  lateral  spines  135,  including 
lateral  spines  154  (from  crab  purchased  in  Mexico 
City  fish  market  by  Edgard  Taissoun  and  Alfredo 
Vidal  after  statistical  analysis  was  completed). 
Largest  female:  length  89,  width  at  base  of  lateral 
spines  160,  including  lateral  spines  178.  Sum- 
mary of  selected  measurements  is  given  in  Tables 
1  and  2. 

Color. — The  only  good  published  color  descrip- 
tion is  that  of  Garth  and  Stephenson  (1966), 
"Carapace  mottled  greenish  yellow  to  brownish 
green,  sometimes  with  dark  spot  on  center  of  orbit 
and  dark  green  areas  roughly  outlining  epibran- 
chial  ridge.  Arms  generally  greenish  yellow  to 
greenish  brown,  wrist  articulations  purple  red. 
Hand  with  blotch  at  level  of  finger  articulation, 
this  blue-green  in  smaller  and  purple  in  larger 


specimens.  Similar  internal  blotch  purple 
throughout.  Inner  surface  hand  and  fingers  cen- 
trally white  to  pale  blue,  dorsally  purple  to  red- 
purple,  and  ventrally  blue  to  purple-blue. 
Cheliped  colors  most  vivid  in  largest  male."  Al- 
most brown  above,  cream  colored  below,  tubercles 
and  ridges  of  hand  tinged  with  red  (Lockington, 
1876). 

Specimens  purchased  at  a  fish  market  in  Mexico 
City  and  preserved  in  Formalin^  about  21  June 
1972,  by  Edgard  Taissoun  and  Alfredo  Vidal  were 
seen  by  me  on  June  23.  Colors  were:  male  tannish 
purple  overall;  ridges  of  chelipeds,  carpi,  and  front 
edge  of  meri  having  deepest  purplish  cast.  Pos- 
terior areas  of  carapace  grading  through  brownish 
cast  to  areas  of  beige  on  posterolateral  slopes  and 
swimming  paddles.  A  round  beige  spot  on  pos- 
terolateral border  just  anterior  to  insertion  of 
swimming  legs.  Upper  surfaces  of  palms  with  a 
reticulate  pattern  of  purple  lines  on  beige  to  off- 
white  background.  Inner  and  outer  surfaces  of 
chelipeds  and  ventral  aspect  off-white  with  sug- 
gestion of  yellow.  Superior  and  inferior  edges  of 
fingers  purple  grading  to  blue  on  inner  face  of 
fingers,  and  a  reticulate  blue  stripe  along  lower 
inner  border  of  palm.  Teeth  of  chelipeds  oyster 
white  at  their  crowns,  but  their  bases  light  purple 
giving  impression  of  a  purple  "gum"  line. 

Female  similar  to  male  but  with  a  more  tan  to 
beige  hue  on  carapace  and  upper  surface  of  palms. 
Blue  color  confined  to  inner  surface  of  propodal 
finger  only. 

Prominent  tubercles  and  tips  of  spines  oyster 
white  in  both  sexes. 

Variation. — Variation  in  C.  bellicosus,  as  in 
other  members  of  the  genus,  seems  largely  a  mat- 
ter of  differential  growth  changes.  Openness  of  the 
inner  orbital  fissures  has  been  used  as  a  key 
character  for  this  species,  but  large  series  show 
the  character  to  vary  individually;  though  usually 
open,  the  fissure  is  often  closed.  The  edge  of  the 
frontal  area  slopes  upward  from  contact  with  the 
exposed  median  epigastric  spine  to  a  row  or  cluster 
of  obsolescent  granules  which  mark  the  site  of 
obsolescent  submesial  frontal  teeth.  In  all  other 
species  the  front  overhangs  this  spine  to  at  least 
some  extent.  The  species  is  notable  for  sharpness 
of  teeth  and  spines.  Anterolaterals  pointing  for- 
ward in  the  young  are  directed  more  outward  in 
mature  specimens.  These  teeth  are  often  almost 

^Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


762 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


rectilinear  but  still  sharp  tipped.  Sub-  and  outer 
orbital  spines  become  increasingly  acuminate 
with  age.  The  mesogastric  area  changes  shape 
with  age,  the  anterior  border  becoming  increas- 
ingly sinuous  and  indistinct.  Adjacent  portions  of 
the  mesobranchial  regions  remain  sharply  out- 
lined in  old  individuals.  Some  older  specimens 
show  "expansion  scars"  on  the  carapace  as  if 
stresses  incurred  while  molting  had  stretched 
the  carapace  during  the  hardening  process.  Such 
"scars"  seem  to  radiate  from  centers  in  the  cardiac 
region. 

The  chelae  sometimes  have  lower  propodal 
margins  slightly  decurved  in  conjunction  with  de- 
velopment of  a  strong  basal  tooth  on  the  opposing 
dactyl.  Except  for  the  sharply  granulate  outer 
propodal  ridge,  usually  smooth  remaining  ridges 
on  the  chelipeds  are  occasionally  as  roughly 
granulate  as  in  C.  exasperatus. 

In  sternal  view,  males  have  a  great  resemblance 
to  C.  similis  in  that  the  abdomen  and  sternum 
are  nearly  plane  and  that  the  anterior  curvature 
of  fused  segments  3-5  is  shallow.  Males  may  show 
a  central  proximal  column  of  indurated  exoskel- 
eton  in  the  6th  abdominal  segment.  The  first 
gonopods  of  mature  males  may  reach  beyond  the 
middle  of  sternite  VI  to  the  suture  between  V 
and  VI. 

Distribution. — San  Diego,  Calif,  to  Bahia  Al- 
mejas  (southeastern  extension  of  Bahia  Mag- 
dalena)  Baja  California;  La  Paz  Harbor  around 
Golfo  de  California  to  Topolabampo,  Sinaloa,  Mex- 
ico (Figure  27).  The  species  is  apparently  absent 
from  the  extreme  southern  tip  of  Baja  California, 
but  was  listed  as  the  commonest  large  crab  in  the 
Golfo  de  California  by  Steinbeck  and  Ricketts 
(1941). 

Habitat. — Garth  and  Stephenson  (1966)  sum- 
marized the  little  available  ecological  data  noting 
that  the  known  depth  range  is  0  to  18  m,  usually 
over  sand  bottom,  and  that  many  crabs  had  been 
captured  swimming  under  lights  at  night.  From 
museum  records  it  is  clear  that  the  species  fre- 
quents estuarine  areas.  A  few  specimens  from 
Espiritu  Santo,  Golfo  de  California  (AHF)  are  cov- 
ered with  a  red  clay  deposit. 

Spawning. — Only  one  lot  taken  in  September 
from  Scammon  Lagoon,  Baja  Calif,  in  water  0.6  m 
deep  contained  ovigerous  females.  This  is  curious 
in  light  of  the  fact  that  more  mature  females  have 


been  collected  than  males  (Tables  1  and  2),  but  the 
record  is  probably  biased  by  times  of  collection.  Of 
94  lots  for  which  collection  date  is  recorded,  the 
monthly  frequency  is:  January  5,  February  11, 
March  43,  April  17,  May  3,  June  2,  August  3, 
September  2,  October  1,  November  5,  and  De- 
cember 2.  Either  spawners  were  beyond  depths 
sampled  (unlikely)  or  early  spring  is  not  the  main 
spawning  period  for  this  species. 

Economic  importance. — No  data  are  available 
on  uses  of  this  crab  other  than  notes  above  on  its 
availability  in  fish  markets  of  Mexico  City.  Thir- 
teen lots  of  fragments,  mostly  parts  of  fingers, 
from  archeological  sites  near  Municipio  Caborca, 
La  Cholla  Bay,  Sonora,  Mexico,  are  recorded  in  the 
USNM  as  Callinectes  (probably  C  bellicosus)  in- 
dicating pre-Columbian  use  of  the  large  crabs  by 
peoples  of  the  area. 

Remarks. — Callinectes  bellicosus  resembles  C. 
similis  of  the  Carolinian  province  of  the  Atlantic 
in  that  both  are  restricted  in  distribution  at  the 
northern  fringes  of  the  tropical  homeland  of  the 
genus,  but  the  analogy  is  a  loose  one  for  C.  bel- 
licosus is  the  more  restricted,  essentially  endemic 
to  the  Golfo  de  California  which  is  a  transitional 
body  of  water  with  Panamanian  relationships 
grading  from  tropical  in  the  south  to  temperate 
(but  warm  in  summer)  in  the  north,  and  the  Pacific 
coast  of  the  Baja  California  peninsula  whose 
marine  climate  is  transitional  between  tropical 
and  dominant  temperate  from  Punta  Entrada 
(Bahia  Magdalena)  to  Point  Conception  north  of 
Santa  Barbara  Channel  (Garth,  1961a).  Temper- 
ate and  tropical  faunas  meet  and  mingle  along 
this  outer  coast,  but  tropical  forms  thin  out  north- 
ward surviving  only  in  protected  shallows.  Rec- 
ords of  C.  bellicosus  are  few  north  of  Scammon 
Lagoon,  northern  extensions  of  range  being  fa- 
vored by  warm  periods  (Garth,  1961a).  The  south- 
ern tip  of  the  peninsula,  from  which  C.  bellicosus 
is  absent,  is  essentially  an  insular  oceanic  region 
distinct  from  adjacent  coastlines  and  dependent 
on  accidental  transport  for  its  marine  fauna 
(Garth,  1961a). 

Belonging  to  the  group  of  species  with  moder- 
ately long  first  gonopods,  C.  bellicosus  has  di- 
verged from  the  remainder  of  the  group  in  having 
gonopods  with  rather  straightened  sinuosity  and 
possession  of  prominent  sternomesial  setae.  The 
form  of  the  body  bears  some  resemblance  to  C. 
similis,   the  distributional  western  Atlantic 


763 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


analog,  in  having  a  smooth  and  finely  granulate 
carapace,  reduced  submesial  frontal  teeth,  shal- 
low anterolateral  teeth,  nearly  plane  sternum  and 
abdomen  in  males,  and  similar  length-width 
proportions  in  mature  males. 

A  Pleistocene  record  for  C.  hellicosus  (USNM 
372804)  is  represented  by  the  distal  two-thirds  of  a 
propodal  finger  from  a  minor  left  chela  of  a  large 
crab  from  the  upper  San  Pedro  formation,  Signal 
Hill,  northeast  of  Long  Beach,  Calif.  (Rathbun, 
1926).  Size  and  tooth  pattern  of  this  specimen  are 
indistinguishable  from  the  modern  form. 

Material  .—Total:  87  lots,  322  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  (4630  not  found)  and  AMNH;  Garth  and 
Stephenson  (1966)  from  AHF  and  USNM. 

USNM.  32  lots,  137  specimens,  including  the 
following  not  cited  above: 

MEXICO 

Baja  California:  12464,  [?]  3  6,  col.  unknown. 
63280,  S  end  Bahia  Magdalena,  20  Mar.  1911,  4  S, 
Albatross.  Uncatalogued,  Ricason  I.,  Bahia 
Concepcion,  7  Apr.  1911,  3  S,  Albatross.  60006, 
Bahia  Concepcion,  mouth  of  Rio  Mulege,  4  Apr. 
1911,  1  6,  Albatross.  57909,  Bahia  de  los  Angeles, 
1921,  1  6,  Calif.  Acad.  Sci.  Sonora:  80666,  Bay  at 
Guaymas,  31  Jan.  1923,  1  S,  2  juv,  B.  F.  Yost. 
97611,  Estero  de  Agiabampo,  no  date,  1  S  (dry),  E. 
F.  Ricketts.  81926,  1  <^,  2  9,  7  juv.  122921, 
Agiabampo,  May  1939,  1  9,  R.  Hermosillo. 

AHF.  44  lots,  158  specimens. 

AMNH.  4  lots,  18  specimens,  including  the  fol- 
lowing not  cited  above: 

MEXICO 

Baja  California:  5498,  Bahia  Tortolo,  Punta  San 
Bartolome,  14  Mar.  1911,  1  S,  Albatross.  5508, 
Bahia  Ballenas,  16  Mar.  1911,  2  c?,  1  9,  Albatross. 
5524,  Bahia  Magdalena,  20  Mar.  1911,  6  <?,  2  9, 
Albatross.  5504,  Bahia  Pichilinque,  27  Mar.  1911, 
3  6,  3  9,  Albatross. 

BMNH.  1  lot,  1  specimen. 

79.1,  off  San  Francisco,  1  S,  E.  Gerrard,  Jr. 
[Error,  or  San  Francisco  I.,  24°50'N,  110°35'W,  G. 
de  Calif.?]. 

MCZ.  1  lot,  3  specimens. 
764 


MEXICO 

Baja  California:  4253,  Shoal  Point,  Colorado 
River,  29  Mar.  1889,  2  <J,  1  9,  Albatross. 

RMNH.  4  lots,  4  specimens. 

MEXICO 

Baja  California:  La  Paz,  15  Oct.  1945,  1  9,  M. 
Cardenas.  Sonora:  7540,  Guaymas,  25  Sept.  1945, 
1  9,  M.  Cardenas.  Sinaloa:  7538,  Ahome,  1  June 
1945,  1  9,  M.  Cardenas.  7539,  Topolobampo,  21 
Apr.  1945,  1  6,  M.  Cardenas. 

Los  Angeles  County  Museum.  1  lot,  1  specimen. 

MEXICO 

Baja  California:  Bahia  Santa  Maria,  Mar.  28, 
year  unknown,  1  9,  A.  E.  Colburn,  A748. 

Supplementary  literature  record. — Punta  Santa 
Ines  [Baja  Calif.]  (Crane,  1937). 

CALLINECTES  TOXOTES  ORDWAY 

Figures  11,  ISi,  201,  22i,  27 

ICallinectes  diacanthus  Stimpson,  1860,  p.  220. 

Callinectes  toxotes  Ordway,  1863,  p.  576  [11]  (syn- 
types:  6,  USNM  2413:  2  S,  MCZ  5182;  6  [dry], 
MCZ  5183;  Cape  San  Lucas  [Baja 
California],  John  Xantus,  col.).-  A.  Milne 
Edwards,  1879,  p.  227  (var.  of  C.  diacan- 
thus).- Rathbun,  1896,  p.  363,  pi.  21;  pi.  24, 
fig.  9;  pi.  25,  fig.  9;  pi.  26,  fig.  9;  pi.  27, 
fig.  8.-  1910,  p.  536,  pi.  55.-  1930,  p.  127, 
figs.  15i,  16g,  17i,  18h,  pi.  54.-  Young,  1900, 
p.  189  (var.  of  C  diacanthus).-  Contreras, 
1930,  p.  237,  fig.  8.-  Garth,  1948,  p.  35.- 1957, 
p.  37.-  1961b,  p.  142.-  Garth  and  Stephenson, 
1966,  p.  50,  pi.  5,  fig.  C;  pi.  8,  fig.  C;  pi.  10,  fig. 
C;  pi.  12,  fig.  F.-  Bott,  1955,  p.  56. 

Callinectes  robustus  A.  Milne  Edwards,  1879,  p. 
227  (var.  of  C.  diacanthus)  (type  locality: 
Colombia;  type  listed  by  Rathbun,  1930,  in 
MNHNP,  not  found  in  1968,  considered  lost, 
1973,  fide  J.  Forest).-  Young,  1900,  p.  189 
(var.  of  C  diacanthus). 

Callinectes  diacanthus.-  Young,  1900,  p.  186 
(part). 

Description. — Carapace  (Figure  11)  bearing 
four  large,  rounded  frontal  teeth;  submesial  pair 
narrower  than,  partially  coalesced  with,  and 
reaching  half  the  length  or  more  of  lateral  pair. 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Metagastric  area  with  length  approximately 
equal  to  posterior  width,  anterior  width  about  2 
times  length.  Anterolateral  margins  moderately 
arched,  teeth  exclusive  of  outer  orbital  and  lateral 
spine  varying  from  triangular  or  inflated  triangu- 
lar at  inner  end  of  row  through  acuminate  forward 
trending  intermediate  teeth  to  forward  curving 
spiniform  tooth  at  outer  end  of  row,  base  of  first 
and  last  tooth  narrowest.  Surface  of  carapace 
coarsely  granulate  and  uneven,  nearly  smooth 
around  margins  and  along  regional  sulci,  more 
granulate  over  branchial  and  gastric  areas,  most 
closely  crowded  granules  on  cardiac,  mesobran- 
chial,  and  anterior  half  of  mesogastric  regions. 
Epibranchial  line  prominent  and  nearly  uninter- 
rupted. 

Propodus  and  carpus  of  chelipeds  with  sharply 
and  rather  coarsely  granulated  ridges,  especially 
on  propodus,  rarely  worn  smooth;  dactyl  of  major 
chela  with  basal  teeth  (often  a  single  strong  tooth) 
closing  against  cuspate  molariform  complex  on 
propodus,  both  chelae  with  sectorial  teeth. 

Male  abdomen  and  telson  reaching  beyond  mid- 
length  of  thoracic  sternite  IV;  telson  much  longer 
than  broad,  triangular  with  inflated  sides;  sixth 
segment  of  abdomen  narrowest  in  proximal  third. 
Mature  female  abdomen  and  telson  reaching  no 
more  than  midlength  of  thoracic  sternite  IV;  tel- 
son elongate  triangular  with  inflated  sides,  sixth 
segment  longer  than  fifth.  First  gonopods  of  male 
(Figures  18i,  201)  very  long,  reaching  to  or  beyond 
suture  between  thoracic  sternites  IV  and  V;  sinu- 
ously curved,  overlapping  proximally,  diverging 
distally,  twisting  mesioventrally  on  axis  at  mid- 
length  of  thoracic  sternite  V  and  recurving  to  ter- 
mination near  midline;  armed  distally  with  lat- 
eral band  of  retrogressive  spinules  thinning  to 
absence  near  tip.  Gonopores  of  female  (Figure  22i) 
asymmetrically  and  narrowly  ovate  in  outline 
with  apex  on  long  axis  directed  anteromesad; 
rounded  borders  with  series  of  wrinkles  conform- 
ing to  contours;  aperture  of  each  sloping  from  sur- 
face on  mesial  side  under  anterolateral  border  su- 
perior to  a  rounded  eminence  on  posterior  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
88,  width  at  base  of  lateral  spines  156,  including 
lateral  spines  193.  Largest  female:  length  74, 
width  at  base  of  lateral  spines  133,  including  lat- 
eral spines  174.  Estevez  (1972)  reported  a  female 
with  carapace  75  mm  long  estimated  to  have  a 
width  including  lateral  spines  of  182  mm,  and 
estimated  general  growth  rate  per  molt  to  be  15% 


in  length,  24%  in  width.  Summary  of  selected 
measurements  is  given  in  Tables  1  and  2. 

Variation. — This  species  attains  the  largest  size 
in  the  genus,  but  old  individuals  apparently  do  not 
show  teeth  or  spines  worn  to  an  extent  comparable 
with  other  species.  Anterolateral  teeth  vary  indi- 
vidually in  degree  of  laterally  progressive  upturn- 
ing in  the  row.  Submesial  frontal  teeth  vary  con- 
siderably in  length  as  well  as  acuity,  but  none  are 
really  sharp  pointed.  Chelae  in  seemingly  old  in- 
dividuals retain  basal  teeth  with  well  defined 
molariform  structure  on  the  major  hand;  sectorial 
tooth  development  seems  more  prominent  on  both 
right  and  left  chelae  than  in  other  species. 
Females  have  granules  more  prominent  and 
closely  crowded  on  the  carapace  than  males.  Male 
first  gonopods  cross  over  each  other  at  the  tips  in 
some  individuals. 

Distribution. — Cabo  de  San  Lucas,  Baja 
California,  to  extreme  northern  Peru;  extrater- 
ritorial, Juan  Fernandez  (Figure  27). 

Habitat. — Ranging  from  shore  to  27-m  depths, 
C.  toxotes  has  been  characterized  as  a  mangrove 
swamp  crab  (Estevez,  1972).  It  occurs  from 
freshwater  streams  to  open  bays,  and  a  number  of 
collections  come  from  lagoons  or  river  mouths. 

Stomachs  of  521  specimens  contained  bivalves, 
gastropods,  inorganic  debris,  crustaceans,  fishes, 
and  polychaetes  in  order  of  precedence  (Estevez, 
1972). 

Spawning. — Material  available  for  study  in- 
cludes only  three  ovigerous  females:  January, 
Panama;  August,  Acapulco,  Mexico;  a  third  un- 
dated specimen  from  Cabo  San  Lucas,  Baja 
California,  in  MCZ  was  collected  by  John  Xantus, 
perhaps  with  the  type  material. 

Only  one-third  of  the  specimens  of  C.  toxotes 
in  museum  collections  are  sexually  mature,  and 
among  these  males  outnumber  females  2:1.  The 
small  number  of  ovigerous  females  should  there- 
fore not  cause  surprise. 

Economic  importance. — The  species  is  used  as 
food  and  sold  at  the  market  of  Buenaventura,  Co- 
lombia. Crabs  there  are  brought  from  Malaga  Bay 
and  others,  many  (mostly  immature)  being  caught 
by  shrimpers  along  the  coast  (Mario  Estevez, 
pers.  commun.).  Collections  from  Estados  de 
Sinaloa  and  Nayarit,  Mexico;  Tumaco,  Colombia; 


765 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


and  Guayaquil,  Ecuador;  are  from  places  where 
fishing  is  active  or  from  fish  markets. 

Remarks.— The  type  locality  lies  at  the  extreme 
northern  end  of  the  distributional  range,  seem- 
ingly so  far  removed  from  the  remainder  of  the 
range  that  one  might  question  origin  of  the  syn- 
types.  Xantus  (Madden,  1949)  was  an  excellent 
and  energetic  collector  for  the  Smithsonian  In- 
stitution who  lived  and  worked  at  Cabo  de  San 
Lucas  from  4  Apr.  1859  to  7  Aug.  1861.  Collectors 
then  were  not  so  precise  about  recording  locality 
data  as  today,  and  Xantus  was  no  exception.  It  is 
known  that  collections  were  brought  to  Xantus 
from  Bahia  Magdalena  to  the  north  and  Revil- 
lagigedo  Island  to  the  south,  etc.,  and  that  he  vis- 
ited Mazatlan  on  the  mainland  in  summer,  1861, 
returning  to  Cape  San  Lucas  on  1  Aug.  Though 
no  collection  date  is  recorded  with  the  types,  MCZ 
received  its  specimens  from  the  Smithsonian 
Institution  on  13  Feb.  1861,  which  would  seem  to 
limit  origin  of  the  specimens  to  the  tip  of  Baja 
California  or  at  least  rule  out  collection  on  the 
mainland  closer  to  the  rest  of  the  range  for  the 
species.  Moreover,  an  ovigerous  female  bearing  a 
Cabo  de  San  Lucas  label  (MCZ  5184),  received 
with  the  mature  types,  suggests  a  breeding  popu- 
lation and  not  an  accidental  occurrence. 

Usual  habitat  of  the  species  suggests  that  the 
Juan  Fernandez  collection  is  extraterritorial.  Set 
of  currents  between  this  isolate  and  the  nearest 
known  population  in  Peru  suggest  that  if  a  breed- 
ing population  does  exist  there,  it  is  introduced. 
Further  collecting  both  here  and  in  the  Cabo  de 
San  Lucas  area  would  be  useful. 

Material. — Total:  30  lots,  120  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  and  MCZ;  Garth  and  Stephenson  (1966) 
from  AHF  and  USNM. 

USNM.  19  lots,  44  specimens,  including  the 
following  not  cited  above: 

MEXICO 

Sinaloa  and  Nayarit:  61023,  1926,  1  6  (dry),  C. 
Stansch,  No.  33. 

COSTA  RICA 

1 12356,  Golfo  de  Nicoya,  Jan.  1952,  2  carapaces 
(dry),  S.  E.  Erdman. 

PANAMA 

73283,  Bahia  Honda,  9  Mar.  1933,  1  juv,  W.  L. 
Schmitt.  122920,  no  date,  1  6. 


COLOMBIA 

77045,  Buenaventura,  18  Nov.  1934,  1  2  juv,  R. 
Mensing. 

AHF.  8  lots,  44  specimens,  including  the  follovv- 
ing  not  cited  above: 

[Nicaragua  material  Stn.  962-39  =  a  Portunus 
species]. 

COSTA  RICA 

Bahia  Carrillo,  6  Feb.  1938,  1  S,Zaca  Stn.  208, 
NYZS  38,194.  Golfito,  Golfo  Dulce,  6  Mar.  1938, 1 
$,Zaca,  NYZS  38,525. 

MCZ.  5  lots,  28  specimens,  including  the  follow- 
ing not  cited  above: 

MEXICO 

Baja  California:  5184,  Cabo  de  San  Lucas,  no 
date,  1  ?  (ov),  J.  Xantus.  (reed,  from  Smithsonian 
Inst.  13  Feb.  1861).  Guerrero:  5185  and  8755, 
Acapulco,  Aug.  1872,  9  <5,  15  $  (1  ov),  Hassler 
Exped. 

AMNH.  1  lot,  3  specimens. 

COLOMBIA 

10587,  Tumaco,  19  Apr.  1941,  2  <J,  1  9,  Askoy 
Exped. 

RMNH.  1  lot,  1  specimen. 

Cat.  a.  South  America,  1  S  (dry),  Latreille. 

Supplementary  literature  records. — Acapulco, 
Guerrero,  Mexico  (Contreras,  1930);  Acajutla, 
Barra  Ciega,  La  Libertad,  La  Union,  El  Salvador 
(Bott,  1955);  NW  Corinto,  Nicaragua  (Garth  and 
Stephenson,  1966);  Baudo,  Juanchaco,  Catripe, 
Togoroma,  Malaga,  Buenaventura,  Guapi,  San 
Juan  del  Sur,  Cabo  Manglares,  Punta  Coco,  and 
Tumaco,  Colombia  (Estevez,  1972). 

CALLINECTES  BOCOURTI 

A.  MILNE  EDWARDS 

Siri  (Brazil) 

Figures  12,  18j,  20m,  22j,  27 

Cancer  pelagicus .-  de  Geer,  1778,  p.  427,  pi.  26, 
figs.  8-11. 


766 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Callinectes  bocourti  A.  Milne  Edwards,  1879,  p. 
226  (syntypes:  2  S,  MNHNP,  Mullins  River, 
20  miles  south  Belize,  [British]  Honduras, 
M.  Bocourt). 

Callinectes  Cayennensis  A.  Milne  Edwards,  1879, 
p.  226  (syntypes:  2  6,  MNHNP  [French] 
Guiana,  M.  Melinon). 

Lupa  diacantha .-  Kappler,  1881,  p.  143. 

?Neptunus  diacanthus.-  Thallwitz,  1892,  p.  53. 

Callinectes  bocourti.-  Rathbun,  1896,  p.  369,  pis. 
19;  24,  fig.  7;  25,  fig.  6;  26,  fig.  6;  27,  fig.  6 
[part].-  1897,  p.  151  [part].-  1901,  p.  49.- 
1930,  p.  128,  text-figs.  15g,  16e,  17h,  18f,  pi. 
55.-  1933,  p.  49.- 1936,  p.  383.-  Young,  1900, 
p.  192.-  Bott,  1955,  p.  56.-  Holthuis,  1959,  p. 
201,  text-fig.  47,  pi.  5,  fig.  2.-  Chace  and 
Hobbs,  1969,  p.  127,  text-figs.  35,  37a.- 
Taissoun,  1969,  p.  57,  figs.  20A-D,  photo  7.- 
1972,  p.  31,  figs,  la-d,  2  [part],  3  [part],  9C, 
lOC-D;  photos  4b,  5-6,  (col.),  7.-  1973,  p.  24, 
figs.  4G,  5G,  photo  2. 

Callinectes  diacanthus.-  Young,  1900,  pis.  2,  3. 

Callinectes  cayennensis.-  Young,  1900,  p.  192. 

Callinectes  danae.-  Tesch,  1914,  p.  195  (fide, 
Holthuis,  1959,  p.  205). 

Description. — Carapace  (Figure  12)  bearing 
four  triangular  frontal  teeth  with  tips  reaching  a 
nearly  common  level,  lateral  pair  obtuse  with 
mesial  side  having  flatter  angle  than  lateral  side, 
submesial  pair  narrower  than  laterals.  Metagas- 
tric  area  with  length  and  posterior  width  about 
equal,  anterior  width  2  times  length.  Anterolat- 
eral margins  moderately  arcuate,  anterolateral 
teeth  exclusive  of  outer  orbital  and  lateral  spine 
swept  forward,  anterior  margin  of  teeth  shorter 
than  posterior  margin,  teeth  in  lateral  half  of  row 
always  acuminate.  Surface  of  carapace  dorsally 
smooth  and  glistening  around  perimeter  (when 
wet)  and  on  epibranchial  surfaces;  central  portion 
granulate,  coarsest  granules  over  mesobranchial 
and  rear  half  of  cardiac  areas  and  lateral  half  of 
branchial  lobes.  Epibranchial  line  prominent  and 
nearly  continuous,  sulci  on  central  part  of 
carapace  deeply  etched. 

Chelipeds  remarkably  smooth  except  for  usual 
spines  and  obsolescent  granules  on  ridges;  fingers 
of  major  chela  heavily  toothed,  lower  margin  of 
propodal  finger  often  decurved  near  base  in  adults. 

Male  abdomen  and  telson  long,  extending 
nearly  to  juncture  between  thoracic  sternites  III 
and  IV;  telson  lanceolate,  much  longer  than  broad; 
sixth  segment  of  abdomen  broadened  distally. 


Mature  female  abdomen  and  telson  reaching  as 
far  forward  as  in  male,  sixth  segment  nearly  as 
long  as  fifth,  its  distal  edge  uniformly  arched, 
telson  elongate-triangular  with  inflated  sides. 
First  gonopods  of  male  (Figures  18j,  20m)  very 
long,  often  exceeding  telson  and  crossed  near  tips; 
sinuously  curved  and  overlapping  in  two  places 
proximally,  diverging  distally,  twisting 
mesioventrally  on  axis  lateral  to  abdominal  lock- 
ing tubercle  and  recurving  gradually  to  termina- 
tion near  midline;  armed  distally  with  a  dorsolat- 
eral band  of  large  and  small  retrogressive 
spinules.  Gonopores  of  female  (Figure  22j)  asym- 
metrically ovate  in  outline  with  apex  on  long  axis 
directed  anteromesad;  aperture  of  each  sloping 
from  surface  on  mesial  side  under  rounded, 
sinuous  anterolateral  border  superior  to  a  low 
rounded  eminence  on  posterior  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
76,  width  at  base  of  lateral  spines  132,  including 
lateral  spines  156.  Largest  female:  length  70, 
width  at  base  of  lateral  spines  121,  including 
lateral  spines  146.  Summary  of  selected  meas- 
urements is  given  in  Tables  1  and  2.  The  species 
characteristically  reaches  fairly  large  size. 

Color. — Complete  color  descriptions  (Chace  and 
Hobbs,  1969;  Taissoun,  1969,  1972)  and  notes 
(Rathbun,  1896,  1930;  Holthuis,  1959)  give  a 
range  of  color  variations.  These  can  be  broadly 
summarized  as:  Overall  cast  olive  green  with 
prominent  reddish  markings.  Carapace  olive, 
grayish  green,  greenish  chestnut,  or  forest  green 
with  variable  purplish  to  red  markings,  especially 
on  branchial,  hepatic,  cardiac,  and  gastric  areas, 
individuals  of  large  size  sometimes  being  dark 
chestnut  tinted  blackish  brown  on  gastric  and 
metagastric  areas,  with  an  oblique  spot  on  sub- 
branchial  region;  anterolateral  teeth  olive  green 
with  brown  to  red  tints  and  yellowish  white  tips. 
Chelipeds  red  to  dark  reddish  brown  above  and 
whitish  below  with  bluish  tints,  main  colors  being 
sharply  separated  on  outer  surface  of  palm;  fingers 
red  to  reddish  brown,  a  purplish  cast  on  internal 
articulation  of  merus  with  carpus  and  this 
member  with  chela;  tubercles,  tips  of  fingers,  and 
spines  on  articles  cream.  Remaining  legs  reddish 
above  with  shades  of  maroon,  yellow,  and  olive 
green  ventrally  except  distal  articles  scarlet  to  red 
or  dark  red  distally;  hairs  olive-tan.  Underparts  of 
body  mainly  dirty  white  to  purplish  red  with 
suffusion  of  blue  marginally,  first  abdominal  seg- 


767 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


ment  mainly  reddish  tan.  Males  tend  to  be  red- 
dish, females  greenish. 

Variation . — This  species  greatly  resembles  both 
C.  rathbunae  and  C.  maracaiboensis  but  generally 
has  more  obtuse  frontal  and  anterolateral  teeth  as 
well  as  more  pronounced  smoothness  on  chelipeds 
and  carapace.  Considerable  variation  attributable 
to  growth  and  age  is  evident.  The  submesial  pair  of 
frontal  teeth  become  relatively  more  slender  with 
age,  but  seldom  extremely  acute.  Some  young 
have  quite  lobate  frontals,  scarcely  separated;  an 
extreme  case  is  represented  by  MCZ  lot  5186  from 
Caruca,  Rio  Maria  [=  Rio  Caragaua  near  Belem?] 
Brazil,  in  which  an  immature  female  has  lobate 
frontal  teeth  partially  coalesced  while  more  ma- 
ture males  in  the  lot  have  fairly  sharp  submesial 
frontals.  There  is  great  variation  in  length  of 
lateral  spines,  the  relationship  of  spine  length  to 
that  of  the  last  anterolateral  tooth  as  cited  by 
Rathbun  (1930)  and  Taissoun  (1972)  not  holding 
up  as  a  key  character  for  large  series  of  specimens. 
Anterolateral  teeth  vary  from  obtuse  to  acumi- 
nate, acuteness  increasing  somewhat  with  age, 
and  edges  of  the  teeth  vary  from  smooth  to 
granulate  with  greatest  amount  of  granulation 
usually  on  the  posterior  margin.  There  is  more 
apparent  variation  in  chelipeds  than  among  other 
species  of  the  genus.  A  character  accentuated  with 
age,  especially  among  males,  is  a  major  cheliped 
with  gaping  fingers  in  which  the  propodus  is 
decurved  along  its  lower  margin.  At  one  extreme 
is  a  heavy  gaping  hand  with  strong  basal  tooth  on 
the  dactyl,  whereas  at  the  other  both  chelae  may 
be  slender  and  almost  symmetrical.  Many  indi- 
viduals have  a  major  chela  that  is  halfway  along 
this  scale  of  development;  others  possess  two 
minor  chelae  of  nearly  uniform  size — evidence  of 
regeneration. 

From  Rio  de  Janeiro  south,  specimens  seen  have 
stronger  and  more  sharply  granulate  ridges  on  the 
chelae  than  those  from  other  parts  of  the  species' 
geographic  range.  Likewise  on  these  southern 
forms,  granules  are  bold  on  the  posterior  slope  of 
the  cardiac  area  and  sometimes  crowded  into 
suggestion  of  a  transverse  ridge  at  summits  of  the 
cardiac  and  mesobranchial  areas.  Both  develop- 
ments are  reminiscent  of  similar  patterns  found  in 
the  acutidens  form  of  C.  sapidus.  Frontal  teeth, 
mesogastric  area,  and  first  pleopods  of  these  forms 
seem  typical  of  C.  bocourti. 

More  obscure  are  other  variations  which  have 
bearing  on  the  separation  of  C.   bocourti  from 


maracaiboensis.  A  series  of  variant  specimens 
from  over  the  geographic  range  of  C.  bocourti 
demonstrate  these. 

Brazil:  An  ovigerous  female  from  Praia  Inglese, 
Sao  Francisco  (USNM  60978)  has  its  sixth  abdom- 
inal segment  relatively  narrow  for  its  length  with 
the  distolateral  edge  angular  (typical),  not 
rounded  as  in  C.  maracaiboensis,  the  anterolat- 
eral teeth  sharp  and  not  curved  forward,  and  the 
frontal  teeth  fairly  sharp. 

Puerto  Rico:  A  mature  female  from  Hucares 
(USNM  24460)  has  an  abdomen  as  above  but 
frontal  teeth  rather  short  and  lobate,  and  an- 
terolateral teeth  short  and  not  curved  forward  but 
with  their  anterior  margin  shorter  than  the  pos- 
terior one.  Another  mature  female  (USNM  24457), 
from  near  Palo  Seco,  has  its  sixth  abdominal 
segment  shaped  as  in  C.  maracaiboensis  (short, 
broad,  rounded  distally),  short  and  rounded  fron- 
tal teeth  (mesial  pair  a  bit  sharper),  and  an- 
terolateral teeth  curved  forward  only  in  the  lat- 
eral half  of  the  row.  A  mature  male  from  Catario 
(USNM  24455)  has  anterolateral  teeth  short  and 
not  trending  forward,  first  gonopods  distorted  in 
preservation  but  armed  with  spinules  typical  of 
C  bocourti  (but  a  tip  as  in  maracaiboensis),  and 
short,  lobulate  frontal  teeth  (mutilated). 

Trinidad:  A  mature  female  (USNM  137731)  has 
the  abdomen  shaped  as  in  C.  maracaiboensis,  and 
lobulate  frontal  and  anterolateral  teeth  quite 
sharp  and  decidedly  curved  forward.  Males  in  this 
lot  have  first  gonopods  typical  of  bocourti  and 
anterolateral  teeth  moderately  curved  forward. 

Venezuela:  A  mature  female  from  Tacarigua  de 
la  Laguna,  Estado  Miranda  (USNM  89644)  has 
the  sixth  abdominal  segment  rounded  distally  and 
relatively  short  for  its  width,  as  in  C 
maracaiboensis,  the  mesial  pair  of  frontal  teeth 
moderately  acute,  lateral  pair  broader  (both  pairs 
fairly  short),  and  sharply  acuminate  anterolateral 
teeth  trending  forward  but  not  curved. 

Costa  Rica:  A  mature  female  (USNM  113279) 
has  very  lobate  frontal  teeth,  erect  anterolateral 
testh  strong  and  trending  forward,  and  the  sixth 
abdominal  segment  broken  but  rather  indetermi- 
nate in  shape  (trending  toward  typical). 

British  Honduras:  A  mature  female  from  near 
Belize  (21377)  has  prominently  lobulate  frontal 
teeth,  anterolateral  teeth  trending  forward  but 
sharp  tipped  only  in  the  lateral  half  of  the  row,  and 
the  sixth  abdominal  segment  halfway  between  the 
two  extremes  for  the  species  (wide  and  broadly 
rounded  distally). 


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WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Taissoun  (1972)  included  some  of  these  speci- 
mens in  his  comparative  study.  From  this  welter 
of  conflicting  trends,  separation  of  C.  bocourti 
from  maracaiboensis  was  a  weighted  decision 
resting  on  characters  prevalent  in  the  Lago  de 
Maracaibo  populations  plus  environmental  sepa- 
ration. 

Distribution. — Jamaica  and  British  Honduras 
to  Estado  de  Santa  Catarina,  Brazil  (Figure  27); 
extraterritorial  occurrences  in  southern  Florida 
and  Mississippi,  USA  (both  mature  males). 

Habitat. — Callinectes  bocourti  is  associated 
with  C.  sapidus  in  many  estuarine  areas,  but 
seems  more  tolerant  of  stagnant,  polluted  situa- 
tions. Around  the  mouth  of  Lago  de  Maracaibo  C. 
bocourti  was  found  in  the  Golfo  de  Venezuela, 
Bahia  de  El  Tablazo,  Rio  Limon,  and  Estrecho  de 
Maracaibo,  but  less  abundantly  in  Lago  de 
Maracaibo  itself  (Taissoun,  1969,  1972).  Only 
adult  females  were  found  in  the  Golfo  de  Ven- 
ezuela, but  elsewhere  both  sexes  in  all  stages  of 
growth  were  common,  abounding  in  Rio  Limon 
and  mangroves  around  Puerto  Caballo  and  in 
Bahia  de  El  Tablazo,  large  males  and  juveniles 
being  especially  numerous  around  sewers  of  San 
Carlos  and  Punta  de  Palmas.  Bottoms  in  this  area 
vary  from  mud  to  sand.  Griffiths,  Cadima,  and 
Rincon  (1972)  presented  a  similar  account,  show- 
ing that  juveniles  recruit  to  a  fishery  there  in  July 
and  November,  with  mature  males  tending  to 
remain  in  low-salinity  water  whereas  females 
move  to  saltier  water  after  mating.  Coelho  (1967a) 
reported  C.  bocourti  (called  the  blue  crab  there) 
abundant  in  a  lagoon  in  Pernambuco  that  varies 
from  5/(0  salinity  in  the  rainy  season  to  29 /to  in 
the  dry  season,  and  from  other  estuaries  in  north- 
eastern Brazil  (1970). 

The  broad  range  of  tolerance  is  emphasized  by 
presence  in  places  such  as  a  pool  inside  porous  old 
coral  rubble  on  Bonaire  (Rathbun,  1936),  and  dark 
somewhat  stagnant,  polluted  water  at  mouths  of 
the  Mero,  Indian,  and  Salisbury  Rivers  on 
Dominica  where  sand  bars  blocked  river  flow  at 
the  time  of  investigation  (Chace  and  Hobbs, 
1969).  Here  the  crabs  actively  fed  on  garbage  in 
daytime  over  a  bottom  of  rock-strewn  sand  covered 
with  silt.  In  other  streams  on  Dominica  whose 
mouths  were  open  to  flow,  only  C.  sapidus  was 
found. 

Spawning . — In  all  of  the  museum  collections 


studied  there  are  many  containing  mature 
females,  but  only  five  in  which  there  are  ovigerous 
specimens  and  only  three  of  these  are  accurately 
dated:  January,  Puerto  Rico,  Panama;  February, 
Curasao;  November,  Sao  Francisco  [Estado  de 
Santa  Catarina],  Brazil.  Taissoun  (1969,  1972) 
found  ovigerous  females  most  abundant  from 
March  to  August  in  the  Golfo  de  Venezuela,  and 
Griffiths  et  al.  (1972)  found  them  most  abundant 
around  the  mouth  of  Lago  de  Maracaibo  in  July. 
These  data  suggest  nearly  year-round  spawning 
(Taissoun,  1972)  in  one  part  or  another  of  the 
range,  perhaps  with  seasonal  peaks  associated 
with  latitude. 

Economic  importance. — Holthuis  (1959)  de- 
scribed a  fishery  for  C.  bocourti  in  brackish  waters 
of  Surinam  where  it  is  the  only  portunid  routinely 
caught,  its  tolerance  of  this  habitat  apparently 
favoring  success  there.  The  crabs  are  sold  alive  on 
the  market  in  Paramaribo.  A  crab  trap  fishery 
around  the  mouth  of  Lago  de  Maracaibo  started 
in  1969  and  is  increasing  rapidly  (Griffiths,  et  al., 
1972).  Though  directed  primarily  at  C.  sapidus, 
a  considerable  number  of  C.  bocourti  are  taken 
as  well.  Second  half  of  the  year  is  the  season  of 
highest  catch  per  unit  effort  in  a  brackish  area 
where  males  make  up  90%  of  the  take. 

Remarks. — The  collections  examined  contain 
an  unusually  large  number  of  mature  females. 

The  type  series  of  C.  bocourti  in  the  MNHNP  is 
somewhat  confused  by  labels.  No  clear  designa- 
tion is  given  on  labels  of  specimens  which,  by 
implication,  can  be  associated  with  the  original 
description.  Two  mature  male  specimens  labelled 
"Callinectes  bocourti  A.  M.  Edw.,  Riviere  de  Mul- 
lins  (12  m.  NNW  Stann  Creek)  au  de  Belize, 
Honduras,  Coll.  Bocourt"  represent  the  types  in 
the  opinion  of  J.  Forest.  Identification,  locality 
(excepting  the  parenthetic  emendation),  sex,  and 
collector  agree  with  Milne  Edwards'  description. 
The  smaller  specimen  (size  of  carapace  in  mm: 
length  48,  width  at  base  of  lateral  spines  80, 
including  lateral  spines  90)  has  more  granulate 
gastric,  metagastric,  cardiac,  and  branchial  areas 
than  the  larger  (length  60,  width  at  base  of  lateral 
spines  102,  including  lateral  spines  120).  A  small 
Chelonibia  is  affixed  over  the  left  epibranchial 
line  on  the  anterolateral  aspect  of  the  mesobran- 
chial  area  of  the  larger  specimen.  Both  specimens 
lack  right  chelae,  but  have  slender  left  minor 
hands  with  smooth  rounded  upper  sides  on  the 


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FISHERY  BULLETIN;  VOL.   72.  NO.  3 


propodus,  that  of  the  smaller  specimen  showing 
obsolescent  granules;  in  both,  the  merus  and 
carpus  are  smooth,  with  a  very  blunt  outer  spine 
on  the  carpus.  The  small  specimen  has  a  missing 
right  third  pereopod.  In  both,  the  first  gonopods 
reach  slightly  beyond  the  telson. 

Two  male  specimens  labelled  ''CaUinectes 
cayennensis  A.  M.  Edw.,  Cayenne,  Coll.  Melinon" 
are  possibly  the  types  of  C.  cayennensis. 
Identification,  locality,  sex,  and  collector  agree 
with  Milne  Edwards's  description.  Both  dark  in 
color,  the  specimens  are  obviously  C.  bocourti.  The 
larger  has  only  seven  anterolateral  teeth  on  the 
right  side,  the  first  tooth  being  enlarged.  Both 
specimens  have  two  apparent  minor  chelae,  the 
larger  of  each  smooth  dorsally.  and  the  smaller 
with  obscurely  granulate  obsolescent  ridges. 

Finally,  a  dry  male  specimen  labelled 
"CaUinectes  bocourti  A.  M.  Edw.,  TYPE?,  Hon- 
duras, Belize  (Crust.  Mexique,  p.  226,  1881, 
Bocourt)  A.  Milne  Edwards  1903"  has  a  badly 
cracked  carapace  and  bears  the  word  "Belize" 
written  obscurely  in  ink  on  the  right  mesobran- 
chial  eminence.  The  specimen,  as  shown  by 
carapacic  and  pleopodal  characters,  is  not  C. 
bocourti,  but  rather  C.  danae,  and  was  undoubt- 
edly mislabelled  subsequent  to  Milne  Edwards's 
death  in  1900,  according  to  J.  Forest.  The  broken 
abdomen  exposes  the  tip  of  an  intact  first  pleopod 
with  tip  turned  ventrolateral ly  at  the  two-thirds 
level  of  sternite  VI  bearing  a  subterminal  hair  on 
the  sternal  aspect. 

In  the  ANSP  collection  is  a  dry  male  specimen  of 
C.  bocourti  (No.  2808  labelled  Lupa  dicantha) 
that  is  badly  shrunken  and  distorted  bearing  the 
label  "North  America,"  but  no  date  of  collection 
nor  indication  of  collector.  The  name  and  speci- 
men suggest  a  collection  made  over  a  century  ago 
representing  a  possible  third  record  of  the  species 
from  somewhere  in  the  United  States. 

North  American  records  may  be  explained  by 
drift  from  the  Caribbean,  possible  routes  being 
suggested  by  drift  bottle  returns  (Brucks,  1971). 

Bott  (1955)  listed  the  species  from  the  west 
rather  than  the  east  coast  of  Middle  America  by 
mistake. 

Material. — Total:  117  lots,  290 -^  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  (24459  not  found)  and  MCZ.  and  in  Hol- 
thuis  (1959)  from  Surinam  in  RMNH. 

USNM.  33  lots,  82  specimens,  including  the 
following  not  cited  above: 


PUERTO  RICO 

123085,  73279,  Boca  de  Congrejos,  7  mi  E  San 
Juan,  31  Mar.  1937,  2  2 ,  W.  L.  Schmitt.  77104, 
beach  near  Ponce,  17  Aug.  1932, 1  9,  T.  J.  Barbour. 

VIRGIN  ISLANDS 

St.  Croix:  72354,  Fairplain  str.  above  bridge, 
1935-36,  2  0,  H.  A.  Beatty,  No.  129.  76963,  Altona 
str.  100  ft  from  sea,  no  date,  3  juv,  H.  A.  Beatty, 
No.  199.  77100,  Salt  River  reefs,  no  date,  17  juv,  H. 
A.  Beatty,  No.  157. 

BRITISH  WEST  INDIES 

St.  Lucia:  123086,  Pigeon  Island,  22  Mar.  1956, 
3  5,  1  9, Freelance,  Stn.  46-56. 

COSTA  RICA 

113279,  Limon  Prov.,  Tortuguero  R.  about  2  mi 
above  mouth  at  Leo's,  28  Apr.  1964, 15,  ljuv,D.P. 
Kelso. 

COLOMBIA 

78382,  Puerto  Colombia,  no  date,  1 9,  Bro.  Elias, 
No.  21. 

VENEZUELA 

89644,  Estado  Miranda,  Tacarigua  de  la 
Laguna,  1  Mar.  1949,  1  9,  Soc.  Ciencias  Nat.  La 
Salle,  Stn.  c-3. 

AHF.  1  lot,  1  specimen. 

BRITISH  WEST  INDIES 

Trinidad,  West  Manzanilla,  10°31'20"N, 
61°02'37"W,  18  Apr.  1939,  1  6,  Velero  III  Stn. 
A36-39. 

AMNH.  4  lots,  4  specimens. 

PUERTO  RICO 

2669,  San  Juan  near  San  Antonio  Bridge,  10 
July  1914,  19,  R.  W.  Miner.  5378,  Culebra 
[18n8'N,  65n8'W],  1926,  U*  ,  H.  E.  Anthony. 

BRITISH  HONDURAS 

Crique  Salada  [16°35'N,  88°37'W],  Apr.  1951,  1 
9,  M.  Gordon,  Chable,  and  George. 

PANAMA 

11241,  Harbor  at  Colon,  no  date,  1  9,Arcturus 
Exped. 

ANSP.  3  lots,  9  specimens. 


770 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


NORTH  AMERICA  [?] 
2808.  no  date,  1  i  (dry). 

[DOMINICAN  REPUBLIC] 

3519,  Santo  Domingo,  no  date,  2  9  (dry),  W.  M. 
Gabb. 

PANAMA 

1305,  5  <j,  1  9,  McNeil  Exped. 

BMNH.  9  lots,  12  specimens. 

BRITISH  WEST  INDIES 

1925.1.28.13,  Tobago,  1  3 ,  P.  L.  Guppy. 
1938.3.29.18,  Tobago,  1  <^,  A.  K.  Totton. 

GUYANA 

1960. 10.5. 15/16,  Georgetown,  Kitty  Jetty,  1  (5 , 1 
9,  R.  H.  McConnell.  44.82,  Georgetown,  1  6  (dry), 
vi/9.  62.93,  2  S  ,  Leadbeater.  1949.5.26. 1/2,  2  9 ,  V. 
Graham. 

SURINAM 

1959.3.20.1,  Suriname  River  near  Paramaribo, 
1  ^ ,  I.  T.  Sanderson. 

BRAZIL 

1923.8.14.1,  Marajo  I.  mouth  of  Amazon,  1  $, 
Erhardt.  80.37,  Pernambuco,  1  9,  W.  Forbes. 

MCZ.  9  lots,  22  specimens,  including  the  follow- 
ing not  cited  above: 

PANAMA 

5472,  Aspinwall  [=  Colon],  no  date  (reed.  13 
Feb.  1861),  19,  J.  Rowell. 

BRAZIL 

5172,  13  Oct.  1873,  1  S  juv,  C.  Linden. 

MNB.  2  lots,  3  specimens. 

BRAZIL 

Pernambuco:  329,  Manques  de  Olinda,  1945,  2 
$  ,  Berla.  Rio  de  Janeiro:  48,  Marica,  no  date,  1  9. 

MNHNP.  2  lots,  4  specimens. 

BRITISH  HONDURAS 

148,  Riviere  de  Mullins  au  Sud  de  Belize,  no 
date,  2  S ,  Bocourt. 

FRENCH  GUIANA 

69,  Cayenne,  no  date,  2  6 ,  Melinon. 


RMNH.  45  lots,  130+  specimens. 

BRITISH  WEST  INDIES 

Barbados:  23456,  Holetown  river  pool,  18  Feb. 
1964,  U  ,  P.  W.  Hummelinck. 

NETHERLANDS  ANTILLES 

Curasao:  23450,  N  part  Piscadera  Baai,  25  Nov. 
1963,  1  5,  P.  W.  Hummelinck.  8122,  Zaquito 
Lagoon,  1  Feb.  1949, 1 6  ,  P.  W.  Hummelinck.  3270, 
Schottegat,  10  Feb.  1939,  1  9  (ov),  H.  S.  C.  Cossee. 
Schottegat  near  Pasanggrahan,  22  Aug.  1948,  1  ? 
(dry),  P.  W.  Hummelinck.  11855  and  11858, 
slough  in  mangroves,  Santa  Cruz,  11  Feb.  1957,  2 
<?,  2  9,  L.  B.  Holthuis,  No.  1099.  11857,  Waaigat, 
Willemstad,  30  Jan.  1957,  many  i6  and  juv,  L.  B. 
Holthuis. 

Bonaire:  Paloe  Lechi,  Apr.  1955, 1  juv  (dry),  J.  S. 
Zaneveld.  Paloe  Lechi,  Dralendijk,  5  Mar.  1957,  3 
adult  carapaces,  (dry),  L.  B.  Holthuis,  No.  1137. 
11856,  Paloe  Lechi,  N  Kralendijke,  5  Mar.  1957, 
$S,  99,  and  juv,  L.  B.  Holthuis. 

VENEZUELA 

Estado  Miranda:  7613,  Laguna  de  Tacarigua, 
1948-49,  2  9  (ov),  G.  Marcuzzi.  Estado  Sucre:  7615, 
beach  by  airfield,  Cumana,  Sept.  1948,  1  9,  G. 
Marcuzzi. 

TRINIDAD 

23403,  Diego  Martin  R.,  1965-66,  1  <?,  H.  A.  van 
Hagen. 

SURINAM 

21163,  coast  off  mouth  of  Suriname  and  Cop- 
pename  R.,  25-27  Aug.  1964,  2  9,  M.  Boeseman. 
21573,  mouth  of  Suriname  R.  at  Leonsberg  near 
Paramaribo,  27  Dec.  1963,  1  S  juv,  P.  Leentvaar. 
5367,  Swamp  near  Agricultural  Experiment  Gar- 
dens, Paramaribo,  10  June  1941,  1  9  juv,  D.  C. 
Geijskes.  22495,  brackish  water  at  Matappica 
near  Paramaribo,  6  Nov.  1965,  $S  and  99,  G.  F. 
Mees.  22598,  shore  at  Matappica  near 
Paramaribo,  8-13  Jan.  1966,  1  6  and  juv,  G.  F. 
Mees. 

SADZ-B.  9  lots,  23  specimens. 

BRAZIL 

Maranhao:  876,  1919,  1S,F.E.  Sawyer,  Smith- 
sonian Inst.  Alagoas:  Lagoa  Jequia  Mangebeira 
Camargo,  Nov.  1952,  3  6,  3  9.  Bahia:  1248, 
Ilheus,  1919,  2  9,  E.  Garbe.  Rio  de  Janeiro:  1729, 


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FISHERY  BULLETIN;  VOL.  72,  NO.  3 


Atafona,  no  date,  2  5,2  9,  Meneses.  3241  Atafona, 
12  July  1963,  3  juv,  N.  Meneses.  399,  Serra  de 
Macae,  1912,  2  5,  E.  Garbe.  Sao  Paulo:  400, 
Ubatuba,  1905,  1  9,  E.  Garbe.  403,  Piassaquera, 
1905,  3  5,  J.  S.  Fialho.  352,  Iquape,  1901,  16,R. 
Krone. 

Gulf  Coast  Research  Laboratory.  1  lot,  1  speci- 
men. 

UNITED  STATES 

Mississippi:  172:1062,  Biloxi  Back  Bay,  No., 
1971,  1  S  ,  from  commercial  fisherman  (Perry, 
1973). 

Supplementary  literature  records. — Biscayne 
Bay,  Fla.  (Provenzano,  1961);  St.  Croix  (Beatty, 
1944);  Dominica  (Chace  and  Hobbs,  1969);  Puerto 
Cortez,  Honduras  (Bott,  1955);  Lake  Maracaibo 
vicinity,  Venezuela  (Taissoun,  1969);  Forteleza, 
Ceara,  Brazil  (Fausto  Filho,  1966). 

CALLINECTES  RATHBUNAE 

CONTRERAS  JAIBA  PRIETA 

(MEXICO) 

Figures  13,  19a,  20n,  22k,  27 

Callinectes  rathbunae  Contreras,  1930,  p.  238, 
text-figs.  9,  10  (type  localities:  Barras  de 
Boca  del  Rio,  Buen  Pais  and  Alvarado, 
Veracruz,  Mexico). -Manrique  Colchado, 
1965,  p.  30,  figs.  10-15.-Taissoun,  1972,  p. 
35,  figs,  li-1,  2  (part),  3  (part),  9A,  lOE-F, 
photos  8-11. 

Callinectes  rathbuni  Pounds,  1961,  p.  42,  pi.  7,  fig. 
2d. 

Description. — Carapace  (Figure  13)  bearing 
four  acuminate  frontal  teeth  with  tips  reaching  a 
nearly  common  level,  submesial  teeth  narrower 
and  slightly  shorter  than  laterals.  Metagastric 
area  with  length  and  posterior  width  about  equal, 
anterior  width  2  times  length.  Anterolateral  mar- 
gins slightly  arcuate,  anterolateral  teeth  exclu- 
sive of  outerorbital  and  lateral  spine  all  acumi- 
nate with  edges  variably  granulate,  anterior  mar- 
gins of  teeth  a  bit  shorter  than  posterior  margins, 
tendency  to  development  of  a  shoulder  on  pos- 
terior margin  of  all  except  last  tooth  in  row.  Sur- 
face of  carapace  dorsally  smooth  and  glistening 
around  perimeter  (when  wet)  and  on  epibranchial 
surfaces;  central  portion  lightly  and  evenly  granu- 


late, cardiac  area  smooth  anteriorly,  granulate 
posteriorly.  Epibranchial  line  prominent  and  sulci 
on  central  part  of  carapace  deeply  etched. 

Chelipeds  with  sharply  granulate  ridges  and 
usual  spines;  fingers  of  major  chela  heavily 
toothed  but  not  gaping. 

Male  abdomen  and  telson  long,  extending 
nearly  to  juncture  between  thoracic  sternites  III 
and  IV;  telson  lanceolate,  much  longer  than  broad; 
sixth  segment  of  abdomen  broadened  distally. 
Mature  female  abdomen  and  telson  reaching  as 
far  forward  as  in  male,  sixth  segment  nearly  as 
long  as  fifth  and  with  mesiodistal  borders  oblique, 
not  markedly  curved;  telson  elongate  triangular 
with  inflated  sides.  First  gonopods  of  male  (Fig- 
ures 19a,  20n)  reaching  nearly  to  tip  of  telson 
beyond  suture  between  sternites  III  and  IV,  over- 
lapping in  proximal  half,  diverging  distally,  twist- 
ing mesioventrally  on  axis  lateral  to  abdominal 
locking  tubercle  on  thoracic  sternite  V  and  recurv- 
ing gradually  to  termination  near  midline;  armed 
distally  with  a  dorsolateral  narrow  band  of  large 
and  small  sharp  retrogressive  spinules.  Gono- 
pores  of  female  (Figure  22k)  ovate  in  outline  with 
apex  on  long  axis  directed  anteromesad;  aperture 
of  each  sloping  from  surface  along  long  mesial  side 
under  rounded,  sinuous  anterolateral  border 
superior  to  prominent  rounded  eminence  on  pos- 
terolateral border. 

Size  of  carapace  in  mm. — Largest  male:  length 
61,  width  at  base  of  lateral  spines  107,  including 
lateral  spines  134.  Largest  female:  length  66, 
width  at  base  of  lateral  spines  116,  including 
lateral  spines  141.  Summary  of  selected  mea- 
surements taken  from  the  small  sample  available 
is  given  in  Tables  1  and  2.  Manrique  Colchado 
(1965)  reported  a  male  with  length  62,  width 
including  lateral  spines  144,  and  a  female  with 
length  62,  width  including  lateral  spines  150. 

Color. — The  only  published  descriptions  of  color 
are  brief.  Pounds's  (1961)  general  account  indi- 
cated that  the  colors  are  "clear  shades  of  green 
and  blue  with  tints  of  red,  orange,  and  purple." 
Manrique  Colchado  (1965)  characterized  the 
carapace  as  obscure  or  dark  green.  Judging  by 
greenish  coloration  of  recently  preserved  speci- 
mens, both  descriptions  apply.  Underparts  are 
white. 

Distribution. — Mouth  of  Rio  Grande,  Texas- 
Mexico  border  to  southern  Veracruz,  Mexico  (Fig- 
ure 27). 


772 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Habitat. — Specimens  available  for  study  came 
from  estuarine  waters  of  ditches,  lagoons,  and 
river  mouths,  the  type  of  environment  reported  by 
Manrique  Colchado  (1965)  as  coastal  lagoons  of 
varying  salinity  at  depths  of  1-3  m. 

Spawning . — Although  mature  females  are  rep- 
resented in  the  small  study  collection,  none  are 
ovigerous. 

Remarks. — Apparently  an  isolate  of  C  bocourti 
stock  confined  to  the  western  and  southwestern 
Gulf  of  Mexico,  C.  rathbunae  has  various  an- 
gularities on  the  body  and  legs  more  accentuated 
than  in  C.  bocourti:  1)  acute  frontal  spines  con- 
trasted with  more  rounded  or  lobate  frontal  spines 
(excepting  juvenile  C.  rathbunae  from  Tamauli- 
pas  having  rounded  lobate  frontals);  2)  all  antero- 
lateral teeth  acute  (or  acuminate)  rather  than 
anterior  portion  of  series  being  rounded  at  tips; 
and  3)  hand  of  chelae  moderately  ridged  rather 
than  smoothly  rounded.  First  gonopods  of  mature 
male  C.  rathbunae  are  not  crossed  at  the  tips  and 
fall  a  bit  short  of  the  telson  tip  whereas  in  mature 
C.  bocourti  they  are  crossed  at  the  tips  and 
slightly  exceed  the  telson. 

Specimens  of  neither  species  from  Yucatan  are 
available,  thus  areas  of  possible  intergradation 
between  seemingly  close  relatives  have  not  been 
studied. 

Material. — Total:  10  lots,  18  specimens. 

USNM.  4  lots,  10  specimens. 

MEXICO 

Tamaulipas:  122925.  Rio  Soto  la  Marina  at  Soto 
la  Marina,  21  Jan.  1959,  1  9  (juv),  R.  R.  Miller  and 
R.  J.  Schultz,  M59-1. 

Veracruz:  122922,  Laguna  de  Alvarado,  27  Apr. 
1966,  1  <? ,  2  9,  S.  de  la  Campa,  E.  Ramirez  and  E. 
Chavez,  L.  B.  5093.  122923,  Laguna  de  Pueblo 
Viejo  off  the  corals,  4  Sept.  1964,  1  <J ,  1  9,  J.  A. 
Macias,  L.  B.  3333.  122924,  Rio  Tuxpan,  taken 
between  Cobos  and  the  Estero  Quetumilco,  21 
Nov.  1964,  2  0,  2  9,  R.  Marquez,  L.  B.  3632. 

A<5  with  carapace  30  mm  long  collected  from  Rio 
Grande  by  Trevino  and  sent  to  USNM  for 
identification  by  H.  Hildebrand,  4  Sept.  1956; 
identified  by  F.  A.  Chace,  Jr.,  and  returned  to 
sender. 

AHF.  2  lots,  3  specimens. 


MEXICO 

Veracruz:  Boca  del  Rio,  seined  in  shallow  water, 
9  Aug.  1949,  1  5,  1  9,  B.  W.  Halstead.  Drainage 
ditch  5  mi  W  Veracruz,  seined  in  brackish  water, 
19  Aug.  1949,  1  9  (juv),  B.  W.  Halstead. 

BMNH.  1  lot,  1  specimen. 

MEXICO 

65.29,  1  9,  (dry),  vi/7. 

RMNH.  1  lot,  2  specimens. 

MEXICO 

Veracruz:  21814,  Laguna  de  Pueblo  Viejo,  25 
Apr.  1964,  1  ^,  1  9,  F.  A.  Manrique  Colchado. 

Instituto  Nacional  de  Investigaciones  Biologico 
Pesqueras,  Mexico,  D.  F.  2  lots,  2  specimens. 

Tamaulipas:  Laguna  del  Chairel  y  rio  Tamesi, 
18  Aug.  1964,  1  cJ ,  J.  A.  Macias.  Veracruz:  Estero 
Jacome,  18  Dec.  1963,  1  9  (juv),  S.  Garcia. 

Supplementary  literature  record. — Mouth  of  Rio 
Grande,  Tex.  (Pounds,  1961). 

CALLINECTES  MARACAIBOENSIS 
TAISSOUN 

Figures  14,  19b,  20o,  221,  27 

Callinectes  sp.,  Taissoun,  1969,  p.  63,  fig.  23,  photo 
8. 

Callinectes  maracaiboensis  Taissoun,  1962,  p.  12, 
23,  figs,  le-h,  2  (part),  3  (part),  4,  9B,  lOA-B; 
photos  1-2  (col.),  3,  4m  (type:  i,  Museo  de 
Ciencias  Naturales,  Caracas,  Venezuela, 
Lago  de  Maracaibo,  Venezuela).-  1973,  p. 
28,  figs.  4F,  5E,  photo  3. 

Description. — Carapace  (Figure  14)  bearing 
four  triangular  frontal  teeth  with  tips  meeting  a 
nearly  common  level,  lateral  pair  moderately 
acute  with  mesial  side  having  a  flatter  angle  than 
lateral  side,  submesial  pair  much  narrower,  acute, 
sometimes  slightly  shorter  than  lateral  pair. 
Metagastric  area  with  length  and  posterior  width 
about  equal,  anterior  width  2  times  length.  An- 
terolateral margins  slightly  arcuate,  teeth  exclu- 
sive of  outer  orbital  and  lateral  spine  with  tips 
directed  outward,  tending  to  be  acuminate  espe- 
cially in  outer  portion  of  row,  posterior  margin  of 
teeth  usually  longer  than  and  more  granulate 


773 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


than  anterior  margin.  Surface  of  carapace  dor- 
sally  smooth  and  glistening  around  perimeter 
(when  wet)  and  on  epibranchial  and  posterolateral 
surfaces;  granules  scattered  on  epibranchial  sur- 
faces, progressively  more  crowded  on  proto-, 
meso-,  and  anterior  portion  of  metagastric  areas 
and  branchial  lobes  and  on  cardiac  area  (espe- 
cially posterior  slope).  Epibranchial  line  promi- 
nent and  relatively  uninterrupted,  sulci  on  cen- 
tral part  of  carapace  deeply  etched. 

Chelipeds  granulate  on  ridges,  fingers  of  major 
chela  heavily  toothed,  lower  margin  of  propodal 
finger  often  decurved  near  base  in  adults. 

Male  abdomen  and  telson  long,  extending  to 
anterior  quarter  of  thoracic  sternite  IV;  telson 
lanceolate,  much  longer  than  broad;  sixth  seg- 
ment of  abdomen  broadened  distally.  Mature 
female  abdomen  and  telson  reaching  at  least  as  far 
forward  as  in  male,  nearly  to  juncture  between 
thoracic  sternites  III  and  IV,  sixth  segment  as  long 
as  fifth  and  fully  rounded  at  its  distolateral 
corners,  telson  elongate-triangular  with  sides 
slightly  inflated.  First  gonopods  of  male  (Figures 
19b,  20o)  very  long,  often  extending  nearly  to  tip  of 
telson  and  crossed  near  tips;  sinuously  curved  and 
overlapping  in  two  places  proximally,  diverging 
distally,  twisting  mesioventrally  on  axis  lateral  to 
abdominal  locking  tubercles  on  thoracic  sternite 
V,  and  recurving  gradually  to  termination  near 
midline;  armed  distally  with  a  dorsolateral  band 
of  large  and  small  retrogressive  spinules.  Gono- 
pores  of  female  (Figure  221)  asymmetrically  ovate 
in  outline  with  apex  on  long  axis  directed  an- 
teromesad;  aperture  of  each  sloping  from  surface 
on  mesial  side  under  rounded  sinuous  anterolat- 
eral border  superior  to  rounded  lateral  and  much 
smaller  mesial  eminences  on  posterior  border. 

Size  of  carapace  in  mm. — Largest  male  avail- 
able: length  78,  width  at  base  of  lateral  spine  134, 
including  lateral  spines  159.  Largest  female 
available:  length  58,  width  at  base  of  lateral 
spines  102,  including  lateral  spines  124.  Taissoun 
(1972)  measured  large  samples  made  up  of  indi- 
viduals whose  mean  sizes  were  comparable  to  the 
above  specimens,  males  generally  being  larger 
than  females.  Summary  of  selected  measurements 
for  the  few  specimens  available  is  given  in 
Tables  1  and  2. 

The  following  account  is  from  Taissoun  (1972), 
the  only  person  who  has  studied  the  species  in 
detail. 


Color. — Adult  male:  carapace  olive  green  with 
tints  of  light  brown  and  blue  toward  central 
region,  anterolateral  region  with  light  chestnut 
areas.  Chelipeds  with  upper  portion  light  chestnut 
and  olive  green  with  orange  tints;  distal  portions 
of  merus,  internal  portion  of  carpus,  internal  and 
external  sides  of  fingers  intense  blue;  spines  of 
merus  brownish  orange  distally  with  tips  light 
chestnut  and  cream,  bases  obscure  brown;  distal 
tubercles  on  propodus  orange  and  intense  blue. 
Ambulatory  legs  cream  proximally,  blue  distally, 
articulations  with  tubercles  intense  orange. 
Swimming  legs  intense  blue  and  cream  dorsally, 
terminal  article  blue,  obscure  brown  and  light 
orange,  tubercles  orange.  Underparts  cream  and 
light  yellow,  except  anterior  portion  and 
pereopods  light  blue. 

Females:  as  males  but  with  more  intense  blue 
on  internal  part  of  chelipeds.  Taissoun  (1972) 
included  colored  illustrations,  but  the  female 
pictured  is  more  reddish  than  as  described  above. 

Variation. — Granulation  of  the  carapace  varies 
from  nearly  smooth  to  fairly  marked,  but  is  not  so 
prominent  as  in  some  specimens  of  C.  bocourti. 
Lateral  spines  of  males  are  occasionally  curved 
forward  at  the  tips,  but  in  females  are  often 
relatively  longer  and  straighter.  Meral  spines  on 
the  chelipeds  vary  in  number  as  usual  in  the  genus 
(four  or  five)  and  all  spines  become  worn  in  old 
individuals. 

Distribution . — Confined  to  the  Lago  de 
Maracaibo  estuarine  system,  roughly  120  km 
wide  X  215  km  long,  extending  from  Bahia  del 
Tablazo  emptying  into  Golfo  de  Venezuela  in 
north,  through  Estrecho  de  Maracaibo  southward 
into  Lake  proper. 

Habitat. — The  species  occurs  on  sandy  and 
muddy  bottoms,  and  among  roots  of  mangroves,  in 
brackish  to  occasionally  fresh  waters  containing 
much  silt  and  decomposing  organic  material.  Both 
C.  maracaiboensis  and  bocourti  occur  in  the  Lake 
and  its  outlet,  apparently  most  abundantly  near 
the  mouth  where  all  developmental  stages  of  both 
are  found,  but  the  majority  of  these  are  adult 
males  in  salinities  ranging  from  0.35  to  15.12/(o. 
Surface  temperatures  in  the  Lake  are  fairly  uni- 
form, ranging  from  27.2°  to  32°C,  and  undergoing 
a  diurnal  change  of  ±  1°C,  but  below  depths  of  10  m 
temperature  remains  even  more  uniform.  Tem- 


774 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


perature  of  surface  water  in  the  Golfo  de  Vene- 
zuela is  less  than  in  the  Lake  (28.6°C  in  October 
and  25.9°C  in  February  were  recorded  by  Taissoun 
(1972)). 

Spawning. — Adaptation  to  the  Lake  environ- 
ment is  shown  by  spawning  habits.  Ovigerous  C. 
maracaiboensis  were  occasionally  taken  in  Bahia 
del  Tablazo  and  Estrecho  de  Maracaibo  from  April 
to  August  where  salinity  ranged  from  3.15  to 
15.13^0.  Ovigerous  female  C.  bocourti  were  usu- 
ally found  in  the  Golfo  de  Venezuela  where  salin- 
ity varied  between  23.9  and  34.6%o,  and  only 
occasionally  in  the  fresher  Bahia  del  Tablazo. 

Economic  importance . — A  developing  fishery  in 
the  Lago  de  Maracaibo  region  employing  crab 
traps  concentrates  chiefly  on  C.  sapidus,  but 
includes  C.  maracaiboensis  and  C.  bocourti. 

Remarks . — Recognition  of  this  new  species  from 
a  restricted  geographic  range  comes  as  some 
surprise  in  view  of  the  broader  distribution  of 
other  members  of  the  genus.  There  is  no  doubt  that 
C.  bocourti,  maracaiboensis,  and  rathbunae  are 
very  closely  related,  the  widely  ranging  bocourti 
probably  being  the  parent  stock  from  which  the 
isolates  in  peripheral  areas  have  evolved. 
Callinectes  maracaiboensis  and  rathbunae  are 
similar  in  having  somewhat  less  robust  bodies 
than  bocourti,  smaller,  sharper,  outwardly  di- 
rected anterolateral  teeth  and,  in  adults,  more 
acuminate  frontal  teeth.  In  this  regard, 
Taissoun 's  (1972:10)  outlined  median  saggital 
sections  of  the  three  species  do  not  seem  to 
represent  the  average.  Shape  of  abdomen  in  adult 
females  is  another  useful  character,  that  of  C. 
maracaiboensis  being  somewhat  smaller,  having 
a  sixth  segment  short  and  evenly  rounded  on  the 
distal  edge,  but  narrower  than  in  rathbunae. 
Typically  mature  C.  bocourti  females  have  a 
relatively  smaller  abdomen  than  either  of  the 
others,  with  the  distal  edge  of  the  sixth  segment 
being  somewhat  angular  distolaterally  rather 
than  broadly  rounded. 

Taissoun  (1972)  marshalled  evidence  for  es- 
tuarine  adaptations  in  C.  maracaiboensis,  which 
apparently  parallels  similar  trends  in  engraulid 
fishes,  the  whole  process  presumably  being  as- 
sociated with  isolation  of  the  Lake  accompanying 
fall  in  sea  level  during  the  Pleistocene.  The 
habitat  of  this  species  suggests  interesting  com- 
parative experiments  on  larval  development  of  a 


form  adapted  to  living  in  lowered  salinity 
throughout  life  as  contrasted  with  the  other  more 
catadromous  species  of  the  genus. 

Material. — Total:  4  lots,  16  specimens. 

USNM 

VENEZUELA 

139621,  Lago  de  Maracaibo,  19  July  1970, 1  5, 1 
$  (Paratypes),  E.  Taissoun.  143392,  Lago  de 
Maracaibo,  no  date,  5  <? ,  1 9 ,  E.  Taissoun.  143391, 
Lago  de  Maracaibo,  23  June  1972,  5  5,  1  9,  E. 
Taissoun.  143393  Puerto  Caballo,  Maracaibo, 
Lago  de  Maracaibo,  17  June  1968,  I  $  ,  1  9,  E. 
Taissoun. 

CALLINECTES  LATIMANUS 
RATHBUN 

Figures  15,  19c,  20p,  23a,  27 

Callinectes  bocourti.-  Rathbun,  1896,  p.  362  (part), 
fide  Rathbun,  1921.-  1897,  p.  151  (part), 
fide  Rathbun,  1921.-  1900a,  p.  290.-  Balss, 
1921,  p.  58. 

Callinectes  latimanus  Rathbun,  1897,  p.  151, 
text-figs.  6-8  (syntypes:  4<5  ,  3  9,  BMNH 
91.4.1.63/69;  1  ?, ,  USNM  19877;  Lagos, 
Bight  of  Benin,  Guinea  [Nigeria],  A.  Molo- 
ny).-  1900a,  p.  291.-  1921,  p.  398,  text-fig.  4, 
pi.  XV,  fig.  2,  pi.  XXL  pl.  XXII,  fig.  1.- 
Odhner,  1923,  p.  22.-  Monod,  1927,  p.  606.- 
1956,  p.  211,  figs.  240-  243.-  Irvine,  1947,  p. 
297,  fig.  202  [?].-  Vilela,  1949,  p.  58.-  Capart, 
1951,  p.  132,  fig.  47.-  Rossignol,  1957,  p.  82.- 
1962,  p.  1 16.-  Forest  and  Guinot,  1966,  p.  65. 

Neptunus  marginatus  var.  truncata  Aurivillius, 
1898,  p.  5,  pl.  1,  figs.  1-4  (type:  1  immature  9 
[not  $],  fide  Rathbun,  1921,  Cameroon). 

Callinectes  diacanthus  var.  africanus .-  A.  Milne 
Edwards  and  Bouvier,  1900,  p.  71  (not  col. 
pl.  4,  fig.  5  =  C.  sapidus).-  Lenz,  1910,  p.  125 
[5].-  Gruvel,  1912,  p.  3,  6,  pl.  2,  fig.  1. 

Callinectes  marginatus .-  Odhner,  1923,  p.  21. 

Callanectes  Sp.  (?).-  Irvine,  1932,  p.  14,  fig.  13. 

Description. — Carapace  (Figure  15)  bearing 
four  frontal  teeth  with  variably  rounded  tips, 
submesial  pair  shorter  than  lateral  pair.  Metagas- 
tric  area  with  length  approximately  equal  to 
posterior  width,  anterior  width  about  2  times 
length.    Anterolateral    margins    moderately 


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FISHERY  BULLETIN:  VOL.  72,  NO.  3 


arched,  anterolateral  teeth  exclusive  of  outer 
orbital  and  lateral  spine  varying  from  acute  with 
serrate  margins  to  increasingly  acuminate  and 
forward  curving  with  nearly  smooth  margins  at 
lateral  end  of  row.  Lateral  spine  relatively  stout. 
Surface  of  carapace  coarsely  granulate,  but 
granules  more  widely  spaced  or  absent  near  mar- 
gins, on  epibranchial  surfaces,  and  along  regional 
sulci;  most  closely  crowded  granules  on  mesogas- 
tric,  cardiac,  and  mesobranchial  areas.  Epibran- 
chial line  prominent  and  nearly  uninterrupted. 

Chelipeds  with  propodus  and  carpus  moderately 
ridged,  granules  on  dorsal  and  lateral  ridges 
becoming  smooth  with  age;  chelae  of  large  speci- 
mens very  strong,  major  one  often  very  broad  with 
fingers  heavily  toothed  (if  not  worn),  lower  margin 
of  propodal  finger  often  decurved  near  base  oppo- 
site enlarged  basal  tooth  of  dactylus. 

Male  abdomen  and  telson  reaching  beyond  mid- 
length  of  thoracic  sternite  IV;  telson  lanceolate, 
much  longer  than  broad;  sixth  segment  of  abdo- 
men broadened  distally.  Mature  female  abdomen 
and  telson  reaching  about  midlength  of  thoracic 
sternite  IV;  telson  elongate  triangular  with 
inflated  sides,  sixth  segment  longer  than  fifth. 
First  gonopods  of  male  (Figures  19c,  20p)  very 
long,  usually  exceeding  telson  and  crossed  near 
tips;  sinuously  curved  and  overlapping  proxi- 
mally,  diverging  distally,  twisting  mesioventrally 
on  axis  lateral  to  abdominal  locking  tubercle  and 
recurving  to  termination  near  midline;  armed 
distally  with  dorsolateral  band  of  large  and  small 
retrogressive  spinules.  Gonopores  of  female  (Fig- 
ure 23a)  ovate  in  outline  with  apex  on  long  axis 
directed  anteromesad;  aperture  of  each  sloping 
from  surface  on  mesial  side  under  rounded,  sinu- 
ous anterolateral  border  superior  to  a  rounded 
eminence  on  posterior  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
71,  width  at  base  of  lateral  spines  125,  including 
lateral  spines  151.  Largest  female:  length  59, 
width  at  base  of  lateral  spines  105,  including 
lateral  spines  127.  Summary  of  selected  mea- 
surements is  given  in  Tables  1  and  2.  The  species 
is  characteristically  large  at  adult  size,  Irvine 
(1947)  reporting  carapace  widths  of  8-12  inches 
(20-30  cm). 

Color. — Uniform  greenish  brown  with  articula- 
tions and  internal  face  of  chela  and  dactyl  bluish; 
ventral  aspect  yellowish  white  (Rossignol,  1957). 
Khaki  colored  with  bluish  tinge  and  bluish  legs 


(Irvine,  1932,  1947);  predominantly  brown, 
perhaps  where  waters  are  often  turbid  with  silt 
(Longhurst,  1958).  A  mottled  olive  coloration 
persists  at  least  as  long  as  20  yr  in  some  preserved 
specimens. 

Variation . — Aptly  named  for  one  of  their  most 
distinctive  features,  adults  of  C  latimanus  have 
broad  major  chelae.  Chelae  with  worn  tooth  rows 
and  gaping  fingers  seem  disproportionately  large 
in  old  males,  and  in  their  smooth  surfaces  these 
may  resemble  the  hands  of  C.  bocourti  (excellent 
example,  AMNH  3111),  but  the  entire  cheliped  is 
shorter  and  thicker  than  in  that  species.  There  is 
usually  a  strongly  developed  proximal  tooth  on 
the  dactyl  of  the  major  hand  and  opposite  it  a 
strongly  decurved  propodal  finger.  The  minor 
chela  (normally  left)  is  much  slimmer  than  the 
major,  its  two  fingers  toothed  with  meshing  secto- 
rial triads  or  variants  of  this  pattern. 

Especially  in  juveniles,  the  submesial  pair  of 
frontal  teeth  often  overhangs  and  obscures  the 
epistomial  tooth,  though  not  so  completely  as  in  C. 
toxotes.  Adult  females  have  coarse  granulations 
over  the  whole  carapace  though  not  so  closely 
crowded  at  the  edges  as  in  central  elevated  parts 
behind  the  epibranchial  line.  There  are  smooth 
areas  between  more  scattered  granules  in  front  of 
the  epibranchial  line  in  both  sexes. 

First  gonopods  of  males  rnay  extend  beyond  the 
telson. 

Distribution.— Baie  de  Saint-Jean  [19°27'N, 
16°22'W],  Mauritania,  to  Cabinda,  Angola  (Fig- 
ure 27).  (Perhaps  farther  south  in  Angola  on  basis 
of  published  accounts  such  as  Gruvel  [1912]  and 
Monod  [1956],  and  specimens  of  uncertain  origin 
[AMNH  5895].) 

Habitat. — In  a  category  Longhurst  (1958)  called 
"mobile  invertebrates,"  the  most  important  es- 
tuarine  species  in  the  Sierra  Leone  River  (site 
studied)  appeared  to  be  C.  latimanus  and 
Parapenaeopsis  atlantica  Balss.  Neither  of  these 
was  completely  restricted  to  the  estuary  but  oc- 
curred only  sporadically  outside  it.  Callinectes 
latimanus  was  most  abundant  in  the  mides- 
tuarine  region  in  many  of  the  otter-trawl  hauls, 
and  extended  far  up  creeks  to  low-salinity  water. 
Sourie  (1954b)  found  C.  latimanus  widely  distrib- 
uted in  estuaries  of  Senegal  ranging  from  fresh 
water  to  salt  concentrations  near  saturation,  and 
Gruvel  (1912)  reported  brackish  water  habitats  in 


776 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Ghana  where  the  species  abounds  on  muddy 
bottoms.  Crosnier  (1964,  and  pers.  data)  and  a 
number  of  others  listed  the  depth  range  as  0-35  m 
in  warm  water. 

Callinectes  latimanus  is  preyed  upon  by 
Galeoides  decadactylus  Bloch  and  Pomadasys 
jubelini  Cuvier  (Longhurst,  19bl) ,  and  Callinectes 
sp.  [probably  latimanus]  by  Dasyatus  margarita 
Gunther  and  Caranx  alexandrinus  Cuvier  and 
Valenciennes  (Monod,.1927). 

Spawning. — In  all  museum  material  available 
to  me  only  four  collections  that  are  dated  contain 
ovigerous  females:  January-February,  Ivory 
Coast;  May,  Senegal,  Nigeria;  October,  Togo. 
In  the  warm  West  African  region  it  is  likely  that 
spawning  occurs  the  year  round,  but  may  be  con- 
centrated at  seasonal  peaks. 

Economic  importance . — There  is  no  literature 
on  strictly  commercial  aspects  of  a  fishery  for  this 
species,  but  it  is  important  as  food  in  coastal 
communities.  Rathbun  ( 1900a)  recounted  an  early 
report  that  the  crab  was  found  only  in  fresh  water 
of  rivers,  and  much  sought  after  for  the  exception- 
ally good  meat.  Monod  (1927)  listed  C.  latimanus 
as  common  in  the  Cameroons  and  customarily 
eaten  there.  Gruvel  (1912)  wrote  that  it  is  ex- 
tremely abundant  along  the  coast  from  Senegal  to 
Angola,  and  so  much  so  in  certain  areas  such  as 
the  Ivory  Coast,  Dahomey,  etc.,  that  the  people 
there  brought  large  basketfulls  alive  to  the  mar- 
kets to  be  either  boiled  in  water  or  fried  in  palm 
oil.  He  regarded  the  crabs  as  extremely  tasty  and 
therefore  subjects  for  a  fishery,  at  least  from 
Senegal  to  the  Cameroons,  where  they  were  cap- 
tured around  lagoons  and  among  mangroves  in 
brackish  water,  generally  on  mud  bottom,  by 
means  of  small  seines,  baited  traps,  or  fishing 
lines.  Irvine  (1947)  listed  similar  fishing  methods 
and  considered  the  crabs  quite  edible,  while  Ros- 
signol  (1957,  1962)  considered  this  crab  the  most 
abundant  in  the  genus,  subject  to  a  regular  fishery 
by  native  peoples  in  estuaries  and  lagoons,  and 
although  acceptable,  not  always  so  savory  as 
Portunus  validus  Herklots. 

Remarks. — The  syntype  male  in  the  USNM 
(19877)  is  a  mature  specimen  with  first  gonopods 
extending  beyond  the  telson,  a  quite  sharply 
granulate  carapace  with  acute  anterolateral  teeth 
(especially  from  the  fourth  tooth  laterad),  and  a 
left  chela  with  strong  proximal  tooth  on  the  dactyl 


heavier  than  the  right,  but  it  is  a  poor  specimen 
because  both  chelipeds  are  detached  from  the  body 
and  parts  of  other  legs  are  detached  or  missing. 
The  series  of  syntypes  in  the  BMNH  (9J. 4. 1.63/69) 
is  in  much  better  condition,  consisting  of  two 
mature  and  two  immature  males,  and  one  mature 
and  two  immature  females.  The  largest  male  is 
the  most  perfect  specimen,  and  the  first  gonopods 
on  it  exceed  the  tip  of  the  telson. 

The  early  confusion  of  this  species  with  the 
American  C.  bocourti  is  easy  to  understand  be- 
cause each  is  described  comparatively  in  terms  of 
the  other,  the  relationships  being  obviously  close. 

Material. — Total:  39  lots,  116  specimens. 

USNM.  9  lots,  16  specimens. 

SENEGAL 

18735,  no  date,  1  5  juv,  from  Mus.  Nat.  Hist., 
Paris. 

LIBERIA 

123087,  Robertsport,  Grand  Cape  Mount  Co.,  28 
Dec.  1947,  1  9,  J.  T.  Baldwin,  Jr. 

NIGERIA 

120943,  Lagos,  06°28'N,  03°23'E,  10  May  1965, 
1  9,Pillsbury.  Lagos,  Guinea  [=  Nigeria],  no  date, 
1  6,  A.  Molony,  (Type). 

ANNOBON  ISLAND 

120944,  01°24'S,05°37'E,  20  May  1965,  2^,2 
inv,Pillsbury,  Stn.  281. 

ZAIRE 

54253,  54254,  54310,  Banana,  mouth  of  Congo 
River,  July- Aug.  1915,  5  ^  ,  2  9 ,  H.  Lang. 

AMNH.  6  lots,  15  specimens. 

ZAIRE 

3326,  no  date,  1  <5 ,  Congo  Exped.  3110,  3111, 
3112,  3417,  Banana,  July-Aug.  1915,  7  5(1  dry),  4 
9  (1  juv),  H.  Lang  and  J.  Chapin. 

ANGOLA  [?] 

5895,  1925,  2  9,  Vernay  Angola  Exped. 

BMNH.  6  lots,  17  specimens. 

SIERRA  LEONE 

1916.6.23.1/2,  Gbanbama,  1  5,  1  9,  N.  W. 
Thomas.  1922.9.13.6/7,  Sherbo  I.,  2  9,  C.  H.  Allan. 


777 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


GHANA 

Accra,  no  date,  Ic?  ,  1  9,  F.  R.  Irvine. 

NIGERIA 

91.4.1.63/69,  Lagos,  Bight  of  Benin,  4  ^  ,  3  2  (2 
juv),  A.  Moloney,  (Types).  1948.4.30.1/2,  Lekki 
Lagoon,  16.2.1947,  2  S  ,  Trewavas. 

ANGOLA 

1912.4.2.4/5,  Chiloango  River,  Cabinda,  July 
1911,  2  S,  Ansorge. 

MNHNP.  5  lots,  7  specimens. 

GAMBIA 

Basse,  Cote  de  Troire,  1907,  1 S  ,  Bouet. 

SENEGAL 

No  number,  15,1  2  juv,  date  and  col.  unknown. 
Bignona,  May  1946,  2  5,  P.  L.  De  Keyser  and  A. 
Villiers. 

GUINEA 

Conakry,  Guinee,  1  2,  Inst.  Fr.  d'Afrique  Noire. 

CONGO 

1892-94,  1  S  juv,  Dybowski. 

RMNH.  6  lots,  20  specimens. 

LIBERIA 

Grand  Cape  Mount,  1881,  1  c^ ,  J.  Biittikofer  and 
J.  A.  Sala.  1864,  Fishermans  Lake,  [35  mi  NW 
Monrovia],  among  stones,  Jan.  1881,  juv  2  c?,  2  2,  J. 
Biittikofer  and  J.  A.  Sala. 

GHANA 

376,  St.  George  d'Elmina,  1  S,  H.  S.  Pel. 

NIGERIA 

20614,  Lagos  harbor,  23  May  1964,  1  2  (ov), 
Pillsbury.  15533,  Niger  Delta,  May-Aug.  1960,  3 
3,  3  2,  H.  J.  G.  Beets. 

CONGO 

No  number,  1880,  (juv)  2  <? ,  5  2,  T.  Kamerman. 

UNC-IMS.  7  lots,  41  specimens,  from  A.  Cros- 
nier. 

TOGO 

2733,  Lagune  D'Anecho,  5  (^,  3  2,  A.  Stauch. 
2734,  Cotes  du  Togo,  06°06'30"N,  01°37'30"E,  16 
Oct.  1963,  1  2  (ov),  A.  Crosnier. 


CAMEROON 

2735,  Cotes  du  Cameroun,  03°34'N,  09°35'E,  23 
Aug.  1963,  1  2,  A.  Crosnier. 

CONGO 

2736,  Lagune  de  Zambi  [03°58'S,  11°17'E],  13 
May,  1964,  2  2,  A.  Stauch.  2737,  Lagune  de 
Conkouati  [03°58'S,  iri9'E],  14  May  1964, 1 2, 17 
juv,  A.  Stauch.  2738,  Plage  de  Pointe-Noire,  no 
date,  2  <S ,  2  2.  A.  Crosnier.  2739,  Plage  de  Pointe- 
Noire,  July  1963,  4  <J,  4  2,  A.  Crosnier. 

Supplementary  literature  records. — Baie  de 
Saint-Jean  [19°27'N,  16°22'W],  Mauritania;  St. 
Louis,  Yof,  Sobane  [=  Sobene?],  Bignona,  Sedhiou 
+  3  nearby  localities,  Ziguinchor,  Senegal;  Tam- 
ara.  He  Poulet,  Guinea;  Abidjan,  Lagune  Ebrie, 
Baie  de  Cocody,  Ivory  Coast;  near  Densu,  Gold 
Coast  [=  Ghana]  (Monod,  1956);  Bissau,  porto  de 
Biombo,  Ilheu  de  Ancora,  Portuguese  Guinea 
(Vilela,  1949);  Sierra  Leone  River  (Longhurst, 
1958);  Gold  Coast  (Irvine,  1947);  Fernando  Poo 
(Crosnier,  1964);  Principe  I.  (Forest  and  Guinot, 
1966);  Senaga,  Cameroon  (Odhner,  1923);  Songolo 
[=  Songololo],  Loya,  Longo,  Djeno,  Congo  (Rossig- 
nol,  1957). 

CALLINECTES  SAPIDUS  RATHBUN 
Blue  Crab 

Figures  1,  16,  17,  19d,  21,  23b-c,  26 

Portunus  hastatus.-  Bosc,  1802,  p.  212-214,219.- 
1830,  p.  234. 

Lupa  hastata.-  Say,  1817,  p.  65  (not  L.  hastata 
Desmarest,  1832  =  Cancer  hastatus 
Linnaeus,  1767). 

Portunus  diacantha  Latreille,  1825,  p.  190  (vari- 
ety) (type  localities:  North  America,  Antil- 
les, Brazil,  etc.;  types  not  extant;  restricted 
to  Philadelphia,  Pa.,  by  Holthuis,  1962,  p. 
232;  name  suppressed  by  International 
Commission  of  Zoological  Nomenclature, 
Opinion  712  [1964,  p.  336]). 

ILupea  dicantha.-  H.  Milne  Edwards,  1834,  p.  451 
(part). 

Lupa  dicantha.-  Gould,  1841,  p.  324.-  de  Kay, 
1844,  p.  10,  pi.  3,  fig.  3.-  Holmes,  1858,  p.  9 
(fossil). 

Callinectes  diacanthus.-  Stimpson,  1860,  p.  220.- 
Young,  1900,  p.  186  (part). 

Callinectes  hastatus .-  Ordw ay ,  1863,  p.  568  [3].- A. 
Milne  Edwards,   1879,  p.  224  (var.  of  C. 


778 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


diacanthus) .-  R.  Rathbun,  1884,  1893,  p. 
775,  pi.  267.-  Young,  1900,  p.  187  (var.  of  C. 
diacanthus). 

?Neptunus  hastatus.-  Brocchi,  1875,  p.  55,  pi.  16, 
fig.  81. 

Neptunus  (Callinectes)  diacanthus.-  Ortmann, 
1894,  p.  77  (part:  specimens  g,  Florida;  1, 
Brazil;  n,  Haiti). 

Callinectes  sapidus  Rathbun,  1896,  p.  352,  pi.  12; 
pi.  24,  fig.  1;  pi.  25,  fig.  1;  pi.  26,  fig.  1;  pi.  27, 
fig.  1  (type  locality  restricted  to  "east  coast 
ofUnited  States"  by  Williams,  1965).- 1929, 
p.  31,  fig.  41.-  1930,  p.  99,  text-figs.  15a,  16c, 
17c,  18a,  19,  pi.  47.-  Bouvier,  1901,  p.  16.- 
Clark,  1906,  p.  172,  pi.  41,  figs.  1-3  (fossil).- 
Verrill,  1908a,  p.  370,  text-figs.  22a,  23a,  24, 
pi.  17,  fig.  2.-  Hay  and  Shore,  1918,  p.  432,  pi. 
35,  fig.  1.-  Chace,  1940,  p.  33.-  Chace  and 
Hobbs,  1969,  p.  133,  figs.  36,  37f.-  Balss, 
1957,  p.  1641.-  Holthuis,  1961,  p.  50,  pi.  1, 
fig.  2,  pi.  2,  fig.  2.-  1969,  p.  34,  pi.  1.-  Hol- 
thuis and  Gottlieb,  1955,  p.  91,  pi.  3,  fig. 
11.-  Pounds,  1961,  p.  42,  unnumbered  col. 
frontis.,  unnumbered  text-fig.  p.  9,  text-figs. 
1-2,  pi.  7,  figs.  1, 2a.-  Futch,  1965,  p.  2,  figs.  1, 
2,  3,  4,  5c.-  Williams,  1965,  p.  168,  fig.  151.- 
Christiansen,  1969,  p.  72,  fig.  29.-  Taissoun, 
1969,  p.  37,  photos  3-6,  figs.  IIA-D.- 1973,  p. 
34,  figs.  4E,  5F,  photo  5. 

Callinectes  sapidus  acutidens  Rathbun,  1896,  p. 
354,  pi.  13;  pi.  24,  fig.  2  (type:  ^,  MCZ  4696, 
Santa  Cruz  [Estado  de  Bahia]  Brazil, 
Thayer  Exped.).-1901,  p.  47.-  1930,  p.  Ill, 
text-fig.  15  c,  pi.  48.-  1933,  p.  48.-  Young, 
1900,  p.  191.-  Contreras,  1930,  p.  228,  fig.  1.- 
Pretzmann,  1966,  p.  305,  2  pis.-  Bulgurkov, 
1968,  fig.  1. 

Callinectes  africanus.-  A.  Milne  Edwards  and 
Bouvier,  1900,  pi.  4,  fig.  5  (not  p.  71,  var.  of 
C  diacanthus  =  C.  marginatus). 

Description. — Carapace  (Figures  16,  17)  bear- 
ing two  broad  either  obtuse  or  acuminate,  triangu- 
lar frontal  teeth  with  mesial  slopes  (incorporating 
a  pair  of  rudimentary  submesial  teeth)  longer 
than  lateral  slopes.  Metagastric  area  with  pos- 
terior width  approximately  1.2  times  length,  an- 
terior width  about  2  times  length.  Anterolateral 
margins  slightly  arched;  anterolateral  teeth  ex- 
clusive of  outer  orbital  and  lateral  spine  obtuse  to 
acuminate  and  directed  outward  more  than  for- 
ward. Much  of  surface  smooth,  with  scattered 
granules,  but  granules  concentrated  locally  on 


mesobranchial,  posterior  slope  of  cardiac,  and 
anterior  portion  of  mesogastric  area;  a  tendency  to 
crowding  of  granules  into  transverse  ridge  at 
summit  of  cardiac  and  mesobranchial  area  in 
some  individuals.  Sculpturing  of  surface  varying 
individually  from  low  to  raised  relief.  Lateral 
spines  varying  from  rather  stout,  blunt,  and 
forward  trending  to  slender,  elongate,  and  slightly 
backward  trending.  Epibranchial  line  nearly 
straight  over  branchial  region,  otherwise  sinu- 
ously curved. 

Propodus  and  carpus  of  chelipeds  with  moderate 
finely  granulate  ridges,  width  of  chelae  similar, 
propodal  finger  of  major  hand  occasionally  with 
lower  margin  decurved  proximally. 

Male  abdomen  and  telson  reaching  about  mid- 
length  of  thoracic  sternite  IV;  telson  lanceolate, 
much  longer  than  broad;  sixth  segment  of  abdo- 
men broadened  distally.  Mature  female  abdomen 
and  telson  reaching  about  midlength  of  thoracic 
sternite  IV;  telson  with  inflated  sides  almost 
equilaterally  triangular,  fifth  and  sixth  abdomi- 
nal segments  equal  in  length.  First  gonopods  of 
male  (Figures  19d,  21)  very  long,  reaching  beyond 
suture  between  thoracic  sternites  IV  and  V  but  not 
exceeding  telson;  sinuously  curved  and  overlap- 
ping proximally,  diverging  distally,  twisting 
mesioventrally  on  axis  lateral  to  abdominal  lock- 
ing tubercle  and  recurving  to  termination  near 
midline;  armed  distally  with  row  of  large  and 
small  retrogressive  spinules  following  ventral  and 
lateral  borders  with  twist  of  axis;  tip  membran- 
ous, flared  portion  suggesting  an  elongate  quad- 
rilateral in  outline.  Gonopores  of  female  (Figure 
23b,  c)  paraboloid  in  outline  with  apex  on  long  axis 
directed  anteromesad,  aperture  of  each  sloping 
from  surface  on  mesial  side  under  irregularly 
rounded  and  linearly  wrinkled  anterior  border 
superior  to  bulbous  posterolateral  border. 

Size  of  carapace  in  mm. — Largest  male:  length 
91,  width  at  base  of  lateral  spines  168,  including 
lateral  spines  209.  Largest  female:  length  75, 
width  at  base  of  lateral  spines  143,  including 
lateral  spines  204.  Mature  size  of  females  varies 
considerably,  the  smallest  examined  having  a 
carapace  length  of  21,  width  at  base  of  lateral 
spines  41,  including  lateral  spines  55.  Summary  of 
selected  measurements  is  given  in  Tables  1  and  2. 

Pretzmann  (1966)  discussed  a  large  immature 
female  with  acute  spines:  length  65,  width  132.5. 
The  largest  immature  female  I  have  seen,  also 
with  fairly  acute  spines,  reached  a  carapace 


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FISHERY  BULLETIN:  VOL.  72.  NO.  3 


length  of  60,  width  at  base  of  lateral  spines  109, 
including  lateral  spines  135.  Some  others  in  ma- 
terial studied  approached  this  size.  All  such  speci- 
mens seen  by  me  are  from  the  Gulf  of  Mexico  and 
may  represent  parasitized  individuals  in  which 
the  maturation  process  has  been  altered. 

Co/or.— Grayish,  bluish,  or  brownish  green  of 
varying  shades  and  tints  dorsally  on  carapace  and 
chelipeds;  spines  may  have  reddish  tints,  tuber- 
cles at  articulations  of  legs  orange,  and  legs 
varyingly  blua.and  white  with  traces  of  red  or 
brownish  green.  Males  with  propodi  of  chelae  blue 
on  inner  and  outer  surfaces,  fingers  blue  on  inner 
and  white  on  outer  surfaces  and  tipped  with  red. 
Mature  females  with  orange  fingers  on  chelae 
tipped  with  purple.  Underparts  off-white  with 
tints  of  yellow  and  pink.  Futch  (1965)  and  Tais- 
soun  (1969)  gave  a  good  description  of  color; 
De  Kay  { 1844),  Milne  Edwards  and  Bouvier  ( 1900; 
plate  IV,  Figure  5),  Churchill  (1919),  and  Pounds 
(1961)  published  colored  illustrations  of  the 
species,  and  still  others  are  scattered  in  popular 
literature. 

Color  variations  other  than  those  associated 
with  sexual  dimorphism  and  molt  cycle  are 
known.  Albinos  or  partial  albinos  are  in  museum 
collections  and  have  been  reported  both  in  sys- 
tematic literature  and  elsewhere  (Gowanloch, 
1952;  Sims  and  Joyce,  1966).  Haefner  (1961) 
reported  an  adult  male  lacking  dorsal  green  col- 
oration and  bright  blue  and  scarlet  markings  on 
the  legs.  Instead,  the  upper  surface  of  the  carapace 
was  "robins  egg  blue"  and  the  appendages  were 
paler  than  usual,  but  the  abdomen  and  underparts 
had  normal  color.  A  similar  blue  specimen  was 
reported  elsewhere  (Maryland  Tidewater  News, 
1950).  Haefner  also  pictured  a  bilateral  gray  and 
brown  colored  specimen  from  the  collection  of  L. 
Eugene  Cronin.  Hopkins  (1962,  1963)  discussed 
biochemistry  of  the  sexual  color  dimorphism. 

Variation. — There  are  morphological  varia- 
tions in  this  species  having  far  greater  systematic 
interest  than  size  and  color.  Study  of  many  speci- 
mens from  throughout  the  range  of  the  species 
bears  out  the  conclusion  of  Chace  and  Hobbs 
(1969)  that  extreme  variants  "are  so  different 
from  each  other  that  they  could  easily  be  inter- 
preted as  distinct  species,"  but  there  is  "no  point 
of  demarcation" — morphological,  geographic, 
bathymetric — between  the  "typical"  rather 
blunt-spined  form  predominating  along  the  east 


coast  of  the  United  States  and  the  acute-spined 
form  named  C.  sapidus  acutidens  by  Rathbun 
predominating  from  Florida  southward. 

Rathbun  (1896)  characterized  the  "acutidens" 
form  (paraphrasing)  as  being  wider  than  the 
"typical"  with  all  prominences  more  strongly 
marked,  areolations  separated  by  deeper  depres- 
sions, granules  more  raised,  gastric  ridges 
stronger  and  more  sinuous,  a  transverse  granu- 
late ridge  on  each  cardiac  lobe,  frontal  teeth 
narrower  and  more  acute  and  bearing  two  small 
intervening  teeth,  anterolateral  teeth  broad  at 
base  and  narrowing  abruptly  to  long  acuminate 
tips  with  margins  granulate,  lateral  spines  longer 
than  in  "typical"  specimens  of  equal  size,  and 
tidges  of  chelipeds  quite  prominent  and  strongly 
granulate.  Figures  16  and  17  show  two  extremes, 
the  first  a  mature  young  male  of  typical  form,  and 
the  second  a  mature  male  of  "acutidens"  form. 

I  thought  for  a  time  that  a  species  distributed 
through  approximately  85°  of  latitude  from  North 
Temperate  through  Tropic  to  South  Temperate 
Zones  might  reflect  responses  to  temperature  in 
spination  or  other  characters,  "typicaF '  structure 
being  prevalent  in  the  temperate  zones  and  sharp 
spination  in  the  tropics,  the  differences  thereby 
justifying  nomenclatural  recognition.  There  is 
weak  but  inconsistent  evidence  for  this  pattern. 
Though  "acutidens"  individuals  are  uncommon 
outside  the  tropics,  intermediates  occur  every- 
where to  some  degree,  and  some  "typical"  indi- 
viduals occur  in  the  tropics.  Genetic  pooling  or 
environmental  response  reflected  in  morphology 
seems  poorly  structured. 

For  example:  Occasional  specimens  found  as  far 
north  as  Woods  Hole,  Mass.,  (USNM  4946,  40723, 
43178)  are  nearly  as  sharp  spined  as  some  Carib- 
bean material.  Churchill  (1919,  plates  53-54) 
pictured  individuals  from  Chesapeake  Bay  that 
approach  the  "acutidens"  form.  In  the  collection 
of  the  USNM  is  a  huge  male  from  Wye  River,  Md., 
(92452)  that  has  acuminate  anterolateral  and 
suborbital  teeth,  though  not  so  attenuated  as  in 
Florida  material;  two  carapaces  from  Virginia 
(76184)  have  such  acute  spines  that  Rathbun 
identified  them  as  the  "acutidens"  form;  and  a 
huge  lot  (60601)  from  Hatteras,  N.C.,  composed  of 
mainly  "typical"  blunt-spined  individuals 
characteristic  of  eastern  United  States  shows 
variation  in  frontal  teeth  from  no  submesial 
frontals  to  rudimentary  evidence  for  their  pres- 
ence. In  Maryland,  few  specimens  examined  show 
easily  identifiable  submesial  teeth  on  the  inner 


780 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


slopes  of  the  prominent  frontal  teeth,  but  in 
material  from  Louisiana  there  is  a  tendency  to 
development  of  the  submesial  frontals,  and  the 
anterolateral  teeth  are  generally  more  acute  than 
in  Chesapeake  Bay  material.  Specimens  from 
Veracruz,  Mexico,  in  the  AHF  collection  show 
rather  blunt  frontal  but  acuminate  anterolateral 
teeth  and  rather  prominent  regions  on  the 
carapace.  Most  specimens  from  southern  Florida 
to  southern  Brazil  approach  the  "acutidens" 
form,  but  throughout  this  vast  region  there  is 
much  variation. 

The  sharpest-  and  longest-spined  forms  with 
most  prominent  development  of  rudimentary 
submesial  frontal  teeth  occur  in  the  western 
Caribbean  Sea  along  the  Guatemala-Panama 
coast.  These  individuals  also  have  regions  on  the 
carapace  more  deeply  and  sharply  sculptured  than 
in  the  "typical"  form,  sharp  granulation  on  both 
carapace  and  chelipeds,  and  cardiac  and  to  some 
extent  mesobranchial  regions  exhibiting  a  crowd- 
ing of  granules  at  the  apex  leading  to  formation  of 
slight  transverse  ridges,  but  with  the  anterior 
slopes  of  these  regions  lacking  granules.  While 
some  specimens  from  Puerto  Rico  approach  those 
from  the  western  Caribbean  in  ornamentation, 
there  is  a  mixture  of  "typical"  features  in  many 
individuals,  as  elsewhere  in  the  Antilles.  Perhaps 
the  best  illustration  of  mingling  features  is  illus- 
trated by  three  lots  of  specimens  in  the  RMNH.  In 
23404  from  Trinidad  are  two  males.  Both  have 
crowding  of  granules  into  a  transverse  ridge  on 
the  cardiac  lobes  with  largest  granules  behind  and 
fewer  on  the  anterior  slope,  and  a  faint  tendency  to" 
ridging  of  granules  on  the  mesobranchial  regions. 
The  smaller  specimen  has  the  more  deeply  sculp- 
tured carapace,  but  rather  blunt  frontal,  outer 
orbital,  and  suborbital  teeth,  and  rather  short, 
acute  anterolateral  teeth  except  for  the  last  two 
which  are  acuminate.  The  larger  specimen  has  a 
rather  smooth  carapace,  but  acuminate,  long,  and 
outwardly  turned  outer  orbital  and  suborbital 
teeth,  rather  acute  frontals  with  rudimentary 
submesial  teeth,  and  quite  acuminate  anterolat- 
eral teeth  throughout  the  length  of  the  row. 
Another  male  from  Trinidad  (17738)  has  a  trans- 
verse row  of  crowded  granules  on  each  cardiac  lobe 
with  the  anterior  slope  relatively  smooth,  and 
mesobranchial  regions  with  crowded  granules  but 
no  ridging.  The  frontal  teeth  are  neither  espe- 
cially sharp  nor  sinuous  mesially,  and  the  an- 
terolateral, outer  orbital,  and  suborbital  teeth, 
like  many  "typical"  specimens,  are  acuminate 


but  not  markedly  so.  Two  females  from  Curacao 
(11881)  seem  to  be  nearly  "typical"  in  all  re- 
spects. One  of  them  has  granules  crowded  into  a 
poorly  defined  transverse  ridge  on  each  cardiac 
lobe;  however,  there  are  granules  on  the  anterior 
slopes  of  these  lobes.  In  sum,  each  of  these  speci- 
mens shows  different  combinations  of  the 
"sapidus"-"sapidus  acutidens"  complex. 

The  paratype  male  "acutidens"  from  Rio  de 
Janeiro  (USNM  19083)  is  not  as  acute  spined  as 
Panamanian  material  and  the  outer  orbitals  are 
rather  blunt  by  "acutidens"  standards. 

In  rather  scanty  material  available  from  south- 
ern Brazil  and  Uruguay,  though  the  "acutidens" 
form  predominates,  teeth  are  not  so  sharp  as  in 
Panama  and  the  ridging  of  granules  on  the 
carapace  is  suppressed  to  give  a  smoothed  effect 
reminiscent  of  that  in  North  American  specimens. 

The  first  gonopods  of  males,  one  of  the  most 
reliable  characters  for  separating  species  of 
Callinectes,  offer  no  help  in  separating  "typical" 
and  "acutidens"  forms  of  sapidus.  This  pair  of 
appendages  shows  individual  variation  on  a  basic 
structural  theme  ( Figure  2 1 )  having  more  correla- 
tion with  age  than  with  general  body  facies  or 
geographic  region.  It  is  apparent  that  movable 
retrogressive  spinules  in  the  main  row  of  spinules 
increase  in  length  with  age,  and  that  there  is  no 
set  arrangement  except  a  tendency  to  an  irregular 
grouping  of  slender  subterminal  spinules  more 
erect  than  the  proximal  ones.  The  flared  mem- 
branous tip  has  an  irregular  quadrilateral  or 
elliptical  shape. 

Abdominal  segments  of  mature  females  vary  in 
shape,  some  (such  as  USNM  126789,  Dominica) 
having  the  distal  edge  of  the  sixth  segment 
broadened  at  its  distal  corners  to  an  almost 
rectilinear  form,  whereas  in  most  this  segment 
tapers  toward  the  telson. 

Gonopores  of  the  females  vary  in  width  of 
aperture  and  ornamentation  of  margins.  The  var- 
iations shown  in  Figure  23b,  c  represent  some 
extremes,  but  there  is  no  association  of  pattern 
with  geography,  the  only  constant  being  the 
elongate  opening  characteristic  of  species  in 
which  gonopods  of  males  are  long. 

Distribution  . — Occasionally  Nova  Scotia, 
Maine,  and  northern  Massachusetts  to  northern 
Argentina,  including  Bermuda  and  the  Antilles; 
Oresund,  Denmark;  the  Netherlands  and  adjacent 
North  Sea;  southwest  France  (found  twice);  Golfo 
di  Genova;  northern  Adriatic;  Aegean,  western 


781 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Black,  and  eastern  Mediterranean  Sea  (Figure 
26). 

The  extreme  southern  record  by  Ringuelet 
(1963)  is  substantiated  by  the  figure  in  his  paper. 
Records  north  of  Cape  Cod  occur  only  during 
favorable  warm  periods  (Scattergood,  1960). 

Holthuis  and  Gottlieb  (1955,  1958).  Holthuis 
(1961,  1969),  and  Christiansen  (1969)  summa- 
rized the  introduction  of  C.  sapidus  into  Europe, 
and  Bulgurkov  ( 1968)  extended  the  known  range, 
recording  an  adult  female  taken  in  the  western 
part  of  Varna  Bay  in  October  1967.  From  these 
accounts  it  is  clear  that  introduction  in  the  Med- 
iterranean and  adjacent  waters  is  an  active  one 
involving  a  breeding  population,  whereas  the 
others  seem  to  be  temporary  occurrences,  but 
all  are  judged  to  have  come  from  transport  of  small 
specimens  in  the  ballast  tanks  of  ships  (op.  cit., 
and  Wolff,  1954a,  1954b).  Banoub  (1963)  pub- 
lished one  of  the  most  complete  accounts,  noting 
that  presence  in  Egypt  does  not  seem  to  have  been 
recorded  before  1940.  When  C.  sapidus  was  first 
noticed  in  Lake  Manzilah,  Egypt,  it  was  confused 
with  Portunus  pelagicus  (Linnaeus),  itself  an 
immigrant  to  the  area  from  the  Indian  Ocean 
via  the  Suez  Canal,  and  this  confusion  has  per- 
sisted in  literature  on  both  species.  Banoub 
thought  that  C.  sapidus  may  have  migrated  from 
Greece  around  the  eastern  Mediterranean  to 
flourish  in  the  brackish  lakes  of  Egypt,  repro- 
ducing the  life  pattern  it  exhibits  in  the  Western 
Hemisphere. 

Habitat. — The  blue  crab  is  a  coastal  creature 
occurring  on  a  variety  of  bottoms  in  fresh,  es- 
tuarine,  and  shallow  ocean  from  the  water's  edge 
to  approximately  90  m  (Franks  et  al.,  1972).  but 
mainly  in  the  shallows  to  depths  of  35  m.  Biolog\' 
of  the  species  is  better  known  than  that  of  any 
other  in  the  genus.  Hatching  in  mouths  of  es- 
tuaries and  shallow  ocean,  development  of  lai'vae 
progresses  in  the  ocean  (development  studied  both 
in  nature  and  the  laboratory),  followed  by  migra- 
tion of  megalopae  and  young  crabs  back  into 
estuaries  to  mature  into  adults  (summarized  in 
Williams,  1965,  1971;  Tagatz,  1968;  Taissoun. 
1969:  and  literature  compilation,  Tagatz  and  Hall, 
1971).  It  is  probable  that  all  species  in  the  genus 
carry  out  their  life  histories  on  this  model. 

Tolerant  of  extremes,  the  species  has  been  found 
from  fresh  water  to  hypersaline  lagoons  such  as 
Laguna  Madre  de  Tamaulipas,  Mexico,  where 
collections  have  been  made  in  salinities  ranging 


from  44  to  48/<''r  and  unproductive  portions  of  the 
lagoon  range  up  to  117^,^  (Hildebrand,  1957),  in 
temperatures  ranging  from  3°  to  35°C,  and  in 
tertiary  sewage  treatment  ponds  in  which  mean 
daily  O2  tension  dropped  as  low  as  0.08  mg/liter  in 
summer  (Smith.  1971).  In  Lebanon  it  has  been 
collected  in  winter  in  39'<r  salinity  water  at 
17.5^C  where  there  is  no  good  place  for  estuarine 
development  because  streams  are  small,  seasonal, 
and  exceedingly  foul  in  dry  weather  (George  and 
Athanassiou,  1965).  In  Marion  Co.,  Fla.,  large 
males  have  been  taken  from  salt  springs  in  the  St. 
Johns  River  over  180  miles  from  the  sea. 

Often  considered  a  scavenger,  which  it  certainly 
is,  the  normal  diet  includes  a  variety  of  materials 
including  fishes,  benthic  invertebrates,  and  plant 
material  (Darnell,  1959;  Tagatz,  1968).  Odum  and 
Heald  (1972)  confirmed  this  assessment,  finding 
mainly  an  abundance  of  small  mussels  in  stomach 
contents  of  individuals  in  a  marsh  in  SW  Florida. 

Spawning. — Most  spawning  occurs  in  spring 
and  early  summer,  warm  months  helping  to  as- 
sure survival  of  larvae.  Females  with  egg  masses 
have  been  found  in  North  Carolina  from  mid- 
March  to  late  November.  Northward  the  season  is 
somewhat  shorter  and  to  the  south  (United  States) 
it  is  longer  (Williams,  1965).  Early  spring  spawn- 
ers  may  cast  a  second  batch  of  eggs  in  late 
summer  contributing  to  a  lengthened  spawning 
season  or  a  secondary  late  summer  peak.  The 
number  of  eggs  per  spaw-ning  has  been  estimated 
at  700,000  to  more  than  2  million  (Williams, 
1965).  Ovigerous  females  in  museum  collections 
are  rare,  but  suggest  that  at  least  some  eggs  are 
spawned  almost  the  year  round  in  tropical  waters. 
Taissoun  ( 1969 )  showed  this  to  be  true  in  the  Golfo 
de  Venezuela  where  ovigerous  females  are  most 
abundant  between  April  and  September,  reaching 
a  sample  maximum  of  15Vc  in  July  and  August. 
Also,  in  the  northern  part  of  Bahia  del  Tablazo, 
Venezuela,  ovigerous  females  occur  during  all  of 
the  year  except  between  August  and  November, 
reaching  a  sample  maximum  of  95*;^  in  May. 
Absence  of  ovigerous  females  there  in  late  sum- 
mer and  fall  occurs  because  heavy  rainfall  and 
increasing  river  flow  freshen  the  area,  driving 
females  downstream  to  areas  of  higher  salinity; 
consequent  increases  of  ovigerous  females  occur  in 
the  Golfo  de  Venezuela  during  August  and  Sep- 
tember. 

Economic  importance. — Though  all  species  of 
Callinectes  are  consumed  as  human  food,  there  is 


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WILLIAMS:  CRABS  OK  THE  GENUS  CALLINECTES 


no  doubt  that  C.  sapidus  is  the  most  valuable  in 
commercial  fisheries,  providing  a  highly  accept- 
able, nutritious  product  worth  several  million  dol- 
lars annually  in  the  United  States  alone.  Tradi- 
tionally, the  seat  of  this  fishery  in  the  United 
States  has  been  Chesapeake  Bay  where  records  on 
the  fishery  have  been  kept  for  about  a  century. 
Pearson  (1948),  summarizing  annual  catch  for 
this  area  from  1880  to  1942,  showed  the  annual 
catch  to  have  increased  from  9.5  million  pounds  in 
1890  to  a  peak  of  68.7  million  pounds  in  1930. 
Catch,  however,  fluctuated  before  and  after  1930, 
declining  to  35.8  million  by  1942  during  World 
War  II.  Van  Engel  ( 1962)  provided  a  history  of  the 
types  of  gear  used  in  this  fishery,  an  evolution 
from  hand-dip  trotline  to  the  baited  crab  pot  (trap) 
and  dredge.  Adoption  of  the  baited  pot  and  its 
spread  to  the  Carolinas  and  elsewhere  during  the 
late  1950 's,  along  with  other  methods  of  capture 
including  incidental  harvest  of  crabs  from  shrimp 
trawls,  greatly  expanded  the  catch.  By  1967 
(latest  available  annual  summary)  the  U.S. 
fishery  landed  nearly  150  million  pounds  of  hard 
and  soft  crabs  worth  10  million  dollars  (Lyles, 
1969). 

The  species  is  harvested  throughout  its  range 
either  as  an  object  of  commercial  enterprise  or  for 
home  use.  Taissoun  (1969,  and  pers.  commun.) 
reported  a  growing  industry  in  Venezuela. 
Banoub  (1963)  reported  growth  of  an  Egyptian 
fishery  in  lakes  (poor  flavor)  and  sea  (good  flavor), 
but  remarked  on  losses  from  damage  to  nets  and 
on  the  myriads  of  crabs  having  no  local  commer- 
cial value  because  the  Egyptians  consider  the 
meat  unpalatable  (Fishing  News  International, 
1965).  A  developing  fishery  in  Northern  Greece 
(Kinzelbach,  1965 )  declined  because  of  overfishing 
(Boschma,  1972). 

Fossil  record. — I  have  reviewed  the  fossil  mate- 
rial treated  by  Rathbun  (1919a,  b,  1935)  and 
more  recent  acquisitions  in  collections  of  the 
USNM  and  U.S.  Geological  Survey  (USGS)  and 
concluded  that  only  two  specimens  can  be  posi- 
tively identified  as  C.  sapidus.  Eighteen  lots  of 
specimens  are  probably  Callinectes,  and  some  of 
these  are  possibly  C.  sapidus,  but  most  of  the 
remains  are  too  fragmentary  for  positive 
identification.  The  entire  record  ranges  from 
lower  Miocene  of  Florida  to  Pleistocene  of  Mary- 
land and  New  Jersey,  material  identifiable  to 
species  probably  being  limited  exclusively  to  the 
Pleistocene. 


Published  records  of  Pleistocene  occurrence  in- 
clude Lupa  dicantha  (=  C.  sapidus)  from  sandy 
beds  in  Wadmalaw  Sound,  S.C.  (Holmes,  1858),  a 
two-thirds  grown  specimen  of  C.  hastatus  (  = 
sapidus)  in  a  concretion  from  excavation  for  a 
Hudson  River  Tunnel  on  the  New  Jersey  side 
(Whitfield,  1891),  a  male  C.  sapidus  from  near 
the  mouth  of  Choptank  River  at  Cook  Point, 
Dorchester  Co.,  Md.,  and  fragmentary  remains 
from  Wailes  Bluff  near  Cornfield  Harbor,  and 
Federalsburg,  Md.,  as  well  as  Heislerville,  N.J. 
(Clark,  1906),  all  cited  by  Rathbun  (1935). 

USGS  25272.  (-  Locality  of  Tulane  University 
Department  of  Geology,  Field  No.  546).  Eight-foot 
(  +  )  vertical  exposure  0.52  mi  (0.84  km)  due  E 
Florida  hwy.  84  (30°29'55"N,  85°1 1  '32"W)  along  N 
bank  of  prominent  sharp  bend  in  Ten  Mile  Creek, 
Calhoun  Co.,  Fla.  Material  collected  "in  situ"  from 
the  lower  3  ft  (0.9  m)  of  section.  Chipola  Forma- 
tion; late  Lower  Miocene.  Paul  E.  Drez,  summer, 
1972,  on  loan  from  Warren  C.  Blow,  Paleontology 
and  Stratigraphy  Branch,  USGS.  (A)  A  well- 
preserved  right  palm  and  one-third  of  propodal 
finger,  facets  bearing  resemblance  to  C.  decliuis 
on  external  face,  but  hand  broad  and  flat  dorsally 
as  in  females  of  modern  Callinectes,  molar  com- 
plex absent.  (B)  One  disarticulated  right  dactyl 
with  broken  tip  having  moderate-sized,  worn, 
proximal  tooth.  (C)  One  rather  large,  straight, 
right  propodal  finger  with  sectorial  teeth. 

USGS  25273.  Fifteen  foot  (4.6m)  vertical  ex- 
posure along  S  bank  Mattiponi  River,  just  below 
White  Oak  Lodge  at  White  Oak  Landing  (about 
2.5  mi  [4  km]  E  King  William  Courthouse)  King 
William  Co.,  Va.  Material  collected  "in  situ"  be- 
tween 1  and  2.5  ft  (30-76  cm)  above  beach  level 
in  a  blue  gray,  highly  burrowed,  sparsely  fossil- 
iferous,  silty  sand  (devoid  of  mollusks)  which 
overlies  a  highly  fossiliferous  shell  bed  consisting 
of  abundant  Turritella.  "Virginia"  St.  Marys 
Formation;  Middle  Miocene.  Lauck  W.  Ward, 
1961,  on  loan  from  Warren  C.  Blow,  Paleontology 
and  Stratigraphy  Branch,  USGS.  An  immature 
female  Callinectes  with  triangular  abdomen 
(length  about  23  mm  from  posterior  edge  of  ex- 
posed segment  3  to  tip  of  telson)  and  broad  ster- 
nites,  few  remnants  of  carapace  not  coarsely 
granulate. 

USGS  25274.  White  Oak  Landing,  about  2.5  mi 
(4  km)  E  King  William  Courthouse,  along  S  bank 
Mattiponi  River,  King  William  Co.,  Va.  Material 
collected  as  "float"  along  400  ft  ( 120  m)  (  +  )  beach 
between  tributary  just  below  landing  proper  and 


783 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


next  tributary  upstream.  The  material,  though 
"float,"  apparently  washed  out  of  the  lower  bed  of 
the  "Virginia"  St.  Marys  Formation,  which  out- 
crops along  this  beach.  Lauck  W.  Ward,  1961,  on 
loan  from  Warren  C.  Blow,  Paleontology  and 
Stratigraphy  Branch,  USGS.  Three  immature 
specimens  ofCallinectes.  Two  females  with  broad 
sternites  and  triangular  abdomen  exposed;  (A)  a 
half-grown  individual  with  fragmented  abdomen 
distorted  (abdomen  length  about  29  mm  from 
posterior  edge  of  exposed  segment  3  to  estimated 
tip  of  telson);  (B)  a  much  smaller  individual  with 
incomplete  abdomen  (abdomen  length  about  12 
mm  from  posterior  edge  of  exposed  segment  3  to 
estimated  tip  of  telson;  (C)  cephalothorax  of  an 
immature  individual  about  45  mm  wide,  with 
broad  sternal  plates  as  well  as  areolations  of 
carapace  suggesting  C.  sapidus,  frontal  and  an- 
terolateral teeth  missing,  abdomen  unexposed, 
shape  of  telson  suggesting  a  female. 

USGS  25275.  "Road  fill"  NW  side  of  Virginia 
hwy.  360,  along  both  sides  of  Manquin  Creek, 
King  William  Co. ,  Va.  Material  is  '  'spoil ' '  thought 
to  be  derived  from  nearby  road  cut(s)  during  con- 
struction of  addition  to  hwy.  360.  Age  unknown, 
probably  Yorktown  Formation;  Late  Miocene. 
Lauck  W.  Ward,  1961,  on  loan  from  Warren  C. 
Blow,  Paleontology  and  Stratigraphy  Branch, 
USGS.  Large,  complete  right  palm  (dorsal  length 
about  30  mm),  propodal  finger,  and  mold  of  dactyl 
broken  out  of  a  concretion;  palm  heavily  ridged, 
facets  between  ridges  reticulated  as  in  C.  retic- 
ulatus  (internal  mold  of  hand),  but  remnants  of 
exoskeleton  externally  smooth  except  for  granules 
on  ridges;  portion  of  finger  remaining  resembling 
Callinectes  with  proximal  enlarged  tooth  on  dactyl 
and  molar  apparatus  on  propodal  finger.  The  palm 
is  compressed  in  preservation,  but  appears  as 
broad  in  restoration  as  a  modern  Callinectes. 

USGS  3859.  Pleistocene  (Miocene?),  "tonged  up 
in  the  Rappahannock  River  near  the  Chesapeake 
Bay  by  an  oysterman"  and  sent  to  the  Smithson- 
ian Institution  in  1902  by  W.  McD.  Lee.  Flat- 
tened partially  crushed  central  portion  of  an  adult 
male  C  sapidus,  including  part  of  carapace  with 
regions  exposed  and  sternum  with  abdomen  miss- 
ing. The  dark  color  of  the  specimen  only  suggests 
similarity  to  other  Pleistocene  (Miocene?)  mate- 
rial from  the 'area  of  origin,  for  exact  horizon  is 
unknown. 

USNM  371729,  Pleistocene,  Broadwater,  Va., 
R.  Phillips.  A  large  adult  male  fragment  consist- 


ing of  a  deformed  carapace  (length  67,  width  at 
base  of  lateral  spines  127  mm)  along  with  a  right 
cheliped  lacking  fingers.  The  chela  is  disarticu- 
lated. Shape  of  abdomen,  carapace,  and  carpus  of 
cheliped  with  no  internal  spine  indicate  C. 
sapidus. 

Seven  lots  from  the  Pleistocene,  Wailes  Bluff, 
St.  Marys  Co.,  Md.,  treated  in  part  by  Rathbun 
( 1935)  and  Blake  ( 1953),  are  similar  to  Modern  C. 
sapidus  but  lack  definitive  characters. 

USNM  145356.  Talbot  Formation,  Bd.  1  (of 
Mansfield),  1937,  S.  F.  Blake.  Immature  male 
with  carapace  and  sternum  exposed. 

USNM  146701.  Frank  Burns,  1886,  Stn.  No. 
2032.  Portion  of  left  minor  dactyl  and  right  pro- 
podal finger. 

USNM  371726.  Talbot  Formation,  L.  W. 
Stephenson,  W.  C.  Mansfield,  and  W.  P.  Popenoe, 
26  June  1925,  (10902).  Portion  of  left  propodal 
finger  and  hand,  and  nearly  intact  right  propodal 
finger. 

USNM  371727.  Talbot  Formation,  W.  C. 
Mansfield,  8-12  June  1920  (8932).  Fragments  of 
a  left  chela  (propodus),  tips  of  two  fingers,  and 
fragments  of  a  minor  chela. 

Uncatalogued  lot.  (Bd.  1),  R.  J.  Taylor,  15  June 
1941.  Mostly  fragments  of  four  right  propodal 
fingers,  six  left  propodal  fingers,  and  one  complete 
right  dactyl. 

Uncatalogued  lot.  (Bd.  1),  R.  J.  Taylor,  15  June 
1941.  Three  immature  female  and  one  immature 
male  fragmentary  sterna. 

Uncatalogued  lot.  Pamlico  Formation,  W.  E. 
Salter.  Two  dactyls  from  right  and  left  chelae. 

Five  lots  from  Pleistocene,  Cape  May  and  At- 
lantic Counties,  N.J.,  similar  to  modern  C. 
sapidus. 

USNM  371930.  Cape  May  Formation,  Stone 
Harbor,  H.  G.  Richards.  A  short  section  of  finger. 

USNM  371933,  Cape  May  Formation,  Two  Mile 
Beach,  H.  G.  Richards.  A  short,  stocky  propodal 
finger  with  well  developed  molar  complex. 

USNM  371934.  Cape  May  Formation,  Two  Mile 
Beach,  H.  G.  Richards.  Five  central  portions  of 
right  propodal  fingers  of  half-  to  full-grown  indi- 
viduals, three  central  portions  of  left  propodal 
fingers  of  comparable  size,  two  proximal  portions 
of  probable  left  dactyls  of  large  crabs,  and  three 
other  pieces  possibly  broken  from  above. 

USNM  371936.  Cape  May  Formation,  Two  Mile 
Beach,  H.  G.  Richards.  Tooth  row  and  tooth  sock- 
ets on  finger,  probably  a  dactyl. 


784 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Uncatalogued  lot.  Brigantine  I.,  Atlantic  Co.,  H. 
B.  Roberts,  May  1953.  A  large,  somewhat  crushed 
right  chela  with  proximal  half  of  fingers. 

Remarks. — Resolution  of  the  taxonomic  confu- 
sion surrounding  the  correct  name  for  C.  sapidus 
by  Holthuis  (1962)  greatly  simplifies  both  discus- 
sion of  the  species'  systematic  history  and  vari- 
ability over  its  range.  From  Latreille's  ( 1825)  de- 
scription, it  is  apparent  that  the  original  material 
from  Philadelphia  (possibly  not  the  actual  site  of 
collection)  indeed  represented  the  "typical"  form 
from  eastern  North  America.  Holthuis'  selection 
of  a  lectotype  from  this  material  and  Williams' 
( 1965)  restriction  of  the  type  locality  to  '  'east  coast 
of  the  United  States"  support  the  facts  as  well  as 
they  can  be  known  today.  Search  of  the  collection 
at  ANSP  revealed  no  specimens  of  C.  sapidus  that 
date  from  the  time  of  Latreille,  and  it  is  almost 
certain  that  specimens  on  which  he  based  his  de- 
scription are  lost.  There  is  no  need  now  to  desig- 
nate a  new  type  specimen,  indeed  selection  of  a 
neotype  would  not  be  in  keeping  with  the  spirit  of 
the  International  Code  (Art.  75),  for  no  complex 
zoological  problem  now  depends  upon  a  specimen 
for  its  solution  in  this  case. 

The  earliest  "scientific"  treatment  of  the 
species  (Bosc,  1802)  was  more  a  natural  history 
account  than  a  description,  the  name  Portunus 
hastatus  being  taken  from  a  description  para- 
phrased from  J.  C.  Fabricius  (1798)  that  applied 
to  the  European  species  originally  described  as 
Cancer  hastatus  by  Linnaeus  (1767). 

I  consider  the  whole  C.  sapidus  complex  to  be  a 
single  species  which  has  diverged  into  ill  defined 
populations  in  certain  portions  of  its  range.  The 
"acutidens"  form  predominates  over  most  of  the 
latitudinal  range,  but  there  are  variations. 
Among  these  are  "typical"  features  that  reach 
their  most  pronounced  expression  in  the  popula- 
tion along  the  east  coast  of  the  United  States. 
Taxonomic  thinking  of  biologists  has  been  clouded 
by  the  fact  that  the  form  originally  described  was 
the  North  American  variant  which  became  the 
standard  against  which  all  comparisons  were 
made. 

Callinectes  sapidus  is  the  member  of  the  genus 
which  has  most  successfully  invaded  the  Temper- 
ate Zone,  and  in  this  respect  it  may  be  that  specia- 
tion  into  forms  associated  with  temperature  re- 
gimes is  progressing,  but  the  process  is  not  yet 
complete  enough  that  morphological  separation  is 
distinct. 


Material. — Total:  460  lots,  1,500-f-  specimens. 

Specimens  listed  in  Rathbun  (1930)  from 
USNM  (45656  and  26092  not  found),  MCZ,  and 
BMNH. 

USNM.  284  lots,  1,060+  specimens,  including 
the  following  not  cited  above  plus  7  lots  and  13 
specimens  from  undetermined  localities  and  2  lots 
of  fingers  from  Indian  mounds. 

UNITED  STATES 

Massachusetts:  122952,  Deadneck,  Cotuit, 
Barnstable  Co.,  1  July  1949,  1  <?,  3  9  (juv),  H.  E. 
Winn. 

New  York:  63260,  Sing  Sing  [Ossing],  no  date,  1 
5,  1  2,  A.  K.  Fisher. 

New  Jersey:  63177,  63178,  63181,  off  New  En- 
gland Creek,  19  Oct.  1^29,  2  <? ,  1  2  (juv),  H.  G. 
Richards.  63179,  1  mi  off  Dennis  Creek,  13  Aug. 
1929,  3  juv,  H.  G.  Richards.  77006,  77041,  Dennis 
Cove,  13  and  25  Aug.  1929,  61  juv,  H.  G.  Richards. 
77007,  77040,  Barnegat  Bay,  Lavalette,  15  Aug. 
1931,  2  5,32,4  juv,  H.  G.  Richards. 

Delaware:  77037,  Delaware  Bay  near  Woodland 
Beach,  no  date,  1  S  (juv),  Coltam  and  Saylor. 
63 180,  Mispillion  River,  10  July  1929, 1  $  (juv),  H. 
G.  Richards.  77039,  Mispillion  Cove,  26  Aug. 

1931,  3  6  (juv),  H.  G.  Richards. 

Maryland:  92452,  Wye  River,  16  Aug.  1951,  IS, 
M.  Sandoz.  113230,  Sullivan  Cove,  Severn  River, 
31  Aug.  1966,  1  0,  deformed  chela,  B.  Truett. 
77036,  Lake  Ovington,  near  Bay  Ridge,  19  July 
1936,  3  d  ,  2  2  (juv),  C.  R.  Aschemeir.  76996,  mouth 
Patuxent  River,  Solomons  I.,  16  July  1934,  2  2 
(juv),  P.  Bartsch.  77033,  Coster,  about  3  mi  N 
Solomons  I.,  no  date,  1  o  ,  deformed  chela,  B.  Cos- 
ter. 67646,  Coster,  no  date,  1  2,  albino,  W.  Everett. 
76148,  Point  Lookout,  9  Sept.  1932,  1  2  (juv),  E. 
Bowles.  77004,  Ridge,  St.  Marys  Co.,  26  Apr.  1930, 
1  S  (juv),  W.  H.  Ball.  76129,  Blakistone  I.,  9  Sept. 

1932,  1  2  (juv),  E.  Bowles.  66326,  Herring  Creek 
(Lower  Potomac),  31  July  1929,  5  2  (juv),  B.  A. 
Bean.  66328, 77000,  Riverside,  21  Nov.  1912, 2^,3 
juv,  U.S.  Bur.  Fish.  66614,  Cobb  I.,  Rock  Point, 
Potomac  River  opposite  Colonial  Beach,  14  Aug. 
1931,  1  <? ,  E.  D.  Reid,  W.  L.  Brown,  and  W.  Pike. 
75448,  Analostan  I.,  Potomac  River  at 
Georgetown,  D.C.,  11  Sept.  1930,  2  <?,  W.  Reynold. 
81473,  81474,  Crisfield,  7  Oct.  1941,  41  juv,  W.  L. 
Schmitt.  95733,  off  Smiths  I.,  20  Aug.  1953,  1  S, 
partial  albino,  J.  M.  Ingley. 

Virginia:  61146,  Tangier,  Dec.  1927, 1  deformed 
chela,  J.  Parks.  76998,  Smiths  I.,  5  July  1935,  4 
juv,  W.  H.  Ball.  77034,  Smiths  I.,  Northampton 


785 


FISHERY  BULLETIN:  VOL.   72,  NO.  3 


Co.,  6  July  1935,  1  S  ,  Lombino.  63320,  Cape 
Charles,  no  date,  IS  ,  1  9  (juv),  H.  G.  Richards. 
112857,  Chesapeake  Bay  (believed  to  be  in  south- 
west middle  grounds  area),  15  Oct.  1964, 1  <? ,  H.  A. 
Martin.  67739,  Elizabeth  River,  Portsmouth,  16 
June  1933,  1  6  ,  deformed  chela,  W.  L.  Hughes. 
81483,  Craney  Island  Lab.,  Norfolk,  no  date,  1  9 
(juv),  F.  F.  Ferguson.  81485,  U.S.  Public  Health 
Serv.,  Craney  I.,  Norfolk,  Aug.  1940,  1  $ ,  F.  F. 
Ferguson.  76184,  Virginia  Beach,  4  July  1932,  2 
carapaces  (dry),  G.  E.  Brandt. 

North  Carolina:  107137,  Currituck  Sound,  15 
Nov.  1960,  1  c?  (juv),  J.  A.  Kerwin.  122964,  Cur- 
rituck Sound,  no  date,  1 S  (juv),  J.  R.  Davis.  60601, 
Hatteras,  May  1927,  67  6*,  23  9,  A.  J.  Poole  and  R. 
Kellogg.  107477,  approx.  Va  mi  S  Silver  Lake 
Inlet  and  Ocracoke  Village,  6  Aug.  1958,  2  9,  col. 
unknown.  62462,  Gallant  Point,  Beaufort  Harbor, 
13  Sept.  1928,  3  9  (juv),  Schmitt  and  Shoemaker. 
76999,  Beaufort,  no  date,  1  6  ,  col.  unknown. 
77002,  Newport  R.  above  "narrows,"  Beaufort,  3 
Apr.  1931,  1  6  (juv),  S.  F.  Hildebrand.  77003, 
Beaufort,  29  Sept,  1929,  1  c?  (juv),  Hobbs  and 
Maloney. 

South  Carolina:  17191,  South  or  North 
Carolina,  no  date,  1  9  ,  Fish  Hawk  Stn.  6850. 

Florida:  99892,  Sewall  Point,  Martin  Co.,  27 
Feb.  1955,  1  6  (juv),  D.  K.  Caldwell,  et  al.  122944, 
Deep  Lake,  Miami,  5  Apr.  1952,  2  <5 ,  H.  Field  and 
Y.  Lazor.  122949,  Little  Duck  Key  on  S  side  of  Rt. 
1,  Dade  Co.,  21  Dec.  1962,  1  juv,  E.  Kotkas  and  R. 
Chandler.  122950,  Beach  area  and  tidal  flats  on  S 
ridge  of  Bahia  Honda  Key,  Monroe  Co.,  3  Aug. 
1965, 1  juv,  N.  R.  Foster  and  D.  G.  Smith.  71606,  S 
side  of  County  Road,  Key  West,  13  Nov.  1922,  1 
juv,  Stephenson.  77038,  Marquesas  Keys,  11  Aug. 
1931, 7  juv,  A.  S.  Pearse.  77031,  between  Long  and 
Bush  Key,  Tortugas,  26  July  1931,  1  9  ,  A.  S. 
Pearse.  77030,  Tortugas,  25  June  1931,  1  <J ,  W.  L. 
Schmitt.  122958,  Charlotte  Harbor,  13  Sept.  1939, 
1  9  (juv),  USFWS  Launch  58,  hauls  1,  2, 3. 122953, 
Sarasota  near  Cape  Haze  Marine  Lab.,  26  Jan. 
1966,  19,4  juv,  R.  F.  Cressey  and  R.  H.  Brown. 
122954,  Sarasota,  near  Cape  Haze  Marine  Lab., 
27  Jan.  1966,  2  juv,  R.  F.  Cressey  and  R.  Brown. 
71654,  Sarasota  Bay,  summer  1930,  4  juv,  W.  W. 
Wallis.  122943,  Homasassa  Springs,  30  Mar.  1946, 
IS,  Herald  and  Strickland.  122929,  Hernando  Co., 
Gulf  of  Mexico,  Gulf  Beach  and  March  outlet  to 
Gulf  at  Pine  I.,  8  mi  NW  Weekiwachee  Springs,  7 
Apr.  1955,  2  6,  3  9  (juv),  R.  D.  Suttkus  and  Sylvia 
A.  Earle.  77566,  Cedar  Key,  25  Jan.  1938,  1<J ,  15 
juv,  C.  R.  Aschmeier.  98085,  Choctawatchee  Bay, 


no  date,  1  deformed  chela,  col.  unknown.  122951, 
Florosa,  Okaloosa  Co.,  3  Dec.  1941,  4  c^  (juv),  W.  F. 
Blair.  66753,  Florida,  no  date,  1  (^ ,  1  9,  Ross  Allen. 

Alabama:  81480,  Big  Lake,  Gulf  State  Park,  14 
Oct.  1939,  1  6 ,  col.  unknown. 

Mississippi:  85543,  Mississippi  Sound,  east 
end,  1  Sept.  1947,  1  <J,  J.  W.  Ward,  et  al.  122947, 
inside  Petit  Bois  I.,  Mississippi  Sound,  20  Apr. 
1967,  Is,  2  9,  George  M.  Bowers  Stn.  4,  5.5  m. 

122938,  Simmons  Bayou  trib.  to  Davis  Bay,  2  mi 
SE  Ocean  Springs,  2  Aug.  1957,  1  S  (juv),  R.  D. 
Suttkus.  90299,  S  side  of  Cat  I.,  Mississippi  Sound, 

9  Aug.  1949,  1  9  (juv),  col.  unknown.  2028, 
Washington  [Adams  Co.],  no  date,  1  S  ,  Wailes. 
77035,  coast.  May  1937,  1  9,  J.  S.  Dolley. 

Louisiana:  69676,  Ycloskey  [Bernard  Parish], 

10  June  1934,  2  9,  J.  N.  Gowanloch.  The  following 
from  Point  aux  Herbes,  Lake  Pontchartrain, 
122940,  15  July  1955,  4  <5 ,  18  9  (juv),  R.  R.  Lubritz. 

122939,  22  June  1955,  83  juv,  R.  R.  Lubritz. 

122927,  4  June  1955,  80+  juv,  R.  D.  Suttkus. 
122926,  4  June  1955,  1  c? ,  1  9  (soft),  R.  D.  Suttkus. 

122928,  W  Pearl  River  immediately  above,  N  of 
Mill  Bayou,  St.  Tammany  Parish,  11  Aug.  1955,  1 
9,  M  V  Lyman  Stn.  136.  122934,  VA  mi  up  West 
Pearl  River  from  mouth,  St.  Tammany  Parish,  11 
Aug.  1955, 1 9 ,  M  V Lyman  Stn.  138. 122933,  Lake 
Pontchartrain,  Salt  Bayou,  9  June  1955, 10  juv,  R. 
D.  Suttkus.  122935,  2.5  mi  NW  Salt  Bayou  on 
Pearl  River,  St.  Tammany  Parish,  11  Aug.  1955, 1 
9,  M  V  Lyman  Stn.  143.  122936,  Va  mi  SE  West 
Pearl  River  Bridge,  Lake  Pontchartrain,  St. 
Tammany  Parish,  11  Aug.  1955,  Is,  M  V Lyman 
Stn.  144.  122930,  Lake  Pontchartrain,  first  point 
W  Liberty  Bayou,  9  June  1955,  2  juv,  M  V Lyman 
Stn.  18.  122931,  St.  Joe  Channel  [Lake  Pontchar- 
train], 21  June  1954,  2  parasitized,  Patursan  and 
Peterson.  97992,  Lake  Pontchartrain  just  S 
mouth  of  Tanipahoa  River,  17  Oct.  1953,  11  cJ,  2 
9,  R.  M.  Carnell.  96990,  Lake  Pontchartrain,  no 
date,  1  9  parasitized,  col.  unknown.  96322, 
Rigolets,  Lake  Pontchartrain,  29  Oct.  1953,  1  9 
deformed  carapace,  L.  Eddy.  122932,  Rigolets 
at  Lake  Borgne,  7  June  1955,  1  9  (juv),  R.  D. 
Suttkus.  122960,  Lake  Pontchartrain  at  mouth 
of  Tchefuncta  River,  St.  Tammany  Parish,  1  Apr. 
1948,  2  9,  R.  M.  and  M.  K.  Bailey.  122945,  Lake 
Pontchartrain,  Aug.  1962,  1  <i ,  J.  Q.  Burch.  64145, 
off  Breton  I.,  Nov.  1930,  lS,S.  Springer.  122963, 
3-6  mi  ESE  of  SW  Pass,  16  Feb.  1934, 1  <? ,  T.  C.  D., 
M.  J.  L.,  and  W.  W.  A.  122959,  [S  of  Plaquemines 
Parish]  29°01  'N, 89°33' W,  8  July  1938, 1 9, Pelican 
Stn.  77-2.   105317,  Barataria  Bay,  Jefferson 


786 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Parish,  27  Feb.  1960,  15,42  (parasitized),  E.  H. 
Behre.  122937,  Grand  Isle,  3  Feb.  1957,  15,15, 
R.  D.  Suttkus.  122961,  [off  Caillou  Bay]  28°39.5'N, 
91°04.5'W,  11  July  1938,  1  9 ,  Pelican  Stn.  81-2. 
122962,  on  9-fathom  line  between  Ship  to  Trinity 
Shoal  Buoy,  28°39.5'N,  91°04.5'W,  llJuly  1938,  3 
9,  Pelican  Stn.  81-2.  122956,  28°51.5'N,  91°33'W 
to  28°56.5'N,  91°50'W,  11  July  1938,  25,  29,  Peli- 
can Stn.  82- 1  to  82-5.  5509,  Louisiana,  1883,  2  5,1 
2,  R.  W.  Shufeldt. 

Texas:  78397,  Galveston  Bay,  Galveston  Co.,  16 
Apr.  1939,  3  2,  C.  E.  Burt.  122957,  Galveston,  4 
May  1941, 15,32  (2  juv),  J.  L.  Baughman.  122955, 
Galveston  south  of  ferry  landing,  27  Aug.  1965, 1 2 
(juv),  J.  McCain.  122948,  south  end,  west  side  new 
Galveston-Houston  causeway,  Galveston,  24  Aug. 
1965,  1  juv,  J.  C.  McCain.  122946,  17  mi  S,  7  mi  E 
Alvin,  Brazoria  Co.,  28  July  1952,  1  5 ,  S.  Alvin. 
122942,  Freeport,  12  May  1940,  1  2  (ov),  J.  L. 
Baughman.  122941,  Alligator  Head,  Matagorda 
Bay,  no  date,  13  juv  of  2  form  parasitized  (dry),  J. 
D.  Mitchell.  81479,  Aransas  Pass,  8  July  1941, 15, 
2  2  (soft  and  2  parasitized),  J.  L.  Baughman. 
99243,  Laguna  Madre,  15  mi  N  of  Port  Isabel,  24 
Jan.  1956,  2  juv,  col.  unknown.  71663,  Texas,  no 
date,  1  5 ,  C.  T.  Reed.  81475,  Texas,  no  date,  1  5 
(juv),  col.  unknown. 

JAMAICA 

120626,  Fresh  River  headwaters,  N  end  of 
Caymanas  Plantation,  St.  Catherine  Parish,  7 
Apr.  1959,  1  5  ,  Hart,  G.  Thomas,  R.  Bengry, 
Thornton. 

PUERTO  RICO 

80667,  no  date,  1  2  (recently  ov,  bearing  jar  label 
"nov.  var?"),  S.  T.  Danforth.  77044,  Rio 
Canovanillas,  Canovanas  [18°23'N,  65°55'W],  16 
Feb.  1934,  2  5 ,  S.  F.  Hildebrand. 

VIRGIN  ISLANDS 

The  following  from  St.  Croix:  71524,  Fairplain, 
no  date,  1  ^,  1  2  (juv),  H.  A.  Beatty.  71794,  Fair- 
plain  Stream,  Dec.  1934,  1  2  (juv),  H.  A.  Beatty. 
72337,  Fairplain  Stream,  1935-36,  1  juv  (soft),  H. 
A.  Beatty.  72356,  Fairplain  stream  below  bridge, 
1935-36,  2  5 ,  H.  A.  Beatty.  77032,  on  sea  coast, 
Rust-op-Twist,  no  date,  1  2,  H.  A.  Beatty. 

GUATEMALA 

123096,  Atlantic  at  Punta  Marrabique,  N  of 
Puerto  Barrios,  1  May  1947,  1  <?  ,  R.  R.  Miller. 
123097,  Lago  de  Izabal,  26  Apr.  1947, 1 5 ,  Miller  et 
al. 


COSTA  RICA 

113278,  Tortuguero,  May  1964,  15  ,  1  2,  D.  P. 
Kelso. 

PANAMA 

77043,  Gatun  Locks,  C.Z.,  21  Feb.  1935,  12  juv, 
S.  F.  Hildebrand. 

VENEZUELA 

The  following  from  Golfo  de  Venezuela:  123099, 
11°46'N,  71°16'W,  6  Oct.  1965,  1  2,  Oregon  Stn. 
5670.  123095,  ir33'N,  71°31'W,  6  Oct.  1965,  1  2 
Oregon  Stn.  5672.  123100,  11°27'N,  7r39'W,  6 
Oct.  1965,  4  2,  Oregon  Stn.  5673.  80649,  Lago  de 
Los  Pajaros,  1  km  above  Lago  de  Maracaibo,  30 
Apr.  1942,  2  5,  L.  P.  Schultz.  80650,  Lago  de 
Maracaibo,  20  Feb.  1942,  2  2  (juv),  L.  P.  Schultz. 
80651,  Lago  de  Maracaibo,  7-9  Apr.  1942,  2  5 ,  L.  P. 
Schultz.  80652,  Cano  de  Sagua,  25  km  N 
Sinamaica,  12  Mar.  1942,  3  2,  L.  P.  Schultz. 

BRAZIL 

Rio  de  Janeiro:  77042,  Recreio  dos  Bandeir- 
antes,  9-16  Feb.  1935,  1  chela,  D.  M.  Cochran. 
Santa  Catarina:  123098,  Nov.  1965,  1  2  (juv), 
Jones-Lowe. 

URUGUAY 

99848,  Roca  Arroya  de  Balizas  [=  Valizes?], 
Jan.-Feb.  1953,  2  2,  R.  Vaz-Ferreira. 

AHF.  6  lots,  10  specimens. 

UNITED  STATES 

Florida:  Pompano  Beach,  Sept.  1943, 1 2,  E.  R.  T. 
Marco  I.,  Collier  Co.,  10  Mar.  1946, 1  2  (juv),  Velero 
A87-46.  Santa  Rosa  Sound  at  Camp  Navarre,  12 
May  1949,  2  6 ,  Stn.  LM4-49. 

Louisiana:  Lake  Borgne,  27  Aug.  1954,  1  2,  R. 
Darnell. 

MEXICO 

Veracruz:  Drainage  ditch  5  mi  W  Veracruz,  19 
Aug.  1949,  1  2  (juv),  B.  W.  Halstead.  Boca  del  Rio, 
9  Aug.  1949,  1  5 ,  3  2,  B.  W.  Halstead. 

AMNH.  19  lots,  26  specimens,  including  4  lots 
with  no  data. 

UNITED  STATES 

Massachusetts:  1002,  Chappaquiddick  I., 
Martha's  Vineyard,  28  July  1909,  1  5  (dry),  R.  W. 
Miner. 


787 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


New  York:  221,  New  York  Harbor,  no  date,  1 S  , 
1  9,  L.  P.  Gratacap.  6267,  Mastic,  Long  Island, 
Aug.  1930,  1  6  ,  J.  T.  Nichols.  9856,  Hudson  River 
opposite  Spuyten  Duyvil,  Sept.  1945,  1  deformed 
chela,  J.  Dvorak.  9778,  Sheepshead  Bay,  N.Y. 
City,  1944,  1  c? ,  H.  Savalli.  6316,  Freeport,  Long 
Island,  5  Oct.  1930,  1 9 ,  F.  Limekiller.  6258,  Inner 
Harbor,  Cold  Spring,  Long  Island,  26  July  1930,  1 
S,  C.  H.  Curran.  983,  Fort  Schuyler,  N.Y.  City,  no 
date,  1  <5 ,  and  extra  chelae,  E.  Forshan. 

New  Jersey:  6491,  Newark  Bay,  foot  27  St., 
Bayonne,  28  Aug.  1931,  1  6  (deformed  chela),  K. 
Wangler.  6653,  Barnegat  Bay,  no  date,  deformed 
right  chela  (dry),  col.  unknown. 

Florida:  Lake  Worth,  July-Aug.  1945, 1  9,  W.  G. 
Van  Name  and  A.  H.  Verrill.  10249,  Destin,  29 
July  1948,  6  juv,  L.  A.  Burry. 

BAHAMAS 

Nassau  and  Andros  I.,  Mar.-Apr.  1930,  1  9, 
Bacon-Miner  Exped.  and  International  Exped.  to 
Andros. 


North  Carolina:  4873,  Fort  Macon,  2  9,  Yarrow. 

Florida:  3481,  Key  West,  no  date,  1  9  (juv),  S. 
Ashmead.  3569,  Manatee  River,  no  date,  1  c5  (dry), 
S.  Ashmead. 

Texas:  Houston-Galveston  Ship  Canal,  July 
1954,  1  <? ,  1  9  (juv),  F.  A.  Aldrich.  Cow  Bayou,  trib. 
of  Sabine  River,  Orange  Co.,  11  Aug.  1962, 1 5  ,  C. 
W.  Hart,  Jr.  Sabine  River,  Orange  Co.,  9  Aug. 
1962, 2  S,  C.  W.  Hart,  Jr.  Sabine  River,  N  of  Sabine 
I.,  Orange  Co.,  13  Aug.  1962,  2  6 ,  C.  W.  Hart,  Jr. 

CUBA 

4697,  Cojimar  near  La  Habana,  10  July  1940,  2 
9,  R.  A.  McLean. 

DOMINICAN  REPUBLIC 

3519,  no  date,  1  6  (dry),  W.  M.  Gabb.  2957,  no 
date,  1  9  (dry),  W.  M.  Gabb. 

PUERTO  RICO 

3179,  off  Guanica  Harbor,  no  date,  1  S    (dry). 
Fowler. 


CUBA 

1024,  1913,  1  juv,  J.  T.  Nichols. 

PUERTO  RICO 

2787,  Tallaboa  [18°00'N,  66°43'W],  29  July 
1914,  is  (juv),  R.  W.  Miner. 

ANSP.  26  lots,  41  specimens. 

UNITED  STATES 

North  America:  35,  [Delaware  Bay],  no  date,  1  9 
(dry)  Blanding. 

New  Jersey:  2798,  along  coast,  no  date,  2  9  (dry), 
W.  M.  Wood.  2933,  Ventnor,  Aug.  1928,  1  de- 
formed chela  (dry),  R.  D.  Benson,  Jr.  3659,  Great 
Egg  Harbor,  no  date,  1  S  (dry),  S.  Ashmead.  3604, 
Point  Breeze,  Delaware  River,  no  date,  carapace, 
F.  L.  LeCompte.  Delaware  River,  30  July  1951,  2 
$,  1  9,  J.  Bates. 

Maryland:  Potomac  River  at  Popes  Creek, 
Charles  Co.,  Aug.  1966,  3  <5,  1  9  (juv),  S.  L.  H. 
Fuller.  Potomac  River  %  mi  above  Lower  Cedar 
Pt.,  WNW  Morgantown,  Charles  Co.,  Aug.  1966,  3 
9  (juv),  S.  L.  H.  Fuller.  3492,  Chesapeake  Bay,  no 
date,  1  <J  (dry),  from  U.S.  Explor.  Exped. 

Virginia:  York  River,  31  May  1956,  1  9 ,  F.  A. 
Aldrich.  York  River,  2  June  1956,  3  9(1  ov),  F.  A. 
Aldrich.  York  River,  21  Sept.  1956,  1  6* ,  1  9,  F.  A. 
Aldrich.  James  River,  17  June  1957,  1  <^  ,  F.  A. 
Aldrich. 


PANAMA 

1305,  no  date,  1  9  (juv),  McNeil  Exped. 

BRAZIL 

3514,  no  date,  3  ci  (dry),  T.  B.  Wilson. 

BMNH.  15  lots,  28  specimens. 

UNITED  STATES 

Connecticut:  98.5.7.312,  Long  Island  Sound,  U  , 
1  9,  Norman.  80.26,  New  Haven,  19,  Norman. 

New  Jersey:  98.5.7.317/18,  3  3,19  (juv)  Verrill 
and  Smith.  Unreg.,  Cape  May,  1  S  (dry)  vi/9,  J.  K. 
Townsend.  Unreg.,  1  9  (juv,  dry)  vi/6. 

Maryland:  1964.9.7.13,  Chesapeake  Biological 
Lab.  Pier,  Solomons,  1  S  (juv),  F.  J.  Schwartz  and 
A.  C.  Edwards.  1964.9.7.14/16,  Patuxent  River  at 
Evans  pier,  Solomons,  1  <5 , 1  9  (juv),  A.  C.  Edwards 
and  F.  J.  Schwartz. 

Florida:  1966.12.5.555/557,  coast  of  Everglades 
Park,  3  juv,  U.  Miami,  Inst.  Mar.  Sci. 
1966.12.5.667,  16  ,  Univ.  Miami,  Inst.  Mar.  Sci. 
1966.12.5.666,  IS  ,  Univ.  Miami,  Inst.  Mar.  Sci. 
1966.12.5.668/671,  4  juv,  Univ.  Miami,  Inst.  Mar. 
Sci. 

TOBAGO 

1925.1.28.11/12,  Icj,  19,  P.  L.  Guppy. 

TRINIDAD 

1940.7.8.15,  1  <?,  A.  K.  Totton. 


788 


WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


BRAZIL 

Unreg.  1  9  (juv,  dry)  vi/6,  col.  unknown. 

MCZ.  42  lots,  159  specimens. 

BERMUDA 

5122,  no  date,  19  (juv),  Bickmore. 


UNITED  STATES 

Massachusetts:  322,  Cohasset,  1922,  1  9,  J.  A. 
Murphy.  5110,  Naushon  I.,  Buzzards  Bay,  1873,  2 
9,  W.  Faxon.  333,  Pocasset,  1919,  1  9,  J.  A.  Cush- 
man. 

Connecticut:  5563,  New  London,  no  date,  2S  ,3 
9,  G.  G.  Hammond,  Aug.  1876.  8510,  New  London, 
no  date,  3  <? ,  10  9 ,  G.  G.  Hammond,  1876. 

New  York:  332,  Fishers  I.,  1874,  1  9  (ov),  Hyatt 
and  Rathbun.  5471,  1  <? ,  2  9,  L.  Agassiz,  1859. 

New  Jersey:  5112,  Somers  Point  [N  shore  across 
from  Ocean  City],  no  date,  3  cj ,  3  9,  W.  Stimpson, 
reed.  Oct.  1864.  5212,  Somers  Point,  no  date,  50 
juv,  W.  Stimpson,  reed.  Dec.  1864. 

Maryland:  5117,  Baltimore,  1860, 2  3,  A.  Hyatt. 

North  Carohna:  11351,  2  mi  SE  Roanoke  I.,  19 
Dec.  1940,  1^  ,  R.  Foster.  11353,  5  mi  SW  Nags 
Head,  near  Roanoke  I.,  Dec.  1940,  1  S  (juv),  R. 
Foster.  5113,  Beaufort,  no  date,  3  5,39  (juv),  A.  S. 
Bickmore. 

South  Carolina:  5116,  Waccamaw,  no  date,  1  9, 
L.  Agassiz.  The  following  from  Charleston:  5114, 
no  date,  2  $ ,  2  9,  L.  Agassiz  (part  of  Ordway's 
material).  5202,  no  date,  2S  ,  12  9,  col.  unknown. 

8751,  no  date,  1  <?,  1  9,  T.  Lyman. 

Georgia:  5201,  May  1859,  1  <J,  T.  S.  Allanson. 
Florida:  5205,  June  1859,  1  9,  G.  Wurdemann. 

8752,  no  date,  6S  ,  col.  unknown.  11936,  Key  West, 
May  1940,  2  juv,  J.  R.Miller.  5118,  Tortugas,  2c5 , 
Jacques,  from  Peabody  Acad.  Sci.  Nov.  1885.  5203, 
Fort  Jefferson,  Tortugas  Is.,  no  date,  2  S  ,  col.  un- 
known. 10163,  Sanibel  I.,  Mar.  1938, 3 c5 ,  3  9,  F.  A. 
Chace,  Jr.  5119,  Charlotte  Harbor,  1 5  ,  L.  Gibbes, 
reed.  13  Feb.  1861.  8334,  Lemon  Bay  and  Gulf, 
Englewood,  Sarasota  Co.,  Jan. -Apr.  1935,  2  5,29, 
3  juv,  D.  J.  Zinn. 

Alabama:  5204,  Mobile,  no  date,  15,19,  2  juv, 
L.  Agassiz. 

Mississippi:  11942,  Ship  I.  off  Biloxi,  June  1941, 
1  juv,  J.  R.  Miller. 

Louisiana:  12046,  Bayou  La  Fourche  near 
Shriever,  June  1941,  1  5,  J.  R.  Miller. 

Texas:  5120,  no  date,  15  ,  G.  Wurdemann.  5121, 
Galveston,  1871,  1  9,  Boll. 


CUBA 

5123,  La  Habana,  no  date,  1  5 ,  S.  Garman. 
10887,  Cienfuegos  [22°09'N,  80°27'W],  19  Feb. 
1938,  1  9 ,  Harvard-Havana  Exped. 

HAITI 

5213,  Jeremie.  Apr.  1865,  1  5 ,  1  9,  D.  F.  Wein- 
land. 

MEXICO 
Yucatan:  8623,  Progreso,  1904,  1  5,  L.  J.  Cole. 

BRAZIL 

The  following  from  Rio  de  Janeiro:  5126,  no 
date,  1  S ,  Thayer  Exped.,  reed.  1865.  5127,  no  date, 
1  5  ,  Thayer  Exped.  Estado  de  Rio  Grande  do  Sul: 
4699,  Rio  Grande,  June  1861,  1  5,  Harrington. 

MNB.  1  lot,  1  specimen. 

BRAZIL 

Santa  Catarina:  57,  Ponta  do  Parol,  Sao  Fran- 
cisco do  Sul,  1  9,  reed.  July  1901. 

MNHNP.  1  lot,  1  specimen,  plus  3  specimens  in 
old  dry  collection. 

FRANCE 

Roehefort,  1900,  1  5  ,  from  M.  Vieuille. 

RMNH.  49  lots,  109+  specimens. 

UNITED  STATES 

East  coast  of  N  America,  Sept.  1836,  1  5 ,  1 9 ,  G. 
Troost. 

Connecticut:  401,  New  Haven,  no  date,  from 
Smithsonian  Inst. 

New  York:  13790,  Shinneeock  Bay,  Long  Island, 
Oct.  1955,  4  juv,  A.  Perlmutter. 

New  Jersey:  15253,  Creek  at  Stone  Harbor, 
Cape  May  Co.,  8  May  1960,  2  9,  juv,  J.  L. 
Seheltema. 

Delaware:  11407,  11408,  Delaware  Bay,  juv, 
date  and  col.  unknown.  11344,  Delaware  Bay 
about  1  mi  off  Lewes,  Sussex  Co.,  27  Apr.  1957, 1 9, 
L.  B.  Holthuis. 

Maryland:  14616,  Mouth  of  Potomac  River, 
Point  Lookout,  St.  Marys  Co.,  20  Mar.  1960,  2  9,  J. 
L.  Seheltema.  9827-9832,  Chesapeake  Bay,  series 
of  juv  from  6  localities,  date  and  col.  unknown. 
9833,  mouth  of  harbor  at  Snowhill  Landing,  Snow- 
hill,  Worcester  Co.,  30  Sept.  1952,  1  5,  juv,  L.  B. 
Holthuis.  9836,  northern  portion  of  Chincoteague 


789 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Bay,  N  of  Snowhill.  Worcester  Co.,  29  Sept.  1952, 1 
(J ,  1  9,  L.  B.  Holthuis.  9837,  Johns  Creek  at  mouth 
of  St.  Leonards  Creek  in  cove  of  Patuxent  River,  W 
of  Lusby,  Calvert  Co.,  16  May  1953,  1  $,  L.  B. 
Holthuis. 

Virginia:  9838,  Harborton,  Accomack  Co.,  28 
Sept.  1952,  1  9,  L.  B.  Holthuis. 

Florida:  The  following  from  Biscayne 
Bay — 21351,  off  Rickenbacker  Causeway,  1  Feb. 
1965,  1  9,  J.  A.  Cabrera  and  L.  B.  Holthuis.  23432, 
near  Mathesan  Hammock  S  of  Miami,  3  Jan.  1965, 
lo  ,juv,  L.  B.  Holthuis.  21346,  S  of  Rickenbacker 
Causeway,  Miami,  4  Feb.  1965,  1  9  (ov),  L.  B. 
Holthuis.  The  following  from  Bear  Cut  near 
Marine  Lab.,  Virginia  Key— 24258,  1  Sept.  1965, 
1  juv,  J.  A.  Cabrera  and  L.  B.  Holthuis.  24259,  22 
Dec.  1964,  1  juv,  L.  B.  Holthuis.  18710,  2-9  Sept. 
1963,  1  9,  L.  B.  Holthuis.  15635,  Marco  Beach  S  of 
Marco,  washed  ashore  by  hurricane  Donna,  12 
Sept.  1960,  1  9,  L.  B.  Holthuis.  15634,  mangroves 
near  Marco  Beach  S  of  Marco,  12  Sept.  1960,  1  9 
(juv),  L.  B.  Holthuis. 

PUERTO  RICO 

23465,  Rio  Guanica,  15  Sept.  1963, 1  <5 , 1  9,  P.  W. 
Hummelinck. 

TRINIDAD 

23404,  mouth  of  Diego  Martin  River  [5  mi  NNW 
Port  of  Spain],  1965-66,  2  5  ,  H.  O.  von  Hagen. 
17738,  Matura,  NE  coast  of  island,  19  June  1961, 1 
(5,  I.  Kristensen. 

CURACAO 

1 1881,  Waaigat,  Willemstad,  30  Jan.  1957,  2  9 , 
L.  B.  Holthuis. 

NETHERLANDS 

23434,  Friesland,  washed  ashore,  7  May  1967,  2 
,5 , 1  9,  T.  P.  Broerse.  24754,  southern  North  Sea  25 
mi  NW  Ijmuiden  [14  mi  WNW  Amsterdam],  19 
Jan.  1968,  1  9,  Rijks.  Inst.  Visserij  Onderzoek. 
Beach  at  Dishoek  between  Flissingen  and 
Zoutelande,  Zeeland,  20  Jan.  1967,  a  large  right 
swimming  leg  (dry),  G.  R.  Heerebout.  Washed 
ashore  at  Vlissingen  in  cooked  condition,  Aug. 
1950,  carapace  of  adult  9  (dry),  A.  C.  Visser. 

GREECE 

Delta  area  of  Axios  and  Gallikos  near  Firgos, 
Thessaloniki,  15  June  1964,  part  of  9  carapace  and 
abdomen,  from  shallow  water  inSalicornia  fields, 
from  fisherman,  W.  J.  Wolff  and  M.  Loosjes.  18689, 


fishmarket  in  Thessaloniki,  from  Gulf  of 
Thessaloniki,  14  Mar.  1963,  1  9 ,  R.  Kinzelbach. 
Beach  at  Strimonikos  Kolpos  (=  Gulf  of  Orfani) 
near  Asprovalta,  about  15  km  W  Tsgezi  (  = 
Iraklitsa),  10  Mar.  1963,  2  rather  worn  carapaces 
(dry),  R.  Kinzelbach.  13082,  Aegean  Sea  near  har- 
bor of  Porto  Lago,  29  June  1959,  2  9,  C.  Swennen. 

TURKEY 

21148,  on  S  coast  near  Silifke  (Seleucia),  19 
Aug.  1964,  1  9,  Turkey  Excursion,  1964  from 
Hamburg  Mus.  13137,  E  coast  of  Akyatan  Lagoon 
45  km  S  Adana,  18  May  1959,  4  6' ,  2  9. 

ISRAEL 

The  following  from  Naaman  River  S  of  Acre: 
18829,  mouth  of  River,  2  Feb.  1955,  1  £  (juv),  A. 
Perlmutter.  13795,  near  Acre,  13  Oct.  1955,  2  juv, 
A.  Perlmutter.  13794,  same,  17  Aug.  1955,  1  9,  E. 
Gottlieb.  17840,  between  railroad  bridge  and 
mouth,  30  Apr.  1962,  2  S,  3  9,  h.  B.  Holthuis. 
Mouth  of  river,  30  April  1962,  carapace  and  chelae 
of  2  or  more  individuals  (dry),  L.  B.  Holthuis. 
18832,  Lagoon  on  Kishon  River,  N  of  Haifa,  31 
Jan.  1955,  1  9,  Sea  Fish  Res.  Stn.,  Haifa.  10722, 
Mouth  of  Tiphlis  River  near  Tantura,  about  half- 
way between  Cesarea  and  Atlit,  26  Oct.  1955,  Is 
encrusted  with  Chelonibia  patula  (Ranzani),  A. 
Perlmutter.  13793,  Mouth  of  Hefzibah  [Hadera?] 
River  near  Hadera,  21  Nov.  1951,  1  9  (juv),  E. 
Gottlieb.  13792,  Hefzibah,  21  Nov.  1951, 1  9  (juv), 
E.  Gottlieb.  13791,  Alexander  River  near  mouth 
[S  Hadera],  20  Dec.  1955,  1  9  (juv),  E.  GottHeb. 

SADZ-B.  7  lots,  27  specimens. 

BRAZIL 

Rio  de  Janeiro:  3240,  Atafona,  12  July  1963, 
10  c?,  8  9,  N.  Meneses.  1721,  Atafona,  1964,  1  <J, 
N.  Meneses.  950,  S.  Joao  da  Barra,  Nov.  1911, 
19,  E.  Garbe. 

Sao  Paulo:  1814,  Santos,  11  Sept.  1962,  1  9, 
G.  Melo.  1727,  Guaruja,  Jan.  1920,  19,  Hempel. 

Santa  Catarina:  664,  Itajai,  Dec.  1914,  Lue- 
derwaldt. 

Rio  Grande  do  Sul:  3234,  Praia  de  Torres, 
5  Oct.  1964,  1^,2  9(1  ov),  J.  Bertoletti. 

UNC-IMS.  8  lots,  34+  specimens. 

UNITED  STATES 

Delaware:  1853,  Near  Port  Mahon,  1  July  1954, 
2  9,  H.  J.  Porter. 


790 


WILLIAMS:  CRABS  OF  THE  GENUS  CALUNECTES 


North  Carolina:  2246,  West  Bay  near  Cedar  I., 
Pamlico  Sound,  Carteret  Co.,  21  July  1969,  2  9 
(ov),  includes  smallest  mature  9  on  record,  from 
fisherman.  821,  Neuse  River  near  New  Bern,  Cra- 
ven Co.,  24  July  1957,  1  S  (juv),  Tagatz  and  Dud- 
ley. 738,  Neuse  River  at  Smith  Farm,  near  North 
Harlowe,  Craven  Co.,  1  Oct.  1957,  3  <5 ,  1  9  ,  juv, 
Judy  and  Dudley.  739,  Neuse  River  at  North  Har- 
lowe, 26  July  1957,  3  9  (juv),  Tagatz  and  Dudley. 
820,  Pivers  Island  near  Beaufort,  Carteret  Co.,  27 
May  1957,  1  c5,  4  9  (juv),  Talbot  and  Fischler.  913, 
off  Beaufort  Inlet,  26  Nov.  1959,  4  9(3  ov),  covered 
with  Chelonibia,  H.  J.  Porter. 

PUERTO  RICO 

2136,  Fresh  water  canal,  5  km  S  Lajas,  10  Feb. 
1967,  3<?  ,  19  juv. 

YPM.  1  lot,  1  specimen. 

BRAZIL 

6399,  Rio  Grande,  7  June  1860,  1  6  bearing 
Chelonibia,  G.  Harrington. 

Supplementary  literature  records . — Nova  Scotia 
(Piers,  1923);  Maine  and  Nova  Scotia  (Scatter- 
good,  1960);  Bermuda  (Verrill,  1908a,  b);  Laguna 
Madre  deTamaulipas,  Mexico  (Hildebrand,  1957); 
Alvarado,  Veracruz,  Mexico  (Contreras,  1930); 
Dominica  (Chace  and  Hobbs,  1969);  Lago  de 
Maracaibo  and  Golfo  de  Venezuela  (Taissoun, 
1969);  Quenquen,  Buenos  Aires,  Argentina 
[?]  (Boschi,  1964);  Elbe  estuary,  Germany  (Kiihl, 
1965);  Netherlands  and  North  Sea  localities 
(Holthuis,  1969);  mouth  of  Gironde,  France 
(Amanieu  and  Dantec,  1961);  Gulf  of  Spezia  and 
Genoa  Harbor,  Italy  (Tortonese,  1965);  northern 
Adriatic  lagoons,  Italy  (Holthuis,  1961  [review]); 
Greece  and  parts  of  eastern  Mediterranean  (Ser- 
betis,  1959);  Beirut,  Lebanon  (George  and 
Athanassiou,  1965);  Buljayrat  Idkii  and  Buljayrat 
Manzilah,  Egypt  (Banoub,  1963). 

QUESTIONABLE  SPECIES 

Rathbun  ( 1907)  described  Callinectes  alexandri 
from  Papeete,  Tahiti,  and  Suva,  Fiji  Islands,  on 
basis  of  two  juveniles,  and  later  (1911)  noted  a 
small  mature  male  from  Cragados,  Carajos 
[Shoals,  Mascarene  Islands,  Indian  Ocean]. 
Stephenson  and  Campbell  (1959)  synonymized 
this  confusing  form  with  Portunus  pelagicus 
(Linn.),  commenting  on  its  close  similarity  to 


members  oi  Callinectes  and  temporarily  question- 
ing the  validity  of  Callinectes.  Later  Stephenson 
et  al.  (1968)  accepted  the  generic  status  quo. 
Stephenson  (1968)  confirmed  his  recognition  of 
Callinectes  and,  after  examination  of  Rathbun 's 
specimens  of  C.  alexandri,  reidentified  the  Tahiti 
and  Fiji  material  as  P.  sanguinolentus  (Herbst) 
and  the  Indian  Ocean  specimen  as  P.  pelagicus. 
The  history  of  these  bleached  specimens  em- 
phasizes the  difficulty  in  identifying  some  juvenile 
portunid  material. 

Chen  (1933)  described  Callinectes  platei  on 
basis  of  a  small  male  (length  14,  width  29  mm), 
and  C.  alcocki  on  basis  of  a  small  ovigerous  female 
(length  10.5,  width  including  lateral  spines  16 
mm)  from  Tuticorin  [Madras,  India].  There  is  no 
sure  way  to  identify  these  forms  because  speci- 
mens from  the  Plate  collection  are  apparently  no 
longer  in  existence.  From  the  descriptions  and 
figures,  the  two  species  possibly  represent  male 
and  female  of  the  same  form,  a  small  portunid 
with  internal  carpal  spine.  This  alone  is  enough  to 
remove  them  from  Callinectes.  Moreover,  no 
known  Callinectes  is  ovigerous  at  the  tiny  size  of 
this  female. 

ACKNOWLEDGMENTS 

The  need  for  taxonomic  reassessment  of  the 
genus  Callinectes  was  first  suggested  to  me  by 
Fenner  A.  Chace,  Jr.,  of  the  USNM,  a  man  whose 
grasp  of  decapod  crustacean  systematics  has  been 
an  inspiration  to  me  for  many  years.  I  am  indebted 
to  him  for  continuing  aid  and  many  kindnesses. 
Numerous  people  and  organizations  have  given 
assistance  in  bringing  the  study  to  completion, 
some  but  not  all  of  whom  can  be  listed  here.  The 
National  Science  Foundation  through  Grant  No. 
GB-6780  provided  means  to  study  major  collec- 
tions over  the  world,  especially  at  the  USNM  for 
an  academic  year,  and  the  University  of  North 
Carolina,  Chapel  Hill,  generously  granted  me 
leave  for  that  period.  Studies  at  the  Allan  Hancock 
Foundation,  University  of  Southern  California, 
were  aided  by  John  S.  Garth;  American  Museum 
of  Natural  History  by  Dorothy  E.  Bliss  and  Harold 
Feinberg;  Academy  of  Natural  Sciences  by  C.  W. 
Hart,  Jr.;  British  Museum  of  Natural  History  by 
Isabella  Gordon,  Anthony  L.  Rice,  and  R.  W.  Ingle; 
Museum  of  Comparative  Zoology  by  Herbert  W. 
Levi;  Museum  National  D'Histoire  Nature  lie, 
Paris,  by  Jacques  Forest;  Rijksmuseum  van 
Natuurlijke  Historie,  Leiden,  by  L.  B.  Holthuis; 


791 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Secretaria  da  Agricultura,  Departamento 
Zoologia,  Sao  Paulo,  (and  loans  from  Museu  Na- 
cional,  Rio  de  Janeiro)  by  Augusto  Melo  and  Paulo 
E.  Vanzolini. 

People  who  assisted  with  specimen  loans,  col- 
lecting, photographs,  literature,  data,  and  counsel 
were:  Warren  C.  Blow,  U.S.  Geological  Survey, 
Washington,  D.C.;  Enrique  E.  Boschi,  Instituto  de 
Biologia  Marina,  Mar  del  Plata;  Henrique  Rod- 
rigues  da  Costa,  Centro  de  Estudos  Zoologicos,  Rio 
de  Janeiro;  Alain  Crosnier,  then  of  ORSTOM  de 
Pointe-Noire,  Republic  de  Congo;  Charles  E.  Cut- 
ress.  University  of  Puerto  Rico,  Mayagiiez;  H. 
Gruner,  Zoologisches  Museum,  Berlin;  Willard  D. 
Hartman,  Peabody  Museum  of  Natural  History, 
Yale  University,  New  Haven;  Neil  C.  Hulings, 
then  of  Mediterranean  Marine  Sorting  Center, 
Tunisia;  Charles  A.  Johnson,  Duke  University 
Marine  Laboratory,  Beaufort;  Alceu  Lemos  de 
Castro,  Universidad  do  Brasil,  Museu  Nacional, 
Rio  de  Janeiro;  Fernando  A.  Manrique  Colchado, 
then  of  Instituto  de  Estudios  Superiores  de 
Monterrey,  Mexico;  Elhott  A.  Norse,  Allan  Han- 
cock Foundation;  Harriett  M.  Perry,  Gulf  Coast 
Research  Laboratory,  Ocean  Springs,  Miss.;  Egon 
Popp,  Zoologische  Sammlung  des  Bayerischen 
Staates,  Munich;  William  Stephenson,  Univer- 
sity of  Queensland,  Brisbane;  Edgard  Taissoun 
N.,  Universidad  del  Zulia,  Maracaibo;  Druid 
Wilson,  U.S.  Geological  Survey,  Washington, 
D.C. 

I  am  especially  indebted  for  assistance  of  col- 
leagues at  the  University  of  North  Carolina  Insti- 
tute of  Marine  Sciences  (A.  F.  Chestnut,  W.  E. 
Fahy,  J.  J.  and  Erika  Kohlmeyer,  H.  J.  Porter,  F. 
J.  Schwartz,  W.  J.  Woods),  the  U.S.  National 
Museum  (H.  H.  Hobbs,  Jr.,  R.  B.  Manning,  I.  Perez 
Farfante,  H.  B.  Roberts),  my  wife  J.  McN.  Wil- 
liams, and  staff  members  and  students  in  the  Uni- 
versity of  North  Carolina  (UNO,  Department  of 
Zoology,  Chapel  Hill.  Photographs  were  taken  by 
Janice  L.  Czikowsky  and  reproduced  at  the  UNC 
Photographic  Laboratory.  Maria  M.  Dieguez  drew 
the  index  and  female  reproductive  figures,  plotted 
distribution  maps,  and  assembled  all  figures. 

LITERATURE  CITED 

Amanieu,  M.,  and  J.  Le  Dantec 

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AURIVILLIUS,  C.  W.  S. 

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K.  Svenska  Vet.-Akad.  Handlingar,  24,  Afd.  4(1):  1-31. 

792 


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1963.  Survey  of  the  blue-crab  Callinectes  sapidus  (Rath.), 
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WILLIAMS:  CRABS  OF  THE  GENUS  CALLINECTES 


Brues,  C.  T. 

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798 


ELECTROPHORETIC  COMPARISON  OF  FIVE  SPECIES  OF 

PANDALID  SHRIMP  FROM 
THE  NORTHEASTERN  PACIFIC  OCEAN 

Allyn  G.  Johnson,  Fred  M.  Utter,  and  Harold  O.  Hodgins^ 

ABSTRACT 

Pandalid  shrimp  from  off  Alaska,  Washington,  and  Oregon  were  investigated  using  starch-gel 
electrophoresis.  Each  species  was  found  to  be  polymorphic  for  phosphoglucomutase,  and  the  general 
protein  patterns  separated  them  into  two  groups — one  consisting  only  oi  Pandalus  hypsinotus  and 
the  other  containing  P.  borealis,  P.  goniurus,  P.jordani,  and  Pandalopsis  dispar. 

A  key  based  on  biochemical  characters  was  developed  which  could  separate  the  five  pandalid 
species  investigated. 


The  increase  of  commercial  fishing  for  shrimp 
along  the  Pacific  coast  of  North  America  in 
recent  years  has  stimulated  interest  in  the 
biology  and  identification  of  species  and  popula- 
tion units.  Ronholt  (1963)  reported  on  the  distribu- 
tion and  relative  abundance  of  five  species  of 
pandalid  shrimp  from  the  northeastern  Pacific 
Ocean.  Butler  (1965)  presented  a  comprehensive 
report  on  the  growth,  reproduction,  and 
distribution  of  pandalid  shrimp  in  British 
Columbia  waters,  demonstrating  the  importance 
of  inlets  and  bays  to  this  group  of  crustaceans. 
Several  reports  on  sampling  techniques,  diel 
vertical  migration,  and  population  movements 
have  occurred  which  emphasize  the  need  for 
additional  information  on  the  biology  of  pandalid 
shrimp  for  optimal  utilization  of  this  resource 
(Barr  and  McBride,  1967;  Barr,  1970,  1971; 
Gotshall,  1972). 

One  of  the  more  promising  techniques  for  the 
detection  of  population  units  is  the  biochemical 
genetic  approach,  utilizing  starch-gel  electro- 
phoretic  separation  of  proteins  coupled  with  histo- 
chemical  staining  procedures  (Hunter  and  Mar- 
kert,  1957).  This  method  has  been  widely  used  and 
successfully  applied  to  fisheries  problems  (re- 
viewed by  de  Ligny,  1969,  1972). 

This  paper  reports  our  application  of  starch- 
gel  electrophoresis  to  separation  of  species  and 
populations  of  five  species  of  shrimp  which  occur 
along  the  coast  of  the  northeastern  Pacific  ocean. 


'Northwest  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  2725  Montlake  Boulevard  East,  Seattle,  WA 
98112. 


MATERIALS  AND  METHODS 

Five  species  of  adult  pandalid  shrimp  from 
two  genera  were  investigated;  Pandalopsis  dis- 
par, Pandalus  borealis,  P.  goniurus,  P.  hypsinotus, 
and  P.  jordani.  All  samples  except  those  of  P. 
jordani  and  one  collection  of  P.  hypsinotus  were 
obtained  from  Marmot  and  Kazakof  Bays  of 
Kodiak  Island,  Alaska,  during  May  1972,  and 
identified  by  personnel  of  the  National  Marine 
Fisheries  Service  at  Kodiak,  Alaska.  These 
samples  were  shipped  frozen  to  our  laboratory 
where  they  were  kept  at  -  15°C  until  tested.  Two 
collections  of  P.  jordani  were  obtained  off  Coos 
Bay  and  Astoria,  Oreg.,  in  1971  and  identified 
by  personnel  of  the  Fish  Commission  of  Oregon, 
shipped  to  us  frozen  and  kept  at  -15°C  until 
tested.  Additional  samples  oi  P.  jordani  and  P. 
hypsinotus  were  obtained  during  December  1972 
from  Bellingham  Bay,  Wash. 

Extracts  of  muscle  tissue  were  prepared  by 
mixing  equal  volumes  of  tissue  and  2%  phenoxy- 
ethanol  in  distilled  water  into  uniform  pastes 
with  glass  rods.  The  starch-gel  electrophoretic 
procedure  followed  the  methods  reported  by 
Johnson,  Utter,  and  Hodgins  (1972).  The  buffer 
system  used  was  described  by  Ridgway,  Sher- 
burne, and  Lewis  ( 1970).  After  electrophoresis  the 
gels  were  sliced  into  four  horizontal  slices  and 
stained  for  phosphoglucomutase  (PGM),  lactate 
dehydrogenase  (LDH),  tetrazolium  oxidase  (TO), 
peptidase  (Johnson  et  al.,  1972),  malate  dehy- 
drogenase NAD  and  NADP  (MDH),  glyceralde- 
hyde-3-phosphate  dehydrogenase  (GAPDH;  Shaw 


Manuscript  accepted  November  197.3. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


799 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


and  Prasad,  1970),  naphthyl  acetate  and  pro- 
pionate esterases  (modified  after  Utter,  Stormont, 
and  Hodgins,  1970),  and  general  protein  (John- 
son et  al.,  1972). 

RESULTS  AND  DISCUSSION 

Bands  of  identical  electrophoretic  mobility  for  a 
given  enzyme  system  were  observed  in  all  species 
for  the  follov^fing  systems:  MDH  (NADP),  one 
anodal  band;  MDH  (NAD),  one  anodal  band; 
peptidase  (valyl-leucine),  three  anodal  bands;  TO, 
one  anodal  band;  and  GAPDH,  three  anodal 
bands. 

Esterase  patterns  varied  among  species;  how- 
ever, the  patterns  were  weak  and  not  completely 
repeatable.  Gasser  and  Rowlands  (1972)  noted 
similar  problems  in  interpreting  esterase  patterns 
from  human  serum  and  related  the  differences  to 
nongenetic  causes.  We  have,  therefore,  excluded 
them  from  further  consideration  in  this  study. 
Esterases  have  been  found  useful  in  studies  of 
other  invertebrates  and  may  indeed  be  of  use  in 
studies  of  pandalid  shrimp  if  reliable  methods 
can  be  developed  for  stabilizing  expression  of 
patterns  (Manwell  and  Baker,  1970;  Barlow  and 
Ridgway,  1971). 

Lactate  dehydrogenase  was  expressed  as  one 
anodal  band — with  a  broad,  faint-staining  area 
anodal  to  it — in  each  species.  The  bands  of 
P.  jordani,  P.  borealis,  and  P.  goniurus  had  an 
identical  mobility  slightly  more  anodal  than  the 
bands  of  P.  hypsinotus  and  Pandalopsis  dispar. 

The  general  protein  patterns  observed  are 
shown  in  Figure  1.  Pandalus  hypsinotus  had 


bands  C,  E,  F,  and  G;  P.  jordani  and  P.  borealis, 
bands  A,  B,  D,  and  G;  and  P.  goniurus  and 
Pandalopsis  dispar,  bands  A,  B,  and  G.  The  B 
band,  although  qualitatively  invariable,  varied 
considerably  in  intensity  in  all  species  expressing 
it.  A  greater  degree  of  difference  in  the  protein 
pattern  was  observed  between  Pandalus  hyp- 
sinotus (processing  three  unique  bands)  and  the 
other  four  species  than  was  observed  among 
these  four  species. 

Phosphoglucomutase  (PGM)  was  polymorphic 
in  all  five  species.  Two-banded  phenotypes  (Figure 
2)  were  observed  in  some  individuals  of  all 
species,  presumably  reflecting  heterozygous 
individuals,  and  the  pattern  suggests  that  the 
active  PGM  enzyme  in  shrimp  is  a  monomer 
(Shaw,  1964).  This  agrees  with  reports  of  PGM 
polymorphisms  found  in  vertebrates  (see  Johnson, 
Utter,  and  Hodgins,  1971).  A  diagrammatical 
representation  of  the  allelic  forms  found  within 
the  five  species  (Figure  3)  shows  the  six  allelic 
bands  that  were  observed  and  designated  (in 
decreasing  anodal  mobility)  A,  B,  C,  D,  E,  and  F. 
The  distribution  of  these  alleles,  as  indicated  in 
Figure  3,  was  P.  hypsinotus,  A,  B,  E,  and  F; 
P.  goniurus,  A  and  B;  P.  borealis,  C,  E,  and  F; 
P.  jordani,  B,  C,  and  E;  and  Pandalopsis  dispar, 
C,  D,  and  E.  The  phenotypic  distributions  of 
PGM  in  the  five  species  of  shrimp  along  with  gene 
frequencies,  Hardy-Weinberg  calculations  and 
collections  data  are  presented  in  Tables  1  and  2. 
With  the  exception  o{  Pandalus  hypsinotus ,  the 
phenotypic  distributions  of  PGM  of  the  collections 
of  shrimp  species  did  not  deviate  significantly 


-A 
B 

■c 


r-G 


—  Upper 
Boundary 


+ 
a 


— ^*^^    -"■«#»' 


Origin 


12     3     4     5 


12    3    4     5 


Figure  1. — Electrophoretic  patterns  on  starch  gel  of  muscle 
protein  of  five  species  of  shrimp  from  the  northeastern  Pacific 
Ocean.  Numbers  below  the  patterns  indicate  the  following 
species:  1.  Pandalus  jordani,  2.  P.  borealis,  3.  P.  goniurus, 
4.  Pandalopsis  dispar,  and  5.  Pandalus  hypsinotus. 


Origin    . 
Phenotypes 


CE    CC     CE     CC     BC 


CE   CC    CE    CC    BC 


Figure  2. — Phosphoglucomutase  phenotypes  of  Pandalus 
jordani  in  starch  gels  suggesting  monomeric  configuration  of 
this  enzyme. 


800 


JOHNSON,  UTTER,  and  HODGINS:  ELECTROPHORETIC  COMPARISON  OF  SHRIMPS 


Origin 

Species:    P  hypsmolus      P  gomufus    Pboreaiis       Pdispor         Pjordoni 

Figure  3. — DiagT^ammatical  representation  of  the  alleles  of 
phosphoglucomutase  in  five  species  of  pandalid  shrimps  as 
shown  by  the  technique  of  starch-gel  electrophoresis. 


from  expected  Hardy-Weinberg  values,  and  the 
gene  frequencies  of  intraspecific  samples  were 
similar  over  the  geographic  range  samples  for 
P.  jordani. 

The  collections  of  P.  hypsinotus  from  Alaska 
showed  highly  significant  deviation  from  Hardy- 
Weinberg  expectations.  Variation  from  expected 
Hardy-Weinberg  proportions  has  also  been  ob- 
served for  PGM  variants  of  Pacific  ocean  perch, 
Sebastes  alutus  (Johnson  et  al.,  1971)  and  related 
to  depth  of  capture.  Gene  frequencies  were  similar 
for  shallow-  and  deepwater  collections;  however, 
deepwater  collections  deviated  significantly  from 
expected  Hardy-Weinberg  frequencies.  Further 


sampling  stratified  by  depth  (or  other  measurable 
variables)  may  reveal  similar  relationships  for 
PGM  variants  of  P.  hypsinotus. 

Inspection  of  the  allele  frequencies  of  the 
Alaskan  and  Washington  collections  of  P.  hyp- 
sinotus showed  marked  differences,  especially 
with  the  A  and  E  alleles  (Table  1).  These 
differences  indicate  that  PGM  variation  may  be 
useful  in  population  identification  of  P.  hypsino- 
tus. Bullini  and  Coluzzi  (1972)  have  presented 
evidence  for  selection  of  PGM  alleles  over  a  broad 
geographic  range  in  mosquitoes  Aedes  aegypti 
and  A.  marine.  Additional  sampling  of  P.  hyp- 
sinotus may  reveal  a  similar  phenomenon  as  that 
found  in  the  mosquito  species. 

The  general  protein,  LDH,  and  PGM  patterns 
observed  in  the  five  species  were  used  to  produce 
a  key  by  which  the  species  can  be  separated 
(Figure  4).  This  type  of  key  should  prove  useful 
in  application  to  shrimp  identification  problems. 

CONCLUSION 

The  general  protein  patterns  separated  the 
species  examined  into  two  groups,  one  consisting 
only  of  P.  hypsinotus  and  the  other  containing 
the  remaining  species  of  Pandalus  and  Pan- 
dalopsis  dispar. 

All  five  species  of  shrimp  studied  were  poly- 
morphic for  PGM,  with  Pandalus  hypsinotus 
possessing  the  greatest  number  of  alleles  (four 


Table  1. — Phosphoglucomutase  phenotypes  of  Pandalus  hypsinotus  taken  off  Alaska  and  Washington,  1971-72.' 

Phenotypes  of  PGM 


Location 

3d[lipie 

size 

AA 

AB 

AE                AF 

88 

BE 

8F 

EE 

EF 

FF 

Alaska: 

Marmot  Bay  and 
Kazakof  Bay 

89 

1 

(1.8) 

15 

(9.0) 

4                  -4 

(8.5)              (4.1) 

11 
(11.5) 

20 

(21.5) 

7 
(10.3) 

9 

(10.2) 

18 

(9.8) 

0 

(2.3) 

Washington: 
Bellingham  Bay 

80 

0 

(0.0) 

0 

(0.0) 

0                  0 

(0.0)             (0.0) 

1 

(0.9) 

15 

(14.6) 

0 

(0.1) 

55 

(55.5) 

8 

(8.9) 

1 

(0.0) 

Allelic  frequencies 

Test  Data 

Location 

A 

B 

E 

F 

df 

X^ 

p 

Alaska: 

Marmot  Bay  and 
Kazakof  Bay 

0.140 

0.360 

0.337 

0.163 

6 

7.23 

20.01  >P>0.001 

Washington: 
Bellingham  Bay 

0.000 

0.106 

0.831 

0.063 

— 

— 

— 

Contingency  test  comparing  allelic  compositior 
Alaska  and  Washington  samples 

of 

3 

89.64 

P<0.001 

Mn  parentheses  are  the  expected  values  of  a  Hardy-Weinberg  distribution. 
^Chi-square  test  of  Hardy-Weinberg  distribution. 


801 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


Table  2. — Phosphoglucomutase  gene  frequencies  of  four  species  of  pandalid  shrimp  taken  off  Alaska,  Oregon,  and  Washington; 

1971-72. 


Species  and  location 


Gene  frequencies 


Sample 
size 


df 


Test  data' 


Pandalus  goniurus 

Alaska: 

Marmot  Bay  and 

Kazakof  Bay 

94 

Pandalus  jordani 

Oregon: 

Coos  Bay 

150 

Astoria 

151 

Washington: 

Bellingham  Bay 

79 

Pandalus  borealis 

Alaska: 

Marmot  Bay  and 

Kazakof  Bay 

418 

Pandalopsis  dispar 

Alaska: 

Marmot  Bay 

269 

0.016 


0984 


0.010 
0.003 

0.000 


0.980 
0.990 

1.000 


0.059 


0  011  0.981 


0010 
0.007 

0.000 


0,934 


0.008 


0.007 


1 

2.34 

0.2>P>0.1 

3 

000 

P>0.99 

3 

0.02 

P>0.99 

0.00 


7.60 


0.00 


P>0.99 


0.1  >P>0.05 


P-.0.99 


'Chi-square  test  of  Hardy-Weinberg  distribution. 
^Indicates  not  observed  in  this  species. 


P  hypsinotus 

P 

aispor 

■ 

inds 

[Generol 

Prolem  1 

/ 

C,E,F  Bonds 

\ 

A. 8  Be 

P.  hypsinotus 

P  dispor 

P  jordani ,  P  boreoMs,  P.goniurus 


,      \ 

PGM,  liiqh  frequency  allele 


B    Bond  C  Bond  E  Band 


P  gonturus 


P  jordani 


P  borealis 


Figure  4. — Key  to  five  species  of  pandalid  shrimp  based 
on  three  biochemical  characters. 

alleles).  This  polymorphism  may  prove  useful  for 
separation  of  breeding  groups  and  as  genetic 
markers  in  shrimp  culturing  experiments. 

All  five  species  could  be  identified  based  on 
a  biochemical  key  that  was  developed. 

LITERATURE  CITED 

Barlow,  J.,  and  G.  J.  Ridgway. 

1971.  Polymorphisms  of  esterase  isozymes  in  the  Ameri- 
can lobster  (Homarus  americanus).  J.  Fish.  Res.  Board 
Can.  28:15-21. 

Barr,  L. 

1970.  Diel  vertical  migration  of  Pandalus  borealis  in 
Kachemak  Bay,  Alaska.  J.  Fish.  Res.  Board  Can. 
27:669-676. 

1971.  Methods  of  estimating  the  abundance  of  juvenile 
spot  shrimp  in  a  shallow  nursery  area.  Trans.  Am. 
Fish.  Soc.  100:781-787. 


Barr,  L.,  and  R.  McBride. 

1967.     Surface-to-bottom  pot  fishing  for  pandalid  shrimp. 
U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish.  560,  7  p. 
Bullini,  L.,  and  M.  Coluzzl 

1972.     Natural  selection  and  genetic  drift  in  protein  poly- 
morphism.    Nature  (Lond.)  239:160-161. 
Butler,  T.  H. 

1965.     Growth,  reproduction,  and  distribution  of  pandalid 
shrimps  in  British  Columbia.     J.  Fish.  Res.  Board  Can. 
21:1403-1452. 
Gasser,  D.  L.,  and  D.  T.  Rowlands,  Jr. 

1972.     Nongenetic  determinants  of  human  serum  es- 
terases.    Am.  J.  Pathol.  67:501-510. 
Gotshall,  D.  W. 

1972.     Population  size,  mortality  rates,  and  growth  rates 
of  northern  California  ocean  shrimp,  Pandalus  jordani, 
1965  through  1968.     Calif  Dep.  Fish  Game,  Fish  Bull. 
155,  47  p. 
Hunter,  R.  L.,  and  C.  L.  Markert. 

1957.     Histochemical  demonstration  of  enzymes  separated 
by  zone  electrophoresis  in  starch  gels.  Science  (Wash., 
D.C.)  125:1294-1295. 
Johnson,  A.  G.,  F.  M.  Utter,  and  H.  O.  Hodgins. 

1971.  Phosphoglucomutase  polymorphism  in  Pacific 
ocean  perch,  Sebastodes  alutus.  Comp.  Biochem. 
Physiol.  39B:285-290. 

1972.  Electrophoretic  investigation  of  the  family  Scor- 
paenidae.  Fish.  Bull.,  U.S.  70:403-413. 

Ligny,  W.  de. 

1969.  Serological  and  biochemical  studies  on  fish  popula- 
tions.    Oceanogr.  Mar.  Biol.  Annu.  Rev.  7:411-513. 

1972.     Blood  groups  and  biochemical  polymorphisms  in 
fish.    In  G.  Kovacs  and  M.  Rapp  (editors),  XII  Eur. 
Conf.  Anim.  Blood  Groups  Biochem.  Polymorph.,  p.  55- 
65.  W.  Junk  N.  V.,  Publ.,  The  Hague. 
Manwell,  C,  and  C.  M.  a.  Baker. 

1970.  Molecular  biology  and  the  origin  of  species.  Univ. 
Wash.  Press,  Seattle,  394  p. 


802 


JOHNSON,  UTTER,  and  HODGINS:  ELECTROPHORETIC  COMPARISON  OF  SHRIMPS 

RiDGWAY,  G.  J.,  S.  W.  Sherburne,  and  R.  D.  Lewis.  of  isozyme  structure.    In  Subunit  structure  of  proteins: 
1970.     Polymorphism  in  the  esterases  of  Atlantic  herring.  biochemical  and  genetic  aspects,  p.   117-130.     Brook- 
Trans.  Am.  Fish.  See.  99:147-151.  haven  Symp.  Biol.  17. 
RoNHOLT,  L.  L.  Shaw,  C.  R.,  and  R.  Prasad. 

1963.  Distribution  and  relative  abundance  of  commer-  1970.     Starch  gel  electrophoresis  of  enzymes — a  compila- 
cially  important  pandalid  shrimps  in  the  northeastern  tion  of  recipes.     Biochem.  Genet.  4:297-320. 

Pacific  Ocean.  U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Utter,  F.  M.,  C.  J.  Stormont,  and  H.  O.  Hodgins. 

Fish.  449,  28  p.  1970.     Esterase  polymorphism  in  vitreous  fluid  of  Pacific 

Shaw,  C.  R.  hake,  Merluccius  productus.     Anim.   Blood  Groups 

1964.  The  use  of  genetic  variation  in  the  analysis  Biochem.  Genet.  1:69-82. 


803 


DISTRIBUTION  AND  RELATIVE  ABUNDANCE  OF 

LARVAE  OF  KING  CRAB,  PARALITHODES  CAMTSCHATICA,  IN 

THE  SOUTHEASTERN  BERING  SEA,  1969-70 


Evan  B.  Haynes^ 


ABSTRACT 

During  the  spring  and  summer  of  1969  and  1970,  larvae  of  the  king  crab,  Paralithodes 
camtschatica,  were  abundant  in  plankton  samples  from  the  southeastern  Bering  Sea.  Abundance 
was  highest  near  shore  and  generally  lowest  in  the  central  and  western  parts  of  the  study  area. 
As  the  season  progressed,  the  center  of  abundance  moved  northeastward  along  the  Alaska  Peninsula 
toward  the  head  of  Bristol  Bay.  This  change  in  distribution  was  apparently  related  to  water  current 
patterns. 


This  report  is  based  on  collections  of  larvae  of  king 
crab,  Paralithodes  camtschatica,  made  by  the 
Auke  Bay  Fisheries  Laboratory,  National  Marine 
Fisheries  Service,  Auke  Bay,  Alaska,  in  the  spring 
and  summer  of  1969  and  1970  in  the  southeastern 
Bering  Sea.  The  larvae  were  collected  during 
studies  of  migrating  salmon  and  exploratory  fish- 
ing for  shellfish.  In  this  report,  I  describe  the 
distribution  and  relative  abundance  of  the  king 
crab  larvae  in  the  southeastern  Bering  Sea  in 
1969  and  1970  and  relate  seasonal  changes  in  the 
distribution  of  the  larvae  to  current  patterns. 

The  only  reports  on  distribution  and  abundance 
of  king  crab  larvae  in  the  study  area  are  those 
by  Takeuchi  (1962,  1968)  and  Rodin.^  Takeuchi 
sampled  with  various  types  of  plankton  nets  from 
Japanese  crab  processing  ships  off  the  Black  Hills- 
Port  Moller  area  in  1957,  1958,  and  1960.  He 
found  more  king  crab  larvae  off  Port  Moller  than 
the  Black  Hills  area,  but  because  his  sampling 
was  restricted  in  area,  he  could  not  determine 
where  the  larvae  had  been  released  or  where  they 
dispersed.  Rodin's  study  encompassed  a  greater 
area  than  Takeuchi's  but  was  of  shorter  duration 
(less  than  1  mo  as  compared  with  an  average  of 
nearly  2  mo).  Rodin  speculated,  however,  that 
king  crab  larvae  were  released  primarily  in  the 
Port  Moller  area. 


'Auke  Bay  Fisheries  Laboratory,  National  Marine  Fisheries 
Service.  NOAA,  P.O.  Box  155,  Auke  Bay,  AK  99821. 

^Rodin,  V.  E.  1966.  Soviet  investigation  in  1965  to  deter- 
mine the  status  of  king  crab  (Paralithodes  camtschatica 
(Tilesius))  stocks  in  southeastern  Bering  Sea.  Unpubl. 
manuscr.,  12  p.  Auke  Bay  Fisheries  Laboratory,  National 
Marine  Fisheries  Service,  NOAA,  Auke  Bay,  AK  99821. 


My  study  provided  further  evidence  that  a 
major  area  of  release  of  king  crab  larvae  occurs 
in  the  Black  Hills-Port  Moller  area  and  the  larvae 
generally  disperse  northeastward  along  the 
Alaska  Peninsula  toward  the  head  of  Bristol  Bay. 

MATERIALS  AND  METHODS 

A  total  of  249  plankton  tows  were  made  in  the 
southeastern  Bering  Sea  from  May  to  September 
1969,  and  237  were  made  from  March  to  Septem- 
ber 1970.  Ten-minute  oblique  hauls  were  taken 
from  the  bottom  to  the  surface  during  daylight 
with  paired  bongo  nets  (Posgay,  Marak,  and 
Hennemuth,  1968),  each  with  a  mouth  area  of 
0.03  m^  and  nylon  netting  of  0.333-mm  mesh. 
Tows  were  made  at  a  speed  of  about  3  knots 
without  regard  to  tide  stage.  The  plankton 
samples  were  preserved  in  d'vc  Formalin^  and  sea- 
water  immediately  after  they  were  collected. 

Although  flowmeters  were  inside  each  sampler 
to  determine  the  amount  of  water  strained, 
mechanical  difficulties  prevented  an  accurate 
measure  for  most  tows.  However,  the  data  have 
been  converted  to  numbers  of  larvae  under  10  m^ 
of  sea  surface,  as  an  index  sufficiently  precise  to 
determine  the  general  distribution  and  relative 
abundance  of  the  larvae.  Because  the  correlation 
between  the  two  nets  fished  simultaneously  was 
high  (r  =  0.979)  and  it  is  desirable  to  use  whole 
numbers,  I  summed  the  catch  of  the  two  nets  in 


■'Reference  to  trade  names  does  not  imply  endorsement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


Manuscript  accepted  October  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


HAYNES;  KING  CRAB  LARVAE  IN  THE  BERING  SEA 


each  tow  rather  than  use  the  average  in  my 
analysis.  The  terms  "positive  tow"  and  "nega- 
tive tow"  are  used  to  describe  plankton  tows  that 
contained  king  crab  larvae  and  those  that  did  not. 
The  station  locations  and  developmental  stages  of 
king  crab  larvae  captured  for  the  positive  tows 
are  given  in  Table  1;  the  locations  of  both 
positive  and  negative  tows  are  indicated  in  the 


charts  showing  distribution  of  larvae  (Figures  1  to 
7).  Charts  showing  distribution  and  abundance  of 
larvae  were  made  by  plotting  the  number  of  larvae 
under  10  m^  of  sea  surface  at  each  station  and  then 
drawing  isopleths.  Identification  of  the  larval 
stages  was  based  on  descriptions  given  by  Maru- 
kawa  ( 1933),  Sato  and  Tanaka  ( 1949),  and  Kurata 
(1964). 


Table   1. — Station  location  and  number  and  stage  of  development  of  king  crab  larvae  captured  for  each 
positive  tow  collected  in  the  southeastern  Bering  Sea,  1969  and  1970. 


Depth 
(m) 

Station 

location 

Larva 

stage 

Zo 

ea 

Glau- 
cothoe 

Date 

Lat   N 

Long   W 

1 

II 

III 

IV 

Total 

1969 

May 
18 

55 

55°00' 

165°00' 

39 

32 

5 





76 

19 

45 

58°00' 

163='22' 

1 

— 

1 

— 

— 

2 

20 

75 

56=20' 

162=12' 

10 

— 

— 

— 

— 

10 

26 

116 

55'20' 

165°45' 

— 

1 

7 

— 

— 

8 

26 

107 

5540' 

165°10' 

— 

4 

10 

7 

— 

21 

27 

116 

55M0' 

165=47' 

— 

— 

6 

4 

— 

10 

29 

44 

57°40' 

163°22' 

— 

1 

— 

— 

— 

1 

June 

3 

45 

56'20' 

161=00' 

5 

18 

8 

4 

— 

35 

3 

63 

57=00' 

160=57' 

4 

13 

6 

— 

— 

23 

3 

63 

57°00' 

159=43' 

49 

60 

1 

— 

— 

110 

3 

47 

57°40' 

159°38' 

5 

1 

1 

— 

— 

7 

4 

57 

57°40' 

160'=53' 

8 

1 

— 

— 

— 

9 

4 

47 

58°00' 

160='51' 

4 

2 

— 

— 

— 

6 

4 

40 

SS'OO' 

162°07' 

1 

— 

— 

— 

— 

1 

5 

75 

56=20' 

162°12' 

— 

2 

2 

— 

— 

4 

17 

19 

56°03' 

160°58' 

— 

— 

— 

2 

— 

2 

18 

63 

57°00' 

160=57' 

— 

— 

— 

2 

— 

2 

19 

63 

57=00' 

159°43' 

2 

23 

20 

6 

— 

51 

19 

47 

57=40' 

159°38' 

2 

9 

— 

— 

— 

11 

19 

57 

57°40' 

160°53' 

2 

3 

1 

— 

— 

6 

19 

47 

58='00' 

1 60°51 ' 

— 

3 

5 

— 

— 

8 

20 

46 

57=40' 

162=08' 

1 

2 

— 

— 

— 

3 

20 

60 

57'00' 

162°10' 

— 

— 

1 

1 

— 

2 

24 

66 

56=40' 

160=59' 

— 

1 

— 

4 

— 

5 

24 

68 

56°30' 

160'=59' 

— 

— 

2 

1 

— 

3 

24 

45 

56=20' 

161=00' 

-     — 

— 

1 

6 

— 

7 

26 

68 

56=30' 

160=59' 

— 

— 

3 

7 

— 

10 

27 

29 

56=54' 

159=08'' 

— 

— 

— 

1 

— 

1 

27 

36 

57=00' 

159=07' 

— 

— 

— 

1 

— 

1 

27 

45 

5709' 

159°05' 

— 

— 

2 

3 

— 

5 

27 

51 

57=20' 

159=04' 

— 

2 

9 

5 

— 

16 

28 

51 

57=29' 

159°03' 

— 

5 

42 

7 

— 

54 

28 

44 

57=40' 

159°01' 

— 

— 

11 

— 

— 

11 

28 

35 

57=49' 

159°00' 

— 

1 

8 

1 

— 

10 

28 

37 

57°55' 

158'=59' 

— 

— 

5 

1 

— 

6 

29 

43 

58°00' 

158=58' 

— 

— 

4 

1 

— 

5 

July 

1 

45 

58°10' 

160°50' 

_ 

_ 

1 



1 

1 

47 

58^00' 

160°51' 

— 

— 

3 

2 

— 

5 

2 

63 

57=00' 

160=57' 

— 

— 

— 

4 

— 

4 

4 

25 

57=31' 

158=54' 

— 

— 

— 

1 

— 

1 

4 

29 

57°41' 

158=17' 

— 

— 

— 

— 

1 

1 

4 

35 

57=47' 

158=23' 

— 

— 

— 

1 

— 

1 

7 

22 

58=33' 

1 59=31 ' 

— 

— 

— 

— 

1 

1 

7 

23 

58=29' 

159=32' 

— 

— 

— 

— 

3 

3 

7 

28 

58=14' 

1 59=30' 

— 

— 

— 

1 

— ■ 

1 

8 

35 

57=55' 

158=33' 

— 

— 

— 

4 

— 

4 

8 

36 

57'44' 

158=20' 

— 

— 

— 

6 

— 

6 

9 

51 

57=20  ■ 

159^04' 

— 

— 

1 

4 

— 

5 

9 

45 

56=20' 

161=00' 

— 

— 

— 

— 

1 

1 

13 

63 

57°00' 

159=43' 

— 

— 

— 

4 

— 

4 

14 

47 

57°40' 

159=38' 

— 

— 

2 

29 

— 

31 

14 

57 

57°40' 

160=53' 

— 

— 

— 

1 

— 

1 

1970 

March 

29 

111 

55'=08' 

165=12' 

1 

— 

— 

— 

— 

1 

805 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Table  1. — Continued. 


Date 


Depth 
(m) 


Larval  stage 


Station  location 


Zoea 


Lat.  N 


Long   W 


IV 


Glau- 
cothoe 


Total 


1970— Continued 
May 


June 


9 

60 

55°00' 

164°35' 

399 

20 

2 

— 

13 

73 

56°40' 

163-23' 

1 

— 

— 

— 

13 

75 

56°20' 

162-48' 

1 

3 

— 

— 

14 

47 

55'40' 

162-50' 

16 

9 

— 

— 

14 

76 

56°00' 

162°14' 

26 

2 

— 

— 

14 

75 

5620' 

162-12' 

2 

— 

— 

— 

15 

65 

56°40' 

162-11' 

1 

— 

— 

— 

15 

65 

57°00' 

161  34' 

1 

— 

— 

— 

16 

65 

57°20' 

161-32' 

2 

— 

— 

— 

16 

55 

57°20' 

160-56' 

1 

— 

— 

— 

16 

58 

57°20' 

160-18' 

11 

2 

— 

— 

16 

63 

57=00' 

159-43' 

1 

— 

— 

— 

17 

35 

56=40' 

159-45' 

9 

1 

— 

— 

17 

58 

56M0' 

160-22' 

9 

— 

— 

— 

17 

58 

57°00' 

160-20' 

12 

1 

— 

— 

17 

63 

57-00' 

160-57' 

7 

— 

— 

— 

18 

66 

56°40' 

160-59' 

14 

2 

— 

— 

18 

86 

56°40' 

161-35' 

20 

1 

— 

— 

18 

61 

56'20' 

161-37' 

40 

10 

2 

— 

19 

45 

56-20' 

161-00' 

163 

106 

— 

— 

19 

25 

56°20' 

160-25' 

5 

3 

— 

— 

22 

73 

56°10' 

162-14' 

11 

4 

— 

— 

22 

52 

se'oe' 

161-53' 

4 

1 

— 

— 

22 

70 

56°26' 

161=59' 

16 

7 

— 

— 

23 

71 

56=40' 

161-22' 

3 

1 

— 

— 

23 

60 

56°26' 

161-33' 

35 

17 

— 

— 

24 

22 

57°07' 

160-52' 

1 

— 

— 

— 

24 

47 

56=19' 

161-04' 

9 

2 

— 

— 

24 

70 

56°31' 

161-17' 

36 

22 

— 

— 

24 

83 

56=43' 

161-30' 

3 

1 

— 

— 

24 

64 

56°55' 

161-42' 

6 

2 

— 

— 

24 

51 

57°07' 

161-55' 

4 

.    — 

— 

— 

25 

36 

58°02' 

161-33' 

1 

— 

— 

— 

25 

22 

58°13' 

160=08' 

1 

— 

— 

— 

26 

45 

57°41' 

1 59=50' 

2 

1 

— 

— 

26 

45 

57°29' 

159-37' 

3 

1 

— 

— 

26 

51 

57°17' 

1 59-25' 

2 

1 

— 

— 

26 

47 

57=06' 

159-12' 

5 

12 

— 

— 

26 

21 

56='54' 

159-00' 

— 

2 

— 

— 

28 

89 

55=52' 

163-17' 

1 

— 

— 

— 

28 

59 

55='39' 

163-04' 

1 

— 

— 

— 

29 

111 

55°33' 

165-36' 

— 

1 

1 

— 

29 

111 

55°21' 

165-24' 

— 

12 

4 

— 

29 

111 

55°08' 

165-12' 

— 

2 

1 

— 

29 

91 

54  "56' 

164-59' 

— 

13 

1 

— 

29 

43 

54°43' 

164=47' 

2 

5 

2 

— 

8 

111 

55°08' 

165-12' 

1 

36 

36 

1 

15 

48 

56°19' 

161-00' 

1 

7 

15 

5 

21 

49 

56°22' 

161=00' 

— 

4 

3 

— 

21 

42 

56=17' 

161-00' 

— 

4 

2 

4 

25 

27 

56°09' 

161-00' 

— 

— 

5 

11 

25 

21 

56°07' 

160-52' 

— 

— 

2 

8 

26 

47 

56=19' 

161-04' 

— 

1 

— 

1 

26 

70 

56°31' 

161-17' 

— 

2 

— 

— 

26 

83 

56=43' 

161-30' 

— 

— 

2 

— 

26 

64 

56"55' 

161-42' 

— 

2 

1 

— 

26 

51 

57°07' 

161-55' 

1 

— 

— 

— 

27 

47 

57°06' 

159-12' 

— 

— 

15 

18 

27 

51 

57-17' 

159-25' 

— 

2 

38 

16 

27 

45 

57-29' 

159-37' 

— 

3 

23 

7 

27 

45 

57-41' 

159-50' 

— 

4 

34 

4 

27 

42 

57=-54' 

159-42' 

— 

— 

15 

9 

27 

22 

57-59' 

157-55' 

— 

— 

— 

27 

33 

58=04' 

158-25' 

— 

— 

— 

28 

22 

58-13' 

160-08' 

— 

— 

— 

2 

28 

41 

58-38' 

162-16' 

— 

— 

— 

29 

40 

58-22' 

163-24' 

— 

1 

— 

— 

30 

59 

55-39' 

163-04' 

— 

— 

1 

30 

28 

55-27' 

162-52' 

— 

— 

— 

421 
1 
4 

25 

28 
2 
1 
1 
2 
1 

13 
1 

10 
9 

13 
7 

16 

21 

52 

269 

8 

15 
5 

23 
4 

52 
1 

11 

58 
4 
8 
4 
1 
1 
3 
4 
3 

17 
2 
1 
1 
2 

16 
3 

14 
9 

74 

28 

7 

10 

16 

10 

2 

2 

2 

3 

1 

33 

56 

33 

42 

24 


July 


111 


55-33' 


165-36' 


806 


HAYNES:  KING  CRAB  LARVAE  IN  THE  BERING  SEA 


1 1 1 r 


—58° 


<p 


I  70° 


'<i-^ 


xs^" 


LARVAE  PER  TOW 


<=o. 


-56° 


N 


I  65° 


170° 


0  50         100        150 

I'll 

KM 


_l L 


0 

0 


56°  — 


<P 


J I I L 


Figure  1 . — Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 
Sea,  29  March-30  April  1969  and  1970.  Solid  circle  indicates  larvae  were  present  at  station. 


—58° 


<? 


I  70' 


-56° 


0  50         100       150 

1  I  I  I 

KM 


170° 
_l L. 


<:y^J^' 


Figure  2. — Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 
Sea,  1-15  May  1969  and  1970.  Solid  circles  indicate  larvae  were  present  at  station. 


807 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


—58° 


<? 


I  70° 


cS."^ 


XX^" 


"^  LARVAE  PER  TOW 

□   26    125 


CO, 


-56° 


N 


165° 


0  50         100        150 

1  I.I  I 

KM 


170° 


HILLS'^     ii 


L.^^- 


.-  ^y\ 


"=0 . 

J i_ 


pN 


.cv 


^^^ 


oC 


t^^ 


160== 


c7 


Figure  3. — Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 
Sea,  16-31  May  1969  and  1970.  Solid  circles  indicate  larvae  were  present  at  station. 


—58° 


<? 


I  70° 


CO, 


-56° 


170° 


0  50         100        150 

1  I  I  I 

KM 


o^:/p^° 


Figure  4. — Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 
Sea,  1-15  June  1969  and  1970.  Solid  circles  indicate  larvae  were  present  at  station. 


808 


HAYNES;  KING  CRAB  LARVAE  IN  THE  BERING  SEA 


—58° 


<? 


I  70° 


^<c-^ 


v.^" 


«=c 


-56° 


170° 


-1 r 


LARVAE  PER  TOW 
m   25    125 


A 

i 


0  50  100        150 

1  I  I  -I 

KM 


<:y^:^''' 


Figure  5. — Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 
Sea,  16-30  June  1969  and  1970.  Solid  circles  indicate  larvae  were  present  at  station. 


—58° 


<? 


I  70° 


cS^^ 


«=c> 


-56° 


170° 


N 


165° 


LARVAE  PER  TOW 


6-25 
26-125 


Q) 


0  50         100        150 

1  I  I  I 

KM 


BLACK  HILLS 


Om, 


56°H 


Figure  6.^Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 
Sea,  1-15  July  1969  and  1970.  Solid  circles  indicate  larvae  were  present  at  station. 


809 


FISHERY   BULLETIN:  VOL.  72,  NO.  3 


—58° 


<? 


-| 1 1 r 


I  70° 


c<i^ 


C-^^^ 


.X^^ 


<=0> 


-56° 


170° 


0  50         100        150 

1  I  I  I 

KM 


165° 


cb      o     o 


>^^^e^° 


^? 


f- 


■d 


,nC> 


O 

e 


160° 


Figure  7. — Distribution  and  relative  abundance  of  king  crab  larvae  sampled  at  stations  in  the  southeastern  Bering 

Sea,  16  July-21  September  1969  and  1970. 


DISTRIBUTION  AND  RELATIVE 
ABUNDANCE 

Although  sampling  locations  and  dates  were 
different  each  year,  I  determined  that  I  could 
combine  the  data  for  both  years  for  consideration 
of  distribution  and  abundance.  For  each  semi- 
monthly period,  I  tabulated  the  degree  squares 
(the  areas  bordered  by  1°  of  latitude  and  longi- 
tude) that  were  sampled  in  both  years.  This  re- 
sulted in  14  degree  squares,  7  each  for  the  latter 
half  of  May  and  June.  For  each  of  the  two  semi- 
monthly periods,  the  median  catch  per  tow  was 
computed  and  the  degree  squares  were  ranked 
"good"  or  "poor"  on  the  basis  of  whether  their 
catch  per  tow  was  greater  or  lesser  than  the 
median.  In  this  manner  it  was  possible  to  compare 
degree  squares  without  considering  the  actual 
abundance  of  larvae.  The  degree  square  data  indi- 
cated that  in  every  instance  except  one  the  same 
degree  squares  for  each  year  were  consistently 
good  or  poor. 

I  assumed  therefore  that  the  distributions  were 
not  random  and  that  the  data  for  the  two  sampling 
years  could  be  combined  for  analyzing  larval 
distribution. 

The  combined  data  on  distribution  of  larvae  in 


1969  and  1970  are  presented  by  time  periods 
(usually  semimonthly)  between  29  March  and  21 
September  (Figures  1  to  7).  Most  of  the  larvae 
were  in  the  southern  and  eastern  portions  of  the 
study  area  and  within  these  areas  were  most 
abundant  close  to  shore.  The  largest  catches  (more 
than  1,000  larvae  under  10  m^  of  sea  surface) 
were  made  near  Unimak  Pass  and  Port  Moller; 
the  smallest  (usually  fewer  than  10  larvae  under 
10  m^  of  sea  surface)  were  generally  made  in  the 
more  central  and  western  parts  of  the  area. 

The  distribution  and  abundance  of  larvae  in  the 
Black  Hills-Port  Moller  area  increased  gradually 
toward  the  head  of  Bristol  Bay.  During  the  first 
half  of  May  (Figure  2),  larvae  were  found  off  the 
Black  Hills  area;  2  wk  later  (Figure  3),  these  lar- 
vae apparently  had  been  carried  northeastward 
along  the  coast  and  became  mixed  with  larvae 
released  off  the  Port  Moller  area.  As  the  season 
continued,  the  center  of  abundance  shifted  farther 
toward  the  head  of  the  bay  (Figures  4  and  5).  This, 
trend  continued  until  mid-July  (Figure  6),  when 
no  more  larvae  were  taken  (Figure  7). 

The  seasonal  progression  of  occurrence  of  larvae 
off  Unimak  Island  is  less  clear.  A  small  concentra- 
tion of  larvae  was  found  in  this  area  in  early  May 
(Figure  2);  2  wk  later  they  were  most  abundant  to 


810 


HAYNES;  KING  CRAB  LARVAE  IN  THE  BERING  SEA 


the  northwest  toward  the  open  sea  (Figure  3).  Too 
few  samples  were  taken  in  the  Unimak  Island 
area  after  May  to  determine  the  extent  of  the 
drift  of  larvae. 

The  four  zoeal  stages  that  king  crab  larvae  pass 


Figure  8. — Percentages  of  four  zoeal  stages  of  king  crab  larvae 
sampled  at  stations  in  the  southeastern  Bering  Sea,  1969  and 
1970.  Data  for  1969  and  1970  combined  by  semimonthly 
periods  (see  Figures  3  to  7). 


through  before  molting  to  the  glaucothoe  (settling) 
stage  were  all  represented  in  my  samples  (Table 
1).  The  percentage  of  larvae  in  each  zoeal  stage  is 
shown  by  semimonthly  intervals  in  Figure  8.  A 
comparison  of  this  figure  with  Figures  1  to  7 
shows  that  the  progression  of  larval  stages 
corresponded  closely  with  the  seasonal  progres- 
sion of  larval  distribution.  For  instance,  the 
abundant  larvae  found  early  in  the  season  off 
Unimak  Island  and  Port  Moller  were  mostly 
stage  I.  As  the  areas  of  greatest  abundance  moved 
toward  the  head  of  the  bay,  the  percentage  of  later 
larval  stages  in  the  samples  increased,  and  by 
July  most  of  the  larvae  were  stage  IV  (Figure  8). 

LARVAL  RELEASE  AREAS 

Areas  of  relatively  high  abundance  of  stage  I 
larvae  are  generally  assumed  to  be  the  areas 
where  the  larvae  were  released  by  the  female. 
This  proved  to  be  true  in  the  present  study:  stage 
I  larvae  were  abundant  near  Unimak  Island 
and  the  Black  Hills-Port  Moller  area  where 
female  king  crabs  with  empty  egg  cases  were  also 
abundant  (Figure  9).  (The  egg  cases  remain 
attached  to  the  pleopods  of  the  female  for  some 
time  after  the  larvae  have  been  released.)  The 


I  70° 


c<C-^ 


0,^" 


—  58° 


<? 


«=e. 


—56° 


17  0° 


A 
J 

N 


50 

=1= 


100 

— 1— 


KM 


150 


165° 


O 

o 


*  BLACK  HILLS-'     |/  '^ 


pN 


.cv 


f\C 


OC 


O 

e 


160° 

L 


56° 


Figure  9. — Trawling  stations  (circles)  in  the  southeastern  Bering  Sea  where  female  king  crabs  were  taken  in  May 
1969  and  1970.  Stations  with  crabs  with  empty  egg  cases  are  designated  by  solid  circles. 


811 


FISHERY  BULLETIN;  VOL.  72.  NO.  3 


distribution  of  egg-bearing  king  crabs  with  empty 
egg  cases  shown  in  Figure  9  was  determined  from 
trawling  in  May  1969  and  1970  (data  combined). 
Weber  (1967)  also  reported  that  in  Bristol  Bay, 
king  crabs  usually  release  their  larvae  in  May. 


ton  was  not  collected  south  of  Unimak  Pass 
during  the  present  study,  and  the  question  of 
recruitment  of  king  crab  larvae  into  Bristol  Bay 
from  areas  south  of  the  Alaska  Peninsula 
must  await  a  more  detailed  investigation. 


RELATION  BETWEEN 

DISTRIBUTION  OF  LARVAE 

AND  CURRENT  PATTERNS 

My  observations  of  the  dispersal  of  stage  I 
larvae  from  the  release  areas  generally  agree 
with  the  known  patterns  of  water  currents  in  the 
study  area.  Hebard  (1959)  found  that  in  the 
southeastern  Bering  Sea  water  moved  counter- 
clockwise toward  Bristol  Bay  along  the  Alaska 
Peninsula  and  away  from  Bristol  Bay  in  the  more 
northern  parts  of  the  southeastern  Bering  Sea. 
Under  these  conditions  larvae  released  in  the 
Black  Hills-Port  Moller  area  would  be  carried 
northeastward  along  the  Alaska  Peninsula 
toward  the  head  of  Bristol  Bay.  The  seasonal 
shift  of  larvae  shown  in  Figures  1  to  7  cor- 
responds closely  with  this  pattern  of  water 
movement. 

Because  of  differences  in  water  currents,  the 
direction  of  seasonal  shift  of  larvae  is  different  in 
the  Unimak  Island  area  than  it  is  to  the  east. 
Oceanographic  studies  in  this  area,  summarized 
by  Dodimead,  Favorite,  and  Hirano  (1963),  show 
that  water  from  the  Gulf  of  Alaska  flows  north- 
ward through  the  interisland  passages  of  the 
Aleutian  Islands  in  the  southeastern  Bering  Sea. 
Such  a  flow  pattern  through  Unimak  Pass  is 
consistent  with  the  apparent  northward  move- 
ment of  king  crab  larvae  from  the  Unimak 
Island  area  (Figure  3). 

On  the  basis  of  his  findings  on  water  currents 
in  the  southeastern  Bering  Sea,  Hebard  (1959) 
postulated  that  recruitment  of  king  crab  larvae 
into  the  Bering  Sea  may  occur  through  the  island 
passages  of  the  Aleutian  Islands,  especially  Uni- 
mak Pass.  If  this  is  so,  then  the  possibility  exists 
that  the  stock  of  king  crabs  in  Bristol  Bay  is 
derived  to  some  extent  from  larvae  released  south 
of  the  Alaska  Peninsula.  Unfortunately,  plank- 


LITERATURE  CITED 

Dodimead,  A.  J.,  F.  Favorite,  and  T.  Hirano. 

1963.  Review  of  oceanography  of  the  subarctic  Pacific 
region.     Int.  North  Pac.  Fish.  Comm.,  Bull.  13,  195  p. 

Hebard,  J.  F. 

1959.  Currents  in  southeastern  Bering  Sea  and  possible 
effects  upon  king  crab  larvae.  U.S.  Fish  Wildl.  Serv., 
Spec.  Sci.  Rep.  Fish.  293,  11  p. 

KURATA,  H. 

1964.  Larvae  of  decapod  Crustacea  of  Hokkaido.  6.  Litho- 
didae  (Anomura).  [In  Jap.,  Engl,  summ.]  Bull.  Hok- 
kaido Reg.  Fish.  Res.  Lab.  29:49-65. 

Marukawa,  H. 

1933.  Biological  and  fishery  research  on  Japanese  king- 
crab,  Paralithodes  camtschatica  (Tilesius).  [In  Jap., 
Engl,  abstr.]  J.  Imp.  Fish.  Exp.  Stn.  4,  152  p.,  19 
plates. 

PosGAY,  J.  A.,  R.  R.  Marak,  and  R.  C.  Hennemuth. 

1968.  Development  and  test  of  new  zooplankton  samplers. 
Int.  Comm.  Northwest  Atl.  Fish.,  Res.  Doc.  68-34,  7  p. 

Sato,  S.,  and  S.  Tanaka. 

1949.  Study  on  the  larval  stage  of  Paralithodes  cam- 
tschatica (Tilesius).  I.  Morphological  research.  Hok- 
kaido Fish.  Exp.  Stn.  Res.  Rep.  1:7-24.  (Translated  by 
L.  M.  Nakatsu,  U.S.  Fish  Wildl.  Serv.,  Seattle  Biol. 
Lab.,  1968,  24  p.,  3  plates;  available  from  Northwest 
Fish.  Cent.,  Natl.  Mar.  Fish.  Serv.,  NOAA,  Seattle,  WA 
98112.) 

Takeuchi,  I. 

1962.  On  the  distribution  of  zoeal  larvae  of  king  crab, 
Paralithodes  camtschatica,  in  the  southeastern  Bering 
Sea  in  1960.  Bull.  Hokkaido  Reg.  Fish.  Res.  Lab. 
24:163-170.  (Translated  by  E.  H.  Ozaki,  U.S.  Fish  Wildl. 
Serv.,  Seattle  Biol.  Lab.,  1967,  10  p.;  available  from 
Northwest  Fish.  Cent.,  Natl.  Mar.  Fish.  Serv.,  NOAA, 
Seattle,  WA  98112.) 
1968.  Nanto  Bering-Kaiiki  ni  okeru  tarabaganizoea 
yochu  no  bumpu  ni  tsuite  (1957-1958)  (On  the  dis- 
tribution of  zoea  larva  of  king  crab,  Paralithodes 
camtschatica,  in  the  southeastern  Bering  Sea  in  1957 
and  1958).  [Engl,  summ.]  Bull.  Hokkaido  Reg.  Fish. 
Res.  Lab.  34:22-29.  (Fish.  Res.  Board  Can.,  Transl. 
Ser.  1195.) 

\Veber,  D.  D. 

1967.  Growth  of  the  immature  king  crab  Paralithodes 
camtschatica  (Tilesius).  Int.  North  Pac.  Fish.  Comm., 
Bull.  21:21-53. 


812 


OCCURRENCE  OF  SILVER  HAKE,  MERLUCCIUS  BILINEARIS, 

EGGS  AND  LARVAE  ALONG  THE  MIDDLE  ATLANTIC 

CONTINENTAL  SHELF  DURING   1966 


Michael  P.  Fahay^ 


ABSTRACT 

During  an  ichthyoplankton  survey  over  the  continental  shelf  between  Martha's  Vineyard,  Mass. 
and  Cape  Lookout,  N.C.,  from  December  1965  to  December  1966,  3,241  eggs  and  11,032  larvae 
of  the  silver  hake,  Merluccius  bilinearis,  were  collected.  Eggs  were  collected  from  May  until 
November,  with  a  peak  in  June.  Most  of  the  eggs  {7T7c)  were  collected  south  of  Martha's 
Vineyard,  Mass.  The  southernmost  occurrence  of  eggs  was  off  North  Carolina  in  November.  Larvae 
were  collected  from  May  until  December,  with  a  peak  in  September.  Larvae  were  most  abundant 
on  the  shelf  between  Hudson  Canyon  and  Martha's  Vineyard.  The  evidence  suggests  that  most 
of  the  eggs  and  larvae  collected  on  the  survey  had  been  spawned  near  the  northeastern  edge  of  the 
survey  area  and  drifted  southwesterly.  There  is  also  evidence  of  a  size-related,  diel,  vertical  migration 
by  the  postlarvae. 


In  December  1965,  the  Sandy  Hook  Marine 
Laboratory  began  a  1-yr  ichthyoplankton  survey 
of  the  continental  shelf  between  Martha's  Vine- 
yard, Mass.  and  Cape  Lookout,  N.C.  The  survey 
was  designed  to  delimit  the  spawning  times  and 
locations  of  marine  game  fishes,  define  dispersal 
patterns  of  larvae,  and  form  the  first  phase  in  a 
study  to  determine  what  species  depend  on  an 
estuarine  environment  during  some  phase  of  their 
early  life  history.  We  placed  emphasis  on  no  one 
species  and  began  the  survey  with  no  preconceived 
notions  on  either  the  geographical  extent  or  the 
seasonality  of  spawning  of  any  species.  This  report 
on  the  eggs  and  larvae  of  silver  hake,  Merluccius 
bilinearis  (Mitchill),  represents  one  of  a  series 
resulting  from  that  survey. 

The  silver  hake  is  an  important  sport  and 
commercial  species  widely  distributed  over  the 
continental  shelf  of  eastern  North  America 
from  the  Gulf  of  St.  Lawrence  (McKenzie  and 
Scott,  1956)  southward  to  South  Carolina,  with 
centers  of  abundance  between  Nova  Scotia  and 
New  York  (Bigelow  and  Schroeder,  1953).  Silver 
hake  are  found  in  both  shoal  and  deep  water 
within  a  wide  temperature  range,  usually  over 
bottoms  of  sand  or  sand-silt  mixtures  (Fritz,  1965). 
When  winter  cooling  occurs  on  the  shelf,  silver 


'Middle  Atlantic  Coastal  Fisheries  Center,  Sandy  Hook 
Laboratory,  National  Marine  Fisheries  Service,  NOAA,  High- 
lands, NJ  07732. 


hake  migrate  to  warmer  waters  on  the  conti- 
nental edge  and  slope. 

Silver  hake  in  the  western  North  Atlantic  con- 
sist of  two  morphologically  separable  and  non- 
mingling  populations  (Conover,  Fritz,  and  Vieira, 
1961)  roughly  separated  by  the  41°30'N  meridian 
(Nichy,  1969).  Hence,  the  Gulf  of  Maine  and 
northern  edge  of  Georges  Bank  contain  one 
population,  while  the  southern  slopes  of  Georges 
Bank  and  continental  shelf  south  and  west  of 
Cape  Cod  contain  the  other.  This  report  concerns 
the  eggs  and  larvae  produced  by  the  latter 
population. 

Spawning  in  the  Gulf  of  Maine  extends  from 
June  to  October,  with  a  peak  in  July  and  August 
(Bigelow  and  Schroeder,  1953).  Kuntz  and  Rad- 
cliffe  (1917)  described  the  embryological  and  lar- 
val development  of  silver  hake  and  suggested 
that  "the  spawning  period  for  this  species  is  a 
protracted  one  and  not  all  the  eggs  mature  at 
one  time."  Sauskan  and  Serebryakov  (1968),  in  a 
study  of  the  gonads  of  silver  hake  from  Georges 
Bank  and  the  Nova  Scotian  shelf,  showed:  1) 
larger  females  mature  and  spawn  earlier  than 
smaller  ones;  2)  vitellogenesis  is  asynchronous, 
and  individual  fish  spawn  in  three  portions  within 
a  season;  3)  the  initial  spawning  of  an  individual 
female  accounts  for  half  the  total  seasonal  pro- 
duction of  oocytes. 

Silver  hake  eggs  and  larvae  have  been  collected 
from  Halifax,  Nova  Scotia  to  Cape  May,  N.J. 
(Bigelow  and  Schroeder,  1953).  Eggs  and  larvae 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


813 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


have  been  reported  in  local  plankton  collections 
as  follow^s:  off  Nova  Scotia  (Dannevig,  1919);  over 
Georges  Bank  (Marak  and  Colton,  1961);  in  Block 
Island  Sound  (Merriman  and  Sclar,  1952).  Saus- 
kan  and  Serebryakov  (1968)  discussed  the  dis- 
tribution of  silver  hake  eggs  and  larvae  but 
limited  their  sampling  and  discussion  to  areas 
east  of  our  1966  sampling  area. 

MATERIALS  AND  METHODS 

We  conducted  eight  cruises  aboard  the  RV 
Dolphin  from  December  1965  to  December  1966. 
On  each  cruise,  we  sampled  92  stations  arranged 
on  14  transects  between  Martha's  Vineyard,  Mass. 
and  Cape  Lookout,  N.C.  (Figure  1).  The  station 
arrangement  allowed  us  to  sample  from  nearshore 
to  the  183-m  (100-fathom)  contour  along  each 
transect.  We  scheduled  cruises  to  occur  at  6-wk 
intervals,  and  the  average  cruise  occupied  17 
days.  We  sampled  four  transects  from  Martha's 
Vineyard  to  New  Jersey  on  a  supplemental  cruise 
in  September  1966.  Dates  and  sampling  sequences 
and  locations  of  collecting  stations  listed  to  the 
nearest  0.8  km  (0.5  nautical  mile)  are  contained 
in  Clark  etal.  (1969). 

We  used  loran,  radar  and,  where  possible,  visi- 
ble ranges  to  position  the  Dolphin  on  station. 
Routine  work  on  station  involved  the  use  of  a 
bathythermograph  to  obtain  temperature  profiles, 
a  stem  thermometer  to  measure  surface  tempera- 
tures, and  a  Beckman^  RS-5  portable  salinometer 
to  obtain  salinities  and  temperatures  from  the 
surface  to  the  maximum  plankton  sampling 
depth.  In  water  deeper  than  the  length  of  the 
salinometer  cable,  we  used  Frautschy  water 
bottles  and  measured  the  salinities  of  these 
samples  with  a  hydrometer  kit.  Temperature  and 
salinity  profiles  resulting  from  the  survey  are 
found  in  Clark  et  al.  (1969). 

We  chose  the  Gulf  V  high-speed  plankton 
sampler  (Arnold,  1959)  to  overcome  many  of  the 
problems  inherent  in  sampling  ichthyoplankton. 
It  samples  at  5  knots,  thus  allowing  capture  of 
organisms  capable  of  avoiding  slower  nets.  Its 
large  mouth  opening  provides  large  quantities  of 
eggs  and  larvae  per  tow  and,  hence,  samples  with 
high  reliability  for  comparative  purposes.  Flow- 
through  characterisitcs  of  the  net  prevent  exten- 
sive damage  to  larvae.  Finally,  the  Gulf  V  is  rug- 
gedly built  and  requires  a  minimum  of  shipboard 


W  '»■ 


'■'Reference  to  trade  names  does  not  imply  endoresement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


Figure  1. — RV  Dolphin  survey,  December  1965  to  December 
1966.  Location  of  transects  and  collecting  stations. 

maintenance.  Our  sampler  (Figure  2)  consists  of  a 
conical  net  of  0.33-mm  (0.013-inch)  Monel  wire 
with  12  meshes/cm  (30  meshes/inch)  and  an 


814 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


Figure  2. — Gulf  V  high-speed  plankton  sampler  with  depressor. 

aperture  size  of  0.52  mm  (0.02  inch).  Other 
dimensions  are  as  described  by  Arnold  (1959). 

Our  method  of  towing  tw^o  samplers  consecu- 
tively was  described  in  detail  in  Clark  et  al. 
(1969),  Richards  and  Kendall  (1973),  and  Smith 
(1973).  Figure  3  illustrates  schematically  our 
towing  methods  over  various  depths  of  water.  As 
illustrated  in  Figure  3,  the  step-oblique  method 
sometimes  resulted  in  unequal  sampling  intensity 
at  certain  depths  under  a  unit  of  surface  area. 
Therefore,  to  diagram  the  horizontal  distribution 
on  maps,  I  combined  the  catch  of  the  two  nets  and 
adjusted  them  as  shown  in  Table  1. 


The  catches  of  the  two  nets  presented  separately 
provide  added  useful  information.  This  is  especial- 
ly true  in  view  of  1)  observed  differences  in  num- 
bers and  length-frequencies  between  the  catches 
of  the  two  nets,  and  2)  the  presence  of  a  thermo- 
cline  within  the  stratum  sampled  by  the  deep  net. 
In  Appendix  Table  1,  I  tabulated  the  catch  of  the 
deep  net  as  observed.  However,  the  deep  net  was 
not  equipped  with  a  closing  device  and  was  sub- 
ject to  contamination  in  the  upper  15  m  during 
setting  out  and  hauling  back  procedures.  There- 
fore, for  study  of  vertical  distribution,  I  adjusted 
the  deep  net  catch  after  assuming  that  it  sampled 
the  upper  zone  for  3  min. 

Tows  are  labeled  "D"  (day),  "N"  (night),  or  "C" 
(crepuscular,  i.e.  within  1  h  of  sunrise  or  sunset) 
in  Appendix  Table  1. 

After  each  tow,  we  washed  the  samplers  down, 
removed  the  cups,  and  preserved  the  samples  in 
buffered  5%  Formalin.  The  samples  were  returned 
to  the  laboratory  where  all  ichthyoplankton  was 
removed  and  larvae  divided  into  family  groups. 
Gadids  and  merlucciids  were  then  identified  to 
species.  Eggs  were  initially  grouped  according  to 
their  diameters.  Early  silver  hake  eggs  are  indis- 
tinguishable from  the  eggs  of  many  other  species 
of  marine  fishes.  Common  characteristics  include: 
outside  diameter  of  about  1.0  mm,  presence  of  a 
single  oil  globule,  narrow  perivitelline  space,  and 
4:1  ratio  of  egg  diameter  to  oil  globule  diameter. 
Consequently,  specific  identifications  were 
limited  to  eggs  in  advanced  stages  of  development. 
I  based  identifications  of  late  stage  M.  bilinearis 
eggs  on  published  descriptions  (Kuntz  and  Rad- 
cliffe,  1917;  Sauskan  and  Serebryakov,  1968)  and 
on  my  own  rearing  experiments  with  artifically 
fertilized  eggs.  The  purpose  of  my  experiment 
was  to  determine  whether  pigment  was  present 
on  the  yolk.  It  was  terminated  before  hatching 
occurred.  Prolarval  offshore  hake,  M.  albidus, 
were  identified  following  the  descriptions  by 
Marak  (1967)  and  removed  from  the  M.  bilinearis 


Table  1. — Method  used  to  combine  the  catches  of  shallow  and  deep  samplers. 


Shallow  net 

Deep 

net 

Number 

Minutes 

Numbe 

Minutes 

of 

per 

of 

per 

Total  station 

steps 

step 

steps 

step 

catch  formula 

2 

15 

0 

0 

'/3  shallow 

3 

10 

0 

0 

V2  shallow 

6 

5 

0 

0 

Total  shallow 

6 

5 

2 

15 

Total  shallow  +  '/a  deep 

6 

5 

3 

10 

Total  shallow  +  Vz  deep 

6 

5 

6 

5 

Total  shallow  +  total  deeo 

815 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


DIRECTION    OF     TOW 


Figure  3. — Six  sampling  methods  for  V^-h  plankton  tows  over  different  water  depths. 


collection.  I  also  removed  several  postlarvae 
recognized  as  Merluccius  sp.  but  which  I  presume 
are  M.  alhidus,  the  postlarvae  of  which  are 
undescribed. 

We  measured  all  specimens,  except  mutilated 
ones,  from  the  tip  of  the  snout  to  the  tip  of  the 
notochord  or  urostyle  with  an  ocular  micrometer 
or  point-to-point  dial  calipers.  Measurements 
are  expressed  as  millimeters  notochord  length 
(mm  NL)  and  recorded  to  the  nearest  0.1  mm. 
Because  preservation  resulted  in  shrinkage  of 
specimens,  the  recorded  size  of  some  larvae  is 
smaller  than  the  reported  hatching  length  of  2.8 
mm  (Kuntz  and  Radcliffe,  1917). 

RESULTS 

Egg  and  larval  distributions  are  shown  in  Ap- 
pendix Table  1  and  Figures  4  through  8.  A  map  is 
not  shown  for  the  one  egg  and  one  larva  caught 


off  the  Virginia  coast  on  May  20  and  22,  re- 
spectively. 

Distribution  of  Eggs 

Eggs  identified  as  silver  hake  for  this  report  are 
in  stages  III  and  IV  of  development,  when  the 
embryo  encompasses  at  least  759^  of  the  yolk  and 
the  tail  tip  is  separated  from  the  yolk  surface.  Fine 
pigment  is  present  on  the  part  of  the  yolk  surface 
lying  under  the  snout  of  the  embryo.  This  is  not 
shown  by  Kuntz  and  Radcliffe  (1917). 

We  collected  3,241  silver  hake  eggs  from  May 
through  November  1966,  with  a  peak  in  June.  The 
temporal  distribution  of  eggs  changed  geographic- 
ally. Spawning  began  earlier  in  the  northeastern 
end  of  our  survey  area  and  progressively  later  to 
the  south.  Table  2  demonstrates  this  trend  for  four 
transect  groups.  According  to  Sauskan  and  Sere- 
bryakov  (1968),  about  half  the  total  seasonal 


816 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


SILVER   HAKE   LARVAE 
CRUISE    D-66-7 
JUNE  17-29.1966 


\... 


Figure  4. — Occurrence  of  silver  hake  eggs  and  larvae,  June  1966. 


817 


FISHERY  BULLETIN;  VOL.  72,  NO.  3 


SILVER  HAKE  EGGS 
CRUISE    D-66-10 
AUGUST  5-26,1966 


Figure  5. — Occurrence  of  silver  hake  eggs  and  larvae,  August  1966. 


818 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


^ V 

SILVER  HAKE  EGGS 

CRUISE    D-66-11 


SEPTEMBER    13-  18,1966 


^ ^ 

SILVER   HAKE   LARVAE 

CRUISE    D-6611 

SEPTEMBER   13-18,1966 


Figure  6. — Occurrence  of  silver  hake  eggs  and  larvae,  September  1966. 


819 


FISHERY  BULLETIN:  VOL.  72.  NO   3 


SILVER   HAKE  EGGS 

CRUISE    D-66-12 

SEPTEMBER    28- 
OCTOBER   20, 1966 


SILVER    HAKE   LARVAE 

CRUISE    D-6612 

SEPTEMBER   28- 
OCTOBER    20,1966 


Figure  7. — Occurrence  of  silver  hake  eggs  and  larvae,  September-October  1966. 


820 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


Figure  8. — Occurrence  of  silver  hake  eggs  and  larvae,  November-December  1966. 


821 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Table  2. — Monthly  distributions  of  silver  hake  eggs  arranged  by  transect-groups. 
Monthly  peak  abundance  for  each  group  indicated  by  bold  type,  ns  =  not  sampled. 


Numbers  of 

eggs  collected 

Transect 
groups 

May 

June 

Aug. 

Sept. 

Oct. 

Nov.- 
Dec. 

Total 

AB 
C 

DEF 

GHJKL 

0 
0 
0 
1 

1,362 

5 
0 
1 

415 

26 

6 

0 

617 
108 

0 
ns 

454 

48 

141 

3 

0 

0 

9 

45 

2.848 
187 
156 

50 

Total 

1 

1,368 

447 

725 

646 

54 

3,241 

production  of  eggs  is  released  in  a  first  batch,  and 
the  second  half  is  divided  between  second  and 
third  batches.  Our  egg  collections  on  the  shelf 
south  of  Montauk  Point  and  Martha's  Vineyard 
(transects  A  and  B  in  Table  2)  are  consistent  with 
their  conclusion.  We  collected  1,362  eggs  in  June, 
the  remainder  during  August  (415),  September 
(617),  and  October  (454). 

The  silver  hake  eggs  collected  during  our  1966 
cruises  originated  principally  over  Nantucket 
Shoals  and  on  the  continental  shelf  south  of 
Martha's  Vineyard.  We  collected  889c  of  the  eggs 
on  the  two  northernmost  transects,  77%  on  the 
Martha's  Vineyard  transect  alone.  Sauskan  and 
Serebryakov  (1968)  found  concentrations  south  of 
Martha's  Vineyard  in  May,  on  the  southern  slopes 
of  Georges  Bank  in  June.  Thus,  this  area  probably 
is  an  important  silver  hake  spawning  center. 
Small,  distinct  spawning  groups  are  also  located 
near  Hudson  Canyon,  on  the  deeper  parts  of  the 
shelf  off  New  Jersey,  and  further  south  off  Dela- 
ware, Maryland,  and  Virginia.  The  small  num- 
bers of  eggs  collected  in  the  latter  areas  probably 
reflect  the  small  numbers  of  adults  occurring 
there. 

Silver  hake  eggs  are  found  in  as  wide  a  range 


of  temperatures  as  the  adults.  The  relation  be- 
tween numbers  of  eggs  collected  and  surface  tem- 
peratures is  shown  in  Table  3.  This  may  be 
misleading  however,  for  we  observed  egg  concen- 
trations in  a  particular  geographic  area  (south  of 
Martha's  Vineyard  and  Montauk  Point)  and  these 
concentrations  were  apparently  independent  of 
prevailing  surface  temperatures  which  ranged 
from  13.5°  to  21.7°C.  It  is  not  known  how  near 
the  bottom  silver  hake  spawn,  nor  in  what  range 
of  temperatures.  Assuming  they  spawn  near  the 
bottom,  the  wide  temperature  range  of  egg  occur- 
rences might  be  due  to  a  wide  range  of  tempera- 
tures in  the  spawning  areas  or  might  simply  be 
the  result  of  extreme  temperature  ranges  in  sur- 
face waters  over  the  spawning  areas,  in  which  case 
the  ascending  eggs  demonstrate  a  wide  tempera- 
ture tolerance. 

Distribution  of  Larvae 

Larval  distributions  are  shown  in  Appendix 
Table  1  and  Figures  4  through  8.  We  collected 
11,032  silver  hake  larvae  from  May  to  December 
1966,  91%  during  August,  September,  and  Octo- 
ber (Table  4).  We  captured  no  postlarvae  larger 


Table  3. — Abundance  of  silver  hake  eggs  relative  to  observed  surface  temperatures. 


Surface 

temperature 

(X) 


1-10 
eggs 


Number  of  tows  which  collected; 


11-100 
eggs 


101-200 
eggs 


200  + 
eggs 


Total 
number 
of  tows 


10.0-10.9 

1 

11.0-11.9 

1 

13.0-13  9 

5 

14.0-14.9 

16 

15.0-15.9 

14 

16.0-16.9 

13 

17.0-17.9 

9 

18.0-18.9 

3 

19.0-19.9 

4 

20.0-20.9 

6 

21.0-21.9 

7 

22.0-229 

1 

Total  tows 

80 

6 
6 
2 
3 
4 
4 
5 
2 

32 


1 

1 

6 

28 

21 

15 

15 

8 

8 

11 

9 

1 

124 


822 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


Table  4. — Numbers  of  silver  hake  larvae  collected  during  six 
cruises  in  1966. 


May 

June 

Aug. 

Sept. 

Oct. 

Nov.- 
Dec. 

Total 

2 

585 

2,989 

3,875 

3.175 

406 

1 1 ,032 

than  18.0  mm  NL  until  the  August  cruise  (Figure 
9).  Since  the  spawning  season  probably  began  in 
early  June,  and  since  18.0  mm  approximates  the 
size  at  which  silver  hake  postlarvae  begin  to  live 
near  the  bottom,  the  length  of  pelagic  life  is 
apparently  about  2  mo. 

Within  our  1966  sampling  area,  larvae  were 
most  densely  concentrated  between  Nantucket 
Shoals  and  Hudson  Canyon.  Progressing  south- 
ward, we  found  larvae  increasingly  restricted  to 
the  offshore  part  of  the  shelf.  Distribution  varied 
according  to  the  size  of  larvae.  Generally,  we 
found  smaller  larvae  inshore  and  near  the  surface. 


and  larger  larvae  offshore  and  deeper.  Smaller 
larvae  were  also  more  numerous  in  the  north- 
eastern part  of  the  survey  area  than  the  south- 
western. Tables  5  through  7  illustrate  this  trend 
for  the  August,  September,  and  October  cruises. 
These  differences  in  distribution  by  size  are  partly 
a  result  of  a  southwesterly  drift  during  grov^h, 
partly  a  preference  by  larger  larvae  for  deeper 
water. 

Silver  hake  larvae  in  1966  were  distributed 
in  areas  where  surface  temperatures  ranged  from 
8.6°  to  25.8°C.  Since  silver  hake  larvae  are  not 
necessarily  surface-dwelling  animals,  the  mean 
observed  temperatures  within  the  depths  sampled 
by  the  two  Gulf  V  nets  may  be  more  significant. 
Table  8  shows  the  number  of  tows  containing 
larvae  (arranged  by  volume  of  catch)  relative  to 
these  temperatures.  The  total  number  of  tows, 
regardless  of  the  presence  of  silver  hake,  is  in- 


130 35' 

NOTOCHORD       LENGTH       (1  -  mm  GROUPS)  .=  less   than  1  per   cent 

Figure  9. — Length-frequency  distributions  of  silver  hake  larvae  during  five  cruises,  1966. 


823 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


Table  5. — Mean  lengths  (mm  NLi  of  silver  hake  larvae  collected  during  Do/p/j in  cruise 
D-66-10  (August  1966),  arranged  by  transect,  net  1  (0-15  m)  or  net  2  ( 18-33  ml,  and  station. 


Net 

Stat 

on 

Mean 
length 

Transect 

1 

2 

3 

4 

5 

6 

7 

8 

N 

A 

1 
2 

3.2 

2.8 

4.0 
5.8 

3.1 
5.1 

5.0 
5.3 

4.0 
5.8 

3.6 
4.2 

3.8 
5.6 

598 
658 

B 

1 
2 

26 

3.8 
3.6 

2.0 
3.3 

39 
5.5 

4.1 
6.2 

5.4 
6.8 

6.6 
8.5 

5.4 

78 

413 

1,037 

C 

1 
2 

2.1 

3.2 

3.6 
4.7 

3.5 

3.2 

5.3 

4.9 
5.4 

3.5 
5.3 

54 
98 

D 

1 
2 

3.8 
3.2 

5.8 

6.0 
12.2 

36 
10.2 

5.6 
10.3 

33 

71 

E 

1 
2 

5.3 
6.0 

3.3 
5.5 

4.0 
5.7 

3 
8 

F 

1 
2 

6.0 
7.0 

7.5 

7.3 
7.0 

8 
2 

G 

1 
2 

3.6 

3.6 

1 

H 

1 
2 

14.8 
14.5 

15.1 

14.8 
15.0 

1 
3 

J 

1 
2 

5.7 

5.7 

1 

Mean  length 

N 

3.0 
18 

3.2 
67 

4.2 
82 

3.6 
357 

5.1 
472 

5.6 
853 

7.9 
987 

7.4 
153 

61 

2,989 

Table  6. — Mean  lengths  (mm  NL)  of  silver  hake  larvae  collected  during  Dolphin  cruise 
D-66-11  (September,  1966),  arranged  by  transect,  net  1  (0-15  m)  or  net  2  (18-33  m),  and 
station. 


Stat 

on 

Mean 

Transect 

Net 

1 

2 

3 

4 

5 

6 

7 

8 

length 

N 

A 

1 

3.0 

3.6 

4.2 

4.5 

5.8 

5.0 

4.7 

478 

2 

3.0 

3.9 

3.8 

4.8 

5.9 

52 

4.9 

529 

B 

1 

27 

28 

4.2 

3.5 

5.6 

7.0 

11.6 

4.8 

79 

2 

5.6 

4.9 

4.1 

6.6 

12.0 

5.7 

921 

C 

1 

3.0 

2.7 

4.4 

3.0 

123 

82 

7.2 

29 

2 

4.2 

6.9 

5.6 

8.5 

9.7 

6.4 

1,011 

D 

1 

3.6 

2.8 

3.4 

3.8 

6.0 

8.8 

4.5 

62 

2 

2.8 

4.9 

5.5 

7.0 

9.1 

5.8 

620 

Mean  length 

2.8 

2.9 

5.4 

4.3 

5.0 

5.7 

7.9 

9.1 

56 

A^ 

14 

22 

615 

730 

799 

840 

650 

59 

3,729 

eluded  in  the  table  to  demonstrate  the  possibility 
that  the  temperature  relationship  is  simply  an 
artifact  created  by  our  cruise  schedule.  The 
probability  of  collecting  these  temperature-tol- 
erant larvae  at  any  temperature  increases  as 
sampling  at  that  temperature  increases. 

Our  maximum  sampling  depth  was  below  the 
thermocline  on  all  stations  where  we  captured 
larval  silver  hake.  Larvae  apparently  were  more 
concentrated  near  the  thermocline  than  near  the 
surface  during  the  summer  months.  Table  9 
compares  the  percentage  of  the  total  catch  con- 


tributed by  the  deep  net  (which  sampled  near  the 
thermocline)  during  each  cruise  with  observed 
surface  temperatures  and  indicates  that  during 
August  and  September,  when  surface  tempera- 
tures were  highest,  silver  hake  larvae  were  dis- 
tributed more  deeply  where  temperatures  were 
lower. 

Our  cruise  schedule  and  sampling  sequence 
resulted  in  many  consecutive  stations  being 
sampled  during  the  same  light  regime.  Thus, 
opportunities  for  comparing  the  diel  differences 
in  the  captures  of  silver  hake  larvae  are  limited. 


824 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 

Table  7. — Mean  lengths  (mm  NL)  of  silver  hake  larvae  collected  during  Dolphin  cruise 
D-66-12  (October,  1966),  arranged  by  transect,  net  1  (0-15  m)  or  net  2  (18-33  m),  and 
station. 

Station 


Transect 

Net 

1 

2 

3 

4 

5 

6 

7 

8 

Mean 
length 

.V 

A 

1 

34 

4.2 

4.7 

3.5 

3,1 

5.5 

9.9 

3.8 

143 

2 

4.1 

4.9 

3.5 

3.0 

4,7 

13.5 

4.7 

554 

B 

1 

2.8 

3.3 

5.8 

96 

10.2 

11.2 

9.7 

77 

2 

5.5 

4.4 

6.4 

7.5 

10.8 

9.6 

8.7 

699 

C 

1 

8.7 

7.1 

5.8 

5.0 

7,6 

13.5 

19.8 

8.3 

157 

2 

5.6 

6.7 

6.0 

7.8 

9.9 

12.8 

8.6 

825 

D 

1 

2.7 

7.1 

62 

6.2 

4.2 

29 

5.6 

172 

2 

150 

6.1 

69 

5.6 

4.5 

6.3 

212 

E 

1 

2.8 

6.4 

66 

8.0 

3.5 

6.4 

67 

2 

5.1 

8.5 

10.0 

3.0 

8.7 

87 

F 

1 

5.6 

6.5 

4.7 

6.3 

70 

2 

3.7 

7.0 

6.3 

6.4 

27 

G 

1 
2 

5.4 

4.6 

7.4 

5.4 
5.5 

1 
3 

H 

1 
2 

15.0 

15.0 

1 

J 

1 
2 

22.5 

22.5 

1 

K 

1 
2 

11.0 

11.0 

1 

Mean  length 

3.2 

4,5 

5,1 

4,8 

6.2 

7.7 

9.6 

4.8 

7.3 

.V 

3 

53 

84 

560 

536 

1,001 

816 

44 

3.097 

Table  8. — Abundance  of  silver  hake  larvae  relative  to  mean  temperature  within  the  sampling 

depths  of  individual  Gulf  V  nets. 


Temperature 
(°C)  within 
samplers' 

depth  range 


Number  ot  tows  which  collected: 


Number  of  tows 


1-10 

larvae 


11-100 
larvae 


101-300 
larvae 


301-500 
larvae 


500  + 
larvae 


Containing 
silver  hake 


Total 


6.0-6.9 
7.0-7.9 
80-8.9 
9.0-9.9 
10.0-10.9 
11.0-11.9 
12.0-12.9 
13.0-13.9 
14.0-14.9 
15.0-15.9 
16.0-16.9 
17.0-17.9 
18.0-18.9 
19.0-19,9 
20.0-20.9 
21,0-21  9 
220-22.9 
23.0-23.9 
24.0-24.9 
25.0-25.9 
260-26.9 

Total  tows 


5 
3 

4 

17 

9 

5 

4 

14 

22 

8 

12 

12 

4 

1 

8 

6 

6 

1 

1 


142 


2 
2 
8 

5 
6 
7 
14 
8 
6 
5 
6 
5 
3 
1 


80 


27 


7 

3 

7 

19 

19 

10 

15 

25 

46 

19 

19 

19 

10 

10 

12 

8 

6 

1 

1 

0 

0 

256 


9 
12 

18 
34 
32 
17 
22 
48 
75 
38 
36 
44 
33 
39 
23 
25 
29 
14 
20 
11 
6 


Although  day  and  night  tows  were  equally  pro- 
ductive (Table  10),  differences  exist  when  larval 
size  is  considered.  Most  of  the  smallest  larvae 
were  taken  during  the  day,  while  most  larger 


larvae  and  postlarvae  were  taken  from  dusk  to 
dawn  (Figure  10). 

There  are  several  possible  explanations  for  the 
higher  incidence  of  larger  larvae  and  postlarvae 


825 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Table  9. — Contribution  of  deep  net  to  total  catch  of  larvae  on  stations  where 
both  nets  were  used,  compared  to  weighted  mean  surface  temperature. 


Cruise 


IVIonth 


D-66-   5 

May 

D-66-  7 

June 

D-66- 10 

Aug. 

D-66- 11 

Sept. 

D-66-12 

Oct. 

D-66- 14 

Nov. -Dec 

Percent 
caught  in 
deep  net 


Weighted  mean 

surface 
temperature  (°C) 


0 
34 
62 
82 
78 
52 


14.4 
14.5 
20.6 
19.9 
15,5 
11.7 


Total  number 
caught  in 
both  nets 


1 

408 

2,940 

3,836 

3,164 

398 


Table   10. — Diel  differences 


in  captures  of  silver  hake  larvae,  cruises  D-66-7  (June)  through 
D-66- 14  (November-December). 


N 

umber 

of  tows 

Number 

of 
larvae 

Weighted 
mean 
length 

(mm  NL) 

Average 

catch 

Light 
regime 

Total 

Contaming 
silver  hake 

Total 
tows 

Tows  containing 
silver  hake 

Dawn 

62 

21 

810 

5.4 

13.1 

38.6 

Day 

265 

112 

4,741 

5.3 

17.9 

42.3 

Dusk 

48 

18 

1,255 

57 

26.1 

69.7 

Night 

240 

104 

4,226 

78 

17.6 

40.6 

z     80- 


6     20- 


ooooooo       ooot 


>oo       oooooo 


I   I   I  I   I  1   I  I 


NOTOCHORD     LENGTH     i  1  < 


Figure  10. — Percentage  of  silver  hake  larvae  collected  in  non- 
day  tows  per  1-mm  size  groups. 


in  night  tows,  the  most  generally  accepted  being 
that  larvae  avoid  the  approaching  sampler  during 
daylight  in  response  to  visual  warning.  The  differ- 
ence cannot  be  attributed  to  vibration  of  the  tow- 
ing cable  or  inefficient  filtration  by  the  sampler 
because  these  factors  are  equal  during  all  light 
regimes.  Undersampling  of  larger  larvae  of  other 
species  during  daylight  has  been  well  documented 
(Silliman,  1943;  Bridger,  1956;  Ahlstrom,  1959; 
Colton,  1965).  These  authors,  however,  noted  diel 
differences  resulting  from  tows  made  at  1  knot. 
Miller,  Colton,  and  Marak  (1963)  towed  a  high- 
speed plankton  sampler  at  7  knots  and  found  no 
significant  differences  in  the  day  and  night 
catches  of  haddock  larvae  and  pelagic  juveniles. 
Ryland  (1963)  concluded  that  a  towing  speed  of 
5  knots  (257.4  cm/s)  was  sufficient  to  prevent  net 
avoidance  by  plaice  larvae  up  to  20.0  mm  whose 


maximum  "darting  velocity"  he  found  to  be  20 
cm/s.  If,  by  towing  at  5  knots,  we  were  able  to 
overcome  net  avoidance  by  larger  larvae,  then  the 
presence  of  larger  larvae  in  night  tows  only  must 
reflect  some  form  of  diel  activity  or  vertical 
migration.  Kelly  and  Barker  (1961)  found  a  sig- 
nificant difference  in  depth  distribution  with 
growth  of  young  redfish,  the  larger  juveniles 
occurring  in  deeper  layers.  A  similar  difference 
plus  a  diel  change  in  depth  distribution  is  ob- 
served with  silver  hake  when  the  light  regime, 
capture  depth  (net  1  vs.  net  2),  and  mean  larval 
length  are  combined  (Figure  11).  The  largest 
larvae  were  captured  in  the  deep  net  during  the 
night,  the  smallest  larvae  in  the  shallow  net 
during  the  day.  In  both  nets,  night  tows  con- 
tained larger  larvae  than  day  tows,  and  in  both 
light  regimes  the  deep  net  contained  larger 
larvae  than  the  shallow  net.  Evidently,  with 
growth,  silver  hake  larvae  seek  deeper  water, 
perhaps  in  response  to  increasing  negative  photo- 
tropism,  perhaps  simply  approximating  the  adult 
habitat. 

During  the  summer  of  1970,  we  made  two 
cruises  to  investigate  the  size  at  which  silver  hake 
larvae  first  occur  on  or  near  bottom.  On  12  stations 
northeast  and  southwest  of  Hudson  Canyon,  we 
made  reciprocal  tows  with  Gulf  V  samplers  and 
an  otter  trawl  (39-foot  headrope)  fitted  with  a  V4- 
inch  mesh  cover  bag  and  separate  cod  end.  Length 
frequencies  of  the  Gulf  V  catches,  compared  with 
those  of  the  otter  trawl  (Figure  12),  indicate  that 
silver  hake  first  become  available  to  bottom 


826 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


z 


< 
> 

< 


14- 

• 

- 

• 

12- 

10- 

- 

• 

• 

8- 

• 

- 

• 

o 

o 

6- 

• 

• 

o 

- 

o 

• 

o 

o 

4- 

o 

o 

o 

" 

O 

2- 

~ 

- 

SBO 

n. 

3  746 

- 

!99S 

- 

!J91 

., 

34J 

Net  1  2 

Cru.se        JUN 


1  2 

AUG 


1  2 

SEP 


1  2 

OCT 


1  2 

NOV- 
DEC 


night    tows  0=    day     tows 


Figure  11. — Comparisons  of  silver  hake  mean  larval  size,  light 
condition,  and  depth  of  capture.  Net  1  sampled  to  a  maximum 
of  15  m;  net  2  to  a  maximum  of  33  m. 

sampling  gear  at  about  17.0  to  20.0  mm  NL. 
This  figure  is  somewhat  smaller  than  that  indi- 
cated by  Nichy  (1969),  whose  smallest  specimens 
taken  by  otter  trawl  were  about  50  mm. 

During  1966,  all  postlarvae  larger  than  21.0 
mm  NL  (except  one)  were  captured  at  night,  and 
most  of  those  were  taken  in  the  deep  net,  which 
sampled  above,  within,  and  below  the  thermo- 
cline,  if  one  was  present.  Postlarvae  larger  than 
21.0  mm  NL  were  taken  in  the  shallow  net  only 
when  the  thermocline  was  weak  or  nonexistent. 
All  this  suggests  that  silver  hake  postlarvae  seek 
the  bottom  at  about  17.0  to  20.0  mm  NL  and 
migrate  vertically  at  night,  ascending  at  least  to 
the  thermocline  depth  or,  in  the  absence  of  a 
thermocline,  to  levels  nearer  the  surface. 

DISCUSSION 

The  area  encompassing  the  southern  slope  of 
Georges  Bank,  Great  South  Channel,  Nantucket 
Shoals,  and  the  shelf  south  of  Martha's  Vineyard 
is  evidently  an  important  spawning  center  for 


silver  hake.  Unfortunately,  neither  the  Dolphin 
survey  nor  the  Soviet  surveys  (Sauskan  and 
Serebryakov,  1968)  sampled  this  area  exten- 
sively enough  to  determine  all  the  possible  drift 
patterns  of  eggs  and  larvae.  The  70°40'W  merid- 
ian approximates  the  eastern  limit  of  the  Dol- 
phin survey  and  the  western  limit  of  the  sampling 
reported  by  Sauskan  and  Serebryakov. 

Within  this  wide  area,  eggs  should  be  expected 
to  drift  in  several  different  directions,  depending 
on  the  location  of  spawning  and  on  long-term  pre- 
vailing winds.  One  component  of  the  westerly 
current  on  the  shelf  south  of  Martha's  Vineyard 
and  Nantucket  Island  originates  on  the  southern 
slope  of  Georges  Bank  where  it  forms  the  southern 
part  of  a  rotational  eddy  (Bigelow,  1927;  Klimen- 
kov  and  Pakhorukov,  1963;  Bumpus  and  Chase, 
1965;  Bumpus  and  Lauzier,  1965;  Harrison  et  al., 
1967).  Eggs  spawned  on  Georges  Bank  may 
1)  drift  wdth  the  eddy,  develop,  and  recruit  back  to 
Georges  Bank,  or  2)  drift  west  and  south  of 
Martha's  Vineyard  where  we  consistently  found 
concentrations.  Walford  (1938)  described  similar 
patterns  for  haddock  larvae  spawned  on  Georges 
Bank.  A  third  possibility  may  result  in  the  loss 
of  the  brood.  Colton  (1959)  reported  that  silver 
hake  larvae  spawned  on  Georges  Bank  were  killed 
when  a  southerly  drift  carried  them  off  the  bank 
and  into  warm  slope  water  (the  rate  of  warming 
exceeding  the  larvae's  rate  of  acclimation).  Pre- 
sumably, in  addition  to  the  perils  of  warming 
waters,  silver  hake  larvae  carried  off  Georges 
Bank  into  the  slope  water  or  Gulf  Stream  would 
be  carried  to  the  east  and,  unable  to  find  suitable 
depths  in  which  to  begin  the  demersal  stage, 
would  perish. 

Eggs  spawned  south  of  Martha's  Vineyard  drift 
west  but  probably  not  far  before  hatching,  for  the 
incubation  period  is  only  48  h  (Kuntz  and  Rad- 
cliffe,  1917).  Unfortunately,  these  authors  did  not 
cite  the  temperature  at  which  incubation  or  hatch- 
ing occurred.  If  we  assume  (as  did  Sauskan  and 
Serebryakov,  1968)  that  Kuntz  and  Radcliffe 
incubated  their  eggs  at  a  maximum  temperature 
of  20°C,  then  the  maximum  incubation  period  in 
degree-hours  would  be  960  (48  x  20  =  960).  We 
encountered  the  heaviest  concentrations  of 
eggs  on  the  Martha's  Vineyard  transect  when  sur- 
face temperatures  ranged  from  13°  to  22°C.  Even 
at  the  minimum  temperature  of  13°C,  incubation 
would  occupy  no  more  than  73.8  h  (960/13  =  73.8). 
Currents  between  Georges  Bank  and  Delaware 


827 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


20-, 


4  8  12  16  20  24  28  32 


o 
< 


o 

Q:: 

UJ 
O- 


LENGTH    FREQUENCIES 
SUMMER,    1970 

I  GULF  V  COLLECTIONS 

I  OTTER   TRAWL    COLLECTIONS 


I  I 

I  I 

JJL 


■  I  • 
111 


44 


4850  53  59 


4  8  12  16  20  24  28  32  36  40 

LARVAL  AND   POSTLARVAL   LENGTH  (mmNL) 

Figure  12. — Comparison  of  length  frequencies  of  silver  hake  larvae  and  post-larvae  captured  in  Gulf  V  plankton  samplers  near 

surface  and  otter  trawl  on  bottom  during  summer  cruises,  1970. 


Bay  flow  west  to  southwest  at  average  speeds  of 
0.93  km/h  over  the  shelf  between  Nantucket 
Shoals  and  New  Jersey  (U.S.  Navy  Hydrographic 
Office,  1965)  to  1.04  km/h  over  the  southeast 
slope  of  Georges  Bank  (Sauskan  and  Serebryakov, 
1968).  Thus,  the  maximum  distance  an  egg  would 
drift  from  spawning  to  hatching  is  76.8  km 
(1.04  X  73.8  =  76.8)  in  the  area  of  greatest  egg 
abundance  which  we  observed.  This  is  substan- 
tiated by  the  fact  that  the  center  of  abundance 
of  the  prolarvae  is  only  slightly  further  to  the 
southwest  than  that  of  the  eggs.  Also  contributing 
to  the  short  drift  of  eggs  and  prolarvae  is  the 
sluggish,  meandering  nature  of  currents  on  the 
shelf  south  of  New  England.  During  the  summer 
of  1971,  while  studying  vertical  distribution  of 
silver  hake  larvae  on  the  shelf  south  of  Montauk 


Point,  we  deployed  a  free-drifting  staff  buoy  and 
sampled  around  it  for  48  h.  The  course  of  the  buoy 
(Figure  13)  demonstrates  the  capriciousness  of 
surface  currents  in  the  area,  while  indicating  a  net 
westerly  drift. 

I  consider  the  silver  hake  eggs  and  larvae 
which  we  collected  to  be  1)  representatives  of  a 
small  brood  spawned  on  the  deeper  portions  of 
the  shelf  between  Hudson  Canyon  and  Cape  Hat- 
teras;  2)  representatives  of  a  brood  spawned  over 
Nantucket  Shoals  and  the  shelf  south  of  New 
England;  3)  survivors  of  a  brood  spawned  over 
Georges  Bank  or  Great  South  Channel. 

It  is  during  the  pelagic  period  of  development 
that  eggs  or  larvae,  unable  to  control  their  own 
movements,  are  most  susceptible  to  prevailing 
currents,  surface  winds,  and  changing  hydro- 


828 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 

^40*30 


7Mb 
LONGITUDE    WEST 


40°25 


O 

3 


40  20 


L40  15 


Figure  13. — Position  of  free-drifting  staff  buoy  at  2-h  intervals 
on  the  continental  shelf  south  of  Montauk  Point,  N.Y. 


ACKNOWLEDGMENTS 

The  author  thanks  especially  Lionel  A.  Walford 
for  reviewing  the  manuscript  and  providing  valu- 
able assistance  in  its  preparation;  the  editorial 
staff  of  the  Middle  Atlantic  Coastal  Fisheries  Cen- 
ter and  Fred  Nichy  of  the  Northeast  Fisheries 
Center,  Woods  Hole  Laboratory,  National  Marine 
Fisheries  Service,  NO  AA,  for  providing  comments 
on  the  manuscript;  technicians  in  the  eggs  and 
larvae  program  at  Sandy  Hook  Laboratory  for 
their  diligence  in  sorting  the  ichthyoplankton; 
Pat  Burke  for  hours  spent  counting  and  measur- 
ing; and  Cindy  deGorgue  and  Alyce  Wells  for  the 
preparation  of  some  of  the  figures. 


graphic  conditions.  The  results  of  the  Dolphin 
survey  indicate  several  things  about  sampling 
fishes  during  this  phase  in  their  development. 
1)  One  cannot  hope  to  fully  understand  the  early 
life  history  of  any  one  species  of  fish  on  explora- 
tory surveys.  Such  facts  as  gross  seasonality  and 
geographic  limits  of  spawning  might  be  revealed 
but  a  complete  evaluation  of  a  species'  early  life 
history  can  only  follow  a  series  of  frequent 
cruises  where  all  efforts  are  focused  on  one  or  a 
very  few  species.  2)  Known  or  suspected  zoo- 
geographic  barriers  should  be  included  well 
within  the  limits  of  a  survey  area,  not  made  to 
coincide  with  the  edge.  3)  Sampling  between  the 
surface  and  levels  immediately  below  the  thermo- 
cline  is  inadequate  when  dealing  with  pelagic 
young  of  groundfish.  A  more  complete  and 
accurate  picture  of  developing  silver  hake  could 
have  been  drawn  if  the  entire  water  column, 
surface  to  bottom,  had  been  sampled  on  all 
stations.  4)  The  diel  activity  and  vertical  distribu- 
tion of  a  postlarval  fish  may  be  directly  related 
to  the  behavior  of  invertebrate  food  organisms. 
An  analysis  of  the  invertebrate  plankton  collected 
with  the  ichthyoplankton  should  be  considered  as 
an  integral  part  of  a  survey.  5)  Unless  discrete- 
level  tows  are  made  with  opening-closing  nets,  an 
exact  temperature-catch  relationship  cannot  be 
determined,  except  in  vertically  isothermal 
conditions. 

I  found  no  evidence  that  silver  hake  depend  on 
or  utilize  estuaries  during  their  early  life  history. 
Their  occasional  presence  in  estuarine  areas  must 
be  considered  accidental. 


LITERATURE  CITED 


Ahlstrom,  E.  H. 

1959.     Vertical  distribution  of  pelagic  fish  eggs  and  larvae 
off  California  and  Baja  California.     U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  60:107-146. 
Arnold,  E.  L.,  Jr. 

1959.  The  Gulf  V  plankton  sampler.  /«  Galveston  Biolog- 
ical Laboratory  fishery  research  for  the  year  ending  June 
30,  1959,  p.  111-113.     U.S.  Fish  Wildl.  Serv.,  Circ.  62. 

BiGELOW,  H.  B. 

1927.  Physical  oceanography  of  the  Gulf  of  Maine.  Bull. 
U.S.  Bur.  Fish.  40(2):511-1027. 

BiGELOW,  H.  B.,  AND  W.  C.  SCHROEDER. 

1953.     Fishes  of  the  Gulf  of  Maine.     U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  53:1-577. 
Bridger,  J.  P. 

1956.     On  day  and  night  variation  in  catches  offish  larvae. 
J.  Cons.  22:42-57. 
BuMPUs,  D.  F.,  AND  J.  Chase. 

1965.     Changes  in  the  hydrography  observed  along  the 
east  coast  of  the  United  States.  Int.  Comm.  Northwest 
Atl.  Fish.,  Spec.  Publ.  6:847-853. 
BuMPUs,  D.  F.,  AND  L.  M.  Lauzier. 

1965.     Surface  circulation  on  the  continental  shelf  off 

eastern  North  America  between  Newfoundland  and 

Florida.  Ser.   Atlas  Mar.  Environ.,  Am.  Geogr.  Soc. 

Folio  7,  4  p.,  8  plates. 

Clark,  J.,  W.  G.  Smith,  A.  W.  Kendall,  Jr.,  and  M.  P.  Fahay. 

1969.  Studies  of  estuarine  dependence  of  Atlantic  coastal 
fishes.  Data  Report  I:  Northern  Section,  Cape  Cod  to 
Cape  Lookout.  R.  V.  Dolphin  cruises  1965-66:  Zoo- 
plankton  volumes,  midwater  trawl  collections,  tempera- 
tures and  salinities.  U.S.  Bur.  Sport  Fish.  Wildl.,  Tech. 
Pap.  28,  132  p. 
CoLTON,  J.  B.,  Jr. 

1959.  A  field  observation  of  mortality  of  marine  fish 
larvae  due  to  warming.     Limnol.  Oceanogr.  4:219-222. 

1965.  The  distribution  and  behaviour  of  pelagic  and 
early  demersal  stages  of  haddock  in  relation  to  sampling 
techniques.  Int.  Comm.  Northwest  Atl.  Fish.,  Spec. 
Publ.  6:317-333. 


829 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


U.S.  Fish 


Canadian 
1914-1915, 


CoNOVER,  J.  T.,  R.  L.  Fritz,  and  M.  Vieira. 

1961.     A  morphometric  study  of  silver  hake. 
Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish.  368,  13  p. 
Dannevig,  a. 

1919.     Biology  of  Atlantic  waters  of  Canada, 
fish-eggs  and  larvae.     Can.  Fish.  Exped. 
p.  1-74. 
Fritz,  R.  L. 

1965.     Autumn  distribution  of  groundfish  species  in  the 
Gulf  of  Maine  and  adjacent  waters,  1955-1961.     Ser. 
Atlas  Mar.  Environ.,  Am.  Geogr.  Sec.  Folio  10,  3  p., 
22  plates. 
Harrison,  W.,  J.  J.  Norcross,  N.  A.  Pore,  and  E.  M.  Stanley. 
1967.     Circulation  of  shelf  waters  off  the  Chesapeake 
Bight.  Surface  and  bottom  drift  of  continental  shelf 
waters  between  Cape  Henlopen,  Delaware,  and  Cape  Hat- 
teras.  North  Carolina  June  1963 — December  1964.     En- 
viron. Sci.  Serv.  Admin.,  Prof.  Pap.  3,  82  p. 
Kelly,  G.  F.,  and  A.  M.  Barker. 

1961.     Vertical  distribution  of  young  redfish  in  the  Gulf 
of  Maine.     Rapp.  P.-V.  Reun.  Cons.  Perm.  Int.  Explor. 
Mer.  150:220-233. 
Klimenkov,  a.  I.,  and  V.  I.  Pakhorukov. 

1963.     Hydrological  observations  in  the  northwest  Atlantic 
in  spring-summer  1960.    In  Y.  Y.  Marti  (editor),  Soviet 
Fisheries  Investigations  in  the  Northwest  Atlantic, 
p.  185-195.  Isr.  Program  Sci.  Transl.,  Jems. 
Kuntz,  a.,  and  L.  Radcliffe. 

1917.     Notes  on  the  embryology  and  larval  development 
of  twelve  teleostean  fishes.     Bull.   U.S.   Bur.   Fish. 
35:87-134. 
Marak,  R.  R. 

1967.     Eggs  and  early  larval  stages  of  the  offshore  hake, 
Merluccius  albidus.     Trans.  Am.  Fish.  Soc.  96:227-228. 
Marak,  R.  R.,  and  J.  B.  Colton,  Jr. 

1961.     Distribution  of  fish  eggs  and  larvae,  temperature, 
and  salinity  in  the  Georges  Bank-Gulf  of  Maine  area, 
1953.     U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish. 
398,  61  p. 
McKenzie,  R.  a.,  and  W.  B.  Scott. 

1956.     Silver  hake,  Merluccius  bilinearis,  in  the  Gulf  of 
St.  Lawrence.     Copeia  1956:111. 


Merriman,  D.,  and  R.  C.  Sclar. 

1952.     The  pelagic  fish  eggs  and  larvae  of  Block  Island 
Sound.     Bull.     Bingham  Oceanogr.  Collect.,  Yale  Univ. 
13(3):165-219. 
Miller,  D.,  J.  B.  Colton,  Jr.,  and  R.  R.  Marak. 

1963.     A  study  of  the  vertical  distribution  of  larval  haddock. 
J.  Cons.  28:37-49. 
NiCHY,  F.  E. 

1969.     Growth  patterns  on  otoliths  from  young  silver  hake, 
Merluccius  bilinearis  (Mitch.).     Int.  Comm.  Northwest 
Atl.  Fish.,  Res.  Bull.  6:107-117. 
Richards,  S.  W.,  and  A.  W.  Kendall,  Jr. 

1973.  Distribution  of  sand  lance,  Ammodytes  sp.,  larvae 
on  the  continental  shelf  from  Cape  Cod  to  Cape  Hatteras 
from  R.  V.  Dolphin  surveys  in  1966.  Fish.  Bull.,  U.S. 
71:371-386. 


Ryland,  J.  S. 

1963.     The  swimming  speeds  of  plaice  larvae. 
Biol.  40:285-299. 


J.   Exp. 


Sauskan,  V.  I.,  and  V.  P.  Serebryakov. 

1968.  Propagation  and  development  of  silver  hake  (Mer- 
luccius bilinearis  Mitchill).  Vopr.  Ikhtiol.  50:500-521. 

Silliman,  R.  p. 

1943.  Thermal  and  diurnal  changes  in  the  vertical  dis- 
tribution of  eggs  and  larvae  of  the  pilchard  (Sardinops 
caerulea).     J.  Mar.  Res.  5:118-130. 

Smith,  W.  G. 

1973.  The  distribution  of  summer  flounder,  Paralichthys 
dentatus,  eggs  and  larvae  on  the  continental  shelf  be- 
tween Cape  Cod  and  Cape  Lookout,  1965-66.  Fish.  Bull., 
U.S.  71:527-548. 

U.S.  Navy  Hydrographic  Office. 

1965.  Oceanographic  Atlas  of  the  North  Atlantic  Ocean. 
Section  I:  Tides  and  Currents.  U.S.  Navy  Hydrogr.  Off. 
Publ.  700,  75  p. 

Walford,  L.  a. 

1938.  Effect  of  currents  on  distribution  and  survival  of 
the  eggs  and  larvae  of  the  haddock  (Melanogrammus 
aeglefinus)  on  Georges  Bank.  Bull.  U.S.  Bur.  Fish. 
49(29):l-73. 


830 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 


Appendix  Table  1. — Silver  hake:  station  data,  number  of  eggs,  and  number  and  length  range  of  larvae  collected  during  1966. 


Depth 

Maximum 

Larvae 

Notochord 

length 

Cruise 

of 

tow 

Total 

Total 

and 

Start 

water 

deptti 

Light 

number 

number 

Number 

Mean 

Range 

station 

Net 

Date 

time 

(m) 

(m) 

regime' 

of  eggs 

captured 

measured 

(mm) 

(mm) 

D-66-5 

EDST 

B-1 

1 

13  V  66 

2233 

24-20 

6 

N 

— 

1 

1 

71.20 

71.2 

H-5 

2 

20  V  66 

0527 

24-40 

24 

0 

1 

— 

— 

— 



K-5 

1 

22  V  66 

0533 

33-35 

15 

C 

— 

1 

1 

2.50 

2.5 

D-66-7 

EDST 

A-1 

1 

1 7  VI  66 

0927 

11-27 

6 

D 

206 

81 

54 

2.40 

1.7-2.8 

A-2 

1 

17  VI  66 

1037 

29-37 

15 

D 

242 

75 

55 

2.28 

1.8-3.2 

A-3 

1 

17  VI  66 

1137 

29-48 

15 

D 

117 

49 

35 

2.21 

1.8-2.6 

A-3 

2 

17  VI  66 

1137 

29-48 

24 

D 

209 

3 

3 

2.10 

1.9-2.3 

A-4 

1 

17  VI  66 

1322 

51-53 

15 

D 

107 

3 

3 

3.33 

3.2-3.6 

A-4 

2 

17  VI  66 

1322 

51-53 

33 

D 

158 

16 

15 

2.43 

2.0-3.1 

A-5 

1 

1 7  VI  66 

1703 

62-62 

15 

D 

123 

4 

3 

2.70 

2.2-3.1 

A-5 

2 

17  VI  66 

1703 

62-62 

33 

D 

79 

1 

1 

2.80 

2.8 

A-6 

1 

17  VI  66 

1919 

73-75 

15 

0 

1 

— 

— 

— 

— 

A-7 

1 

17  VI  66 

2343 

117-102 

15 

N 

1 

— 

— 

— 

— 

B-1 

1 

18  VI  66 

1732 

24-24 

15 

D 

4 

3 

3 

2.77 

2.5-3.3 

B-2 

1 

18  VI  66 

1622 

46-42 

15 

D 

16 

18 

16 

2.61 

2.0-5.3 

B-2 

2 

18  VI  66 

1622 

46-42 

24 

D 

3 

— 

— 

— 

— 

B-3 

1 

18  VI  66 

1525 

53-51 

15 

D 

— 

15 

15 

2.95 

2.1-4.4 

B-3 

2 

18  VI  66 

1525 

53-51 

33 

D 

— 

4 

4 

2.55 

2.4-2.8 

B-4 

1 

18  VI  66 

1402 

62-64 

15 

D 

20 

15 

14 

3.34 

2.8-4.1 

B-4 

2 

18  VI  66 

1402 

62-64 

33 

D 

7 

6 

3 

3.63 

2.7-5.0 

B-5 

1 

18  VI  66 

1036 

77-75 

15 

D 

1 

120 

116 

3.33 

2.4-5.7 

B-5 

2 

18  VI  66 

1036 

77-75 

33 

D 

64 

62 

56 

3.33 

2.4-4.7 

B-6 

1 

18  VI  66 

0833 

86-86 

15 

D 

— 

24 

24 

3.93 

2.7-4.6 

B-6 

2 

1 8  VI  66 

0833 

86-86 

33 

D 

3 

60 

60 

3.65 

2.9-4.4 

B-7 

1 

18  VI  66 

0412 

88-99 

15 

0 

— 

1 

1 

3.10 

3.1. 

B-7 

2 

18  VI  66 

0412 

88-99 

33 

0 

1 

— 

— 

— 

— 

C-1 

1 

19  VI  66 

0628 

20-29 

15 

D 



8 

2 

3.60 

2.7-4.5 

0-2 

2 

19  VI  66 

0733 

31-31 

27 

D 

— 

1 

1 

2.90 

2.9 

C-3 

1 

19  VI  66 

0827 

35-37 

15 

D 

— 

2 

2 

4.15 

4.1-4.2 

C-6 

1 

19  VI  66 

1531 

58-58 

15 

D 

— 

1 

1 

5.20 

5.2 

C-6 

2 

19  VI  66 

1531 

58-58 

33 

D 

— 

5 

5 

5.74 

5.1-6.3 

C-7 

1 

19  VI  66 

2043 

79-77 

15 

0 

— 

4 

3 

6.30 

5.8-6.9 

0-8 

1 

19  VI  66 

2310 

112-320 

15 

N 

4 

2 

2 

4.90 

4.7-5.1 

0-8 

2 

19  VI  66 

2310 

112-320 

33 

N 

1 

— 

— 

— 

— 

H-6 

1 

27  VI  66 

0654 

79-97 

15 

D 

— 

1 

1 

6.30 

6.3 

H-7 

2 

27  VI  66 

0758 

102-214 

33 

D 

1 

— 

— 





K-6 

1 

25  VI  66 

2205 

42-49 

15 

N 

— 

1 

1 

7.80 

7.8 

D-66-10 

EDST 

A-1 

1 

5  VIII  66 

0502 

9-22 

6 

C 

1 

14 

13 

3.15 

2.2-5.6 

A-2 

1 

5  VIII  66 

0607 

26-33 

15 

0 

47 

31 

29 

2.82 

1.6-5.1 

A-3 

1 

5  VIII  66 

0701 

33-35 

15 

D 

73 

41 

34 

4.02 

2.2-6.2 

A-3 

2 

5  VIII  66 

0701 

33-35 

24 

D 

18 

20 

20 

5.78 

2.2-8.6 

A-4 

1 

5  VIII  66 

0840 

49-55 

15 

D 

119 

217 

193 

3.14 

1.6-5.7 

A-4 

2 

5  VIM  66 

0840 

49-55 

33 

D 

4 

54 

49 

5.11 

2.4-6.9 

A-5 

1 

5  VIII  66 

1219 

58-57 

15 

D 

6 

144 

141 

5.03 

2.7-8.1 

A-5 

2 

5  VIM  66 

1219 

58-57 

33 

D 

8 

120 

116 

5.26 

2.1-8.6 

A-6 

1 

5  VIII  66 

1441 

68-71 

15 

D 

71 

144 

131 

4.00 

2.2-6.6 

A-6 

2 

5  VIII  66 

1441 

68-71 

33 

D 

— 

424 

401 

5.79 

2.0-9.2 

A-7 

1 

5  VIII  66 

1741 

102-113 

15 

D 

5 

7 

5 

3.58 

2.3-4.3 

A-7 

2 

5  VIII  66 

1741 

102-113 

33 

D 

10 

40 

36 

4.18 

2.2-10.1 

B-1 

1 

6  VIII  66 

1349 

24-16 

15 

D 

— 

2 

1 

2.60 

2.6 

B-2 

1 

6  VIII  66 

1149 

38-29 

15 

D 

9 

7 

7 

3.83 

2.5-4.7 

B-2 

2 

6  VIII  66 

1149 

38-29 

21 

D 

1 

29 

22 

3.58 

2.1-7.1 

B-3 

1 

6  VIII  66 

1101 

46-42 

15 

D 

22 

2 

2 

2.05 

1  9-2.2 

B-3 

2 

6  VIII  66 

1101 

46-42 

33 

D 

2 

10 

10 

3.34 

2.1-6.5 

B-4 

1 

6  VIM  66 

0720 

60-58 

15 

D 

4 

29 

25 

3.90 

1.7-6.4 

B-4 

2 

6  VIII  66 

0720 

60-58 

33 

D 

— 

15 

15 

5.53 

2.9-9.2 

B-5 

1 

6  VIII  66 

0544 

73-73 

15 

0 

12 

112 

88 

4.07 

2.0-5.7 

B-5 

2 

6  VIM  66 

0544 

73-73 

33 

0 

2 

85 

65 

6.22 

2.2-13.0 

8-6 

1 

6  VIII  66 

0133 

87-82 

15 

N 

1 

98 

96 

5.37 

2.6-15.1 

B-6 

2 

6  VIM  66 

0133 

87-82 

33 

N 

— 

172 

149 

6.81 

3.0-16.7 

B-7 

1 

5  VIM  66 

2340 

91-99 

15 

N 

— 

163 

162 

6.58 

3.2-15.3 

B-7 

2 

5  VIII  66 

2340 

91-99 

33 

N 

— 

726 

701 

8.53 

3.5-25.9 

0-1 

1 

7  VIII  66 

0043 

18-20 

6 

N 

— 

2 

2 

2.10 

1.8-2.4 

C-2 

1 

7  VIM  66 

0137 

27-29 

15 

N 

1 

— 

— 

— 

— 

0-3 

1 

7  VIII  66 

0239 

31-33 

15 

N 

— 

9 

9 

3.19 

2.6-5.5 

0-4 

1 

7  VIII  66 

0413 

40-40 

15 

N 

4 

41 

39 

3.66 

1.7-6.3 

0-4 

2 

7  VIM  66 

0413 

40-40 

33 

N 

— 

1 

1 

4.70 

4.7 

0-5 

1 

7  VIM  66 

0745 

48-48 

15 

D 

2 

— 

— 

— 

— 

0-5 

2 

7  VIM  66 

0745 

48-48 

33 

D 

— 

3 

3 

3.50 

2.8-4.8 

831 


FISHERY  BULLETIN:  VOL.  72.  NO.  3 


Appendix  Table  1. — Continued. 


Depth 
of 

Maximum 

Total 

Larvae 

Total 

Notochord  length 

Cruise 

tow 

and 

Start 

water 

depth 

Light 

number 

number 

Number 

Mean 

Range 

station 

Net 

Date 

time 

(m) 

(m) 

regime' 

of  eggs 

captured 

measured 

(mm) 

(mm) 

D-66-10— Contin 

ued 

EDST 

C-6 

1 

7  VIII  66 

1005 

55-55 

15 

D 

19 

1 

1 

3.20 

3.2 

C-7 

2 

7  VIII  66 

1406 

70-60 

33 

D 

— 

7 

6 

5.30 

4.5-6.0 

C-8 

1 

7  VIM  66 

1630 

108-210 

15 

D 

— 

1 

1 

4.90 

4.9 

C-8 

2 

7  VIII  66 

1630 

108-210 

33 

D 

— 

87 

73 

5.39 

3.3-7.3 

D-5 

1 

8  VIII  66 

0615 

40-33 

15 

D 

6 

4 

4 

3.75 

2.4-7.1 

D-5 

2 

8  VIII  66 

0615 

40-33 

24 

D 

— 

1 

1 

3,20 

32 

D-6 

1 

8  VIII  66 

0422 

48-54 

15 

N 

— 

7 

6 

5.77 

45-6.5 

D-7 

1 

8  VIII  66 

0018 

77-75 

15 

N 

— 

21 

20 

5.95 

4.5-135 

D-7 

2 

8  VIII  66 

0018 

77-75 

33 

N 

— 

6 

6 

12.25 

6.4-17.6 

D-8 

1 

7  VIM  66 

2221 

110-126 

15 

N 

— 

1 

1 

360 

3,6 

D-8 

2 

7  VIM  66 

2221 

110-126 

33 

N 

— 

64 

61 

10.21 

6,0-19,9 

E-6 

1 

9  VIII  66 

1306 

44-42 

15 

D 

— 

1 

1 

5.30 

5,3 

E-6 

2 

9  VIII  66 

1306 

44-42 

33 

D 

— 

3 

3 

5.97 

5.8-6,2 

E-7 

1 

9  VIII  66 

1505 

64-64 

15 

D 

— 

2 

2 

330 

2.9-37 

E-7 

2 

9  VIM  66 

1505 

64-64 

33 

D 

— 

5 

5 

5.54 

4.2-7.2 

F-6 

1 

9  VIII  66 

2306 

55-53 

15 

N 

— 

1 

1 

6.00 

6.0 

F-6 

2 

9  VIM  66 

2306 

55-53 

33 

N 

— 

2 

2 

7.05 

6.9-7.2 

F-7 

1 

9  VIM  66 

2118 

77-71 

15 

N 

— 

7 

7 

7.50 

5.5-10  1 

G-5 

1 

21  VIII  66 

1355 

51-48 

15 

D 

— 

1 

1 

3.60 

3,6 

H-5 

1 

22  VIII  66 

0239 

37-44 

15 

N 

— 

1 

1 

14.80 

14.8 

H-5 

2 

22  VIM  66 

0239 

37-44 

24 

N 

— 

1 

1 

14.50 

14.5 

H-7 

2 

21  VIII  66 

2130 

95-163 

33 

N 

— 

2 

2 

1510 

15.0-15.2 

J-7 

2 

23  VIM  66 

0717 

86-119 

33 

0 

— 

1 

1 

5.70 

5.7 

D-66-1 1 

EDST 

A-2 

1 

13  IX  66 

1133 

29-31 

15 

D 

15 

2 

2 

2.95 

2.6-3.3 

A-2 

2 

13  IX  66 

1133 

29-31 

24 

D 

7 

9 

7 

3.03 

2.6-3.7 

A-3 

1 

13  IX  66 

1243 

38-42 

15 

D 

190 

13 

12 

3.65 

2.5-4,8 

A-3 

2 

13  IX  66 

1243 

38-42 

24 

D 

23 

9 

8 

3.86 

2,8-4,6 

A-4 

1 

13  IX  66 

1415 

46-53 

15 

D 

7 

136 

131 

4,17 

22-6,2 

A-4 

2 

13  IX  66 

1415 

46-53 

33 

D 

22 

91 

86 

378 

2.3-6.5 

A-5 

1 

13  IX  66 

1816 

60-60 

15 

C 

112 

197 

187 

4.49 

18-6  7 

A-5 

2 

13  IX  66 

1816 

60-60 

33 

0 

116 

201 

198 

4.77 

1.8-7.5 

A-6 

1 

13  1X66 

2030 

68-68 

15 

N 

— 

86 

83 

5.82 

2.7-11.9 

A-6 

2 

13  IX  66 

2030 

68-68 

33 

N 

9 

131 

123 

5.86 

4.1-11.5 

A- 7 

1 

14  IX  66 

0104 

113-112 

12 

N 

— 

81 

63 

5.00 

3.7-20,0 

A- 7 

2 

14  IX  66 

0104 

113-112 

30 

N 

— 

113 

107 

5.24 

2.9-21,0 

B-1 

1 

14  IX  66 

2304 

26-26 

6 

N 

— 

13 

10 

2.70 

2,4-3,2 

B-2 

1 

14  IX  66 

0025 

33-35 

15 

N 

— 

13 

9 

276 

2.4-3,1 

B-3 

1 

17  IX  66 

0033 

49-51 

15 

N 

36 

38 

32 

4.18 

23-94 

B-3 

2 

17  IX  66 

0033 

49-51 

33 

N 

19 

567 

558 

5.60 

2.4-17.3 

B-4 

1 

14  IX  66 

1743 

60-66 

15 

0 

9 

12 

12 

3.50 

2.3-5.8 

B-4 

2 

14  IX  66 

1743 

60-66 

33 

C 

3 

178 

178 

4.86 

2.4-13.0 

B-5 

1 

14  IX  66 

1359 

73-71 

15 

D 

22 

2 

2 

5.60 

4.8-6.4 

B-5 

2 

14  IX  66 

1359 

73-71 

33 

D 

23 

103 

96 

4.14 

2.0-11.0 

B-6 

1 

14  IX  66 

1004 

80-84 

15 

D 

4 

12 

4 

7.05 

4.9-88 

B-6 

2 

14  IX  66 

1004 

80-84 

33 

D 

— 

39 

38 

6.57 

5.1-7.8 

B-7 

1 

14  IX  66 

0457 

95-93 

15 

0 

— 

10 

10 

11  65 

67-400 

8-7 

2 

14  IX  66 

0457 

95-93 

33 

0 

— 

53 

51 

12.05 

6,5-41,1 

C-1 

1 

17  IX  66 

0850 

18-16 

9 

D 

— 

4 

4 

3.05 

2.7-3,7 

C-2 

1 

17  IX  66 

0758 

29-26 

15 

D 

— 

5 

3 

2.73 

2,6-2.8 

C-3 

1 

17  IX  66 

0707 

38-29 

15 

C 

56 

— 

— 

— 

— 

C-4 

1 

17  IX  66 

1640 

40-42 

15 

D 

8 

1 

1 

4.40 

4.4 

C-4 

2 

17  IX  66 

1640 

40-42 

33 

D 

4 

312 

300 

4.20 

2.3-10.3 

C-5 

1 

17  IX  66 

1835 

49-47 

15 

0 

16 

8 

7 

3.04 

2.5-4.5 

C-5 

2 

17  IX  66 

1835 

49-47 

33 

0 

1 

157 

157 

6.92 

2  8-11,9 

C-6 

2 

17  1X66 

2033 

57-57 

33 

N 

23 

208 

207 

5.61 

2,1-19,5 

C-7 

1 

17  IX  66 

2247 

71-77 

15 

N 

— 

13 

12 

12.32 

3,1-22.5 

C-7 

2 

17  IX  66 

2247 

71-77 

33 

N 

— 

351 

345 

8.49 

3.1-32.8 

C-8 

1 

18  IX  66 

0049 

110-519 

15 

N 

— 

2 

2 

825 

79-86 

C-8 

2 

18  IX  66 

0049 

110-519 

33 

N 

— 

2 

2 

9.70 

9.4-10.0 

D-2 

1 

18  1X66 

1421 

22-20 

6 

D 

— 

1 

1 

3.60 

3.6 

D-3 

1 

18  1X66 

1326 

20-26 

15 

D 

— 

6 

5 

2.80 

2.2-40 

D-4 

1 

18  1X66 

1159 

33-27 

15 

D 

— 

12 

11 

3.39 

2.6-4.2 

D-4 

2 

18  tX  66 

1159 

33-27 

24 

D 

— 

11 

11 

278 

2.2-4.2 

D-5 

1 

18  1X66 

1043 

35-35 

15 

D 

— 

25 

22 

3.82 

26-5.9 

D-5 

2 

18  1X66 

1043 

35-35 

33 

D 

— 

136 

130 

4.93 

26-112 

D-6 

1 

18  IX  66 

0843 

55-53 

15 

D 

— 

22 

22 

5.99 

4  1-88 

D-6 

2 

18  IX  66 

0843 

55-53 

33 

D 

— 

372 

363 

5.48 

3  1-12.2 

D-7 

1 

18  1X66 

0624 

73-70 

15 

C 

— 

1 

1 

880 

8.8 

D-7 

2 

18  IX  66 

0624 

73-70 

33 

C 



61 

61 

6.96 

35-10.2 

D-8 

2 

18  IX  66 

0424 

121-115 

33 

N 

— 

56 

55 

9.14 

6.5-12.7 

832 


FAHAY:  OCCURRENCE  OF  SILVER  HAKE  EGGS  AND  LARVAE 
Appendix  Table  1. — Continued. 


Depth 

Maximum 

Larvae 

Notochord  length 

Cruise 

of 

tow 

Total 

Total 

and 

Start 

water 

depth 

Light 

number 

number 

Number 

Mean 

Range 

station 

Net 

Date 

time 

(m) 

(m) 

regime' 

of  eggs 

captured 

measured 

(mm) 

(mm) 

D-66-12 

EDST 

A-1 

1 

15  X  66 

0402 

24-9 

6 

N 

— 

3 

2 

3.40 

3.1-3.7 

A-2 

1 

15  X  66 

0309 

31-29 

15 

N 

— 

16 

15 

4.21 

3.2-5.8 

A-2 

2 

15  X  66 

0309 

31-29 

24 

N 

— 

31 

30 

406 

2.8-5.3 

A-3 

1 

15  X  66 

0209 

42-37 

15 

N 

— 

8 

8 

4.72 

2.8-6.7 

A-3 

2 

15  X  66 

0209 

42-37 

33 

N 

1 

37 

33 

4.94 

2.6-26.5 

A-4 

1 

15  X  66 

0715 

48-51 

15 

C 

31 

105 

102 

3.47 

2.3-6.9 

A-4 

2 

15X  66 

0715 

48-51 

33 

C 

63 

216 

207 

3.47 

2.3-5.7 

A-5 

1 

15  X  66 

0843 

58-60 

15 

D 

12 

6 

6 

3.07 

2.7-3.7 

A-5 

2 

15  X  66 

0843 

58-60 

33 

D 

275 

73 

67 

2.98 

2.0-4.6 

A-6 

1 

15  X  66 

1032 

68-71 

15 

D 

1 

8 

8 

5.51 

3.1-11.5 

A-6 

2 

15  X  66 

1032 

68-71 

33 

D 

2 

191 

177 

4.69 

1.8-12.8 

A-7 

1 

15  X  66 

1226 

108-115 

15 

D 

— 

2 

2 

9.90 

3.0-16.8 

A-7 

2 

15X  66 

1226 

108-115 

33 

D 

— 

40 

40 

13.54 

3.7-21.5 

B-1 

1 

14  X  66 

1930 

7-18 

6 

N 

2 

— 

— 

— 

— 

B-2 

1 

14  X  66 

2037 

33-37 

15 

N 

6 

1 

1 

2.80 

2.8 

B-2 

2 

14  X  66 

2037 

33-37 

24 

N 

14 

4 

4 

5.47 

3.2-6.8 

B-3 

1 

14  X  66 

2134 

42-48 

15 

N 

10 

1 

1 

3.30 

3.3 

B-3 

2 

14  X  66 

2134 

42-48 

33 

N 

19 

19 

19 

4.39 

2.2-8.8 

B-4 

1 

14  X  66 

1406 

62-58 

15 

D 

6 

6 

6 

5.75 

4.2-6.8 

B-4 

2 

14  X  66 

1406 

62-58 

33 

D 

9 

145 

142 

6.36 

2.5-18.5 

B-5 

1 

14X66 

1238 

71-71 

15 

D 

2 

24 

23 

9.59 

4.1-14.1 

B-5 

2 

14  X  66 

1238 

71-71 

33 

D 

1 

204 

200 

7.51 

2.7-13.8 

B-6 

1 

14  X  66 

0850 

82-80 

15 

D 

— 

31 

31     • 

10.20 

4.3-16.5 

B-6 

2 

14  X  66 

0850 

82-80 

33 

D 

— 

276 

276 

10.81 

2.2-21.0 

B-7 

1 

14  X  66 

0710 

91-90 

15 

C 

— 

15 

15 

11.16 

6.3-15.7 

B-7 

2 

14X  66 

0710 

91-90 

33 

C 

— 

59 

58 

9.63 

3.5-15.0 

C-2 

1 

13  X  66 

1012 

22-27 

15 

D 

— 

3 

3 

8.73 

4.2-15.2 

C-3 

1 

13X66 

1105 

31-31 

15 

D 

1 

5 

5 

7.14 

3.5-13.2 

C-3 

2 

13  X  66 

1105 

31-31 

24 

D 

2 

15 

15 

5.65 

4.4-7.2 

C-4 

1 

13  X  66 

1233 

37-40 

15 

D 

— 

38 

38 

5.77 

2.6-9.2 

C-4 

2 

13  X  66 

1233 

37-40 

33 

D 

2 

65 

62 

6.74 

2.6-13.0 

C-5 

1 

13X  66 

1555 

48-46 

15 

D 

11 

34 

33 

4.98 

2.6-7.3 

C-5 

2 

13  X  66 

1555 

48-46 

33 

D 

7 

161 

161 

5.99 

2.6-11.7 

C-6 

1 

13  X  66 

1814 

55-55 

15 

C 

1 

34 

34 

7.64 

3.1-12.2 

C-6 

2 

13  X  66 

1814 

55-55 

33 

C 

17 

100 

99 

7.84 

2.2-16.3 

C-7 

1 

13  X  66 

2147 

77-70 

15 

N 

4 

45 

43 

13.54 

3.9-29.2 

C-7 

2 

13X66 

2147 

77-70 

33 

N 

3 

490 

487 

9.90 

2.3-33.8 

0-8 

1 

13X66 

2359 

198-787 

15 

N 

— 

1 

1 

19.80 

19.8 

C-8 

2 

13  X  66 

2359 

198-787 

33 

N 

— 

1 

1 

12.80 

12.8 

D-1 

1 

6X66 

0224 

16-20 

6 

N 

— 

1 

1 

2.70 

2.7 

D-3 

1 

6X  66 

0408 

26-22 

15 

N 

— 

3 

3 

7.13 

6.9-7.4 

D-4 

2 

13  X  66 

0036 

31-22 

24 

N 

2 

1 

1 

15.00 

15.0 

D-5 

1 

12X66 

2304 

35-37 

15 

N 

1 

1 

1 

6.20 

6.2 

D-5 

2 

12X  66 

2304 

35-37 

24 

N 

30 

4 

4 

6.07 

4.6-8.3 

D-6 

1 

12X66 

1901 

55-53 

15 

C 

8 

125 

121 

6.18 

2.5-18.3 

D-6 

2 

12  X  66 

1901 

55-53 

33 

C 

3 

134 

130 

6.94 

1.6-17.7 

D-7 

1 

12  X  66 

1702 

70-75 

15 

C 

5 

46 

45 

4.18 

3.0-6.7 

D-7 

2 

12  X  66 

1702 

70-75 

33 

C 

7 

42 

42 

5.58 

3.4-8.3 

D-8 

1 

12  X  66 

1313 

99-121 

15 

D 

36 

1 

1 

2.90 

2.9 

D-8 

2 

12X  66 

1313 

99-121 

33 

D 

9 

39 

35 

4.50 

2.8-6.7 

E-4 

1 

11  X  66 

2134 

29-29 

15 

N 

33 

1 

1 

2.80 

2.8 

E-5 

1 

11  X  66 

2310 

35-35 

15 

N 

1 

21 

21 

6.37 

2.9-20.2 

E-5 

2 

11  X  66 

2310 

35-35 

24 

N 

1 

15 

15 

5.10 

2.7-7.6 

E-6 

1 

12  X  66 

0250 

44-42 

15 

N 

3 

35 

34 

6.64 

3.1-25.0 

E-6 

2 

12X66 

0250 

44-42 

33 

N 

— 

18 

18 

8.49 

4.5-23.4 

E-7 

1 

12  X  66 

0452 

64-66 

15 

N 

1 

7 

7 

7.99 

4.7-14.1 

E-7 

2 

12  X  66 

0452 

64-66 

33 

N 

— 

52 

52 

10.04 

2.8-31.4 

E-8 

1 

12  X  66 

0903 

157-121 

15 

D 

— 

4 

4 

3.52 

2.8-4.4 

E-8 

2 

12X66 

0903 

157-121 

33 

D 

— 

2 

2 

3.00 

2.8-3.2 

F-5 

1 

4X66 

2251 

37-33 

15 

N 

— 

2 

2 

5.60 

4.2-7.0 

F-5 

2 

4X66 

2251 

37-33 

24 

N 

1 

1 

1 

3.70 

3.7 

F-6 

1 

4X  66 

2053 

53-55 

15 

N 

— 

63 

62 

6.54 

2.9-23.3 

F-6 

2 

4X  66 

2053 

53-55 

33 

N 

— 

10 

9 

7.03 

3.7-13.8 

F-7 

1 

4X  66 

1652 

104-79 

15 

D 

— 

6 

6 

4.68 

3.0-7.0 

F-7 

2 

4  X66 

1652 

104-79 

33 

D 

— 

21 

17 

6.33 

3.0-9.3 

G-4 

1 

4  X  66 

0727 

29-33 

15 

C 

— 

1 

1 

5.40 

5.4 

G-5 

2 

4  X66 

0916 

49-53 

33 

D 

— 

2 

2 

4.65 

3.5-5.8 

G-6 

2 

4  X66 

1309 

95-75 

33 

D 

1 

1 

1 

7.40 

7.4 

H-6 

1 

3X  66 

0711 

88-66 

15 

C 

2 

— 

— 

— 

— 

H-6 

2 

3X66 

0711 

88-66 

33 

C 

— 

1 

1 

15.00 

15.0 

J-7 

2 

3  X  66 

0055 

79-91 

33 

N 

— 

1 

1 

22.50 

22.5 

K-7 

1 

30  IX  66 

1950 

823-914 

15 

N 

— 

1 

1 

11.00 

11.0 

833 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Appendix  Table  1. — Continued. 


Depth 

Maximum 

Larvae 

Notochord  length 

Cruise 

of 

tow 

Total 

Total 

and 

Start 

water 

depth 

Light 

number 

number 

Number 

Mean 

Range 

station 

Net 

Date 

time 

(m) 

(m) 

regime' 

of  eggs 

captured 

measured 

(mm) 

(mm) 

D-66-14 

EST 

A-1 

1 

4  XII  66 

1956 

26-9 

3 

N 

— 

2 

1 

650 

6.5 

A-2 

1 

4  XII  66 

1857 

33-29 

15 

N 

— 

2 

2 

5.60 

5.4-58 

A-3 

1 

4  XII  66 

1750 

44-33 

15 

N 

— 

2 

2 

5.95 

5.9-6.0 

A-3 

2 

4  XII  66 

1750 

44-33 

24 

N 

— 

1 

1 

3.10 

3.1 

A-4 

1 

4  XII  66 

1618 

53-51 

15 

C 

— 

5 

5 

5.44 

4.9-5.7 

A-4 

2 

4  XII  66 

1618 

53-51 

33 

C 

— 

6 

6 

5.00 

4.2-6.4 

A-5 

2 

4  XII  66 

1449 

58-58 

33 

D 

— 

3 

3 

493 

4.1-5.5 

A-6 

1 

4  XII  66 

1255 

73-68 

15 

D 

— 

3 

3 

6.30 

6.0-6.6 

A-6 

2 

4  XII  66 

1255 

73-68 

33 

D 

— 

2 

2 

360 

2.8-4.4 

B-1 

1 

3  XII  66 

1937 

18-22 

6 

N 

— 

1 

1 

6.10 

6.1 

B-2 

1 

3  XII  66 

2056 

31-42 

15 

N 

— 

1 

1 

3.60 

3.6 

B-2 

2 

3  XII  66 

2056 

31-42 

24 

N 

— 

2 

2 

5.60 

3.0-8.2 

B-3 

1 

3  XII  66 

2210 

44-51 

15 

N 

— 

19 

18 

5.55 

3.2-7.2 

B-3 

2 

3  XII  66 

2210 

44-51 

33 

N 

— 

25 

25 

5.93 

4.2-7.6 

B-4 

1 

3  XII  66 

2351 

62-71 

15 

N 

— 

4 

4 

4.10 

2.9-6.5 

B-4 

2 

3  XII  66 

2351 

62-71 

33 

N 

— 

5 

5 

8.70 

4.5-23.2 

B-5 

1 

4  XII  66 

0113 

73-73 

15 

N 

— 

2 

2 

8.80 

57-11.9 

B-6 

1 

4  XII  66 

0310 

84-84 

15 

N 

— 

1 

1 

8.50 

8.5 

B-6 

2 

4  XII  66 

0310 

84-84 

33 

N 

— 

1 

1 

6.50 

6.5 

C-3 

2 

3  XII  66 

1047 

33-37 

24 

D 

— 

1 

1 

5.10 

5.1 

C-4 

1 

3  XII  66 

0412 

42-40 

15 

N 

— 

5 

5 

15.56 

4.1-56.9 

C-4 

2 

3  XII  66 

0412 

42-40 

33 

N 

— 

8 

8 

4.99 

3.6-7.4 

C-5 

-1 

2  XII  66 

2302 

49-47 

15 

N 

— 

25 

25 

5.67 

3.5-7.4 

C-5 

2 

2  XII  66 

2302 

49-47 

33 

N 

— 

22 

22 

5.74 

35-8.4 

C-6 

1 

2  XII- 66 

2022 

57-57 

15 

N 

— 

19 

19 

7.29 

3.1-33.9 

C-6 

2 

2  XII  66 

2022 

57-57 

33 

N 

— 

21 

21 

5.06 

3.1-7.7 

C-7 

1 

2  XII  66 

1727 

77-70 

15 

N 

— 

17 

15 

7.13 

3.2-12.8 

C-7 

2 

2  XII  66 

1727 

77-70 

33 

N 

— 

7 

7 

11.56 

4.4-43.1 

D-6 

1 

2  XII  66 

0652 

51-53 

15 

C 

— 

18 

17 

4.78 

3.1-6.9 

D-6 

2 

2  XII  66 

0652 

51-53 

33 

C 

— 

18 

17 

5.07 

2.7-6.5 

D-7 

1 

2  XII  66 

0920 

73-79 

15 

D 

— 

1 

1 

6.20 

6.2 

D-7 

2 

2  XII  66 

0920 

73-79 

33 

D 

— 

1 

1 

6.10 

6.1 

E-6 

1 

10  XI  66 

0722 

42-40 

15 

C 

1 

1 

1 

3.60 

3.6 

E-6 

2 

10X1  66 

0722 

42-40 

33 

C 

— 

4 

4 

382 

3.5-4.2 

E-7 

1 

10X1  66 

1200 

68-62 

15 

D 

— 

1 

1 

29.60 

29.6 

E-7 

2 

10X1  66 

1200 

68-62 

33 

D 

— 

2 

2 

5.05 

4.0-6.1 

E-8 

1 

19X1  66 

0201 

110-95 

15 

N 

8 

1 

1 

23.80 

23.8 

E-8 

2 

19X1  66 

0201 

110-95 

33 

N 

— 

1 

1 

6.00 

6.0 

F-5 

1 

11  XI  66 

0126 

37-38 

15 

N 

— 

1 

1 

3.80 

3.8 

F-6 

1 

10  XI  66 

2303 

51-51 

15 

N 

— 

4 

4 

15.90 

8.5-24.2 

F-6 

2 

10  XI  66 

2303 

51-51 

33 

N 

— 

4 

4 

8.22 

6.0-12.9 

F-7 

1 

18X1  66 

2203 

68-70 

15 

N 

— 

36 

36 

29.49 

20.4-36.5 

F-7 

2 

18  XI  66 

2203 

68-70 

33 

N 

— 

61 

61 

28.63 

16.7-39.3 

G-5 

1 

11  XI  66 

2234 

51-46 

15 

N 

1 

4 

4 

12.75 

3.8-22.6 

G-5 

2 

11  XI  66 

2234 

51-46 

33 

N 

— 

1 

1 

7.30 

7.3 

G-6 

1 

12  XI  66 

0050 

79-97 

15 

N 

8 

6 

6 

15.17 

5.7-24.6 

G-6 

2 

12  XI  66 

0050 

79-97 

33 

N 

2 

9 

9 

6.99 

2.5-17.9 

H-5 

1 

12  XI  66 

0754 

40-44 

15 

D 

— 

2 

2 

6.80 

6.6-7.0 

H-5 

2 

12X1  66 

0754 

40-44 

33 

D 

— 

1 

1 

7.10 

7.1 

H-6 

1 

12  XI  66 

0609 

84-82 

15 

C 

1 

— 

— 

— 

— 

H-6 

2 

12X1  66 

0609 

84-82 

33 

C 

3 

3 

3 

4.73 

3.9-5.2 

H-7 

1 

12X1  66 

0503 

97-172 

15 

N 

5 

— 

— 

— 

— 

H-7 

2 

12  XI  66 

0503 

97-172 

33 

N 

5 

4 

4 

5.60 

2.4-10.4 

J-5 

1 

14  XI  66 

1727 

26-27 

15 

G 

— 

1 

1 

6.70 

6.7 

J-6 

1 

14  XI  66 

1935 

35-35 

15 

N 

— 

1 

1 

760 

7.6 

J-6 

2 

14  XI  66 

1935 

35-35 

24 

N 

— 

2 

2 

8.20 

7.6-8.8 

J-7 

2 

14  XI  66 

2329 

90-71 

33 

N 

— 

3 

3 

4.83 

3.2-6.3 

K-1 

1 

18  XI  66 

0842 

13-16 

6 

D 

— 

1 

1 

3.10 

3.1 

K-6 

1 

17  XI  66 

2236 

53-40 

15 

N 

13 

— 

— 

— 

— 

K-6 

2 

17  XI  66 

2236 

53-40 

33 

N 

4 

— 

— 

— 

— 

K-7 

2 

17  XI  66 

2127 

483-311 

33 

N 

2 

— 

— 

— 

— 

L-5 

2 

17  XI  66 

1545 

88-622 

33 

C 

1 

1 

1 

4.30 

4.3 

M-4 

1 

16  XI  66 

2339 

58-24 

6 

N 

— 

1 

1 

2.90 

2.9 

'Light  regi 

me:  D  = 

=  day  tow;  N  = 

=  night  tow; 

C  =  crepu 

scular  tow  (when 

any  part  of 

a  tow  occurred  within  1 

h  of  sunrise  or 

sunset). 

834 


DISTRIBUTION,  VARIATION,  AND  SUPPLEMENTAL  DESCRIPTION 

OF  THE  OPOSSUM  SHRIMP,  NEOMYSIS  AMERICANA 

(CRUSTACEA:     MYSIDACEA) 

Austin  B.  Williams/  Thomas  E.  Bowman,^  and  David  M.  Damkaer' 

ABSTRACT 

Neomysis  americana  ranges  from  the  Gulf  of  St.  Lawrence  to  northeastern  Florida  in  estuaries 
and  nearshore  ocean  and  to  depths  of  100  m  on  Georges  Bank.  Samples  studied  from  localities 
between  Nova  Scotia  and  Georgia  show  no  consistent  geographic  variation.  Specific  characters 
are  illustrated  and  discussed. 


Neomysis  americana  (S.  I.  Smith,  1873)  is  the  most 
common  mysid  in  shallow  marine  waters  of 
eastern  North  America.  In  his  monograph,  W.  M. 
Tattersall  (1951)  gave  the  range  as  "from  the 
Gulf  of  St.  Lawrence  to  the  coast  of  Virginia  in 
shallow  water."  Since  then  its  known  distribution 
has  been  extended  south  to  North  Carolina  (Wig- 
ley  and  Burns,  1971)  and  recently  to  South 
Carolina  and  Georgia  (Sikora,  Heard,  and  Dahl- 
berg,  1972;  Williams,  1972).  Further  details  of  its 
distribution  are  given  below. 

Published  and  unpublished  distributional  data 
available  to  us  before  the  present  study  was 
undertaken  suggested  the  possible  existence  of 
two  isolated  populations  of  Neomysis:  1)  a  popu- 
lation north  of  Cape  Henry,  Va.,  mostly  in  coastal 
waters  but  also  occurring  in  large  numbers  on 
Georges  Bank;  2)  a  population  confined  mainly 
to  sounds  and  estuaries  from  North  Carolina  to 
Georgia.  We  suspected  that  there  might  be  taxo- 
nomic  differences  between  these  or  other  popu- 
lations, a  likelihood  that  had  occurred  inde- 
pendently to  other  investigators  (Bousfield,  in 
litt.;  Heard,  in  \itt.). Neomysis  americana  develops 
two  or  more  generations  per  year,  at  least  in  the 
United  States  (Hopkins,  1965),  small  summer 
animals  and  large  winter  animals.  The  latter 
from  North  Carolina  estuaries  showed  apparent 
differences  that  we  felt  merited  further  investi- 
gation. We  decided  to  determine  variation  and 
geographic  distribution  more  precisely  in  A^. 
americana. 


•Systematics  Laboratory,  National  Marine  Fisheries  Service, 
NOAA,  U.S.  National  Museum,  Washington,  DC  20560. 

^Department  of  Invertebrate  Zoology,  National  Museum  of 
Natural  History,  Washington,  DC  20560. 


The  study  is  a  complement  to  current  ecological 
investigations  in  coastal  environments.  A/^eom>'s is 
americana  is  probably  an  omnivore  like  its  near 
relative  A'^.  integer  (Mauchline,  1971)  or  Mysis 
relicta  (Lasenby  and  Langford,  1973),  consuming 
organic  detritus,  smaller  crustaceans,  and  diatoms 
and  fitting  the  trophic  role  attributed  to  other 
mysids  preyed  upon  by  fishes  in  Florida  estuaries 
(Odum  and  Heald,  1972)  and  Japan  (li,  1964). 
It  is  known  to  be  a  significant  element  in  the  diet 
of  fishes  such  as  flounder,  shad,  mackerel,  and 
anchovy  (Hopkins,  1965),  Paralichthys  dentatus 
andP.  lethostigma  (Powell,  in  litt.),  and  the  hakes, 
Urophycis  regius  and  U .  floridanus  (Sikora  et  al., 
1972)  as  well  as  other  fishes  (Taylor,  in  litt.). 

MATERIALS  AND  METHODS 

Our  materials  for  study  were  both  reliable 
literature  records  and  museum  specimens.  Cana- 
dian occurrences  have  been  reported  by  Bous- 
field (1955,  1956a,  b,  1958,  1962),  O.  S.  Tattersall 
(1955a),  Bousfield  and  Leim  (1960),  Prefontaine 
and  Brunei  (1962),  and  Brunei  (1970).  Records 
from  the  United  States  included  those  of  White- 
ley  (1948),  Hulbert  (1957),  Herman  (1963),  and 
Wigley  and  Burns  (1971)  in  addition  to  others 
cited  previously.  Southern  range  limits  and  off- 
shore distribution  were  partly  established  by 
examination  of  plankton  samples  taken  in  waters 
between  Cape  Hatteras,  N.C.,  and  Jupiter  Inlet, 
Fla.,  during  cruises  4,  5,  7,  8,  9  of  MV  Theodore 
N.  Gill  (October  1953-December  1954),  concen- 
trating on  nearshore  samples  where  the  species 
was  expected  to  occur  (station  data  in  Anderson, 
Moore,  and  Gordy,  1961a,  b).  Specimens  studied 


Manuscript  accepted  October  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


835 


FISHERY  BULLETIN;  VOL.  72,  NO.  3 


for  variation  were  from  collections  in  the  National 
Museum  of  Natural  History  (USNM),  including 
new  collections  acknowledged  below. 

Measurements  and  counts  used  in  assessing 
variation  were:  1)  carapace  length  from  rear  edge 
of  orbit  to  posterolateral  margin,  2)  length  and 
width  of  antennal  scale  (ventral  view),  3)  lengths 
of  inner  and  outer  uropods,  4)  number  of  spines 
in  ventral  comblike  row  on  inner  uropod  near 
distomesial  margin  of  statocyst  vesicle,  5)  length 
of  this  row  of  spines,  6)  number  of  spines  per  0.01 
mm  in  this  row,  7)  number  of  spines  on  margin  of 
telson,  and  8)  relative  widths  of  cornea  and 
eyestalk.  External  morphology  of  representative 
specimens  from  over  the  range  was  studied  and 
compared. 

Specimens  measured  for  comparisons  were 
mature  adults  (mainly  females)  from  the  follow- 
ing collections:  USNM  89736,  St.  Andrews,  near 
Atlantic  Biological  Station,  N.B.;  USNM  82658 
and  82651,  Woods  Hole,  Mass.,  received  2  January 
1907,  Vinal  N.  Edwards,  collector;  USNM  78734, 
Amityville,  Long  Island,  N.Y.,  6  August  1938, 
H.  K.  Townes,  collector;  USNM  143770,  York 
River  below  West  Point,  Va.,  14  January,  1964, 
W.  A.  Van  Engel,  collector;  USNM  143771,  Gar- 


bacon  Shoal,  6  May  1964,  W.  C.  Noe,  collector, 
and  USNM  143772,  Wilkinson  Point,  17  June 
1964,  Frank  Holland,  collector,  Neuse  River,  N.C.; 
USNM  143773,  Wassau  Sound,  Ga.,  29  August 
1972,  and  USNM  143774,  mouth  of  St.  Catherines 
Sound,  Ga.,  30  January  1970,  Richard  W.  Heard, 
Jr.,  collector.  All  specimens  were  large  winter 
animals  except  the  samples  of  summer  animals 
from  Amityville,  N.Y.,  and  Wassau  Sound,  Ga. 

RESULTS  AND  DISCUSSION 

Morphological  Analysis 

Proportional  and  meristic  characters  were 
evaluated  for  variation  in  different  parts  of  the 
range.  Mean  carapace  length  in  millimeters  (rear 
edge  of  orbit  to  posterolateral  margin)  for  the 
samples  analyzed  were:  (Figure  1)  New  York, 
2.95;  (Figures  1,  2)  New  Brunswick,  3.03;  Mas- 
sachusetts, 3.25;  Virginia,  3.51;  North  Carolina, 
3.03;  Georgia,  St.  Catherines  Sound,  3.91  -  Was- 
sau Sound,  2.09;  (Figure  3)  New  Brunswick,  3.01; 
North  Carolina,  2.74;  Georgia,  as  above.  There  is 
no  detectable  difference  in  size  between  males  and 
females  of  assumed  comparable  age. 


26 


24 


22 

o 
o 

I  20 

3 


2   18 

o 
^6 


§14 
(J 


12  - 


10 


8  - 


♦     • 


*  * 


O    * 


o      o 
o    o  o     o 


♦  ® 

*  •  ♦ 

*♦    ♦*         • 

♦  ♦A    ♦*  ♦ 

*♦  ♦*  ♦*  ♦•♦® 

4*  *  ♦A  A   a 

4     4  4M     *  Ok  A  a  a 

A  a  ▲  a      oD  o 

A  qA     A  o     o  o 


® 


♦   o 


♦ 


A  =  N.B. 
a  =  MASS. 

*  =  N.Y. 

♦  =  VA. 

♦  -N.C. 
O^WASSAU    SD..  GA. 

•  =ST.  CATHERINES  SD.,  GA. 


I 


_1_ 


_L 


_L 


_L 


_L 


_L 


_1_ 


_1_ 


2.0  2  .4  .6  .8  3.0  .2  .4  .6  .8  4.0  .2 

LENGTH  CARAPACE   (MM)   REAR  OF  ORBIT  TO  POSTEROLATERAL    MARGIN 


.6 


Figure  1. — Relation  between  number  of  spines  in  comblike  row  on  inner  uropod  and  length  of  carapace  from  rear 
edge  of  orbit  to  posterolateral  margin  in  seven  populations  of  Neomysis  americana.  Framed  points  =  replicates. 


836 


WILLIAMS,  BOWMAN,  and  DAMKAER:  THE  OPOSSUM  SHRIMP,  NEOMYSIS  AMERICANA 


-\ 1 1 1 1 1 1 1 1 1 1 1 1 1        I         I         I        I         r 


A=  N.B. 

♦  =  N.C. 
0=  WASSAU   SD..  GA. 

•  =  ST.  CATHERINES  SD..  GA. 


.24  .26  .28  .30 

WIDTH    ANTENNAL   SCALE    (MM) 


Figure  2. — Relation  between  length  and  width  of  antennal  scale  in  four  populations  of  Neomysis  americana.  Framed 

points  =  replicates 


3.0 


(J  .2 


2.0 


.6  - 


D 

0  a         a 

a 

o 

l 

A 

a 

c 

1 

1                J 

1              1 

A     N.B. 

n-MASS. 

*-VA. 

♦  -N.C. 
O  -WASSAU    SD.,   GA. 

•  -ST.    CATHERINES   SD.     GA        . 

1 1 1 1 1 

.8     2D 


.2     i  6     8     3.0     2     -4     .6     .8    4.0     .2     .4 

LENGTH  CARAPACE  (MM)  REAR  OF  ORBIT  TO  POSTEROLATERAL  MARGIN 


Figure  3. — Relation  between  length  of  antennal  scale  and  length  of  carapace  from  rear 
edge  of  orbit  to  posterolateral  margin  in  six  populations  of  Neomysis  americana.  Framed 
points  =  replicates. 


837 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


The  number  of  spines  in  the  ventral  comblike 
row  on  the  inner  uropod  first  suggested  that 
northern  populations  might  have  fewer  spines 
than  those  in  the  south.  This  proves  not  to  be  true; 
rather,  the  number  of  spines  is  apparently  a  func- 
tion of  body  size  (Figure  1).  A  regression  analysis 
shows  that  the  relationship  is  nonlinear  {Y  = 
3.39X  +  6.08,  r  =  0.579,  z  -  0.661,  P>0.05), 
falling  short  of  statistical  significance.  Inspection 
of  the  scatter  of  points  indicates  that  number  of 
spines  more  or  less  levels  off  at  upper  size  limits, 
but  distribution  is  fairly  broad  at  all  sizes. 

Two  other  relationships  do  yield  statistically 
significant  correlations  but  show  no  geographic 
association.  Length  of  the  antennal  scale  is  cor- 
related with  its  width  (Figure  2)  {Y  =  9.726X 
-  0.177,  r  =  0.967,2  =  2.043,  P<0.05)  and  with 
carapace  length  (Figure  3)  (Y  =  0.813X  -  0.264, 
r  =  0.822,2  =  1.162,  P<0.05). 

Other  plots  analyzed  but  not  discussed  in  detail 
here  show  similar  relationships  which  further 
substantiate  the  facts  given  above:  length  of  comb- 
like row  of  spines  on  inner  uropod  plotted  against 
length  of  carapace;  length  of  comblike  row  of 
spines  on  inner  uropod  plotted  against  longest 
spine  in  row;  length  of  inner  uropod  plotted 
against  length  of  carapace;  number  of  spines  per 
0.01  mm  in  comblike  row  of  spines  on  inner 
uropod  plotted  against  length  of  carapace.  Size  of 
cornea,  shape  of  rostrum,  shape  of  antennal  scale, 
spination  of  telson,  and  relative  lengths  of  uropods 
on  specimens  from  throughout  the  range  were 
compared.  No  constant  differences  were  noted 
that  would  define  geographic  races. 

Supplemental  Description 

Despite  its  abundance,  A/^eom_ysis  americana  has 
not  been  described  and  illustrated  fully.  The 
reason  for  this  omission  is  obvious:  of  the  16 
known  species  of  Neomysis,  it  is  the  only  one  that 
occurs  in  the  western  North  Atlantic  and  is  not 
likely  to  be  confused  with  any  other  mysid  within 
its  range.  Three  mysid  genera  are  similar  to 
Neomysis:  Acanthomysis,  Paracanthomysis ,  and 
Proneomysis.  The  last  two  are  confined  to  the 
North  Pacific,  and  the  only  Atlantic  representa- 
tive of  the  13  known  species  of  Acanthomysis, 
A.  longicornis  (Milne  Edwards),  is  limited  to 
European  waters. 

However,  the  lack  of  an  adequate  description 
of  N.  americana  gave  li  ( 1964)  some  difficulty 
before  he  decided  not  to  identify  a  Neomysis  from 


Korea  asN.  americana  but  to  describe  it  as  a  new 
species,  N.  orientalis.  To  obviate  problems  such  as 
this,  we  offer  Figures  4A-K  and  5A-J  and  com- 
ments on  some  characters  for  which  adequate 
illustrations  are  not  available. 

The  rostrum  (Figure  4A)  is  broadly  rounded  as 
inA^.  intermedia  and  N.japonica.  The  eyes  are  as 
described  by  W.  M.  Tattersall  (1951),  with  a  broad 
cornea  occupying  half  the  eyestalk.  Medially,  just 
before  the  eyestalk  narrows,  it  is  produced  into  a 
low  protuberance  armed  with  short  setae.  W.  M. 
Tattersall  described  the  telson  (Figure  4K)  as 
having  about  40  spines  on  each  lateral  margin;  the 
number  of  spines  depends  on  the  body  size  and 
ranges  from  about  20  to  40.  The  peduncle  of 
antenna  1  is  shown  in  Figure  4B,  C,  D,  the  latter 
showing  the  male  lobe.  W.  M.  Tattersall's  (1951) 
Figure  77 A  shows  the  antennal  scale  without  a 
suture,  which  would  be  unique  for  the  genus.  Our 
specimens  have  a  distinct  suture  (Figure  4D) 
setting  off  a  short  distal  segment.  As  in  other 
species  of  Neomysis  the  labrum  is  produced  an- 
teriorly into  a  spiniform  process  (Figure  4E,  F), 
and  the  terminal  segment  of  the  mandibular  palp 
(Figure  4G)  is  relatively  slender. 

According  to  W.  M.  Tattersall  (1951)  the 
"tarsus"  of  pereopods  2-7  is  8-9  segmented.  We 
find  that  the  number  of  segments  increases  with 
body  size  (Figure  5A,  C)  as  inN.  patagona  (O.  S. 
Tattersall,  1955b;  Holmquist,  1957).  The  proxi- 
mal suture  may  be  incomplete,  not  present  medi- 
ally; in  such  pereopods  an  additional  tarsal  seg- 
ment would  be  counted  when  viewed  laterally. 
Our  counts  are  in  lateral  view  and  include  both 
partly  fused  proximal  segments.  Small  juveniles 
have  6  segments;  small  adults  from  Pamlico 
Sound,  N.C.,  7  segments;  large  adults  from  Woods 
Hole,  Mass.,  8  segments;  and  large  adults  from 
the  York  River,  Va.,  9  segments.  The  number 
appears  to  be  rather  constant  among  the  pereo- 
pods of  an  individual,  but  may  differ  by  1  segment 
in  one  or  two  of  the  pereopods. 

The  genns  Neomysis  is  unique  in  having  median 
fingerlike  papillae  on  the  last  two  or  three 
pereonal  sterna  of  gravid  females  (W.  M.  Tatter- 
sall, 1932).  W.  M.  Tattersall  (1951)  found  these 
papillae  on  the  last  two  sternae  of  A'^.  americana, 
and  we  show  them  in  Figure  4J.  Their  function 
is  unknown.  Other  characters  of  Neomysis  are 
the  presence  of  a  bailing  lobe  on  the  posterior 
margin  of  the  oostegite  of  pereopod  6  (Figure 
5E)  and  a  rudimentary  oostegite  on  pereopod  5 
(Figure  5D). 


838 


WILLIAMS,  BOWMAN,  and  DAMKAER:  THE  OPOSSUM  SHRIMP,  NEOMYSIS  AMERICANA 


Figure  4. — Neomysis  americana.  A,  Rostrum  and  eyes,  dorsal  (2  ,  New  Brunswick).  B,  Right  antenna  1  peduncle, 
dorsal,  (?,  New  Brunswick).  C,  Antenna  1  peduncle,  ventral,  {$,  York  River,  Va.).  D,  Antenna  2,  ventral  {$, 
Adams  Creek,  N.C.).  E,  Labrum,  ventral  (  9 ,  Pamlico  Sound,  N.C.).  F,  Same,  lateral.  G,  Left  mandible  ( ? ,  New 
Brunswick).  H,  Incisor  of  same.  I,  Right  maxilliped,  posterior,  setae  omitted  (  S ,  York  River).  J,  Sternal  pro- 
cesses of  pereonites  VI  and  VII.  K,  Telson,  dorsal  (  S  ,  Adams  Creek). 


839 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Figure  5. — Neomysis  americana.  A,  Endopod  of  pereopod  6(9,  New  Brunswick).  B,  Apex  of  same.  C,  Endopod 
of  pereopod  7(9,  New  Brunswick).  D,  Oostegite  of  pereopod  5.  E,  Oostegite  of  pereopod  6  (arrow  points  to  bailing 
lobe).  F,  Pleopod  4,S  .  G,  Apex  of  same.  H,  Uropod,  ventral  ( 9  ,  Pamlico  Sound,  N.C.).  I,  Spine  row  of  inner  uropod 
(  S  ,  Nova  Scotia).  J,  Same,  (  S  ,  Adams  Creek,  N.C.). 


840 


WILLIAMS,  BOWMAN,  and  DAMKAER:  THE  OPOSSUM  SHRIMP,  NEOMYSIS  AMERICANA 


Distribution 

Neomysis  americana  inhabits  estuaries  and 
nearshore  ocean  from  mesohaline  reaches  of  the 
St.  Lawrence  River  near  St.  Joachim  on  the  north 
shore  and  Montmagny  on  the  south,  downstream 
around  the  Gaspe  Peninsula,  and  from  southern 
Newfoundland  southward  through  the  maritime 
provinces  of  Canada,  along  the  United  States  to 
St.  Augustine,  Fla.  Collections  south  of  St. 
Augustine  yielded  no  specimens,  but  the  species 
may  range  as  far  southward  as  Cape  Canaveral. 

Prominent  in  estuaries,  N.  americana  is  also 
found  at  sea.  Whiteley  (1948)  recorded  it  on 
Georges  Bank  inside  the  100-m  margin  but  most 
abundantly  in  water  75  m  deep  or  less.  Wigley 
and  Burns  (1971)  showed  essentially  this  pattern 
in  their  distribution  summary.  It  was  partly  the 
distribution  shown  by  these  samples  produced 
with  the  aid  of  grab  samplers  and  dredges  at  a 
great  number  of  stations  to  depths  beyond  100  m 
between  Nova  Scotia  and  southern  Florida  that 
suggested  an  oceanic  population  north  of  Cape 
Henry,  Va.,  separated  from  a  southern  estuarine 
one.  None  of  their  southern  samples  contained 
N.  americana. 

Neomysis  americana  was  found  in  only  four 
samples  (total  of  10  specimens)  from  the  Theodore 
N.  Gill  material.  These  were:  Cruise  4,  5  October- 
4  November  1953,  Station  56  off  Myrtle  Beach, 
S.C.  (2)  -  Cruise  9,  3  November-12  December  1954, 
Station  22  off  St.  Augustine,  Fla.  (1);  Station  23 
off  mouth  of  St.  Johns  River,  Fla.  (6);  Station  56 
(1).  All  these  stations  were  in  water  10  m  deep 
or  less. 

ACKNOWLEDGMENTS 

We  are  indebted  to  Richard  W.  Heard,  Jr.,  Mar- 
vin W.  Wass,  and  Thomas  D.  Myers  for  material 
from  Georgia-Florida,  Virgini-a,  and  Delaware 
respectively,  and  to  the  University  of  North  Carol- 
lina  Institute  of  Marine  Sciences  for  transfer  of 
specimens  to  the  USNM  collections.  We  thank 
George  R.  Zug  for  help  with  the  statistical  analy- 
sis and  Bruce  B.  Collette  and  Isabel  Perez  Far- 
fante  for  critical  review  of  the  manuscript.  Maria 
M.  Dieguez  drafted  the  graphs. 

LITERATURE  CITED 

Anderson,  W.  W.,  J.  E.  Moore,  and  H.  R.  Gordy. 

1961a.     Water  temperatures  off  the  south  Atlantic  coast  of 


the  United  States,  Theodore  N.  Gill  Cruises  1-9,  1953-54. 
U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish.  380,  206  p. 
1961b.     Oceanic  salinities  off  the  south  Atlantic  coast  of  the 
United  States,  Theodore  N.  Gill  Cruises  1-9,  1953-54. 
U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish.  389,  207  p. 

BOUSFIELD,  E.  L. 

1955.     Studies  on  the  shore  fauna  of  the  St.  Lawrence 

Estuary  and  Gaspe  Coast.     Natl.  Mus.  Can.  Bull. 

136:95-101. 
1956a.     Studies  on  the  shore  Crustacea  collected  in  eastern 

Nova  Scotia  and  Newfoundland,  1954.     Natl.  Mus.  Can. 

Bull.  142:127-152. 
1956b.     Malacostracan  crustaceans  from  the  shores  of 

western  Nova  Scotia.    Proc.  N.S.  Inst.  Sci.  24:25-38. 
1958.     Littoral  marine  arthropods  and  moUusks  collected 

in  western  Nova  Scotia,   1956.     Proc.  N.S.  Inst.  Sci. 

24:303-325. 

1962.  Studies  on  littoral  marine  arthropods  from  the 
Bay  of  Fundy  region.     Natl.  Mus.  Can.  Bull.  183:42-62. 

BousFiELD,  E.  L.,  AND  A.  H.  Leim. 

1960.     The  fauna  of  Minas  Basin  and  Minas  Channel. 
Natl.  Mus.  Can.  Bull.  166:1-30. 
Brunel,  p. 

1970.  Catalogue  d'invertebres  benthiques  du  Golfe 
Saint-Laurent  recueillis  de  1951  a  1966  par  la  Station 
de  Biologie  Marine  de  Grande-Riviere.  Trav.  Biol. 
Univ.  Montreal  53,  54  p. 

Herman,  S.  S. 

1963.  Vertical  migration  of  the  opossum  shrimp, Neomysis 
americana  Smith.     Limnol.  Oceanogr.  8:228-238. 

HOLMQUIST,  C. 

1957.     Mysidacea  of  Chile.     Lunds  Univ.  Arsskr.  N.F. 
Avd.  2,  53(6),  52  p. 
Hopkins,  T.  L. 

1965.     Mysid  shrimp  abundance  in  surface  waters  of  Indian 
River  Inlet,  Delaware.     Chesapeake  Sci.  6:86-91. 
Hulbert,  E.  M. 

1957.     The  distribution  of  Neomysis  americana  in  the 
estuary  of  the  Delaware  River.    Limnol.  Oceanogr.  2:1-11. 
h,  N. 

1964.  Fauna  Japonica,  Mysidae  (Crustacea).  Biogeogr. 
Soc.  Jap.,  Natl.  Sci.  Mus.,  Tokyo,  610  p. 

Lasenby,  D.  C,  and  R.  R.  Langford. 

1973.     Feeding  and  assimilation  of  Mysisrelicta.     Limnol. 
Oceanogr.  18:280-285. 
Mauchline,  J. 

1971.  The  biology  of  Neomysis  integer  [Crustacea,  Mysi- 
dacea].   J.  Mar.  Biol.  Assoc.  U.K.  51:347-354. 

Odum,  W.  E.,  and  E.  J.  Heald. 

1972.  Trophic  analyses  of  an  estuarine  mangrove  com- 
munity.    Bull.  Mar.  Sci.  22:671-738. 

Prefontaine,  G.,  and  p.  Brunel. 

1962.     Liste  d'invertebres  marins  recueillis  dans  I'es- 
tuaire  du  Saint-Laurent  de  1919  a  1934.     Nat.  Can. 
89:237-263. 
SiKORA,  W.  B.,  R.  W.  Heard,  and  M.  D.  Dahlberg. 

1972.     The  occurrence  and  food  habits  of  two  species  of 
hake,  Urophycis  regius  and  U.  floridanus  in  Georgia 
estuaries.     Trans.  Am.  Fish  Soc.  101:513-525. 
Tattersall,  O.  S. 

1955a.     Shallow-water  Mysidacea  from  the  St.  Lawrence 

estuary,  eastern  Canada.     Can.  Field-Nat.  68:143-154. 
1955b.     Mysidacea.     Discovery  Rep.  28:1-190. 


841 


FISHERY  BULLETIN:  VOL.  72,  NO.  3 


Tattersall.  W.  M. 

1932.  Contributions  to  a  knowledge  of  the  Mysidacea  of 
California.  II:  The  Mysidacea  collected  during  the  sur- 
vey of  San  Francisco  Bay  by  the  U.S.S.  "Albatross"  in 
1914.     Univ.  Calif  Publ.  Zool.  37:315-347. 

1951.     A  review  of  the  Mysidacea  of  the  United  States 
National  Museum.     U.S.  Natl.  Mus.  Bull.  201,  292  p. 
Verrill.  a.  E. 

1873.  Report  upon  the  invertebrate  animals  of  Vinyard 
Sound  and  the  adjacent  waters,  with  an  account  of  the 
physical  characters  of  the  region.  Rep.  U.S.  Comm. 
Fish  Fish.  1:295-778. 


Whiteley,  G.  C,  Jr. 

1948.  The  distribution  of  larger  planktonic  Crustacea  on 
Georges  Bank.     Ecol.  Monogr.  18:233-264. 

WiGLEY,  R.  L.,  AND  B.  R.  BURNS. 

1971.  Distribution  and  biology  of  mysids  (Crustacea, 
Mysidacea)  from  the  Atlantic  coast  of  the  United  States 
in  the  NMFS  Woods  Hole  collection.  Fish.  Bull.,  U.S. 
69:717-746. 

Williams,  A.  B. 

1972.  A  ten-year  study  of  meroplankton  in  North  Caro- 
lina estuaries:  Mysid  shrimps.  Chesapeake  Sci.  13:254- 
262. 


842 


NOTES 


THE  MEAN  ANNUAL  CYCLE  OF 

COASTAL  UPWELLING  OFF  WESTERN 

NORTH  AMERICA  AS  OBSERVED  FROM 

SURFACE  MEASUREMENTS 

One  of  the  world's  major  upwelling  regions  lies  off 
the  west  coast  of  the  United  States  and  northern 
Mexico.  This  paper  summarizes  marine  surface 
observations  to  describe  the  normal  yearly  cycle  of 
intensity  of  upwelling  for  the  major  portion  of  the 
northeastern  Pacific  coastal  upwelling  region. 

Sverdrup  (1938J  applied  Ekman's  (1905)  theory 
to  account  for  a  coastal  upwelling  situation 
observed  off  southern  California.  He  proposed  a 
mechanism  by  which  water  is  transported  off- 
shore in  the  surface  Ekman  layer  due  to  the  stress 
of  the  wind  on  the  sea  surface  and  is  replaced 
by  water  upwelled  from  depth.  Wooster  and  Reid 
(1963)  presented  evidence  that  this  is,  indeed, 
the  dominant  mechanism  acting  in  regions  of 
slow,  diffuse  eastern  boundary  currents  wherein 
lie  the  major  coastal  upwelling  areas  of  the  world, 
including  that  of  the  northeastern  Pacific. 

Our  approach  is  to  define  the  mean  annual 
cycle  of  offshore  Ekman  transport  along  the  west 
coast  of  the  United  States  and  the  immediately 
adjacent  regions  of  Canada  and  Mexico  and  to 
correlate  this  with  features  indicative  of  upwell- 
ing which  appear  in  the  long-term  mean  monthly 
distributions  of  sea  surface  temperature. 

Marine  surface  weather  observations  for  this 
study  were  obtained  from  a  version  of  the  National 
Climatic  Center's  tape  deck  of  marine  surface 
observations  'Tape  Data  Family-11)  in  use  at  the 
U.S.  Navy  Fleet  Numerical  Weather  Central.  The 
observations  in  this  file  come  primarily  from 
merchant  and  naval  ships  and  sometimes  contain 
various  errors  in  position,  measurement,  or 
processing.  Consequently,  the  sea  surface 
temperature  data  were  subjected  to  an  editing 
process  which  consisted  of  two  filters.  First,  a 
gross  error  check  was  performed  to  eliminate 
nontemperatures.  Second,  the  data  were  checked 
by  comparison  with  a  running  mean  of  10  reports. 
When  a  report  of  sea  surface  temperature  differed 
from  the  running  mean  by  greater  than  9'C,  the 
report  was  rejected.  Wind  speeds  of  greater  than 
100  m/s  were  rejected.  "Variable"  winds  (no 


direction  reported,  low  reported  speedj  were 
treated  as  calms. 

The  Ekman  transport  was  calculated  by  the 
following  procedure.  The  stress  vector  was 
computed  from  each  wind  observation  according 
to  the  classical  square  law: 


a       L) 


\vW , 


where  f  is  the  stress  of  the  wind  on  the  sea 
surface,  fj,^  is  the  density  of  air  (0.00122  g/cm''), 
Cd  is  an  empirical  drag  coefficient  '0.0013), 
V  is  the  observed  wind  velocity  vector,  and 
\~i>  \  is  the  observed  wind  .speed  The  resultant 
Ekman  wind  stress  transport,  M,  was  computed 
according  to , 


M    =   -T 


X  k 


where  r  is  the  wind  stress  vector,  f  is  the  Coriolis 
parameter,  and  ^  is  a  unit  vector  directed 
vertically  upward. 

Figure  1  displays  composite  monthly  values  of 
these  data  for  the  20-yr  period,  1948-67.  The  plot 
on  the  left  displays  time  series  i.sograms  of 
offshore  component  of  Ekman  tran.sport  while  the 
central  plot  shows  .similar  i.sograms  of  .sea  sur- 
face temperature.  The  coordinates  are  north- 
south  di.stance  on  the  ordinate  and  time  by  month 
on  the  ab.sci.s.sa.  Each  plot  represents  about  75,000 
individual  observations  made  within  the  l'^ 
squares  shown  in  the  coastline  plot  to  the  right. 
The  number  of  reports  per  Y'  square  per  month 
was  in  the  range  22  'in  January  off  Vancouver 
Island)  to  1,884  'in  October  off  Los  Angeles). 

The  sea  surface  temperature  plot  reveals  a 
normal  north-south  gradation  of  temperature  and 
a  seasonal  warming-cooling  cycle  with  minima 
from  February  to  April  and  maxima  in  August 
and  September.  The  effects  of  upwelling  are  seen 
as  distortions  of  this  general  pattern. ^ 

In  the  northern  portion.  Cape  Blanco  to 
Vancouver  Island,  offshore  Ekman  transport  is 
weak  and  occurs  from   about  May  through 


'The  fine  scale  detail.s  of  the  temperature  distribution  are 
masked  by  the  1'  square  spatial  averages.  For  a  detailed 
treatment  of  the  mean  temperature  cycle  in  the  southern  portion 
of  the  region  the  reader  is  referred  to  Lynn  '1967;. 


843 


SON 


45N 


J       FMAMJJASONDJJ 


AMJJASONDJ 


40N 


3  5N 


30N 


OFFSHORE  EKMAN  TRANSPORT    (M^'/sec/M)  SEA    SURFACE     TEMPERATURE  (°C) 


I25W  I20W 

VANCOUVER  I.   ' 


II5W 
SON 


45N 


40N 


35  N 


30  N 


Figure  1. — Time  series  isograms  of  long-term  composite  monthly  offshore  Ekman  transports  (m%  per  meter  of  coastline)  and  sea 
surface  temperature  (degrees  Celsius)  for  the  20-yr  (1948-67)  period  within  the  indicated  1°  coastal  squares. 


September.  The  weakness  of  the  transport  is 
reflected  by  the  presence  of  substantial  seasonal 
warming.  The  region  defined  by  temperatures 
greater  than  15°C,  located  off  Washington- 
Oregon  during  late  summer,  probably  reflects  the 
warming  of  the  low-salinity  Columbia  River 
plume  water  which  spreads  over  a  large  area  of 
ocean  surface.  Some  of  the  apparent  warming 
may  be  due  also  to  the  concavity  of  the  coastline 
in  this  area  which  could  cause  a  greater  proportion 
of  the  observations  to  be  taken  farther  offshore, 
both  because  the  1°  squares  extend  farther  off  the 
coast  and  because  the  coastwide  shipping  tracks 
may  be  displaced  offshore. 

South  of  Cape  Blanco  an  abrupt  increase  of 
summer  offshore  Ekman  transport  is  indicated, 
particularly  during  June  and  July.  This  is 
associated  with  a  suppression  of  seasonal  warm- 
ing during  early  summer.  Consequently,  the 
period  of  maximum  sea  surface  temperature  is 
delayed  until  September  when  offshore  transport 
has  relaxed  considerably. 

South  of  Cape  Mendocino  Ekman  transport  is 
directed  offshore  for  virtually  the  entire  year  and 
reaches  its  greatest  value  for  the  whole  coast  at 
about  lat.  39°N  during  May  through  August.  This 
maximum  corresponds  to  an  extreme  suppression 
of  seasonal  warming  indicated  by  nearly  hori- 
zontal isotherms  in  the  figure. 

South  of  Point  Conception,  the  offshore  Ekman 
transport,  although  remaining  generally  positive 
throughout  the  year,  is  small  and  an  abrupt 


southward  increase  in  temperature,  particularly 
during  the  summer,  is  apparent.  Due  to  the 
tendency  for  a  cyclonic  eddy  to  form  in  the 
Southern  California  Bight  (Reid,  Roden,  and 
Wyllie,  1958),  warm  advection  not  directly  related 
to  upwelling  may  be  an  important  factor  in  this 
increase. 

Literature  Cited 

Ekman,  V.  W. 

1905.     On  the  influence  of  the  Earths  rotation  on  ocean 
currents.     Ark.  Mat.  Astron.  Fys.  2(ll):l-55. 
Lynn,  R.  L. 

1967.     Seasonal  variation  of  temperature  and  salinity  at 
10  meters  in  the  California  Current.     Calif.  Coop. 
Oceanic  Fish.  Invest.,  Rep.  11:157-186. 
Reid,  J.  L.,  Jr.,  G.  I.  Roden,  and  J.  G.  Wyllie. 

1958.     Studies  of  the  California  Current  system.     Calif. 
Coop.  Oceanic  Fish.  Invest.,  Prog.  Rep.,  1  July  1956  to  1 
Jan.  1958,  p.  27-57. 
SVERDRUP,  H.  U. 

1938.     On   the   process   of  upwelling.     J.    Mar.   Res. 
1:155-164. 
Wooster,  W.  S.,  and  J.  L.  Reid,  Jr. 

1963.  Eastern  boundary  currents.  In  M.  N.  Hill  (editor). 
The  sea,  ideas  and  observations  on  progress  in  the  study 
of  the  seas.  Vol.  2,  p.  253-280.  Interscience  Publ.,  N.Y. 

Andrew  Bakun 

Douglas  R.  McLain 

Frank  V.  Mayo 

Pacific  Environmental  Group 

National  Marine  Fisheries  Service 

NOAA 

Monterey,  CA  93940 


844 


THE  RESIDUAL  LIPIDS 
OF  FISH  PROTEIN  CONCENTRATES 

Previous  papers  (Medwadowski,  Van  der  Veen, 
andOIcott,  1967, 1968;  Medwadowskietal.,  1971), 
presented  data  on  the  residual  lipids  in  fish  pro- 
tein concentrates  (FPCs)  from  red  hake,  Uro- 
phycis  chuss;  Gulf  menhaden,  Breuoortia  pa- 
tronus;  pout,  Macrozoarces  americanus;  and 
alewife,  Alosa  pseudoharengus;  and  some  pre- 
liminary data  on  the  effects  of  storage  on  the 
lipids.  After  6  mo  at  37°  or  SOT,  there  were 
decreases  in  the  contents  of  highly  unsaturated 
fatty  acids  (C20:5  for  alewife  and  C20:5  and 
C22:6  for  pout  and  Gulf  menhaden),  and  an 
appreciable  decrease  in  the  amount  of  lipid 
extractable  from  a  menhaden  FPC  that  origi- 
nally contained  0.56%  lipid,  but  no  change  in 
the  amount  extractable  from  FPCs  that  origi- 
nally contained  0.11%  (pout)  or  0.06%  (alewife) 
lipids. 

In  this  paper  we  present  data  on  the  composi- 
tion of  lipids  extracted  from  additional  samples  of 
FPCs  (from  Pacific  hake,  Merluccius  productus; 
northern  anchovy,  Engraulis  mordax;  Atlantic 
menhaden,  Brevoortia  tyrannus;  and  Atlantic 
herring,  Clupea  harengus  harengus)  and  also  on 
the  effects  of  storage,  at  several  temperatures 
and  humidities,  on  the  composition  of  the  residual 
lipids  in  a  hake  FPC  preparation. 

Materials  and  Methods 

The  FPCs  had  been  prepared  at  National 
Marine  Fisheries  Service  laboratories  by  counter- 
current  extraction  of  ground  fish  with  hot  iso- 
propyl  alcohol,  followed  by  solvent  removal  and 
milling  (Knobl  et  al.,  1971). 

Samples  of  a  hake  FPC  were  stored  at  the 
College  Park  Fishery  Products  Technology  Labo- 
ratory at  21. r,  32.3°,  and  43.3°C  and  at  50% 
and  90%  relative  humidities  for  each  temperature 
for  periods  of  1,  3,  6,  and  12  mo  (Green,  1972). 
The  control  was  held  at  -29°C  and  ambient 
freezer  humidity.  The  samples  were  shipped  in 
plastic  bags,  cooled  with  dry  ice  (except  for  the  zero 
time  control  sample  which  was  shipped  at  ambient 
temperature),  and  stored  at  -18°C  pending 
analyses. 

Two  procedures  for  determining  moisture 
content  (volatile  matter)  of  the  hake  FPC  samples 
were  compared:  30-45  h  at  110°-115°C,  and  1  h 
at  130°C  (Association  of  Official  Analytical 
Chemists  method,  Horwitz,   1970:211).  In  the 


latter  case,  the  drying  was  interrupted  after  30 
min;  the  caked  meal  was  broken  with  a  stirring 
rod;  and  the  meal  adhering  to  the  rod  was  brushed 
back  into  the  glass-stoppered  weighing  bottle  in 
which  the  sample  was  being  dried  and  weighed. 
Results  from  the  two  methods  were  in  close  agree- 
ment. The  shorter  method  with  the  modification 
of  the  intermittent  stirring  was  used  thereafter. 
The  lipids  were  extracted  (Soxhlet)  in  duplicate 
or  triplicate  with  chloroform-methanol  (2:1)  from 
200-g  portions  of  the  FPCs  in  large  prewashed 
thimbles  and  analyzed  as  described  by  Medwadow- 
ski et  al.  (1971)  with  the  following  modifications 
in  some  cases.  Purification  was  accomplished  with 
a  2  X  22  cm  Sephadex^  column  chromatography 
(Siakotas  and  Rouser,  1965;  Rouser,  Kritchevsky, 
and  Yamamoto,  1967)  and  flow  was  by  gravity. 
The  saponification-methylation  procedure  used 
for  determination  of  fatty  acids  was  that  described 
by  Metcalfe,  Schmitz,  and  Pelka  (1966).  The 
amounts  of  lipid  were  determined  by  drying 
aliquots  of  their  solutions  on  a  warm  hot  plate 
in  preweighed  disposable  aluminum  pans  (Rouser 
et  al.,  1967). 

Results  and  Discussion 

Yields  and  fatty  acid  composition  of  the  lipids 
extracted  from  seven  separate  runs — three  from 
Pacific  hake,  two  from  northern  anchovy,  and  one 
each  from  Atlantic  herring  and  Atlantic  men- 
haden— are  shown  in  Table  1. 

The  two  anchovy  FPCs  had  somewhat  similar 
fatty  acid  compositions;  the  main  differences  were 
in  the  amounts  of  C16:0  and  C20:5.  Herring  FPC 
contained  relatively  larger  percentages  of  C20:l 
and  C22:l.  The  Pacific  hake  FPCs,  samples  8, 
9,  and  10,  were  similar  in  fatty  acid  composition 
but  contained  relatively  more  C18:1  than  the 
FPCs  from  the  other  fish.  The  lipids  of  samples 
8,  9,  and  10,  in  general,  resembled  those  of  a 
red  hake  FPC,  P-5  (reported  previously  by 
Medwadowski  et  al.,  1967),  and  those  of  fresh 
red  hake  (Medwadowski  et  al.,  1967,  1968).  The 
Pacific  hake  FPCs,  samples  8.  9,  10,  and  78-103 
(Table  3),  contained  higher  percentages  of  C20:5 
and  C22:6  than  red  hake  FPC  P-5  and  fresh 
red  hake.  Possibly  less  oxidation  had  occurred 
during  processing,  or  the  fish  from  which  the  FPCs 
were  made  had  been  subsisting  on  different 
foodstuffs. 


'Reference  to  trade  names  does  not  imply  endorsement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


845 


Table  1. — A  comparison  of  lipids  extracted  from  several  fish  protein  concentrates. 


Volatile 

matter 

(%) 

Lipid^ 
(%) 

Fatty  acid  composition'(%) 

FPC 

14:0 

15:0 

16:0 

16:1 

17:0 

iso 
18:0 

18:0 

18:1 

18:2 

18:4 

20:0 

20:1 

20:5 

22:1 

22:5 

22:5 

Anchovy 

_ 

0.08 

8.0 

1.0 

26.2 

7.4 

1.3 

0.2 

7.0 

13.9 

2.3 

1.2 

0.7 

1.9 

9.5 

2.4 

0.5 

13.0 

Anchovy 
(80308) 

2.17 

0.28 

8.2 

1.2 

16.7 

10.6 

1.4 

0.6 

5.8 

18.1 

1.8 

tr 

20 

0.9 

15.4 

tr 

0.8 

14.7 

Hake  -  8 

4.12 

0.12 

4.1 

0.4 

17.0 

10.2 

— 

— 

4.4 

29.2 

1.1 

— 

— 

3.3 

15.4 

— 

0.4 

11.3 

Hake  -  9 

3.95 

0.28 

4.4 

0.4 

18.2 

9.6 

— 

— 

5.7 

28.2 

1.2 

— 

— 

3.9 

14.4 

— 

0.8 

10.0 

Hake-  10 

3.77 

021 

3.3 

0.3 

21.1 

8.5 

— 

— 

4.2 

31.5 

1.0 

— 

— 

2.7 

14.2 

— 

0.5 

10.5 

Menhaden 
(B0204) 

2.89 

0.30 

9.6 

1.1 

17.9 

14.3 

2.3 

2.4 

7.7 

16.8 

1.8 

1.8 

1.6 

12.5 

_ 

1,7 

5.5 

Herring 

— 

0.17 

5.8 

0.6 

15.9 

4.6 

0.1 

3.4 

12.2 

1.9 

0.2 

132 

5.7 

24.3 

" 

8.8 

'Number  of  carbon  atoms:  number  of  double  bonds.  Additional  fatty  acids,  tentatively  identified  but  present  in  amounts  of  1%  or  less,  were: 
12:0.  anteiso  15:0.  iso  16:0.  16:2.  18:3,  19:0,  iso  20:0.  20:2,  20:3,  21:0,  22:2,  22:3,  22:4,  24:1. 
^Dry  basis 


The  percentages  of  volatile  matter  in  the  Pacific 
hake  (78-103)  samples  stored  at  different  tempera- 
tures and  humidities  are  shown  in  Table  2.  The 
moisture  content  of  the  different  samples  was 
relatively  constant  during  several  month's  storage 
in  plastic  bags  at  -18°C.  The  increase  in  volatile 
matter  after  equilibrium  had  presumably  been 
reached,  in  the  samples  stored  at  90%  relative 
humidity  might  indicate  gradual  changes  in  the 
affinity  of  the  FPC  samples  for  water  or,  possibly, . 
the  formation  of  volatile  components  other  than 
water. 

Gas  chromatographic  analyses  of  the  methyl 
esters  of  the  fatty  acids  from  the  Pacific  hake 
FPC  show  that  it  was  relatively  stable  under  most 
of  the  storage  conditions  described  (Table  3). 
Shono  and  Toyomizu  (1972)  suggested  that  the 
rate  of  decrease  of  C22:6  acid  could  be  used  as 
an  indication  of  oxidative  deterioration  in  fish 
products.  There  were  no  apparent  decreases  in 
C22:6  acid  content  at  50%  relative  humidity. 
However,  at  90%  relative  humidity,  there  were 
very  significant  decreases  of  C22:6  acid  content  of 


from  8.9  to  26.1%  in  the  temperature  range  of 
21°  to  43°C.  Thus  water  activity  had  more  effect 
than  temperature  on  the  stability  of  this  FPC 
preparation. 

Each  hake  FPC  extract  described  in  this  paper 
was  separated  by  silicic  acid  chromatography  into 
three  separate  fractions,  as  previously  described 
(Medwadowski  et  al.,  1971).  There  were  little  or 
no  significant  changes  in  the  amounts  recoverable 
from  each  fraction  (not  shown),  and  they  were  not 
analyzed  further. 

In  general,  these  observations  confirm  the 
relative  stability  of  FPC  during  storage,  even 
under  adverse  conditions  of  temperature  and 
humidity. 

Acknowledgments 

This  investigation  was  supported  in  part  by 
contract  no.  USDC  1-36062  NOAA,  U.S.  De- 
partment of  Commerce,  and  in  part  by  a  grant 
from  the  Tuna  Research  Foundation,  Inc., 
Terminal  Island,  Calif. 


Table  2. — Changes  in  the  volatile  matter  of  Pacific  hake  FPC  (78-103)  with  storage  at 
different  temperatures  and  humidities. 


Storage 

time 
(month) 


Control 


Average  volatile  matter  (%] 


21-50 


Storage  conditions': 
21-90  32-50  32-90 


43-50 


43-90 


0 
1 
3 
6 
12 


5.2 
5.4 
5.2 
5.3 
5.8 


7.6 

10.5 

7.8 

12.8 

7.9 

12.5 

7.8 

10.7 

8.1 

13.1 

8.0 

12.4 

8.1 

11.5 

8.7 

14.2 

7.9 

13.4 

7.9 

12.2 

8.3 

14.8 

7.7 

15.4 

'Hyphens  separate  degrees  Celsius  and  percent  relative  humidity. 


846 


Table  3.— Effect  of  storage  on  the  lipid  composition  of  Pacific  hake  FPC  (78-103).' 


Storage 
conditions^ 

Storage 

time 
(month) 

Total 

lipid^ 

(%) 

Percentagi 

Bs  Of  the 

major  fatty 

acids" 

Reduction 
of  C22:6 

(%) 

T              RH 

(°C)            (%) 

14:0 

16:0 

161 

18:0 

18:1 

20:1 

20:4 

20:5 

22:5 

22:6 

0 

0.09 

1.3 

15.8 

3.1 

7.5 

25.3 

3.3 

2.9 

9.9 

1.9 

29.1 

1 

0.09 

1.4 

15.6 

3.1 

7.4 

25.3 

3.3 

2.8 

10.1 

1.9 

29.2 

-20            AF 

3 

0.10 

1.5 

15.9 

3.2 

70 

24.9 

3.1 

2.8 

10.2 

2.0 

29.4 

6 

0.10 

2.3 

15.1 

5.0 

6.0 

22.8 

2.2 

2.5 

15.1 

1.4 

27.5 

5.5 

12 

0.12 

2.2 

15.4 

4.8 

6.4 

23.7 

2.2 

2.8 

13.7 

1.4 

27.5 

5.5 

1 

0.10 

1.4 

15.6 

3.1 

7.3 

25.4 

3.0 

2.9 

10.3 

2  1 

289 

3 

0.11 

1.4 

15.6 

3.4 

8.4 

22.8 

2.8 

3.0 

11.1 

1.8 

29.8 

21               50 

6 

0,10 

1.8 

13.7 

4.3 

7.8 

23.2 

2.7 

3.1 

12.9 

18 

28.6 

1.7 

12 

0.12 

2.1 

16.2 

4.9 

6.8 

242 

2.2 

2.8 

12.9 

1.1 

26.9 

7.6 

1 

0.11 

1.4 

15.4 

3.0 

7.5 

25.1 

3.1 

2.9 

10.2 

2.0 

29.2 

3 

0.12 

1.3 

15.2 

3.2 

9.0 

23.7 

3.6 

2.9 

10.2 

1.8 

29.3 

21               90 

6 

0.10 

1.9 

16.8 

4.7 

7.2 

24.1 

2.3 

2.8 

12.3 

1.5 

26.5 

8.9 

12 

0.12 

2.3 

16.1 

5.2 

6.4 

24.1 

2.0 

3.0 

12.9 

1.5 

26.5 

8.9 

1 

0.10 

1.4 

15.9 

2.9 

7.5 

25.3 

3.3 

2.8 

10.6 

2.0 

28.4 

3 

0.10 

1.5 

15.4 

3.3 

8.0 

23.5 

3.2 

2.8 

10.6 

2.0 

29.8 

32              50 

6 

0.11 

1.9 

15.2 

4.9 

8.5 

25.1 

2.4 

2.8 

11.5 

1.6 

26.0 

10.7 

12 

0.10 

2.2 

16.7 

5.4 

5.6 

24.4 

1.4 

2.7 

13.9 

1.0 

26.6 

8.6 

1 

0.11 

1.4 

15.5 

3.2 

7.5 

24.3 

2.9' 

2.9 

10.1 

2.1 

30.0 

3 

0.12 

1.5 

16.3 

3.6 

8.0 

23.5 

3.0 

3.0 

10.5 

1.9 

28.8 

32              90 

6 

0.12 

1.6 

16.4 

4.2 

8,1 

25.3 

2.6 

26 

11.2 

1.2 

26.8 

7.9 

12 

0.12 

2.1 

17.6 

5.0 

70 

25.8 

2.2 

2.5 

11.4 

1.1 

25.3 

13.1 

1 

0.10 

1.5 

15.2 

3.0 

8.4 

24,7 

3.2 

3.0 

9.6 

2.0 

29.4 

3 

0.12 

1.4 

16.5 

3.1 

8.4 

25.2 

3.4 

2.8 

9.3 

1.8 

28.1 

3.4 

43              50 

6 

0.10 

1.8 

16.6 

4.5 

7.9 

25,6 

2.3 

2.6 

11.5 

1.1 

26.0 

10.7 

12 

0.12 

2.2 

15.6 

4.9 

6.9 

24,4 

2.1 

2.7 

12.9 

1.2 

27.0 

7.2 

1 

0.10 

1.3 

15.5 

3.1 

8.5 

25.9 

3.6 

3.0 

9.0 

1.8 

28.2 

3.1 

3 

0.12 

1.5 

17.0 

3.4 

8.6 

24.9 

3.2 

2.9 

9.1 

1.8 

27.6 

5.2 

43              90 

6 

0.12 

2.4 

16.7 

4.9 

7.7 

25.3 

2.3 

2.7 

11.3 

1.3 

25.5 

12.4 

12 

0.13 

3.1 

18.8 

5.8 

7.9 

27.9 

2.3 

2.4 

9.7 

0.7 

21.5 

26.1 

'Values  are  averages  from  duplicate  or  triplicate  samples. 
2T — Temperature,  RH — Relative  humidity,  AF — Ambient  freezer  humidity. 
^Based  on  dry  w/eight  of  FPC. 

"Number  of  carbon  atomnumber  of  double  bonds.  The  weight  percentages  were  calculated  on  the  basis  of  the  10  major  acids  (shown) 
constituting  100°'o. 


Literature  Cited 

Green,  J.  H. 

1972.  Storage  stability  of  fish  protein  concentrate  under 
varying  conditions  of  temperature  and  time.  Presented 
at  32d  Annual  Meeting.  Institute  of  Food  Technologists, 
Minneapolis,  May  1972  (Abstr.  211). 

HoRWiTZ,  W.  (editor). 

1970.  Official  methods  of  analysis  of  the  Association  of 
Official  Analytical  Chemists,  11th  ed. 

Knobl,  G.  M.,  Jr.,  B.  R.  Stillings,  W.  E.  Fox,  and  M.  B.  Hale. 

1971.  Fish  protein  concentrates.  Commer.  Fish.  Rev. 
33(7-8):54-63. 

Medwadowski,  B.  F.,  J.  Van  der  Veen,  and  H.  S.  Olcott. 

1967.  Nature  of  the  residual  lipids  in  fish  protein  con- 
centrate (FPC).     J.  Food  Sci.  32:361-365. 

1968.  Nature  of  residual  lipids  in  menhaden  fish  protein 
concentrate.     J.  Am.  Oil  Chem.  Soc.  45:709-710. 

Medwadowski,  B.,  A.  Haley,  J.  Van  der  Veen,  and 
H.  S.  Olcott. 

1971.     Effect  of  storage  on  lipids  of  fish  protein  concen- 
trate.    J.  Am.  Oil  Chem.  Soc.  48:782-783. 
Metcalfe,  L.  D.,  A.  A.  Schmitz,  and  J.  R.  Pelka. 

1966.  Rapid  preparation  of  fatty  acid  esters  from  lipids 
for  gas  chromatographic  analysis.  Anal.  Chem. 
38:514-515. 


Rouser,  G.,  G.  Kritchevsky,  and  A.  Yamamoto. 

1967.  Column  chromatographic  and  associated  procedures 
for  separation  and  determination  of  phosphatides  and 
glycolipids.  In  G.  Marinetti  (editor),  Lipid  chromato- 
graphic analysis.  Vol.  1,  p.  99-162.  Marcel  Dekker, 
Inc.,  N.Y. 

Shono,  T.,  and  M.  Toyomizu. 

1972.  Decrease  rate  of  C  22  e  ^"^  ^^  ^"  index  to  oxida- 
tive deterioration  of  lipids  in  fish  products.  Sci.  Bull. 
Fac.  Agric.  Kyushu  Univ.  26:233-239. 

SiAKOTOs,  A.  N.,  and  G.  Rouser. 

1965.  Analytical  separation  of  nonlipid  water  soluble 
substances  and  gangliosides  from  other  lipids  by  dextran 
gel  column  chromatography.  J.  Am.  Oil  Chem.  Soc. 
42:913-919. 


Vega  J.  Smith 

James  S.  Linn 

Harold  S.  Olcott 

Institute  of  Marine  Resources 
Department  of  Food  Science  and  Technology 
University  of  California  at  Davis 
Davis,  CA  95616 


847 


LENGTH-WEIGHT  RELATIONS  FOR 

FIVE  EASTERN  TROPICAL 

ATLANTIC  SCOMBRIDS 

This  paper  presents  an  analysis  of  fork  lengths 
and  body  weights  of  five  species  of  scombrids 
measured  from  landings  at  several  ports  on  the 
west  coast  of  Africa  during  1967  and  1968: 
yellowfin  tuna,  Thunnus  albacares;  skipjack  tuna, 
Katsuwonus  pelamis;  bigeye  tuna,  T.  obesus; 
little  tunny,  Euthynnus  alletteratus;  and  frigate 
mackerel,  Auxis  sp.  Sampling  of  landings  took 
place  between  26  September  1967  and  22  May 
1968  at  the  ports  of  Dakar,  Senegal;  Freetown, 
Sierra  Leone;  Abidjan,  Ivory  Coast;  Tema,  Ghana; 
and  Benguela,  Angola.  Samples  were  also  taken 
from  fish  stored  at  a  cannery  in  Mocamedes, 
Angola.  Fish  were  captured  by  bait  (pole-and- 
line)  boats,  purse  seiners,  and  combinations  of 
both.  Only  whole  fish  were  used  for  this  study, 
landed  in  fresh,  iced,  frozen,  and  indeterminate 
conditions.  Fork  lengths  were  usually  measured 
to  the  nearest  centimeter.  Weight  was  usually 
measured  to  the  nearest  0.1  kg.  All  nonmetric 
data  were  converted  to  centimeters  and  kilograms. 
The  allometric  length-weight  equation  is  used 
to  describe  the  relation  between  length  and 
weight: 

W  =  aL^e  (1) 

where  W  =  weight  in  kilograms 

L  =  length  in  centimeters 
a  and  6  =  estimated  parameters. 
e  =  error  term 

Results 

Estimates  of  a  and  b  were  made  for  each  sample. 
A  wide  range  in  values  of  a  and  b  occurred  for 
the  same  species  and,  in  some  cases,  for  the  iden- 
tical sample  category  (category  is  defined  as  port, 
gear,  and  method  of  preservation  offish),  that  was 
at  first  alarming.  However,  examination  of  plots  of 
the  estimated  curves  revealed  only  minor  dif- 
ferences among  samples  at  sizes  included  in  the 
samples.  It  was  also  noted  that  estimates  of  a 
are  closely  related  to  estimates  of  b  (Figure  1), 
again  indicating  the  fish  at  the  same  length 
weighed  approximately  the  same. 

Analyses  of  covariance  were  used  to  test  the 
statistical  significance  of  differences  among 
length-weight  relations  within  a  sample  category. 
F-tests  for  the  significance  of  differences  of  the 


.001 


-J 1 I I 1 I I I I I 


2.3       2.4      2.5       2.6      2.7       2.8       2.9       3.0       3.1       3.2       3.3      3.4       3.5       3.6 

b 

Figure  1. — Relation  between  estimates  of  a  and  b  of  the  allo- 
metric length- weight  relation  from  samples  of  Atlantic  yellow- 
fin  tuna. 

estimates  of  both  parameters  a  and  b^  were  made 
instead  of  F-tests  for  each  parameter  as  is  usually 
done,  because  I  believe  that  the  close  relation 
between  estimates  of  a  and  b  demonstrates  that 
no  additional  useful  information  would  be 
obtained  by  making  the  separate  tests.  F-values 
for  differences  among  samples  within  a  category 
were  almost  always  significant  for  all  species  with 
more  than  one  sample.  As  mentioned  previously, 
plots  of  the  fitted  lines  showed  only  minor  dif- 
ferences between  samples  for  sizes  found  in  both 
samples. 

Analyses  of  covariance  were  also  used  to  test 
whether  differences  among  sample  categories 
were  present.  Nested  models  were  used  because 
the  significant  differences  among  lines  within 
sample  categories  indicated  that  samples  rather 
than  individual  fish  should  be  used  to  estimate 
the  error  term  of  the  model.  Only  data  for  yellow- 
fin  and  skipjack  tunas  were  examined  because 
there  were  insufficient  data  for  the  other  species. 
Table  1  presents  the  analysis  of  covariance  of 
differences  among  all  sample  categories  for 
yellowfin  tuna.  The  F-value  for  difference  among 
sample  categories  is  statistically  significant  at  the 


'Hr 


and 


of  a  from  (th  sample,  6j 


bj     =     bj     where    Cj     =     value 
=   value  of  b  from  ;th  sample  and 


848 


Table  1.— Analysis  of  covariance  of  length-weight  relation  of 
yellowfin  tuna. 


Source 


Degrees  of      Sum  of  Mean 

freedom        squares        square        F-value 


Categories 

Samples  witfiin  categories 

Residual 

Total 


24  1.321851  0.0550771      3.4115* 

128  2.066484  0.0161444     6.7748" 

3,485  8.304751  0.0023830 

3.637  11693086 


'Significant  at  ^°c  level. 

Table  2. — Analysis  of  covariance  of  length-weight  relation  of 
skipjack  tuna. 


Source 


Degrees  of      Sum  of  Mean 

freedom        squares        square        F-value 


Categories  20  2.560355     0.128018      5.0189- 

Sample  within  categories  84  2.142605     0.0255072    7.3030* 

Residuals  2,448  8.550099     0.0034927 

Total  2,552         13.253059 

"Significant  at  1%  level. 

1%  level.  The  F-value  for  difference  among 
samples  within  a  category  is  greater  than  that 
among  categories.  Table  2  presents  results  for 
skipjack  tuna.  Again  the  F-value  is  statistically 
significant  at  the  1%  level,  and  the  F-value  among 
samples  within  categories  is  greater  than  that 
among  categories.  The  reasons  for  the  differences 
are  not  known.  Although  there  was  considerable 
overlap  of  sizes  of  fish  encountered  among  the 
samples,  size  composition  of  the  samples  did  differ 
and  may  have  contributed  to  the  differences  in 
the  length-weight  relations  because  Equation  (1) 
may  not  perfectly  describe  the  length-weight 
relation  for  fish  of  all  sizes.  Figure  2  illustrates 
the  variability  found  in  the  length-weight 
relations  of  yellowfin  tuna.  The  variability  among 
the  relations  increases  with  size  as  Equation  (1) 
assumes. 

Statistics  of  length-weight  relations  from 
combined  samples  for  each  species  are  presented 
in  Table  3. 

Discussion 

Length-weight  relations  for  yellowfin  tuna  from 
the  Pacific  (Chatwin,  1959),  from  the  Atlantic 
(Poinsard,  1969),  and  from  the  present  study  are 
illustrated  in  Figure  3.  There  is  reasonably  close 
agreement  among  the  three  curves  at  small  sizes. 
The  Pacific  yellowfin  tuna  appear  to  be  heavier 
at  larger  sizes  than  fish  from  the  Atlantic,  but 
Chatwin  did  not  include  fish  larger  than  115  cm 
in  his  work.  Two  relations  are  used  in  Poinsard's 
work.  A  relation  between  fork  length  and  predor- 


/  /,/ 


90. 6  112.5 

FORK  LENGTH  (cm.) 


Figure  2. 


-Estimated  length-weight  relations  for  all  sample 
categories  of  Atlantic  yellowfin  tuna. 


sal  length  and  one  between  predorsal  length  and 
weight.  Poinsard  tried  several  functions  to  ex- 
plain the  relations.  In  the  case  of  fork  length  and 
predorsal  length  he  chose  the  following  function: 


(2) 


LD^  =  -16.58774  +  4.66294  JL 
where  LD^  =  predorsal  length 


He  based  his  choice  on  the  fact  that  Equation 
(2)  resulted  in  the  highest  value  of  r  (correlation 
coefficient)  of  the  several  functions  he  tried.  The 
value  of  r  when  Equation  (2)  was  used  was 
0.99402,  but  when  a  power  relation  similar  to 
Equation  (1)  was  used  the  value  of  r  (0.99386)  is 
only  slightly  less.  Figure  3  is  based  on  the  square 
root  relation  between  fork  length  and  predorsal 
length  as  recommended  by  Poinsard.  It  is  very 
difficult,  however,  to  interpret  differences  be- 
tween r  values  when  different  dependent  vari- 
ables are  used:  predorsal  length  in  one  case,  log 
(predorsal  length)  in  the  other.  Equation  (2)  seems 
a  poor  choice  because  it  implies  that  LD^  <  0 
when  L  <  12.65.  The  estimated  weights  using 
Poinsard's  logarithmic  relation  are  illustrated  in 
Figure  4 — the  two  curves  are  very  similar  for 
all  lengths.  This  similarity  indicates  that  the 
results  of  Poinsard  and  of  this  study  are  accurate 
estimates  of  the  average  length- weight  relation- 
ship of  eastern  tropical  Atlantic  yellowfin  tuna. 


849 


I20r 


PRESENT  STUDY 
POINSARD  (v^l 
CHATWIN 


100  120  140 

FORK    LENGTH    (cm.) 


160 


Figure  3. — Estimated  length-weight  relations  for  yellowfin 
tuna  (Chatwin,  1959;  Poinsard,  1969).  Poinsard's  relation  based 
on  square  root  relation  between  predorsal  and  fork  length. 
Chatwin's  study  did  not  include  fish  longer  than  115  cm. 

Since  it  is  desirable  to  utilize  the  function  which 
was  estimated  directly  from  either  predorsal  or 
fork  length  data,  the  results  of  Poinsard  should  be 
used  when  predorsal  lengths  are  measured  and 
the  results  of  the  present  study  should  be  used 
when  fork  lengths  are  measured. 

Beardsley^  (pers.  commun.)  allowed  me  to 
examine  length  and  weight  measurements  of 
more  than  2,000  yellowfin  tuna  captured  in  the 
western  Atlantic.  These  data  are  very  similar  to 
the  data  used  in  the  present  study. 

Beardsley  and  Richards  (1970)  estimated  the 
parameters  of  Equation  (1)  for  skipjack  tuna  and 
little  tunny  captured  off  the  coast  of  Florida.  Their 
estimate  of  the  equation  for  skipjack  tuna  is 

W  =  0.00007927L3-22750 
and  for  little  tunny  is 

W    =    0.0000181L3-02838 


no 

1 

100 

- 

1 

90 

- 

80 

- 

1 . 

70 

- 

/ 

S  60 

- 

/ 

I 
o 

^    50 

- 

/ 

40 

- 

/ 

30 

- 

Jf                     o     PRESENT   STUDY 
Jf                        •     POINSARD   (LOG) 

20 

- 

/ 

10 

■^ 

0 

\        II        1 

100  120  140 

FORK    LENGTH    (cm.) 


160 


180 


200 


Figure  4. — Estimated  length-weight  relations  for  yellowfin 
tuna  (Poinsard,  1969).  Poinsard's  relation  based  on  logarithmic 
relation  between  predorsal  and  fork  length. 

These  results  are  quite  similar  to  the  results  of  the 
present  study.  The  range  in  fork  length  of  skip- 
jack tuna  in  their  study  was  38-78  cm  and  for  little 
tunny  34-87  cm.  Since  these  size  ranges  exceed 
the  ranges  encountered  in  this  study  their  results 
should  be  used.  Chatwin  (1959)  obtained  similar 
results  for  skipjack  tuna  from  the  Pacific,  and 
Batts  (1972)  for  skipjack  tuna  from  the  western 
Atlantic. 

The  number  of  frigate  mackerel  used  in  this 
study  is  too  small  to  produce  very  meaningful 
results.  The  results  are  presented  here  only  to 
make  them  available  to  other  workers. 

Several  authors  including  Pienaar  and  Thom- 
son (1969)  have  questioned  the  validity  of  assump- 
tions made  about  the  error  term  in  Equation 
(1).  Also,  the  logarithmic  transformation  results 
in  weight  being  slightly  underestimated  even  if 
Equation  ( 1)  is  correct.  Results  of  simulations  by 
Fox  (1973)^  indicate  that  6  is  unbiased  and  an 
unbiased  estimate  of  a  is  given  by 

a'  =a  exp    (1/2  (s^^,;))  (3) 


^Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Miami,  FL  33149. 


■■'Fox,  W.  W.,  Jr.   1973.  Some  simple  biologically  useful 
functions  and  multiplicative  error  regression  models.  Unpubl. 


manuscr.  Southwest  Fish.  Cent. 
La  Jolla,  CA  92037. 


Natl.  Mar.  Fish.  Serv.,  NOAA, 


850 


Table  3. — Statistics  of  length-weight  relations  for  all  data  used  in  study. 


Number 

Mean 

tvlinimum 

Maximum 

of 

square 

fork  length 

fork  length 

Species 

fish 

a 

'b 

error 

(cm) 

(cm) 

Yellowflntuna 

3,689 

0.000021804 

2.96989 

0.003265 

40 

170- 

Skipjack  tuna 

2.554 

0.00000561 1 

3.31497 

0.005193 

36 

64 

Bigeye  tuna 

190 

0.000012494 

3.12082 

0  003405 

41 

132 

Little  tunny 

753 

0.000012000 

3.08340 

0.006935 

41 

57 

Auxis  sp. 

50 

0.000000280 

4.13514 

0.030871 

30 

45 

'All  estimates  are  significantly  different  than  0  at  the  1%  level. 


where  a'  =  unbiased  estimate  of  a 

(s^w'l)  ^  mean  square  error  about  the  re- 
gression line. 

The  mean  square  errors  for  this  study  are  low 
(Table  3).  Thus  the  bias  should  be  negligible.  The 
results  of  this  study  were  examined  by  comparing 
average  weights  of  yellowfin  used  in  the  study 
against  predicted  weights.  Differences  were 
negligible  as  expected. 

The  significant  differences  found  among 
samples  and  categories  indicate  that  the  variance 
of  estimated  numbers  of  fish  caught,  estimated 
from  length  frequency  samples,  could  be  reduced 
by  a  sophisticated  sampling  scheme  which  is 
stratified  by  category  if  not  sample.  Obviously 
it  would  be  simpler  to  weigh  fish  from  each 
sample  rather  than  measure  lengths,  if  one 
desired  to  stratify  by  sample.  Logistics  rule  out 
this  possibility.  A  formal  cost-benefit  analysis  of 
the  effort  required  to  develop  an  adequate 
sampling  scheme  stratified  by  category  probably 
would  rule  out  this  scheme.  The  significant 
differences  among  samples  do  point  out  the 
desirability  of  obtaining  large  numbers  of  samples 
rather  than  large  sample  sizes  in  further  study 
of  length- weight  relations. 

Acknowledgments 

E.  Scott  of  the  Southeast  Fisheries  Center, 
National  Marine  Fisheries  Service,  NOAA, 
Miami,  Fla.,  measured  fish  under  the  supervision 
of  J.  Wise  of  the  same  laboratory.  I  thank  both  of 
these  individuals  for  their  helpful  suggestions  on 
this  paper.  E.  Holzapfel  and  M.  Kimura  of  the 
Southwest  Fisheries  Center,  National  Marine 
Fisheries  Service,  NOAA,  La  Jolla,  Calif.,  also 
deserve  thanks  for  performing  most  of  the  data 
compilations  and  calculations  used  in  the  study. 
I  also  thank  D.  Kramer  of  the  Southwest  Fisheries 
Center  for  his  technical  editing  of  the  paper. 


Literature  Cited 


Batts,  B.  S. 

1972.     Age  and  growth  of  the  skipjack  tuna,  Katsuwonus 
pelamis  (Linnaeus),  in  North  Carolina  waters.     Chesa- 
peake Sci.  13:237-244. 
Beardsley,  G.  L.,  Jr.,  and  W.  J.  Richards. 

1970.     Size,  seasonal  abundance,  and  length-weight  rela^ 
tion  of  some  scombrid  fishes  from  southeast  Florida. 
U.S.  Fish  Wildl.  Serv.,  Spec.  Sci.  Rep.  Fish.  595,  6  p. 
Chatwin,  B.  M. 

1959.  The  relationships  between  length  and  weight  of 
yellowfin  tuna  (Neothunnus  macropterus)  and  skipjack 
tuna  {Katsuwonus  pelamis)  from  the  Eastern  Tropical 
Pacific  Ocean.  Bull.  Inter-Am.  Trop.  Tuna  Comm.  3:307- 
352. 

PlENAAR,  L.  v.,  AND  J.  A.  THOMSON. 

1969.     AUometric  weight-length   regression  model.     J. 
Fish.  Res.  Board  Can.  26:123-131. 
Poinsard,  F. 

1969.  Relations  entre  longueur  predorsale,  longueur  a 
la  fourche  et  poids  des  albacores  Thunnus  albacares 
(Bonnaterre)  peches  dans  le  sud  du  Golfe  de  Guinee. 
Cah.  ORSTOM.  (Off.  Rech.  Sci.  Tech.  Outre-Mer),  Ser 
Oceanogr.  7(2):89-94. 

WiLUAM  H.  Lenarz 

Southwest  Fisheries  Center 

National  Marine  Fisheries  Service,  NOAA 

La  Jolla,  CA  92037 


ELECTRICAL  THRESHOLD  RESPONSE  OF 
SOME  GULF  OF  MEXICO  FISHES 

Threshold  voltage  is  the  minimum  electrical  po- 
tential to  which  an  animal  responds  (Vibert, 
1967).  Usually  threshold  measurements  are  inex- 
pensive and  easy  to  obtain,  and  they  provide 
guidelines  for  designing  electrical  fishing  sys- 
tems. Bary  (1956)  and  Kessler  (1965)  showed  that 
threshold  voltage  varied  according  to  water  temp- 
erature, size  of  animal,  and  width  of  the  pulse. 
Earlier  workers  clearly  demonstrated  that 
threshold  voltages  are  affected  by  the  position  of 
the  animal  in  the  electrical  field.  Klima  (1968) 
documented  experimentally  the  mathematical  re- 
lationship between  the  ^ngle  of  the  animal  in  the 


851 


electrical  field  and  its  threshold  voltage.  These 
authors  have  defined  the  basic  physical  and 
biological  factors  which  affect  the  response  of 
selected  marine  animals  to  electricity. 

To  understand  more  clearly  the  basic  charac- 
teristics of  electrical  fields  which  control  marine 
fishes,  threshold  response  of  selected  Gulf  of  Mex- 
ico species  was  investigated.  I  determined  the 
minimum  threshold  voltage  (in  a  field  with  other 
specific  characteristics)  for  Atlantic  croaker, 
Micropogon  undulatus;  spot,  Leiostomus 
xanthurus;  \ongsp\ne porgy, Stenotomus  caprinus; 
chub  mackerel,  Scomber  Japonicus;  and  scaled 
sardine,  Harengula  pensacolae.  I  further  attempt- 
ed to  determine  the  minimal  effective  pulse  width 
by  estimating  the  threshold  voltage  at  selected 
pulse  widths. 

Procedure 

Spot,  Atlantic  croaker,  and  longspine  porgy 
were  trawled  in  Mississippi  Sound;  minimizing 
injury  to  fish  was  accomplished  by  towing  for  only 
10  min.  Chub  mackerel  and  scaled  sardines  were 
caught  by  night-lighting  off  the  Mississippi  Coast 
(Wickham,  1970).  The  experimental  animals  were 
held  in  shipboard  tanks  of  circulating  seawater 
while  being  transported  to  the  Laboratory.  Only 
fish  acclimated  for  more  than  3  days  and  in  good 
physical  condition  were  used.  Threshold  voltages 
were  determined  for  140  individuals.  Each  speci- 
men was  subjected  to  only  one  test  and  discarded. 

Studies  were  conducted  in  a  72  x  45  x  45  cm, 
190-liter  plexiglass  aquarium  at  temperatures  be- 
tween 15°  and  17.5°C;  salinities  ranged  from  19.6 
to  26AVco. 

An  electrical  system  providing  a  uniform  elec- 
trical field  was  used.  It  had  a  capacitor-discharge 
stimulation  pulse  that  could  be  monitored  from 
the  center  of  the  aquarium.  Pulse  shapes  which 
exhibit  a  rapid  rise  in  amplitude  and  slow  rate  of 
decay,  such  as  capacitor-discharge  pulses,  are  the 
most  effective  for  controlling  fish  (Taylor,  Cole, 
and  Sigler,  1956;  Vibert,  1967;  Klima,  1972). 

A  pulse  generator  was  used  for  the  stimulation 
pulses.  Pulses  were  applied  to  two  monel  elec- 
trodes mounted  at  opposite  ends  of  the  aquarium. 
Pulse  characteristics  were  measured  with  a  pair  of 
pickup  probes.  These  were  constructed  from  two 
3-mm  diameter  bronze  rods  10  cm  apart  and  insu- 
lated so  that  only  the  bottom  10  mm  of  each  rod 
was  exposed.  Pulse  characteristics  were  displayed 


on  an  oscilloscope  as  a  graph  of  voltage  against 
time. 

Threshold  voltages  were  determined  with  the 
fish  held  immobile  parallel  to  the  electric  field  in  a 
plastic  mesh  tube  in  the  center  of  the  aquarium 
facing  either  the  positive  or  negative  electrode. 
Voltage  was  slowly  increased  until  the  fish  re- 
sponded by  fluttering  of  the  body.  This  value  was 
then  recorded  from  the  oscilloscope  and  assumed 
to  be  the  threshold  voltage. 

Results  and  Discussion 

Kessler  (1965)  found  that  variations  in  pulse 
width  alter  the  threshold  voltage  for  shrimp. 
Pulse  widths  longer  than  150  /js  are  satisfactory 
for  stimulating  shrimp,  whereas  below  that  width 
the  power  required  for  stimulation  would  be 
significantly  greater.  Longspine  porgies  stimu- 
lated with  less  than  100  /us  pulse  widths  required 
at  least  four  times  more  voltage  to  respond  than 
fish  stimulated  with  a  wider  pulse  (Table  1).  At 
narrow  pulse  widths  threshold  voltage  was  high; 
at  the  longer  widths  it  was  low,  forming  an  inverse 
relationship. 

Scaled  sardine  required  higher  voltages  to  elicit 
a  response  at  narrower  pulse  widths  than  at  wider 
pulse  widths.  At  45 /js  it  took  almost  1.9  V/lOcmto 
elicit  a  minimum  response,  but  at  100  yus  it  took 
only  1.3  V/10  cm,  and  at  250  and  1,000  a^s  it  took 
only  1.0  and  0.9  V  across  10  cm.  A  comparison  of 
threshold  voltages  of  scaled  sardines  at  different 
pulse  widths  shows  a  significant  difference  be- 
tween the  threshold  values  at  pulse  widths  tested 
(Table  1).  Student's  ^-test  was  used  in  making 
these  comparisons: 

«=  6.316,  <  0  975, ig)     =2.101)    45  and  100  ^s, 


(t  =  3.815,  t  Q  g^g  ,  jgj     =  2.101)  100  and  250  /js. 


(t  =  5.000,  t  0.975  (18)    =  2.101)  250  and  1,000  ^s. 


Although  there  was  a  difference  in  the 
minimum  voltage  within  the  250  fus  to  1.0  ms 
range,  as  shown  by  the  reactions  of  scaled  sardine, 
the  difference  in  actual  voltage  was  minimal.  For 
scaled  sardine  the  most  efficient  pulse  width  in 
terms  of  electrical  power  would  be  not  less  than 
250  IJ.S.  Generally,  threshold  voltages  at  pulse 


852 


Table  1. — A  summay  of  threshold  voltages. 


Pulse 

Electrode 

Range 

Average 

widtti 

which 

Sample 

fish  length 

Species 

V/10  cm 

Variance 

(ms) 

fish  faces 

size 

(mm) 

Atlantic  croaker 

0.39 

0.006 

2.500 

+ 

10 

130-150 

Atlantic  croaker 

0.30 

0.001 

2.500 

- 

10 

120-150 

Spot 

Chub  mackerel 

038 

0.048 

2.300 

+ 

10 

102-132 

0.31 

0.005 

2.300 

+ 

15 

175-189 

Longspine  porgy 

2.90 

0.004 

0.045 

+ 

10 

90-106 

Longspine  porgy 

1,82 

0,004 

0.100 

+ 

10 

91-106 

Longspine  porgy 

0.35 

0.001 

0.250 

+ 

10 

93-111 

Longspine  porgy 

0.35 

0001 

2.500 

+ 

10 

92-110 

Scaled  sardines 

1  89 

0.331 

0.045 

+ 

10 

85-98 

Scaled  sardines 

1.00 

0.010 

0045 

- 

5 

78-93 

Scaled  sardines 

1.29 

0056 

0.100 

+ 

10 

80-101 

Scaled  sardines 

0.83 

0,003 

0.100 

- 

5 

84-91 

Scaled  sardines 

1.00 

0020 

0.250 

+ 

f      10 

79-94 

Scaled  sardines 

0,80 

0.300 

0.250 

— 

5 

88-98 

Scaled  sardines 

090 

0.020 

1  000 

+ 

10 

80-99 

widths  greater  than  2,000  a'S  were  similar  be- 
tween species. 

Atlantic  croaker  were  used  to  test  the 
hypothesis  that  fish  require  more  voltage  to  show 
a  threshold  reaction  when  facing  the  positive  elec- 
trode. Analysis  of  the  average  threshold  voltages 
of  croakers  facing  the  positive  and  negative  elec- 
trode by  Student's  ^-test  shows  a  significant  differ- 
ence between  the  values 


it  =  3.60  and  t 


0.975  (18) 


2.101). 


Scaled  sardines  showed  a  similar  response  (Table 
1).  These  results  confirm  those  of  Bary  (1956) 
where  he  showed  that  mullet  required  more  vol- 
tage to  respond  when  facing  the  anode  than  the 
cathode. 

The  cost  of  producing  a  useful  electrical  field  in 
seawater  is  dependent  upon  the  power  required  to 
elicit  specific  responses  in  the  desired  species. 
Pulse  width  obviously  is  a  major  factor  which  af- 
fects the  power  requirements  along  with  voltage 
and  pulse  rate  (Klima,  1972).  Narrow  pulse 
widths  require  proportionately  less  power  than 
wider  ones.  Engineering  design  criteria  for  pulse 
generators  are  usually  based  on  the  minimum 
pulse  width  electronically  possible.  These  results, 
however,  indicate  that  pulse  width  should  not  be 
less  than  250  jUS  and  probably  should  range  be- 
tween 250  and  1,000  ms. 


Literature  Cited 

Bary,  B.  M. 

1956.  The  effect  of  electric  fields  on  marine  fishes.    Scotl. 
Home  Dep,  1,  32  p. 

Kessler,  D.  W. 

1965.   Electrical  threshold  responses  of  pink  shrimp 
Penaeus    duorarum,    Burkenroad.    Bull.    Mar.    Sci. 
15:885-895. 
Klima,  E.  F. 

1968.  Shrimp-behavior  studies  underlying  the  develop- 
ment of  the  electric  shrimp-trawl  system.  U.S.  Fish  Wildl. 
Serv.,  Fish.  Ind.  Res.  4:165-181. 
1972.  Voltage  and  pulse  rates  for  inducing  electrotaxis  in 
twelve  coastal  pelagic  and  bottom  fishes.  J.  Fish.  Res. 
Board  Can.  29:1605-1614. 
Taylor,  G.  N.,  L.  S.  Cole,  and  W.  F.  Sigler. 

1957.  Galvanotoxic  response  offish  to  pulsating  direct  cur- 
rent. J.  Wildl.  Manag.  21:201-213 

ViBERT,  R. 

1967.  Part  I  —  General  report  of  the  working  party  on  the 
applications  of  electricity  to  inland  fishery  biology  and 
management. /^  R.  Vibert  (editor).  Fishing  with  electric- 
ity —  Its  applications  to  biology  and  management,  p. 
31-73.  Fishing  News  (Books)  Ltd.,  Lond. 
Wickham,  D.  a. 

1970.  Collecting  coastal  pelagic  fishes  with  artificial  light 
and  a  5-meter  lift  net.  Commer.  Fish.  Rev.  32(  12):52-57. 


Edward  F.  Klima 


Southeast  Fisheries  Center 

National  Marine  Fisheries  Service,  NOAA 

Pascagoula,  MS  39567 

Present  address: 

Office  of  Living  Resources,  NOAA 

6010  Executive  Boulevard 

Rockville,  MD  20852 


853 


OCCURRENCE  OF  A  RATFISH 
IN  THE  COLUMBIA  RIVER  ESTUARY 

A  ratfish,  Hydrolagus  colliei  (Lay  and  Bennett), 
was  captured  in  the  Columbia  River  estuary,  near 
the  Oregon  shore,  on  24  August  1972.  Commercial 
fishermen  Howard  and  Mark  Simonsen  captured 
the  specimen  near  buoy  21,  approximately  8  km 
upstream  from  the  mouth  of  the  river.  They  were 
fishing  for  salmon  in  8  m  of  water  with  a  dacron 
gillnet  of  8  %-inch  mesh  and  an  effective  fishing 
depth  of  between  10  and  12  m.  The  fish  was  caught 
at  2030  h  during  an  incoming  tide;  the  actual 
depth,  temperature,  and  salinity  at  place  of  cap- 
ture are  unknown.  At  the  time  of  capture,  how- 
ever, our  monitoring  station,  3.2  km  farther  up- 
stream, indicated  a  water  temperature  of  13.4''C 
and  a  salinity  of  bYco  at  a  depth  of  10  m.  The 
salinity  was  increasing  and  reached  31 /{o  5  h 
later.  The  ratfish  was  an  adult  male,  445  mm  in 
length,  weighing  460  gm  (Figure  1).  There  are  no 
known  methods  of  determining  the  ages  of 
chimaeroids,  including  the  ratfish  (Simmons  and 
Laurie,  1972).  The  specimen  was  preserved  and  is 
now  part  of  the  collection  at  the  facility  of  the 
Northwest  Fisheries  Center,  National  Marine 
Fisheries  Service,  at  Hammond,  Greg.  Although 
ratfish  are  distributed  along  the  coast  of  western 
North  America  from  southeastern  Alaska  to  Baja 
California,  including  the  upper  Gulf  of  California 


(Hart,  1973),  this  is  the  first  record  of  one  appear- 
ing in  the  Columbia  River  estuary.  In  fact,  no 
chimaeroid  has  been  recorded  from  any  estuarine 
water  (Carl  L.  Hubbs,  Scripps  Institution  of 
Oceanography,  University  of  California  at  San 
Diego,  La  Jolla,  CA  92037,  pers.  commun). 

"Hydrolagus  colliei  is  the  only  species  of  chi- 
maera  reported  from  the  west  coast  of  the  United 
States,  and,  unlike  other  species  in  the  family,  it 
generally  inhabits  relatively  shallow  water." 
(Halstead,  1970).  According  to  Hart  ( 1973),  ratfish 
ai-e  common  visitors  to  shallow  Canadian  waters 
but  are  most  abundant  at  92  to  275  m  in  inside 
waters  and  at  183  to  366  m  in  outside  waters.  He 
also  reports  that  they  are  "in  deeper  water  toward 
the  south  (as  in  northern  California)".  The  occur- 
rence in  the  deeper  water  toward  the  south  is  real 
and  significant,  but  they  may  not  occur  in  deeper 
waters  off  northern  California  because  that  is  an 
area  of  extremely  cold  ocean  temperatures  (Carl 
L.  Hubbs,  pers.  commun.).  Day  and  Pearcy  (1968) 
captured  ratfish  off  the  Oregon  coast  at  depths 
between  40  and  200  m.  Ratfish  are  weak  swim- 
mers, mostly  noctural  in  behavior,  but  have  been 
seen  swimming  at  the  surface  in  southeastern 
Alaska  and  British  Columbia  waters  (Goode  and 
Bean,  1895). 

Maximum  spawning  activity  is  in  late  summer 
and  early  fall  (Sathyaneson,  1966).  On  26  June 
1957,  a  large  concentration  of  ratfish  became 


Figure  1. — Ratfish, /f>'£/ro/agi/s  colliei,  captured  in  the  Columbia  River  estuary. 


854 


trapped  in  the  tide  pools  of  Cape  Arago,  Oreg.  It 
was  suspected  they  were  spawning  near  shore 
(Jopson,  1958). 

Literature  Cited 


Service  on  the  Oregon  side  of  the  Columbia  River 
about  75  km  upstream  from  Astoria.  The  fish, 
shown  in  Figure  1,  was  taken  in  shallow  water 
with  a  100-m  long  beach  seine.  River  temperature 


Day,  D.  S.,  and  W.  G.  Pearcy. 

1968.  Species  associations  of  benthic  fishes  on  the  continen- 
tal shelf  and  slope  off  Oregon.  J.  Fish.  Res.  Board  Can. 
25:2665-2675. 
GooDE,  G.  B.,  AND  T.  H.  Bean. 

1895.  Oceanic  ichthyology.  U.S.  Natl.  Mus.,  Spec.  Bull.  2, 
553  p. 
Halstead,  B.  W. 

1970.  Poisonous  and  venomous  marine  animals  of  the 
world,  Vol.  3-Vertebrates  (continued^.  U.S.  Gov.  Print. 
Off.,  Wash.,  D.  C,  1,006  p. 
Hart,  J.  L. 

1973.  Pacific  fishes  of  Canada.  Fish.  Res.  Board  Can.,  Bull. 
180,  740  p. 
Jopson,  H.  G.  M. 

1958.  A  concentration  of  the  ratfish,  Hydrolagus  colliei 
Cape  Arago,  Oregon.  Copeia  1958:232. 
Sathyanesan,  a.  G. 

1966.  Egg-laying  of  the  chimaeroid  fish.  Hydrolagus  colliei. 
Copeia  1966:132-134. 
Simmons,  J.  E.,  and  J.  S.  Laurie. 

1972.  Study  of  Gyrocotyle  in  the  San  Juan  Archipelago, 
Paget  Sound,  U.S.A.,  with  observations  on  the  host, 
Hydrolagus  colliei  (Lay  and  Bennett).  Int.  J.  Parasitol. 
2:59-77. 


Joseph  T.  Durkin 
David  A.  Misitano 

Northwest  Fisheries  Center 
National  Marine  Fisheries  Service,  NOAA 
2725  Montlake  Boulevard  East 
Seattle,  WA  98112 


Figure  1. — Eastern  banded  killifish,  Fundulus  diaphanus 
diaphanus,  captured  in  the  lower  Columbia  River. 

on  the  date  of  capture  was  19°C.  The  specimen  was 
59  mm  in  standard  length,  and  coloration  was 
similar  to  that  described  by  Trautman  (1957)  for 
the  species,  olivaceous  on  the  dorsal  surface  with  a 
light  yellow  ventral  surface.  This  specimen  also 
possessed  an  iridescent  blue-green  stripe  horizon- 
tally along  each  side,  which  faded  rapidly  after 
capture.  It  is  now  in  the  collection  of  the  National 
Marine  Fisheries  Service  Biological  Field  Station 
at  Hammond,  Oreg.  Additional  specimens  have 
not  been  taken  in  the  area,  and  the  authors  con- 
clude that  the  presence  of  the  fish  was  probably 
due  to  an  unauthorized  release. 

The  authors  wish  to  thank  Carl  E.  Bond,  Oregon 
State  University,  Corvallis,  Oreg.  and  Carl  L. 
Hubbs,  University  of  Cahfornia,  La  Jolla,  Cahf. 
for  verifying  the  identification  of  the  killifish  and 
their  review  of  the  manuscript. 


UNUSUAL  OCCURRENCE  OF 

AN  EASTERN  BANDED  KILLIFISH 

IN  THE  LOWER  COLUMBIA  RIVER 


The  recorded  geographic  range  for  the  eastern 
banded  killifish, Fwncfw/ws  diaphanus  diaphanus, 
is  in  the  waters  of  the  Atlantic  coastal  states  from 
South  Carolina  north  to  Newfoundland.  They 
occur  in  lakes,  quiet  rivers,  and  Atlantic  coast 
estuaries  (Hubbs  and  Lagler,  1958). 

On  19  August  1971,  an  eastern  banded  killifish 
was  collected  by  the  National  Marine  Fisheries 


Literature  Cited 

Hubbs,  C.  L.,  and  K.  F.  Lagler. 

1958.  Fishes  of  the  Great  Lakes  region.  Revised  ed.  Cran- 
brook  Inst.  Sci.,  Bull.  26,  213  p. 
Trautman,  M.  B. 

1957.  The  fishes  of  Ohio.  Waverly  Press,  Inc.,  Baltimore, 
683  p. 

David  A.  Misitano 
Carl  W.  Sims 

Northwest  Fisheries  Center 
National  Marine  Fisheries  Service,  NOAA 
2725  Montlake  Boulevard  East 
Seattle.  WA  98112 


855 


IN  MEMORIAM:  ROBERT  LOUIS  DRYFOOS,  1939-1974 


A  modest  and  understanding  man,  an  unselfish 
and  loving  husband,  an  affectionate  father,  a 
devoted  son  and  grandson,  and  a  dedicated  and 
accomplished  scientist,  this  is  a  rich  life  of 
accomplishment,  Robert  Louis  Dryfoos. 

He  was  always  willing  to  lend  a  hand  to  his 
many  friends  and  colleagues,  always  dependable 
in  responsibilities,  and  solid  in  his  accomplish- 
ments. He  could  achieve,  whether  it  meant 
leading  a  local  centennial  parade  high  up  on  a 
Rotarian  float  as  an  old  New  England  sea  cap- 
tain, or  elucidating  the  complexities  of  the 
migrations  of  a  million  fish  from  Cape  Cod  to  the 
Gulf  of  Mexico.  His  quiet  nature  belied  his 
status  as  a  respected  fisheries  expert  and  research 
administrator.  As  an  authority  on  the  dynamics 
of  fish  populations  he  made  significant  contribu- 
tions to  a  better  understanding  of  the  complex 
fisheries  in  the  northeast  Pacific,  the  Atlantic 


coast,  and  in  his  most  recent  work,  the  fishery 
resources  of  the  entire  United  States. 

He  had  a  natural  curiosity  that  led  him  to  the 
ocean  at  an  early  age.  As  a  young  boy  in  San 
Francisco  he  was  never  far  from  the  sea,  the  fresh 
wet-smell  of  the  surf,  the  screeching  gulls,  and  the 
small  fishing  boats  plying  their  catches  under  the 
Golden  Gate.  His  curiosity  and  his  willingness 
and  ability  to  help  others  was  to  be  satisfied  in 
a  decade  of  productive  fisheries  research.  Not 
esoteric  problem  solving  for  problem  sake,  but 
rather  a  dedication  to  learn  about  the  sea  and 
unravel  its  vagaries  of  protein  production.  He 
collected,  sifted,  and  synthesized  previously  un- 
known bits  of  information,  pieced  them  together 
meticulously,  systematically,  and  with  keen  intel- 
ligence and  patience  he  would  tell  us  more  about 
how  to  develop  and  maintain  our  fragile  fisheries. 
He  teamed  with  other  young  and  dedicated  men, 
in  Seattle,  in  Beaufort,  at  Charleston,  Woods 
Hole,  La  Jolla,  Narragansett,  and  in  Washington. 
He  was  intent  on  learning  how  to  better  define 
and  manage  the  wild  populations  in  their  tempest 
environment.  And  this  was  a  pressing  national 
need,  not  headline  stuff,  but  the  necessary  and 
critical  steps  to  be  taken  for  the  fisheries,  that 
all  too  often  are  abused,  overexploited,  and  in 
some  cases  damaged  beyond  repair.  He  chose  this 
direction.  He  worked.  He  sweated.  He  persevered, 
and  he  accomplished. 

His  earliest  work  was  done  as  a  young  college 
undergraduate  with  the  International  Halibut 
Commission  in  Seattle.  He  spent  months  at  a  time 
in  the  north  Pacific,  rubbing  shoulders  with 
halibut  fishermen  on  the  banks.  They  ran  their 
trawls  from  Seattle  up  to  Sitka  in  the  Aleutians 
and  into  the  Bering  Sea.  Bob's  affinity  to  help 
and  make  a  significant  contribution  was  evident 
in  his  interest  in  going  to  sea  with  all  the 
discomforts  of  tossing  ship,  hip  boots  deep  in 
gurry,  fish  filled  checkers,  and  cold  night  watches. 
He  learned  first  hand  about  fishermen,  their 
problems,  the  declining  stocks,  and  pondered  on 
how  best  to  rebuild  their  catches.  This  early  work 
began  a  decade  of  scientific  output.  While  an 
undergraduate  at  the  University  of  Washington 
in  1960  he  published  his  first  paper  on  new  range 
extensions  of  fish  in  the  north  Pacific.  His  next 
contribution  was  made  during  his  graduate 


856 


studies,  while  working  part-time  and  summers  for 
the  College  of  Fisheries  at  the  University.  He  and 
his  professor  reported  on  their  discovery  of  the 
egg  maturation,  embryo  development,  and  birth 
rates  of  the  ocean  perch  of  the  northeast  Pacific. 

It  was  at  the  University  of  Washington,  as  an 
undergraduate  that  he  caught  the  eye  of  his  senior 
colleagues  as  a  "comer."  They  saw  in  Bob,  that 
all-too-rare  combination  of  an  individual  with  the 
ability  to  detect  a  problem,  the  desire  to  get  the  job 
done,  and  the  mental  prowess  to  have  it  done 
correctly.  He  was  one  of  the  few  selected  as  a 
Bureau  of  Commercial  Fisheries  Fellow,  and 
worked  under  this  fellowship  grant  from  1962  to 
1964,  earning  his  doctorate  in  fisheries  in  1965 
from  the  University  of  Washington.  His  doctoral 
thesis  is  an  important  contribution  on  the  life 
history  and  ecology  of  populations  of  smelt  in 
Lake  Washington.  This  study  of  the  smelt  and 
associated  limnetic  species  in  Lake  Washington 
also  has  provided  a  data  base  for  future  examina- 
tions of  changes  in  the  fauna.  The  study  was 
conducted  at  a  peak  of  eutrophication  in  Lake 
Washington.  Public  concern,  aroused  in  1956, 
culminated  in  the  creation  of  the  Municipality  of 
Metropolitan  Seattle  (Metro)  in  1958  which  was 
charged  to  develop  an  effective  sewage-disposal 
system  for  the  entire  area.  The  Metro  Program, 
at  a  total  cost  of  about  $121  million,  began 
diverting  sewage  from  the  lake  in  1963  and  was 
completed  in  1968.  In  1968  experts  described  Lake 
Washington  as  a  classic  case  history  study  of 
eutrophication  and  recovery.  Changes  in  the 
lake's  fish  populations  since  this  study  of  the  smelt 
have  been  marked  and  are  the  subject  of  more 
recent  studies  at  the  College  of  Fisheries,  Univer- 
sity of  Washington. 

The  young  scientist  then  moved  from  Seattle  to 
Beaufort,  N.  C,  to  take  up  the  challenge  of  Govern- 
ment efforts  to  assist  in  the  revitalization  of  an 
ailing  menhaden  industry.  Under  his  super- 
vision, an  ambitious  and  successful  program  was 
undertaken  to  solve  the  mystery  of  menhaden 
migrations.  His  team  tagged  an  unprecedented 
number  offish,  some  one  million,  from  Long  Island 
to  Florida.  They  proved  conclusively  that  men- 
haden move  north  in  spring  and  summer  and 
south  in  fall.  Vital  information  on  fishing  mor- 
tality and  natural  mortality  was  obtained  for  this 
resource.  His  menhaden  work  for  the  7  yr  from 
1965  to  1971  laid  the  foundation  for  what  is  to 
become  the  model  program  for  State-Federal 
partnership  in  managing  our  domestic  fisheries. 


During  early  1974  in  Washington,  an  historic 
meeting  took  place  where  his  former  colleagues 
presented  the  first  comprehensive  plan  for  man- 
aging this  valuable  but  overexploited  resource, 
worth  some  $50  million  a  year  to  the  economy. 
This  plan  could  not  have  been  prepared  without 
the  inspired  and  dedicated  work  of  Bob  Dryfoos. 

With  his  menhaden  work  completed.  Bob  moved 
on  to  greater  responsibility  at  Narragansett,  R.  I. 
He  was  instrumental  in  developing  the  first  com- 
prehensive national  program  for  assessing  the 
important  living  resources  of  our  coastal  and 
continental  shelf  waters.  The  new  initiative  is 
called  MARMAP  for  the  Marine  Resources  Moni- 
toring, Assessment,  and  Prediction  Program.  In 
his  April  1972  budget  message  to  Congress,  the 
President  cited  this  program  as  one  of  the  more 
significant  contributions  to  our  civilian  oceano- 
graphic  effort.  MARMAP  was  another  "first"  for 
Bob  Dryfoos.  He  helped  shape  the  concept,  and 
mold  the  national  fiber.  Like  other  new  initia- 
tives it  was  subjected  to  criticism  and  doubt.  But 
Bob  believed  in  the  concept,  and  with  his  col- 
leagues he  persevered.  Nationally  coordinated 
assessments  of  fishery  resources  are  now  being 
made  from  the  Gulf  of  Maine  to  the  Caribbean, 
the  Florida  Keys  to  the  Bay  of  Campeche,  from 
Baja  California  to  the  east  Bering  Sea  and  in  the 
oceanic  waters  of  the  tropical  Atlantic  and  Pacific. 
The  results  of  his  MARMAP  efforts  are  just  now 
bearing  fruit,  and  will  continue  to  yield  more 
important  results  in  the  latter  half  of  this  decade, 
in  the  1980's  and  beyond. 

Bob  will  be  missed  by  his  many  friends  and 
colleagues.  His  accomplishments  were  consider- 
able. A  fine  heritage  for  his  dedicated  wife  Carol, 
son  Ricky,  daughter  Janet,  and  his  parents.  He 
always  found  time  in  a  busy  schedule  for  civic 
activities.  Rotary,  the  kids'  skating.  Cub  Scouts, 
swimming,  and  clamming,  and  all  those  wonder- 
ful pursuits  that  bring  enrichment  to  a  family  and 
their  friends,  and  their  community.  He  leaves 
behind  many  wonderful  memories.  We  are  all 
richer  from  our  association  with  him. 

His  outstanding  record  remains  with  us,  and 
from  his  contributions  we  will  move  on,  we  will 
keep  building,  for  a  better  and  rational  and  more 
enlightened  tomorrow. 


Kenneth  Sherman 


Resource  Assessment  Division 
National  Marine  Fisheries  Service,  NOAA 
3300  Whitehaven  Street  Northwest 
Washington,  DC  20235 


857 


ERRATA 

Fishery  Bulletin,  Vol.  72,  No.  1 

Wahle,  Roy  J.,  Robert  R.  Vreeland,  and  Robert  H.  Lander,  "Bioeconomic  contribution  of  Columbia 
River  hatchery  coho  salmon,  1965  and  1966  broods,  to  the  Pacific  salmon  fisheries,"  p.  139-169. 

The  captions  of  the  Appendix  Tables  on  pages  162-165  are  correct,  but  the  tabular  entries  below  were 
transposed: 

1)  Tabular  material  on  page  165  should  have  appeared  on  page  162; 

2)  Tabular  material  on  page  162  should  have  appeared  on  page  163; 

3)  Tabular  material  on  page  163  should  have  appeared  on  page  165. 

Fishery  Bulletin,  Vol.  72,  No.  2 

Aprieto,  Virginia  L.,  "Early  development  of  five  carangid  fishes  of  the  Gulf  of  Mexico  and  the  south 
Atlantic  coast  of  the  United  States,"  p.  415-443. 

1)    Page  419,  left  column,  lines  13  and  14  should  read:  hemal  spine  of  the  first  caudal  vertebra.  In 
adults,  these  spines  are  only  slightly  differentiated  from 


INFORMATION  FOR  CONTRIBUTORS  TO  THE  FISHERY  BULLETIN 

Manuscripts  submitted  to  the  Fishery  Bulletin  will  reach  print  faster  if  they  conform  to 
the  following  instructions.  These  are   not  absolute  requirements,    of  course,  but  desiderata. 


CONTENT  OF  MANUSCRIPT 

The  title  page  should  give  only  the  title  of 
the  paper,  the  author's  name,  his  affiliation,  and 
mailing  address,  including  Zip  code. 

The  abstract  should  not  exceed  one  double- 
spaced  page. 

In  the  text,  Fishei-y  Bulletin  style,  for  the 

most  part,  follows  that  of  the  Style  Manual  for 
Biological  Journals.  Fish  names  follow  the  style 
of  the  American  Fisheries  Society  Special  Pub- 
lication No.  6,  A  List  of  Common  and  Scientific 
Names  of  Fishes  front  the  United  States  and 
Canada,  Third  Edition,  1970.  The  Merriam- 
Wehster  Third  New  Internatio)ial  Dictio)tary  is 
used  as  the  authority  for  correct  spelling  and 
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Text  footnotes  should  be  typed  separately 
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under  the  heading  "Literature  Cited."  Only  the 
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the  literature  cited.  The  accuracy  of  the  lit- 
erature cited  is  the  responsibility  of  the  author. 
Abbreviations  of  names  of  periodicals  and  serials 
should  conform  to  Biological  Abstracts  List  of 
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TITLE  PAGE 

ABSTRACT 

TEXT 

LITERATURE  CITED 

APPENDIX 

TEXT  FOOTNOTES 

TABLES  (Each  table  should  be  numbered  with 
an  arable  numeral  and  heading  provided) 

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with  an  arable  numeral ;  legends  are  desired) 

ADDITIONAL  INFORMATION 

Send  the  ribbon  copy  and  two  duplicated  or 
carbon  copies  of  the  manuscript  to: 

Dr.  Reuben  Lasker,  Scientific  Editor 

Fishery  Bulletin 

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Southwest  Fisheries  Center 

P.O.  Box  271 

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(Contents-continued) 


KLIM  A,  EDWARD  F.  Electrical  threshold  response  of  some  Gulf  of  Mexico  fishes  .  851 
DURKIN,  JOSEPH  T.,  and  DAVID  A.  MISITANO.  Occurrence  of  a  ratfish  in  the 

Columbia  River  estuary   854 

MISITANO,  DAVID  A.,  and  CARL  W.  SIMS.  Unusual  occurrence  of  an  eastern 

banded  killifish  in  the  lower  Columbia  River 855 

SHERMAN,  KENNETH.  In  Memoriam:  Robert  Louis  Dryfoos,  1939-1974 856 


NUAA  hbVb-A  /2-4 


■^^ATF^  O^ 


Fishery  Bulletin 

:^        National  Oceanic  and  Atmospheric,Administration  •  National  Marine  Fisheries  Service 

5  A»V  'i  '^ 


\J  ■ 


Vol.  72,  No.  4  xA/^^J.  n  October  1974 


Woo 


vj>' 


GUSHING,  D.  H.  A  link  between  science  and  management  in  fisheries 859 

MOSER,  H.  GEOFFREY.  Development  and  distribution  of  larvae  and  juveniles  of 

Sebastolobus  (Pisces;  Family  Scorpaenidae) 865  - 

VLYMEN,  WILLIAM  J.  III.  Swimming  energetics  of  the  larval  anchovy,  Engraulis 

mordax   885 

MATHER,  F.  J.  Ill,  B.  J.  ROTHSCHILD,  G.  J.  PAULIK,  and  W.  H.  LENARZ. 
Analysis  of  migrations  and  mortality  of  bluefin  tuna,  Thunnus  thynnus,  tagged  in 
the  northwestern  Atlantic  Ocean   900 

HOBSON,  EDMUND  S.  Feeding  relationships  of  teleostean  fishes  on  coral  reefs  in 

Kona,  Hawaii  915 

CRAWFORD,  L.,  D.  W.  PETERSON,  M.  J.  KRETSCH,  A.  L.  LILYBLADE,  and  H.  S. 
OLCOTT.  The  effects  of  dietary  a -tocopherol  and  tuna,  safflower,  and  linseed  oils 
on  the  flavor  of  turkey 1032 

GOPALAKRISHNAN,  K.  Zoogeography  of  the  genus  Nematoscelis  (Crustacea, 

Euphausiacea) 1039 

TSUCHIYA,  MIZUKI.  Variation  of  the  surface  geostrophic  flow  in  the  eastern  inter- 
tropical Pacific  Ocean 1075 

BEITINGER,  THOMAS  L.  Thermoregulatory  behavior  and  diel  activity  patterns  of 
bluegill,  Lepomis  macrochirus ,  following  thermal  shock  1087 

QUAST,  JAY  C.  Density  distribution  of  juvenile  Arctic  cod,  Boreogadus  saida,  in  the 
eastern  Chukchi  Sea  in  the  fall  of  1970 •  1094 

HOUDE,  EDWARD  D.,  WILLIAM  J.  RICHARDS,  and  VISHNU  P.  SAKSENA. 

Description  of  eggs  and  larvae  of  scaled  sardine,  Harengula  jaguana  1106 

RICHARDS,  WILLIAM  J.,  ROBERT  VICTOR  MILLER,  and  EDWARD  D.  HOUDE. 

Egg  and  larval  development  of  the  Atlantic  thread  herring,  Opisthonema  oglinum  .  1 123 

LEIGHTON,  DAVID  L.  The  influence  of  temperature  on  larval  and  juvenile  growth  in 

three  species  of  southern  California  abalones 1137 

KREKORIAN,  C.  O'NEIL,  DAVID  C.  SOMMERVILLE,  and  RICHARD  F.  FORD. 
Laboratory  study  of  behavioral  interactions  between  the  American  lobster, 
Homarus  americanus,  and  the  California  spiny  lobster,  Panulirus  interruptus, 
with  comparative  observations  on  the  rock  crab,  Cancer  antennarius  1146 


I 


(Continued  on  back  cover) 
Seattle,  Washington 


U.S.  DEPARTMENTOFCOMMERCE 

Frederick   B.    Dent,   Secretary 

NATIONALOCEANIC  AND  ATMOSPHERIC  ADMINISTRATION 

Robert  M.  White,  Administrator 


NATIONALMARINE  FISHERIES  SERVICE 
Robert  W.  Schoning,  Director 


Fishery  Bulletin 


I 


The  Fishery  Biillciln  carries  Driginal  research  reports  and  technical  notes  on  investigations  in  fishery  science, 
engineering,  and  economics.  The  Bulletin  of  the  United  States  Fish  Commission  was  begun  in  1881;  it  became  the 
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Beginning  with  volume  70,  number  1.  January  1972.  the  Fishery  Bullciin  became  a  periodical,  issued  quarterly.  In  this 
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I 


EDITOR 

Dr.  Reuben  Lasker 

Scientific  Editor,  Fishery  Bulletin 

National  Marine  Fisheries  Service 

Southwest  Fisheries  Center 
La  Jolla,  California  92037 


Editorial  Committee 

Dr.  Elbert  H.  Ahlstrom 

National  Marine  Fisheries  Service 

Dr.  William  H.  Bayliff 

Inter-American  Tropical  Tuna  Commission 

Dr.  Daniel  M.  Cohen 

National  Marine  Fisheries  Service 

Dr.  Howard  M.  Feder 
University  of  Alaska 

Mr.  John  E.  Fitch 

California  Department  of  Fish  and  Game 

Dr.  Marvin  D.  Grosslein 
National  Marine  Fisheries  Service 


Dr.  J.  Frank  Hebard 

National  Marine  Fisheries  Service 

Dr.  John  R.  Hunter 

National  Marine  Fisheries  Service 

Dr.  Arthur  S.  Merrill 

National  Marine  Fisheries  Service 

Dr.  Virgil  J.  Norton 
University  of  Rhode  Island 

Mr.  Alonzo  T.  Pruter 

National  Marine  Fisheries  Service 

Dr.  Theodore  R.  Rice 

National  Marine  Fisheries  Service 

Dr.  Brian  J.  Rothschild 

National  Marine  Fisheries  Service 

Mr.  Maurice  E.  Stansby 
National  Marine  Fisheries  Service 

Dr.  Maynard  A.  Steinberg 
National  Marine  Fisheries  Service 

Dr.  Roland  L.  Wigley 

National  Marine  Fisheries  Service 


Kiyoshi  G.  Fukano,  Managing-  Editor 


The  Secretary  of  Commerce  has  determined  that  the  publication  of  this  periodical  is  necessary  in  the  transaction  of 
the  public  business  required  by  law  of  this  Department.  Use  of  funds  for  printing  of  this  periodical  has  been  approved 
by  the  Director  of  the  Office  of  Management  and  Budget  through  May  31,  1977. 


Fishery  Bulletin 


CONTENTS 
Vol.  72,  No.  4  October  1974 

GUSHING,  D.  H.  A  link  between  science  and  management  in  fisheries 859 

MOSER,  H.  GEOFFREY.  Development  and  distribution  of  larvae  and  juveniles  of 
Sebastolobus  (Pisces;  Family  Scorpaenidae) 865 

VLYMEN,  WILLIAM  J.  III.  Swimming  energetics  of  the  larval  anchovy,  Engraulis 

mordax   885 

MATHER,  F.  J.  Ill,  B.  J.  ROTHSCHILD,  G.  J.  PAULIK,  and  W.  H.  LENARZ. 
Analysis  of  migrations  and  mortality  of  bluefin  tuna,  Thunnus  thynnus,  tagged  in 
the  northwestern  Atlantic  Ocean   900 

HOBSON,  EDMUND  S.  Feeding  relationships  of  teleostean  fishes  on  coral  reefs  in 

Kona,  Hawaii  915 

CRAWFORD,  L.,  D.  W.  PETERSON,  M.  J.  KRETSCH,  A.  L.  LILYBLADE,  and  H.  S. 
OLCOTT.  The  effects  of  dietary  a -tocopherol  and  tuna,  safflower,  and  linseed  oils 
on  the  flavor  of  turkey 1032 

GOPALAKRISHNAN,  K.  Zoogeography  of  the  genus  Nematoscelis  (Crustacea, 
Euphausiacea) 1039 

TSUCHIYA,  MIZUKI.  Variation  of  the  surface  geostrophic  flow  in  the  eastern  inter- 
tropical Pacific  Ocean 1075 

BEITINGER,  THOMAS  L.  Thermoregulatory  behavior  and  diel  activity  patterns  of 
bluegill,  Lepomis  macrochirus ,  following  thermal  shock  1087 

QUAST,  JAY  C.  Density  distribution  of  juvenile  Arctic  cod,  Boreogadus  saida,  in  the 

eastern  Chukchi  Sea  in  the  fall  of  1970   1094 

HOUDE,  EDWARD  D.,  WILLIAM  J.  RICHARDS,  and  VISHNU  P.  SAKSENA. 

Description  of  eggs  and  larvae  of  scaled  sardine,  Harengula  jaguana  1106 

RICHARDS,  WILLIAM  J.,  ROBERT  VICTOR  MILLER,  and  EDWARD  D.  HOUDE. 

Egg  and  larval  development  of  the  Atlantic  thread  herring,  Opisthonema  oglinum  .  1123 

LEIGHTON,  DAVID  L.  The  influence  of  temperature  on  larval  and  juvenile  growi;h  in 

three  species  of  southern  California  abalones 1137 

KREKORIAN,  C.  O'NEIL,  DAVID  C.  SOMMERVILLE,  and  RICHARD  F.  FORD. 
Laboratory  study  of  behavioral  interactions  between  the  American  lobster, 
Homarus  americanus,  and  the  California  spiny  lobster,  Panulirus  interruptus, 
with  comparative  observations  on  the  rock  crab,  Cancer  antennarius  1146 

(Continued  on  next  page) 


Seattle,  Washington 


For  sale  by  the  Superintendent  of  Documents,  U.S.  Government  Printing 
Office,  Washington,  DC.  20402  —  Subscription  price:  $10.85  per  year  ($2.75 
additional  for  foreign  mailing).  Cost  per  single  issue  -  $2.75. 


{Contents — continued) 


KENNEDY,  V.  S.,  W.  H.  ROOSENBURG,  M.  CASTAGNA,  and  J.  A.  MIHURSKY. 
Mercenaria  mercenaria  (MoUusca:  Bivalvia):  Temperature-time  relationships  for 
survival  of  embryos  and  larvae 1160 


INDEX,  VOLUME  72   1167 


The  National  Marine  Fisheries  Service  (NMFS)  does  not  approve,  rec- 
ommend or  endorse  any  proprietary  product  or  proprietary  material 
mentioned  in  this  publication.  No  reference  shall  be  made  to  NMFS,  or  to 
this  publication  furnished  by  NMFS,  in  any  advertising  or  sales  promo- 
tion which  would  indicate  or  imply  that  NMFS  approves,  recommends  or 
endorses  any  proprietary  product  or  proprietary  material  mentioned 
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rectly the  advertised  product  to  be  used  or  purchased  because  of  this 
NMFS  publication. 


A  LINK  BETWEEN  SCIENCE  AND  MANAGEMENT 

IN  FISHERIES 

D.  H.  CUSHINGI 


ABSTRACT 

In  this  paper  a  link  is  traced  between  science  and  management  in  that  good  conservation  results  from 
good  science  and  that  failure  in  management  may  be  the  result  of  scientific  failure;  but  management 
failure  is  of  course  not  the  exclusive  province  of  scientists.  The  argument  is  developed  from  a  historical 
study  of  practice  by  fisheries  scientists  in  the  International  Commissions. 


The  central  problem  of  fisheries  biology  is  to  esti- 
mate the  catch  that  can  be  safely  taken  from  a 
stock.  In  Europe  the  problem  was  formulated  by 
Petersen  (1894)  and  Garstang  (1900),  who 
realized  that  if  catches  were  too  great  they  might 
subsequently  decrease  because  the  stock  had  been 
reduced  too  much.  In  the  first  decade  of  the  present 
century  exploratory  voyages  were  made  in  the 
North  Sea  under  the  auspices  of  the  International 
Council  for  the  Exploration  of  the  Sea  (ICES).  The 
high  variability  of  the  catches  "precluded  the  pos- 
sibility of  any  reliable  combination  of  the  trawling 
records"  (Garstang,  1904).  At  the  same  time, 
Petersen  said  that  overfishing  was  not  the  essen- 
tial question  and  that  the  ICES  should  study  the 
transplantation  of  small  plaice  as  a  method  of 
conserving  the  weight  of  catch.  Small  plaice  were 
caught  in  large  numbers  close  to  the  continental 
coasts  and,  in  summertime,  the  discards  exceeded 
the  retained  catch  by  a  factor  of  six.  Petersen, . 
Garstang,  and  Kyle  (1907)  subsequently  wrote 
that  "the  plaice  can  be  returned  alive  to  the  sea, 
where  they  .  .  .  grow  so  much  in  size  and  value  that 
the  same  fishermen  who  caught  them  in  the  first 
instance  have  a  good  chance  of  recapturing  them 
when  they  have  a  greatly  increased  value."  Dur- 
ing their  adult  lives  some  demersal  fish,  such  as 
plaice,  grow  by  an  order  of  magnitude  or  so,  and  if 
fished  heavily  the  mean  weight  of  the  stock  is 
reduced  because  the  little  fish  do  not  have  the 
chance  to  grow.  The  problem  of  growth  overfishing 
as  stated  by  Petersen  is  to  conserve  this  loss  of 
catch  in  weight. 

The  scientific  judgment  that  catches  were  too 
variable  led  to  a  second  judgment  that  manage- 
ment was  impossible.  The  name  of  the 
"overfishing"  committee  in  ICES  was  changed  to 


'Ministry  of  Agriculture,  Fisheries  and  Food,  Fisheries 
Laboratory,  Lowestoft,  Suffolk,  UK. 


Manuscript  accepted  February  1974. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 


that  "investigating  the  biology  of  the  Pleuronec- 
tidae  and  other  trawl-caught  fish."  The  solution 
recommended  for  the  small  plaice  problem  was  to 
transplant  them  from  the  continental  coasts  to 
feeding  grounds  on  or  around  the  Dogger  Bank. 
The  ICES  did  not  discuss  the  problem  of 
overfishing  again  until  after  the  first  world  war. 
Management  depends  on  the  quality  of 
scientific  advice.  Good  science  should  lead  to  good 
management  and  failure  in  management  is  often 
due  to  scientific  failure,  although  failure  in  man- 
agement might  be  due  to  other  causes.  It  has  not 
been  established  yet  whether  the  plaice  stocks  in 
the  southern  North  Sea  needed  international 
management  before  the  first  world  war,  but  the 
lack  of  management  was  not  based  on  such  a 
judgment;  it  was  because  the  scientists  could  not 
assess  the  variability  of  catches,  which  was  not 
surprising  at  that  time  because  statistical  tech- 
niques were  not  very  well  developed.  This  paper 
traces  similar  links  between  science  and  man- 
agement in  the  subsequent  history  of  fisheries  sci- 
ence; the  historical  information  is  taken  from  a 
study  of  the  development  of  the  fisheries  commis- 
sions in  Gushing  (1972). 

THE  DESCRIPTIVE  MODEL 

During  the  thirties,  changes  in  populations 
were  accounted  for  in  the  theory  of  balance;  for 
example,  a  decrement  in  stock  is  compensated  by 
an  increment  in  recruitment  per  unit  stock,  and  as 
fishing  mortality  increases  a  relative  increase  in 
recruitment  is  to  be  expected.  Thompson  and  Bell 
(1934)  and  Graham  (1935)  stated  explicitly  that 
recruitment  would  not  be  reduced  in  magnitude 
by  fishing  at  the  stock  levels  normally  exploited; 
they  both  worked  on  flatfish  and  their  conclusion 
was  well  fitted  to  flatfish  biology,  if  not  to  clupeids 


859 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


or  gadoids.  Both  plaice  and  halibut  grow  by  more 
than  an  order  of  magnitude  during  their  adult 
lives.  Gushing  (1972)  distinguished  growth 
overfishing  from  recruitment  overfishing.  In  the 
first  the  stock  loses  weight  by  too  much  fishing,  as 
Petersen  suggested,  but  recruitment  is  not  af- 
fected. In  the  second,  recruitment  is  affected;  it  is 
noticeable  in  the  pelagic  stocks  at  a  lower  rate  of 
exploitation  than  in  the  demersal  stocks  because 
the  pelagic  fishes  have  less  capacity  for  stabiliza- 
tion, being  less  fecund. 

Populations  were  well  described  by  the  logistic 
curve,  which  expressed  the  theory  of  balance  in 
stating  that  any  change  in  the  carrying  capacity  of 
the  environment  was  compensated  by  a  change  in 
the  net  rate  of  increase  of  the  stock.  From  the 
changes  in  biomass  in  time,  average  estimates  of 
the  two  parameters  (net  rate  of  increase  and  carry- 
ing capacity)  can  be  obtained.  Such  models  are 
called  descriptive  because  the  parameters  are  not 
estimated  independently  but  are  derived  from  the 
changes  in  biomass.  In  fish  populations  the  con- 
tributions of  growth  and  recruitment  are  com- 
pounded in  the  application  of  the  logistic  curve, 
whereas  it  would  be  desirable  to  distinguish  them. 
Both  Thompson  and  Bell  (1934)  and  Graham 
(1935)  concluded  from  the  application  of  the  logis- 
tic curve  that  age  determination  was  no  longer 
necessary.  Had  this  conclusion  been  applied  quite 
firmly  the  distinction  between  the  effects  of 
growth  and  recruitment  in  fish  populations  would 
have  become  impossible. 

Graham's  (1935)  major  explicit  achievement 
was  the  application  of  the  logistic  curve  to  fish 
populations.  Another  achievement,  an  implicit 
one,  was  to  encourage  the  application  of  the 
methods  of  operational  research  arising  from  the 
second  world  war  to  fish  population  dynamics  by 
Beverton  and  Holt  (1957),  which  led  to  the  solu- 
tion of  the  problem  of  growth  overfishing.  The 
logistic  curve  was  developed  more  fully  by 
Schaefer  (1954,  1957).  He  derived  a  catchability 
coefficient  from  the  relation  of  stock  density  to 
fishing  effort  and  used  it  to  obtain  catch,  which  he 
then  related  to  effort  in  the  form  of  a  parabola. 
Over  a  long  time  period,  enough  annual  observa- 
tions give  an  estimate  of  maximum  sustainable 
yield.  The  advantage  of  this  method  is  that  the 
result  can  be  expressed  simply  and  convincingly. 
The  disadvantages  are  1)  that  at  least  a  patient 
decade  of  data  collection  is  needed  to  establish  the 
position  of  the  maximum,  given  a  sufficient  spread 
of  fishing  effort  and  2)  that  upward  or  downward 


trends  in  recruitment  would  be  distinguished  with 
difficulty. 

THE  ANALYTIC  MODEL 

The  first  analytic  model  was  Russell's  (1931)  in 
which  the  changes  in  stock  were  separated  into 
components  of  growth,  recruitment,  and  mortal- 
ity. Beverton  and  Holt  (1957)  devised  a  series  of 
models,  including  the  well-known  yield  per  re- 
cruit one  and  the  less  well-known  self-regener- 
ating yield  curve,  in  which  they  incorporated  their 
stock  and  recruitment  relationships.  The  catch, 
or  yield,  was  expressed  as  a  function  of  fishing 
mortality  and  of  the  age  at  first  capture.  The  most 
important  point  about  the  yield  per  recruit  model 
is  that  the  maximum  yield  is  obtained  from  infor- 
mation on  growth  and  fishing  mortality,  inde- 
pendently of  the  catches.  There  is  no  need  to  wait 
for  a  long  time  to  establish  the  curve,  and  manage- 
ment decisions  can  be  taken  quickly,  other  con- 
siderations being  equal. 

The  yield  per  recruit  model  was  the  theoretical 
solution  to  the  problem  of  growth  overfishing,  and 
the  practical  solution  was  to  increase  the  age  at 
first  capture  with  increased  mesh  size  in  the 
trawls.  For  management  it  is  a  clear  solution  and 
it  is  likely  that  the  present  agreement  on  man- 
agement in  the  North  Atlantic  originated  in  its 
simplicity.  There  were  lengthy  discussions  on  the 
science  and  on  the  technology,  but  there  are  now 
agreed  minimum  landed  sizes  and  minimum  mesh 
sizes  for  a  number  of  species  throughout  the  North 
Atlantic.  It  must  be  said,  however,  that  conserva- 
tion by  mesh  regulation  is  least  conservation  be- 
cause it  is  adapted  to  the  smaller  and  numerous 
species  like  the  haddock  in  the  North  Sea;  larger 
species  (for  example,  cod  or  turbot)  are  not  neces- 
sarily conserved  there  as  well  as  they  might  be. 

In  the  yield  per  recruit  model  it  is  assumed  that 
recruitment  does  not  decline  under  the  pressure  of 
fishing.  The  argument  presented  by  Beverton  and 
Holt  was  that  recruitment  is  so  variable  that  the 
downward  trend  at  low  stock  would  be  very 
difficult  to  detect.  In  management  there  was  an 
unforeseen  consequence:  that  fishing  could  con- 
tinue until  recruitment  was  seen  to  fail.  Then, 
because  of  the  same  high  variability  of  recruit- 
ment, fishing  would  continue  until  it  was  too  late. 
However,  with  care,  the  yield  per  recruit  model 
can  be  used  when  the  stock  and  recruitment  rela- 
tionship is  unknown;  for  example,  if  fishing  is 
reduced,  the  yield  per  recruit  will  not  decline  and 


860 


GUSHING:  LINK  BETWEEN  SCIENCE  AND  MANAGEMENT 


may  even  rise  if  recruitment  rises  with  reduced 
fishing. 

It  is  Hkely  that  if  fishing  mortality  is  restrained 
to  the  maximum  of  the  yield  per  recruit  curves  of 
most  demersal  fishes,  recruitment  would  not  be 
very  much  impaired.  However,  the  curve  for  the 
herring  is  asymptotic  and  it  was  tacitly  believed 
that  the  herring  could  be  fished  very  hard  merely 
because  of  the  shape  of  the  yield  per  recruit  curve. 
Another  consequence  was  that  the  maximum  for 
the  cod  in  the  Barents  Sea  was  overshot  because  in 
international  terms  a  high  catch  was  needed  at 
the  cost  of  a  decreased  catch  per  effort.  The  re- 
cruitment to  the  Barents  Sea  stock  was  severely 
reduced. 

The  collapse  of  herring  fisheries  throughout  the 
northeast  Atlantic  and  the  failure  of  recruitment 
to  the  Arcto-Norwegian  cod  stock  have  been  attri- 
buted to  failure  in  the  Commissions.  These  Com- 
missions, however,  are  only  as  good  as  their 
scientific  advice,  and  the  two  great  failures  are 
attributable  to  the  unstated  concept  that  fishing 
could  continue  until  recruitment  was  seen  to  fail. 
Then  failure  had  to  be  attributed  either  to  natural 
causes  or  to  fishing,  and  stocks  collapsed  while  the 
scientists  disputed  the  two  possibilities.  If  re- 
cruitment overfishing  had  been  recognized  as  a 
problem,  perhaps  collapse  might  have  been 
avoided.  The  solution  to  the  problem  of  growth 
overfishing  inadvertently  generated  the  problem 
of  recruitment  overfishing. 

STOCK  AND  RECRUITMENT 

The  dependence  of  recruitment  on  parent  stock 
was  formulated  by  Ricker  (1954,  1958),  but  the 
variability  of  recruitment  is  very  high  and  the 
curve  can  only  be  fitted  when  decades  of  annual 
data  have  been  collected.  Any  decision  on  how 
much  fishing  should  be  allowed  is  perhaps  delayed 
for  statistical  reasons  and  management  cannot 
proceed.  On  the  other  hand,  if  recruitment  were 
considered  to  be  independent  of  parent  stock, 
management  could  start  to  take  decisions  more 
quickly.  With  hindsight,  the  assumption  made  by 
Thompson  and  Bell  ( 1934)  and  Graham  ( 1935)  can 
be  justified  because  their  work  formed  the 
scientific  basis  of  all  international  conservation  in 
the  North  Atlantic  and  North  Pacific.  However, 
the  danger  of  such  a  procedure  is  that  any  decline 
in  recruitment  tends  to  be  attributed  to  natural 
causes  rather  than  to  fishing,  and  this  step  has 
sometimes  been  taken  without  evidence. 


It  is  in  the  nature  of  the  stock  and  recruitment 
problem  that  there  should  be  confusion  about  at- 
tributing decline  in  recruitment  to  natural  or  to 
man-made  causes.  However,  Gushing  and  Harris 
( 1973)  have  devised  a  method  of  fitting  the  Ricker 
curve  which  sets  confidence  limits  to  the  position 
of  the  curve  itself;  the  standard  deviation  of  re- 
siduals sets  limits  to  the  variation  of  recruitment. 
Then  if  stock  is  near  that  value  which  generates 
maximum  recruitment  per  unit  stocK,  any  re- 
cruitment that  falls  below  the  standard  deviation 
of  the  residuals  has  failed  through  natural  causes. 
If  stock  is  low,  such  a  distinction  cannot  be  made 
(because  any  recruitment  below  the  standard 
deviation  of  the  residuals  is  zero)  and  failure  is 
attributed  to  natural  or  to  man-made  causes  with- 
out evidence  either  way;  however,  a  prudent 
manager  might  prefer  to  assume  that  recruitment 
declined  under  the  pressure  of  fishing  and  to  take 
appropriate  action  in  the  hope  that  the  stock 
would  recover,  as  recently  happened  with  the 
British  Columbia  herring  stock. 

The  stocks  that  have  failed  because  of  this  di- 
lemma are  the  California  sardine,  the  Japanese 
sardine,  and  the  northeast  Atlantic  herring;  the 
Arcto-Norwegian  cod  stock  might  fail  for  the  same 
reason.  The  failures  of  the  first  three  were  attrib- 
uted to  environmental  factors  on  evidence  that  is 
only  circumstantial;  more  recent  evidence  sug- 
gests that  failure  might  have  been  due  to  fishing. 
To  pursue  the  argument  further  is  sterile.  The 
scientific  failure  was  the  inability  to  make  clear 
the  distinction  between  natural  and  man-made 
causes.  The  failure  in  management  was  to  delay 
action  until  the  distinction  could  be  made, 
whereas  a  prudent  manager  should  have  feared 
the  effect  of  fishing  upon  recruitment. 

In  the  stock  and  recruitment  problem,  long  data 
series  are  needed  before  any  management  deci- 
sion can  be  taken.  When  the  development  of  a 
fishery  proceeded  slowly,  this  may  not  have  mat- 
tered because  the  maximum  yield  was  attained  by 
gentle  increments.  Today,  however,  stocks  are  ex- 
ploited rapidly,  and  there  is  the  possibility  that 
recruitment  will  be  diminished  before  the  data  are 
available  to  describe  the  maximum  sustained 
yield.  What  is  needed  is  an  analytic  model  of  the 
stock  and  recruitment  relationship  on  the  lines  of 
that  of  the  yield  per  recruit  one,  on  the  basis  of 
which  decisions  on  management  can  be  made 
quickly  without  the  laborious  acquisition  of  long 
series  of  data. 


861 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


There  are  two  large  fisheries  in  the  Pacific,  on 
the  Peruvian  anchoveta  and  on  the  Alaska  pol- 
lack. Recently  the  anchoveta  recruitment  failed, 
possibly  due  to  fishing  and  possibly  due  to  El  Nino 
and  perhaps  due  to  both;  because  there  is  only 
about  one  decade  of  observations,  the  cause  of  fail- 
ure will  probably  remain  unknown,  although  it 
must  always  be  admitted  that  the  fishing  mortal- 
ity is  high.  In  the  Bering  Sea  there  is  a  rising 
fishery  on  the  Alaska  pollack  that  also  had  been  in 
existence  for  less  than  a  decade.  The  potential 
managers  of  this  fishery  might  like  to  have  avail- 
able now  a  yield  curve  before  the  data  are  avail- 
able to  describe  the  stock  and  recruitment  curve. 
The  source  of  scientific  failure  here  is  the  inability 
to  generate  an  analytic  stock  and  recruitment 
model. 

SCIENCE  AND  MANAGEMENT 
IN  THE  COMMISSIONS 

When  a  fish  stock  fails  the  question  arises 
whether  the  failure  should  be  attributed  to  the 
Commission  charged  with  its  management  or  to 
the  scientists.  There  is  a  distinction  between  the 
North  Atlantic  Commissions  and  those  in  the 
North  Pacific.  In  the  North  Atlantic  the  two  insti- 
tutions (International  Commission  for  the  North- 
west Atlantic  Fisheries  and  Northeast  Atlantic 
Fisheries  Commission)  are  responsible  for  all 
stocks  exploited  in  the  area,  whereas  in  the  east- 
ern North  Pacific  only  those  of  interest  to  North 
American  fishermen  are  conserved.  Consequently 
the  Commissions  in  the  North  Atlantic  cannot 
disclaim  responsibility  for  any  failures  that  occur 
in  their  area,  whereas  the  North  Pacific  Commis- 
sions may  be  able  to  do  so. 

In  the  North  Atlantic,  decline  of  the  main  de- 
mersal stocks  has  with  one  exception  been  pre- 
vented. The  best  conservation  has  not  yet  been 
achieved,  but  with  the  use  of  catch  quotas  and 
international  enforcement  there  is  considerable 
hope  that  conservation  will  ultimately  be  very 
effective.  The  scientific  basis  for  this  was  the  ini- 
tial use  of  the  yield  per  recruit  model  and  in  recent 
years  the  successful  application  of  first,  cohort 
analysis  (Gulland,  1967),  and  secondly,  the 
Clayden  model  (Clayden,  1972).  On  the  other 
hand,  the  collapse  of  herring  stocks  in  the  north- 
east Atlantic  was  due  entirely  to  the  scientific 
failure  to  understand  the  nature  of  the  stock  and 
recruitment  problem.  Both  success  and  failure  in 
the  Commissions  can  be  linked  to  success  or  fail- 
ure in  the  science. 


In  the  North  Pacific  there  are  large  areas  of 
unregulated  fishery,  which  the  North  Pacific 
Commission  has  not  taken  under  its  aegis.  The 
cause  of  the  increase  in  the  maximum  sustainable 
yield  of  the  yellowfin  tuna  in  the  area  of  the 
Inter-American  Tropical  Tuna  Commission  is  un- 
known, although  a  number  of  possible  reasons 
have  been  cited.  Halibut  are  caught  by  trawl  by 
nations  outside  the  control  of  the  International 
Pacific  Halibut  Commission.  The  question  of  the 
offshore  exploitation  of  the  Pacific  salmon  stocks 
remains  unresolved  because  the  boundary  be- 
tween the  North  American  and  Asian  stocks  is  not 
precise  and  the  degree  of  mixture  in  the  exploited 
area  has  not  been  established. 

It  remains  true,  of  course,  that  the  stock  density 
of  the  halibut  recovered  from  1930  to  1960  by  the 
action  of  the  Halibut  Commission,  that  the 
offshore  exploitation  of  the  North  American  salm- 
on was  prevented  by  the  abstention  principle, 
and  that  the  yellowfin  tuna  stock  is  well  exploited. 
Some  of  the  failures  in  the  North  Pacific,  like  those 
in  the  North  Atlantic,  are  rooted  in  scientific 
deficiencies  (apart  from  the  North  Pacific  failure 
to  consider  stocks  that  are  outside  the  aegis  of  the 
Commissions). 

The  International  Whaling  Commission  failed 
to  conserve  the  stock  of  blue  whales.  The  problem 
was  solved  in  principle  for  the  fin  whale  by  Ruud 
(International  Whaling  Commission,  1956)  but 
the  solution  was  rejected  by  Schlijper  (Interna- 
tional Whaling  Commission,  1957)  who  said  that 
the  age  determination  was  faulty.  The  Committee 
of  Four  evaded  this  by  expressing  the  results  in 
the  form  of  a  Schaefer  curve  (International  Whal- 
ing Commission,  1964);  Schlijper  never  saw  that 
age  determination  was  used  in  the  estimation  of 
(recruitment  less  mortality)  which  played  a  con- 
siderable part  in  the  solution.  Part  of  the  failure  to 
conserve  the  stock  was  the  delay  in  reaching  an 
agreed  scientific  solution. 

In  contrast  to  the  Whaling  Commission,  the 
North  Pacific  Fur  Seal  Commission  has  been  well 
served  by  its  scientists.  A  form  of  stock  and  re- 
cruitment relation  has  been  established  and  the 
surplus  stock  is  taken  each  year  at  somewhere 
near  the  best  point  for  exploitation,  and  some 
progress  has  been  made  towards  establishing  the 
nature  of  the  density-dependent  control  in  the 
population.  The  Fur  Seal  Commission  is  the  oldest 
of  the  international  commissions  and  its  records 
go  back  a  long  way,  into  the  early  19th  century. 

From  this  very  brief  account  of  the  role  of 


862 


GUSHING:  LINK  BETWEEN  SCIENCE  AND  MANAGEMENT 


fisheries  science  in  the  Commissions  there  is  one 
general  conclusion,  that  when  the  science  is  suc- 
cessful the  Commissions  can  work  well  but  when 
the  scientific  evidence  is  confused  the  Commis- 
sions may  fail.  Of  course,  failure  may  occur  for 
other  reasons;  for  example,  a  proposal  in  the  ICES 
to  close  the  small  plaice  grounds  in  1923  was  re- 
jected by  the  British  fishing  industry  in  1926. 

THE  NATURE  OF 
FISHERIES  SCIENCE 

The  organization  of  knowledge  into  science  is 
based  on  the  establishment  of  laws  that  interlock. 
Each  law  subsumes  much  information  and  the 
network  of  laws  comprises  the  body  of  the  science. 
Advance  in  science  is  made  by  the  addition  to  or 
the  rearrangement  of  the  network.  Any  scientific 
conclusion  is  judged  in  relation  to  the  general 
framework,  and  it  is  tested  in  the  premises  and 
extensions  of  the  argument  in  the  network.  It  is 
sometimes  said  that  the  end  of  a  scientific  proce- 
dure is  to  establish  a  correlation;  without  denying 
the  use  of  correlation,  the  most  important  point  is 
to  establish  whether  the  correlation  is  likely  and 
how  it  fits  into  the  general  scientific  framework. 

In  a  highly  developed  science  such  judgments 
are  made  frequently,  but  in  a  more  primitive  one 
like  fisheries  biology  the  necessary  network  has 
not  yet  been  established.  For  example,  all  our  in- 
formation on  stocks  depends  on  catches,  with  the 
various  biases  in  availability  included;  indepen- 
dent methods  of  estimating  stock  are  being  de- 
veloped but  they  are  not  yet  reliable.  In  a  highly 
developed  science,  a  number  of  methods  indepen- 
dently yield  the  same  result;  fisheries  biologists 
are  pleased  to  estimate  fishing  mortality  but  very 
rarely  is  more  than  one  method  used.  Natural 
mortality  is  estimated  as  the  difference  between 
total  mortality  and  fishing  mortality,  and  there  is 
very  little  independent  evidence  of  its  magnitude. 
The  information  needed  is  accumulating  quite 
quickly  but  the  science  remains  a  little  weak. 

Because  biological  material  is  highly  variable, 
any  biologist  needs  a  working  knowledge  of  statis- 
tics. Without  denigrating  this  very  real  need,  the 
science  needs  more  than  statistics,  more  informa- 
tion, more  hjqjotheses,  and  more  insight.  It  has 
sometimes  been  stated  that  fish  stocks  could  be 
assessed  by  the  study  of  ecosystems  rather  than  by 
the  study  of  single  populations.  This  is  rubbish;  it 
is  my  view  that  not  enough  is  known  of  any  one 
population  primarily  because  we  have  examined 


adult  animals  to  the  exclusion  of  the  juveniles.  I  do 
not  mean  that  we  know  nothing  of  fish  larvae  or 
0-group  fish,  but  that  we  know  too  little  of  their 
growth  rates  and  death  rates.  With  more  knowl- 
edge of  this  sort,  the  problems  of  the  regulation  of 
numbers  and  of  competition  might  be  solved  and 
we  might  at  the  same  time  learn  something  of  how 
an  ecosystem  itself  is  regulated. 

It  has  been  said  that  fisheries  science  is  fully 
developed  and  that  its  techniques  are  quite  reli- 
able. Much  is  known  about  the  Pacific  salmon  but 
it  is  only  a  small  fraction  of  what  is  needed.  It  has 
been  said  that  stock  and  recruitment  is  the  last 
problem  in  fish  population  dynamics.  It  is  the 
study  of  the  regulation  of  numbers,  of  competition 
between  species,  and  of  the  variability  of  recruit- 
ment. In  other  words,  it  is  the  central  problem  of 
population  dynamics.  There  is  a  sense  in  which 
fisheries  biologists  have  passed  through  a  long 
apprenticeship  before  they  have  embarked  on  the 
real  problem  that  concerns  them. 

CONCLUSION 

The  international  management  of  fisheries  has 
developed  slowly  since  it  started  during  the  second 
and  third  decades  of  the  present  century.  There 
are  many  reasons  for  this,  economic,  social,  and 
political;  indeed  the  agreement  achieved  between 
nations  is  considerable  when  one  considers  all  the 
difficulties  involved.  One  of  the  reasons  for  this 
slow  development,  but  not  the  only  one,  is  that 
where  the  science  has  failed,  so  has  management. 
Conversely,  where  the  science  has  been  success- 
ful, management  can  proceed  with  confidence, 
other  things  being  equal.  One  would  expect  a  link 
to  exist  between  science  and  management,  as  it 
does  in  other  fields. 

LITERATURE  CITED 

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1957.  On  the  dynamics  of  exploited  fish  populations.  Fish. 
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Clayden,  a.  D. 

1972.  Simulation  of  the  changes  in  abundance  of  the  cod 
(Gadus  morhua  L.)  and  the  distribution  of  fishing  in  the 
North  Atlantic.  Fish.  Invest.  Minist.  Agric,  Fish.  Food  (G. 
B.),  Ser.  2,  27(1),  58  p. 
Gushing,  D.  H. 

1972.  A  history  of  some  of  the  International  Fisheries 
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73:361-390. 

Gushing,  D.  H.,  and  J.  G.  K.  Harris. 

1973.  Stock  and  recruitment  and  the  problem  of  density 


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Garrod,  D.  J. 

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Petersen,  C.  G.  J. 

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per  unit  of  gear.  Rep.  Int.  Fish.  Comm.  8,  49  p. 


864 


DEVELOPMENT  AND  DISTRIBUTION  OF  LARVAE 

AND  JUVENILES  OF  SEBASTOLOBUS 

(PISCES;  FAMILY  SCORPAENIDAE) 


H.  Geoffrey  Moser' 


ABSTRACT 

The  North  Pacific  scorpaenid  genus  Sebastolobus  is  composed  of  three  deepwater  coastal  species  of 
potential  commercial  importance.  They  are  oviparous  and  produce  bilobed  gelatinous  egg  sacs  that 
float  to  the  surface  waters  where  hatching  and  larval  development  occur.  Transformation  into  pelagic 
juveniles  occurs  at  about  20  mm  length.  The  pelagic  stage  of  S.  alascanus  is  relatively  short-lived,  as 
they  transform  into  benthic  juveniles  at  22  to  27  mm  length.  In  the  deep-living  S.  altivelis  the 
juveniles  remain  pelagic  for  well  over  a  year  and  grow  as  large  as  56  mm. 

Larvae  of  the  two  species  mentioned  are  collected  regularly  on  plankton  surveys  of  the  California 
Cooperative  Oceanic  Fisheries  Investigations  (CalCOFI)  and  pelagic  and  benthic  juveniles  are  com- 
mon constituents  of  mid-water  and  bottom  trawls  taken  in  the  CalCOFI  region.  In  this  paper  speci- 
mens from  these  sources  are  used  to  describe  the  larval  and  juvenile  stages  of  the  two  species  and  to 
show  the  striking  morphological  changes  which  occur  during  development.  Also  presented  are  data 
on  geographic  distribution  and  patterns  of  seasonal  abundance  of  larvae.  Larvae  of  Sebastolobus 
smaller  than  10.0  mm  could  not  be  distinguished  to  species. 


Knowledge  of  the  life  history  of  the  scorpionfish 
genus  Sebastolobus  is  scanty.  Pearcy  (1962)  de- 
scribed the  floating  egg  masses,  the  developing 
embryos,  and  the  newly  hatched  larvae  of  Sebas- 
tolobus. The  larvae  of  Sebastolobus  occur  in  the 
plankton  collections  of  the  California  Coopera- 
tive Oceanic  Fisheries  Investigations  (CalCOFI) 
and  can  be  differentiated  from  those  of  Sebastes 
on  the  basis  of  the  spination  of  the  parietal  ridge 
(Ahlstrom,  1961).  Information  on  the  distribution 
and  abundance  of  Sebastolobus  larvae  in  Cal- 
COFI has  hitherto  not  appeared  in  the  literature, 
nor  has  a  description  of  the  larval  stages.  It  is  the 
purpose  of  this  paper  to  fill  that  void  and  also  to 
describe  the  distinctive  juvenile  stages  of  S.  al- 
tivelis and  S.  alascanus,  which  are  common  con- 
stituents of  mid-water  trawl  catches  in  the  east- 
ern North  Pacific. 

The  three  known  species  of  Sebastolobus 
inhabit  the  coastal  waters  of  the  North  Pacific. 
Sebastolobus  altivelis  ranges  from  the  southern 
tip  of  Baja  California  to  the  Aleutian  Islands 
while  S.  alascanus  is  found  from  northern  Baja 
California  to  the  Bering  Sea  and  the  Commander 
Islands  off  the  Asiatic  mainland.  The  Asian 
species,  S.  macrochir,  ranges  from  the  coast  of 
Japan  northward  to  the  Bering  Sea  south  of  Cape 


'Southwest  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  La  Jolla,  CA  92037. 


Navarin  and  into  the  Sea  of  Okhotsk  (Barsukov, 
1964).  At  present  the  commercial  catch  of  Sebas- 
tolobus is  small,  however,  data  of  Best  (1964)  and 
Alverson,  Pruter,  and  Ronholt  (1964)  suggest 
that  these  fishes  may  constitute  a  substantial  re- 
source in  the  deep  coastal  waters  of  the  northeast 
Pacific. 

The  taxonomic  characters  of  the  adult  mem- 
bers of  this  genus  have  been  reviewed  by  a 
number  of  investigators  (Starks,  1898;  Hubbs, 
1926;  Matsubara,  1943;  Phillips,  1957;  Barsukov, 
1964;  Miller  and  Lea,  1972).  Sebastolobus  is  dis- 
tinguished from  other  scorpaenid  genera  by  the 
unusual  pectoral  fins,  each  of  which  is  separated 
by  a  notch  into  dorsal  and  ventral  lobes,  by  pos- 
sessing more  vertebrae  (28  to  31)  and  dorsal 
spines  (15  to  17),  a  complete  set  of  circumorbital 
bones,  an  uppermost  pectoral  radial  which  is  free 
from  the  scapula,  and  by  a  suborbital  stay  with  a 
broad  posterior  end  anchored  firmly  onto  the 
preopercular  bone.  The  two  North  American 
species  may  be  separated  on  the  basis  of  the 
shape  and  number  of  rays  in  the  spinous  dorsal 
fin.  In  S.  altivelis  the  third  spine  is  the  longest 
while  in  S.  alascanus  the  fourth  or  fifth  spine  is 
the  longest.  The  former  species  usually  has  15 
(rarely  16)  spinous  dorsal  rays  while  the  latter 
has  16  or  17  (rarely  15)  rays.  Also,  S.  altivelis 
usually  has  29  (rarely  28)  vertebrae  and  S.  alas- 
canus has  30  (rarely  31).  The  Asian  species,  S. 


Manuscript  accepted  January  1974. 
FISHERY  BULLETIN;  VOL.  72.  NO.  4.  1974. 


865 


macrochir,  is  deeper  bodied  than  the  North 
American  species  and  has  a  relatively  narrower 
caudal  peduncle.  Counts  of  its  spinous  dorsal  rays 
and  vertebrae  are  close  to  those  of  S.  altivelis. 

Hubbs  ( 1926),  Barsukov  ( 1964),  and  Miller  and 
Lea  (1972)  have  given  information  on  the 
bathymetric  ranges  of  the  adults.  In  summary,  S. 
altivelis  occurs  typically  at  550  to  1,300  m  with 
known  depth  extremes  of  200  to  1,550  m.  Every- 
where along  its  latitudinal  range  S.  altivelis  is 
deeper  living  thanS.  alascanus,  although  there  is 
some  overlap  and  the  two  species  are  occasionally 
taken  in  the  same  trawls.  Sebastolobus  alascanus 
commonly  occurs  at  180  to  440  m,  with  known 
depth  extremes  of  18  to  1,524  m.  Sebastolobus 
macrochir  occurs  commonly  at  400  to  640  m. 

MATERIALS  AND  METHODS 

Larvae  of  Sebastolobus  from  2  yr  (1960,  1966) 
of  CalCOFI  survey  cruises  were  identified  and 
counted.  From  these  a  developmental  series  that 
encompassed  the  entire  larval  period  was  estab- 
lished. Larvae  of  this  series  were  measured  with 
the  ocular  micrometer  of  a  stereoscopic  micro- 
scope, according  to  the  methods  of  Moser  (1967, 
1972),  to  produce  the  tables  of  morphometries 
(Tables  1-3)  needed  for  comparison  of  body  pro- 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

portions  of  S.  altivelis  and  S.  alascanus.  This 
series  also  provided  the  specimens  needed  to  de- 
scribe the  general  morphology  and  melanophore 
pattern  of  the  larvae.  Measurements  of  four 
pelagic  juveniles  of  S.  macrochir  are  given  in 
Table  4.  An  abbreviated  series  of  S.  altivelis  and 
S.  alascanus  was  selected,  cleared  with  a  graded 
series  of  KOH-glycerin  solutions  and  stained 
with  Alizarin  Red-S  to  produce  tables  of  meristics 
(Tables  5,  6). 

The  pelagic  juvenile  stages  of  the  two  species 
were  obtained  from  the  mid-water  trawl  collec- 
tions of  the  Los  Angeles  County  Museum  of 
Natural  History  (LACM),  the  Scripps  Institution 
of  Oceanography  (SIO),  and  the  Southwest 
Fisheries  Center.  Demersal  juveniles  were  ob- 
tained from  otter  trawl  collections  of  LACM  and 
SIO.  As  for  larvae,  series  of  juveniles  were  estab- 
lished for  analysis  of  morphometries  (Tables  2-4), 
pigment  pattern,  and  meristic  characters  (Tables 
5,  6).  In  this  paper  the  term  "body  length"  refers 
to  the  distance  from  the  snout  to  the  tip  of  the 
notochord  in  larvae  which  have  not  yet  formed 
the  caudal  fin.  After  dorsad  flexion  of  the  tip  of 
the  notochord  and  completion  of  caudal  fin  forma- 
tion "body  length"  refers  to  standard  length  (dis- 
tance from  snout  to  posterior  edge  of  hypural 
plate). 


Table  1. — Measurements  (mm)  oi Sebastolobus  spp.  larvae.  Specimens  bet 

ween  dashed  lines  are  undergoing  notochord  flexion. 

Standard 

Snout-anus 

Head 

Snout 

Eye 

Body 

Pectoral 

Pectoral 

Pelvic 

Snout- 

Snout- 

length 

distance 

length 

length 

diameter 

depth 

fin  length 

fin  base  depth 

fin  length 

dorsal  fin 

anal  fin 

3.0 

1.3 

0.50 

0.08 

0.20 

0.60 

0.3 

0.  14 

3.5 

1.4 

0.80 

0.18 

0.25 

0.52 

0.23 

0.20 

3.8 

1.6 

1.0 

0.22 

0.27 

0.68 

0,40 

0.38 

4.2 

1.8 

1.2 

0.25 

0.30 

0.86 

0.45 

0.40 

4.7 

1.9 

1.2 

0.31 

0.30 

0.80 

0.46 

- 

5.0 

2.0 

1.4 

0,35 

0.33 

0.90 

0.65 

0.50 

5.2 

2.1 

1.4 

0.43 

0.40 

1.0 

0.62 

0.55 

5.5 

2.3 

1.6 

0.42 

0.35 

1.1 

0.65 

0.58 

5.7 

2.3 

1.7 

0.56 

0.40 

1.2 

0.95 

0.85 

5.8 

2.4 

1.7 

0.51 

0.39 

1.2 

1.0 

0.78 

5.9 

2.6 

1.8 

0.62 

0.47 

1.6 

1.0 

0.75 

6.0 

2.7 

1.8 

0.55 

0.51 

1.8 

1.3 

0.85 

0.22 

2.3 

3.4 

6.2 

2.7 

1.9 

0.70 

0.48 

1.6 

1.4 

0.90 

0.20 

- 

- 

6.4 

2.7 

1.8 

0.60 

0.45 

1.5 

1.2 

0.85 

0.13 

- 

- 

6.7 

3.  1 

1.9 

0.82 

0.55 

1.8 

1.4 

1.0 

0,15 

3.9 

3.9 

6.8 

2.8 

2.0 

0.82 

0.52 

1,8 

1.4 

1.1 

0.  17 

- 

3.2 

6.9 

3.3 

2.2 

0.80 

0.58 

2.0 

1.5 

1.2 

0.25 

2.7 

4.  1 

7.1 

3.5 

2.5 

0.82 

0.71 

2.4 

1.8 

1.2 

0.80 

2.5 

4.2 

JTS   _ 

7.7 

3.8 

4.2 

2.5 
2.7 

0.95 
1.1 

0.76 
0.75 

2.4 
2.8 

1.8 
2.1 

1.4 
1.5 

0.85 
0.85 

2.7 
^       2.9 

4,4 
4.5 

7.8 

4.3 

3.1 

1.  1 

0.82 

2.6 

2.1 

1.4 

1.2 

3.2 

4.8 

8.3 

4.4 

3.1 

1.1 

0.79 

2.6 

2.0 

1.4 

1.0 

3.  1 

4.9 

8.6 

4.8 

3,2 

1.2 

0.92 

3.1 

2.4 

1.7 

1.4 

3.5 

5.3 

8.9 

5.2 

3.3 

1.2 

1.0 

3.1 

2,5 

1.7 

1.4 

3,8 

5.4 

9.2 

5.2 

3.5 

1.2 

1,0 

3.2 

2,7 

1.5 

1.5 

3.8 

5.6 

9.6 

5.4 

3.5 

1.2 

1,1 

3.7 

2.8 

1.8 

1.7 

4.1               5.8 

866 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 

Table  2. — Measurements  (mm)  of  Sebastolobus  altivelis.  Specimens  below  dashed  line  have  completed  transformation  into 

pelagic  juvenile  stage. 


Standard 

Snout-anus 

Keatl 

Snout 

Eye 

Body 

Pectoral 

Pectoral 

Pelvic 

Snout- 

Snout- 

length 

distance 

length 

length 

diameter 

depth 

fin  length 

fin  base  depth 

fin  length 

dorsal  fin 

anal  fin 

10.1 

6.2 

3.8 

1.2 

1.2 

3.8 

2.8 

1.8 

1.7 

4.2 

6.4 

10.5 

6.5 

4.2 

- 

1.2 

3.9 

3.0 

1.9 

1.8 

4.4 

6.  7 

11.2 

6.9 

4.5 

1.3 

1.4 

4.2 

3.5 

2.1 

2.4 

5.2 

7.3 

12.7 

7.3 

4.6 

1.3 

1.5 

4.7 

3.8 

2.0 

2.5 

5.4 

7.9 

13.4 

8.0 

5.0 

1.5 

1.6 

4.8 

3.7 

2.0 

2.5 

5.4 

8.3 

U.  4 

8.8 

6.2 

1.7 

2.  1 

5.7 

5.0 

2.7 

3.1 

6.0 

9.6 

15.2 

10.1 

6.  1 

1.8 

1.9 

6.3 

5.2 

2.8 

2.9 

6.7 

10.6 

15.4 

9.8 

6.0 

1.7 

2.2 

6.4 

4.7 

2.8 

2.9 

6.9 

10.1 

15.4 

9.9 

6.5 

1.9 

2.2 

6.3 

5.8 

2.9 

3.8 

6.8 

11.0 

15.7 

10.3 

6.8 

2.1 

2.1 

6.9 

5.8 

2.9 

3.8 

6.  7 

10.8 

16.0 

10.3 

6.2 

1.8 

2.0 

7.1 

5.4 

3.1 

3.3 

7.0 

10.6 

16.3 

10.3 

7.2 

2.1 

2,2 

6.6 

6.2 

3.0 

4.0 

6.8 

11.2 

16.6 

10.8 

7.4 

1.8 

2.4 

6.6 

6.4 

3.0 

3.4 

7.6 

11.8 

16.7 

11.2 

6.7 

1.9 

2.2 

7.  5 

5.8 

3.2 

3.3 

7.  1 

11.3 

17.6 

11.5 

7.6 

2.0 

2.5 

7.2 

6.8 

3.2 

4.2 

7.1 

12.2 

17.6 

11.7 

7.0 

1.9 

2.4 

7.3 

5.9 

3.1 

3.8 

7.7 

12.0 

18.2 

12.0 

7.  7 

2.1 

2.6 

7.3 

6.3 

3.1 

4.2 

7.8 

12.7 

18.4 

12.5 

7.  1 

2.0 

2.5 

8.3 

6.2 

3.6 

4.2 

7.5 

12.8 

19.3 

13.2 

7.9 

2.1 

2.5 

8.5 

6.  7 

3.8 

3.8 

8.3 

13.4 

19.4 

13.0 

8.5 

2.3 

2.5 

8.7 

7.6 

3.8 

4.7 

8.4 

14.0 

20.7 

13.8 

8.5 

2.6 

2.3 

8.4 

7.6 

3.7 

4.8 

8.6 

14.7 

21.3 

14.9 

9.2 

2.8 

2.8 

9.0 

8.1 

3.8 

4.8 

9.5 

15.2 

22.6 

15.9 

9.6 

2.5 

3.1    ~^ 

9.2 

8.8 

4.2 

5.6 

9.5 

16.7 

23.4 

16.6 

9.8 

2.5 

2.  7 

10.1 

9.  0 

4.4 

5.6 

9.5 

17.4 

24.5 

17.7 

10.8 

2.9 

3.4 

11.0 

10.0 

4.5 

5.8 

10.1 

18.1 

25.8 

18.6 

10.6 

2.9 

2.9 

11.3 

9.3 

4.4 

5.9 

10.1 

18.9 

26.8 

17.7 

10.6 

2.8 

3.8 

10.6 

11.0 

4.8 

6.5 

10.1 

18.8 

27.7 

20.3 

11.5 

2.9 

3.6 

12.2 

11.0 

5.4 

7.  1 

11.7 

22.0 

28.3 

20.3 

12.0 

3.2 

3.7 

12.2 

11.5 

5.0 

7.1 

11.5 

21.8 

29.4 

20.4 

12.3 

3.3 

3.8 

11.5 

11.5 

5.2 

7.2 

12.3 

21.1 

30.5 

21.1 

13.0 

3.8 

3.6 

11.7 

11.7 

5.4 

7.6 

12.3 

23.0 

31.4 

21.1 

19     o 

3.2 

3.5 

13.7 

12.2 

5.8 

7.5 

12.3 

22.9 

32.4 

21.1 

12.5 

3.5 

3.6 

13.0 

12.8 

5.8 

8.3 

12.5 

22.2 

33.6 

23.1 

14.0 

4.2 

4.2 

13.5 

11.  7 

5.8 

7.5 

12.8 

25.  1 

34.6 

23.5 

13.4 

3.8 

3.8 

14.2 

13.5 

6.0 

8.2 

13.7 

25.5 

36.5 

25.0 

15.2 

4.2 

4.8 

15.5 

14.  7 

6.7 

9.2 

14.9 

27.5 

37.5 

25.8 

15.0 

4.2 

4.6 

15.9 

14.4 

6.7 

8.3 

14.7 

27.6 

38.5 

25.6 

15.2 

4.0 

4.8 

16.0 

15.7 

6.6 

9.8 

15.2 

27.5 

39.5 

27.9 

16.2 

5.0 

4.8 

16.0 

15.0 

6.7 

8.9 

16.0 

29.9 

40.4 

27.1 

16.4 

5.0 

4.8 

15.2 

15.0 

6.8 

10.8 

16.0 

30.0 

41.6 

27.9 

16.4 

4.3 

5.8 

15.9 

15.2 

7.1 

10.1 

16.2 

29.6 

42.3 

28.1 

16.9 

4.6 

5.2 

17.4 

15.2 

7.2 

10.0 

15.9 

29.4 

43.5 

30.1 

16.9 

5.2 

5.4 

16.0 

14.7 

6.7 

9.5 

17.4 

32.4 

44.4 

30.0 

17.9 

- 

4.8 

16.4 

16.4 

7.1 

9.5 

17.2 

32.2 

45.1 

29.5 

18.2 

4.8 

5.4 

17.6 

16.0 

7.8 

10.1 

17.2 

32.0 

46.2 

30.7 

17.9 

5.0 

4.9 

17.7 

17.1 

8.1 

11.5 

17.  1 

33.5 

47.1 

30.2 

18.1 

5.0 

5.6 

17.1 

15.2 

7.0 

10.3 

17.7 

33.0 

48.5 

32.0 

18.6 

5.4 

5.8 

18.6 

16.9 

7.8 

10.5 

17.7 

34.7 

49.5 

32.2 

19.8 

5.0 

5.8 

18.6 

18.  1 

8.3 

11.8 

16.4 

36.2 

51.3 

37.0 

20.6 

6.7 

5.8 

18.8 

17.4 

8,0 

11.3 

18.9 

40.0 

53.5 

35.7 

20.6 

6.2 

7.5 

18.6 

16.9 

8.2 

11.0 

18.7 

37.8 

56.0 

37.6 

21.4 

5.8 

7.7 

19.2 

19.8 

8.3 

12.3 

20.3 

40.6 

*42.0 

26.8 

16.6 

4.6 

5.6 

12.0 

12.7 

6.0 

9.3 

16.4 

29.0 

*47.4 

29.6 

17.7 

4.7 

6.9 

13.9 

13.5 

6.8 

10.1 

18.1 

31.7 

*48. 1 

31.4 

19.1 

5.2 

7.3 

14.4 

15.2 

7.0 

11.5 

17.9 

33.5 

*50.3 

33.0 

19.2 

5.4 

7.3 

14.0 

13.8 

7.1 

11.8 

18.8 

35.3 

*51.0 

33.0 

19.5 

4.7 

7.2 

15.0 

16.2 

7.5 

11.2 

18.7 

35.2 

*53.0 

33.4 

20.5 

5.4 

8.6 

14.6 

15.5 

7.0 

12.1 

19.9 

37.7 

*54.  0 

35.4 

19.7 

5.9 

7.3 

15.5 

17.7 

7.8 

12.6 

20.6 

38.4 

*56.0 

35.2 

21.1 

5.6 

7.7 

15.5 

16.4 

7.4 

12.6 

20.8 

38.  1 

*57.5 

37.2 

21.4 

5.6 

8.0 

15.3 

16.7 

8.1 

12.5 

21.1 

40.3 

*58.6 

37.9 

22.6 

6.0 

8.7 

16.5 

16.9 

8.2 

12.7 

21.6 

40.6 

*60.0 

38.0 

22.0 

6.0 

8.4 

16.2 

15.  1 

8.1 

12.8 

21.5 

41.6 

*Benthic  juvenile. 


867 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Table  3. — Measurements  (mm)  of  larvae  and  juveniles  of  Sebastolobus  alascanus. 


Standard 

Snout-anus 

Head 

Snout 

Eye 

Body 

Pectoral 

Pectoral 

Pelvic 

Snout- 

Snout 

length 

distance 

length 

length 

diameter 

depth 

fin  length 

fin  base  depth 

fin  length 

dorsal  fin 

anal  fin 

10.3 

6.2 

4.2 

1.5 

1.2 

4.0 

3.2 

1.6 

1.9 

4.3 

6.8 

11.2 

7.4 

5.0 

1.8 

1.3 

4.1 

3.2 

1.7 

2.1 

5.0 

7.7 

11.7 

7.2 

5.0 

- 

1.3 

3.9 

3.1 

1.8 

2.1 

5.1 

7.7 

12.5 

7.7 

4.7 

1.7 

1.5 

4.5 

3.6 

1.8 

2.4 

5.4 

8.3 

13.2 

7.3 

5.0 

1.6 

1.8 

4.6 

3.9 

1.9 

2.7 

5.8 

8.2 

14.0 

8.1 

5.7 

1.8 

2.  1 

4.9 

4.  1 

1.9 

2.5 

6.2 

8.8 

14.4 

8.4 

5.6 

1.4 

1.8 

5.2 

4.2 

2.1 

2.6 

5.7 

9.  1 

15.2 

9.2 

6.2 

1.8 

2.0 

5.2 

4.4 

2.1 

2.9 

6.3 

10.0 

16.0 

9.3 

6.2 

2.0 

2.0 

5.2 

4.8 

2.2 

2.9 

7.  1 

10.0 

16.4 

9.8 

6.7 

1.8 

2.5 

5.7 

4.7 

2.3 

3.2 

7.  1 

10.5 

16.9 

10.0 

6.8 

1.9 

2.3 

5.9 

4.8 

2.4 

3.1 

7.3 

10.8 

17.6 

10.6 

6.7 

2.1 

2.2 

6.1 

4.9 

2.3 

3.5 

7.1 

11.3 

18.6 

12.7 

- 

- 

2.8 

6.8 

5.4 

2.8 

3.8 

8.5 

13.2 

19.8 

12.0 

7.7 

2.0 

2.8 

7.1 

5.9 

2.9 

4.0 

8.3 

13.0 

20.0 

12,0 

8.1 

2.2 

2.9 

7.1 

6.4 

2.8 

4.2 

8.4 

13.0 

20.3 

12.8 

8.2 

1.8 

3.1 

7.2 

6.2 

7.8 

4.0 

8.1 

13.5 

21.0 

13.5 

8.6 

1.9 

3.  1 

7.5 

6.5 

3.0 

4.6 

8.1 

14.4 

21.4 

12.8 

8.3 

2.4 

2.9 

7.1 

6.2 

2.8 

3.8 

8.6 

14.4 

21.9 

12.8 

8.5 

2.1 

3.1 

7.1 

G.? 

2.8 

4.2 

8.8 

14.9 

22.3 

14.2 

9.6 

- 

2.8 

7.9 

6.5 

3.2 

4.4 

9.1 

15.4 

22.9 

14.4 

9.8 

2.6 

3.2 

7.5 

6.7 

3.1 

4.6 

9.3 

15.5 

23.2 

14.7 

9.5 

2.5 

2.9 

7.9 

7.2 

3.0 

5.0 

9.6 

16.0 

23.4 

14.9 

9.0 

2.2 

3.3 

8.0 

7.1 

3.2 

5.0 

9.3 

16.4 

24.0- 

14.4 

9.8 

2.2 

3,2 

8.0 

6.8 

3.3 

5.0 

9.8 

15.9 

24.3 

15.5  , 

10.0 

2.8 

3.2 

8.6 

7.3 

3.3 

5.0 

9.8 

16.9 

25.  1 

15.9 

10.0 

3.0 

3.3 

8.4 

7.0 

3.4 

5.0 

10.1 

17.2 

25.5 

16.0 

10.1 

2.8 

3.5 

8.8 

8.2 

3.7 

5.5 

10.1 

17.6 

2G.4 

17.9 

10.6 

3.2 

3.5 

9.0 

8.0 

3.7 

5.7 

11.3 

19.1 

27.2 

17.9 

11.2 

3.0 

- 

8.3 

8.1 

3.3 

5.4 

10.8 

19.3 

*22.5 

13.0 

8.7 

2.1 

3.2 

7.2 

6.3 

2.9 

4.6 

9.6 

14.  7 

*25.3 

16.9 

10.3 

3.5 

3.2 

8.1 

6.8 

3.3 

5.0 

11.2 

18.9 

*37.8 

22.0 

12.7 

2.9 

5.0 

10.1 

9.6 

4.2 

8.2 

13.5 

24.3 

*39.0 

24.0 

14.1 

4.0 

5.1 

9.9 

9.8 

4.0 

8.8 

15.0 

26.7 

*40.8 

25.1 

14.8 

3.8 

5.3 

10.0 

9.7 

3.8 

8.8 

15.3 

27.3 

*42.3 

27.7 

15.4 

4.3 

5.8 

10.1 

10.0 

4.2 

9.0 

16.3 

29.6 

*43.6 

26.3 

15.4 

4.1 

5.8 

9.5 

10.6 

4.4 

9.4 

16.1 

29.5 

*44.7 

26.2 

15.9 

4.3 

5.8 

11.2 

10.5 

4.8 

8.1 

16.9 

29.  7 

*46.2 

28.  1 

16.2 

4.4 

6.4 

10.8 

10.8 

4.7 

9.9 

16.7 

31.2 

*48.  8 

29.1 

16.8 

4.7 

6.5 

11.4 

11.4 

4.7 

10.5 

18.0 

32.9 

*50.3 

29.4 

17.4 

4.8 

7.0 

12,4 

12.2 

5.0 

10.6 

18.0 

33.0 

*51.  0 

30.6 

17.5 

5.0 

6.8 

11,8 

11.5 

5.2 

10.5 

17.5 

33.6 

*59.2 

36.6 

20.6 

5.4 

8.4 

13.0 

13.5 

5.6 

12.1 

20.8 

40.0 

*60.0 

36.8 

21.6 

5.7 

9.0 

14.3 

14.3 

5.9 

13.0 

21.5 

39.  7 

♦  Benthic  juvenile. 


Table  4. — Measurements  (mm)  of  pelagic  juveniles  of  Sebastolobus  macrochir. 


Standard 

Snout-anus 

Head 

Snout 

Eye 

Body 

Pectoral 

Pectoral 

Pelvic 

Snout - 

Snout- 

length 

distance 

length 

length 

diameter 

depth 

fin  length 

fin  base  depth 

fin  length 

dorsal  fin 

anal  fin 

21.0 

14.5 

9.2 

2.5 

3.  1 

9.  1 

9.2 

3.8 

5.4 

10.0 

15.0 

25.5 

17.9 

10.8 

3.0 

■1.5 

11.2 

11.2 

4.7 

7.  1 

11.3 

18.2 

27.2 

18.6 

11.8 

3.8 

4.3 

12.5 

11.0 

4.8 

7.7 

12.2 

19.  1 

29.8 

19.2 

13.2 

3.0 

5.0 

13.2 

13.2 

5.7 

8.5 

13.5 

20.8 

868 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 


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MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 

DESCRIPTION  OF  DEVELOPMENT 

Distinguishing  Features 

Early  Sebastolobus  larvae  (up  to  6  mm)  can  be 
distinguished  from  those  of  all  other  genera  of 
eastern  Pacific  Scorpaenidae  on  the  basis  of  pig- 
mentation. Sebastolobus  larvae  of  this  size  range 
are  unique  in  having  two  large  melanistic 
blotches  about  midway  along  the  tail,  one  at  the 
dorsal  midUne  and  one  at  the  ventral  midline 
(Figure  lA,  B).  These  are  sometimes  expanded  to 
form  a  solid  band  on  the  tail.  Early  larvae  of  all 
other  eastern  Pacific  scorpaenid  genera  have  a 
series  of  melanophores  along  the  ventral  midline 
of  the  tail,  and  in  some  species  of  Sebastes  an 
opposing  row  is  present  at  the  dorsal  midline.  The 
large  tail  blotches  of  Sebastolobus  disappear  in 
larvae  between  5.0  and  6.5  mm.  Soon  after  the 
loss  of  these  large  tail  blotches  in  Sebastolobus 
the  larvae  develop  prominent  crestlike  parietal 
ridges  that  terminate  in  double  spines,  the  pos- 
terior (nuchal)  spine  being  longer  and  more  prom- 
inent than  the  anterior  (parietal)  spine  (Figure 
IF).  Of  the  other  eastern  Pacific  scorpaenid  gen- 
era, only  the  larvae  of  Scorpaenodes  have 
parietal  ridges  and  spines  like  Sebastolobus.  If 
two  spines  are  present  on  the  parietal  ridges  of 
other  genera,  the  anterior  spine  is  always  longer 
and  more  prominent  than  the  posterior.  Sebas- 
tolobus larvae  may  be  distinguished  from  those  of 
Scorpaenodes  on  the  basis  of  a  melanistic  shield, 
which  covers  the  dorsolateral  surface  of  the  gut  in 
the  former  and  is  absent  in  the  latter.  Larvae  of" 
Sebastolobus  smaller  than  10.0  mm  could  not  be 
distinguished  to  species.  Larvae  larger  than  this 
can  be  identified  to  species  by  a  combination  of 
characters.  The  pectoral  fins  of  S.  altivelis  larvae 
are  relatively  longer  and  are  wider  at  the  base 
than  in  S.  alascanus.  Also,  larvae  of  S.  altivelis 
are  deeper  bodied  than  those  of  S.  alascanus. 
Details  of  the  structui-al  and  pigmentary  charac- 
ters that  differentiate  the  larvae  and  juveniles  of 
the  two  species  are  given  below. 

General  Morphology 

Sebastolobus  larvae  hatch  and  are  freed  from 
their  transparent  gelatinous  egg  masses  at  about 
2.6  mm  (Pearcy,  1962).  The  smallest  larvae  in  our 
plankton  collections  are  about  3.0  mm  long  and 
still  have  the  elliptical  yolk  sac  with  a  posteriorly 
positioned  oil  droplet  (Figure  lA).  When  the  lar- 
vae reach  approximately  3.5  mm,  the  yolk  sac  has 


been  resorbed  and  the  jaws  and  feeding  apparatus 
are  well  formed  (Figure  IB).  Flexion  of  the 
notochord  begins  in  larvae  about  6.0  mm  long  and 
is  completed  in  larvae  about  7.5  mm  (Figure  IE, 
F).  Larvae  larger  than  10.0  mm  and  pelagic  and 
benthic  juveniles  can  be  identified  to  species  on 
the  basis  of  characters  mentioned  above  (Figures 
2-7).  In  both  species,  transformation  into  the 
pelagic  juvenile  stage  is  initiated  within  the  size 
range  of  14.0  to  20.0  mm.  All  specimens  larger 
than  20.0  mm  have  some  juvenile  pigmentation. 
The  largest  pelagic  juvenile  of  S.  alascanus 
encountered  was  27.2  mm,  whereas  the  smallest 
benthic  juvenile  was  22.5  mm.  In  contrast,  in  the 
protracted  pelagic  juvenile  stage  of  S.  altivelis, 
individuals  may  attain  56.0  mm  in  length.  The 
smallest  benthic  juvenile  of  this  species  in  the 
collection  was  42.0  mm.  Pelagic  juveniles  of  S. 
macrochir  are  similar  in  shape  and  pigmentation 
to  those  of  S.  altivelis.  Although  the  largest 
pelagic  specimen  available  was  only  30  mm  long, 
it  is  probable  that  pelagic  juveniles  of  S.  mac- 
rochir grow  larger  than  this  and  have  a  pro- 
tracted mid- water  life  as  in  S.  altivelis. 

Relative  body  depth  (maximum  body  depth/ 
standard  length)  changes  markedly  during  de- 
velopment and  is  an  important  taxonomic 
character  in  the  pelagic  juveniles  (Figure  8).  It  is 
15%  at  the  beginning  of  the  larval  period,  almost 
doubles  by  the  onset  of  notochord  flexion,  and  av- 
erages 28%  during  flexion.  It  increases  further  to 
35%  in  larvae  7.5  to  10.0  mm.  Relative  body 
depth  remains  at  about  this  percentage  in  larvae 
and  pelagic  juveniles  of  S.  alascanus  but  de- 
creases sharply  to  an  average  of  25%  (range  of  22 
to  32%)  in  benthic  juveniles.  Late-stage  larvae 
and  pelagic  juveniles  of  S.  altivelis  are  much 
more  robust  and  deeper  bodied,  averaging  41% 
(range  of  36  to  45%)  in  the  10-  to  40-mm  size 
range.  Pelagic  juveniles  40  to  50  mm  long  begin 
to  show  a  decrease  in  body  depth  (mean  38%; 
range  of  36  to  41%  ),  50-  to  55-mm  specimens  show 
a  further  decrease  (mean  35%;  range  of  34  to 
37%)  and  the  decrease  is  precipitous  in  benthic 
juveniles  (mean  28%;  range  of  27  to  30%).  Body 
depth  in  21-  to  30-mm  pelagic  juveniles  of  S. 
macrochir  averaged  37.5%  of  the  body  length 
(range  of  34  to  42%). 

The  gut  has  an  unusual  shape  in  early  larvae  up 
to  about  5.5  mm.  The  narrow,  dorsally  positioned 
esophagus  runs  posteriad  from  the  head  for  some 
distance  before  entering  the  principal  mass  of  the 
gut.  The  effect  of  this  is  to  produce  a  space  between 

871 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


B 


€rif 


872 


Figure  1.— Larvae  of  Sebastolobus  spp.  from  CalCOFI  plankton  samples.  A.  3.0  mm;  B.  3.5  mm; 
C.  5.2  mm:  D.  5.7  mm:  E.  6.2  mm;  F.  7.7  mm. 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 


Figure  2. — Larvae  of  Sebastolobus  altivelis  from  CalCOFI  plankton  samples.  A.  11.2  mm;  B.  11.2  mm,  dorsal  view; 

C.  15.4  mm. 


873 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  3. — Developmental  stages  ofSebastolobus  altivelis  from  mid-water  trawl  samples.  Above,  16.3-mm  transforming  specimen. 

Below,  26.8-mm  pelagic  juvenile. 


the  head  and  the  gut  (Figure  IB).  The  space 
gradually  diminishes  as  the  gut  enlarges  and  is 
absent  in  larvae  larger  than  6.0  mm.  Relative  gut 
length  increases  markedly  during  development. 
Snout-anus  distance  averages  41%  of  the  body 
length  up  to  the  stage  of  notochord  flexion,  46% 
during  flexion,  and  56%  in  post-flexion  larvae  up 
to  10  mm  in  length.  In  larvae  and  transforming 
specimens  of  10-  to  20-mm  S.  altivelis  there  is  an 
increase  to  a  mean  of  64%  and  in  20-  to  56-mm 
pelagic  juveniles  there  is  a  further  increase  to  a 
mean  of  68% .  In  early  benthic  juveniles  snout- 


anus  length  averages  64%  of  body  length.  The  gut 
is  slightly  shorter  in  S.  alascanus;  snout-anus 
length  averages  61%  of  body  length  for  the  larvae 
and  for  the  pelagic  and  early  benthic  juveniles. 

The  head  is  moderate  in  size  in  early  larval 
stages  but  enlarges  markedly  with  development. 
Head  length  increases  from  23%  of  body  length  at 
hatching  to  an  average  of  31%  during  notochord 
flexion  and  is  37%  in  7.5-  to  10.0-mm  larvae.  Rela- 
tive head  length  in  larvae  and  pelagic  juveniles  of 
S.  altivelis  in  the  10.0-  to  40.0-mm  size  range  av- 
erages 41%.  A  slight  decrease  to  a  mean  of  39% 


874 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 


Figure  4. — Developmental  stages  of  Sebastolobus  altivelis.  Above,  53.5-mm  late  pelagic  juvenile  from  mid-water  trawl.  Below,  53.0- 

mm  benthic  juvenile  from  bottom  trawl. 


occurs  in  40.0-  to  56.0-mm  specimens  and  early 
benthic  juveniles  average  38'7c .  Virtually  the 
same  changes  in  relative  head  size  occur  in  S. 
alascanus. 

The  eyes  of  early-stage  Sebastolobus  larvae  are 
relatively  smaller  than  in  Sebastes  larvae  of  com- 
parable size.  Eye  diameter  averages  26%  of  the 
head  length  for  larvae  up  to  the  beginning  of 
notochord  flexion,  27%  during  flexion,  and  28%  in 
post-flexion  larvae  up  to  10.0  mm  in  length. 


Sebastes  larvae  average  33  to  35%  during  com- 
parable stages.  Eye  diameter  in  larvae  and  pelagic 
juveniles  of  S.  altivelis  10.0-  to  56.0-mm  range) 
averages  31%  of  the  head  length,  while  in  those  of 
S.  alascanus,  eye  diameter  is  slightly  larger 
(mean  33%).  In  early  benthic  juveniles  of  both 
species,  relative  eye  diameter  increases  sharply  to 
a  mean  of  38%  of  head  length.  The  snout  is  rela- 
tively short  in  pre-flexion  larvae  o(  Sebastolobus 
where  snout  length  averages  27%  of  head  length. 


875 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Figure  5. Developmental  stages  of  Sebastolobus  alascanus.  Above,  10.3-mm  larva  from  mid-water  trawl.  Below,  16.0-mm 

transforming  specimen  from  mid- water  trawl. 


This  increases  to  an  average  36%  in  6.0-  to 
10.0-mm  larvae.  Later  stages  of  S.  altiuelis 
average  28% .  Sebastolobus  alascanus  in  the  10.0- 
to  20.0-mm  range  average  31% ,  but  this  is  reduced 
to  27%  in  the  remaining  stages. 

Fin  Development 

The  pectoral  fins  of  Sebastolobus  are  undif- 
ferentiated buds  in  newly  hatched  larvae,  how- 
ever, when  the  larvae  reach  a  length  of  3.0  mm 
the  base  and  blade  portions  of  each  fin  are  begin- 
ning to  differentiate.  From  this  stage  until  the 
initiation  of  notochord  fiexion  at  6.0  mm  the 
rayed  portion  of  the  fin  enlarges  rapidly  to  form 
the  large  fan-shaped  structure  characteristic  of 
Sebastolobus.  At  this  stage  the  fin  length  is  about 


17%  of  the  body  length.  This  increases  to  an  av- 
erage of  22%  during  notochord  flexion  and  27%  in 
post-flexion  larvae  up  to  10  mm  length. 

In  specimens  larger  than  10  mm  the  relative 
length  of  the  pectoral  fin  differs  considerably  be- 
tween S.  altiuelis  and  S.  alascanus  (Figure  9).  In 
specimens  of  S.  altiuelis  in  the  10-  to  20-mm  size 
range,  the  pectoral  fin  length  averages  34%  of  the 
body  length  (range  of  29  to  39% h  The  pectorals 
reach  their  maximum  relative  length  in  20-  to 
40-mm  pelagic  juveniles  where  they  average  39% 
of  the  body  length  (range  of  35  to  41%).  In  pelagic 
juveniles  40  to  50  mm  long  the  average  is  35% 
(range  of  32  to  37%  ),  and  the  fins  are  still  shorter 
in  early  benthic  juveniles  42  to  60  mm  long  where 
they  average  29^7r  of  the  body  length  (range  of  25 


876 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 


*V''-v!??"c'«^-^-."pV---V-'\Vv'-*''""-';^"'*-^  '''~^~^'-'yk'  '  -'fc'^\* '  ~i'  '■  ^ 


Figure  6. — Juveniles  oi  Sebastolobus  alascanus.  Above,  25.3-mm  newly  transformed  benthic  juvenile  from  bottom  trawl.  Below, 

50.3-mm  benthic  juvenile  from  bottom  trawl. 


to  33^).  The  pectoral  fins  ofS.  alascanus  are  con- 
siderably shorter  than  those  of  S.  altivelis  at 
comparative  sizes.  In  specimens  10  to  20  mm  long 
fin  length  averages  29%  of  body  length  (range  of 
26  to  31%).  In  10-  to  27-mm  pelagic  specimens 
pectoral  fin  length  averages  29%  of  the  body 
length  (range  of  26  to  32%).  In  early  benthic 
juveniles  22  to  60  mm  long,  fin  length  is  reduced 
to  an  average  of  24%  (range  of  23  to  28%).  The 
pectoral  fin  in  pelagic  juveniles  of  S.  macrochir  is 
even  longer  than  in  S.  altivelis.  In  21-  to  30-mm 
specimens  fin  length  averaged  43%  of  the  body 
length  (range  of  40  to  44%). 

The  depth  of  the  pectoral  fin  base  is  a  particu- 
larly useful  character  in  distinguishing  the  lar- 
vae of  Sebastolobus  from  those  of  Sebastes  and  is 
also  useful  in  separating  the  two  species  of 
Sebastolobus  (Figure  10).  In  larvae  of  Sebastes 


examined  (e.g.,  S.  paucispinis)  the  depth  of  the 
fin  base  is  about  9  or  10%  of  the  body  length 
through  notochord  flexion;  thereafter  it  gradually 
diminishes,  relative  to  body  length,  to  about  5  or 
6%  in  the  smallest  pelagic  juveniles.  In  Sebas- 
tolobus there  is  an  opposite  trend  of  relative  in- 
crease from  an  average  of  ll%f  (range  of  10  to 
15%  )  in  pre-flexion  larvae,  to  18%  (range  of  15  to 
20%)  in  subsequent  stages  of  S.  altivelis  up  to 
about  40  mm  in  length.  In  larger  pelagic 
juveniles  of  S.  altivelis  the  depth  of  the  pectoral 
fin  base  begins  to  decrease  in  relation  to  body 
length.  In  40-  to  50-mm  specimens  the  average  is 
16.5%  (range  of  15  to  18%)  and  in  50-  to  56-mm 
pelagic  juveniles  it  is  15%  (range  of  15  to  16%).  It 
is  further  reduced  to  14%  (range  of  13  to  15%)  in 
42-  to  60-mm  benthic  juveniles.  The  pectoral  fin 
base  in  S.  alascanus  is  significantly  shallower 


877 


FISHERY  BULLETIN:  VOL.   72,  NO.  4 


Figure  7. — Pelagic  juvenile  of  Sebastolobus  macrochir  from  off  Kamchatka  (27.2  mm). 


than  in  S.  altivelis.  In  S.  alascanus  larvae  and 
pelagic  juveniles  10  to  30  mm  long  the  fin  depth 
averages  14%  of  the  body  length  (range  of  12  to 
16%).  In  22-  to  60-mm  benthic  juveniles  this  is 
reduced  to  an  average  of  10%  (range  of  9  to  11%). 

Ossification  of  the  pectoral  fin  rays  begins  in 
6.0-mm  larvae  of  Sebastolobus  (Table  5).  The  full 
complements  of  pectoral  rays,  23  to  24  for  S.  al- 
tivelis and  21  to  22  for  S.  alascanus,  are  present 
in  7-mm  larvae  (Tables  5,  6). 

The  pelvic  fin  buds  appear  in  larvae  of  about 
6.0  mm  and  elongate  to  about  12%  of  the  body 
length  by  the  completion  of  notochord  flexion.  Fin 
length  increases  to  about  17  to  18%  of  the  body 
length  in  post-flexion  larvae  up  to  10  mm  in 
length.  In  S.  altivelis  this  increases  further  to 
about  24%  in  pelagic  juveniles  20  mm  long,  and 
averages  24%  (range  of  21  to  27%)  for  the  re- 
mainder of  the  pelagic  phase.  There  is  a  slight 
decrease  to  22%  (range  of  21  to  24%)  in  benthic 
juveniles  up  to  60  mm  long.  The  pelvic  fin  is 
slightly  shorter  in  S.  alascanus  averaging  19% 
(range  of  18  to  20% )  in  10-  to  20-mm  specimens, 
and  21%  (range  of  18  to  33%)  in  larger  pelagic 
juveniles  and  in  benthic  juveniles  up  to  60  mm 
long.  The  full  complements  of  one  spinous  ray 
and  five  soft  rays  are  beginning  to  ossify  in  7-mm 
larvae  ofS.  altivelis  and  S.  alascanus. 

The  hypural  thickening  of  the  caudal  fin  first 
appears  in  larvae  about  3.5  mm  long.  The  hypu- 
rals  begin  to  ossify  in  7-mm  larvae  of  both  species 


and  the  full  complements  of  two  superior  and  two 
inferior  elements  are  ossified  in  12-mm  larvae  of 
both  species.  The  full  complements  of  eight 
superior  and  seven  inferior  principal  caudal  rays 
are  beginning  to  ossify  in  7-mm  larvae  o{ Sebas- 
tolobus. The  procurrent  caudal  rays  also  begin  to 
ossify  in  7-mm  larvae.  The  full  complements  of  6 


.•'' 


STONDiRD    LENGTH    Imiu) 


Figure  8. — Relationship  of  body  depth  to  body  length  in  de- 
velopmental stages  of  Sebastolobus.  Small  dots  =  larvae  less 
than  10  mm  not  identifiable  to  species.  Large  open  circles  = 
larvae  and  pelagicjuveniles  ofS.  altivelis.  Large  dots  =  benthic 
specimens  of  S.  altivelis.  Open  triangles  =  larvae  and  pelagic 
juveniles  of  S.  alascanus.  Solid  triangles  =  benthic  specimens  of 
S.  alascanus.  Solid  squares  =  pelagic  specimens  of  S.  mac- 
rochir. Lines  fitted  by  method  of  least  squares.  No  regression 
line  drawn  for  S.  macrochir. 


878 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 


to  9  superior  and  7  to  9  inferior  procurrent  rays 
are  present  in  10-mm  larvae  of  S.  altivelis  and  the 
full  complements  of  8  to  10  superior  and  inferior 
elements  are  present  in  12-  to  13-mm  larvae  of  S. 
alascanus. 

The  dorsal  and  anal  fins  begin  to  develop  in 
6-mm  larvae  of  Sebastolobus  and  the  full  com- 
plements of  rays  are  ossifying  in  7-mm  larvae  of 
both  species.  In  S.  altivelis  the  usual  number  of 
spinous  dorsal  rays  is  15  and  in  S.  alascanus  the 
usual  number  is  16.  Both  species  have  8  to  10  soft 
dorsal  rays  with  a  usual  number  of  9. 

Pigmentation 

The  melanophore  pattern  of  embryos  and  yolk- 
sac  larvae  of  Sebastolobus  has  been  described  by 
Pearcy  ( 1962 ).  At  the  beginning  of  the  larval  stage 
(3.5  mm)  the  melanophore  pattern  is  distinctive. 
Large  median  melanistic  blotches  oppose  each 
other  about  midway  back  on  the  tail  (Figure  lA, 


30  30  ' 

STANDARD    LENGTH    (mm) 


Figure  9. — Relationship  of  pectoral  fin  length  to  body  length  in 
Sebastolobus.  Symbols  as  in  Figure  8. 


.,^' 


20  30  40 

STANDARD    LENGTH  Imml 


Figure  10. — Relationship  of  depth  of  pectoral  fin  base  to  body 
length  in  Sebastolobus.  Symbols  as  in  Figure  8. 


B).  In  some  specimens,  the  blotches  are  expanded 
to  form  a  band.  Also,  melanophores  cover  the  dor- 
solateral surfaces  of  the  posterior  region  of  the 
gut.  The  melanistic  tail  blotches  are  transitory; 
they  are  lost  in  some  larvae  as  small  as  4.2  mm 
and  one  or  both  are  absent  in  most  larvae  between 
5.0  and  6.0  mm  in  length.  The  dorsal  spot  was 
absent  in  all  larvae  larger  than  6.0  mm  and  the 
ventral  spot  was  absent  in  all  larger  than  6.4  mm. 
In  contrast,  the  gut  pigment  is  augmented 
throughout  the  larval  period,  extending  forward 
to  the  axillary  region  and  internally  anterior  to 
the  cleithrum  in  larvae  about  5.0  mm  long.  When 
the  larvae  reach  6.0  mm  the  pigment  extends  onto 
the  ventral  surface  of  the  gut  and  dorsally  as 
deeply  embedded  pigment  at  the  nape.  With  con- 
tinued development  the  melanophores  form  a 
solid  sheath  on  the  peritoneum  surrounding  the 
gut. 

Melanophores  appear  at  the  posterior  margin  of 
each  pectoral  fin  in  some  larvae  as  small  as  4.0 
mm.  About  half  the  larvae  examined  between  4.0 
and  5.0  mm  have  this  posterior  margin  of  fine 
melanophores  and  the  pigment  is  present  in  all 
larvae  in  the  5.0-  to  11.0-mm  range.  The 
melanophores  are  then  lost,  and  almost  all  larvae 
larger  than  11.0  mm  have  pigmentless  fins. 

Melanophores  appear  on  the  posterior  lobes  of 
the  brain  in  5.2-  to  7.0-mm  larvae  and  are  present 
in  all  larvae  larger  than  this.  They  also  appear 
above  the  anterior  lobes  of  the  brain  in  larvae 
between  7.0  and  9.0  mm  in  length  and  in  most 
larvae  larger  than  9.0  mm. 

Juvenile  pigmentation  begins  to  appear  in  some 
specimens  of  S.  altivelis  of  the  14-  to  20-mm  size 
range.  On  the  head,  patches  of  melanophores  ap- 
pear on  the  opercle,  cheek,  snout,  and  jaws.  In 
most  specimens  larger  than  22  mm,  the  patches 
are  confluent,  and  the  head  is  generally  dusky 
with  darker  areas  at  the  opercle  and  along  the 
upper  jaw. 

A  patch  of  melanophores  appears  superficially 
over  each  side  of  the  gut  in  specimens  as  small  as 
14  mm.  These  patches  expand  to  form  a  solid 
melanistic  sheath  in  some  specimens  of  the  14-  to 
20-mm  size  range.  The  posterior  margin  of  the 
sheath  is  an  arc  running  from  the  vent  to  the  nape 
and  stands  out  sharply  against  the  pigmentless 
region  of  the  trunk  posterior  to  the  sheath.  With 
continued  development  the  pigment  sheath  ex- 
pands posteriad  and  is  a  striking  feature  of  the 
pelagic  juveniles.  In  the  20-  to  30-mm  size  range 
the  sheath  extends  posteriad  to  a  vertical  from  the 


879 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


first  or  second  anal  fin  spines.  In  the  30-  to  40-mm 
size  range  the  sheath  extends  posteriad  to  the  2nd 
or  3rd  anal  spine  in  most  specimens  and  to  the  soft 
dorsal  fin  in  some.  In  most  pelagic  juveniles  of  the 
40-  to  50-mm  size  range  the  dusky  sheath  extends 
back  to  the  soft  dorsal  and  it  does  so  in  all  speci- 
mens of  the  50-  to  60-mm  size  range.  When  the 
juveniles  become  benthic,  the  dusky  sheath  ex- 
tends posteriad  to  the  caudal  fin. 

The  fins  become  deeply  and  characteristically 
pigmented  in  juveniles  of  S.  altivelis.  The  an- 
terior portion  of  the  spinous  dorsal  fin  becomes 
melanistic  in  specimens  as  small  as  18  mm.  In 
juveniles  of  the  20-  to  25-mm  size  range  the  an- 
terior one-half  to  two-thirds  of  the  fin  is  melanis- 
tic. In  the  25-  to  30-mm  range  three-fourths  or 
more  of  the  fin  is  black.  In  pelagic  juveniles 
larger  than  this  the  pigment  has  spread  onto  the 
soft  dorsal  fin,  and  covers  both  the  soft  dorsal  and 
soft  anal  fins  in  benthic  juveniles. 

The  bases  of  the  pectoral  fins  begin  to  be  covered 
with  melanophores  in  specimens  as  small  as  14 
mm.  In  specimens  as  small  as  18  mm  the  melano- 
phores extend  onto  the  basal  region  of  the 
rays.  With  further  growth  this  black  basal  zone 
enlarges  posteriad  and  becomes  a  highly  charac- 
teristic feature  of  the  pelagic  juveniles.  The  pos- 
terior mar^n  of  this  zone  contrasts  sharply  with 
the  distal  clear  region  of  the  fin.  In  juveniles  of  the 

19-  to  25-mm  size  range  the  width  of  the  black 
basal  zone  averaged  20%  of  the  fin  length.  En- 
largement of  this  zone  is  shown  by  the  average 
relative  widths  for  successive  size  ranges  (25  to  30 
mm,  38% ;  30  to  35  mm,  46% ;  35  to  40  mm,  54% ;  40 
to  45  mm,  65%;  45  to  50  mm,  72%;  50  to  55  mm, 
76%).  Towards  the  end  of  the  pelagic  juvenile 
stage  a  pale  translucent  layer  covers  the  basal 
region  of  the  pectoral  fin  and  thus  gives  the  black 
zone  the  appearance  of  a  band.  The  huge  pectoral 
fins,  each  with  their  broad  black  band,  are  dis- 
tinctive features  of  the  pelagic  juveniles  of  S.  al- 
tivelis. When  the  juveniles  become  benthic  the 
black  zone  extends  to  the  tips  of  the  fins.  Like  the 
pectoral  fins,  the  pelvic  fins  also  develop  a  black- 
pigment  zone  that  enlarges  with  development.  In 

20-  to  25-mm  juveniles  the  basal  one-quarter  to 
three-quarters  of  each  fin  may  be  black,  although 
in  the  majority  of  specimens  the  basal  one-half  is 
black.  In  the  25-  to  30-mm  range  most  specimens 
have  three-fourths  or  more  of  the  fin  black  and  in 
juveniles  larger  than  30  mm  either  the  fin  is  en- 
tirely black  or  the  extreme  tips  of  the  rays  are 
pigmentless. 


Juvenile  pigment  begins  to  appear  in  S.  alas- 
canus  in  the  14-  to  20-mm  size  range.  The  first 
head  pigment  to  appear  is  a  melanistic  blotch  on 
the  posterior  region  of  the  opercle.  This  gradually 
spreads  anteriorly  onto  the  cheek  and  in  late- 
stage  pelagic  juveniles  the  entire  head  is  speckled 
with  melanophores.  A  blotch  begins  to  form  over 
each  side  of  the  gut  in  larvae  as  small  as  15  mm. 
These  enlarge  dorsad  onto  the  spinous  dorsal  fin 
and  posteriad  as  an  irregular  mottled  sheath  that 
contrasts  markedly  with  the  solidly  pigmented 
sheath  of  S.  altivelis  juveniles.  In  the  largest 
pelagic  juveniles  the  mottling  on  the  dorsal  fin  and 
trunk  extends  posteriad  to  a  vertical  from  the 
vent.  When  the  juveniles  become  benthic  the 
mottling  spreads  onto  the  remainder  of  the  body 
and  median  fins.  Melanophores  appear  on  the 
bases  of  the  pectoral  fins  in  specimens  of  the  14-  to 
20-mm  size  range.  A  faint  band  of  melanophores 
appears  on  the  rays  in  some  specimens  of  this  size 
range  but  never  becomes  highly  developed  and 
covers  only  the  basal  one-third  of  the  fin  in  the 
largest  pelagic  juveniles.  Likewise  a  faint  band  of 
pigment  develops  on  each  pelvic  fin  in  specimens 
as  small  as  16  mm  and  only  covers  the  basal  half  of 
the  fin  in  the  largest  pelagic  juveniles.  When  the 
juveniles  become  benthic  the  pectoral  fins  develop 
a  pattern  of  four  narrow  irregular  bands. 

DISTRIBUTION 

The  genus  Sebastolobus  has  an  exceptionally 
wide  latitudinal  distribution  in  the  eastern 
Pacific.  Sebastolobus  altivelis  ranges  from  the 
Aleutian  Islands  southward  to  Cape  San  Lucas, 
Baja  California,  andS.  alascanus  inhabits  waters 
from  the  Bering  Sea  to  northern  Baja  California 
(Barsukov,  1964;  Miller  and  Lea,  1972).  The  ex- 
tensive north-south  range  of  Sebastolobus  is 
probably  related  to  habitat  depth  rather  than 
eurythermy.  They  are  deep-living  species 
throughout  their  latitudinal  range  and,  as  such, 
experience  little  change  in  habitat  temperature 
towards  the  southern  end  of  their  range.  Alver- 
son  et  al.  (1964)  reported  that  significant  catches 
of  Sebastolobus  are  taken  at  depths  shallower 
than  150  fathoms  in  the  trawl  fishery  from 
Oregon  to  southeastern  Alaska,  but  that  the  per- 
centage contribution  of  Sebastolobus  increased 
with  depth.  At  the  maximum  depth  range  sam- 
pled, 500  to  600  fathoms,  Sebastolobus  accounted 
for  about  70%  of  the  total  fish  catch.  Southward  of 
Oregon  the  shoaler  elements  of  the  Sebastolobus 
populations  are  gradually  eliminated  and,  off 


880 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 


southern  California,  adults  of  even  the 
shallower-living  species,  S.  alascanus,  are  gener- 
ally restricted  to  waters  deeper  than  150  fathoms. 

Curtailment  of  spawning  or  mortality  of  fer- 
tilized eggs  off  southern  California  is  evident 
from  the  distribution  of  Sebasfolobus  larvae  in 
the  CalCOFI  sampling  area  (Figures  11,  12).  In 
1966,  there  were  no  occurrences  south  of  line  97, 
which  runs  seaward  from  the  Mexican  border, 
and  in  1969  Sebastolobus  occurred  on  only  two 
stations  below  this  line.  It  is  apparent  that  the 
CalCOFI  sampling  pattern  did  not  encompass  the 
offshore  limits  of  larval  distribution  and  that  lar- 
vae occur  well  seaward  of  the  200  to  250  mile 
coastal  zone  sampled  during  these  years. 

The  seasonal  abundance  of  Sebastolobus  larvae 
for  1966  and  1969  is  shown  in  Table  7.  In  1966 
larvae  were  taken  from  April  to  October  in  cen- 
tral and  southern  California.  Numbers  of  larvae 
and  occurrences  were  highest  in  April  and  di- 
minished in  subsequent  months.  No  larvae  were 


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Figure  11. — Stations  at  which  larvae  of  Sebastolobus  were  col- 
lected during  CalCOFI  survey  of  1966.  Dots  indicate  stations 
where  numbers  of  Sebastolobus  larvae  exceeded  mean  number 
(7.2)  for  all  positive  stations.  Area  of  frequent  occupancy  is 
outlined  (see  Ahlstrom,  1961,  for  complete  grid). 


Figure  12. — Stations  at  which  larvae  of  Sebastolobus  were  col- 
lected during  CalCOFI  survey  of  1969.  Symbols  as  in  Figure  11. 

taken  south  of  southern  California  in  1966.  In 
1969,  larvae  appeared  earlier  in  the  year,  from 
January  to  December  off  central  California,  from 
January  to  October  off  southern  California,  and 
from  June  to  September  off  northern  Baja 
California.  Again,  numbers  of  larvae  and  occur- 
rences peaked  in  April  off  central  and  southern 
California.  Data  for  the  two  species  are  lumped 
together  in  Table  7.  Of  the  larvae  identifiable  to 
species,  those  over  10  mm,  6%  were  S.  alascanus 
in  1966  and  12%  wereS.  alascanus  in  1969.  Thus, 
the  data  in  Table  7  pertain  largely  to  S.  altivelis. 

Although  Sebastolobus  larvae  are  taken  in 
plankton  tows  over  a  large  proportion  of  the  year, 
the  spawning  season  is  relatively  short.  Table  8 
shows  the  seasonal  change  in  the  size  of  Sebas- 
tolobus larvae.  The  mean  size  increases  steadily 
throughout  the  year  and  small,  recently  spawned 
larvae,  less  than  5  mm,  do  not  occur  after  June  in 
1966  and  May  in  1969.  This  indicates  a  spawning 
season  of  4  or  5  mo. 

Information  on  the  growth  rate  of  the  pelagic 
juveniles  of  both  species  of  Sebastolobus  was  ob- 
tained by  examining  mid-water  trawl  samples 


881 


FISHERY  BULLETIN:   VOL.  72,  NO.  4 


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from  the  Los  Angeles  County  Museum,  Scripps 
Institution  of  Oceanography,  and  the  Southwest 
Fisheries  Center.  A  total  of  260  samples  from  the 
years  1950  to  1969  were  examined.  Most  of  the 
samples  were  taken  in  the  deepwater  basins  off 
southern  California,  but  two  samples  of  S.  alas- 
canus  were  taken  as  far  north  as  Crescent  City, 
Calif.,  and  one  sample  of  S.  altiuelis  was  from  the 
vicinity  of  Guadalupe  Island,  Baja  California. 

The  composite  monthly  size  frequencies  of 
mid-water  trawl  specimens  of  S.  altiuelis  are 
shown  in  Figure  13.  Two  major  size  classes  are 
present  from  May  through  September.  One  class 
is  formed  by  larvae  and  transforming  specimens, 
less  than  20  mm  in  length,  from  the  January- 
May  spawning  season.  The  other  class  is  formed 


STANDARD    LENGTH  (mm) 


Figure  13. — Composite  monthly  size  frequencies  for  larvae  and 
pelagic  juveniles  of  Se6asto/o6usa/<((;e/£s  from  mid- water  trawls. 


882 


MOSER:  DEVELOPMENT  AND  DISTRIBUTION  OF  SEBASTOLOBUS 

Table  8. — Mean  lengths  with  standard  deviations  in  mm  (A)  and  size  ranges  in  mm  (B)  of  Sebastolobus 
larvae  taken  during  2  yr  of  the  California  Cooperative  Oceanic  Fisheries  Investigations. 


year 

Month 

Jan. 

Feb. 

Apr. 

May 

Jun. 

A 

B 

A 

B 

A 

B 

A 

B 

A 

B 

1966 
1969 

3.1  ±  0.65 

2.8  -  3.4 

3.0  +  0.47 

2.8  -  3.4 

4.3  ±  1.07 
3.6  ±  0.76 

2.2-6.9 
2.6  -  4.7 

6.2  ±  1.16 
4.2  ±0.98 

4.2  -  7.8 
3.1  -  5.2 

7.4  ±  1.  1" 
8.6  +  0.68 

5.  1  -  10.0 
8.1-     8.9 

V>.-ir 

Month 

Jul. 

Aug. 

Sep. 

Oct. 

Dec.          1 

A 

B 

A 

B 

A 

B 

A 

B 

A 

B 

19G6 
ri,9 

3.  7  i  1. 15 
10.8  ±  1.15 

6.2  -  11.2 
8.9  -  13.2 

U.6  ±  1.42 
11.8  ±  1.58 

9.2  -  15.2 
9.2  -  18.2 

14.0  +  1.57 
17.0  ±  1.  10 

9.2  -  17.7 
16.2  -  17.9 

16.4  +  1.37 
16.3  ±  1.43 

14.4  -  19.3 
15.2  -  18. G 

15.0 

15.0 

by  large  pelagic  juveniles  from  the  previous 
year's  spawning  season.  A  single  size  class  of 
transforming  specimens  is  present  in  October  and 
November,  however,  the  absence  of  the  large 
pelagic  juveniles  is  probably  due  to  inadequate 
sampling,  since  they  are  present  in  December. 
From  January  through  April  a  single  class  of 
pelagic  juveniles  is  present.  In  summary,  the 
early  life  history  of  S.  altiuelis  is  as  follows:  lar- 
vae are  produced  in  a  4-  or  5-mo  spawning  season 
that  peaks  in  April.  Transformation  into  pelagic 
juveniles  begins  as  early  as  July  and  by  the  end  of 
December  most  have  completed  transformation. 
The  prolonged  pelagic  juvenile  stage  lasts  until 
the  following  summer  when  the  juveniles  begin 
to  settle  to  the  bottom.  This  process  probably  ex- 
tends over  a  6-  to  8-mo  period  with  some  juveniles 
remaining  pelagic  until  December.  The  total 
period  spent  in  the  pelagic  environment  from 
spawning  to  settling  is  about  20  mo.  The  means  of 
the  composite  monthly  length  frequencies  are 
plotted  in  Figure  14  to  give  an  estimation  of 
growth  of  this  species. 

The  composite  monthly  length  frequencies  for 
mid-water  trawl-caught  specimens  of  S.  alas- 
canus  are  shown  in  Figure  15.  In  contrast  to 
S.  altivelis,  only  a  single  size  class  is  present 
each  month.  From  July  to  December  a  single 
class  of  larval  and  transitional  specimens  less 
than  20  mm  long  is  present.  Some  pelagic 
juveniles  are  present  in  December  and  by 
January  most  of  the  specimens  have  completed 
transformation.  Successive  samples  from  Feb- 
ruary to  May  contain  only  pelagic  juveniles.  In 
summary,  the  planktonic  and  early  pelagic  life 
history  of  S.  alascanus  is  similar  to  that  of  S. 


altivelis.  A  probable  4-  or  5-mo  spawning  period 
that  peaks  in  April  gives  rise  to  larvae  that  ap- 
pear in  mid-water  trawl  samples  in  summer. 
Transformation  into  the  pelagic  juveniles  begins 
as  early  as  August  and  most  have  completed 
transformation  by  the  end  of  December.  A  class  of 
pelagic  juveniles  is  present  from  December 
through  May,  however,  the  size  ranges  for  these 
months  overlap  the  range  at  which  S.  alascanus 
juveniles  begin  to  settle  to  the  bottom,  and  it  is 


E 
S 

I 
o 


Q 

a: 
< 

a 

z 
< 

h- 
tn 


Figure  14. — Means  of  composite  monthly  size  frequencies  of 
larvae  and  pelagic  juveniles  of  Sebastolobus  altivelis  and  S. 
alascanus  from  mid- water  trawls. 


883 


FISHERY   BULLETIN:   VOL.   72,  NO.  4 


oi— 


a. 


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UJ 
OD 

3 


2- 

3- 

2- 

0  — 
2 

0 


4 
2 

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0 
4 
2 
0 

4 

2 

0 

4|- 

2- 

0 

4 

2 

0 


10 


15 


20 


STANDARD     LENGTH   ( 


Figure  15. — Composite  monthly  size  frequenc 
pelagic  juveniles  of  Sebastolobus  alascanus 
trawls. 


MAY 

-I — I 

APR 

— ' — I 

MAR 


FEB 


JAN 


DEC 


NOV 

— ' — I 


OCT 

—I — I 


AUG 


JUL 
30 


25 

mm) 

es  for  larvae  and 
from  mid-water 


probable  that  settling  begins  as  early  as  January. 
Most  have  become  benthic  by  May  or  June.  The 
pelagic  juvenile  stage  in  this  species  is  short- 
lived compared  with  S.  altivelis  and  the  total 
period  spent  in  the  pelagic  environment  from 
spawning  to  settling  is  about  14  or  15  mo.  The 
means  of  the  composite  monthly  frequencies  are 
plotted  in  Figure  14. 

ACKNOWLEDGMENTS 

The  illustrations  of  the  larvae  and  juveniles 
were  prepared  by  George  Mattson.  Makoto  Ki- 
mura  helped  greatly  in  analyzing  the  length- 
frequency  data  on  trawl-caught  specimens.  John 
Butler,  William  Lenarz,  and  Richard  Rosenblatt 
provided  valuable  advice  and  Elaine  Sandknop 
and  Elizabeth  Stevens  furnished  technical  assis- 
tance. I  am  especially  indebted  to  Elbert  Ahlstrom 
for  his  help  and  encouragement  throughout  this 
study.  Lo-chai  Chen  of  California  State  Univer- 


sity, San  Diego,  read  the  manuscript  and  offered 
helpful  suggestions. 

LITERATURE  CITED 

Ahlstrom,  E.  H. 

1961.  Distribution  and  relative  abundance  of  rockfish 
(Sebastodes  spp.)  larvae  off  California  and  Baja  Califor- 
nia. Rapp.  P.-V.  Reun.  Cons.  Perm.  Int.  Explor.  Mer 
150:169-176. 

Alverson,  D.  L.,  a.  T.  Pruter,  and  L.  L.  Ronholt. 

1964.  A  study  of  demersal  fishes  and  fisheries  of  the  north- 
eastern Pacific  Ocean.  H.  R.   McMillan  Lectures  in 
Fisheries,  Inst.  Fish.,  Univ.  B.  C,  Vancouver,  190  p. 
Barsukov,  V.  V. 

1964.  Key  to  the  fishes  of  the  family  Scorpaenidae.  In  P.  A. 
Moiseev  (editor),  Soviet  fisheries  investigations  in  the 
northeast  Pacific.  Part  3,  p.  226-262.  (Translated  from 
Russ.  by  Israel  Program  Sci.  Transl.,  1968;  available 
U.S.  Dep.  Commer.,  Clearinghouse  Fed.  Sci.  Tech.  Inf., 
Springfield,  VA,  as  TT  67-51205.) 
Best,  E.  A. 

1964.   Spawning  of  longspine  channel  rockfish,  Sebas- 
tolobus altivelis  Gilbert.  Calif.  Fish  Game  50:265-267. 
HUBBS,  C.  L. 

1926.  The  supposed  intergradation  of  the  two  species  of 
Sebastolobus  (a  genus  of  scorpaenoid  fishes)  of  western 
America.  Am.  Mus.  Novit.  216,  9  p. 
Matsubara,  K. 

1943.  Studies  on  the  scorpaenoid  fishes  of  Japan.  Part  I. 
Trans.  Sigenkagaku  Kenkyusyo  1,  170  p. 
Miller,  D.  J.,  and  R.  N.  Lea. 

1972.  Guide  to  the  coastal  marine  fishes  of  California. 
Calif.  Dep.  Fish  Game,  Fish  Bull.  157,  235  p. 
Moser,  H.  G. 

1967.  Reproduction  and  development  of  Sebastodes 
paucispinis  and  comparison  with  other  rockfishes  off 
southern  California.  Copeia  1967:773-797. 
1972.  Development  and  geographic  distribution  of  the 
rockfish,  Sebastes  macdonaldi  (Eigenmann  and  Beeson, 
1893),  family  Scorpaenidae,  off  southern  California  and 
Baja  California.  Fish.  Bull.,  U.S.  70:941-958. 
Pearcy,  W.  G. 

1962.  Egg  masses  and  early  developmental  stages  of  the 
scorpaenid  fish,  Sebastolobus.  J.  Fish.  Res.  Board  Can. 
19:1169-1173. 

Phillips,  J.  B. 

1957.  A  review  of  the  rockfishes  of  California  (family  Scor- 
paenidae). Calif.  Dep.  Fish  Game,  Fish  Bull.  104,  158  p. 
Starks,  E.  G. 

1898.  The  osteological  characters  of  the  genus  Sebas- 
tolobus. Proc.  Calif.  Acad.  Sci.,  Ser.  3,  Zool.  1:361-370. 


884 


SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY, 

ENGRAULIS  MORDAX 

William  J.  Vlymen  in* 

ABSTRACT 

A  modification  of  Gray  and  Hancock's  theoretical  method  for  studying  propulsion  of  spermatozoa  was 
used  to  estimate  the  energy  expenditure  of  swimming  anchovy,  Engraulis  mordax,  larvae.  Wave 
parameters  obtained  from  photographs  of  feeding  anchovy  larvae  were  incorporated  into  a  time 
dependent  sinusoidal  body  displacement  function  which  is  used  in  the  iterated  energy  integrals  of  the 
model.  The  integrals  were  numerically  evaluated  by  2-dimensional  16-point  Gaussian-Legendre 
quadrature.  The  results  for  the  mean  larval  length  of  1.4  cm  was  144.8  ergs/swimming  excursion  or 
4.91  X  lO'^^cal/Ti  using  known  excursion  rates.  O2  consumption  measurement  of  similar  size  larvae 
indicate  a  2.19  x  IQ-^cal/h  requirement.  Extension  to  other  larval  sizes  can  be  made  using  this  model 
with  certain  qualifications.  The  relationships  of  swimming  energetics  to  larval  fish  behavior  are 
discussed.  Current  theories  of  large  amplitude  intermittent  swimming  are  also  discussed  in  light  of 
the  high  swimming  efficiencies  encountered  in  this  study. 


The  theoretical  evaluation  of  swimming  fish 
energetics  by  hydrodynamic  analysis  has  been  an 
extensively  treated  subject  in  recent  years.  Most 
of  these  treatments  however  have  concentrated 
on  calculation  of  thrust  and  thrust  efficiencies 
with  the  exception  of  Lighthill  (1970,  1971)  who 
gave  direct  estimates  for  the  mean  swimming 
work  rate  and  has  drawn  attention  to  the  impor- 
tance of  the  accelerative,  virtual  mass  contribu- 
tions in  estimates  of  mean  swimming  work  rate. 
Most  expositions,  however,  deal  with  situations 
where  inertial  effects  predominate  with  all  sub- 
sequent derivations  being  consistent  with  that 
assumption  (Taylor,  1952a).  The  low  Reynolds 
number  range  of  swimming  energetics  primarily 
of  spermatozoa,  has  also  been  extensively  treated 
(Taylor,  1951,  1952b;  Gray  and  Hancock,  1955; 
Carlson,  1959;  Holwill  and  Miles,  1971).  All  these 
treatments  disregard  inertial  and  accelerative  ef- 
fects in  comparison  with  viscous  effects  in  their 
treatment.  Also,  both  viscous  and  inertial  treat- 
ments calculate  or  estimate  the  mean  swimming 
work  rate  after  steady  motion  has  been  estab- 
lished. 

The  problem  attacked  in  this  paper  is  a  syn- 
thesis and  extension  of  the  two  classes  of  treat- 
ments discussed  above,  specifically  to  determine 
the  energy  expended  per  excursion  by  the  1-cm 


'Southwest  Fisheries  Center,  National  Marine  Fisheries  Ser- 
vice, NOAA,  P.O.  BOX  271,  La  Jolla,  CA  92037  and  Scripps 
Institution  of  Oceanography,  University  of  California,  San 
Diego,  La  Jolla,  CA  92037. 


larval  anchovy,  Engraulis  mordax.  The  term  ex- 
cursion as  used  here  requires  some  elaboration. 
Larval  anchovies  have  a  peculiar  swimming  be- 
havior because  they  do  not  continuously  propa- 
gate caudally  directed  waves.  In  the  adult  form 
this  behavior  is  noticeable  by  observing  the  tail, 
i.e.,  it  does  not  beat  continuously  even  though  the 
fish  appears  to  maintain  constant  forward  mo- 
tion. In  the  larval  stages,  however,  this  behavior 
results  in  an  obvious  discontinuous  motion.  The 
result  is  a  series  of  bursts  of  motion  from  rest  to 
rest  which  hereafter  I  refer  to  as  excursions. 

The  estimation  of  excursion  energetics  by  a 
theoretical  model  rather  than  indirect  metabolic 
estimators  during  excursions  is  demanded  be- 
cause of  the  small  size  of  the  organisms  consid- 
ered, their  discontinuous  motion,  and  the  inves- 
tigator's inability  to  determine  which  fraction  of 
the  total  energy  consumption  is  due  to  swimming 
alone. 

The  parameters  used  in  the  model  to  calculate 
the  excursion  energy  are  taken  from  photographs 
of  a  larval  anchovy  of  a  specified  size  executing 
excursions  in  search  of  prey  organisms.  Since  the 
search  for  prey  constitutes  a  large  proportion  of 
the  larva's  activity,  following  Kerr  ( 1971)  we  can 
write  the  total  metabolism  of  the  larva  as, 


where  T  j       =  total  metabolism 


=  cost  of  search  for  prey 


Manuscript  accepted  January  1974. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 


885- 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Tr 


standard  metabolism 

internal  cost  of  food  utilization. 


The  growth  efficiency  and  subsequent  relations 
derived  from  Ty.  are  important  in  estimating  fish 
yields  in  relation  to  standing  food  resources  and 
other  factors  important  to  fisheries  management. 
It  is  this  larger  view  which  gives  relevance  to  the 
rather  involved  procedure  of  simply  calculating 
one  part  of  the  value  of  T-,,  namely  Tp. 

THEORY 

The  derivation  of  the  excursion  energy  esti- 
mate is  based  on  Gray  and  Hancock's  (1955)  de- 
velopment for  spermatozoa.  Instead  of  a  cylinder 
with  an  inert  head  attached,  the  anchovy  larva  is 
regarded  here  as  a  ribbon  or  plate  of  specified 
width  attached  to  an  inert  head  (Figure  1).  The 
assumption  that  the  body  is  a  ribbon  is  justified 
only  if  the  ratio  of  the  width  to  thickness  (Wit)  is 
»  1.  In  the  larvae  examined  in  this  study  this 
ratio  averaged  2.5.  While  this  ratio  is  not  »  1  I 
have  assumed  that  it  is  to  simplify  the  problem. 
However,  the  error  introduced  is,  I  believe,  min- 
imal. 

From  Figure  1  the  following  relation  is  noted 
and  will  be  used  in  the  following  derivations: 


With  the  body  approximated  as  an  inextensible 
ribbon  we  find  the  use  of  the  normal  drag 
coefficient,  Ca^  ,  and  the  tangential  drag 
coefficient,  C^,  convenient  in  addition  to  an  ap- 
propriate sagittal  contour  function  h{s  )  where  s 
denotes  distance  along  the  spine  of  the  fish  (see 
Figure  4). 

The  expression  for  the  velocities  Vy  and  Vj  is 
first  expressed  in  terms  of  the  function  which  rep- 
resents the  propagated  wave  along  the  body 
y{x,t),  and  V^^  .  By  noting, 

dy  dy 

Vy  =  —  and  tan  9  =^- 

dt  dx 

we  can  rewrite  Equations  (1)  and  (2)  as. 


V^         dy  dy 

T-  ■=  — Vr  —, —  and 

cos  Q       dt  dx 


Vj     _   dy   dy 
COS0   ~  ~dt  ~dx 


Given    cos  Q 


1 


[1  +  tan2  0]i2 


1  + 


m 


1/2 


we 


-'  -^- 1 -.!][€): 


-1/2 


(!') 


y  V  =  ^v  cos  e   -  y,  sin  e 

Vr^  =  Vy  sin  e   +  V,  COS  B 

where  V^  =  normal  velocity  of  an  element 
of  body 
Vf  =  tangential  component 
Vy   =  ^-component 
V^  =  x-component. 


(1) 


(2) 


Figure  1. — Diagram  illustrating  the  relationship  of  the  velocity 
components  of  an  element  of  body  when  moving  transversely  in 
the  X-direction. 


i. 


^^      \dt  dx       ^' 


]  [  ^m 


-1/2 


(2') 


Now  we  may  proceed  to  write  the  contributions  to 
the  total  work  of  excursion  made  by  the  head, 
body  viscous  reactive  terms,  and  accelerative 
body  virtual  mass. 

The  element  of  work  performed  in  moving  the 
inert  head  is  given  by, 

dV 
dW^  =1/2  p  Cf^A  ^3  dt  +  (m  +  M)  ^  V,  dt 


(Vlymen,  1970) 

where 

dW^ 

=  element  of  work  performed 
the  head 

Ch 

=  drag  coefficient  of  the  head 

A 

=  cross-sectional  area 

m 

=  virtual  mass  of  head 

M 

P 

=  mass  of  head 

=  density  of  seawater. 

886 


VLYMEN:  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 

Thus,  given  the  time  of  excursion  as  t^  we  get, 


Wh   =  1/ 


2/      (pChAV.^ 

•/o 


dV. 


+  2{m  +  M)-^  V,)dt> 


(3) 


The  element  of  work  performed  by  the  body 
contributed  by  viscous-reactive  forces  can  be  ap- 
proximated using  experimental  values  for  the 
normal  and  tangential  drag  coefficient  of  a 
smooth  plate.  The  choices  made  are 


^  V  —  3: — 


20.37 


'iV 


Re        Re 


(Hoerner,  1965) 


(4) 


VWe     VRe 


(Schlicting,  1960)         (5) 


where  Re  is  the  appropriate  Reynolds  number  re- 
spectively. Although  these  are  primarily  low 
Reynolds  number  approximations  they  are 
within  107f  at  Re  =  30.  ThusFy,  the  normal  force 
on  a  plate  of  frontal  area  A  is  given  by 

F„=  112  O  C^;V'  A. 


N 


P   ^NV  fsl 


Since  for  any  position  along  the  fish  body 


Re  = 


2Y^h{s) 


V  the  kinematic  viscosity,  we  get  using  C^  from 
Equation  (4)  the  normal  force  dF^^  on  an  element 
of  body  ribbon  as. 

In  a  similar  manner  F^^. ,  the  tangential  force  on  a 
plate  of  total  wetted  surface  area  A,  is 

F^  =  V2pCjV^  A. 

Since  the  formula  for  Cj  above  uses  Re  =  — 7- 
where  /  is  distance  measured  along  the  body,  we 
get  the  tangential  force  dFj  on  an  element  of 
body  ribbon  as 


dFr, 


2pk, 


\rvZs 


Vj  hfs)  ds 


=  2pkr\^v1.'^^ds. 


(7) 


Multiplying  each  element  of  force  above  by  the 
element  of  distance  in  the  direction  of  that  force 
and  summing  yields, 


dW 


V.R. 


^k  ^,  V  V^    dsdt 


■N 


N 


+  2Pk^^/^Vp-^    his)  dsdt 


where  dW^f^  is  the  element  of  viscous  reactive 
work  performed  by  an  element  of  body  ribbon. 
Using  the  Equations  (1')  and  (2')  for  Vj^  and  Vt 
and  integrating  over  the  excursion  time  t^  and 
projected  body  length  excluding  the  head  we 
get, 


dsdt 


^[-(^J" 


dsdt 


where /ff  is  thejc-projected  length  ofthe  inert  head. 
Eliminating  ds  by  the  relation, 


yields  finally, 


/2 


dx 


b^mT 


As  will  be  noted  s  is  present  in  the  second  of  the 

887 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


integrals  above;  however,  later  in  the  discussion 
s  and  his)  will  be  converted  to  appropriate  func- 
tions of  X  and  t  so  that  the  integrations  may  be 
performed. 

The  accelerative  or  virtual  mass  element  of 
work  can  be  calculated  using  the  fact  that  the 
virtual  mass  of  a  flat  plate  accelerating  parallel 
to  its  normal  vector  is  equal  to  the  mass  of  the 
fluid  enclosed  in  a  circumscribing  cylinder  hav- 
ing the  plate  chord  as  diameter  (Fung,  1969). 
Hence  from  Figure  2  the  virtual  mass  is  given  by 

dM  =  p  TTh^(s)  ds 
and  the  magnitude  of  the  acceleration  by 
a  sin  ©1=  a  sinie  -  02^ 


where       a  =     a 


-1  c/v  -1    V'y 

Now  ^  =  tan     -f- and  89  =  tan      ^jf^ 

ax  y  X 

^j,        dVy       J  ,r,        dVx      .    . 
where  V  y  =  —jf-  and  V  x  =  —j^,  giving 


Figure  2. — Diagram  illustrating  body  element  undergoing  ac- 
celeration d  and  relationships  of  orientation  of  element  to  vector 
a  in  terms  of  the  angles  0,  6  i ,  82- 


dx 


and 

COSiFy  H] 


dx) 


iVy     +  Vx  ) ''-  dt 


-1  V'y  -1  Vy 

cos(tan      pTT^  -  tan     -y^ 


dt 


dt 


we  get  finally 


a  s\niQ-Q.,) 
Since 


a  sinie  -  e. 


.      /       _i  dy     ^     -1    V'y\ 
as.n(^tan      ^  ^  tan       ^j 

^   iv'y    +  V'i    Y'^  ,  we  get 


sin 


/f     -1   dy 
('""      Tx 


tan 


-1  K 

V 


^) 


Thus  the  magnitude  of  force  F^•^;  on  an  element 
of  body  ribbon  due  to  induced  mass  dM  is 

Fy,j  I  =  adM  =  pTTh'\s){V'y    +  V'x  )'''' 

.    ,,      .,  dy      ^      _,    V'y  , 
•sinltan     -^  -tan       tti-  '• 
dx  V  X 


Since  the  element  of  work  is  given  by 

dW=  \Fy!^^  \-\dx\  ■  cos(Fv'M   |  dx) 

where 
888 


dW  =  pirh^  is)  iVy  +  Vl )  ''''      {Vy  +  V'h  ''^ 


5in  ( 


sin  I  tan     -f —  tan 


-1  vy\ 

V'x  j 


■cos 


(,     -^V'y 

i'""  vi 


-  tan" 


Vy_ 
Yx 


dsdt. 


Using  the  identities  for  cos  (a  -  6  ),  sin  (a  -  b), 
and  ds  gives  finally, 

dW^  = 


where  c?W^  is  part  I  of  the  element  of  work  per- 
formed by  the  acceleration  of  the  surrounding 
fluid. 

In  addition  to  c?W/^,  above  we  also  want  the 
work  done  in  accelerating  the  body  itself  Calling 
Pg  (s)  the  linear  mass  density  of  the  body  we  get, 
using  Figure  2, 


VLYMEN:  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 

•  (vi  +  vj  )  ''» 

•  cos^tan"^  7J7 —  tan'^  -r^  )  dsdt 
where    {vl  +(4^)^)'^^    = 

P  g{s)  ds  =  dm. 


dx 


When  the  above  terms  are  expanded  we  get,  tak- 
ing account  of  f/s, 

/  dv   d  y  \ 

dW^  =  P  As)  (Vx  Vx  +—  — f) 
^11        ^        ^  dt    dt^ 

(i.(gr)-'=dxA. 

4  A 

Integrating  dW^.^  +  dW^^^iYOva  0  to  tg  in  t  and  /// 
to  /  in  X  we  get  the  accelerative  body  work, 


pendent  analogue  of  the  function  chosen  in  Hol- 
will  and  Miles  (1971). 

The  motion  pictures  used  were  obtained  from 
John  Hunter  of  the  Southwest  Fisheries  Center, 
National  Marine  Fisheries  Service,  NOAA,  and 
the  techniques  used  in  obtaining  them  are  de- 
scribed fully  (Hunter,  1972).  The  particular  se- 
quences used  were  of  fish  larvae  varying  in 
length  from  1.2  to  1.7  cm  standard  length.  All 
sequences  were  analyzed  starting  with  the  larvae 
at  rest  through  the  sine-wave  execution  and  sub- 
sequent forward  movement  to  rest  again.  The 
X-axis  was  considered  to  be  parallel  to  the  direc- 
tion of  forward  motion  as  monitored  by  a  point 
midway  between  the  eyes  of  the  fish.  This  point 
was  also  used  to  monitor  forward  progression. 

The  sequences  were  projected  with  a  16-mm 
Kodak^  analyst  projector  on  an  elevated  stand, 
through  a  right-angle  mirror  onto  a  table  en- 
closed with  a  darkened  viewing  hood.  At  the  be- 
ginning of  an  excursion  the  contour  of  the  body 
was  outlined  with  a  fine-point  pen  on  heavy-duty, 
low-absorbance  paper.  Once  the  outline  was 
traced,  the  next  frame  was  advanced  (each  frame 
representing  Vi28   of  a  second)  until  the  larva 


dsdt 


(8) 


+  ^f  f     Trh^is) 


\fv'x-V'.'\\vxV'x^^^] 
Ldx  ^  J  L  dt   dt     -■ 


[-i^(0)T 


—   dxdt. 


The  total  work  estimated  per  excursion  is  then 


given  by  the  sum  of  W'g,  W^    ,  and  W 


H- 


METHODS 

Motion  picture  photographs  (16  mm,  128  fps)  of 
swimming  and  feeding  anchovy  larvae  were  used 
to  ascertain  the  various  parameters  in  the  pro- 
posed body  displacement  function  y{x,  t)  =  A  {t) 


sm 


277 


{X  + 


dx  u- 


,^  ,  t)  where  A  (t)  is  the  wave  amp 

K{t)  dt 

litude    of    the    propagated    wave,    A  (0 


the 


wavelength  andx^.  (0  the  wave  position  as  func- 
tions of  time.  Because  of  the  intermittent  charac- 
ter of  the  motion,  variance  with  x  was  not  consi- 
dered as  important  an  independent  variable  as  t 
in  the  various  functions  comprising  3'  (x,  t).  The 
above  displacement  function  is  a  general  time  de- 


came  to  rest  again.  The  mean  excursion  time  of 
the  larvae  examined  was  12.9  frames.  The  contour 
sequences  thus  obtained  were  taken  to  be  repre- 
sentative of  the  feeding-searching  behavior  and 
were  used  in  elucidating  the  wave-form  param- 
eters. In  addition  to  the  wave-contour  param- 
eters, the  midpoint  between  the  eyes  was  moni- 
tored for  use  in  determining  Vx  and  Vx. 

When  the  above  contours  and  position  points 
were  obtained  along  with  the  proper 
magnification  factors  derived  from  knowledge  of 
the  lengths  of  the  fish  in  a  particular  film,  rele- 
vant parameter  values  from  the  tracings  were 


^Reference  to  trade  names  does  not  imply  endorsement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


889 


FISHERY  BULLETIN:  VOL,  72,  NO.  4 


directly  measured  using  a  set  of  dial  calipers 
read  to  0.01  cm. 

Many  of  the  initial  sequences  of  an  excursion 
when  viewed  with  respect  to  the  x -axis  as  defined 
above  showed  the  appearance  of  a  wave  along  the 
proximal  portion  of  the  fish  while  the  rest  of  the 
body  coincided  closely  to  thex-axis.  This  indicated 
strong  X -dependence  of  the  amplitude  in  the  ini- 
tial portion  of  the  excursion.  However,  after  three 
frames  an  almost  symmetrical  amplitude  wave 
was  observed.  Thus  the  amplitude  in  the  first  sev- 
eral frames  was  taken  as  the  maximum  length  of 
the  wave  above  the  x-axis  (Figure  3). 

The  wave  length  was  taken  as  that  length  be- 
tween two  successive  crossings  of  thex-axis  by  the 
displacement  wave  form.  During  the  later  part  of 
the  excursions  no  crossings  from  positive  to  nega- 
tive were  observed  and  at  this  point  the 
wavelength  was  taken  as  twice  the  value  from  one 
tangent  of  the  body  on  the  line  of  motion  to  the 
other  (Figure  3). 

The  position  of  the  midpoint  between  the  eyes 
after  each  frame  was  monitored  to  yield  x(0.  Each 
successive  movement  of  that  reference  point  was 
recorded  in  the  manner  outlined  above  and  the 
distance  moved  during  each  frame  noted. 

The  projected  length  xp(t)  was  taken  as  the 
length  between  the  two  points  representing  the 
projection  of  the  tail  and  snout  tip  position  on  the 
X-axis  and  was  used  in  a  manner  to  be  described 
later. 

The  wave  position  Xuit)  was  taken  as  the  pro- 
jected length  of  the  body  from  the  point  where  A  (^ 
is  measured  to  the  snout  tip  (Figure  3). 

The  points  representing  the  functions  described 
above  at  each  unit  of  time,  i.e.,  one  frame,  were 
collected  for  18  excursions  which  were  randomly 
selected  from  the  larval  anchovy  feeding  films. 
The  functions  were  then  nondimensionalized  by 


division  by  body  length  and  plotted.  The  geometric 
form  of  the  resulting  function  was  then  used  as  a 
guide  in  selecting  an  appropriate  descriptive  func- 
tion. The  parameters  of  these  functional  forms 
were  then  fitted  by  computer  in  the  least  squares 
sense  using  a  nonlinear  steepest  descent  approach 
(Conway,  Glass,  Wilcox,  1970).  The  graphical  rep- 
resentation of  the  proposed  body  displacement 
function  with  the  internal  functions  fitted  in  this 
manner  was  found  to  coincide  very  closely  with 
the  actual  body  displacements  seen  in  the  films. 

In  the  derivations  for  total  excursion  work, 
W^ ,  the  integral  for  tangential  viscous  reactive 
work  contains  s,  the  distance  along  the  fish 
body,  explicitly.  The  function  satisfying  F{x,  t) 
=  s  is  extremely  complicated  for  the  complete 
wave-form  displacement  function  using  all  the 
fitted  internal  functions  and  is  almost  impossible 
to  calculate  explicitly.  The  alternative  used 
here  is  to  extrapolate  back  from  the  measured 
X;,(^)  to  yield  s  (x,  t). 

We  know  the  function  F(x,  t)  =  s  satisfies 

F(Xp,  t)  =  L 

where  L  is  the  length  of  the  fish  body.  Since  the 
maximum  amplitude  ever  encountered  in  this 
study  was  around  0.2  L  and  the  mean  integra- 
tion distance  never  greater  than  ttI2,  we  can 
calculate,  for  purposes  of  comparison,  the  differ- 
ences between  the  true  length  of  a  pure  sine 
wave  of  amplitude  A  and  its  projected  length. 

The  unperturbed  or  no  sine-wave  form  for  a 
7r/2  interval  of  integration  yields  simply  jtI2. 
The  sine-wave  projected  length  is,  for  y  =  As\YiQ, 


I 


77/2 


Vl  +  A'"  cos""  e  d  G 


Direction  of 
forward  movement 


=  V 


1  +  A^  E  \7r/2 


W: 


A 


1  +  A- 


where  E{<^  ,k)  is  the  elliptic  integral  of  the  sec- 
ond kind  (in  this  case  a  complete  elliptic  in- 
tegral of  the  second  kind).  Taking  A  ^  2.0  cm 
we  get  using  A  =  0.2L. 


Figure  3.— Diagram  illu.strating  the  identification  of     (t)l2, 
Xw(t)  and  A(t)  from  photographic  records  (see  text). 


=   Vl  +  0.16    E{ttI2,  0.37)  =  1.625. 


890 


VLYMEN:  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 


The  difference  between  this  and  77/2  is  about 
4'7(: .  Thus,  we  expect  the  projected  length  and 
real  body  length  to  differ  only  slightly.  With 
this  confidence  we  make  the  following  addi- 
tional assumptions: 


F(Xxp,  t)  =  XL. 


This  assumption  based  on  the  error  calculation 
above  postulates  a  linear  relation  between  pro- 
jected length  and  real  length.  Now  xp/L  =xp(t) 
and  is  obtained  from  excursion  analyses.  We 
can  rewrite  this  as 


=  L 


Xp(t) 

XXp 

Xp(t) 

X 

Xp  ( t) 


XL 


=  s 


A^l 


X^Xr 


Thus  we  chose  to  identify 

F(x,  t)  =  xlxp(t)  =  s(x,  t). 


The  determination  of  the  contour  his)  was 
made  using  biologically  accurate  drawings  of  a 
1.84-cm  anchovy  larva.  The  term  h(s)  was  es- 
tablished for  the  body  distal  to  a  vertical  line 
tangent  to  the  gill  plate  as  shown  in  Figure  4. 


— /h 

/t  — 

■ 

""^l"* 

^ 

H/^'^ 

L*  > 

.. 

„/L  =  QI55 
t/L  =  0.751 
l/L-- 0.094 
„/L  =  O.M 

18.4  mm 

Figure  4. — Lateral  cross  section  of  1.84-cm  anchovy  larvae  dis- 
playing relationship  of  idealized  contour  function  h{s)  (see  text) 
to  appropriate  nondimensionalized  morphometric  parameters. 

From  that  point  to  the  beginning  of  the  tail  h{s) 
was  taken  as  a  constant  and  the  relation  his)  = 
0.038  L  was  found  to  hold.  The  dorsal  and  anal 
fin  contributions  were  neglected  because  the 
plate  approximation  already  constitutes  an 
upper  bound  estimate  for  Wj..  Thus,  the  neglect 


of  these  fins  quantitatively  yields  a  more  realis- 
tic estimate  ofWj^.  Using  the  notation  of  Figure 
4  we  have, 


his) 


0  fors^/ 


H 


X^l  his)     =  0.038  L  for  l^  <s^iljf  +  Ij.) 


(Th  -  0.038  L) 
his)     =  0.038  L  +  ^-^ [s  -  ilfj  +  I  J, )] 

for  (//y  +  It)  <s^L 

or  using  values  in  Figure  4  the  last  relation 
may  be  written 

his)  =  0.038L  +  0.766  is  -  0.906L;. 

The  cross-sectional  area  A^  which  appears  in 
the  work  integral  for  the  head  was  determined 
by  randomly  selecting  Formalin-preserved  an- 
chovy larvae  from  0.5  to  1.5  cm  in  length  and 
affixing  them,  via  the  Formalin  surface  tension 
on  their  bodies,  upright  on  the  side  of  a  small 
inverted  beaker.  The  largest  cross  section  of  the 
head  was  then  viewed  directly  with  a  Nikon  op- 
tical comparator  and  an  outline  traced  from  the 
lighted  viewing  screen.  Lengths  of  the  bodies 
were  also  measured  with  dial  calipers  at  the 
time  the  tracings  were  made.  Subsequently  the 
tracing  areas  were  measured  with  a  planimeter 
and  corrected  to  the  true  value.  A  least  squares 
analysis  of  the  results  yielded  the  relation 
Ah  =  0.00423L  where  L  is  in  centimeters  and 
Af^  is  in  square  centimeters.  The  graph  is  plot- 
ted along  with  the  data  in  Figure  5. 

The  representation  for  pis),  the  linear  density 
of  the  body,  was  regarded  as  constant  for  any 
given  length  and  calculated  from  data  in 
Lasker,  et  al.,  (1970).  Assuming  90%  water,  the 
wet  weight  of  0.5-  to  1.6-cm  larvae  is  then 
given  by  0.00319L^^^^'  =  pis)  where  L  is  in 
centimeters  and  pis)  is  in  grams  per  centime- 
ter. 

The  density  of  the  seawater  was  taken  for 
T  =  17°C  and  was  1.02454.  This  value  was  ob- 
tained from  tables  published  by  the  U.S.  Navy 
Hydrographic  Office  (1956). 

In  my  formulation  I  assume  that  the  head  is 
propelled  through  the  water  as  an  inert  object 
attached  to  an  undulating  body.  We  want  to 
know  the  virtual  mass  and  drag  coefficient  of 
the  inert  head  for  use  in  the  W^^  integral.  Since 
the   shape   of  the   anchovy   larva's   head   is 


891 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


0.0       02        0.4        0.6 


0.8         1.0         1.2 

L{cm) 


1.4 


1.6 


Figure  5. — Cross  sectional  area  of  larval  anchovy  head,  A^ ,  as  a 
function  of  length  L. 

roughly  ellipsoidal  or  a  bluff  body,  I  decided  to 
modify,  with  due  consideration  for  the  geomet- 
ric differences,  the  drag  relationship  observed 
for  a  copepod  (Lahidocera  trispinosa),  w^hich  is  a 
naturally  occurring  bluff  body  of  similar  shape, 
to  represent  the  relevant  characteristics  of  the 
anchovy  larvae  head. 

If  the  copepod  is  taken  as  an  equivalent  ellip- 
soid, we  get,  from  data  in  Vlymen  (1970), 


(e)  -  '■'■ 


where  a,,  is  the  major  axis  length  and  b^  is  the 
semimajor  axis  length  of  the  copepod  L.  tri- 
spinosa and  is  given  respectively  by  a^  =  -^^ 


m 


(one-half  the  metasome  length)  and  b, 

For  the  anchovies  studied  -j-  =  0.155  (Figure  4) 
and  fori  =  1^4cmandA;/ =  0.007  cm^,/;/ =  0.217 
cm  yielding /^\  =  2.3. 

For  high  Reynolds  numbers  (~10  -10  )  and 
rotationally  symmetrical  bluff  bodies  of  various 
l/d  ratios,  where  I  is  the  bluff  body  length  and  d  is 
diameter,  we  have 

(Hoerner,  1965) 


where  Cf  is  the  frictional  drag  coefficient  based 
on  wetted  surface  area  and  Cp.  is  the  drag 
coefficient  based  on  frontal  area.  We  can  use 
this  relation  to  approximate  C^.  (lid  =2.9)  as- 

Co-  Wd  =2.3) 
suming  Cfdid  =  2.9)  =  Cfilld  =  2.3),  and  use 
the  above  ratio  to  modify  the  measured  drag  re- 
lation already  obtained  for  the  copepod.  Sub- 
stituting lid  =  2.9  and  lid  =  2.3  into  the  rela- 
tion for  CoJCf  we  get  on  dividing 

Cp  .  (lid  =  2.9)   ^     ^^ 

Cd  ■  (lid  =  2.3) 
At  lower  Reynolds  numbers  we  expect  the 
geometric  differences  to  cause  a  greater 
discrepancy  between  Cp  (lid  =  2.9)  and  Cp  (lid 
=  2.3).  In  particular  Cp  (lid  =  2.9)>  Cp(lld  = 
2.3).  However,  since  in  my  experiments  Re  was 
from  0-  to  100,  the  region  where  we  expect  the 
Cp  (Re)  curve  to  flatten  out  to  a  fairly  constant 
value  we  take  Cp  (Re)  for  the  copepod  as  a  first 
approximation  to  the  Cp  (Re)  for  the  anchovy 
head.  That  function  is  Cp  (Re)  =  85.2/Re-8o, 
Vlymen  (1970).  The  virtual  mass,-  m,  occurring 
in  the  integrals  for  W^  is  then  calculated  by 
considering  the  head  as  if  it  were  an  equivalent 
ellipsoid.  Using  (ajba)  =  2.3  we  can  calculate 


m  as  m  =  kj  p  Vp  where  k^ 


J 


(2  -7) 


7  =  2 


(i#)  •"  "•  m) 


i  -  S)" 


V^  =  4/37ra„6„2  Vlymen  (1970). 

For  a  1.4-cm  larva  m  has  a  value  of  1.80  x  10^^  g 
and  assuming  the  head  density  is  the  same  as 
seawater  we  get  M  =  7.9  x  lO"'*  g.  Thus  Wf^ 
may  be  rewritten  as 


W„  =  1/2 


•^    0 


80 


vrA,,dt 


■I 


4dV, 
(9.7  xlO    -^V,dt 


892 


VLYMEN:  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 


where  ^■  is  the  kinematic  viscosity  of  seawater 

U.S.    Navy   Hydrographic 


2-c-l 


0.0119   cm2-s 
Office,  1956). 

A  computer  program  by  Stroud  (1971)  using 
16-point  Gauss-Legendre  integration,  and  the 
above  outlined  integration  scheme  was  used  to 
compute  the  integrals  comprising  W.^.  The  pro-> 
gram  was  translated  into  Algol  and  executed 
on  a  Burroughs  6700  at  the  University  of  Cali- 
fornia, San  Diego  Computer  Center.  Accuracy 
of  the  program  was  checked  by  evaluation  of  the 
iterated  integrals 


/     e       c/v/ 

Jo  "Jo 


e^'  dx  for  various  w  and 


The  results  showed  the  integration  scheme  to  be 
accurate  to  the  eighth  decimal  place  in  the  former 
integral  when  compared  with  tables  in  Rosser 
(1948)  and  accurate  to  the  fourth  decimal  place  in 
the  latter  integral  using  standard  tables.  Details 
of  the  mathematical  scheme  are  found  in  the  ap- 
pendix. 

In  the  integrations  of  Wj  a  relative  convergence 
was  computed  by  first  doing  the  integration  over 
the  whole  interval,  that  is, 


/o 


"    J  fit) 


F(x,  t)  dxdt. 


Then  the  value  corresponding  to  one  subdivi- 
sion is  computed,  namely, 


Hi    r   Hit  I 

lx=   I      I         Fix,  t)  dxdt 


11 

Jo      J  fit 

i  I 

J  tl-i    J n, 


t       fgiti 

+  1       /        F(x.  t)  dxdt. 


The  relative  convergence  is  then  computed  as 


C 


h  -h 


If  this  value  is  less  than  0.05,  the  value  4  is  taken 
as  the  value  of  the  integral.  If  it  is  greater,  the 
intervals  comprising  I^   are  further  subdivided 


and  the  process  continued  until  convergence  is 
reached.  Thus,  if /„,  corresponding  to  2  "  subdivi- 
sions, and  /„  +1,  corresponding  to  2„  +  i  subdivi- 
sions, are  of  such  values  that 


-  1 


In 


<0.05, 


n   +  2 


then  /y  is  assigned  the  value  /„  ^  i. 

The  convergence  is  set  higher  than  one  might 
expect  because  computation  of  the  complex  in- 
tegrals of  the  type  used  in  this  study  is  manifested 
by  slow  and  oscillatory  relative  convergences 
necessitating  a  great  deal  of  computer  time.  How- 
ever, when  the  convergence  criteria  was  set  at 
0.05  in  the  integrations  performed,  convergences 
were  better  than  the  critical  value.  The  effect  of 
the  higher  convergence  criteria  is  thus  seen  as 
being  an  economic  and  computational  conveni- 
ence. 

RESULTS 

The  plotted  values  of  the  nondimensional 
amplitude,  A{t)IL,  wave  position,  Xw(t)IL,  and 
projected  length,  Xp{t)IL,  along  with  the  de- 
scriptive functions  fitted  by  the  methods  discus- 
sed are  shown  in  Figures  6  and  7.  The  points 
comprising  the  curves  of  each  represent  the 
mean  value  of  the  particular  parameter  in 
question  at  successive  units  of  time  where  one 
time  unit  is  Vr28  s. 


MEASURED   MEANS 
FITTED    FUNCTION 


A|t)/L!  0.206  cxp  [-0.044(1 -7.19)^] 


9        10        II        12        13        14       15 


Figure  6. — Nondimensional  amplitude,  A (H/L  and  wave  posi- 
tion, Xu,  (t)IL,  of  body  displacement  function  as  functions  of 
time,  t,  in  motion  frame  units.  The  graphs  display  the  fitted 
curves  (line)  together  with  the  original  data  (open  circles)  and 
points  of  the  fitted  curve  at  corresponding  time  units  (closed 
circles). 


893 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


MEASURED  MEANS 
FITTED  FUNCTION 


Xp(t)/L  =  0.0029lt'-0.04l2t  +  1.00 


a.    ao' 

0.20 

15 

!         0.12 

i§ 

;  E    0.08 

'■  'A 
>  ? 

■■^    0.04 
0.00, 


X(l)/L  =  -0.00009654l'  +0.002551^+0.00061  +0.0001396 


10        II        12 


Figure  7. — Nondimensional  position,  X(t)IL ,  and  projected  body_ 
length,  XpitVL,  as  functions  of  time,  t,  in  motion  frame  units. 
The  graphs  display  the  fitted  curves  (lines)  together  with  the 
original  data  (open  circles)  and  points  of  the  fitted  curve  at 
corresponding  time  units  (closed  circles). 

The  curve  for  X  (t)/L,  deserves  some  discussion. 
Since  the  amplitude  of  the  propagated  wave  was 
known  to  be  zero  at  ^  =  0,  both  X  =  =«  or  X  =0  would 
be  descriptive  of  the  initial  straight-line 
configuration.  However,  X  =  0  implies  an  infinite 
number  of  oscillations  varying  like  sin  t/\  with 
neither  the  function  nor  the  first  derivative  exist- 
ing as  X  ^  0.  Since  at  the  end  points  of  an  excur- 
sion a  slightly  perturbed  wave  form  was  observed, 
i.e.,  a  finite  wavelength,  the  nondimensional 
wavelength  of  the  t  =  0  excursion  wave  form  was 
adjusted  to  be  equal  to  the  last.  A  perfect  relation 


2.4|- 


2.0, 


X 

I- 
o 


1.6 


I    1.2 


2    0.8 
to 


Q    0.4 

z 

o 


0.0 


o  MEASURED    MEANS 
•  FITTED   FUNCTION 


A(t)/L=  11.16 


/  0.947  y-°  /  0.947  \ 
\l+l.02/       \t  +  l.02/ 


I.I 


+2.29 


J I I I L 


I       I       I 


■0  2  4  6  8  10  12  14 

t 

Figure  8. — Nondimensional  wavelength,  X  {t)IL,  as  a  function  of 
time,  t,  in  motion  frame  units.  The  graph  displays  the  fitted 
function  (line)  together  with  the  original  data  (open  circles)  and 
points  of  the  fitted  curve  at  corresponding  time  units  (closed 
circles).  The  dotted  portion  of  the  fitted  curve  is  discussed  in  the 
text. 


would  have  X  =  »=  at  both  end  points.  This,  I 
believe,  does  not  drastically  affect  the  results 
since  the  only  modulatory  component  at  the  end 
points  is  the  amplitude  which  is  zero  at  these 
points.  This  accounts  for  the  Lennard-Jones  type 
of  function  which  was  chosen  as  a  functional  rep- 
resentation of  X(t)/L  and  is  shown  in  Figure  8 
along  with  the  function  itself.  The  values  at  other 
than  the  end  points  together  with  the  fact  that 
A{t)  ^  0  at  these  points  is  sufficiently  descriptive 
of  the  contour  wavelength  to  vitiate  any  physical 
inconsistencies  or  mathematical  problems  that 
may  arise  from  the  end  point  modification  of 
X  it)/L  discussed. 

The  integrals  representing  the  work  per  excur- 
sion namely  W^g  ^ ,  Wg,  VT^  were  subdivided 
further  into  smaller  iterated  integrals  and,  using 
the  mean  excursion  time  of  12.9  frame  time  units 
(-O.lOs)  integrated  by  the  method  already  out- 
^lined.  The  values  obtained  were  taken  to  repre- 
sent the  work/excursion  of  an  anchovy  larvae  of 
length  equal  to  the  mean  of  the  animals  used  in 
the  study  or  1.4  cm. 

The  values  of  the  work  are  divided  into  five 
categories  as  follows:  1)  head  energy  representing 
the  value  of  the  integral  in  Equation  (3),  2)  normal 
energy  representing  the  value  of  the  1st  integral 
of  H^B  ^,  3)  tangential  energy  representing  2nd 
integral  of  W  q"^  ,  4)  body  inertial  energy  rep- 
resenting the  1st  integral  ofW^  ,  and  5)  inertial 
energy  representing  the  2nd  integral  of  W^  .  The 
value  of  these  five  integrals  in  ergs/excursion 
and  their  fraction  of  the  total  excursion  energy 
is  given  in  Table  1.  It  is  observed  from  the  table 
that  accelerative  terms  such  as  body  inertial  and 
inertial  energies  account  for  more  than  three- 
fourths  of  all  the  energy  used  in  swimming.  It 
is  worthwhile  noting  that  although  this  is  an  ex- 
pected outcome  of  the  peculiar  behavior  of  the 
anchovy  larvae,  it  is  possibly  true  that  neglect  of 
such  terms  in  many  analyses  of  fish  energetics 
is  cause  for  errors.  Attention  to  these  matters  has 
been  given  thorough  theoretical  discussion  in 
Lighthill  (1970, 1971).  The  analysis  in  this  paper. 

Table  1. — Excursion  energy  components  in  ergs  for  the  1.4-cm 
anchovy  larva. 


Item 

Energy/ 
excursion 

Percent 
of  total 

Normal  energy 
Tangential  energy 
Inertial  energy 
Body  inertial  energy 
Head  energy 

Total  energy 

11.5 
0.35 
33.6 
99.2 

0.15 

144.8 

7.9 

0.2 

23.2 

68.5 

0.2 

894 


VLYMEN;  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 


however,  depends  on  incorporating  what  actually 
occurs  into  an  easily  manipulated  theoretical 
energy  construct. 

Although  the  point  of  this  study  is  to  evaluate 
the  swimming  energetics  in  an  indirect  but  non- 
manometric  manner,  it  is  nevertheless  interest- 
ing to  compare  the  calculated  energy  using  the 
theoretical  model  wdth  values  obtained  using  O2 
consumption  measurements  obtained  with  an- 
chovy larvae.  Such  experiments  in  limited  num- 
bers have  been  performed  by  Lasker  (pers.  com- 
mun.)  using  more  than  one  larva  per  experiment 
and  with  the  animals  confined  to  small  volume 
containers.  No  knowledge  of  activity  levels  was 
possible  during  these  experiments  and  the  values 
obtained  reflect  total  O2  uptake  per  experimental 
period  averaged  for  the  number  of  larvae  per  con- 
tainer. Lasker  believes,  however,  that  activity 
levels  during  such  experiments  are  below  natural 
levels  because  of  the  inhibiting  effects  of  the  con- 
tainer surfaces  and  crowding.  The  value  obtained 
from  such  experiments  was  4.36  ±  1.05  A/lOa/mg 
dry  wt/h.  Assuming  an  RQ  of  0.70  we  get  1  ^il  O2 
=  0.005  cal  ±  0.00035  (Lasker,  1962).  Thus,  the 
caloric  equivalent  of  the  anchovy  larval  respira- 
tory rate  is  between  0.0153  cal/mg  dry  wt/h  and 
0.0289  cal/mg  dry  wt/h  with  a  mean  value  of 
0.0218  cal/mg/h  {n  =  23).  A  comparison  between 
the  theoretically  determined  energy  value  and  the 
mean  O2  uptake  value  given  above  requires  a 
simultaneous  knowledge  of  swimming  activity 
expressed  as  an  excursion  frequency.  Such  infor- 
mation is  not  available  and  it  is  precisely  our 
inability  to  make  simultaneous  observations  of  O2 
consumption  and  activity  offish  larvae  that  neces- 
sitates the  type  of  study  undertaken  in  this  paper. 
Excursion  rates  observed  during  5-min  feeding- 
searching  periods  have  been  measured  (Hunter, 
1972)  using  large  containers.  For  the  periods  ob- 
served the  excursion  rate  appropriate  to  a  1.4-cm 
larvae  was  found  to  be  1.57  ±  0.03  excursions/s 
with  the  mean  time  devoted  to  intermittent 
swimming  being  82.6%  ±  1.2% .  This  value  is  prob- 
ably a  maximum  for  activity  since  satiation  would 
probably  lead  to  a  decrease  in  excursions  as  would 
the  lack  of  observable  food  particles.  Since  avail- 
able O2  measurements  were  not  collected  during 
feeding,  some  modification  of  the  above  activity 
value  has  to  be  made  to  compensate  for  the  inhibi- 
tion of  the  container  and  the  absence  of  food  before 
these  values  can  be  used  for  comparison. 

The  O2  consumption  measurements  of  anchovy 
larvae  were  performed  in  small  70-ml  containers 


in  light  and  darkness.  The  only  relative  activity 
measurements  that  have  been  performed  for  simi- 
lar situations  were  on  28-day-old  herring  larvae 
ca.  1  cm  in  length  in  a  variety  of  light  conditions  by 
Blaxter  (1973).  Although  herring  are  continuous 
swimmers,  unlike  anchovy  larvae,  the  use  of  rela- 
tive activities  was  deemed  an  appropriate  way  of 
estimating  the  activity  variation  of  a  similar  sized 
nonfeeding  organism  in  the  following  manner.  For 
herring  larvae  at  10  different  light  levels  the 
mean  percent  difference  between  maximum  and 
mimimum  activity  levels  was  found  by  Blaxter 
(1973)  to  be  78.6%,  maximum  activity  being 
defined  as  mean  activity  plus  two  standard  errors 
and  minimum  activity  as  mean  activity  minus  two 
standard  errors.  Although  this  change  is  large,  it 
probably  reflects  behavioral  modulation  more 
than  effects  of  the  container  since  in  Blaxter's 
experiment  the  container  (a  long  tube)  contained 
approximately  1,500  ml  of  seawater.  Thus,  re- 
garding the  O2  consumption  experiments  on  the 
anchovy  as  repiesenting  the  minimum  activity 
levels  of  that  organism  in  the  same  relationship  of 
active  to  inactive  as  found  from  Blaxter  ( 1973),  we 
can,  using  known  maximum  excursion  rates  dur- 
ing feeding  from  Hunter  (1972),  calculate  the 
minimum  excursion  rate  or  activity  correspond- 
ing to  our  O2  measurements  and  hence  the  energy 
consumption  for  swimming  based  on  that  excur- 
sion rate.  This  analysis  assumes  the  geometric 
swimming  behavior  during  feeding  and  nonfeed- 
ing is  the  same,  an  assumption  confirmed  by  ob- 
servation. 

Using  the  mean  O2  consumption  value  0.0218 
cal/mg  dry  wt/h  and  the  dry  weight  of  a  1.4-cm 
larva  from  Lasker  et  al.  (1970)  we  get  an  expendi- 
ture of  22.6  X  10'  cal/h.  Taking  1.57  excursions/s 
as  the  mean  maximum  activity  value,  decreased 
by  78.6%  to  convert  to  minimum  activity  levels, 
and  multiplied  by  the  theoretically  determined 
energy  per  excursion  of  the  1.4-cm  larva  of  144.8 
ergs/excursion,  we  get  4.91  x  10  cal/h.  This  value 
yields  an  estimate  of  metabolic  swimming 
efficiency  of  24.6%  for  the  1.4-cm  larval  anchovy 
assuming  a  poikilothermic  basal  metabolic  rate  of 
0.05  iu\  Og/mg  wet  wt/h.  This  efficiency  is  quite 
high  when  compared  to  valiles  obtained  for  larger 
fish  where  efficiencies  in  the  range  of  8  to  15% 
(Webb,  1971)  are  observed.  However,  such  exper- 
iments are  usually  done  on  large  fish  constrained 
by  relatively  small  tanks,  swimming  continu- 
ously, and  using  a  caudal  propeller  mode  of  pro- 
pulsion. Thus  any  comparison  of  the  above  results 

895 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


with  the  wide-range  Reynolds  number  motions 
and  large  amplitude  wave  forms  encountered  in 
this  study  must  be  done  cautiously  and  with  ap- 
propriate consideration  of  hydrodynamical  dis- 
similarities. However,  using  the  most  obvious  be- 
havioral differences  between  the  two  types  of 
studies,  a  higher  overall  efficiency  might  be  sus- 
pected based  on  the  viewpoint  of  Lighthill  (1971) 
that  the  large  amplitude  tail  motions  exhibited  by 
some  fishes  be  interpreted  as  a  means  of  producing 
reactive  thrusts  which  balance  the  enhanced  vis- 
cous drag  produced  upon  the  commencement  of  lat- 
eral movements.  Lighthill  thus  implies  that  large 
amplitude  movements  interspersed  with  periods 
of  gliding  are  more  efficient  than  continuous  small 
amplitude  oscillations  as  a  mode  of  propulsion. 
This  appears  to  be  confirmed  in  the  results  of  this 
study  where  the  behavior  is  of  this  type  and  the 
efficiency  apparently  high.  It  should  be  stressed 
that  a  range  of  efficiencies  can  exist  due  to  the 
intrinsic  variability  in  O2  consumption  values 
and  associated  activity  measurements  and  the 
fact  that  synchronous  determinations  of  both  have 
not  yet  been  performed.  The  purpose  of  the  swim- 
ming efficiency  calculation  and  the  associated 
comparison  curves  with  O2  values  (Figure  9)  is  to 
demonstrate  the  relationship  the  theoretical  val- 
ues determined  here  have  to  the  available 
physiological  parameters  obtained  with  simple 
experimental  designs.  If  excursion  energies  could 
be  obtained  by  simpler  means,  one  could  circum- 
vent the  involved  procedures  presented  in  this 
paper. 

It  is  interesting  to  note  that  the  Pacific  sardine, 
Sardinops  caerulea,  whose  ecological  niche  was 
primarily  taken  over  by  the  anchovy,  Engraulis 
mordax,  in  the  California  Current  (Murphy,  1966) 
does  not  exhibit,  in  the  larval  stages,  the  same 
swimming  behavior  as  the  anchovy,  i.e.,  swim- 
ming bursts  followed  by  glides.  Instead  it  swims 
by  constant,  small  amplitude  oscillating  move- 
ments of  the  body.  In  light  of  the  results  here  and 
theoretical  work  by  Lighthill  it  is  possible  that  the 
propulsive  efficiencies  in  the  larval  stages  of  the 
sardine  and  anchovy  are  slightly  different,  the 
sardine  being  less  efficient.  Thus  a  small 
behavioral-propulsive  difference  between  the  an- 
chovy and  the  sardine  might  have  permitted  the 
anchovy  to  compete  more  favorably  when  there 
was  a  decline  in  sardine  population. 

The  evaluation  of  propulsive  energetics  as 
outlined  in  this  study  is  directed  at  only  one 
size  of  the  anchovy  larva  because  the  method 


10" 


r    o 


o 
o 


CURVE  OBTAINED    FROM  Oj 
CONSUMPTION   MEASUREMENTS 
{SEE  TEXT). 

THEORETICAL    MODEL    VALUE 
COMPUTED   WITH   WAVE   PARA- 
METERS FITTED  TO   1.4  cm 
LARVAE   (SEE  TEXT). 

HUNTER  AMPLITUDE    INTERCEPT 
MODIFICATION  OF  THEORETICAL 
MODEL    FOR   LENGTHS   OTHER 
THAN    1.4cm  (SEE   TEXT). 


Figure  9. — Energy  consumption  of  swimming  based  on  theoret- 
ical model  (open  circles  and  open  square)  and  total  energy  con- 
sumption based  on  O2  utilization  (closed  circles)  as  a  function  of 
length.  Vertical  lines  on  both  curves  span  one  standard  error  of 
the  data. 

requires  detailed  knowledge  of  the  various 
wave-form  parameters  as  functions  of  time  for 
each  length  of  the  organism  studied.  Valid  re- 
sults cannot  be  obtained  for  other  sizes  by  a 
mere  alteration  of  the  length  of  the  organism  in 
the  wave-parameter  functions.  By  the  method 
outlined  here,  the  only  way  to  properly  evaluate 
propulsive  energetic  costs  for  different  lengths 
would  be  to  repeat  the  course  of  wave- 
parameter  determination  completely.  However, 
with  such  limitations  in  mind  it  is  interesting 
to  compare  results  obtained  when  modification 
of  the  existing  wave-parameter  functions  is 
made  using  extensions  of  known  length- 
dependent  wave-parameter  quantities  which 
have  been  measured  for  larval  anchovies.  The 


896 


VLYMEN:  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 


only  such  wave  parameter  available  for 
modification  and  incorporation  into  the  energy 
formulation  is  the  wave  amplitude. 

Hunter  (1972)  measured  the  relationship  be- 
tween tail-beat  amplitude  and  larval  length  for 
intermittent  swimming  and  found  the  relation- 
ship, 

A  =  0.112  +  0.170L 

where  L  and  A  are  in  centimeters.  Since  minimal 
amplitude  dependence  on  length  exists  because  of 
the  exaggerated  whiplike  motion  of  the  tail, 
Hunter's  amplitude  value  is  greater  than  my 
value  for  the  maximum  wave  amplitude  of  1.4-cm 
larvae.  This  is  because  amplitudes  used  in  this 
study  are  measured  as  the  wave  crest  progresses 
caudally  at  each  successive  time  unit,  whereas  at 
the  tail,  wave  progression  ceases  along  the  body 
and  may  even  become  retrograde  due  to  the  whip- 
like motion.  The  important  point  is  the  intercept 
at  zero  length  where  both  measurements  must  be 
consistent,  i.e.,  equal.  Thus,  admitting  equality  of 
the  interception  point  at  L  =  0  and  adjusting  the 
first  order  coefficient  in  Hunter's  equation  to  yield 
the  correct  value  for  maximum  amplitudes  at  L  = 
1.4  cm  we  get, 

An,ax=  0.112  +  0.094  L 

This  value  was  substituted  for  A^^^  =  0.026  L 
in  the  amplitude  function  A(t)  =  0.206  L  exp 
[-0.044  (t  -7.19)^]  and  its  first  two  derivatives 
used  in  the  L  =  1.4  cm  formulation.  The  work 
integrals  were  then  recomputed  at  the  three 
new  points  L  =  0.4  cm,  L  =  0.7  cm,  and  L  = 
2.0  cm.  Because  the  A, nax  values  coincided  at  L 
=  1.4  for  both  treatments  this  value  was  not 
used  again  in  the  integration  procedure.  The 
values  obtained  are  shown  in  Table  2.  Least 
squares  regression  of  the  data  assuming  the 
functional     form     E     =     aL^    where     E     is 

Table  2.— Excursion  energies  for  five  larval  anchovy  lengths 
using  Hunter's  modified  intercept  amplitude  function  (see  text 
for  complete  discussion)  for  extension  to  larval  lengths  other 
than  1.4  cm. 


Length 
(cm) 


Energy/ 

excursion 

(ergs) 


2.0 

1.4 

1.0 

0.70 

0.40 


881,4 

144.8 

16.3 

3.6 

0.76 


energy/excursion  in  ergs  and  L  length  in  cen- 
timeters yielded  E  =  21  .b  L  ^  *^  The 
energy/excursion  calculated  for  the  four  addi- 
tional lengths  was  then  converted  to  hourly 
energy  rates  using  the  excursion  frequencies 
cited  earlier.  The  results  obtained  were  plotted 
with  scales  of  calories  per  hour  vs.  length  in 
centimeters.  For  comparison,  another  curve  of 

the  form  4Q2_=  f[L)  was  computed  and  plotted 

dt 
along  with  the  curve  formed  using  the  addi- 
tional model  points  above  (Figure  9).  The  line 
shown  connecting  these  points  is  fitted  by  eye. 
The  comparison  curve  was  based  on  the  respira- 
tion value  of  0.0218  cal/mg  dry  wt/h  and  the 
following  relationship  between  dry  weight  in 
milligrams  and  length  in  millimeters,  log  W  = 
3.3237  log  L  -  3.8205  (Lasker  et  al.,  1971). 
This  comparison  curve  is  isomorphic  to  the 
length-weight  curve  with  no  allowance  being 
made  for  specific  respiration  changes  with  in- 
creasing weight.  Therefore  the  curve  is  to  be 
regarded  as  the  best  approximation  to  the  total 
O2  consumption  rate  for  swimming  larval  an- 
chovies. It  provides  only  a  means  of  judging  the 
physiological  reliability  of  the  energy  summa- 
tion method  employed  here.  However,  because 
the  changes  in  specific  respiration  as  a  function 
of  weight  would  not  change  this  comparison 
curve  appreciably,  it  can  probably  be  regarded 
as  sufficiently  reliable.  With  this  understanding 
some  comparison  of  these  curves  can  be  made. 

From  laboratory  observation  of  larvae  it 
seems  apparent  that  nondimensional  amplitude 
and  wavelength  do  not  remain  constant  but  de- 
crease in  absolute  value  as  length  is  increased. 
That  is,  functions  descriptive  of  these  non- 
dimensional  parameters  do  not  remain  descrip- 
tive of  animals  of  all  lengths.  That  is  exactly 
what  is  observed  as  we  deviate  from  the  origi- 
nal L  =  1.4  cm  point  where  the  nondimensional 
wave  parameters  are  fitted.  Even  with 
modification  of  A  max  used  to  compute  the  origi- 
nal curve  this  effect  is  still  observable.  Part  of 
the  deviation  is,  however,  due  to  the  behavior  of 
the  larvae  as  age  increases.  Very  small  larvae 
float  907f  of  the  time  with  occasional  bursts  of 
intensive  activity  (Hunter,  1972)  which,  as  I 
pointed  out  earlier,  is  quite  inefficient.  As  the 
larvae  get  older,  however,  intermittent,  more 
efficient  swimming  becomes  the  dominant  mode 
of  locomotion.  This  trend  is  partially  reflected 
in  these  two  curves.  As  the  larvae  get  older  and 


897 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


larger  the  intermittent  swimming  rate  de- 
creases and  the  nondimensional  amplitude  and 
wave  functions  decrease  also.  This  accounts  for 
the  large  locomotion  energy  computed  for  lar- 
vae greater  than  1.4-cm  in  length.  It  is  interest- 
ing to  note  how  behavioral  factors,  when  un- 
avoidably neglected  in  extending  this  curve, 
become  evident  when  compared  with  reasonable 
estimates  for  total  energy  consumption. 

In  view  of  the  behavioral-mathematical  fac- 
tors influencing  the  shape  of  the  theoretical 
curve  in  the  directions  observed  here  and  the 
physiologic  reasonableness  of  the  metabolic 
swimming  efficiencies  obtained  when  exact 
wave  parameters  descriptive  of  the  L  =  1.4-cm 
larva  are  used,  it  is  reasonable  to  conclude  that 
the  energies  calculated  from  the  model  are  the 
best  estimates  of  the  swimming  energetic  re- 
quirement per  excursion  of  the  larval  anchovy, 
excursion  being  regarded  as  a  discrete,  repro- 
ducible behavioral  entity,  currently  available. 

Therefore,  the  major  results  of  this  study  are 
1)  the  demonstration  that  modifications  of  exist- 
ing methods  of  computing  energy  of  translation 
yield  information  on  behavior  when  consider- 
ation is  given  to  differences  in  behavior,  shape, 
and  flow  scale,  2)  that  a  good  correlation  exists 
in  terms  of  metabolic  swimming  efficiency  ob- 
tained between  direct  O2  measurements  and 
the  model,  3)  a  confirmation  of  the  high 
efficiency  of  large  amplitude,  intermittent 
swimming  behavior,  and  4)  quantitative  esti- 
mates of  swimming  energy  requirements  de- 
rived from  this  model  may  be  used  for  other 
larval  anchovy  research. 

Theoretical  studies  such  as  random  walk 
analyses  and  correlations  with  feeding  behavior 
and  migration  which  are  being  studied  cur- 
rently could  incorporate  these  data  to  provide  a 
comprehensive  and  quantitative  picture  of  lar- 
val anchovy  energetics  and  behavior. 

ACKNOWLEDGMENTS 

I  thank  Reuben  Lasker  of  the  Southwest 
Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  for  proposing  this  study,  donation 
of  facilities,  critical  reading  of  the  manuscript, 
and  kind  and  constant  encouragement  throughout 
its  execution.  I  would  also  like  to  thank  John 
Hunter,  Southwest  Fisheries  Center,  National 
Marine  Fisheries  Service,  NOAA,  for  numerous 
helpful  discussions  on  aspects  of  larval  behavior 


and  loan  of  larval  anchovy  feeding  films.  Appreci- 
ation is  also  expressed  to  the  staff  of  the  National 
Marine  Fisheries  Service  computer  facility  for 
their  assistance  in  this  project.  This  work  was 
supported  by  NOAA,  Office  of  Sea  Grant,  Depart- 
ment of  Commerce,  under  grant  #UCSD 
04-3-158-22. 

LITERATURE  CITED 

Abramowitz,  M.,  and  I.  A.  Stegun  (editors). 

1966.  Handbook  of  mathematical  functions  with  formulas, 
graphs,  and  mathematical  tables.  National  Bureau  of 
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Blaxter,  J.  H.  S. 

1973.  Monitoring  the  vertical  movements  and  light  re- 
sponses of  herring  and  plaice  larvae.  J.  Mar.  Biol.  Assoc. 
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Carlson,  F.  D. 

1959.  The  motile  power  of  a  swimming  spermatozoon.  In 
H.  Quastler  and  H.  J.  Morowitz  (editors),  Proceedings  of 
the  First  National  Biophysics  Conference,  Columbus, 
Ohio,  March  4-6,  1957,  p.  443-449.  Yale  Univ.  Press,  New 
Haven. 

Conway,  G.  R.,  N.  R.  Glass,  and  J.  C.  Wilcox. 

1970.  Fitting  nonlinear  models  to  biological  data  by 
Marquardt's  algorithm.  Ecology  51:503-507. 

Fung,  Y.  C. 

1969.  An  introduction  to  the  theory  of  aeroelasticity.  Dover 
Publ.  Inc.,  N.Y.,  406  p. 

Gary,  J.,  and  G.  J.  Hancock. 

1955.  The  propulsion  of  sea-urchin  spermatozoa.  J.  Exp. 
Biol.  32:802-814. 
Hoerner,  S. 

1965.  Fluid  dynamic  drag.  Publ.  by  author  Midland  Park, 
N.J. 

HoLwiLL,  M.  E.  J.,  and  C.  A.  Miles. 

1971.  Hydrodynamic  analysis  of  non-uniform  flagellar  un- 
dulations. J.  Theor.  Biol.  31:25-42. 

Hunter,  J,  R. 

1972.  Swimming  and  feeding  behavior  of  larval  anchovy, 
Engraulis  mordax.  Fish.  Bull.,  U.S.  70:821-838. 

Kerr,  S.  R. 

1971.   Prediction  offish  growth  efficiency  in  nature.  J.  Fish. 
Res.  Board  Can.  28:809-814. 
Lasker,  R. 

1962.   Efficiency  and  rate  of  yolk  utilization  by  developing 
embryos  and  larvae  of  the  Pacific  sardine  Sardinops 
caerulea  (Girard).  J.  Fish.  Res.  Board  Can.  19:867-875. 
Lasker,  R.,  H.  M.  Feder,  G.  H.  Theilacker,  and  R.  C.  May. 

1970.  Feeding,  growth,  and  survival  of^  Engraulis  mordax 
larvae  reared  in  the  laboratory.  Mar.  Biol.  (Berl.) 
5:345-353. 

LiGHTHILL,  M.  J. 

1970.  Aquatic  animal  propulsion  of  high  hydromechanical 
efficiency.  J.  Fluid  Mech.  44:265-301. 

1971.  Large-amplitude  elongated  body  theory  of  fish 
locomotion.  Proc.  R.  Soc.  Lond.,  Ser.  B,  179:125-138. 

Murphy,  G.  I. 

1966.  Population  biology  of  the  Pacific  sardine  (Sardinops 
caerulea).  Proc.  Calif.  Acad.  Sci.,  Ser.  4,  34:1-84. 


898 


VLYMEN:  SWIMMING  ENERGETICS  OF  THE  LARVAL  ANCHOVY 


ROSSER,  J.  B. 

1948.  Theory  and  application  of /Qe"''^dx  and  Jga'P^y^'dy 
J  -^  e  ""^  dx.  Part  I.  Methods  of  computation.  Mapleton 
House,  Brooklyn,  N.Y.,  192  p. 

SCHLICTING,  H. 

1960.   Boundary  layer  theory.  2d  ed.  McGraw-Hill  Book  Co., 
N.Y.,  122  p. 
Stroud,  A.  H. 

1971.  Approximate  calculation  of  multiple  integrals. 
Prentice-Hall  Inc.,  Englewood  Cliffs,  N.J. 
Taylor,  G. 

1951.  Analysis  of  the  swimming  of  microscopic  organisms. 

Proc.  R.  Soc.  Lond.  Ser.  A,  209:447-461. 
1952a.  The  action  of  waving  cylindrical  tails  in  propelling 


microscopic  organisms.  Proc.   R.  Soc.  Lond.,  Ser.   A, 
211:225-239. 

1952b.  Analysis  of  the  swimming  of  long  and  narrow  ani- 
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U.S.  Navy  Hydrographic  Office. 

1956.  Tables  for  rapid  computation  of  density  and  electrical 
conductivity  of  sea  water.  H.O.  ( Hydrogr.  Off. )  Sp- 1 1 ,  24  p. 

Vlymen,  W.  J. 

1970.  Energy  expenditure  of  swimming  copepods.  Limnol. 
Oceanogr.  15:348-356. 

Webb,  P.  W. 

1971.  The  swimming  energetics  of  trout.  II.  Oxygen  con- 
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55:521-540. 


APPENDIX 


The  integration  of  the  iterated  integrals  was 
accomplished  via  a  two-dimensional  extension  of 
the  standard  Gauss-Legendre  guadrature.  The 
one-dimensional  fixed  limit  integration  formula 
was  used  by  Holwell  and  Miles  (1971)  for  similar 
classes  of  functions  with  good  results.  The  type  of 
integrals  requiring  evaluation  were  of  the  general 
form 


fh    rgit) 
J"  Jm 


F(x,  t)  dxdt 


a,  b,  fixed. 


Defining 


rgit) 
Jf^t) 


G(t)  =  |_^^     Fix,  t)  dx, 


we  get 


/  y ' 


■git)  fb 

Fix,  t)dxdt  =     L     G(t)dt. 


i: 


By  n- point  Gauss-Legendre  quadrature  Ab- 
ramovitz  and  Stegun  (1966)  this  is  given  approxi- 
mately by, 


/' 


Git)dt  =  ^-—^  X  f^,G(^) 


where?,  =  ^-^  v, 


i  =  1 


b  +  a 


y,  =  ith  zero  of  P„(x),  the  n- order 
Legendre  polynomial  and 

u-,=   2/(1-^,2)  [P'„  (?,)]'  . 


Using  Gauss-Legendre  quadrature  on  Gi^^) 
yields, 


/■ 


Git)dt 


b  -  a 


1: 


(^,) 


I  =  1       •'  'y^ii 


b^±    a;i^zf^t     u,;nn,i,), 


I    =    1 


J    =    1 


where  t?^  =  2 _ '-  y^  + 

w*  =  2/il  -  y^)  [p;,iVj)y     and 
y^    =  Jth  root  ofP^fjr). 
We  have  finally  the  result. 


a    J  fit  I 


Fix,  t)  dxdt  ^  ^      "    f 


I  =  1 


i    w,wrS(^^      f^''^  Fin,,^,), 


J  =  1 
where  the  above  definitions  hold. 


899 


ANALYSIS  OF  MIGRATIONS  AND  MORTALITY  OF 

BLUEFIN  TUNA,  THUNNUS  THYNNUS, 

TAGGED  IN  THE  NORTHWESTERN  ATLANTIC  OCEAN^'^ 

F.  J.  Mather  iii,^  B.  J.  Rothschild,'*  G.  J.  Paulik,^  and  W.  H.  Lenarz* 

ABSTRACT 


An  analysis  is  presented  on  the  release  and  return  data  from  bluefin  tuna,  Thiinnus  thynnus,  tagged 
in  the  northwest  Atlantic  Ocean  from  1954  to  1970.  There  was  an  apparent  northward  movement  of 
fish  from  the  New  Jersey  area  as  the  fishing  seasons  progressed.  Tag  returns  from  bluefin  released  in 
the  Long  Island  and  southern  New  England  areas  tended  to  be  to  the  north  at  first  and  then  to  the 
south.  Mean  distances  between  release  and  return  tended  to  be  greater  for  fish  released  in  the  New 
Jersey  area  than  for  the  other  two  areas.  Estimates  of  mortality  rates  for  tagged  bluefin  were  made 
using  the  Chapman-Robson  method  and  then  adjusted  for  Type-I  and  Type-II  tag  shedding  and  Type-I 
tagging  mortality.  The  average  estimate  of  instantaneous  fishing  mortality  is  0.57  and  other  losses 
(natural,  tagging,  and  emigration)  is  0.68  on  an  annual  basis.  The  estimate  of  other  losses  is  consid- 
erably higher  than  the  natural  mortality  that  would  be  expected  for  bluefin.  Evidence  is  presented 
suggesting  that  the  rate  of  emigration  may  be  quite  high.  The  average  single  season  exploitation  rate 
of  tagged  bluefin  was  estimated  to  be  0.33.  It  was  noted  that  since  bluefin  may  be  both  immigrating  to 
and  emigrating  from  the  fishery  the  estimate  of  exploitation  may  not  be  representative  of  the  entire 
population.  Even  though  validity  of  available  effort  data  is  questionable,  regression  estimates  of 
mortality  and  survival  rates  were  made  using  catch  per  effort  data.  These  estimates  of  survival  are 
lower  than  those  obtained  using  the  Chapman-Robson  method. 


The  data  which  form  the  basis  for  this  report 
were  assembled  by  the  first  author.  This  study  is 
based  upon  releases  of  tagged  bluefin  tuna, 
Thunnus  thynnus,  that  were  made  by  a  variety  of 
organizations  and  individuals  under  the  coordi- 
nation of  the  Woods  Hole  Oceanographic  Institu- 
tion Cooperative  Game  Fish  Tagging  Program  at 
various  locations  along  the  middle  Atlantic  bight 
of  North  America  from  July  1954  to  August  1970 
and  returns  of  these  tags  to  the  end  of  1970.  Addi- 
tional returns  are  expected  in  the  future  from 
more  recent  releases. 

MIGRATIONS 

Because  of  the  variety  of  methods,  locations, 
and  dates  of  release,  we  needed  to  assemble  the 
data  by  relatively  homogeneous  release  groups. 
The  criterion  for  constructing  a  release  group  for 


'This  paper  is  dedicated  to  the  memory  of  Gerald  J.  Paulik. 
He  was  a  good  friend  and  colleague  and  made  important  con- 
tributions to  the  theory  of  tagging. 

^Contribution  No.  3180,  Woods  Hole  Oceanographic  Institu- 
tion, Woods  Hole,  MA  02543. 

'Woods  Hole  Oceanographic  Institution,  Woods  Hole,  MA 
02543. 

^Southwest  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  P.O.  Box  271,  La  Jolla,  CA  92037. 

^College  of  Fisheries,  University  of  Wtishington,  Seattle,  WA 
98195.  Deceased. 


analysis  of  migrations  was  to  develop  homoge- 
neous time-location  strata  of  releases  from  which 
a  minimum  of  20  tags  were  recovered.  This  proce- 
dure allowed  us  to  work  with  homogeneous 
groups,  but  eliminated  roughly  10'7r  of  the  recov- 
ered tags  from  our  analysis.  Table  1  summarizes 
these  release  groups  and  Figure  1  shows  their 
localities.  We  can  see  from  Table  1  that  during  the 
study  period  the  tagging  operations  tended  to  shift 
from  the  New  Jersey  coast,  to  the  New  York  coast, 
to  the  southern  New  England  coast,  and  that  re- 
leases in  July  tended  to  be  south  of  those  made  in 
August  or  September. 

Tagging  data  have  been  used  to  show  some  of 
the  longer  migrations  of  the  bluefin  tuna  (Food 
and  Agriculture  Organization,  1972).  We  ex- 
amined the  shorter  term  recoveries  from  an  ana- 
lytic point  of  view.  In  order  to  do  this,  we  made  use 
of  a  method  developed  by  Rothschild  (Bayliffand 
Rothschild,  in  press).  Using  this  method  each  release 
group  was  stratified  into  intervals  of  time  at  lib- 
erty. Release  vectors  (latitude  and  longitude)  for 
each  release  group  were  used  to  compute  an  aver- 
age or  common  release  vector.  Each  recapture  vec- 
tor for  the  group  was  then  standardized  to  the 
common  release  vector.  The  standardized  vectors 
were  then  used  to  find  1)  the  average  recapture 
vector  and  2)  the  determinant  of  the  recapture 


Manuscript  accepted  January  1974. 
FI.SHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 

900 


MATHER  ET  AL  :  TAGGED  BLUEFIN  TUNA 

Table  1. — Release  groups  used  for  analysis  of  migrations  of  tagged  bluefin  tuna. 


General  location  of 

release 

New  Jersey  Coast 

Long 

Islan 

d  Coast 

Southern  New  England 

Group 

No.  Of 

Group 

No.  of 

Group 

No.  of 

Release  date 

No 

returns 

No, 

returns 

No. 

returns 

July  1964 

2A 
2B 
2C 

33 
32 
27 

Aug.  1964 

3 

33 

July  1965 

4A 
4B 
4C 

36 
86 
38 

Aug.  1965 

5A 

22 

58 

47 

5C 

24 

July  1966 

6A 
6B 
6C 

114 
127 

45 

6D 

85 

6E 

62 

Aug    1966 

7A 

20 

7C 

85 

78 

81 

7D 
7E 
7F 
7G 

36 

55 

203 

177 

Sept.-Oct.  1966 

8 

23 

July  1967 

9A 
98 

23 
94 

Sept.  1967 

10 

27 

July  1968 

11A 

21 

11B 

39 

July  1969 

12 

24 

Aug    1969 

13 

40 

Sept.  1969 

14 

22 

July  1970 

15 

17 

Aug.  1970 

16 

25 

1954-63 

17 

24 

variance-covariance  matrix.  The  determinant  of 
the  recapture  variance-covariance  matrix  is  pro- 
posed by  Bayliff  and  Rothschild  as  an  index  of  the 
dispersal  of  the  fish.  When  the  distance  of  the 
recoveries  from  one  another  is  large,  the  deter- 
minant is  large. 

It  should  be  noted  that  the  vectors  computed  by 
this  method  are  not  on  a  per-unit-effort  basis  so 
that  "migration  patterns"  reflect  not  only  the  ap- 
parent movement  of  the  fish,  but  also  the  distribu- 
tion of  fishing  effort.  In  order  to  more  fully  under- 
stand the  nature  of  short-term  movements,  it  will 
be  necessary  to  study  in  some  detail  the  complex 
problem  of  the  distribution  of  bluefin  tuna  in  the 
northwest  Atlantic.  Preliminary  to  more  detailed 
analysis  of  these  statistics,  we  surveyed  some  of 
the  main  features  of  the  data,  of  which  some  are 
tabulated  in  Table  2. 

First  we  considered  the  direction  of  movement. 
Figure  2  contains  a  synthesis  of  these  data  and 
shows  the  direction  of  movement  by  tagging  loca- 
tion and  time  at  liberty.  It  is  implicit  that  we 
treated  each  symbol  as  reflecting  the  behavior  of  a 
sample  of  fish  from  the  same  statistical  popula- 
tion. The  main  features  of  Figure  2  are  that  fish 


tagged  off  New  Jersey  in  July  tended  to  move  in  an 
eastward  direction  and  both  north  and  south  dur- 
ing the  first  2  wk  at  liberty,  but  then  movement 
became  strongly  directed  to  the  northeast.  Fish 
released  in  the  Long  Island  area  initially  tended  to 
move  toward  the  north,  but  after  the  first  30  days, 
their  movement  appeared  to  have  been  concen- 
trated to  the  west  and  south.  The  same  conclusion 
may  be  obtained  from  the  southern  New  England 
releases. 

An  examination  of  the  mean  distance  (Figure  2) 
shows  fish  released  off  New  Jersey  tended  to  be 
recovered  at  a  slightly  greater  distance  to  the 
north  than  the  south.  The  fish  moved  approxi- 
mately 7  or  8  miles  per  day.  By  the  second  15-day 
period,  the  fish  moved  about  60-100  miles  to  the 
northeast.  The  pattern  for  Long  Island  releases, 
based  on  only  a  few  observations,  shows  that 
movement  distance  of  these  fish  during  1-15  days 
was  approximately  the  same  as  that  for  the  New 
Jersey  releases.  The  short-term  recoveries  of 
southern  New  England  tagged  fish  refiect  even 
less  average  distances  than  New  Jersey  short- 
term  releases  suggesting  that  either  the  fish  off 
southern  New  England  moved  less  than  off  New 


901 


75" 


41' 


40« 


39° 


74° 

— r 


75° 


4A 


4B 


74° 


73" 

— r- 


72° 

— r 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 
71°  70" 


n»*G 


^^^'j;^- 


°^^ 


6E 


IIA 


6D 


6B    r 


6A 


6C 


4C 


73° 


SOUTHERN  NEW  ENGLAND         <i^^„J^ 


72» 


A 


7I» 


<> 


<d 


-,— '"""^N.^^^^ 

13 

f—f^y^ 

8 

14 

-^ 

7E 

.::>" 

7B 

1 
1 
1 
1 

L 

7C 

7G 

7D 

7F 

7A 

1 

1 

IIB 

40° 


39° 


70° 


75° 


74° 


73° 

— r 


72° 


70° 


^ ^"^Ir^off^ 

SOUTHERN  NEW  ENGLAND 


S^ 


40° 


39< 


-L 


5C 


J- 


<?> 


<^,. 


15 


17 


41° 


40° 


39° 


75°  74°  73°  72°  71°  70° 

Figure  1. — Part  A  and  Part  B:  Map  of  middle  Atlantic  bight  showing  release  group  locations  of 

tagged  bluefin  tuna. 


902 


MATHER  ET  AL.:  TAGGED  BLUEFIN  TUNA 


Table  2. — Summary  of  statistics  on  movements  of  tagged  bluefin  tuna. 
All  distance  measures  are  nautical  miles. 


Release 
group 


Time  at 
liberty 
(days) 


Mean 
miles 
N-S' 


Mean 
miles 
E-W2 


Deter- 
minant 
(X  10^) 


Mean 
distance 


No. 

of 

fish 


Release 
month 


General 
release 
location 


2A 


2B 


2C 


4A 


4B 


4C 


5A 


5B 


5C 


6A 


68 


6C 


6D 


1-15 

26.5 

34.1 

2.3 

50.5 

13 

July 

16-30 

74.2 

74,9 

26.0 

114.0 

9 

1964 

31-60 

1 

61-180 

0 

1-15 

-9.2 

11.4 

2.9 

31.8 

18 

July 

16-30 

25.1 

58.5 

1,4 

897 

7 

1964 

31-60 

2 

61-180 

0 

1-15 

-7.2 

-15.0 

1.3 

296 

14 

July 

16-30 

1 

1964 

31-60 

1 

61-180 

0 

1-15 

8.0 

12.2 

0.3 

32.6 

12 

Aug. 

16-30 

1 

1965 

31-60 

0 

61-180 

0 

1-15 

12.0 

18.3 

3.8 

336 

18 

July 

16-30 

83.6 

52.8 

11.7 

102.0 

8 

1965 

31-60 

1 

61-180 

1 

1-15 

209 

7.4 

8.7 

46,4 

39 

16-30 

70.8 

21.2 

0.2 

74.6 

28 

31-60 

3 

61-180 

0 

1-15 

253 

-16.6 

13.4 

47.9 

17 

July 

18-30 

62.3 

3.1 

1.1 

64,8 

13 

1965 

31-60 

0 

61-180 

0 

1-15 

25,8 

-15.4 

19.4 

48,5 

9 

Aug. 

16-30 

53.5 

5.4 

17.2 

60.4 

12 

1965 

31-60 

0 

61-180 

0 

1-15 

24.8 

-17.9 

9.5 

47.2 

8 

Aug. 

16-30 

44.8 

-1.8 

36.0 

54,9 

5 

1965 

31-60 

0 

61-180 

- 

0 

1-15 

0 

Aug. 

16-30 

0 

1965 

31-60 

0 

61-180 

0 

1-15 

2 

July 

16-30 

3 

1966 

31-60 

59.1 

25.9 

18.7 

86,4 

11 

61-180 

57.0 

-11.1 

0.01 

58.6 

23 

1-15 

4 

July 

16-30 

528 

396 

0.2 

76.7 

5 

1966 

31-60 

622 

70.0 

90.9 

112.0 

20 

61-180 

4 

1-15 

0 

July 

16-30 

2 

1966 

31-60 

1 

61-180 

39.9 

-23.7 

0,002 

46.7 

9 

1-15 

-5.5 

5.6 

623 

41.1 

10 

July 

16-30 

4.0 

3.3 

1.7 

20.7 

6 

1966 

31-60 

30.6 

15  6 

51.9 

64.7 

9 

61-180 

30.0 

-13.2 

0,006 

33.1 

14 

N.J.- 


N,J 


N.J. 


L.I.' 


N-J. 


N.J. 


N.J. 


N.J. 


L.I. 


S.N.E.5 


N.J. 


N.J. 


N.J 


N.J. 


See  footnotes  at  end  of  table. 


903 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  2.- 

—Continued. 

Time  at 

Mean 

Mean 

Deter- 

No 

General 

Release 

liberty 

miles 

miles 

minant 

Mean 

of 

Release 

release 

group 

(days) 
1-15 

N-S' 

E-W2 

(xW) 

distance 

fish 

month 

location 

6E 

-282 

30 

1.8 

359 

14 

July 

L.I. 

16-30 

5.0 

58  1 

36.0 

824 

6 

1966 

31-60 

3 

61-180 

-38 

-3.6 

1.2 

16.8 

10 

7A 

1-15 
16-30 
31-60 
61-180 

1 
2 
1 
0 

Aug. 
1966 

L.I. 

7B 

1-15 

0.6 

221 

0.8 

268 

11 

Aug. 

L.I. 

16-30 

-11.4 

-15.5 

8.8 

524 

7 

1966 

31-60 

1 

61-180 

0 

7C 

1-15 

-2.0 

6.0 

1.3 

17.9 

9 

Aug. 

S.N.E. 

16-30 

-3.6 

6.0 

1.0 

289 

8 

1966 

31-60 

1 

61-180 

0 

7D 

1-15 

13.2 

25 

6.2 

28.2 

10 

Aug. 

S.N.E. 

16-30 

7.2 

-14.9 

120 

46.5 

8 

1966 

31-60 

1 

61-180 

0 

7E 

1-15 

-17.3 

26 

8.8 

29.3 

15 

Aug. 

S.N.E. 

16-30 

-8.8 

-21.7 

30.3 

50.3 

5 

1966 

31-60 

1 

61-180 

0 

7F 

1-15 

7.5 

-200 

4.5 

36.0 

39 

Aug. 

S.N.E. 

16-30 

7.5 

-17.4 

3.3 

28.9 

65 

1966 

31-60 

1.3 

-26.2 

15.6 

48.0 

14 

61-180 

1 

7G 

1-15 

-3.8 

-19.1 

3.0 

32.2 

37 

Aug. 

S.N.E. 

16-30 

-0.7 

-15.9 

3.1 

299 

50 

1966 

31-60 

-4.6 

-24.6 

12.8 

48.0 

14 

61-180 

1 

8 

1-15 
16-30 
31-60 
61-180 

1 
0 
0 
0 

Sept.- 
Oct. 
1966 

L.I. 

9A 

1-15 

2 

July 

N.J. 

16-30 

87.7 

12.7 

0.003 

69.1 

9 

1967 

31-60 

86.8 

26.8 

9.4 

76.6 

8 

61-180 

0 

9B 

1-15 

-18.4 

-7.1 

1.0 

27.4 

14 

July 

N.J. 

16-30 

13  1 

-3.6 

1.7 

24.0 

12 

1967 

31-60 

27.0 

7.1 

13.5 

39.3 

47 

61-180 

2 

10 

1-15 
16-30 
31-60 
61-180 

0 
0 
2 
0 

Sept 
1967 

L.I. 

11A 

1-15 
16-30 
31-60 

0 
2 

0 

July 
1968 

N  J. 

61-180 

^.0 

0.008 

228 

9 

11B 

1-15 

5.8 

22.4 

4.2 

32.8 

13 

July 

L.I. 

16-30 

10.4 

35.8 

0.3 

39.9 

11 

1968 

31-60 

1 

61-180 

4 

12 

1-15 
16-30 
31-60 
61-180 

4 
0 
4 
0 

July 
1969 

L.I. 

See  footnotes  at  end  of  table. 

904 


MATHER  ET  AL.:  TAGGED  BLUEFIN  TUNA 
Table  2. — Continued 


Release 
group 

Time  at 
liberty 
(days) 

Mean 
miles 

Mean 
miles 
E-W2 

Deter- 
minant 
(X  My) 

Mean 
distance 

No. 
of 
fisti 

Release 
month 

General 
release 
location 

13 

1-15 
16-30 
31-60 
61-180 

1 

1 
1 
0 

Aug. 
1969 

S.N.E. 

14 

1-15 
16-30 
31-60 
61-180 

0 
0 
0 
0 

Sept. 
1969 

S.N.E. 

15 

1-15 
16-30 
31-60 
61-180 

-1.7 
-24.4 

-20.6 
-6.8 

3.5 
0.5 

28.1 
28.2 

3 
9 
5 
0 

July 
1970 

S.N.E. 

16 

1-15 
16-30 
31-60 
61-180 

-13.1 
-33.0 

-14.7 
-11.6 

2.0 
69.6 

28.3 
67.7 

9 

7 
3 
1 

Aug. 
1970 

SN  E 

17 

1-15 
16-30 
31-60 
61-180 

-.2 

-10.4 

222.9 

57.1 

0 
3 
5 
0 

1954-63 

S.N.E. 

'Positive  values  signify  northward  movement.  Negative  values  signify  southward  movement. 
^Positive  values  signify  eastward  movement.  Negative  values  signify  westward  movement. 
^New  Jersey. 
*Long  Island. 
^Southern  New  England. 


Jersey  or  that  the  intensity  of  the  southern  New 
England  fishery  was  greater  than  that  off  New 
Jersey.  While  the  latter  may  be  true,  there  may  be 
alternative  interpretations  and  additional 
analysis  is  required.  It  is  also  suggested  that 
analysis  be  undertaken  for  tags  returned  after  the 
season  of  release. 

MORTALITY  ESTIMATION 

The  number  of  recoveries  per  year  from  releases 
by  year,  months  within  years,  and  various  group- 
ings of  years,  months,  and  release  locations  were 
employed  to  estimate  the  survival  rates  for  young 
bluefin  in  the  middle  Atlantic  bight  of  North 
America.  The  first  analyses  were  run  using  only 
the  data  employed  to  form  the  basic  groups  as 
defined  in  the  migration  analysis,  thus  eliminat- 
ing some  releases  which  were  substantially  differ- 
ent with  respect  to  their  location  and/or  time  of 
release  than  for  most  of  the  fish  tagged.  Although 
this  reduced  the  numbers  of  returns  used,  it  prob- 
ably did  not  greatly  affect  the  estimates  of  mortal- 
ity rates. 

Method  of  Release 

In  all  years  since  1961,  with  the  exception  of 
1963,  tuna  were  captured  for  tagging  by  both  sport 
and  commercial  gear  (purse  seine).  In  Table  3  the 


TIME  AT  LIBERTY  IN  DAYS 


< 

q: 

UJ 


NEW 
JERSEY 
COAST 


LONG 
ISLAND 
COAST 


SOUTHERN 

NEW 

ENGLAND 

COAST 


4e5(5Al 
..■'7  914CI 


29  6(2C) 
27  4(93 


46  4(46) 
33  6(4  A) 

31  6(28)  " 


32  6(1161 
26.6(76] 
326(3)    ^ 


,  24.0(96! 


393(96) 
69  I  (9A) 
20.7(6D) 
76  7(66) 
60-4(5A) 
64.6(4(3 
74  6(48) 
I02.0(4A) 
897^8) 


897(2' 

i<.oS 


766(9A) 
64  7(60) 
112  0(681 
66  4(6AI, 


22B(IIA) 

53  I  (60 

46  7(6C) 

.,5e6(6A) 


39.911161 
824(6E)^ 


.  360(7F1 

'  32  2(76) 

28  3(161 


I7  9(7cr 
29.3(7E) 


269(7F) 
..  ■'6.5(701 


'50,3(7E) 
299(761 
28.1(151 
67  7(16) 


28  9(7C)  ^       * 


4e0(7n 
4eof7G) 
282(15) 
57  1(17) 


Figure  2. — Summary  of  mean  distance  and  direction  of  migra- 
tion of  tagged  bluefin  tuna  stratified  by  time  at  liberty  and  by 
general  area  of  release.  Distances  are  in  nautical  miles.  Release 
group  numbers  are  given  in  parentheses. 

proportions  of  tagged  fish  returned  were  compared 
for  the  two  methods  of  original  capture.  Five  of  the 
nine  chi-square  tests  of  the  hypotheses  of 
homogeneity  indicate  highly  significant  differ- 
ences in  the  return  percentages  between  the  types 
of  gear  used  to  capture  the  tuna  for  tagging.  When 
only  the  5  yr  with  significantly  different  return 
rates  for  the  types  of  gear,  i.e.,  1965,  1966,  1968, 
1969,  and  1970  are  considered,  higher  return  per- 
centages were  obtained  for  sport  tagged  fish  in  4  of 


905 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Table  3.— Chi-square  tests  of  equality  of  return  probabilities  between  sport  and  commercial  gear  releases  of  tagged 
bluefin  tuna  in  the  northwestern  Atlantic  Ocean.  Each  test  has  1  degree  of  freedom. 


Sport 

Commercial 

Return 

Return 

rate 

rate 

Chi-square 

Year 

Release 

Return 

{9c ) 

Release 

Return 

rn 

value 

1961 

129 

7 

5.4 

21 

0 

0 

1.20 

1962 

52 

4 

7.7 

25 

0 

0 

2.03 

1964 

10 

3 

30.0 

455 

128 

28.1 

0.02 

1965 

43 

17 

39.5 

1,629 

244 

15.0 

19.18** 

1966 

187 

84 

44.9 

3,772 

1,094 

29.0 

21  60** 

1967 

14 

3 

21.4 

614 

183 

29.8 

0.46 

1968 

41 

11 

26.8 

219 

104 

47.5 

5.98* 

1969 

244 

91 

37.3 

92 

15 

16.3 

1 3.63** 

1970 

425 

162 

38.1 

32 

6 

188 

4.80* 

**Signi 

ficant  at  the  0.01  level. 

*Signi 

ficant  at  the  0.05  level. 

the  5  yr.  The  data  cannot  be  pooled  over  years  to 
increase  the  numbers  in  individual  cells  in  the 
chi-square  tables  since  the  recovery  percentages 
and  numbers  tagged  vary  so  greatly  from  year- 
to-year. 

However,  the  Mantel-Haenszel  test  can  be  used 
to  examine  the  data  in  toto  (Snedecor  and  Coch- 
ran, 1967:255-256).  The  calculations  resulted  in 
a  value  of  8.89,  which  is  highly  significant.  As  is 
discussed  in  a  later  section,  we  think  that  most  of 
the  difference  between  return  rates  of  sport  and 
commercial  tagged  fish  is  caused  by  immediate 
tagging  mortality.  Immediate  tagging  mortality 
does  not  affect  estimates  of  instantaneous  total 
mortality.  Therefore,  we  decided  to  use  as  much  of 
the  available  data  as  possible  and  combined  the 
data  for  estimates  of  mortality  rates.  Immediate 
tagging  mortality  does  affect  estimates  of  rates  of 
exploitation  and  the  components  of  mortality.  Ad- 
justments were  made  in  an  attempt  to  remove  the 
effects  of  immediate  tagging  mortality  and  tag 
shedding. 

Total  Mortality  Estimates  - 
Chapman  and  Robson  Method 

Following  the  notation  of  Bayliff  and  Mobrand 
( 1972),  the  number  of  tags  remaining  on  bluefin  at 
time  t  (years)  is  given  by 


p     =    portion  of  tags  which  are  retained 
after  Type-I  shedding  takes  place 

Z     =    instantaneous  total  losses  on  an 
annual  basis. 

Z  ^F  +  X 

where  F     =    instantaneous  fishing  mortality 
on  an  annual  basis 
X     =    instantaneous  other  losses  on 
an  annual  basis. 

X=M+G+L+E 

where  M    =    instantaneous  natural  mortality 

on  an  annual  basis 
G     =    instantaneous  Type-II  tagging 

mortality  on  an  annual  basis 
L      =    instantaneous  Type-II  tag 

shedding  on  an  annual  basis 
E     =    instantaneous  emigration  from 

fishing  grounds  on  an 

annual  basis. 

The  number  of  tags  returned  during  a  year  is 
given  by 


n,   = 


FcN, 


a-e'^) 


(2) 


A^,  =A^,  TTpe-^' 


(1) 


where  Nf     =    Number  of  tags  remaining  on 
bluefin  at  time  t 
number  of  released  tags 
portion  of  bluefin  which  remain 
alive  after  Type-I,  immediate, 
tagging  mortality  takes  place 


Nn       = 


77  - 


where  rii     = 


c       = 


number  of  tags  returned 
between  t  and  t  +  1 

portion  of  recovered  tags 
that  are  returned. 


Many  assumptions  are  implicit  in  the  above 
model.  An  exponential  model  is  assumed  to  be 


906 


MATHER  ET  AL.:  TAGGED  BLUEFIN  TUNA 


correct.  It  is  assumed  that  all  instantaneous  shed- 
ding, mortality,  and  emigration  rates  are 
constant — within  years  and  among  years.  Since 
fishing  was  concentrated  during  the  summer  sea- 
son, the  assumption  of  constant  fishing  mortality 
is  not  valid.  Also  fishing  effort  probably  varied 
over  the  years  of  the  study.  Available  measures  of 
fishing  effort  are  thought  to  be  inaccurate  but 
were  used  in  the  last  part  of  the  analysis.  The 
validity  of  the  assumption  of  constant  rate  of 
emigration  is  not  known,  but  tag  returns  suggest 
that  transatlantic  migrations  are  sporadic.  This 
suggests  that  the  assumption  of  constant  emigra- 
tion is  not  valid.  While  we  recognize  that  some  of 
our  assumptions  probably  are  invalid,  it  is  our 
judgment  that  the  effect  of  the  violations  on  our 
results  is  not  serious. 

For  the  first  part  of  the  analysis  we  assumed 
that  c,  77,  and  p  equal  one.  In  the  first  analysis 
minimum  variance  unbiased  estimates  of  the  total 
annual  survival  rates  were  computed  by  the 
method  developed  by  Chapman  and  Robson  ( 1960) 
for  the  recovery  data  by  year  pooled  in  a  variety  of 
different  ways  over  release  categories.  Confidence 
intervals  were  computed  fors,  the  fraction  surviv- 
ing per  year,  andZ,  the  associated  instantaneous 
mortality  rate.  A  chi-square  test  was  used  to  de- 
termine if  the  number  of  recaptures  in  the  first 
recovery  period  is  compatible  with  the  survival 
pattern  exhibited  by  the  rest  of  the  data,  i.e.,  if  the 
hypothesis  of  constant  F  and  X  is  true.  This  test 
was  applied  sequentially,  i.e.,  the  second  year  was 
defined  as  the  first  recapture  category  and  the  test 
repeated  until  either  all  recapture  years  were 
eliminated  or  a  survival  rate  was  obtained  from 
some  subset  of  the  data.  For  all  releases  the  tag- 
ging year  was  taken  as  the  first  recapture  category 
at  the  start  of  the  analysis.  The  results  of  the 
survival  rate  computations  are  shown  in  Table  4 
for  the  following  data  groupings: 

1)  Over  all  years 

2)  Over  three  adjacent  release  years 

3)  Individual  years 

4)  July  releases  for  three  adjacent 

release  years 

5)  Individual  months  within  years 

6)  Release  groups  as  defined  in  Table  1. 

An  obvious  feature  of  this  analysis  is  that  in 
many  of  the  recapture  series,  the  numbers  recov- 
ered the  first  year  or  two  were  higher  than  ex- 
pected from  the  entire  recapture  series.  This  re- 


sult is  somewhat  surprising  because  it  might  be 
expected  that  the  number  recaptured  the  first  year 
would  be  underrepresented  because  of  less  expo- 
sure to  the  fishery.  Three  possible  factors  that  could 
have  caused  the  higher  than  expected  recaptures 
in  the  first  year  or  two  after  release  are: 

1 )  Tagged  fish  were  released  into  an  area  where 

fishing  activity  was  concentrated. 

2)  The  proportion  of  the  population  migrating 

into  the  fishing  area  decreased  as  the  fish 
became  older;  thus  the  availability  of  the 
tagged  fish  in  the  fishing  area  may  have 
fallen  off  rapidly  enough  in  later  years  to 
have  caused  a  disproportionate  number 
of  recaptures  in  the  first  and  second  years 
after  release. 

3)  The  method  of  estimation  assumes  constant 

fishing  mortality  rates  and  other  loss 
rates;  variability  in  recovery  effort  could 
have  caused  the  number  of  recaptures  per 
year  to  deviate  from  a  simple  exponential 
decline  with  time. 

Several  aspects  of  the  data  emerge  from  Table  4. 
The  estimates  of  survival  rates  are  low  but  highly 
erratic;  restricting  the  releases  to  finer  time- 
location  grids  did  not  improve  the  stability  of  the 
estimates  as  might  be  expected.  Since  no  time 
trend  in  survival  is  evident,  pooling  overyears  is  a 
useful  device  to  average  out  some  of  the  fluctu- 
ations in  the  data.  In  one  sense  this  is  a  substi- 
tute for  use  of  recapture  effort  statistics  and  work- 
ing with  the  number  of  recoveries  per  unit  of 
recovery  effort.  The  recaptures  per  year  were 
combined  over  years  using  various  weighting  fac- 
tors to  develop  adjusted  numbers  recaptured  per 
year.  None  of  these  weighting  schemes  offered  an 
improvement  in  the  use  of  the  simple  unweighted 
average  percent  recapture  per  year  at  liberty  for 
the  years  1964-68.  The  proportion  surviving  per 
year  as  estimated  from  the  simple  average  of  the 
percentages  was  0.188.  This  value  is  well  within 
the  confidence  interval  of  the  s -value  of  0.231  es- 
timated from  the  actual  numbers  pooled  over  all 
years.  For  the  latter  estimate,  however,  we  did  not 
use  the  recoveries  made  during  the  first  2  yr  at 
liberty. 

Inclusion  of  the  first  two  recapture  periods  in 
the  Chapman-Robson  analysis,  particularly  for 
the  last  set  of  release  groups  which  are  fairly 
homogeneous,  had  the  general  effect  of  reducing 
the  survival  estimates.  The  numbers  of  recaptures 


907 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 
Table  4. — Survival  rate  estimates  for  various  release  group  categories  of  tagged  hluefin  tuna. 


Type  of 

Recapture  years  used 

s{9&i  confidence 

Z{9Sf',  confidence 

group' 

Group 

in  s  and  Z  computation 

interval) 

interval) 

1 

All 

'(1,  2),  3,  4.  5 

0.231  (.16,  .30) 

1,44  (1.14,  1.75) 

1963-65 

. 

Not  constant  (NO) 

1964-66 

2(1,  2),  3,  4,  5 

.174(09,  .26) 

1.70  (1.23,  2.16) 

12 

1965-67 

(1)',  2,  3,  4,  5 

.118  (.10,  .14) 

2  13  (1.93,  2.32) 

1966-68 

2(1,  2),  3,  4,  5 

.254  (.14,  .37) 

1.32  (0.88,  1.77) 

1 967-69 

2(1),  2,  3,4 

.103(04,  .17) 

2.19(1.60,  2.79) 

1968-70 

- 

NO 

3 

1964 

. 

NO 

1965 

1,  2,  3,  4 

.343  (.29,  .39) 

1.07  (93,  1.21) 

1966 

2(1,  2),  3,  4,  5 

.233  (.14,  .32) 

1.42(1.03,  1.81) 

1967 

(1)',  2,  3,  4 

.323(24,  .41) 

1.11  (0.86,  1.37) 

1968 

1.  2.  3 

.243  (.17,  .31) 

1.39(1.11,  1  68) 

1969 

NO 

July  1963-65 

1,  2,  3 

.146  (.10,  .19) 

1.90(1,61,  2.19) 

July  1964-66 

2(1,  2),  3,4,  5 

.400  (.20,  .60) 

0.87  (0.39,  1.34) 

4 

July  1965-67 

2(1,  2),  3,  4,  5 

.355  (.18,  .53) 

0.99(0.51,  1.46) 

July  1966-68 

2(1,  2),  3,4,  5 

.367  (.19,  .55) 

0.96  (0,49,  1.42) 

July  1967-69 

1,  2,  3,  4 

.246  (.19,  .30) 

1.39(1.17,  1,61) 

July  1968-70 

NO 

July  1964 

1,  2 

.128  (.06,  .19) 

2.00  (1.50,  2.49) 

Aug-  1964 

- 

NO 

July  1965 

1,  2,  3 

.160  (.11,  .21) 

1.81  (1.48,  2.13) 

Aug    1965 

NO 

35 

July  1966 

2(1,  2),  3,  4,  5 

.407  (.21,  .60) 

0.85(0,40,  1.30) 

Aug.  1966 

2(1,  2),  3,  4,  5 

.085(05,  .12) 

2.43(2.08,  2  79) 

July  1967 

1,  2',  3,  4 

.244  (.18,  .31) 

1.39(1.13,  1.66) 

Aug.  1967 

- 

NO 

July  1968 

1,2,3 

.201  (.13,  .27) 

1.57(1.23,1.92) 

July  1969 

- 

NO 

Aug.  1969 

- 

NO 

G1 

1,  2,  3,  4 

.582  (.45,  .72) 

0.53(0-31,  0.75) 

G2A 

1,  2 

.189  (.06,  .32) 

1.57(0.90,  2.24) 

G2B 

1,2 

.065(00,  .15) 

2.45(1.10,  3.79) 

G2C 

1,  2 

.160  (.01,  .31) 

1  68  (0.78,  2.58) 

3 

- 

NO 

4A 

1,  2,3 

.190(07,  .31) 

1.57  (0.95,  2.20) 

4B 

1,  2,  3 

.165(09,  .24) 

1.75  (1.30,  2.21) 

4C 

1,  2 

.083  (.00,  .18) 

2.27  (1,18,  3.36) 

5A 

- 

NO 

5B 

- 

NO 

5C 

- 

NO 

6A 

- 

NO 

68 

- 

NO 

60 

- 

NO 

6D 

- 

NO 

6 

6E 

- 

NO 

7A 

- 

NO 

78 

2(1,  2),  3,  4,  5 

.375(01,  .74) 

0.88(0.04.  1  71) 

70 

2(1),  2,  3,  4 

.083  (.01,  .16) 

2.34  (1.49,  3.19) 

7D 

- 

NO 

7E 

- 

NO 

7F 

- 

NO 

7G 

- 

NO 

8 

2(1),  2,  3,  4 

.125  (.00,  .26) 

1.88(0.83.  2.94) 

9A 

1,  2 

.154  (.01,  .30) 

1.72(0.82,  2.62) 

98 

1,  2,  3,  4 

.205  (.13,  .28) 

1,55  (1,19,  1,92) 

10 

- 

NO 

11A 

1.  2,  3 

.357  (.17,  .54) 

0.98(0.48,  1-47) 

11B 

1,2,3 

.240  (.12,  .36) 

1-37  (0.87,  1.87) 

12 

. 

NO 

13 

. 

NO 

14 

- 

NO 

'Includes  tacfs  assigned  by  cruise  number 

2Recapture  years  eliminated  by  chi-square  test  of  full  recruitment  to  tagged  population  are  shown  in  parentheses. 

'July  results  include  tags  assigned  by  cruise  number. 


908 


MATHER  ET  AL.:  TAGGED  BLUEFIN  TUNA 


dropped  off  so  rapidly,  however,  after  the  first  two 
recapture  periods  that  little  reliability  can  actu- 
ally be  placed  on  estimates  using  only  data  from 
the  tail  end  of  the  time  series. 

This  first  examination  of  the  recaptures  by  time 
at  liberty  was  followed  by  a  revised  analysis  of  the 
July  releases  each  year  and  all  releases  each  year 
for  1964  through  1968.  An  attempt  to  include  all 
tags  in  the  analysis  was  made  by  assigning  tags 
without  recorded  release  dates  to  most  likely  re- 
lease dates  by  means  of  the  accompanying  infor- 
mation, e.g.,  by  cruise  number.  For  the  most  part 
this  revision  produced  minor  changes  in  the  esti- 
mates of  total  survival  rates.  Raw  exploitation 
rates  were  estimated  from  the  total  number  of 
recaptures  per  release  using  all  data  whether  or 
not  any  information  was  available  on  date  of  re- 
capture. 

Estimates  of  Fishing  and  Other  Losses 

We  used  the  following  equations  to  estimate 
rates  of  exploitation,  fishing,  and  other  losses: 

where  ii  7^    =    estimate  of  total  exploitation  of 
tagged  bluefin  tuna  over  n  years 

R      =    number  of  tag  returns. 

n 


where  s      = 


Ui 


survival  rate  estimated  from 

revised  data  by  the  Chapman- 

Robson  method 
estimate  of  single  season 

exploitation  of  tagged 

bluefin  tuna. 

F  =  u    (-In  s)/(l  -  s) 


X  =   ln(s)  -  F 

These  estimates  for  July  releases  are  shown  in 
Part  A  of  Table  5,  and  in  Part  B  of  the  same  table, 
estimates  of  the  same  set  of  parameters  for  all 
releases  are  given  with  the  exception  of  the  single 
season  exploitation  rates.  We  believe  that  dis- 
tributing the  releases  during  the  entire  fishing 
season,  rather  than  restricting  them  to  the  first 
part  of  the  season,  July,  makes  it  impossible  to 
estimate  a  single  season  exploitation  rate.  It  will 
be  noted  that  the  actual  observed  exploitation 
rates  are  high,  especially  in  view  of  the  fact  that 
no  corrections  were  made  for  either  immediate 
tagging  mortality,  tag  shedding,  or  nonreporting. 
The  total  recapture  percentages  range  from  16% 
to  48%. 

Lenarz  et  al.  (1973)  estimated  that  the  rate  of 
immediate  tag  shedding  (1  -  p  )  for  Atlantic 
bluefin  tuna  is  0.027  and  that  the  instantaneous 
rate  of  tag  shedding  (L)  is  0.310.  Their  estimates 
were  used  to  correct  our  estimates  of  exploitation 
and  mortality  rates  for  shedding  as  follows: 


Table  5. — Estimates  of  total  survival,  rate  of  exploitation,  fishing  mortality  rate  and  total  other  loss  rate  of 
tagged  bluefin  tuna  for  July  releases  and  for  all  releases  by  year  of  release. 


Item 

1964 

1965 

1966 

1967 

1968 

Part  A.  July  releases  only; 

(N)  Numbers  released 

397 

951 

2,047 

448 

226 

(R)  Numbers  recovered 

96 

169 

461 

131 

108 

s 

0.128 

0  160 

0.407 

0.244 

0.201 

"1 

0.211 

0.150 

0.143 

0.224 

0.385 

U   rp 

0.242 

0.178 

0.225 

0.292 

0.478 

F 

0.497 

0.327 

0.217 

0.418 

0.773 

je 

1.558 

1.506 

0.697 

0.999 

0.838 

[F  +  X) 

2.056 

1.833 

0.899 

1.411 

1.604 

Part  B,  All  releases  by  year; 

(N)  Numbers  released 

465 

1,672 

3.959 

628 

260 

(R)  Numbers  recovered 

132 

262 

1,177 

187 

116 

s 

0.196 

0.343 

0.233 

0.323 

0.243 

Uj. 

0284 

0.157 

0.297 

0.298 

0.446 

F 

0.463 

0.168 

0.433 

0.337 

0.631 

^ 

1.167 

0.902 

1.024 

0.793 

0.784 

(F  +  A') 

1  630 

1.070 

1.457 

1.130 

1.415 

909 


FISHERY  BULLETIN:   VOL.   72,  NO.  4 


(F  +Xf    =F  +X   -L 

where  (F  +  X)*  =  estimate  of  total  instantaneous 
apparent  mortality  corrected 
for  tag  shedding  rate, 


Table  6. — Estimates  of  rates  of  exploitation  and  mortality  of 
bluefin  tuna  corrected  for  tag  shedding. 


where  s* 


where  u^ 


where  Uj 


where  F* 


where  X* 


s*  =e-'^  +  ^'' 


=  estimate  of  annual  survival 
corrected  for  shedding  rate, 

=  estimate  of  total  exploitation 
of  tagged  bluefin  tuna  cor- 
rected for  immediate  tag 
shedding, 

«1     =   Uilp 

=  estimate  of  seasonal  exploi- 
tation corrected  for  immediate 
tag  shedding, 

F*  =ut    (-InsVd  -s) 

=  estimate  of  F  corrected  for 
immediate  tag  shedding, 

X*  =  -ln(s*)  -F* 

=  estimate  of  X  corrected  for 
immediate  tag  shedding. 


"1 


F* 


F=^  +  X'' 


(1  -  s*) 


where  u  ^ 


estimate  of  single  season 
exploitation  of  tagged  and 
untagged  bluefin  corrected 
for  all  tag  shedding,  and 


U  T 


Z 


where  u 


** 


estimate  of  total  exploitation 
of  tagged  and  untagged  bluefin 
corrected  for  all  tag  shedding. 


The  estimates  are  shown  in  Table  6.  Estimates 
ofX*  (other  losses)  range  from  0.366  to  1.234  (av- 
erage =  0.792).  The  estimates  ofX*  are  considera- 
bly higher  than  expected  values  of  M  (natural 


Item 

1964 

1965 

1966 

1967 

1968 

(F  +  .Y)' 

1.746 

1,523 

0589 

1  101 

1.294 

s* 

0.174 

0.218 

0.555 

0333 

0.274 

0.249 

0.183 

0.231 

0.300 

0.401 

"l 

0.217 

0.154 

0.147 

0230 

0,396 

F* 

0512 

0.336 

0.223 

0429 

0.795 

X* 

1.234 

1.187 

0.366 

0.671 

0.499 

uT 

0.242 

0-172 

0.168 

0.260 

0.446 

-** 

0,284 

0,218 

0.342 

0.388 

0.611 

mortality)  for  bluefin.  Bluefin  are  very  long-lived 
fish  and  values  of  M  of  0.1  to  0.2,  if  M  is  constant, 
would  seem  reasonable.  Thus,  there  may  be 
significant  amounts  of  Type-I  (immediate)  and 
Type-II  (long-term)  tagging  mortality,  nonreport- 
ing,  and/or  apparent  mortality  caused  by  emigra- 
tion. 

It  seems  plausible  that  some  Type-I  tagging 
mortality  exists.  In  an  earlier  section  it  was  noted 
that,  more  returns  were  obtained  from  sport  gear 
releases  than  from  commercial  gear  releases. 
Statistically  significant,  more  returns  were  ob- 
tained from  sport  releases  than  commercial  re- 
leases in  1965,  1966,  1969,  and  1970.  A  possible 
cause  of  the  difference  in  return  rates  could  be  that 
sport  tagged  bluefin  are  of  different  ages  than 
commercially  tagged  bluefin.  Bluefin  of  different 
ages  could  suffer  different  rates  of  tagging  mortal- 
ity and  shedding,  and  could  behave  differently. 
Data  have  not  been  compiled  in  a  fashion  that 
allows  examination  of  the  age  at  release  by  the 
two  gear  t3^es.  We  recommend  that  it  be  and 
assume  for  the  present  that  age-dependent  effects 
are  negligible.  The  differences  in  return  rates 
could  also  be  caused  by  Type-I  tagging  mortality. 
Experienced  taggers  report  that  sport-gear- 
caught  bluefin  appear  to  be  in  better  condition 
than  those  caught  by  commercial  gear.  Also, 
commercial  gear  tends  to  capture  entire  schools  of 
bluefin  while  sport  gear  captures  one  bluefin  at  a 
time.  Thus,  bluefin  released  from  sport  gear  tend 
to  be  released  into  the  immediate  area  of  a  school 
of  bluefin  while  bluefin  released  from  commercial 
gear  are  not.  There  may  be  an  advantage  for 
bluefin  to  be  in  a  school.  Bayliff  ( 1973)  found  that 
return  rates  of  purse-seine-caught  yellowfin  tuna 
tagged  immediately  after  a  set  is  made  can  be 
more  than  two  times  higher  than  yellowfin  tagged 
at  a  later  time  (Table  7).  This  evidence  suggests 
that  Type-I  tagging  mortality  is  very  important 


910 


MATHER  ET  AL.:  TAGGED  BLUEFIN  TUNA 


Table  7. — Releases,  returns,  and  percentages  of  return  of 
yellowfin  tuna  for  lATTC  Cruise  1055,  by  time  between  com- 
mencement of  tagging  and  release  offish  (from  Bayliff,  1973). 


where  X** 


Time 

Number 

Number 

(min) 

released 

returned 

';  returned 

0-10 

1.920 

277 

14.4 

10-20 

1.972 

195 

9.9 

20-30 

1.563 

86 

5.5 

30-40 

1,145 

47 

4.1 

40-50 

934 

44 

4.7 

>50 

975 

23 

2.4 

Total 

8.509 

672 

7.9 

'Inter-American  Tropical  Tuna  Commission. 

for  purse-seine-caught  yellowfin  tuna.  Bayliff^ 
(pers.  commun.)  believes  that  bluefin  tuna  are 
more  hardy  than  yellowfin  tuna  and  thus  expects 
that  Type-I  tagging  mortality  is  lower  for  bluefin 
than  for  yellowfin. 

Assuming  that  sport  releases  suffered  insig- 
nificant amounts  of  Type-I  tagging  mortality 
and  using  the  Mantel-Haenszel  weighting  proce- 
dure, the  1964-68  average  Type-I  tagging  mortal- 
ity for  commercial  tagged  fish  was  21%.  During 
this  period,  96%  of  the  releases  were  commercial 
tagged  fish.  The  average  Type-I  tagging  mortality 
for  all  releases  during  1964-68  was  20%. 

The  rates  of  exploitation  and  mortality  were 
corrected  for  Type-I  tagging  mortality  as  follows: 


Un^'^ 


=  Uj^  /n 


where  u 


*^^ 


where  w'j"' 


estimate  of  total  exploitation 
corrected  for  shedding  and 
Type-I  tagging  mortality. 


Uy  =     «    J       /77 


estimate  of  seasonal 
exploitation  corrected  for 
shedding  and  Type-I 
tagging  mortality. 


=  «r""  (-  lns*)/(l 


s*) 


where  F*' 


=      estimate  of  F  corrected  for 
shedding  and  Type-I  tagging 
mortality,  and 

X**  =  -  In  (s*)  -  F** 


estimate  of  X  corrected  for 
shedding  and  Type-I 
tagging  mortality. 


The  estimates  are  shown  in  Table  8.  The  values 
ofZ**  range  from  0.300  to  1.109  (average  =  0.678) 
and  are  still  higher  than  the  expected  rate  of 
natural  mortality  for  bluefin.  The  large  difference 
between  values  for  1964-65  and  the  values  for 
1966-68  is  worth  noting.  Food  and  Agriculture 
Organization  ( 1972)  reports  that  a  relatively  large 
number  of  bluefin  tuna  tagged  in  the  northwest 
Atlantic  in  1965  were  recovered  in  the  Bay  of 
Biscay  during  the  following  year.  This  suggests 
that  a  large-scale  transatlantic  migration  oc- 
curred between  the  1965  and  1966  fishing  seasons. 
Thus  migration  from  the  fishery  is  a  plausible 
explanation  for  a  portion  of  X**. 

Table  8. — Estimates  of  rates  of  exploitation  and  mortality  for 
northwest  Atlantic  bluefin  tuna.  The  rates  have  been  corrected 
for  tag  shedding  and  a  hypothetical  value  of  Type-I  tagging 
mortality. 


1964 

1965 

1966 

1967 

1968 

Average 

u^ 

0.355 

0272 

0.428 

0,485 

0,764 

'0,456 

u*r 

0302 

0.215 

0.210 

0325 

0,558 

'0,327 

F** 

0.639 

0.419 

0,278 

0,536 

0995 

0,573 

X** 

1.110 

1.104 

0.311 

0,564 

0,300 

0,678 

«Bayliff,  W.  H.  Inter- Am.  Trop.  Tuna  Comm.,  P.  O.  Box  271,  La 
Jolla,  CA  92037. 


'Calculated  from  averages  ofF**  andX**, 

Total  Mortality  Estimates  - 
Regression  Method 

We  next  used  available  effort  data  for  examin- 
ing the  effect  of  changes  in  effort  on  our  estimates 
of  mortality.  The  effort  data  were  obtained  from 
inquiries  and  logbooks  of  purse  seiners  that  par- 
ticipated in  the  commercial  fishery  for  bluefin  in 
the  northwestern  Atlantic.  The  data  have  not 
been  standardized  by  vessel  class.  We  question  the 
validity  of  the  data  as  a  measure  of  fishing  effort, 
i.e. ,  proportional  to  F,  because  a  varying  portion  of 
the  fleet  relied  heavily  on  airplane  scouting.  Con- 
version of  the  data  to  a  standard  unit  of  effort  is 
worth  a  study  in  itself  and  we  recommend  that 
such  a  study  be  carried  out. 

In  another  attempt  to  estimate  total  mortality 
the  natural  logarithm  of  the  number  of  returns  per 
unit  effort  (Table  9),  taking  the  number  of  boat- 
days  recorded  per  season  as  a  legitimate  measure 
of  effort,  was  regressed  on  time  as  measured  to  the 
center  of  each  year  following  the  release.  An  exact 


911 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  9. — Returns  of  tagged  bluefin  tuna  per  boat-day  by  years 

at  liberty. 


Year 

0 

1 

2 

3 

4 

Part  A.  July  releases  only; 

1964 

00902 

0.0344 

1965 

0.3538 

00968 

0.0374 

1966 

0.9839 

1.3957 

0.1059 

0.0526 

0.0111 

1967 

0.5080 

0.3647 

0,0421 

0.0037 

1968 

1.0235 

0.1579 

0.0222 

Part  B.  All  releases; 

1964 

0.1100 

0.0786 

1965 

0.4029 

0.3280 

0.1925 

00718 

1966 

2.8495 

3.1016 

0.6235 

0.0842 

0.0222 

1967 

0.5241 

0.7059 

0.1684 

0.0481 

1968 

1.0353 

0.2000 

00333 

analytical  formulation  of  this  mortality  model  has 
two  independent  variates — cumulative  time  and 
cumulative  effort.  Not  only  are  these  two  vari- 
ables so  highly  correlated  that  it  is  virtually  im- 
possible to  obtain  useful  estimates  of  the  two  re- 
gression coefficients,  but  also  there  are  too  few 


data  points  available  for  multiple  regression 
analysis.  The  regression  coefficient  of  the  simple 
cumulative  time  regression  is  a  crude  measure 
of  the  total  mortality  rate.  The  fitted  regression 
lines  are  shown  in  Figure  3  for  July  releases  and 
in  Figure  4  for  all  releases  for  each  year.  The 
values  of  the  coefficients  are  given  in  Table  10. 

With  the  exception  of  1966,  when  the  returns 
per  boat-day  increased  during  the  year  following 
release  (and  the  data  were  eliminated  from  the 
regression),  the  logarithms  of  the  recaptures  per 
unit  effort  decrease  in  a  linear  fashion  and  it  is 
clear  the  regressions  provide  reasonable  fits  to  the 
data  points.  Seven  of  the  eight  estimated  survival 
rates  shown  in  Table  10  are  lower  than  their  coun- 
terparts in  Table  5.  Both  of  these  analyses  provide 
at  best  only  crude  approximations  of  the  true  sur- 
vival rates;  however,  they  do  show  fair  general 
agreement.  The  catch-per-effort  estimates  indi- 
cate the  loss  rates  are  tending  to  increase  with 
time. 


< 
o 

CD 

oc 

LiJ 
Q. 

C/) 
UJ 
(£ 

3 


< 
O 
Ijj 


5.0 


Q05  - 


Q02 


0.01 


0.006  - 


0.002' 1 1 1 L 


0        0.5        1.0        1.5       20        2.5       3.0        3.5        4.0       4.5        5.0 

YEARS    AT  LIBERTY 

Figure  3. — Regression  of  recaptures  per  boat-day  vs.  time  at 
liberty  for  July  releases  of  tagged  bluefin  tuna. 


o 

I 

I- 
< 
o 

CD 

ca 

LlI 
Q. 

CO 
UJ 

q: 

t- 

Q. 
< 
O 


0.05  - 


0.02  - 


0.01  - 


0.005  - 


0.002 


0        05        1.0        1.5        2.0       2.5      3.0       3.5       4.0       4.5 

YEARS    AT  LIBERTY 


5.0 


Figure  4. — Regression  of  recaptures  per  boat-day  vs.  time  for  all 
releases,  by  year,  of  tagged  bluefin  tuna. 


912 


MATHER  ET  AL.:  TAGGED  BLUEFIN  TUNA 


Table  10. — Estimates  of  total  survival  rates  of  tagged  bluefin 
tuna  from  regression  analysis  of  return  per  unit-of-effort  data. 


July  releases  only 

All  releases 

Year 

Z                                   6 

Z 

s 

1965 

1.12                 0.33 

1.08 

0.34 

1966' 

1.51                 0.22 

1.68 

0.19 

1967 

1.70                  0.18 

1.41 

0.24 

1968 

1.87                  015 

1.73 

0.18 

Average^ 

1.55                30.21 

1.48 

30.23 

'Recaptures  in  release  year  not  included  in  1966  regression  analysis. 

^Regression  estimates  using  average  unweighted  percentage  returns 
for  1964-68  are:  Z  =  1.67  and  s  =  0.19.  This  estimate  happens  to  be  exactly 
the  same  as  the  estimate  of  Z  =  1.67  =  (average  time  at  liberty)  '  where 
average  time  at  liberty  is  0.60  yr. 

^Survival  rate  computed  from  average  Z-value. 


sizes  are  more  vulnerable  than  others,  a  Peterson 
tagging  experiment  is  apt  to  overemphasize  the 
vulnerable  ones  both  in  respect  to  tags  put  out  and 
recaptures  made;  hence  the  estimate  of  rate  of 
exploitation  is  too  high  and  the  population  esti- 
mate is  too  low."  Future  analysis  stratifying  the 
data  by  age  at  release  would  help  to  answer  some 
questions  that  arise  because  of  the  migratory  be- 
havior of  bluefin.  We  suggest  cohort  analysis  in 
the  fashion  of  Bayliff  (1971)  as  a  productive 
method  of  analysis. 

ACKNOWLEDGMENTS 


DISCUSSION 

Exactly  what  these  "survivals"  are  measuring 
is  of  prime  interest.  They  are  properly  thought  of 
as  the  results  of  disappearance  rates  which  are 
composed  of  mortalities  {F,  M,  and  G),  tag  shed- 
ding, and  changing  migratory  patterns  with  age. 
Apparently  few  of  the  older  fish  entered  the  sur- 
face fishery  in  the  western  north  Atlantic  during 
the  period  of  the  study  and  the  decreasing  propor- 
tion of  the  population  that  entered  the  fishery  is  a 
primary  factor  lowering  the  apparent  survival.  In 
1966  when  the  fish  tagged  were  significantly 
younger  than  in  the  other  years — having  an  aver- 
age age  of  1.4  yr  as  opposed  to  average  ages  of  at 
least  a  year  older  in  other  tagging  years — the 
greatest  return  of  tags  occurred  during  the  year 
after  release.  For  these  younger  bluefin,  a  higher 
proportion  returned  to  the  fishing  area  the  year 
after  they  were  released  than  for  the  older  tagged 
fish. 

The  exploitation  rate  on  the  tagged  fish  was 
exceedingly  high  when  they  were  in  the  fishery. 
The  high  fishing  mortality  rates  in  Table  8  may 
underestimate  the  true  rates  for  tagged  bluefin; 
most  of  the  various  sources  of  error  that  may  bias 
these  estimates  act  to  decrease  the  estimate  of  the 
fishing  rate  relative  to  its  true  value.  However,  it 
is  known  that  bluefin  available  to  the  northwest 
Atlantic  fisheries  are  not  a  closed  population. 
Tagging  studies  have  revealed  transatlantic  mi- 
grations to  and  from  the  fishery.  Migration  could 
also  occur  from  the  middle  Atlantic.  Thus  it  must 
still  be  determined  whether  the  high  exploitation 
rate  applied  to  the  population  or  just  to  the  portion 
of  the  population  that  entered  the  fishery.  Ricker 
(1958:35)  describes  the  effects  of  tagging  fish  that 
are  more  vulnerable  to  fishing  than  other  mem- 
bers of  the  population.  "Again,  if  fish  of  certain 


We  are  greatly  indebted  to  W.  H.  Bayliff  of  the 
Inter-American  Tropical  Tuna  Commission,  La 
Jolla,  for  reviewing  an  early  version  of  this  paper 
and  providing  many  useful  suggestions.  During 
the  course  of  the  study,  discussions  with  W.  W. 
Fox,  Jr.,  T.  D.  Smith,  and  J.  R.  Zweifel  of  the 
Southwest  Fisheries  Center,  National  Marine 
Fisheries  Service,  NOAA,  La  Jolla,  proved  quite 
fruitful.  We  thank  D.  Kramer  also  of  the  South- 
west Fisheries  Center  for  his  technical  editing  of 
the  paper.  We  greatly  appreciate  the  extensive 
efforts  of  M.  R.  Bartlett  and  J.  M.  Mason,  Jr.  of  the 
Woods  Hole  Oceanographic  Institution,  Woods 
Hole,  Mass.,  towards  the  tagging  of  bluefin  tuna 
and  collection  of  associated  data. 

The  principal  financial  support  of  the  WHOI 
Cooperative  Game  Fish  Tagging  Program 
since  1956  has  been  from  the  National  Science 
Foundation  (Grants  G-861,  G-2102,  G-8339, 
G-6172,  G-19601,  GB-3464,  and  GH-82), 
the  Bureau  of  Commercial  Fisheries  (now 
National  Marine  Fisheries  Service)  (Contracts 
14-17-0007-272,  -547,  -870,  -975,  and  -1110),  and 
the  Office  of  Sea  Grant,  National  Oceanic  and 
Atmospheric  Administration,  U.S.  Department  of 
Commerce  (Grant  GH-82).  Important  additional 
support  has  been  received  from  the  Sport  Fishing 
Institute;  the  Charles  W.  Brown,  Jr.,  Memorial 
Foundation;  the  Tournament  of  Champions 
(through  Mrs.  R.  C.  Kunkel  and  E.  D.  Martin);  A. 
Minis,  Jr.;  the  Joseph  A.  Teti,  Jr.,  Foundation;  the 
Port  Aransas  Rod  and  Reel  Club;  P.  A.  B.  Widener; 
the  Jersey  Cape  Fishing  Tournament;  the  As- 
sociates of  the  Woods  Hole  Oceanographic  Institu- 
tion; and  many  other  sportsmen's  organizations 
and  individual  sportsmen. 

The  National  Marine  Fisheries  Service  and  its 
predecessor,  the  Bureau  of  Commercial  Fisheries, 
the  Inter-American  Tropical  Tuna  Commission, 

913 


the  Fisheries  Research  Board  of  Canada,  the  Food 
and  Agriculture  Organization  of  the  United  Na- 
tions, and  many  other  national  and  private  re- 
search organizations  have  assisted  in  the  promot- 
ing of  the  tagging  of  fishes,  and  the  return  of  tags 
with  recapture  data. 

The  tagging  results  were  made  possible  by  the 
thousands  of  anglers,  captains,  and  mates  who 
have  tagged,  and  released  many  of  their  catches, 
the  commercial  tuna  fishermen  who  have  cooper- 
ated with  the  tagging  program,  and  the  clubs, 
committees  and  individuals  who  have  encouraged 
tagging.  We  regret  that  space  does  not  permit 
individual  acknowledgments  here;  the  major  par- 
ticipants are  listed  in  the  informal  progress  re- 
ports which  are  issued  periodically  by  the  Woods 
Hole  Oceanographic  Institution.  The  press  and 
the  broadcasting  media  have  also  done  much  to 
encourage  tagging  and  the  return  of  tags. 

LITERATURE  CITED 

Bayliff,  W.  H. 

1971.  Estimates  of  the  rates  of  mortality  of  yellowfin  tuna 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 

in  the  eastern  Pacific  Ocean  derived  from  tagging  experi- 
ments. Bull  Inter-Am.  Trop.  Tuna  Conim.  15:381-436. 

1973.  Materials  and  methods  for  tagging  purse  seine-  and 
baitboat-caught  tunas.  Bull.  Inter-Am.  Trop.  Tuna 
Comm.  15:465-503. 
Bayliff,  W.  H.,  and  L.  M.  Mobrand. 

1972.  Estimates  of  the  rates  of  shedding  of  dart  tags  from 
yellowfin  tuna.  Bull.  Inter-Am.  Trop.  Tuna  Comm. 
15:441-462. 
Bayliff,  W.  H.,  and  B.  J.  Rothschild. 

In  press.  Migrations  of  yellowfin  tuna  tagged  off  the  south- 
ern coast  of  Mexico  in  1960  and  1969.  Bull.  Inter-Am. 
Trop.  Tuna  Comm.  16:1-64. 

Chapman,  D.  G.,  and  D.  S.  Robson. 

1960.  The  analysis  of  a  catch  curve.  Biometrics  16:354-368. 
Food  and  Agriculture  Organe  ation  of  the  United  Nations. 

1972.  Final  report  of  the  working  party  on  tuna  and 
billfish  tagging  in  the  Atlantic  and  adjacent  seas.  FAO 
(Food  Agric.  Organ.  U.N.)  Fish.  Rep.  118,  Suppl.  1,  37  p. 

Lenarz,  W.  H.,  F.  J.  Mather  III,  J.  S.  Beckett,  A.  C.  Jones,  and 
J.  Mason,  Jr. 

1973.  Estimation  of  rates  of  tag  shedding  by  northwest 
Atlantic  bluefin  tuna.  Fish.  Bull.,  U.S.  71:1103-1105. 

Kicker,  W.  E. 

1958.  Handbook  of  computations  for  biological  statistics  of 
fish  populations.  Fish  Res.  Board  Can.  Bull.  119,  300  p. 
Snedecor,  G.  W.,  and  W,  G.  Cochran. 

1967.  Statistical  methods.  6th  ed.  Iowa  State  College  Press, 
Ames,  Iowa,  593  p. 


914 


FEEDING  RELATIONSHIPS  OF  TELEOSTEAN  FISHES 
ON  CORAL  REEFS  IN  KONA,  HAWAII 


Edmund  S.  Hobson^ 


ABSTRACT 

Feeding  relationships  of  teleostean  fishes  on  coral  reefs  at  Kona,  Hawaii,  were  studied  during  1969  and 
1970. 

Fishes  that  have  a  generalized  feeding  mechanism,  including  those  carnivores  whose  morphologies 
place  them  close  to  the  main  line  of  teleostean  evolution,  are  predominantly  nocturnal  or  crepuscular. 
These  include  holocentrids,  scorpaenids,  serranids,  apogonids,  priacanthids,  and  lutjanids.  The  major 
prey  of  the  nocturnal  species  are  small,  motile  crustaceans,  which  are  most  available  to  the  direct 
attacks  of  generalized  predators  when  they  leave  their  shelters  after  dark.  The  major  prey  of  the 
crepuscular  species  are  smaller  fishes,  whose  defenses  against  direct  attacks  of  generalized  predators 
are  less  effective  during  twilight.  Feeding  by  generalized  predators  during  the  day  depends  largely  on 
being  within  striking  distance  of  prey  that  make  a  defensive  mistake,  a  position  best  attained  by  those 
predators  that  ambush  their  prey  from  a  concealed  position,  or  by  those  that  stalk. 

Ambushing  and  stalking  tactics  have  produced  some  highly  specialized  forms  that,  during  the  day, 
prey  mostly  on  smaller  fishes.  Diurnal  ambushers  include  the  highly  cryptic  synodontids,  scorpaenids, 
and  bothids;  diurnal  stalkers  include  aulostomids,  fistulariids,  belonids,  and  sphyraenids — all  of  them 
long,  attenuated  fishes. 

Some  predators — most  notably  the  muraenid  eels — are  specialized  to  hunt  deep  in  reef  crevices,  and 
here  they  capture  some  of  the  many  small  animals  that  shelter  themselves  in  those  crevices,  day  and 
night,  when  resting,  injured,  or  distressed.  Mullids  use  their  sensory  barbels  to  detect  small  animals 
that  have  sheltered  themselves  amid  the  superficial  covering  on  the  reef,  or  in  the  surrounding  sand;  at 
least  some  mullids  further  use  their  barbels  to  drive  these  prey  into  the  open. 

Most  of  the  fishes  on  Kona  reefs  are  among  the  more  highly  evolved  teleosts,  having  reached,  or 
passed,  the  percoid  level  of  structural  development.  The  adaptability  of  the  feeding  apparatus  in  these 
more  advanced  groups  has  given  rise  to  a  wide  variety  of  specialized  species,  including  both  carnivores 
and  herbivores,  that  have  diverged  from  one  another  mostly  on  the  basis  of  differing  food  habits.  These 
fishes,  most  of  which  are  diurnal,  include  the  chaetodontids,  pomacentrids,  labrids,  scarids,  blenniids, 
acanthurids,  and  Zanclus,  among  the  perciforms;  and  the  balistids,  monacanthids,  ostraciontids, 
tetraodontids,  canthigasterids,  and  the  nocturnal  diodontids,  among  the  tetraodontiforms.  With  their 
specialized  feeding  structures  and  techniques,  these  fishes  consume  organisms  like  sponges,  coelenter- 
ates,  large  mollusks,  tunicates,  and  tiny  or  cryptic  Crustacea  that  are  protected  by  behavioral  or 
anatomical  features  from  fishes  not  appropriately  specialized. 


Many  important  ecological  relations  among 
marine  fishes  are  understood  only  by  considering 
in  broad  overview  during  both  day  and  night  the 
different  forms  living  together  under  natural  con- 
ditions. With  this  in  mind,  I  undertook  a  broad 
study  of  reef  fishes  at  Kona,  Hawaii,  between  June 
1969  and  August  1970.  A  segment  of  this  study 
dealing  with  the  twilight  situation  was  published 
earlier  (Hobson,  1972).  The  present  report  de- 
scribes the  situations  that  prevail  throughout  day 
and  night.  The  work  is  centered  on  direct  observa- 
tions of  activity  in  the  fishes,  as  was  my  earlier 
study  of  predatory  behavior  of  shore  fishes  in  the 
Gulf  of  California  (Hobson,  1968a),  but  here  with 


'Southwest  Fisheries  Center  Tiburon  Laboratory,  National 
Marine  Fisheries  Service,  NOAA,  P.O.  Box  98,  Tiburon,  CA 
94920. 


greater  emphasis  on  detailed  analysis  of  food 
habits. 

Several  other  workers  adopted  broad  overviews 
in  considering  fishes  of  various  areas.  Limbaugh 
(1955)  studied  fishes  in  California  kelp  beds  dur- 
ing the  day,  whereas  Starck  and  Davis  (1966) 
described  the  habits  of  fishes  in  the  Florida  Keys 
at  night;  both  of  these  studies  present  extensive 
direct  observations  of  activity,  but  little  data  on 
food  habits.  On  the  other  hand,  Hiatt  and  Stras- 
burg  ( 1960),  as  well  as  Randall  ( 1967 ),  and  Quast 
(1968 ),  treated  extensively  the  food  habits  of  fishes 
collected  during  daylight  in  the  Marshall  Islands, 
the  West  Indies,  and  southern  California,  respec- 
tively, but  offered  relatively  few  direct  observa- 
tions of  activity.  Suyehiro  (1942)  comprehensively 
treated  the  feeding  morphology  of  fishes  in  Japan 


Manuscript  accepted  February  1974. 
FISHERY  BULLETIN;  VOL.  72,  NO.  4,  1974. 


915 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


and  included  data  on  food  habits;  however,  he  in- 
cluded little  information  on  activity.  The  1970 
United  States  Tektite  II  program  provided  many 
scientists  with  the  opportunity  to  make  direct  ob- 
servations on  a  Virgin  Island  reef,  and  reports 
concerning  the  fishes  have  been  published  in  one 
volume  (Collette  and  Earle,  1972).  Many  other 
reports  of  limited  scope  are  scattered  through  the 
literature,  most  of  them  being  fragmented  data  on 
food  habits;  nevertheless,  accounts  of  activity 
based  on  direct  observations  are  sparse,  especially 
of  nocturnal  activity. 

The  great  variety  of  feeding  mechanisms  for 
which  teleostean  fishes  are  so  well  known  occur 
among  coral-reef  fishes  far  more  so  than  among 
the  fishes  of  any  other  habitat.  I  take  advantage  of 
this  circumstance  in  the  discussion  that  concludes 
the  present  report  and  consider  the  feeding  rela- 
tionships among  fishes  on  Kona  reefs  in  the  con- 
text of  teleostean  evolution. 

METHODS 

Direct  Observations 

I  observed  activity  of  the  fishes  during  632  h 
underwater  at  all  periods  of  day  and  night  using 
scuba  and  by  snorkeling.  Except  when  collecting 
specimens,  I  tried  not  to  influence  the  fishes  or 
their  environment,  hoping  that  events  were  tak- 
ing a  natural  course.  Fishes  considered  in  this 
report  are  those  that  can  be  seen  by  an  underwater 
observer  at  some  time  during  day  or  night.  Al- 
though this  includes  by  far  most  of  the  reef  fishes, 
some  abundant  species  are  not  included  because 
they  remain  secreted  in  the  reef  at  all  hours. 

Food  Habits 

The  gut  contents  of  1,547  fish  specimens  of  102 
species  were  analyzed.  With  a  few  isolated  excep- 
tions, noted  below,  all  the  specimens  were  col- 
lected with  spears.  I  find  spearing  the  most  effec- 
tive way  to  collect  fishes  for  study  of  food  habits. 
Using  this  method,  specimens  were  collected  in 
specific  locations  at  the  times  of  day  and  night  that 
best  define  diurnal-nocturnal  activity  patterns. 
Because  I  speared  all  the  specimens  myself,  I 
know  what  each  individual  was  doing  when  cap- 
tured, and  this  knowledge  significantly  influenced 
analysis  of  the  data.  Even  the  response  of  the 
various  fishes  to  being  stalked  and  speared  (or 
missed)  provided  certain  behavioral  insights. 


Food  habits  change  over  the  life  of  at  least  most 
fishes,  usually  along  wdth  recognizable  changes  in 
behavior  and  morphology.  Unless  otherwise  indi- 
cated, specimens  selected  for  this  study  showed 
behavior  and  morphology  judged  typical  of  adults. 

The  collections  were  spread  over  time  and  space, 
so  that  possible  effects  of  transient  localized, 
perhaps  atypical,  situations  were  reduced.  Gener- 
ally, only  a  single  individual  of  any  one  species 
was  collected  during  a  single  period  of  observa- 
tions; thus,  for  a  given  species,  most  individuals 
each  represent  a  separate  collecting  station.  For 
these  reasons,  I  judge  the  data  from  the  food  habit 
analysis  to  accurately  represent  the  situation  ex- 
isting on  Kona  reefs  over  the  15  mo  of  this  study. 

The  collections  were  spaced  throughout  day  and 
night,  so  that  relative  digestion  of  gut  contents 
supplements  direct  observations  of  activity  in  de- 
termining specific  feeding  times.  All  specimens 
were  sealed  in  individual  plastic  bags  im- 
mediately after  being  speared,  most  while  still 
underwater.  Gut  contents  of  specimens  collected 
while  snorkeling  were  preserved  immediately  by 
injecting  a  concentrated  formaldehyde  solution 
directly  into  the  gut  cavity,  whereas  gut  contents 
of  fishes  taken  by  scuba  were  preserved  as  soon  as 
possible  after  emerging  from  the  water.  I  was  un- 
able to  see  a  difference  in  the  digestion  undergone 
by  material  collected  in  each  of  these  two  ways, 
suggesting  that  digestion  is  sharply  curtailed  by 
the  death  of  the  fish.  Where  practical, 
identifications  of  items  in  the  guts  were  carried  far 
enough  to  establish  such  general  prey  characteris- 
tics as  habitat  and  mode  of  life. 

Quantifying  Food  Habits 

For  those  species  represented  by  enough  num- 
bers in  the  analysis  of  gut  contents,  I  state:  1)  the 
number  offish  of  that  species  containing  each  food 
item,  and  2)  the  mean  percent  of  that  item  in  the 
diet  volume,  which  is  the  total  volume  of  gut  con- 
tents in  all  specimens  of  that  species.  This  second 
figure  was  calculated  from  estimates  of  the  per- 
cent each  item  taken  by  the  species  contributed  to 
the  gut  contents  of  each  individual  fish  (0  to 
100%).  The  food  items  are  listed  in  order  of  a 
ranking  index,  which  is  computed  by  multiplying 
the  ratio  offish  containing  the  item  to  the  number 
of  fish  sampled,  by  the  mean  percent  that  item 
represented  of  the  diet  volume.  Thus,  for  example, 
for  Holocentrus  sammara  (Table  10),  the  number 
one  prey,  xanthid  crabs,  has  a  ranking  index  of 


916 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


12/17  X  52.5  =  37.05.  The  data  are  tabulated  when 
there  are  more  than  a  few  items  in  the  gut  con- 
tents of  a  given  species. 

In  species  with  a  well-defined  stomach,  usually 
only  stomach  contents  were  analyzed,  as  materi- 
als in  the  intestines  generally  were  too  far  di- 
gested for  satisfactory  analysis.  On  the  other 
hand,  some  fishes  that  do  not  have  a  well-defined 
stomach  have  much  material  in  their  intestine 
that  is  suitable  for  study,  and  so  was  included  in 
the  analysis.  Thus  data  sometimes  are  specified  as 
being  from  stomach  contents,  but  at  other  times 
the  more  general  term  gut  contents  is  used. 

Transect  Counts 

To  characterize  the  fishes  inhabiting  each  of  the 
various  inshore  habitats  described  below,  100-m 
transect  lines  were  established  in  locations  judged 
typical  of  each  habitat.  Twenty-two  counts  of 
fishes  within  5  m  of  transect  lines  at  17  sites  rep- 
resenting five  habitat  categories  (see  below)  were 
made  between  September  1969  and  May  1970;  at 
least  1  mo  passed  between  counts  in  any  one 
habitat. 

Quantifying  Relative  Abundance 

In  the  Tables  below  that  present  data  from  the 
transect  counts,  the  relative  abundance  of  the  dif- 
ferent species  is  represented  by  a  relative  abun- 
dance index.  This  is  the  percentage  that  species 
represented  of  all  fishes  (individuals)  counted 
along  all  transect  lines  in  that  habitat. 

Assessing  Nocturnal  Colorations 

A  number  of  species  possess  distinctive  day  and 
night  differences  in  coloration.  Earlier  (Hobson, 
1968b),  I  discussed  the  problem  of  distinguishing 
true  nocturnal  hues  from  those  elicited  as  a  re- 
sponse to  the  diving  light — a  frequent  source  of 
error  in  literature  reports  of  nocturnal  color  pat- 
terns. No  color  pattern  that  becomes  intensified 
under  the  diving  light  is  considered  here  to  be  a 
nocturnal  pattern;  the  vast  majority  described 
herein  were  in  fact  almost  immediately  lost  when 
the  fish  was  illuminated. 

Study  Area 

The  study  area  extends  7.7  km  along  the  south- 
western shore  of  the  Island  of  Hawaii,  from 


Keawekaheka  Point  just  north  of  Kealakekua 
Bay,  to  Alahaka  Bay,  south  of  Honaunau  (Figure 
1).  This  is  part  of  what  is  known  as  the  Kona  coast. 
Except  for  short  stretches  of  sand  and  cobble 
beaches  at  Napoopoo  and  Keei,  the  shoreline  is  a 
rough  basalt  face  that  drops  abruptly  into  the  sea 
from  2  to  3  m  above  the  water's  surface  (Figure  2), 
to  a  similar  depth  below.  From  the  base  of  this  face 
the  sea  floor  slopes  down  to  water  depths  of  about 
20  to  30  m,  about  50  to  600  m  from  shore,  then  falls 
away  sharply  to  much  greater  depths.  Thus,  along 
this  coast  water  less  than  20  m  deep  is  limited  to  a 
relatively  narrow  shelf,  the  outer  rim  of  which 
provided  a  convenient  natural  boundary  to  the 
study  area  (Figure  1). 

Environmental  conditions  in  Kona  are  remark- 
ably constant,  which  greatly  aided  this  study.  Sur- 
face water  temperatures  ranged  from  29°C  in  the 
fall  to  22°C  in  the  spring,  but  I  noted  no  marked 
seasonal  variations  among  the  fishes  either  in 
their  activity  or  species  composition.  Conditions 


1     KILOMETER 


NAPOOPOO 


I9°25.0 


'  '~3  QjHU 

HONOLULU 


CHART  AREA- 


I55°575 


I55°550 


Figure  1. — The  study  area  along  the  Kona  coast,  Island  of 
Hawaii.  Adapted  from  C.  &  G.S.  chart  4123.  Depth  contour  in 
meters. 


917 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


are  especially  moderate  on  the  Kona  coast,  in  part 
because  towering  volcanoes  shelter  the  area  from 
the  trade  winds. 


THE  INSHORE  HABITATS  AND 
THEIR  CHARACTERISTIC  FISHES 

The  study  area  in  Kona  encompasses  a  variety 
of  submarine  habitats,  each  with  a  distinctive  as- 
semblage of  fishes.  For  convenience,  these 
habitats  are  here  grouped  subjectively  into  five 
categories:  1)  coral-rich  habitat,  2)  boulder 
habitat,  3)  shallow  reef-flat  habitat,  4)  reef-face 
habitat,  and  5)  outer  drop-off  habitat.  Along  with 
the  following  habitat  descriptions,  there  are  listed 
the  10  fish  species  most  often  seen  in  each  habitat, 
as  observed  in  the  transect  counts. 

Coral-Rich  Habitat 

In  many  places  where  there  is  shelter  from  the 
long  Pacific  swells,  the  sea  floor  in  water  between 
2  and  12  m  deep  is  richly  overgrown  with  corals 


(Figure  3).  The  predominant  coral  is  Pontes 
pukoensis,  which  grows  in  a  variety  of  massive 
formations.  Examples  occur  in  Honaunau  Bay,  in 
the  lee  of  Palemano  Point,  and  in  the  sheltered 
waters  on  the  north  side  of  Kealakekua  Bay  (Fig- 
ure 1).  Overall  in  the  parts  of  the  study  area  that 
are  richly  overgrown  with  corals,  P.  pukoensis 
variably  shares  dominance  with  another  form,  P. 
co>7jpressus,  that  grows  as  fingerlike  branches  10 
to  20  mm  in  diameter.  Pontes  compressus  is  dom- 
inant where  there  is  increased  exposure  to  the 
prevailing  swell,  but  where  there  is  still  some 
protection  from  a  lee  shore  or  increased  water 
depth.  Thus,  in  the  middle  of  both  Kealakekua 
Bay  and  Honaunau  Bay,  as  well  as  in  much  of  the 
study  area  where  the  water  is  more  than  about  15 
m  deep,  broad  fields  of  fingerlike  P.  compressus 
dominate  the  scene.  In  extreme  situations, 
habitats  dominated  by  either  one  of  these  coral 
forms  are  as  distinct  from  one  another  in  their 
characteristic  faunas  as  any  two  habitat  types 
characterized  here.  I  group  the  two  coral  habitats 
together  because  in  most  of  the  coral-rich  areas 
where  observations  were  made  during  this  study 


Figure  2. — The  shoreline  at  Cook  Point,  Kealakekua  Bay  (looking  southeast),  which  is  typical  of  the  shoreline 

throughout  most  of  the  study  area. 


918 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  3. — Coral-rich  habitat.  Fishes  shown  include:  Chaetodon  multicinctus,  Ctenochaetus  strigosus,  Zebrasoma 

flavescens,  Acanthiirus  nigrofuscus,  and  Zanclus  canescens. 


the  two  forms  o^Porites  share  dominance.  Never- 
theless, the  fishes  listed  in  Table  1,^  which  are 
characteristic  of  those  seen  in  the  coral-rich 
habitat  by  day,  were  observed  where  P.  pukoensis 
was  the  more  dominant  coral.  Table  2  ^  lists  fishes 
characteristic  of  those  seen  in  this  same  habitat  at- 
night.  Because  of  difficulties  inherent  in  making 
transect  counts  after  dark,  data  in  Table  2  are  only 
rough  approximations;  they  are  presented  primar- 
ily to  illustrate  the  differing  situation  after  dark, 
and  to  emphasize  that  the  other  counts  reflect  a 
situation  characteristic  of  daytime  only. 


^Table  1  is  based  on  data  from  five  transects  at  four  coral-rich 
sites — two  at  Honaunau,  and  two  at  Kaopapa  in  Kealakekua 
Bay  (see  Figure  1 ).  Total  number  of  species  observed  on  these  five 
transects:  82;  mean  number  of  individuals  of  all  species  for  a 
single  transect:  522. 

^Table  2  is  based  on  data  from  three  nocturnal  transects  (one 
on  a  dark  night,  two  on  moonlit  nights)  at  three  coral-rich 
sites — two  at  Honaunau,  one  at  Kaopapa  in  Kealakekua  Bay 
(see  Figure  1),  all  three  of  which  were  also  used  in  daytime 
counts  (Table  1).  Counts  were  made  by  switching  on  a  light 
briefly  about  every  10  m  as  we  swam  along  the  line.  Listing  of  a 
species  does  not  necessarily  imply  activity;  as  becomes  clear  in 
the  species  accounts,  below,  some  of  these  fishes  are  inactive  on 
or  near  the  reef  at  night.  Total  number  of  species  observed  on 
these  three  transects:  36;  mean  number  of  individuals  of  all 
species  for  a  single  transect:  165. 


Boulder  Habitat 

From  shore  to  depths  of  about  15  m  throughout 
that  part  of  the  study  area  lying  off  exposed 
shorelines,  the  sea  floor  is  strewn  with  basalt 
boulders.  Often  these  boulders  are  dotted  with 
various  algae  and  corals — mostly  encrusting 
varieties — but  because  these  forms  are  small,  the 

Table  1. — The  10  fish  species  most  frequently  seen  along  trans- 
ect lines  in  the  coral-rich  habitat  during  the  day. 


No.  times  in 

Relative 

top  10  of 

abundance 

Individual 

Rank 

Species 

index 

transects  n  =  5 

1 

Ctenochaetus  strigosus 

15,45 

5 

2 

Chromis  leucurus' 

12.30 

5 

3 

Zebrasoma  flavescens 

10.58 

5 

4 

Pomaentrus  lenkinsi 

6.71 

5 

5 

Thalassoma  duperrey 

5.71 

5 

6 

Chaetodon  multicinctus 

441 

5 

7 

Acanthurus  nigrofuscus 

4.37 

5 

8 

Acanthurus  nigroris 

3.64 

3 

9 

Plectroglyphidodon  johnstonianus 

3.07 

5 

10 

Centropyge  potteri 

2.49 

2 

Mn  making  transect  counts  I  tollowed  Gosllne  and  Brock  (1960)  in 
recognizing  Chromis  leucurus  to  Include  two  color  forms.  Furtfier  study 
may  sfiow  thiat  two  (or  more)  species  are  Included  here  (see  species 
account  for  C.  leucurus  in  this  report). 


919 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  4. — Boulder  habitat.  Fishes  shown  include:  Aphareus  furcatus,  Monotaxis grandoculis  (showing  barred  color 

pattern),  Acanthurus  leucopareius,  and  Zebrasoma  flavescens. 


Table  2. — The  10  fish  species  most  frequently  seen  along  trans- 
ect lines  in  the  coral-rich  habitat  at  night. 


No.  times  in 

Relative 

top  5  of 

abundance 

individual 

Rank 

Species 

index 

transectsn  =  3 

1 

Myripristis  kuntee 

23.61 

3 

2 

Apogon  menesemus 

14.52 

3 

3 

Myripristis  murdjan 

12.33 

2 

4 

Apogon  snyderi 

11.90 

3 

5 

Zebrasoma  flavescens 

6.85 

2 

6 

Chaetodon  multicinctus 

4.03 

0 

7 

Acanthurus  sandvicensis 

2.40 

1     • 

8 

Acanthurus  nigroris 

2.22 

0 

9 

Holocentrus  lacteoguttatus 

1.21 

0 

10 

Chaetodon  ornatissimus 

1.21 

0 

Table  3. — The  10  fish  species  most  frequently  seen  along  trans- 

ect  lines  in  the  boulder  habitat  during  the  day. 

No.  times  m 

Relative 

top  10  of 

abundance 

individual 

Rank 

Species 

index 

transects  n  =  4 

1 

Acanthurus  nigrofuscus 

13.74 

4 

2 

Ctenochaetus  stngosus 

10.77 

4 

3 

Zebrasoma  flavescens 

9.61 

4 

4 

Acanthurus  achilles 

8.00 

4 

5 

Thalassoma  duperrey 

6.44 

4 

6 

Pomacentrus  jenkinsi 

5.25 

4 

7 

Acanthurus  nigroris 

4.88 

3 

8 

Acanthurus  leucopareius 

4.73 

4 

9 

Abudefduf  sindonis 

3.64 

4 

10 

Chromis  vanderbilti 

2  35 

3 

general  appearance  is  one  of  bare  rocks  (Figure  4). 
Especially  in  the  shallower  regions,  but  decreas- 
ing with  greater  depths,  this  habitat  is  regularly 
swept  by  a  strong  surge.  At  depths  varying  with 
the  relative  proximity  of  a  lee  shore  or  protecting 
reef,  but  usually  at  about  12  to  17  m,  the  boulder 
habitat  in  many  locations  grades  into  the  fields  of 
fingerlike  Pontes  compressus,  one  of  the  coral-rich 
habitats  described  above.  Fishes  listed  in  Table  3  '* 
are  characteristic  of  those  seen  in  the  boulder 
habitat  during  the  day. 

Shallow  Reef-Flat  Habitat 

Shallow  surge-swept  reefs,  the  remains  of  an- 
cient lava  flows,  extend  offshore  in  several  loca- 
tions (Figure  5).  Here,  a  solid  pavement  of  exposed 
basalt,  containing  many  cracks  and  crevices,  sup- 
ports a  distinctive  array  of  marine  organisms.  The 
predominant  benthic  life  form  is  the  coral 


''Table  3  is  based  on  data  from  four  transects  at  four  boulder 
sites — one  at  Cook  Point,  one  at  Mokuakae  Bay,  and  two  at 
Alahaka  Bay  (see  Figure  1).  Total  number  ofspecies  observed  on 
these  four  transects:  77;  mean  number  of  individuals  of  all 
species  for  a  single  transect:  672. 


920 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  5. — Shallow  reef-flat  habitat.  Most  of  the  fishes  shown  are  acanthurids,  and  include  Naso  lituratus  and 

N.  unicornis. 


Pocillopora  meandrina,  growing  as  isolated  heads 
10  to  50  cm  wide.  The  outstanding  characteristics 
of  this  habitat,  which  generally  has  a  maximum 
water  depth  of  only  about  3  to  4  m,  are  extreme 
water  movement  and  wave  shock.  The  fishes  listed 
in  Table  4  ^  are  characteristic  of  those  seen  on 
shallow  reef  flats  during  the  day. 


^Table  4  is  based  on  data  from  three  transects  at  three  shallow 
reef-flat  sites  at  Palemano  Point  (see  Figure  1).  Note:  one  of  the 
transect  counts  was  aborted  after  60  m  when  the  surge  became 
too  strong  to  continue.  Total  number  of  species  observed  on  these 
three  transects:  54;  mean  number  of  individuals  of  all  species  for 
a  single  transect:  578. 

Table  4. — The  10  fish  species  most  frequently  seen  along  trans- 
ect lines  in  the  shallow  reef-flat  habitat  during  the  day. 


No.  times  in 

Relative 

fop  10  of 

abundance 

individual 

Rank 

Species 

index 

transects  n  =  3 

1 

Acanthurus  nigrofuscus 

20,23 

3 

2 

Thalassoma  duperrey 

17.41 

3 

3 

Abudefduf  imparipennis 

15.12 

3 

4 

Chromis  vanderbilti 

10.33 

3 

5 

Thalassoma  fuscus 

4.78 

3 

6 

Stethojulis  balteata 

2.88 

3 

7 

Gomphosus  varius 

2.78 

3 

8 

Naso  literatus 

2.02 

1 

9 

Zebrasoma  flavescens 

1.79 

1 

10 

Pomacentrus  jenkinsi 

1.67 

1 

Reef-Face  Habitat 

At  the  offshore  edge  of  the  shallow  reef  flats,  and 
at  many  locations  along  the  shore,  a  sheer  basalt 
face  falls  precipitously  to  water  depths  of  10  to  15 
m  (Figure  6).  This  situation  produces  a  wide  range 
of  conditions  within  a  limited  area.  In  its  upper 
regions  the  surge  and  wave  shock  are  that  of  the 
reef-top  habitat,  but  these  rapidly  abate  with  in- 
creasing depth.  Conditions  adjacent  to  the  base  of 
the  reef  face  are  essentially  those  of  the  boulder 
habitat,  with  fragmented  pieces  of  the  reef  lying 
about  as  large  boulders.  The  predominant  forms  of 
benthic  life,  dotting  the  rock  surfaces,  are 
Pocillopora  meandrina  (in  the  shallower  regions), 
and  smaller  encrusting  corals  and  algae.  Many 
planktivorous  fishes  are  concentrated  in  the  water 
column  adjacent  to  the  reef  face.  Understandably, 
there  is  a  greater  variety  of  fishes  in  this  habitat 
than  in  the  other  habitats  characterized  here. 
Fishes  listed  in  Table  5  ®  are  characteristic  of  those 
seen  along  the  reef  face  during  the  day. 


^Table  5  is  based  on  data  from  three  transects  at  two  reef-face 
sites  at  Palemano  Point  (see  Figure  1).  Total  number  of  species 
observed  on  these  three  transects:  89;  mean  number  of  individu- 
als of  all  species  for  a  single  transect:  937. 


921 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  6.^Reef-face  habitat.  Most  of  the  fishes  shown  swimming  at  the  base  of  the  reef  are  Acanthurus  leucopareius. 

The  reef  face  shown  here  drops  8  to  10  m. 


Table  5. — The  10  fish  species  most  frequently  seen  along  trans- 
ect lines  in  the  reef-face  habitat  during  the  day. 


No.  times  In 

Relative 

top  10  of 

abundance 

Individual 

Rank 

Species 

Index 

transects  n  =  3 

1 

Chromis  vanderbiiti 

11.74 

3 

2 

Ctenochaetus  strigosus 

9.54 

3 

3 

Zebrasoma  flavescens 

9.11 

3 

4 

Acanthurus  leucopareius 

7.18 

3 

5 

Acanthurus  nigrofuscus 

6.17 

3 

6 

Thalassoma  duperrey 

4.41 

3 

7 

Pomacentrus  jenkinsi 

3.95 

3 

8 

Abudefduf  abdominalis 

3.56 

3 

9 

Acanthurus  achilles 

3.56 

3 

10 

Melichthys  niger 

3.38 

3 

Outer  Drop-Off  Habitat 

At  the  rim  of  the  outer  drop-off,  50  to  600  m  from 
shore,  where  the  sea  floor  falls  abruptly  from 
about  25  m  to  much  greater  depths,  the  sea  floor 
generally  is  overgrown  with  the  fingerlike  form  of 
Pontes  compressus,  interspersed  with  massive 
heads  of  P.  pukoensis,  bare  basalt  boulders,  and 
sand  patches  (Figure  7).  The  most  striking  charac- 
teristic of  this  habitat,  aside  from  the  spectacular 
way  the  sea  floor  falls  away,  is  the  large  number  of 


planktivorous  fishes  that  abound  in  the  water  col- 
umn. Obviously  conditions  for  feeding  on  plank- 
ton are  especially  well  developed  here.  The  fishes 
listed  in  Table  6  '^  are  characteristic  of  those  seen 
on  the  rim  of  the  outer  drop-off  during  the  day. 


''Table  6  is  based  on  data  from  four  transects  at  four  outer 
drop-off  sites — two  at  Palemano  Point  and  two  at  Puuhonua 
Point  (see  Figure  1).  Total  number  of  species  observed  on  these 
four  transects:  78;  mean  number  of  individuals  of  all  species  for  a 
single  transect:  478. 

Table  6. — The  10  fish  species  most  frequently  seen  along  trans- 
ect lines  in  the  outer  drop-off  habitat  during  the  day. 


Rank       Species 


No.  times  in 
Relative  top  10  of 

abundance         individual 
Index         transects  n  =  4 


1 

Waso  hexacanthus 

11,39 

4 

2 

Chromis  leucurus' 

11.19 

4 

3 

Xanthichthys  ringens 

10.50 

4 

4 

Thalassoma  duperrey 

6.64 

4 

5 

Zebrasoma  flavescens 

4.76 

3 

6 

Ctenochaetus  strigosus 

3.87 

2 

7 

Chaetodon  multicinctus 

3.76 

3 

8 

Centropyge  potteri 

3.45 

3 

9 

Chromis  verater 

3.24 

2 

10 

Pseudocheihnus  evanidus 

2.40 

2 

Mn  making  transect  counts  I  follow/ed  Gosline  and  Brock  (1960)  In 
recognizing  Chromis  leucurus  to  Include  two  color  forms.  Further  study 
may  show  that  two  (or  more)  species  are  included  here  (see  species 
account  for  C.  leucurus  In  this  report) 


922 


HOBSON;  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  7. Outer  drop-off  habitat.  Most  of  the  fishes  shown  in  the  water  column  are  Acunthurus  thompsoni. 


Fishes  Observed  on  Transect  Lines 

All  fishes  observed  on  transect  lines  in  the  five 
Kona  habitats  are  listed  in  Table  7,  where  the 
value  given  for  each  species  in  each  habitat  is  the 
relative  abundance  index,  as  defined  in  the 
methods.  Transect  data  for  each  habitat  category 
(number  of  transects,  total  number  of  species  ob- 
served, and  mean  number  of  individuals  on  a 
single  transect)  are  given  in  footnotes  2  to  7. 

SPECIES  ACCOUNTS 

Family  Page 

Muraenidae:  moray  eels  926 

Congridae:  conger  eels 929 

Synodontidae:  lizardfishes   929 

Brotulidae:  brotulas 930 

Atherinidae:  silversides    931 

Holocentridae:  squirrelfishes 932 

Aulostomidae:  trumpetfishes 942 

Fistulariidae:  cornetfishes    944 

Scorpaenidae:  scorpionfishes  944 

Serranidae:  sea  basses 947 

Kuhliidae:  aholeholes    948 

Priacanthidae:  bigeyes    948 

Apogonidae:  cardinalfishes 950 

Carangidae:  jacks 954 


Lutjanidae:  snappers  955 

Sparidae:  porgies 956 

Mullidae:  goatfishes 957 

Kyphosidae:  sea  chubs 964 

Chaetodontidae:  angelfishes  and  butterflyfishes 964 

Pomacentridae:  damselfishes 978 

Cirrhitidae:  hawkfishes 986 

Labridae:  wrasses 989 

Scaridae:  parrotfishes    995 

Blenniidae:  combtooth  blennies   998 

Acanthuridae:  surgeonfishes  1000 

Zanclidae:  moorish  idol 1003 

Bothidae:  left-hand  flounders    1005 

Balistidae;  triggerfishes    1005 

Monacanthidae:  filefishes 1009 

Ostraciontidae:  boxfishes   1011 

Tetraodontidae:  balloonfishes    1012 

Canthigasteridae:  sharp-backed  puffers 1013 

Diodontidae:  spiny  puffers  1015 

This  study  treats  only  teleostean  fishes,  as  these 
were  almost  the  only  kind  observed  on  Kona  reefs 
during  this  study.  Elasmobranchs  occurred  infre- 
quently and  seemed  to  have  little  impact  on  the 
reef  situation.  No  marine  animals  are  more  prom- 
inent than  sharks  in  Hawaiian  lore  (e.g.  Hobson 
and  Chave,  1972),  yet  compared  with  most  other 
tropical  Pacific  Islands,  relatively  few  sharks  are 
seen  in  Hawaiian  nearshore  waters  today. 

923 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 
Table  7. — Relative  abundance  of  fish  species  observed  along  transect  lines  in  each  of  the  Kona  reef  habitats. 


Species 


Outer 

Coral-rich 

Coral-rich 

Boulder 

Reef-flat 

Reef-face 

Drop-off 

habitat 

habitat 

habitat 

habitat 

habitat 

habitat 

Daytime 

Nighttime 

Daytime 

Daytime 

Daytime 

Daytime 

Superorder  Elopomorpha: 
Order  Anguilliformes: 

Family  Muraenidae: 
Gymnolhorax  meleagris 
Superorder  Protacanthopterygii; 
Order  Myctophiformes: 

Family  Synodontidae: 
Synodus  vanegatus 

Superorder  Acanthopterygii: 
Order  Beryciformes: 

Family  Holocentridae: 
Holocentrus  sammara 
H.  tiere 

H.  xantherythrus 
H.  diadema 
H.  lacteoguttatum 
Holotrachys  lima 
Mynpristis  kuntee 
M.  murdjan 

M.  sp.  (uncertain:  either 
M.  murdjan  or  M.  amaenus) 
Order  Gasterostelformes: 

Family  Aulostomidae: 
Aulostomus  chmensis 

Family  Fistulariidae: 
Fistularia  petimba 

Order  Scorpaeniformes: 

Family  Scorpaenidae: 
Taenianotus  triacanthus 
Scorpaena  coniorta 
Scorpaenopsis  cacopsis 
Order  Perciformes: 

Family  Serranidae: 
Cephalapholis  argus 

Family  Priacanthidae: 
Priacanthus  cruentatus 

Family  Apogonidae: 
Apogon  menesemus 
A.  snyderi 

Family  Malacanthidae: 
Malacanthus  hoedtii 

Family  Carangidae: 
Caranx  melampygus 

Family  Lutjanidae: 
Aphareus  lurcatus 

Family  Sparidae: 
Monotaxis  grandoculis 

Family  Mullidae: 
Mulloidichthys  aunflamma 
M.  samoensis 
Parupeneus  multifasciatus 
P.  bifasciatus 
P.  chryserydros 
P  porphyreus 
P-  pleurostigma 

Family  Kyphosidae: 
Kyphosus  cinerascens 

Family  Chaetodontidae: 
Holacanthus  arcuatus 
Centropyge  potteri 
C.  lisheri 

Forcipiger  flavissimus 
F.  longirostns 

Hemitaunchthys  Ihompsoni 
H.  zoster 

Chaetodon  corallicola 
C.  miliaris 
C.  quadrimaculatus 
C.  unimaculatus 
C.  multicinctus 
C.  ornatissimus 
C.  auriga 
C.  fremblii 
C.  lunula 
C.  lineolatus 


0.04 


0.04 

060 

— 

0.81 

— 

060 

— 

1.01 

— 

1.21 

— 

0.81 

0.23 

23.61 

008 

12.33 

0.12 


0.04 


0.15 
0.12 


0.12 
0.58 
0  12 
0.27 
008 
0.04 


5.24 


0,40 


0.20 


0.20 

14.52 
11.90 


0.20 


0,04 


0,04 


0.19 


0-04 
0-11 
004 


0.45 
0.07 
0.15 


022 


0  06 


0.12 


0.23 


0.43 
0.25 


0.36 


0.07 


0.04 


0.11 


0.21 


1.25 


0.11 


005 


005 


0,26 
0,31 


005 


0,16 


005 


0.93 

— 

0.14 

— 

0.82 

1,41 

0.71 

0,05 

0.25 

— 

005 


— 

— 

— 

— 

0.11 

0.10 

2,49 

— 

— 

— 

1.00 

3-45 

— 

— 

— 

— 

— 

0-16 

0  96 

— 

1  01 

0.35 

0.78 

1-41 

0.50 

0.40 

— 

0.12 

0.07 

0-31 

— 

0.40 

— 

— 

— 

0-73 

— 

— 

026 

— 

— 

209 

— 

— 

— 

— 

— 

1-05 

— 

— 

— 

— 

— 

1-05 

069 

— 

089 

1-44 

0.53 

0,10 

— 

— 

0-22 

1  21 

— 

— 

4.41 

4.03 

1  08 

058 

0.82 

3.76 

1  80 

1.21 

0.68 

0.29 

0.25 

0.31 

— 

— 

— 

— 

0.04 

0-05 

0.08 

0.20 

0,30 

0  12 

0.32 

0.05 

0.69 

1.21 

0,15 

0.40 

2.03 

0-58 

— 

0.20 

0-11 

— 

0.11 

— 

924 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 
Table  7. — Continued. 


Species 


Coral-rich 
habitat 
Daytime 


Coral-rich 

habitat 
Nighttime 


Boulder 
habitat 
Daytime 


Reef-flat 
habitat 
Daytime 


Reef-face 
habitat 
Daytime 


Outer 
Drop- off 

hatjitat 
Daytime 


C,  reticulatus 
C.  trifasciatus 

Family  Pomacentridae: 
Plectroglyphidodon  lohnstonianus 
Pomacentrus  jenkinsi 
Abudefduf  sindonis 
A.  sordidus 
A.  imparipennis 
A.  abdominalis 
Dascyllus  albisella 
Chromis  vanderbiiti 
C.  leucurus 
C   verater 
C  ovalis 

Family  Cirrhitidae: 
Paracirrhites  arcatus 
P.  forsteri 

Cirrhitops  fasciatus 
Cirrhitus  pinnulatus 

Family  Labridae: 
Bodianus  bilunulatus 
Cheilinus  rhodochrous 
Pseudocheilinius  octotaenia 
P.  tetrataenia 
P.  evanidus 

Labroides  phthirophagus 
Thalassoma  duperrey 
T.  fuscus 
T.  ballieui 
T.  lutescens 
T.  quinquevittata 
Halichoeres  ornatissimus 
Stethojulis  balteata 
Anampses  cuvier 
Cons  gaimard 
C.  flavovittata 
C.  venusta 

Macropharyngodon  geoffroy 
Gomphosus  varius 
Cirrhilabrus  jordani 
Pseudojuloides  cerasinus 
Hemipteronotus  taeniourus 

Family  Scaridae: 
Scarus  sordidus 
S.  taeniurus 
S.  dubius 
S.  perspicillatus 
S.  rubroviolaceus 
Calotomus  spinidens 
Unidentified  juveniles 

Family  Blenniidae: 
Exallias  brews 
Cirripectus  obscurus 
C  vanolosus 
Plagiotremus  goslinei 
P.  ewaensis 

Family  Acanthuridae: 
Acanthurus  achilles 
A.  dussumien 
A.  glaucopareius 
A.  guttatus 
A.  leucopareius 
A.  nigrofuscus 
A.  nigroris 
A.  olivaceus 
A.  sandvicensis 
A.  thompsoni 
A.  xanthopterus 
Ctenochaetus  strigosus 
C.  hawaiiensis 
Zebrasoma  flavescens 
Z  veliferum 
Naso  brevirostris 
N.  hexacanthus 
N.  Iituratus 
N.  unicornis 


0.04 

3.07 
6.71 


0.35 

0.19 

0.15 

230 

0.96 

0.11 

0.69 

0.23 

0.12 

0.04 

1.57 

1.30 

0.31 

0.04 

0.31 

5.71 

0.04 

0.08 

1.15 

2.15 

0.08 

0.81 

0.15 

1.00 

1.73 
0.19 
0.46 
0.35 
0.35 
0.50 


0.15 
0.31 


0.69 

0.35 

0,04 

0.69 

4.37 

3.64 

0.19 

012 

15.45 

0.58 

10.58 

0.15 

1.46 

0.35 

0.20 


0.20 
1.21 


0.80 
0.40 


0.20 
0.20 


1.41 


1.01 
0.40 
2.22 

2.40 


6.85 


1.21 


0.07 
5.25 
3.64 
0.22 
022 

0.07 
2.35 

0.11 


0.74 
0.34 


0.15 
0.07 
0.04 


6.44 
1-97 
0.15 


1.67 
1.56 
0.34 

0.26 


0.07 
1.53 


0.82 
0.63 
0.52 

1.53 
0.04 
0.04 


0.11 
015 
0.04 
0.19 


8.00 
0.74 
0.19 
1.64 
4.73 
13.74 
4.88 
0.11 
1.64 


10.77 
0.82 
9.61 
0.22 


0.74 
0.60 


0.12 
0.12 

1.04 
1.67 


15  12 


10.33 


0.86 
0.12 
0.17 
0.52 


0.23 


7.41 

478 

0.17 

0.23 

0.58 

2.88 

0.06 

0.35 

0.52 

2.78 

1.04 
0.98 


0.29 
0.12 


0.06 


0  98 


0.35 


0.40 

20.23 

1.38 

0.12 


1.79 


2.02 
1.50 


0.25 
3.95 

0.39 

3.56 

11.74 
0.82 
0.14 


0.89 
0.11 
0.82 
0.18 


0.57 
0.82 
0.07 


4.41 
0.21 


0.53 
1.35 
0.07 
0.71 
0.04 
0.11 
0.21 
0.60 


1.81 
0.43 
0.50 
0.28 
0.50 
0.11 
0.89 

0.11 

0.07 
0.04 
0.04 

3.56 
0.28 
0.07 

7.18 
6.17 
1.60 
0.07 
0.71 

0.43 
9.54 
0.75 
9.11 


1.28 
1.07 
0.25 


1.25 
0.68 


2.30 
084 

11.19 
3.24 


0.99 

0.47 
0.05 

0.05 
1.41 
1.93 
0.42 
2.40 
0.05 
6.64 

0.05 


1.15 
0.68 
0.05 
1.31 


0.73 
0.78 
0.16 
0.05 
0.16 

1.93 

0.16 
0.10 
0.10 
0.26 


0.05 


0.10 


1.62 
1.57 
0.31 

1.88 

3.87 
0.05 
4.76 

0.10 

11.39 

1.20 

0.05 


925 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  7. — Continued. 


Outer 

Coral-nch 

Coral-rich 

Boulder 

Reef-flat 

Reef-face 

Drop-off 

habitat 

habitat 

habitat 

habitat 

habitat 

haljitat 

Species 

Daytime 

Nighttime 

Daytime 

Daytime 

Daytime 

Daytime 

Family  Zanclidae: 

Zanclus  canescens 

0.38 

— 

1.38 

1.21 

0.82 

1.10 

Order  Tetraodontiformes: 

Family  Balistidae: 

Melichthys  niger 

1,00 

— 

0.82 

0.12 

3.38 

— 

M.  vidua 

0,04 

— 

— 

— 

— 

0.15 

Xanthichthys  ringens 

— 

— 

0.04 

— 

0.39 

10.50 

Rhinecanthus  rectangulus 

— 

— 

0.19 

1.33 

— 

— 

Sulflamen  bursa 

073 

— 

0.37 

— 

1.57 

1.57 

Balistid  sp. 

— 

— 

— 

— 

0.04 

— 

Family  Monacanthidae; 

Cantherines  dumenli 

0.15 

— 

— 

0  12 

0.11 

— 

C  sandwichiensis 

0.15 

— 

0.40 

0.64 

0.32 

0.16 

Pervagor  spilosoma 

0.35 

— 

— 

— 

0,04 

0.10 

P.  melanocephalus 

0.42 

— 

0.19 

— 

— 

0.10 

Alutera  scripta 

— 

— 

— 

— 

0.04 

— 

Family  Ostraciontidae: 

Ostracion  meleagris 

0.19 

— 

0.86 

0.12 

0,18 

— 

Family  Tetraodontidae: 

Arothron  hispidus 

— 

— 

— 

— 

004 

— 

A.  meleagris 

— 

— 

0.04 

0.06 

— 

— 

Family  Canthigasteridae: 

Canthigaster  amboinensis 

0.12 

— 

0.22 

0  17 

0.11 

— 

C.  jactator 

0.46 

— 

0.04 

— 

0.78 

0.05 

C.  coronatus 

— 

— 

— 

— 

0.04 

0.10 

The  observations  for  each  species  are  grouped 
by  order  and  family  in  phylogenetic  sequence,  as 
listed  by  Greenwood  et  al.  (1966).  Species  names 
generally  are  those  used  by  Gosline  and  Brock 
(1960),  except  where  more  recent  taxonomic 
studies  indicate  change.  All  sizes  given  are  stan- 
dard length.  For  most  species,  the  number  of 
specimens  collected  is  followed  by,  in  parenthesis, 
their  mean  size  and  the  range  in  their  sizes.  All 
species  accounts  consider  individuals  showing 
morphology  and  behavior  of  adults. 

Order  Anguilliformes 

Family  Muraenidae:  moray  eels 

Most  Hawaiian  eels  belong  to  this  family,  which 
comprises  the  moray  eels,  or  puhi,  as  Hawaiians 
call  them  (Gosline  and  Brock,  1960).  Morays  are 
denizens  of  crevices  in  the  reefs,  and  because  most 
remain  secreted  under  cover,  their  great  abun- 
dance cannot  be  appreciated  by  a  casual  observer. 
Nevertheless,  the  morays  include  more  species  (32 
reported)  on  Hawaiian  reefs  than  any  other  family 
of  fishes,  except  perhaps  the  wrasse  family  Lab- 
ridae  (Gosline  and  Brock,  1960).  Most  Hawaiian 
morays  do  not  grow  to  more  than  about  60  cm  long, 
although  a  few  may  attain  a  length  of  about  2  m 
(Gosline  and  Brock,  1960).  Most  of  them  remain 
secreted  in  reef  crevices,  but  the  five  species  con- 


sidered below  are  examples  of  those  that  are  often 
exposed  on  the  reef  top. 

Gijmnothorax  meleagris  (Shaw  and  Nodder) 
— spotted  moray,  puhi  'oni'o 

This  medium-sized  eel  characteristically  pro- 
trudes its  head  from  crevices  during  the  day  (Fig- 
ure 8),  and  thus  is  the  moray  most  often  in  view  on 
the  reef;  however,  I  seldom  saw  it  after  dark.  Of 
the  nine  specimens  collected,  the  stomachs  of  five 
were  empty,  although  three  of  these  contained 
unidentified  fragments  at  the  posterior  end  of 
their  intestines.  Of  the  four  with  prey  in  their 
stomachs,  one  (455  mm)  taken  during  midmorn- 
ing  contained  a  fresh  damselfish,  Abudefduf  im- 
paripennis  (40  mm)  that  appeared  to  have  been 
recently  captured.  Two  others  with  full  stomachs 
were  collected  during  late  afternoon:  one  (321 
mm)  contained  a  moderately  digested  xanthid 
crab,  whereas  the  other  (121  mm)  contained  a 
well-digested  fish.  On  the  other  hand,  the  fourth 
specimen  (361  mm)  contained  a  moderately  di- 
gested xanthid  crab  that  appeared  to  have  been  in 
the  eel's  stomach  at  least  several  hours  when  it 
was  collected  during  morning  twilight. 

CONCLUSION. — Gymnothorax  meleagris 
captures  small  fishes  and  crustaceans  by  day  and 
probably  also  at  night. 


926 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  8. — Gymnothorax  meleagris,  a  moray  eel,  showing  daytime  attitude. 


Gymnothorax  eurostus  (Abbott) 

This  small  species,  which  attains  a  maximum 
length  of  about  60  cm,  is  probably  the  most 
numerous  moray  in  Hawaii  (Gosline  and  Brock, 
1960).  However,  it  is  a  secretive  species,  only  occa- 
sionally visible  on  the  reef.  Although  the  four  in- . 
dividuals  collected  (360:  294-432  mm)  were 
speared  as  they  protruded  their  heads  from  holes 
in  the  reef  during  the  day,  this  habit  is  not  charac- 
teristic of  G.  eurostus,  as  it  is  of  G.  meleagris, 
above.  Two  of  those  collected  had  empty  stomachs, 
but  the  other  two,  both  taken  during  midday,  con- 
tained relatively  fresh  prey — a  caridean  shrimp  in 
one,  a  xanthid  crab  in  the  other. 

CONCLUSION.— G.vm/^oMorax  eurostus 
captures  crustaceans  during  the  day.  The  night- 
time situation  remains  uncertain. 

Gymnothorax  flavimarginata   (Riippell) — puhi 
paka 

This  eel,  which  attains  a  length  of  about  120  cm 
(Gosline  and  Brock,  1960),  is  the  most  numerous  of 
the  larger  muraenids  in  Kona.  Being  so  abundant. 


as  well  as  large,  this  heavy-bodied  eel  probably 
represents  the  greatest  threat  among  morays  to 
humans.  It  is  the  species  that  most  often  appears 
when  a  fish  has  been  speared  during  daylight.  The 
regularity  and  promptness  of  these  appearances 
make  it  clear  that  G.  flavimarginata  is  especially 
sensitive  to  fish  that  are  injured,  or  perhaps 
otherwise  under  stress.  In  this  respect  it  is  similar 
to  G.  castaneus  in  the  Gulf  of  California  (Hobson, 
1968a).  Usually  when  a  reef  fish  is  injured,  or 
seriously  threatened,  it  takes  cover  in  a  reef  crev- 
ice. Usually  such  individuals  are  to  some  extent 
incapacitated,  and  thus  vulnerable  to  preda- 
tors equipped  to  seek  them  out.  Probably  G. 
flavimarginata  is  adapted  to  this  task.  Other  large 
morays  on  the  reef  show  the  same  behavior,  but  to 
a  lesser  degree.  Most  encounters  with  G. 
flavimarginata  were  by  day;  although  its  behavior 
would  seem  equally  adaptive  to  nocturnal  condi- 
tions, it  was  only  occasionally  observed  after  dark. 

CONCLUSION. — Gymnothorax  flavimarginata 
is  especially  sensitive  to  stimuli  emanating  from 
a  fish  in  distress,  and  appears  adapted  to  seeking 
out  such  individuals  when  they  have  sought 
shelter  in  reef  crevices. 


927 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Gijmnothorax  petelli   (Bleeker) — broad-banded 
moray 

The  broad-banded  moray  generally  is  out  of 
sight  within  the  reef  during  daylight,  but  often 
active  in  exposed  locations  after  dark  (Figure  9).  A 
second  species,  G.  undulatus,  similarly  forays 
away  from  cover  at  night,  but  during  this  study 
was  seen  less  often  than  G.  petelli.  Although  no 
specimens  were  examined,  one  G.  petelli  seen  on 
the  reef  at  night  was  grasping  between  its  jaws  a 
pufFerfish,  Canthigaster  jactator.  Additional  evi- 
dence of  nocturnal  habits  in  G.  petelli  was  given  by 
Chave  and  Randall  ( 197 1),  who  described  it  pursu- 
ing crabs  over  underwater  sand  patches  at  night. 

CONCLUSION. — Gymnothorax  petelli  is  a  noc- 
turnal predator. 


suited  to  grasping  prey,  but  the  zebra  moray,  like 
other  species  of  the  genus  Echidna,  has  blunt, 
pebblelike  teeth  that  are  suited  to  crushing  prey. 
Gut  contents  are  consistent  with  this  observation: 
all  four  specimens  (750:  485-835  mm)  taken  at 
various  times  of  the  day  contained  the  crushed 
remains  of  relatively  large  crabs — considerably 
larger  than  crabs  found  in  comparably  sized  indi- 
viduals of  Gymnothorax.  The  zebra  moray  is  a 
sluggish  animal,  even  for  a  moray,  and  is  gener- 
ally secretive.  Usually  all  one  sees  of  this  animal, 
day  or  night,  is  a  motionless  segment  of  its  body, 
visible  at  a  narrow  opening  in  the  reef. 

CONCLUSION. — Echidna  zebra  captures  crus- 
taceans within  reef  crevices,  taking  larger  indi- 
viduals of  the  more  heavily  armored  prey  than  do 
species  of  Gymnothorax. 


Echidna  zebra  (Shaw) — zebra  moray 

The  zebra  moray  has  a  blunter  snout  than  the 
species  oi^ Gymnothorax  treated  above,  but  its  den- 
tition is  even  more  distinctive.  Morays  of  the 
genus  Gymnothorax  have  fanglike  teeth  that  are 


General  Remarks  on  Moray  Eels 

Morays  have  been  widely  considered,  collec- 
tively, as  nocturnal  animals  (e.g.  Winn  and  Bar- 
dach,  1959;  Starck  and  Davis,  1966;  Randall, 


Figure  9. — Gymnothorax  petelli,  a  moray  eel,  on  the  reef  top  at  night. 


928 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


1967;  Collette  and  Talbot,  1972).  Hiatt  and  Stras- 
burg  ( 1960)  attributed  the  high  incidence  of  empty 
stomachs  in  morays  from  the  Marshall  Islands 
during  daylight  to  nocturnal  habits;  however,  I 
concur  with  Gosline  and  Brock  (1960),  who  attri- 
buted the  empty  stomachs  of  Hawaiian  morays 
during  the  day  to  infrequent  feeding,  rather  than 
necessarily  to  nocturnal  feeding.  Certainly  some 
morays  seem  to  be  primarily  nocturnal — Gymno- 
thorax  petelli  and  G.  undulatus,  described  above, 
are  examples.  But  others  described  here,  such  as 
G.  meleagris,  G.  eurostus,  and  G.  flavimarginata, 
feed  regularly  in  daylight.  That  some  morays  are 
primarily  diurnal  was  illustrated  by  Chave  and 
Randall  (1971),  who  described  a  diurnally  active, 
nocturnally  inactive  pattern  for  G.  pictus  in  the 
central  Pacific.  Conclusions  on  relative  activity 
between  day  and  night  for  moray  eels  remain 
tenuous  if  based  solely  on  how  often,  and  at  what 
time,  the  species  is  seen  in  exposed  positions. 
Moray  eels  are  adapted  to  activity  within  reef 
crevices,  and  one  would  expect  at  least  most  of 
them  to  best  capture  their  prey  there;  indeed,  most 
species  rarely  expose  themselves,  day  or  night. 


Family  Congridae:  conger  eels 

Conger  marginaius  Valenciennes — white  eel, 
puhi  uha 

The  white  eel,  which  may  exceed  a  length  of  1  m 
(Gosline  and  Brock,  1960),  is  relatively  numerous 
in  Kona.  It  moves  about  in  the  open  on  the  reef 
after  dark  and  rests  in  reef  crevices  during 
daylight.  In  the  Marshall  Islands,  Hiatt  and 
Strasburg  (1960)  reported  similar  behavior  in  C. 
noordzieki,  which  preys  on  both  fishes  and 
invertebrates. 

CONCLUSION. — Conger  marginaius  is  active 
in  exposed  locations  on  the  reef  after  dark. 

Order  Myctophiformes 
Family  Synodontidae:  lizardfishes 

Sai<n'rfogracj7is(QuoyandGaimard)-"K/ae 
nihoa 

Attaining  lengths  of  over  300  mm,  this  is  the 
largest  of  those  lizardfishes  that  are  numerous  on 
the  reef.  During  both  day  and  night  it  rests  mo- 
tionless and  fully  exposed  on  sand  patches,  rock,  or 
coral.  Despite  these  exposed  positions,  it  is 


difficult  to  detect,  so  closely  does  its  coloration 
match  the  surroundings.  Six  specimens  (223: 
165-315  mm)  were  examined.  The  guts  were 
empty  in  five— four  speared  at  night,  between 
2300  h  and  dawn,  and  one  taken  during  midday. 
The  sixth  specimen  (165  mm),  taken  1  h  before 
midnight,  contained  the  well-digested  anterior 
halfofatrumpetfish,  A i//ostomasc/zmens/s  (about 
90  mm  when  intact).  Because  digestion  was  far 
advanced,  this  prey  may  have  been  ingested  dur- 
ing the  previous  day  or  evening  twilight.  These 
limited  data  suggest  that  attacks  are  infrequent, 
or  perhaps  that  feeding  habits  are  diurnal  or  cre- 
puscular. Hiatt  and  Strasburg  (1960)  reported 
strictly  piscivorous  habits  for  this  species  in  the 
Marshall  Islands,  and  described  daylight  attacks 
in  which  it  darted  upward  from  a  resting  spot  on 
the  sea  floor. 

CONCLUSION. — Saurida  gracilis  attacks 
small  fishes  in  daylight. 

Synodus  variegatus  (Lacepede) — ulae  'ula 

This  is  the  most  numerous  synodontid  on  Kona 
reefs.  During  both  day  and  night  it  rests  on  the  sea 
floor  (Figure  10),  as  does  Saurida  gracilis,  above. 
Although  usually  in  exposed  positions,  it  is 
difficult  to  detect  because  its '  coloration  closely 
matches  the  background.  Frequently  it  becomes 
even  more  inconspicuous  by  burying  in  the  sand, 
leaving  only  its  eyes  and  the  tip  of  its  snout  ex- 
posed. 

Once,  during  early  afternoon,  an  individual  of 
this  species  shot  up  from  the  coral  and  captured  a 
small  wrasse,  Thalassoma  lutescens,  that  I  was 
stalking.  The  wrasse  was  watching  me  when  the 
lizardfish  struck,  and  the  attacker  may  have 
sensed  this  distraction  in  its  prey.  I  speared  the 
predator  immediately  after  the  attack,  and  found 
it  to  be  166  mm  long  (it  lost  the  wrasse  when 
speared  and  is  included  below  among  those  with 
an  empty  gut).  Two  other  noteworthy  incidents 
occurred  at  night:  On  both  occasions  I  was  hunting 
specimens  among  the  coral,  and  my  spear,  project- 
ing into  my  path,  was  faintly  illuminated  by  my 
companion's  diving  light.  Suddenly,  an  individual 
of  this  species  darted  up  and  struck  the  silver  barb 
on  the  otherwise  grey  spear.  Although  the  nearby 
diving  light  created  here  an  unnatural  nocturnal 
situation,  these  two  fish  obviously  were  alert  for 
prey  at  these  times. 

Twelve  specimens  (142:  94-158  mm)  were  col- 
lected during  day  and  night  from  exposed  posi- 


929 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  10. — Synodus  variegatus,  a  lizardfish,  poised  to  strike  at  prey  in  the  water  overhead. 


tions  on  the  sea  floor.  Of  nine  speared  during  af- 
ternoons, six  had  empty  guts,  but  two  contained 
fish  fragments,  and  one  contained  three  fish — two 
digested  beyond  recognition,  and  one  relatively 
fresh  Plagiotremus  gosUnei  (32  mm).  Of  two  col- 
lected during  morning  twilight,  one  was  empty, 
while  the  other  contained  an  extensively  digested 
fish  (25  mm).  Finally,  one  collected  at  night,  5  h 
after  sunset,  contained  fish  fragments. 

CONCLUSION.— nSvnof/i/s  variegatus  attacks 
small  fishes  during  the  day  and  probably  also  at 
night. 

General  Remarks  on  Lizardfishes 

Similar  behavior  is  widely  reported  for  the 
synodontids  of  tropical  seas.  In  the  Florida  Keys, 
Starck  and  Davis  (1966)  reported  that  Synodus 
synodus  andTrachinocephalus  myops  lie  partially 
buried  in  the  sand  and  erupt  to  capture  prey 
swimming  overhead  during  the  day.  Similarly, 
Randall  ( 1967)  noted  that  lizardfishes  in  the  West 
Indies,  including  S.  synodus,  S.  intermedius,  and 
S.foetens,  may  rest  on  rocks,  sand,  or  mud,  where 
they  sometimes  partially  bury  themselves.  Hart- 
line  et  al.  (1972)  observed  on  several  occasions 
during  the  day  Synodus  sp.  in  the  Virgin  Islands 


attacking  the  damselfish  Chromis  cyaneus  from 
resting  positions  on  the  substratum.  Similar  ob- 
servations were  also  reported  by  Smith  and  Tyler 
( 1972).  Although  fishes  seem  to  be  the  major  prey 
of  synodontids,  Randall  (1967)  found  some 
shrimps  and  squids  in  the  predominantly  pis- 
civorous diet  of  lizardfishes  in  the  West  Indies. 
Suyehiro  (1942)  also  reported  shrimps  and  squid 
secondary  prey  to  fishes  in  the  diet  of  Saurida 
undosquamis  in  Japan.  Probably  any  free- 
swimming  animal  of  appropriate  size  becomes 
prey  if  it  passes  close  above  a  waiting  lizardfish 
when  conditions  are  suitable  for  attack.  The  jaws 
of  lizardfishes  are  profusely  rimmed  with  sharp, 
inwardly  depressible  canine  teeth,  like  those  of 
many  morays,  and  this  type  of  dentition  is  espe- 
cially well  suited  to  grasping  small  fishes. 

Order  Gadiformes 
Family  Brotulidae:  brotulas 

Brotula  nuiltiharhata  Temminck  and 
Schlegel — puhi  palcihoana 

This  fish  is  not  in  view  during  daylight,  except 
to  one  who  enters  some  of  the  darker  caves.  Al- 
though diurnally  secretive,  it  swims  into  the  open 


930 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


on  the  reef  after  dark,  but  even  then  is  mostly 
exposed  only  during  transit  from  one  crevice  to 
another. 

Seven  individuals  (169:  73-250  mm)  were 
speared  during  day  and  night.  Two  collected  about 
2  h  before  daybreak  as  they  swam  close  among 
rocks  were  both  full  of  prey,  including  fresh  mate- 
rial. Of  three  others  collected  in  dark  caves  during 
midmorning,  one  was  empty  and  the  other  two 
contained  only  well-digested  fragments.  Finally, 
two  individuals  collected  within  1  h  after  nightfall 
as  they  swam  in  exposed  locations  among  rocks 
were  both  empty — apparently  having  not  yet  cap- 
tured prey  on  their  nocturnal  foray.  The  four  indi- 
viduals containing  identifiable  prey  had  fed  on  the 
items  listed  in  Table  8. 

CONCLUSION.— Brofulo  multibarbata  is  a 
nocturnal  predator  that  feeds  mostly  on  crusta- 
ceans and  fishes. 

General  Remarks  on  Brotulas 

Hiatt  and  Strasburg  (1960)  concluded  that 
Dinematichthys  ilucoeteoides  in  the  Marshall  Is- 
lands is  very  secretive  because  they  never  saw  a 
live  one,  but  did  not  suggest  that  it  might  be  noc- 
turnal. They  believed  that  by  concealing  itself  in 
crevices  this  brotulid  is  able  to  dash  out  and  cap- 
ture small  fishes  and  crustaceans  that  unsuspect- 


ingly venture  close  to  its  hiding  place.  Starck  and 
Davis  (1966)  recognized  nocturnal  habits  in  an 
Atlantic  species,  Petrotyx  sanguineus,  which  is 
unseen  in  daylight,  but  swims  close  among  reef 
ledges  at  night. 

Order  Atheriniformes 

Family  Atherinidae:  silversides 

Pranesus  insularum  (Jordan  and 
Evermann) — lao 

This  silverside  is  not  numerous  in  Kona,  but  in 
daylight  small  schools  of  relatively  inactive  indi- 
viduals occur  at  various  places  along  the  rocky 
shore,  right  at  the  water's  edge.  At  nightfall  these 
schools  disperse,  and  the  members  move  away 
from  shore,  over  the  reef.  They  swim  high  in  the 
water  column,  just  under  the  water  surface,  and 
some  of  them  range  out  at  least  as  far  as  the 
offshore  drop-off. 

Using  a  hard  net,  13  individuals  (47:  39-70  mm) 
were  collected  during  both  dark  nights  and  moon- 
lit nights — 9  between  4  and  6  h  after  sunset  and  4 
during  the  2  h  before  first  morning  light.  Although 
the  gut  of  1  was  empty,  the  other  12  were  full, 
including  fresh  material,  as  listed  in  Table  9. 

CONCLUSION. — Pranesus  insularum  is  a  noc- 
turnal planktivore  that  takes  mostly  crustaceans 
and  foraminiferans. 


Table  8. — Food  of  Brotula  multibarbata. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  {n  =  4) 

diet  volume 

index 

1 

Xanthid  crabs 

25.0 

6.25 

2 

Fish 

16,3 

4.08 

3 

Decapod  shrimps 

6,3 

1  58 

4 

Mysids 

5,0 

1,25 

5 

Crab  megalops 

0.3 

0,08 

Also, 

crustacean  fragments 

2 

37.5 

18.75 

Unidentified  fragments 

3 

9,6 

7.20 

Table  9. 

—Food  of  Pranesus  insularum. 

No,  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  12) 

diet  volume 

index 

1 

Mysids 

5 

14.2 

5.92 

2 

Decapod  shrimp  larvae 

5 

6.7 

2.79 

3 

Foraminiferans 

4 

6.3 

2.10 

4 

Calanoid  copepods 

2 

4.2 

0,70 

5 

Larvaceans 

1 

2.1 

0,18 

6 

Crab  zoea 

1 

1.7 

0.14 

7 

Spider 

1 

0.4 

0.03 

Also. 

crustacean  fragments 

12 

40.8 

40.80 

Unidentified  fragments 

7 

236 

13,79 

931 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


General  Remarks  on  Silversides 

It  is  widely  recognized  that  silversides  prey 
largely  on  zooplankton.  Hiatt  and  Strasburg 
(1960)  found  mostly  zooplankton  in  three  species 
in  the  Marshall  Islands,  as  did  Randall  (1967)  in 
two  species  from  the  West  Indies.  Each  report 
listed  shrimp  larvae  and  copepods  among  the 
major  food  items,  but  neither  mentioned  noctur- 
nal habits.  At  Majuro  Atoll,  Marshall  Islands, 
Pranesus  pinguis  is  inactive  in  schools  along 
lagoon  beaches  during  the  day,  and  then  migrates 
offshore  into  the  lagoon  at  nightfall,  where  it  dis- 
perses and  feeds  on  zooplankton  in  the  surface 
waters  (Hobson  and  Chess,  1973).  The  closely  re- 
lated P.  insularum  does  not  move  so  far  from 
shore  at  night  in  Kona,  presumably  because  its 
feeding  grounds  are  over  the  nearshore  reefs. 

Order  Beryciformes 

Family  Holocentridae:  squirrelfishes 

The  squirrelfishes  compose  one  of  the  more 
prominent  groups  of  fishes  on  Hawaiian  reefs.  The 
species  fall  into  two  major  categories:  those  in  one 
group  include  members  of  the  genus  Holocentrus, 
which  are  known  by  the  generic  Hawaiian  name 
ala  'ihi,  and  one  species  of  the  genus  Ho lotrachys; 
those  in  the  second  group  include  species  of  the 
genus  Myripristis,  which  are  known  by  the 
generic  Hawaiian  name  'u'u,  or  perhaps  more 
often  today  by  the  Japanese  equivalent  menpachi. 

Holocentrus  sammara  (Forskal) 

This  solitary  fish  is  numerous  in  coral-rich  sur- 
roundings at  depths  between  4  and  20  m.  It  is  a 
relatively  large  species — up  to  300  mm  long  (Gos- 
line  and  Brock,  1960) — and  characteristically  hov- 
ers in  visible  locations  at  the  openings  of  reef  caves 
during  the  day.  During  evening  twilight  it  moves 
away  from  its  daytime  shelter-sites  and  through- 
out the  night  ranges  over  the  nearby  areas  of  the 
reef,  staying  close  to  the  sea  floor.  During  morning 
twilight  it  gradually  moves  closer  to  cover  and  by 
sunrise  has  resumed  its  daytime  mode  of  be- 
havior. After  dark  the  coloration  of  this  fish  differs 
from  its  coloration  in  daylight  (Figure  11a  andb). 

Twenty-one  specimens  (162:  128-202  mm)  were 
collected  during  day  and  night  for  food-habit 
study.  All  13  that  were  speared  as  they  swam  in 
exposed  positions  on  the  reef  during  the  last  hours 


of  darkness,  before  daybreak,  and  during  morning 
twilight  contained  prey  in  varying  stages  of  diges- 
tion. In  comparison,  of  seven  speared  as  they 
hovered  close  among  coral  shelter  during  the  after- 
noon, four  were  empty,  two  contained  only  well- 
digested  fragments,  and  one  contained  an  appar- 
ently recently  ingested  crab.  Finally,  one  that  was 
speared  in  the  open  4  h  after  nightfall  was  full  of 
prey,  most  of  it  fresh.  Items  in  the  17  specimens 
containing  identifiable  material  are  listed  in 
Table  10. 

CONCLUSION. — Holocentrus  sammara  is  a 
nocturnal  predator  that  feeds  mostly  on  benthic 
crustaceans,  especially  xanthid  crabs  and  carid- 
ean  shrimps,  but  some  feed  diurnally. 

Holocentrus  spinifera  (Forskal) 

This  is  the  largest  squirrelfish  on  Kona  reefs, 
and  of  those  considered  in  this  report  it  is  also  the 
least  numerous.  A  solitary  species  during  both  day 
and  night,  it  is  secretive  within  reef  crevices  in 
daylight,  but  ranges  out  and  forages  close  to  the 
reef  after  dark.  In  daylight,  the  body  of  this  fish  is 
a  plain  rosy-red,  and  its  dorsal  fin  is  yellow;  in 
darkness,  however,  a  small  but  prominent  white 
spot  appears  on  each  side  of  its  body,  just  behind 
its  dorsal  fin.  Because  this  large  fish  is  not  numer- 
ous, I  came  to  recognize  certain  individuals  and 
found  that  after  nocturnal  forays  on  the  reef  each 
tended  to  return  each  morning  to  its  particular 
shelter  spot. 

Six  specimens  (213:  68-350  mm)  were  speared 
during  day  and  night  for  study  of  food  habits.  The 
one  that  was  taken  during  midday  contained  a 
large  caridean  shrimp,  Saron  jnarmoratus  (about 
40  mm),  that  was  extensively  damaged  by  diges- 
tion and  could  have  been  taken  during  the  previ- 
ous night.  A  second,  taken  as  it  emerged  from 
cover  at  nightfall,  was  the  only  one  taken  with  an 
empty  gut.  Of  the  other  four,  all  of  which  con- 
tained relatively  fresh  prey,  three  were  collected 
as  they  swam  in  the  open  at  night,  more  than  3  h 
after  sunset,  and  the  fourth  was  collected  under  a 
ledge  during  morning  twilight. 

All  five  specimens  containing  food  had  fed  on 
crustaceans  exclusively.  Three  had  taken  carid- 
ean shrimps  (mean  percent  of  diet  volume:  34; 
ranking  index:  20.4),  three  had  taken  xanthid 
crabs  (mean  percent  of  diet  volume:  31;  ranking 
index:  18.6),  and  one  had  taken  a  scyllarid  lobster 
(mean  percent  of  diet  volume:  11;  ranking  index: 


932 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  11. — Holocentrus  sammara,  a  squirrelfish:  a,  showing  its  diurnal  coloration  under  a  ledge  during  the  day;  b, 
showing  nocturnal  coloration  as  it  swims  close  to  the  reef  at  night. 


933 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  10. — Food  of  Holocentrus  sammara. 


N 

3.  fish 

Mean  percent 

Wl 

th  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  17) 

diet  volume 

index 

1 

Xanthid  crabs 

12 

52.5 

37.08 

2 

Candean  shrimps 

4 

12.2 

2.88 

3 

Portunid  crabs 

2 

7.8 

0.92 

4 

Fish 

2 

7.8 

0.92 

5 

Penaeid  shrimps 

1 

5.9 

0.35 

Also. 

crustacean  fragments 

4 

13.8 

3.25 

2.2).  Three  contained  unidentified  crustacean 
fragments  (mean  percent  of  diet  volume:  24;  rank- 
ing index:  14.4). 

CONCLUSION. — Holocenti'us  spinifera  is  a 
nocturnal  predator  that  feeds  mostly  on  benthic 
crustaceans,  especially  caridean  shrimps  and 
xanthid  crabs. 

Holocentrus  Here  Cuvier 

This  relatively  numerous  holocentrid  is  mostly 
secreted  in  reef  caves  during  the  day,  but  after 
dark  sw^ims  in  exposed  locations  at  depths  below  5 
m,  especially  along  reef  ledges.  It  emerges  from 
cover  after  last  evening  light  and  regains  shelter 
before,  or  at,  first  morning  light.  Like//,  sammara 
and  //.  spinifera,  above,  //.  tiere  has  distinctive 
diurnal  and  nocturnal  color  patterns  (Figure  12a 
and  b). 

Fifteen  specimens  (141:  67-160  mm)  were 
speared  as  they  swam  in  the  open  at  night,  or  just 
after  they  had  returned  to  shelter  at  daybreak:  1 1 
of  these  had  food  in  their  stomachs;  3  taken  within 
4  h  after  sunset  were  empty — apparently  their 
nocturnal  hunt  had  not  yet  been  successful;  1 
taken  under  a  ledge  during  morning  twilight  also 
had  an  empty  gut,  indicating  that  it  had  passed 
the  night  without  feeding.  Items  in  the  11  speci- 
mens containing  identifiable  material  are  listed 
in  Table  11. 

CONCLUSION.— //o/ocen^rws  tiere  is  a  noc- 
turnal predator  that  feeds  mostly  on  benthic  crus- 
taceans, especially  xanthid  crabs  and  caridean 
shrimps. 

Holocentrus  xantherijthrus  Jordan  and  Ever- 
mann 

During  the  day  this  relatively  small  holocentrid 
aggregates  in  crevices  and  under  overhangs  of 
basalt  reefs  (Figure  13)  in  water  deeper  than  6  m, 
but  especially  below  20  m.  After  dark  it  ranges  out 


from  this  shelter  and  into  the  surrounding  areas, 
where  solitary  individuals  are  active  close  to  rock, 
coral,  or  pockets  of  sand.  By  first  morning  light  it 
has  returned  to  its  daytime  retreats.  At  night  this 
fish  has  prominent  white  vertical  markings  on  its 
body  like  those  illustrated  for  //.  tiere  (Figure 
12b). 

Of  the  29  individuals  (106:  88-123  mm)  speared 
at  different  times  of  day  and  night,  the  stomachs  of 
all  15  that  were  active  in  exposed  locations  on  the 
reef  during  the  2  h  immediately  before  daybreak, 
or  were  under  reef  shelter  within  an  hour  of  sun- 
rise, contained  prey  in  varying  stages  of  digestion, 
whereas  the  stomachs  of  all  11  taken  from  reef 
crevices  during  afternoons  were  empty.  The  re- 
maining three  were  taken  within  2  h  after  last 
light,  shortly  after  they  had  begun  their  nightly 
foraging,  and  although  one  was  empty,  the  other 
two  contained  fresh  prey.  Items  in  the  17  speci- 
mens that  contained  identifiable  material  are 
listed  in  Table  12. 

CONCLUSION. — Holocentrus  xantherythrus  is 
a  nocturnal  predator  that  feeds  mostly  on  benthic 
crustaceans,  although  some  free-swimming  crus- 
taceans are  also  taken  close  to  the  bottom. 

Holocentrus  diadema  Lacepede 

After  dark,  many  individuals  of  this  relatively 
small  squirrelfish  swim  close  to  the  sea  floor  where 
coral  growth  is  rich  at  depths  below  3  to  4  m. 
Holocentrus  diadema  is  secretive  by  day,  gener- 
ally remaining  out  of  sight  within  the  many  nar- 
row interstices  of  its  coral-rich  habitat,  but  is  oc- 
casionally glimpsed  in  the  shadows  at  the  base  of 
coral  heads.  Generally,  it  does  not  leave  its  day- 
time shelter  until  after  last  evening  light,  and 
returns  to  cover  before  or  at  first  morning  light.  At 
night  this  fish,  like  //.  xantherythrus,  above,  has 
prominent  white  vertical  markings  on  its  body 
that  are  similar  to  those  on  the  nocturnally  active 
//.  tiere  (Figure  12b). 


934 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  12. — Holocentrus  Here,  a  squirrelfish:  a,  showing  diurnal  coloration  under  a  ledge  during  the  day;  b,  showing 

nocturnal  coloration  as  it  swims  close  to  the  reef  at  night. 


935 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  11. — Food  oi  Holocentrus  Here. 


N 

3.  fish 

Mean  percent 

Wl 

th  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  11) 

diet  volume 

index 

1 

Xanthid  crabs 

8 

387 

28.15 

2 

Caridean  shrimps 

5 

24.7 

11.23 

3 

Crab  megalops 

5 

4.8 

2.18 

4 

Fish 

1 

1.8 

0.16 

5 

Polychaetes 

1 

0.2 

0.02 

6 

Sipunculid  introverts 

1 

0.1 

<0.01 

Also, 

crustacean  fragments 

8 

29.7 

21.60 

Table  12. — Food  of  Holocentrus  xantherythrus. 


N 

o.  fish 

Mean  percent 

w 

th  this 

of 

Ranking 

Rank 

Items 

item 

{n  =  17) 

diet  volume 

index 

1 

Xanthid  crabs 

12 

42.3 

29.86 

2 

Crab  megalops 

11 

14.8 

9.58 

3 

Caridean  shrimps 

7 

15.1 

6.22 

4 

Prosobranch  gastropods 

4 

2.3 

0.54 

5 

Stomatopods 

2 

1.9 

0.22 

6 

Opisthobranch  gastropods 

1 

0.9 

0.05 

7 

Sipunculid  introverts 

1 

0.8 

0.05 

8 

Pelecypods 

1 

0.6 

0.04 

9 

Euphausiids 

1 

0.3 

0.02 

10 

Oxyrhynchid  crabs 

1 

0.3 

0.02 

11 

Tanaids 

2 

0.2 

0.02 

12 

Flabelliferan  isopods 

1 

0.1 

0.01 

13 

Mysids 

1 

0.1 

0.01 

Also, 

crustacean  fragments 

10 

20.3 

11.94 

Figure  13. — Holocentrus  xantherythrus,  a  squirrelfish,  aggregated  under  a  ledge  during  the  day. 


936 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  13. — Food  of  Holocentrus  diadema. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  26) 

diet  volume 

index 

1 

Xanthid  crabs 

17 

26.7 

17.46 

2 

Ophiuroids 

12 

12.0 

5.54 

3 

Crab  megalops 

11 

12.4 

5.25 

4 

Carldean  shrimps 

11 

9.7 

4.10 

5 

Prosobranch  gastropods 

13 

6.2 

3.10 

6 

Polychaetes 

6 

6.1 

1.41 

7 

Gammaridean  amphlpods 

5 

1.7 

0.33 

8 

Penaeid  shrimps 

2 

2.3 

0.18 

9 

Isopods 

3 

1.4 

0.16 

10 

Chitons 

1 

1.7 

0.07 

11 

Mysids 

2 

0.8 

0.06 

12 

Portunid  crabs 

0.8 

0.03 

13 

Holothurians 

0.6 

0.02 

14 

Oxyrhynchid  crabs 

0.4 

0.02 

15 

Tanaids 

0.4 

0.02 

16 

Calanoid  copepods 

0.4 

0.02 

17 

Pelecypods 

0.4 

0.02 

18 

Opisthobranch  gastropods 

0.2 

0.01 

19 

Echinoids 

0.2 

0.01 

20 

Harpacticoid  copepods 

0.1 

<0.01 

21 

Limpets 

0.1 

<0.01 

Also. 

crustacean  fragments 

15 

11.3 

6.63 

Unidentified  fragments 

4 

39 

060 

Twenty-eight  specimens  ( 109:  85-127  mm)  were 
speared  as  they  swam  in  exposed  locations  on  the 
reef  at  various  times  during  the  night.  Only  two 
had  empty  stomachs:  in  one  of  these,  taken  shortly 
after  nightfall,  the  entire  gut  was  empty,  which 
indicated  it  had  not  as  yet  hunted  successfully 
that  night;  the  other,  taken  with  an  empty 
stomach  just  before  daybreak,  had  a  full  intestine, 
suggesting  that  it  had  fed  early  but  not  late  during 
the  night.  The  other  26  specimens  all  contained 
food  in  varying  stages  of  digestion,  most  of  it 
identifiable,  as  listed  in  Table  13. 


CONCLUSION.— //o/oce/?^ri/s  diadema  is  a 
nocturnal  predator  that  feeds  mostly  on  benthic 
crustaceans,  although  it  also  takes  free- 
swimming  forms  close  to  the  bottom. 

Holocentrus  lacteoguttatiim  Cuvier 

This  small  squirrelfish  is  similar  toH.  xanthery- 
thrus  and  H.  diadema,  but  frequents  shallower 
water  than  the  other  two,  being  most  numerous 
during  the  day  in  rocky  crevices  along  surge- 
swept  shores,  often  where  the  water  is  only  1  to  4 
m  deep.  It  aggregates  in  these  crevices,  and  after 
nightfall  ranges  out  over  coral,  rock,  or  pockets  of 
sand  on  the  surrounding  reef.  Gosline  and  Brock 
(1960)  also  noted  the  shallowwater  habits  of  this 
species,  but  in  at  least  some  situations  it  occurs  in 


depths  below  30  m  (Gosline,  1965).  These  habitat 
distinctions  are  clearest  in  daylight,  when  the 
three  species  have  retired  to  their  shelters.  The 
differences  are  less  clear  at  night,  when  their  ac- 
tivity ranges  overlap.  Holocentrus  lacteoguttatum 
does  not  seem  to  have  prominent  nocturnal  color 
features,  as  do  certain  other  species  of 
Holocentrus,  treated  above;  however,  several  in- 
dividuals after  having  been  speared  at  night 
showed  faint  traces  of  essentially  the  same  white 
markings  characteristic  of  nocturnally  active  in- 
dividuals of  H.  xantherythrus,  H.  diadema,  and 
H.  tiere  (see  Figure  12b). 

Twenty-one  specimens  (88:  52-104  mm)  were 
collected  at  various  times  of  day  and  night.  All  but 
1  of  13  active  individuals  that  were  speared  in  the 
open  at  night  (more  than  4  h  after  sunset  and 
before  they  had  returned  to  shelter  at  daybreak) 
had  food  in  their  stomachs;  the  lone  exception, 
collected  4  h  after  sunset,  had  a  completely  empty 
gut,  indicating  it  had  not  yet  hunted  successfully 
that  night.  In  comparison,  only  one  of  five  col- 
lected from  aggregations  under  shelter  during 
midmorning  had  material  in  its  stomach,  and  this 
was  extensively  digested  (all  had  full  intestines, 
however).  Finally,  all  three  that  were  collected 
from  aggregations  under  shelter  during  late  af- 
ternoon had  completely  empty  guts,  except  for  a 
few  well-digested  fragments  posteriorly.  Items  in 
the  13  specimens  containing  identifiable  material 
are  listed  in  Table  14. 


937 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 


Table  14. — Food  of  Holocentrus  lacteoguttatum. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  13) 

diet  volume 

Index 

1 

Xanthid  crabs 

13 

36.3 

36.30 

2 

Crab  megalops 

9 

8.0 

5.54 

3 

Gammaridean  amphipods 

8 

5.1 

3.14 

4 

Tanalds 

6 

3.7 

1.71 

5 

Polychaetes 

4 

4.9 

1.51 

6 

Caridean  shrimps 

3 

1.9 

0.44 

7 

Harpactlcoid  copepods 

3 

0.8 

0.19 

8 

Echlnolds 

3 

0.8 

0.19 

9 

SIpunculid  introverts 

1.8 

0.14 

10 

Prosobranch  gastropods 

1.0 

0.08 

11 

Oxyrhynchid  crabs 

0.3 

0.02 

12 

Calanoid  copepods 

0.3 

0.02 

13 

Limpets 

0.2 

0.02 

14 

Ophiurolds 

0.1 

0.01 

Also, 

crustacean  fragments 

13 

28.1 

28.10 

Unidentified  fragments 

4 

6.7 

2.06 

CONCLUSION.^f/^o/ocen^ri/s  lacteoguttatum 
is  a  nocturnal  predator  that  feeds  primarily  on 
benthic  crustaceans,  although  some  free- 
swimming  forms  close  to  the  bottom  are  also 
taken. 

Holotrachijs  lima  (Valenciennes) 

This  fish  is  secreted  far  back  in  reef  crevices 
during  daylight.  After  dark,  however,  solitary  in- 
dividuals are  widespread  in  exposed  positions, 
swimming  even  closer  to  the  reef  than  do  the 
species  of  Holocentrus,  discussed  above.  Unlike 
the  others,  which  often  swim  over  sand  patches, 
this  species  stays  over  rock  or  coral.  It  did  not 
display  distinctive  day  or  night  color  features, 
being  at  all  times  a  solid  rose-red. 

Twenty  specimens  (91:  70-113  mm)  were  col- 
lected during  day  and  night.  Thirteen  were  active 
in  exposed  positions  on  the  reef  at  night  when 
speared,  and  the  stomachs  of  eight  contained  prey, 
much  of  it  fresh.  Of  the  five  taken  after  dark  with 
empty  stomachs,  the  entire  gut  was  empty  in  three 
collected  before  midnight,  indicating  they  had  not 
yet  hunted  successfully  that  night;  however,  the 
gut  was  also  empty  in  one  speared  just  before 


dawn,  indicating  it  had  passed  the  entire  night 
without  feeding;  the  fifth  individual  with  an 
empty  stomach  also  was  collected  just  before 
dawn,  but  its  intestine  was  full,  indicating  that  it 
probably  had  fed  earlier  during  the  night.  Six  of 
seven  specimens  collected  from  deep  crevices  dur- 
ing late  morning  had  empty  stomachs,  and  the 
extensively  damaged  material  in  the  seventh  in- 
dividual probably  had  been  ingested  during  the 
previous  night.  (Rotenone  was  used  to  collect  this 
species  during  the  day,  a  departure  from  the  stan- 
dard collecting  method  that  was  necessary  be- 
cause this  secretive  fish  is  only  rarely  seen  in 
daylight.)  Items  in  the  10  specimens  containing 
identifiable  material  are  listed  in  Table  15. 

CONCLUSION.— Holotrachys  lima  is  a  noc- 
turnal predator  that  feeds  mostly  on  benthic  crus- 
taceans, although  some  free-swimming  forms 
close  to  the  bottom  also  are  taken. 

Myripristis  kuntee  Cuvier 

This  is  the  smallest  of  the  three  species  of 
Myripristis  that  are  numerous  on  the  nearshore 
Xona  reefs.  It  remains  secreted  in  small  crevices 


Table  15. — Food  of  Holotrachys  lima. 


N 

0.  fish 

Mean  percent 

w 

th  this 

of 

Ranking 

Rank 

Items 

Item 

(n  =  1 

0) 

diet  volume 

Index 

1 

Caridean  shrimps 

6 

31.5 

18.90 

2 

Xanthid  crabs 

5 

33.0 

16.50 

3 

Crab  megalops 

2 

7.0 

1.40 

4 

Fish 

1 

3.5 

0.35 

5 

Gammaridean  amphipods 

1 

0.5 

0.05 

Also, 

crustacean  fragments 

5 

24.5 

12.25 

938 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


and  coral  interstices  during  the  day,  but  emerges 
and  aggregates  in  the  lower  levels  of  the  water 
column,  above  the  reef,  about  30  min  after  sunset. 
After  remaining  active  during  the  night,  it  re- 
turns to  its  daytime  shelter  on  the  reef  about  30 
min  before  sunrise  (Hobson,  1972,  as  M. 
multiradiatus) .  When  this  fish  is  under  cover  dur- 
ing the  day  its  body  is  solid  red,  but  when  active  in 
the  water  column  after  dark,  its  lower  sides  are 
silvery,  affording  countershading  like  that  de- 
scribed for  nocturnally  active  M.  leiognathus  in 
the  Gulf  of  California  (Hobson,  1968a).  This  noc- 
turnal pattern  was  illustrated  earlier  (Hobson, 
1972:  Figure  6). 

Thirty-nine  specimens  (120:  74-145  mm)  were 
speared  at  different  times  of  the  day  and  night.  All 
20  that  were  collected  either  over  the  reef  at  night 
(later  than  4  h  after  sunset),  or  from  shelter  sites 
within  an  hour  of  sunrise,  had  their  guts  full  of 
food.  In  contrast,  13  of  14  collected  from  shelter 
sites  during  the  afternoon  and  evening  twilight 
had  empty  guts  (3  had  a  few  fragments  posteriorly 
in  their  intestines),  and  the  14th  had  in  its 
stomach  only  well-digested  fragments.  Of  the  re- 
maining five,  collected  above  the  reef  early  during 
the  night  (within  1  h  after  last  light),  four  had 
their  guts  completely  empty,  indicating  they  had 
not  as  yet  hunted  successfully  at  that  early  hour, 
but  the  fifth  was  full  of  fresh  calanoid  copepods  of  a 
species  that  was  exceptionally  numerous  around 
our  diving  lights  for  about  45  min  shortly  after 
last  light  on  that  particular  evening.  Items  in  the 
22  individuals  that  contained  identifiable  mate- 
rial are  listed  in  Table  16. 

CONCLUSION.— Myripris^is   kuntee   is   a 


nocturnal  planktivore  that  takes  mostly  crab 
megalops  and  other  Crustacea. 

Mijripristis  murdjan  (Forskal) 

This  holocentrid  is  numerous  in  Kona,  where 
during  the  day  it  aggregates  in  reef  crevices  and 
under  coral  overhangs,  especially  where  there  is 
shelter  from  prevailing  seas  (Figure  14).  The 
twilight  activity  of  this  species  has  been  described 
(Hobson,  1972,  as  M.  berndti).  About  30  min  after 
sunset  it  emerges  from  its  daytime  shelter  and 
aggregates  in  the  water  column  above  the  reef, 
generally  rising  to  levels  higher  than  those  at- 
tained by  M.  kuntee  (see  above).  Immedi- 
ately, there  is  a  general  movement  offshore. 
It  remains  uncertain  how  far  it  swims  offshore 
— perhaps  it  does  not  go  much  beyond  the  drop-off 
into  deep  water,  which  is  a  major  feeding  ground 
for  diurnal  planktivores  (Hobson,  1972).  The 
offshore  move  is  obscured  by  the  circumstance 
that  at  any  given  time  during  the  night  many 
individuals  of  this  species  are  swimming  over  the 
inshore  reefs.  Nevertheless,  there  are  consistently 
fewer  of  them  over  inshore  reefs  on  dark  nights 
than  on  moonlit  nights.  Gosline  (1965)  also  noted 
offshore  migrations  at  night  by  species  of 
Myripristis  in  Hawaii.  About  40  min  before  sun- 
rise this  species  begins  to  assemble  above  its  diur- 
nal shelter,  and  within  10  min  all  have  taken 
cover  for  the  coming  day.  This  species  shows  es- 
sentially the  same  day-night  difference  in  color 
patterns  as  M.  kuntee,  above. 

Of  25  individuals  (169:  139-270  mm)  speared  at 
different  times  of  day  and  night,  all  16  that  were 
taken  above  the  reef  at  night  (later  than  4  h  after 


Table  16. — Food  of  Myripristis  kuntee. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  {n  =  22) 

diet  volume 

index 

1 

Crab  megalops 

19 

25.2 

21.76 

2 

Decapod  shrimps 

9 

11.8 

4.83 

3 

Calanoid  copepods 

9 

8.0 

3.27 

4 

Mysids 

7 

9.3 

2.96 

5 

Polychaetes 

4 

4.8 

0.87 

6 

Fish 

3 

4.6 

0.63 

7 

Stomatopods 

4 

2.8 

0.51 

8 

Gammaridean  amphipods 

7 

0.9 

0.29 

9 

Gnathiid  isopod  larvae 

2 

1.8 

0.16 

10 

Ostracods 

2 

0.1 

0.01 

11 

Tanaids 

1 

0.1 

0.01 

12 

Invertebrate  eggs 

1 

0.1 

0.01 

Also, 

crustacean  fragments 

14 

27.8 

17.69 

Unidentified  fragments 

3 

2.7 

0.37 

939 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Figure  14. — Mynpnstis  murdjan,  a  squirrelfish,  aggregated  under  a  coral  ledge  during  the  day. 


sunset)  contained  food,  whereas  8  of  9  that  were 
collected  from  shelter  sites  during  the  afternoon 
were  empty  (the  ninth  specimen,  collected  during 
late  afternoon,  had  only  well-digested  fragments 
in  its  stomach).  Items  in  the  17  individuals  con- 
taining identifiable  material  are  listed  in  Table 
17. 

Hiatt  and  Strasburg  (1960)  found  shrimp  frag- 
ments in  M.  murdjan  (reported  as  M.  benidti)  in 
the  Marshall  Islands,  and  suspected  nocturnal 
habits,  as  did  Randall  (1955)  for  this  species  in 
the  Gilbert  Islands. 


CONCLUSION.— MjTJpns^is  murdjan  is  a  noc- 
turnal planktivore  that  takes  mostly  crab 
megalops  and  other  crustaceans. 

Myripristis  amaenus  (Castelnau) 

This  squirrelfish,  which  congregates  during  the 
day  in  large  caves  cut  into  reefs  exposed  to  an 
open-sea  swell,  is  very  similar  to  the  preceding,  M. 
murdjan,  but  is  less  numerous  in  most  Kona 
habitats.  Its  behavior  during  twilight  was  de- 
scribed earlier  (Hobson,  1972,  as  M.  argyromas). 


Table  17. — Food  of  Myripristis  murdjan. 


N 

3.  fish 

Mean  percent 

wi 

th  this 

of 

Ranking 

Rank 

Items 

Item 

(n  =  17) 

diet  volume 

mdex 

1 

Crab  megalops 

16 

53.5 

50.35 

2 

Decapod  shrimps 

3 

8.1 

1.43 

3 

Myslds 

3 

6.5 

1.15 

4 

Fish 

2 

2.0 

0.24 

5 

Polychaetes 

2 

1.5 

0.18 

6 

Stomatopods 

2 

0.9 

0.11 

7 

Euphausiids 

1.2 

0.07 

8 

Cephalopods 

1.2 

0.07 

9 

Gammaridean  amphipods 

0.5 

0.03 

10 

Prosobranch  gastropods 

0.3 

0.02 

11 

Calanoid  copepods 

0.1 

<0.01 

12 

Ostracods 

0.1 

<0.01 

Also, 

crustacean  fragments 

8 

14.5 

682 

Unidentified  fragments 

4 

9.6 

2.26 

940 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Myripristis  arnaenus,  like  its  congeners,  emerges 
from  its  daytime  retreats  about  30  min  after  sun- 
set, and  at  least  many  individuals  move  offshore, 
especially  when  there  is  no  moonlight.  Myripristis 
arnaenus  shows  essentially  the  same  day-night 
distinction  in  coloration  that  is  described  above 
for  its  congeners. 

Of  19  individuals  (176:  116-210  mm)  speared  at 
different  times  of  day  and  night,  all  14  collected 
above  the  reef  at  night  (later  than  4  h  after  sun- 
set), or  from  shelter  sites  within  2  h  after  the 
species  had  returned  to  cover  in  the  morning,  con- 
tained food,  whereas  all  5  collected  from  shelter 
sites  during  late  afternoon  were  empty.  Items  in 
the  14  individuals  containing  identifiable  prey  are 
listed  in  Table  18. 

CONCLUSION. — Myripristis  arnaenus  is  a 
nocturnal  planktivore  that  takes  mostly  crab 
megalops  and  other  crustaceans. 

General  Remarks  on  Squirrelfishes 

Squirrelfishes  are  known  throughout  tropical 
seas  to  hunt  prey  after  dark.  For  example,  they 
have  been  thus  described  in  the  Marshall  Islands 
(Hiatt  and  Strasburg,  1960),  the  Gulf  of  California 
(Hobson,  1965,  1968a),  and  the  West  Indies  (Ran- 
dall, 1967).  Similar  behavior  has  been  noted  in  the 
Florida  Keys  by  Starck  and  Davis  (1966),  who 
noted  there  were  no  distinctive  nocturnal  color 
features  in  tropical  Atlantic  holocentrids,  such  as 
are  reported  for  all  but  two  of  the  Hawaiian 
species  above. 

The  two  major  categories  noted  above  in  the 
introduction  to  the  squirrelfishes  each  represents 
a  generally  different  mode  of  predation.  All  feed 
primarily  on  crustaceans,  but  whereas  species  of 


Holocentrus  and  Holotrachys  lima  capture  their 
prey  close  to  the  sea  floor,  species  of  Myripristis 
hunt  prey  up  in  the  water  column. 

BOTTOM  FEEDERS.— The  seven  holocentrids 
in  this  category  feed  mostly  on  benthic  forms,  but 
also  take  some  prey  that  are  free-swimming  at  the 
base  of  the  water  column.  Xanthid  crabs  com- 
prised the  major  prey  item  for  all  species  except 
the  largest,  Holocentrus  spinifera,  which  con- 
tained a  slightly  larger  volume  of  caridean 
shrimps.  Xanthid  crabs  are  ubiquitous  benthic 
animals  in  all  Kona  inshore  habitats,  and  are 
widely  active  in  exposed  positions  after  dark. 

Of  the  seven  bottom-feeding  squirrelfishes,  only 
three  similar  species,  Holocentrus  diadema,  H. 
lacteoguttatum,  and  H.  xantherythrus,  hunt 
significantly  over  sand  in  addition  to  feeding  on 
hard  reef  substrata;  however,  even  these  three  do 
not  range  away  from  cover  during  this  activity, 
which  is  limited  to  sand  pockets  on  the  reef  and 
only  the  fringes  of  more  extensive  sandy  areas. 
Nevertheless,  it  is  probably  because  of  this  habit 
that  these  three  have  more  varied  diets  than  do 
the  others.  Hiatt  and  Strasburg  (1960)  reported 
that  some  of  the  holocentrids  in  the  Marshall  Is- 
lands forage  on  sandy  bottoms,  citing  sand- 
dwelling  gastropods  as  being  prominent  prey  of//. 
diadema  in  that  area. 

The  other  four  bottom  feeders,  Holocentrus 
sammara,  H.  spinifera,  H.  tiere,  and  Holotrachys 
lima,  restrict  their  activity  largely  to  hard  sub- 
strata on  the  reef,  and  prey  more  heavily  on  carid- 
ean shrimps — especially  on  snapping  shrimps. 
Some  of  the  larger  individuals  of  Holocentrus 
sammara  and  H.  spinifera  capture  the  caridean 
Saron  marmoratus;  although  individuals  of  this 
shrimp  exceeding  a  length  of  30  mm  are  numerous 


Table  18.- 

-Food  of  Myripristis  arnaenus. 

No.  fish                   r^ean  percent 

with  this                             of 

Ranking 

Rank 

Items 

item  {n  =  14)                diet  volume 

index 

1 

Crab  megalops 

14                                 75.1 

75.10 

2 

Decapod  shrimps 

4                                  9.3 

2.66 

3 

Fish 

3                                  2.9 

0.62 

4 

Cephalopods 

1                                   1.4 

0.10 

5 

Mysids 

4                                     0.3 

0.09 

6 

Prosobranch  gastropods 

2                                     0.4 

0.06 

7 

Polychaetes 

1                                     0.4 

0.03 

8 

Gammarldean  amphipods 

1                                   0.2 

0.01 

9 

Calanoid  copepods 

1                                   0.1 

<0.01 

10 

Stomatopods 

1                                   0.1 

<0.01 

11 

Isopods 

1                                   0.1 

<C.01 

Also. 

crustacean  fragments 

8                                  9.7 

5.54 

941 


in  exposed  positions  on  the  reef  after  dark,  most 
are  too  large  to  serve  as  prey  for  all  but  the  biggest 
squirrelfishes. 


WATER-COLUMN  FEEDERS.— These  are  the 
species  of  Myripristis,  all  of  which  are  primarily 
planktivores.  This  habit  is  reflected  in  their 
sharply  upturned  mouths,  a  feature  well  known  as 
adaptive  to  feeding  on  plankton  (e.g.  Rosenblatt, 
1967).  Based  on  the  food-habit  data,  crab 
megalops  are  the  major  prey  of  all  three  species 
reported  here. 

Earlier  (Hobson,  1965,  1968a),  I  reported  that 
M.  leiognathus  in  the  Gulf  of  California  feeds  in 
the  water  column  after  dark  on  planktonic  crusta- 
ceans, including  crab  larvae.  Similarly,  Randall 
(1967)  reported  that  M.  jacobus  in  the  tropical 
Atlantic  feeds  at  night  primarily  on  planktonic 
organisms,  especially  crustacean  larvae,  and  Col- 
lette  and  Talbot  (1972)  noted  that  this  species 
feeds  at  least  3  m  above  the  reef.  Probably  similar 
habits  are  universal  in  species  of  Myripristis. 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

Order  Gasterosteiformes 
Family  Aulostomidae:  trumpetfishes 

Aulostonius  chinensis  (Linnaeus) — niinu 

This  distinctive,  solitary  fish  (Figure  15)  is 
numerous  on  Kona  reefs,  where  it  attains  the 
length  of  at  least  700  mm.  It  exhibits  three  basic 
color  forms:  plain  reddish  brown,  brown  with  light 
striping  and  other  marks,  and  plain  yellow.  Sev- 
eral trumpetfish  recognized  as  individuals  were 
seen  repeatedly  in  the  same  areas  throughout  the 
study,  and  none  changed  coloration  during  this 
time.  The  habitat  of  this  species  is  in  water  deeper 
than  about  5  m  close  to  coral  or  irregular  rocky 
substrata  that  offer  many  ledges  and  crevices. 

I  observed  no  difference  in  the  behavior  of  this 
fish  between  day  and  night.  At  all  hours  it  moves 
slowly,  close  to  cover,  propelling  its  long,  cylindri- 
cal, rod-straight  body  mainly  by  undulating  its 
soft  dorsal  and  anal  fins,  which  are  set  far  back 
near  the  tail.  The  trumpetfish  is  a  stalking  pred- 
ator, and  on  a  few  scattered  occasions  I  saw  it 


Figure  15. — Aulostomus  chinensis,  the  trumpetfish,  a  stalking  predator. 


942 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


capture  prey  during  daylight.  After  gaining  a  posi- 
tion close  to  its  quarry,  the  attack  is  consum- 
mated with  a  short  dart  forward,  the  victim  being 
literally  sucked  in  with  a  sudden  expansion  of  its 
tubular  snout.  Hiatt  and  Strasburg  (1960)  did  not 
observe  feeding,  but  speculated  that  this  species  in 
the  Marshall  Islands  probes  with  its  long  snout  in 
shallow  holes  and  interstices  of  the  reef  and  cap- 
tures prey  there  by  rapidly  dilating  its  mouth. 
They  found  a  small  atherinid  fish  in  the  gut  on  one 
specimen.  Sometimes  trumpetfish  accompany 
schools  of  grazing  surgeonfishes — usually  mixed 
groups  of  Acanthurus  sandvicensis  and  A.  ni- 
groris,  which  frequently  move  across  the  reef.  At 
these  times,  small  organisms  probably  are  driven 
out  from  algal  cover  by  the  grazing  herbivores  and 
become  available  as  prey  to  the  trumpetfish.  Occa- 
sionally, the  trumpetfish  swims  close  beside  large 
herbivores,  especially  parrotfishes,  apparently 
using  these  large  fishes  as  shields  behind  which  to 
get  close  to  prey  not  threatened  by  the  herbivore. 

Although  52  individuals  (410:  220-621  mm) 
were  speared  at  different  times  of  day  and  night, 
no  pattern  was  evident  in  the  condition  of  the  gut 
contents  from  specimens  taken  at  these  different 
times.  Of  27  that  contained  food  in  their  stomachs, 
18  had  captured  fishes  (mean  percent  of  diet  vol- 
ume: 63;  ranking  index:  42),  and  11  had  taken 
caridean  shrimps  (mean  percent  of  diet  volume: 
37;  ranking  index:  15.07). 

It  probably  is  significant  that,  with  only  two 
exceptions,  those  sampled  had  preyed  on  either 
fishes  or  shrimps — not  both.  The  data  cannot  re- 
late this  selectivity  to  day  or  night  activity  or  to 
size  of  predator.  The  16  individuals  that  had 
preyed  exclusively  on  fishes  were  within  exactly 
the  same  size  range  (241-528  mm)  as  the  9  indi- 
viduals that  had  preyed  exclusively  on  shrimps. 
Furthermore,  the  mean  sizes  of  the  two  groups 
differed  only  slightly — 401  mm  for  the  fish  eaters, 
396  mm  for  the  shrimp  eaters.  The  two  individuals 
that  had  taken  both  fishes  and  shrimps  were  241 
and  337  mm  long. 

Aulostomus  chinensis  takes  relatively  large 
prey:  the  15  fish  items  (representing  among  others 
Apogon  snyderi,  Acanthurus  nigrofuscus,  Can- 
thigaster  sp.,  and  a  labrid)  that  could  be  measured 
accurately  had  a  mean  standard  length  of  58  mm 
(range  25-88  mm)  whereas  the  11  shrimps  that 
could  be  measured  accurately  had  a  mean  total 
length  of  55  mm  (range  13-110  mm).  Ten  of  the  11 
shrimps  were  Saron  marmoratus,  the  only  shrimp 
this  large  that  was  numerous  in  exposed  locations 


on  the  reef.  Although  this  shrimp  occupies  ex- 
posed positions  only  at  night,  I  have  no  evidence 
that  it  is  taken  hy  Aulostomus  chinensis  in  greater 
numbers  after  dark. 

Because  the  trumpetfish  has  an  especially  long, 
attenuated  body,  and  because  it  takes  relatively 
large  prey,  individuals  that  have  recently  in- 
gested a  meal  often  can  be  recognized  by  their 
distended  bellies.  Such  individuals  were  occasion- 
ally seen  during  all  periods  of  day  and  night,  but 
most  often  during,  or  shortly  after,  twilight.  Con- 
sistent with  this,  all  three  specimens  that  con- 
tained fresh  prey  (little  or  no  damage  by  digestion) 
were  collected  during  late  twilight:  in  two  of  these 
instances  (one  in  the  morning,  one  in  the  evening) 
the  prey  were  fishes;  in  the  other  instance  (eve- 
ning), the  prey  was  a  shrimp,  S.  marmoratus. 
Beyond  this,  the  gut  contents  were  of  little  help  in 
establishing  a  pattern  to  feeding  times;  nor  did  the 
incidence  of  individuals  with  empty  stomachs  in- 
dicate a  pattern,  for  they  were  collected  during  all 
periods  of  day  and  night. 

CONCLUSION. — Aulostomus  chinensis  stalks 
prey,  mostly  fishes  and  caridean  shrimps,  most 
successfully  during  twilight,  but  also  during  the 
day  and  perhaps  also  at  night. 


General  Remarks  on  Trumpetfishes 

The  activity  of  Aulostomus  chinensis  in  Kona 
seems  to  be  typical  of  the  genus  in  other  seas. 
Randall  (1967)  reported  only  fishes  and  caridean 
shrimps  in  79  A.  maculatus  from  the  West  Indies, 
and  also  remarked  on  the  large  size  of  these  prey, 
as  well  as  the  way  this  trumpetfish  sucks  them 
into  its  mouth  by  expanding  its  tubular  snout. 
Randall  often  observed  A.  maculatus  hovering 
vertically  in  the  water  over  small  fishes  and  sev- 
eral times  darting  down  on  them  (I  did  not  see  A. 
chinensis  feed  this  way).  Collette  and  Talbot 
(1972)  judged  A.  maculatus  in  the  Virgin  Islands 
to  be  primarily  crepuscular.  They  were  uncertain 
about  its  nocturnal  activity,  but  judged  one  they 
saw  in  a  gorgonian  at  2330  h  to  be  quiescent. 
Eibl-Eibesfeldt  (1955)  described  the  way 
trumpetfish  in  the  Indian  Ocean  use  other  fishes 
as  cover  behind  which  to  approach  small  prey,  and 
this  was  also  reported  by  Collette  and  Talbot 
(1972)  from  the  Virgin  Islands. 


943 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Family  Fistulariidae:  cornetfishes 

Fistularia  petimha  Lacepede 

The  cornetfish  (see  Hobson,  1968a:  Figure  9) 
looks  much  like  the  trumpetfish,  but  grows  con- 
siderably larger,  many  being  over  1  m  long.  It  is  a 
pale-green  fish  with  light-blue  markings,  and 
under  certain  circumstances  instantaneously  dis- 
plays a  series  of  broad  bands  along  its  body.  Ear- 
lier I  (Hobson,  1968a)  reported  that  this  species  in 
the  Gulf  of  California  displays  these  bands  when 
poised  to  strike  prey.  In  Kona,  the  bands  appear  in 
similar  circumstances  and  also  in  situations  that 
suggest  the  fish  might  feel  threatened,  as  when 
it  is  approached  underwater  by  a  human — 
especially  a  human  carrying  a  diving  light  at 
night.  Fistularia  petimha  frequently  swims  in 
loosely  spaced  groups  of  several  individuals, 
generally  in  exposed  shallowwater  locations  over 
the  reef  top. 

Occasionally,  F.  petimha  was  seen  in  Kona 
stalking  its  prey  during  daylight,  as  observed  in 
the  Gulf  of  California  (Hobson,  1968a).  It  does  not 
move  suddenly  until  within  a  few  centimeters 
of  its  prey.  When  positioned  for  attack,  it  often 
draws  its  midsection  into  a  modified  "s"  (as 
viewed  from  above),  then  darts  forward  for  the 
capture.  Fistularia  petimha  is  more  agile  than 
A.  chinensis,  and  undulating  body  movements 
not  seen  in  the  latter  are  regularly  used  to  provide 
greater  thrust  in  attacks  and  accelerated  swim- 
ming. In  the  Gulf  of  California,  I  saw  F.  petimha 
use  other  fish  as  shields  behind  which  to  approach 
prey,  as  described  above  for  A.  chinensis,  but 
did  not  see  this  in  Kona.  The  behavior  of  F.  petima 
was  not  seen  to  differ  between  day  and  night. 

The  10  specimens  (673:  363-1,069  mm),  al- 
though collected  during  both  day  and  night,  were 
too  few  to  provide  much  evidence  on  feeding  times; 
however,  of  the  2  with  empty  guts,  1  was  collected 
during  late  afternoon,  and  the  other  just  before 
first  morning  light,  indicating  that  these  2  had  not 
fed  during  the  preceding  day  and  night,  respec- 
tively. Only  two  specimens  contained  fresh  prey, 
and  both  were  collected  shortly  after  twilight 
— one  after  evening  twilight,  the  other  after  morn- 
ing twilight.  Though  limited,  these  data  suggest 
crepuscular  feeding.  Although  prey  in  the  other 
six  specimens  were  in  stages  of  digestion  not  in- 
consistent with  predominantly  crepuscular  feed- 
ing, they  clearly  showed  that  prey  are  also  taken 
at  other  times.  All  eight  individuals  with  material 


in  their  stomachs  had  fed  on  fishes  exclusively; 
only  two  prey  could  be  identified  to  species,  one  a 
70-mm  cardinalfish,  Apogon  snyderi,  the  other  a 
52-mm  6.a.mse\fish.,Ahudefdufimparipennis.  Both 
of  these  prey  could  have  been  captured  close  to  reef 
crevices  during  the  day. 

Thus,  F.  petimha  in  Kona,  as  in  the  Gulf  of 
California  (Hobson,  1968a),  was  found  to  prey  only 
on  fishes.  Hiatt  and  Strasburg  ( 1960)  also  reported 
this  species  in  the  Marshall  Islands  to  be  exclu- 
sively piscivorous.  My  data  suggest  that  F. 
petimha  takes  somewhat  smaller  prey  than  does 
A.  chinensis  of  comparable  length,  as  might  be 
expected  in  view  of  the  deeper  body  and  snout  of 
the  latter.  The  mean  length  of  the  seven  F. 
petimha  containing  measurable  prey  was  593  mm 
(range:  363-795  mm).  The  11  measurable  prey  in 
these  individuals  had  a  mean  length  of  32  mm 
(range:  8-70).  Comparable  data  for  A.  chinensis 
are  given  above. 

CONCLUSION.— F/s^?//ar/a  petimha  stalks 
fishes  most  successfully  during  twilight,  but 
also  during  the  day  and  perhaps  at  night. 


General  Remarks  on  Cornetfishes 

The  exclusively  piscivorous  habits  of  Fistularia 
petimha  are  paralleled  by  the  similar  diet  of  F. 
tahacaria  in  the  tropical  Atlantic  (Randall,  1967). 
Suyehiro  (1942)  claimed  that/^.  petimha  feeds  on 
tiny  floating  organisms  by  using  its  snout  like  a 
pipette,  but  I  join  Hiatt  and  Strasburg  (1960)  and 
Randall  (1967)  in  contesting  this  opinion  of  the 
size  of  its  prey.  Starck  and  Davis  (1966)  found  F. 
tahacaria  to  be  more  numerous  on  Florida  reefs  at 
night  than  during  the  day,  but  did  not  speculate 
that  this  reflected  differences  in  feeding  behavior. 

Order  Scorpaeniformes 
Family  Scorpaenidae:  scorpionfishes 

Pterois  sphex  Jordan  and  Evermann  — 
lionfish,  nohu  pinao 

The  lionfish  is  a  sluggish,  solitary  species  that 
usually  rests  motionless  on  the  reef,  yet  draws 
attention  by  its  spectacular  appearance  (Figure 
16).  Perhaps  because  its  fin  spines  carry  a  potent 
toxin,  this  fish  makes  little  effort  to  evade  a 
human  collector.  It  is  not  numerous  in  Kona,  and 


944 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  16. — Pterois  sphex,  a  lionfish,  swimming  close  to  the  reef  at  night. 


occurs  in  visible  locations  on  the  reef  most  often 
after  dark — though  never  far  from  shelter. 

Fourteen  specimens  (83:  58-121  mm)  were 
speared  during  day  and  night.  Of  nine  that  were 
collected  during  the  afternoon  or  evening  twilight, 
the  guts  in  six  were  empty,  and  three  had  only 
well-digested  crustacean  fragments  in  their 
stomachs.  On  the  other  hand,  all  five  specimens 
collected  at  night  (more  than  2  h  after  sunset)  con- 
tained relatively  fresh  prey  in  their  stomachs. 

All  eight  specimens  that  contained  food  had  fed 
on  crustaceans  exclusively.  Caridean  shrimps, 
which  occurred  in  six,  were  the  major  food  item 
(mean  percent  of  diet  volume:  56.3;  ranking  index: 
42.19).  Other  food  items  were:  xanthid  crabs  in 
three  (mean  percent  of  diet  volume:  13.8;  ranking 
index:  5.16)  and  pagurid  crabs  in  one  (mean  per- 
cent of  diet  volume:  0.6;  ranking  index:  0.08).  Five 
individuals  contained  unidentified  crustacean 
fragments  (mean  percent  of  diet  volume:  29.4; 
ranking  index:  18.36). 

CONCLUSION.^J^^erois  sphex  is  a  nocturnal 
predator  that  takes  benthic  crustaceans,  espe- 
cially caridean  shrimps. 


Scorpaena  coniorta  (Jenkins) 

Although  this  small  species  is  the  most  numer- 
ous scorpaenid  on  Kona  reefs,  the  casual  observer 
will  encounter  it  only  at  night.  During  the  day 
individuals  more  than  about  50  mm  long  are  deep 
in  reef  crevices,  whereas  many  smaller  individu- 
als are  motionless  among  the  branches  of  the  coral 
Pocillopora  meandrina  (Figure  17).  After  night- 
fall, many  of  these  fish  occur  in  exposed  positions: 
the  larger  individuals  are  spread  widely  across 
the  reef,  resting  immobile  on  rock  or  coral, 
whereas  the  smaller  ones  are  perched  motionless 
on  the  sea  floor  close  by  the  same  coral  heads  that 
shelter  them  during  the  day.  However,  at  any 
given  time  of  night  some  of  these  fish  are  among 
the  coral  branches,  just  as  in  daylight. 

Thirty-four  specimens  (46:  36-67  mm)  were  col- 
lected during  various  times  of  day  and  night.  Of 
12  that  were  taken  during  afternoon  or  early  eve- 
ning, most  from  among  coral  branches,  only  1  had 
food  in  its  gut  (3  had  a  few  fragments  posteriorly  in 
their  intestine).  The  one  containing  food,  taken 
from  a  coral  head,  had  in  its  stomach  a  crab  that, 
based  on  damage  by  digestion,  probably  had  been 


945 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  17. — Scorpaena  coniorta,  a  scorpionfish,  nestled  among  coral  branches  during  the  day. 


captured  during  the  day.  In  comparison,  14  of  22 
individuals  collected  at  night,  between  3  h  after 
sunset  and  first  morning  light,  had  food  in  their 
stomachs.  Brachyuran  crabs,  almost  all  of  them 
xanthids,  occurred  in  7  of  the  15  individuals  that 
contained  identifiable  items  (mean  percent  of  diet 
volume:  39;  ranking  index:  18.2).  Caridean 
shrimps  occurred  in  six  (mean  percent  of  diet  vol- 
ume: 28.3;  ranking  index:  11.33),  and  fishes  in  one 
(mean  percent  of  diet  volume:  6.7;  ranking  index: 
0.45).  Unidentified  crustacean  fragments  oc- 
curred in  six  (mean  percent  of  diet  volume:  26; 
ranking  index:  10.4).  Many  of  the  xanthids  and 
carideans  found  in  specimens  less  than  50  mm 
long  are  forms  that  cooccur  with  these  fish  among 
the  coral  branches. 

CONCLUSION. — Scorpaena  coniorta  is  a  noc- 
turnal predator  that  takes  benthic  crustaceans, 
mostly  xanthid  crabs  and  caridean  shrimps.  Some 
prey  are  also  captured  during  the  day. 

Scorpaenopsis  cacopsis  Jenkins — nohu  'oniakaha 

This  species,  the  largest  Hawaiian  scorpaenid, 
grows  to  over  50  cm  long  (Gosline  and  Brock, 
1960)  I  observed  no  overt  difference  in  its  be- 
havior between  day  and  night  as  it  was  seen  rest- 


ing immobile  on  the  reef  at  all  hours,  often  fully 
exposed.  Despite  its  large  size  and  frequent  dis- 
dain for  cover,  this  fish  remains  virtually  unseen, 
owing  to  body  hues  and  texture  that  render  it 
much  like  the  reef  on  which  it  rests.  It  was  not  seen 
feeding,  but  its  morphology  and  behavior  suggest 
that  it  lunges  forward  to  attack  prey  that  have 
strayed  within  range,  and  sucks  them  in  with  a 
sudden  expansion  of  its  cavernous  mouth. 

Of  the  five  specimens  (256:  73-375  mm)  ex- 
amined, three  had  prey  in  their  stomachs:  one, 
taken  within  1  h  after  sunrise,  contained  a  fresh 
fish,  Pomacentrus  jenkinsi  (104  mm);  a  second 
taken  at  night,  4  h  after  sunset,  contained  a  rel- 
atively fresh  octopus;  and  the  third,  taken  late  in 
the  afternoon,  contained  fish  fragments.  The 
other  two,  both  empty,  were  collected  during 
morning  twilight. 

CONCLUSION. — Scorpaenopsis  cacopsis 
attacks  fishes  and  motile  invertebrates  during  the 
day.  Its  nocturnal  activity  remains  uncertain. 

General  Remarks  on  Scorpionfishes 

Scorpionfishes  on  tropical  reefs  are  widely  de- 
scribed as  predators  that  rest  on  the  bottom,  and 


946 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


because  they  resemble  their  surroundings  they 
remain  unseen  by  small  prey  that  swim  within 
striking  range  (Longley  and  Hildebrand,  1941; 
Hiatt  and  Strasburg,  1960;  Starck  and  Davis, 
1966;  Randall,  1967).  This  behavior  is  descriptive 
of  some  scorpaenids,  but  probably  is  overdrawn  as 
a  generalization  encompassing  the  entire  family. 
Such  a  tactic  is  adaptive  to  daylight,  and  is  used  by 
Scorpaenopsis  cacopsis  in  Hawaii  (the  one  fish 
identified  as  prey  of  this  predator,  a  damselfish,  is 
strictly  a  diurnal  species  that  is  not  active  over  the 
reef  at  night).  Significantly,  the  fishes  that  have 
been  reported  by  other  investigators  as  prey  of 
scorpaenids  on  tropical  reefs  similarly  imply 
diurnal  predations:  blennies  (Longley  and  Hilde- 
brand, 1941);  a  wrasse  and  a  parrotfish  (Hiatt  and 
Strasburg,  1960);  and  an  angelfish,  a  surgeonfish, 
a  sardine,  a  sea  horse,  and  a  conger  eel  (Randall, 
1967).  With  perhaps  the  lone  exception  of  the  con- 
ger eel,  these  are  fishes  that  swim  close  to  the  reef 
during  daylight,  and  at  that  time  would  be  vul- 
nerable to  the  ambushing  tactic  of  scorpaenids; 
however,  they  would  not  be  readily  available  after 
dark  when  most  of  them  rest  under  cover  on  the 
reef  or,  in  the  case  of  the  sardine,  swim  away  from 
the  reef.  Conspicuously  absent  among  the  re- 
ported prey  are  the  many  species  of  comparable 
size  that  are  numerous  close  above  the  reef  at 
night,  including  apogonids  and  holocentrids.  One 
can  readily  see  how  camouflage  and  ambush 
would  be  especially  suited  to  daylight,  but  less 
significant  after  dark.  Randall  (1967),  basing  his 
generalization  on  the  West  Indian  situation, 
characterized  the  scorpaenids  as  diurnal.  In 
Hawaii,  most  species  are  predominantly  noctur- 
nal. In  addition  to  Pterois  sphex  and  Scorpaena 
coniorta,  which  prey  largely  on  benthic  crusta- 
ceans, as  described  above,  other  members  of  the 
family  that  appear  on  the  reef  in  greater  numbers 
at  night  include  Dendrochirus  brachypterus, 
Scorpaenodes  parvipinnis,  and  Scorpaena  bal- 
lieui.  Among  feeding  scorpaenids,  camouflage 
does  not  seem  to  play  the  important  role  at  night 
that  it  does  during  the  day.  When  these  predators 
are  abroad  after  dark  they  often  contrast  mark- 
edly with  their  surroundings.  Although  fishes  do 
not  seem  to  be  significant  prey  at  night,  the  be- 
havior of  these  nocturnal  scorpaenids  indicates 
that  their  tactic  remains  a  short  lunge  from  a 
resting  position  to  capture  prey  that  have  inadver- 
tently come  within  range. 


Order  Perciformes 

Family  Serranidae:  sea  basses 

Sea  basses  are  prominent  on  most  tropical  reefs, 
but  the  family  has  no  representatives  native  to 
shallow  Hawaiian  reefs  (Gosline  and  Brock, 
1960).  Nevertheless,  the  widespread  Indo-Pacific 
serranid  Cephalopholis  argus  has  been  intro- 
duced into  Hawaii  from  the  Society  Islands,  the 
first  time  in  1956,  and  has  since  become  well  es- 
tablished in  Kona. 

Cephalopholis  argus  Bloch  and  Schneider 

This  solitary  fish,  numerous  on  Kona  reefs, 
swims  close  among  overhanging  ledges  and  crev- 
ices during  the  day,  but  is  seen  less  often  at  night. 
Because  it  generally  is  wary  of  humans,  lack  of 
nocturnal  observations  could  mean  that  it  avoided 
our  diving  lights  at  night. 

Although  6  of  10  specimens  (319:  232-520  mm) 
speared  at  various  times  of  day  were  empty,  no 
temporal  pattern  is  recognized,  as  the  6  were 
taken  from  early  morning  to  late  afternoon.  All 
four  that  contained  food,  also  taken  at  various 
times  during  the  day  (on  four  different  occasions 
over  3  mo),  had  fed  exclusively  on  fishes.  One, 
taken  during  midmorning,  contained,  because  of 
digestion,  what  was  recognizable  only  as  a  fish 
(125  mm).  The  other  three — one  collected  during 
midday,  and  two  late  in  the  afternoon — each  con- 
tained a  single  moderately  digested  squirrelfish, 
Holocentrus  xantherythrus  (80,  110,  and  130  mm, 
respectively).  Holocentrus  xantherythrus 
congregates  under  ledges  during  the  day  in  areas 
where  C.  argus  is  active  (see  the  species  account 
for  H.  xantherythrus  above),  and  thus  is  available 
as  prey  for  the  sea  bass  at  this  time.  Cephalopholis 
argus  has  been  reported  to  feed  on  shrimps  as  well 
as  fishes  in  the  Marshall  Islands  (Hiatt  and  Stras- 
burg, 1960)  and  on  shrimps  in  the  Gilbert  Islands 
(Randall,  1955).  In  a  sample  of  98  specimens  from 
Tahiti,  Randall  and  Brock  (1960)  found  that  77.5% 
contained  fishes,  whereas  22.5%  contained  crusta- 
ceans (shrimps  and  crabs). 

CONCLUSION. — Cephalopholis  argus  preys 
on  fishes  among  reef  crevices  during  the  day.  Its 
nocturnal  habits  remain  uncertain. 

General  Remarks  on  Sea  Basses 

Diurnal  piscivorous  habits  were  reported  in 
Mycteroperca  rosacea  in  the  Gulf  of  California, 


947 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


with  peaks  during  twilight  (Hobson,  1965, 1968a). 
On  the  other  hand,  nocturnal  habits  were  noted  in 
Alphestes  multiguttatus  and  Rypticus  bicolor  (the 
latter  is  often  placed  in  a  separate  family,  the 
Grammistidae),  both  of  which  prey  chiefly  on 
benthic  crustaceans  (Hobson,  1965,  1968a).  In  the 
same  reports,  a  fourth  sea  bass,  Epinephelus  lab- 
riformis,  was  reported  to  feed  by  both  day  and 
night,  chiefly  on  fishes  in  daylight  and  on  benthic 
crustaceans  after  dark.  These  data  suggest  that 
fishes  may  be  the  major  prey  of  sea  basses  in  day- 
light with  crustaceans  predominating  after  dark, 
a  generalization  consistent  with  the  limited  ob- 
servations on  Cephalopholis  argus  in  Kona. 

Starck  and  Davis  (1966)  noted  that  serranids  of 
the  genera  Epinephelus,  Mycteroperca,  and 
Petrometopon  behave  similarly  day  and  night  in 
the  Florida  Keys,  with  probable  feeding  peaks 
around  sunrise  and  sunset.  Longley  and  Hilde- 
brand  (1941)  reported  that  Epinephelus  morio 
feeds  during  both  day  and  night  in  the  Dry  Tor- 
tugas,  Fla.,  and  Randall  (1967)  noted  that  larger 
serranids  in  the  West  Indies  feed  both  day  and 
night,  with  greatest  activity  at  dawn  and  dusk. 
Collette  and  Talbot  (1972),  on  the  other  hand, 
reported  E.  guttatus  in  the  Virgin  Islands  to  be 
active  by  day  and  apparently  asleep  at  night.  They 
also  found  E.  fulvus  and  E.  cruentatus  active  in 
daylight  and  suspected  that  these  sea  basses  rest 
at  night.  Randall  (1967)  considered  the  smaller 
serranids,  in  general,  to  be  primarily  diurnal. 
In  Florida,  Starck  and  Davis  (1966)  regarded 
certain  small  serranids  of  such  genera  as  Diplec- 
trum,  Hypoplectrus,  and  Serranus  to  be  active  by 
day  and  inactive  by  night.  None  of  these  authors 
attempted  to  relate  time  of  activity  with  kinds 
of  prey. 

Family  Kuhliidae:  aholeholes 

Kuhlia  sandvicensis  (Steindachner) — aholehole 

This  predator  occurs  in  only  a  few  locations 
within  the  Kona  study  area,  and  there  just 
sparsely,  compared  to  its  large  numbers  elsewhere 
in  Hawaiian  nearshore  waters.  Juveniles  and 
young  adults  live  in  tide  pools  or  in  schools  close  to 
shore  (Gosline  and  Brock,  1960),  but  the  larger 
adults  congregate  during  the  day  under  low  ledges 
and  boulders,  usually  in  water  less  than  5  m  deep 
farther  from  shore.  They  emerge  from  shelter  at 
nightfall,  and  the  few  observed  after  dark  during 
this  study  were  solitary  in  the  water  column  over 


the  reef.  Gosline  and  Brock  (1960)  noted  that  the 
adults,  at  least,  are  nocturnal,  a  conclusion  consis- 
tent with  the  large  eyes  of  the  species. 

Of  the  13  specimens  (164:  132-202  mm)  col- 
lected, 8  speared  during  midmorning  from  under 
rocky  cover  contained  in  their  stomachs  exten- 
sively digested  crustacean  fragments  (including 
crab  megalops),  1  taken  under  a  rock  at  noon  con- 
tained only  well-digested  material  scattered 
through  its  intestine,  and  4  speared  under  rocks 
late  in  the  afternoon  were  empty. 

CONCLUSION. — Kuhlia  sandvicensis  is  a 
nocturnal  predator  that  feeds  on  free-swimming 
crustaceans. 

Family  Priacanthidae:  bigeyes 

Priacanthus  cruentatus  (Lacepede) — bigeye, 
aweoweo 

This  priacanthid  (Figure  18)  is  numerous  in 
Kona,  where  it  takes  shelter  under  rocks  or  coral 
during  the  day,  often  in  groups,  and  is  active  in  the 
open  at  night.  After  emerging  from  shelter  at 
nightfall,  many  individuals  assemble  in  schools 
high  in  the  water  column  and  then  migrate 
offshore.  These  do  not  return  inshore  until  about 
40  min  before  sunrise,  but  a  lesser  number  of  other 
individuals,  mostly  solitary  or  in  small  groups, 
remain  over  the  inshore  reefs  throughout  the 
night.  All  of  these  fish  return  to  their  daytime 
shelter  by  30  min  before  sunrise,  at  least  many  of 
them  to  specific  home  caves  (Hobson,  1972). 

Forty  specimens  (173:  115-255  mm)  were  col- 
lected during  day  and  night.  All  17  that  were 
speared  during  morning  twilight  (shortly  after 
they  had  reappeared  near  their  diurnal  shelter, 
but  before  they  had  taken  cover)  had  relatively 
fresh  prey  in  their  stomachs.  Four  others  were 
collected  from  under  cover  during  late  morning, 
and  although  all  had  full  stomachs,  with  many 
items  identifiable,  digestion  was  advanced,  and 
most  of  the  material  was  damaged  beyond  recog- 
nition. The  other  19  were  collected  from  caves  late 
in  the  afternoon,  and  although  only  4  of  these  had 
empty  stomachs,  the  material  in  the  other  15  was 
reduced  to  unidentified  fragments.  Items  in  the  21 
specimens  containing  identifiable  material  are 
listed  in  Table  19. 

Hiatt  and  Strasburg  (1960)  acknowledged  that 
species  of  Priacanthus  generally  are  thought  to  be 
nocturnal,  but  contested  this  opinion  as  far  as  P. 


948 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  18. — Priacanthus  cruentatus,  a  bigeye,  showing  the  plain  red  coloration  typical  of  this  species  when  among  the 

coral  during  the  day. 


cruentatus  in  the  Marshall  Islands  is  concerned. 
Although  conceding  the  possibility  of  some  noc- 
turnal feeding,  they  believed  that  this  species  cap- 
tures octopods,  a  major  food  there,  in  reef  crevices 
and  caves  during  the  day.  This  conclusion  was 
heavily  influenced  by  finding  food  in  the  stomachs 
of  this  priacanthid  during  the  day,  but  none  in 
stomachs  of  the  nocturnally  active  holocentrids. 
As  noted  above,  I  found  a  similar  difference  be- 
tween P.  cruentatus  and  holocentrids  in  Kona,  but 
attribute  this  to  the  priacanthid  retaining  food  in 
its  stomach  longer  during  digestion  than  do 
holocentrids. 


Longley  and  Hildebrand  (1941)  noted  that  this 
circumtropical  species  feeds  chiefly  at  night  in 
Florida,  a  conclusion  with  which  Starck  and  Davis 

(1966)  concurred.  In  the  West  Indies,  Randall 

(1967)  was  of  the  same  opinion,  but  he  also  felt 
that  the  condition  of  prey  in  some  specimens  indi- 
cated diurnal  feeding  as  well;  Randall  noted  that 
P.  cruentatus  preys  mostly  on  the  larger  animals 
in  the  plankton.  Collette  and  Talbot  (1972)  con- 
cluded that  in  the  Virgin  Islands  this  is  a  crepus- 
cular species  that  continues  to  feed  in  caves  and 
under  ledges  during  daytime. 

Gosline  (1965)  reported  that  P.  cruentatus  in 


Table  19. — Food  of  Priacanthus  cruentatus. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  21) 

diet  volume 

index 

1 

Crab  megalops 

17 

32.3 

26  15 

2 

Cephalopods 

8 

20.4 

7.77 

3 

Fish 

6 

11.2 

3.20 

4 

Decapod  shrimps 

5 

3.6 

0.86 

5 

Adult  crabs 

2 

7.6 

0.72 

6 

Mysids 

1 

0.4 

0.02 

7 

Stomatopods 

1 

0.1 

0.01 

Also, 

crustacean  fragments 

11 

13.4 

7.02 

Unidentified  fragments 

8 

11.0 

4.19 

949 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Hawaii  migrates  offshore  at  night.  In  Florida, 
however,  Starck  and  Davis  (1966)  noted  only  that 
it  is  active  at  night  in  the  same  areas  where  it  is 
sheltered  in  daylight;  they  illustrated  this  species 
with  a  mottled  color  pattern,  which  they  believed 
to  be  its  nocturnal  coloration.  The  same  mottled 
pattern  occurs  regularly  at  night  in  Kona  when 
the  fish  is  held  in  the  beam  of  a  diving  light,  and  I 
believe  it  is  a  response  to  the  light,  rather  than  a 
nocturnal  coloration — especially  because  the  pat- 
tern is  intensified  upon  moving  the  light  progres- 
sively closer  to  the  fish.  In  the  absence  of  a  diving 
light  at  night,  this  species  is  either  plain  red  (as  it 
usually  is  in  daylight),  or,  more  often  with  indi- 
viduals in  mid-water,  overall  pale-silver  (occa- 
sionally this  pale-silver  coloration  is  displayed 
under  cover  during  the  day).  The  blotched  pattern 
is  the  red  and  silver  hues  in  combination. 


CONCLUSION. — Priacanthus  cruentatus  is  a 
nocturnal  predator  that  feeds  on  free-swimming 
organisms,  mostly  crustaceans  and  cephalopods. 


Family  Apogonidae:     cardinalfishes 

Apogon  erythrinus  Snyder 

After  dark,  this  small  solitary  cardinalfish  is 
numerous  close  to  basalt  reefs  in  water  less  than  6 
m  deep,  usually  in  small  sand  and  cobble  pockets. 
The  smaller  ones  are  largely  transparent,  and 
transparency  remains  a  characteristic  of  even  the 
largest  individuals,  despite  an  increased  pinkish 
hue  (Figure  19).  During  the  day  A.  erythrinus 
remains  out  of  sight,  secreted  deep  in  reef  crevices. 

Of  14  individuals  (36:  22-42  mm)  examined,  4 
that  had  been  collected  together  from  a  deep  crev- 
ice 4  h  after  sunrise  were  empty  (rotenone  was 
used  to  collect  these  4,  a  departure  from  the  stan- 
dard collecting  method  necessary  here  because  the 
species  was  never  visible  during  the  day).  The 
other  10  specimens  were  speared  from  among 
those  active  in  exposed  locations  on  the  reef  at 
night  (more  than  4  h  after  sunset),  and  although  2 
were  empty,  the  other  8  contained  prey  in  their 
stomachs. 

All  eight  with  material  in  their  stomachs  con- 
tained crustaceans  exclusively.  Xanthid  crabs 


Figure  l9.~Apogon  erythrinus,  a  cardinalfish,  showing  the  transparency  t5T)ical  of  this  species  as  it  swims  close  to 

the  reef  at  night. 


950 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


were  the  major  item,  occurring  in  five  individuals 
(mean  percent  of  diet  volume:  50;  ranking  index: 
31.25).  Most  of  these  xanthids  were  in  the 
megalops  stage,  except  that  their  abdomens  were 
reflected  under  their  carapaces.  The  only  other 
identifiable  prey,  occurring  in  three  specimens, 
were  gammaridean  amphipods  (mean  percent  of 
diet  volume:  20;  ranking  index:  7.5).  Four  con- 
tained unidentified  crustacean  fragments  (mean 
percent  of  diet  volume:    30;  ranking  index:    15). 

CONCLUSION. — Apogon  erythrinus  is  a  noc- 
turnal predator  that  takes  mostly  benthic  crusta- 
ceans. 

Apogon  menesemus  Jenkins — \ipapalu 

This  species  and  the  very  similar  A.  snyderi 
(below)  are  the  largest  and  most  abundant 
apogonids  in  Hawaii  (Gosline  and  Brock,  1960), 
and  they  were  the  apogonids  seen  most  often  dur- 
ing the  present  study.  During  the  day,  A. 
menesemus  hovers  quietly  in  the  deep  shadows  of 
reef  crevices,  but  during  late  evening  twilight 
emerges  into  the  open.  Throughout  the  night  sol- 
itary individuals  hover  about  1  m  above  the  coral. 
On  several  occasions  after  dark  this  cardinalfish 
struck  at  the  silver  barb  on  my  otherwise  dark 
spear:  sometimes  when  this  happened  the  spear 
was  faintly  illuminated  by  my  partner's  diving 
light,  but  other  times  moonlight  provided  the  only 
illumination.  At  first  morning  light  A. 
menesemus  moves  close  to  cover  on  the  reef,  and 
during  morning  twilight  returns  to  its  daytime 
shelter.  When  under  cover  during  the  day  its  col- 
oration is  relatively  featureless,  but  when  in  the 
open  at  night  distinctive  fin  markings  appear 
(Figure  20a  and  b). 

Fifty-nine  specimens  (114:  90-134  mm)  were 
collected  during  day  and  night.  Of  the  14  that  were 
speared  from  reef  caves  during  late  afternoon, 
only  2  had  food  in  their  stomachs — one  contained 
an  extensively  digested  piece  of  meat  that  proba- 
bly was  the  remains  of  prey  captured  the  previous 
night,  whereas  the  other  contained  a  relatively 
fresh  xanthid  crab  that  appeared  to  have  been 
captured  earlier  that  day.  In  comparison,  25  of  40 
specimens  collected  at  night,  between  3  h  after 
sunset  and  first  morning  light,  had  food  in  their 
stomachs — much  of  it  fresh.  Finally,  of  five  speci- 
mens collected  from  caves  during  early  morning, 
within  3  h  after  sunrise,  four  had  food  in  their 
stomachs.  Items  in  the  31  individuals  containing 
identifiable  material  are  listed  in  Table  20. 


Two  individuals  that  each  contained  just  a 
single  xanthid  crab  are  the  only  ones  that  indi- 
cated exclusively  benthic  feeding;  significantly, 
one  of  these  was  the  lone  individual,  noted  above, 
that  appeared  to  have  fed  while  under  cover  dur- 
ing the  day.  The  other,  collected  in  the  open  just  3 
h  after  sunset,  may  also  have  taken  its  prey  before 
leaving  shelter  in  the  evening.  A.  menesemus 
takes  mostly  free-swimming  prey,  presumably  at 
its  regular  nocturnal  station  above  the  reef. 
Nevertheless,  judging  from  the  sand  mixed  with 
food  in  one  individual  collected  at  midnight,  some 
prey  are  taken  from  the  sea  floor  after  dark. 

CONCLUSION. — Apogon  menesemus  is  a  noc- 
turnal predator  that  feeds  mostly  on  free- 
swimming  crustaceans. 

Apogon  snyrferi  Jordan  and  Evermann — upapalu 

This  cardinalfish  cooccurs  with  the  very  similar 
A.  menesemus,  above,  but  the  two  species  remain 
at  least  partially  segregated.  During  the  day  both 
species  occupy  the  same  caves,  but  A.  snyderi  is 
not  so  deep  in  the  shadows  and,  in  fact,  frequently 
hovers  at  the  entrances.  Like  A.  menesemus,  A. 
snyderi  emerges  into  the  open  during  evening 
twilight,  but  during  the  night  stays  closer  to  the 
sea  floor;  furthermore,  whereas  A.  menesemus 
mostly  remains  over  coral,  A.  snyderi  tends  to 
move  over  the  sand  patches  within  the  reef  and  in 
the  fringes  of  the  more  extensive  sand  areas  adja- 
cent to  the  reef.  On  several  occasions  at  night,  A. 
snyderi  struck  at  the  silver  barb  on  my  spear,  just 
as  described  above  for  A.  menesemus.  Apogon 
snyderi  does  not  have  prominent  nocturnal  color 
features,  as  does  A.  menesemus.  When  over  sand 
at  night  its  body  has  a  highly  reflective  bluish 
cast,  also  shown  to  a  lesser  extent  by  A. 
menesemus,  but  which  is  largely  lost  by  both 
species  soon  after  they  move  over  coral  or  rocks. 

Thirty  specimens  (96:  82-130  mm)  were 
speared  during  day  and  night.  All  3  that  were 
taken  from  caves  during  the  afternoon  had  empty 
stomachs,  whereas  of  24  collected  in  the  open  at 
night,  between  2  h  after  sunset  and  first  morning 
light,  22  had  food  in  their  stomachs.  The  remain- 
ing three  were  collected  from  caves  during  the  4  h 
after  sunrise,  and  while  two  of  these  had  food  in 
their  stomachs,  the  third  was  empty.  Items  in  the 
24  individuals  containing  identifiable  material 
are  listed  in  Table  21. 


951 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


a 

.a^^  \* 

T^     ' :  % 

!t^l 

'J^^^^^^^^^^^^^^^Ik^ 

Figure  20. — Apogon  menesemus,  a  cardinalfish:  a,  showing  its  diurnal  coloration  under  a  ledge  during  the  day;  b, 
showing  its  nocturnal  coloration  as  it  swims  above  the  reef  at  night. 


952 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  20. — Food  of  Apogon  menesemus. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =31) 

diet  volume 

index 

1 

Crab  megalops 

10 

17.6 

5.68 

2 

Decapod  shrimps 

11 

15.7 

5.57 

3 

Xanthid  crabs 

2 

6.9 

0.45 

4 

Mysids 

3 

2.9 

0.28 

5 

Fish 

1 

2.0 

0.07 

6 

Gammaridean  amphipods 

1 

0.8 

0.03 

7 

Isopods 

1 

0.2 

<0.01 

8 

Copepods 

2 

0.1 

<0.01 

9 

Gastropod  larvae, 

echinospira 

1 

0.1 

<0.01 

Also, 

crustacean  fragments 

20 

40.0 

25.81 

Unidentified  fragments 

6 

13.7 

2.65 

Table  21. 

— Food  of  Apogon  snyderi 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  [n  =  24) 

diet  volume 

Index 

1 

Decapod  shrimps 

12 

34.3 

17.15 

2 

Xanthid  crabs 

6 

14.6 

3.65 

3 

Crab  megalops 

4 

7.5 

1.25 

4 

Fish 

2 

5.6 

0.47 

5 

Mysids 

2 

2.1 

0.18 

6 

Hippid  crabs 

4.2 

0.18 

7 

Polychaetes 

2.9 

0.12 

8 

Copepods 

1.3 

0.05 

9 

Gammaridean  amphipods 

1.3 

0.05 

10 

Sipunculid  introverts 

0.2 

<0.01 

Also, 

crustacean  fragments 

12 

25.4 

12.70 

Unidentified  fragments 

1 

0.6 

0.03 

The  diet  of  A.  snyderi,  compared  with  that  of  A. 
menesemus,  includes  a  greater  proportion  of 
benthic  organisms,  especially  forms  from  sandy 
bottom,  like  hippid  crabs.  Nevertheless,  many  of 
the  prey  of  A.  snyderi  are  free-swimming  forms 
that  may  or  may  not  have  been  in  the  water  col- 
umn when  captured.  The  major  item,  decapod 
shrimps,  were  mostly  in  their  planktonic  larval 
stage. 

CONCLUSION. — Apogon  snyderi  is  a  noctur- 
nal predator  that  feeds  on  both  free-swimming 
and  benthic  forms,  mostly  crustaceans. 


General  Remarks  on  Cardinalfishes 

Cardinalfishes  are  widely  recognized  as  being 
nocturnal.  For  example,  Starck  and  Davis  (1966) 
reported  that  all  of  the  apogonids  they  studied  in 
Florida  Keys  are  nocturnal,  and  Randall  (1967) 
came  to  the  same  conclusion  for  species  in  the 
West  Indies;  Randall  provided  food-habit  data  on 
two  forms,  Apogon  conklini  and  A.  maculatus, 
both  of  which  prey  primarily  on  plankton. 


In  the  Gulf  of  California,  A.  retrosella,  a  rela- 
tively small  nocturnal  species  (mostly  <100  mm 
long),  aggregates  above  the  reef  at  night,  preys  on 
plankton,  and  its  aggregations  are  more  compact 
under  moonlight  than  on  dark  nights  (Hobson, 
1965,  1968a).  Although  the  relatively  large  A. 
menesemus  is  solitary  when  feeding  on  free- 
swimming  prey  above  Kona  reefs,  it  remains 
within  about  1  m  of  the  reef,  never  far  from  cover. 

Another  apogonid  occasionally  seen  in  Kona,  A. 
maculiferus,  has  behavior  more  like  that  of  A. 
retrosella  in  the  Gulf  of  California.  Apogon 
maculiferus  is  abundant  on  some  Hawaiian  reefs 
and  attains  a  length  of  about  150  mm  (Gosline  and 
Brock,  1960).  It  was  not  abundant  during  this 
study,  however,  and  all  those  seen  apparently 
were  juveniles  that  ranged  between  about  20  and 
60  mm  long.  On  nights  of  bright  moonlight  these 
small  individuals  were  in  aggregations  2  to  3  m 
above  the  reef;  however,  on  dark  nights  they 
ranged  even  higher  in  the  water  column,  their 
aggregations  were  more  loosely  formed,  and  many 
of  them  were  solitary.  Significantly,  limited  ob- 
servations indicate  that  juveniles  of  both  A. 
menesemus  and  A.  snyderi  ( <  50  mm  long)  behave 


953 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


more  like  these  small  individuals  of  A. 
macuUferus  than  they  do  like  the  adults  of  their 
own  species,  so  this  behavior  may  be  characteris- 
tic only  of  the  smaller  representatives  of  all  three 
species. 

Finally,  a  fourth  apogonid,  Pseudamiops 
gracilicauda,  is  relatively  numerous  in  Kona,  but 
does  not  seem  to  grow  longer  than  about  30  mm. 
Being  such  a  small  species,  P.  gracilicauda 
generally  went  unnoticed  by  me  and,  in  fact,  was 
seen  only  on  dark  nights  when  solitary  individu- 
als hovered  1  to  2  m  above  the  reef. 

Suyehiro  (1942),  Hiatt  and  Strasburg  (1960), 
and  Hobson  (1965),  all  reported  that  certain 
apogonids  cease  to  feed  sometime  during  repro- 
ductive activity.  Perhaps  this  phenomenon  ac- 
counts for  the  relatively  high  incidence  of  empty 
stomachs  at  night  in  A.  menesemus  from  Kona  (15 
of  40),  especially  considering  that  species  of  other 
nocturnal  groups  with  similar  diets,  like  the  vari- 
ous holocentrids  (see  above),  are  almost  always 
full  of  food  at  night. 

E.  H.  Chave,  University  of  Hawaii,  is  currently 
working  on  the  ecology  of  Hawaiian  apogonids. 


Family  Carangidae:  jacks 

The  jacks  are  prominent  fishes  on  Hawaiian 
reefs,  but  although  many  species  were  seen  occa- 
sionally during  this  study,  only  one,  presented 
below,  was  observed  regularly. 

Caranx  melampygits  Cuvier — blue  ulua,  omihi 

This  jack  (Figure  21),  attains  a  length  of  about  1 
m  in  Hawaii  (Gosline  and  Brock,  1960),  but  most 
of  those  present  in  Kona  during  this  study  were 
less  than  half  this  size.  During  the  day  it  usually  is 
solitary,  or  in  groups  of  several  individuals.  Typi- 
cally, it  swims  actively  about  1  m  above  the  reef  in 
a  manner  that  suggests  it  is  patrolling  over  a 
relatively  large  area.  Frequently  several  of  these 
jacks  accompany  the  large  piscivorous  goatfish, 
Parupeneus  chryserydros  (see  account  for  this 
species,  below),  probably  to  capture  prey  that  are 
driven  out  of  hiding  as  the  goatfish  probes  the 
substratum.  This  jack  swims  over  the  reef 
throughout  the  day,  but  occurs  there  most  fre- 
quently during  early  morning  and  late  afternoon 


Figure  21. — Caranx  melampygus,  a  jack,  swimming  close  above  the  reef  during  the  day. 


954 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


or  evening.  It  was  only  occasionally  seen  at  night, 
perhaps  because  it  avoided  our  diving  lights  after 
dark. 

Six  specimens  (337:  245-570  mm)  were  collected 
at  various  times  of  the  day.  The  only  one  (248  mm) 
that  contained  relatively  fresh  prey  (three  larval 
fishes,  about  10  mm  long,  and  a  number  of  mysids) 
was  collected  3  h  after  sunrise.  A  second  indi- 
vidual (315  mm),  taken  shortly  after  noon,  con- 
tained in  its  stomach,  an  unidentified  fish  (about 
80  mm)  and  a  shrimp,  both  moderately  digested. 
Three  other  individuals  (245-330  mm)  were  col- 
lected late  in  the  afternoon,  and  their  stomachs 
contained  well-digested  fragments — in  at  least 
one,  the  fragments  of  a  fish.  The  last  specimen 
(570  mm)  behaved  as  if  sick  when  speared  early  in 
the  afternoon,  and  its  gut  was  empty.  Hiatt  and 
Strasburg  (1960)  found  only  fishes  in  the  two 
specimens  of  this  species  that  they  examined  from 
the  Marshall  Islands,  as  did  Randall  ( 1955)  in  the 
four  specimens  that  he  examined  from  the  Gilbert 
Islands. 

CONCLUSION. — Caranx  melampygus  preys 
on  free-swimmirig  fishes  and  crustaceans, 
probably  most  often  early  and  late  in  the  day. 

General  Remarks  on  Jacks 

Jacks  are  major  predators  on  many  widespread 
tropical  reefs  (e.g.  Marshall  Islands:  Hiatt  and 
Strasburg,  1960;  Gulf  of  Cahfornia:  Hobson,  1965, 
1968a;  Florida  Keys:  Starck  and  Davis,  1966; 
West  Indies:  Randall,  1967).  The  larger  piscivor- 
ous jacks,  like  Caranx  hippos  caninus,  are  primar- 
ily crepuscular  in  the  Gulf  of  California  (Hobson, 
1965,  1968a)  and  in  the  Florida  Keys  (Starck  and 
Davis,  1966). 

Family  Lutjanidae:     snappers 

As  is  true  of  the  sea  basses,  Hawaiian  inshore 
reefs  lack  native  species  of  snappers,  a  family 
whose  members  are  prominent  on  shallowwater 
reefs  elsewhere  in  the  tropical  Pacific  (Gosline  and 
Brock,  1960;  Randall  and  Brock,  1960).  Only  one 
species  of  this  family  was  seen  regularly  on  the 
Kona  study  reefs  during  this  project. 

Aphareiis  fiircatus  (Lacepede) — giirutsu 

During  the  day  this  solitary  predator  swims 
slowly,  1  to  2  m  above  the  reef,  with  never  more 


than  a  few  individuals  in  any  one  place.  It  was  not 
seen  at  night  during  this  study,  perhaps  because  it 
avoided  our  lights.  Only  once  did  I  see  one  attack 
prey:  5  min  before  sunrise  this  individual  sud- 
denly broke  from  its  patrolling  attitude  2  m  above 
the  reef  and  dived  among  a  cluster  of  small  fishes, 
mostly  pomacentrids,  that  were  in  the  process  of 
emerging  from  their  nocturnal  shelters  (see  Hob- 
son, 1972).  The  success  of  the  strike  was  undeter- 
mined, but  at  the  instant  of  attack  all  small  fishes 
within  a  radius  of  about  15  m  shot  under  cover. 
Three  specimens  (253:  244-262  mm)  were 
speared  for  study.  One  taken  during  midafternoon 
contained  a  Plagiotremus  goslinei,  a  blenny  that 
swims  above  the  reef  only  in  daylight  (see  account 
for  this  species,  below);  because  this  prey  was  rela- 
tively fresh,  it  almost  certainly  was  captured  ear- 
lier that  day.  Another  A .  furcatus  collected  during 
midafternoon  contained  moderately  digested  crab 
megalops  and  gammaridean  amphipods;  although 
megalops  are  more  typically  food  of  nocturnal 
predators,  the  relatively  good  condition  of  these 
small  prey  indicated  they  had  been  collected  ear- 
lier that  day.  The  third  A.  furcatus,  speared 
during  midmorning,  was  empty.  Randall  (1955) 
examined  four  specimens  of  this  snapper  in  the 
Gilbert  Islands,  and  the  two  with  prey  contained 
only  fishes. 

CONCLUSION. — Aphareus  furcatus  preys 
on  free-swimming  fishes  and  crustaceans  during 
daylight.  Its  habits  at  night  remain  unknown. 

General  Remarks  on  Snappers 

\{  Aphareus  furcatus  hunts  prey  mostly  in  day- 
light, it  would  seem  an  atypical  lutjanid.  Gener- 
ally lutjanids  are  described  as  nocturnal  fishes 
(e.g.  Hobson,  1965,  1968a:  Gulf  of  California; 
Starck  and  Davis,  1966:  Florida  Keys;  Randall, 
1967:  West  Indies). 

The  efforts  that  successfully  introduced  the  sea 
bass  Cephalopholis  argus  into  Hawaiian  waters 
(see  account  for  that  species,  above)  also  included 
the  snapperLu(/araus  vaigiensis,  which  now  too  is 
well  established  in  Kona.  Although  L.  vaigiensis 
was  not  numerous  in  the  study  area  during  this 
work,  one  school  was  seen  consistently  during 
daylight  on  irregular  visits  to  a  location  in 
Kealakekua  Bay,  and  soHtary  individuals  occa- 
sionally were  encountered  on  the  reef  after  dark. 
Thus,  the  habits  of  this  fish  appear  to  be  similar  to 
those  of  certain  other  species  of  Lutjanus 


955 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


elsewhere;  that  is,  it  forms  relatively  inactive 
schools  during  the  day,  then  disperses  at  nightfall 
and  hunts  prey  after  dark.  This  pattern  is  known 
for  L.  argentiuentris  in  the  Gulf  of  California 
(Hobson,  1965,  1968a),  and  for  L.  griseus  and 
others  in  the  tropical  Atlantic  (Starck  and  Davis, 
1966).  Randall  and  Brock  (1960)  reported  pre- 
dominantly nocturnal  feeding  by  L.  vaigiensis  in 
Tahiti  and  often  found  this  snapper  in  large  ag- 
gregations during  the  day. 


Family  Sparidae:     porgies 

Monotaxis  grandoculis  (Forskal) — inu 

In  Kona,  this  porgy  is  most  numerous  near 
basalt  reefs  that  are  exposed  to  the  prevailing  sea. 
During  the  day  it  typically  hovers  2  to  3  m  above 
the  reef,  either  in  loose  aggregations  of  4  to  10  fish, 
or  as  solitary  individuals.  When  congregated, 
most  individuals  display  broad  bars  on  their  sides 
dorsally;  although  this  same  color  pattern  occurs 
frequently  in  solitary  fish,  these  often  are  overall 
pale  grey.  Those  I  observed  in  Kona  during  the  day 


always  seemed  inactive;  however,  Hiatt  and 
Strasburg  ( 1960)  reported  individuals  in  the  Mar- 
shall Islands  excavating  prey  buried  in  the  sand, 
presumably  during  daylight.  In  Kona,  M.  grand- 
oculis disperses  from  its  daytime  assemblages  at 
nightfall  and  forages  as  solitary  individuals 
throughout  the  night.  After  dark,  many  move  into 
shallower  water  than  is  frequented  by  the  species 
in  daylight.  The  nocturnally  active  individuals 
sometimes  show  the  barred  color  pattern  but  are 
most  often  plain  grey  (Figure  22). 

Of  five  specimens  (312:  244-397  mm)  speared 
during  day  and  night,  one  that  was  taken  from  an 
aggregation  late  in  the  afternoon  was  empty, 
whereas  all  four  that  were  speared  at  night  (later 
than  4  h  after  sunset  and  before  first  morning 
light)  were  full  of  food,  as  listed  in  Table  22. 

Although  the  gut  contents  were  relatively  fresh, 
the  shelled  items  had  been  reduced  to  crushed 
fragments — presumably  by  the  large  molarform 
jaw  teeth  of  this  fish. 

Prey  taken  by  this  porgy  in  Kona  are  much  the 
same  as  taken  by  the  same  species  in  the  Marshall 
Islands  (Hiatt  and  Strasburg,  1960)  and  Gilbert 
Islands  (Randall,  1955). 


Figure  22. — Monotaxis  grandoculis,  a  porgy,  showing  its  plain  grey  coloration  as  it  swims  close  to  the  reef  at  night. 


956 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 

Table  22. — Food  of  Monotaxis  grandoculis. 


Nc 

.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  4) 

diet  volume 

index 

1 

Prosobranch  gastropods 

4 

21.3 

21.30 

2 

Ophluroids 

3 

27.1 

20.33 

3 

Echlnoids 

3 

21.3 

15.98 

4 

Opisthobranch  gastropods 

2 

11.8 

5.90 

5 

Pagurid  crabs 

2 

3.8 

1.90 

6 

Polychaetes 

3.8 

0.95 

7 

Brachyuran  crabs 

2.5 

0.63 

8 

Tunicates 

2.5 

0.63 

9 

Egg  masses  (unldent.) 

1.3 

0.33 

10 

Holothurians 

0.8 

0.20 

Also. 

crustacean  fragments 

2.5 

0.63 

Algal  fragments 

1.3 

0.33 

CONCLUSION. — Monotaxis  grandoculis  is  a 
nocturnal  predator  that  feeds  on  benthic  inverte- 
brates, most  of  them  heavily  shelled. 

General  Remarks  on  Porgies 

Porgies  are  closely  related  to  the  snappers,  most 
of  which  seem  to  be  mainly  nocturnal.  Neverthe- 
less, porgies  have  been  reported  as  diurnal,  for 
example  species  of  Archosargus,  Diplodus,  and 
Calamus  in  the  tropical  Atlantic  (Randall,  1967). 
Still,  Starck  and  Davis  (1966)  recognized  that 
species  of  Calamus  in  Florida  may  also  feed  at 
night.  Diurnal  habits  in  porgies  may  be  attributed 
to  their  habit  of  excavating  buried  prey,  which 
makes  available  to  them  certain  nocturnal  forms 
that  have  concealed  themselves  in  the  sand  during 
daylight. 

Family  Mullidae:     goatfishes 

Mulloidichthys  auriflamma  (Forskal) — weke'ula 

During  the  day  this  goatfish,  which  is  relatively 
numerous  in  Kona,  hovers  in  schools  above  the 
reef,  or  (occasionally)  under  ledges.  Individuals 
recognized  by  distinguishing  marks  occurred  in 
schools  at  the  same  locations  each  day,  even 
though  these  schools  disperse  at  nightfall.  After 
dark,  solitary  or  in  small  groups,  this  species 
probes  with  its  barbels  in  the  sandy  areas  adjacent 
to  the  reef,  and  in  some  of  the  larger  sand  patches 
on  the  reef.  When  illuminated  by  a  diving  light  at 
night,  it  often  shows  a  deep  reddish  hue  that  seems 
to  be  a  reaction  to  the  light,  not  a  nocturnal  colora- 
tion. 

Of  the  22  individuals  (170:  110-235  mm) 
speared  during  day  and  night,  all  12  collected  from 
schools  during  the  afternoon  were  either  empty  or 


contained  only  well-digested  fragments,  whereas 
of  the  10  collected  at  night  (later  than  3  h  after 
sunset  and  before  sunrise),  all  contained  food,  in- 
cluding fresh  material,  as  listed  in  Table  23. 

Thus  my  observations  concur  with  those  of  Gos- 
line  and  Brock  (1960),  who  reported  that  M. 
auriflamma  does  not  feed  during  the  day,  but  in- 
stead schools  quietly  in  certain  established  areas 
and  then  disperses  to  forage  at  night. 

Although  crab  megalops,  a  primary  food,  are  a 
major  element  of  the  plankton,  most  of  those  cap- 
tured by  this  goatfish  probably  were  taken  from 
the  sand. 

CONCLUSION.^Ma//oj(iicA^y's  auriflamma  is 
a  nocturnal  predator  that  feeds  on  invertebrates 
that  live  in  the  sand. 

Mulloidichthys  samoensis  (Giinther) — 
tveke  'a' a 

This  goatfish,  widespread  in  Kona,  often  hovers 
in  quiet  schools  over  the  reef  during  the  day, 
where  it  looks  much  like  M.  auriflamma,  above. 
Although  M.  samoensis  is  a  more  elongated  fish, 
the  two  must  be  seen  together  before  this  distinc- 
tion is  obvious.  Sometimes  the  two  species  school 
together,  but  more  often  they  are  segregated.  Fre- 
quently instead  of  schooling  during  the  day,  M. 
samoensis,  but  not  M.  auriflamma,  moves  as  soli- 
tary individuals  or  in  small  groups  over  sand 
patches  on  the  reef,  and  there  actively  probes  with 
its  barbels  in  the  sediment.  These  active  individu- 
als have  a  color  pattern  distinct  from  that  of  rela- 
tively inactive  conspecifics  in  schools.  When 
schooling,  M.  samoensis  has  a  prominent  yellow 
stripe  running  from  eye  to  tail  along  its  upper 
sides,  as  does  M.  auriflamma  in  similar  schools 
(Figure  23a);  however,  this  stripe  is  not  present  (or  ■■ 
at  least  is  indistinct)  when  M.  samoensis  actively 


957 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  23. — Food  of  Mulloidichthys  auriflamma. 


Ni 

0.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  10) 

diet  volume 

index 

1 

Crab  megalops 

6 

11.5 

6.90 

2 

Ophluroids 

4 

14.5 

5.80 

3 

Polychaetes 

4 

11.7 

4.68 

4 

Xanthid  crabs 

6 

7.0 

4.20 

5 

Prosobranch  gastropods 

7 

4.7 

3.29 

6 

Echinoids 

6 

4.7 

2.82 

7 

Gammaridean  amphipods 

5 

1.3 

0.65 

8 

Isopods 

4 

1.1 

0.44 

9 

Ostracods 

2 

0.6 

0.12 

10 

Sipunculld  introverts 

1 

0.5 

0.05 

11 

Pelycypods 

1 

0.5 

0.05 

12 

Penaeid  shrimps    - 

1 

0,5 

0.05 

13 

Portunid  crabs 

1 

0.2 

0.02 

Also, 

crustacean  fragments 

4 

8.5 

3.40 

Unidentified  fragments 

2 

12.0 

2.40 

Algal  fragments 

1 

1.0 

010 

Sand,  foraminiferans. 

and  debris 

7 

19.7 

13.79 

forages  on  the  reef,  it  being  replaced  by  a  black 
spot  on  the  fish's  side,  below  the  dorsal  fin  (Figure 
23b). 

At  nightfall,  those  individuals  of  M.  samoensis 
that  had  been  hovering  over  the  reef  in  quiet 
schools  disperse.  After  dark  the  species  not  only 
continues  the  activity  that  some  members  had 
pursued  over  reef  sand  patches  in  daylight,  but 
also  extends  this  activity  in  some  areas  farther  out 
over  the  more  extensive  sandy  areas  adjacent  to 
the  reef.  When  illuminated  by  a  light  at  night, M. 
samoensis  frequently  displays  a  color  pattern  of 
red  blotches  that  seems  to  be  a  response  to  the 
light,  rather  than  being  a  nocturnal  color  feature. 
Its  coloration  at  night  is  as  described  above  for 
foraging  individuals  in  daylight.  After  a  night  of 
foraging,  many  individuals  regroup  in  the  morn- 
ing, forming  schools  that  reappear  in  the  same 
locations  each  day. 

Twenty-three  specimens  (182:  136-283  mm) 
were  speared  during  day  and  night.  Of  four  taken 
during  afternoons  as  they  probed  sand  patches  on 
the  reef,  swimming  in  small  groups  or  as  indi- 
viduals, two  had  full  stomachs  that  included  rela- 
tively fresh  prey;  the  other  two  contained  only 
debris.  Of  three  individuals  taken  while  they  hov- 
ered in  schools  over  the  reef  during  the  after- 
noon, one  had  an  empty  stomach,  and  the  other 
two  contained  only  well-digested  fragments.  Con- 
trasting data  were  provided  by  16  specimens 
speared  as  they  actively  probed  in  sand  patches  on 
the  reef  during  the  2  h  immediately  before  first 
morning  light,  and  during  the  first  30  min  of 
morning  twihght.  Of  these,  11  had  full  stomachs, 
including  much  fresh  material,  2  contained  only 
bits  of  debris,  and  only  3  were  empty.  Items  in  the 


13  individuals  containing  identifiable  prey  are 
listed  in  Table  24. 

No  obvious  difference  was  noted  between  prey 
taken  during  day  and  night  although  pertinent 
data  are  too  few  for  meaningful  comparison.  Hiatt 
and  Strasburg  (1960)  reported  that  fishes  are  an 
important  food  of  this  goatfish  in  the  Marshall 
Islands.  Otherwise,  they  listed  foods  similar  to 
those  taken  by  the  species  in  Kona. 

CO^CUJSIO^ .—Mulloidichthys  samoensis 
preys  on  sand-dwelling  invertebrates,  mostly  at 
night,  but  to  some  extent  during  the  day. 

Panipeneus  niultifasciatiis  (Quoy  and  Gaimard) 
— moano 

This  is  the  most  numerous  and  widespread 
goatfish  on  Kona  reefs.  During  the  day  solitary 
individuals  and  groups  of  two  or  three  actively 
probe  with  their  barbels  among  cracks  and  crev- 
ices on  the  reef,  especially  in  pockets  where  sand 
and  debris  have  accumulated.  This  species  is  ac- 
tive through  twilight,  but  generally  appears  inac- 
tive after  dark,  when  solitary  individuals  rest  in 
exposed  locations  on  the  reef.  To  some  extent  these 
immobile  nocturnal  attitudes  may  be  influenced 
by  the  diving  light,  but  not  to  the  extent  indicated 
for  P.  bifasciatus,  below;  certainly  the  blotched 
red  color  pattern  often  displayed  at  this  time  is  a 
reaction  to  the  light.  On  nights  of  bright  moon- 
light, at  least  some  individuals  of  P.  multifas- 
ciatus  swim  over  the  reef 

Thirty  specimens  (162:  125-212  mm)  were 
speared  during  day  and  night.  Of  14  collected  dur- 
ing the  hour  immediately  before  first  morning 


958 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Hv:*^. 


a.  3j.'  •  A 


Figure  23. — MuUoidichthys  samoensis,  a  goatfish:  a,  with  the  coloration  shown  when  schooling  during  the  day;  b, 
with  the  coloration  shown  when  feeding  as  a  solitary  individual  or  in  small  groups  during  both  day  and  night. 


959 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  24. — Food  of  Mulloidichthys  samoensis. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  13) 

diet  volume 

index 

1 

Pelecypods 

7 

10.0 

5.39 

2 

Polychaetes 

5 

11.2 

4.31 

3 

Gammarldean  amphipods 

7 

6.7 

3.61 

4 

Prosobranch  gastropods 

6 

3.1 

1.43 

5 

Sipunculid  introverts 

3 

5.4 

1.25 

6 

Crab  megalops 

3 

3.1 

0.72 

7 

Isopods 

3 

2.8 

0.65 

8 

Hippid  crabs 

1 

0.8 

0.06 

9 

Echinoids 

1 

0.8 

0.06 

10 

Xanthid  crabs 

1 

0.4 

0.03 

11 

Shrimps 

1 

0.2 

0.02 

Also. 

crustacean  fragments 

5 

7.1 

2.73 

Unidentified  fragments 

3 

11.6 

2.68 

Sand  and  debris,  mclud- 

ing  foraminiferans 

13 

36.8 

36.80 

Table  25. — Food  of  Parupeneus  mu 

Itifasciatus. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  18) 

diet  volume 

index 

1 

Xanthid  crabs 

14 

30.6 

23.80 

2 

Caridean  shrimps 

8 

15.4 

6.84 

3 

Crab  megalops 

5 

8.6 

2.39 

4    • 

Prosobranch  gastropods 

3 

1.8 

0.30 

5 

Tanaids 

2 

0.6 

0.07 

6 

Gammarldean  amphipods 

2 

0.4 

0.04 

7 

Stenopid  shrimps 

1 

0.6 

0.03 

8 

Ostracod 

1 

0.1 

0.01 

Also, 

crustacean  fragments 

14. 

29.4 

22.87 

Unidentified  fragments 

1 

0.8 

0.04 

Debris 

7 

11.7 

4.55 

light,  and  through  morning  twihght,  the  stomachs 
of  12  were  empty,  but  the  other  2  contained  prey  in 
varying  stages  of  digestion  that  appeared  to  have 
been  taken  during  the  night  (one  night  with,  the 
other  without,  moonlight).  In  contrast,  all  16 
specimens  speared  on  the  reef  during  the  after- 
noon contained  prey  in  varying  stages  of  diges- 
tion, including  fresh  material.  Items  in  the  18 
containing  identifiable  material  are  listed  in 
Table  25. 

No  obvious  difference  in  diet  was  noted  between 
the  2  individuals  of  P.  multifasciatus  that  appar- 
ently had  captured  their  prey  at  night  and  the  14 
that  had  been  feeding  in  daylight;  however,  the 
data  are  too  few  for  a  meaningful  comparison. 

Juveniles  of  P.  multifasciatus  sometimes 
aggregate  up  in  the  water  column  where  plankton 
abounds,  apparently  feeding  on  these  organisms, 
but  none  of  these  individuals  were  collected.  The 
relatively  high  incidence  of  crab  megalops  in  the 
diet  of  this  and  other  bottom-feeding  goatfishes 
may  reflect  some  predation  on  free-swimming 
forms  in  the  water  column,  but  I  believe  that  at 
least  most  of  these  megalops  were  taken  off  the  sea 
floor. 


CONCLUSION. — Parupeneus  multifasciatus  is 
primarily  a  diurnal  predator  that  takes  benthic 
crustaceans. 

Parupeneus  bifasciatus  (Lacepede) — munu 

This  goatfish,  which  exceeds  300  mm  when  fully 
grown,  is  especially  numerous  among  basalt 
boulders — frequently  solitary,  but  also  in  groups 
of  two  or  three.  In  daylight,  its  actions  appear 
much  like  those  of  P.  multifasciatus,  which  it  re- 
sembles, but  after  dark,  when  P.  multifasciatus 
generally  rests  on  the  reefs,  P.  bifasciatus  usually 
moves  about.  Nevertheless,  when  P.  bifasciatus  is 
illuminated  by  the  diving  light  it  often  settles 
immobile  onto  the  reef^an  action  that  compli- 
cates assessing  its  nocturnal  activity.  Like  P.  mul- 
tifasciatus, P.  bifasciatus  often  displays  at  this 
time  a  blotched  red-colored  pattern  that  seems  to 
be  a  response  to  the  diving  light. 

Twenty-seven  specimens  (229:  164-300  mm) 
were  speared  during  day  and  night.  Of  1 1  taken  as 
they  swam  close  to  the  reef  during  early  morning 
(between  flrst  light  and  3  h  after  sunrise),  the 
stomachs  of  2  were  empty,  but  the  other  9  con- 
tained prey  in  varying  stages  of  digestion,  some  of 


960 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


it  fresh.  Similarly,  of  12  individuals  collected  as 
they  swam  close  to  the  reef  during  afternoons, 
only  1  had  an  empty  stomach,  whereas  the  other 
11  contained  prey  in  varying  stages  of  digestion, 
some  of  it  fresh.  Finally,  of  four  specimens  speared 
at  night  (between  4  and  5  h  after  sunset)  the 
stomach  of  one  was  empty,  but  the  other  three 
contained  prey  in  varying  stages  of  digestion, 
some  of  it  fresh. 

These  data  indicate  that  P.  bifasciatus  feeds 
regularly  during  both  day  and  night.  Recognizing 
that  the  contrasting  conditions  under  which  it 
hunts  may  be  reflected  in  the  composition  of  its 
diet,  I  attempted  to  distinguish  prey  that  had  been 
taken  by  day  from  that  taken  at  night.  Although, 
undoubtedly  there  is  overlap,  generally  specimens 
collected  during  the  night  and  early  morning 
should  contain  mostly  prey  captured  after  dark, 
whereas  specimens  taken  during  afternoons 
should  contain  mostly  prey  taken  in  daylight. 

Thus,  the  12  P.  bifasciatus  taken  during  the 
night  and  early  morning  with  identifiable  mate- 
rial in  their  stomachs  presumably  represent  most- 
ly nocturnal  feeding.  Items  in  these  individuals 
are  listed  in  Table  26.  Using  the  same  rationale, 
diurnal  feeding  presumably  is  reflected  in  the  11 
P.  bifasciatus  collected  with  identifiable  material 
in  their  stomachs  during  afternoons.  Items  in 
these  individuals  are  listed  in  Table  26. 

Although  xanthid  crabs  are  the  major  prey  day 
and  night,  they  assume  greater  relative  impor- 


tance in  daylight,  as  do  caridean  shrimps.  Xan- 
thids  and  carideans  are  largely  under  cover  in  day- 
light, where  they  may  be  especially  vulnerable  to 
this  predator's  probing  actions.  Crab  megalops  be- 
come increasingly  important  to  this  goatfish  at 
night,  but  the  circumstances  surrounding  their 
capture  remain  uncertain;  megalops  are  the  major 
prey  of  many  nocturnal  planktivores,  such  as 
Myripristis  spp.  (see  accounts  for  these  species, 
above),  but  are  also  taken  day  and  night  by  pred- 
ators like  certain  goatfishes  that  probe  the  sea 
floor. 

Based  on  the  above  data,  fishes  seem  to  be  more 
available  as  prey  to  P.  bifasciatus  at  night.  Prey 
fishes  that  could  be  identified  were  blennies  and 
pomacentrids,  which  are  diurnal  fishes  that  take 
cover  after  dark.  Apparently  P.  bifasciatus  is 
adapted  to  capture  these  resting  diurnal  fishes  at 
night,  but  is  less  effective  in  capturing  the  fishes 
that  are  under  cover  during  daylight. 

CONCLUSION. — Parupeneus  bifasciatus 
hunts  prey  on  the  reef  during  both  day  and  night. 
Adult  crabs  and  shrimps  are  more  important  as 
prey  during  the  day  than  at  night,  whereas  the 
reverse  is  true  of  fishes  and  crab  megalops. 

Parupeneus  porphyreus  (Jenkins) — kumu 

This  is  the  most  numerous  goatfish  on  some 
Hawaiian  reefs  (Gosline  and  Brock,  1960),  but 


Table  26.— Food  of 

Parupeneus  bifasciatus 

No.  fish 

Mean  oercent 

Nighttime 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  12) 

die 

volume 

index 

1 

Xanthid  crabs 

10 

29.0 

24.17 

2 

Fish 

6 

17.0 

8.50 

3 

Crab  megalops 

5 

19.4 

8.08 

4 

Caridean  shrimps 

7 

8.0 

4.67 

5 

Octopods 

2 

3.9 

0.65 

6 

Oxyrhynchid  crabs 

2 

1.7 

0.28 

7 

Prosobranch  gastropods 

2 

0.6 

0.10 

8 

Polychaetes 

1 

0.4 

0.03 

9 

Gammaridean  amphipods 

1 

0.3 

0.03 

Also. 

crustacean  fragments 

7 

15.5 

9.04 

Debris 

2 

4.2 

0.70 

No.  fish 

Mean  percent 

Daytime 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  11) 

diet  volume 

Index 

1 

Xanthid  crabs 

9 

43.3 

35.43 

2 

Caridean  shrimps 

9 

15.5 

12.68 

3 

Crab  megalops 

3 

3.5 

0.95 

4 

Octopods 

1 

7.1 

0.65 

5 

Grapsid  crabs 

1 

3.9 

0.35 

6 

Oxyrhynchid  crabs 

1 

1.1 

0.10 

7 

Fish 

1 

0.7 

0.06 

8 

Gammaridean  amphipods 

2 

0.2 

0.04 

Also, 

crustacean  fragments 

8 

24.7 

17.96 

961 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


there  are  relatively  few  in  the  Kona  study  area. 
During  the  day  this  species  stays  close  to  cover, 
where  it  usually  occurs  in  small  groups  under 
ledges.  At  night  solitary  individuals  are  active 
close  among  rocks  and  coral  on  the  reef. 

Of  the  11  specimens  (157:  137-173  mm)  col- 
lected, 6  speared  close  to  reef  crevices  late  in  the 
afternoon  either  were  empty  or  contained  only  a 
few  well-digested  fragments,  whereas  all  5  col- 
lected in  the  same  places  within  1  h  after  sunrise 
had  stomachs  full  of  prey,  some  of  it  fresh,  as  listed 
in  Table  27. 

CONCLUSION .—Parupeneus  porphyreus  is  a 
nocturnal  predator  that  feeds  mostly  on  benthic 
crustaceans. 

Parupeneus  chrtjserydros  (Lacepede) — moano 
kea 

The  scientific  name  of  this  goatfish  remains  un- 
certain. I  follow  Gosline  and  Brock  (1960)  in  rec- 
ognizing the  nominal  P.  chryserydros,  even 
though  some  authors  (e.g.  Lachner,  1960)  refer 
this  form  to  P.  cyclostomus  (Lacepede).  Growing  to 
about  600  mm  long  (Gosline  and  Brock,  1960),  P. 
chryserydros  is  the  largest  of  the  goatfishes  occur- 
ring regularly  on  Kona  reefs. 

During  the  day,  solitary  individuals  or  groups  of 
two  to  five  move  over  the  reef,  where  their  excep- 
tionally long  barbels  work  through  the  covering 
on  rocky  substrata.  More  often  than  not,  groups  of 
P.  chryserydros  are  accompanied  by  a  single  jack, 
Caranx  melampygus,  which  follows  close  behind 
them.  For  1  mo  I  recorded  all  sightings  of  P. 
chryserydros  that  swam  in  groups  of  two  or  more, 
and  of  24  such  groups,  16  were  accompanied  by  a 
jack.  Usually  solitary  individuals  of  this  goatfish 
are  not  thus  accompanied,  but  this  too  was  seen 
four  times  during  the  month.  Clearly,  it  is  the  jack 
that  maintains  the  association,  probably  as  a  tac- 


tic to  capture  prey  driven  from  cover  as  the  forag- 
ing goatfish  disturb  the  substratum.  Apparently 
the  jack  finds  this  advantage  only  with  P. 
chryserydros,  as  it  was  not  seen  similarly  follow- 
ing other  species.  Titcomb  and  Pukui  ( 1952)  listed 
many  ancient  Hawaiian  fish  names  which  they 
were  unable  to  associate  with  species  recognized 
today.  One  of  these,  moano  ukali  ulua,  translates 
as  "moano  with  ulua  following,"  and  probably  re- 
fers to  P.  chryserydros.  Whereas  the  adults  of  P. 
chryserydros  are  followed  by  the  jack,  the 
juveniles  of  this  goatfish  frequently  swim  close 
beneath  various  labrids,  especially  Thalassoma 
duperrey,  and  here  it  is  the  goatfish  that  main- 
tains the  associations,  though  to  what  advantage  I 
do  not  know. 

Of  the  20  specimens  (261:  123-363  mm)  col- 
lected, all  3  that  were  speared  as  they  rested  on  the 
reef  at  night  (between  4  h  after  sunset  and  first 
morning  light)  had  empty  guts,  whereas  15  of  17 
taken  as  they  swam  close  to  the  reef  at  various 
times  of  the  day  (between  midmorning  and  late 
afternoon)  had  prey  in  their  stomachs,  and  only 
the  other  2  were  empty. 

Fish  were  the  major  item,  occurring  in  13  of  the 
15  individuals  that  contained  food  (mean  percent 
of  diet  volume:  83.1;  ranking  index:  72.02).  Other 
food  items  were:  xanthid  crabs  in  two  individuals 
(mean  percent  of  diet  volume:  8.3;  ranking  index: 
1.11),  caridean  shrimps  in  one  (mean  percent  of 
diet  volume:  1.3;  ranking  index:  0.09),  and 
unidentified  fragments  in  two  (mean  percent  of 
diet  volume:  7.3;  ranking  index:  0.97). 

The  fishes  in  the  diet  ranged  between  25  and  102 
mm  long,  and  included  the  following  species: 
Abudefduf  imparipennis  (1),  Cirrhitops  fasciatus 
(2),  Istiblennius  gibbifrons  (1),  Plagiotremus gos- 
linei  (1),  Cirripectus  sp.  (4),  and  a  labrid  (1).  All  of 
these  are  diurnal  fishes  that  swim  close  to  the  reef 
in  daylight,  but  take  cover  when  a  predator  ap- 
proaches. Judging  by  how  P.  chryserydros  feeds. 


Table  27. — Food  of  Paruperfus  porphyreus. 


Nc 

.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  5) 

diet  volume 

index 

1 

Xanthid  crabs 

5 

65.2 

65.20 

2 

Hippid  crabs 

10.0 

2.00 

3 

Caridean  shrimps 

2.0 

0,40 

4 

Prosobranch  gast 

ropods 

0.2 

0,04 

5 

Chitons 

0.2 

0.04 

6 

Gammarldean  am 

phlpods 

0.2 

0.04 

Also. 

crustacean  fragments 

3 

21.2 

12,72 

Debris 

1 

1.0 

0,20 

962 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


small  fishes  that  have  taken  shelter  on  its  ap- 
proach probably  are  detected  and  even  driven  out 
from  under  cover  by  the  exceptionally  long  barbels 
of  this  goatfish.  If  the  probing  barbels  do  in  fact 
drive  small  fishes  from  their  hiding  places,  this 
would  account  for  the  behavior  of  the  jacks  that 
follow  them,  described  above.  These  same  prey 
fishes  also  shelter  themselves  at  night  when  they 
are  inactive,  so  one  might  ask  why  this  goatfish 
does  not  hunt  for  them  at  that  time  too.  As  re- 
ported above,  P.  bifasciatus  preys  on  some  of  these 
same  fishes  (pomacentrids  and  blennies)  when 
they  are  inactive  under  shelter  at  night.  But  cap- 
turing a  relatively  inert  diurnal  fish  that  is  rest- 
ing under  cover  after  dark  probably  presents  dif- 
ferent problems  for  a  predator  than  capturing  an 
alert  fish  that  has  taken  refuge  from  some  specific 
threat  in  daylight.  It  appears  that  P.  bifasciatus  is 
adapted  to  taking  these  fishes  when  they  rest 
under  cover  at  night,  whereas  P.  chryserydros  is 
adapted  to  take  them  when  they  seek  shelter  in 
daylight.  After  dark,  P.  chryserydros  is  inactive, 
resting  under  reef  cover  (Figure  24). 

Parupeneus  cyclostomus  in  the  Marshall  Is- 
lands, which  is  closely  related  to  P.  chryserydros. 


if  not  conspecific,  was  reported  by  Hiatt  and  Stras- 
burg  (1960),  on  the  basis  of  16  specimens,  to  be  an 
"active  feeder  on  small  benthonic  fishes,"  but  may 
prey  more  heavily  on  crustaceans  than  does  the 
Hawaiian  form. 

CONCLUSION. — Parupeneus  chryserydros  is  a 
diurnal  predator  that  feeds  mostly  on  small  fishes. 

General  Remarks  on  Goatfishes 

Despite  their  supei'ficial  similarity,  the  various 
goatfishes  behave  distinctively.  Some,  such  as 
Mulloidichthys  auriflamma  and  Parupeneus  por- 
phyreus,  are  primarily  nocturnal;  others,  includ- 
ing P.  chryserydros  and  P.  multifasciatus ,  are 
mostly  diurnal;  and  still  others,  like  P.  bifasciatus 
and  M.  samoensis,  regularly  hunt  prey  during 
both  day  and  night.  One  might  suppose  that  fishes 
which  probe  the  sea  floor  for  food  would  be  indif- 
ferent to  changes  associated  with  day  and  night, 
but  obviously  this  is  not  so.  Whether  a  given 
species  of  goatfish  is  primarily  diurnal  or  noctur- 
nal probably  relates  to  the  differential  day-night 
habits  of  its  specific  prey.  That  some  goatfishes  are 


Figure  24. — -Parupeneus  chryserydros, 


a  goatfish,  resting  under  a  ledge  at  night,  with  its  exceptionally  long  chin 
barbels  spread  out  before  it. 


963 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


nocturnal,  whereas  other  are  diurnal,  is  also  rec- 
ognized from  other  seas.  In  Florida,  Starck  and 
Davis  (1966)  suspected  that  Mulloidichthys 
martinicus  feeds  at  night,  whereas  they  recog- 
nized diurnal  feeding  habits  in  Pseudupeneus 
maculatus.  Longley  and  Hildebrand  (1941),  as 
well  as  Collette  and  Talbot  (1972),  also  regarded 
M.  martinicus  as  nocturnal  and  P.  maculatus  as 
diurnal.  Randall  (1967)  reported  that  M.  mar- 
tinicus feeds  by  day  as  well  as  night,  and  described 
a  diet  much  like  that  of  the  two  species  of 
Mulloidichthys  from  Kona. 

Family  Kyphosidae:     sea  chubs 

Kyphosus  cinerascens  Forskal — nenue 

In  Kona,  K.  cinerascens  is  most  numerous 
where  a  basalt  reef  face  confronts  the  prevailing 
swell  in  water  deeper  than  about  8  m.  Often  over 
500  mm  long,  this  fish  is  active  throughout  the 
day — usually  in  groups  of  up  to  10  or  more  indi- 
viduals, and  often  swimming  high  in  the  water 
column.  At  night,  solitary  individuals  swimming 
above  the  sea  floor  are  often  encountered  in  the 
same  areas. 

All  three  specimens  (205:  166-250  mm)  col- 
lected for  study  had  guts  full  of  a  wide  variety  of 
benthic  algae  exclusively.  Although  two  of  these 
fish  were  taken  during  midday,  the  other  was 
taken  at  night,  within  1  h  before  first  morning 
light.  No  sedimentary  material  was  mixed  in 
these  gut  contents,  indicating  that  the  algae  had 
been  bitten,  not  scraped,  off  the  rocks,  or  else  had 
been  taken  as  fragments  drifting  in  mid-water. 
Hiatt  and  Strasburg  (1960)  found  the  same  gut 
contents  in  specimens  from  the  Marshall  Islands. 

CONCLUSION. — Kyphosus  cinerascens  feeds 
during  the  day,  cropping  algae  from  rocks  or  tak- 
ing them  as  drifting  algal  fragments.  Its  nocturnal 
habits  remain  uncertain. 

General  Remarks  on  Sea  Chubs 

Sea  chubs  generally  are  described  as  diurnal 
herbivores  (e.g.  Longley  and  Hildebrand,  1941; 
Starck  and  Davis,  1966;  Randall,  1967).  Smith 
(1907)  reported  crabs  and  bivalved  mollusks 
among  algae  in  the  diet  of  Kyphosus  sectatrix  in 
the  Atlantic  Ocean,  but  these  items  probably  were 
taken  incidentally  with  the  algae.  Randall  (1967) 
found  only  algae  and  a  bit  of  sea  grass  in  K.  secta- 


trix from  the  West  Indies.  Starck  and  Davis  (1966) 
reported  that  K.  incisor  rests  in  sheltered  loca- 
tions on  Floridian  reefs  at  night  after  having  fed  on 
drifting  sargassum  at  the  water's  surface  during 
the  day.  In  the  East  Indies,  however,  William  N. 
McFarland,  Cornell  University  (pers.  commun.) 
observed  kyphosids  active  at  night. 

Family  Chaetodontidae: 
angelfishes  and  butterflyfishes 

The  chaetodontids  comprise  two  distinct  groups: 
the  angelfishes,  subfamily  Pomacanthinae;  and 
the  butterflyfishes,  subfamily  Chaetodontinae.  Of 
the  species  treated  below,  the  first  two  are 
angelfishes,  the  remainder  are  butterflyfishes. 

Holocanthus  arcuatus  Gray — angelfish 

This  angelfish  is  sparsely  distributed  on  Kona 
reefs,  but  being  relatively  large  and  distinctive  is 
readily  noticed  where  it  occurs.  Usually  solitary  or 
paired,  it  swims  close  among  rock  ledges  and  boul- 
ders at  depths  below  about  8  m.  During  the  day  it 
picks  material  from  the  surface  of  rocks,  but  was 
not  seen  active  at  night. 

Six  specimens  ( 136:  123-150  mm)  were  speared 
during  afternoons,  and  all  had  full  stomachs. 
They  had  fed  almost  exclusively  on  sponges  (mean 
percent  of  diet  volume  and  ranking  index:  98.3). 
The  only  other  items — algae  and  hydroids — 
probably  were  taken  incidentally  with  the 
sponges. 

CONCLUSION. — Holacanthus  arcuatus  is  a 
diurnal  species  that  feeds  on  sponges. 

Centropyge  potteri  (Jordan  and  Metz) — 
potter's  angelfish 

An  abundant  species  in  coral-rich  surround- 
ings, this  small  angelfish  behaves  more  like  some 
of  the  damselfishes  than  it  does  other  members  of 
its  family.  A  given  individual  limits  its  move- 
ments to  restricted,  well-defined  locations  close 
among  fingerlike  growths  of  the  coral  Porites 
compressus.  During  the  day  it  swims  about,  pick- 
ing at  material  growing  over  dead  coral.  At  night 
it  is  alert,  but  secreted  deep  among  the  coral,  ap- 
parently inactive. 

All  five  specimens  (80:  69-86  mm  long)  speared 
at  various  times  during  the  day  were  full  of  food. 
Filamentous  algae  were  the  major  identifiable 
item  in  the  gut  contents  of  all  five  (mean  percent  of 


964 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


diet  volume  and  ranking  index:  41.7).  There  also 
was  much  unidentified  debris,  including  sand  and 
foraminiferans  (mean  percent  of  diet  volume  and 
ranking  index:  42.3)  that  all  five  apparently  had 
scraped  from  the  substratum,  and  which  probably 
included  substantial  nourishment  in  the  form  of 
organic  detritus.  The  other  components  of  the  diet, 
all  minor,  were:  diatoms  in  all  five  (mean  percent 
of  diet  volume  and  ranking  index:  3.3),  sponges  in 
all  five  (mean  percent  of  diet  volume  and  ranking 
index:  2.3),  and  harpacticoid  copepods  in  one 
(mean  percent  of  diet  volume:  0.3;  ranking  index: 
0.06). 

CONCLUSION.— Cen^rop3'^e  potteri  is  a 
diurnal  species  that  feeds  on  benthic  algae  and 
probably  on  organic  detritus. 

Forcipiger  flavissimus  Jordan  and 
McGregor — Ian  wiliwili  nukiinitkii   oi  oi 

This  long-snouted  species  (Figure  25a),  numer- 
ous in  Kona,  and  widespread  throughout  the 
Indo-Pacific  region,  was  long  called  F.  longiros- 
tris.  Only  recently  has  the  distinction  between  F. 
flavissimus  and  the  true  F.  longirostris  (Figure 
25b  and  c;  treated  below)  been  recognized 
(Wheeler,  1964;  Randall  and  Caldwell,  1970). 
Forcipiger  flavissimus  occurs  singly,  or,  more 
often,  in  groups  of  two  or  three.  It  is  active 
throughout  the  day,  especially  over  coral-rich 
reefs,  where  it  picks  at  objects  on  a  variety  of 
surfaces.  At  night  it  is  alert  close  among  rock  and 
coral  cover  but  apparently  inactive. 

Twenty-seven  specimens  (116:  94-137  mm) 
were  speared  during  day  and  night.  Of  11  that 
were  taken  either  at  night  (later  than  4  h  after 
sunset)orduringearly  morning  twilight,  the  stom- 
achs of  9  were  empty,  and  those  of  2  (collected 
between  4  and  5  h  after  sunset)  contained  only  a 
few  well-digested  fragments.  In  contrast,  all  16 
specimens  taken  at  various  times  of  the  day  had 
full  stomachs,  including  relatively  fresh  material, 
as  listed  in  Table  28. 

Most  of  the  unidentified  fragments  among  the 
gut  contents  were  relatively  fresh  pieces  that  this 
fish  apparently  had  recently  torn  from  the  bodies 
of  larger  animals.  The  similarity  of  its  elongated 
snout  and  mouth  to  a  pair  of  needle-nosed  pliers 
(Figure  26,  lower)  underscores  the  adaptiveness  of 
its  feeding  apparatus  to  this  habit.  Even  the  grip- 
ping surfaces  on  the  pliers  are  paralleled  in  the 
snout  of  F.  flavissimus  by  expanded  contact- 


surfaces  in  both  upper  and  lower  jaws — both  of 
which  carry  multiple  rows  of  short,  inwardly  curv- 
ing teeth  (Figure  27b). 

CONCLUSION. — Forcipiger  flavissimus  is  a 
diurnal  predator  that  tears  pieces  off  larger 
benthic  animals. 

Forcipiger  longirostris  (Broussonet) — 
lau  wiliwili  nukunuku   oi  oi 

This  species  is  relatively  numerous  in  Kona, 
although  it  appears  to  be  rare  elsewhere  in 
Hawaii.  Both  color  varieties — the  yellow  form 
(Figure  25b),  which  is  essentially  identical  to  F. 
flavissimus,  discussed  above,  and  the  dark  brown 
form  (Figure  25c) — were  observed  regularly 
throughout  the  study.  Like  F.  flavissimus,  F.  lon- 
girostris occurs  typically  over  coral-rich  reefs,  and 
the  two  species  overlap  extensively;  however,  in 
areas  where  one  is  numerous,  the  other  occurs  less 
frequently.  Despite  this,  I  was  unable  to  relate 
observed  differences  in  relative  numbers  to 
specific  habitat  differences.  Forcipiger  longiros- 
tris is  generally  larger,  but  the  most  obvious  mor- 
phological distinction  between  the  two  lies  in  the 
relative  lengths  of  their  snouts  and  in  their  differ- 
ent mouth  structures  (Figure  26).  Less  noticeable, 
but  probably  also  related  to  feeding,  F.  longiros- 
tris has  relatively  larger  eyes.  Like  its  congener, 
F.  longirostris  is  active  on  the  reef  by  day,  swim- 
ming singly  or  in  groups  of  two  or  three,  and  prob- 
ing with  its  long  snout  in  cracks  and  crevices.  At 
night  it  is  close  among  cover  of  rocks  or  coral 
— alert,  but  apparently  inactive. 

Of  the  26  specimens  (136:  98-162  mm)  col- 
lected, all  4  that  were  speared  at  night  (later  than 
4  h  after  sunset  and  before  first  light  in  the  morn- 
ing) had  empty  stomachs,  whereas  the  stomachs  of 
all  22  collected  at  various  times  during  the  after- 
noon were  full  (including  relatively  fresh  items). 
Decapod  shrimps  were  the  major  prey,  occurring 
in  all  22  individuals  that  contained  food  (mean 
percent  of  diet  volume  and  ranking  index:  88.4). 
Other  food  items  were:  pagurid  crabs,  without  the 
mollusk  shell,  in  two  individuals  (mean  percent  of 
diet  volume:  1.9;  ranking  index:  0.17),  fish  frag- 
ments in  one  (mean  percent  of  diet  volume:  0.5; 
ranking  index:  0.02),  and  crustacean  fragments  in 
nine  (mean  percent  of  diet  volume:  9.2;  ranking 
index:  3.76). 

In  contrast  to  the  omnivorous  F.  flavissimus,  F. 
longirostris  has  a  restricted  diet.  It  does  not  tear 


965 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  25. — a,  Forcipiger  flavissimus,  a 
longsnouted  butterflyfish,  active  on  the  reef  during 
the  day;  b,  F.  longirostris  (yellow  form),  a 
longsnouted  butterflyfish,  active  on  the  reef  during 
the  day;  c,  F.  longirostris  (brown  form),  active  on 
the  reef  during  the  day. 


966 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  28.- 

-Food  of  Forcipiger  flavissimus. 

No.  fish 

Mea 

n  percent 

with  this 

of 

Ranl<ing 

Rank 

Items 

item  (n  =  16) 

diet  volume 

index 

1 

Radicles  of  sabellid 

polychaetes 

10 

15.4 

9.63 

2 

Nemerteans 

7 

11.9 

5.21 

3 

Podia  and  pedicellaria 

of  echiinolds 

9 

7.0 

3.94 

4 

Calanold  copepods 

8 

4.1 

2.05 

5 

Tentacles  of  terebellid 

polychaetes 

7 

3.6 

1.58 

6 

Gammaridean  amphipods 

7 

2.3 

1.01 

7 

Hydroids 

8 

1.0 

0.50 

8 

Caridean  shrimps 

2 

1.3 

0.16 

9 

Caprellid  amphipods 

4 

0.5 

0.13 

10 

Sipunculid  introverts 

3 

0.6 

0.11 

11 

Prosobranch  gastropod 

egg  capsules 

3 

0.5 

0.09 

12 

Crab  megalops 

2 

0.1 

0.01 

13 

Isopods 

1 

0.1 

<0.01 

14 

Demersal  fish  eggs 

1 

0.1 

<0.01 

Also. 

crustacean  fragments 

2 

0.9 

0.11 

Algal  fragments 

2 

0.2 

0.03 

Unidentified  fragments 

15 

50.4 

47.25 

1  cm 


off  pieces  of  larger  organisms,  as  does  its  congener, 
but  instead  takes  only  whole  prey.  The  sharp  dif- 
ference between  their  diets  is  reflected  in  differing 
feeding  structures.  The  snout  and  mouth  of  F. 
longirostris  do  not  suggest  needle-nosed  pliers,  as 
do  those  of  F.  flavissimus;  indeed,  for  F.  longiros- 
tris, the  generic  name  Forcipiger  (from  the  Latin 
forcipis,  meaning  pincers)  is  a  misnomer.  Com- 
pared with  F.  flavissimus,  the  mouth  of  F.  lon- 
girostris is  smaller  and  its  jaws  do  not  have  the 
greatly  expanded  contact  surfaces;  the  teeth  are 
inwardly  curved,  as  in  F.  flavissimus,  but  are 
longer  and  confined  to  only  two  or  three  rows  at 
the  front  of  the  mouth  (Figure  27a).  Clearly,  F. 
longirostris  is  adapted  to  grasping  the  tiny  prey  on 
which  it  feeds,  but  not  to  tearing  pieces  free. 

CONCLUSION. — Forcipiger  longirostris  is  a 
diurnal  predator  that  takes  small  benthic  ani- 
mals, mostly  decapod  shrimps. 

Hemitaiirichthys  thompsoni  Fowler 

This  plain  dark-brown  chaetodontid  seems  to  be 
generally  rare  in  Hawaii  (Gosline  and  Brock, 
1960),  but  is  numerous  in  several  locations  near 

Figure  26. — The  head  and  snout  of:  a,  Forcipiger  longirostris, 
102mm  long;  F.  flavissimus,  103  mm  long.  (Note:  to  discount  the 
size  difference  in  their  snouts,  lengths  were  measured  from  the 
posterior  edge  of  the  maxillary.) 


967 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 


UPPER 


1  mm 


1  mm 


LOWER 


"AV^ 


Figure  27. — Dentition  of:  a,  Forcipiger  longirostris;  b,  F.  flavissimus. 


♦the  outer  drop-off  at  Puuhonua  Point,  Honaunau. 
During  the  day  it  is  active  in  large  aggregations 
high  in  the  water  column,  but  at  nightfall  de- 
scends to  the  reef  and  remains  close  among  cover 
until  morning. 

Of  the  11  specimens  (167:  127-185  mm)  col- 
lected, all  5  that  were  taken  from  under  cover  on 
the  reef  at  night  (between  4  h  after  sunset  and 


daybreak)  had  empty  guts,  whereas  all  6  taken 
during  afternoons  from  aggregations  in  mid- 
water  were  full  of  food,  as  listed  in  Table  29. 

I  saw  no  evidence  of  benthic  feeding  by  this  fish. 
The  circumstance  that  various  planktonic 
copepods  made  up  over  8&7c  of  its  diet  indicates 
that  H.  thompsoni  is  a  more  specialized  feeder 
than  its  congener  H.  zoster  below. 


Table  29. — Food  of  Hemitaurichthys  thompsoni. 


Rank 


Items 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

item  in  =  6) 

diet  volume 

index 

Calanoid  copepods 


2 

Blue-green  algae  in 

gelatinous  sacs 

3 

Cyclopoid  copepods 

4 

Fish  eggs,  planktonic 

5 

Harpacticoid  copepods 

6 

Hyperiid  amphipods 

7 

Gastropods,  planktonic 

8 

Unidentified  egg  masses 

in  gelatinous  matrix 

g 

Mysids 

10 

Larvaceans 

Also,  unidentified  fragments 


81  9 


81  90 


3.5 

2.33 

3.5 

2.33 

1.0 

0.67 

0.7 

0.47 

03 

0.15 

0.3 

0.05 

0.2 

0.03 

0.2 

0.03 

0.2 

0.03 

8.2 

5.47 

968 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


CONCLUSION. — Hemitaurichthys  thompsoni 
is  a  diurnal  planktivore  that  takes  mostly 
copepods. 

Hemitaurichthys  zoster  (Bennett) — 
blackface  butterflyfish 

Gosline  and  Brock  ( 1960)  stated  that  the  color- 
ful H.  zoster  (Figure  28a)  and  H.  thompsoni  attain 
a  similar  size  (about  175  mm),  but  of  those  seen 
during  this  project,  H.  zoster  was  consistently 
smaller.  Of  the  two,  H.  zoster  also  was  by  far  the 
more  numerous  and  more  widespread.  During  the 
day  H.  zoster  aggregates  much  like  H.  thompsoni, 
especially  where  the  reefs  drop  abruptly  into 
water  deeper  than  about  10  m.  Where  H.  thomp- 
soni occurred,  H.  zoster  was  always  nearby,  but 
mixed  aggregations  of  the  two  species  were  never 
seen.  Unlike  H.  thompsoni,  which  was  seen  feed- 
ing only  in  mid-water,  H.  zoster  sometimes  is  ac- 
tive in  small  groups  close  to  the  reef.  At  night  H. 
zoster  is  generally  solitary,  close  among  cover  in 
the  same  areas  where  it  is  active  in  daylight.  Al- 
though H.  thompsoni  has  the  same  coloration  day 
and  night,  H.  zoster  displays  a  color  pattern  at 
night  that  differs  strikingly  from  its  daytime 
coloration  (Figure  28a  and  b). 

Twelve  specimens  (119:  100-128  mm)  were 
collected  during  day  and  night.  Four  were  speared 
during  morning  twilight  from  a  group  milling 
about  close  above  the  reef  just  prior  to  rising  into 
mid-water.  Two  of  these,  taken  18  and  20  min 
before  sunrise,  respectively,  both  had  empty 
stomachs;  the  third,  taken  15  min  before  sunrise, 
contained  calanoid  copepods  in  varied  stages  of 
digestion;  the  fourth,  taken  10  min  before  sunrise, 
contained  more  than  100  calanoid  copepods  and 
assorted  other  prey  in  varied  stages  of  digestion.  I 
cannot  believe  that  all  these  prey  had  been  taken 
since  first  light  that  morning,  especially  as  no 
feeding  was  observed,  and  these  fish  had  not  yet 
risen  to  their  customary  plankton-feeding  levels. 
And  yet  H.  zoster  was  never  seen  above  the  reef  at 
night.  Until  additional  data  are  available,  these 
two  specimens  remain  anomalous.  The  other  eight 
specimens,  taken  at  various  times  during  daylight 
from  small  aggregations  above  the  reef,  all  had 
full  stomachs.  Items  in  the  10  individuals  contain- 
ing identifiable  prey  are  listed  in  Table  30. 

These  data  indicate  that  H.  zoster  has  feeding 
habits  that  are  less  specialized  than  those  of  H. 
thompsoni.  Planktonic  copepods,  constituting  al- 
most 62%  of  its  diet,  are  still  the  major  prey. 


but  are  less  dominant  than  in  H.  thompsoni. 
Furthermore,  H.  zoster  appears  to  feed  signif- 
icantly on  benthic  prey:  the  alcyonarian  Sarco- 
thelia  edmondsoni  constituted  over  60%  of  the 
material  in  each  of  the  three  specimens  in  which 
it  occurred. 

CONCLUSION. — Hemitaurichthys  zoster  is 
chiefly  a  diurnal  planktivore  that  takes  primarily 
copepods,  but  also  feeds  on  benthic  organisms, 
especially  alcyonarians. 

Chaetodon  corallicola  Snyder 

Observations  in  the  western  Pacific  have  indi- 
cated that  the  Hawaiian  C.  corallicola  is  closely 
related  to,  if  not  conspecific  with,  the  widespread 
Indo-Pacific  C.  kleini.  In  Kona,  this  species  is  rela- 
tively numerous  at  depths  below  20  m  along  the 
edge  of  the  outer  drop-off  In  daylight  it  generally 
swims  in  loosely  associated  pairs  that  pick  free- 
swimming  organisms  from  the  water  column 
within  a  meter  or  so  of  the  reef.  At  night  it  remains 
close  among  the  coral — alert,  but  apparently  inac- 
tive. 

All  11  specimens  (89:  75-96  mm)  collected  for 
study  during  afternoons  had  full  stomachs  (in- 
cluding fresh  material),  as  listed  in  Table  31.  The 
only  evidence  of  bottom  feeding  among  this  mate- 
rial is  the  capreUid  amphipods  and  hydroids,  both 
taken  from  the  same  individual. 

CONCLUSION  .—Chaetodon  corallicola  is 
primarily  a  diurnal  planktivore  that  feeds  largely 
on  copepods. 

Chaetodon  miliaris  Quoy  and  Gaimard 

Gosline  and  Brock  (1960)  noted  that  C.  miliaris 
is  one  of  the  commonest  inshore  fishes.  Although  it 
is  numerous  in  shallow  water  around  Oahu,  Brock 
and  Chamberlain  (1968),  using  a  submarine  off 
that  island,  found  it  even  more  abundant  in  deeper 
water.  They  discovered  it  to  be  a  dominant  form  at 
depths  below  120  m,  where  it  hovered  in  aggrega- 
tions 15  to  40  m  above  the  sea  floor,  apparently 
feeding  on  plankton.  In  the  Kona  study  area,  this 
species  rarely  occurs  in  water  shallower  than  20 
m,  but  is  numerous  along  the  outer  drop-off  at  30 
m  and  deeper.  During  the  day  it  aggregates  2  to  3 
m  above  the  reef,  where  it  picks  organisms  from 
the  plankton.  At  night  it  is  scattered  among  the 
rocks  and  ledges,  alert  but  apparently  inactive. 


969 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  28. — Hemitaurichthys  zoster,  a  butterflyfish:  a,  showing  its  diurnal  coloration  while  swimming  in  the  water 
column  during  the  day;  b,  showing  its  nocturnal  coloration  while  close  to  the  reef  at  night. 


970 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 

Table  30. — Food  of  Hemitaurichthys  zoster. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  10) 

diet  volume 

index 

1 

Calanoid  copepods 

10 

55.3 

55.30 

2 

Alcyonarians 

3 

18.2 

5.46 

3 

Cyclopold  copepods 

8 

6.1 

4.88 

4 

Fish  eggs,  planktonic 

6 

1.9 

1.14 

5 

Larvaceans 

4 

1.0 

0.40 

6 

Blue-green  algae  in 

gelatinous  sacs 

3 

1.3 

0.39 

7 

Hydroids 

2 

1.9 

0.38 

8 

Harpacticoid  copepods 

3 

0.3 

0.09 

9 

Gastropod  veligers 

2 

0.3 

0.06 

10 

Penaeid  shrimps 

1 

0.2 

0.02 

11 

Gastropod  larvae. 

echinospira 

1 

0.1 

0.01 

12 

Pelycypod  larvae 

1 

0.1 

0.01 

13 

Foraminiferans 

1 

<0.1 

<0.01 

14 

Ostracods 

1 

<0.1 

<0.01 

Also. 

unidentified  fragments 

5 

9.9 

4.95 

Crustacean  fragments 

2 

3.2 

0.64 

Table  31.- 

-Food  of  Chaetodon  core 

llicola. 

No  fish 

Mec 

n  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  [n  =  ^^) 

diet  volume 

index 

1 

Calanoid  copepods 

11 

52.6 

52.60 

2 

Cyclopoid  copepods 

11 

12.1 

12.10 

3 

Fish  eggs,  planktonic 

9 

1.3 

1.06 

4 

Larvaceans 

2 

5.5 

1.00 

5 

Ostracods 

3 

0.5 

0.14 

6 

Lobster  phyllosomes 

3 

0.5 

0.14 

7 

Mysids 

2 

0.3 

0.06 

8 

Caprellid  amphipods 

0.5 

0.05 

9 

Salps 

0.2 

0.02 

10 

Shrimp  larvae 

0.2 

0.02 

11 

Hydroids 

0.1 

<0.01 

12 

Gammaridean  amphipods 

<0.1 

<0.01 

13 

Blue-green  algae  in 

gelatinous  sacs 

<0.1 

<0.01 

Also. 

unidentified  fragments 

11 

26.0 

26.00 

Of  eight  specimens  (118:  110-125  mm)  col- 
lected, one  that  was  taken  during  early  morning 
twilight  close  among  cover  contained  only  a  few 
well-digested  fragments,  whereas  all  seven  that 
were  active  above  the  reef  when  taken  during  the 
afternoon  were  full  of  food  (much  of  it  fresh),  as 
listed  in  Table  32. 

CONCLUSION. — Chaetodon  miliaris  is  a  diur- 
nal planktivore  that  takes  mostly  copepods. 

Chaetodon  quadrimaculatus  Gray — 
four-spot  butterflyfish 

This  butterflyfish  is  especially  numerous  where 
the  water  is  less  than  10  m  deep  over  reefs  rich  in 
the  coral  Pocillopora.  During  the  day  it  is  active, 
solitary  or  paired,  close  to  the  sea  floor.  Feeding 
strictly  on  the  bottom,  it  mostly  picks  at  the  sur- 
face of  living  coral  or  in  cracks  within  dead  coral 
and  basalt.  It  occurs  in  the  same  areas  at  night, 
but  though  alert,  seems  relatively  inactive. 


Twenty-six  specimens  (92:  43-110  mm)  were 
speared  during  day  and  night.  All  15  collected 
during  midday  were  full  of  food,  as  were  4  of  5 
taken  at  night  during  the  2  h  immediately  before 
midnight  (the  fifth  was  empty).  The  remaining  six 
were  collected  at  night  during  the  hour  im- 
mediately before  daybreak,  and  while  three  of 
these  had  empty  stomachs,  the  other  three  were 
full.  Whether  these  findings  indicate  nocturnal 
feeding  or  slow  digestion  remains  uncertain.  No 
differences  were  recognized  in  composition  or  con- 
dition of  gut  contents  between  specimens  taken 
day  and  night.  Items  in  the  22  individuals  contain- 
ing identifiable  material  are  listed  in  Table  33. 

At  least  some  of  the  corals  taken  by  this  fish 
probably  are  soft  corals.  Most  material  in  the  gut 
appeared  as  amorphous  clumps  rich  in  nemato- 
cysts  and  zooxanthellae.  That  much  of  this  is  soft 
coral  seems  likely  considering  how  often  C.  quad- 
rimaculatus nibbles  about  reef  crevices  where  liv- 
ing stony  corals  are  absent. 


971 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Table  32. — Food  of  Chaetodon  miliaris. 


No  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  7) 

diet  volume 

index 

1 

Calanoid  copepods 

7 

686 

68.60 

2 

Cyclopoid  copepods 

7 

2.8 

2.80 

3 

Salps 

1 

3.0 

0.43 

4 

Hyperlid  amphipods 

3 

0.4 

0.17 

5 

Fish  eggs,  planktonic 

3 

04 

0.17 

6 

Larvaceans 

1 

09 

0.13 

7 

Egg  masses  in 

gelatinous  sacs 

2 

0.4 

0.11 

8 

Ostracods 

1 

0  1 

0.01 

9 

Harpactlcoid  copepods 

1 

0.1 

0.01 

10 

Myslds 

1 

0.1 

0.01 

Also, 

unidentified  fragments 

6 

23.2 

1989 

Table  33. — Food  of  Chaetodon  quadrimaculatus. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  22) 

diet  volume 

index 

1 

Anthozoans  (no 

skeletal  material) 

22 

81.4 

81  40 

2 

Polychaetes  (mostly 
tentacles  and 

fragments) 

13 

6.2 

3.66 

3 

Hydroids 

13 

1.6 

0,95 

4 

Sipunculid  introverts 

7 

i.a 

0.60 

5 

Opisthobranch  gastropods 

3 

1.3 

0.18 

6 

Caprellid  amphipods 

6 

0.4 

0.11 

7 

Gammaridean  amphipods 

4 

0.2 

0.04 

8 

Cyclopoid  copepods 

2 

0.1 

<0.01 

9 

Calanoid  copepods 

1 

<0,1 

<0.01 

10 

Mites 

1 

<0.1 

<001 

11 

Demersal  eggs 

1 

<0.1 

<0.01 

Also, 

unidentified  fragments 
Algal  fragments. 

5 

4.5 

1.02 

including  diatoms 

12 

2.1 

1.15 

Opisthobranch  gastropods  had  been  taken  by 
three  of  the  individuals  collected  at  night.  Perhaps 
significantly,  these  same  opisthobranchs  are  a 
major  prey  of  C.  lunula  after  dark  (see  below). 

CONCLUSION. — Chaetodon  quadrimaculatus 
feeds  during  the  day  mostly  on  corals,  but  also  on 
polychaetes  and  other  benthic  organisms.  Some 
nocturnal  feeding  is  likely. 

Chaetodon  unimaculatiis  Bloch — 
one-spot  butterflyfish 

This  chaetodontid  is  numerous  on  shallow  reefs 
exposed  to  a  strong  surge  where  the  coral 
Pocillopora  is  also  abundant.  Generally  occurring 
in  pairs,  it  is  active  during  the  day,  picking  at  the 
surface  of  living  Pocillopora,  and  to  a  lesser  extent 
other  reef  surfaces.  At  night  it  is  alert,  but  appears 
inactive  as  it  hovers  close  among  cover  on  the  reef. 

Twenty-six  specimens  (85:  66-102  mm)  were 
speared  during  night  and  day.  Of  three  that  were 


collected  during  the  2  h  immediately  before  mid- 
night, two  had  empty  stomachs,  and  the  third  con- 
tained a  few  well-digested  fragments.  Of  four 
collected  during  the  hour  immediately  before 
daybreak,  two  had  empty  stomachs,  and  two  con- 
tained only  well-digested  fragments.  Thus,  there 
was  no  evidence  of  recent  feeding  by  individuals 
taken  after  dark.  In  contrast,  all  19  specimens 
collected  during  the  day  had  full  stomachs,  includ- 
ing fresh  material,  as  listed  in  Table  34. 

The  major  food  item,  scleractinian  corals 
(mostly  Pocillopora),  included  many  skeletal 
fragments. 

CONCLUSION. — Chaetodon  unimaculatus 
feeds  during  the  day,  mostly  on  the  coral 
Pocillopora. 

Chaetodon  multicinctus  Garrett — 
pebbled  butterflyfish 

Chaetodon  multicinctus  is  probably  the  most 
numerous  chaetodontid  on  Kona  reefs  in  water 


972 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  34. — Food  of  Chaetodon  unimaculatus. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  19) 

diet  volume 

mdex 

1 

Scleractinian  corals 

15 

45.3 

35.76 

2 

Sponges 

5 

12.4 

3.26 

3 

Gammaridean  amphlpods 

4 

1.3 

0.27 

4 

Pelycypods 

1 

3.2 

0.17 

5 

Sipunculid  introverts 

1 

1.6 

0.08 

6 

Calanoid  copepods 

2 

0.3 

0.03 

Also, 

unidentified  fragments 
Algal  fragments 

18 

29.1 

27.57 

and  diatoms 

9 

6.8 

3.22 

Table  35.— 

Food  of  Chaetodon  multicinetus. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  11) 

diet  volume 

index 

1 

Scleractinian  coral 

polyps 

11 

91.6 

91.60 

2 

Gammaridean  amphipods 

7 

1.8 

1.15 

3 

Sipunculid  introverts 

5 

1.3 

0.59 

4 

Polychaetes  (fragments 

and  tentacles) 

3 

0.4 

0.11 

5 

Hydroids 

2 

0.2 

0.04 

6 

Calanoid  copepods 

1 

0.1 

001 

Also, 

unidentified  fragments 
Algal  fragments 

2 

3.4 

0.62 

and  diatoms 

6 

1.2 

0.66 

shallower  than  20  m,  especially  where  stony  cor- 
als abound.  During  the  day  it  generally  occurs  in 
pairs,  and  is  active  close  to  the  reef,  often  picking 
at  living  corals — both  Pontes  and  Pocillopora.  At 
night  it  rests  close  among  cover  on  the  reef,  alert 
but  apparently  inactive. 

Of  the  26  specimens  (84:  78-94  mm)  examined, 
all  15  that  were  collected  at  night  (between  4  h 
after  sunset  and  first  morning  light)  were  empty, 
whereas  all  11  that  were  collected  during  midday 
were  full  of  food  (including  fresh  material),  as 
listed  in  Table  35. 

More  so  than  the  other  butterflyfishes  that  feed 
on  stony  corals,  C.  multicinetus  does  so  without 
also  taking  fragments  of  the  surrounding  skele- 
ton. 

CONCLUSION. — Chaetodon  multicinetus  is  a 
diurnal  predator  that  feeds  primarily  on  sclerac- 
tinian corals  (mostly  Pontes  and  Pocillopora) . 

Chaetodon  ornatissimiis  Solander — 
ornated  butterflyfish 

This  butterflyfish  is  numerous  over  coral-rich 
reefs,  generally  swimming  in  pairs  during  the 
day.  It  moves  from  one  growth  of  coral  to  another, 
locating  and  working  its  mouth  over  abrasions  on 
the  surface  of  the  coral.  In  this  way  it  feeds  on  a 


variety  of  scleractinian  corals,  including  Pontes, 
Pauona,  and  Cyphastrea.  At  night  it  rests  quiet, 
but  alert,  close  among  cover  on  the  reef.  Its  day- 
time and  nighttime  colorations  differ  strikingly 
(Figure  29a  and  b). 

Nineteen  specimens  (119:  95-140  mm)  were 
examined.  All  eight  that  were  collected  at  night, 
later  than  4  h  after  sunset  and  before  first  morning 
light,  had  the  stomachs  and  anterior  half  of  the 
intestines  empty.  All  four  that  were  taken  during 
morning  twilight — the  earliest  25  min  before 
sunrise — had  material  in  their  stomachs,  but 
their  intestines  were  empty  (apparently  they  had 
just  begun  to  feed).  Finally,  all  seven  that  were 
collected  during  midday  were  full  of  food. 

All  11  specimens  with  material  in  their 
stomachs  contained  only  a  thick  mucus  rich  in 
nematocysts,  zooxanthellae,  and  organic  debris 
(mean  percent  of  diet  volume  and  ranking  index: 
99.8).  The  balance  of  the  gut  contents  was  made  up 
of  diatoms  and  a  few  algal  fragments. 

It  is  well  known  that  stony  corals  increase  their 
production  of  mucus  when  injured,  so  this 
chaetodontid's  habit  of  seeking  out  abrasions  on 
coral  may  explain  why  its  gut  contents  include  so 
much  mucus.  This  species  probably  obtains 
significant  nourishment  from  coral  mucus,  but 
judging  from  the  numbers  of  zooxanthellae  and 


973 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  29.— Chaetodon  ornatissimus,  a  butterflyfish:  a,  showing  its  diurnal  coloration  while  swimming  above  the 
reef  during  the  day;  b,  showing  its  nocturnal  coloration  while  close  to  the  reef  at  night. 


974 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


nematocysts  present,  at  least  some  coral  tissue  is 
also  taken  (although  nothing  was  found  recogniz- 
able as  such).  Presumably  at  least  much  of  this 
material  had  been  freshly  ingested,  because  it 
came  from  individuals  that  were  actively  feeding 
when  collected.  Johannes  (1967)  and  Coles  and 
Strathman  (in  press)  have  shown  there  are 
significant  quantities  of  organic  material  in  coral 
mucus  that  could  nourish  a  wide  range  of  animals, 
including  fishes.  A  similar  butterflyfish, 
Chaetodon  trifasciatus ,  not  numerous  in  Kona, 
has  feeding  behavior  similar  to  C.  ornatissimus. 

CONCLUSION. — Chaetodon  ornatissimus  is  a 
diurnal  fish  that  feeds  on  coral  during  the  day, 
obtaining  significant  nourishment  from  coral 
mucus. 

Chaetodon  aiiriga  Forskal 

In  Kona  this  chaetodontid  is  less  abundant  than 
many  of  its  congeners.  Generally  paired,  it  swims 
close  to  the  reef  in  daylight,  occasionally  picking 
at  objects  on  the  sea  floor.  At  night  it  is  alert  close 
among  ledges  and  other  reef  irregularities. 

All  six  specimens  (151:  132-160  mm)  collected 
had  full  stomachs  including  four  taken  during  the 
afternoon  and  two  taken  on  a  dark  night,  3  h  after 
sunset.  All  these  specimens  contained  similar 
prey  in  what  seemed  similar  condition.  The  data 
are  too  few  to  draw  conclusions  regarding  noctur- 
nal activity,  but  suggest  that  this  species  may  feed 
after  dark.  Items  in  the  stomachs  of  these  six 
specimens  are  listed  in  Table  36. 


Most  of  the  food  items  were  fragmented,  includ- 
ing the  unidentified  material,  and  many  of  them 
were  relatively  fresh.  Clearly,  this  chaetodontid 
obtains  most  of  its  food  by  tearing  pieces  from 
larger  sessile  organisms.  Hiatt  and  Strasburg 
(1960)  found  similar  prey  in  C.  auriga  from  the 
Marshall  Islands. 

CONCLUSION. — Chaetodon  auriga  preys  on  a 
wide  variety  of  benthic  organisms  during  the  day, 
obtaining  most  of  its  food  by  tearing  off  pieces  of 
larger  sessile  animals.  It  also  seems  to  feed  to 
some  extent  after  dark. 

Chaetodon  fremblii  Bennett — 
blue-striped  butterflyfish 

This  butterflyfish  is  most  numerous  where  large 
basalt  boulders  are  interspersed  with  small  pock- 
ets of  sand.  Sometimes  paired,  but  more  often  sol- 
itary, this  chaetodonid  picks  at  objects  on  the 
rocks  and  in  the  sand  during  the  day.  At  night  it 
occurs  close  among  cover,  alert  but  seemingly  in- 
active. 

Fourteen  specimens  (103:  86-120  mm)  were 
speared  during  day  and  night.  All  eight  collected 
during  the  afternoon  had  full  stomachs,  whereas 
the  two  taken  from  among  rocks  at  night,  between 
4  and  5  h  after  sunset,  were  empty.  On  the  other 
hand,  three  others  collected  together  among  the 
rocks  during  morning  twilight,  about  25  min  be- 
fore sunrise  after  a  moonless  night,  had  material 
in  their  stomachs.  Two  of  them  contained  only  a 
few  well-digested  fragments  that  could  have  been 


Table  36. — Food  of  Chaetodon  auriga. 


No  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  6) 

diet  volume 

index 

1 

Alcyonarians 

5 

31.0 

25.83 

2 

Terebellid  polychaete 

tentacles 

6 

18.4 

18.40 

3 

Gastropod  egg  masses 

6 

88 

8.80 

4 

Errant  polychaete 

fragments 

5 

5.4 

4.50 

5 

Sabellld  polychaete 

radioles 

4 

2.2 

1.47 

6 

Echlnold  podia 

4 

2.0 

1.33 

7 

Caridean  shrimps 

4 

1.4 

0.93 

8 

Anemones 

1 

4.0 

0.67 

9 

Sponges 

1 

3.1 

0.52 

10 

Sipunculid  introverts 

3 

0.4 

0.20 

11 

Gammaridean  amphipods 

3 

0.4 

0.20 

12 

Hydroids 

1 

0.2 

0.03 

13 

Serpulid  polychaete 

fragments 

1 

0.2 

0.03 

Also. 

Unidentified  fragments 

6 

20.7 

20.70 

Algal  fragments 

3 

1.8 

0.90 

975 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


taken  the  previous  day,  but  in  the  third  individual 
a  wide  variety  of  differentially  digested  items  in- 
dicated either  nocturnal  feeding  or  unusually  slow 
digestion.  A  fourth  individual  taken  during  morn- 
ing twilight  was  empty.  Items  in  the  eight  speci- 
mens containing  identifiable  material,  much  of  it 
fragments  torn  from  larger  sessile  animals,  are 
listed  in  Table  37. 

CONCLUSION. — Chaetodon  fremblii  preys  on 
a  wide  variety  of  benthic  organisms  during  the 
day,  obtaining  much  of  its  food  by  tearing  off 
pieces  of  larger  sessile  animals.  With  some  un- 
certainty, it  seems  largely  inactive  after  dark. 

Chaetodon  lunula  (Lacepede) — 
masked  butterflyfish 

This  butterflyfish,  one  of  the  more  numerous  in 
Kona,  is  most  abundant  where  a  coral-crested  reef 
face  falls  among  basalt  boulders,  yet  occurs  in  a 
variety  of  habitats.  Setting  it  apart  from  all  other 
chaetodontids  reported  here,  I  never  saw  this 
species  feed  during  the  day.  It  generally  hovers 
close  to  the  reef  in  daylight,  sometimes  solitary,  or 
in  twos  or  threes,  and  often  in  large  aggregations 
(Figure  30).  These  aggregations  form  day  after 
day  in  the  same  locations,  and  several  occurred  in 
the  same  places  over  the  entire  15-mo  period  of  the 
study.  The  aggregations  disperse  at  nightfall,  and 
after  dark  the  species  scatters  over  the  reef,  either 
solitarily,  or  in  twos  or  threes. 

Of  the  26  specimens  (134:  112-150  mm)  ex- 
amined, all  14  speared  at  night  (more  than  4  h 
after  sunset),  or  during  morning  twilight,  had 
stomachs  full  of  food  in  varying  stages  of  diges- 
tion, much  of  it  fresh;  the  other  12  were  collected 


during  afternoons  (some  from  the  daytime  ag- 
gregations), and  although  they  too  had  full 
stomachs,  the  contents  generally  were  further  di- 
gested. There  was  no  recognizable  difference  in 
the  composition  of  the  diet  between  specimens  col- 
lected during  each  of  these  three  periods.  Items  in 
the  stomachs  are  listed  in  Table  38. 

Clearly,  C.  lunula,  like  C.  auriga  and  C.  fremb- 
lii, habitually  tears  pieces  off  the  bodies  of  larger 
sessile  animals,  but,  more  so  than  the  others,  also 
takes  whole  organisms.  In  fact,  its  major  prey, 
based  on  these  data,  are  opisthobranch  gas- 
tropods, which  it  takes  whole.  The  opisthobranchs 
are  mostly  one  form  of  Anaspidea  and  one  form  of 
Cephalaspidea.  Significantly,  all  individuals  of  C 
lunula  that  contained  what  seemed  to  be  freshly 
ingested  opisthobranchs  were  speared  at  night. 
Opisthobranchs  in  C.  lunula  speared  during  the 
afternoon  were  consistently  far  digested.  These 
opisthobranchs  are  mostly  about  4  to  10  mm  long, 
and  are  relatively  solid  pieces  of  meat  that  may 
take  longer  to  digest  than  many  other  kinds  of 
food.  Similarly,  the  polychaete  heads  and  proso- 
branch  gastropod  heads  taken  by  this  fish  are  rela- 
tively dense  pieces  of  meat  that  probably  resist 
digestion  (the  shells  of  the  prosobranch  gastropods 
were  never  present — only  the  heads,  which  this 
butterflyfish  apparently  is  adept  at  snipping  off). 
Smaller  organisms  that  would  be  rapidly  digested 
like  the  amphipods  and  isopods,  generally,  but 
with  two  exceptions,  were  absent  in  specimens 
speared  during  the  afternoon.  Generally  then,  the 
stomach  contents  appeared  to  have  been  taken 
mostly  at  night.  Finally,  it  may  be  significant  that 
the  eyes  of  C  lunula  are  relatively  larger  than  the 
eyes  of  all  other  species  of  this  genus  studied  at 
Kona. 


Table  37. — Food  of  Chaetodon  fremblii. 


Nc 

.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  8) 

diet  volume 

index 

1 

Terebellid  polychaete 

tentacles 

6 

25.0 

18.75 

2 

Sipunculid  introverts 

6 

15.0 

11.25 

3 

Gammarldean  amphipods 

8 

10.1 

10.10 

4 

Errant  polychaete 

fragments 

4 

3.1 

1.55 

5 

Hydroids 

2 

2.9 

0.73 

6 

Isopods 

3 

1.6 

0.60 

7 

Gastropod  egg  capsules 

3.6 

0.45 

8 

Caprellid  amphipods 

2.3 

0.29 

9 

Acorn  worms 

2.3 

0.29 

10 

Opisthobranch  gastropods 

1.4 

0.18 

11 

Caridean  shrimps 

0.1 

0.01 

12 

Gastropod  opercula 

0.1 

0.01 

Also, 

unidentified  fragments 

6 

21.3 

15  98 

Algal  fragments 

7 

11,2 

9.80 

976 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


iJi^jMf^ 


Figure  30. — Diurnal  aggregation  of  Chaetodon  lunula,  a  butterflyfish. 


Table  38. — Food  oi  Chaetodon  lunula. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  26) 

diet  volume 

Index 

1 

Opisthobranch  gastropods 

21 

29.2 

23.58 

2 

Terebellld  polychaete 

tentacles 

11 

8.7 

3.68 

3 

Errant  polychaete 

fragments 

17 

2.2 

1.44 

4 

SIpunculid  mtroverts 

9 

1.7 

0.59 

5 

Polychaete  heads 

8 

1.9 

0.58 

6 

Prosobranch  gastropod 

heads 

7 

0.7 

0.19 

7 

Gammaridean  amphlpods 

9 

0.3 

0.10 

8 

Holothurlans 

2 

1.3 

0.10 

9 

Fish  eggs 

2 

1.1 

0.08 

10 

Caridean  shrimps 

4 

0.3 

0.05 

11 

Echinoid  podia 

4 

0.2 

0.03 

12 

Alcyonanans 

2 

0.3 

0.02 

13 

Sabellid  polychaete 

radioles 

3 

0.2 

002 

14 

Caprellid  amphlpods 

3 

0.1 

0.01 

15 

Crustacean  eggs 

1 

0.2 

<0.01 

16 

Tanaids 

2 

0.1 

<0.01 

17 

Hydrolds 

2 

0.1 

<0.01 

18 

Anemones 

1 

0.1 

<0.01 

19 

Calanoid  copepods 

1 

0.1 

<0.01 

20 

Crabs 

1 

0.1 

<0.01 

21 

Tunicates 

1 

0.1 

<0.01 

Also. 

unidentified  fragments 

24 

50.3 

43.43 

Algal  fragments 

5 

0.5 

0.10 

Crustacean  fragments 

4 

0.2 

0.03 

977 


i 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Hiatt  and  Strasburg  (1960)  noted  only  tips  of 
coral  polyps  in  one  C.  lunula  from  the  Marshall 
Islands.  Although  the  diet  of  this  individual  di- 
verges sharply  from  that  of  representatives  in 
Kona,  one  cannot  speculate  on  its  significance 
from  one  specimen. 

CONCLUSION. — Chaetodon  lunula  preys  on 
benthic  invertebrates,  especially  opisthobranchs, 
at  night. 

General  Remarks  on  Angelfishes 
and  Butterflyfishes 

The  two  Hawaiian  angelfishes,  Holacanthus  ar- 
cuatus  and  C entropy ge potter i,  have  feeding  habits 
that  set  them  apart  from  the  butterflyfishes. 
Holacanthus  arcuatus  is  the  only  chaetodontid 
that  feeds  strictly  on  sponges,  and  C.  potteri  is  the 
only  one  that  takes  just  algae  and  detritus.  Thus 
the  Hawaiian  situation  parallels  that  in  the  tropi- 
cal Atlantic,  where  species  o^ Holacanthus  and  of 
Pomacanthus  (another  genus  of  angelfish)  feed 
mostly  on  sponges  and  where  species  of 
Centropyge  feed  almost  exclusively  on  algae  and 
detritus  (Randall,  1967).  Similarly,  Hiatt  and 
Strasburg  (1960)  reported  a  strictly  herbivorous 
diet  for  C.  flavissimus  in  the  Marshall  Islands. 

Although  butterflyfishes  in  Kona  are  more 
strictly  predators  in  the  conventional  sense  than 
are  the  angelfishes,  Hiatt  and  Strasburg  (1960) 
reported  Chaetodon  reticulatus  in  the  Marshall 
Islands  to  be  strictly  herbivorous.  That  species  is 
seen  only  occasionally  in  Kona,  and  so  was  not 
included  in  the  present  study.  Otherwise,  Hiatt 
and  Strasburg  found  scleractinian  corals  and 
polychaetes  to  be  the  major  food  of  butterflyfishes 
in  the  Marshall  Islands,  and  this  is  in  broad  accord 
with  the  habits  of  certain  species  in  Kona.  Randall 
(1967)  reported  that  West  Indian  butterflyfishes 
feed  primarily  on  anthozoans  and  the  tentacles  of 
polychaetes,  again  paralleling  the  habits  of  cer- 
tain Kona  species.  On  the  other  hand,  the  number 
of  planktivorous  butterflyfishes  in  Kona  seems  on 
a  scale  without  parallel  in  published  accounts  of 
other  reef  areas. 

Chaetodontids  have  been  widely  described  as 
diurnal  fishes,  e.g.  in  the  tropical  Atlantic  (Starck 
and  Davis,  1966;  Collette  and  Talbot,  1972),  and  in 
the  Gulf  of  California  (Hobson,  1965,  1968a).  Al- 
though diurnal  habits  are  generally  characteristic 
of  chaetodontids  in  Kona,  the  fact  that  at  least  one, 
Chaetodon  lunula,  is  nocturnal  and  that  several 


others  feed  at  least  somewhat  after  dark  may 
reflect  increased  interspecific  pressures  associated 
with  the  large  number  of  Chaetodon  species  on 
Kona  reefs.  I  treat  the  nine  most  numerous  species 
of  Chaetodon  here,  but  also  saw  five  others  during 
this  study. 


Family  Pomacentridae:     damselfishes 


Plectroglyphidodon  johnstonianiis 
Fowler  and  Ball 

This  solitary  species  is  most  numerous  where 
stony  corals  abound.  During  the  day  it  swims  close 
to  the  reef,  each  individual  seemingly  associated 
with  a  particular  location,  and  here  it  picks  fre- 
quently at  the  substratum,  especially  around 
coral.  At  night  it  is  secreted  deep  among  the  coral, 
relatively  inactive,  but  alert. 

Of  the  eight  specimens  (60:  39-70  mm)  ex- 
amined, the  stomachs  of  two  that  were  speared 
among  the  coral  shortly  before  dawn  contained 
only  a  few  well-digested  fragments  (probably 
material  that  had  been  ingested  during  the  previ- 
ous day),  whereas  the  stomachs  of  all  six  taken 
during  midday  were  full  of  food,  much  of  it  fresh. 

The  major  food  item  in  all  six  was  anthozoans: 
nematocysts  and  zooxanthellae,  with  tissue 
fragments  and  mucus,  but  no  skeletal  material 
(mean  percent  of  diet  volume  and  ranking  index: 
94.3).  All  other  items  made  up  only  a  minor  part  of 
the  diet:  algal  fragments  in  three  (mean  percent  of 
diet  volume:  2;  ranking  index:  1),  sipunculid  in- 
troverts in  one  (mean  percent  of  diet  volume:  0.2; 
ranking  index:  0.03),  and  unidentified  fragments 
in  four  (mean  percent  of  diet  volume:  3.5;  ranking 
index:  2.33).  Because  P .  johnstonianus  is  closely 
associated  with  scleractinian  corals,  these  proba- 
bly are  the  anthozoans  so  prominent  in  its  diet. 
However,  specific  identifications  of  the  frag- 
mented gut  contents  remain  uncertain,  and  be- 
cause direct  observations  of  feeding  are  limited, 
other  anthozoans  may  also  be  involved.  In  any 
event,  the  observations  indicate  that  this  fish  is 
adept  at  snipping  off  pieces  of  anthozoan  tissue 
and  mucus  without  taking  any  of  the  surrounding 
skeletal  material. 

CONCLUSION.— P/ec^ro^/jp^irforfon  john- 
stonianus is  a  diurnal  predator  that  feeds  chiefly 
on  anthozoans. 


978 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 

Pomacentrus  jenkinsi  Jordan  and  Evermann 

This  species  is  one  of  the  more  widespread  and 
numerous  in  Kona,  especially  in  relatively  quiet 
water  over  coral  and  rocks.  During  the  day,  indi- 
viduals are  scattered  among  reef  irregularities, 
each  seemingly  associated  with  specific  locations, 
and  here  they  pick  at  coral  and  rock  surfaces.  At 
night  they  hover  under  cover,  remaining  alert  but 
relatively  inactive  until  shortly  after  first  light, 
when  diurnal  activity  is  resumed. 

Twenty-two  specimens  (89:  80-100  mm)  were 
collected  during  day  and  night.  All  12  that  were 
speared  as  they  swam  close  to  the  reef  during 
midday  were  full  of  food,  much  of  it  fresh,  whereas 
of  5  that  were  speared  in  reef  crevices  at  night 
(between  4  and  5  h  after  last  evening  light),  the 
stomachs  of  3  were  empty  and  those  of  the  other  2 
contained  only  a  few  well-digested,  unidentified 
fragments.  Finally,  of  five  active  individuals  that 
were  collected  during  morning  twilight  and  dur- 
ing the  first  30  min  after  sunrise,  two  were  empty, 
and  three  contained  in  their  stomachs  a  few  fresh 
fragments  that  appeared  to  have  been  recently 
ingested.  The  15  specimens  that  contained  at  least 
some  fresh  material  had  consumed  the  items 
listed  in  Table  39. 

The  amorphous  organic  fragments  that  consti- 
tuted the  bulk  of  the  gut  contents  in  this  fish  were 
in  part  items  that  had  been  digested  beyond  rec- 
ognition; however,  most  of  this  material  appeared 
to  be  detritus — organic  deposits — that  had  been 
scraped  from  the  reef.  Gosline  and  Brock  (1960) 
noted  that  P.jenkinsi  inhabits  quiet  water,  where 
it  feeds  on  algae,  and  perhaps  detritus.  Hiatt  and 
Strasburg  (1960)  also  found  this  fish  in  quiet 
water  in  the  Marshall  Islands  and  reported  it  to  be 
primarily  a  herbivore  that  feeds  occasionally  on 
small  fishes. 


CONCLUSION. — Pomacentrus  jenkinsi  is  a 
diurnal  omnivore  that  takes  mostly  organic  de- 
tritus, algae,  and  small  animals  from  reef  sur- 
faces. 

Abiidefdiif  sindonis  (Jordan  and  Evermann) 

This  damselfish  occurs  where  basalt  boulders 
are  swept  by  a  strong  surge.  Activity  is  limited  to 
daylight;  at  night  it  remains  under  cover  among 
the  rocks. 

All  five  specimens  (91:  81-102  mm)  were 
speared  during  the  day,  and  their  guts  were  full  of 
the  material  listed  in  Table  40,  much  of  it  fresh. 
The  amorphous  organic  fragments,  the  major  food 
item,  probably  are  largely  detritus  from  the  reef, 
such  as  is  also  taken  by  Pomacentrus  jenkinsi, 
discussed  above.  Where  a  strong  surge  sweeps  the 
boulder  habitat,  A.  sindonis  replaces  P.jenkinsi 
in  depths  shallower  than  about  3  m. 

Gosline  and  Brock  ( 1960)  noted  that  A.  sindonis 
seems  restricted  to  surge  areas  among  lava  rocks 
and  appears  to  be  omnivorous. 

CONCLUSION. — Ahudefduf  sindonis  is  a  diur- 
nal omnivore  that  takes  mostly  organic  detritus, 
algae,  and  small  animals  from  the  substratum. 


Abudefduf  sordidus  (Forskal) — kiipipi 

Although  juveniles  of  A.  sordidus  are  promi- 
nent in  tide  pools,  the  adults,  which  are  the  largest 
of  the  Hawaiian  pomacentrids,  seem  to  occur  only 
where  a  precipitous  basalt  reef  face  confronts  a 
prevailing  swell.  In  this  situation  large  individu- 
als of  this  species  are  fairly  numerous  among 
rocky  crevices  and  close  to  boulders  at  the  base  of 
the  reef.  Generally  a  solitary  fish,  A.  sordidus  is 


Table  39. — Food  of  Pomacentrus  jenkinsi. 


No.  fish 

Mea 

n  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  1 5) 

diet  volume 

index 

1 

Algae. 

Including  diatoms 

15 

24.1 

24.10 

2 

Sponges 

6 

5.7 

2.28 

3 

Calanoid  copepods 

1 

4.6 

0.31 
0  27 

4 

Errant  polychaetes 

2 

2.0 

5 

Fish  eggs,  demersal 

2 

1.0 

0,13 

6 

Cyclopoid  copepods 

4 

0.4 

0,11 

7 

Gammaridean  amphlpods 

2 

0.2 

0,03 

8 

Barnacle  cirri 

1 

0.1 

<0,01 

9 

Pelecypod  mollusks 

1 

0.1 

<0.01 

Also. 

amorDhous  oraanic 

fraQ 

ments 

15 

60,1 

60.10 

Sand 

4 

1,7 

0,45 

979 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  40. — Food  of  Abudefduf  sindonis. 


No.  fish 

Mean  percent 

with  this 

of 

Rankmg 

Rank 

Items 

item  [n  =  5) 

diet  volume 

mdex 

1 

Algae, 

including  diatoms 

5 

39.4 

39.40 

2 

Polychaetes 

4 

2.2 

1.76 

3 

Gammaridean  amphipods 

4 

2.2 

1.76 

4 

Caridean  shrimps 

1 

7.0 

1.40 

5 

Cyclopoid  copepods 

4 

1.0 

0.80 

6 

Hydroids 

1 

1.0 

0.20 

7 

SipuncuMd  introverts 

1 

0.2 

0.04 

8 

Insects 

1 

02 

0.04 

Also. 

amorphous  organic 

fragments 

5 

46.8 

4680 

Table  41.- 

—Food  of  Abudefduf  sordidus. 

No,  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  5) 

diet  volume 

index 

1 

Algae, 

including  diatoms 

5 

35.0 

35.00 

2 

Crabs 

4 

20.0 

16.00 

3 

Sponges 

4 

12.2 

9.76 

4 

Prosobranch  gastropods 

4 

9.2 

7.36 

5 

Gammaridean  amphipods 

5 

4.4 

4.40 

6 

Prosobranch  gastropod 

eggs 

2 

1.2 

0.48 

7 

Tanaids 

3 

0.6 

0.36 

8 

Hydroids 

2 

04 

0.16 

9 

Bryozoans 

2 

04 

0.16 

10 

Polychaetes 

2 

0.4 

0.16 

11 

Pycnogonids 

2 

04 

0.16 

12 

Insects 

1 

0.4 

0.08 

Also. 

unidentified  fragments 

5 

15.4 

1540 

active  only  during  daylight,  close  to  the  sub- 
stratum. After  dark  it  is  secreted  under  rocky 
cover,  alert  but  relatively  inactive. 

All  five  specimens  (147:  129-160  mm)  were 
speared  during  midday,  and  their  guts  were  full  of 
the  material  listed  in  Table  41,  much  of  it  fresh. 
Gosline  and  Brock  ( 1960)  reported  that  the  young 
of  A.  sordidus  are  very  prominent  tide-pool  in- 
habitants and  that  the  omnivorous  adults  appar- 
ently live  just  outside  of  the  reef  edge. 

CONCLUSION.— Abudefduf  sordidus  is  a  diur- 
nal omnivore  that  takes  chiefly  algae  and  small 
animals  from  the  substratum. 

Abudefduf  itnparipennis  (Sauvage) 

This  pomacentrid  is  numerous  on  shallow, 
surge-swept  reefs  where  exposed  basalt  is  dotted 
by  the  coral  Pocillopora  meandrina.  It  is  a  soli- 
tary, bright-eyed  little  fish  that  is  active  in  day- 
light, and  does  not  swim  away  from  the  sub- 
stratum. Appearing  tense  and  alert,  even  when 
hovering  motionless  at  the  base  of  a  coral  head,  its 


movements  are  short  but  rapid  darts  from  one  spot 
to  another.  At  night  it  takes  shelter  deep  within 
reef  crevices. 

All  15  specimens  (42:  29-50  mm)  were  active  on 
the  reef  during  the  day  when  collected,  and  all 
contained  food,  including  fresh  material,  as  listed 
in  Table  42.  Goshne  and  Brock  (1960)  noted  that 
this  fish  seems  to  occur  over  all  rocky  areas  in  the 
surge  zone,  and  that  it  appears  to  be  entirely  car- 
nivorous, with  the  predominant  food  organism 
being  a  polychaete  annelid. 

CONCLUSION. — Abudefduf  imparipennis  is  a 
diurnal  predator  that  feeds  mainly  on  small 
benthic  crustaceans  and  polychaetes. 


Abudefduf  abdoniinalis  (Quoy  and  Gaimard) — 
maomao 

This  damselfish  is  most  numerous  where  basalt 
boulders  lie  at  the  base  of  a  vertical  reef  face  in 
water  5  to  10  m  deep.  During  daylight  it  hovers  in 
aggregations  high  in  the  water  column  close  to  the 


980 


HOBSON;  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  42. — Food  of  Abudefduf  imparipennis. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  15) 

diet  volume 

index 

1 

Gammaridean  amphipods 

12 

12.6 

10.08 

2 

Polychaetes 

7 

17.6 

8.21 

3 

Cyclopoid  copepods 

9 

7.1 

4.26 

4 

Sipunculid  introverts 

8 

1.9 

1.01 

5 

Fish  eggs,  demersal 

3 

3.1 

0.62 

6 

Unidentified  eggs. 

demersal 

4 

1.8 

0.48 

7 

Opisthobranch  gastropods 

2 

1.7 

0.23 

8 

Diatoms 

6 

0.5 

0.20 

9 

Algae  fragments 

2 

0.8 

0.11 

10 

Prosobrancfi  gastropod  eggs 

1 

0.8 

0.05 

11 

Isopods 

2 

0.4 

0.05 

12 

Sponge  spicules 

0.3 

0.02 

13 

Caprellid  ampfiipods 

<0.1 

<0.01 

14 

Harpacticoid  copepods 

<0.1 

<0.01 

15 

Caridean  sfinmps 

<0.1 

<0.01 

16 

Mites 

<0.1 

<0.01 

17 

Insects 

<0.1 

<0.01 

Also, 

unidentified  fragments 

15 

50.9 

50.90 

Table  43. — Food  of  Abudefduf  abdominalis. 

No   fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  10) 

diet  volume 

index 

1 

Calanoid  copepods 

10 

54.0 

54.00 

2 

Cyclopoid  copepods 

8 

6.5 

5.20 

3 

Fragments  of  algae 

2.6 

1.04 

4 

Fish  eggs,  planktonic 

2.0 

0.80 

5 

Polychaetes 

1.9 

0.76 

6 

Decapod  shrimps 

1.7 

0.68 

7 

Larvaceans 

4.0 

0.40 

8 

Harpacticoid  copepods 

0.8 

0.32 

9 

Gelatinous  clumps  of 

blue-green  algae 

2 

1.3 

0.26 

10 

Pelecypod  larvae 

2 

0.2 

0.04 

11 

Penaeid  shrimp  larvae 

1 

0.2 

0.02 

12 

Gastropod  veligers 

1 

0.1 

0.01 

13 

Naupilius  larvae 

1 

0.1 

0-01 

Also, 

unidentified  fragments 

9 

246 

22.14 

reef,  where  it  picks  organisms  from  the  plankton. 
Although  members  of  an  aggregation  are  close  to 
one  another,  each  feeds  independently.  The  plank- 
ters  are  taken  with  what  seems  to  be  a  visually 
directed  action  in  which  the  fish  suddenly  thrusts 
both  jaws  forward,  then  immediately  retracts 
them.  Presumably  the  sudden  expansion  of  the 
oral  cavity  sucks  the  prey  in. 

A  given  aggregation  maintains  station  over  a 
particular  location  although  its  position  in  the 
water  column  is  influenced  by  several  factors.  Fish 
size  is  important,  because  the  larger  individuals 
tend  to  be  farther  above  the  reef  than  the  smaller 
ones.  Prevailing  light  is  another  factor;  thus, 
when  clouds  pass  in  front  of  the  sun,  and  light 
diminishes,  individuals  of  all  sizes  descend  closer 
to  the  reef.  In  addition,  the  appearance  of  a  large 
predator,  or  some  other  disturbance,  intermit- 
tently sends  this  fish  diving  to  cover  on  the  reef. 


However,  after  such  an  event  it  quickly  returns  to 
its  feeding  stations  in  the  water  column. 

As  light  progressively  fades  late  in  the  day,  this 
species  gradually  descends  to  the  reef  so  that  by 
evening  twilight  it  is  sheltered  among  the  coral 
(Hobson,  1972).  On  dark  nights  it  remains  under 
cover,  relatively  inactive  but  alert;  however, 
under  bright  moonlight  it  swims  in  exposed  posi- 
tions close  to  the  reef.  Then,  during  morning 
twilight,  it  begins  to  ascend  to  its  daytime  feeding 
stations  in  the  water  column  (Hobson,  1972). 

Of  14  specimens  ( 142:  105- 162  mm)  examined, 
the  4  that  were  speared  as  they  hovered  among  the 
rocks  on  dark  nights  (between  4  and  6  h  after 
sunset)  contained  only  well-digested  fragments, 
whereas  all  10  that  were  speared  from  mid-water 
aggregations  during  afternoons  had  their  stomach 
full  of  food  (including  much  fresh  material),  as 
listed  in  Table  43. 


981 


CONCLUSION.— Abudefduf  abdominalis  is  a 
diurnal  planktivore  that  preys  primarily  on 
copepods. 

Dascyllus  albisella  Gill 

Where  corals  are  abundant,  this  damselfish  is 
numerous  to  depths  of  at  least  35  m.  During  day- 
light, it  aggregates  in  the  water  column  and  picks 
small  organisms  from  the  plankton,  much  as  does 
Abudefduf  abdominalis ,  described  above,  and  its 
aggregations  rise  and  fall  in  the  water  column  in 
response  to  the  same  variables  that  influence  that 
species.  Also  like  A.  abdominalis,  D.  albisella 
descends  to  the  reef  during  evening  twilight  and 
spends  the  night  close  among  the  rocks — under 
cover  on  dark  nights,  and  in  exposed  positions 
when  there  is  moonlight. 

Twelve  specimens  (79:  42-95  mm)  were  col- 
lected during  day  and  night.  The  six  that  were 
speared  shortly  before  first  morning  light  as  they 
hovered  among  the  coral  contained  only  a  few 
well-digested  fragments  (five  were  taken  after 
nights  of  bright  moonlight,  one  after  a  dark  night). 
On  the  other  hand,  the  six  that  were  collected  from 
aggregations  in  the  water  column  during  after- 
noons had  stomachs  full  of  food,  including  much 
fresh  material  as  listed  in  Table  44. 

Gosline  and  Brock  (1960)  reported  that  D.  al- 
bisella occurs  in  small  schools  around  certain 
large  coral  heads  and  listed  stomach  contents  as 
follows:  shrimp  and  crab  larvae,  mysids,  and 
calanoid  copepods. 

CONCLUSION.— Dascy//us  albisella  is  a  diur- 
nal planktivore  that  takes  primarily  larvaceans 
and  copepods. 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

Chromis  vanderhilti  (Fowler) 

This,  the  smallest  pomacentrid  in  Kona,  is 
numerous  where  exposed  basalt  ledges  are  inter- 
spersed with  coral.  During  the  day  it  aggregates  in 
the  water  column,  but  even  under  bright  sunlight 
rarely  moves  more  than  50  cm  above  the  reef  On 
overcast  days  it  generally  remains  sheltered,  and 
shortly  before  sunset  is  the  first  planktivorous 
damselfish  to  descend  to  cover  on  the  reef  (Hobson, 
1972).  At  night,  it  usually  remains  out  of  sight 
deep  within  reef  crevices,  and  in  the  morning  is 
the  last  pomacentrid  to  appear. 

All  12  specimens  (38:  17-46  mm)  taken  from 
feeding  aggregations  during  midday  had  stom- 
achs full  of  food,  including  fresh  material,  as 
listed  in  Table  45. 

CONCLUSION.— C/?rom/s  vanderbilti  is  a 
diurnal  planktivore  that  takes  primarily  copepods 
and  larvaceans. 

Chromis  leucurus  Gilbert 

Gosline  and  Brock  (1960)  considered  C. 
leucurus  to  include  two  distinct  color  phases:  in 
one  the  body  is  very  dark  anteriorly  and  abruptly 
white  posteriorly;  in  the  other,  the  whole  body, 
except  black  pectoral  base  and  white  caudal  fin,  is 
mostly  plain  orange-brown.  Although  I  followed 
this  judgment  when  making  the  fish  counts,  the 
probability  that  at  least  two  species  are  rep- 
resented, and  that  neither  one  may  in  fact  be  C. 
leucurus,  is  currently  under  study  by  John  E. 
Randall,  B.  P.  Bishop  Museum,  and  Stanley 
Swerdloff,  Government  of  American  Samoa.  In 
any  event,  the  specimens  collected  for  study  of  food 


Table  44.— Food  of  Dascvllus  albisella. 


No.  fish 

Mean  percent 

w/ith  this 

of 

Ranking 

Rank 

Items 

item  {n  =  6) 

diet  volume 

index 

1 

Larvaceans 

6 

43.1 

43.10 

2 

Calanoid  copepods 

6 

11.2 

11.20 

3 

Cyclopold  copepods 

6 

9.2 

9.20 

4 

Gelatinous  clumps  of 

blue-green  algae 

4 

7.2 

4.80 

5 

Fragments  of  algae 

4 

1.5 

1.00 

6 

Decapod  shrimp  larvae 

2 

2.2 

0.73 

7 

Fish  eggs,  planktonic 

2 

1.1 

037 

8 

Hydroid  fragments 

1 

0.2 

0.03 

9 

Pelecypod  larvae 

1 

0.2 

0.03 

10 

Gammaridean  amphipods 

1 

0.2 

0.03 

11 

Harpacticoid  copepods 

1 

0.2 

0.03 

Also, 

unidentified  fragments 

5 

23.7 

19.75 

982 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  45. — Food  of  Chromis  vanderhilti. 


N 

0.  fish 

Mean  percent 

Wl 

th  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  12) 

diet  volume 

index 

1 

Calanoid  copepods 

11 

30.5 

27.96 

2 

Larvaceans 

8 

21.7 

14.47 

3 

Cyclopold  copepods 

12 

8.8 

8.80 

4 

Polychaetes 

5 

0.9 

0.38 

5 

Fish  eggs,  planktonic 

4 

0.9 

0.30 

6 

Decapod  shrimps 

2 

1.7 

0.28 

7 

Harpacticoid  copepods 

3 

1.1 

0.28 

8 

Siphonophores 

1 

1.7 

0.14 

9 

Gelatinous  clumps  of 

blue-green  algae 

2 

0.5 

0.08 

10 

Ostracods 

1 

0.5 

0.04 

11 

Hyperiid  amphipods 

1 

0.1 

0.01 

Also, 

unidentified  fragments 

12 

31.1 

31.10 

habits,  below,  all  represent  the  orange-brown 
form. 

Of  the  two,  the  orange-brown  form  is  the  more 
numerous  in  Kona,  but  both  abound  over  coral- 
rich  reefs,  often  together  in  plankton-feeding  ag- 
gregations that  hover  within  1  m  of  the  sub- 
stratum during  the  day.  As  is  true  of  Abudefduf 
abdominalis  and  Dascyllus  albi sella,  described 
above,  C.  leucurus  remains  closer  to  the  reef  when 
light  is  diminished,  and  dives  to  cover  when 
threatened  (Figure  31).  At  night  it  generally  is  out 
of  sight  within  crevices. 


All  five  specimens  (57:  37-70  mm)  speared  dur- 
ing midday  had  their  stomachs  full  of  food,  includ- 
ing fresh  material,  as  listed  in  Table  46. 

Swerdloff  (1970a)  described  the  behavior  of  two 
spatially  related  species  of  Chromis  in  the  Mar- 
shall Islands,  C.  leucurus,  and  C.  dimidiatus,  and 
reported  their  food  to  be  calanoid  copepods,  fish 
eggs,  and  larval  tunicates. 

CONCLUSION. — Chromis  leucurus  is  a  diur- 
nal planktivore  that  takes  primarily  copepods 
and  larvaceans. 


Figure  31. — Members  of  an  aggregation  of  Chromis  leucurus,  a  damselfish,  having  been  threatened,  dive  from  their 
plankton-feeding  location  in  the  water  column  toward  shelter  among  the  coral  below. 


983 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  46. — Food  of  Chromis  leiiciirus. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  5) 

diet  volume 

index 

1 

Cyclopoid  copepods 

5 

19.0 

19.00 

2 

Larvaceans 

3 

22.0 

13.20 

3 

Calanoid  copepods 

3 

4.0 

2.40 

4 

Fish  eggs,  planktonic 

4 

2.8 

2  24 

5 

Gelatinous  clumps  of 

blue-green  algae 

3 

3.6 

2.16 

6 

Fragments  of  algae 

2 

2.0 

0.80 

7 

Harpacticoid  copepods 

1 

0.4 

0.08 

Also, 

unidentified  fragments 

5 

46.2 

46,20 

Table  47.- 

—Food  of  Chromis  verater 

No,  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  5) 

diet  volume 

index 

1 

Calanoid  copepods 

5 

29.6 

29.60 

2 

Larvaceans 

4 

36.0 

28.80 

3 

Cyclopoid  copepods 

5 

2.2 

220 

4 

Fish  eggs,  planktonic 

3 

2.4 

1,44 

5 

Decapod  shrimps 

7.0 

1,40 

6 

Siphonophores 

0.8 

0,16 

7 

Mysids 

0.4 

0.08 

8 

Chaetognaths 

0.4 

0.08 

9 

Polychaetes 

0.2 

0.04 

10 

Harpacticoid  copepods 

0.2 

0.04 

Also, 

unidentified  fragments 

5 

20.8 

20,80 

Chromis  verater  Jordan  and  Metz 

This  damselfish  is  one  of  the  more  prominent 
fishes  over  both  coral  and  basalt  reefs  in  Kona  at 
depths  below  about  15  m.  During  the  day  it  swims 
in  plankton-feeding  aggregations  that  hover  2  to  5 
m  above  the  reef,  where  changing  light  levels  and 
the  appearance  of  certain  predators  produce  ef- 
fects much  as  described  above  for  Abudefduf  ab- 
dominalis  and  other  planktivorous  pomacentrids. 
Also  as  in  these  other  species,  C  verater  passes  the 
night  among  cover  on  the  reef,  relatively  quiet  but 
alert.  It  moves  about  under  moonlight,  but  rests  in 
crevices  on  dark  nights. 

Of  the  seven  specimens  (120:  100-141  mm)  ex- 
amined, two  that  were  collected  from  among  cover 
on  the  reef  shortly  before  first  morning  light  (one 
after  a  night  of  bright  moonlight,  the  other  after  a 
dark  night)  contained  only  a  few  well-digested 
fragments,  whereas,  all  five  speared  from  aggre- 
gations above  the  reef  during  afternoons  were  full 
of  food  (including  fresh  material),  as  listed  in 
Table  47. 

Swerdloff  (1970b),  who  recognized  that  C.  vera- 
ter inhabits  relatively  deep  water,  reported  the 
following  categories  of  prey  in  13  specimens  from 
one  collection  on  the  island  of  Oahu  (ranked  as 
percent  of  the  diet):  copepods,  71.5%;  tunicates. 


17.6%;  malacostracans,  4.7%;  mollusks,  2.5%;  fish 
eggs,  1.7%;  and  siphonophores,  1.7%.  He  also  pre- 
sented additional  data  of  food  habits,  as  he 
compared  the  ecology  of  C.  verater  with  that  of 
its  congener  C.  ovalis  see  below). 

Gosline  and  Brock  (1960)  noted  that  C  verater 
occurs  in  deeper  water  than  other  Hawaiian 
pomacentrids.  This  conclusion  was  later  sup- 
ported by  Brock  and  Chamberlain  (1968)  who, 
making  observations  from  a  submarine,  found  C 
verater  to  be  the  most  abundant  reef  fish  around 
rocky  outcrops  at  a  depth  of  70  m. 

CONCLUSION. — Chromis  verater  is  a  diurnal 
planktivore  that  takes  primarily  copepods  and 
larvaceans. 

Chromis  ovalis  (Steindachner) 

This  species  is  less  numerous  in  Kona  than  any 
of  the  other  planktivorous  damselfishes  described 
above.  It  occurs  over  irregular  substrata  of  ex- 
posed basalt  interspersed  with  coral  at  depths  be- 
tween 5  and  20  m.  During  the  day  it  aggregates  2 
to  5  m  above  the  reef — at  about  the  same  level  as 
C.  verater.  with  which  it  often  forms  mixed  groups 
(Swerdloff,  1970b).  Its  reactions  to  changing  light 
and  threatening  situations  are  as  described  above 


984 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Rank 


Table  48. — Food  of  Chromis  ovalis. 


Items 


1 

Calanoid  copepods 

2 

Larvaceans 

3 

Cyclopold  copepods 

4 

Mysids 

5 

Decapod  shrimps 

Also,  unidentified  fragments 


No  fish 

with  this 

item  (n  =  2) 


Mean  percent 

of 
diet  volume 


Ranking 
index 


2 

47.5 

47,50 

2 

7.5 

7.50 

2 

3.0 

3.00 

1 

2.5 

1.25 

1 

25 

1.25 

2 

37.0 

37.00 

for  Abudefduf  abdominalis  and  for  other  plank- 
tivorous  pomacentrids;  its  nocturnal  behavior  also 
is  like  that  described  for  these  other  species. 

Of  six  specimens  ( 124:  121-138  mm)  examined, 
all  four  that  were  speared  among  corals  shortly 
before  first  morning  light  (two  after  dark  nights, 
two  after  moonlit  nights)  contained  only  a  few 
well-digested  fragments,  whereas  two  that  were 
speared  from  aggregations  above  the  reef  during 
midafternoon  were  full  of  food  (including  fresh 
items),  as  listed  in  Table  48. 

Swerdloff  (1970b)  reported  the  following 
categories  of  prey  in  eight  C  ovalis  from  one  col- 
lection on  the  island  of  Oahu  (ranked  as  percent 
of  the  diet):  copepods,  60.1%;  tunica tes,  16.9%; 
malacostracans,  9.5%;  mollusks,  9.5%;  poly- 
chaetes,  2.3% ;  fish  eggs,  0.8%;  and  siphonophores, 
0.8%.  Gosline  and  Brock  (1960)  reported  "a  mass 
of  copepods"  in  the  stomach  of  one  individual  of 
this  species. 

CONCLUSION. — Chromis  ovalis  is  a  diurnal 
planktivore  that  takes  primarily  copepods. 

General  Remarks  on  Damselfishes 

Pomacentrids  are  widely  recognized  as  being 
active  by  day  and  relatively  inactive  at  night.  For 
example,  they  were  so  described  in  the  Gulf  of 
California  (Hobson,  1965,  1968a),  and  also  in  the 
tropical  Atlantic  (Starck  and  Davis,  1966;  Collette 
and  Talbot,  1972).  Food-habit  data  from  the  vari- 
ous members  of  this  family  in  areas  as  widely 
separated  as  the  West  Indies  (Randall,  1967)  and 
the  Marshall  Islands  (Hiatt  and  Strasburg,  1960) 
show  widely  divergent  habits:  some  are  strictly 
herbivorous,  others  are  omnivorous,  and  still 
others  are  strictly  carnivorous. 

The  habitat  of  each  pomacentrid  in  Kona  is 
especially  well  defined.  Two  major  categories 
exist:  those  that  forage  on  the  bottom  and  those 
that  feed  in  the  water  column. 


BOTTOM  FEEDERS.— Pomacentrids  that  for- 
age on  the  sea  floor  have  especially  diverse  diets. 
Algae  and  organic  detritus  are  the  major  foods  of 
many,  especially  among  species  of  Pomacentrus 
(Hiatt  and  Strasburg,  1960;  Randall,  1967).  In 
Kona,  P.  jenkinsi  is  in  this  category,  but  P.  pavo 
in  the  Marshall  Islands  is  primarily  a  predator  on 
small  fishes  and  crustaceans  (Hiatt  and  Stras- 
burg, 1960).  The  diets  of  species  of  Abudefduf 
appear  even  more  diverse.  Abudefduf  sindonis  in 
Kona  has  food  habits  similar  to  those  of  P.  jen- 
kinsi, but  the  highly  omnivorous  A.  sordidus 
forages  on  a  wide  variety  of  benthic  animals  and 
plants,  whereas  the  predaceous  A.  imparipennis 
takes  mostly  benthic  crustaceans  and  poly- 
chaetes.  Abudefduf  saxatilus  in  the  West  In- 
dies is,  according  to  Randall  (1967),  "one  of  the 
most  diversified  of  all  fishes  in  its  food  habits," 
feeding  as  it  does  on  a  wide  assortment  of  plants 
and  animals  from  both  sea  floor  and  water  column. 
Similarly,  A.  troschelii  in  the  Gulf  of  California 
feeds  on  zooplankton  and  bits  of  algae  from  the 
water  column,  as  well  as  organisms  from  the  sub- 
stratum (Hobson,  1968a). 

WATER-COLUMN  FEEDERS.— Planktivor- 
ous  pomacentrids  are  prominent  on  coral  reefs 
throughout  tropical  seas.  Their  characteristic 
mid-water  aggregations  have  been  described  in 
the  Indian  Ocean  (Eibl-Eibesfeldt,  1962),  central 
Pacific  (Hiatt  and  Strasburg,  1960),  Gulf  of 
California  (Hobson,  1965, 1968a),  and  the  tropical 
Atlantic  (Starck  and  Davis,  1966).  In  the  Ba- 
hamas, Stevenson  (1972)  showed  that  the  height 
in  the  water  column  at  which  Eupomacentrus 
partitus  feeds  on  plankton  is  determined  largely 
by  light  and  current.  The  progressive  ascent  of 
planktivorous  pomacentrids  into  the  water 
column  during  morning  twilight,  as  they  rise  to 
their  mid-water  feeding  grounds,  and  their 
subsequent  descent  to  the  reef  during  evening 
twilight,  has  been  described  in  Kona  (Hobson, 


985 


1972)  and  the  West  Indies  (Collette  and  Talbot, 
1972). 

Some  of  these  planktivorous  pomacentrids,  for 
example  Abudefduf  saxatilus  and  A.  troschelii, 
noted  above,  also  forage  part  time  on  the  sea  floor. 
However,  most  of  them,  including  the  species  of 
Chromis  and  Dascyllus,  are  specialized  as  pred- 
ators on  zooplankton,  especially  copepods.  Ex- 
amples include  the  representatives  of  these  gen- 
era on  Kona  reefs,  described  in  the  present  report, 
as  well  as  others  from  the  central  Pacific  (Hiatt 
and  Strasburg,  1960)  and  tropical  Atlantic  (Ran- 
dall, 1967). 

Family  Cirrhitidae:  hawkfishes 

Paracirrhites  arcatus  (Cuvier) — pili  ko'a 

This  hawkfish  is  numerous  in  areas  richly 
overgrown  by  the  coral  Pocillopora  meandrina. 
Typically,  it  rests  immobile  on  the  coral  heads 
during  day,  and  takes  shelter  among  the  coral 
branches  at  night.  Individuals  shorter  than  about 
50  mm  are  among  the  coral  branches  day  and 
night,  whereas  those  longer  than  about  90  mm 
frequently  occur  on  the  other  hard  substrata — 
perhaps  because  they  are  too  large  to  fit  between 
the  branches  of  most  Pocillopora  heads.  Para- 
cirrhites arcatus  moves  only  infrequently — a 
short  dash  to  capture  prey,  or  when  threatened. 

Forty-five  specimens  (82:  49-101  mm)  were  col- 
lected during  day  and  night.  The  nighttime  situa- 
tion is  reflected  in  the  17  that  were  speared  during 
the  2  h  before  first  morning  light  (13  on  moonlit 
nights,  4  on  dark  nights).  Of  these,  16  (52  to  95 
mm)  were  resting  among  branches  of  Pocillopora, 
whereas  the  other  (99  mm)  was  amid  a  fingerlike 
growth  ofPorites  compressus.  The  stomachs  were 
empty  in  13  and  contained  only  well-digested 
fragments  in  3.  The  last  individual,  taken  during 
new  moon,  contained  a  caridean  shrimp  that 
probably  had  been  captured  that  night. 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

The  daytime  situation  is  reflected  in  the  12  in- 
dividuals speared  during  afternoons,  all  perched 
in  exposed  positions  on  the  reef  when  collected. 
Ten  of  these  (71  to  101  mm)  rested  on  Pocillopora, 
and  two  (95  and  97  mm)  rested  on  rocks.  Ten  had 
stomachs  full  of  food,  much  of  it  fresh,  and  al- 
though the  remaining  two  had  empty  stomachs, 
their  intestines  were  full. 

Specimens  collected  at  other  times  of  day  and 
night  offer  less  conclusive  data.  Of  nine  speared  at 
night  (between  3  and  5  h  after  sunset),  seven  were 
deep  among  coral  branches,  but  two  rested  in  ex- 
posed positions  (the  latter  situation  was  only 
rarely  seen).  Six  of  these  had  food  in  their 
stomachs,  but  although  the  material  was  well- 
digested  in  five,  the  sixth  was  full  of  a  species  of 
cyclopoid  copepod  that  often  swarmed  around  our 
diving  lights  for  about  30  min,  an  hour  or  so  after 
last  evening  light.  Finally,  of  the  seven  speared 
within  2  h  after  sunrise  as  they  rested  on  top  of 
Pocillopora  heads,  four  had  the  stomachs  empty 
and  three  contained  fresh  prey.  Identifiable  ma- 
terial occurred  in  20  of  the  46  specimens  exam- 
ined, as  listed  in  Table  49. 

Hiatt  and  Strasburg  (1960),  reporting  on  this 
species  from  the  Marshall  Islands,  remarked  that 
it  habitually  lies  motionless  on  the  upper  surface 
of  living  coral  heads  and  listed  a  diet  of  crusta- 
ceans and  fishes. 

CONCLUSION. — Paracirrhites  arcatus  is  a 
diurnal  predator  that  feeds  primarily  on  xanthid 
crabs  and  other  benthic  crustaceans. 

Paracirrhites  forsteri  (Bloch  and  Schneider) — 
hi! II  pili  ko'a 

This  hawkfish  is  numerous  in  coral-rich  areas, 
where  it  rests  immobile  in  exposed  positions  on 
the  reef  during  the  day  (Figure  32).  Its  attitude  is 


Table  49. — Food  of  Paracirrhites  arcatus. 


No,  fish 

Mean  percent 

wl 

th  this 

of 

Ranking 

Rank 

Items 

Item 

(n  =  20) 

diet  volume 

Index 

1 

Xanthid  crabs 

12 

43.3 

25.98 

2 

Decapod  shrimps 

6 

15.5 

4.65 

3 

Fish 

3 

10,5 

1.58 

4 

Ophlurolds 

1 

5.0 

0.25 

5 

Calapid  crabs 

1 

4.3 

0.22 

6 

Cyclopoid  copepods 

1 

4,0 

0.20 

7 

Crab  megalops 

2 

1.8 

0.18 

8 

Gammarldean  amphipods 

2 

0.5 

0.05 

9 

Calanoid  copepods 

1 

0.3 

0.02 

Also. 

crustacean  fragments 

6 

13.5 

4.05 

Unidentified  fragments 

1 

1.3 

0.07 

986 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  32. — Paracirrhites  forsteri,  a  hawkfish,  seated  on  the  reef  during  the  day. 


much  like  that  of  P.  arcatus,  above,  but  it  occurs 
widely  on  different  hard  surfaces,  rather  than 
being  mostly  associated,  as  is  P.  arcatus,  with  one 
type  of  coral.  In  the  manner  typical  of  hawkfishes, 
P.  forsteri  moves  only  infrequently,  attacking 
prey  that  have  come  within  range  of  a  short,  ex- 
plosive dash.  Such  attacks  were  seen  only  during 
the  day;  at  night  P.  forsteri  generally  is  out  of 
sight  in  reef  crevices. 

Thirty-six  specimens  (139:  93-181  mm)  were 
collected  during  day  and  night.  Of  the  28  that  were 
speared  as  they  rested  during  midday  on  a  variety 
of  reef  substrata,  18  contained  food  in  the  stomach, 
much  of  it  relatively  fresh  (although  in  1  the  ma- 
terial was  reduced  to  unidentifiable  fragments).  In 
contrast,  among  eight  others  that  were  speared 
from  deep  within  reef  crevices  during  the  2  h  im- 
mediately before  first  morning  light,  four  had 
empty  stomachs  and  three  contained  only  well- 
digested  fi-agments;  only  the  eighth  specimen  con- 
tained relatively  fresh  prey — a  shrimp,  Saron 
marmoratus — that  appeared  to  have  been  taken 
that  night. 

Fish  were  the  major  prey,  occurring  in  14  of  the 
21  individuals  that  contained  identifiable  mate- 
rial (mean  percent  of  diet  volume:  66.6;  ranking 


index:  44.4).  Other  food  items  were:  caridean 
shrimps  in  four  (mean  percent  of  diet  volume: 
16.2;  ranking  index:  3.09),  xanthid  crabs  in  one 
(mean  percent  of  diet  volume:  4.8;  ranking  index: 
0.23),  and  unidentified  crustacean  fragments  in 
three  (mean  percent  of  diet  volume:  12.4;  ranking 
index:  1.77).  The  only  identifiable  fish  among  the 
gut  contents  was  a  wrasse,  Thalassoma  duperrey. 
Three  of  the  four  individuals  containing  caridean 
shrimps  had  preyed  on  Saron  marmoratus.  Of  the 
larger  shrimps  (to  about  50  mm),  this  was  the  one 
most  frequently  seen  after  dark,  but  only  one  of 
these,  noted  above,  appeared  to  have  been  cap- 
tured at  night.  Perhaps  significantly,  the  speci- 
mens of  P.  forsteri  that  were  examined  had  preyed 
on  either  fishes  or  crustaceans,  but  never  on  both. 
Hiatt  and  Strasburg  (1960),  citing  the  similar- 
ity in  habits  between  P.  forsteri  and  P.  arcatus, 
noted  that  the  diet  of  P.  forsteri  runs  more  to 
fishes  than  crustaceans.  I  agree  with  them  that 
this  difference  probably  relates  to  the  size  dif- 
ference between  these  two  congeners. 


CONCLUSION.^PamcjrrAi^es  forsteri  is  a 
diurnal  predator  that  preys  mostly  on  small  fishes. 


987 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 


Cirrhitops  fasciatus  (Bennett)  — 
'o'opu  kaha  'iha  'i 

This  hawkfish  is  numerous  on  both  coral  and 
basah  reefs,  and  unhke  the  two  species  of  Para- 
cirrhites,  above,  occurs  in  exposed  positions  at 
night  as  well  as  during  the  day.  In  typical  hawk- 
fish  fashion,  it  generally  rests  immobile  on  the  sub- 
stratum, except  when  attacking  prey;  thus,  it  is 
difficult  to  differentiate  periods  of  activity  from 
periods  of  inactivity. 

Twenty-three  specimens  (76:  39-91  mm)  were 
collected  during  night  and  day.  Seven  of  nine 
speared  from  exposed  positions  under  moonlight 
between  4  and  5  h  after  sunset  contained  prey  that 
appeared  to  have  been  recently  ingested.  In  addi- 
tion, three  of  six  individuals  taken  during  the 
hour  immediately  before  first  morning  light  also 
contained  relatively  fresh  prey.  The  daytime  situ- 
ation is  reflected  by  specimens  that  were  collected 
during  afternoons,  where  the  stomachs  from  six  of 
eight  individuals  contained  prey,  much  of  it  rela- 
tively fresh.  Items  in  the  16  specimens  containing 
identifiable  prey  are  listed  in  Table  50. 


CONCLUSION. — Cirrhitops  fasciatus  regu- 
larly feeds  during  both  day  and  night,  mostly 
on  xanthid  crabs  and  other  benthic  crustaceans. 


Cirrhitus  pinnulatus  (Bloch  and  Schneider) — 
po'o  pa  a 

This  hawkfish  is  numerous  at  depths  of  less 
than  5  m  in  and  around  crevices  on  surge-swept 
basalt  reefs  (Figure  5).  Corals  in  this  habitat  are 
mostly  isolated  heads  of  Pocillopora  meandrina 
and  encrusting  patches  ofPorites  compressus.  As 
do  other  hawkfishes,  C.  pinnulatus  generally  rests 
motionless  on  the  substratum.  During  the  day  it 
usually  remains  under  at  least  partial  cover;  at 
night  it  more  frequently  occurs  in  exposed  posi- 
tions on  the  reef. 

All  32  specimens  ( 152:  103-221  mm)  that  were 
examined  were  resting  immobile  on  the  reef  when 
speared,  most  of  them  partially  concealed  in  crev- 
ices. Of  17  taken  during  the  afternoon,  14  had 
empty  stomachs,  and  3  contained  material  exten- 
sively damaged  by  digestion.  In  contrast,  of  15 
that  were  taken  between  1  h  before  first  morning 
light  and  2  h  after  sunrise,  only  4  had  empty 
stomachs,  whereas  each  of  the  other  11  had  the 
stomach  full  of  food,  much  of  it  fresh.  Items  in  the 
14  individuals  containing  identifiable  material 
are  listed  in  Table  51. 

Most  of  the  xanthid  crabs  among  these  gut  con- 
tents were  Trapezia,  a  genus  common  among 
branches  of  the  coral  Pocillopora.  Hiatt  and 
Strasburg  ( 1960)  also  reported  a  crab  of  this  genus 
in  one  C.  pinnulatus  that  they  examined  from  the 


Table  50. — Food  of  Cirrhitops  fasciatus. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  16) 

diet  volume 

index 

1 

Xanthid  crabs 

7 

30.9 

13.52 

2 

Decapod  shrimps 

5 

20.9 

653 

3 

Crab  megalops 

2 

7.8 

0.98 

4 

Ophiuroids 

1 

6.3 

0.39 

5 

Octopods 

1 

6.3 

0.39 

6 

Gammarldean  amphlpods 

1 

0.6 

0.04 

Also,  crustacean  fragments 

5 

22.2 

694 

Unidentified  fragments 

1 

50 

0.31 

Table  51.- 

— Food  of  Cirrhitus  pinnulatus. 

No   fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  14) 

diet  volume 

index 

1 

Xanthid  crabs 

11 

60.0 

47.14 

2 

Oxyrhynchan  crabs 

3 

7.5 

1.61 

3 

Decapod  shrimps 

3 

2.9 

0.62 

4 

Ophiuroids 

1 

7.1 

0.51 

5 

Octopods 

1 

7.1 

0.51 

6 

Echinoids 

1 

3.2 

0.23 

7 

Pagurid  crabs 

1 

1.1 

0.08 

Also, 

crustacean  fragments 

3 

11.1 

2.38 

988 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 

Marshall  Islands.  Randall  (1955)  reported  only 
brachyuran  crabs  in  the  diet  of  two  specimens  that 
he  examined  from  the  Gilbert  Islands. 

CONCLUSION.— Cirrhituspinnulatus  is  a  noc- 
turnal predator  that  hunts  mostly  xanthid  crabs. 

Family  Labridae:     wrasses 

Bodianus  bihiniilatus  (Lacepede)  —  aawa 

This  relatively  large,  solitary  wrasse  occurs 
only  infrequently  on  the  shallow  reefs  in  Kona  as 
it  lives  mostly  at  depths  below  15  m.  Two  indi- 
viduals (172  and  283  mm)  were  speared  during 
midafternoon  as  they  moved  actively  among  coral 
at  25  m  along  the  outer  drop-off,  and  the  guts  of 
both  were  full  of  crushed  mollusks. 

CONCLUSION.— Bo<:/jrtni<.s  bilunulatus  feeds 
on  mollusks  during  the  day. 

Cheilinus  rhodochrous  Giinther — po'ou 

This  labrid  is  numerous  over  both  coral  and 
rocky  substrata  deeper  than  about  10  m.  It  is  a 
solitary  species  that  hovers  close  to  the  reef  during 
the  day  and  takes  shelter  in  the  reef  at  night. 
Several  times  larger  individuals  attempted  to 
take  fish  that  were  impaled  on  my  spear,  and  twice 
they  succeeded  despite  my  attempts  to  drive  them 
away. 

Among  16  specimens  (175:  129-242  mm)  col- 
lected during  afternoons,  6  contained  only  a  few 
well-digested  fragments  posteriorly  in  the  gut, 
and  most  of  the  material  in  the  other  10  was  far 
digested.  Fish  were  the  major  prey,  occurring  in  4 
of  the  10  individuals  that  contained  identifiable 
material  (mean  percent  of  diet  volume:  40;  rank- 
ing index:  16).  Other  food  items  were:  decapod 
shrimps  in  three  (mean  percent  of  diet  volume:  30; 
ranking  index:  9),  brachyuran  crabs  in  one  (mean 
percent  of  diet  volume:  8;  ranking  index:  0.8),  un- 
identified crustacean  fragments  in  two  (mean  per- 
cent of  diet  volume:  12;  ranking  index:  2.4),  and 
other  unidentified  fragments  in  two  (mean  per- 
cent of  diet  volume:  10;  ranking  index:  2).  The  only 
fish  that  could  be  identified  was  a  pomacentrid, 
-  Pomacentrus  jenkinsi,  and  the  only  identifiable 
shrimp  was  Saron  marmoratus.  Generally  C. 
rhodochrous  preys  on  large  organisms,  but  be- 
cause it  crushes  them  upon  ingestion, 
identifications  are  difficult.  Presumably  crushing 


the  food  items  accelerates  digestion,  thus  con- 
tributing to  the  poor  condition  of  this  material. 
However,  because  all  these  specimens  were  col- 
lected during  afternoons,  the  advanced  digestion 
could  also  reflect  early  morning  feeding. 

Cheilinus  rhodochrous  is  a  stalking  predator, 
equipped  by  a  relatively  large  mouth  and  pair  of 
large  canine  teeth  at  the  front  of  each  jaw  to  hunt 
prey  that  are  relatively  larger  and  more  active 
than  those  taken  by  most  other  labrids.  Most  of  the 
specimens  that  were  examined  contained  a  single 
large  prey  organism,  indicating  that  feeding  is 
infrequent  and  that  each  successful  attack  pro- 
vides enough  nourishment  to  sustain  the  predator 
for  some  time. 

CONCLUSION. — Cheilinus  rhodochrous  is  a 
diurnal  predator  that  stalks  relatively  large  fishes 
and  crustaceans.  It  may  have  peaks  in  feeding 
early  and  late  in  the  day,  but  is  inactive  at  night. 

Pseudocheilinus  octotaenia  Jenkins 

This  small  species  is  one  of  the  more  numerous 
labrids  on  coral-rich  reefs  at  depths  to  at  least  30 
m,  but  its  large  numbers  are  difficult  to  appreciate 
because  it  occurs  close  among  the  many  narrow 
interstices  of  the  reef.  It  is  strictly  a  diurnal 
species  that  takes  shelter  in  the  reef  at  night. 

All  12  specimens  (77:  50-95  mm)  taken  during 
afternoons  had  material  in  their  stomachs,  but  the 
food  items  were  difficult  to  identify  because  they 
were  small  and  had  been  crushed  when  ingested. 
Thus,  most  of  the  gut  contents  of  all  10  individuals 
that  contained  recognizable  material  can  be  listed 
only  as  unidentified  crustacean  fragments  (mean 
percent  of  diet  volume  and  ranking  index:  71.9). 
Items  that  could  be  identified  are:  brachyuran 
crabs  in  three  (mean  percent  of  diet  volume:  22; 
ranking  index:  6.6),  echinoids  in  one  (mean  per- 
cent of  diet  volume:  5;  ranking  index:  0.5),  demer- 
sal fish  eggs  in  one  (mean  percent  of  diet  volume: 
1;  ranking  index:  0.1),  and  copepods  in  one  (mean 
percent  of  diet  volume:  0.1;  ranking  index:  0.01). 

CONCLUSION  .—Pseudocheilinus  octotaenia  is 
a  diurnal  predator  that  feeds  mostly  on 
brachyuran  crabs  and  other  benthic  crustaceans. 

Labroides  phthirophagus  Randall 

This  small  wrasse  (most  are  less  than  100  mm 
long)  is  specialized  to  pick  ectoparasites  from  the 

989 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


bodies  of  other  fishes  at  well-defined  cleaning  sta- 
tions (Figure  33).  Usually  two  or  several  of  these 
cleaners  are  active  at  each  station.  It  is  a  diurnal 
species  that  shelters  in  reef  crevices  at  night  (Hob- 
son,  1972). 

This  is  the  major  cleaner  fish  on  Hawaiian  reefs, 
and  its  habits  are  well  known  (e.g.  Randall,  1958; 
Youngbluth,  1968;  Losey,  1971;  Hobson,  1971). 
Because  the  activity  of  this  species  has  been 
extensively  documented,  it  was  only  incidentally 
observed  during  the  present  study. 

CONCLUSION. — Lahroides  phthirophagus 
cleans  ectoparasites  from  the  bodies  of  other  fishes 
during  the  day. 

Thalassotna  duperrey  (Quoy  and  Gaimard)  — 
hinalea  lauwili 

This  is  probably  the  most  ubiquitous  fish  on 
Kona  reefs  (Figure  33):  it  is  numerous  every- 
where, from  the  surge-swept  reef  tops  to  the  outer 
drop-off  on  both  coral-rich  and  exposed  basalt  sub- 
strata. In  the  daytime  fish  counts  along  transect 
lines,  T.  duperrey  ranked  among  the  five  most 
numerous  species  in  all  the  sampled  habitats.  An 


opportunist,  it  is  consistently  the  first  fish  to  ap- 
pear when  a  sea  urchin  has  been  crushed,  or  when 
a  rock  has  been  overturned  and  vulnerable  or- 
ganisms exposed.  Sometimes  it  follows  close  to  the 
feeding  jaws  of  scarids  to  snap  up  prey  uncovered 
when  these  herbivores  disturb  the  substratum. 
This  wrasse  is  adapted  to  a  wide  range  of  habits:  it 
forages  in  the  water  column  when  plankton  are 
abundant,  but  mostly  picks  organisms  off  a  vari- 
ety of  substrata.  It  is  strictly  a  diurnal  species  that 
shelters  in  reef  crevices  at  night  (Hobson,  1972). 
Many  of  the  juveniles  are  cleaners  and  maintain 
stations  at  certain  prominent  coral  heads.  On  one 
survey  5  m  deep  along  approximately  1  km  of  the 
north  shore  of  Honaunau  Bay,  I  found  a  cleaning 
station  maintained  by  these  fish  at  every  large 
head  of  Porites  pukoensis  that  was  of  a  distinctive 
mustardlike  hue  and  characterized  by  golf-ball- 
sized  nodules  separated  by  narrow,  shallow  de- 
pressions. The  general  extent  of  this  cleaner's  re- 
lationship to  this  type  of  coral  was  not  determined, 
but  I  saw  cleaning  stations  nowhere  else  during 
the  survey.  Because  the  juveniles  of  T.  duperrey 
always  discontinued  cleaning  when  a  human  was 
near,  incidental  observations  of  this  activity  were 
rare.  And,  as  noted  above  in  discussing  La6roj(ies 


Figure  33. — A  wrasse,  Thalassoma  duperrey,  being  cleaned  by  another  wrasse,  Labroides  phthirophagus. 


990 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


phthirophagus,  my  observations  of  cleaning  were 
mostly  incidental.  Nevertheless,  it  was  evident 
that  cleaning  by  T.  duperrey  is  mostly  an  activity 
of  juveniles.  Adults  clean  only  infrequently,  and 
not  at  well-defined  cleaning  stations. 

To  indicate  the  food  of  the  post  juveniles  of  this 
species,  24  specimens,  125  (103-146)  mm  long, 
were  speared  during  the  day  as  they  swam  ac- 
tively over  the  reef.  All  contained  identifiable 
items,  as  listed  in  Table  52.  In  contrast  with  the 
diet  of  most  fishes  examined  during  this  study,  no 
single  item  or  certain  few  items  predominate  in 
the  diet  of  T.  duperrey,  a  circumstance  that  un- 
doubtedly relates  to  its  populating  a  wide  range  of 
habitats. 


All  14  specimens  (132:  60-200  mm)  speared  as 
they  swam  on  the  reef  during  daylight  contained 
identifiable  food  material,  as  listed  in  Table  53. 
Hiatt  and  Strasburg  (1960)  reported  on  two 
specimens  of  this  species  (as  T.  umhrostigma)  in 
the  Marshall  Islands:  one  had  consumed  a 
stomatopod,  the  other  a  fish.  Randall  (1955)  re- 
ported (also  as  T.  umbrostigma)  that  one  speci- 
men taken  in  the  Gilbert  Islands  contained  a  crab. 

CONCLUSION. — Thalassoma  fuscus  is  a  diur- 
nal predator  that  feeds  mostly  on  crabs  and  mol- 
lusks. 

Halichoeres  ornatissimus  (Garrett) — /o'o 


CONCLUSION. — Thalassoma  duperrey  is  a 
diurnal  predator  that  feeds  on  a  very  wide  range  of 
shelled  organisms,  most  of  them  benthic. 

Thalassoma  fuscus  (Lacepede) — hou 

This  species  was  shown  by  numerous  observa- 
tions of  spawning  aggregations  to  include  the 
nominal  T.  umbrostigma  (which  represents  the 
juveniles  and  females).  It  is  a  fish  of  shallow  water 
along  rocky,  surge-swept  shores  and  is  one  of  the 
most  numerous  species  on  the  shallow  reef  flats. 
Generally  it  does  not  occur  in  water  deeper  than 
about  5  m  and  is  strictly  a  diurnal  fish  that  shel- 
ters in  reef  crevices  after  dark. 


In  Kona  this  labrid  is  nowhere  particularly 
numerous,  yet  it  occurs  regularly  in  all  inshore 
habitats.  It  is  generally  solitary  and  swims  close  to 
cover  during  the  day.  At  night  it  is  out  of  sight, 
presumably  resting  in  crevices  or  under  the  sand. 

All  13  specimens  (96:  76-115  mm),  speared 
during  daylight,  had  a  full  gut  that  included  fresh 
material,  as  listed  in  Table  54.  Food  items  more 
than  about  4  mm  in  greatest  dimension  were 
crushed,  and  this  included  most  of  the  mollusks. 
Probably  at  least  much  of  the  unidentified  mate- 
rial constituted  fragmented  molluscan  soft  parts. 
This  fish  plucks  small  benthic  organisms  off  the 
substratum,  including  some  forms,  like  the  di- 
demnid  tunicates,  that  are  attached  to  the  reef. 


Table  52. — Food  of^  Thalassoma  duperrey. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  24) 

diet  volume 

index 

1 

Gastropod  mollusks 

9 

7.5 

2.81 

2 

Echinolds 

3 

7.9 

0.99 

3 

Brachyuran  crabs 

3 

6.1 

0.76 

4 

Pelecypod  mollusks 

3 

5.0 

0.63 

5 

Gammaridean  amphipods 

9 

1.5 

0.56 

6 

Calanoid  copepods 

2 

6.3 

0.53 

7 

Tanaids 

6 

1.3 

0.33 

8 

Cyclopoid  copepods 

4 

1.4 

0.23 

9 

Scleractinian  corals 

2 

2.5 

0.21 

10 

Polychaetes 

2 

2.1 

0  18 

11 

Ophiuroids 

2 

1.5 

0,13 

12 

Tunicates 

2 

1.5 

0.13 

13 

Isopods 

2 

0.9 

0.08 

14 

Fish  eggs 

2 

0.6 

0.05 

15 

Caprellid  amphipods 

2 

0.4 

0.03 

16 

Pagurid  crabs 

2 

0.4 

0.03 

17 

Foraminiferans 

0.2 

<0.01 

18 

Sipunculid  Introverts 

0.2 

<0.01 

19 

Fish 

0.2 

<0.01 

20 

Unidentified  eggs 

<0.1 

<0.01 

Also, 

crustacean  fragments 

11 

9.4 

4.31 

Algae  fragments 

8 

11.5 

3.83 

Unidentified  material 

15 

31.5 

1969 

991 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  53.- 

—Food  of  Thalassoma  fuscus. 

No,  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  14) 

diet  volume 

index 

1 

Brachyuran  crabs 

7 

35.5 

17.75 

2 

Mollusks 

5 

17.2 

6.14 

3 

Octopods 

1 

7.1 

0.51 

4 

Ophluroids 

1 

5.0 

0.36 

5 

Polychaetes 

2 

1.8 

0.26 

6 

Sipunculid  introverts 

2 

1.4 

0.20 

7 

Crab  megalops 

1 

2.8 

0.20 

8 

Fish 

1 

2.5 

0.18 

9 

Gammaridean  amphipods 

3 

0.7 

0,15 

10 

Cyclopoid  copepods 

3 

0.6 

0.13 

11 

Calanoid  copepods 

1 

1.4 

0.10 

12 

Isopods 

1 

0.1 

<0.01 

Also, 

crustacean  fragments 

2 

3.7 

053 

Unidentified  fragments 

8 

20.2 

11.54 

Table  54.— Food  oi Halichoeres  ornatissimus . 

No   fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  13) 

diet  volume 

index 

1 

Mollusks 

6 

13.5 

6,23 

2 

Gammaridean  amphipods 

7 

7.7 

4.15 

'3 

Colonial  diatoms 

4 

6.9 

212 

4 

Didemnid  tunicates 

3 

8.8 

203 

5 

Tanaids 

5 

1.5 

058 

6 

Harpacticoid  copepods 

4 

1.7 

0,52 

7 

Sipunculid  introverts 

3 

1.2 

0.28 

8 

Ophluroids 

1 

3.1 

024 

9 

Cyclopoid  copepods 

2 

0.8 

012 

10 

Polychaetes 

1 

1.5 

0  12 

11 

Isopods 

2 

0.5 

0  08 

12 

Demersal  eggs 

1 

0.8 

006 

13 

Echinoids 

1 

0.4 

0.03 

14 

Ostracods 

1 

0.1 

<0.01 

Also, 

crustacean  fragments 

7 

10.8 

5.82 

Sand  and  foraminiferans 

3 

4.5 

1,04 

Algal  fragments 

2 

1.2 

0  18 

Unidentified  fragments 

10 

35.0 

2692 

The  widespread  occurrence  of  this  fish  probably 
relates  to  the  fact  that  no  single  item,  or  certain 
few  items,  especially  predominate  in  its  diet.  This 
is  true  to  an  even  greater  degree  in  the  ubiquitous 
Thalassoma  duperrey,  above,  but  is  unlike  most 
fishes  on  Kona  reefs. 


All  five  specimens  (90:  76-102  mm)  collected 
during  daylight  had  a  gut  full  of  material,  some  of 
it  fresh,  as  listed  in  Table  55.  The  major  food 
items — small  crustaceans  shorter  than  about  4 
mm — were  mostly  intact.  Larger  items,  such  as 
some  of  the  gastropods,  were  crushed. 


CONCLUSION. — Halichoeres  ornatissimus  is  a 
diurnal  predator  that  picks  a  wide  variety  of  small 
benthic  animals  from  the  sea  floor. 


COnCUJSlO^. —Stethojulis  balteata  is  a  diur- 
nal predator  that  mostly  picks  small  crustaceans 
and  gastropods  off  the  sea  floor. 


Stethojulis  balteata    (Quoy  and  Gaimard)  — 
'omaka 

This  wrasse  is  most  numerous  on  the  shallow 
reef  flats  and  on  some  of  the  reefs  richly  overgrown 
with  corals.  During  the  day  it  swims  close  to  rocks 
or  coral,  at  which  it  periodically  picks.  At  night  it 
rests  in  reef  crevices,  or  buried  in  the  sand. 


Anavipses  cuvier  Quoy  and  Gaimard — 'opule 

Although  this  wrasse  occupies  all  inshore  reef 
habitats  in  Kona,  it  is  most  numerous  where  the 
sea  floor  consists  of  basalt  boulders.  During  the 
day,  solitary  individuals  swim  close  to  the  sub- 
stratum, where  they  inspect  the  surface,  and  fre- 
quently pluck  at  the  low  growth  of  algae  on  the 


992 


HOBSON;  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  55. — Food  of  Slethojulis  balteata. 


No,  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  5) 

diet  volume 

index 

1 

Harpactlcoid  copepods 

5 

19.4 

19.40 

2 

Prosobranch  gastropods 

4 

15.6 

12.48 

3 

Gammaridean  amphlpods 

3 

8.6 

5.16 

4 

Tanalds 

3 

5.0 

3.00 

5 

Foraminiferans 

2 

2.4 

0.96 

6 

Isopods 

2 

2.4 

0.96 

7 

Polychaetes 

1 

4.0 

0.80 

8 

Echinoids 

1 

10 

0.20 

9 

Sipunculid  introverts 

1 

0.6 

0.12 

10 

Cyclopoid  copepods 

1 

0.4 

0.08 

Also, 

crustacean  fragments 

5 

15.0 

15.00 

Sand  and  debris 

4 

10.2 

8.16 

Unidentified  fragments 

4 

15.4 

12.32 

Table  56. 

—Food  of  Anampses 

cuvier. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  12) 

diet  volume 

index 

1 

Gammaridean  amphipods 

10 

28.9 

24.08 

2 

Mollusks 

10 

18.1 

15.08 

3 

Polychaetes 

3 

4.3 

1.08 

4 

Xanthid  crabs 

3 

18 

0.45 

5 

Fish  eggs,  demersal 

1 

5.0 

0.42 

6 

Echinoids 

2 

1.9 

0.32 

7 

Tanalds 

3 

0.3 

0.08 

8 

Isopods 

3 

0.3 

0.08 

9 

Didemnid  tunicates 

2 

0.3 

0.05 

Also, 

crustacean  fragments 

9 

14.1 

10.58 

Sand  and  foraminiferans 

4 

4.3 

1.43 

Algal  fragments 

3 

19 

0.48 

Unidentified  fragments 

8 

18.8 

12.53 

rocks.  Much  sand  has  accumulated  here,  and 
periodically  they  pause  during  their  foraging  to 
blow  a  small  cloud  of  sand  and  debris  from  their 
mouths.  At  night  this  wrasse  is  out  of  sight,  pre- 
sumably resting  in  reef  crevices. 

All  12  specimens  (169:  110-225  mm)  speared 
during  daylight  had  a  gut  full  of  material,  much  of 
it  fresh,  as  listed  in  Table  56.  The  gammaridean 
amphipods,  all  shorter  than  3  mm,  were  the  major 
prey  of  even  the  largest  individuals.  Furthermore, 
the  mollusks,  which  were  the  only  other 
significant  prey,  were  mostly  prosobranch  gas- 
tropods also  shorter  than  3  mm. 

Undoubtedly,  the  small  size  and  other  charac- 
teristics of  these  prey  are  reflected  in  the  feeding 
morphology  of  A.  cuvier  and  its  congeners,  certain 
features  of  which  set  them  apart  from  most  other 
labrids  in  Kona.  In  dentition,  the  species  of 
Anampses,  with  two  flattened  teeth  projecting 
forward  from  the  front  of  each  jaw,  are  unlike 
those  of  any  other  genus  of  Hawaiian  fishes  (Gos- 
line  and  Brock,  1960).  Obviously  this  specialized 
dentition  effectively  captures  gammarideans  that 
inhabit  the  low  stubble  of  algae  overgrowing  most 
basalt  boulders.  Compared  with  most  other  lab- 


rids,  species  of  Anampses  have  the  pharyngeal 
teeth  reduced,  which  is  expected  considering  the 
relatively  small  proportion  of  crushed  items  in  the 
diet.  The  food  items  are  mostly  so  small  they  need 
not  be  crushed  upon  ingestion.  Gammarideans 
and  certain  other  prey  of  similar  size  regularly 
pass  intact  through  the  pharynx  of  even  those 
labrids  with  well-developed  pharyngeal  teeth  (see 
accounts  of  other  labrids  in  this  report). 

CONCLUSION. — Anampses  cuvier  is  a  diurnal 
predator  that  mostly  plucks  small  benthic  or- 
ganisms, especially  gammarideans,  from  rocky 
substrata. 

Coris  gaimard  (Quoy  and  Gaimard) — 
hinalea  lolo 

This  wrasse  is  most  numerous  where  the  reef  is 
interspersed  with  small  patches  of  sand.  It  forages 
in  this  sand  during  daylight,  usually  close  to  the 
base  of  rock  or  coral.  Of  all  the  wrasses  treated  in 
this  report,  this  one  is  the  most  adept  at  excavat- 
ing buried  organisms.  Moving  its  head  sidewise,  it 
effectively  overturns  small  stones  or  digs  in  the 


993 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 


Table  57. — Food  of  Coris  gaimard. 


Rank 


Items 


Mollusks 

Echinoids 

Crabs 

Didemnid  tunlcates 

Gammaridean  amphipods 


Also,  crustacean  fragments 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

item  (n  =  9) 

diet  volume 

index 

9 

72.2 

72.20 

3 

9,8 

3.27 

1 

2.2 

2.44 

1 

0.6 

0.C7 

1 

0.2 

0.02 

5 

15.0 

8.33 

Table  58. — Food  of  Macropharyngodon  geoffroy. 


Rank 


Items 


No.  fish 

with  this 

item  (n  =  8) 


Mean  percent 

of 
diet  volume 


Ranking 
index 


1                      Prosobranch  gastropods 

8 

37.8 

37.80 

2                      Foraminiferans 

8 

35.3 

35.30 

3                    Harpacticoid  copepods 

2 

0.4 

0.10 

4                    Gammaridean  amphipods 

1 

0.1 

0.01 

Also,  crustacean  fragments 

2 

0.6 

0.15 

Sand  and  algae 

5 

8.4 

5.25 

Unidentified  fragments 

6 

17,4 

13.05 

sand,  exposing  hidden  prey.  It  is  not  seen  at  night, 
when  presumably  it  is  buried  in  the  sand,  or  se- 
creted in  reef  crevices. 

All  nine  specimens  (117:  81-164  mm),  speared 
during  daylight,  contained  relatively  fresh  mate- 
rial, but  items  longer  than  a  few  millimeters  were 
crushed  so  extensively  that  precise  identifications 
were  difficult.  The  gut  contents  are  itemized  in 
Table  57. 

CONCLUSION. — Coris  gaimard  is  a  diurnal 
predator  that  mostly  excavates  mollusks  and 
other  prey  that  are  buried  in  the  sand. 

Macropharyngodon  geoffroy 
(Quoy  and  Gaimard) 

This  solitary  little  wrasse  is  widespread  on 
Kona  reefs,  but  is  nowhere  numerous.  It  swims 
close  among  coral  and  rocks  during  daylight,  but 
is  not  seen  after  dark,  when  presumably  it  secretes 
itself  in  reef  crevices,  or  under  the  sand. 

All  eight  specimens  (99:  74-120  mm)  collected 
during  the  day  had  the  gut  full  of  the  items  listed 
in  Table  58,  almost  all  crushed. 

The  exceptionally  large  pharyngeal  teeth  of  this 
wrasse  obviously  are  adapted  to  a  diet  of  heavily 
shelled  organisms.  The  specimens  examined, 
which  had  fed  mostly  on  gastropods  and  forami- 
niferans, are  undoubtedly  representative.  The 
foraminiferans  were  almost  all  Marginospora 
vertebralis,  which  is  an  abundant  benthic  form  on 
shallow  reefs  in  the  Marshall  Islands  (Cushman, 
Todd,  and  Post,  1954). 


CONCLUSION.^MacropAaryn^ocfon  geoffroy 
is  a  diurnal  predator  that  feeds  mostly  on  benthic 
gastropods  and  foraminiferans. 

Gomphosus  varius  Lacepede — 
bird  wrasse,  hinalea  IHwi 

This  wrasse  is  numerous  on  shallow  surge- 
swept  reefs,  especially  where  the  coral  Pocillopora 
meandrina  abounds.  During  daylight  solitary  in- 
dividuals swim  among  the  coral  heads,  probing 
with  their  elongated  snouts  among  the  coral 
branches.  At  night  the  species  lies  quietly  in  reef 
crevices. 

All  12  specimens  (142:  114-180  mm)  collected 
during  the  day  had  their  guts  full  of  the  items 
listed  in  Table  59.  Most  of  this  material  was 
crushed.  The  xanthid  crabs  were  mostly  Trapezia 
sp.  They  and  the  alpheids  are  species  that  live 
among  the  branches  of  P.  meandrina.  Hiatt  and 
Strasburg  (1960)  noted  that  this  labrid's  major 
prey  in  the  Marshall  Islands  are  xanthids  and 
alpheids  that  live  in  the  interstices  of  ramose  cor- 
als. Randall  (1955)  similarly  reported  alpheid 
shrimps  and  also  stomatopods  in  the  diet  of  this 
species  (as  G.  tricolor)  in  the  Gilbert  Islands. 

Gomphosus  varius  takes  relatively  large  motile 
prey,  and  with  its  large  mouth  does  not  pluck  them 
from  the  substratum  in  the  manner  characteristic 
of  the  many  other  wrasses  that  prey  on  relatively 
tiny  or  sessile  organisms.  Rather,  this  wrasse  vig- 
orously wrests  its  prey  from  the  reef  crevices  in 
which  they  are  secreted. 


994 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  59. — Food  of  Gomphosus  varius. 


No,  fisfi 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  1 

2) 

diet  volume 

Index 

1 

Xanthid  crabs 

7 

37,9 

22.11 

2 

Alpheid  shrimps 

2 

6,7 

1.12 

3 

Pelecypods 

1 

4.2 

0.35 

4 

Gastropods 

2 

2.1 

0.35 

Also, 

crustacean  fragments 

8 

25.8 

17.20 

Unidentified  fragments 

4 

23.3 

7.77 

CONCLUSION. — Gomphosus  varius  is  a  diur- 
nal predator  that  takes  relatively  large  crusta- 
ceans from  reef  crevices. 

General  Remarks  on  Wrasses 

Kona  reefs,  like  tropical  reefs  the  world  over, 
are  populated  by  a  diverse  array  of  wrasses,  most 
of  them  with  strong  pharyngeal  teeth  adapted  to 
crush  hard-bodied  prey.  Macropharyngodon  geof- 
froy,  for  example,  preys  on  more  heavily  armored 
prey — in  this  case  mollusks  and  foramini- 
ferans.  Others,  like  Anampses  cuvier,  have  the 
pharyngeal  teeth  less  developed  and  prey  mostly 
on  tiny  crustaceans.  Some  of  the  wrasses,  espe- 
cially Thalassoma  duperrey,  are  highly  oppor- 
tunistic, and  these  tend  to  be  the  most  widespread 
and  have  the  most  varied  diets. 

It  is  well  known  that  wrasses  are  active  only 
during  the  day;  at  night  they  rest  in  reef  crevices 
and  under  the  sand  (Longley  and  Hildebrand, 
1941;  Goshne  and  Brock,  1960;  Hobson,  1965, 
1968a,  1972;  Starck  and  Davis,  1966;  Collette  and 
Talbot,  1972).  They  are  among  the  first  diurnal 
fishes  on  the  reef  to  seek  cover  at  day's  end,  and 
among  the  last  to  leave  cover  in  the  morning  ( Hob- 
son,  1965, 1968a,  1972;  Collette  and  Talbot,  1972). 

Family  Scaridae:     parrotfishes 

Scarus  sordidus  Forskal — uhu 

This  is  one  of  the  more  numerous  parrotfishes  in 
Kona,  especially  over  coral-rich  reefs.  During  the 
day,  it  swims  actively  close  to  the  substratum, 
often  in  groups.  With  its  parrotlike  beak,  it 
scrapes  away  the  fine  filamentous  algae  that 
grows  over  the  surface  of  dead  coral,  especially 
Pontes.  Although  frequently  it  scrapes  up  to  the 
edge  of  living  coral,  it  stops  there  (Figure  34). 
During  twilight,  this  species  migrates  in  schools 
from  one  part  of  the  reef  to  another,  but  the  mi- 
gratory pattern  remains  unclear  (Hobson,  1972). 


At  night  S.  sordidus  rests  solitarily  in  reef  crev- 
ices. Because  some  parrotfishes  are  known  to  se- 
crete a  mucous  envelope  around  themselves  at 
night  (Winn,  1955),  during  a  series  of  night  obser- 
vations over  3  mo  I  estimated  the  standard  length 
of  each  resting  parrotfish,  and  noted  whether  or 
not  it  was  encased  in  mucus.  During  these  obser- 
vations, 20  individuals  of  this  species  were  seen, 
estimated  to  be  between  150  and  350  mm  long.  All 
eight  that  appeared  to  be  shorter  than  300  mm 
were  in  mucous  envelopes,  whereas  all  six  without 
envelopes  were  judged  to  be  longer  than  300  mm. 
The  other  six,  all  estimated  to  exceed  about  300 
mm  long,  were  in  envelopes.  Thus,  all  the  smaller 
individuals,  but  only  some  of  the  larger  ones,  were 
in  envelopes. 

The  guts  of  all  seven  S.  sordidus  (195:  150-213 
mm)  that  were  speared  during  midday  were  full  of 
bits  of  algae,  mixed  with  calcareous  powder,  or- 
ganic slurry,  and  sand  (proportions  undeter- 
mined, but  the  algae  constituted  less  than  207f ). 
No  evidence  was  found  in  these  specimens  of  coral 
tissues  or  mucus  (the  latter  is  prominent  in  the  gut 
contents  of  fishes  known  to  feed  on  coral),  even 
though  Hiatt  and  Strasburg  (1960)  reported  that 
coral  polyps  constituted  the  major  food  of  this 
parrotfish  in  the  Marshall  Islands.  These  authors 
stated  (p.  103):  "Scraping  living  coral  heads  seems 
to  be  its  predominant  mode  of  feeding."  This  ob- 
servation contrasts  with  mine  in  Kona,  where  S. 
sordidus  avoids  the  living  coral  when  feeding. 

CONCLUSION. — Scarus  sordidus  is  a  diurnal 
herbivore  that  feeds  mostly  by  scraping  fine 
benthic  algae  that  have  overgrown  the  surface  of 
dead  coral. 

Scarus  taeniurus  Valenciennes — uhu 

My  observations  of  their  social  interactions  ren- 
der it  clear  that  the  two  forms  Schultz  (1969) 
distinguished  in  Hawaii  as  S.  taeniurus  and  S. 
forsteri  are  conspecific  and  that  his  "S.  forsteri" 
represents  the  large  male  of  the  species. 


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FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  34. — Area  of  the  reef  showing  scrape  marks  made  by  the  teeth  of  grazing  parrotfishes,  mostly  Scarus  sordidus. 
Note  that  grazing  has  occurred  only  where  dead  coral  is  overgrown  with  algae — no  living  coral  has  been  scraped. 


This,  the  smallest  Hawaiian  species  of  Scarus 
(not  exceeding  a  length  of  about  300  mm),  is  by  far 
the  most  numerous  parrotfish  over  exposed  basalt 
on  shallow  reef  flats  and  adjacent  reef  faces.  The 
smaller  juveniles  and  females,  usually  in  aggrega- 
tions, tend  to  occupy  the  shallow  flats,  the  larger, 
distinctively  hued  males,  which  are  usually  soli- 
tary, tend  to  occupy  the  reef  faces.  This  species  is 
like  S.  sordidus  in  grazing  during  the  day;  how- 
ever, whereas  S.  sordidus  usually  scrapes  algae 
from  the  surface  of  dead  coral,  S.  taeniurus 
ordinarily  scrapes  algae  from  the  surface  of  rocks. 

At  night  S.  taeniurus  rests  in  reef  crevices.  Dur- 
ing the  series  of  night  observations  in  which  I 
checked  the  incidence  of  mucous  envelopes,  all  11 
S.  taeniurus,  which  were  less  than  300  mm  long, 
were  in  envelopes  (Figure  35). 

The  two  individuals  ( 150  and  243  mm)  that  were 
collected  during  midday  were  full  of  bits  of  algae, 
mixed  with  calcareous  powder,  organic  slurry,  and 
sand  (proportions  undetermined,  but  the  algae 
made  up  less  than  20%),  with  no  evident  trace 
of  coral  tissue  or  mucus. 


CONCLUSION. — Scarus  taeniurus  is  a  diurnal 
herbivore  that  usually  feeds  by  scraping  benthic 
algae  from  rock  surfaces. 

Scarus  rubroviolaceus  Bleeker — tthu  palukaluka 

During  the  day  this  parrotfish  ranges  over  the 
reef,  usually  in  mixed  groups  of  several  males  and 
females.  It  occurs  on  all  the  inshore  reefs,  but 
mostly  on  rock  substrata.  Generally,  using  the 
sides  of  its  jaws,  it  takes  one  bite  and  then  with- 
draws a  few  centimeters  before  approaching  for 
another  bite. 

At  night  S.  rubroviolaceus  rests  in  reef  crevices. 
While  surveying  the  incidence  of  mucous  en- 
velopes in  resting  parrotfishes  (see  accounts  for  S. 
sordidus  and  S.  taeniurus  above),  of  the  nine  S. 
rubroviolaceus  that  were  observed,  including  both 
males  and  females  approximately  200  to  500 
(mean  394)  mm  long,  none  were  in  envelopes  (Fig- 
ure 36).  Because  the  large  and  distinctive  males  of 
S.  rubroviolaceus  are  not  numerous,  I  came  to 
recognize  some  individuals.  These  often  returned 


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HOBSON;  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  35. — Scarus  taeniurus,  a  parrotfish,  resting  in  a  mucous  envelope  at  night,  a  habit  apparently  shared  by  all 

members  of  this  relatively  small  species. 


Figure  36. — Scarus  rubroviolaceus,  female,  a  parrotfish,  resting  under  a  ledge  at  night.  Members  of  this  species  were 

never  seen  in  mucous  envelopes. 


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FISHERY  BULLETIN:  VOL.  72,  NO.  4 


night  after  night  to  caves  in  the  same  areas,  but 
not  necessarily  to  the  same  cave,  as  has  been  re- 
ported for  some  parrotfishes  elsewhere  (e.g.  Winn 
and  Bardach,  1960;  Starck  and  Davis,  1966). 

The  guts  of  two  males  (340  and  410  mm)  that 
were  speared  during  midday  were  full  of  bits  of 
algae  mixed  with  calcareous  powder,  organic 
slurry,  and  sand  (proportions  undetermined,  but 
the  algae  constituted  less  than  20%),  with  no 
evident  trace  of  coral  tissue  or  mucus. 

CONCLUSION. — Scarus  ruhroviolaceus  is  a 
diurnal  herbivore  that  typically  scrapes  benthic 
algae  from  rock  surfaces. 

General  Remarks  on  Parrotfishes 

It  is  well  known  that  parrotfishes  are  quiescent 
at  night.  They  have  been  thus  described  in  the 
tropical  Atlantic  (Winn,  1955;  Winn  and  Bardach, 
1959,  1960),  eastern  Pacific  (Hobson,  1965; 
Rosenblatt  and  Hobson,  1969),  Hawaii  (Hobson, 
1972),  and  elsewhere.  EarHer  (Hobson,  1965),  I 
suggested  that  mucous  envelopes  in  resting 
parrotfishes  at  night  are  characteristic  of  certain 
small  individuals,  or  of  individuals  suffering  in- 
jury or  stress.  The  relation  between  small  size  and 
envelope  secretion  was  also  noted  by  Starck  and 
Davis  (1966)  and  by  Casimir  (1971).  Winn  and 
Bardach  (1959)  believed  that  the  envelope  is  a 
defense  against  nocturnal  predators,  especially 
those  that  sense  prey  by  olfaction  or  gustation,  as 
do  certain  moray  eels  (Bardach,  Winn,  and  Men- 
zel,  1959).  Because  the  threat  from  predators  in- 
creases with  decreasing  size,  obviously  the  smal- 
ler individuals  are  in  greatest  need  for  protection. 
Similarly,  it  is  known  that  injured  or  distressed 
fishes  are  particularly  attractive  to  predators  (e.g. 
Hobson,  1968a),  so  envelope  secretion  by 
parrotfishes  suffering  these  conditions  is  consis- 
tent with  the  idea  that  the  envelopes  provide  pro- 
tection. The  survey  of  mucous  envelopes  in  Kona 
shows  a  decreasing  incidence  with  increasing  size. 
Nevertheless,  Winn  and  Bardach  (1960),  working 
with  Scarus  vetula  at  Bermuda,  found  that  certain 
individuals  in  aquaria  produced  the  envelope  ir- 
regularly, and  Smith  and  Tyler  (1972)  found  that 
one  individual  of  that  species  observed  on  a  reef  in 
the  Virgin  Islands  formed  an  envelope  on  some 
nights,  but  not  on  others.  Probably  this  variation 
within  individuals  occurs  in  other  species  too,  but 
the  question  was  not  examined  in  Kona,  where 
only  certain  males  of  iS.  ruhroviolaceus  were  rec- 


ognized as  individuals,  and  these  were  never  seen 
in  envelopes. 

There  is  controversy  over  the  diet  of 
parrotfishes.  Hiatt  and  Strasburg  (1960)  reported 
a  diet  of  living  coral  not  only  in  S.  sordidus,  as 
noted  above,  but  also  in  all  other  scarids  they 
examined  in  the  Marshall  Islands.  I  found  no  evi- 
dence that  any  of  the  species  in  Kona,  including  S. 
sordidus,  feed  on  living  coral.  Randall  ( 1967)  simi- 
larly concluded  that  parrotfishes  in  the  West  In- 
dies do  not  feed  on  living  coral;  he  noted  the  large 
amount  of  sand  in  the  guts  of  parrotfishes,  and 
suggested  that  this  material,  taken  purposefully, 
aids  in  grinding  plant  tissue — the  primary  food 
— in  the  pharyngeal  mill. 

Although  I  classify  all  parrotfish  species  in 
Kona  as  herbivores,  their  large  gut  loads  of  cal- 
careous powder,  organic  slurry,  and  sand  seem,  too 
great  a  proportion  of  the  total  contents  to  have 
been  taken  only  incidentally,  or  to  be  adaptive 
only  because  it  aids  in  grinding  up  plant  tissue. 
There  is  need  to  look  closer  at  how  parrotfishes 
utilize  the  material  they  ingest. 

Family  Blenniidae:    combtooth  blennies 

The  combtooth  blennies  are  most  numerous  in 
tide  pools  and  close  to  rocky  shores,  where  fre- 
quently they  are  the  dominant  fishes.  However, 
this  report  considers  only  those  species  that  occur 
regularly  in  water  deeper  than  5  m. 

Exallias  brevis  (Kner) — pao'o  kattila 

Because^',  brevis  is  distinctively  hued  and  habit- 
ually perches  in  exposed  positions  during  the  day 
(Figure  37),  it  is  frequently  noticed  even  though  it 
is  not  especially  numerous.  It  rarely  leaves  the  sea 
floor  and  usually  rests  immobile  except  when 
scraping  the  surface  of  living  coral  with  its  comb- 
like teeth.  After  dark,  it  is  secreted  in  reef  crev- 
ices and  seen  only  occasionally. 

Of  the  10  specimens  (94:  70-106  mm)  ex- 
amined, 2  that  were  taken  from  under  partial 
cover  at  night  (between  4  and  5  h  after  sunset) 
contained  only  well-digested  fragments,  whereas 
only  1  taken  during  the  day  was  empty,  and  the 
other  7  were  full  of  food,  including  fresh  material. 
The  major  item  in  all  seven  (over  90%  of  the  con- 
tents in  each)  was  scleractinian  corals — both 
skeletal  and  tissue  fragments,  along  with  much 
mucus.  The  remaining  identifiable  items  in  the 
diet  were  fine  filamentous  algae  and  diatoms. 


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HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  37. — Exallias  brevis,  a  blenny,  showing  typical  diurnal  attitude. 


In  contrast  to  these  food  data,  Hiatt  and  Stras- 
burg  (1960)  found  only  filamentous  algae  and  de- 
tritus in  the  single  E.  brevis  (80  mm)  that  they 
examined  in  the  Marshall  Islands. 

CONCLUSION. — Exallias  brevis  is  a  diurnal 
species  that  feeds  largely  on  scleractinian  corals, 
both  tissue  and  mucus. 

Cirripectits  variolosus  (Valenciennes) 

During  the  day,  this  relatively  small  blenny 
moves  about  close  to  cover  on  the  reef,  remaining 
in  contact  with  the  substratum.  Though  numer- 
ous, it  is  not  seen  after  dark,  when  presumably  it  is 
secreted  in  reef  crevices. 

The  guts  of  both  specimens  (66  and  80  mm) 
collected  during  midday  contained  filam.entous 
algae  (about  40%  of  the  diet  volume)  and  what 
appeared  to  be  detritus  (50  to  60%).  In  addition, 
one  contained  a  few  scleractinian  coral  fragments 
(5%).  Except  for  the  coral  fragments,  the  diet  of 
these  two  individuals  was  the  same  as  that  of  one 
specimen  of  this  species  examined  by  Hiatt  and 
Strasburg  (1960)  in  the  Marshall  Islands. 


CONCLUSION. — Cirripectus  variolosus  is  a 
diurnal  species  that  feeds  mostly  on  algae  and 
detritus. 

Plogiotremus  goslinei  (Strasburg) — 
sabre-toothed  blenny 

During  the  day,  P.  goslinei  hovers  a  meter  or  so 
above  the  reef,  from  which  position  it  attacks 
larger  fishes  that  incidentally  pass  by,  striking 
them  unseen  from  below  and  behind,  much  as  does 
P.  azalea  in  the  eastern  Pacific  (Hobson,  1968a, 
1969).  But  whereas  P.  azalea  usually  aggregates 
when  hovering  above  the  reef,  P.  goslinei  usually 
is  solitary.  No  specimens  of  P.  goslinei  were  col- 
lected, but  presumably  it  feeds  on  the  mucus  and 
dermal  tissue  of  its  victim,  as  do  other  species  of 
this  genus,  including  P.  rhinorhynchus  (Wickler, 
1960).  P.  azalea  (Hobson,  1968a),  and  P.  town- 
sendi  (Springer  and  Smith- Vaniz,  1972).  These 
species  are  called  sabre-toothed  blennies  because 
each  carries  in  its  lower  jaw  a  pair  of  enormous 
fangs.  Eibl-Eibesfeldt  ( 1955)  and  Strasburg  ( 1960) 
believed  that  these  fangs  are  used  in  feeding,  but 
Wickler  (1960)  concluded  from  work  in  aquaria 


999 


that  P.  rhinorhynchus  uses  its  fangs  not  to  feed, 
but  rather  to  defend  its  territory. 

Plagiotremus  goslinei  hovers  above  the  reef 
during  only  part  of  the  day.  Much  of  the  time  it 
occupies  abandoned  mollusk  and  worm  tubes  on 
the  rocks,  and  these  retreats  also  serve  as  resting 
places  at  night.  In  the  eastern  Pacific,  P.  azalea 
uses  similar  tubes  in  the  same  way  (Hobson, 
1968a,  1969). 

CONCLUSION.— P/a^to^remus  goslinei  is  a 
diurnal  predator  that  feeds  on  mucus  and  dermal 
tissue  of  larger  fishes. 

General  Remarks  on  Combtooth  Blennies 

The  combtooth  blennies  are  generally  regarded 
as  diurnal.  For  example,  Starck  and  Davis  ( 1966) 
did  not  see  members  of  the  family,  known  to  be 
present,  during  many  night  observations  on 
Florida  reefs,  and  Randall  (1967)  reported  the 
group  to  be  diurnal  in  the  West  Indies. 

Although  food  habits  remain  unknown  or  un- 
certain for  most  combtooth  blennies,  reportedly 
many  feed  by  scraping  filamentous  algae  and  de- 
tritus from  rocks.  These  items  predominated  in 
the  diet  of  all  four  blenniid  species  that  Randall 

( 1967 )  examined  in  the  West  Indies,  and  in  all  five 
studied  by  Hiatt  and  Strasburg  ( 1960)  in  the  Mar- 
shall Islands.  In  Kona,  this  mode  of  feeding  occurs 
in  Cirripectus  variolosus,  hni  Exallias  brevis  may 
be  exceptional  in  feeding  mostly  on  the  tissue  and 
mucus  of  scleractinian  corals.  The  significance  of 
coral  mucus  as  food  of  £.  breuis  may  relate  to  the 
significance  of  fish  mucus  as  food  for  blennies  of 
the   genus  Plagiotremus.    Bbhlke   and   Chaplin 

(1968)  suggested  that  at  least  some  combtooth 
blennies  which  scrape  algae  from  rocks  may  gain 
most  of  their  nourishment  from  small  organisms 
living  on  or  around  the  algae.  Clearly,  much  about 
blenniid  feeding  remains  unknown.  Because  these 
small  fishes  scrape  their  food  from  various  sub- 
strata, their  gut  contents  are  difficult  to  analyze. 
One  can  easily  see  that  species  of  Plagiotremus 
have  a  mode  of  feeding  that  differs  from  those  of 
other  blenniids,  because  their  manner  of  taking 
food  is  uniquely  spectacular.  In  comparison,  dif- 
ferences distinguishing  the  feeding  modes  of  other 
combtooth  blennies  are  relatively  subtle. 

Family  Acanthuridae:     surgeonfishes 

The  surgeonfishes  are  the  predominant  fishes 
over  most  Hawaiian  inshore  reefs,  but  this  report 

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FISHERY  BULLETIN:  VOL.  72,  NO.  4 

treats  only  the  two  species  that  feed  on  zooplank- 
ton  in  the  water  column.  The  habits  of  these  two 
were  only  superficially  touched  on  by  Jones 
(1968),  who  provided  a  thorough  treatment  of  the 
many  species  occurring  in  Kona  that  take  their 
food  directly  from  the  substratum  (see  general 
remarks  on  surgeonfishes,  below). 

Acanthurus  thompsoni  (Fowler) 

Acanthurus  thompsoni  (Figure  38)  swims  in 
stationary  aggregations  in  the  water  column 
above  the  reef  in  several  locations  along  the  outer 
drop-off,  20  to  30  m  deep.  Often  mixed  with  this 
surgeonfish  in  these  groups  are  several  other 
species,  especially  Chromis  verater,  C.  ovalis,  and 
Naso  hexacanthus.  At  nightfall,  A.  thompsoni 
descends  to  the  reef  below  where,  inactive  but 
alert,  it  remains  under  cover  until  morning. 

Fourteen  individuals  (141:  128-185  mm)  were 
speared  at  different  times  of  day  and  night.  All  six 
that  were  taken  from  crevices  during  the  hour 
before  daybreak  had  empty  stomachs,  whereas,  all 
seven  collected  from  aggregations  in  the  water 
column  at  various  times  during  afternoons  had 
full  stomachs,  including  fresh  material.  Finally, 
one  solitary  individual  speared  during  midafter- 
noon  close  among  the  coral  in  about  6  m  of  water, 
approximately  200  m  from  the  nearest  feeding 
aggregation,  had  its  stomach  empty.  The  seven 
individuals  with  material  in  their  stomachs  con- 
tained the  items  listed  in  Table  60. 

The  data  show  a  strong  trend  in  the  diet  toward 
relatively  large,  semitransparent,  and  often 
gelatinous  prey.  Some  planktivorous  fishes  from 
other  families  feed  heavily  on  one  or  another  of 
these  prey,  as  does  the  pomace ntrid  Chromis  vera- 
ter, which  feeds  heavily  on  larvaceans  (see  species 
account,  above).  But  in  none  of  these  others  is  the 
diet  similarly  dominated  by  an  array  of  such  prey. 
However,  the  sparse  information  on  the  food  hab- 
its of  A.  thompsoni  given  by  other  authors  does 
not  show  this  trend.  Gosline  and  Brock  (1960) 
reported  only  mollusk  eggs  and  copepods,  whereas 
Jones  (1968)  noted  copepods,  crab  zoea,  crab 
megalops,  and  mysids.  But  these  reports  did  not 
indicate  how  many  specimens  were  examined,  nor 
the  relative  proportion  of  each  type  of  prey  in  the 
diet.  Most  important,  they  did  not  indicate  how 
much  of  the  gut  contents  remained  unidentified. 
The  major  food  items  that  I  found  in  A.  thompsoni 
are  types  quickly  rendered  unidentifiable  by  di- 
gestion, and  thus  easily  missed  if  the  sample  is  not 
fresh. 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  38. — Acanthurus  thompsoni,  a  zooplanktivorous  surgeonfish.  In  comparison  with  its  bottom-feeding  conge- 
ners, this  species  carries  its  more  upturned  mouth  higher  on  its  head,  its  body  is  more  fusiform,  and  its  tail  is  more 
deeply  lunate.  These  morphological  tendencies  occur  in  many  unrelated  zooplanktivorous  fishes. 


CONCLUSION. — Acanthurus  thompsoni  is  a 
diurnal  planktivore  that  feeds  mostly  on  semi- 
transparent,  often  gelatinous,  organisms — 
especially  chaetognaths,  salps,  siphonophores, 
and  lai'vaceans. 

Naso  hexacanthus  (Bleaker) — kala 

During  daylight,  this  relatively  large 
surgeonfish  swims  above  the  outer  drop-off  in 


schools  that  periodically  range  farther  offshore  to 
yet  unknown  distances.  Brock  and  Chamberlain 
(1968)  found  this  species  at  depths  below  120  m 
when  diving  in  the  research  submarine  Asherah, 
but  it  is  not  known  whether  these  fish  had  mi- 
grated from  shallower  water  or  are  of  deepwater 
populations,  although  the  latter  possibility  seems 
the  more  probable.  Generally,  individuals  in  less 
than  10  m  of  water  over  inshore  reefs  during  the 
day  are  relatively  small,  and  swim  in  groups  of 


Table  60. — Food  oi  Acanthurus  thompsoni. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  7) 

diet  volume 

index 

1 

Chaetognaths 

6 

37.1 

31.80 

2 

Salps 

7 

18.6 

18.60 

3 

Siphonophores 

4 

10.0 

5.71 

4 

Larvaceans 

5 

7.4 

5.29 

5 

Calanoid  copepods 

4 

6.6 

4,91 

6 

Gelatinous  egg  masses 

2 

1.7 

0.49 

7 

Gelatinous  clumps  of 

blue-green  algae 

2 

1.6 

0.46 

8 

Fish  eggs,  planktonic 

2 

1.3 

0.37 

9 

Hyperiid  amphipods 

3 

0.7 

0.30 

10 

Polychaetes 

2 

0.9 

0.26 

11 

Decapod  shrimps 

1 

0.3 

0.04 

12 

Harpacticoid  copepods 

1 

0.1 

0.01 

Also. 

unidentified  fragments 

4 

11.7 

6.69 

1001 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


only  a  few  individuals,  often  close  to  the  sub- 
stratum. Most  representatives  seen  inshore  are 
not  feeding,  but  rather  move  uniformly  together 
closely  spaced  in  schools  When  they  do  feed,  the 
schools  are  abandoned  for  aggregations  in  which 
loosely  spaced  individuals  act  independently. 

During  evening  twilight  many  individuals 
move  in  from  deeper  water  over  the  shallower 
parts  of  the  reef.  Larger  representatives  are  in  the 
shallows  only  after  dark.  On  dark  nights,  the 
species  is  scattered  close  among  rocks  and  corals, 
relatively  inactive,  but  alert.  However,  on  moonlit 
nights  some  swim  above  the  reef  in  small  groups. 

Sixteen  individuals  (261:  202-392  mm)  were 
speared  at  various  times  of  night  and  day.  Because 
larger  individuals  are  less  accessible,  especially 
during  the  day,  the  sample  is  biased  toward  small- 
er members  of  the  species.  All  four  solitary  indi- 
viduals taken  close  among  rocks  or  coral  at  night 
(later  than  4  h  after  sunset  and  before  daybreak) 
had  empty  stomachs,  whereas  only  one  of  nine 
others  taken  from  schools  above  the  reef  at  various 
times  of  day  had  material  in  its  stomach,  and  this 
one  came  from  a  school  that  had  just  appeared  over 
the  reef  from  offshore  during  midafternoon.  Fi- 
nally, all  three  that  had  been  observed  feeding 
when  speared  above  inshore  reefs  (on  three  after- 
noons over  2  mo)  had  full  stomachs.  Items  in  the 
four  individuals  whose  stomachs  contained  food 
are  listed  in  Table  61. 

Like  Acanthurus  thompsoni,  this  acanthurid 
feeds  mostly  on  semitransparent,  often  gelati- 
nous, prey.  Of  the  four  that  contained  food,  the 
three  taken  from  inshore  feeding  aggregations 
were  relatively  small  fish  (233-238  mm)  whose 
major  food  was  planktonic  fish  eggs.  Perhaps 
significantly,  thei'e  were  no  fish  eggs  in  the  fourth 
specimen,  which  had  just  appeared  over  the  reef 
from  offshore.  This  individual  was  larger  than  the 


others,  about  300  mm  long,  but  was  collected 
within  30  min  of  one  of  them.  The  major  item  in  its 
stomach  was  filamentous  red  algae,  which  did  not 
occur  in  the  smaller  three.  Only  chaetognaths  and 
larvaceans  occurred  in  the  stomachs  of  all  four 
specimens.  These  limited  data  suggest  there  may 
be  distinctive  differences  in  diet  and  feeding 
grounds  over  the  size  range  of  individuals  sam- 
pled. 

The  high  incidence  of  empty  stomachs  among 
individuals  over  the  inshore  reefs  during  the  day, 
as  well  as  at  night,  suggests  that  many  may  feed 
offshore,  and  be  relatively  inactive,  or  at  least  not 
feeding,  when  they  are  inshore. 

Jones  (1968)  included  N.  hexacanthus  with  A. 
thompsoni  when  reporting  the  diet  of  copepods, 
crab  zoea,  crab  megalops,  and  mysids  noted  above. 
My  comments  concerning  the  reported  diet  of  A. 
thompsoni  (see  above)  apply  equally  here. 

CONCLUSION. — Naso  hexacanthus  is  a  diur- 
nal planktivore  that  takes  mostly  semitranspar- 
ent, often  gelatinous,  prey — especially  chaeto- 
gnaths, larvaceans,  and  fish  eggs.  Limited  data 
suggest  that  drifting  pieces  of  filamentous  algae 
may  also  be  important. 

General  Remarks  on  Surgeonfishes 

Surgeonfishes  are  widespread  on  tropical  reefs, 
and  usually  are  described  in  a  general  way  as 
herbivores  (e.g.  in  the  Bahamas  by  Bbhlke  and 
Chaplin,  1968;  and  in  the  West  Indies  by  Randall, 
1967).  Jones  (1968)  grouped  the  many  Hawaiian 
surgeonfishes  according  to  their  habitats  and 
methods  of  foraging.  In  categorizing  the  bottom- 
foraging  species,  not  studied  by  me,  he  defined 
three  types  of  habitats,  and  listed  the  surgeon- 
fishes characteristic  of  each:     1)  The  turbulent 


Table  61. 

— Food  of  Niiso  hexdcanthiis. 

No,  fish 

Mean  percent 

wi 

h  this 

of 

Rankmg 

Rank 

Items 

item 

(n  -  4) 

diet  volume 

index 

1 

Chaetognaths 

4 

21.3 

21.30 

2 

Fish  eggs,  planktonic 

3 

25.0 

18.75 

3 

Larvaceans 

4 

16.3 

16.30 

4 

Filamentous  red  algae 

1 

18.4 

4.60 

5 

Decapod  shrimps 

3 

2.3 

1.73 

6 

Calanoid  copepods 

2 

2.3 

1.15 

7 

Siphonophores 

2 

2.0 

1.00 

8 

Polychaetes 

1 

1.3 

033 

9 

Hyperiid  amphipods 

1 

0.5 

0.13 

10 

Mollusk  veligers 

1 

0.3 

008 

11 

Gammaridean  amphipods 

1 

0.3 

0,08 

Also. 

unidentified  fragments 

2 

10,0 

5,00 

1002 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


waters  of  the  surge  zone  are  frequented  by 
four  species  of  Acanthurus  (achilles,  glau- 
copareius,  guttatus,  and  leucopareius).  2)  The 
sand  patches  on  deeper,  more  tranquil  reefs  are 
home  to  four  species  of  Acanthurus  {dussumieri, 
mata,  olivaceus,  and  xanthopterus).  3)  Finally, 
basalt  and  coral  substrata  on  reefs  below  the  surge 
zone  (to  a  depth  of  about  90  m)  are  inhabited  by 
three  species  of  Acanthurus  (nigrofuscus,  ni- 
groris,  and  sanduicensis);  two  species  of 
Ctenochaetus  {hawaiiensis  and  strigosus);  two 
species  of  Zebrasoma  iflauescens  and  veliferum; 
the  adults  of  the  latter  often  occur  in  the  surge 
zone);  and  three  species  of  Naso  {brevirostris, 
lituratus,  and  unicornis). 

In  erecting  categories  according  to  foraging 
types,  Jones  (1968)  classified  the  bottom  feeders 
either  as  browsers  or  grazers.  The  browsers  are 
described  as  "strictly  herbivores  that  bite  and  tear 
off  bits  of  multicellular  benthic  algae,  generally 
without  ingesting  any  of  the  inorganic  sub- 
stratum." Browsing  surgeonfishes  include  those 
characteristic  of  the  surge  zone  and  those  char- 
acteristic of  subsurge  reefs,  except  for  the 
two  Ctenochaetus.  The  browsing  species  of 
Acanthurus  and  Zebrasoma  feed  chiefly  on  fine 
filamentous  algae,  whereas  the  browsing  species 
of  Naso  tend  to  feed  on  the  leafy  and  fleshy  forms. 

Surgeonfishes  classified  by  Jones  (1968)  as 
grazers  are  described  as  "Fishes  that  purposely 
pick  up  large  quantities  of  the  substratum  while 
feeding.  .  .  irrespective  of  whether  the  material  is 
rasped  away  from  rocks,  or  picked  up  as  loose 
sand."  This  category  includes  the  surgeonfishes 
characteristic  of  the  sand  patches,  all  of  which  are 
species  of  Acanthurus,  and  the  two  reef-dwelling 
species  of  Ctenochaetus.  The  sand-patch  Acan- 
thurus species  pick  up  mouthfuls  of  sand, 
whereas  the  reef-dwelling  Ctenochaetus  species 
ingest  sediment  that  has  accumulated  over  rocks 
and  dead  coral.  In  examining  these  sediment- 
packed  guts,  Jones  found  material  from  the  two 
groups  distinguishable  by  particle  size — being 
coarse  and  grainy  in  the  sand-patch  Acanthurus, 
fine  and  silty  in  the  reef  Ctenochaetus.  He  con- 
cluded that  the  major  food  of  both  groups  are 
diatoms  and  detritus  that  have  accumulated 
around  the  particles  in  the  surface  layers  of  the 
sediment. 

Surgeonfishes  are  widely  recognized  to  be  active 
by  day  and  relatively  inactive  at  night  (e.g.  in  the 
Gulf  of  CaUfornia  by  Hobson,  1965;  and  in  the 


Florida  Keys  by  Starck  and  Davis,  1966).  Al- 
though quiescent,  these  nocturnally  resting  acan- 
thurids  are  most  often  described  as  alert;  how- 
ever, Collette  and  Talbot  (1972)  reported  that 
Acanthurus  coeruleus  sleeps  while  sheltered 
among  coral  at  night  in  the  Virgin  Islands.  In 
the  Gulf  of  California,  Prionurus  punctatus 
aggregates  above  the  reef  on  bright  moonlit  nights 
(Hobson,  1965),  as  does  Naso  hexacanthus  in 
Kona. 


Family  Zanclidae:     moorish  idol 


Zanclus  canescens  (Linnaeus 
moorish  idol,  kihikihi 


The  moorish  idol  (Figure  39a)  is  closely  related 
to  the  surgeonfishes,  and  some  ichthyologists  (e.g. 
Greenwood  et  al. ,  1966)  consider  it  to  be  a  member 
of  that  family.  It  lacks  the  caudal  spine  common  to 
all  surgeonfishes,  however,  and  most  classi- 
fications assign  it  to  the  monotypic  family 
Zanclidae. 

This  fish  is  numerous  in  all  Kona  inshore 
habitats,  where  it  swims  over  the  reef  during  the 
day,  usually  in  groups  of  four  to  six  individuals. 
When  feeding,  it  regularly  probes  the  narrow 
cracks  and  crevices  of  the  reef  with  its  elongated 
snout.  At  night  it  is  relatively  inactive,  but  alert, 
close  among  rocks  or  coral,  and  at  this  time  its 
coloration  differs  strikingly  from  that  displayed  in 
daylight  (compare  Figure  39a  and  b). 

Of  21  specimens  (108:  74-137  mm)  speared  at 
various  times  of  day  and  night,  all  9  that  were 
collected  at  night  (later  than  4  h  after  sunset  and 
before  sunrise)  had  empty  stomachs,  whereas  all 
12  that  were  taken  during  the  day  (between  mid- 
morning  and  late  afternoon)  had  full  stomachs 
that  included  fresh  material.  Items  in  the  speci- 
mens containing  identifiable  material  are  listed  in 
Table  62. 

The  sponges,  which  greatly  predominate  in  the 
diet,  were  all  small  species  that  presumably  live  in 
narrow  reef  crevices.  This  fish  appears  to  be 
specialized  in  this  diet,  although  Randall  (1955) 
reported  only  algae  in  two  specimens  from  the 
Gilbert  Islands. 

CONCLUSION.— ZancZus  canescens  is  a  diur- 
nal species  that  feeds  mostly  on  small  sponges. 


1003 


FISHERY  BULLETIN.  VOL  72,  NO.  4 


Figure  39. — Zanclus  canescens,  the  moorish  idol:  a,  showing  diurnal  coloration  while  swimming  over  the  reef  during 
the  day;  b,  showing  nocturnal  coloration  while  close  to  the  reef  at  night. 


1004 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Table  62. 

— Food  of  Zanclus  canescens. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  12) 

diet  volume 

index 

1 

Sponges 

12 

84.5 

84.50 

2 

Coralline  algae 

12 

5.7 

5.70 

3 

Other  algae 

12 

5.6 

5.60 

4 

Bryozoans 

8 

1.1 

0.73 

5 

Pelecypod  mollusks 

8 

0.9 

0.60 

6 

Gammaridean  amph 

pods 

6 

0.5 

0.25 

7 

Polychaetes 

4 

0.6 

0.20 

8 

Foramlnlferans 

3 

0.3 

0.08 

9 

Hydroids 

2 

0.2 

0.03 

10 

Barnacle  cirri 

2 

0.2 

0.03 

11 

DIdemnid  tunicates 

1 

0.2 

0.02 

12 

Tanaids 

1 

0.1 

<0.01 

13 

Decapod  shrimps 

1 

0.1 

<0.01 

Order  Pleuronectiformes 
Family  Bothidae:     left-hand  flounders 

Bothiis  manciis  (Broussonet) — pakVi 

This  flatfish  is  most  numerous  lying  immobile 
where  rocks  are  interspersed  with  small  patches  of 
sand.  It  changes  its  coloration  to  match  closely 
that  of  whatever  substratum  it  happens  to  lie  on, 
rocks  or  sand.  When  on  sand,  it  is  frequently 
buried  except  for  its  eyes.  No  change  was  noted  in 
the  overt  behavior  of  this  fish  between  day  and 
night. 

Eight  specimens  (223:  137-277  mm)  were 
speared  at  various  times  of  the  day.  Both  indi- 
viduals collected  within  an  hour  after  sunrise 
were  empty,  whereas  of  six  taken  during  after- 
noons, two  were  empty  and  four  contained  well- 
digested  fish  remains  that  appeared  to  have  been 
in  the  stomachs  at  least  several  hours  when  col- 
lected. 

Hiatt  and  Strasburg  (1960)  reported  this 
flounder  on  both  rocks  and  sand  in  the  Marshall 
Islands  and  noted  a  diet  comprised  primarily  of 
flshes  that  live  in  sandy  areas  adjacent  to  coral. 
Most  prey  species  listed  by  them  are  fishes  (balis- 
tids,  labrids,  pomacentrids,  and  blennies)  that 
probably  are  active  in  exposed  positions  only  dur- 
ing daylight.  They  believed  that  B.  mancus 
responds  only  to  moving  prey;  if  so,  at  least  most  of 
its  prey,  which  rests  at  night,  would  not  be  avail- 
able after  dark.  The  prey  listed  by  Hiatt  and  Stras- 
burg also  included  two  species  of  apogonids,  mem- 
bers of  what  seems  to  be  a  universally  nocturnal 
group;  however,  during  daylight  these  particular 
apogonid  species  congregate  in  exposed  positions 
close  among  the  coral,  where  they  would  seem 
available  to  diurnal  predators. 


CONCLUSION. — Bothus  mancus  preys  on 
small  fishes  during  the  day.  Its  nocturnal  habits 
remain  uncertain. 

General  Remarks  on  Left-hand  Flounders 

Bothids  are  the  most  numerous  flatfishes  on 
tropical  reefs.  In  the  West  Indies,  Randall  (1967) 
found  fishes  the  major  prey  of  Bothus  lunulatus 
and  B.  ocellatus,  both  of  which  occur  on  sand 
patches  around  coral  reefs,  often  largely  buried.  In 
the  Florida  Keys,  Starck  and  Davis  (1966)  found 
B.  ocellatus  in  sandy  areas  of  all  reef  zones,  and 
although  they  did  not  examine  its  food  habits, 
they  inferred  from  its  behavior  that  it  preys  after 
dark  on  the  various  small  nocturnal  invertebrates 
active  on  the  sand  at  night. 

Order  Tetraodontiformes 

Family  Balistidae:  triggerfishes 

Melichthys  niger  (Bloch) — humuhumu  'eleele 

During  the  day,  M.  niger  typically  hovers  in 
loosely  spaced  aggregations  several  meters  above 
the  reef.  Each  individual  independently  picks 
material  drifting  in  the  mid-waters.  It  is  a 
wary  animal  that  dives  to  holes  in  the  reef  when 
alarmed.  It  enters  these  same  holes  at  nightfall 
and  rests  there  on  its  side  until  morning. 

All  seven  individuals  (165:  122-195  mm) 
speared  from  among  those  active  above  the  reef 
during  the  day  were  full  of  food,  as  listed  in  Table 
63.  The  major  food  items  are  fragments  of  fleshy 
algae — filamentous  and  foliaceous — probably 
most  of  which  are  drifting  in  the  mid-waters  when 
taken.  This  triggerfish  feeds  at  least  occasionally 
on  the  sea  floor,  as  indicated  by  the  relatively  high 


1005 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  63. — Food  of  Melichthys  niger. 


No.  fish 

Mean  percent 

wi 

h  this 

of 

Ranking 

Rank 

Items 

item 

(n  =  7) 

diet  volume 

index 

1 

Fleshy  algae 

7 

52.3 

52.30 

2 

Coralline  algae 

7 

18.7 

18.70 

3 

Calanoid  copepods 

5 

2.7 

1.93 

4 

Carjdean  shrimps 

4 

1.1 

0.63 

5 

Harpacticold  copepods 

4 

0.6 

0.34 

6 

Scleractinlan  coral 

1 

2.1 

0.30 

7 

Insects 

2 

0.4 

0.11 

8 

Foraminlferans 

2 

0.3 

0.09 

9 

Heteropods 

2 

0.3 

0.09 

10 

Cyclopoid  copepods 

1 

0.6 

0.09 

11 

Crab  megalops 

1 

0.4 

0.06 

12 

Mollusk  veligers 

1 

0.1 

0.01 

13 

Natlcid  gastropods 

1 

0.1 

0.01 

14 

Ostracods 

1 

0.1 

0.01 

15 

Gammaridean  amphipods 

1 

0.1 

0.01 

16 

Fish  eggs,  planktonic 

1 

0.1 

0.01 

Also,  sand 

1 

29 

0.41 

Unidentified  fragments 

6 

17.1 

14.66 

proportion  of  coralline  algae  in  its  diet  and  also  by 
the  stony  coral,  bitten  off  in  chunks,  in  one  indi- 
vidual; nevertheless,  most  of  its  food  is  planktonic. 
Certainly  the  relatively  minor  status  of  the  many 
zooplankters  in  the  above  list  far  understates 
their  relative  significance  to  this  fish.  The  ranking 
is  biased  toward  the  more  bulky  items;  thus,  one 
algal  fragment,  in  terms  of  volume,  may  be  equiv- 
alent to  a  hundred  or  more  copepods.  And  yet  the 
effort  expended  in  taking  the  algal  fragment 
may  have  been  no  greater  than  that  expended  in 
taking  a  single  copepod.  A  given  volume  of 
copepods  (and  many  other  zooplankters)  probably 
is  far  more  nutritious  than  the  same  volume 
of  algae. 

In  the  West  Indies,  this  circumtropical  trigger- 
fish  similarly  feeds  on  algae  and  zooplank- 
ton  in  the  mid-waters,  taking  the  algae  from  the 
benthos,  or  as  drifting  fragments  (Randall,  1967). 

CONCLUSION.— Melichthys  niger  is  a  diurnal 
omnivore  that  feeds  mostly  on  drifting  algal  frag- 
ments and  zooplankton,  along  with  some  benthic 
vegetation. 


Xanthichthys  ringens  (Linnaeus) 

This  triggerfish  (Figure  40)  is  one  of  the  most 
numerous  fishes  at  depths  below  25  m  along  the 
outer  drop-off  Like  so  many  fishes  that  concen- 
trate in  this  location,  it  aggregates  in  the  water 
column  and  picks  plankton,  an  activity  that  is 
limited  to  daylight;  at  nightfall,  it  shelters  in  reef 
crevices,  where  it  rests  on  its  side  until  morning. 


Of  the  11  specimens  ( 125:  98-145  mm)  speared 
during  day  and  night,  2  that  were  collected  from 
reef  crevices  during  the  last  hour  before  daybreak 
were  empty,  whereas  all  9  that  were  taken  from 
mid-water  aggregations  at  various  times  during 
the  day  were  full  of  food,  as  listed  in  Table  64. 

I  found  no  evidence  that  this  triggerfish  takes 
food  from  the  sea  floor.  Like  Melichthys  niger,  X. 
ringens  is  circumtropical  (Bohlke  and  Chaplin, 
1968);  perhaps  the  planktivorous  habits  of 
these  two  triggerfishes  permit  survival  over  long 
periods  in  the  open  sea  where  their  bottom-feeding 
relatives  would  perish.  Gosline  and  Brock  (1960), 
whose  data  were  mostly  from  relatively  shallow 
water,  reported  X.  ringens  uncommon  in  Hawaii. 
The  large  numbers  of  this  species  occurring  along 
the  outer  drop-off  in  Kona,  however,  indicates  a 
habitat  in  Hawaii  similar  to  that  in  the  West  In- 
dies, where  it  rarely  occurs  in  less  than  35  m  of 
water,  but  is  one  of  the  most  numerous  fishes 
below  that  depth  (Randall,  1968). 

CONCLUSION  .—Xanthichthys  ringens  is  a 
diurnal  planktivore  that  feeds  mostly  on  calanoid 
copepods. 

Rhinecanthus  rectangtilus  (Bloch  and 
Schneider) — humithumu  nukuniiku  a  piiaa 

This  triggerfish  is  most  common  on  shallow, 
surge-swept,  basalt  reefs.  It  is  a  solitary  fish  that 
swims  close  to  the  reef  top  during  the  day,  picking 
at  organisms  on  the  bottom.  A  wary  animal,  it 
quickly  takes  refuge  in  the  reef  when  threatened. 


1006 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  40. — Xanthichthys  ringens,  a  zooplanktivorous  triggerfish.  In  comparison  with  bottom-feeding  triggerfishes, 
this  species  has  a  more  upturned  mouth  that  is  higher  on  its  head,  and  its  body  is  more  fusiform.  Both  features  are 
widespread  among  zooplanktivorous  fishes. 


Its  shelters,  like  those  of  Melichthys  niger,  above, 
are  small  enough  so  that  the  fish  can  wedge  itself 
in  by  locking  its  large  dorsal  spine  erect.  Each 
individual  fish  seems  to  resort  to  a  specific  hole 
that  serves  as  a  refuge  by  day,  and  also  as  a  resting 
place  at  night  when  the  species  is  inactive. 

All  nine  individuals  (142:  114-170  mm)  speared 
at  various  times  of  the  day  from  among  those 
active  close  to  the  reef  were  full  of  food,  as  listed 


in  Table  65.  Food  items  were  mostly  small  organ- 
isms between  1  and  6  mm  in  their  greatest 
dimension,  taken  intact;  the  few  exceptions 
are  fragments  of  about  this  size  from  larger  or- 
ganisms. 

Hiatt  and  Strasburg  (1960)  found  this  species 
numerous  on  shallow  reefs  in  the  Marshall  Islands 
and  reported  a  crustacean  and  algal  diet  similar  to 
that  of  the  species  in  Kona. 


Table  64.- 

-Food  of  Xanthichthys 

ringens. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  {n  =  9) 

diet  volume 

index 

1 

Calanoid  copepods 

9 

43.9 

43.90 

2 

Mollusk  vellgers 

6 

0.8 

0.53 

3 

Fish  eggs,  planktonic 

2 

1.4 

0.31 

4 

Chaetognaths 

2 

1.3 

0.29 

5 

Siphonophores 

2 

1.2 

0.27 

6 

Pteropods 

2 

1.2 

0.27 

7 

Ostracods 

4 

0.6 

0.27 

8 

Cyclopoid  copepods 

1 

0.8 

0.09 

9 

Heteropods 

2 

0.3 

0.07 

10 

Hyperlld  amphipods 

2 

0.2 

0-04 

11 

Gammarldean  amphipods 

1 

0.2 

0.02 

Also, 

crustacean  fragments 

4 

4.6 

2.04 

Unidentified  fragments 

9 

43.5 

43.50 

1007 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  65. — Food  oi Rhinecanthus  rectangulus. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  9) 

diet  volume 

index 

1 

Gammaridean  amphipods 

9 

19.4 

19.40 

2 

DIdemnid  tunlcates 

9 

8.6 

8.60 

3 

Filamentous  algae 

6 

7.8 

5.20 

4 

Xanthid  crabs 

4 

6.7 

2.98 

5 

Polychaetes 

4 

6.3 

280 

6 

Decapod  shrimps 

5 

4.2 

2.33 

7 

Tanaids 

4 

2.9 

1.29 

8 

Coralline  algae 

4 

2.6 

1.16 

9 

Prosobranch  gastropods 

4 

2.4 

1.07 

10 

Echinoids 

3 

2.9 

0.97 

11 

Isopods 

3 

2.6 

0.87 

12 

Bryozoans 

2 

0.7 

0.16 

13 

Caprellid  amphipods 

1 

0,6 

0.07 

14 

Pelecypods 

1 

0.3 

0.03 

15 

Crab  megalops 

1 

0.2 

0.02 

Also, 

crustacean  fragments 

4 

6.2 

2.76 

Unidentified  fragments 

7 

25.6 

19.91 

Table  66.- 

—Food  of  Sufflamen 

bursa. 

No  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  9) 

diet  volume 

index 

1 

Echinoids 

9 

9.1 

910 

2 

Gammaridean  amphipods 

7 

8.3 

6.46 

3 

Polychaetes 

8 

4,6 

4.09 

4 

Prosobranch  gastropods 

9 

3.8 

3.80 

5 

Brachyurans 

5 

4.8 

2.67 

6 

Sponges 

8 

2.6 

2.31 

7 

Tanaids 

6 

2.8 

1.87 

8 

Opisthobranchs 

6 

2.3 

1.53 

9 

Cyclopoid  copepods 

9 

1.2 

1.20 

10 

Isopods 

7 

1.3 

1.01 

11 

Ostreid  pelecypods 

7 

1.0 

0.78 

12 

Caridean  shrimps 

3 

0,8 

0.27 

13 

Foraminiferans 

4 

0,4 

0.18 

14 

Ostracods 

4 

.    0.4 

0.18 

15 

Crab  megalops 

2 

0.3 

007 

16 

Bryozoans 

1 

0.1 

001 

17 

SIpunculid  introverts 

1 

0.1 

0.01 

18 

Harpacticoid  copepods 

1 

0.1 

0.01 

19 

Barnacle  cirri 

1 

0.1 

001 

20 

Mites 

1 

0.1 

0.01 

Also. 

crustacean  fragments 

5 

3.8 

2.11 

Algal  fragments 

5 

1.2 

0.67 

Unidentified  fragments 

9 

508 

50.80 

CONCLUSION. — Rhinecanthus  rectangulus  is 
a  diurnal  omnivore,  feeding  mostly  on  gammari- 
dean amphipods  and  other  small  organisms. 


Sufflamen  bursa  (Bloch  and  Schneider 
humuhumu  umaiima  lei 


This  is  the  most  numerous  and  widespread 
triggerfish  on  Kona  reefs.  A  solitary  species,  ac- 
tive by  day  close  to  rocks  and  coral,  it  picks  at 
organisms  on  the  sea  floor.  It  is  less  inclined  to 
seek  cover  in  reef  crevices  than  are  Melichthys 
niger  and  Rhinecanthus  rectangulus,  above,  but 
nevertheless  is  a  wary  animal  that  shys  away 
from  humans.  At  night  it  is  inactive,  resting  on  its 
side  under  cover  on  the  reef  until  morning. 


Thirteen  individuals  (140:  109-164  mm)  were 
speared  at  various  times  of  day  and  night.  The  four 
that  were  collected  in  darkness  as  they  rested  in 
reef  crevices  during  the  last  2  h  before  daybreak 
were  empty,  whereas  the  nine  that  were  collected 
at  various  times  during  the  day  as  they  swam  over 
the  reef  were  full  of  food,  as  listed  in  Table  66.  As 
was  true  of  the  food  of  R.  rectangulus,  these  food 
items,  including  the  echinoids,  are  mostly  small 
animals  between  1  and  6  mm  in  their  greatest 
dimension,  taken  intact;  the  exceptions  are  frag- 
ments of  about  this  size  from  larger  organisms. 
Unlike  the  omnivorous  R.  rectangulus,  however, 
S.  bursa  seems  to  be  strictly  carnivorous  (the  few 
algal  fragments  among  its  gut  contents  probably 
were  taken  incidentally  along  with  prey).  No 


1008 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


single  item  greatly  predominates  in  its  diet,  a 
circumstance  that  may  relate  to  its  widespread 
occurrence  in  a  variety  of  habitats. 

CONCLUSION.— Sufflamen  bursa  is  a  diurnal 
predator  that  feeds  on  a  variety  of  benthic  ani- 
mals. 


General  Remarks  on  Triggerfishes 

The  balistids  are  known  for  their  powerful  jaws 
and  sharp  cutting  teeth,  which  enable  them  to 
prey  on  a  variety  of  armored  invertebrates  denied 
as  food  to  most  other  fishes  (Randall,  1967).  Most 
triggerfishes  seem  to  make  full  use  of  this  equip- 
ment: in  the  Virgin  Islands  5a/js^es  vetula  preys 
on  the  large  echinoid  Diadema  (often  attacking 
this  sea  urchin  from  its  oral  surface,  where  the 
spines  are  shortest)  and  on  relatively  large  queen 
conchs,  Stromhus,  which  it  crushes  upon  inges- 
tion (Randall,  1967).  Similarly,  in  the  Marshall 
Islands  several  triggerfishes  use  their  powerful 
feeding  apparatus  to  crush  mollusks  and  hard- 
shelled  crustaceans,  as  well  as  to  break  off  the  tips 
of  cespitose  corals  (Hiatt  and  Strasburg,  1960). 
Rhinecanthus  rectangulus  and  Sufflamen  bursa 
in  Kona  may  be  exceptional  among  bottom- 
foraging  balistids  in  that  they  feed  so  heavily  on 
small  organisms,  ingested  intact.  On  the  other 
hand,  it  may  be  that  the  high  proportion  of 
unidentified  fragments  in  the  guts  of  both  species 
are  the  crushed  remains  of  larger  organisms  not 
properly  ranked  among  the  data.  Nevertheless, 
the  capacity  to  feed  on  tiny  organisms  is  probably 
well  established  among  the  balistids,  as  demon- 
strated by  the  exclusively  zooplanktivorous  habits 
o{ Xanthichthys  ringens. 

Triggerfishes  are  well  known  to  be  active  by  day 
and  to  rest  under  cover  at  night,  usually  lying  on 
their  sides.  Diurnal  habits  were  reported  in  balis- 
tids of  the  Gulf  of  California  (Hobson,  1965, 1968a) 
and  the  West  Indies  (Randall,  1967).  Collette  and 
Talbot  ( 1972)  described  Balistes  vetula  sleeping  at 
night  in  exposed  positions  on  reefs  in  the  Virgin 
Islands,  and  Earle  (1972)  reported  that  in  the  Vir- 
gin Islands  B.  vetula  frequently  returns  nightly  to 
the  same  hole  in  the  reef.  There  is  at  least  some 
activity  among  triggerfishes  on  moonlit  nights, 
however,  as  for  example  in  B .  polylepis  in  the  Gulf 
of  California  (Hobson,  1965),  but  it  is  unknown 
whether  this  activity  involves  feeding. 


Family  Monacanthidae:     file  fishes 

Cantherines  dumerili  (Hollard) — 'o'i7i 

During  daylight,  this  filefish  swims  several 
meters  above  coral-rich  reefs,  usually  in  loosely 
associated  pairs  that  move,  often  on  their  sides, 
back  and  forth  in  restricted,  well-defined  areas. 
Because  it  swims  in  the  water  column  and  because 
it  is  relatively  large,  this  filefish  is  a  conspicuous 
component  of  the  fauna,  even  though  relatively 
few  occur  on  the  reef.  Despite  the  time  it  spends  in 
mid-water,  C.  dumerili  was  obsei'ved  feeding  only 
on  the  sea  floor,  where  it  bites  off  the  tips  of  coral 
branches.  During  evening  twilight  it  settles  into 
holes  in  the  reef,  where  it  remains  inactive  until 
morning. 

All  eight  individuals  (200:  171-240  mm) 
speared  from  among  those  hovering  above  the  reef 
during  midday  were  full  of  food.  Scleractinian  cor- 
als were  the  major  food  items,  occurring  in  seven 
of  the  eight  specimens  (mean  percent  of  diet  vol- 
ume: 80;  ranking  index:  70),  always  as  chunks  of 
Pocillopora  and  Porites.  about  4  mm  in  diameter. 
Other  food  items  were:  echinoids,  all  tips  of  the 
clublike  spines  of  Heterocentrotus  mammillatus , 
in  two  (mean  percent  of  diet  volume:  7.4;  ranking 
index:  1.85),  a  variety  of  bryozoans,  both  encrust- 
ing and  arborescent,  that  were  almost  the  total 
contents  of  one  (mean  percent  of  diet  volume: 
12.5;  ranking  index  volume:  1.56),  and  pelecypods 
in  one  (mean  percent  of  diet  volume:  0.1;  ranking 
index:  0.01). 

Hiatt  and  Strasburg  (1960)  found  that  of  the  two 
specimens  of  this  species  (reported  as  Amanses 
carolae)  that  they  examined  in  the  Marshall  Is- 
lands, one  had  fed  on  scleractinian  corals  exclu- 
sively, whereas  the  other  had  mixed  a  coral  diet 
with  sponges  and  algae.  Apparently  this  species 
does  not  feed  during  the  considerable  time  that  it 
spends  in  the  water  column,  as  its  diet  seems  to 
comprise  only  benthic  organisms. 

CONCLUSION  .—Cantherines  dumerili  is  a 
diurnal  predator  that  feeds  mainly  on  scleractin- 
ian corals. 

Cantherines  sandwichiensis 
(Quoy  and  Gaimard) — oili  lepa 

This,  the  most  numerous  filefish  in  Kona,  espe- 
cially on  basalt  reefs  in  less  than  10  m  of  water,  is  a 
solitary  fish  that  swims  close  over  the  reef  during 


1009 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  67. — Food  of  Canthehnes  sandwichiensis. 


No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  7) 

diet  volume 

index 

1 

Filamentous  algae 

7 

35.7 

35.70 

2 

Coralline  algae 

7 

32.1 

32.10 

3 

Didemnid  tunicates 

7 

6.1 

6.10 

4 

Gammaridean  amphipods 

6 

4.0 

3.43 

5 

Scleractinian  corals 

2 

5.0 

1.43 

6 

Sponges 

2 

2.2 

0.63 

7 

Diatoms 

3 

1.1 

0.47 

8 

Bryozoans 

2 

1.0 

0.29 

9 

Hydroids 

2 

0.4 

0.11 

10 

Polychaetes 

1 

1.4 

0.20 

11 

Ostreid  pelecypods 

2 

0.6 

0.17 

12 

Caprellid  amphipods 

2 

0.6 

0.17 

13 

Gastropod  eggs 

1 

0.3 

0.04 

14 

Prosobranch  gastropods 

1 

0.3 

0.04 

15 

Tanaids 

1 

0.1 

0.01 

16 

Ophiuroids 

1 

0.1 

0.01 

Also, 

unidentified  fragments 

5 

8.3 

5.93 

Sand 

1 

0.7 

0.10 

Table  68.- 

-Food  of  Pervagor  spilosoma. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  6) 

diet  volume 

index 

1 

Scleractinian  corals 

5 

35.8 

29,83 

2 

Filamentous  algae 

4 

19.3 

12.87 

3 

Coralline  algae 

6 

7.7 

7.70 

4 

Sponges 

1 

3.3 

0.55 

5 

Polychaetes 

2 

1.5 

0.50 

6 

Echinoids 

3 

0.8 

0.40 

7 

Gammaridean  amphipods 

3 

0.7 

0.35 

8 

Tanaids 

2 

0.5 

0.16 

9 

Diatoms 

2 

0.3 

0.10 

10 

Fish  eggs 

1 

0.5 

0.08 

11 

Hydroids 

2 

0.3 

0.10 

12 

Opisthobranch  gastropods 

0.2 

0.03 

13 

Ostracods 

0.2 

0.03 

14 

Cyclopoid  copepods 

0.2 

0.03 

15 

Crab  megalops 

0.2 

0.03 

16 

Ophiuroids 

0.2 

0.03 

Also, 

unidentified  fragments 

5 

28.1 

23.41 

Sand 

1 

0.2 

0.03 

the  day,  picking  at  objects  on  the  bottom.  During 
evening  twilight,  it  moves  from  sight  and  is  not 
visible  at  night  when  presumably  it  rests  in  reef 
crevices. 

All  seven  individuals  (116:  84-132  mm) 
speared  from  among  those  active  close  to  the  reef 
during  the  day  were  full  of  food,  much  of  it  fresh, 
as  listed  in  Table  67. 

CONCLUSION.— Can^/?^rznes  sandwichiensis 
is  a  diurnal  omnivore  that  feeds  on  a  wide  variety 
of  benthic  algae  and  invertebrates. 

Pervagor  spilosoma  (Lay  and 
Bennett) — oili   uwfuwi 

This,  the  most  colorful  filefish  in  Kona,  as  well 
as  the  smallest  of  the  three  considered  there,  is 


most  numerous  on  coral-rich  reefs.  It  is  a  solitary 
fish,  active  close  among  the  corals  in  daylight,  but 
not  seen  after  dark  when  presumably  it  rests  in 
reef  crevices. 

Of  the  seven  specimens  (85:  64-120  mm)  col- 
lected, one  that  was  speared  close  to  coral  just  be- 
fore sunrise  (the  first  individual  of  the  species  to 
appear  that  morning)  had  an  empty  gut,  whereas 
all  six  that  were  speared  from  among  those  active 
on  the  reef  between  midmorning  and  midafter- 
noon  were  full  of  food,  as  listed  in  Table  68. 

As  is  true  of  Cantherines  dumerili,  above,  the 
major  food  of  this  filefish  is  scleractinian  coral; 
however,  whereas  C.  dumerili  bites  off  relative- 
ly large  chunks  of  coral,  each  containing  many 
polyps,  P.  spilosoma  seems  to  pluck  at  only  one 
polyp  at  a  time,  as  do  certain  chaetodontids.  Never- 
theless, judging  from  its  gut  load  of  skeletal 


1010 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


fragments,  P.  spilosoma  does  not  neatly  snip  off 
the  polyps  so  much  as  coarsely  gouge  them  from 
their  thecae. 

CONCLUSION. — Peruagor  spilosoma  is  a 
diurnal  omnivore  that  feeds  mainly  on  scleractin- 
ian  corals,  to  a  lesser  extent  on  algae  and  other 
benthic  invertebrates. 

General  Remarks  on  Filefishes 

In  summarizing  their  treatment  of  monacan- 
thids  in  the  Marshall  Islands,  Hiatt  and  Strasburg 
(1960:105)  stated:  "There  is  no  question  that 
filefishes  derive  the  bulk  of  their  nutriment  from 
living  corals."  All  of  the  Oxymonocanthus  lon- 
girostris  (a  widespread  Indo-Pacific  species  that 
does  not  occur  in  Hawaii)  examined  by  them  con- 
tained only  coral  polyps,  with  no  skeletal  mate- 
rial. Their  account  indicates  that  this  species, 
which  has  a  very  long,  narrow  snout,  with  teeth 
protruding  from  its  mouth  as  long,  cupshaped  in- 
cisors, may  be  among  the  most  highly  specialized 
of  coral-feeding  filefishes.  On  the  other  hand, 
Randall  (1967)  found  corals  to  be  insignificant  as 
food  for  West  Indian  filefishes;  of  the  six  species  he 
examined,  corals  were  in  the  diet  of  only  one,  and 
only  as  a  minor  component.  According  to  Randall, 
the  West  Indian  filefishes  take  a  diverse  array  of 
benthic  organisms:  Algae  and  sea  grasses  are 
major  items,  along  with  a  variety  of  benthic  in- 
vertebrates. Thus,  Cantherines  sandwichiensis  in 
Kona  has  a  diet  much  like  the  West  Indian  species 
described  by  Randall,  whereas  C.  dumerili  takes 
largely  corals  in  Kona,  just  as  Hiatt  and  Strasburg 
reported  it  and  other  filefishes  doing  in  the  Mar- 
shall Islands.  Clearly,  many  filefishes,  especially 
certain  Indo-Pacific  species,  feed  heavily  on  corals, 
whereas  various  other  filefishes  find  their  food 
from  among  other  elements  of  the  benthos. 


Filefishes  are  recognized  as  being  diurnal.  For 
example,  Starck  and  Davis  (1966)  described  C. 
pullus  as  resting  at  night  wedged  in  rocky  holes  on 
reefs  in  Florida. 

Family  Ostraciontidae:    boxfishes 

Ostracion  meleagris  (Shaw) — pahii 

This  boxfish  is  widespread  on  nearshore  reefs  in 
Kona,  but  is  nowhere  numerous,  except  occasion- 
ally in  some  parts  of  the  boulder  habitat.  During 
the  day  it  swims,  slowly,  close  among  rocks  and 
coral,  now  and  then  picking  at  the  substratum.  I 
saw  several  in  the  same  places  at  night,  but  at  the 
time  felt  they  had  been  disturbed  from  resting 
places  by  my  activity.  It  was  difficult  to  appraise 
the  nocturnal  behavior  of  this  species,  owing  to  its 
relatively  low  numbers  on  the  reef  and  the  re- 
duced visibility  after  dark,  and  because  the  few 
observations  were  somewhat  ambiguous. 

Of  the  six  individuals  (65:  43-80  mm)  collected, 
one  speared  within  15  min  after  sunrise  as  it  swam 
close  to  the  reef  had  an  empty  gut,  whereas  all  five 
taken  under  similar  circumstances,  except  later  in 
the  day  (between  late  morning  and  late  afternoon) 
had  food  throughout  the  gut.  The  items  in  the 
foregut  are  listed  in  Table  69. 

CONCLUSION. — Ostracion  meleagris  feeds  on 
benthic  invertebrates  during  the  day.  Its  noctur- 
nal status  remains  uncertain,  although  tenuous 
data  indicate  relative  inactivity  after  dark. 

General  Remarks  on  Boxfishes 

Boxfishes  in  the  tropical  Atlantic  generally  are 
described  as  active  during  both  day  and  night 
(Starck  and  Davis,  1966;  Earle,  1972;  Collette  and 
Talbot,  1972).  Tunicates,  the  major  prey  of 
Ostracion  meleagris  in  Kona,  were  ranked  either 


Table  69. — Food  of  Ostracion  meleagris. 


No 

.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item 

{n  =  5) 

diet  volume 

index 

1 

Didemnid  tunicates 

3 

42.8 

25.68 

2 

Polychaetes 

2 

13.0 

5.20 

3 

Algae 

2 

7.4 

2.96 

4 

Sponges 

2.0 

0.40 

5 

Pelecypods 

1.0 

0.20 

6 

Prosobranch  gastro 

pods 

1.0 

020 

7 

Copepods 

0.4 

0  08 

Also. 

sand  and  debris 

6.0 

1.20 

Unidentified  fragments 

2 

264 

10.56 

1011 


first  or  second  as  prey  of  three  of  the  five  West 
Indian  boxfishes  studied  by  Randall  (1967). 
Furthermore,  polychaetes  and  sponges  also  were 
found  to  be  important  prey  in  the  Atlantic  species 
just  as  they  are  in  O.  meleagris  from  Kona.  In  the 
Marshall  Islands,  the  major  foods  of  O.  cubicus 
are  mollusks,  polychaetes,  and  algae  (Hiatt  and 
Strasburg,  1960). 

At  least  some  boxfishes,  including  O.  meleagris 
in  Hawaii  (Gosline  and  Brock,  1960;  Thomson, 
1964),  release  a  substance  that  is  toxic  to  other 
fishes.  This  may  give  them  some  immunity  from 
predation,  as  suggested  for  some  tropical  Atlantic 
species  by  Randall  (1967). 

Family  Tetraodontidae:    balloonfishes 

Arothron  hispidus  (Linnaeus) — opn  hue,  keke 

This  solitary  balloonfish  is  widespread  on  Kona 
reefs,  but  is  nowhere  numerous.  In  daylight  it 
frequently  hovers  inactively  several  meters  above 
the  reef,  although  just  as  often  it  swims  slowly 
among  the  rocks  and  coral.  After  dark  it  continues 
to  swim  actively,  close  to  the  reef. 

Nine  individuals  (253:  187-332  mm)  were 
speared  during  day  and  night.  The  guts  of  two 
were  empty:  one  of  these  was  hovering  high  in  the 
water  column  during  early  afternoon  when  col- 
lected; the  other  was  swimming  close  among  rocks 
during  the  hour  immediately  before  first  morning 
light.  All  of  the  other  seven,  taken  as  they  swam 
close  to  the  reef — five  during  midday,  two  during 
midnight — contained  identifiable  material,  as 
listed  in  Table  70.  The  tunicates  taken  by  this 
balloonfish  include  several  benthic  species,  both 
compound  and  simple  forms;  the  echinoids  are  the 
crushed  tests  and  spines  of  echinometrids  and 
cidarids;  the  asteroids  are  mostly  tips  of  the  ap- 
pendages from  Linckia. 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

Generally  the  items  are  hard-bodied  forms  that 
remain  recognizable  for  a  relatively  long  time 
after  ingestion;  nevertheless,  material  from  the 
two  individuals  collected  at  night  appeared 
fresher  overall  than  that  from  the  individuals  col- 
lected during  midday. 

In  the  Marshall  Islands,  the  single  A.  hispidus 
examined  by  Hiatt  and  Strasburg  (1960)  had  fed 
on  much  the  same  material  as  listed  above,  except 
that  it  also  had  ingested  some  living  scleractinian 
corals. 

CONCLUSION. — Arothron  hispidus  preys  on 
a  variety  of  benthic  invertebrates,  especially 
those  having  a  hard  or  leathery  external  covering. 
Limited  evidence  indicates  it  is  active  during 
both  day  and  night. 

Arothron  meleagris  (Bloch  and  Schneider) — 
'opu  hue,  keke 

Like  its  congener  A.  hispidus,  above,  the  soli- 
tary species  A.  meleagris  (Figure  41)  is  wide- 
spread on  Kona  reefs,  but  is  nowhere  numerous.  It 
does  not  hover  inactively  above  the  reef  during 
the  day  as  A.  hispidus  often  does,  and  on  the  few 
occasions  when  it  was  seen  at  night — always 
under  ledges  or  in  crevices — A.  meleagris  seemed 
inactive.  During  daylight  it  swims  slowly  among 
the  rocks  or  corals. 

Eleven  individuals  (221:  146-393  mm)  were 
collected  during  the  day.  Of  three  whose  guts  were 
empty,  two  were  speared  as  they  swam  close  to  the 
reef  within  an  hour  after  sunrise,  and  one  was 
taken  from  a  small  cave  during  midafternoon.  The 
remaining  eight,  taken  as  they  swam  close  to  the 
reef  during  midday,  all  contained  identifiable 
material.  Seven  of  these  had  taken  scleratinian 
corals  (mean  percent  of  diet  volume:  43.1;  ranking 
index:  37.71),  mostly  small  chunks  of  encrusting 


Table  70.- 

—Food  of  Arothron  hispidus. 

No.  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  (n  =  7) 

diet  volume 

index 

1 

Tunicates 

5 

33.7 

24.07 

2 

Echinoids 

5 

28.1 

20.07 

3 

Ophiuroids 

3 

13.4 

5.74 

4 

Asteroids 

3 

8.3 

356 

5 

Brachyurans 

2 

6.4 

1.83 

6 

Sponges 

2.9 

041 

7 

Hydroids 

2.9 

0.41 

8 

Prosobranch 

jastropods 

0.1 

0.01 

9 

Pagurid  crabs 

0.1 

0.01 

Also, 

algae 

0.3 

004 

Unidentifiable 

frag 

ments 

3 

38 

1.63 

1012 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Figure  41. — Arothron  meleagris,  a  balloonfish.  By  inflating  its  saclike  body  with  water,  this  slow-swimming  fish 
increases  its  size,  which  presumably  decreases  its  vulnerability  to  predators. 


Pontes,  whereas  six  had  taken  tunicates  (mean 
percent  of  diet  volume:  44.4;  ranking  index:  33.3), 
all  of  them  a  large  colonial  form  with  a  heavy, 
black  integument  that,  like  the  coral,  encrusts  on 
rocks.  The  only  other  recognizable  items  were  pec- 
tinid  pelecypods  in  one  (mean  percent  of  diet  vol- 
ume: 0.6;  ranking  index:  0.08).  Three  contained 
unidentifiable  fragments  (mean  percent  of  diet 
volume:  11.9;  ranking  index:  4.46).  Thus,  these 
data  indicate  that,  compared  with  A.  hispidus,  A. 
meleagris  is  a  relatively  specialized  feeder.  The 
three  A.  meleagris  that  Hiatt  and  Strasburg 
(1960)  examined  in  the  Marshall  Islands  had  fed 
almost  exclusively  on  living  corals. 

CONCLUSION. — Arothron  meleagris  is  a  diur- 
nal predator  that  feeds  mostly  on  corals  and  tuni- 
cates which  encrust  on  rocks. 

General  Remarks  on  Balloonfishes 


fishes  crush  an  array  of  armored  organisms  that 
are  unavailable  as  prey  to  most  other  fishes  (Hiatt 
and  Strasburg,  1960). 

Family  Canthigasteridae:     sharpbacked 

puffers 

Canthigaster  amhoinensis  Bleaker  — 
pu'j/  ola'i 

This  pufferfish  occurs  chiefly  in  relatively  shal- 
low water  where  there  is  much  exposed  basalt.  It  is 
a  solitary  fish,  active  close  to  the  sea  floor  during 
the  day,  but  only  infrequently  in  view  after  dark, 
when,  presumably,  it  generally  retires  to  reef 
crevices. 

All  11  individuals  (69:  31-91  mm)  that  were 
speared  at  various  times  during  daylight  con- 
tained identifiable  material  (much  of  it  fresh),  as 
listed  in  Table  71. 


The  dentition  of  tetraodontids  consists  of  heavy 
plates,  two  in  each  jaw,  that  form  a  sharp  beak. 
With  this  exceptionally  strong  apparatus,  these 


CONCLUSION. — Canthigaster  amboinensis 
is  a  diurnal  omnivore  that  feeds  mostly  on  coral- 
line algae  and  various  hard-bodied  invertebrates. 


1013 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  71. — Food  of  Canthigaster  amboinensis. 


No  fish 

Mean  percent 

with  this 

of 

Ranking 

Rank 

Items 

item  {n  =  11) 

diet  volume 

index 

1 

Coralline  algae 

10 

42.5 

38.64 

2 

Filamentous  algae 

8 

9.4 

6.84 

3 

Scleractinlan  corals 

6 

7.7 

4.20 

4 

Pectinid  pelecypods 

2 

7.8 

1.42 

5 

Brachyurans 

2 

7.3 

1.33 

6 

Ophiuroids 

2 

4.9 

0.89 

7 

Echlnolds 

4 

2.4 

0.87 

8 

Sponges 

5 

1.3 

0.59 

9 

Prosobrancti  gastropods 

4 

0.6 

0.22 

10 

Bryozoans 

2 

06 

0.11 

11 

Sipunculid  Introverts 

2 

0.3 

0.05 

12 

Foramlniferans 

3 

0.2 

0.05 

13 

Gammaridean  amphipods 

2 

02 

0.04 

14 

Didemnid  tunlcates 

1 

03 

0.03 

15 

Polychaetes 

1 

0.2 

0.02 

Also, 

unidentified  fragments 

6 

14.3 

7,80 

Table  72.- 

-Food  of  Canthigaster 

jactator. 

No.  fish 

Mean  percent 

Viiith  this 

of 

Ranking 

Rank 

Items 

Item  (n  =  6) 

diet  volume 

index 

1 

Coralline  algae 

3 

15.7 

7.85 

2 

Prosobrancti  gastropods 

4 

11.2 

7.47 

3 

Sponges 

3 

6.8 

3.40 

4 

Scleractinlan  corals 

2 

10.0 

3.33 

5 

Filamentous  algae 

5 

3.7 

3.08 

6 

Didemnid  tunicates 

3 

6.0 

3.00 

7 

Sipunculid  introverts 

3 

4.3 

2.15 

8 

Ectiinoids 

2 

55 

1.83 

9 

Bryozoans 

2 

1.3 

0.43 

10 

Brachyurans 

2 

1.3 

0.43 

11 

Diatoms 

3 

0.7 

0.35 

12 

Foramlniferans 

2 

0.3 

0.10 

13 

Optiiuroids 

03 

0.05 

14 

Ostracods 

0.2 

0.03 

15 

Gammaridean  amphipods 

02 

0.03 

16 

Isopods 

0.2 

0.03 

17 

Caridean  shrimps 

02 

0.03 

Also, 

crustacean  fragments 

5.0 

0.83 

Sand 

3 

1.5 

0.75 

Unidentified  fragments 

5 

256 

21.33 

Canthigaster  jactator  (Jenkins) 

This  small  pufferfish  lives  mostly  where  corals 
are  well  developed.  Like  its  congener  C  am- 
boinensis, above,  it  is  mostly  solitary,  although 
sometimes  several  occur  together.  It  swims  close 
among  the  coral  during  daylight,  but  is  only  occa- 
sionally in  view  at  night,  probably  because  it  usu- 
ally rests  in  reef  crevices  after  dark.  Once  during 
the  predawn  hours,  as  noted  above,  I  observed  a 
nocturnally  active  moray  eel,  Gymnothorax 
petelli,  grasping  one  of  these  puffers  between  its 
jaws. 

Thirteen  individuals  (50:  40-70  mm)  were 
speared  at  various  times  of  day  and  night.  Four 
were  taken  during  daylight,  and  these  were  the 
only  ones  that  had  material  in  the  anterior  third  of 
their  gut,  much  of  it  relatively  fresh.  In  two  others 


taken  at  night  (one  4  h  after  sunset,  the  other 
during  the  last  hour  before  daybreak),  food  was 
confined  to  the  posterior  two-thirds  of  their  guts, 
but  much  of  it  was  still  largely  identifiable.  In 
comparison,  the  remaining  seven,  collected  either 
at  night  (more  than  4  h  after  sunset),  or  during 
morning  twilight,  were  empty.  Items  in  the  six 
specimens  that  contained  identifiable  material 
are  listed  in  Table  72. 

CONCLUSION. —Canthigaster  jactator  is  a 
diurnal  omnivore  that  feeds  mostly  on  coralline 
algae  and  various  hard-bodied  benthic  inver- 
tebrates. 

Remarks  on  Sharpbacked  Puffers 

The  canthigasterids  are  widely  recognized  as 
omnivorous  fishes  that  feed  on  benthic  plants  and 


1014 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


invertebrates  (e.g.  in  the  tropical  Atlantic  by 
Randall,  1967;  and  in  the  western  Pacific  by  Hiatt 
and  Strasburg,  1960).  Most  investigators  have 
considered  them  diurnal.  Smith  and  Tyler  (1972) 
described  Canthigaster  rostratus  sleeping  at  night 
on  reefs  in  the  Virgin  Islands;  Collette  and  Talbot 
(1972)  also  suspected  C.  rostratus  to  be  noctur- 
nally  inactive,  and  suggested  that  some  they  saw 
swimming  at  night  had  been  disturbed  by  their 
lights.  To  Starck  and  Davis  (1966),  however,  at 
least  some  individuals  of  C  rostratus  appeared  to 
be  nocturnally  active  in  the  Florida  Keys;  how- 
ever, they  recognized  that  this  species  is  active  in 
daylight  as  well. 

Family  Diodontidae:     spiny  puffers 

Diodon  holocanthits  Linnaeus  — kokala 

This  spiny  puffer  is  numerous  in  Kona,  where  it 
frequently  swims  close  above  the  reef  at  night; 
nevertheless,  I  never  saw  one  there  in  daylight. 
Undoubtedly,  it  is  under  shelter  during  the  day, 
probably  deep  within  the  coral  caverns  that  hon- 
eycomb much  of  the  reef.  In  the  Gulf  of  California, 
where  the  rocky  sea  floor  offers  mostly  ledges  and 
relatively  shallow  caves,  one  often  sees  the  noc- 
turnally active  D.  holocanthus  resting  in  these 
places  during  the  day. 

All  five  individuals  (211:  175-239  mm)  that 
were  speared  as  they  swam  in  exposed  locations  on 
the  reef  after  dark  contained  identifiable  material 
in  their  guts,  much  of  it  relatively  fresh.  Proso- 
branch  gastropods,  which  occurred  in  all  five 
specimens,  were  the  major  food  item  (mean  per- 
cent of  diet  volume  and  ranking  index:  54.1),  with 
pagurid  crabs  also  important  prey  of  all  five  ( mean 
percent  of  diet  volume  and  ranking  index:  24). 
Other  food  items  were:  echinoids,  aWEchinometra 
mathaei,  in  four  (mean  percent  of  diet  volume:  18; 
ranking  index:  14.4),  and  ophiuroids  in  two  (mean 
percent  of  diet  volume:  3.9;  ranking  index:  1.56). 
Although  this  material  had  been  crushed  by  the 
powerful  jaws  and  beaklike  dentition  of  the  fish,  it 
was  apparent  that  at  least  many  of  the  gastropod 
shells  actually  had  housed  pagurid  crabs;  thus  the 
pagurids,  not  the  gastropods  themselves,  may 
have  been  the  major  food.  It  remains  uncertain 
how  many  living  gastropods  are  in  fact  taken, 
although  opercula  among  the  gut  contents  showed 
that  living  gastropods  are  important  prey. 

This  circumtropical  species  has  a  similar  diet  in 
the  Atlantic  Ocean,  as  determined  by  Randall 


(1967),  who  also  listed  prosobranch  gastropods  as 
the  major  food  item.  He  listed  pagurid  crabs  too, 
but  did  not  suggest  that  some  of  the  gastropods  on 
his  list  may  have  been  shells  that  housed  these 
crabs. 

Diodon  holocanthus  is  nocturnal  in  the  Florida 
Keys,  where  it  stays  under  ledges  or  in  holes  dur- 
ing the  day,  but  emerges  at  night  to  feed  on  vari- 
ous invertebrates,  particularly  larger  shelled 
forms  (Starck  and  Davis,  1966). 

CONCLUSION. — Diodon  holocanthus  is  a  noc- 
turnal predator  that  feeds  mostly  on  prosobranch 
gastropods  and  pagurid  crabs. 

Diodon  hijstrix  Linnaeus — kokala 

During  the  day,  D.  hystrix  either  is  secreted 
under  ledges,  or  hovers  inactively  high  in  the 
water  column,  often  several  together.  At  night, 
solitary  individuals  (Figure  42)  swim  in  exposed 
locations  close  above  the  reef,  especially  among 
basaltic  boulders. 

Of  the  16  individuals  (263:  244-333  mm) 
speared  during  day  and  night,  only  4  had  empty 
guts,  and  these  were  collected  during  late  after- 
noon, either  from  holes  under  rocks,  or  as  they 
hovered  in  the  water  column.  The  only  ones  that 
carried  food  in  the  anterior  third  of  their  gut  were 
taken  at  night — two  during  the  hour  before  mid- 
night and  one  2  h  before  daybreak.  Although  the 
anterior  third  of  the  gut  was  empty  in  the  other 
nine,  all  carried  material  posteriorly,  which,  com- 
posing entirely  shelled  organisms,  was  readily 
identifiable:  two  of  these  specimens  were  col- 
lected at  night — one  at  midnight,  the  other  just 
before  daybreak;  the  remaining  seven  were  taken 
during  the  day — four  of  them  in  the  morning, 
three  early  in  the  afternoon.  In  all,  12  specimens 
contained  identifiable  prey. 

Echinoids,  including  both  cidarids  and 
echinometrids,  occurred  in  11  of  the  12  specimens 
and  were  the  major  food  item  (mean  percent  of  diet 
volume:  55;  ranking  index:  50.42).  Prosobranch 
gastropods,  present  in  11  (mean  percent  of  diet 
volume:  27.1;  ranking  index:  24.84),  were  ranked 
second,  and  pagurid  crabs,  also  present  in  11 
(mean  percent  of  diet  volume:  12.9;  ranking  index: 
11.83),  were  ranked  third.  Thus,  the  diet  includes 
items  similar  to  those  taken  by  D.  holocanthus, 
above,  but  ranked  in  a  different  order  As  is  true  of 
the  material  from  D.  holocanthus,  many  of  the 
gastropod  shells  had  housed  pagurid  crabs,  but  the 


1015 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  42. — Diodon  hystrix,  a  spiny  puffer,  swimming  above  the  reef  at  night.  With  its  heavy,  beaklike  dentition,  this 

fish  crushes  its  shelled  prey. 


number  remains  unknown.  Nevertheless,  the 
pagurids  may  actually  rank  second  as  prey  even 
though  the  opercula  among  this  material  show 
that  living  gastropods  are  important  prey.  One  D. 
hystrix  also  contained  ostreid  pelecypods  (mean 
percent  of  diet  volume:  0.8;  ranking  index:  0.07), 
and  one  contained  unidentified  fragments  (mean 
percent  of  diet  volume:  4.2;  ranking  index:  0.35). 

Randall  (1967)  similarly  found  echinoids  the 
major  food  of  this  circumtropical  species  in  the 
West  Indies.  For  this  species  as  well  as  D.  holocan- 
thus,  Randall  listed  gastropods  and  pagurids 
separately,  without  suggesting  that  some  of  the 
gastropods  may  have  been  only  shells  which 
housed  pagurids.  Randall  recognized  that  D.  hys- 
trix feeds  partly  by  night,  but  believed  it  to  be 
primarily  diurnal.  Starck  and  Davis  (1966),  how- 
ever, reported  strictly  nocturnal  habits  for  D.  hys- 
trix in  the  Florida  Keys. 

The  strong,  sharp  spines  that  cover  D.  hystrix 
and  D.  holocanthus  are  perhaps  their  most  dis- 
tinctive morphological  characteristic.  These 
spines  lie  flat  against  their  bodies  most  of  the  time, 
but  when  the  bodies  inflate  with  water — a  regular 
response  to  threats — the  spines  stand  straight  out. 
Although  this  formidable  defense  probably  deters 


most  predators,  the  slow-moving  Diodon  would  be 
ready  prey  for  those  predators  able  to  tolerate  the 
spines  and  inflated  body.  In  Hawaii,  the  tiger 
shark,  Galeocerdo  cuvieri,  regularly  preys  on 
full-grown  adults  of  D.  hystrix  (Tester,  1963). 

CONCLUSION. — Diodon  hystrix  is  a  nocturnal 
predator  that  feeds  mostly  on  echinoids,  and  to  a 
lesser  extent  on  prosobranch  gastropods  and 
pagurid  crabs. 


General  Remarks  on  Spiny  Puffers 

The  teeth  in  both  upper  and  lower  jaws  of  the 
diodontids  are  fused  together  to  produce  a  solid, 
heavy  beak,  and  this  apparatus  enables  them  to 
crush  some  of  the  larger,  heavily  shelled  prey  that 
are  beyond  the  capacity  of  other  fishes — even  their 
relatives  the  balloonfishes. 

The  nocturnal  habits  of  the  two  species  of 
Diodon,  described  above,  may  be  a  family  charac- 
teristic. Starck  and  Davis  ( 1966)  reported  that  two 
species  of  Chilomycterus  in  Florida — antillarum 
and  schoepfi — are  active  at  night  and  inactive 
during  the  day. 


1016 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


DISCUSSION 

The  habits  of  fishes  on  Kona  reefs  exempHfy  the 
habits  of  fishes  on  coral  reefs  around  the  world. 
The  following  discussion  relates  these  habits  to 
the  evolution  of  fishes  on  modern  tropical  reefs, 
stressing  the  selective  pressures  that  have  shaped 
the  diverse  array  of  forms  coexisting  on  these  reefs 
today.  I  refer  to  some  of  these  forms  as  more  ad- 
vanced, or  specialized  than  others,  even  though  all 
are  products  of  an  equally  long  evolution,  and  each 
is  well  adaptated  to  its  own  specific  way  of  life. 
Some,  nevertheless,  have  diverged  more  than 
others  from  the  generalized  carnivores  that  gave 
rise  to  them  all,  and  in  this  fact  lies  the  basis  for 
the  discussion. 

The  categories  erected  for  presentation  have  in- 
distinct, overlapping  limits,  and  some  species  are 
discussed  under  one  category,  rather  than 
another,  quite  arbitrarily.  Nevertheless,  the 
synthesis  presented,  though  an  oversimplifi- 
cation, provides  a  frame  of  reference  within 
which  new  information  may  be  assessed.  Reem- 
phasizing  a  point  made  above,  this  report  deals 
only  with  individuals  of  the  various  species  that 
behave  as  adults. 

Coral  Reefs  as  a  Habitat  for  Fishes 

Most  fishes  that  inhabit  coral  reefs  are  among 
the  more  recently  evolved  teleosts  (Schaeffer  and 
Rosen,  1961;  and  others).  Indeed,  much  of  the  di- 
versity among  higher  teleosts  expresses  adapta- 
tions to  reef  habitats.  Of  the  fishes  observed  along 
Kona  transect  lines  (Table  7),  98.5%  are 
acanthopterygians.^ 

To  properly  appreciate  the  relation  of  modern 
coral-reef  fishes  to  their  habitat,  one  should  be 
familiar  with  the  history  of  tropical  reefs.  The 
following  outline  is  based  on  Newell  (1971). 

The  evolution  of  tropical  reefs  can  be  traced 
through  a  fossil  record  that  reaches  back  into  the 
Precambrian.  By  the  Mid-Ordovician,  over  400 


'Because  most  of  the  transect  counts  were  made  in  daylight, 
there  is  a  bias  toward  the  more  advanced  forms  in  numbers  of 
species  (the  greater  incidence  of  diumally  secretive  habits 
among  the  more  primitive  forms,  and  of  diumally  exposed  habits 
among  the  more  highly  evolved  forms,  is  discussed  below).  Even 
so,  however,  the  preponderance  of  acanthopterygians  is  over- 
whelming, especially  if  one  also  considers  numbers  of  individu- 
als. On  Kona  reefs  such  advanced  groups  as  the  labrids, 
pomacentrids,  and  acanthurids  are  among  the  species  vnth  the 
largest  numbers  of  individuals.  And  although  among  the 
nonacanthopterygians  the  numerous  muraenid  eels  are  not 
properly  represented  in  the  counts,  neither  are  such  noctvimal 
acanthopterygians  as  the  numerous  holocentrids. 


million  years  ago,  animal  communities  had  be- 
come associated  with  coral-algal  reefs.  A  succes- 
sion of  reef  comftiunities  then  evolved  during  sub- 
sequent geological  history,  each  with  its  own 
characteristic  assemblage  of  animals,  and  each 
achieved  marked  stability  before  crashing  into  ob- 
livion during  worldwide  environmental  upheav- 
als. Between  each  of  these  periods  of  stable  reef 
communities,  a  long  time  passed  without  known 
reefs. 

The  scleractinian  corals,  which  dominate  mod- 
ern reefs,  first  appeared  during  the  Triassic,  and 
by  Jurassic  times,  about  150  million  years  ago,  the 
lithothamnion-scleractinian  reef  community  was 
well  established.  Significantly,  the  teleostean 
radiation  also  began  during  the  Jurassic  (Gosline, 
1971),  indicating  that  their  history  may  closely 
interrelate  with  that  of  the  lithothamnion- 
scleractinian  reef  community.  But  Smith  and 
Tyler  (1972)  suggested  that  the  preacanthop- 
terygian  teleosts  and  their  forebearers  were 
maladapted  to  reef  conditions.  They  contended 
that  fishes  entered  reef  habitats  only  upon  acquir- 
ing certain  of  the  morphological  advances  that 
marked  the  first  appearance  of  acanthopterygians 
early  during  the  Cretaceous,  over  100  million 
years  ago.  Newell  (1971),  on  the  other  hand,  be- 
lieved that  fishes  have  had  a  much  longer  history 
as  reef  inhabitants.  He  attributed  their  absence  in 
the  fossil  record  of  early  reefs  to  their  skeletal 
remains  having  been  "destroyed  by  scavengers 
that  abound  in  this  strongly  oxidizing  environ- 
ment." 

It  is  unquestioned,  nevertheless,  that  early 
acanthopterygian  fishes — the  Beryciformes 
— were  better  adapted  than  were  their  predeces- 
sors for  reef  habitats.  Their  increased  success 
probably  was  based  mostly  on  increased  ma- 
neuverability and  a  more  adaptive  feeding 
mechanism — the  features  which  Smith  and  Tyler 
(1972)  felt  were  especially  suited  for  coral  reefs. 
Patterson  (1964)  underscored  this  point  when  he 
concluded  that  most  skeletal  differences  between 
acanthopterygians  and  their  primitive  elopidlike 
ancestors  resulted  from  changes  that  permitted 
the  fish  better  maneuverability:  most  significant, 
the  fins,  given  increased  rigidity  by  replacing  the 
anterior  soft  rays  with  spines,  were  more  effec- 
tively positioned,  and  the  body  was  shortened  and 
deepened.  The  advances  these  fishes  made  in  their 
feeding  mechanism  was  especially  significant,  as 
attested  by  Schaeffer  and  Rosen  (1961),  who 
stated:    "It  is  primarily  the  acanthopterygian 


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FISHERY  BULLETIN:  VOL.  72,  NO.  4 


mouth  that  has  given  rise  to  the  enormous  variety 
of  specialized  feeding  mechanisms  for  which  tele- 
osts  are  so  v^ell  known.  Presumably,  the  evolution 
of  the  acanthopterygian  jaw  mechanism  promoted 
the  successful  exploitation  of  food  sources  that 
previously  were  largely  unavailable  to  actinop- 
terygian  fishes."  They  referred  to  the  protrusible 
premaxillary  of  acanthopterygians,  which  per- 
mits them  to  project  their  upper  jaw  at  food.  Fishes 
with  this  mouth  construction  can  accommodate 
the  shape  and  size  of  the  mouth  opening  more 
appropriately  to  the  shape  of  the  food  item  than 
can  fishes  without  a  protusible  premaxillary 
(Alexander,  1967;  GosHne,  1971). 

During  the  Cretaceous,  in  which  the  be- 
ryciforms  flourished,  the  ecological  role  of  the 
scleractinian  corals  was  challenged  by  a  group  of 
bivalved  mollusks,  the  rudists,  which  underwent 
an  extraordinary  radiation  and  became  the  center 
of  a  highly  successful  and  widespread  reef  com- 
munity. But  at  the  end  of  the  Cretaceous,  about  70 
million  years  ago,  these  and  other  reef  com- 
munities collapsed  in  sweeping  extinctions  as- 
sociated with  the  worldwide  biological  revolution 
that  marked  the  close  of  the  Mesozoic  (Newell, 
1971). 

Tertiary  seas  over  most  of  the  world  were  with- 
out known  coral-reef  communities  until  litho- 
thamnion-scleractinian  reefs  underwent  a  second 
major  radiation  during  the  Eocene,  about  50  mil- 
lion years  ago  (Newell,  1971).  The  communities 
that  developed  in  association  with  these  reefs  are 
essentially  those  of  our  time.  And  in  what  would 
seem  a  related  phenomenon,  the  explosive  radia- 
tion of  acanthopterygians  into  the  types  that  in- 
habit modern  reefs  also  occurred  during  the 
Eocene  (Patterson,  1964).  Of  the  families  living  on 
reefs  today,  only  a  relatively  few  can  be  traced 
back  in  time  earlier  than  the  Eocene  (Berg,  1940), 
and  yet  by  the  end  of  that  period,  which  spanned 
about  15  million  years,  representatives  of  almost 
every  major  type  of  modern  fish  had  appeared 
(Romer,  1966). 

This  most  recent  proliferation  of  acanthop- 
terygians probably  radiated  from  a  line  of 
generalized  percoidlike  carnivores  that  had  arisen 
from  among  the  Beryciformes  during  the  late  Cre- 
taceous (Gosline,  1966).  Above,  I  note  that  98.5% 
of  the  fishes  seen  on  Kona  transect  lines  are  acan- 
thopterygians; more  specifically,  90.4%  are  acan- 
thopterygians that  have  reached,  or  passed,  the 
percoid  level  of  structural  development,  and 
75.5%  belong  to  the  order  Perciformes  (see  foot- 


note 7).  Only  the  holocentrids  represent  the  ances- 
tral Beryciformes.  In  fact,  worldwide  the  Holocen- 
tridae,  and  a  few  species  of  Anamalopidae,  are  the 
only  representatives  of  this  once  prolific  order  that 
have  survived  on  nearshore  reefs. 

Obviously  the  percoid  level  of  development  has 
been  highly  successful.  Gosline  ( 1971 )  pointed  out: 
'  In  no  single  way  does  it  seem  to  differ  from  that  of 
the  now  unimportant,  perhaps  relic  Beryciformes 
from  which  it  was  presumably  derived.  Possibly 
the  percoids  have  developed  some  distinct  and  as 
yet  unknown  biological  advantage  over  the  Be- 
ryciformes, but  for  the  moment  one  can  only  as- 
sume that  the  percoids  represent  a  successful 
integration  of  minor  advances."  The  minor  ad- 
vances which  Gosline  cited  include  increased 
maneuverability  and  adaptability  of  the  protrusi- 
ble jaw  mechanisms,  which  are  refinements  on 
those  same  features  adaptive  to  reef  living  that 
probably  gave  the  Beryciformes  an  advantage 
over  their  progenitors. 

Generalized  Carnivores: 
Main  Line  of  Teleostean  Evolution 

From  early  Mesozoic  times  the  main  line  of  ac- 
tinopterygian  evolution  has  progressed  through  a 
series  of  generalized  carnivores;  with  each  step 
forward,  the  basic  feeding  mechanism  has  im- 
proved, and  the  potential  for  adaptive  radiation 
has  increased  (Schaeffer  and  Rosen,  1961).  Al- 
though this  progression  has  been  marked  by 
periodic  bursts  of  specialized  offshoots,  the  pri- 
mary stem,  the  generalized  carnivore,  has  re- 
mained relatively  conservative  (Gosline,  1959). 

The  generalized  predator,  in  simplified  form, 
has  a  large  mouth  and  is  adapted  to  directly  ap- 
proach, and  seize,' prey  that  are  fully  exposed  to 
the  attack.  Its  prey  are  small  enough  to  be  ma- 
nipulated, yet  large  enough  to  be  grasped; 
moreover,  the  prey  are  not  sealed  in  heavy  ar- 
mour, nor  do  they  carry  strong  spines,  spicules,  or 
other  noxious  components  for  which  the  un- 
specialized  digestive  tract  of  the  generalized  pred- 
ator is  maladapted.  Although  even  the  most 
primitive  of  today's  predators  have  acquired  at 
least  some  feeding  specializations,  the  closer  one 
approximates  this  simplified  form,  the  closer  its 
feeding  habits  fit  this  description. 

With  the  generalized  predaceous  feeding 
mechanism  being  a  relatively  conservative  mor- 
phological link  between  periods  of  adaptive  radia- 
tion in  actinopterygian  fishes,  one  would  expect 


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HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


conservative  predatory  behaviors  to  be  associated 
with  this  morphology,  and  just  such  behaviors  are 
centered  around  nocturnal  and  crepuscular  feed- 
ing habits.  The  nocturnal  habit  involves  mostly 
predation  on  small,  motile  crustaceans,  the  cre- 
puscular habit  mostly  predation  on  smaller  fishes. 
Together,  crustaceans  and  fishes  are  the  two 
major  types  of  prey  taken  by  the  generalized 
predator. 

Nocturnal  and  crepuscular  habits  among 
generalized  carnivores  are  discussed  separately  in 
the  following  sections.  The  separation  is  artificial, 
as  is  the  delimitation  of  a  third  category,  that 
dealing  with  generalized  carnivores  that  feed  reg- 
ularly by  day.  In  fact,  as  illustrated  below,  the 
behavior  patterns  associated  with  these  three 
types  of  activity  are  closely  interrelated. 

Generalized  Carnivores  as 
Nocturnal  Predators 

Early  in  the  evolving  relation  between  fishes 
and  their  prey,  the  evolutionary  lines  of  many 
small,  vulnerable  organisms  probably  increas- 
ingly shifted  activity  to  periods  of  darkness.  There 
scarcely  could  be  a  more  elementary  solution  for 
animals  threatened  by  active,  visually  orienting 
predators.  And  because  effective  defense  adjust- 
ments in  prey  pressure  predators  to  modify  their 
offense,  it  seems  certain  that  various  predators 
early  aquired  means  to  follow  their  prey  into  the 
night.  Thus,  in  predatory  fishes  the  nocturnal 
habit  itself  would  be  a  specialization,  but  a 
specialization  probably  adopted  in  early  pre- 
teleostean  times  that  has  permitted  much  of  the 
continued  widespread  success  of  the  generalized 
predaceous  feeding  mechanism. 

The  smaller  generalized  carnivores  on  reefs 
today  find  their  major  prey  among  the  abundant 
crustaceans,  which,  as  follows  from  the  above,  are 
mostly  nocturnal  animals  that  expose  themselves 
at  night  (Longley,  1927;  and  others).  Many 
generalized  predators  that  would  feed  on  these 
organisms  have  found  nocturnal  habits  adaptive, 
because  only  after  dark  does  their  straightforward 
attack  find  suitable  prey  in  the  required  exposed 
position.  In  this  feeding  relation,  the  relatively 
small  size  of  the  crustaceans  undoubtedly  has 
influenced  the  size  of  the  predatory  fishes,  most  of 
which  are  of  small  to  medium  size  (less  than  about 
300  mm  long). 

Most  nocturnal  fishes  in  Kona  prey  on  benthic 
crustaceans,  especially  xanthid  crabs;  however,  a 


number  are  adapted  to  take  crustaceans  and  other 
forms  from  the  water  column.  The  prey  of  these 
fishes  are  mainly  relatively  large  zooplankters  (a 
broad,  perhaps  loose  concept  of  the  term  "zoo- 
plankton"  is  used  in  this  report),  like  crab 
megalops,  that  are  most  abundant  in  the  water 
column  at  night.  Adults  of  most  nocturnal  plank- 
tivorous  fishes  in  Kona  do  not  feed  significantly  on 
the  many  small  plankters,  like  calanoid  copepods, 
that  predominate  in  the  water  column  during  both 
day  and  night. 

The  extent  to  which  the  more  primitive  reef 
fishes  feed  at  night  seems  not  properly  ap- 
preciated. Nocturnal  habits  are  widespread 
among  basal  percoids,  whereas  diurnal  habits 
tend  to  be  characteristic  of  certain  more 
specialized  offshoots.  Even  if  one  considers  only 
families  that  occur  in  Kona,  all  nearshore  species 
of  the  Kuhliidae,  Priacanthidae,  and  Apogonidae 
seem  to  be  nocturnal,  as  are  many  species  among 
the  Serranidae,  Carangidae,  Lutjanidae, 
Sparidae,  and  Mullidae. 

Probably  the  nocturnal  habits  of  these  more 
generalized  percoids  were  inherited  from  ances- 
tral beryciforms.  The  Holocentridae  are  the  major 
representatives  of  this  once  diverse  order  on  near- 
shore  reefs  today,  yet  as  illustrated  by  their  prom- 
inence in  Kona,  they  nonetheless  are  numerous, 
widespread,  and  obviously  successful.  All  of  them 
for  which  there  are  data  are  nocturnal,  and  there 
is  no  reason  to  believe  that  this  is  not  a  primitive 
characteristic.  The  anamalopids,  which  are  the 
only  other  beryciforms  on  nearshore  reefs,  also  are 
nocturnal  (e.g.  Harvey,  1922).  Presumably  these 
modern  beryciforms  have  competed  successfully 
with  nocturnal  forms  among  the  more  advanced 
teleosts  by  having  refined  certain  features  that 
are  highly  adaptive  to  feeding  in  the  dark.  Thus, 
although  much  of  their  anatomy  is  essentially 
that  of  their  ancestors,  they  have  acquired  highly 
specialized  features — at  least  many  of  them 
sensory — that  have  permitted  more  effective  use 
of  this  equipment.  All  other  present-day  be- 
ryciforms live  in  the  twilight  zone  of  middepths  or 
in  the  deep  sea,  and  their  suitability  to  the  di- 
minished light  of  this  habitat  suggests  that  their 
shallowwater  ancestors  perhaps  were  nocturnal 
(Richard  H.  Rosenblatt,  Scripps  Institution  of 
Oceanography,  pers.  commun.).  Perhaps  during 
the  Cretaceous  certain  more  specialized  be- 
ryciforms possessed  diurnal  habits,  much  as  many 
specialized  perciforms  do  today.  But  if  so,  these 


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FISHERY  BULLETIN:  VOL.  72,  NO.  4 


probably  did  not  survive  the  widespread  extinc- 
tions that  decimated  reef  communities  at  the  close 
of  the  Mesozoic. 

If,  as  suggested,  many  reef  fishes  close  to  the 
main  line  of  actinopterygian  evolution  long  ago 
assumed  nocturnal  habits  in  answ^er  to  the  noctur- 
nal habits  of  their  prey,  then  one  is  not  surprised 
to  find  that  widespread  predator-prey  relations 
are  centered  around  the  nocturnal  habit  and  that 
the  participants  are  mostly  among  the  more 
generalized  members  of  the  reef  community.  One 
especially  widespread  activity  pattern  is  dis- 
played by  the  many  fishes  that  assemble  in  schools 
on  or  close  to  nearshore  reefs  during  the  day,  then 
disperse  at  nightfall  and  feed  on  small  organisms 
that  become  exposed  after  dark.  This  is  the  basic 
activity  pattern  of  many  carangids,  lutjanids, 
pomadasyids,  and  sciaenids — all  among  the  more 
generalized  perciforms  (Hobson,  1965,  1968a, 
1972,  1973). 

In  addition  to  these  basal  percoids,  it  is 
significant  that  of  the  relatively  few  fishes  of 
preacanthopterygian  groups  associated  with 
modern  reefs,  many  either  follow  this  pattern 
themselves,  or  closely  relate  as  predators  to  other 
fishes  that  do  (see  next  section).  A  diurnally 
schooling-nocturnally  active  pattern  is  especially 
widespread,  if  not  universal,  among  the  inshore 
clupeids,  order  Clupeiformes — as  described  ear- 
lier for  Harengula  thrissina,  an  exceedingly 
numerous  fish  close  to  shore  in  the  Gulf  of  Califor- 
nia (Hobson,  1965,  1968a).  Starck  and  Davis 
(1966)  found  this  same  pattern  in  all  five  clupeids 
that  they  studied  on  reefs  in  Florida,  and  I  ob- 
served it  in  Herklotsichthys  punctatus  in  the  Mar- 
shall Islands  (unpubl.  data).  Pertinent  informa- 
tion on  nearshore  clupeids  is  limited  because  so 
few  investigators  have  distinguished  between 
diurnal  and  nocturnal  activity;  nevertheless, 
there  are  at  present  no  data  refuting  the  general- 
ization that  these  fishes  feed  at  night. 

There  are  fewer  of  these  diurnally  schooling, 
nocturnally  active  fishes  on  Kona  reefs  than  on 
most  other  tropical  reefs,  perhaps  for  reasons  dis- 
cussed earlier  (Hobson,  1972).  Still,  the  pattern  is 
well  defined  there  in  certain  of  the  mullids,  genus 
Mulloidichthys,  and  in  the  lutjanid  Lutjanus  vai- 
giensis,  and  is  especially  apparent  in  the  atherinid 
Pranesus  insularum,  just  as  in  its  congener  P. 
pinguis  of  the  Marshall  Islands  (Hobson  and 
Chess,  1973) — both  of  the  preacanthopterygian 
order  Atheriniformes. 


Generalized  Carnivores  as 
Crepuscular  Predators 

In  the  same  way  that  many  generalized  pred- 
ators are  nocturnal  because  suitable  prey  are 
most  available  to  them  after  dark,  other 
generalized  predators — those  that  prey  mostly  on 
smaller  fishes — are  primarily  crepuscular  be- 
cause that  is  when  these  prey  become  most  vul- 
nerable to  their  mode  of  attack  (Hobson,  1968a). 
Moreover,  just  as  is  true  of  the  nocturnal  forms, 
the  crepuscular  piscivores,  which  also  are  among 
the  more  generalized  of  the  reef  fishes,  experience 
certain  long-established  predator-prey  relations. 
Significantly,  many  of  these  crepuscular  pisciv- 
ores are  members  of  the  same  basal  percoid 
families,  the  Serranidae,  Carangidae,  and  Lut- 
janidae,  that  have  produced  some  of  the  nocturnal 
predators  discussed  above.  Many  of  the  crepuscu- 
lar piscivores,  however,  tend  to  be  larger  than  the 
nocturnal  species,  which  might  be  expected,  in- 
asmuch as  the  nocturnal  fishes  are  among  their 
major  prey  (Hobson,  1968a).  Schools  of  nocturnal 
carangids,  pomadasyids,  mullids  and,  especially, 
clupeids,  are  well-known  targets  of  such  pisciv- 
ores. 

During  the  twilight  periods  of  greatest  piscivo- 
rous activity  (Hobson,  1968a,  1972),  these  noctur- 
nal fishes  are  still  in  their  diurnal  schools.  And 
although  the  schools  effectively  protect  them  from 
predators  during  most  of  the  day  (Manteifel  and 
Radakov,  1961;  Eibl-Eibesfeldt,  1962;  Hobson, 
1968a),  this  protection  is  reduced  during  twilight 
(Hobson,  1968a).  At  this  time  of  maximum  danger 
from  predators,  most  other  smaller  reef  fishes, 
both  diurnal  and  nocturnal,  are  under  cover;  thus, 
the  schooling  fishes,  which  are  still  in  the  water 
column,  become  the  most  numerous  prey  of  proper 
size  exposed  to  the  space-demanding  attacks  of  the 
generalized  piscivores  (Hobson,  1968a).  After 
dark,  the  smaller  fishes  seem  relatively  safe  from 
at  least  most  such  predators  (Hobson,  1973),  but 
during  the  changeover  between  day  and  night, 
they  are  vulnerable  (Hobson,  1968a;  Munz  and 
McFarland,  1973). 

The  large  piscivores  are  exceptionally  abundant 
in  certain  parts  of  the  Gulf  of  California  where  the 
diurnally  schooling,  nocturnallj  active  fishes  are 
numerous  (Hobson,  1968a).  As  suggested  earlier 
(Hobson,  1972),  the  relatively  few  such  large  pred- 
ators on  Hawaiian  reefs,  compared  with  most 
other  tropical  areas,  may  relate  to  the  relative 
dearth  in  Hawaii  of  schooling  prey. 


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HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Thus,  a  major  activity  pattern  of  these  large 
piscivores  closely  interrelates  with  a  major  activ- 
ity pattern  of  the  smaller  nocturnal  predators.  For 
this  reason,  and  because  so  many  members  of  the 
two  groups  are  closely  related  taxonomically,  it  is 
apparent  that  the  crepuscular  pattern  probably 
has  had  a  longevity  comparable  to  that  of  the 
nocturnal  pattern.  A  good  indication  of  this  long 
history  exists  in  the  Gulf  of  California,  where  the 
day-night  activity  pattern  of  the  nocturnal  clupeid 
Harengula  thrissina  closely  interrelates  with  the 
crepuscular  activity  not  only  of  certain  basal  per- 
coids,  but  also  o{  Elops  affinis,  order  Elopiformes, 
a  member  of  the  most  primitive  of  all  extant  tele- 
ostean  genera  (Hobson,  1968a). 

Generalized  Carnivores  as  Diurnal  Predators 

Thus,  nocturnal  or  crepuscular  habits  are  adap- 
tive for  many  generalized  carnivores.  Others  with 
basically  the  same  feeding  mechanism,  however, 
have  acquired  morphological  and  behavioral 
characteristics  suited  to  capture  small,  motile 
crustaceans  and,  especially,  fishes  in  daylight. 
Despite  the  fact  that  crustaceans  are  most  exposed 
to  direct  attacks  at  night,  and  smaller  fishes  gen- 
erally are  most  vulnerable  to  such  attacks  during 
twilight,  various  predators  are  equipped  to  exploit 
the  exceptions  to  these  generalizations. 

True,  selective  pressures  applied  by  generations 
of  visually  orienting  predators  have  refined  the 
defense  mechanisms  that  protect  so  many  prey 
organisms  during  daylight.  But  there  are  occa- 
sional lapses  in  all  these  defenses  when  the  prey 
are  briefly  vulnerable.  For  example,  nocturnal  or- 
ganisms resting  under  a  thin  layer  of  sand  occa- 
sionally betray  their  presence  by  moving.  And 
small  fishes  that  usually  are  within  retreating 
distance  from  cover  sometimes  stray  too  far  into 
the  open;  or  others,  enjoying  the  security  of  a 
school,  occasionally  drift  too  far  from  their  fellows. 
Still  others,  normally  alert  to  surrounding 
danger,  are  momentarily  distracted.  At  such 
times,  these  organisms  are  open  to  attack.  But 
normally  such  events  fail  to  occur  in  the  presence 
of  large,  free-swimming  predators  that  are  ac- 
tively hunting.  Potential  prey  are  sensitive  to  cues 
that  mark  the  hunting  predator,  and  take  defen- 
sive action  when  a  hunter  appears — cryptic  forms 
stop  moving,  others  move  closer  to  cover,  and 
schooling  forms  draw  themselves  closer  together 
(Hobson,  1965,  1968a).  Above  all,  in  this  alerted 
state  the  prey  are  less  likely  to  make  a  defensive 


mistake.  This  does  happen  occasionally,  of  course, 
as  when  large  carangids  swim  slowly  among 
schooling  prey  for  hours  during  the  day  without  an 
aggressive  move,  and  then  suddenly  attack 
— presumably  having  sensed  a  vulnerable  target 
(Hobson,  1968a).  Probably  this  offensive  tactic  de- 
pends on  the  prey  eventually  becoming  con- 
ditioned to  the  predator's  presence,  and  finally 
making  a  mistake.  But  it  seems  unlikely  that  such 
predators  could  depend  on  these  relatively  infre- 
quent successes.  They  remain  best  suited  for  cre- 
puscular attacks. 

The  problem  of  being  within  striking  range 
when  prey  are  momentarily  available  during  the 
day  because  of  a  defensive  lapse  is  probably  best 
solved  by  those  predators  that  lie  in  wait  under 
concealment — the  ambushers — or  by  those  that 
stalk.  Both  tactics  have  produced  some  highly 
specialized  forms  that  are  more  appropriately  con- 
sidered in  the  next  section.  However,  many  of 
those  that  use  concealment  to  ambush  their  prey 
look  much  like  the  nocturnal  or  crepuscular  pred- 
ators discussed  above,  and  so  are  considered 
here. 

This  is  especially  true  among  certain  basal  per- 
coids,  like  the  serranids.  For  example,  many 
species  of  Epinephelus  ambush  prey  from  a  con- 
cealed position,  and  much  of  this  activity  occurs  in 
daylight  (Hiatt  and  Strasburg,  1960;  and  others). 
Most  of  these  predators  are  cryptically  hued  for  a 
sedentary  existence  among  rocks  or  coral — 
usually  they  are  brown  or  grey,  with  the  hues 
often  arranged  in  blotches  or  spots.  Such  predators 
rest  unseen  until  a  small  organism  within  strik- 
ing distance  makes  a  defensive  error. 

Generalized  predators  adapted  for  this  tactic 
are  well  known  to  feed  regularly  during  both  day 
and  night,  as  exemplified  by  certain  species  of 
Epinephelus  (Longley  and  Hildebrand,  1941; 
Starck  and  Davis,  1966;  Hobson,  1968a).  There  is 
evidence,  however,  that  feeding  habits  of  these 
predators  differ  between  day  and  night.  In  the 
Gulf  of  California,  E.  labriformis  preys  almost 
entirely  on  crustaceans  at  night,  but  heavily  on 
fishes  during  the  day  (Hobson,  1968a).  I  have  al- 
ready commented  on  the  increased  vulnerability 
of  small  crustaceans  at  night;  apparently  fishes 
are  more  vulnerable  to  the  predatory  tactics  of  this 
fish  in  daylight.  The  diurnal  piscivorous  habit  of 
Cephalopholis  argus  {Epinephelus  argus  of  some 
authors,  e.g.  Smith,  1971)  in  Kona  is  consistent 
with  this  probability. 


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Predators  having  obvious  morphological  and 
behavioral  specializations  that  increase  their 
proficiency  as  ambushers  or  as  stalkers  are  consid- 
ered in  the  next  section. 


Specialized  Offshoots  from  the  Main 
Line  of  Teleostean  Evolution 


Most  fishes  inhabiting  tropical  reefs  today,  as 
exemplified  by  species  in  Kona,  represent 
specialized  offshoots  from  the  main  teleostean 
line. 

Predators  Specialized  to  Ambush  Prey 

As  emphasized  in  the  introductory  remarks,  the 
categories  erected  in  this  discussion  overlap.  This 
is  especially  true  of  predators  that  ambush  their 
prey.  By  using  this  tactic,  predators  with  the 
generalized  feeding  mechanism  increase  their 
capacity  to  capture  prey  in  daylight.  But  many 
ambushers,  like  certain  species  of  Epinephelus, 
are  so  similar  in  both  morphology  and  habits  to 
many  of  the  nocturnal  and  crepuscular  forms  dis- 
cussed above  that  one  can  only  arbitrarily  distin- 
guish them  as  being  specialized  in  this  activity. 
Nevertheless,  some  forms  have  retained  the 
generalized  feeding  mechanism  while  diverging 
widely  from  the  primitive  form  in  other  respects. 
And  the  divergence  is  based  on  features  that  bet- 
ter adapt  these  fishes  for  the  ambushing  tactic. 

The  synodontids,  order  My ctophi formes,  which 
are  prominent  ambushers  in  Kona,  as  they  are  on 
most  other  tropical  reefs,  are  products  of  an 
evolutionary  offshoot  that  diverged  from  the  main 
line  at  a  preacanthopterygian  level.  Thus,  the 
ambushing  tactic  has  had  a  long  history.  The  scor- 
paenids,  order  Scorpaeniformes,  and  the  bothids, 
order  Pleuronectiformes,  both  of  whose  Kona  rep- 
resentatives include  specialized  ambushers,  be- 
long to  groups  that  diverged  from  the  mainstream 
near  the  percoid  level  (Gosline,  1971;  and  others). 
Significantly,  the  adults  of  all  these  forms  seem  to 
be  primarily  piscivorous  during  the  day. 

The  synodontids,  scorpaenids,  and  bothids  that 
ambush  their  prey  have  acquired  characteristics 
that  camouflage  them  as  they  lie  on  the  sea  floor. 
Clearly,  it  is  important  for  these  predators  to  go 
unseen  by  their  victims.  In  this  respect,  many  of 
the  cirrhitids,  order  Perciformes,  might  seem  a 


puzzle.  An  example  from  Kona  is  Paracirrhites 
forsteri  (Figure  32),  which  preys  mostly  on  smaller 
fishes  during  the  day.  Although  attacking  prey  in 
much  the  same  manner  as  other  ambushers,  this 
colorful  fish  is  clearly  visible  as  it  rests  in  exposed 
positions  on  the  reef.  Selection,  in  this  case,  may 
have  in  fact  favored  coloration  that  attracts  atten- 
tion. Conceivably  this  could  be  an  effective  offen- 
sive characteristic,  just  so  long  as  its  use  among 
predators  is  limited.  It  is  well  known  that  certain 
small  fishes  are  attracted  to  conspicuous  objects  on 
the  sea  floor — one  needs  only  to  place  a  small, 
shiny  artifact  on  the  bottom  to  see  this.  Perhaps  P. 
fosteri  actually  finds  prey  among  small  fishes  that 
approach  to  investigate  its  conspicuous  features. 


Predators  Specialized  to  Stalk  Prey 

Many  predators  specialized  to  stalk  prey  in  the 
water  column  belong  to  groups  whose  ancestors 
diverged  from  the  main  teleostean  line  below  the 
percoid  level.  Characteristically,  they  have  long, 
attenuated  bodies.  Among  species  whose  behavior 
in  Kona  is  described  above  are  the  trumpetfish, 
Aulostomus  chinensis,  and  the  cornetfish, 
Fistularia  petimba — both  of  the  order  Gasteros- 
tei  formes. 

Two  other  highly  specialized  stalkers  on  Kona 
reefs  were  not  included  in  the  species  accounts 
above  because  observations  on  them  were  infre- 
quent; these  are  the  needlefish,  Strongylura 
gigantea,  order  Atheriniformes,  and  the  bar- 
racuda, Sphyraena  barracuda,  order  Perciformes. 
The  various  species  of  needlefishes  and  bar- 
racudas are  widespread  on  tropical  reefs,  and  their 
stalking  habits  are  well  documented.  Hiatt  and 
Strasburg  (1960)  reported  that  Strongylura 
gigantea  feeds  on  small  fishes  in  the  Marshall 
Islands  by  "drifting  up  to  them  and  suddenly  lash- 
ing out  with  its  jaws."  On  the  basis  of  similar 
observations  in  the  tropical  Atlantic,  Randall 
(1967)  reported  that  needlefishes  are  almost  ex- 
clusively piscivorous,  and  that  they  "drift  slowly 
into  range  of  one  of  their  prey  before  making  a 
quick  rush."  Regarding  barracudas,  Hiatt  and 
Strasburg  (1960)  told  of  Sphyraena  genie  in  the 
Marshall  Islands  "drifting  solitary  near  the  sur- 
face stalking  its  prey"  and  stated  that  "it  surprises 
its  victim  with  a  sudden  lunge."  Randall  (1967) 
noted  that  barracudas  in  the  tropical  Atlantic  feed 
primarily  on  fishes  during  the  day,  a  statement 
probably  true  of  at  least  most  stalking  predators. 


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HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Predators  Specialized  to  Seek  Prey 
in  Reef  Crevices 

Here  I  am  concerned  primarily  with  muraenid 
eels,  order  Anguilliformes,  and  the  brotulids, 
order  Gadiformes.  Members  of  both  groups,  but 
the  eels  in  particular,  have  elongated  bodies 
suited  to  maneuvering  through  the  crevices  that 
honeycomb  coral  reefs.  Their  similar  mor- 
phologies led  early  Hawaiians  to  group  eels  and 
brotulids  together  by  the  generic  term  puhi.  There 
are  a  number  of  other  secretive  forms  on  Kona 
reefs — small  inconspicuous  fishes  like  the 
pseudochromid  Pseudogramma  polyaccanthus, 
which  were  occasionally  visible  at  night  during 
this  study — but  because  I  have  little  knowledge  of 
their  habits  they  are  not  considered  here. 

The  muraenid  eels  are  products  of  an  evolution 
that  has  diverged  widely  from  the  main  teleostean 
line:  today  they  possess  many  specialized  features 
that  equip  them  for  hunting  in  reef  crevices.  The 
primary  specializations,  for  example  their  excep- 
tionally solid  skulls,  are  adaptive  for  wedging 
through  small  openings,  and  they  can  back  out  of 
any  hole  they  enter  (Gosline,  1959, 1971 ).  Many  of 
the  morays,  and  at  least  some  of  the  brotulids,  for 
example  Brotula  multibarbata  in  Kona,  are  noc- 
turnal; however,  other  morays  are  diurnal.  Obvi- 
ously hunting  conditions  in  reef  crevices  differ 
between  day  and  night. 

Reef  crevices  are  havens  for  numerous  crea- 
tures. Many  diurnal  forms  rest  there  at  night, 
some  of  them  virtually  asleep,  and  many  noctur- 
nal forms  shelter  themselves  there  in  daylight 
(Hobson,  1968a,  1972).  Moreover,  most  reef  ani- 
mals find  refuge  in  these  crevices  when  they  are 
injured  or  distressed;  obviously,  sheltering  in  reef 
crevices  is  adaptive  for  prey  threatened  by  the 
many  predators  on  the  surface  of  the  reef  But  it  is 
equally  obvious  from  their  long  successful  history 
on  tropical  reefs  that  eels  have  acquired  adaptive 
means  to  exploit  such  prey. 

Predators  with  Sensory  Specializations 
That  Detect  Concealed  Prey 

In  this  category  I  am  concerned  with  the  mul- 
lids,  order  Perciformes,  which  are  prominent  on 
Kona  reefs.  Their  distinctive  sensory  chin  barbels 
permit  them  to  locate  prey  that  go  undetected  by 
other  fishes.  And,  like  the  muraenid  eels,  above, 
their  numbers  include  both  diurnal  and  nocturnal 
forms,  as  well  as  species  that  hunt  effectively  dur- 


ing both  day  and  night.  This  fact,  and  the  great 
diversity  in  their  prey,  shows  that  mullids,  with 
their  distinctive  modes  of  feeding,  have  available 
to  them  a  broad  range  of  predatory  activity  denied 
most  other  fishes. 

Although  seeking  refuge  under  rocks,  algae,  or 
sand  is  adaptive  for  many  small  animals  ap- 
proached by  a  predator,  this  tactic  probably  plays 
to  the  advantage  of  some  mullids.  For  example, 
the  diurnal  Parupeneus  chryserydros  preys 
mostly  on  small  diurnal  fishes  that  typically  take 
cover  when  threatened.  This  mullid  may  use  its 
exceptionally  long  barbels  not  only  to  locate  such 
animals,  but  also  to  drive  them  into  the  open. 

Many  small  organisms  that  seek  cover  when 
threatened  rest  in  the  same  refuges  when  they  are 
inactive,  and  at  such  times  may  be  prey  for  other 
mullids,  notably  P.  bifasciatus.  This  species  seems 
to  feed  with  equal  effectiveness  day  and  night, 
although  its  food  habits  differ  between  these  two 
periods.  In  this  respect,  a  comparison  with  the 
serranid  Epinephelus  labriformis  in  the  Gulf  of 
California  is  insightful.  As  noted  above,  E.  lab- 
riformis also  feeds  regularly  day  and  night,  taking 
mostly  crustaceans  after  dark  and  small  fishes  in 
daylight;  thus,  its  food  habits  agree  with  the 
generalization  that  crustaceans  are  most  vulner- 
able at  night,  and  fishes  most  vulnerable  in  day- 
light. Parupeneus  bifasciatus  seems  to  be  a  suc- 
cessful exception  to  this  generalization,  because  it 
takes  fishes  more  often  at  night  than  during  the 
day  and  crustaceans  more  during  the  day  than  at 
night.  Apparently,  P.  bifasciatus  is  specialized  to 
capture  prey  that  rest  under  cover,  safe  from  pred- 
ators with  generalized  feeding  equipment. 

Thus,  at  least  some  mullids  find  prey  among 
animals  that  have  sheltered  themselves  in  the 
reef,  just  as  do  some  of  the  muraenid  eels,  so  that, 
like  the  eels,  they  have  gained  advantage  from 
what  generally  are  successful  defensive  behaviors 
in  their  prey.  But  whereas  the  eels  probe  deep  into 
reef  interstices,  the  mullids  confine  their  activity 
to  the  superficial  covering  on  the  reef. 

Predators  Specialized  to  Take  Prey  Among 
the  Plankton  During  the  Day 

There  are  clear  distinctions  between  diurnal 
and  nocturnal  planktivorous  fishes  on  coral  reefs, 
with  the  diurnal  species  inactive  at  night  and  the 
nocturnal  species  inactive  during  the  day  (Hob- 
son,  1965,  1968a,  1972;  Starck  and  Davis,  1966). 
Emery  (1968)  showed  that  the  composition  of 


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FISHERY  BULLETIN:  VOL.  72,  NO.  4 


plankton  over  reefs  in  Florida  also  differs  between 
day  and  night,  a  fact  undoubtedly  related  to  the 
diurnal-nocturnal  dichotomy  among  the  plank- 
tivorous  fishes.  As  described  above,  planktivorous 
fishes  that  feed  in  the  water  column  at  night,  for 
example  Myripristis  and  Apogon,  have  the 
generalized  carnivore's  large  mouth  and  prey 
largely  on  the  relatively  large  plankters,  like  crab 
megalops,  that  are  mostly  in  the  water  column 
above  the  reef  after  dark. 

Although  a  large  array  of  plankters  inhabit  the 
water  column  during  the  day,  generally  they  seem 
too  small  for  adults  of  the  large-mouthed  noctur- 
nal planktivores.  Significantly,  diurnal  planktiv- 
ores  all  have  a  small  mouth,  and  their  major 
prey,  calanoid  copepods,  are  generally  smaller 
than  the  prey  of  their  nocturnal  counterparts. 
Moreover,  diurnal  planktivores  among  adult  reef 
fishes  generally  are  among  the  more  advanced 
teleosts,  having  attained,  or  passed,  the  percoid 
level  of  development.  There  are  no  basal  percoids 
among  the  prominent  diurnal  planktivores  in 
Kona,  but  in  the  tropical  Atlantic  certain  ser- 
ranids,  lutjanids,  and  pomadasyids  specialized  in 
this  habit  are  numerous  (Starck  and  Davis,  1966; 
Randall,  1967).  Most  diurnal  planktivores  on 
coral  reefs,  however,  are  among  the  higher  Per- 
ciformes.  These  include  the  pomacentrids,  which 
probably  include  a  higher  proportion  of  plank- 
tivorous species  than  any  other  major  family  of 
coral-reef  fishes.  The  balistids,  order  Tetraodon- 
tiformes,  are  among  the  most  advanced  teleosts 
and  include  several  specialized  diurnal  planktiv- 
ores: species  of  Melichthys  and  Xanthichthys 
ringens  are  prominent  on  coral  reefs  over  much  of 
the  tropical  world. 

Many  unrelated  species  that  forage  on  zoo- 
plankton  in  the  water  column  during  the  day  dis- 
play convergent  morphologies.  Features  charac- 
teristic of  these  fishes  were  identified  by  Davis  and 
Birdsong  (1973),  who  did  not  distinguish  between 
diurnal  and  nocturnal  forms,  however.  Drawdng 
examples  from  the  tropical  Atlantic  Ocean,  they 
illustrated  certain  unrelated  planktivorous  fishes, 
for  example  Paranthias  furcifer  (a  serranid)  and 
Chromis  cyanea  (a  pomacentrid),  that,  on  casual 
inspection,  look  more  like  one  another  than  they 
do  members  of  their  own  families  that  feed  on  the 
benthos.  The  similarity  among  these  unrelated 
forms  is  based  mainly  on  their  common  increased 
tendency  toward  a  fusiform  body,  a  deeply  incised 
(forked  or  lunate)  caudal  fin,  and  a  small,  up- 


turned mouth  that  gives  their  heads  a  characteris- 
tic appearance.  Presumably  diurnal  planktivores 
that  tend  toward  a  more  fusiform  body  and  deeply 
incised  caudal  fin — both  well-known  characteris- 
tics of  rapid-swimming  oceanic  fishes — can  swim 
faster  than  relatives  in  which  these  tendencies  are 
less  developed.  Considering  the  many  active  pred- 
ators at  large  during  the  day,  increased  speed 
clearly  is  adaptive  for  small  reef  fishes  that  swim 
at  that  time  in  open  water,  high  above  the  shelter- 
ing reef.  The  advantage  of  the  upturned  mouth 
may  be  indirect:  Rosenblatt  (1967)  acknowledged 
Walter  A.  Starck  II  for  pointing  out  that  this 
mouth  construction  gives  the  fish  a  shortened 
snout,  which  permits  close-range  binocular 
vision — an  obvious  advantage  in  capturing  tiny 
organisms  in  the  water  column.  A  number  of  diur- 
nal planktivorous  fishes  in  Kona  possess  one  or 
more  of  these  characteristics,  as  described  and 
illustrated  above  (e.g.  Figures  38  and  40). 

Significantly,  none  of  the  nocturnal  planktiv- 
ores in  Kona  tend  toward  having  either  a  more 
fusiform  body,  or  a  more  deeply  incised  caudal  fin. 
In  fact,  planktivorous  squirrelfishes  of  the  genus 
Myripristis  are  actually  deeper  bodied  than  their 
bottom-feeding  relatives  of  the  genus 
Holocentrus,  and  the  caudal  fins  of  most  are  less 
deeply  incised  (compare,  for  example,  Figures  11a 
and  14).  If,  as  suggested  above,  these  features  gain 
selective  advantage  in  the  planktivores  by  provid- 
ing added  speed  to  elude  predators  in  open  water, 
then  their  absence  among  forms  that  rise  into  the 
water  column  after  dark  is  consistent  with  the 
contention  (above,  and  Hobson,  1973)  that  small 
free-swimming  fishes  face  a  much  diminished 
threat  from  predators  at  night.  Many  of  the  noc- 
turnal species,  including  species  of  Myripristis, 
have  the  sharply  upturned  mouth;  but  it  is  a  large 
structure,  as  noted  above,  suited  to  taking  the 
larger  zooplankters  that  appear  in  the  water  col- 
umn after  dark. 

Not  all  of  the  diurnal  planktivores  in  Kona  tend 
toward  fusiform  bodies,  deeply  incised  caudal  fins, 
or  sharply  upturned  mouths.  None  of  these  fea- 
tures occur  in  the  planktivorous  chaetodontids,  for 
example  Hemitaurichthys  zoster  (Figure  28a), 
which  nevertheless  are  well  suited  to  feed  on 
copepods,  and  other  tiny  zooplankters  in  the  water 
column  by  day.  Obviously  many  conflicting  pres- 
sures have  differentially  affected  the  mor- 
phologies of  the  various  fishes  that  forage  on  tiny 
organisms  in  the  mid-waters. 


1024 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Predators  Specialized  to  Prey  on 
Benthic  Invertebrates  During  the  Day 

A  wide  variety  of  fishes  prey  on  benthic  inver- 
tebrates during  the  day.  They  include  most  of  the 
labrids,  chaetodontids,  baUstids,  canthigasterids, 
monacanthids,  ostraciontids,  and  tetraodontids, 
as  well  as  many  of  the  pomacentrids,  blenniids, 
and  others — all  of  them  higher  perciforms  or  tetra- 
odontiforms.  Their  prey  are  among  the  more 
prominent  invertebrates  on  the  reef,  including 
such  sessile  forms  as  sponges,  coelenterates,  and 
tunicates;  and  also  various  slow  moving  animals 
like  echinoids  and  gastropods.  Typically,  these 
prey  are  fortified  with  toxic  or  noxious  compo- 
nents, like  spines,  spicules,  nematocysts,  or  tough, 
fibrous  components;  or  they  are  encased  in  heavy 
armour.  Because  of  these  defensive  features, 
fishes  that  prey  on  such  forms  must  have 
specialized  feeding  structures  or  techniques — the 
unspecialized  feeding  apparatus  of  generalized 
predators  is  maladapted  for  this  task.  Also  un- 
available to  generalized  predators  are  the  many 
very  small  organisms  whose  capture  requires 
delicate  manipulations  or  movements  for  which 
large-mouthed  fishes  are  unsuited.  Moreover, 
many  of  these  prey  are  diurnal  ly  cryptic  or  secre- 
tive, thus  requiring  still  additional  specializations 
to  capture  them  in  daylight. 

Thus,  fishes  that  successfully  feed  on  most 
benthic  reef  invertebrates  during  the  day  are  ad- 
vanced species  whose  evolution  has  been  mostly 
one  of  perfecting  means  to  feed  in  daylight  on  prey 
that  are  beyond  the  capacity  of  fishes  with  gen- 
eralized feeding  equipment.  Certain  mullids, 
discussed  above,  are  adapted  to  feed  on  many  of 
these  prey,  but  mullids  use  nonvisual  means, 
whereas  fishes  considered  here  are  primarily  vi- 
sual feeders. 

These  are  fishes  that  have  passed  the  percoid 
level  of  development.  The  evolution  of  the  percoid 
morphology,  especially  with  its  highly  adaptive 
feeding  mechanism,  gave  fishes  added  potential  to 
adjust  to  a  wide  variety  of  feeding  situations.  But 
although  percoids  appeared  first  during  the  Cre- 
taceous (Patterson,  1964),  not  until  modern  reef 
communities  appeared  during  the  Eocene 
(Newell,  1971)  does  it  appear  they  began  to  fully 
realize  this  potential. 

Bakus  (1964,  1966,  1969)  concluded  that  the 
secretive  habits  and  defensive  structures  of  many 
benthic  invertebrates  on  coral  reefs  today,  includ- 
ing sponges,  didemnid  tunicates,  and  others,  are 


the  result  of  predation  pressures  from  fishes. 
Whether  or  not  this  is  so,  certainly  the  array  of 
specialized  feeding  habits  and  structures  that 
characterize  diurnal  bottom-feeding  fishes  on 
coral  reefs  are  mostly  adaptations  which  cope  with 
specific  defensive  characteristics  of  their  prey.  Be- 
cause predation  pressures  lead  to  defensive  ad- 
justments in  prey,  and  these  in  turn  stimulate 
further  offensive  modifications  in  predators,  it  is 
not  surprising  that  the  diverse  array  of  defenses  in 
benthic  invertebrates  today  is  matched  in  the 
fishes  that  feed  on  them  by  an  equally  diverse 
array  of  solutions.  These  solutions  to  invertebrate 
defenses  are  manifest  in  the  extremely  varied 
feeding  structures  and  behaviors  that  occur 
among  diurnal  fishes.  Most  diurnal  fishes  special- 
ized for  diets  of  benthic  invertebrates  have  rel- 
atively small  mouths,  but  beyond  this  their  feed- 
ing morphologies  have  diverged  widely. 

Sessile  invertebrates  seem  to  be  significant  prey 
only  during  the  day,  perhaps  because  an  animal 
must  move  to  be  sensed  by  most  predaceous  fishes 
at  night  (Hobson,  1968a).  Thus,  the  few  highly 
specialized  fishes  that  feed  on  sponges  are  strictly 
diurnal.  In  Kona,  the  chaetodontid  Holacanthus 
arcuatus  feeds  on  some  of  the  larger  sponges  that 
encrust  in  exposed  locations  on  rocks,  whereas  the 
zanclid  Zanclus  canescens  uses  its  elongated 
snout  to  feed  on  some  of  the  smaller  sponges  that 
are  attached  within  crevices  or  depressions  on  the 
reef.  Randall  and  Hartman  (1968),  in  studying 
sponge-feeding  chaetodontids  and  monacanthids 
in  the  West  Indies,  noted  that  sponges  cannot  be 
digested  by  most  fishes,  and  concluded  that  these 
organisms  have  become  available  as  food  for  only 
a  few  highly  specialized  teleosts  in  geologically 
recent  times. 

Some  diurnal  predators,  for  example  Forcipiger 
flavissimus,  Chaetodon  auriga,  and  C  fremblii, 
among  chaetodontids  in  Kona,  habitually  tear  off 
pieces  of  larger  sessile  invertebrates,  including 
polychaetes,  tunicates,  and  alcyonarians.  The 
analogy  drawn  above  between  the  snout  and  jaws 
of  F.  flavissimus  and  a  pair  of  needle-nosed  pliers 
underscores  the  suitability  of  this  fish's  feeding 
morphology  for  its  feeding  habit. 

One  of  the  most  obvious  potential  foods  for  car- 
nivorous bottom-feeding  fishes  on  coral  reefs 
would  seem  to  be  the  corals  themselves.  Neverthe- 
less only  some  of  the  most  advanced  teleosts  ex- 
ploit this  resource.  In  Kona,  coral  eaters  include 
certain  chaetodontids,  pomacentrids,  and  blen- 
niids  (all   higher  Perciformes)   and   certain 

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FISHERY  BULLETIN:  VOL.  72,  NO.  4 


monacanthids  and  tetraodontids  (all  Tetraodon- 
tiformes).  In  pointing  out  that  coelenterates  are 
not  food  for  fishes  in  most  marine  communities, 
Hiatt  and  Strasburg  (1960)  cited  various 
specialized  features  of  fishes  that  prey  on  corals  in 
the  Marshall  Islands:  for  chaetodontids  and 
monacanthids  that  snip  off  individual  polj^DS,  they 
listed  the  produced  snouts,  small  terminal 
mouths,  and  fine  protruding  incisiform  teeth;  for 
tetraodontids  and  balistids  that  bite  off  larger 
pieces  of  coral,  they  noted  very  heavy,  strong  den- 
tition. All  fishes  that  feed  on  coral,  including 
those  that  feed  heavily  on  coral  mucus,  seem  to  be 
diurnal.  Obviously  a  predator  that  bites  off  large 
chunks  of  coral,  or  w^hich  scrapes  away  mucus, 
would  find  diurnal  habits  adaptive — its  food  is 
equally  accessible  day  or  night,  and  its  own  activ- 
ity would  benefit  from  daylight.  On  the  other 
hand,  the  polyps  of  some  coral  species  are  most 
expanded  at  night,  suggesting  that  perhaps  pred- 
ators that  would  snip  them  off  might  find  them 
most  accessible  after  dark;  however,  the  precise 
manipulations  involved  in  this  activity  probably 
require  the  light  of  day ,  because  without  exception 
all  such  predators  are  diurnal. 

Daylight  and  precise  manipulations  also  seem 
required  of  predators  that  pluck  tiny  cryptic  or- 
ganisms, notably  amphipods,  from  amid  benthic 
cover.  An  example  from  Kona  is  the  labrid 
Anampses  cuvier,  whose  prey  are  amphipods  and 
other  organisms  too  small  for  large-mouthed 
generalized  predators  of  comparable  size.  Taking 
such  prey  requires  a  specialized  tactic  and  feeding 
mechanism.  Characteristically  such  predators 
hover  within  a  few  centimeters  of  the  substratum, 
inspecting  the  surface.  When  they  spot  prey 
— perhaps  through  movement  or  an  unusual 
contour — they  take  it  in  a  characteristic  plucking 
manner. 

Probably  this  way  of  plucking  tiny  prey  from  a 
substratum  preadapted  precursors  of  those  fishes 
that  are  specialized  as  cleaners.  Most  cleaner 
fishes,  which  include  certain  labrids,  pomacen- 
trids,  and  chaetodontids,  pluck  various  materials, 
mostly  ectoparasitic  crustaceans,  from  the  bodies 
of  other  fishes.  Possessing  both  the  necessary 
techniques  and  morphology,  certain  fishes  in  this 
category  were  prepared  to  adopt  the  cleaning 
habit  when  their  concept  of  a  suitable  feeding  sub- 
stratum broadened  to  include  the  bodies  of  other 
fishes  (Hobson,  1971).  A  few  species,  like 
Labroides  phthirophagus  in  Kona,  are  specialized 
as  cleaners,  having  refined  both  their  feeding 


morphologies  and  techniques  to  more  efficiently 
practice  this  habit.  All  known  cleaner  fishes  are 
diurnal. 

Most  of  the  invertebrate  prey  of  diurnal  fishes 
are  insignificant  as  prey  of  nocturnal  fishes.  How- 
ever, the  specializations  that  permit  certain  diur- 
nal fishes  to  seek  out  secretive  prey  in  daylight 
make  available  to  them  at  that  time  some  of  the 
forms — motile  crustaceans  in  particular — that 
are  important  prey  of  various  generalized  pred- 
ators after  dark.  For  some  fishes,  the  adaptations 
that  permit  them  to  take  crustaceans  and  other 
forms  from  under  reef  cover  in  daylight  are  mor- 
phological. Thus,  the  chaetodontid  Forcipiger 
longirostris  and  the  labrid  Gomphosus  varius  both 
have  elongated  snouts  with  which  they  reach  deep 
into  reef  crevices  for  crustaceans.  In  other  fishes 
the  adaptations  that  make  secretive  prey  avail- 
able are  more  strictly  behavioral.  Thus,  the  labrid 
Thalassoma  duperrey  follows  close  to  the  feeding 
jaws  of  large  herbivores  and  other  fishes  that  dis- 
turb the  substratum,  and  snaps  up  tiny  crusta- 
ceans driven  from  cover.  This  behavior  is  wide- 
spread, occurring  in  other  wrasses  in  Kona  and 
also  in  the  Gulf  of  California  (Hobson,  1968a). 
Some  species  lower  on  the  evolutionary  scale  seem 
to  have  similar  behavior:  as  suggested  above,  the 
carangid  Caranx  melampygus  may  enjoy  this  ad- 
vantage by  following  the  mullid  Parupeneus 
chryseydros,  as  may  the  aulostomid  Aulostomus 
chinensis  by  accompanying  grazing  schools  of 
acanthurids — in  these  two  situations,  however, 
the  prey  seem  to  be  mostly  small  fishes. 

Some  diurnal  predators  excavate  buried  prey, 
as  when  the  labrid  Coris  gainiard  overturns  small 
stones  with  its  snout  and  feeds  on  animals  thus 
exposed.  And  in  the  eastern  Pacific  the  balistid 
Sufflamen  verres  uncovers  prey  buried  in  the  sand 
by  exposing  them  with  a  jet  of  water  from  its 
mouth,  or  by  rapidly  undulating  dorsal  and  anal 
fins  while  lying  on  its  side,  thereby  generating 
currents  that  sweep  the  sand  away  (Hobson,  1965, 
1968a).  Similarly,  the  ostraciontid  Lactophrys 
triqueter  in  the  tropical  Atlantic  by  jetting  water 
from  its  mouth  uncovers  prey  buried  in  the  sand 
(Longley,  1927). 

Related  Problems  of  Species  Recognition. — The 
enormous  potential  for  varied  feeding  adaptations 
in  these  advanced  teleostean  groups  has  led  to  the 
occurrence  on  most  coral  reefs  of  large  numbers  of 
closely  related  species  that  seem  to  have  diverged 
from  one  another  chiefly  on  the  basis  of  differing 
food  habits.  For  example,  14  species  of  the  genus 


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HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


Chaetodon  occur  together  on  Kona  reefs — all  very 
similar  in  general  body  form,  but  with  distinctive 
differences  in  diet  and  related  morphology.  Obvi- 
ously, such  situations  can  exist  only  if,  in  addition 
to  having  acquired  adaptations  suited  to 
specialized  diets,  closely  related  forms  have  also 
acquired  effective  barriers  to  interbreeding.  Cen- 
tral to  this  is  the  ability  of  each  individual  to 
recognize  others  of  its  own  kind,  which  probably 
relates  to  the  circumstance  that  most  species  in 
this  category  have  highly  visible  species-specific 
color  patterns. 

It  is  logical  that  diurnal  fishes  would  employ 
visual  cues  to  identify  one  another.  But  the  dis- 
tinctive nocturnal  colorations  of  many  chaetodon- 
tids  suggest  that  members  of  some  species  need  to 
recognize  each  other  after  dark  as  well.  Nocturnal 
colorations  that  occur  among  chaetodontids  in 
Kona  tend  to  accentuate  a  contrast,  thus  making 
them  more  visible  at  lower  light  levels  (e.g.  Fig- 
ures 28a  and  b;  29a  and  b).  Although  the  nocturnal 
colorations  of  some  fishes,  such  as  those  that  be- 
come mottled,  make  them  more  difficult  to  see  in 
the  dark  (Schroeder,  1964),  certain  chaetodontids 
in  Kona  seem  to  be  effecting  a  nocturnal  display. 
This  phenomenon  appears  most  pronounced 
among  fishes  in  the  present  category,  but  others 
show  it  as  well;  for  example,  in  Kona  certain  of  the 
nocturnal  squirrelfishes,  Holocentrus  (Holocen- 
tridae:  Beryciformes)  display  characteristic 
white  bars  or  spots  at  night  that  are  more 
visible  under  reduced  light  than  their  daytime 
colorations  would  be  (e.g.  Figure  12a  and  b).  Prob- 
ably one  can  generalize  only  to  the  extent  that 
distinctive  day/night  colorations  in  coral  reef 
fishes  reflect  distinctive  day/night  situations. 

Fishes  Specialized  to  Feed  on  Vegetation 

Vegetation,  which  carpets  much  of  the  rocky  sea 
floor  inshore,  would  seem  ready  food  for  fishes.  Yet 
relatively  few  species  utilize  this  resource,  even 
though,  as  in  Kona,  they  often  predominate  on 
tropical  reefs.  The  herbivorous  habit  is  an  ad- 
vanced trait  among  marine  fishes,  a  fact  recog- 
nized by  Hiatt  and  Strasburg  (1960). 

In  general,  herbivorous  fishes  on  coral  reefs 
share  many  characteristics  with  the  diurnal  pred- 
ators that  are  specialized  to  prey  on  benthic  in- 
vertebrates, discussed  in  the  previous  section. 
Like  the  fishes  grouped  together  in  that  category, 
at  least  most  coral  reef  herbivores  are  active  by 
day  and  relatively  inactive  at  night;  furthermore, 


they  too  tend  to  be  colorful  animals  that  have 
small  mouths  which  are  part  of  highly  evolved 
feeding  systems.  In  fact,  several  families  of  fishes 
span  both  categories;  for  example,  the  Chaetodon- 
tidae,  Pomacentridae,  Blenniidae,  Balistidae, 
Monacanthidae,  and  others  include  gradations  of 
species  from  some  that  are  strictly  carnivorous,  to 
others  that  feed  on  both  plants  and  animals,  to 
still  others  that  are  strictly  herbivorous.  Within 
these  groups,  which  have  favored  plasticity  in 
feeding  habits  and  structures,  it  seems  that 
characteristics  adaptive  to  plucking  benthic  in- 
vertebrates from  the  sea  floor  have  been  modified 
in  some  species  for  grazing  on  plants. 

Nocturnal  Activity  Among  Advanced  Teleosts 

Not  all  the  more  advanced  fishes  are  diurnal. 
The  chaetodontid  Chaetodon  lunula  seems  to  be 
nocturnal  in  Kona,  and  at  least  some  of  its 
congeners — notably  C.  quadrimaculatus  and  C. 
auriga — may  feed  to  some  extent  after  dark.  But 
these  are  exceptional  cases  in  an  overwhelmingly 
diurnal  group.  As  suggested  above,  nocturnal  ac- 
tivity in  these  instances  may  relate  to  competition 
among  the  exceptionally  large  number  of 
Chaetodon  species  that  cooccur  on  Kona  reefs. 

Nocturnal  habits  cannot  be  regarded  as  excep- 
tional where  they  occur  among  the  diodontids, 
however,  because  night  feeding  seems  to  be  the 
rule  in  this  family.  And  these  members  of  the 
order  Tetraodontiformes  are  among  the  most 
highly  evolved  of  all  reef  fishes.  The  prey  of 
Diodon  hystrix  and  D.  holocanthus  in  Kona 
— large  echinoids,  gastropods,  and  pagurid 
crabs — are  more  exposed  at  night  than  during  the 
day.  And  because  they  are  relatively  large  and 
move  at  least  intermittently  after  dark,  one  can 
predict  they  would  be  suitable  quarry  for  noctur- 
nal predators  having  means  to  crush  heavy  ar- 
mour. These  are  large  prey,  so  a  predator  must 
carry  its  crushing  mechanism  in  its  mouth,  rather 
than  in  its  throat — as  do  many  of  the  labrids  and 
other  predators  that  feed  on  smaller  mollusks  and 
echinoids  during  the  day.  The  highly  evolved 
diodontids  accomplish  this  job  with  their  powerful 
crushing  jaws,  but  the  problem  has  also  been 
solved  at  a  more  primitive  level  by  certain  basal 
percoids.  In  Kona,  the  nocturnal  sparid  Monotaxis 
grandoculis,  with  its  molariform  dentition,  has 
feeding  habits  similar  to  those  of  the  diodontids, 
but  with  less  emphasis  on  heavily  armoured 
forms.  Clearly,  the  diodontids,  with  more  powerful 
jaws  and  heavier  dentition,  are  better  adapted 


1027 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


than  the  sparids  for  this  particular  task.  Of  even 
more  primitive  stock  than  the  sparid,  the 
muraenid  eel  Echidna  zebra  has  crushing  denti- 
tion, but  its  prey  seem  to  be  primarily  large  crabs 
that  it  takes  regularly  from  reef  crevices  in  day- 
light. There  is  no  evidence  that  it  can  crush  the 
heavy  gastropods  so  prominent  in  the  diets  of  the 
more  advanced  sparids  and  diodontids. 

CONCLUSIONS 

1.  The  feeding  relationships  of  fishes  on  coral 
reefs  in  Kona,  Hawaii,  follow  essentially  the  same 
pattern  as  do  feeding  relationships  of  fishes  on 
coral  reefs  elsewhere. 

2.  Nocturnal  habits  have  had  a  long  history  in 
teleostean  fishes,  and  are  widespread  among  the 
more  generalized  forms,  including  many  of  the 
clupeids,  holocentrids,  serranids,  kuhliids, 
priacanthids,  apogonids,  lutjanids,  and  others. 
These  large-mouthed  predators  find  night  feeding 
adaptive  because  that  is  when  their  prey — mostly 
small,  motile  crustaceans — are  in  exposed  loca- 
tions and  thus  vulnerable  to  their  straightfor- 
ward attack. 

3.  Piscivorous  predators  that  have  a 
generalized  feeding  mechanism,  and  which  attack 
with  a  straightforward  charge,  for  example  cer- 
tain large  carangids,  are  mostly  crepuscular. 

4.  Certain  piscivorous  predators  that  have  a 
generalized  feeding  mechanism  feed  effectively 
during  the  day,  as  well  as  during  twilight,  by 
ambushing  or  stalking  their  prey.  The  ambushers, 
which  include  certain  synodontids,  serranids, 
scorpaenids,  and  bothids,  typically  have  cryptic 
morphology,  coloration,  and  behavior.  The  stalk- 
ers, which  include  the  aulostomids,  fistulariids, 
belonids,  and  sphyraenids,  typically  have  long, 
attenuated  bodies. 

5.  In  acquiring  features  adaptive  for  hunting 
in  reef  crevices,  muraenid  eels  have  become 
highly  successful,  capitalizing  on  the  otherwise 
effective  shelter-seeking  habits  of  small  reef  ani- 
mals. Although  many  small  reef  animals  become 
more  vulnerable  to  eels  when  they  shelter  in  reef 
crevices,  they  find  these  refuges  adaptive  when 
resting,  injured,  or  distressed,  because  they  are 
relatively  safe  here  from  the  even  greater  threat 
from  predators  that  exists  on  the  surface  of  the 
reef. 

6.  The  mullids  use  their  distinctive  sensory 
barbels  to  locate  prey  that  are  sheltered  under  the 
superficial  covering  of  the  reef  and  adjacent  sand. 


Some  mullids  are  best  adapted  to  capture  such 
prey  at  night,  others  to  capture  such  prey  in  day- 
light, and  some  feed  effectively  during  both  day 
and  night.  At  least  some  use  their  barbels  not  only 
to  detect  prey,  but  also  to  drive  them  into  the  open. 

7.  Most  fishes  on  Kona  reefs,  like  fishes  on 
coral  reefs  elsewhere,  are  among  the  more  re- 
cently evolved  teleosts,  having  reached,  or  passed, 
the  percoid  level  of  structural  development. 

8.  The  adaptability  of  the  perciform  feeding 
apparatus  has  given  rise  to  a  wide  variety  of  forms 
that  have  diverged  from  one  another  primarily  on 
the  basis  of  differing  food  habits.  Much  of  this 
diversity  has  resulted  from  adaptations  that  cope 
with  specific  defensive  characteristics  of  the  or- 
ganisms on  which  these  fishes  feed. 

9.  Just  as  nocturnal  and  crepuscular  habits 
predominate  among  the  more  generalized  coral- 
reef  fishes,  diurnal  habits  predominate  among  the 
more  advanced,  specialized  forms,  including  most 
of  the  higher  Perciformes,  and  Tetraodontiformes. 
Some  of  the  most  advanced  of  all,  however,  includ- 
ing the  diodontids,  are  nocturnal. 

10.  Some  higher  teleosts,  including  certain 
chaetodontids,  labrids,  and  balistids,  have 
specializations  that  permit  them  to  capture,  dur- 
ing daylight,  nocturnal  forms  hidden  under  cover. 
Such  prey  include  forms  like  motile  crustaceans 
that  expose  themselves  at  night,  and  at  that  time 
become  the  major  prey  of  generalized  nocturnal 
fishes. 

11.  Some  advanced  teleosts,  including  certain 
chaetodontids,  labrids,  and  pomacentrids,  are 
specialized  to  pluck  tiny  prey,  such  as  amphipods, 
from  among  vegetation  and  other  benthic  cover. 
These  prey  are  too  small,  and  too  cr5q)tic,  to  be 
taken  after  dark  or  by  predators  with  a  large 
mouth.  This  plucking  habit  preadapted  certain 
species  for  cleaning  ectoparasites  and  other  ma- 
terial from  the  bodies  of  other  fishes. 

12.  Fishes  that  prey  mostly  on  sessile  inverte- 
brates, like  sponges  and  coelenterates,  are  highly 
evolved  diurnal  species,  including  certain 
chaetodontids,  pomacentrids,  balistids,  and 
monacanthids.  These  predators  have  specialized 
feeding  structures  and  techniques  that  handle 
various  noxious  or  toxic  defensive  features  in  their 
prey,  including  spines,  spicules,  nematocysts, 
tough  fibrous  tissues,  and  heavy  armour.  And  they 
take  these  sessile  animals  in  daylight  because 
only  moving  prey  are  effectively  sensed  by  visu- 
ally feeding  predators  after  dark. 


1028 


HOBSON:  FEEDING  RELATIONSHIPS  OF  FISHES 


13.  Characteristics  developed  in  feeding  on  ses- 
sile benthic  invertebrates  have  been  modified  in 
some  fishes  for  grazing  on  benthic  vegetation. 
Thus,  many  families,  for  example  the  Chaetodon- 
tidae,  Pomacentridae,  Balistidae,  and  Monacan- 
thidae,  include  some  strictly  carnivorous  forms 
that  prey  on  benthic  invertebrates,  other  forms 
that  feed  on  both  benthic  invertebrates  and  vege- 
tation, and  still  others,  strictly  herbivorous,  that 
only  graze  on  benthic  vegetation. 

14.  On  coral  reefs  there  is  no  sharp  distinction 
between  fishes  that  feed  on  sessile  invertebrates 
and  those  that  graze  on  benthic  vegetation: 
species  in  both  categories  tend  to  be  colorful  diur- 
nal fishes  with  a  small  mouth  that  is  part  of  a 
highly  evolved  digestive  apparatus. 

15.  The  plasticity  in  feeding  habits  and  struc- 
tures characteristic  of  higher  teleosts  that  feed  on 
benthic  organisms  has  led  to  the  multiplicity  of 
closely  related,  and  morphologically  similar 
species  that  live  together  on  coral  reefs.  This  situ- 
ation could  not  have  evolved  without  effective 
barriers  to  interbreeding,  which  in  turn  requires 
that  individuals  recognize  others  of  their  own  kind 
from  among  many  very  similar  forms.  This  re- 
quirement has  been  met  by  having  developed 
highly  visible,  species-specific  color  patterns.  The 
distinctive  nocturnal  color  patterns  of  some  forms, 
for  example  Zanclus  and  certain  chaetodontids, 
indicate  that,  although  they  are  diurnal,  certain  of 
them  need  identifying  features  at  night,  as  well  as 
during  the  day. 

16.  The  small  mouth  of  higher  teleosts  is  adap- 
tive for  feeding  on  the  smaller  plankters,  like 
calanoid  copepods,  that  compose  the  vast  majority 
of  organisms  in  the  water  column.  This  charac- 
teristic distinguishes  diurnal  planktivores,  in- 
cluding certain  pomacentrids,  chaetodontids,  and 
balistids,  from  the  nocturnal  planktivores,  which 
include  certain  holocentrids  and  apogonids.  Most 
nocturnal  planktivores  have  the  larger  mouth  of 
the  generalized  predators,  and  most  of  them  feed 
primarily  on  the  larger  plankters,  like  crab 
megalops  and  mysids,  that  are  most  numerous  in 
the  water  column  over  the  reef  at  night. 

ACKNOWLEDGMENTS 

Lloyd  D.  Richards  assisted  in  all  phases  of  the 
field  work,  and  James  R.  Chess  made  many  of  the 
identifications  of  items  in  the  gut  contents,  espe- 
cially from  the  chaetodontids  and  pomacentrids.  I 
am  grateful  to  John  A.  Maciolek,  U.S.  Bureau  of 


Sport  Fisheries  and  Wildlife,  and  Maxwell  S. 
Doty,  University  of  Hawaii,  for  their  help  in  mak- 
ing preliminary  arrangements  for  our  stay  in 
Kona.  William  A.  Gosline,  University  of  Hawaii, 
and  John  E.  Randall,  B.  P.  Bishop  Museum,  Hono- 
lulu, provided  taxonomic  information  on  various 
fishes.  Kenneth  Raymond,  National  Marine 
Fisheries  Service,  made  the  drawings  that  appear 
as  Figures  1,  26,  and  27a  and  b.  Finally,  I  thank 
Carl  L.  Hubbs  and  Richard  H.  Rosenblatt,  Scripps 
Institution  of  Oceanography,  for  helpful  com- 
ments on  the  manuscript. 

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1031 


THE  EFFECTS  OF  DIETARY  « -TOCOPHEROL  AND  TUNA, 
SAFFLOWER,  AND  LINSEED  OILS  ON  THE  FLAVOR  OF  TURKEY 

L.  Crawford,!  j)  w  Peterson,^  M.  J.  Kretsch,i  A.  L.  Lilyblade,^  and  H.  S.  Olcott^ 


ABSTRACT 

Turkeys  were  fed  varying  levels  of  a -tocopherol  acetate  and  oils  containing  linolenates  (linseed  and 
tuna  oils).  As  expected,  these  oils  caused  a  fishy  flavor  to  develop  in  the  turkey  carcass,  anda  -tocopherol 
fed  concomitantly,  greatly  retarded  development  of  this  fishy  flavor,  but  did  not  affect  the  uptake  of 
linolenates  by  the  turkey  carcass.  These  and  other  observations  pointed  to  the  conclusion  that  linole- 
nates do  not  by  their  simple  presence  in  turkey  carcass  cause  fishy  flavor,  but  that  perhaps  their  in  vivo 
and/or  postmortem  oxidation  are  responsible  for  the  development  of  this  flavor. 


Several  investigators  have  reported  that  fishy 
flavors  develop  in  poultry  carcass  when  diets  are 
supplemented  with  oils,  such  as  linseed  oil  ( Klose 
et  al.,  1951)  and  fish  oil  (Neudoerffer  and  Lea, 
1966,  1967,  1968;  Miller  et  al.,  1967a,  1967b;  Mil- 
ler and  Robisch,  1969;  Dreosti,  1970;  Opstvedt, 
Olsen,  and  Urdahl,  1970;  Opstvedt,  Nygard,  and 
Olsen,  1970,  1971).  The  latter  investigators 
showed  that  this  off  flavor  is  related  to  the  linole- 
nate  content  of  the  oil,  especially  the  long  chain 
homologues.  Miller  and  Robish  ( 1969)  showed 
that  fishy  flavors  were  eliminated  with  the  with- 
drawal offish  oils  and  substitution  of  a  more  satu- 
rated fat  (like  tallow)  in  the  diet.  Lineweaver 
(1970)  reported  that  practical  experience  has 
shown  that  the  amount  of  fish  oil  in  the  diet  of 
poultry  should  not  exceed  0.3%  if  fishy  flavors  are 
to  be  avoided.  However,  it  was  not  clear  whether 
the  specific  character  of  the  oil  (co3  fatty  acid  con- 
tent) was  a  factor  to  be  considered. 

Lea  et  al.  ( 1966),  Dreosti  ( 1970),  and  Opstvedt  et 
al.  (1971)  reported  that  antioxidant-treated  fish 
meal  is  more  likely  to  cause  fishiness  than  un- 
treated meal.  They  reasoned  that  the  unsaturated 
fatty  acids  of  the  untreated  meal  become  oxidized 
and,  perhaps,  polymerized,  thereby  becoming  un- 
available for  uptake  in  the  tissue. 

The  research  of  Mecchi,  Pool,  Beham,  Hamachi, 
and  Klose  (1956)  showed  that  the  stability  of  tur- 
key fat  closely  paralleled  the  tocopherol  content  of 
the  fat.  Other  work  by  Mecchi,  Pool,  Nonaka, 
Klose,  Marsden,  and  Lillie  (1956)  whereby  chick- 
ens and  turkeys  were  fed  varying  levels  of  dietary 

'Western  Regional  Research  Laboratory,  Agricultural  Re- 
search Service,  U.S.  Department  of  Agriculture,  Berkeley,  CA 
94710. 

^Department  of  Avian  Science,  University  of  California  Ag- 
ricultural Experiment  Station,  Davis,  CA  95616. 

^Institute  of  Marine  Resources,  University  of  California, 
Davis,  CA  95616. 


tocopherol,  further  substantiated  that  in  fact  to- 
copherol uptake  was  possibly  singularly  impor- 
tant to  the  stability  of  carcass  fat.  These  findings 
are  corroborated  in  more  detailed  studies  by 
Webb,  Marion,  and  Hayse  ( 1972)  and  Webb,  Brun- 
son,  and  Yates  (1972). 

Dreosti  (1970)  and  Opstvedt  et  al.  (1971)  re- 
ported that  dietary  a  -tocopherol  acetate  sup- 
plementation (above  levels  required  to  prevent 
nutritional  disease)  significantly  reduced  fishy 
flavors  in  poultry  fed  fish  oils. 

It  is  clear  that  dietary  oils  containing  cj  3  fatty 
acids  do  in  some  way  contribute  to  fishy  flavors  in 
poultry  and  that « -tocopherol  acetate  supplemen- 
tation reduces  the  development  of  this  flavor.  It  is 
not  clear  howa;3  fatty  acids,  when  ingested  by 
poultry,  result  in  fishy  flavored  carcasses  or  how 
a; -tocopherol  reduces  the  development  of  this 
flavor.  This  paper  reports  on  the  fatty  acid  compo- 
sition of  extracted  lipids  and  on  the  flavor  of  the 
meat  from  turkeys  fed  fish  oil  and  linseed  oil  to  6 
wk  and  to  8  wk  of  age  using  safflower  oil  or  beef  fat 
to  bring  diets  into  lipid  isocaloric  balance.  Sup- 
plemental tocopherol  acetate  was  added  to  some  of 
the  diets.  The  flavor  of  adult  turkeys  fed  tuna  oil 
for  2  wk  was  also  observed. 

While  it  is  not  a  practice  to  raise  turkeys  to  only 
6  and  8  wk  of  age  or  to  feed  fish  oil  midstream  for 
only  2  wk,  it  was  convenient  and  expedient  for  the 
present  study.  Additionally,  observations  can  be 
made  on  the  relative  uptake  of  dietary  fats  and  the 
influence  of  metabolic  rate. 

EXPERIMENTS 
Oils 

Linseed  oil,  refined  safflower  oil,  freshly  ren- 
dered beef  fat,  and  fresh  polished  tuna  oil  (alba- 
core)  were  obtained  unstabilized.  The  oils  were 


Manuscript  accepted  January  1974. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 

1032 


CRAWFORD  ET  AL.:  FLAVOR  OF  TURKEY 


deaerated  under  vacuum  and  twice  flushed  w^ith 
nitrogen.  To  part  of  each  oil  was  added  0.31259^^ 
ethoxyquin  (this  will  give  125  ppm  when  added  to 
diet).  The  stabilized  oils  were  again  evacuated, 
flushed  under  nitrogen,  and  stored  at  -26°C  until 
use.  The  rendered  beef  fat  was  stored  at  -26°C 
until  used. 

Feed 

The  following  basal  diet  was  used  in  the  feeding 
of  turkeys: 


Ingredients 

%  of  diet 

Soybean  oil  meal  (50%) 

50.00 

Mineral  mix 

2.58 

Vitamin  mix  (in  corn 

starch) 

1.00 

CaHPO4-2H20 

1.70 

CaCO.3 

1.90 

Choline  CI  (50%) 

0.40 

DL-Methionine 

0.20 

Ground  corn 

38.42 

Diets  contained  10  mg  vitamin  E  (cf/- a -tocopherol 
acetate)  per  kilogram  and  0.66  ppm  sodium  sele- 
nite.  Oils  were  preweighed  and  stored  at  —  26°C 
under  nitrogen  before  incorporation  into  diets. 
Diets  were  mixed  with  the  oils  every  1  or  2  wk  and 
stored  in  a  refrigerator  and  fed  fresh  daily. 

Diets  and  Feeding 
Experiment  I 

Eighty  White  Broad  Breasted  poults  (unsexed) 
were  fed  chick  starter  (about  7%  fish  meal)  on  day 
1.  On  days  2  and  3,  they  were  fed  one-half  starter 
and  one-half  basal  diet.  On  day  4,  they  were  di- 
vided into  eight  groups  of  10  turkeys  each,  equally 
distributed  by  weight,  and  fed  to  6  wk  of  age  on  the 
following  experimental  diets: 

Group         Oil  supplement  to  basal  diet^ 

1  4%  SO 

2  4%  SO  +  125  ppm  EMQ 

3  1%  SO  +  3%  LO 

4  1%  SO  +  3%  LO  +  125  ppm  EMQ 

5  3.5%  SO  +  0.5%  TO 

6  3.5%  SO  +  0.5%  TO  +  125  ppm  EMQ 

7  3%  SO  +  1%  TO 

8  3%  SO  +  1%  TO  +  125  ppm  EMQ 

^SO  =  safflower  oil;  EMQ  =  ethoxyquin,  an  an- 
tioxidant; LO  =  linseed  oil;  TO  =  tuna  oil. 


Experiments  II  and  III 

Eighty-one  White  Broad  Breasted  poults  were 
obtained  sexed  (male  only)  for  Experiments  II  and 
III.  Starter  diet  containing  7%  fish  meal  was  fed 
day  1,  and  one-half  starter  and  one-half  basal  diet 
were  fed  on  days  2  and  3.  On  day  4,  the  poults  were 
divided  into  nine  groups  of  nine  turkeys  each, 
equally  distributed  by  weight.  Groups  1  through  8 
were  fed  the  experimental  diets  described  below 
for  8  wk.  These  turkeys  constituted  Experiment  II. 
Group  9  was  fed  the  basal  diet  wdthout  oil  sup- 
plementation to  14  wk  of  age  and  was  then  divided 
into  three  groups  of  three  turkeys  each  which  were 
designated  as  Groups  A,  B,  and  C.  For  2  wk  (until 
16  wk  of  age),  Group  A  was  fed  Diet  1  (control  4% 
beef  fat)  and  Groups  B  and  C  were  fed  Diets  3  and  5 
( 3%  beef  fat  +  1%  tuna  oil  and  2%  beef  fat  +  2% 
tuna  oil),  respectively.  These  turkeys  constituted 
Experiment  III. 

Group  Oil  supplement  to  basal  diet^ 

1  4%  BE 

2  3.5%  BF  +  0.5%  TO 

3  3%  BF  +  1%  TO 

4  3%  BF  +  1%  TO  +  200  mg 

vitamin  E/kilogram 

5  2%  BF  +  2%  TO 

6  2%  BF  +  2%  TO  +  200  mg 

vitamin  E/kilogram 

7  3%  SO  +  1%  TO 

8  2%  SO  +  2%  TO 

9  No  oil  supplement  until  14  wk  of  age 

iBF  =  beef  fat;  TO  =  tuna  oil;  vitamin  E  = 
c?/- a -tocopherol  acetate;  SO  =  safflower  oil. 

Sampling  and  Analysis 

All  turkeys  were  sacrificed  at  the  appropriate 
time  by  cutting  the  jugular  vein  with  an  electrified 
knife  and  bleeding  for  2  min.  The  turkeys  were 
then  scalded  at  60°C,  defeathered,  eviscerated, 
dressed,  packed  in  ice  overnight,  vacuum  sealed, 
blast  frozen,  and  stored  at  -  30°C  for  about  4-6  wk. 
All  birds  were  halved  in  the  frozen  state,  with  half 
being  reserved  for  chemical  analyses  and  half  for 
baking  and  subsequent  organoleptic  analyses. 

The  halves  for  chemical  analyses  were  thawed 
overnight  in  a  2°C  cold  room.  Thighs  and  breasts 
were  removed  and  minced  individually  after  re- 
moval of  skin  and  subcutaneous  fat.  Minced 
thighs  and  breasts  from  individual  birds  were 


1033 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


wrapped  in  Saran**  film  and  aluminum  foil, 
identified,  and  stored  at  -30°C  until  analyzed. 

Oil  content  was  determined  on  composites  of 
18-g  samples  of  the  individual  thighs  and  breasts 
from  each  bird  by  the  modified  method  of  Smith, 
Ambrose,  and  Knobl  (1964).  Methyl  esters  for 
gas-liquid  chromatography  (GLC)  analyses  were 
prepared  from  the  same  oil  extract  by  the  method 
of  Metcalfe,  Schmitz,  and  Pelka  (1966).  The  GLC 
column  was  10%  diethylene  glycol  adipate  on  Gas 
Chrom  Q.  GLC  conditions  were  as  follows:  column, 
196°C;  injector,  250°C;  flame  ionization  detector, 
300°C;  carrier  gas  flow,  24.6  cm^/min. 

Organoleptic  analyses  for  the  turkeys  in  Exper- 
iment I  were  performed  by  ranking.  The  panelists 
ranked  four  samples  per  session  (of  which  one 
sample  was  a  control).  Comments  about  off 
flavors,  if  present,  were  solicited  (e.g.,  fishy,  ox- 
idized, rancid,  etc.).  In  Experiments  II  and  III, 
organoleptic  analyses  were  performed  by  scoring, 
using  a  balanced  incomplete  block  technique. 
Analyses  of  variance  and  a  Duncan  multiple 
range  test  were  calculated  for  Experiment  II.  Re- 
gression equations  were  calculated  for  breast  and 
thigh  meat  and  skin  for  Experiment  III. 

RESULTS  AND  DISCUSSION 

Experiment  I 

All  turkeys  in  Experiment  I  seemed  to  have 
grown  normally  and  to  have  been  in  good  nutri- 


■'Reference  to  a  company  or  product  name  does  not  imply 
approval  or  recommendation  of  the  product  by  the  U.S.  Depart- 
ment of  Agriculture  or  the  National  Marine  Fisheries  Service, 
NOAA,  to  the  exclusion  of  others  that  may  be  suitable. 


tional  health.  The  mean  dressed  weight  was  991  g, 
with  no  significant  weight  differences  between 
groups. 

Table  1  gives  the  results  of  GLC  analyses  and 
lipid  content  (grams/100  g)  of  breast  and  thigh 
meat  from  the  turkeys  fed  linseed  and  tuna  oils  to 
6  wk  of  age.  As  expected,  the  thigh  contained 
nearly  twice  the  amount  of  lipid  as  the  breast, 
(about  2%  and  1%  extracted  lipid,  respectively). 
The  distribution  of  the  methyl  esters  of  fatty  acids 
showed  consistently  higher  percentages  of  C  16:0, 
C18:0,  C20:4,  C22:5,  and  C22:6  in  the  breast,  but 
higher  C 18: 3  (when  present  in  the  diet),  C 18: 2  and 
C18:1  in  the  thigh  for  all  treatments.  The  lipid 
composition  of  the  leg  and  breast  reflect  generally 
that  of  the  dietary  oils. 

Results  of  organoleptic  evaluation  of  the  tur- 
keys are  reported  in  Table  2.  The  scoring  (by  rank) 
shows  that  1%  tuna  oil  imparts  oflfflavor  (slight)  in 
breast  and  thigh  meat  and  somewhat  the  same 
trend  is  indicated  for  odor  evaluation,  especially 
in  the  breast  meat.  But  no  clear  trend  is  indicated 
for  the  skin.  In  general,  flavor  was  judged  as  excel- 
lent. Ofttimes,  there  were  no  clear  differences  in  a 
given  set  of  comparisons.  There  were  only  a  few 
scattered  comments  that  described  the  flavor  as 
fishy.  No  consistent  differences  were  found  be- 
tween samples  with  and  without  ethoxyquin. 

The  lack  of  the  development  of  positive  fishy 
flavor  in  this  experiment  was  unexpected  since  the 
oils  fed  to  the  turkeys  contained  high  levels  of 
linolenicacid  (linseed  oil,  ca.  57%Cl8:3co3)or  one 
of  its  longer-chained  homologues  (tuna  oil,  ca.  32% 
C22:6c<j3). Fishy  flavors  have  been  induced  in  poul- 
try by  other  investigators  using  oils  that  con- 
tained far  less  linolenates  than  used  in  this  exper- 


Table  1. — Methyl  ester  fatty  acid  composition'  of  linseed  oil  and  tuna  oil  and  lipids  extracted  from  turkeys^  fed  to  6  wk  of  age  diets 
containing  varying  levels  of  safflower,  linseed,  and  tuna  oils  with  and  without  ethoxyquin. 


Fatty  acid 


Linseed 
oil 


Tuna 
oil 


IB 


IT 


2B 


2T 


38        3T        48        4T 


58 


5T 


68       6T 


78 


7T 


88        8T 


C16:0  + 

ISO  C16:0 
C18:0 
018:1 
018:2 
C18:3u)3 
C20:4uj6 
C20:5oj3 
C22:3lo3 
C22:5tj3 
C22:6u;3 
'/,  lipid. 

g/IOOg 

tissue 


5.3  14.2  18.4  12.1  18.2  13.6  19.0  11.5  15.7     11.1  17.5  12,5  19.0  14.0  18.5  13.0  17.5  13.1 

3.8  5.5  12.3  8.4  13.0       9  0  14  9  10  1  11.9       6.7  12.8       8.5  12  6  7.5  10.3  8.9  9.5  5.7 

18.1  15.8  10.2  13.9  9.1  16.6  11.4  15.7  14.6     18.8  10,3  14.2       9.5  14.8  9.3  13.7  11.7  17.3 

150  4.8  37.8  52.0  40  3  47.1  28.6  35.3  33.5     36.9  33.7  49.2  34.2  48.5  32.5  46.0  38.8  48.0 

57.8  —  —         —  —         —  4,1  14.6  10.5     19.6        —         —         —  —         —  —  —  — 

—  3.0  12.0  6.3  10.1        5.6  7.1  4.0       4.3        19  8.9       4  8       9.1  3.9  8.9  4  3  5  6  2  6 

—  7.9  —        —  —        —  2.3        —        —        —        —        —        —  —  1.8  —  —  — 

—  —  2.5  —  2.3       —        —        —        —        —        —        —        —  —        —  —  —  — 

—  1.8—         —  —         —  3.4        —        2.2—         —         —         —  —         —  —  —  — 

—  32.5  —         —  —         —  3.9        —        1.9        —  79       37       79  32  11.6  5.2  8.9  4,0 

—  —  0,88  1,87  0,92     2,12  0,95  1,86      1,40     3,01      1,22     2,12      1,02  2,29  0,92  1.97  1,17  3,03 


'Fatty  acids  in  amounts  of  2ri  or  less  omitted,  8  =  Breast  meat;  T  =  thigh  meat, 

K^JIi^l^^'^^  °'  '^'■'^^ys  were  fed  a  basal  diet  plus  an  oil  supplement  for  6  wk.  Group  1  =  4^:i  safflower  oil  (SO),  Group  2  =  (same  as  1 )  +  125  ppm  ethoxyquin 
L.J^°"^^"  ^"'  SO +  3'^?^  linseedoil(LO),Group4  =  (sameas3)  +  125  ppm  EMQ,Group5  =  3.59f  SO  +  0.5':?:  tuna  oil  (TO),  Group  6  =  (same  as  5)  +  125 
Dm  EMC,  Group  7  =  3't  SO  +  Vr,  TO,  Group  8  =  (same  as  7)  +  125  ppm  EMQ 


1034 


CRAWFORD  ET  AL.:  FLAVOR  OF  TURKEY 


Table  2. — Taste  panel  scores  (rank)  on  breast  and  thigh  meat 
and  skin  of  turkeys  fed  to  6  wk  of  age  diets  containing  varjdng 
levels  of  safflower  oil,  linseed  oil,  and  tuna  fish  oil  with  and 
without  ethoxyquin. 


Breast 

Thigh 

Group' 

meat 

meat 

Skin 

Odor2 

Without  antioxidant 

1 ,  4f>  SO 

1.9 

2.4 

2.9 

3,  3^f  LO 

2.4 

3.0 

2.6 

5.  0.5^r  TO 

25 

1.9 

2.3 

7,  ^n  TO 

3.2 

2.8 

2.4 

With  antiox 

dant 

2.  4'i  SO 

19 

2.2 

2.5 

4,  39,  LO 

26 

2.2 

2.7 

6,  O.S^'r  TO 

2.1 

2.4 

2.2 

8,  1<5  TO 

35 

Flavor^ 

2.9 

2.7 

Without  antic 

xldant 

:.A9(  SO 

1.9 

2.3 

2.5 

3,  39c  LO 

24 

33.2  (4F) 

33.0  (IF) 

5.  Om  TO 

2.7 

2.1 

1.9 

7.  ^9c  TO 

3.0 

32.4  (IF) 

32  6  (IF) 

With 

antioxidant 

2,  49c  SO 

23 

1.9 

2.6 

4,  3^*  LO 

2.3 

2.3 

29 

6.  0.5^7r  TO 

2  1 

2.4 

2  1 

8,  ^9c  TO 

33.3  (2F) 

33.3  (IF) 

25 

'All  groups  of  turkeys  were  fed  a  basal  diet  plus  an  oil  supplement  for  6 
wk.  Group  1  =  4'y  safflower  oil  (SO),  Group  2  =  (same  as  1)  ♦  125  ppm 
ethoxyquin  (EMQ),  Group  3  =  Vi  SO  *  3'>  linseed  oil  (LO).  Group  4  = 
(same  as  3)  ^  125  ppm  EMQ,  Group  5  =  3.5';  SO  ~  0.5'f  tuna  oil  (TO), 
Group  6  =  (same  as  5)  *  1 25  ppm  EMQ,  Group  7  =  3"^';  SO  +  V'i  TO,  Group 
8  =  (same  as  7)  ~  125  ppm  EMQ 

^Rank  1  =  least  off  odor  or  off  flavor. 

^F  =  number  of  fishiness  comments. 


iment  (Miller  and  Robish,  1969;  Dreosti,  1970; 
Opstvedt,  Nygard,  and  Olsen,  1970). 

Some  suggestions  may  be  offered  as  to  why  no 
clear  fishy  flavors  were  induced,  even  though 
there  was  uptake  of  linolenates  in  the  turkey  car- 
cass. For  example,  the  use  of  safflower  oil  to 
achieve  lipid  isocaloric  balance  may  have  de- 
pressed the  uptake  of  linolenates.  Edwards  and 
May  (1965)  observed  this  effect  when  they  fed 
mixtures  of  corn  and  menhaden  oil.  Certainly  the 
metabolism  of  the  young  birds  (in  this  experiment 
6  wk  of  age)  must  be  considered.  Their  cell  turn- 
over is  considerably  higher  than  that  of  adult 
birds;  phospholipid  (an  integral  part  of  cell  mem- 
branes) turnover  is  proportional  to  mitotic  rate, 
and  long-chained  fatty  acids  are  more  readily 
found  in  phospholipids. 

Experiment  II 

As  before,  all  turkeys  appeared  to  be  in  good 
nutritional  health.  The  mean  dressed  weight  was 
1,377  g  for  turkeys  fed  to  8  wk  of  age. 

Table  3  shows  the  results  of  fatty  acid  (methyl 
esters)  determination  by  GLC  of  lipids  extracted 
from  the  breast  of  turkeys  fed  fish  oil  and  safflower 
oil  to  8  wk  of  age.  The  fatty  acids  C20:5a;3  and 


Table  3. — Methyl  ester  fatty  acid  composition  of  tuna  oil  and  lipids  extracted  from  the  breast  of 
turkeys'  fed  to  8  wk  of  age  diets  containing  varying  levels  of  tuna  oil  and  beef  fat  or  safflower  oil 
with  and  without  vitamin  E  idl-a  -tocopherol  acetate)  supplementation. 


, . 

distribution 

in  extracted  oil 

Fatty 

Tuna 

acid 

oi|2 

Group  1 

Group  2 

Group 

3     Group  4 

Group  5 

Group  6 

Group  7 

Group  8 

014 

3.1 

0.7 

10 

0.7 

0.5 

0.4 

0,5 

0,3 

0.5 

014:1 

— 

0.2 

0.2 

0.1 

0.1 

0.1 

0.1 

0,0 

0.1 

015 

— 

0,2 

0.2 

0.2 

0.2 

0.3 

0.2 

0,1 

0.2 

ISO  016 

— 

3.3 

3.3 

3.1 

3.5 

3.9 

3.7 

2,6 

3.3 

016 

— 

14.8 

14.3 

14.3 

13.7 

14.5 

14.3 

15.2 

14.9 

016:1 

4.7 

1.1 

12 

0.9 

06 

0.6 

0.9 

0.3 

0.6 

017 

— 

0.5 

0.6 

0.5 

06 

08 

0.7 

0.7 

0,7 

ISO  018 

— 

1.7 

14 

1.4 

2.1 

1.3 

1.6 

0.7 

0.9 

018 

5.5 

15.4 

14.9 

15.0 

15.3 

14.9 

146 

13.6 

11.2 

018:1 

15.8 

20.8 

18.9 

17.4 

15.7 

14.7 

14.9 

11.1 

12.8 

018:2 

4.8 

24.8 

20.6 

19.9 

18.5 

18.0 

181 

30.9 

28.9 

018:3 

— 

0.8 

0.7 

0.5 

0.3 

0.5 

0.5 

0.5 

0.7 

020:4 

3.0 

6.6 

5.9 

6.5 

7.4 

62 

6.4 

88 

6.5 

020:5 

7.9 

0.7 

2.4 

33 

3.4 

4.2 

4.3 

1.8 

3.3 

022:5 

1.8 

1.2 

1.6 

1.5 

1.6 

2.0 

1.5 

1.0 

1.0 

022:6 

32.5 

3.3 

10,3 

11.9 

13.4 

14.9 

15,5 

9.2 

11.8 

Others 

21  0 

3.9 

25 

2.8 

3,1 

2.7 

2,2 

3.2 

2.6 

9c  lipid. 



0.89 

0.95 

098 

0.86 

084 

0  90 

0.93 

084 

g/100  g 

tissue 

'All  groups  of  turkey  were  fed  a  basal  diet  plus  an  oil  supplement  for  8  wk.  Group  1  =  4%  beef  fat  (BF),  Group 
2  =  3.5'7f  BF  +  0.5^  tuna  oil  (TO),  Group  3  =  3^7,  BF  +  ^9c  TO,  Group  4  =  (same  as  3)  +  200  mg/kg  vitamin  E, 
Group  5  =  ?7r  BF  +  27f  TO,  Group  6  =  (same  as  5)  +  200  mg/kg  vitamin  E,  Group  7  =  3<7f  safflower  oil  (SO)  + 
^9c  TO,  Group  a  =  29c  SO  +  2Vc  TO, 


1035 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  4. — Methyl  ester  fatty  acid  composition  of  lipids  extracted 
from  the  cooked  breast  of  turkeys'  fed  to  8  wk  of  age  diets 
containing  varying  levels  of  beef  fat  and  tuna  oil  writh  and  with- 
out vitamin  E  (c?/ -a -tocopherol  acetate)  supplementation. 


'J, 

distribution  In  extracted 

oil 

Fatty 

acicJ 

Group  1 

Group  5 

Group  6 

014 

0.8 

1.1 

0,9 

014:1 

0,1 

0.3 

02 

CIS 

0.2 

0.3 

0.3 

ISO  016 

2.7 

2.3 

1,8 

016 

15.9 

16.6 

15  9 

016:1 

0.8 

2.2 

1,7 

017 

0.6 

0.9 

08 

ISO  018 

1.6 

1.4 

1,1 

018 

17.1 

14.1 

14.5 

018:1 

19.1 

21.2 

18.8 

018:2 

22.5 

19.3 

19.7 

018:3 

0.6 

0.9 

08 

C20:4 

5.1 

3.4 

4.7 

020:5 

1.8 

2.5 

3.1 

022:5 

1.0 

1.1 

1,1 

022:6 

6.6 

9.2 

11.5 

%  lipid, 

g/100  g 

tissue 

1  10 

1  15 

1  10 

'All  groups  of  turkeys  were  fed  a  basal  diet  plus  an  oil  supplement  for  8 
wk.  Group  1  =  4%  beef  fat  (BF),  Group  5  =  2%  BF  +  2'7r  tuna  oil.  Group  6  = 
(same  as  5)  +  200  mga-tocopfierol  acetate  per  kilogram. 

C22:6uj 3  increase  as  the  amount  of  tuna  oil  in- 
creases in  the  diet.  Safflower  oil  added  to  Diets  7 
and  8  seemed  to  reduce  the  uptake  of  these  fatty 
acids.  Tocopherol  acetate  supplementation  did  not 
seem  to  have  any  effect  on  the  uptake  of  cj3  fatty 
acids.  Fatty  acid  distribution  analyses  (Table  4)  on 
lipids  extracted  from  cooked  turkey  breast  from 
Groups  1,  5,  and  6  show  thata -tocopherol  did  not 
have  an  effect  on  the  relative  stability  of  the  long- 
chain  fatty  acids  during  cooking. 
The  results  of  taste  panel  evaluations  (Table  5) 


show  that,  while  « -tocopherol  supplementation 
did  not  change  thecjS  fatty  acid  distribution,  it 
greatly  reduced  fishy  flavor  as  judged  by  the  taste 
panel.  Opstvedt,  Nyard,  and  Olsen  (1970)  also  re- 
ported these  findings.  On  the  other  hand,  safflower 
oil  (used  to  achieve  isocaloric  balance)  reduced  the 
uptake  of Gj3  fatty  acids,  but  there  were  no  differ- 
ences in  flavor  when  compared  to  the  flavor  of 
turkeys  fed  the  same  amount  of  tuna  oil  but  using 
beef  fat  for  isocaloric  balance.  There  was  a  strong 
relationship  between  the  amount  ofC20:5cj3 
and/or  C22:6cxj3  and  fishy  flavor  when  no 
a-tocopherol  or  safflower  oil  supplementation  was 
present  in  the  diets.  This  agrees  with  the  findings 
of  Neudoerffer  and  Lea  ( 1966,  1967),  Miller  et  al. 
(1967a),  Miller  and  Robish  (1969),  and  Dreosti 
(1970).  However,  a  comparison  of  the  fatty  acid 
distributions  and  lipid  contents  found  by  these 
investigators  with  those  in  this  experiment  and 
Experiment  I,  shows  that  the  levels  of  C20:5u;3 
and  C22:6cd3  present  when  fishy  flavors  are  de- 
tected are  higher  in  these  experiments.  We  should 
also  note  that  the  fish  oils  used  by  other  investi- 
gators contained  about  2-129^  C22:6u)3,while  the 
tuna  oil  used  in  these  experiments  contained  32% 
C22:6w3. 

Experiment  III 

These  16-wk-old  turkeys  had  been  fed  diets  con- 
taining 3^f  beef  fat  plus  Yk  tuna  oil  and  29f  beef 
fat  plus  Ific  tuna  oil  for  the  2  wk  prior  to  slaughter. 
The  control  diet  contained  4*^  beef  fat.  All  turkeys 
apparently  enjoyed  good  nutritional  health  and 
the  mean  dressed  weight  was  3,585  g. 


Table  5. — Mean'  taste  panel  scores*  and  Duncan's  multiple  range  test  of  mean  scores  on  thigh  and 
breast  meat  and  skin  of  turkeys  fed  to  8  wk  of  age  diets  containing  varying  levels  of  tuna  fish  oil  and 
beef  fat  or  safflower  oil  with  and  without  vitamin  E  {dl  a  -tocopherol  acetate)  supplementation. 


Groups       Breast  meat 

Groups       Thigh  meat 

Groups             Skin 

5,  2%  TO  +  2%  BF 
8,  2%  TO  -F  2%  SO 

3,  19f  TO  +  3%  BF 

2,  0,5%  TO  +  3.5%  BF 

6,  2%  TO  +  2%  BF  +  E 

7,  1%r  TO  +  3%  SO 
1,4%  BF 

4,  1%  TO  +  3%  BF  +  E 

3.91 
3.35 
3.04 
2.94 
2.48 
2.30 
1.33 
1.24 

8. 
5, 
6, 
2, 
7, 
3, 
4, 
1, 

2%  TO  +  2%  SO         3.56 
20f  TO  +  2%  BF          3.28 
2%  TO  +  27c  BF  +  E  2.41 
0.5%  TO  +  3.5%  BF    2.20 
1%  TO  +  3%  SO         2.03 
1%  TO  +  3%  BF          1 .85 
1%  TO  +  3%  BF  4-  E  1.22 
4%  BF                           0.95 

8 

5, 
3, 
6, 
7, 
1, 
2, 
4, 

2%  TO  +  2%  SO         3.37 
2%  TO  -h  2%  BF          2.69 
1%  TO  +  3%  BF          1.99 
2%  TO  +  2%  BF  +  E  1.98 
1%  TO  -1-  3%  SO          1.69 
4%  BF                           1,27 
0.5%  TO  +  3.5%  BF    1.26 
1%  TO  -1-  3%  BF  +  E  1.04 

Sx 

0.228 

0.211 

0.252 

'Means  connected  by  a  common  line  are  not  significantly  different  at  the  0.05  probability  level 

^1  =  no  fishy  flavor,  5  =  very  fishy. 

MM  groups  of  turkeys  were  fed  a  basal  diet  plus  an  oil  supplement  for  8  wk.  Group  1  =  4%  beef  fat  (BF),  Group  2 
=  0.5%  tuna  oil  (TO)  +  3.5%  BF,  Group  3-  1%  TO  +  3%  BF,  Group  4  =^  (same  as  3)  +  200  mg/kg  vitamin  E(e)  Group 
5  =  2%  TO  +  2%  BF,Group6  =  (sameas5)  +  200mg/kg  vitamin  E,  Group  7  =  1%^  TO  +  3%  safflower  oil  (SO),  Group 
8  =  2%  TO  -^  2%  SO. 


1036 


CRAWFORD  ET  AL.:  FLAVOR  OF  TURKEY 


Table  6. — Methyl  ester  fatty  acid  composition  of  lipids  extracted 
from  the  thighs  of  turkeys'  fed  from  14  wk  to  16  wk  of  age  diets 
containing  varv'ing  levels  of  beef  fat  and  tuna  oil. 


^i  distribution  in  extracted  oil 


Fatty 
acid 


Group  A 


Group  B 


Group  C 


C14 

C14:1 

C15 

Iso  C16 

C16 

C16:1 

CI  7 

ISO  CI 8 

C18 

CIS: 


C18 
C18 
C20 
C20 
C22 
C22 


'>  lipid. 
g/100  g 
tissue 


0.4 

0.1 

0.1 

1.9 

17.7 

5.8 

0.3 

0.9 

10.6 

21.7 

30.7 

1.6 

5.2 

0.2 

0.5 

0.5 


2  10 


1.0 

0.1 

0.2 

2.1 

16.8 

1.8 

0.5 

0.8 

13.8 

20.3 

26.4 

1.3 

62 

0.9 

0.8 

4.5 


2  12 


1.0 

0.1 

0.2 

1.6 

18.7 

1.9 

0.6 

0.7 

12.1 

20.4 

26.2 

1.5 

5.0 

1.4 

0.7 

6.1 


2  55 


'All  turkeys  were  fed  a  basal  diet  without  oil  supplement  to  14  wk  of  age 
and  to  16wkof  age  with  oil  Group  A  =  40  beef  fat.  Group  B  =  3'>  beef  fat 
-r  Vt  tuna  oil.  Group  C  =  2*;  beef  fat  -  2'>  tuna  oil. 


Fatty  acid  distributions  and  percent  extracted 
lipids  from  the  thighs  of  these  turkeys  are  shown 
in  Table  6.  (The  same  analyses  were  not  possible 
for  the  breast  meat  because  it  was  used  in  another 
experiment.)  As  before, the  amount  of  C22:6oj3 
increased  as  the  amount  of  fish  oil  in  the  diet 
increased.  It  is  of  interest  that  the  lipid  level  was 
only  slightly  higher  in  the  16-wk  turkeys  fed  fish 
oil  for  2  wk  than  in  the  6-  or  8-wk  turkeys  fed  from 
day  4  to  slaughter.  Yet,  the  percentof  C22:6u;3  was 
less  than  half  that  of  the  8-wk  birds,  while  the 
flavor  reported  in  Table  7  was  at  least  as  fishy,  if 
not  more  so. 

In  conclusion,  if  consideration  is  given  to  1)  the 
effects  of  a -tocopherol  on  (reducing)  the  fishy 
flavor,  while  not  affecting  the  uptake  of  linole- 
nates,  and  2)  the  different  levels  of  long-chain 
linolenates  present  when  fishiness  is  detected,  one 
has  to  reason  that  the  long-chained  u;  3  fatty  acids 
do  not  of  themselves  cause  fishy  flavor  by  their 
simple  presence.  It  is  plausible  that  the  fishy 
flavors  result  at  least  in  part  from  the  oxidation  (in 
vivo?  postmortem?)  of  linolenates  and  that 
o-tocopherol  limits  the  oxidation.  It  is  further  col- 
orable that  the  amount  of  linolenate  oxidation 
needed  to  produce  fishy  flavor  may  be  smaller  than 
the  inherent  error  in  fatty  acid  analyses  and 
therefore,  no  differences  would  be  observed  in  the 
amount  of  linolenates  in  the  carcass  of  turkeys  fed 
fish  oils  with  and  without  oi-tocopherol. 


Table  7. — Mean  taste  panel  scores'  and  regression  equations  (% 
tuna  fish  oil  supplement  vs.  mean  taste  panel  scores)  for  thigh 
and  breast  meat  and  skin  of  turkeys  fed  diets  containing  varying 
amounts  of  beef  fat  and  tuna  oil. 


Groups 

Breast  meat 

Th 

gh  meat 

Skin 

A,  control 

1.44 

1.11 

1.06 

B.  1  TO 

2.06 

2.50 

1.89 

0,2  TO 

328 

4.11 

2.94 

Sx 

026 

0.21 

0.28 

Regression 

equations: 

V  =  1.343 

+ 

0.91 7X 

- 

y  =  1.074 

+ 

1.500X 

V  =  1.018 

^ 

0.944X 

'  =  no  fishy  flavor.  5  =  very  fishy. 

'All  groups  of  turkeys  were  fed  a  basal  diet  without  oil  supplementation 
to  14  wk  of  age  and  to  16  wk  with  oil.  Group  A  =  4'~f  beef  fat.  Group  B  =  3% 
beef  fat  -  1<7  tuna  oil  (TO).  Group  C  =  2rf  beef  fat  ^  20  TO. 


ACKNOWLEDGMENT 

We  wish  to  acknowledge  the  very  able  assis- 
tance rendered  by  Helen  H.  Palmer,  Hans 
Lineweaver,  Ed  Mecchi,  J.  S.  Lin,  Carol  Hudson, 
and  our  (Western  Regional  Research  Laboratory) 
very  able  Biometrical  Services  staff.  Further 
gratitude  is  expressed  to  Hoffman  LaRoche  Inc., 
Pacific  Vegetable  Oil  International,  Inc.,  Mon- 
santo Co.,  Star-Kist  Foods,  and  Van  Camp  Sea 
Food  for  their  contributions  of  some  of  the  materi- 
als used  in  this  experiment. 

LITERATURE  CITED 

Dreosti,  G.  M. 

1970.  Good  quality  fish  meals.  Fish.  Ind.  Res.  Inst.  Prog. 
Rep.  197,  Univ.  Cape  Town,  Cape  Town,  S.  Afr. 
Edwards,  H.  M.,  Jr.,  and  K.  N.  May. 

1965.  Studies  with  menhaden  oil  in  practical-type  broiler 
rations.  Poult.  Sci.  44:685-689. 

Klose,  a.  a.,  E.  p.  Mecchi,  H.  L.  Hanson,  and  H.  Lineweaver. 
1951.  The  role  of  dietary  fat  in  the  quality  of  fresh  and 
frozen  storage  turkeys.  J.  Am.  Oil  Chem.  Soc.  28: 162- 164. 
Lea,  C.  H.,  L.  J.  Parr,  J.  L.  L'Estrange,  and  K.  J.  Carpenter. 

1966.  Nutritional  effects  of  autoxidized  fats  in  animal  diets. 
Br.  J.  Nutr.  20:123-133. 

Lineweaver,  H. 

1970.  Effect  of  feed  ingredients  on  the  development  of  off 
flavors  in  turkey  meat.  Feedstuffs  42(9):30. 
Mecchi,  E.  P.,  M.  F.  Pool,  G.  A.  Beham,  M.  Hamachi,  and  A.  A. 
Klose. 

1956.  The  role  of  tocopherol  content  in  the  comparative 
stability    of  chicken    and    turkey   fat.    Poult.    Sci. 
35:1238-1246. 
Mecchi,  E.  P.,  M.  F.  Pool,  M.  Nonaka,  A.  A.  Klose,  S.  J. 

MaRSDEN,  and  R.  J.  LiLLIE. 

1956.  Further  studies  on  tocopherol  content  and  stability  of 
carcass  fat  of  chickens  and  turkeys.  Poult.  Sci. 
35:1246-1251. 


1037 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Metcalfe,  L.  D.,  A.  A.  Schmitz,  and  J.  R.  Pelka. 

1966.  Rapid  preparation  of  fatty  acid  esters  from  lipids  for 
gas  chromatographic  analysis.  Anal.  Chem.  38:514-515. 
Miller,  D.,  E.  H.  Gruger,  Jr.,  K.  C.  Leong,  and  G.  M.  Knobl, 
Jr. 

1967a.   Effect  of  refined  menhaden  oils  on  flavor  and  fatty 

acid  composition  of  broiler  flesh.  J.  Food  Sci.  32:342-345. 

1967b.   Dietary  effect  of  menhaden-oil  ethyl  esters  on  the 

fatty  acid  pattern  of  broiler  muscle  lipids.  Poult.  Sci. 

46:438-444. 

Miller,  D.,  and  P.  Robisch. 

1969.  Comparative  effect  of  herring,  menhaden,  and 
safflower  oils  on  broiler  tissues  fatty  acid  composition  and 
flavor.  Poult.  Sci.  48:2146-2157. 

Neudoerffer,  T.  S.,  and  C.  H.  Lea. 

1966.  Effects  of  dietary  fish  oil  on  the  composition  and  sta- 
bihty  of  turkey  depot  fat.  Br.  J.  Nutr.  20:581-594. 

1967.  Effects  of  dietary  polyunsaturated  fatty  acids  on  the 
composition  of  the  individual  lipids  of  turkey  breast  and 
leg  muscle.  Br.  J.  Nutr.  21:691-714. 


1968.   Effects  of  dietary  fat  on  the  amounts  and  proportions 
of  the  individual  lipids  in  turkey  muscle.  Br.  J.  Nutr. 
22:115-128. 
Opstvedt,  J.,  E.  Nygard,  and  S.  Olsen. 

1970.  Influence  of  residual  lipids  on  the  nutritive  value  of 
fish  meal  (II).  Acta  Agric.  Scand.  20:185-193. 

1971.  Influence  of  residual  lipids  on  the  nutritive  value  of 
fish  meal  (III).  Acta  Agric.  Scand.  21:126-143. 

Opstvedt,  J.,  S.  Olsen,  and  N.  Urdahl. 

1970.  Influence  of  residual  lipids  on  the  nutritive  value  of 
fish  meal  (I).  Acta  Agric.  Scand.  20:174-184. 
Smith,  P.,  Jr.,  M.  E.  Ambrose,  and  G.  M.  Knobl,  Jr. 

1964.  Improved  rapid  method  for  determining  total  lipids 
in  fish  meal.  Commer.  Fish.  Rev.  26(7):  1-5. 
Webb,  J.  E.,  C.  C.  Brunson,  and  J.  D.  Yates. 

1972.  Effects  of  feeding  antioxidants  on  rancidity  develop- 
ment in  pre-cooked,  frozen  broiler  parts.  Poult.  Sci. 
51:1601-1605. 

Webb,  R.  W.,  W.  W.  Marion,  and  P.  L.  Hayse. 

1972.  Tocopherol  supplementation  and  lipid  stability  in  the 
turkey.  J.  Food  Sci.  37:496. 


1038 


ZOOGEOGRAPHY  OF  THE  GENUS  NEMATOSCELIS 
(CRUSTACEA,  EUPHAUSIACEA) 


K.  GiOPALAKRISHNAnI 


ABSTRACT 

The  International  Indian  Ocean  Expedition  provided  zooplankton  samples  to  study  the  distribution 
and  seasonal  changes  in  numerical  abundance  of  Nematoscelis  in  the  Indian  Ocean.  Distributional 
boundaries  of  species  of  this  genus  in  the  Atlantic  and  Pacific  oceans  were  determined  mainly  on  the 
basis  of  mid- water  trawls.  All  seven  species  of  this  genus  occur  in  the  Pacific,  whereas  only  five  species 
are  present  in  the  Indian  and  four  in  the  Atlantic.  Two  forms  ("old"  and  "new")  q{N.  gracilis ,  considered 
to  be  ecophenotyp)es,  but  distinguished  on  the  basis  of  morphological  differences  observed  in  the 
petasma,  occupy  the  tropical  Indo-Pacific  subregion.  The  "old  form"  is  most  abundant  in  the  oxygen- 
poor  waters  of  the  Arabian  Sea,  Bay  of  Bengal,  and  also  in  the  eastern  tropical  Pacific.  The  "new  form" 
is  mostly  confined  to  areas  of  the  South  Equatorial  Current.  The  present  study  indicates  that  N. 
gracilis  does  not  occupy  the  equatorial  zone  of  the  Atlantic  Ocean,  but  "new  forms"  are  transported 
from  the  Indian  Ocean  up  to  the  southern  tip  of  South  Africa.  Nematoscelis  atlantica  is  distributed  in 
the  central  water  masses  of  the  Pacific  and  Indian  oceans,  whereas  in  the  Atlantic  its  distribution 
extends  also  to  the  equatorial  zone.  Nematoscelis  microps  and  N.  tenalla  are  warmwater  species  and 
are  distributed  between  lat.  40°N  and  40°S,  although  lacking  in  most  areas  of  low  oxygen  water. 
Nematoscelis  lobata  has  restricted  distribution  in  the  region  of  the  Philippines.  Nematoscelis  megalops 
occupies  the  circumpolar  transitional  regions  of  the  Southern  Hemisphere  and  also  the  subarctic  and 
transition  subregions  of  the  North  Atlantic.  Nematoscelis  difficilis  is  endemic  to  the  North  Pacific 
transition  zone.  The  basins  of  Timor  and  Banda  Seas  and  their  associated  straits  in  the  Indo- Australian 
Archipelago  appear  to  allow  inter-ocean  gene  flow  among  populations  of  N .  gracilis  ,N .  Microps,  andN. 
tenella.  A  similar  communication  exists  between  Atlantic  and  Indian  Ocean  populations  of  these 
species  through  the  oceanic  waters  around  the  tip  of  South  Africa. 


Zoogeography  of  the  order  Euphausiacea  is 
reasonably  well  known  for  the  Pacific  Ocean 
(Brinton,  1962).  The  study  on  the  distribution  of 
euphausiids  in  the  Indian  Ocean  is  still  in  its  pre- 
liminary phase.  Available  data  from  this  ocean 
are  adequate  to  make  possible  estimates  of  species 
ranges  only.  The  role  of  the  biological  program 
during  the  International  Indian  Ocean  Expedition 
(IIOE)  (1960-65)  was  to  provide  materials  from 
wide  areas  of  the  ocean  to  facilitate  a  better  under- 
standing of  distributions  of  many  zooplankton 
taxa  in  the  Indian  Ocean.  Therefore,  in  the  pres- 
ent study  it  was  decided  to  put  more  effort  into 
understanding  the  geographical  distribution  and 
seasonal  abundance  of  Indian  Ocean  species  of 
Nematoscelis  than  those  from  the  Pacific  and  At- 
lantic oceans.  Preliminary  observations  on  the 
distribution  of  Euphausiacea  as  a  whole  were 
made  by  Gopalakrishnan  and  Brinton  (1969). 
Subsequently,  Brinton  and  Gopalakrishnan 
(1973)  brought  the  distributional  information  up 


'Scripps  Institution  of  Oceanography,  La  Jolla,  CA  92037; 
present  address:  The  Hawaii  Institute  of  Marine  Biology,  Uni- 
versity of  Hawaii,  P.O.  Box  1346,  Kaneohe,  HI  96744. 


Manuscript  accepted  February  1974. 
FISHERY  BULLETIN;  VOL.  72,  NO.  4,  1974. 


to  date  on  the  basis  of  IIOE  samples  studied  up  to 
that  time. 

Ocean-wide  records  of  species  of  euphausiids  in 
the  Indian  Ocean  come  from  three  major  expedi- 
tions: the  Percy  Sladen  Trust  Expedition  (Tatter- 
sall,  1912),  the  Deutsche  Tiefsee  Expedition  (Illig, 
1930),  and  the  John  Murray  Expedition  (Tatter- 
sall,  1939).  Studies  on  the  regional  fauna  are 
available  for  the  eastern  waters  of  South  Africa 
(Boden,  1951),  Red  Sea,  Arabian  Sea,  and  Bay  of 
Bengal  (Ponomareva,  1964,  1968).  Species  of 
Nematoscelis  of  the  southwest  coast  of  India  were 
provided  by  Sebastian  (1966).  Only  four  of  the 
seven  species  of  this  genus  have  been  reported 
from  the  Indian  Ocean:  A^.  gracilis,  N.  megalops, 
N.  microps,  and  A^.  tenella.  The  present  study 
confirms  the  presence  of  a  fifth  species,  A^.  atlan- 
tica, in  the  southern  Indian  Ocean.  Nematoscelis 
megalops  was  described  by  Boden  (1951)  from  the 
southern  African  waters.  Three  females  of  this 
species  were  reported  by  Illig  (1930)  from  south- 
west of  Ceylon  in  the  northern  Indian  Ocean.  The 
present  investigation  does  not  confirm  its  dis- 
tributional range  in  that  region. 

Nematoscelis  difficilis  is  an  endemic  species  of 

1039 


the  transition  zone  in  the  North  Pacific  and  is  not 
reported  from  anywhere  else.  Previous  studies  on 
the  distribution  of  all  seven  species  of 
Nematoscelis  in  the  Pacific  Ocean  are  sum- 
marized by  Brinton  (1962). 

Only  four  species  of  Nematoscelis  have  been 
reported  from  the  Atlantic  Ocean.  Moore  (1952) 
studied  ocean-wide  distributions  of  many 
euphausiids  in  the  North  Atlantic  Ocean,  includ- 
ing N.  microps  and  A^.  megalops.  Einarsson  (1945) 
also  reported  TV.  megalops  from  the  northeastern 
Atlantic.  From  the  Mediterranean  Sea  N. 
megalops,  N.  microps,  and  N.  atlantica  were  re- 
ported by  Ruud  (1936)  and  Casanova-Soulier 
(1968).  Incorporating  all  previous  records  Mauch- 
line  and  Fisher  ( 1969)  have  provided  a  generalized 
picture  of  the  distribution  of  Nematoscelis  in  the 
Atlantic  Ocean.  Gopalakrishnan  (1973)  examined 
the  pattern  of  vertical  distribution  of 
Nematoscelis  species  of  the  Pacific  Ocean. 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 

METHODS  AND  MATERIALS 

The  Indian  Ocean  portion  of  the  present  study  of 
Nematoscelis  is  based  on  samples  collected  during 
the  IIOE.  This  expedition  was  a  collaborative  ven- 
ture in  which  10  countries  participated  and  16 
vessels  collected  zooplankton  samples  as  part  of 
the  biological  program  during  1960-65.  The  com- 
posite pattern  of  stations  occupied  during  70 
cruises  provided  coverage  of  most  geographical 
provinces  of  the  Indian  Ocean  (Figure  la,  b).  A 
standard  procedure  was  followed  by  all  participat- 
ing vessels  for  collecting  zooplankton  samples. 
Accordingly,  each  sample  was  obtained  by  using 
the  Indian  Ocean  Standard  Net  (lOSN)  which  was 
specially  devised  for  the  IIOE  (Currie,  1963).  It  is  a 
ring  net  with  a  mouth  area  of  1  m^  and  a  length  of 
5  m.  The  straining  surface  is  nylon  gauze  of 
0.33-mm  mesh.  Hauls  were  as  nearly  vertical  as 
possible,  from  approximately  200-m  depth  to  the 


20»    io»    «•    w    w    70-    ac    so-    IOC    no-   i20*    ixr  i4o-  iso* 


Figure  1. — Plankton  samples  examined  for  Nematoscelis  of  the  Indian  Ocean;  a  -  SW  Monsoon  period. 


1040 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  NEMATOSCELIS 


surface.  Assuming  0°  wire  angle  the  net  would  be 
expected  to  filter  approximately  200  m^  of  water; 
but  0°  wire  angle  was  rarely  attained  at  sea. 
Moreover,  Tranter  and  Smith  ( 1968)  showed  that 
the  initial  filtering  efficiency  of  this  net  is  0.96; 
subsequent  clogging  does  not  reduce  the  filtering 
volume  significantly. 

Plankton  samples  collected  according  to  these 
procedures  are  classified  as  "standard."  In  waters 
over  the  continental  shelf  where  the  depth  was 
less  than  200  m,  the  net  was  usually  hauled  up 
from  within  a  few  meters  of  the  bottom;  such  col- 
lections were  also  treated  as  standard  since  the 
full  water  column  was  filtered.  Samples  collected 
from  less  than  approximately  200-m  depth  in  the 
open  ocean,  where  the  depth  was  far  greater  than 
200  m,  were  designated  as  "nonstandard." 

All  samples  were  processed  and  sorted  at  the 
Indian  Ocean  Biological  Centre  situated  in 
Cochin,  India.  The  list  of  plankton  samples  pro- 


cessed at  this  center  is  included  in  a  handbook  to 
the  international  collections  (Indian  Ocean 
Biological  Centre,  1969).  The  locality,  time,  and 
depth  of  haul  at  each  station  are  given  in  this  list, 
along  with  total  displacement  volume  of  the  sam- 
ple and  fraction  of  each  sample  that  was  sorted 
into  major  taxa.  At  the  sorting  center  a  3-  to  4-ml 
portion  of  each  sample  was  sorted  into  its  con- 
stituent major  taxa  after  removing  large  indi- 
viduals from  the  sample.  Individuals  in  each 
group  were  then  counted  to  give  an  estimate  of 
numbers  in  the  whole  sample.  The  sorted  fractions 
ranged  from  dVc  to  907f  of  the  whole  sample  on  the 
basis  of  the  initial  displacement  volume  of  the 
sample.  Further  details  of  the  sorting  procedure 
were  described  by  Hansen  (1966).  The  unsorted 
portion  (archive)  of  all  samples  were  deposited  at 
the  Indian  Ocean  Biological  Centre.  About  215  of 
them  were  examined  during  the  present  study  in 
order  to  check  whether  the  fractionating  proce- 


•^r  ■  'jt  -^■gT'"WiaF-»«^ 


"'      o 


o^ie 


^ 


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'-So 


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.  °    ^ 


••  oo  •„  o  tt 


}ioal.- 


*^°'.l 


°  o'o 


l'°  8 


ft. 


cf 

Ol 


•   o«    o 


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STATIONS    FROM    WHICH 
STANDARD   ZOOPLANKTON 

SAMPLES  WERE  TAKEN 
DURING  OCT  16  -APRIL  15 

0    DAY 

H    NIGHT 


.fJ-^ 


\        c 


I       ■       •       I       <l— J_— ^ 

2(r     50*      40*     W     60*     70*      80*     W     ItXT     110*    120*     130*    140*    IW 


Figure  1. — Plankton  samples  examined  for  Nematoscelis  of  the  Indian  Ocean:  b  -  NE  Monsoon  period. 


1041 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


dure  was  efficient  enough  to  retain  all  species  of 
Nematoscelis  present  in  the  whole  sample.  Only 
26  archives  were  found  to  have  contained  one  or 
more  species  not  present  in  their  subsamples. 
Therefore  it  is  assumed  that  the  subsampling  pro- 
cedure was  usually  adequate. 

The  wind  system  over  the  Indian  Ocean  is  mon- 
soonal.  The  two  monsoon  phases  are  designated  as 
the  Southwest  (SW)  and  Northeast  (NE)  mon- 
soons, indicating  the  predominant  wind  directions 
in  the  northern  Indian  Ocean  during  each  phase. 
The  bulk  of  the  samples  were  grouped  into  two 
categories:  those  collected  during  16  April  to  15 
October  falling  in  the  SW  monsoon  and  those  col- 
lected during  16  October  to  15  April  falling  in  the 
NE  monsoon.  The  period  16  April  to  15  October 
generally  agrees  with  that  of  the  wind  regime  of 
the  SW  monsoon  (Wooster,  Schaefer,  and  Robin- 
son, 1967). 

Of  the  1,927  samples  processed  at  the  Indian 
Ocean  Biological  Centre,  1,732  samples  were  ex- 
amined for  the  study  of  Nematoscelis.  Of  these, 
879  samples  were  taken  during  the  SW  monsoon 
and  853  during  the  NE  monsoon.  Since  a  compari- 
son of  day  and  night  catches  of  total  euphausiids 
showed  differences  in  day  and  night  estimates 
(Gopalakrishnan  and  Brinton,  1969),  it  was  de- 
cided to  group  day  and  night  counts  separately  for 
each  season.  There  were  401  night  and  478  day 
samples  for  the  SW  monsoon  period  and  413  night 
and  440  day  samples  for  the  NE  monsoon. 

In  order  to  fill  gaps  in  certain  geographical 
areas,  some  samples  collected  by  using  gear  other 
than  the  lOSN  have  also  been  used  in  the  prepara- 
tion of  charts.  Kistna  cruises  2  to  6  used  an  or- 
gandy net  with  50-cm  mouth  diameter.  Natal 
cruises  1  and  4  used  the  N-70  net  with  70-cm 
mouth  diameter.  These  samples  were  standard- 
ized for  comparing  with  lOSN  samples:  the  or- 
gandy net  samples  were  multiplied  by  a  factor  of 
5.1  and  N-70  net  samples  by  a  factor  of  2.6.  In 
addition  to  these  samples,  26  nonstandard  surface 
samples  taken  during  the  Patanela  cruise  were 
also  examined  for  qualitative  information.  Argo 
Monsoon  Expedition  stations  9-27  (ref  Snyder 
and  Fleminger,  1972)  have  also  been  used  in  the 
preparation  of  present  charts.  These  samples  were 
collected  using  1-m  nets. 

The  observed  differences  between  day  and  night 
catches  of  adult  euphausiids  are  due  to  the  fact 
that  during  day  time  many  species  either  migrate 
to  deeper  layers  or  are  able  to  dodge  the  net.  Total 
euphausiids  were  1.5-2.0  times  more  abundant  in 


night  samples  than  in  day  samples  (Gopalakrish- 
nan and  Brinton,  1969).  The  mouth  area  of  the 
lOSN  is  only  1  m^  and  it  is  probable  that  many 
large  zooplankters  can  avoid  the  net.  However, 
most  samples  taken  at  night  contained  many 
adult  euphausiids,  including  some  of  the  large 
thysanopods  that  migrated  into  the  upper  layer. 
All  species  of  Nematoscelis  are  smaller  than  most 
Thysanopoda  species.  It  is  reasonable  to  believe 
that  the  lOSN  tows  taken  at  night  would  have 
been  adequate  to  representatively  sample  adult 
species  of  Nematoscelis. 

The  present  distributional  study  of 
Nematoscelis  in  the  Indian  Ocean  is  limited  to  the 
upper  200  m  only.  The  geographical  distribution 
of  each  species  of  this  genus  is  compared  with  the 
pattern  of  water  circulation  in  the  upper  layer. 
Larvae  and  juveniles  of  all  Nematoscelis  species 
are  confined  to  the  upper  200-m  layer  during  both 
day  and  night,  whereas  adults  undertake  diurnal 
vertical  migration  (Gopalakrishnan,  1973).  Dur- 
ing daytime  the  distribution  of  adults  extends 
from  the  upper  200-m  layer  to  about  600-800  m; 
but  at  night,  because  of  their  upward  migration, 
the  range  extends  from  the  surface  to  about 
400-600  m  only,  with  the  maximum  above  200  m 
in  most  geographical  regions.  It  is  therefore  prob- 
able that  the  lOSN  would  have  caught  adults  bet- 
ter at  night  than  during  the  day.  For  this  reason 
only  night  samples  were  considered  in  charting 
the  distribution  of  adults.  However,  a  few  trawls 
(Isaacs-Kidd  Mid-water  trawl)  fished  from  depths 
greater  than  200  m,  were  also  used  for  examining 
overall  geographical  range.  Station  positions  of 
these  are  included  in  Figures  7, 11,  and  18.  Most  of 
these  reached  as  deep  as  ca.  900-1,000  m,  some- 
what deeper  than  the  lower  limit  of  the  vertical 
range  of  Nematoscelis.  The  geographical  coverage 
of  these  trawls  was  not  sufficient  to  examine  the 
influence  of  deep  circulation  on  the  distribution  of 
species.  A  total  of  286  mid-water  trawl  samples 
were  examined  from  the  Pacific,  Atlantic,  and  In- 
dian oceans.  [Collections  from  the  Pacific  and  In- 
dian oceans  are  located  at  the  Scripps  Institution 
of  Oceanography.  Collecting  data  regarding  many 
of  these  appear  in  Clarke  (1963).]  The  approxi- 
mate boundaries  of  distribution  of  each  species  are 
shown  on  the  basis  of  present  evidence,  including 
literature  records. 

The  distributional  ranges  of  species  of 
Nematoscelis  in  the  Atlantic  Ocean  were  based  on 
specimens  sorted  from  fractions  of  plankton  sam- 
ples obtained  by  the  Woods  Hole  Oceanographic 


1042 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  NEMATOSCELIS 


Institution.  Most  of  the  samples  were  from  the 
North  Atlantic.  Charts  were  prepared  for  each 
species  of  Nematoscelis;  but  the  abundance  is  ex- 
pressed only  as  the  percentage  of  the  total 
Nematoscelis  present  in  the  aliquot,  because  the 
aliquot  itself  was  an  unknown  quantitative  frac- 
tion of  the  whole  sample.  Atlantis  II  and  Chain 
cruises  took  samples  using  a  75-cm  net  from  above 
100  m;  Delaware  samples  were  also  taken  from 
similar  depths,  but  by  using  1-m  nets.  Lusiad  VII 
cruise  in  the  South  Atlantic  collected  samples 
from  200  m  to  surface.  In  all,  217  plankton  sam- 
ples were  examined  from  the  Atlantic  Ocean. 

HYDROGRAPHY  OF  THE  INDIAN 
OCEAN 

In  the  upper  strata  of  the  sea,  the  general  circu- 
lation may  be  related  to  the  prevailing  wind  sys- 
tem. This  wind-driven  oceanic  circulation  affects 
and  modifies  the  distribution  of  water  masses  in 
the  upper  strata;  the  wind-driven  circulation 
penetrates  into  deeper  layers  and  can  be  recog- 
nized at  intermediate  depths  (Reid,  1965).  The 
thermohaline  circulation,  caused  by  density  dif- 
ferences in  the  ocean  due  to  heat  and  water  ex- 
changes with  the  atmosphere,  is  thought  to  be 
responsible  for  formations  of  deepwater  masses 
and  the  deep  circulation  (Neumann  and  Pierson, 
1966).  As  a  result  of  these  types  of  circulations, 
properties  such  as  temperature,  salinity,  oxygen, 
and  nutrients  show  distinct  features  in  their  dis- 
tributions in  different  oceanic  areas,  providing 
different  characteristic  habitat  conditions  for  in- 
dividual species  or  communities  of  organisms. 

Since  a  major  part  of  the  present  study  deals 
with  the  seasonal  distributions  of  Indian  Ocean 
species  of  Nematoscelis,  it  is  pertinent  to  provide  a 
general  background  of  the  available  information 
on  the  monsoonal  seasons  prevailing  over  the  In- 
dian Ocean.  The  surface  currents  of  the  Indian 
Ocean  during  the  monsoon  periods  are  described 
by  Taft  (1971)  and  for  the  present  study  I  will 
follow  his  discussion  of  the  wind  and  current  pat- 
terns (see  Neumann  and  Pierson,  1966,  and  Taft, 
1971,  for  illustrations  of  surface  currents  of  the 
Indian  Ocean).  Hydrographical  changes  as- 
sociated with  the  monsoon  are  well  documented 
for  the  Arabian  Sea  (Wooster  et  al.,  1967 ).  During 
the  NE  monsoon  the  northeast  winds  of  the 
Northern  Hemisphere  cross  the  Equator  into  the 
Southern  Hemisphere,  there  becoming  north- 
westerly. This  monsoon  phase  is  established  in 


November  and  persists  through  March;  its  max- 
imum intensity  is  in  January.  During  this  phase  a 
broad  doldrum  belt  develops  at  about  lat.  5°S  to 
lat.  10°S  between  weak  northerly  winds  and  the 
southeast  trade  winds.  In  the  SW  monsoon,  south- 
east trades  from  the  Southern  Hemisphere  cross 
the  Equator  and  gradually  turn  into  southerly  and 
southwesterly  directions  in  the  Northern  Hemi- 
sphere. Winds  are  especially  intense  during  this 
period  near  the  African,  Somali,  and  Arabian 
coasts.  The  SW  monsoon  is  well  established  in 
May  and  persists  through  September.  It  is  most 
intense  in  July. 

The  onset  of  monsoon  periods  in  the  Indian 
Ocean  is  found  to  be  symmetrical  in  time  (Wooster 
et  al.,  1967;  Taft,  1971).  Each  period  lasts  for  5  mo; 
April  and  October  are  transition  periods.  Because 
of  these  short  periods  of  transition  in  the  monsoon 
system,  it  was  decided  to  divide  each  April  and 
October  period  into  two  halves  and  add  the  first 
half  of  April  and  the  latter  half  of  October  to  NE 
monsoon.  The  latter  half  of  April  and  the  first  half 
of  October  were  similarly  added  to  the  SW  mon- 
soon period.  The  overall  winds  and  surface  cur- 
rents are  far  stronger  in  the  SW  monsoon  than  in 
the  NE  monsoon. 

The  surface  circulation  plays  an  important  role 
in  the  distribution  of  planktonic  animals  in  the 
ocean.  In  the  Indian  Ocean  the  surface  circulation 
is  subjected  to  a  longer  seasonal  change  than  in 
other  oceans.  The  outstanding  features  of  the  sur- 
face circulation  are:  1)  currents  that  follow  in  a 
more  or  less  zonal  direction  far  from  the  conti- 
nents, and  2)  currents  near  continental  coasts. 
During  the  NE  monsoon  the  North  Equatorial  and 
the  South  Equatorial  currents  flow  westward  and 
the  Equatorial  Countercurrent  flows  eastward  be- 
tween these  two  currents.  Unlike  those  in  the 
Pacific  and  Atlantic,  the  countercurrent  in  the 
Indian  Ocean  is  situated  in  the  Southern  Hemi- 
sphere. This  is  related  to  the  position  of  the  dol- 
drums south  of  the  Equator.  The  South  Equatorial 
Current,  after  reaching  the  African  coast,  con- 
tributes water  to  the  Agulhas  Current  flowing 
southwest  and  also  to  the  eastward  flowing  Coun- 
tercurrent. During  the  NE  monsoon  the  Somali 
Current,  flowing  southwest  with  a  speed  of  about 
100  cm/s,  merges  into  the  Mozambique  Current 
(Neumann  and  Pierson,  1966),  thereby  bringing 
many  tropical  species  as  far  south  as  lat.  35°-40°S 
along  the  coast  of  Africa.  At  this  time  the  surface 
current  off  the  southwest  coast  of  India  is  also 
weak  and  flows  in  a  southeast  direction.  In  the  Bay 


1043 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


of  Bengal  the  general  circulation  is  counter- 
clockwise. Unlike  in  the  Pacific  and  Atlantic 
oceans,  there  is  little  evidence  of  an  eastern 
boundary  current  in  the  Indian  Ocean  along  the 
west  coast  of  Australia.  According  to  Wyrtki 
(1973),  water  movements  in  this  region  are  weak 
and  variable  and  most  of  the  northward  flow  is 
situated  farther  offshore  between  long.  95°E  and 
105°E.  In  the  Indian  Ocean  the  Equatorial  Under- 
current is  also  seasonal,  being  more  pronounced 
during  the  NE  monsoon  than  in  the  opposite  sea- 
son (Taft  and  Knauss,  1967;  Taft,  1971). 

At  the  onset  of  the  SW  monsoon  the  surface 
currents  in  the  Indian  Ocean  change  dramati- 
cally. The  westward  flowing  North  Equatorial 
Current  is  replaced  by  an  eastward  flowing 
Southwest  Monsoon  Current,  thereby  reversing 
the  surface  circulation  in  that  region.  Together 
with  the  Somali  Current  it  is  the  outstanding  cur- 
rent in  these  latitudes.  The  surface  current  north 
of  lat.  5°S  is  then  directed  eastward  and  the 
Equatorial  Countercurrent  is  not  distinguishable 
as  a  separate  flow.  This  is  contrary  to  the  condi- 
tions prevailing  in  other  oceans  where  the  inten- 
sity of  the  Countercurrent  reaches  a  maximum 
during  this  period.  The  Somali  Current,  now 
flowing  northeast  as  an  intense  western  boundary 
current,  extends  to  about  lat.  8°N.  The  current 
transports  southern  forms  into  the  Arabian  Sea 
thereby  serving  to  increase  the  faunal  complexity 
of  the  region.  In  addition,  enrichment  of  surface 
water  north  of  the  current  produces  zooplankton 
blooms.  North  of  lat.  8°N  the  data  suggest  that  this 
current  leaves  the  coast  and  turns  eastward  (Taft, 
1971).  The  South  Equatorial  Current  becomes 
intensified  in  the  western  Indian  Ocean;  near  the 
African  coast  it  contributes  to  part  of  the  northern 
flow.  This  brings  species  of  the  southern  latitudes 
close  to  the  Equator  in  the  western  Indian  Ocean 
and  even  occasionally  farther  north  to  about  lat. 
10°N  along  the  western  boundary.  During  the  SW 
monsoon  the  flow  off  the  Arabian  coast  is  toward 


the  east  and  northeast  but  is  much  less  intense 
than  the  Somali  Current.  This  flow  starts  in  April 
and  is  reported  to  persist  until  August.  The  south- 
eastward flow  off  the  southwest  coast  of  India  re- 
mains the  same  as  in  the  NE  monsoon.  In  this 
region  the  current  flows  northward  only  for  2  mo 
and  it  is  essentially  opposite  to  the  prevailing 
wind  stress.  Taft  ( 1971 )  pointed  out  that  the  circu- 
lation in  the  eastern  Arabian  Sea  is  therefore 
influenced  by  thermohaline  processes. 

During  the  SW  monsoon  three  areas  are  promi- 
nent in  the  Arabian  Sea  for  upwelling:  off  the 
Somali,  Arabian,  and  southwest  Indian  coasts. 
There  is  evidence  that  the  upwelling  off"  the  Ara- 
bian coast  is  wind  driven;  that  off" the  Somali  coast 
is  partly  wind  driven  and  partly  due  to  dynamic 
constraint  on  the  current  (Taft,  1971 );  and  that  off 
the  coast  of  southwest  India  is  due  to  the  dynamic 
response  which  involves  tilting  of  the  thermocline 
up  toward  the  coast  (Darbyshire,  1967;  Banse, 
1968).  The  cool  surface  waters  off  the  coasts  of 
Arabia  and  Somalia  during  the  SW  monsoon  are 
clear  indication  of  intense  upwelling  (See  Wyrtki, 
1971:45).  Along  the  western  Indian  Ocean  Diiing 
(1971)  commented  on  the  presence  of  many 
offshore  anticyclonic  and  cyclonic  vortices  which 
are  indicated  by  alternating  highs  and  lows  of 
dynamic  height  persisting  through  both  monsoon 
phases.  Taft  (1971)  singled  out  the  importance  of 
these  vortices  in  the  mixing  processes  of  the  near- 
surface  waters  which  would  increase  the  rate  of 
nutrient  enrichment  of  the  surface  layer.  In  the 
western  Arabian  Sea  such  enrichments  are  max- 
imum during  the  June-August  period  (Table  1). 
High  values  of  NO3-N  and  SiOa-Si  persist  for  a 
longer  period  along  the  coast  of  Somalia  than  off 
the  Arabian  coast.  The  plankton  atlas  of  the  IIOE 
(Indian  Ocean  Biological  Centre,  1968)  shows  that 
the  maximum  abundance  of  zooplankton  is  also 
associated  with  these  upwelling  areas. 

The  distribution  of  surface  temperature  during 
the  NE  monsoon  indicates  no  cool  surface  water  in 


Table  1. — Surface  nutrients  at  four  coastal  regions  of  the  Arabian  Sea.  A  =  off  the  coast  of  Arabia,  lat.  20°N;  B  =  off  the  coast  of  India, 
lat.  20°N;  C  =  off  the  coast  of  Somalia,  lat.  10°N;  D  =  off  the  coast  of  southwest  India,  lat.  10°N.  All  values  are  in  fjg-at/\.  (Data  from 
Wooster  et  al.,  1967.) 


Dec. -Feb. 

Mar. -May 

June 

-A 

ug 

Sept. 

-Nov. 

Nutrients 

A 

B             C 

D 

A 

B             C 

D 

A 

B 

C 

D 

A 

B 

C 

D 

POj-P 

0.75 

0.25        0,25 

050 

>0.25 

0.25        025 

0.25 

>2.0 

0.50 

1.0 

-0.25 

-1.0 

■0.25 

1.0 

0.25 

NO3-N 

all  values  '2.5 

all  values  <  2.5 

>25.0 

2.50 

■15.0 

<.2.5 

■::;2.5 

.2.5 

15.0 

2.5 

SIO:)-SI 

all  values  5.0 

all  values  •  5.0 

■20.0 

<5.0 

-20.0 

■5.0 

10.0 

■  5.0 

15.0 

-  5.0 

1044 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  NEMATOSCELIS 


the  Arabian  Sea  (see  Wyrtki,  1971:38).  Isotherms 
slope  southwestward  toward  the  African  coast. 
During  this  period  no  upwelHng  is  observed  off  the 
southwest  coast  of  India,  although  the  Ekman 
theory  would  predict  upwelling  in  this  area  since 
the  surface  winds  blow  equatorward  and  parallel 
the  coast.  Taft  (1971)  suggested  that  this  may  be 
due  to  the  low  speed  of  the  northeasterly  wind. 

In  the  Bay  of  Bengal  upwelling  has  been  re- 
ported to  occur  seasonally  along  the  east  coast  of 
India  and  west  coast  of  Burma  (La  Fond,  1954, 
1957;  Banse,  1960;  La  Fond  and  La  Fond,  1968). 
During  the  early  part  of  the  NE  monsoon,  the 
northeasterly  winds  displace  subsurface  water 
offshore  along  the  Burmese  coast.  Wyrtki  (1961) 
also  reported  upwelling  along  the  coast  of  Burma 
and  Thailand  during  the  December-February 
period.  The  general  surface  circulation  of  the  Bay 
of  Bengal  is  clockwise  during  January  through 
July  and  it  becomes  counterclockwise  from  Au- 
gust to  December  (La  Fond  and  La  Fond,  1968). 
The  southwesterly  winds  prevail  over  the  north- 
ern Bay  of  Bengal  in  March  and  over  the  entire 
region  in  April.  During  these  months  an  intense 
upwelling  is  noticed  along  the  east  coast  of  India 
(La  Fond  and  La  Fond,  1968).  In  this  region,  along 
with  the  nearshore  occurrence  of  dense  water,  the 


average  sea  level  also  reaches  a  minimum  height 
during  this  period  (La  Fond,  1954). 

A  remarkable  feature  of  the  Indian  Ocean  is  the 
rapid  attenuation  of  dissolved  oxygen  with  depth; 
at  200  m  values  become  0.2  ml/1  or  less  in  the 
Arabian  Sea  and  Bay  of  Bengal  (Wyrtki,  1971). 
Vinogradov  and  Voronina  (1961)  and  Vinogradov 
(1968)  have  discussed  the  association  of  low  zoo- 
plankton  biomass  within  the  oxygen  minimum 
layer  in  the  Arabian  Sea.  North-south  and  east- 
west  transects  in  the  Arabian  Sea  indicate  that 
oxygen  values  as  low  as  0. 1  ml/1  occur  below  200  m 
during  both  seasons  (Figure  2A,  B).  According  to 
Wyrtki  ( 1971)  the  concentrations  of  oxygen  in  the 
minumum  layer  do  not  vary  seasonally,  although 
the  depth  of  this  layer  changes.  The  vertical 
profile  at  four  north-south  transects  across  the 
equatorial  Indian  Ocean  show  the  occurrence  of 
very  low  oxygen  concentrations  below  100  m  (Fig- 
ure 3).  Since  these  profiles  were  taken  during  dif- 
ferent months,  it  appears  that  this  feature  persists 
throughout  the  year. 

The  vertical  distribution  of  temperature  along 
four  north-south  transects  (same  transects  as 
shown  in  Figure  3)  indicates  that  the  thermocline 
is  situated  between  75  and  100  m  in  the  regions 
north  of  lat.  10°S.  The  South  Equatorial  Current 


4000 


Figure  2. — Vertical  distribution  of  oxygen  in  the 
Arabian  Sea:  A.  East-west  transect  along  lat. 
11°N,  long.  45°E  to  lat.  16°S,  long.  72°E  (July- 
August);  B.  North-south  transect  along  lat.  24°N, 
long.  60°E  to  lat.  20°S,  long.  67°E  (November- 
May).  (Charts  reproduced  from  Wyrtki,  1971.) 


24N     20° 

15° 

10° 

O 

5 

O 

0 

O 

5 

10° 

15 

20S 

60E    65° 

70° 

68° 

68° 

68° 

68° 

6/ 

67 

67E 

1045 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


30  60  100  140 


40S 


400 


Figure  3. — Vertical  distribution  of  oxygen  along  four  north-south  transects  in  the  Indian  Ocean:  A  -  lat.  14°N  to  36°S  at  long.  55°E 
(February-March);  B  -  lat.  24°N  to  4rS  at  long.  60°E  (August-November);  C  -  lat.  18°N  to  37°S  at  long.  70°E  (May-July);  D  -  lat.  13°N  to 
30°S  at  long.  92°E  (August-September).  (Charts  reproduced  from  Wyrtki,  1971.) 


flows  along  the  zone  where  the  thermochne  slopes 
upward  toward  the  Equator  between  lat.  10°S  and 
20°S.  The  general  distribution  of  subsurface 
isotherms  is  more  or  less  similar  across  the  full 
breadth  of  the  equatorial  region. 

Wyrtki's  figure  { 1971:38)  indicates  the  presence 
of  cold  surface  water  in  the  northern  part  of  the 
Bay  of  Bengal  during  the  NE  monsoon.  Banse 
(1960)  pointed  out  that  the  cold  surface  water  in 
this  region  may  not  be  attributed  to  upwelling,  but 
to  a  high  rate  of  evaporation  caused  by  the  dry  air 
from  the  continent.  The  coasts  of  northwest  Aus- 
tralia and  Java  are  other  regions  reported  to  have 
seasonal  upwelling.  Wyrtki  (1961)  pointed  out 
that  there  was  intense  upwelling  in  these  two 
areas  during  the  SW  monsoon. 

It  is  postulated  that  in  the  Indian  Ocean  wind- 
driven  equatorial  upwelling  is  less  intense  than  in 
the  Atlantic  and  Pacific  oceans  and  may  be  totally 
absent  (Taft,  1971).  The  absence  of  substantial 
peaks  in  the  zooplankton  biomass  along  the 
equatorial  regions  of  the  Indian  Ocean  is  consis- 
tent with  the  idea  of  there  being  little  equatorial 
upwelling,  compared  at  least  with  the  Pacific 
(King  and  Demond,  1953;  Reid,  1962;  Heinrich, 
1968)  and  the  Atlantic  (Hentschel,  1933). 


In  the  Indian  Ocean  seasonal  changes  in  surface 
salinity  are  more  pronounced  in  the  Arabian  Sea 
and  the  Bay  of  Bengal  than  in  any  other  region 
(see  Wyrtki,  1971).  Throughout  the  year  the  sur- 
face salinity  was  greater  in  the  Arabian  Sea  than 
in  the  Bay  of  Bengal.  During  the  NE  monsoon 
surface  salinity  becomes  very  low  (30-33%o  in  the 
Bay  of  Bengal;  advection  of  low-salinity  water  oc- 
curs from  the  Bay  of  Bengal  toward  the  western 
Indian  Ocean.  As  the  Monsoon  Current  develops 
during  the  SW  monsoon,  a  tongue  of  high-salinity 
water  flows  eastward. 

RESULTS 

Geographical  Distribution  of 

Neniatoscelis  gracilis 

Indian  Ocean 

Two  forms  considered  to  be  ecophenotypes  of  A^. 
gracilis  are  recognized  to  occur  in  the  Indian 
Ocean:  an  "old  form"  which  is  identical  in  mor- 
phological character  to  the  typical  form  described 
by  Hansen  (1910)  from  waters  of  the  Indo- 
Australian  Archipelago,  and  a  "new  form"  which 


1046 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCEUS 


is  distinguished  from  the  typical  form  on  the  basis 
of  the  difference  in  dimension  of  the  proximal  pro- 
cess of  the  petasma.  In  the  old  form  the  proximal 
process  does  not  reach  the  distal  end  of  the  median 
lobe,  whereas  in  the  new  form  it  is  extremely  long, 
reaching  far  beyond  the  distal  end  of  the  median 
lobe.  The  proximal  process  of  the  old  form  is  ser- 
rated at  the  distal  end  and  that  of  the  new  form  is 
without  any  serration.  There  is  also  an  apparent 
size  difference  between  the  two  forms;  the  body 
length  of  the  old  form  is  found  to  be  significantly 
larger  than  that  of  the  new  form.  Moreover,  the 
upper  lobe  of  the  eye  of  the  new  form  is  narrower 
than  that  of  the  old  form.  Along  the  equatorial 
zone,  where  the  distributions  of  the  two  forms 
overlap,  another  form,  which  is  recognized  to  be 
"intermediate"  of  the  old  and  new  forms  with  re- 
gard to  the  length  of  the  proximal  process,  is  also 
encountered.  All  three  forms  are  distinguishable 
only  in  mature  adults:  males  on  the  basis  of  struc- 
tural differences  of  the  petasma  and  females  on 
the  basis  of  differences  in  the  body  lengths  and  eye 
shape.  Further  discussion  of  them  will  appear  in  a 
forthcoming  taxonomic  paper  (manuscript). 

Nematoscelis  gracilis  is  by  far  the  most  abun- 
dant species  of  Nematoscelis  in  the  tropical  re- 
gions of  the  Indian  Ocean,  including  the  Arabian 
Sea  and  the  Bay  of  Bengal  ( Figures  4,  5).  Along  the 
full  extent  of  the  ocean  at  the  Equator  this  species 
was  found  to  be  distributed  between  lat.  20°N  and 
20°S.  The  southern  limit  extended  farther  south 
along  the  regions  of  the  western  and  eastern 
boundary  currents,  the  Mozambique  Current,  and 
the  West  Australian  Current,  respectively.  Lar- 
vae and  juveniles  were  caught  year-round  from  all 
geographical  areas  within  the  distributional 
range  of  the  species.  Therefore,  spawning  appar- 
ently occurred  everywhere  within  that  range. 
Larvae  consisted  of  metanauplii,  calyptopes,  and 
furcilias;  metanauplii  were  undoubtedly  under- 
estimated since  they  (body  length  <  1  mm)  could 
have  been  washed  away  through  mesh  apertures 
of  the  net. 

During  the  NE  monsoon  maximum  numbers  of 
larvae  and  juveniles  per  sample  were  caught  off 
the  coast  of  southeast  India  (Figure  4a).  For  ex- 
ample, during  Kistna  cruise  26,  840  individuals 
were  caught  at  station  704  (lat.  13°N,  long.  81°E); 
and  764  individuals  from  station  705.  Four  sta- 
tions had  numbers  exceeding  300  per  sample  from 
the  same  area.  However,  during  the  SW  monsoon 
maximum  abundance  was  in  the  western  Indian 
Ocean  north  of  the  Equator  (Figure  4b).  Both  lar- 


vae and  juveniles  were  absent  from  the  northern 
and  northeastern  Arabian  Sea.  There  the  oxygen 
concentration  in  the  subsurface  waters  is  as  low  as 
0.1  ml/1  (see  Figure  2B).  They  were  also  absent  to 
the  north  of  lat.  10°N  along  the  west  coast  of  India; 
but  during  the  NE  monsoon  they  were  caught  as 
far  north  as  lat.  15°N  in  the  coastal  waters  of 
southwest  India.  The  North  Equatorial  Current, 
flowing  westward,  has  a  northwestward  compo- 
nent after  passing  the  southern  tip  of  India  during 
the  early  part  of  the  NE  monsoon,  bringing  a 
spawning  population  of  this  species  as  far  north  as 
lat.  15°N.  In  the  area  of  the  Mozambique  Current, 
larvae  and  juveniles  were  caught  only  as  far  south 
as  lat.  30°S. 

Adults  of  the  old  form  are  confined  mostly  to  the 
Arabian  Sea  and  the  Bay  of  Bengal  and  the  new 
form  to  areas  of  the  Southwest  Monsoon  Current 
and  the  South  Equatorial  Current  which  is 
situated  south  of  the  Equator.  During  the  NE 
monsoon  old  forms  are  frequently  caught  in  the 
areas  of  the  North  Equatorial  Current,  whereas 
new  forms  occur  only  in  the  Equatorial  Counter- 
current  and  south  of  it.  The  two  forms  overlap  in 
distribution  along  the  northern  boundary  of  the 
Countercurrent  from  east  of  long.  75°E.  In  the 
eastern  Indian  Ocean  the  distribution  of  old  forms 
extends  farther  south  (as  far  as  lat.  14°S)  (Figure 
5a).  "Intermediate  forms"  were  encountered  all 
along  the  overlapping  zone.  They  were  present 
along  the  western  and  eastern  boundaries  of  the 
ocean.  Most  transport  of  the  intermediate  forms  to 
the  west  is  through  the  North  Equatorial  Current. 
In  the  South  Equatorial  Current  it  was  found  only 
at  one  station  (Koyo  Maru  cruise  14,  station  19: 
lat.  13°49'S,  long.  94°16'E).  In  the  western  Indian 
Ocean  there  was  no  overlap  in  distribution  of  the 
forms,  and  the  new  forms  did  not  occur  north  of  the 
Equator.  Moreover,  during  this  period  the  Somali 
Current  flows  southwestward  so  that  it  brings  the 
old  form  as  far  south  as  lat.  3°S.  Therefore,  the 
pattern  of  distribution  of  the  two  forms  in  the 
upper  layer  may  be  influenced  by  the  direction  of 
water  flow  in  the  equatorial  current  system  which 
is  subject  to  seasonal  changes.  During  the  NE 
monsoon  no  samples  were  taken  from  the  Mozam- 
bique Current  area  north  of  lat.  30°S.  However, 
mature  adults  of  the  new  form  were  caught  in  one 
sample  taken  from  the  southeast  coast  of  Africa 
(Natal  cruise  6,  day  station  161:  lat.  34°21  'S,  long. 
26°21'E).  Thus  it  appears  likely  that  the  Mozam- 
bique Current,  which  is  stronger  during  the  NE 
monsoon  than  in  the  opposite  season  (as  judged 


1047 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


wo-  ISO- 


20*      30-      40*      50* 


30*    IW*     IW 


Figure  4. — Locality  records  and  daytime  abundance  of  larvae  and  juveniles  of  Nematoscelis  gracilis  and  N.  megalops  in  the  Indian 
Ocean:  a  -  NE  Monsoon  period.  (Solid  lines  represent  approximate  distribution  boundaries  of  N.  gracilis  and  wavy  lines  represent  those 
of  AT.  megalops. ) 


from  Figures  14.1  and  14.2  of  Neumann  and  Pier- 
son,  1966)  and  to  which  the  South  Equatorial  Cur- 
rent contributes,  transports  some  of  the  new  forms 
to  the  south  and  the  Agulhas  Current  transports 
them  to  the  tip  of  South  Africa. 

During  the  SW  monsoon  the  distribution  of  the 
new  form  is  much  broader  in  the  west  than  in  the 
east  (Figure  5b).  As  the  strong  Somali  Current 
begins  to  flow  northeastward,  a  great  deal  of 
Southern  Hemisphere  water  is  brought  to  the 
north  along  the  African  coast.  Thus  the  population 
of  the  new  form  is  brought  north  of  the  Equator.  It 
was  caught  as  far  north  as  lat.  8°N  along  the  coast 
of  Somalia;  but  it  did  not  reach  the  upwelling 
areas  of  the  Arabian  coast.  It  has  been  suggested 
that  the  Somali  Current  turns  eastward  after 
reaching  lat.  8°N  and  joins  the  Southwest  Mon- 


soon Current  flowing  east  (Taft,  1971);  the  dis- 
tribution of  the  new  form  in  the  upper  layer  fol- 
lows the  same  pattern  (Figure  5b).  Except  in  the 
area  of  the  Somali  Current,  the  overlapping  zone 
was  conflned  to  the  eastern  ocean.  The  inter- 
mediate forms  were  distributed  across  the 
equatorial  ocean.  In  the  region  of  the  Mozambique 
Current  new  forms  were  found  as  far  south  as  lat. 
30°S. 

Populations  of  the  old  form  in  the  Bay  of  Bengal 
and  the  Arabian  Sea  show  seasonal  changes  in  the 
abundance  of  larvae  and  juveniles  (Figure  6).  All 
the  available  IIOE  plankton  samples  from  these 
two  areas  were  used  to  prepare  these  monthly 
frequency  distributions.  In  the  Bay  of  Bengal  the 
highest  frequency  of  calyptopis  larvae  was  ob- 
served in  February,  whereas  in  the  Arabian  Sea  it 


1048 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


^ 


20"     so-      W     SO"     so-     TO*      W     90*     IOC      no-    120"     130*    ►40'    too- 


Figure  4. — Locality  records  and  daytime  abundance  of  larvae  and  juveniles  of  Nematoscelis  gracilis  and  A^.  megalops  in  the  Indian 
Ocean:  b  -  SW  Monsoon  {jeriod.  (Solid  lines  represent  approximate  distribution  boundaries  of  N.  gracilis  and  wavy  lines  represent  those 
of  N.  megalops . ) 


was  during  August  and  December.  (In  both  areas 
metanauplii  were  clearly  underestimated.)  A 
Student's  t  -test  carried  out  on  means  of  develop- 
mental stages  during  February,  August,  and  De- 
cember indicated  that  the  frequencies  of  larvae  in 
the  Bay  of  Bengal  were  significantly  different 
(P<0.01)  from  those  in  the  Arabian  Sea  during 
the  same  months.  Frequencies  during  other 
months  were  not  significantly  different  between 
the  two  populations.  Since  most  of  the  develop- 
mental stages  were  caught  each  month,  it  appears 
that  spawning  is  continuous;  only  the  rate  of  pro- 
duction is  subjected  to  seasonal  changes. 

The  distributional  patterns  of  the  two  forms  of 
A^.  gracilis  so  far  discussed  are  based  on  adults 
caught  from  the  upper  200-m  layer.  As  pointed  out 
before,  the  vertical  distribution  of  this  species  ex- 


tends much  greater  than  this  depth.  Figure  7a 
shows  the  distributions  of  new  and  old  forms  based 
on  deeper  samples.  Evidently  these  are  similar  to 
those  based  only  on  the  upper  layer  samples  (cf. 
Figures  5,  7a).  Both  forms  were  caught  from  the 
same  station  only  near  the  Equator,  and  inter- 
mediate forms  were  found  only  at  the  areas  of 
overlap  near  the  Equator. 

Atlantic  Ocean 

Nematoscelis  gracilis  has  not  been  reported 
from  the  tropical  Atlantic  Ocean,  nor  was  it  found 
in  any  collections  examined  during  the  present 
survey.  The  only  record  from  the  Atlantic  Ocean 
was  from  the  southwest  coast  of  Africa  (Lusiad 
VII-IKMT,  station  63-539,  lat.  33°47'S,  long. 


1049 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


140*  IW 


Figure  5. — Locality  records  and  nighttime  abundance  of  Nematoscelis  gracilis  and  N.  megalops  adults  in  the  Indian  Ocean:  a  -  NE 
Monsoon  period.  (Solid  lines  represent  approximate  boundaries  of  distribution  of  A^.  gracilis  "old  form,"  broken  lines  represent  those  of 
"new  form,"  and  wavy  lines  those  of  N.  megalops. ) 


15°47'E,  5  June  1963).  (See  Figure  14b.)  Three 
adult  males  and  one  female  belonging  to  the  new 
form  were  caught  at  this  station,  but  no  old  form 
was  found.  Probably  these  new  forms  were  trans- 
ported westward  by  the  Agulhas  Current  (Figure 
7a). 


Pacific  Ocean 

Nematoscelis  gracilis  is  recorded  from  the 
equatorial  zone  of  the  Pacific  (Brinton,  1962). 
Populations  of  this  species  were  also  shown  to 
have  been  carried  by  the  Kuroshio  system  to  as  far 
as  lat.  40°N,  east  of  Japan.  The  numerical  density 
was  found  to  be  much  higher  in  the  east  than  in 
the  west.  In  the  present  survey  based  on  mid- 


water  trawls  from  the  Pacific,  a  similar  pattern  of 
distribution  was  observed  (Figure  7a).  The  new 
forms  were  also  found  to  occur  in  the  Pacific,  but 
only  south  of  the  Equator.  There  Reid  (1965)  rec- 
ognized an  eastward  flow  at  about  400-800  m  (on 
the  basis  of  acceleration  potentials  at  125  cl/ton 
(lat.  2°-8°S)  and  80  cVton  (lat.  8°  -  20°S)  8  T).  How- 
ever, in  the  eastern  Pacific  the  same  latitudes  are 
occupied  by  old  forms  where  Reid  (1965)  and  Love 
(1972)  reported  a  narrow  tongue  of  low  oxygen,  as 
low  as  0.2-0.5  ml/1,  extending  westward.  The  con- 
tour of  oxygen  concentration  of  0.5  ml/1  extended 
as  far  west  as  long.  130°W  between  the  Equator 
and  lat.  10°S  (at  160  cl/ton  ft  T  surface,  150-200  m). 
This  may  account  for  the  fact  that  new  forms  do 
not  reach  eastward  to  the  coasts  of  Chile  and  Peru. 
The  association  of  old  forms  with  oxygen-poor 


1050 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


APRIL  16  -  OCTOBER  15 
(NIGHT  STATIONS) 

Number  of  ADULTS  per  ca.  200m' ' 

Nematoscelis  gracilis 
old  form"    "new  form"    "intermediate  form* 

•  1-24        ©     1-24  <^     1-24 

•  25-224  0    25-74 
^     >225 

N  mega/ops 


■f-J^W 


20"       3CP       40*       W       60' 


80*      90"      100" 


10*    l?0*      150-    -40*    ISO* 


Figure  5. — Locality  records  and  nighttime  abundance  oi  Nematoscelis  gracilis  and  N.  megalops  adults  in  the  Indian  Ocean:  b  -  SW 
Monsoon  period.  (Solid  lines  represent  approximate  boundaries  of  distribution  o{N.  gracilis  "old  form,"  broken  lines  represent  those  of 
"new  form,"  and  wavy  lines  those  of  A^.  megalops. ) 


water  is  evident  from  these  comparisons. 
Nematoscelis  gracilis  old  form  is  the  dominant 
Nematoscelis  species  occurring  in  the  eastern 
tropical  Pacific.  Along  the  coasts  of  Peru  and  Chile 
this  form  is  now  known  to  be  distributed  as  far 
south  as  lat.  33°S  (personal  observation  in  a  sam- 
ple collected  by  Antezana).  Only  old  forms  were 
found  in  the  China  Sea  and  in  oceanic  waters  of 
the  Kuroshio  system.  However,  the  new  and  old 
forms  cooccurred  in  the  Timor,  Banda,  Celebes, 
Halmahera,  and  Molucca  seas.  The  Indian  Ocean 
populations  of  both  forms  are  therefore  in  con- 
tinuity with  those  of  the  Pacific.  In  the  Pacific  the 
eastern  and  western  populations  of  the  species  as  a 
whole  are  linked  along  the  equatorial  zone  be- 
tween lat.  0°  and  10°N  (Brinton,  1962).  Brinton 
has  pointed  out  that  the  lat.  20°N-20°S  range  of  iV. 


gracilis  in  the  east  and  the  lat.  10°N-10°S  range  in 
the  west  corresponds  reasonably  well  to  the  range 
of  the  equatorial  water  mass  (Sverdrup,  Johnson, 
and  Fleming,  1942). 

Geographical  Distribution  of 

N.  megalops 

Indian  Ocean 

Nematoscelis  megalops  was  recorded  during  the 
IIOE  between  lat.  30°S  and  45°S.  This  is  the  area 
of  transition  between  subantarctic  and  Indian 
Central  water  (Sverdrup  et  al.,  1942).  The  number 
of  samples  collected  from  this  zone  is  too  scanty  to 
permit  a  seasonal  study.  Larvae,  juveniles,  and 
adults  were  caught  during  both  seasons  along  the 


1051 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


BAY  OF  BENGAL 


ARABIAN    SEA 


DEVELOPMENTAL  STAGES 

Figure  6. — Frequency  distribution  of  developmental  stages  of  Nematoscelis  gracilis  "old 
form"  in  the  Bay  of  Bengal  and  the  Arabian  Sea.  (Number  of  samples  used  to  calculate 
monthly  averages  ranged  from  11  to  18.) 


full  extent  of  the  transition  zone  (Figures  4,  5).  In 
the  western  Indian  Ocean,  the  maximum  number 
of  larvae  (as  many  as  280  larvae  per  sample)  was 
caught  during  October  1962  (Natal  cruise  5).  In 
the  east,  Diamantina  cruise  3/62  caught  up  to  90 
larvae  per  sample  during  September  1962.  Al- 
though Boden  (1954)  reported  this  species  in  the 
region  of  the  Mozambique  Current,  I  did  not  find  it 


in  meter-net  samples  or  mid-water  trawls  taken 
north  of  lat.  34°S  in  waters  of  southeast  Africa 
(Figure  7b).  (Trawls  were  made  during  the 
October- November  period.)  However,  the  north- 
ern boundary  of  distribution  appears  to  lie  be- 
tween lat.  28°S  and  30°S.  The  northernmost  record 
of  this  species  was  at  lat.  28°18'S,  long.  62°33'E 
{Vitiaz  36,  station  5323). 


1052 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  NEMATOSCELIS 


Figure  7. — Worldwide  distribution  ofNematoscelis  based  on  mid-water  trawls:  a  -  A^.  gracilis  "old"  and  "new"  forms;  b  -  N.  difficilis  and 
A^.  megalops.  (Solid  lines  represent  approximate  boundaries  of  distribution  of  old  form,  broken  lines  represent  those  of  new  form,  and 
wavy  lines  represent  distributional  boundaries  of  AT.  difficilis  and  N.  megalops.  Boundaries  are  based  on  literature  records  and  present 
evidence.) 


Atlantic  Ocean 

Nematoscelis  megalops  appears  to  have  a  wider 
north-south  range  in  the  Atlantic  than  in  other 
oceans.  The  southernmost  record  in  the  North  At- 
lantic was  in  the  region  of  the  Canary  Current 
(Figure  8a).  Larvae  and  juveniles  were  frequently 


caught  between  lat.  40°N  and  53°N.  Literature 
records  of  this  species  in  the  North  Atlantic  are  as 
far  north  as  lat.  68°N  (Zelikman,  1964).  Moore 
( 1952)  recorded  this  species  from  lat.  35°N  to  55°N. 
It  occurs  in  the  Mediterranean  Sea  (Ruud,  1936). 
In  the  South  Atlantic  it  was  collected  by  the 
Lusiad  Expedition  between  lat.  25°S  and  30°S 


1053 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Nematoscelis  mega  lops 

•       I  -  24%   OF  THE  SAMPLE 

■  25-49% 

■  >50% 


a 

Figure  8. — Distribution  of  Nematoscelis  in  the  Atlantic  Ocean  based  on  plankton  samples:  a  -  N. 

megalops. 


(Figure  8a).  Boden  (1954)  recorded  this  species 
from  the  Benguela  Current  as  far  north  as  lat. 
22°S.  From  the  western  part  of  the  South  Atlantic 
no  data  is  available.  The  only  literature  record  is 
from  the  Brazil  Current  area,  between  lat.  45°S 
and  50°S  and  long.  62°W  and  68°W  (Ramirez, 
1971). 

Pacific  Ocean 

Nematoscelis  megalops  and  N.  difficilis  are  a 
recognized  sibling  species  pair,  occupying  trans- 
oceanic belts  of  the  transition  zones  of  the  South 
and  North  Pacific  oceans  respectively  (Brinton, 
1962).  During  the  Downwind  Expedition,  Brinton 
found  N.  megalops  distributed  between  lat.  33°S 
and  48°S  in  midocean.  The  Monsoon  Expedition 
caught  it  as  far  south  as  lat.  54°21'S  (Figure  7b). 


Along  the  coasts  of  Chile  between  lat.  30°S  and 
50°S  this  species  was  caught  by  MV-65  (Anton 
Bruun  ),  Piquero  III,  and  Scorpio  I  expeditions. 

Geographical  Distribution  of 

N.  difficilis 

Nematoscelis  difficilis  is  endemic  to  the  North 
Pacific,  occupying  the  North  Pacific  Drift  and  the 
California  Current  (Figure  7b).  It  was  reported 
during  Transpacific  Expedition  from  seven  sta- 
tions located  east  of  Japan  (Brinton,  1962).  In  the 
present  study  it  was  found  in  mid-water  trawls 
from  near  lat.  40°N  between  long.  130°W  and 
160°W.  Along  the  North  American  coast,  the  dis- 
tribution extends  northward  to  lat.  51°N  (Banner, 
1949)  and  southward  to  lat.  20°N  (Brinton,  1962). 
It  is  common  in  the  cold  water  of  the  California 


1054 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


Nematoscelis  atlantica 

•       I  -24%  OF  THE  SAMPLE 


Figure  8. — Distribution  of  Nematoscelis  in  the  Atlantic  Ocean  based  on  plankton  samples:  b  -  A'^. 

atlantica. 


Current  and  caught  frequently  in  mid-water 
trawls  in  the  San  Diego  Trough  area.  This  species 
was  also  caught  in  the  Gulf  of  California  by  the 
Vermilion  Sea  Expedition;  however,  this  popula- 
tion is  believed  to  be  separated,  perhaps  season- 
ally, from  that  on  the  west  side  of  Baja  California 
due  to  the  influx  of  warm  water  from  the  south  at 
the  mouth  of  the  Gulf  (Brinton,  1962).  Literature 
records  and  present  evidence  indicate  that  the 
ranges  of  A'^.  megalops  and  A'^.  difficilis  do  not 
overlap. 

Geographical  Distribution  of 
IV.  atlantica 

Indian  Ocean 

This  species  has  not  been  reported  previously 
from  the  Indian  Ocean.  In  the  IIOE  collections 


there  were  frequent  occurrences  of  this  species, 
but  only  in  the  midlatitudes  (lat.  15°-40°S) 
of  the  Southern  Hemisphere  (Figure  9a,  b). 
Nematoscelis  atlantica  lives  in  the  region  of  the 
Indian  Ocean  central  water  mass.  Larvae  and 
juveniles  were  caught  from  most  stations  occupied 
within  the  range  of  distribution  of  the  species. 
Moreover,  there  were  no  obvious  differences  be- 
tween seasonal  distributions.  IIOE  samples  in- 
cluded many  adults  from  west  of  Australia  and  the 
Agulhas  Current  (Figure  10a,  b).  In  the  mid- water 
trawls  it  was  caught  between  lat.  11°S  and  42°S 
along  long.  60°E  (Figure  11a). 

Atlantic  Ocean 

Nematoscelis  atlantica  was  observed  in  many 
samples  from  the  North  Atlantic  (Figure  8b).  Un- 


1055 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


120" 


130* 


OCTOBER  16 -APRIL  15 
(DAY  STATIONS) 

NO.  of  INDIVIDUALS  per  ca.  ZOOm^ 


NematosceKs  atlantica 

•  1-9 

•  10-49 

•  >  50 


'# 


■» — t-wvr 


2Cr    scr    40*    50»    60*    70*    ao*    90*    lOO*    no"   izo*    isc  (40"  ISO- 


Figure  9. — Locality  records  and  daytime  abundance  of  larvae  and  juveniles  oi  Nematoscelis  atlantica  in  the  Indian  Ocean:  a  -  NE 

Monsoon  period. 


like  in  the  Pacific  and  Indian  oceans,  this  species 
also  occupies  the  Atlantic  equatorial  zone  provid- 
ing communication  between  North  and  South 
Atlantic  populations.  The  German  South  Polar 
Expedition  (Zimmer,  1914)  first  recorded  the 
north-south  continuity  of  A^.  atlantica  in  the 
Atlantic.  In  the  eastern  Atlantic  between  the 
Equator  and  lat.  40°N,  A^.  atlantica  constituted 
over  50%  of  the  total  Nematoscelis  present  in  each 
sample.  The  northernmost  record  was  at  lat.  52°N 
{Atlantis  11-9,  station  371).  This  species  was  not 
reported  previously  from  the  North  Atlantic 
central  gyre  (Mauchline  and  Fisher,  1969).  In 
the  present  collection  many  larvae,  juveniles, 
and  mature  adults  were  recorded  from  this  area. 
Mediterranean  Sea  records  come  from  Ruud 
(1936)  and  Casanova-Soulier  (1968).  In  the  South 
Atlantic  it  was  present  in  the  Lusiad  collections 
(Figure   11a).   Literature  records  in  the  South 


Atlantic  show  that  it  occurs  in  the  Benguela  Cur- 
rent, extending  as  far  as  lat.  40°S  (Mauchline 
and  Fisher,  1969).  No  samples  were  available 
from  the  areas  of  the  Argentine  Basin. 

Pacific  Ocean 

In  the  Pacific,  A^.  atlantica  lives  in  the  central 
water  masses  of  both  hemispheres  (Figure  11a). 
Tfte  approximate  boundaries  of  distribution  are 
between  lat.  13°  and  38°  in  each  hemisphere  (Brin- 
ton,  1962).  It  was  not  caught  in  the  Naga  collec- 
tions from  the  Indo-Australian  Archipelago.  The 
North  Pacific  population  of  this  species  appears  to 
be  separated  from  those  of  the  South  Pacific  and 
Indian  Ocean  regions.  It  may  be  possible  that 
communication  exists  between  Indian  and  South 
Pacific  populations  through  the  oceanic  waters 
south  of  Australia. 


1056 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


120" 

-=r= 


130" 


APRIL  16  -  OCTOBER  15 
(DAY  STATIONS) 

No.  of  INDIVIDUALS  per  co  200m' 

Nematoscelis  atlantica 

•  1-24 

•  25-74 


MO"  ISO- 


20»     50"      40"     5<r     60*     TO"      •O'     W     (OCT     IIC    120*     130*    t4(r    ISO* 


Figure  9. — Locality  records  and  daytime  abundance  of  larvae  and  juveniles  of  Nematoscelis  atlantica  in  the  Indian  Ocean:  b  -  SW 

Monsoon  period. 


Geographical  Distribution  of 

N.  microps 

Indian  Ocean 

Nematoscelis  microps  has  wider  ranges  of  dis- 
tribution than  N.  gracilis  and  N.  atlantica.  This 
species  penetrates  the  Arabian  Sea  and  the  Bay  of 
Bengal  only  at  their  western  and  eastern  sides 
respectively  (Figure  12a,  b).  The  northernmost 
record  of  this  species  in  the  western  Arabian  Sea 
was  at  lat.  14°N  and  that  in  the  eastern  side  of  the 
Bay  of  Bengal  at  lat.  19°N  off  the  coast  of  Burma.  It 
does  not  live  in  the  poorly  oxygenated  subsurface 
waters  of  the  Arabian  Sea  and  Bay  of  Bengal.  In 
midocean  the  northern  boundary  does  not  extend 
north  of  lat.  6°N  and  the  southern  boundary  not 
beyond  lat.  30°S.  It  was  caught  less  frequently 


from  the  southern  central  gyre  south  of  lat.  10°S. 
Nematoscelis  microps  is  a  predominant  species  of 
the  South  Equatorial  Current  and  the  West  Aus- 
tralian area.  The  Agulhas  Current  apparently 
brings  it  around  the  tip  of  South  Africa. 

There  was  not  much  seasonal  change  in  the 
distribution  of  this  species  in  the  Indian  Ocean. 
Larvae  and  juveniles  were  present  in  the  Somali 
Current  area  during  both  monsoon  seasons  but 
were  carried  as  far  north  as  lat.  14°N  only  during 
the  SW  monsoon.  They  were  present  throughout 
the  year  in  the  Andaman  Sea  area.  During  the  NE 
monsoon  adults  were  not  caught  in  the  Somali 
Current  area  north  of  the  Equator,  whereas  they 
were  present  as  far  north  as  lat.  12°N  during  the 
opposite  season  when  the  flow  is  northeastward 
(Figure  13a,  b).  Adults  occurred  in  the  North 
Equatorial  Current  area  during  the  NE  monsoon 


1057 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


T 


100* 


»" 


»  , 


••  •\ 


a 


\i 


OCTOBER  16  -  APRIL  15 
(NIGHT  STATIONS) 

Number  of  ADULTS  per  co.  ZOOm' 

Nematoscelis  atlantica 

•  1-4 

•  5-24 


o«^ 


P«d«^^^ 


u 


^ 


z^*°' 


*         *  t  t  I  I  I  I    iiifciiiiili        <Tii 

20*      SO-      40*      50-      60'      70*      80"      90"      lOCf      HO*     120*      ISC    r«0'     150* 


Figure  10. — Locality  records  and  nighttime  abundance  of  Nematoscelis  atlantica  adults  in  the  Indian  Ocean:  a  -  NE  Monsoon  period. 


but  were  not  caught  there  during  the  opposite 
season  when  the  Monsoon  Current  replaces  the 
North  Equatorial  Current.  During  the  SW  mon- 
soon none  of  the  stations  north  of  the  Equator 
between  long.  50°E  and  90°E  contained  adult 
specimens  (Figure  13b).  Evidently  this  species 
does  not  reach  the  coast  of  India.  In  the  mid-water 
trawls  N.  microps  was  caught  between  lat.  10°N 
and  41°S  (Figure  lib),  but  north  of  lat.  2°N  this 
species  was  caught  from  only  one  station  {Anton 
Bruun  cruise  3,  station  146,  lat.  10°09'N,  long. 
59°55'E). 


Atlantic  Ocean 


From  the  Atlantic  Ocean  there  are  literature 


records  of  scattered  occurrences  of  this  species  be- 
tween lat.  40°N  and  40°S.  Moore  (1952)  reported 
that  this  species  occurred  in  the  western  Atlantic 
north  of  the  equator  to  lat.  40°-45°N,  in  the  region 
of  the  Gulf  Stream.  The  most  northerly  record  in 
the  eastern  ocean  was  from  lat.  59°39'N  (Illig, 
1930),  although  most  other  records  lie  south  of  lat. 
40°N.  In  the  present  survey  it  was  caught  between 
the  Equator  and  lat.  40°N  and  was  relatively  more 
abundant  in  the  western  ocean  than  in  the  east 
(Figure  14a).  It  was  not  present  in  many  samples 
taken  from  the  North  Atlantic  central  gyre.  There 
were  a  few  doubtful  records  of  this  species  from  the 
Mediterranean  Sea  (Ruud,  1936;  Bacescu  and 
Mayer,  1961).  In  the  South  Atlantic  it  was  caught 
by  Lusiad  and  Atlantis  77-31  expeditions  (Figure 
lib). 


1058 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


70*  80' 


90* |00- 110^ 120*       !»•  M<r  IW 


APRIL  16  -  OCTOBER  15 
(NIGHT  STATIONS) 


Number  of  ADULTS  per  ca.  200  m' 

Nematoscelis  atlantica 

•  1-9 

•  10-19 


Figure  10. — Locality  records  and  nighttime  abundance  of  Nematoscelis  atlantica  adults  in  the  Indian  Ocean:  b  -  SW  Monsoon  period. 


Pacific  Ocean 

North  and  South  Pacific  populations  of  N.  mi- 
crops  are  in  communication  with  each  other  across 
the  western  equatorial  Pacific  (Figure  lib).  This 
species  is  absent  along  the  eastern  boundary  cur- 
rents (California  Current  and  Peru  Current)  and 
also  from  the  poorly  oxygenated  subsurface  wa- 
ters of  the  eastern  tropical  Pacific.  Nematoscelis 
microps  was  also  caught  less  frequently  in  the 
eastern  North  Pacific  central  water  mass  than  in 
the  western  North  Pacific  central  water  mass.  In 
the  equatorial  region  this  species  is  known  to 
occur  only  west  of  long.  110°W  (Brinton,  1962).  It 
is  also  recorded  from  the  China  Sea  and  the  re- 
gions of  the  Timor,  Molucca,  and  Banda  seas.  The 
populations  of  the  Indian  and  Pacific  oceans  are 


probably  in  communication  with  each  other 
through  the  straits  of  Timor,  Banda,  Molucca,  and 
Halmahera. 

Geographical  Distribution  of  N.  lobata 

Hansen  (1916)  described  A'^.  lobata  from  the 
Philippines.  He  found  it  at  only  two  localities:  lat. 
13°43'N,  long.  121°E  and  lat.  7°07'N,  long. 
125°40'E.  Nematoscelis  lobata  appears  to  be  en- 
demic to  the  semi-isolated  seas  around  the  west- 
ern side  of  the  Philippines.  In  the  present  survey  it 
was  caught  mostly  from  the  Sulu  Sea  area  (Naga 
Expedition)  (Figure  15).  At  station  SllB-205,  five 
mature  males  and  six  females  were  caught  in  a 
2-m-net  collection,  0-500  m  (lat.  6°35'N,  long. 


1059 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  11. — Worldwide  distribution  of  Nematoscelis  based  on  mid-water  trawls:  a  -  N.  atlantica;  h  -  N.  microps.  (Broken  lines 
represent  approximate  boundaries  of  distribution  of  the  species  based  on  literature  records  and  present  evidence.) 


122°27'E;  29  April  1961).  At  six  other  stations 
only  mature  females  were  caught.  The  petasma, 
particularly  the  broad  median  lobe  with  its  convex 
inner  and  outer  margins,  is  an  excellent  diagnos- 
tic feature  of  this  species.  The  shape  of  the  keel  on 
the  carapace  of  both  sexes  is  also  different  from 
other  Nematoscelis  species.  Nematoscelis  lobata  is 


not  reported  from  any  other  place,  including  the 
Siboga  collections  from  the  East  Indian  Ar- 
chipelago and  the  Troll  Expedition  collections 
made  along  the  eastern  coast  of  the  Philippines 
(Figure  15).  This  species  appears  to  be  absent  from 
the  South  China  Sea  and  the  Gulf  of  Thailand 
(Brinton,  manuscript). 


1060 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  NEMATOSCELIS 


Geographical  Distribution  of  N.  tenella 

Indian  Ocean 

The  geographical  distribution  of  A^.  tenella  is 
similar  to  that  of  A'^.  microps.  This  species  lives  in 
the  equatorial  and  central  water  masses  of  all 
oceans.  In  the  Indian  Ocean  most  records  came 
from  between  lat.  7°N  and  38°S  except  in  the  east- 
ern and  western  boundary  current  areas  (Figures 
16a,  b;  17a,  b).  It  was  most  frequently  caught  in 
the  equatorial  zone  and  in  the  eastern  ocean  south 
of  the  Equator.  Larvae  and  juveniles  occurred 
throughout  the  range  of  distribution.  There  were 
no  seasonal  differences  in  the  distribution  of  lar- 
vae and  juveniles;  however,  in  the  western  Indian 
Ocean  north  of  the  Equator  they  were  more  abun- 
dant during  the  SW  monsoon  than  in  the  opposite 
season.  This  species  penetrates  into  the  Arabian 
Sea  only  in  the  western  side.  It  is  absent  from  the 
Bay  of  Bengal.  The  pattern  of  distribution  of 
adults  was  like  that  of  larvae  and  juveniles  (Fig- 
ure 17a,  b).  Mid- water  trawls  caught  A'^.  tenella 
between  lat.  8°N  and  40°S  (Figure  18). 

Atlantic  Ocean 

Illig  (1930)  recorded  A'',  tenella  from  lat. 
59°39'N,  long.  8°49'W,  but  all  other  records  are 
from  lat.  35°N  to  35°S.  Lewis  (1954)  reported  this 
species  off  southern  Florida.  In  the  present  study 
larvae  and  juveniles  were  found  to  be  more  abun- 
dant in  the  western  North  Atlantic  than  on  the 
eastern  side  (Figure  14b).  Around  lat.  40°N,  its 
northern  limit,  it  was  caught  in  five  plankton 
samples.  It  has  not  been  reported  from  the 
Mediterranean  Sea.  In  the  South  Atlantic  this 
species  was  found  in  the  Lusiad  collections  off 
South  Africa.  No  samples  were  available  from  the 
western  South  Atlantic  nor  has  it  been  reported 
from  that  region.  It  is  also  not  known  whether  this 
species  occurs  in  the  Benguela  Current. 

Pacific  Ocean 

Nematoscelis  tenella  lives  in  both  hemispheres 
of  the  Pacific,  lat.  35°N-34°S.  It  does  not  occupy  the 
more  coastal  areas  of  the  California  Current  or  its 
southward  extension  into  the  eastern  equatorial 
region  (Figure  18).  It  is  also  scarce  in  the  region  of 
the  Peru  Current  (Brinton,  1962).  In  midocean, 
Brinton  recorded  it  as  far  south  as  lat.  34°S.  This 
species  appears  to  be  more  abundant  in  the  north- 


ern central  gyre  than  in  the  south.  It  occurs 
farther  east  in  the  tropical  belt  than  N.  microps. 
The  north-south  range  is  continuous  across  the 
Equator.  It  is  a  common  species  in  the  South  and 
East  China  seas  and  also  in  the  Banda,  Molucca, 
and  Timor  seas.  Apparent  communication  exists 
between  the  Indian  and  Pacific  populations. 

Faunal  Zones  and  Biogeography 
of  Nematoscelis 

Faunal  regions  of  the  oceanic  environment  are 
not  as  well  defined  as  in  the  terrestrial  habitats. 
The  oceanic  environment,  as  distinguished  by 
Hedgpeth  (1957),  consists  of  a  system  of  zonally 
oriented  hydrographic  provinces  arranged  in 
latitudinal  succession  within  each  ocean.  In  the 
Atlantic  Ocean,  Dahl  (1894)  recognized  four 
epipelagic  faunal  regions:  arctic,  subarctic  (tem- 
perate), subtropical,  and  tropical.  Steuer  (1933) 
described  a  similar  system  of  classification  but  in- 
cluded the  Pacific  and' Indian  oceans.  He  recog- 
nized circumpolar  arctic,  circumequatorial  tropi- 
cal, and  circumpolar  antarctic  on  a  global  scale. 
The  arctic  region  was  subdivided  into  a  circumpo- 
lar subregion  as  well  as  Atlantic  and  Pacific  sub- 
arctic subregions.  The  antarctic  region  includes 
the  circumpolar  antarctic  and  subantarctic  sub- 
regions.  The  tropical  region  was  subdivided  into 
Atlantic  and  Indo-Pacific  provinces.  A  system  of 
classification  based  on  this  and  other  subsequent 
works  [for  example:  Deacon  (1933,  1937);  Rad- 
zikhovskaya  (1965);  Stepanov  (1965);  Frost 
(1969);  McGowan  (1971)]  is  adapted  here  and 
shown  in  Table  2.  The  division  of  the  epipelagic 
environment  into  faunal  zones  agrees  with  the 
distributional  patterns  of  many  planktonic  or- 
ganisms [see  McGowan  (1971)  for  examples]. 
Species  oi  Nematoscelis  occupy  one  or  more  of  the 
subregions  (Table  3).  As  mentioned  before,  A^. 
difficilis  is  endemic  to  a  zone  of  transition  between 
subarctic  and  central  water  in  the  North  Pacific. 
Even  though  this  zone  (Johnson  and  Brinton, 
1963)  does  not  have  as  well  defined  a  tem- 
perature-salinity envelope  as  other  water 
masses,  it  maintains  endemic  species,  as  well  as 
the  densest  part  of  the  overall  populations  of  some 
subarctic  and  central  species.  Evidence  is  ac- 
cumulating for  the  existence  of  a  unique  water 
body  in  this  zone  with  characteristic  hydrographi- 
cal  and  faunal  properties  (McGowan,  1971).  The 
extent  and  location  of  an  analogous  transition 
zone  in  the  North  Atlantic,  if  such  exists,  is  not 


1061 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


,  ,     II  ,j,M«i„L_Jl 


20"     50*      40*     50*     6<r     TO*      eo*     9(r     100"     MO"    120"     ISO"    wo"    190" 


Figure  12. — Locality  records  and  daytime  abundance  of  larvae  and  juveniles  of  Nematoscelis  microps  in  the  Indian  Ocean:  a  -  NE 

Monsoon  period. 


Table  2. — Biogeographical  zones  of  the  oceanic  environment. 


Zones 


Terminology  (Regions) 


Latitude 
(approximate) 


Subregion 


Northern  Cold  Water 


Northiern  Transitional 


(Cir 
tsul 


cumpolar  Arctic 
barctic  (Cold  Temperate) 


Northern  Subtropical 
(Warm  Temperate) 


Warm  Water 


Southern  Transitional 


Southern  Cold  Water 


Tropical 


Southern  Subtropical 
(Warm  Temperate) 


Circumpolar  Subantarctic 

(Cold  Temperate) 
^  Circumpolar  Antarctic 


>67  N 
45=-67  N 

35°-45"N 

23°-35°N 

23°S-23  N 
23'-35°S 
35°-45°S 


45'-67=S 
>67°S 


(Subarctic  Atlantic 
Subarctic  Pacific 

(Transitional  North  Atlantic 
Transitional  North  Pacific 

(Subtropical  North  Atlantic 
Subtropical  North  Pacific 

I  Tropical  Atlantic 
Tropical  Indo-West  Pacific 
Eastern  Tropical  Pacific 

I  Subtropical  South  Atlantic 
Subtropical  South  Pacific 
Subtropical  South  Indian 

I  Circumpolar  Transitional 
Region  of  the  Southern 
Hemisphere 


1062 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


Figure  12. — Locality  records  and  daj^ime  abundance  of  larvae  and  juveniles  of  Nematoscelis  microps  in  the  Indian  Ocean:  b  -  SW 

Monsoon  period. 


Table  3. — Biogeographical  zones  of  the  oceanic  environment  and  the  distribution  of  Nematoscelis. 
*  Both  new  and  old  forms.  **01d  forms  only.  ***  New  form  expatriate  adults  only.  ****New  forms 
in  Mozambique  Current  area  only. 


Subreglons 

Subarctic  Atlantic 
Transitional  North  Atlantic 
Transitional  North  Pacific 
Subtropical  North  Atlantic 
Subtropical  North  Pacific 
Tropical  Atlantic 
Tropical  Indo-West  Pacific 
Eastern  Tropical  Pacific 
Subtropical  South  Atlantic 
Subtropical  South  Pacific 
Subtropical  South  Indian 
CIrcumpolar  Transitional  Region 
of  the  Southern  Hemisphere 


N. 

N. 

N. 

N. 

N. 

N^ 

difficilis 

megalops 

atlantica 

gracilis 

microps 

ten  el  la 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X- 

X 

X 

x" 

X 

X 

x"* 

X 

X 

X 

X 

X 

X 

x"" 

X 

X 

1063 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  13. — Locality  records  and  nighttime  abundance  of  Nematoscelis  microps  adults  in  the  Indian  Ocean:  a  -  NE  Monsoon  period. 


clearly  understood.  However,  lat.  35°-45°N,  cor- 
responding to  the  North  Pacific  transition,  seems 
to  be  the  extent  of  the  region  in  the  North  Atlantic 
where  N.  megalops  (instead  of  N.  difficilis  )  is  the 
most  common  Nematoscelis.  Nematoscelis  atlan- 
tica,  N.  microps,  and  N.  tenella  also  appear  in  the 
transition  zone  of  the  North  Atlantic  but  not  in  the 
corresponding  zone  in  the  North  Pacific.  The 
northeasterly  North  Atlantic  Current  carries 
warmwater  species  farther  north  into  the  transi- 
tion zone  or  even  beyond  to  the  subarctic  subre- 
gion.  For  example,  the  present  survey  recorded  N. 
atlantica  from  lat.  52°N  {Atlantis  II -9,  station 
371).  Outside  of  its  main  zone  in  the  North  Atlan- 
tic, N.  megalops  occasionally  occurs  in  the 
subtropical  and  subarctic  subregions.  It  is  also  the 
most  common  Nematoscelis  species  of  the  circum- 
polar  transitional  regions  of  the  Southern  Hemi- 
sphere, while  A^.  atlantica,  N.  microps,  and  N. 


tenella  also  were  occasionally  caught  there,  from 
the  Indian  Ocean  sector. 

The  eastern  tropical  Pacific  Ocean  is  considered 
a  subregion  of  the  warmwater  zone  because  of  its 
characteristic  hydrographical  and  faunal  proper- 
ties. Nematoscelis  gracilis  old  form  is  part  of  that 
faunal  assemblage.  The  Indo-West  Pacific  and 
eastern  tropical  Pacific  subregions  were  consid- 
ered separate  from  the  Atlantic  tropical  subre- 
gion (Ekman,  1953).  The  distribution  ofN.  gracilis 
and  A^.  atlantica  presents  evidence  for  this. 
Nematoscelis  microps  and  A^.  tenella  are  warmwa- 
ter species,  occupying  both  tropical  and  subtropi- 
cal regions  (Table  3).  Many  warmwater  plank- 
tonic  species  are  restricted  to  tropical  latitudes, 
whereas  others  are  found  only  outside  of  this  re- 
gion (examples  in  Bieri,  1959;  Brinton,  1962; 
Alvarino,  1965;  Baker,  1965;  McGowan,  1971).  In 
this  respect  N.  gracilis  is  tropical  and  N.  atlantica 


1064 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


20-  30- 


20-     ISO-    140"    150* 


Figure  13. — Locality  records  and  nighttime  abundance  oi Nematoscelis  microps  adults  in  the  Indian  Ocean:  b  -  SW  Monsoon  period. 


is  subtropical.  Because  the  boundaries  between 
the  full  breadth  of  tropical  and  subtropical  regions 
are  not  well  defined  hydrographically,  it  is  usually 
difficult  to  correlate  species'  distributional  pat- 
tern to  the  hydrographical  zones  of  these  two 
areas. 

DISCUSSION 

The  distributions  of  Nematoscelis  species  are 
associated  with  general  hydrographical  features 
in  each  ocean.  In  the  Indian  Ocean  the  seasonality 
in  abundance  of  this  genus  is  more  pronounced  in 
the  Northern  Hemisphere  than  in  the  south;  and  it 
is  probably  related  to  changes  in  monsoonal  re- 
gimes. The  hydrographical  features  of  the  Ara- 
bian Sea  and  Bay  of  Bengal  limit  the  northern 
boundary  of  distribution  of  all  species  of 
Nematoscelis  except  A^.  gracilis  old  form.  There 


appears  to  be  a  general  break  in  the  north-south 
midocean  distribution  of  N.  microps  and  N. 
tenella  near  the  equatorial  zone  of  the  Indian 
Ocean.  Their  northern  boundary  of  distribution 
corresponds  to  the  approximate  southern  extent  of 
oxygen-poor  waters  ( <  1  ml/1)  of  the  Arabian  Sea 
and  the  Bay  of  Bengal. 

Wyrtki  (1973)  proposed  a  division  of  the  Indian 
Ocean  into  three  circulation  systems:  a  seasonally 
changing  monsoon  gyre,  a  southern  subtropical 
anticyclonic  gyre,  and  the  antarctic  waters  with 
the  Circumpolar  Current.  One  unique  feature  of 
the  Indian  Ocean  is  the  persistence  of  a  hydro- 
chemical  front  at  about  lat.  10°S,  separating  the 
high-nutrient,  low-oxygen  content  waters  of  the 
monsoon  gyre  from  the  low-nutrient,  high-oxygen 
content  waters  of  the  subtropical  gyre.  The  exis- 
tence of  such  a  front  is  very  well  reflected  by  the 
chemical  characteristics  of  the  subsurface  water 


1065 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


Nematoscelis  microps 


24%   OF  THE  SAMPLE 

•  25-49% 

•  >50% 


a 


Figure  14. — Distribution  of  Nematoscelis  in  the  Atlantic  Ocean  based  on  plankton  samples:  a  -  N. 

microps. 


(Wyrtki,  1973).  The  boundaries  of  distribution  of 
many  zooplankton  species  appear  to  fall  within 
this  zonal  band.  This  is  also  the  area  of  the  north- 
ern boundary  of  the  subtropical  species  N.  atlan- 
tica.  Evidently  the  southern  boundary  of  A^. 
gracilis  new  form  is  not  confined  to  this  zone;  since 
the  South  Equatorial  Current  carries  it  as  far 
south  as  lat.  20°S.  The  subtropical  convergence 
located  at  about  lat.  40°-41°S  separates  the  south- 
ern subtropical  anticyclonic  gyre  and  the  antarc- 
tic circumpolar  water.  This  is  the  region  of  the 
southern  boundary  of  distribution  of  both  the  sub- 
tropical species  N.  atlantica  and  the  warmwater 
species  A^.  microps  and  A^.  tenella. 

Brinton  and  Gopalakrishnan  (1973)  recognized 
different  euphausiid  faunal  assemblages  in  the 
Indian  Ocean,  each  of  which  is  bounded  mainly 
around  lat.  10°N,  0°,  10°S,  25°-30°S.  Latitude  10°N 


delimits  the  northern  distribution  of  not  only  A^. 
microps  and  N.  tenella  but  also  other  euphausiid 
species  such  as  Euphausia  tenera,  Thysanopoda 
monacantha,  T.  tricuspidata,  Nematobrachion 
flexipes,  Stylocheiron  abbreviatum,  and  S.  lon- 
gicorne  (Brinton  and  Gopalakrishnan,  1973). 
Therefore,  the  Arabian  Sea  and  Bay  of  Bengal 
north  of  lat.  10°N  contains  large  numbers  of  only 
A'^.  gracilis  old  form  along  with  Stylocheiron  indi- 
cum,  S.  carinatum,  S.  affine,  Pseudeuphausia 
latifrons,  Euphausia  diomediae,  and  E.  distin- 
guenda.  In  both  the  Arabian  Sea  and  the  Bay  of 
Bengal  a  low  level  of  oxygen  (as  low  as  0.1  ml/1) 
persists  year-round  in  the  upper  oxygen  minimum 
layer  (Wyrtki,  1971).  However,  temperature  and 
salinity  vary  seasonally  in  these  areas.  The  sur- 
face salinity  ranges  are  30-33%o  for  the  Bay  of 
Bengal  and  34-37%o  for  the  Arabian  Sea.  Biologi- 


1066 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF NEMATOSCELIS 


Nematoscelis  tenello 


-  24%   OF   THE   SAMPLE 

*    25  -  49% 

A         >50% 


Figure  14. — Distribution  of  Nematoscelis  in  the  Atlantic  Ocean  based  on  plankton  samples:  b  -  N. 

tenella  and  A^.  gracilis. 


cal  and  oceanographical  differences  between  these 
two  parts  of  the  Indian  Ocean  were  discussed  by 
Panikkar  and  Jayaraman  ( 1966).  Throughout  the 
year  N.  gracilis  old  form  maintains  spawning 
populations  in  these  two  areas. 

Nematoscelis  gracilis  new  and  old  forms,  A^. 
microps,  and  A^^.  tenella  are  part  of  the  faunistic 
assemblage  between  lat.  0°  and  10°S.  The  occur- 
rence of  A/^.  gracilis  new  form  in  the  mid-Pacific 
agrees  with  the  distribution  of  Euphausia 
pseudogibba  and  Thysanopoda  subaequalis  in  the 
zone  lat.  10°-20°S  (cf  Brinton,  1962:212).  South 
of  lat.  25°-30°S,  N.  gracilis  is  replaced  by  A'^.  atlan- 
tica.  Other  species  of  this  zone  are  Euphausia 
brevis,  E.  mutica,  Stylocheiron  suhmii,  and 
Thysanopoda  subaequalis.  In  the  Indian 
Ocean  all  of  these  central  species,  including  N. 
atlantica,  occur  only  in  the  Southern  Hemisphere. 


ISO"  :30- 

Figure  15. — All  known  records  of  Nematoscelis  lobata. 


1067 


30"  40' 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


(30*  140*  150- 


20*      30"      40"      W      60*      70*      80"      90*      lOC      HO*     120*      130*    140'    ISO* 


Figure  16. — Locality  records  and  daytime  abundance  of  larvae  and  juveniles  of  Nematoscelis  tenella  in  the  Indian  Ocean:  a  -  NE 

Monsoon  period. 


The  distributions  of  N.  gracilis  new  and  old 
forms  in  the  Indian  and  Pacific  oceans  appear  re- 
spectively to  be  associated  with  areas  of  high  and 
low  oxygen  concentration  in  the  water  column.  In 
the  Indian  Ocean,  Gibbs  and  Hurwitz  (1967)  re- 
ported a  similar  association  of  species  distribution 
and  oxygen  concentration  in  the  water  column  for 
two  mesopelagic  fish  species,  Chauliodus  pam- 
melas  and  C.  sloani.  Like  A^.  gracilis  old  form,  C. 
pammelas  is  only  in  the  oxygen-poor  waters  of  the 
Arabian  Sea  and  the  Bay  of  Bengal.  The  old  form 
is  largely  confined  to  the  tropical  areas  where  the 
oxygen  concentration  in  the  upper  minimum  is 
less  than  2  ml/1  (Figure  3);  whereas  the  new  form 
occurs  in  those  equatorial  regions  where  the  ox- 
ygen values  in  the  upper  minimum  layer  is  never 
less  than  1  ml/1.  Since  the  adults  have  to  pass 
through  the  oxygen  minimum  layer  during  their 


diurnal  migrations,  the  old  forms  might  have  at- 
tained physiological  adaptations  to  the  lower  ox- 
ygen levels.  It  has  been  documented  experimently 
(Teal  and  Carey,  1967)  that  Euphausia  mu- 
cronata,  one  of  the  common  residents  in  the 
oxygen-poor  waters  of  the  Peru-Chile  Current, 
can  withstand  the  stress  of  oxygen  pressure  as  low 
as  that  in  the  oxygen  minimum  layer. 

Low  oxygen  values  in  the  upper  minimum  layer 
of  the  tropical  Indian  and  Pacific  oceans  reflect  the 
presumed  high  productivity  of  the  surface  layers 
(Vinogradov  and  Voronina,  1961;  Longhurst, 
1967).  Old  forms  occur  in  these  areas  of  high  zoo- 
plankton  abundance,  particularly  in  the  eastern 
tropical  Pacific,  Arabian  Sea,  and  Bay  of  Bengal. 
Reid  (1962)  plotted  the  distribution  of  zooplankton 
abundance  in  the  Pacific.  In  the  area  of  the  North 
Equatorial  Current  the  zooplankton  biomass  is 


1068 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  SEMATOSCELIS 


9Cr      90*      IOC      110"     120*      ISO*    ^MT    ISC 


sw 


Figure  16. — Locality  records  and  da3rtime  abundance  of  larvae  and  juveniles  of  Nematoscelis  tenella  in  the  Indian  Ocean:  b 

Monsoon  period. 

Nematoscelis  gracilis  old  forms  in  the  northern 


much  higher  than  in  the  area  of  the  South 
Equatorial  Current.  Correspondingly,  N.  gracilis 
old  forms  are  distributed  in  the  northern  part  of 
the  equatorial  current  systems  and  new  forms  to 
the  south  in  less  rich  waters.  The  same  relation- 
ship exists  in  the  Indian  Ocean  [cf.  the  Interna- 
tional Indian  Ocean  Expedition  Plankton  Atlas. 
Indian  Ocean  Biological  Centre  (1968)]. 

Each  form  ofN.  gracilis  is  considered  to  be  an 
ecophenotype.  Mayr  (1971)  recognized  ecopheno- 
type  as  a  nongenetic  modification  of  the  pheno- 
type  in  response  to  an  environmental  condi- 
tion. However,  the  observed  morphological  differ- 
ences, associated  with  reproductive  structures, 
suggest  the  possibility  of  genetic  divergence  of  the 
two  demes.  The  intergradation  (intermediate 
forms)  along  the  overlapping  zones  suggest  in- 
complete genetic  isolation. 


part  of  the  Indian  Ocean  differ  from  those  of  the 
eastern  tropical  Pacific  in  that  the  Indian  Ocean 
forms  are  smaller  in  size.  The  degree  of  similarity 
of  these  two  populations  is  expressed  quantita- 
tively in  a  separate  paper. 

Brinton  (1962)  pointed  out  that  most  of  the 
inter-ocean  waterways  in  the  Indo- Australian  Ar- 
chipelago, (e.g.,  the  Strait  of  Malacca,  Sunda 
Strait,  and  Torres  Strait)  are  too  shallow  (<  100 
m)  to  allow  interoceanic  transport  of  the  oceanic 
euphausiid  species.  The  deep  pathway  is  through 
the  straits  of  Molucca  and  Halmahera,  and  the 
Banda  and  Timor  seas.  Even  central  species  like 
Euphausia  mutica  are  found  along  this  route. 
Nematoscelis  gracilis  new  and  old  forms,  A^.  mi- 
crops,  and  N.  tenella  show  similar  communication 
between  Pacific  and  Indian  Ocean  populations. 


1069 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  17. — Locality  records  and  nighttime  abundance  of  Nematoscelis  tenella  adults  in  the  Indian  Ocean:  a  -  NE  Monsoon  period. 


However,  the  absence  of  A^.  atlantica  from  the 
region  of  the  Indo-AustraHan  Archipelago  sug- 
gests the  lack  of  inter-ocean  communication  of 
this  species.  Moreover,  N.  lobata,  w^hich  is  mor- 
phologically most  similar  to  A^.  atlantica,  is  en- 
demic to  a  part  of  this  region,  mainly  the  Sulu  and 
Celebes  seas.  These  basins  are  connected  with  the 
open  ocean  by  relatively  shallow  channels.  This 
region  is  well  known  for  its  endemic  species.  Gil- 
bert and  Hubbs  (1920)  pointed  out  that  the  pecu- 
liar characteristics  of  the  isolated  basin  of  the 
Sulu  Sea  might  have  caused  the  evolution  of  many 
fish  species.  Because  of  morphological  similarities 
and  non-overlapping  distribution  (geographical 
isolation),  N.  lobata  and  A^.  atlantica  may  have  de- 
rived from  the  same  stock. 

The  North  Pacific  central  population  of  A'^.  at- 
lantica is  also  isolated  from  its  southern  counter- 
part. However,  it  is  not  known  whether  the  dis- 


juncts  are  genetically  different.  Analyses  per- 
formed by  both  numerical  and  conventional  ways 
indicate  no  morphological  differences. 

Another  region  of  importance  in  considering 
gene  flow  between  Indian  and  Pacific  populations 
is  the  South  Australian  Basin  and  the  Tasman 
Sea.  The  Bass  Strait  between  Australia  and  Tas- 
mania is  probably  too  shallow  to  allow  passage  of 
adult  oceanic  euphausiids.  However,  larvae  and 
juveniles  may  be  transported  across  this  passage. 
The  only  route  for  adults  is  south  of  Tasmania,  but 
this  is  almost  certainly  too  far  south  for  the 
tropical-subtropical  species  including  N.  tenella, 
N.  microps,  and  N.  atlantica.  Evidence  from  south 
of    Australia    (Monsoon    Expedition,    long. 
120°E-175°W)  indicates  that  populations  of  A^. 
megalops  are  in  communication  between  the 
South  Pacific  and  Indian  oceans.  The  Pacific  popu- 
lation evidently  does  not  mix  with  the  South  At- 


1070 


GOPALAKRISHNAN:  ZOOGEOGRAPHY  OF  NEMATOSCELIS 


I4<r  IKT 


Figure  17. — Locality  records  and  nighttime  abundance  of  Nematoscelis  tenella  adults  in  the  Indian  Ocean:  b  -  SW  Monsoon  period. 


lantic  counterpart  at  the  Drake  Passage  (An- 
tezana,  manuscript).  The  morphological  differ- 
ences between  A'',  megalops  and  A^.  difficilis 
already  reflect  presumed  genetic  differences. 

Atlantic  populations  of  A^.  atlantica,  N.  microps, 
and  A^.  tenella  are  not  in  direct  communication 
with  their  respective  counterparts  in  the  Pacific, 
but  the  North  and  South  Atlantic  populations  are 
in  communication  at  the  Equator.  It  appears  that 
the  Atlantic  and  Indian  Ocean  populations  of 
these  species  are  in  at  least  seasonal  communica- 
tion around  the  tip  of  South  Africa. 

A  further  aspect  of  the  zoogeography  of 
Nefnatoscelis  in  the  Atlantic  lies  in  the  fact  that 
A^.  atlantica,  not  A^.  gracilis,  occupies  the  equator- 
ial belt,  permitting  north-south  continuity  of  the 
species.  Atlantic  expatriates  of  A'^.  gracilis  new 
form  are  found  only  off  southwest  Africa,  probably 
transported  by  the  Mozambique  Current.  The  cool 


Benguela  Current  region  may  then  limit  northern 
transport  of  this  tropical  form,  or  the  low  oxygen 
(0.5  ml/1)  in  the  minimum  layer  of  the  current,  lat. 
10°S  and  15°S  (Bubnov,  1966),  might  be  a  barrier 
to  the  new  forms  as  it  appears  to  be  in  the  northern 
Indian  Ocean. 

There  are  similarities  between  distributions  of 
species  of  Nematoscelis  and  those  of  other  zoo- 
plankters.  For  example,  the  distribution  of  N. 
megalops  is  like  that  of  a  copepod,  Clausocalanus 
ingens  (Frost,  1969)  and  Thysanoessa  gregaria 
(Brinton,  1962);  horizontal  boundaries  of  A'^.  mi- 
crops  and  A^.  tenella  are  like  those  of  other 
tropical-subtropical  species,  C.  mastigophorus 
and  Stylocheiron  carinatum .  It  is  likely  that  both 
biological  (species  interaction)  and  physical 
[water  mass,  Sverdrup  et  al.  (1942)]  reasons  are 
responsible  for  the  numerous  similarities. 

McGowan  (1971)  classified  the  patterns  of  dis- 


1071 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  18. — Worldwide  distribution  of  Nematosce lis  tenella  based  on  mid- water  trawls.  (Broken  lines  represent  approximate  bound- 
aries of  distribution  of  the  species  based  on  literature  records  and  present  evidence.) 


tribution  of  many  zooplankton  species  into  four 
types  on  the  basis  of  their  association  with  water 
masses.  They  are:  1)  species  that  show  patterns  of 
distribution  whose  boundaries  are  almost  identi- 
cal with  the  boundaries  of  the  physical  water 
masses;  2)  species  which  have  areas  of  highest 
levels  of  abundance  within  a  water  mass,  but 
whose  boundaries  extend  somewhat  beyond  the 
boundary  of  the  water  mass;  3)  species  that  have 
distributions  throughout  several  water  masses; 
and  4)  species  having  limited  distributions  in 
parts  of  some  water  masses.  Nematoscelis  gracilis 
and  N.  atlantica  fall  in  the  first  category,  A'^. 
megalops  in  the  second,  and  N.  tenella  and  A^. 
microps  in  the  third.  Nematoscelis  difficilis  is  re- 
stricted to  the  North  Pacific  transition  zone 
whereas  N.  megalops  is  distributed  in  the  central, 
transitional,  and  subarctic  water  masses  of  the 
Atlantic  and  in  the  southern  transitional  zones  of 
the  Indian  and  Pacific  oceans. 

ACKNOWLEDGMENTS 

The  work  was  supported  in  part  by  National 
Science  Foundation  Grant  GA-31783  and  in  part 
by  the  Marine  Life  Research  Program,  the  Scripps 
Institution  of  Oceanography's  component  of  the 
California  Cooperative  Oceanic  Fisheries  Inves- 
tigations, a  project  sponsored  by  the  Marine  Re- 


search Committee  of  the  State  of  California.  I  wish 
to  thank  E.  Brinton,  M.  M.  Mulhn,  B.  Taft,  and  P. 
Dayton  for  their  comments  on  the  manuscript.  I 
am  specially  grateful  to  E.  Brinton  for  his  constant 
encouragement  and  guidance  during  the  course  of 
this  research. 

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1074 


VARIATION  OF  THE  SURFACE  GEOSTROPHIC  FLOW  IN 
THE  EASTERN  INTERTROPICAL  PACIFIC  OCEAN 

MiZUKI  TSUCHIYA^ 


ABSTRACT 

A  sequence  of  seven  maps  is  presented  to  show  the  distribution  of  geopotential  anomaly  at  the  sea 
surface  in  the  eastern  intertropical  Pacific  Ocean.  Each  map  represents  a  2-mo  period  during  the 
EASTROPAC  expedition  from  February  1967  to  April  1968. 

The  most  striking  feature  revealed  by  these  maps  is  the  variation  of  the  North  Equatorial  Counter- 
current  in  response  to  the  annual  variation  of  the  atmospheric  circulation.  In  February-April  (both 
1967  and  1968),  when  the  atmospheric  intertropical  convergence  zone  (ITCZ)  lay  near  its  southernmost 
position  at  lat.  2°-6°N,  the  Countercurrent  was  discontinuous  and  was  rapidly  changing  in  intensity.  In 
August-September,  when  the  ITCZ  lay  near  its  northernmost  position  at  lat.  11°-15°N,  the  Countercur- 
rent was  strong,  broad,  and  extended  east  all  the  way  to  the  coast  of  Costa  Rica. 

In  southern  summer  a  weak  and  narrow  eastward  current  was  indicated  along  about  lat.  10°S 
between  long.  112°  and  90°W  within  the  westward  flow  of  the  South  Equatorial  Current.  This  current 
is  so  weak  that  it  is  probably  buried  in  the  westward  Ekman  drift  due  to  the  southeast  trades  and  can  be 
observed  only  when  the  trade  winds  are  unusually  weak. 

An  eastward  current,  which  can  be  interpreted  as  the  Equatorial  Undercurrent  breaking  the  sea 
surface,  was  indicated  within  about  2°  of  the  equator  in  April-May,  when  the  southeast  trades  were 
relatively  weak  near  the  equator. 

The  distributions  of  relative  geostrophic  flow  in  February-March  1967  and  February-April  1968 
were  remarkably  similar  over  the  entire  study  area. 


The  purpose  of  this  paper  is  to  present  a  sequence 
of  seven  maps  (Figures  1-7)  showing  the  distribu- 
tion of  geopotential  anomaly  at  the  sea  surface  of 
the  eastern  intertropical  Pacific  Ocean  from  Feb- 
ruary 1967  to  April  1968  and  to  discuss  the  varia- 
tions of  the  circulation  revealed  by  these  maps. 
Each  map  represents  a  2-mo  period  during  the 
EASTROPAC  expedition,  which  was  an  interna- 
tional cooperative  oceanographic  investigation 
coordinated  by  the  Bureau  of  Commercial 
Fisheries  (now  National  Marine  Fisheries  Ser- 
vice). 

Prior  to  EASTROPAC  a  considerable  number  of 
expeditions  took  place  in  the  eastern  intertropical 
Pacific  Ocean;  consequently,  its  principal  ocean- 
ographic features  were  reasonably  well  known 
(e.g.,  Wooster  and  Cromwell,  1958;  Bennett,  1963; 
Wyrtki,  1966,  1967;  Tsuchiya,  1968;  Stroup, 
1969).  However,  the  accumulated  data  were  too 
sparse  in  time  and  space  to  give  insight  into 
monthly  or  seasonal  variations  in  the  distribution 
of  oceanographic  properties.  The  EASTROPAC 
expedition  was  designed  to  acquire  data  to  bring  to 
light  these  time  variations. 


'Institute  of  Marine  Resources,  Scripps  Institution  of 
Oceanography,  University  of  California  at  San  Diego,  La  JoUa, 
CA  92037. 


Manuscript  accepted  January  1974. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 


The  expedition  was  divided  into  seven  2-mo 
cruise  periods.  During  each  period,  a  single-ship 
or  multiship  cruise  was  carried  out.  Multiship 
cruises  took  place  in  February-March,  August- 
September  1967,  and  February- April  1968.  These 
cruises  covered  the  area  between  lat.  20°N  and 
20°S  (15°S  in  August-September  1967)  and  from 
the  coast  of  the  American  continents  westward  to 
long.  119°W  (126°W  in  February-March  1967). 
Single-ship  cruises  took  place  in  April-May, 
June-July,  October-November  1967,  and  De- 
cember 1967-January  1968  in  time  intervals  be- 
tween the  multiship  cruise  periods.  Each  of  these 
cruises  covered  the  area  between  lat.  20°N  and  3°S 
and  between  long.  98°  and  119°W. 

Details  of  the  observational  program,  the  list  of 
participating  vessels,  and  track  charts  have  been 
published  in  the  EASTROPAC  atlas  (Love, 
1972a). 

DATA 

Almost  all  EASTROPAC  stations  with  observa- 
tions to  500  m  or  deeper  were  used  in  this  study. 
These  stations  are  listed  in  Table  1  and  can  be 
identified  on  the  track  charts  included  in  the 
EASTROPAC  atlas  (Love,  1972a). 

1075 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  1. — List  of  stations  used  in  Figures  1-7. 


Number 

of 

Ship  and 

stations 

Data 

Figure 

cruise 

Stations 

Dates 

used 

type' 

number 

Argo  11 

2.  25-328 

25  Jan. -2  Mar.  1967 

152 

a 

Jordan  12 

2-284 

12  Feb. -21  Mar,  1967 

129 

a 

Fig.  1 

Rockaway  13 

1-265,  318-342 

1  Feb. -20  Mar.  1967 

129 

b 

Alaminos  14 

1-101,  110-159,  194-267,  301, 
309,  332,  333,  340-342 

31  Jan. -3  Apr.  1967 

143 
Total  553 

a,  b 

Jordan  20 

5-264 

13  Apr.-24  May  1967 

129 

a 

Fig.  2 

Jordan  30 

8-264 

17  June-27  July  1967 

149 

a,  c 

Fig.  3 

Washington  45 

7-206,  282-387 

6  Aug. -15  Sept.  1967 

177 

a 

Undaunted  46 

2-189 

16  Aug  -22  Sept    1967 

141 

a 

Fig.  4 

flockaivay  47 

1-40,  49-113,  124-258,  268-382, 
402-527 

1  Aug.-23  Sept.  1967 

212 
Total  530 

b 

Jordan  50 

5-249 

20  Oct. -26  Nov.  1967 

126 

a 

Fig.  5 

Jordan  60 

2-289 

21  Dec.  1967-28  Jan.  1968 

166 

a 

Fig.  6 

Washington  75 

1-144,  187-258 

18  Feb. -8  Apr.  1968 

160 

a 

Jordan  76 

1-255 

21  Feb. -30  Mar.  1968 

131 

a 

Fig.  7 

floc/oway  77 

6-103,  113-278,  302-438,  475-571 

30  Jan. -18  Apr   1968 

263 
Total  554 

b 

'a:  STD  digital  data  logger;  b:  STD  analogue  ctiarts;  c:  Nansen-bottle  casts. 


Temperature  and  salinity  data  used  for  comput- 
ing geopotential  anomaly  were  collected  with  in 
situ  salinity-temperature-depth  recorders  (STD) 
except  for  those  from  EASTROPAC  cruise  David 
Starr  Jordan  30,  on  which  a  breakdown  of  the  STD 
necessitated  the  use  of  Nansen  bottles  during  the 
last  half  of  the  cruise.  Most  of  the  STD  data  were 
obtained  from  digital  data  loggers,  but  some  were 
digitized  from  analogue  charts  (Table  1).  The 
method  of  processing  STD  data  is  described  in  the 
EASTROPAC  atlas  (Love,  1972a). 

From  these  temperature  and  salinity  data, 
geopotential  anomaly  at  the  sea  surface  was  com- 
puted with  reference  to  500  db.  Because  of  rela- 
tively homogeneous  water  at  depths  greater  than 
500  m  in  the  intertropical  ocean,  this  reference  is 
believed  to  be  adequately  deep  for  estimating  the 
geostrophic  current  at  the  sea  surface.  The  unit  of 
geopotential  anomaly  is  chosen  to  be  joule  per 
kilogram  (abbreviated  J/kg;  equivalent  to 
dynamic  decimeter). 

Computed  geopotential  anomaly  was  plotted  on 
each  map,  and  smooth  isopleths  were  drawn  at 
intervals  of  1.0  or  0.5  J/kg.  The  base  map  is  a 
Mercator  projection  and  was  adapted  from  U.S. 
Navy  H.  O.  526  and  823. 

THE  SURFACE  GEOSTROPHIC 
FLOW 

The  surface  geostrophic  flow  revealed  by  the 

1076 


maps  of  geopotential  anomaly  is  described  below. 
A  comparison  of  these  maps  with  other  maps 
based  on  long-term  averages  of  set  and  drift  of 
ships  is  also  made.  The  atlas  of  the  monthly  aver- 
age surface  currents  in  the  eastern  North  Pacific 
published  by  the  U.S.  Navy  Hydrographic  Office 
(H.  O.  570,  1947)  and  the  atlas  of  the  quarterly 
average  surface  currents  in  the  South  Pacific  pub- 
lished by  the  Meteorological  Office  (M.  O.  435, 
1939)  are  pertinent  to  the  comparison.  There  are 
also  monthly  drift  charts  by  Cromwell  and  Ben- 
nett ( 1959)  for  the  northern  hemisphere  and  those 
by  Puis  (1895)  and  Wyrtki  (1965)  for  both  hemi- 
spheres. The  charts  by  Cromwell  and  Bennett  are 
simply  a  different  presentation  of  the  H.  O.  570 
charts  for  the  area  east  of  long.  120°W  and  south  of 
lat.  30°N.  Puis'  charts  show  the  current  direction 
and  relative  intensity  for  the  area  between  lat. 
20°N  and  10°S.  Wyrtki's  charts  are  based  on  aver- 
ages over  1-degree  squares,  but  it  is  not  clear  how 
he  smoothed  or  interpolated  the  original  1-degree 
averages  to  obtain  the  current  patterns  shown  on 
his  charts. 

Various  sources  of  errors  and  disparities  in  the 
geostrophic  calculation  and  set-and-drift  observa- 
tions should  be  kept  in  mind.  Geopotential  anom- 
aly computed  from  oceanographic  data  may  in- 
clude short-period  density  fluctuations  that  are 
not  necessarily  associated  with  fluctuations  of  the 
actual  current.  The  calculation  of  geostrophic  flow 
neglects  the  direct  frictional  effect  of  wind  stress. 


TSUCHIYA:  SURFACE  GEOSTROPHIC  FLOW 


On  the  other  hand,  set-and-drift  observations  are 
affected  by  strong  winds,  sea,  swell,  and  tidal  cur- 
rents. 

South  Equatorial  Current  Region 

The  South  Equatorial  Current  is  well  defined 
west  of  long.  90°W  on  the  maps  for  February- 
March  1967,  August-September  1967,  and 
February- April  1968  (Figures  1,4,  and  7).  South  of 
lat.  10°S  the  direction  of  geostrophic  flow  is  pre- 
dominantly to  the  northwest,  whereas  the  drift 
charts  (Meteorological  Office,  1939;  Wyrtki,  1965) 
for  the  corresponding  months  indicate  that  the 
surface  current  flows  almost  due  west  in  this  re- 
gion. This  disagreement  may  be  due  to  the  effect  of 
the  Ekman  drift.  The  trade  winds  in  this  area  are 
from  the  southeast  to  east,  so  that  if  the  Ekman 
drift  is  added  to  the  geostrophic  flow,  the  resultant 
surface  current  would  be  nearly  to  the  west. 

North  of  lat.  10°S  the  South  Equatorial  Current 
becomes  more  zonal  and  flows  almost  due  west.  In 
February-March  1967  (Figure  1)  the  westward 
flow  of  the  South  Equatorial  Current  extends 
across  the  equator  to  about  lat.  5°N,  and  the  cur- 
rent near  the  equator  west  of  the  Galapagos  Is- 
lands is  also  westward.  In  April-May  1967  (Figure 
2)  the  westward  flow  of  the  South  Equatorial  Cur- 
rent is  interrupted  by  an  eastward  current  within 
about  2°  of  the  equator.  Puis'  (1895)  charts  of  the 
surface  current  for  March  and  April  clearly  show 
an  eastward  current  at  the  equator  between  long. 
110°W  and  the  Galapagos  Islands.  Such  an  east- 
ward current  can  be  interpreted  as  the  Equatorial 
Undercurrent  breaking  the  sea  surface  during 
local  weakening  of  the  easterly  trades  (Cromwell, 
Montgomery,  and  Stroup,  1954;  Montgomery, 
1962;  Montgomery  and  Stroup,  1962:59-60).  Jones 
(1969)  has  presented  evidence  of  a  surfacing  of  the 
Undercurrent  on  the  basis  of  direct  current  mea- 
surements made  at  long.  98°W  in  April  1968 
(EASTROPAC  cruise  Thomas  Washington  75). 
The  distribution  of  geopotential  anomaly  from 
this  cruise,  however,  does  not  suggest  a  surfacing 
of  the  Undercurrent  (Figure  7). 

On  the  other  maps  (Figures  3-7)  flow  is  west- 
ward from  the  equator  to  about  lat.  5°N,  and  in 
some  longitudes  an  eastward  current  is  revealed 
just  south  of  the  equator,  because  geopotential 
anomaly  does  not  show  a  minimum  at  the  equator 
but  a  few  degrees  of  latitude  south  of  the  equator. 
The  same  distribution  of  geopotential  anomaly 
can  be  seen  on  Bennett's  (1963,  Figure  6)  map 


based  on  EASTROPIC  data.  This  distribution  is 
associated  with  a  thermocline  ridge  that  tends  to 
occur  at  lat.  1°-3°S  (instead  of  the  equator)  in  the 
eastern  Pacific.  This  southward  displacement  of 
the  ridge  from  the  equator  is  clearly  evident  on 
many  of  EASTROPAC  vertical  sections  of  tem- 
perature or  thermosteric  anomaly  and  maps  of  the 
topography  of  the  300-cl/t  isanosteric  surface, 
which  lies  close  to  the  center  of  the  thermocline 
(Love,  1971,  1972b,  1973,  in  press).  According  to 
Cromwell's  (1953)  simple  model  of  the  wind- 
driven  meridional  circulation,  the  direction  of  the 
wind  near  the  equator  determines  the  position  of 
the  maximum  divergence  of  the  Ekman  transport 
in  the  surface  layer.  He  points  out  that  the  merid- 
ional component  of  the  southeast  trades  shifts  the 
maximum  divergence,  which  would  correspond  to 
a  ridge  of  the  thermocline,  to  the  south  of  the 
equator. 

The  eastward  geostrophic  flow  between  the 
equator  and  the  ridge  was  first  discussed  by  Aus- 
tin ( 1960)  and  later  commented  upon  by  Stroup 
(1969:35).  It  is  not  certain,  however,  that  the  ac- 
tual surface  current  is  eastward  south  of  the 
equator.  Estimates  of  the  magnitudes  of  terms  in 
the  equation  of  motion  suggest  that  the  southward 
pressure  gradient  is  in  approximate  balance  with 
the  northward  component  of  wind  stress.  The  M. 
O.  435  drift  chart  for  the  May-July  quarter  shows 
very  weak  easterly  components  just  south  of  the 
equator  at  long.  100°-110°W  between  strong 
westward  currents  to  the  north  and  south.  The 
drift  charts  for  the  other  quarters  show  no  evi- 
dence of  an  eastward  current  south  of  the  equator. 

The  southern-summer  maps  (Figures  1  and  7) 
exhibit  a  weak  eastward  current  along  about  lat. 
10°S  from  long.  112°W  to  about  90°W.  Examina- 
tion of  vertical  sections  of  temperature  and  maps 
of  surface  temperature  in  the  EASTROPAC  atlas 
(Love,  1972a,  in  press)  indicates  that  this  current 
is  associated  with  a  slight  southward  shoaling  of  a 
shallow  summer  thermocline  and  with  a  merid- 
ional temperature  gradient  developed  during 
summer  between  a  pool  of  warm  surface  water 
south  of  the  equator  and  cold  surface  water  farther 
south  that  appears  to  be  coming  from  the  Chile 
Current  (Wooster,  1970).  This  suggests  that  the 
eastward  geostrophic  current  along  lat.  10°S  is 
found  only  in  southern  summer.  (It  is  interesting 
to  note  that  the  North  Equatorial  Countercurrent, 
which  flows  east  at  roughly  the  same  latitude  in 
the  northern  hemisphere,  is  most  strongly  de- 
veloped during  the  same  season,  i.e.,  northern 


1077 


30'U|i|l|l|ljl|l|l|l|l 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 
80°  70° 


Figure  1. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  February- 
March  1967.  EASTROPAC  cruises  Ar^go  11,  David  Starr  Jordan  12, Rockaway  13,  and  Alaminos  14.  The  position  of  the  intertropical 
convergence  zone  at  the  eastern  and  western  ends  of  the  map  is  indicated  by  triangles. 


summer.)  However,  the  coverage  of  the 
southern-winter  map  (Figure  4)  is  limited  to  lat. 
10°S,  and  this  suggestion  cannot  be  confirmed  by 
winter  data.  None  of  the  drift  charts  examined 
shows  an  eastward  current  near  this  latitude  in 
the  eastern  South  Pacific,  but  their  data  are  too 
sparse  to  draw  a  definite  conclusion.  Because  of  its 
low  speed,  the  countercurrent,  indicated  by  the 
distribution  of  geopotential  anomaly  (Figures  1 
and  7),  may  well  be  buried  in  the  westward  Ekman 
drift  due  to  the  prevailing  southeasterly  trades 
and  may  be  observed  only  when  the  trade  winds 
are  unusually  weak. 


Peru  Current 

In  the  region  south  of  the  equator  and  between 
long.  90°W  and  the  coast  of  South  America,  the 
distribution  of  geopotential  anomaly  is  irregular, 
and  its  spatial  variation  is  not  large  (Figures  1,  4, 
and  7).  This  distribution  suggests  a  dominance  of 
weak  and  broad  flow  with  small-scale  ir- 
regularities such  as  eddies  and  countercurrents 
(Wooster  and  Reid,  1963;  Wyrtki,  1963).  Partly 
because  of  this  fact  and  partly  because  of  a  rather 
inadequate  orientation  of  ship  tracks  in  this  area, 
contouring  is  difficult;  there  are  many  other  ways 


1078 


TSUCHIYA:  SURFACE  GEOSTROPHIC  FLOW 

130"  120°  no 


30' 


I  I  I  I  I  I  I  I  I  I  I  I  U  I  I  I  I  I 


,! '  I '  I '  I '  I  M  '  I '  I '  1 1 1  M  1 1 '  I '  1 1 1 1 1 1  M 

Geopotential   Anomaly,  J/kg 

0  db   Over  500    db 

April -May  1967 


20' 


10° 


0° 


10° 


1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  i  1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1  L 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 


iiii Iiiiiiiii- 


130° 


120° 


110° 


100° 


90° 


80° 


70° 


Figure  2. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  April-May 
1967.  EASTROPAC  cruise,  Dai'jc?  Starr  Jordan  20.  The  position  of  the  intertropical  convergence  zone  at  the  eastern  and  western  ends 
of  the  map  is  indicated  by  triangles. 


to  draw  isopleths.  Consequently,  the  deduced, 
geostrophic-flow  pattern  is  not  everywhere  reli- 
able. Nevertheless,  the  general  trend  of  flow  indi- 
cated by  the  present  maps  is  parallel  to  the  coast 
and  toward  the  equator.  There  is  not  much  change 
in  general  flow  patterns  during  the  EASTROPAC 
period. 

Eastern  Boundary  Currents  in 
the  Northern  Hemisphere 

In  this  region  flow  also  tends  to  follow  the 
coastline.  On  the  map  for  February-March  1967 
(Figure  1),  there  is  an  indication  of  a  northward 
current,  the  Colombia  Current  (Wooster,  1959; 
Stevenson,  1970),  flowing  close  to  the  coast  of  Co- 
lombia toward  the  Gulf  of  Panama.  On  the  maps 
for  August-September  1967  and  February- April 
1968  (Figures  4  and  7)  the  distribution  of  stations 
is  inadequate  for  defining  the  Colombia  Current. 

Off  Costa  Rica  the  direction  of  flow  varies,  de- 


pending on  the  development  of  an  anticyclonic 
eddy  farther  offshore.  The  strong  southeastward 
flow  indicated  by  the  map  for  February-March 
1967  (Figure  1)  is  associated  with  the  northern 
edge  of  an  anticyclonic  eddy  centered  at  lat.  5°N, 
long.  85°W.  A  similar  anticyclonic  eddy  is  ob- 
served in  February-April  1968  (Figure  7),  but  is 
centered  at  lat.  5°N,  long.  88°W,  farther  west 
than  in  1967;  and  the  flow  near  the  coast  of  Costa 
Rica  is  northwestward.  As  Puis  (1895:24  and  27), 
Cromwell  (1958),  and  Wyrtki  (1965)  have  noted, 
their  drift  charts  also  show  a  well-developed  an- 
ticyclonic eddy  in  this  area  from  February  to 
March.  This  anticyclonic  eddy  seems  to  be  a  nor- 
mal feature  in  these  months.  In  August- 
September  (Figure  4),  when  no  such  anticyclonic 
eddy  develops,  the  area  off  the  coast  of  Costa  Rica 
is  dominated  by  the  northwestward  return  flow  of 
the  North  Equatorial  Countercurrent. 

A  cyclonic  circulation  is  well  developed  around 
the  Costa  Rica  thermal  dome  centered  near  lat. 


1079 


\Z0' 


30°  M  1 1 1 1 1 1 1 1 1 1 1 1  M  M 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 
80°  70° 


I  I  I  I  I  I  I  I  U  30' 


20' 


10° 


10° 


-I  I  I  I  I  I  '  I  I  I  I  1  I  i  I  I  I  I  I  I  ■  I  I  I  I  I  I  I  I  I  i  I  I  I  I  I  i  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  1  I  I  I  ■  1  I  I  I  I  I  I  ■  I  ■  I  I  I  .  I  I  i  ■  I  I  I  i  I  i 


130° 


120° 


110° 


100° 


90° 


80° 


70° 


Figure  3. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  June-July 
1967.  EASTROPAC  cruise  ZJacfc/  Starr  Jordan  30.  The  position  of  the  intertropical  convergence  zone  at  the  eastern  and  western  ends 
of  the  map  is  indicated  by  triangles. 


9°N,  long.  89°W  (Brandhorst,  1958;  Cromwell, 
1958;  Wooster  and  Cromwell,  1958;  Wyrtki, 
1964)  in  February-March  1967  and  February- 
April  1968  (Figures  1  and  7),  but  is  less  well 
defined  in  August-September  1967  (Figure  4). 

Between  Costa  Rica  and  Cape  Corrientes  (lat. 
20°N),  nearshore  flow  is  generally  northwestward 
in  August-September  (Figure  4),  when  the  North 
Equatorial  Countercurrent  is  strongly  developed. 
In  the  other  months  (Figures  1-3  and  5-7)  flow  is 
southeastward  from  Cape  Corrientes  at  least  as 
far  south  as  the  Gulf  of  Tehuantepec  (lat.  16°N). 
This  sense  of  flow  is  in  agreement  with  that  found 
on  the  H.  O.  570  drift  charts  except  for  June- July, 
when  the  nearshore  current  is  northwestward  on 
the  drift  charts.  Puis'  (1895)  charts,  however,  in- 
dicate easterly  components  of  flow  near  the  coast 
between  Cape  Corrientes  and  the  Gulf  of  Tehuan- 
tepec in  all  months  of  the  year. 


North  Equatorial  Countercurrent 

Previous  studies  (e.g.,  Wyrtki,  1965)  have  indi- 
cated that  the  North  Equatorial  Countercurrent 
is  subject  to  a  large  variation  in  response  to  that 
of  the  atmospheric  circulation,  particularly  the 
annual  meridional  migration  of  the  intertropical 
convergence  zone  (ITCZ).  During  EASTROPAC 
the  North  Equatorial  Countercurrent  exhibited  a 
high  level  of  variability  in  position  and  intensity. 
The  Countercurrent  was  weak  and  discontinuous 
in  February-April  1967  and  1968,  when  the  ITCZ 
lay  near  its  southernmost  position  at  lat.  2°-6°N. 
It  was  strong,  broad,  and  extended  all  the  way  to 
the  coast  of  Costa  Rica  in  August-September 
1967,  when  the  ITCZ  lay  near  its  northernmost 
position  at  lat.  11°-15°N.  (The  position  of  the 
ITCZ  during  EASTROPAC  can  be  inferred  from 
surface-wind  charts  in  the  EASTROPAC  atlas. 


1080 


TSUCHIYA:  SURFACE  GEOSTROPHIC  FLOW 

120"  110 


I  SO- 
SO"  njTjT] 


20' 


90° 80' 

'l'|i|'|'M|'|i|'|iM|iMI'|M 


Geopotential   Anomaly,  J/kg 

0  db   Over  500    db 
August  -  September  1967 


70' 

I  I  I  I  I  L]  30° 


10° 


10° 


20° 


■10 
9  5 
9 


''I I  '  I I  .  I  .  I  .  I  I  I  I  I  I  I  I  I  I  I  , I  I  I  I  I  ,  I  I  I  I  I  ,  I  ,  I  I  I  ,  I  I  I  I  I  I  I  I  I  I  I  ,  I  I  I  I  I  I  I  I  I  I  I  I  I  :  I  .  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  l1 

130°  120°  110°  100°  90°  80°  70° 

Figure  4. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  August- 
September  1967.  EASTROPAC  cruises  Thomas  Washington  45,  Undaunted  46,  and  Rockaway  47.  The  position  of  the  intertropical 
convergence  zone  at  the  eastern  and  western  ends  of  the  map  is  indicated  by  triangles. 


The  position  at  the  easternmost  and  westernmost 
meridional  sections  is  indicated  by  triangles  on 
each  map  in  Figures  1-7.) 

In  February-March  1967  (Figure  1)  the  North 
Equatorial  Countercurrent  is  present  between 
lat.  5°  and  8°N2  at  long.  126°  and  119°W,  but  it  is 
practically  missing  at  long.  112°W  and  only 
weakly  developed  at  long.  105°W.  At  long.  98°W 


^Near  the  northern  edge  of  the  North  Equatorial  Countercur- 
rent, flow  is  usually  weak,  and  the  current  boundary  is  not 
always  well  defined  by  the  distribution  of  geopotential  anomaly. 
The  northern  boundary  cited  here  is  that  of  the  band  of  strong 
current.  Weak  eastward  flow  may  extend  farther  north. 


the  Countercurrent  is  entirely  absent.  From  long. 
95°  to  85°W  a  strong  eastward  current,  which  can 
be  identified  as  the  North  Equatorial  Counter- 
current,  is  found  along  lat.  5°-6°N  between  the 
cyclonic  and  anticyclonic  eddies  mentioned  ear- 
lier. In  April-May  (Figure  2)  no  countercurrent  is 
found  at  long.  119°,  112°,  and  105°W,  but  a  strong 
countercurrent  is  indicated  between  lat.  4°  and 
7°N  at  long.  98°W.  In  April-May  the  ITCZ  starts 
returning  to  the  north  and  is  located  north  of  lat. 
6°N. 

The  development  of  the  North  Equatorial 
Countercurrent  in  February- April  1968  (Figure 


1081 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


90°  80° 70* 

I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  I  ij  30' 


110°  100° 

Figure  5. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  October- 
November  1967.  EASTROPAC  cruise  David  Starr  Jordan  50.  The  position  of  the  intertropical  convergence  zone  at  the  eastern  and 
western  ends  of  the  map  is  indicated  by  triangles. 


7)  is  much  like  that  in  February- April  1967  (Fig- 
ure 1).  In  1968  the  Countercurrent  is  present  be- 
tween lat.  4°  and  7°N  at  long.  119°,  112°,  and 
105°W,  but  is  not  found  at  long.  98°  and  95°W. 
Farther  east  at  long.  88°  and  85°W  the  Counter- 
current  is  strongly  developed  along  lat.  5°-8°N  be- 
tween cyclonic  and  anticyclonic  eddies  similar  to 
those  observed  in  1967. 

By  June-July  1967  (Figure  3)  the  North 
Equatorial  Countercurrent  is  well  established 
between  lat.  6°  and  10°N  on  all  four  meridional 
sections.  In  Figure  3  a  weak  eastward  current, 
separated  from  the  Countercurrent  by  a  narrow 
band  of  westward  flow,  can  be  seen  about  200  km 
south  of  the  southern  boundary  of  the  Counter- 
current.  This  secondary  countercurrent  repre- 
sents a  surfacing  of  a  narrow  but  stable  sub- 
surface eastward  current,  which  has  its  maximum 
speed  at  a  depth  of  50-200  m  just  south  of  the 
North  Equatorial  Countercurrent  (Tsuchiya, 
1972). 


In  August-September  (Figure  4)  the  North 
Equatorial  Countercurrent  is  fully  developed  and 
extends  east  to  the  coast  of  Costa  Rica,  where  it 
turns  to  the  northwest  along  the  coast.  In  these 
months  the  Countercurrent  is  wider  and  is  lo- 
cated farther  north  than  in  the  February-April 
periods  of  1967  and  1968.  In  August-September  it 
lies  between  lat.  7°  and  11°N  at  long.  119°  and 
112°W  and  between  lat.  5°  and  10°N  east  of  long. 
105°W  (Figure  4).  About  the  same  condition  con- 
tinues through  November  (Figure  5),  although 
the  ITCZ  starts  shifting  south  in  October.  In 
December-January  (Figure  6)  the  Countercur- 
rent starts  moving  south,  following  the  ITCZ's 
southward  shift,  which  began  2  mo  earlier. 

The  variation  of  the  North  Equatorial  Coun- 
tercurrent revealed  by  the  present  maps  of  geopo- 
tential anomaly  generally  agrees  with  the  results 
of  set-and-drift  observations  discussed  by  Puis 
( 1895),  Cromwell  and  Bennett  ( 1959),  and  Wyrtki 
(1965). 


1082 


TSUCHIYA:  SURFACE  GEOSTROPHIC  FLOW 

130°  120"  110 


30' 


-iMI'|i|i|i|'IMMi 


20' 


10° 


10° 


1 1 1 1 1 1 1 '  M 1 1  m  30' 


Geopotential   Anomaly,  J/kg 

0  db   Over  500    db 

December  1967-  January  1968 


-I  I  I  I  I  I  I  I  i  I  I  I  I  I  I  I  I  I 


lilililililiM'I'I'l I'I'li 


70° 


130°  120°  110°  100°  90°  80° 

Figure  6. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  December 
1967-January  1968.  E  ASTROPAC  cruise  David  Starr  Jordan  60.  The  position  of  the  intertropical  convergence  zone  at  the  eastern 
and  western  ends  of  the  map  is  indicated  by  triangles. 


North  Equatorial  Current 
Region 

North  of  the  North  Equatorial  Countercurrent, 
the  North  Equatorial  Current  is  found  on  all 
seven  maps  (Figures  1-7).  On  the  maps  for 
February-March  1967  and  February-April  1968 
(Figures  1  and  7)  the  westward  flow  of  the  North 
Equatorial  Current  starts  off  the  Gulf  of  Tehuan- 
tepec  with  a  major  contribution  of  water  coming 
from  the  northwest  along  the  Mexican  coast. 
Water  coming,  from  the  southeast  appears  to  re- 
turn to  the  east  forming  a  cyclonic  eddy  around 
the  Costa  Rica  thermal  dome. 

In  February-March  1967  (Figure  1)  the  North 
Equatorial  Current  is  interrupted  by  a  continu- 
ous eastward  flow  indicated  along  lat.  15°N  from 
long.  126°W  to  the  coast  of  Mexico,  where  it  turns 
to  the  south  to  feed  the  North  Equatorial  Cur- 
rent. This  eastward  flow  is  broadly  developed  at 


long.  112°W  and  extends  from  lat.  10°  to  18°N. 
There  is  a  suggestion  that  a  similar  eastward 
flow  is  present  in  April-May  1967  and 
February- April  1968  (Figures  2  and  7).  Reid's 
(1961)  map  of  the  surface  geostrophic  flow  also 
indicates  an  eastward  current  at  about  the  same 
latitude  from  long.  130°  to  95°W,  but  his  data  in 
this  area  are  principally  from  northern  fall  and 
winter.  The  surface  drift  charts  (Puis,  1895;  U.S. 
Navy  Hydrographic  Office,  1947)  do  not  show 
such  an  eastward  flow  west  of  long.  110°W,  possi- 
bly because  of  the  westward  Ekman  drift  and 
leeway  of  ships  due  to  the  strong  northeasterly 
trades. 

On  the  map  for  August-September  (Figure  4) 
the  North  Equatorial  Current  starts  off  the  coast 
of  Costa  Rica.  East  of  long.  100°W  it  is  fed  almost 
entirely  by  the  return  flow  of  the  North  Equator- 
ial Countercurrent,  which  is  fully  developed  in 
these  months. 


1083 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 
60°  70'. 


Figure  7. — Geopotential  anomaly,  in  joules  per  kilogram  (dynamic  decimeters),  at  the  sea  surface  relative  to  500  db  in  February- 
April  1968.  EASTROPAC  cruises  r/!owa.s  Washington  75, David  Starr  Jordan  76,  and  Rockaway  77.  The  position  of  the  intertropical 
convergence  zone  at  the  eastern  and  western  ends  of  the  map  is  indicated  by  triangles. 


DISCUSSION 

As  was  noted  earlier,  geopotential  anomaly 
computed  from  oceanographic  data  contains 
short-period  nongeostrophic  fluctuations  of  the 
mass  field,  but  there  is  no  way  of  removing  them 
from  the  data.  Consequently,  not  all  of  the  fea- 
tures indicated  by  the  present  maps  may  be  real. 
Despite  this  problem,  EASTROPAC  data  are 
unique  in  their  time  and  space  coverage  and  in 
the  close  spacing  of  stations  on  tightly  coordi- 
nated ship  tracks  and,  thus,  reveal  some  interest- 


ing features  that  have  not  been  observed  previ- 
ously. 

A  zonal  discontinuity  of  the  North  Equatorial 
Countercurrent  in  the  months  when  the  ITCZ  lies 
near  its  southernmost  position  is  suggested  by 
the  monthly  average  drift  charts  (U.S.  Navy 
Hydrographic  Office,  1947;  Wyrtki,  1965);  how- 
ever, the  present  maps  (Figures  1,  2,  and  7)  are 
the  first  to  show  it  on  the  basis  of  quasi-synoptic 
oceanographic  data  from  the  entire  eastern  inter- 
tropical North  Pacific.  (It  is  highly  unlikely  that 
the  breakup  of  the  Countercurrent  as  shown  on 


1084 


TSUCHIYA:  SURFACE  GEOSTROPHIC  FLOW 


these  maps  is  an  artifact  of  short-period 
fluctuations  of  the  mass  field.)  In  these  months 
the  Countercurrent  shows  a  drastic  change  in  in- 
tensity; its  rapid  disappearance  and  reappear- 
ance on  this  sequence  of  maps  (Figures  1-3,  6,  and 
7)  are  remarkable.  The  maps  demonstrate  that 
the  Countercurrent  can  either  disintegrate  or 
reestablish  itself  on  a  time  scale  less  than  2  mo. 

A  comparison  of  the  present  maps  (Figures  1-7) 
with  meteorological  charts  in  the  EASTROPAC 
atlas  (Love,  1971,  1972a,  1972b,  1973,  in  press. 
See  also  the  position  of  the  ITCZ  indicated  at  the 
eastern  and  western  ends  of  each  map.)  reveals  a 
rather  good  correlation  between  the  positions  of 
the  North  Equatorial  Countercurrent  and  the 
ITCZ.  The  northern  boundary  of  the  Countercur- 
rent (minimum  of  geopotential  anomaly)  coin- 
cides approximately  with  the  ITCZ  except  in 
February-March  and  August-September.  In 
February-March  the  southern  boundary  of  the 
Countercurrent,  if  it  is  present,  more  nearly  coin- 
cides with  the  ITCZ;  in  August-September  the 
ITCZ  is  located  far  to  the  north  of  the  northern 
boundary.  This  finding  is  in  agreement  with  what 
can  be  seen  on  Wyrtki's  ( 1965)  long-term  average 
charts. 

There  is  a  high  degree  of  similarity  in 
geostrophic-flow  patterns  between  February- 
March  1967  (Figure  1)  and  February- April  1968 
(Figure  7).  The  major  features  are  much  the  same 
for  the  two  maps;  even  the  development  of  the 
cyclonic  and  anticyclonic  eddies  off  Costa  Rica, 
the  discontinuity  of  the  North  Equatorial  Coun- 
tercurrent near  long.  98°W,  and  the  eastward 
flow  along  about  lat.  10°S  are  similar.  In  view  of 
the  large  variations  observed  between  the  two 
cruise  periods,  this  similarity  is  perhaps  surpris- 
ing. The  only  notable  difference  is  the  latitude  of 
the  minimum  of  geopotential  anomaly  near  the 
equator  (discussed  in  the  preceding  section)  west 
of  the  Galapagos  Islands;  the  minimum  is  located 
at  the  equator  in  1967  (Figure  1),  while  it  is  lo- 
cated a  few  degrees  south  of  the  equator  in  1968 
(Figure  7).  The  southward  shift  of  the  minimum 
in  Figure  7  is  probably  due  to  the  more  southerly 
trade  winds  near  the  equator  in  1968  than  in 
1967  (Cromwell,  1953). 

The  eastward  current  indicated  along  about 
lat.  10°S  on  the  southern-summer  maps  (Figures 
1  and  7)  is  of  particular  interest,  because  no  pre- 
vious data  from  the  eastern  Pacific  have  sug- 
gested it.  This  countercurrent  is  very  weak  (the 
average  geostrophic  speed  from  seven  meridional 


sections  is  7  cm/s)  and  was  not  noticed  in  earlier 
examination  of  vertical  sections  based  on  EAS- 
TROPAC data  (Tsuchiya,  1972).  It  is  a  narrow  and 
thin  current  (about  50  m  thick)  and  is  completely 
separate  from  a  subsurface  eastward  current 
which  has  its  maximum  speed  at  a  depth  of  70-200 
m  and  which  flows  along  about  lat.  6°S  (Stroup, 
1969;  Tsuchiya,  1972).=^  More  data  are  needed  to 
determine  the  relation  of  this  surface  eastward 
countercurrent  with  the  South  Equatorial  Count- 
ercurrent, which  is  well  developed  near  lat.  10°S 
at  the  sea  surface  of  the  central  and  western 
Pacific  (Reid,  1959,  1961;  Merle,  Rotschi,  and  Voi- 
turiez,  1969;  Rotschi,  1970;  Tsuchiya,  1970;  Don- 
guy  and  Rotschi,  1970).  As  was  mentioned  in  the 
preceding  section,  the  former  countercurrent  is 
defined  only  between  long.  112°W  and  long.  90°W 
and  is  not  found  in  the  west  of  the  EASTROPAC 
area. 

ACKNOWLEDGMENTS 

This  work  was  part  of  the  Scripps  Tuna  Ocean- 
ography Research  Program,  Institute  of  Marine 
Resources,  Scripps  Institution  of  Oceanography, 
and  was  supported  by  National  Science  Founda- 
tion Grant  GA-29748  and  by  Contract  03-3-208-36 
between  the  National  Marine  Fisheries  Service 
and  the  Institute  of  Marine  Resources.  Support 
was  also  provided  by  the  Marine  Life  Research 
Program  of  the  Scripps  Institution  of  Oceanog- 
raphy. 

I  especially  wish  to  thank  Daniel  R.  Cayan  for 
his  assistance  throughout  the  course  of  this  study. 
I  also  thank  Forrest  R.  Miller  for  supplying  some 
of  the  EASTROPAC  meteorological  data  prior  to 
publication. 

LITERATURE  CITED 

Austin,  T.  S. 

1960.  Oceanography  of  the  east  central  equatorial  Pacific 
as  observed  during  expedition  Eastropic.  U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  60:257-282. 
Bennett,  E.  B. 

1963.  An  oceanographic  atlas  of  the  eastern  tropical  Pacific 
Ocean,  based  on  data  from  EASTROPIC  Expedition, 
October-December  1955.   [In  Engl,  and  Span.]   Bull. 
Inter-Am.  Trop.  Tuna  Comm.  8:31-165. 
Brandhorst,  W. 

1958.  Thermocline  topography,  zooplankton  standing 
crop,  and  mechanisms  of  fertilization  in  the  eastern  trop- 
ical Pacific.  J.  Cons.  24:16-31. 


^A  detailed  report  on  this  subsurface  eastward  countercurrent 
is  being  prepared  for  publication  elsewhere. 


1085 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


U.S.  Dep.  Commer. 


U.S 


Cromwell,  T. 

1953.  Circulation  in  a  meridional  plane  in  the  central 
equatorial  Pacific.  J.  Mar.  Res.  12:196-213. 

1958.  Thermocline  topography,  horizontal  currents  and 
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Span.]  Bull.  Inter- Am.  Trop.  Tuna  Comm.  3:133-164. 

Cromwell,  T.,  and  E.  B.  Bennett. 

1959.  Surface  drift  charts  for  the  Eastern  Tropical  Pacific 
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Comm.  3:215-237. 

Cromwell,  T.,  R.  B.  Montgomery,  and  E.  D.  Stroup. 

1954.  Equatorial  Undercurrent  in  Pacific  Ocean  revealed 
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DONGUY,  J.-R.,  AND  H.  ROSCHL 

1970.  Bur  un  courant  Est  dans  le  Pacifique  central  tropical 
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Jones,  J.  H. 

1969.  Surfacing  of  Pacific  Equatorial  Undercurrent:  direct 
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1971.  EASTROPAC  atlas.  Vol.  3. 
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1972a.  EASTROPAC  atlas.  Vol.   1. 

Natl.  Mar.  Fish.  Serv.,  Circ  330. 
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No.,  p.  91-98. 
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Lond.,  M.  O.  435,  3  tables,  11  fig.,  and  8  charts. 
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1962.  Equatorial  Undercurrent  observations  in  review.  J. 

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PULS,  C. 

1895.    Oberflachentemperaturen   und   Stromungsverhalt- 
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1959.  Evidence  of  a  South  Equatorial  Countercurrent  in 
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(editor),  Scientific  exploration  of  the  South  Pacific,  p. 

75-83.  Natl.  Acad.  Sci.  Wash.,  D.C. 
Stevenson,  M. 

1970.   Circulation  in  the  Panama  Bight.  J.  Geophys.  Res. 

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TSUCHIYA,  M. 

1968.  Upper  waters  of  the  intertropical  Pacific  Ocean. 
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U.S.  Navy  Hydrographic  Office. 

1947.   Atlas  of  surface  currents,  northeastern  Pacific 
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1959.  Oceanographic  observations  in  the  Panama  Bight, 
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Wooster,  W.  S.,  and  T.  Cromwell. 

1958.  An  oceanographic  description  of  the  eastern  tropical 
Pacific.  Bull.  Scripps  Inst.  Oceanogr.  7:169-282. 
Wooster,  W.  S.,  and  J.  L.  Reid,  Jr. 

1963.  Eastern  boundary  currents.  In  M.  N.  Hill  (editor). 
The  sea:  Ideas  and  observations  on  progress  in  the  study 
of  the  sea.  Vol.  2,  p.  253-280.  Interscience  Publ.,  N.Y. 
Wyrtki,  K. 

1963.  The  horizontal  and  vertical  field  of  motion  in  the 
Peru  Current.  Bull.  Scripps  Inst.  Oceanogr.  8:313-345. 

1964.  Upwelling  in  the  Costa  Rica  Dome.  U.S.  Fish  Wildl. 
Serv.,  Fish.  Bull.  63:355-372. 

1965.  Surface  currents  in  the  Eastern  Tropical  Pacific 
Ocean.  [In  Engl,  and  Span.]  Bull.  Inter-Am.  Trop.  Tuna 
Comm.  9:269-304. 

1966.  Oceanography  of  the  eastern  equatorial  Pacific 
Ocean.  Oceanogr.  Mar.  Biol.  Annu.  Rev.  4:33-68. 

1967.  Circulation  and  water  masses  in  the  eastern 
equatorial  Pacific  Ocean.  Int.  J.  Oceanol.  Limnol. 
1:117-147. 


1086 


THERMOREGULATORY  BEHAVIOR  AND 

DIEL  ACTIVITY  PATTERNS  OF  BLUEGILL, 

LEPOMIS  MACROCHIRUS,  FOLLOWING  THERMAL  SHOCK 


Thomas  L.  Beitinger^ 


ABSTRACT 


Individual  bluegill  were  allowed  to  thermoregulate  for  3  days  in  a  temperature-preference  apparatus 
and  then  were  exposed  for  30  min  to  one  of  three  temperature  treatments:  21.0°,  31.0°,  or  36.1°C.  Fish 
exposed  to  31°C  served  as  controls  for  handling  procedures.  Thermoregulatory  performance  of  surviv- 
ing fish  was  monitored  for  an  additional  3  days.  Pretreatment  results  indicated  mean  lower  and  upper 
avoidance  temperatures  of  29.3°  and  33. 1°,  and  3 1 .2°C  as  the  midpoint  of  the  preferred  range.  All  20  fish 
exposed  to  21°  and  31°C  survived  treatment  and  demonstrated  no  significant  differences  between 
pretreatment  and  posttreatment  thermoregulatory  performance.  Thirty-five  percent  offish  (7  of  20) 
exposed  to  36.1°C  died  during  treatment.  Fish  surviving  the  36.1°C  treatment  retained  the  ability  to 
thermoregulate;  however,  their  mean  lower  and  upper  avoidance  temperatures  increased  0.6°  and 
0.7°C,  respectively.  Activity  patterns  were  typically  diurnal,  but  variable,  in  all  three  treatment 
groups.  Immediately  after  treatment,  the  activity  offish  exposed  to  21°  and  36.1°C  was  markedly 
decreased.  Thereafter,  activity  tended  to  be  higher  in  the  21°C  group  and  lower  in  the  36.1°C  group 
than  during  the  pretreatment  p)eriod. 


Opportunities  for  temperature  shock  occur 
wherever  sharp  temperature  gradients  are  pres- 
ent. Fish  may  be  exposed  to  a  sudden  temperature 
change  when  penetrating  the  thermocline;  in 
areas  containing  springs,  upwellings  or  natural 
allochthonous  inputs  of  water;  in  sharp  horizontal 
temperature  gradients  characteristic  of  shallow 
waters;  and  during  the  passage  of  weatherfronts. 
Also,  fish  species  migrating  through  or  residing 
within  waters  under  the  influence  of  electric 
generating  companies  may  be  subjected  to  sudden 
temperature  changes. 

Investigations  concerning  thermal  shock  of 
fishes  have  mainly  been  limited  to  descriptions  of 
morbidity  stages  and  determinations  of  species' 
lethal  temperatures.  Noteworthy  exceptions  are 
studies  by  Sylvester  ( 1972)  and  Coutant  ( 1972a,  b, 
1973)  that  demonstrate  enhanced  vulnerability  of 
thermally  stressed  fishes  to  predation.  Fish  mor- 
talities owing  to  natural  and  artificially  induced 
temperature  shock  have  been  reported  in  marine, 
estuarine,     and     freshwater     environments 
(Gunther,  1936;  Gunter,  1941;  Huntsman,  1942; 
Gunter  and  Hildebrand,   1951;  Bailey,   1955; 
Threinen,  1958;  Colton,  1959;  Alabaster,  1963; 
Clark,  1969),  but  the  majority  of  work  has  in- 


'Laboratory  of  Limnology,  Department  of  Zoology,  Univer- 
sity of  Wisconsin,  Madison,  WI  53706. 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  3,  1974. 


volved  laboratory  determinations  of  thermal  re- 
sistance. 

An  important  question  is:  does  a  sublethal 
temperature  shock  disrupt  subsequent  ther- 
moregulatory behavior  of  a  fish?  The  objective  of 
this  study  was  to  assess  effects  of  temperature 
shock  upon  the  thermoregulatory  ability,  selected 
temperatures,  and  locomotor  activity  patterns  of 
individual  hluegiW,  Lepomis  macrochirus. 

MATERIALS  AND  METHODS 
Specimen 

Juvenile  bluegill  (mean  length  86.3  mm,  range 
72-105  mm)  were  captured  during  summer  with 
electroshocking  gear  from  Lake  Wingra  (Dane 
County,  Wis.)  and  maintained  in  the  laboratory  at 
25°C  under  constant  photoperiod  (LD  14:10  with 
0.5  h  dawn  and  dusk  intervals)  for  at  least  2  wk 
prior  to  experimentation.  Throughout  the  preex- 
perimental  and  experimental  periods  fish  were  fed 
pelleted  food  daily  at  1630  h  ±  15  min. 

Apparatus 

The  thermoregulatory  apparatus  was  derived 
from  that  of  Neill  and  Magnuson  (in  press)  with 
temperature  control  and  rate-change  modi- 

1087 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


fications  reported  by  Beitinger  et  al.  (in  press). 
The  design  (Neill,  Magnuson,  and  Chipman,  1972) 
substitutes  a  temperature  gradient  over  time 
for  the  spatial  gradient  typical  of  most  tempera- 
ture preference  studies  and  allows  an  individual 
fish  to  serve  as  its  own  tank  thermostat.  Each 
50-liter  test  tank  was  divided  into  halves  with 
a  molded  fiber  glass  partition.  A  tunnel  in  the 
partition  allowed  the  fish  to  choose  between  halves 
differing  by  a  fixed  2°C  temperature  interval. 
When  a  fish  selected  the  higher  temperature,  the 
temperature  of  the  tank  increased  at  a  constant 
rate  of  3°C/h  while  the  2°C  differential  between 
halves  remained  constant.  When  the  fish  moved  to 
the  cooler  tank  half,  the  temperature  decreased  at 
the  same  rate  (3°C/h)  until  the  fish  again  moved  to 
the  warmer  tank  half.  By  moving  from  one  side  to 
the  other,  a  fish  was  able  to  control  the  tempera- 
ture to  which  it  was  exposed.  For  this  study,  a 
potential  temperature  range  of  4°  to  55°C  was 
available. 

Temperatures  of  each  tank  half  were  monitored 
by  a  thermistor-wheatstone  bridge  circuit  con- 
nected to  a  multichannel  analog  recorder.  Avoid- 
ance temperatures  (i.e.,  turnaround  tempera- 
tures), preferred  temperature  range  and  midpoint 
of  the  preferred  range  (midpoint  temperature) 
were  the  same  as  defined  by  Neill  and  Magnuson 
(in  press).  During  the  experiment,  tunnel  passes, 
recorded  on  an  event  recorder,  were  utilized  as  a 
measure  of  fish  activity. 

PROCEDURE 

One  fish  was  introduced  per  tank  and  allowed  to 
experience  the  static  system  for  2.5  days  with  the 
tank  halves  set  at  24°  and  26°C.  The  test  period 


then  began  and  tank  temperature  control  was  re- 
linquished to  each  fish.  Thermoregulatory  per- 
formance during  the  second,  third,  and  fourth 
days  constituted  the  pretreatment  data.  Then  fish 
were  removed  and  individually  subjected  to  a  sud- 
den  temperature  change  in  3.5-liter  cylindrical 
chambers.  The  water  in  each  chamber  was  well 
aerated  and  "conditioned"  with  150  ml  of  that 
fish's  thermoregulatory  tank  water.  High  temper- 
ature treatment  was  36.1  ±  0.1°C  and  low  temper- 
ature treatment  was  21.0  ±  0.1°C.  For  control  pur- 
poses, a  third  group  offish  was  treated  at  31. 0± 
O.lC,  a  temperature  approximating  the  preferred 
range  midpoint  for  bluegill.  A  series  of  cursory 
experiments  indicated  that  fish  body  tempera- 
tures equilibrated  to  the  treatment  temperature 
during  exposure.  Fish  were  randomly  allocated  to 
the  three  treatment  temperatures.  Following  a 
30-min  exposure,  each  surviving  fish  was  re- 
turned to  its  respective  thermoregulatory  tank  for 
an  additional  3-day  posttreatment  period.  Ther- 
moregulatory tank  temperatures  at  fish  reentry 
were  the  same  as  those  at  fish  removal.  Finally, 
fish  were  isolated  and  observed  for  1  wk  for  possi- 
ble latent  effects. 

RESULTS 

Prior  to  treatment,  there  were  no  statistically 
significant  differences  in  thermoregulatory  per- 
formance among  the  three  groups  (Kruskal- 
Wallis  one  way  analysis  of  variance;  Siegel,  1956; 
lower  and  upper  avoidance  temperatures,  mid- 
point temperature,  and  width  of  preferred  range, 
all  F>0.20).  Fish  had  mean  lower  and  upper 
avoidance  temperatures  of  29.3°  and  33.1°C 
and  mean  preferred  range  width  of  3.8°C.  The 


Table  1. — Lower  and  upper  avoidance  temperatures,  preferred  range  midpoint  and  width,  pretreat- 
ment and  posttreatment,  for  each  of  the  three  groups.  Means  ±  standard  deviations  are  given. 


Controls 

Cold  shocked 

Heat  shocked 

Grand 

Item 

31.0=C 

21.0°C 

36.  rc 

mean 

N 

10 

10 

'12 

Lower  avoidance  temperature,  "C: 

Pretreatment 

29.4  ± 

0.7 

29.2  ± 

0.9 

29.4  ±  0.9 

29.3 

Posttreatment 

29.4  ± 

0.8 

29.1  ± 

1.0 

30.0  ±  0.8 

Upper  avoidance  temperature,  °C: 

Pretreatment 

33.1  ± 

0.6 

33.1  ± 

0.5 

33.1  ±  0.9 

33.1 

Posttreatment 

33.1  ± 

0.7 

33.1  ± 

0.5 

33.8  ±  0.9 

Midpoint  of  preferred  range,  °C: 

Pretreatment 

31 .3  ± 

0.6 

31 .2  ± 

0.6 

31 .2  ±  0.8 

31.2 

Posttreatment 

31 .2  ± 

0.7 

31.1  ± 

0.7 

31.9  ±  0.8 

Width  of  preferred  range,  °C: 

Pretreatment 

3.7  ± 

0.6 

3.8  ± 

0.7 

3.7  i  0.7 

3.7 

Posttreatment 

3.6  ± 

0.5 

4.0  ± 

0.8 

3.8  ±  0.5 

3.8 

'One  fish  survived  treatment  but  died  durmg  the  first  posttreatment  night,  owing  to  electronic  failure. 


1088 


BEITINGER:  THERMOREGULATORY  BEHAVIOR  OF  BLUEGILL 


midpoint  of  the  preferred  range  was  31.2°C 
(Table  1). 

Pretreatment  and  posttreatment  comparison  of 
preferred  range  midpoints  for  individual  fish  are 
illustrated  in  Figure  1.  Of  the  20  control  and  cold- 
treated  fish  ( lb,  a),  18  had  posttreatment  midpoint 


33- 
32- 


< 1 < 1- 


30         31  32         33 

PRETREATMENT   MIDPOINT    (°C) 


Figure  1. — Mean  preshock  and  postshock  midpoints  of  preferred 
range  for  individual  bluegills  in  each  of  the  treatment  groups. 
Points  falling  on  the  45°  line  indicate  no  change  in  midpoint 
temperatures. 


temperatures  within  0.3''C  of  their  pretreatment 
values.  None  of  the  individual  control  fish  had 
significant  pretreatment  and  posttreatment 
changes  in  mean  avoidance  temperatures  U-test, 
P>0.05).  Among  the  cold-treated  fish,  two  had 
significant  downward  changes  in  lower  avoidance 
temperatures  and  one  had  a  significant  downward 
change  in  its  upper  avoidance  temperature.  In  the 
control  and  cold-treated  groups,  five  fish  each  had 
lower  posttreatment  midpoint  temperatures; 
however,  there  were  no  significant  trends  (Wil- 
coxon  matched  pairs,  signed  ranks;  controls  and 
cold-treated  P>0. 10). 

Eleven  of  the  twelve  heat-treated  fish  had 
higher  posttreatment  midpoint  temperatures 
(Figure  Ic).  This  trend  was  highly  significant 
(Wilcoxon  matched  pairs,  signed  ranks,  P<0. 01). 
The  mean  posttreatment  midpoint  temperatures 
for  heat-treated  fish  during  each  of  the  3  days  were 
31.9°,  32.0°,  and  31.9°C,  indicating  no  return  to- 
wards the  pretreatment  preference  level. 

Whereas  all  of  the  control  and  cold-treated  fish 
survived  the  treatment  process,  7  of  the  20  fish 
(35%)  exposed  to  36.1°C  died  during  treatment. 
All  fish  that  died  lost  equilibrium  early  in  the 
treatment  and  were  dead  within  5  min.  The  mean 
pretreatment  midpoint  temperature  of  those  that 
died  was  significantly  lower  than  that  of  the  sur- 
vivors (Mann- Whitney  U  testP<0.05);  however, 
temperatures  experienced  immediately  prior  to 
exposure  were  the  same  for  both  groups. 

Although  visual  observations  during  the  post- 
treatment  period  of  this  study  were  limited  to 
avoid  disturbing  the  fish,  the  typical  immediate 
posttreatment  behavior  of  both  the  heat-  and 
cold-treated  fish  was  submissive;  often  fish  were 
hiding  behind  objects  in  their  experimental 
tanks.  However,  at  the  feeding  time,  4.5  h  follow- 
ing exposure,  nearly  all  fish  actively  fed. 

A  distinct  diurnal  pattern  of  activity  was  ob- 
served for  each  of  the  treatment  groups  through- 
out the  6-day  experiment  (Figure  2).  Daytime 
hourly  activities  were  typically  two  to  three  times 
higher  than  nighttime  activities.  The  median 
activity  (tunnel  passes)  of  the  cold-  and,  partic- 
ularly, heat-treated  fish  dropped  appreciably  the 
hour  following  exposure  (Figure  2).  For  general 
activity  comparisons  (Figure  3a,  b)  diurnal  and 
nocturnal  periods  were  separately  analyzed 
(dawn  and  dusk  excluded).  With  the  pretreatment 
activity  of  each  group  serving  as  its  own  control, 
a  series  of  Mann-Whitney  U  tests,  with  ties 
correction  and  z  transformation  were  performed 


1089 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


50 


2A.    36.I*C     EXPOSURE 


t    TREATMENT 


90 


2B.    21*  C   EXPOSURE 


1200       0000      1200       0000      1200       0000       1200        0000       1200        0000      1200       0000       1200 

TIME(H) 

Figure  2. — Median  hourly  tunnel  passes  by  fish  throughout  the  entire  6-day  experiment  for  each  treat- 
ment group.  The  arrow  indicates  time  of  treatment. 


to  compare  the  3-day  pretreatment  and  3-day 
posttreatment  median  hourly  activities.  The  pre- 
treatment and  posttreatment  activity  levels  of 
the  control  group  were  not  significantly  different. 
The  daytime  posttreatment  activity  of  cold- 
treated  fish,  although  higher  and  more  variable, 
was  not  significantly  changed;  however,  night 
activity  increased  (P<0.001).  Heat-treated  fish 
demonstrated  the  greatest  change  in  activity. 


Both  night  and  daytime  activities  decreased 
(P<0.01,P<0.001  respectively). 

DISCUSSION 

Combined  pretreatment  data  demonstrate  that 
the  32  test  bluegills  maintained  their  environ- 
mental temperatures  within  well-defined  limits 
relative  to  the  available  temperature  range.  The 


1090 


BEITINGER:  THERMOREGULATORY  BEHAVIOR  OF  BLUEGILL 


O 

z 


< 

a. 


35 


30 


25- 


20- 


Z 
Z 
3 
fZ       15 


< 

Z 
< 

o 

lU 

S 


10- 


5- 


3A. DAY 

-- 

o 

[ 

< 

1             J_ 

o 

- 

9 

J 

. 

- 

i 

1 

1 

-l 

r 

o 

- 

L 

3B.  NIGHT 

i 

1 

i 

'-       I 

•    PttETREATMENT 
O     POSTTRtAIMtNT 

2rC  EXPOSURE 


31°C   EXPOSURE 
iCONTROLSi 


36rC  EXPOSURE 


Figure  3. — Medians  (circles)  and  95%  confidence  limits  for  pre- 
treatment  and  posttreatment  bluegill  hourly  activities  for  the 
three  treatment  groups.  Day  and  night  activities  are  presented 
separately. 

calculated  midpoint  of  the  preferred  range, 
31.2°C,  is  similar  to  that  of  Neill  and  Magnuson 
(in  press),  30.4°  and  0.8°C  below  the  final  tem- 
perature preferendum  for  bluegill  reported  by 
Fry  and  Pearson  (1952).^  The  effect  of  sudden 
temperature  stress  on  thermoregulatory  behavior 
has  not  been  previously  examined.  However, 
several  other  external  factors  have  been  reported 
to  influence  temperature  preferenda,  including 
season  (Sullivan  and  Fisher,  1953;  Zahn,  1963; 
Barans  and  Tubb,  1973),  light  intensity  (Sullivan 
and  Fisher,  1954),  starvation  (Javaid  and 
Anderson,  1967)  and  exposure  to  chlorinated 
hydrocarbons  (Ogilvie  and  Anderson,  1965; 
Peterson,  1973). 

Pretreatment  and  posttreatment  comparisons 
in  the  grouped  control  data  clearly  indicate  no 
change  in  thermoregulatory  performance.  The 


^Fry,  F.  E.  J.,  and  B.  Pearson.  1952.  Some  temperature 
relations  of  the  pumpkinseed  and  bluegill  sunfish.  Unpubl. 
manuscr.,  10  p.  Ont.  Fish.  Res.  Lab.  R.R.  2,  Maple,  Ont.,  Can. 


A  t  experienced  by  control  fish  was  minimal  and 
changes,  if  any,  could  be  ascribed  to  handling  or 
time-dependent  variations  in  temperature 
preference. 

Cold-  and  heat-treated  fish  actually  experienced 
two  temperature  shocks.  One  occurred  when  the 
fish  were  introduced  into  the  treatment  chambers 
and  the  second  when  they  were  returned  to  their 
experimental  tanks.  Both  cold  and  heat  treat- 
ments were  conducted  at  temperatures  actively 
avoided  by  fish  while  in  their  thermoregulatory 
tanks. 

Cold  exposure  did  not  significantly  change  any 
of  the  four  measured  parameters  of  thermo- 
regulatory behavior.  These  fish  experienced  a 
At  of  approximately  10°C,  but  the  exposure 
temperature,  21°C,  is  near  the  middle  of  the  toler- 
ance zone  for  bluegill.  That  these  fish  did  not  select 
lower  temperatures  was  expected,  owing  to  the 
slow  rate  of  downward  temperature  acclimation 
characteristic  of  fishes  (Brett,  1944,  1946).  The 
lethal  rates  of  temperature  increase  are  at  least 
20  times  the  corresponding  lethal  rates  of  tem- 
perature decrease  for  bluegill  (Speakman  and 
Krenkel,  1971).  Apparently,  the  30-min  exposure 
was  not  sufficient  to  change  the  acclimation  state 
and,  hence,  the  preferred  temperature  range  of 
these  fish. 

Fish  exposed  to  36. 1°C  experienced  a  smaller  A  t 
(about  5''C)  during  treatment,  but  this  exposure 
was  to  within  approximately  0.5°C  of  the  bluegill's 
incipient  upper  lethal  temperature  (Hart,  1952; 
Cairns,  1956).  The  ability  of  surviving  bluegills  to 
thermoregulate  was  not  deleteriously  affected  by 
the  30-min  exposure  to  36.1°C,  however,  statisti- 
cally significant  changes  in  avoidance  and  mid- 
point temperatures  did  occur.  Thus,  the  ther- 
moregulatory performance  of  bluegill  was 
influenced  more  by  exposure  either  to  1)  tem- 
peratures closer  to  lethal  limits  than  exposure  to 
large  Afs  per  se  or  to  2)  temperatures  above 
rather  than  those  below,  the  acclimation  state  of 
the  fish. 

Of  the  three  exposure  temperatures,  only 
36.1°C  resulted  in  fish  mortality.  The  pretreat- 
ment midpoint  temperatures  of  these  fish  were 
significantly  lower  than  those  of  fish  surviving 
heat  treatment,  indicating  a  relationship  be- 
tween preferred  and  upper  lethal  temperatures. 
That  a  considerable  proportion,  35^^ ,  of  fishes 
exposed  to  36.1°C  died,  is  more  important  to  the 
population  than  the  observation  that  surviving 


1091 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


fish  had  a  0.7°C  increase  in  preferred  range 
following  exposure. 

Use  of  tunnel  passes  as  an  index  of  locomotor 
activity  is  discussed  by  Beitinger  et  al.  (in  press). 
The  diurnal  activity  pattern  continued  after  treat- 
ment in  all  three  groups  (Figure  2).  Immediately 
subsequent  to  treatment,  a  marked  decrease  in 
activity  occurred  in  cold-  and  heat-treated  fish 
but  not  in  the  control  group  (Figure  2).  This 
decrease  might  help  explain  the  increased 
susceptibility  of  thermally  shocked  fish  to 
predation  reported  by  Coutant  (1972a,  b,  1973) 
and  Sylvester  (1973).  Hocutt  (1973)  found  that 
exposure  to  rapid  temperature  changes,  as  large 
as  12°C  below  and  8°C  above  ambient  tempera- 
tures, resulted  in  decreased  swimming  perfor- 
mance in  juvenile  largemouth  bass,  Micropterus 
salmoides;  spotfin  shiner,  Notropis  spilopterus; 
and  channel  catfish,  Ictalurus  punctatus. 

Due  to  their  mobility  and  acute  temperature 
sensitivity,  fishes  are  able  to  avoid  environments 
of  unfavorable  temperatures.  If  trapped  at  these 
temperatures,  fish  possess  the  ability  to  resist 
thermal  death.  Ecologically,  resistance  ability 
affords  a  fish  the  opportunity  to  escape  potentially 
lethal  conditions  at  least  until  they  lose 
equilibrium.  Fish  are  exposed  to  stressful 
conditions  when  existing  within  their  thermal 
resistance  zone  or  when  experiencing  large  tem- 
perature changes.  The  major  objective  of  this 
research  was  to  examine  the  thermoregulatory 
performance  of  bluegill  following  "high"  and 
"low"  thermal  exposure.  Nevertheless,  the  35% 
mortality  among  36.1°C  treated  fish  and  the  se- 
vere depression  in  immediate  posttreatment  ac- 
tivity of  both  the  21.0°  and  36. 1°C  treated  fish  were 
the  two  most  ecologically  important  findings.  All 
fish  surviving  treatment  retained  the  ability  to 
behaviorally  thermoregulate,  hence,  disruption  of 
thermoregulatory  behavior  is  not  a  likely  outcome 
of  thermal  shock  in  fishes. 


ACKNOWLEDGMENTS 

I  wish  to  thank  John  J.  Magnuson,  William  H. 
Neill,  Charles  C.  Coutant,  and  Robert  F.  Carline 
for  their  valuable  reviews  of  the  manuscript. 
Technical  assistance  was  provided  by  William 
R.  Shaffer,  Gerald  G.  Chipman,  and  Sharon  A. 
Klinger.  This  study  was  jointly  supported  by  the 
National  Oceanic  and  Atmospheric  Adminis- 
tration's office  of  Sea  Grant  through  an  insti- 


tutional grant  to  The  University  of  Wisconsin 
and  by  the  Madison  Gas  and  Electric  Company. 


LITERATURE  CITED 

Alabaster,  J.  S. 

1963.  The  effect  of  heated  effluents  on  fish.  Int.  J.  Air  Water 
Pollut.  7:541-563. 
Bailey,  R.  M. 

1955.  Differential  mortality  from  high  temperature  in  a 
mixed  population  of  fishes  in  southern  Michigan.  Ecology 
36:526-528. 

Barans,  C.  a.,  and  R.  a.  Tube. 

1973.  Temperatures  selected  seasonally  by  four  fishes  from 
Western    Lake    Erie.    J.    Fish.    Res.    Board    Can. 
30:1697-1703. 
Beitinger,  T.  L.,  J.  J.  Magnuson,  W.  H.  Neill,  and  W.  R. 
Shaffer. 
In  press.  Behavioural  thermoregulation  and  activity  pat- 
terns in  the  green  sunfish,  Lepomis  cyanellus.  Anim. 
Behav. 
Brett,  J.  R. 

1944.  Some  lethal  temperature  relations  of  Algonquin 
Park  fishes.  Univ.  Toronto  Stud.  Biol.  52.,  Publ.  Ont.  Fish. 
Res.  Lab.  63:5-49. 
1946.  Rate  of  gain  of  heat-tolerance  in  goldfish  (Carassius 
auratus).  Univ.  Toronto  Stud.  Biol.  53,  Publ.  Ont.  Fish. 
Res.  Lab.  64:9-28. 
Cairns,  J.,  Jr. 

1956.  Effects  of  heat  on  fish.  Ind.  Wastes  1:180-183. 
Clark,  J.  R. 

1969.   Thermal  pollution  and  aquatic  life.   Sci.   Am. 
220(3):19-27. 
Colton,  J.  B.,  Jr. 

1959.  A  field  observation  of  mortality  of  marine  fish  larvae 
due  to  warming.  Limnol.  Oceanogr.  4:219-222. 
Coutant,  C.  C. 

1972a.  Effect  of  thermal  shock  on  vulnerability  to  preda- 
tion in  juvenile  salmonids.  I.  Single  shock  temperatures. 
U.S.  AEC  Res.  Dev.  Rep.  BNWL-1521,  17  p. 

1972b.  Effect  of  thermal  shock  on  vulnerability  to  preda- 
tion in  juvenile  salmonids.  II.  A  dose  response  by  rainbow 
trout  to  three  shock  temperatures.  U.S.  AEC  Res.  Dev. 
Rep.  BNWL-1519,  12  p. 

1973.  Effect  of  thermal  shock  on  vulnerability  of  juvenile 
salmonids  to  predation.  J.  Fish.  Res.  Board  Can. 
30:965-973. 

GUNTER,  G. 

1941.  Death  of  fishes  due  to  cold  on  the  Texas  coast, 
January,  1940.  Ecology  22:203-208. 

GuNTER,  G.,  AND  H.  H.  HiLDEBRAND. 

1951.  Destruction  of  fishes  and  other  organisms  on  the 
South  Texas  Coast  by  the  cold  wave  of  January 
28-Febmary  3,  1951.  Ecology  32:731-736. 

GUNTHER,  E.  R. 

1936.  A  report  on  oceanographical  investigations  in  the 
Peru  Coastal  Current.  Discovery  Rep.  13:107-276. 
Hart,  J.  S. 

1952.  Geographic  variations  of  some  physiological  and 
morphological  characters  in  certain  freshwater  fish. 
Univ.  Toronto  Biol.  60,  Publ.  Ont.  Fish.  Res.  Lab.  72, 
79  p. 


1092 


BEITINGER:  THERMOREGULATORY  BEHAVIOR  OF  BLUEGILL 


HOCUTT,  C.  H. 

1973.  Swimming  performance  of  three  warmwater  fishes 
exposed  to  a  rapid  temperature  change.  Chesapeake  Sci. 
14:11-16. 

HUTSMAN,  A.  G. 

1942.  Death  of  salmon  and  trout  with  high  temperature.  J. 
Fish.  Res.  Board  Can.  5:485-501. 
Javaid,  M.  Y.,  and  J.  M.  Anderson. 

1967.  Influence  of  starvation  on  selected  temperatures  of 
some  salmonids.  J.  Fish.  Res.  Board  Can.  24:1515-1519. 
Neill,  W.  H.,  J.  J.  Magnuson,  and  G.  G.  Chipman. 

1972.  Behavioral  thermoregulation  by  fishes:  A  new  ex- 
perimental approach.  Science  (Wash.,  D.C.) 
176:1443-1445. 

Neill,  W.  H.,  and  J.  J.  Magnuson. 

In  press.  Distributional  ecology  and  behavioral  ther- 
moregulation of  fishes  in  relation  to  heated  effluent  from  a 
power  plant  at  Lake  Monona,  Wisconsin.  Trans.  Am.  Fish. 
Soc. 

Ogilvie,  D.  M.,  and  J.  M.  Anderson. 

1965.  Effect  of  DDT  on  temperature  selection  by  young 
Atlantic  salmon,  Salmo  salar.  J.  Fish.  Res.  Board  Can. 
22:503-512. 

Peterson,  R.  H. 

1973.  Temperature  selection  of  Atlantic  salmon  [Salmo 
salar)  and  brook  trout  (Salvelinus  fontinalis)  as 
influenced  by  various  chlorinated  hydrocarbons.  J.  Fish. 
Res.  Board  Can.  30:1091-1097. 


Siegel,  S. 

1956.  Nonparametric  statistics  for  the  behavorial  sciences. 
McGraw-Hill,  N.Y.,  312  p. 
Speakman,  J.  N.,  and  p.  A.  Krenkel. 

1971.  Quantification  of  the  effects  of  rate  of  temperature 
change  on  aquatic  biota.  Vanderbilt  Univ.,  Dep.  Environ. 
Water  Resour.  Eng.,  Rep.  6. 

Sullivan,  C.  M.,  and  K.  C.  Fisher. 

1953.  Seasonal  fluctuations  in  the  selected  temperature  of 
speckled  trout,  Salvelinus  fontinalis  (Mitchill).  J.  Fish. 
Res.  Board  Can.  10:187-195. 

1954.  The  effects  of  light  on  temperature  selection  in  speck- 
led trout  Salvelinus  fontinalis  (Mitchill).  Biol.  Bull. 
(Woods  Hole)  107:278-288. 

Sylvester,  J.  R. 

1972.  Effect  of  thermal  stress  on  predator  avoidance  in 
sockeye  salmon.  J.  Fish.  Res.  Board  Can.  29:601-603. 

Threinen,  C.  W. 

1958.  Cause  of  mortality  of  a  midsummer  plant  of  rainbow 
trout  in  a  southern  Wisconsin  lake,  with  notes  on  acclima- 
tion and  lethal  temperatures.  Prog.  Fish-Cult.  20:27-32. 

Zahn,  M. 

1963.  Jahreszeitliche  Veranderungun  der  Vorzugstem- 
peraturen  von  Scholle  (Pleuronectes  platessa  Linne)  und 
Bitterling  (Rhodeus  sericeus  Pallas).  Verb.  Dtsch.  Zool. 
Ges.  p.  562-580.  [Not  seen,  from  Fry,  F.  E.  J.  1969.  In  W.  S. 
Hoar  and  D.  J.  Randall  (editors)  Fish  physiology.  Vol.  VI. 
Academic  Press,  N.Y.] 


1093 


DENSITY  DISTRIBUTION  OF  JUVENILE  ARCTIC  COD, 
BOREOGADUS  SAIDA,  IN  THE  EASTERN  CHUKCHI  SEA 

IN  THE  FALL  OF  1970 

Jay  C.  Quasti 
ABSTRACT 


The  Arctic  cod,  Boreogadus  saida,  is  a  key  element  in  the  ecosystem  of  the  Arctic  Ocean. 
Juveniles,  principally  young-of-the-year,  were  taken  by  Isaacs-Kidd  mid-water  trawl  at  night 
during  September  and  October  1970  in  the  eastern  Chukchi  Sea.  Their  average  concentration  was 
about  28/1,000  m^  and  their  average  biomass  about  0.7  metric  ton/km^  of  ocean  surface.  In  20 
stations  (representing  about  30  x  10^  km^,  or  8,714  square  nautical  miles),  the  number  of 
juvenile  cod  {N)  per  standard  haul  (about  8,223  m^  of  water  filtered  per  haul)  increased  with 
depth  in  meters  {D)  at  about  the  same  rate  [logio  (A^  +  1)  =  0.0669Z)].  Yet  the  depth  at  which 
equivalent  concentrations  occurred  varied  over  a  range  of  38  m  between  stations.  The  zone  of 
increased  concentration  with  depth,  called  a  density  structure,  appears  to  be  the  nighttime  relict 
of  a  graded  negatively  phototactic  response  to  sunlight  by  the  juvenile  cod  during  preceding  daylight. 
Apparently  the  structure  was  vertically  displaced  after  dark  by  wand-induced  upwelling  and  down- 
welling.  The  juvenile  cod  may  have  originated  in  the  northwestern  Bering  Sea,  off  Arctic 
Siberia,  or  within  the  Chukchi  Sea,  and  probably  had  recycled  in  the  Chukchi  Sea  prior  to 
capture. 


This  study  of  biomass  and  distribution  of  juvenile 
Arctic  cod,  Boreogadus  saida  (Lepechin),  in  the 
Chukchi  Sea  is  an  outgrowth  of  the  Western 
Beaufort  Sea  Ecological  Cruise  of  1970  (WEBSEC- 
70)  sponsored  by  the  U.S.  Coast  Guard.  My 
original  objective  was  to  explore  the  fishes  of  the 
marine  ecosystem  in  the  Arctic  Ocean  east  of 
Point  Barrow,  Alaska,  and  if  possible  to  quantify 
the  occurrence  of  important  forms.  Because  of  an 
early  southward  shift  of  the  arctic  ice  pack,  the 
study  was  moved  to  the  eastern  Chukchi  Sea. 
The  sampling  schedule — date,  location,  depth  of 
water,  and  number  and  types  of  hauls — is  given 
in  Table  1  and  Figure  1.  The  species  offish  and 
where  they  occurred  are  summaried  in 
Quast  (1972). 

Juvenile  Arctic  cod  and  Pacific  sand  lance, 
Ammodytes  hexapterus  Pallas,  were  virtually  the 
only  fish  species  trawled  in  the  surface  and  mid- 
depths  at  night.  The  cod  occurred  at  every  station; 
also  they  were  more  numerous  and  had  a  larger 
biomass  than  the  sand  lance — a  subjective 
estimate  suggests  a  minimum  10  fold  difference  in 
both  respects.  Although  sand  lance  were  chiefly 
taken  at  the  surface,  the  number  of  Arctic  cod 


'Auke  Bay  Fisheries  Laboratory,  National  Marine  Fisheries 
Service,  NOAA,  Auke  Bay,  AK  99821. 


usually  increased  with  depth.  Because  of  the 
apparent  importance  of  the  Arctic  cod  in  the  off- 
bottom  marine  ecosystem  of  the  eastern  Chukchi 
Sea  during  WEBSEC-70, 1  further  analyzed  their 
data  to  estimate  their  numbers  and  biomass 
over  the  study  area. 

General  life  history,  distribution,  and  literature 
on  Arctic  cod  are  summarized  by  Andriyashev 
(1954:195-198).  The  species  is  circumpolar  and 
occurs  to  or  nearly  to  the  North  Pole.  Off  Alaska, 
it  occurs  along  the  Arctic  coast,  in  the  Chukchi 
Sea,  and  in  the  Bering  Strait;  it  also  has  been 
recorded  in  the  winter  from  Norton  Sound  and  the 
Gulf  of  Anadyr.  Although  most  authors  term  the 
species  "pelagic,"  "demersal"  is  probably  better 
because  adults  appear  to  be  associated  with  a 
shallowwater  substrate,  whether  it  be  ocean 
bottom  over  the  continental  shelf  or  the  under- 
surface  of  ice.  Maximum  size  is  about  320  mm 
total  length  (TL).  Association  with  low  tempera- 
tures is  an  important  characteristic:  Rass  ( 1968: 
136)  gives  the  thermal  environment  of  eggs  as 
0°  to  2°C,  of  larvae  as  2°  to  5°C,  and  of  fry  as 
5°  to  7°C  and  probably  higher.  During  WEBSEC- 
70,  specimens  of  0-age  fish  occurred  at  -1.5° 
to  3.5°C.  According  to  Andriyashev  (1954),  Arctic 
cod  mature  when  about  4  yr  old  and  190  mm  TL; 
they  spawn  near  coasts,  principally  in  January 


Manuscript  accepted  February  1974. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 

1094 


QUAST:  DISTRIBUTION  OF  ARCTIC  COD 


Table  1. — Station  data  for  trawl  collections  in  the  eastern  Chukchi  Sea  during  WEBSEC-70. 


Date  and  inclusive  time         Approximate  position 


Hauls 


tatlon 

(Bering  Standard) 

Lat.  N 

Long.  W 

water  (m) 

No. 

Type' 

Depths  (m)2 

10 

27  Sept.  (1917-2207) 

70=04' 

165=57' 

44 

4 

R 

11 

14 

29  Sept.  (0518-0817) 

70°17' 

1 65°02' 

51 

4 

R 

11 

16 

29  Sept.  (1721-2002) 

70=16' 

163=58' 

53 

4 

R 

11 

20 

30  Sept.  (1740-2025) 

70=20' 

163=24' 

42 

4 

R 

12 

22 

1  Oct.  (1734-2103) 

70=20' 

163=25' 

35 

4 

R 

12 

25 

2  Oct.  (1731-2036) 

70=07' 

163=14' 

33 

4 

R 

12 

30 

4  Oct.  (1756-2137) 

69=58' 

1 64=07 ■ 

31 

5 

M 

2.5,10,13.19 

32 

5  Oct.  (1831-2104) 

69=48' 

163=49' 

26 

4 

R 

12 

37 

6  Oct.  (1727-1956) 

70=07' 

167=36' 

49 

4 

R 

12 

41 

7  Oct.  (1752-2014) 

69=57' 

167=31- 

44 

4 

M 

10,10.12,22 

45 

8  Oct.  (1816-2058) 

69=57' 

168=38' 

44 

4 

M 

2,9,13,20 

51 

9  Oct.  (1744-2024) 

69=36' 

167=36' 

48 

4 

M 

2,7,14,20 

56 

10  Oct.  (1940-2229) 

69=14' 

166=53' 

44 

4 

M 

2,9,18,23 

61 

11  Oct.  (1755-2015) 

69=05' 

166=13' 

29 

4 

M 

8,13,16,23 

65 

12  Oct.  (1755-2016) 

69=21  ■ 

166=45' 

36 

4 

M 

8,13,16,22 

70 

13  Oct.  (1735-1958) 

69=12' 

167=38' 

39 

4 

M 

8,13,18,22 

74 

14  Oct.  (1723-1946) 

69=35' 

164=29' 

22 

4 

M 

2,8,13,18 

80 

15  Oct.  (1814-2055) 

69=27' 

164=43' 

30 

4 

M 

2,8,13,22 

88 

16  Oct.  (1917-2205) 

68=55' 

166=47' 

45 

4 

M 

2,11,24.40-45 

92 

17  Oct.  (1733-2014) 

68=36' 

167=41' 

54 

4 

M 

2.13.17.33 

^M  =  multldepth  hauls  with  1.8-m  (6-foot)  Isaacs-Kidd  mid-water  trawl,  and  R 
^Depth  at  depressor. 


=  replicate  hauls  at  single  depth. 


I 

168° 


166" 


164" 


162° 


ICY  CAPE 


Figure  1. — Sequence  and  position  of  IKMT  stations  (circles)  in  the  eastern  Chukchi  Sea  in  1970. 
Dashed  lines  indicate  time  spans  for  groups  of  stations. 


and  February,  and  their  eggs  are  large — 
approximately  1.5-1.9  mm  in  diameter.  Rass 
(1968:136)  adds  that  the  first  larvae  appear  in 
the  sea  in  May-July;  the  larval  stage  (5.4-15.0 
mm)  lasts  about  2  mo  (in  the  Barents  and  Siberian 
Seas  through  June-July);  and  transition  to 
juveniles  is  at  30-50  mm,  in  August. 


Arctic  cod  appear  to  be  a  key  species  in  the 
ecology  of  the  arctic  seas.  They  are  widespread, 
locally  abundant,  and  probably  are  a  major 
element  of  the  secondary  consumer  level  in  the 
trophic  pyramid.  Ponomarenko  (1967:8)  found 
that  cod  larvae  and  fry  fed  successively  on 
copepod  eggs,  nauplii,  and  copepodites,  and 


1095 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Hognestad  (1968:130)  reported  that  adults 
trawled  from  the  eastern  Barents  Sea  in  Sep- 
tember 1966  fed  principally  on  the  copepod 
Calanus  finmarchicus.  In  turn,  Arctic  cod  are 
important  as  forage  for  higher  level  consumers. 
Andriyashev  (1954:194-198)  cites  literature 
records  for  predation  on  Arctic  cod  by  a  long 
list  of  species,  including  char,  saffron  cod, 
flounders,  sculpins,  seals,  walrus,  beluga,  sea 
gulls,  alcids,  and  skuas.  Tuck  (1960:166)  stresses 
the  importance  of  Arctic  cod  in  the  diet  of  common 
and  thick-billed  murres  of  the  polar  basin,  whose 
total  populations  contain  at  least  15  million 
birds  (p.  51). 


METHODS 

Studies  with  the  1.8-m  (6-foot)  Isaacs-Kidd  mid- 
water  trawl  (IKMT)  involved  81  30-min  tows  (at 
depth)  at  20  stations  (Table  1).  All  stations  were 
occupied  for  periods  of  about  2  h  or  more,  and 
all  but  one  started  at  late  dusk  or  dark.  The 
IKMT  was  similar  in  dimensions  to  the  trawl 
tested  and  figured  by  Friedl  ( 1971 );  it  had  a  section 
of  coarse  mesh  (3.8-cm  bar)  preceding  0.6-cm  bar 
mesh.  The  cross-sectional  area  at  the  mouth  was 
calculated  as  2.87  m'-^  and  at  the  beginning  of  the 
0.6-cm  mesh  as  1.55  m^.  To  compensate  for  the 
possibility  that  fish  would  be  herded  into  the 
small-mesh  section  by  the  coarse  anterior  mesh,  a 
middle  value  between  the  two  cross-sectional 
areas,  2.21  m^,  was  arbitrarily  used  as  the 
effective  cross-sectional  area  of  that  portion  of  the 
net  that  captured  juvenile  cod.  Calculation  of  the 
horizontal  and  vertical  dimensions  of  the  net 
swath  was  simplified  by  treating  the  effective 
cross-sectional  area  as  a  square — 1.49  m  on  a  side. 
Tows  were  standardized  at  2  nautical  miles 
(3,704  m)  at  depth  by  maintaining  a  vessel 
speed  of  4  knots  (estimated  by  engine  revolutions) 
over  30  min.  The  resulting  horizontal  swath  was 
calculated  as  5,519  m^  and  the  volume  filtered 
as  8,223  m^.  At  least  four  tows  were  made  at 
each  station,  either  at  the  same  depth  or  at  four 
different  depths  (Table  1) — -two  on  one  bearing 
and  the  remainder  on  its  reciprocal. 

Sampling  followed  a  zigzag  pattern  (Figure  1) 
before  a  southward-advancing  ice  front.  Because 
blocks  of  ice  are  sometimes  difficult  to  see  or 
become  too  abundant  to  avoid,  mid- water  trawling 
at  night  even  in  the  presence  of  light  pack  ice 
is  hazardous.  The  trawl  can  be  seriously  damaged 


or  lost  outright  if  a  large  block  of  ice  becomes 
trapped  beneath  a  trawl  warp  and  causes  the 
trawl  to  be  lifted  to  the  surface  where  the  ice 
would  be  fed  into  its  mouth  at  trawling  speed. 
Consequently,  trawling  was  usually  done  in  the 
relatively  open  water  of  broad  leads  or  ahead  of 
the  ice  pack. 

Two  types  of  IKMT  station  were  occupied.  In 
one  type  (eight  stations),  nektonic  organisms  at  a 
single  depth  within  stations  were  sought  by 
conducting  four  "replicate"  hauls  at  11  or  12  m 
(Table  1).  In  the  other  type  (12  stations),  the 
vertical  distribution  of  nektonic  organisms  was 
sought  by  making  four  or  five  hauls  at  different 
depths  (Table  1);  the  depths,  which  were  usually 
verified  with  a  bathykymograph,  were  selected 
after  study  of  a  Simrad^  echogram  (Model  ER2 — 
38  kHz).  No  reliable  association  was  detected 
between  presence  or  absence  of  bands  on  echo- 
grams and  catch  at  those  depths. 

Data  obtained  on  juvenile  Arctic  cod  in  the 
IKMT  hauls  included  counts,  range  of  standard 
lengths,  and  volumes.  When  large  numbers  of  cod 
were  captured,  usually  the  total  volume  was 
measured  and  the  number  of  cod  was  estimated 
from  the  average  volume  per  individual  in  a 
subsample.  When  there  appeared  to  be  negligible 
differences  in  size  of  cod  between  hauls,  the 
average  volume  per  individual  in  one  haul  was 
used  to  estimate  the  number  of  juveniles  in  a 
volume  taken  in  another  haul  at  the  same  station. 


RESULTS 

The  juvenile  Arctic  cod  appeared  to  be  prin- 
cipally of  0  age-class  (young-of-the-year),  based  on 
a  comparison  between  length  frequencies  of  the 
Chukchi  specimens  and  age-length  data  reported 
in  the  literature.  For  the  comparison,  the  Chukchi 
data  were  converted  from  standard  to  total  length 
by  a  regression  based  on  data  from  the  Chukchi 
Sea  specimens  (Table  2),  because  the  measure- 
ment employed  for  data  in  the  literature  was  not 
specific  and  therefore  was  assumed  to  be  total 
length  (the  measurement  usually  used  in  fishery 
studies).  Modal  size  of  the  Chukchi  Sea  specimens 
was  44  mm,  slightly  higher  than  the  average  size 
for  age  0  cod,  35  mm,  from  the  Barents  Sea  and 
Spitzbergen  cited  by  Hognestad  (1968:130).  The 


^Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


1096 


QUAST:  DISTRIBUTION  OF  ARCTIC  COD 


Table  2. — Regressions  of  total  length  and  volume  on  standard 
(body)  length  (X)  in  juvenile  Arctic  cod  from  eastern  Chukchi 
Sea.  Least  squares  fit  to  power  equation,  Y  =  aXf^ ,  for  83 
specimens  over  sizes  30<SL  mm<74. 


Measurement  {Y) 


Correlation 
coefficient 


Total  length  (mm) 
Volume  (ml) 


1,4429 
0,4454   •  10' 


0,9478 
3  1678 


0,996 
0  984 


upper  limits  of  nearly  all  size  distributions  by  haul 
from  the  Chukchi  Sea,  35  of  40,  were  below  the 
mean  size  for  age  I  cod  cited  by  Hognestad. 
Because  the  cod  from  the  Chukchi  Sea  were 
captured  in  September  and  October,  at  a  later 
date  than  Hognestad's  specimens,  there  is  little 
doubt  that  most  specimens  captured  in  the  eastern 
Chukchi  Sea  were  age  0. 

Homogeneity  of  sampling  variance  was  then 
examined  in  the  data  on  frequency  of  occurrence 
of  juvenile  cod  in  the  hauls  by  comparing  within- 
station  (single  depth)  standard  deviations  from 
the  replicate  stations.  Three  hauls  also  were 
included  from  one  multidepth  station  because 
they  were  taken  at  about  the  same  depth,  11m, 
as  the  hauls  at  the  replicate  stations.  Standard 
deviation  appeared  to  be  proportional  to  the  mean 
in  the  comparisons  (Table  3 ),  strong  evidence  that 
the  sampling  variance  was  not  homogeneous.  The 
variance  appeared  to  be  stabilized  by  logarithmic 
transformation  of  the  frequencies  [logio  {N  +  1)] 
which  then  passed  Bartlett's  test  (Table  3).  As 
a  result,  the  logarithmic  transformation  was 
applied  to  the  analysis  of  frequencies. 

The  frequency  data  were  examined  by  analysis 
of  variance  to  determine  the  significance  of 
between-station  differences  in  population  density. 
Data  from  multidepth  stations  were  not  used 
because  these  stations  were  not  standardized  for 


depth.  Significant  between-station  differences 
were  present  (Table  4),  evidence  that  there  were 
important  horizontal  differences  in  density  of 
Arctic  cod  over  the  sampling  area,  at  least  at 
depths  of  11-12  m. 

Table  4. — Analysis  of  variance  of  numbers  (transformed)  of 
juvenile  Arctic  cod  in  IKMT  hauls  at  eight  replicate  stations  in 
eastern  Chukchi  Sea. 


Source 

d.f. 

S,S, 

M.S, 

F 

Among  stations 
Witfiin  stations 

7 
24 

10,60984 
4.11693 

1,51569 
0,17154 

8.84:P<0.001 

Total 

31 

14,72677 

— 

— 

Capture  rate  of  juvenile  cod  consistently 
increased  with  depth  and  the  slope  of  regressions 
of  number  of  captures  on  depth  was  similar  among 
the  multidepth  stations.  Also,  regressions  at  the 
stations  appeared  to  bear  no  direct  relationship 
to  salinity  structure  nearby  (Figure  2).  Sig- 
nificance of  differences  between  the  regressions 
was  tested  by  analysis  of  covariance  with  the 
result  that  differences  in  slope  were  judged  as 
insignificant.  Differences  in  level,  however,  did 
appear  to  be  significant  (Table  5).  Apparently 
concentration  of  juvenile  Arctic  cod  increased  at 
about  the  same  logarithmic  rate  (0.0669)  with 
depth,  but  the  depth  at  which  a  given  concentra- 
tion occurred  varied  between  stations.  This 
triangular  area  on  the  plots  (Figure  2),  with  its 
apex  toward  the  surface,  was  regarded  as  the 
graphic  analog  of  the  relationship  between  con- 
centration and  depth  in  the  juvenile  cod;  it  was 
termed  a  "density  structure."  Evidently  the 
density  structure  was  relatively  stable  relative  to 
the  time  span  of  sampling  at  a  station  (about 
2  h)  because  the  structure  was  always  evident 
despite  the  depth  sequence  of  hauls  (Figure  2). 


Table  3. — Comparison  of  means,  standard  deviations,  and  variances  for  raw  and 
transformed  frequencies  of  occurrence  [log,o  (A^  +  1)]  of  juvenile  Arctic  cod  between 
replicate  stations  in  eastern  Chukchi  Sea.  Data  arranged  in  order  of  increasing  means 
in  the  transformed  data. 


No.  replicate 
hauls 

Raw  data 

Transformed  data 

Station 

Mean 

SD 

Variance 

Mean 

SD 

Variance' 

37 

4 

3.3 

4.0373 

16.3 

0.4758 

0.4273 

0  1826 

32 

4 

6.3 

5.4406 

29.6 

0.7751 

0.3079 

0  0948 

14 

4 

20.8 

220681 

4876 

1.0397 

07333 

0.5377 

25 

4 

23.3 

31.9312 

1,019.6 

1.1380 

0.5011 

0.2511 

20 

4 

51.8 

47.7169 

2,276.9 

1.6159 

0.3260 

0.1063 

22 

4 

57.0 

56.3090 

3,170.7 

1 .6399 

0.3516 

0  1236 

16 

4 

62.5 

28.2436 

797.7 

1.7612 

0.2347 

0.0551 

41 

23 

277.7 

202  5075 

41,009.3 

2.3101 

04795 

02299 

10 

4 

2580 

872221 

7,607.7 

2.3954 

0.1453 

0  0211 

'Bartlett's  Test  for  Homogeneity  (Sokal  and  Rohlf.  1969:370.  371):  x  ^  =  4.004,  P>0.5. 
^A  multidepth  station  in  which  three  hauls  were  at  approximately  11  m. 


1097 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


STATION   30   1291 


REGRESSION  OF  NUMBER  OF  COD 


SALINITY 


N  =  0.0111   •  0.0619D 


O5  DEPTH  TO 

BOTTOM 


STATION  11    (121 

- 

r^ 

- 

O1    ^ 

^l 

lOj^^ 

/ 
/ 
/ 

~       J-^ 

/ 

~ 

■^     0' 

/ 
/ 

N  -  \.i'm 
1 

0.0512D 
1                      1 

,    1 

- 

STATION   51    (501 


U   1.0  -         ,0 


STATION  56   (551 

- 

- 

N  =  0.5371 

0.0208D 

" 

■ 

O2 

■^1 

- 

3i 

1                  1 

1 

1 

STATION  61    (621 


O2 


N  =   1.1733  ♦  0.0271D 


U  2.0 


STATION  65   (611 

- 

/ 

- 

y 

/ 

o, 

1^5 

-       y/ 

/            N  =  0.225t 

♦  0.11660 

STATION  80   (811 


N  -   1 .7130  •  0.0573D 


-J l_ 


10  20  30  10 


-  31.00  < 


20  30 

DEPTH    (M 


Figure  2. — Depth  distribution  of  juvenile  Arctic  cod  and  salinity  at  the  12  multidepth  stations.  Salinities  from  the  nearest  oceano- 
graphic  station  (number  in  parentheses)  from  Ingham  and  Rutland  (1972 )  and  U.S.  National  Oceanographic  Data  Center.  Numbers  on 
points  indicate  sequence  of  hauls.  Regressions  of  number  of  cod  (N)  on  depth  in  meters  (D)  fitted  by  least  squares.  Pooled  slopes  for  all 
data  =  0.0669. 


Table  5. — Analysis  of  co variance  on  data  for  abundance  and  depth  of  juvenile 
Arctic  cod  at  12  multidepth  stations  in  eastern  Chukchi  Sea. 


Source 


d.i.  SS. 


M.S. 


1.  Individual  regressions  23 

2.  Difference  between  1  and  3 
for  testing  slopes  1 1 

3.  Individual  regressions  fitted 
with  a  common  slope  34 

4.  Difference  between  3  and  5 
for  testing  levels  11 

5.  Regressions  fitted  to  a 

single  line  45         28.96030 


3,91335 

0,17015 

1.48432 

0,13494 

5.39767 

0,15876 

3.56263 

2,14206 

(2)/(1)  =  0,79;  n  s. 


(4)/(3)  =  13.49;  P<0.005 


1098 


QUAST:  DISTRIBUTION  OF  ARCTIC  COD 

DISCUSSION 

Possible  Causes  of  the  Density 

Structure  and  Its  Vertical 

Displacement 

The  steady  increase  of  number  of  cod  in  the 
density  structure  with  depth  indicated  a  graded 
rather  than  a  threshold  response  to  some  environ- 
mental factor,  because  if  the  response  depended 
on  a  threshold,  one  would  expect  a  sudden 
increase  in  density  of  juvenile  cod  when  that 
threshold  was  reached.  Salinity  relationships  in 
the  water  column  did  not  appear  to  be  a  cause  of 
the  density  structure  because  the  water  column 
was  usually  nearly  isohaline  through  the  region 
of  greatest  change  in  concentration  of  juvenile 
cod  (Figure  2) — the  density  structure  evidently 
persisted  despite  forces  that  contributed  to  oceanic 
mixing.  Predation  by  aquatic  predators  did  not 
seem  to  be  a  reasonable  cause  because  the  only 
evident  potentially  effective  fish  or  invertebrate 
predator  on  the  cod  was  large  jellyfish,  which 
occurred  in  approximately  equal  numbers 
throughout  the  water  column.  Reaction  of  the 
juvenile  cod  to  a  pressure  gradient  also  was 
dismissed,  for  reasons  discussed  below. 

A  graded  negative  phototaxis  either  in  the 
juvenile  cod  or,  possibly,  in  the  prey  they  were 
following  seemed  to  offer  the  best  hypothesis  for 
the  cause  of  the  density  structure  and  its 
variations.  A  gradient  of  increasing  darkness 
with  depth  could  coincide  closely  with  the 
gradient  for  increase  in  number  of  cod.  This  type 
of  gradient  is  illustrated  in  Figure  3  (shown  here 
for  the  English  Channel — the  slope  in  regard  to 
perception  by  the  cod  should  be  dependent  on 
turbidity  as  well  as  the  spectral  sensitivity  of  the 
juvenile  cod).  Under  this  hypothesis  the  density 
structure  of  juvenile  cod  found  at  night  was  a 
relict  of  earlier  daylight  hours,  during  which  the 
density  structure  was  maintained  despite 
turbulence,  upwelling,  and  downwelling.  With 
onset  of  darkness  the  means  of  orientation  by  the 
fish  was  removed  and  the  density  structure  was 
elevated  or  depressed,  depending  on  whether  it 
occurred  in  cells  of  upwelled  or  downwelled  water. 
The  density  structure  presumably  persisted  into 
the  early  night  when  most  hauls  were  made 
because  of  the  short  period  of  time  elapsing  before 
trawling  began  and  also  because  the  cod  were 
relatively  inactive  at  the  low  sea  temperatures 


3.0 


20  30 

DEPTH    (M) 


50 


Figure  3. — Conformity  of  the  variables — density  of  juvenile 
Arctic  cod,  loss  of  light  (blue-green,  English  Channel),  and 
pressure  at  increasing  depths.  Regression  of  fish  with  depth 
(D),  I^f  =  0.0699D,  where  N  =  most  likely  number  of  fish  in  a 
trawl  swath  (see  text);  index  of  light  loss  based  on  I  =  log,o 
(1/p  X  100),  where  p  =  percent  of  illumination  at  surface, 
from  data  of  Nicol  (1960:22);  and  pressure  (atmosphere)  based 
on  an  increase  of  1  atm/lO-m  depth,  after  Nicol  (1960:22). 


(-1.5°  to  3.5°C).  The  freshly  trawled  specimens 
were  markedly  inactive.  The  validity  of  the 
gradient  hypothesis  possibly  could  have  been 
evaluated  further  had  trawl  data  been  available 
for  daylight  hours.  Data  on  vertical  distribution  of 
zooplankton  were  not  available  because  sampling 
was  entirely  by  vertical  tows  (Wing,  in  press). 

Orientation  by  the  cod  to  a  pressure  gradient 
was  dismissed  as  an  explanation  of  the  density 
structure  for  two  reasons:  the  shape  of  the  curve 
of  pressure  on  depth  differs  from  that  of  the 
density  structure  (Figure  3),  and  orientation  to  a 
pressure  gradient  should  be  the  same  during  the 
day  as  at  night  and  should  not  allow  the 
density  structure  to  be  elevated  or  depressed. 

If  the  density  structure  were  a  result  of  behavior 
in  the  juvenile  cod,  it  may  have  been  evolved  in 
response  to  predation  by  birds.  Undoubtedly,  such 
predation  is  a  factor  of  tremendous  ecological 
importance  to  juvenile  cod,  primarily  during 
summer  when  bird  populations  are  at  their 
peak.  Arctic  piscivorous  birds  form  a  spectrum  of 
depth  capabilities,  and  because  their  feeding  is 
based  at  the  surface,  intensity  of  predation  should 
decline  with  depth,  i.e.,  complement  the  density 
structure.  Watson  and  Divoky  (1972)  give  an 
extensive  list  of  bird  species  observed  in  the 
Chukchi  Sea  during  WEBSEC-70,  the  majority  of 
which  are  either  recorded  as  predators  or  are 
assumed  to  have,  and  to  make  use  of,  the  potential 
for  predation  on  juvenile  Arctic  cod.  Included  are 
loons,     slender-billed     shearwater,     pelagic 


1099 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


cormorant,  red  phalarope,  glaucous  gull,  herring 
gull,  ivory  gull,  black-legged  kittiwake,  Ross's 
gull,  Sabine's  gull,  murres,  guillemot,  Kittlitz's 
murrelet,  parakeet  auklet,  and  horned  puffin. 
Swartz  (1966:674)  estimated  a  population  of  about 
600,000  piscivorous  birds  (adults  and  fledglings) 
at  Cape  Thompson,  which  is  south  of  Cape  Lis- 
burne,  in  1960;  murres  and  kittiwake  gulls 
accounted  for  90%  of  the  population.  He  estimated 
that  the  birds  consumed  approximately  13.5  x  10^ 
metric  tons  of  food  during  their  breeding  season. 
Tuck  (1960:166)  found  that  Arctic  cod  were  the 
most  important  fish  in  the  diet  of  murres,  as  did 
Swartz  (1966:667)  in  his  studies  at  Cape  Thomp- 
son. Tuck  cited  depth  records  for  murres  which 
indicate  that  they  are  able  to  feed  throughout 
the  entire  water  column  over  the  shelf  portion  of 
the  Chukchi  Sea.  Since  the  birds  at  Cape 
Thompson  are  undoubtedly  only  a  small  fraction 
of  the  birds  that  utilize  the  southern  Chukchi 
Sea,  predation  on  fishes  by  birds  must  be  intense 
over  the  entire  region.  However,  bird  predation 
could  not  have  been  a  direct  cause  of  the  density 
structure  during  WEBSEC-70  because  most  birds 
appeared  to  have  left  the  region  prior  to  the  time 
of  our  visit. 

The  hypothesis  of  negative  phototaxis  in  ju- 
venile Arctic  cod  had  further  appeal — it  seems 
congruent  to  presumed  needs  for  lowering  vulner- 
ability to  predation  by  birds  during  summer  when 
subsurface  illumination  is  high  while  allowing  for 
vertical  foraging  by  the  cod  when  illumination  is 
low.  Because  piscivorous  birds  undoubtedly  are 
visual  feeders,  directed  or  passive  movement 
toward  the  surface  by  juvenile  cod  at  night  should 
not  be  counterselective.  During  the  prolonged 
periods  of  low  illumination  of  arctic  winter,  and 
under  ice  cover,  juveniles  presumably  would  be 
able  to  occupy  the  entire  water  column  over  the 
continental  shelf.  However,  because  larger  ju- 
veniles, about  15  cm  TL,  were  commonly  seen  in 
daylight  near  ice  that  had  been  broken  by  the 
icebreaker,  negative  phototaxis  of  the  juveniles,  if 
present,  must  decrease  with  growth  in  favor  of 
life  near  a  substrate.  Changes  from  a  pelagic 
to  demersal  existence  during  early  grow^th  stages 
is  a  commonplace  in  fishes. 

Upwelling  and  downwelling  seemed  a  plausible 
explanation  of  the  differences  in  depth  noted  for 
the  density  structure.  Salinity  of  the  upper  water 
column  and  an  index  of  elevation  or  submergence 
of  the  density  structure,  explained  below,  showed 


good  correlation  (Table  6).  The  index  was  obtained 
for  each  station  by  algebraically  projecting  the 
pooled  value  for  slopes  of  all  regressions  of 
number  vs.  depth,  multidepth  and  replicate 
stations,  through  the  station  data,  to  the  hypo- 
thetical apex  of  the  density  structure  at  the 
station.  If  the  apex  lay  above  the  ocean  surface 
(e.g..  Figure  2,  stations  41  and  70),  the  converted 
amount  in  meters  was  negative  and  was  taken  as 
the  amount  the  density  structure  was  elevated.  If 
the  apex  lay  below  the  ocean  surface  (e.g.,  Figure 
2,  stations  88  and  92),  the  converted  amount  in 
meters  was  positive  and  was  taken  as  the  amount 
the  density  structure  was  submerged.  For  each 
replicate  station  the  regression  was  based  on  a 
point  determined  by  depth  of  trawling  and  the 
average  number  of  juvenile  cod  captured  at  the 
station.  All  indices  for  salinity  were  based  on  data 
for  10-18  m  because  this  zone  was  the  common 
depth  of  the  replicate  hauls;  however,  the  water 
column  was  usually  nearly  isohaline  from  the 
surface  to  considerably  below  this  depth  (Figure  2). 
Two  sources  of  upwelling  seemed  possible — an 
accelerated  current  around  the  Cape  Lisburne- 
Point  Hope  headland  and  wind  over  the  sampling 

Table  6. — Comparison  of  hypothetical  elevation  of  the  density 
structure  of  juvenile  Arctic  cod  at  the  trawl  stations  taken  at 
late  dusk  or  after  dark,  based  on  density  distribution  of  cod 
at  each  station,  with  surface  salinity  at  a  nearby  station. 
Stations  in  order  from  greatest  submergence  (positive  values) 
to  greatest  elevation  (negative  values)  of  the  density  structure. 
Projections  for  the  multidepth  stations  were  based  on  the  data 
of  Figure  2  fit  to  the  standard  slope  of  0.0669;  methods  for 
obtaining  projections  from  the  replicate  data  are  explained 
in  the  text. 


Indicated 

Closest 

Average 

IKMT  station 

level  of 

oceanograptiic 

salinity 

and  type  ' 

apex  in  meters 

station 

at10-18m 

88(M) 

11-9 

90 

30.72 

92(M) 

10.5 

91 

30.67 

37(R) 

4.9 

36 

31.65 

32(R) 

0.5 

31 

30.85 

30(M) 

-0.7 

29 

31.11 

51  (M) 

-2  1 

50 

31.32 

65(M) 

-3.4 

64 

31.19 

25(R) 

-5,0 

24 

31.00 

56(M) 

-8,0 

55 

31.43 

20(R) 

-12.2 

19 

31.72 

22(R) 

-12.5 

19 

31.72 

45(M) 

-12.8 

43 

31.76 

16(R) 

-15.3 

18 

31.11 

74(M) 

-17.3 

73 

31.77 

70(M) 

-17.4 

55 

31.43  ' 

61(M) 

-22.0 

62 

30,76 

10(R) 

-24.8 

9 

31.56 

41(M) 

-  26.0 

42 

31.63 

80(M) 

-  26.1 

84 

31.47 

r  =  -0.514; 

P<0.05 

'M  =  multidepth  station;  R  =  replicate  station. 


1100 


QUASI:  DISTRIBUTION  OF  ARCTIC  COD 


area.  Both  should  produce  transient  cells  of 
upwelling  and  downwelling,  but  the  wind-caused 
cells  should  have  broader  distribution. 

Currents  apparently  flow  predominantly  north- 
ward in  the  southern  Chukchi  Sea  and  accelerate 
around  headlands  (Fleming  and  Heggarty,  1966: 
744).  Therefore,  at  an  early  stage  in  analysis, 
it  appeared  that  the  density  structure  of  juvenile 
cod  encountered  during  WEBSEC-70  may  have 
been  a  result  of  bird  predation  off  the  Cape 
Lisburne-Point  Hope  headland  or  in  Kotzebue 
Sound  with  subsequent  vertical  displacement  of 
the  density  structure  in  an  eddy  north  of  Cape 
Lisburne.  However,  this  hypothesis  was  rejected 
because,  as  mentioned  previously,  birds  were  not 
abundant  during  WEBSEC-70;  most  of  them  had 
probably  left  the  region  at  least  a  month  pre- 
viously. Moreover,  oceanic  mixing  should  quickly 
dissipate  a  density  structure  that  formed  near  the 
cape.  The  apparent  occurrence  of  the  structure 
over  the  entire  sampling  area  indicated  that  it 
1)  was  quite  permanent,  2)  was  probably  main- 
tained by  the  juvenile  cod,  and  3)  was  not  in  very 
large  measure  induced  by  currents  around  Cape 
Lisburne.  These  requirements  were  satisfied  by 
the  hypothesis  of  negative  phototaxis  and  wind- 
induced  upwelling. 


Horizontal  Density  Distribution 
of  Juvenile  Cod 

Regardless  of  possible  origins  of  the  density 
structure  or  reasons  for  its  vertical  displacement, 
it  was  necessary  to  take  the  vertical  elevation 
of  the  density  structure  (Table  7)  into  considera- 
tion when  estimating  the  concentration  and  bio- 
mass  of  juvenile  cod  at  each  station.  This  correc- 
tion was  accomplished  by  regarding  the  density 
structure  as  a  unit  that  extended  downward  47 
m  (the  depth  equivalent  on  the  density  structure 
of  the  highest  number  of  cod  sampled)  in  un- 
disturbed water.  The  structure  would  be  trun- 
cated in  its  upper  part  by  the  ocean  surface 
when  raised,  or  truncated  in  its  lower  part  when 
it  intersected  the  ocean  bottom  because  of  lower- 
ing of  the  structure  or  shallowness  of  the  sea. 
Thus,  for  a  structure  that  appeared  to  be  raised 
10  m  in  the  water  column,  the  number  of  cod 
remaining  in  the  structure  was  taken  as  the 
number  that  occurred  between  10  and  47  m  in  an 
entire  structure.  If  a  structure  appeared  to  be 
truncated  by  the  ocean  bottom  for  17  m,  the 
number  of  cod  remaining  in  the  structure  was 
taken  as  the  number  between  0  and  30  m  in  an 
entire  structure.  Estimation  of  the  density  of 


Table  7. — Reconstruction  of  numbers  of  juvenile  cod  beneath  a  standard  swath  at  the  IKMT  stations,  eastern 

Chukchi  Sea. 


Depth 
of 

Indicated 

Density 

structure 

Depth 
of 

No  cod 
below 

Total  for 
column 

Station 

tows 

Average 

level  of  apex 

Depth  of 

Juvenile 

water 

density 

beneath 

(type) 

(m) 

log,o(/V  -  1) 

in  meters' 

base(m) 

cod  (no.) 

(m) 

structure 

swath 

10(R) 

11 

2  3954 

-24  8 

22.2 

4,698 

44 

7.883 

12,581 

14(R) 

11 

1  0397 

-4.5 

42.5 

5.184 

51 

3.222 

8,406 

16(R) 

11 

1,7612 

-153 

31.7 

5,138 

53 

8,073 

13.211 

20(R) 

12 

1  6159 

-12.2 

34.8 

5,179 

42 

2,729 

7,908 

22(R) 

12 

1  6399 

-12.5 

34.5 

5,176 

35 

I') 

5,366 

25(R) 

12 

1  1380 

-5.0 

42.0 

2,462 

33 

e) 

2.462 

30(M) 

— 

regression 

-0.7 

46.3 

1,268 

31 

{') 

1.268 

32(R) 

12 

0.7751 

05 

47.5 

547 

26 

{') 

547 

37(R) 

12 

0.4758 

4.9 

51.9 

4,162 

49 

{') 

4,162 

41(M) 

— 

regression 

-26.0 

21.0 

4.595 

44 

8,717 

13,312 

45(M) 

— 

regression 

-12.8 

34.2 

5,173 

44 

3,714 

8,887 

51(M) 

— 

regression 

-2.1 

44.9 

5.181 

48 

1,175 

6,356 

56(M) 

— 

regression 

-80 

390 

35,190 

44 

1,895 

7.085 

61(M) 

— 

regression 

-22.0 

250 

4,891 

29 

1.516 

6,407 

65(M) 

— 

regression 

-3.4 

43.6 

2,798 

36 

{') 

2,798 

70(tVI) 

— 

regression 

-17.4 

296 

5,088 

39 

3,563 

8,651 

74(M) 

— 

regression 

-17.3 

29.7 

2,681 

22 

{'} 

2,681 

80(M) 

— 

regression 

-26.1 

20.9 

4,586 

30 

3,449 

8,035 

88(M) 

— 

regression 

11.9 

58.9 

1,492 

45 

e) 

1,492 

92(M) 

— 

regression 

10.5 

57.5 

3.968 

54 

{') 

3,968 

'Negative  values  indicate  apex  above  the  surface. 

^Stations  at  which  hypothetical  depth  of  bottom  of  density  structure  is  deeper  than  the  bottom.  The  number  of  juvenile 
cod  represented  by  the  overlap  is  subtracted  from  the  total. 

3|n  some  instances  the  number  of  juvenile  cod  estimated  for  a  density  structure  that  was  truncated  at  the  surface  was 
slightly  higher  than  the  theoretical  number  in  an  entire  density  structure.  This  discrepancy  seems  to  be  due  to  rounding 
errors  in  the  Integrations  about  the  point  where  the  parabolic  equation  approaches  and  forms  a  small  angle  with  the 
X-axis.  Since  very  few  juvenile  cod  were  present  in  the  apex  of  the  density  structure,  the  error  is  small  and  probably  unimportant. 


1101 


juvenile  cod  below  the  presumed  density  structure 
was  a  problem  because  data  from  near  bottom 
were  not  available  for  many  stations.  Therefore, 
the  density  of  juvenile  cod  below  the  structure 
was  assumed  to  be  the  maximum  calculated  for 
the  density  structure  (i.e.,  that  at  47  m  in  an 
entire  structure).  The  possible  error  in  estimating 
biomass  of  juvenile  Arctic  cod  at  the  stations 
under  this  assumption  was  not  judged  to  be 
serious  because  the  sampling  area  was  so  shallow 
that  the  bottom  of  the  density  structure  was 
usually  close  to  the  ocean  bottom. 

Although  the  transformed  data  on  cod 
abundance  vs.  depth  were  useful  for  analyzing 
the  density  structure  at  the  stations,  back 
transformation  of  the  estimates  offered  problems 
of  interpretation.  At  present  there  appears  to  be 
no  practical  procedure  for  back  transforming  the 
variance  and  estimates  of  a  logarithmic-arith- 
metic regression.  Consequently,  the  density 
structure  was  redescribed  from  the  untrans- 
formed  data  by  fitting  a  parabolic  regression  with 
least  squares  (Figure  4).  The  variables  were 


1,300  - 


1,200 


.  1,  100 


-1 

,000 

o 

z 

l/l 

ton 

z 

7 

LU 

800 

< 

1- 

o 

o 

im 

u 

m 

-J 

z 

bOO 

UJ 

> 

D 

—1 

son 

LL 

o 

tr 

lU 

too 

CO 

5 

3 

Z 

200 


100 


Y  =  6.72605  -  3.631466X  +  0.33017x2 

A  REPLICATE  TOW 
«  MULTIDEPTH  TOW 


20  30 

CORRECTED  DEPTH   (M) 


50 


Figure  4. — Number  of  juvenile  Arctic  cod  per  Isaacs-Kidd  tow, 
the  depths  corrected  for  apparent  emergence  or  submergence 
of  the  density  structure  (Tables  6  and  7).  Weighted  regression 
(1/X^)  fitted  by  least  squares. 


FLSHERY  BULLETIN:  VOL.  72,  NO.  4 

weighted  by  the  inverse  of  the  corrected  depth 
squared  because  the  variance  of  number  of  cod 
vs.  depth  appeared  to  be  linearly  related  to  the 
square  of  the  corrected  depth.  The  result  was 

Y  =  6.72605  -  3.63466X  +  0.33017X2 

and  its  integration 


./ 


y*  =    /  y  (X)  dx 

V. 

=  4.51413  (L  -  [/)  -  1.21968  (L^  -  U^) 
+  0.07386  (L3  -  f/3) 

where  Y    =  most  likely  estimate  of  number  of  cod 

in  a  tow  at  corrected  depth. 
X    =  corrected  depth  in  meters, 
y*  =  most  likely  estimate  ofthe  number  of 

cod  over  the  depth  interval  U-L  in  a 

trawl  swath. 
U    =  upper  (shallower)  level  of  depth 

interval,  where  0^t/^L^47. 
L     =  lower  (deeper)  level  of  depth 

interval. 

Accordingly,  the  density  structure  contained 
approximately  5,186  juvenile  cod  over  its  depth 
range  (0-47  m)  over  the  area  of  a  trawl  swath. 
The  most  likely  estimate  of  maximum  density,  at 
47  m,  was  379  cod/m  of  depth  over  the  area  of 
a  trawl  swath  (5,519  m^). 

Under  these  assumptions,  composite  estimates 
ofthe  number  of  juvenile  Arctic  cod  in  the  water 
column  beneath  a  standard  trawl  swath  was  cal- 
culated for  all  IKMT  stations  (Table  7).  Totals 
for  each  station  were  obtained  by  adding  the 
number  of  juvenile  cod  estimated  for  that  section 
of  the  water  column  occupied  by  the  density 
structure — 5,186  over  47  m  of  depth  except  when 
the  structure  was  truncated  by  the  surface  or 
bottom — to  the  hypothetical  number  in  the 
column  below  the  structure,  or  379/m  of  depth. 
For  the  replicate  stations,  where  only  one  depth 
was  sampled,  the  hypothetical  depth  ofthe  struc- 
ture was  obtained  by  comparing  the  average 
catch  (log  transformed  data)  at  the  trawling  depth 
with  the  catch  (log  transformed  data)  that  would 
be  expected  at  that  depth  if  the  apex  of  the 
density  structure  coincided  with  the  ocean  sur- 
face. If  this  comparison  indicated  that  the  apex 
ofthe  hypothetical  structure  was  projected  above 


1102 


QUASI:  DISTRIBUTION  OF  ARCTIC  COD 


the  ocean  surface  (indicated  by  minus  values  for 
level  of  apex  in  Tables  6  and  7)  or  below  the 
ocean  bottom,  then  the  appropriate  adjustments, 
discussed  previously,  were  made.  As  a  result, 
estimates  of  juvenile  cod  at  the  IKMT  stations 
were  influenced  by  both  an  inferred  height  of  the 
density  structure  and  the  depth  of  water  beneath 
the  structure.  Stations  in  relatively  shallow  water 
and  with  a  deeply  submerged  density  structure 
had  the  lowest  estimates,  and  stations  in  water 
deeper  than  average  and  with  density  structures 
that  reached  to  the  surface  had  the  highest.  The 
average  for  all  stations  was  28.5  juvenile  cod/ 
1,000  m3  (Table  8).^ 

Biomass  of  juvenile  Arctic  cod  in  the  area 
surveyed  by  WEBSEC-70  was  estimated  by  con- 
verting the  overall  average  concentration  to 
volume  and  weight.  Average  volume  of  indi- 
viduals in  samples  was  0.618  ml,  with  no  apparent 
size  segregation  with  depth  (Figure  5).  If  we 
assume  that  the  specific  gravity  of  the  cod 
approximated  unity  (actually  they  were  heavier), 


^This  compares  with  an  arithmetic  average  of  7.3/1,000  m^ 
for  the  replicate  hauls  and  19.5  for  the  multidepth  hauls— an 
average  of  13.4  for  all  hauls.  Thus,  simple  arithmetic  averaging 
Yould  seriously  underestimate  the  value  obtained  under  the 
liypothesis  of  density  structure  with  upwelling  and  down- 
welling.  Even  higher  values  would  be  obtained  if  it  is  assumed 
that  the  density  structure  continued  to  increase  at  the  same 
logarithmic  rate  below  its  depth  of  47  m  until  the  bottom 
was  reached,  instead  of  having  the  increase  truncated  at  47  m. 
This  approach  would  require  extrapolation  well  beyond  all 
observed  values  for  fish  densities  and  would  not  be  fully  con- 
sistent with  the  welling  part  of  the  hypothesis. 


1.6 


1.5 


1.14 


_  1  .3 


Q  1  .2 

O 

u 


I-  '   ' 

u 

< 

u,    1  .  0 


>  0.9 


<  0.8 

Q 

> 

Q  0.7 


0.5 


5  OS 
> 

UJ 

<  o.a 

IT 
LU 
> 

<0.3 


0.2  - 


0.1  - 


0.0 


•  • 


WEIGHTED  MEAN  =  0.618  ML 


•    • 


10 


20  30 

DEPTH  OF  TOW   (M) 


140 


50 


Figure  5. — Relation  of  average  volume  (milliliters)  of  indi- 
vidual juvenile  Arctic  cod  in  IKMT  tow  to  depth  of  capture, 
eastern  Chukchi  Sea. 


Table  8. — Estimated  volume  of  water  and  number  of  juvenile 
cod  beneath  a  standard  swath  at  the  IKMT  stations,  eastern 
Chukchi  Sea. 


Volume  of  water 

Juvenile 

Station 

beneath  trawl  swath  (m^) 

cod'1,000m3 

10 

242,836 

51-8 

14 

281,469 

29.9 

16 

292.507 

45.2 

20 

231.798 

34,1 

22 

193,165 

27.8 

25 

182,127 

13.5 

30 

171,089 

7.4 

32 

143,494 

3.8 

37 

270.431 

15.4 

41 

242,836 

54.8 

45 

242,836 

36.6 

51 

264,912 

24.0 

56 

242,836 

29.2 

61 

160,051 

40.0 

65 

198,684 

14.1 

70 

215,241 

40.2 

74 

121,418 

22.1 

80 

165,570 

48.5 

88 

248,355 

60 

92 

298,026 

13.3 

Weighted 

average 

— 

28.5 

then  the  stations  averaged  17.6  g  of  juvenile 
cod/1,000  m^.  If  we  take  the  area  surveyed  in  the 
eastern  Chukchi  Sea  as  approximately  30  x  10^ 
km^  (8,714  square  nautical  miles)  and  the 
average  depth  as  40.0  m  (the  average  for  the 
20  IKMT  stations),  then  approximately  12  x  lO^^ 
m^  of  ocean  were  contained  in  the  sampling 
area.  Thus,  it  appears  that  211.2  x  10^  g  of 
fish  were  represented  by  this  volume,  or  211.2 
X  10^  metric  tons,  for  an  average  of  0.7  metric 
ton/km^  of  ocean  surface. 

Where  did  the  juvenile  cod  originate?  Likely 
sources  appear  to  be  the  Bering  Sea,  the  East 
Siberian  Sea,  or  the  Chukchi  Sea  itself.  The  north- 
western part  of  the  Bering  Sea  has  particularly 
low  temperatures  (Zenkevitch,  1963:824, 825)  and 
water  from  the  Gulf  of  Anadyr  tends  to  flow 
northeastward  (Zenkevitch,  1963:821).  The  East 
Siberian  Sea,  of  course,  also  has  low  temperatures 
and  apparently  has  an  eastward-flowing  current 


1103 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


into  the  Chukchi  Sea  (Zenkevitch,  1963:262). 
The  near  absence  of  high-arctic  zooplankton  in  the 
eastern  Chukchi  Sea  (Zenkevitch,  1963:268), 
verified  during  WEBSEC-70  by  Wing  (in  press), 
is  only  weak  evidence  that  the  cod  did  not 
originate  in  the  East  Siberian  Sea:  the  cod 
probably  spawned  in  January  and  February 
(Rass,  1968:136),  approximately  8  mo  before 
WEBSEC-70,  and  it  seems  possible  that  the 
juveniles  could  have  lost  their  arctic  ecological 
associates  over  that  period  of  time.  In  any  event, 
the  apparent  short  time  that  cod  spent  in  some 
sections  of  the  Chukchi  Sea — about  10  days  in 
the  southeastern  part  according  to  the  oceano- 
graphic  data  of  Fleming  and  Heggarty  (1966: 
724) — and  the  time  elapsed  between  spawning 
and  capture  at  our  IKMT  stations  is  evidence 
that  the  juvenile  cod  either  originated  at  consider- 
able distances  from  the  Chukchi  Sea  or  had  been 
cycled  in  the  Chukchi  Sea.  Since  there  is  reason 
to  believe  that  a  portion  of  the  Chukchi  Sea 
circulates  in  a  counterclockwise  gyre  (Zenkevitch, 
1963:262),  similar  cycling  of  eggs  and  larvae 
seems  possible. 

SUMMARY 

1.  Twenty  stations  in  the  eastern  Chukchi 
Sea  between  Icy  Cape  and  Cape  Lisburne  were 
sampled  with  a  1.8-m  (6-foot)  Isaacs-Kidd 
mid-water  trawl  (IKMT)  during  September 
and  October  1970. 

2.  Only  two  species  of  fish  occurred  in  any 
abundance  in  the  middle  and  upper  water  column 
at  night,  juvenile  Pacific  sand  lance  and  juvenile 
Arctic  cod  (mostly  age  0).  Because  the  Arctic 
cod  were  most  abundant  and  were  distributed 
through  most  of  the  water  column,  their  occur- 
rence was  given  a  detailed  analysis. 

3.  Two  types  of  IKMT  stations  were  occupied; 
one  in  which  hauls  were  replicated  at  the  same 
depth,  and  another  in  which  hauls  were  made  at 
several  depths.  All  stations  but  one  (a  replicate 
station)  were  occupied  starting  at  late  dusk  or  at 
night. 

4.  The  standard  deviation  in  frequency  of 
juvenile  cod  occurrence  at  the  replicate  stations 
seemed  to  be  proportional  to  the  means.  The 
variance  was  stabilized  by  log^j  (A^  +  1)  trans- 
formation of  the  data. 

5.  Analysis  of  variance  of  the  transformed 
data  from  the  replicate  stations  disclosed  signifi- 


cant between-station  variation  in  number  of  cod 
occurring  at  11-12  m. 

6.  Number  of  juvenile  cod  per  unit  volume  of 
water  increased  with  depth  at  all  multidepth 
stations. 

7.  Analysis  of  covariance  on  regressions  of  cod 
abundance  (logxo  transformed)  vs.  depth  disclosed 
no  significant  differences  in  slope  of  the  regres- 
sions between  stations  but  significant  differences 
in  level. 

8.  The  characteristics  of  slope  and  level  in  the 
regressions  for  multidepth  stations  described  a 
depth  region  of  logarithmic  increase  in  con- 
centrations of  juvenile  cod.  This  region  was  at  a 
different  depth  at  some  stations  than  at  others 
and  was  called  a  density  structure. 

9.  It  appeared  that  the  density  structure 
resulted  from  a  graded  rather  than  a  threshold 
response  to  subsurface  illumination.  Such  a 
response  seems  to  be  a  suitable  behavioral 
strategy  for  lessening  predation  by  piscivorous 
birds. 

10.  The  hypothesis  is  presented  that  the 
density  structure  was  formed  during  daylight 
hours  and  that  differences  in  its  vertical  dis- 
placement between  stations  at  night  were  caused 
by  wind-induced  upwelling  or  downwelling. 

11.  Average  number  of  juvenile  cod  calculated 
for  the  stations  was  28/1,000  m^  or  approximately 
0.7  metric  ton/km^  of  ocean  surface. 

12.  The  origin  of  juvenile  cod  could  have  been 
in  the  northeastern  Bering  Sea,  the  East  Siberian 
Sea,  the  Chukchi  Sea,  or  all  three.  Regardless 
of  origin,  a  cycling  of  eggs  and  larvae  within  the 
Chukchi  Sea  seems  likely. 


ACKNOWLEDGMENTS 

Merton  C.  Ingham,  Atlantic  Environmental 
Group,  National  Marine  Fisheries  Service, 
NOAA,  directed  the  cruise  and  coordinated 
investigations  aboard  the  vessel.  Bruce  L.  Wing, 
Auke  Bay  Fisheries  Laboratory,  National  Marine 
Fisheries  Service,  NOAA,  assisted  in  the  sam- 
pling; and  James  C.  Olsen  and  Jerome  J.  Pella, 
of  the  same  laboratory,  advised  on  methods  of 
mathematical  computation.  I  am  indebted  to  those 
who  read  and  commented  on  the  manuscript,  in 
particular  to  Ingham,  Wing,  Olsen,  and  Pella, 
mentioned  above,  and  to  Paul  E.  Smith,  South- 
west Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  and  George  E.  Watson,  Smith- 


1104 


QUAST:  DISTRIBUTION  OF  ARCTIC  COD 


sonian  Institution.  Special  thanks  to  the  officers 
and  crew  of  the  U.S.C.G.  icebreaker  Glacier  for 
their  cooperation  during  WEBSEC-70 — in 
particular  to  the  Marine  Science  Technicians  who 
served  long  hours  under  severe  conditions  to 
insure  that  the  expedition  would  be  a  success. 


LITERATURE  CITED 

Andriyashev,  a.  p. 

1954.  Ryby  severnykh  morei  SSSR  (Fishes  of  the  northern 
seas  of  the  USSR).  Akad.  Nauk  SSSR,  Zool.  Inst., 
Opredehteli  po  Faune  SSSR  53,  566  p.  (Translated  by 
Israel  Program  Sci.  Transl.,  1964,  617  p.;  available 
U.S.  Dep.  Commer.,  Natl.  Tech.  Inf.  Serv.,  Springfield, 
Va.,  as  OTS63-11160.) 

Fleming,  R.  H.,  and  D.  Heggarty. 

1966.  Oceanography  of  the  southeastern  Chukchi  Sea. 
In  N.  J.  Wilimovsky  and  J.  N.  Wolfe  (editors).  Environ- 
ment of  the  Cape  Thompson  region,  Alaska,  p.  697- 
754.     U.S.  Atomic  Energy  Commission,  Wash.,  D.C. 

Friedl,  W.  a. 

1971.  The  relative  sampling  performance  of  6-  and  10-foot 
Isaacs-Kidd  midwater  trawls.  Fish.  Bull.,  U.S.  69:427- 
442. 

HOGNESTAD,  P.  T. 

1968.     Observations  on  polar  cod  in  the  Barents  Sea. 
Rapp.  P.-V.  Reun.  Cons.  Perm.  Int.  Explor.  Mer  158: 
126-130. 
Ingham,  M.  C,  and  B.  A.  Rutland. 

1972.  Physical  oceanography  of  the  eastern  Chukchi 
Sea  off  Cape  Lisburne-lcy  Cape.  U.S.  Coast  Guard 
Oceanogr.  Rep.  50:1-86. 

NicoL,  J.  A.  C. 

1960.  The  biology  of  marine  animals.  Interscience 
Publishers,  N.Y.,  707  p. 


Ponomarenko,  v.  p. 

1967.  Pitanie  lichinok  i  mal  "kov  salki  {Boreogadus  saida 
Lepechin)  V  Barentsevom  i  Karskom  Moryakh  (Feeding  of 
the  larvae  and  fry  of  the  Arctic  cod  (Boreogadus  saida 
Lepechin)  in  the  Barents  and  Kara  Seas).  Polyam. 
Nauchno-Issled.  Proektnyi  Inst.  Morsk.  Rybn.  Khoz. 
Okeanogr.,  Materialy  Rybokhoz.  Issled.  Sevemogo  Bas- 
seina  10:20-27.  [Transl.  from  Russian  by  U.S.  Bur.  Sport 
Fish.  Wildl.,  1968.] 

QuAST,  J.  C. 

1972.     Preliminary  report  on   the   fish  collected   on 
WEBSEC-70.     U.S.  Coast  Guard  Oceanogr.  Rep.  50:203- 
206. 
Rass,  T.  S. 

1968.  Spawning  and  development  of  Polar  cod.  Rapp. 
P.-V.  Reun.  Cons.  Perm.  Int.  Explor.  Mer  158:135-137. 

SOKAL,  R.  R.,  and  F.  J.  ROHLF. 

1969.  Biometry.  W.  H.  Freeman  and  Company,  San 
Francisco,  776  p. 

SWARTZ,  L.  G. 

1966.     Sea-cliff  birds.    In   N.  J.  Wilimovsky  and  J.  N. 
Wolfe  (editors).  Environment  of  the  Cape  Thompson 
region,  Alaska,  p.  611-678.     U.S.  Atomic  Energy  Com- 
mission, Wash.,  D.C. 
Tuck,  L.  M. 

1960.     The  murres.     Can.   Dep.   North.   Affairs  Natl. 
Resour.,  Can.  Wildl.  Serv.,  Ottawa,  Can.,  260  p. 
Watson,  G.  E.,  and  G.  J.  Divoky. 

1972.     Pelagic  bird  and  mammal  observations  in  the 
eastern  Chukchi  Sea,  early  fall  1970.     U.S.  Coast  Guard 
Oceanogr.  Rep.  50:111-172. 
Wing,  B.  L. 

In  press.     Kinds  and  abundance  of  zooplankton  collected 
by  the  USCG  icebreaker  Glacier  in  the  eastern  Chukchi 
Sea,  September-October   1970.     U.S.   Dep.  Commer., 
NOAA  Tech.  Rep.  NMFS  SSRF. 
Zenkevitch,  L. 

1963.  Biology  of  the  seasof  the  U.S.S.R.  Interscience  Pub- 
lishers, N.Y.,  955  p. 


1105 


DESCRIPTION  OF  EGGS  AND  LARVAE  OF  SCALED  SARDINE, 

HARENGULA  JAGUANA'  ^ 

Edward  D.  Houde,^  William  J.  Richards,''  and  Vishnu  P.  Saksena^ 

ABSTRACT 

Eggs  and  larvae  of  scaled  sardine,  Harengula  jaguana,  were  described  from  specimens  reared 
in  the  laboratory.  Meristics,  morphometries,  osteology,  and  pigmentation  were  examined  as 
development  proceeded.  Transformation  of  larvae  to  the  juvenile  stage  was  complete  at  22  to  24 
mm  standard  length.  During  transformation  outstanding  features  included  forward  movement 
of  the  dorsal  fin,  shortening  of  the  gut,  and  forward  movement  of  the  anal  fin.  Eggs  and  larvae 
of  scaled  sardine  were  compared  with  those  of  other  clupeids  that  may  occur  in  the  same  areas.  An 
illustrated  series  of  scaled  sardine  eggs  and  larvae,  including  details  of  the  caudal  fin,  was  presented  to 
show  changes  that  occur  during  development. 


Scaled  sardines,  Harengula  jaguana  Poey,  are 
common  clupeids  in  the  tropical  western  Atlantic 
(Rivas,  1963).  Until  recently  they  were  known 
as  H.  pensacolae  Goode  and  Bean,  1879,  but 
Whitehead  (1973)  has  concluded  that  the  correct 
name  for  the  species  is  Harengula  jaguana  Poey, 
1865.  Scaled  sardines  prefer  coastal  habitats 
and  have  been  reported  from  New  Jersey  to  Brazil; 
they  are  abundant  in  the  Gulf  of  Mexico  (Briggs, 
1958;  Rivas,  1963;  Berry,  1964b).  Despite  their 
common  occurrence,  larvae  have  not  been  de- 
scribed. Matsuura  (1972)  has  described  arti- 
ficially fertilized  and  planktonic  eggs  of  this 
species.  Fecundity,  maturation,  and  spawning  of 
scaled  sardines  recently  were  reported  by  Mar- 
tinez (1972).  Eggs  have  been  collected  in  south 
Florida,  and  the  larvae  reared  to  juvenile  sizes 
in  the  laboratory  (Houde  and  Palko,  1970; 
Detwyler  and  Houde,  1970;  Saksena  and  Houde, 
1972).  Eggs  and  larvae  from  these  experiments 
have  provided  us  with  material  to  describe  early 
development. 

Scaled  sardines  support  a  small  bait  fishery 
in  south  Florida  and  are  important  forage  for 


'Contribution  No.  1786,  Rosenstiel  School  of  Marine  and  At- 
mospheric Science,  University  of  Miami,  Miami,  FL  33149. 

^Contribution  No.  235,  Southeast  Fisheries  Center,  National 
Marine  Fisheries  Service,  NOAA,  Miami,  FL  33149. 

''Rosenstiel  School  of  Marine  and  Atmospheric  Science, 
University  of  Miami,  Division  of  Fisheries  and  Applied 
Estuarine  Ecology,  10  Rickenbacker  Causeway,  Miami,  FL 
33149. 

■•Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  75  Virginia  Beach  Drive,  Miami,  FL  33149. 

^Department  of  Biology,  Muskingum  College,  New  Con- 
cord, OH  43762. 


predatory  fishes  like  Spanish  mackerel, Scombero- 
niorus  maculatus  (Klima,  1959).  They  are  caught 
for  human  consumption  throughout  the  West 
Indies  and  are  canned  in  Cuba  and  Venezuela 
(Rivas,  1963).  Scaled  sardines  are  one  of  the 
clupeid  species  that  may  have  potential  to 
support  reduction  fisheries  in  the  tropical 
Atlantic. 

Eggs  and  larvae  of  other  species  attributed 
to  the  genus  Harengula  have  been  described. 
Uchida  et  al.  (1958)  described  larvae  and  juve- 
niles of//,  zunasi  from  Japan,  and  Takita  (1966) 
described  eggs  and  newly  hatched  larvae  of  that 
species.  Whitehead,  Boeseman,  and  Wheeler 

(1966)  stated  that  this  species  is  in  fact  a 
Sardinella,  based  on  skeletal  characters.  Marchal 

(1967)  included  //.  rouxi  in  his  key  to  some  west 
African  clupeid  eggs  and  larvae.  Berry  (1964a) 
and  Berry  and  Whitehead  (1968)  restricted  the 
genus  Harengula  to  members  having  paired 
hypomaxillary  bones.  Neither  //.  rouxi  nor  //. 
zunasi  have  hypomaxillaries,  and  both  species 
presumably  belong  in  the  genus  Sardinella. 

METHODS 

Eggs  were  collected  in  surface  tows  of  plankton 
nets  near  Miami  Beach  and  in  Biscayne  Bay, 
Fla.  during  1969  through  1971.  A  total  of  10 
embryos  and  165  larvae  from  rearing  experi- 
ments were  preserved  in  5%  Formalin*'  to  describe 


•^Reference  to  trade  names  does  not  imply  endorsement 
by  the  National  Marine  Fisheries  Service,  NOAA. 


Manuscript  accepted  December  197.3. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 

1106 


HOUDE',  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


development.  Rearing  methods  have  been  de- 
scribed (Houde  and  Palko,  1970;  Saksena  and 
Houde,  1972).  Scaled  sardines  can  be  reared 
successfully  at  temperatures  from  21°  to  33.5°C 
(Saksena,  Steinmetz,  and  Houde,  1972),  and 
salinities  have  ranged  from  29  to  37%o.  Larvae 
and  juveniles  up  to  38.7  mm  standard  length  are 
included  in  this  description,  but  we  have  reared 
scaled  sardines  to  more  than  100  mm  in  some 
experiments. 

Morphometries 

Eggs  and  larvae  were  measured  with  an  ocular 
micrometer  in  a  dissecting  microscope.  The 
following  measurements  were  made: 

Total  length  (TD— Tip  of  snout  to  end  of 
caudal  fin. 

Standard  length  (SL) — Tip  of  snout  to  tip  of 
notochord  on  small  larvae,  before  notochord 
flexure;  tip  of  snout  to  base  of  hypural  plate 
on  larger  larvae,  after  notochord  flexure.  Unless 
otherwise  noted,  all  references  to  lengths  of 
larvae  in  text  refer  to  standard  lengths. 

Preanus  length — Tip  of  snout  to  anus,  measured 
along  midline.  This  measurement  is  equivalent  to 
preanal  fln  length  for  specimens  that  have  the 
anal  fin  developed. 

Predorsal  length — Tip  of  snout  to  origin  of 
dorsal  fin,  measured  along  midline  of  body. 

Prepelvic  length — Tip  of  snout  to  origin  of  pelvic 
fins,  measured  along  midline  of  body. 

Head  length — Tip  of  snout  to  posterior  margin 
of  otic  capsules  in  yolk-sac  larvae;  tip  of  snout 
to  opercular  margin  in  older  larvae. 

Snout  length — Tip  of  snout  to  anterior  margin 
of  eye. 

Eye  diameter — Horizontal  distance  between 
anterior  and  posterior  edges  of  the  fleshy  orbit. 

Body  depth — Vertical  height  of  the  body  at  the 
pectoral  symphysis. 

Meristies 

Fin  rays  were  counted  in  each  of  the  develop- 
ing fins  (Table  4).  Myomeres  were  counted  and 
designated  as  follows: 

Total  myomeres. 

Preanal  myomeres:  number  anterior  to  the 
anus. 


Postanal  myomeres:  number  posterior  to  the 
anus. 

Predorsal  myomeres:  number  anterior  to  the 
dorsal  fin  origin. 

Postdorsal — preanal  myomeres:  number  be- 
tween the  posterior  insertion  of  the  dorsal 
fin  and  the  anus. 

Osteology 

Sequence  of  ossification  was  determined  from  a 
total  of  16  specimens  ranging  in  length  from  4.8 
to  22.4  mm.  They  were  cleared  with  trypsin 
and  stained  with  alizarin  using  the  method  of 
Taylor  (1967).  Development  of  the  caudal  fin 
bones  was  examined  in  detail.  Ossification  of  fin 
rays,  vertebrae,  and  head  bones  also  was 
examined. 


DESCRIPTION 
Description  and  Occurrence  of  Embryos 

Ten  fertilized  eggs  from  plankton  collections 
were  spherical,  ranging  from  1.55  to  1.78  mm  in 
diameter  (mean  =  1.66  mm).  They  had  a  single, 
light  yellow  oil  globule  ranging  from  0.07  to  0.10 
mm  in  diameter  (mean  =  0.09  mm).  Measure- 
ments did  not  differ  from  artificially  fertilized 
eggs  described  by  Matsuura  (1972).  Embryos  were 
well  developed  when  preserved  (Figure  6A), 
and  yolk  diameters  ranged  from  0.63  to  0.72 
mm  at  that  time.  The  perivitelline  space  was 
wide,  averaging  589c  of  the  egg  diameter  for 
the  10  preserved  specimens.  In  living  embryos, 
the  yolk  is  clearly  segmented,  but  segments  are 
difficult  to  see  in  preserved  specimens.  The 
chorion  is  thin,  unpigmented,  and  unsculptured; 
it  is  fragile  and  easily  broken  compared  to  most 
teleost  eggs.  Preserved  embryos  had  no  discern- 
ible pigment.  Living  embryos,  just  prior  to  hatch- 
ing, had  tiny  melanophores,  which  were  diffi- 
cult to  see,  in  a  paired  dorsolateral  series  near 
the  dorsal  midline. 

Embryos  that  were  collected  from  mid-May 
through  July  were  well  developed  by  noon  when 
our  collections  were  examined  (Figure  7).  Sur- 
face water  temperatures  were  28°C  or  higher  in  the 
spawning  area.  Spawning  presumably  occurs  only 
at  night  because  embryos  are  all  at  similar 
stages  of  development  when  collected  in  the 
morning.  Hatching  usually  began  by  late  after- 


1107 


noon,  less  than  24  h  after  the  presumed  spawning 
time. 

The  spawning  season  extends  from  February 
through  July  near  Miami,  based  on  our  collec- 
tions of  planktonic  eggs.  Spawning  may  occur 
within  Biscayne  Bay  from  late  February  through 
early  May  but  is  confined  to  more  offshore  areas 
later  in  the  season.  Biggest  egg  collections  were 
made  about  4  km  east  of  Miami  Beach  during 
May  and  June.  Martinez  (1972)  confirmed  the 
spawning  season  of  scaled  sardines  by  deter- 
mining gonad  indices  and  examining  ovarian 
maturation  of  adults  collected  throughout  the 
year  from  south  Florida. 

Description  of  Larvae 

Body  Shape 

Larvae  were  2.4  mm  at  hatching.  The  head  was 
bent  over  the  large,  nearly  spherical  yolk  sac. 
Yolk  was  absorbed  and  the  body  axis  straight- 
ened during  the  next  12  h  at  26°  to  28°C.  By  12  to 
15  h  after  hatching,  larvae  were  typically  clupe- 
oid  (Figure  8A).  They  were  elongate,  thin  larvae 
averaging  4.4  mm  at  15  h  after  hatching.  The 
gut  was  a  long  straight  tube  at  this  stage.  Little 
growth  occurred  during  the  first  3  days  after 
hatching.  Thereafter,  growth  was  rapid  and 
temperature-dependent  (Saksena  et  al.,  1972). 
Larvae  retained  the  typically  elongate  and  rodlike 
shape  until  they  transformed  to  juveniles  when 
they  became  deeper  bodied  and  laterally  com- 
pressed. Proportional  measurements  of  larvae 
in  relation  to  standard  length  are  given  in 
Table  1. 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

Yolk  Absorption  and  Gut  Differentiation 

Absorption  of  the  nearly  spherical  yolk  mass 
in  newly  hatched  larvae  was  rapid  at  26°  to 
28°C.  The  oil  globule  was  located  ventrally  and 
just  posterior  to  the  middle  of  the  yolk  mass  in 
newly  hatched  larvae  (Figure  8A).  By  48  h  after 
hatching  the  yolk  sac  and  oil  globule  had  been 
absorbed,  and  larvae  were  actively  feeding.  The 
gut  was  a  straight  tube  at  15  h  after  hatching 
(Figure  8A),  but  a  distinct  foregut  and  hindgut 
were  present  at  2  days  (Figure  8B).  By  4  days 
(at  about  5.0  mm)  the  hindgut  appeared  to  be 
composed  of  a  series  of  adjacent  muscular  rings, 
typical  of  clupeid  larvae. 

Total  Length  and  Standard  Length 

Standard  length  was  used  to  examine  develop- 
ment of  scaled  sardine  larvae  with  respect  to 
other  morphometric  data.  The  relation  between 
standard  length  and  total  length  (Table  1,  Figure 
1)  was  not  linear  over  all  sizes  of  larvae  that 
were  available.  Standard  length  decreased  rela- 
tive to  total  length  as  larvae  grew.  Standard 
length  was  about  97'7f  TL  for  larvae  between  4  and 
8  mm  TL  but  decreased  to  857c  TL  for  larvae  be- 
tween 8  and  25  mm  TL.  The  ratio  averaged  about 
83%  TL  for  individuals  longer  than  25  mm  TL.  The 
observed  decrease  between  8  and  25  mm  TL  was 
related  to  development  of  the  caudal  fin,  particu- 
larly notochord  flexure  and  hypural  plate  de- 
velopment. 

Preanus  Length 

Preanus  length  averaged  83%  SL  at  15  h  after 


Table  1. — Summary  of  relationships  between  total  lengths  (TL)  and  standard  lengths  (SL),  and  proportional  measurements  relative  to 
standard  lengths  for  larvae  used  to  describe  Harengulajaguana  development.  Proportions  are  from  data  fitted  by  eye  to  relationships  in 
Figures  1  to  5. 


Preanus 

Predorsal 

Body 

Head 

Snout 

Eye 

Prepelvic 

TL 

SL 

length: 

length: 

depth: 

length: 

length: 

diameter: 

length: 

(mm) 

(mm) 

SL  TL 

SL 

SL 

SL 

SL 

SL 

SL 

SL 

4.3 

4,2 

0.977 

0.833 

— 

0.064 

0.119 

0.017 

0.045 



6.2 

6,0 

,968 

.867 

— 

.067 

.133 

.025 

.042 

— 

82 

8,0 

.978 

,888 

0.680 

.064 

.138 

.031 

.041 

— 

10,8 

10,0 

.926 

,890 

648 

.081 

.157 

.036 

.041 

— 

13.0 

120 

923 

,900 

626 

.087 

.167 

.040 

.043 

0.440 

15.4 

14,0 

.909 

,864 

.600 

.100 

.185 

.047 

.050 

.447 

185 

16,0 

.865 

,838 

.556 

.125 

.204 

.052 

.056 

.466 

20.8 

18,0 

,865 

,822 

.517 

.142 

.217 

.057 

.057 

.467 

23.1 

20.0 

,866 

.780 

.478 

.162 

.240 

.066 

.064 

.462 

25.6 

22.0 

859 

.764 

.441 

.184 

.264 

,072 

.073 

.465 

29.0 

24.0 

828 

.775 

.417 

.219 

.262 

.072 

.075 

.482 

31.5 

26.0 

,825 

.758 

.404 

.236 

.260 

.072 

.077 

.485 

33,6 

28.0 

,833 

.750 

.408 

.245 

.257 

.071 

.075 

.481 

36.0 

30.0 

.833 

.750 

.410 

.252 

.257 

.071 

.074 

.482 

38.5 

32.0 

.831 

.750 

409 

.262 

.250 

.071 

.073 

482 

1108 


HOUDE,  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


—  30 

E 
E 


.y 


20  25  30 

TOTAL    LENGTH    (mml 


Figure  1. — Relation  between  standard  length  and  total  length 
for  larvae  of  Harengula  jaguana. 


38.7  mm,  which  falls  within  the  range  of  varia- 
tion in  head  lengths  reported  for  juvenile  and 
adult  H.  pensacolae  pensacolae  (Rivas,  1950). 

Eye  Diameter 

Eye  diameters  averaged  4.0  to  4.5%  SL  for 
specimens  4.2  to  12  mm  (Table  1,  Figure  4). 
A  rapid  increase  in  eye  diameters  from  4.3  to 
7.39c  SL  occurred  in  specimens  12  to  22  mm. 
Eye  diameters  on  specimens  longer  than  22  mm 
varied,  but  no  increasing  trend  relative  to  stan- 
dard length  was  observed.  A  38.7-mm  specimen 
had  an  eye  diameter  of  7.8%  SL.  Eye  diameters 
were  variable  for  larvae  of  a  given  length  (Figure 
4);  for  example,  at  12  mm,  eye  diameters  varied 
from  about  3.5  to  5.5%   SL.  Rivas  (1950)  and 


hatching  and  increased  to  about  90%  SL  when 
larvae  were  12  mm  (Table  1,  Figure  2).  A 
gradual  decrease  in  preanus  length  occurred  in 
larger  larvae.  At  22  mm,  preanus  length  was 
76%  SL;  juveniles  28  to  32  mm  had  preanus 
lengths  that  averaged  75%  SL.  Decreasing  pre- 
anus length  in  larger  larvae  was  caused  by 
shortening  of  the  gut  during  transformation  to 
the  juvenile  stage. 

Head  Length 

Head  length  increased  relative  to  standard 
length  from  12%  at  4.2  mm  to  26%  at  22.0  mm 
(Table  1,  Figure  3).  The  ratio  was  constant  at 
25  to  26%   SL  for  specimens  between  22  and 


+  =  PREPELVrC  LENGTHS 

•■  HEaO    LENGTHS 


..^^^* 


,r'*' 


ii-  >■■ 


12  16  20  24  2B 

STANDARD  LENGTH    (mm) 


Figure  3. — Relation  of  head  length  and  prepelvic  length  to 
standard  length  for  larvae  oi Harengula  jaguana. 


5  200 


PREANAL  LENGTHS 
PREDORSAL  LENGTHS 


/ 


J* 


STANDARD    LENGTH    (mml 


O 
Q     6 


■  BOOT  DEPTH 

■  EYE    DIAMETER 


16  20  24  28 

STANDARD   LENGTH    (mm) 


Figure  2. — Relation  of  preanal  length  and  predorsal  length 
to  standard  length  for  larvae  of  Harengula  jaguana. 


Figure  4. — Relation  of  eye  diameter  and  body  depth  to  standard 
length  for  larvae  of  Harengula  jaguana. 


1109 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Storey  (1938)  found  eye  diameters  to  be  variable 
for  juvenile  and  adult  H.  pensacolae. 

Snout  Length 

Snout  length  increased  from  1.7  to  7.2%  SL 
for  larvae  between  4.2  and  22.0  mm  (Table  1, 
Figure  5).  It  remained  constant  for  longer  larvae 
at  about  1.2%,  which  is  within  the  range  of 
variation  for  juvenile  and  adult  H.  pensacolae 
(Rivas,  1963).  Like  eye  diameters,  snout  lengths 
varied  considerably  for  larvae  of  a  given  size; 
for  example,  at  12  mm,  snout  length  varied 
from  about  3.1  to  4.8%  SL. 

Body  Depth 

Body  depth  at  the  pectoral  symphysis  was 
constant  at  about  6.5%  SL  for  larvae  from  4.2 
to  9.0  mm.  Body  depth  then  increased  rapidly 
from  7.0  to  21.9%  SL  for  specimens  between 
9.0  and  24.0  mm  SL.  A  slow  increase  continued 
to  occur  for  larger  individuals  (Table  1,  Figure  4). 

Predorsal  Length 

Predorsal  lengths,  as  measured  from  the  snout 
to  the  first  developing  ray  in  the  dorsal  fin, 
were  recorded  on  specimens  7.5  mm  and  longer, 
when  the  rays  Ibegan  to  develop.  The  dorsal  fin 
moves  forward  as  development  proceeds,  causing 
predorsal  length  to  decrease  from  68.0%  SL  to 
41.7%  SL  for  larvae  between  7.5  and  24.0  mm 
(Table  1,  Figure  2).  Predorsal  lengths  averaged 
41%  SL  for  specimens  longer  than  24.0  mm. 


16  20  24  28  32  36  40 

STANDARD  LENGTH    (mm) 


Prepelvic  Length 

Prepelvic  lengths  were  measured  on  larvae  that 
had  pelvic  fin  buds  or  fins.  At  11  to  12  mm, 
prepelvic  lengths  averaged  about  44%  SL,  in- 
creasing to  46%  SL  for  larvae  up  to  22  mm 
(Table  1;  Figure  3).  Prepelvic  lengths  averaged 
48%  SL  for  specimens  between  24  and  38.7  mm. 
Pelvic  fins  moved  slightly  posterior  as  larvae 
transformed  to  juveniles,  causing  the  observed 
small  increase  in  prepelvic  length. 


Meristics 


Myomeres 


Total  numbers  of  myomeres  ranged  from  39 
to  42;  most  larvae  had  40  or  41.  Numbers 
of  myomeres  and  distribution  of  myomeres  in 
relation  to  other  body  parts  can  be  useful  for 
identifying  clupeid  genera  (Ahlstrom,  1968). 
Total  myomeres  could  be  counted  accurately  on 
144  of  our  larvae.  Frequencies  were  as  follows: 


Number  of  myomeres 
Frequency 


39 

2 


40 
68 


41 
67 


42 

7 


Figure  5. — Relation  of  snout  length  to  standard  length  for 
larvae  oi Harengula  jaguana. 


The    mean    number    of   myomeres    was    40.56 
(Si  =  0.2861). 

Distribution  of  myomeres  in  relation  to  the 
dorsal  fin  and  anus  was  examined  for  larvae  in 
2-mm  size  classes  (Table  2).  Preanal  myomeres 
decreased  as  larvae  grew  from  about  35  for  the 
smallest  larvae  to  27  at  transformation.  Postanal 
myomeres  increased  from  a  mean  number  of  5.7 
for  the  smallest  larvae  to  more  than  12  for  trans- 
formed specimens.  Shortening  of  the  gut  during 
development  accounted  for  the  observed  changes 
in  preanal  and  postanal  myomere  counts.  Mean 
numbers  of  predorsal  myomeres  decreased  rapidly 
from  about  25  to  10  as  development  proceeded, 
reflecting  the  anterior  movement  of  the  dorsal  fin. 
Considerable  variation  in  predorsal  myomere 
numbers  was  present  for  larvae  of  a  given  length 
(Table  2).  Postdorsal-preanal  myomeres  ranged 
from  5  to  7  for  larvae  of  all  sizes,  but  the  mean 
number  tended  to  decrease  as  larvae  grew  from  8 
to  22  mm. 

Fin  Development 

Newly  hatched  larvae  had  a  fin  fold  that  in- 
vested much  of  the  body  and  which  persisted  in 


1110 


HOUDE,  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 

Table  2. — Distribution  of  myomeres  relative  to  other  body  parts  for  Harengula  jaguana  larvae. 


Preanal  myomeres 

Postanal  myomeres 

Predorsal  myomeres 

Postdorsal-p 
Number  of 

reanal 

myomeres 

Size  class 

Number 

of 

Number 

of 

Number 

of 

(mm,  SL) 

specimens 

Mean 

Range 

specimens 

Mean 

Range 

specimens 

Mean 

Range 

specimens 

Mean 

Range 

4.0-  6.0 

34 

34.85 

34-36 

36 

5.67 

5-7 

_ 

_ 

_ 

6.1-  8.0 

16 

35.00 

34-36 

17 

5.53 

5-7 

11 

24.82 

23-26 

12 

667 

5-7 

8.1-10.0 

22 

34.68 

33-36 

22 

6.09 

5-7 

22 

23.41 

22-25 

22 

6.50 

5-7 

10.1-12.0 

18 

33.72 

32-35 

18 

6.89 

6-8 

18 

21.61 

20-24 

18 

6.00 

5-7 

12.1-14.0 

15 

33.47 

32-35 

15 

7.20 

6-8 

15 

21.07 

20-23 

15 

5.67 

5-7 

14.1-16.0 

12 

32.08 

30-34 

12 

8.25 

7-9 

12 

18.75 

16-22 

12 

5.42 

5-6 

16.1-18.0 

6 

31.67 

31-33 

6 

8.50 

8-9 

6 

17.17 

16-19 

6 

5.50 

5-6 

18.1-20.0 

4 

31.00 

31 

4 

9.25 

9-10 

4 

15.25 

15-16 

4 

5.50 

5-6 

20.1-22.0 

1 

29  00 

29 

1 

11.00 

11 

1 

13.00 

13 

1 

5.00 

5 

>22.0 

4 

27.25 

26-28 

4 

12.75 

12-14 

4 

10.00 

8-11 

4 

6.25 

6-7 

part  until  larvae  were  about  16  mm.  Pectoral 
fin  buds  were  present  at  hatching  (Figure  8A), 
but  no  other  fins  were  developed  at  this  stage. 
An  opaque  area  in  the  fin  fold  was  the  first  indi- 
cation of  median  fin  development.  Rayed  fins 
developed  in  the  following  sequence:  dorsal,  cau- 
dal, anal,  pelvics,  pectorals.  Fin  rays  first  develop 
as  cartilaginous  structures;  thus,  the  sizes  of 
larvae  at  which  full  complements  are  present 
may  be  smaller  than  the  sizes  at  which  rays  are 
fully  ossified.  Tables  3  and  4  summarize  fin  de- 
velopment sequence  of  scaled  sardine  larvae, 
and  details  are  discussed  in  the  osteological 
development  section. 

Median  fin  development  usually  was  com- 
pleted at  16.0  mm.  Dorsal  fin  rays  first  ap- 
peared between  7.0  and  7.5  mm.  A  full  com- 
plement of  17  to  19  rays  was  present  at  14.0 
to  17.0  mm.  Principal  caudal  rays  were  first  seen 


at  7.4  to  8.0  mm,  and  the  full  complement  of  19 
usually  was  attained  at  10.0  mm.  Some  specimens 
as  small  as  8.5  mm  had  the  full  complement  of 
principal  caudal  rays;  a  few  specimens  did  not 
have  a  full  complement  until  they  were  longer 
than  11.0  mm.  Secondary  caudal  rays  developed  at 
10.8  to  12.8  mm,  and  the  full  complement  of  8  or  9 
dorsal  and  7  ventral  secondary  caudal  rays  was 
present  at  16.5  to  19.0  mm.  Notochord  flexure, 
which  occurs  during  caudal  fin  development, 
began  at  the  same  size  that  principal  caudal  rays 
first  developed.  Anal  fin  rays  usually  began  to 
develop  at  9.0  to  9.3  mm,  but  two  specimens  8.5  to 
9.0  mm  had  some  anal  rays.  A  full  complement  of 
17  or  18  anal  rays  was  present  at  13.0  to  15.0  mm. 
Although  principal  caudal  and  anal  fin  rays  began 
to  develop  after  dorsal  fin  rays,  the  dorsal  was  the 
last  median  fin  to  attain  its  full  ray  complement. 
Paired  fins  began  to  develop  after  median 


Table  3. — Summary  of  fin  development  sequence  in  larvae  of  Harengula  jaguana. 


Buds  first 
appear 

Standard 

length]  (mm)' 

Fin 

Rays  first 
appear 

Full  complement 
of  rays 

Number  of  rays 

in  fully  developed 

fin 

Dorsal 

— 

7.0  to  7.5 

14.0  to  16.0 

17  to  19 

Caudal 
Principal 

Secondary 

— 

7.4  to  8.0 
10.8  to  12.8 

8.5  to  11.0 

(most  by  10.0) 

16.5  to  19.0 

19 

8  or  9  dorsally 
7  ventrally 

Anal 

— 

9.0  to  9.3 
(rarely  at 
8.5  to  9.0) 

13.0  to  15.0 

17  or  18 

Pelvic 

11.0-12.0 

(rarely  at 

smaller  size) 

13.0  to  14.0 

(rarely  at 

<13.0) 

14.6  to  17.8 
(most  by  15.5) 

7  or  8 
(usually  8) 

Pectoral 

<4.0 

15.0  to  16-0 

(rarely  at 
smaller  size) 

18.5  to  19.5 

14  to  16 

'Rays  were  present  at  the  tabulated  lengtfis.  but  not  necessarily  ossified  at  those  sizes. 


1111 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 
Table  4. — Some  meristic  characters  oflarval  andiuvenileHarengulajaguana 


Standard 
length 
(mm) 


Caudal 
rays 


Dorsal 
rays 


Anal 
rays 


Pectoral 
rays 


Pelvic 
rays 


Standard 
length       Caudal        Dorsal  Anal         Pectoral       Pelvic 

(mm)  rays  rays  rays  rays  rays 


2.3-6.9 

No  el 

ements  present 

on  ' 

7.0 

— 

5 

— 

7.3 

No  elements 

pre 

7.4 

3 

6 

— 

7.4 

— 

6 

— 

7.5 

— 

8 

— 

7.5 

— 

3 

— 

7.6 

No  elements 

pre 

7.6 

— 

9 

— 

7.7 

— 

7 

— 

7.8 

2 

9 

— 

7.9 

3 

8 

— 

7.9 

5 

9 

— 

8.0 

— 

8 

— 

8.0 

2 

5 

— 

8.1 

3 

6 

— 

8.3 

6 

11 

— 

8.5 

19 

14 

3 

8.6 

6 

11 

— 

8.6 

10 

11 

— 

8.6 

— 

2 

— 

8.9 

4 

8 

— 

9.1 

15 

8 

— 

9.1 

15 

12 

5 

9.4 

8 

12 

3 

9.4 

19 

12 

8 

9.4 

19 

13 

5 

9.4 

10 

9 

3 

9.5 

15 

10 

— 

9.5 

3 

9 

— 

9.7 

19 

12 

8 

9.7 

19 

12 

8 

9.8 

19 

14 

6 

9.8 

17 

13 

7 

9.8 

19 

12 

6 

10.0 

19 

14 

9 

10.0 

8 

10 

— 

10.4 

19 

14 

9 

10.4 

18 

16 

15 

10.5 

19 

15 

10 

10.5 

19 

13 

10 

10.9 

14 

11 

2 

10.9 

19 

16 

12 

11.0 

17 

14 

3 

11.0 

17 

9 

3 

11.2 

19 

14 

11 

11.3 

19 

16 

12 

11.3 

19 

15 

11 

11.5 

19 

13 

10 

11.7 

19 

17 

4 

11.7 

19 

13 

9 

11.9 

19 

14 

13 

— 

— 

11.9 

19 

16 

15 

11 

5 

12.0 

19 

14 

10 

— 

— 

12.1 

19 

14 

8 

— 

— 

12.2 

19 

16 

13 

— 

— 

12.3 

19 

15 

9 

— 

12.4 

19 

14 

8 

— 

— 

12.7 

19 

15 

12 

— 

— 

12.8 

19 

15 

12 

— 

— 

12.8 

19 

15 

10 

— 

13.0 

19 

17 

17 

9 

5 

13.1 

19 

17 

16 

— 

2 

13.1 

19 

17 

15 

— 

6 

13.5 

19 

14 

11 

— 

13.6 

19 

15 

9 

— 

13.7 

19 

16 

12 

— 

13.9 

19 

17 

11 

— 

14.0 

19 

16 

12 

— 

14.2 

19 

16 

14 

— 

14.6 

19 

17 

17 

12 

7 

14.9 

19 

16 

16 

— 

4 

14.9 

19 

17 

16 

— 

6 

15.2 

19 

17 

17 

— 

7 

15.2 

19 

17 

17 

5 

6 

15.2 

19 

18 

15 

— 

3 

15.5 

19 

17 

15 

10 

8 

15.6 

19 

18 

15 

10 

7 

15.8 

19 

17 

17 

13 

7 

15.9 

19 

17 

17 

— 

7 

16.4 

19 

18 

17 

11 

7 

16.6 

19 

17 

17 

12 

8 

17.3 

19 

19 

17 

14 

8 

17.4 

19 

19 

17 

13 

8 

17.5 

19 

18 

17 

— 

6 

17.8 

19 

18 

17 

12 

6 

18.0 

19 

18 

17 

12 

7 

18.4 

19 

18 

18 

13 

8 

18.6 

19 

18 

16 

15 

7 

19.3 

19 

17 

17 

14 

8 

21.3 

19 

18 

17 

15 

8 

22.4 

19 

17 

17 

14 

8 

24.2 

19  . 

17 

18 

14 

8 

24.2 

19 

18 

17 

15 

7 

24.7 

19 

18 

18 

14 

7 

26.7 

19 

17 

18 

14 

8 

27.5 

19 

18 

18 

15 

7 

289 

19 

17 

18 

15 

8 

30.2 

19 

17 

18 

15 

8 

31.4 

20 

18 

17 

16 

8 

31.8 

19 

17 

18 

14 

8 

38.7 

19 

17 

17 

15 

7 

fins.  Rayless  pectoral  fins  were  present  soon  after 
hatching,  but  rays  usually  did  not  develop  until 
larvae  were  15.0  to  16.0  mm.  One  specimen 
had  some  pectoral  rays  at  only  11.9  mm,  but  this 
was  unusual.  Full  complements  of  14  to  16 
pectoral  rays  were  attained  at  18.5  to  19.5  mm. 
Pectorals  were  the  last  fins  to  complete  develop- 
ment. Pelvic  fins  first  appeared  as  buds  when 
larvae  were  11.0  to  12.0  mm;  most  specimens 
had  pelvic  buds  at  11.3  mm.  Pelvic  rays  usually 
began  to  develop  at  13.0  to  14.0  mm,  but  one 
11.7-mm  specimen  had  rays.  A  full  complement 
of  7  or  8  (usually  8)  pelvic  rays  was  present 
at  14.6  to  17.8  mm.  Most  specimens  had  complete 
pelvic  fins  by  15.5  mm. 


Scales 

Scale  development  apparently  occurred  at  21 
to  22  mm.  No  specimens  from  18.5  to  21.2  mm 
were  scaled.  The  illustrated  specimen  21.3  mm 
(Figure  IOC)  was  fully  scaled  as  were  4  speci- 
mens from  22.4  to  24.2  mm. 

Osteological  Development 

Sixteen  cleared  and  stained  specimens  pro- 
vided a  record  of  sequence  of  development  of 
skeletal  structures  in  scaled  sardine  larvae.  Bones 
stain  as  a  result  of  calcification,  but  many 
bones,  though  unstained,  were  discernible  before 


1112 


HOUDE,  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


calcification  as  distinct  cartilaginous  structures. 
Our  four  smallest  specimens  (4.8,  6.2,  6.5,  and 
8.9  mm)  showed  no  evidence  of  staining  and 
only  slight  indication  of  developing  bone  struc- 
tures. Our  first  specimen  to  show  clear  evidence 
of  stain  uptake  and  well-formed  cartilaginous 
structures  was  10.9  mm.  The  only  bone  which 
was  stained  in  this  specimen  was  the  cleithrum. 
The  next  bones  to  stain  (an  11.5-mm  specimen) 
were  the  maxillaries,  dentaries,  principal  caudal 
fin  rays,  hypurals,  and  parhypural.  Ossification 
then  proceeded  rapidly  as  larvae  grew. 

The  Caudal  Fin  Complex 

Clupeids  have  a  complex  caudal  fin,  and  for 
descriptive  purposes  we  follow  the  terminology 
of  Nybelin  (1963).  The  adult  caudal  fin  has  the 
following  structures:  2  ural  vertebrae,  6  hy- 
purals, a  parhypural  associated  with  the  first 
preural  vertebra,  19  principal  caudal  rays  (the 
lower  and  upper  are  unbranched,  the  remainder 
branched),  2  or  3  epurals,  3  pairs  of  uroneurals, 
8  or  9  dorsal  secondary  caudal  rays,  7  ventral 
secondary  caudal  rays,  and  a  modified  neural 
arch  and  spine  on  the  first  preural  vertebra. 
In  a  9.9-mm  specimen  the  parhypural  and  the 
first  four  hypurals  were  visible  (but  not  stained) 
as  distinct  cartilage  entities  (Figure  6A).  A  notice- 
able gap  was  present  between  the  second  and 
third  hypural  which  persisted  to  the  adult  stage 
and  separated  the  9  lower  from  the  10  upper 
principal  caudal  rays. 

The  association  of  individual  principal  caudal 
fin  rays  with  the  parhypural  and  hypurals  was 
nearly  constant.  Our  method  of  counting  princi- 
pal caudal  rays  was  anterior  to  posterior  or, 
after  notochord  flexion,  ventral  to  dorsal.  The 
hjqjurals  were  counted  similarly.  The  first  two 
principal  rays  articulated  with  the  parhypural, 
rays  3  to  7  articulated  with  the  first  hypural 
(in  specimens  larger  than  15.0  mm  ray  8  also 
associated  with  this  hypural);  rays  8  and  9  with 
the  second  hypural;  rays  10  to  14  with  the 
third  hypural;  rays  15  and  16  with  the  fourth 
hypural;  rays  17  and  18  with  the  fifth  hypural; 
and  ray  19  with  the  sixth  hypural.  Rays  1  and  19 
were  stained  deepest,  and  staining  decreased 
medially  indicating  that  rays  9  and  10  were 
the  last  to  ossify  although  these  rays  were  the 
first  to  develop. 

In  the  11.5-mm  specimen  (Figure  6B)  there 


was  a  slight  indication  of  ossification  of  the  first 
pair  of  uroneurals  and  the  neural  arch  of  the 
first  preural  vertebra.  The  hypurals  were  all 
stained  as  was  the  parhypural  and  hemal  spine 
of  the  second  preural  vertebra.  In  the  11.9-mm 
specimen  the  first  uroneural  pair  was  well  stained 
as  was  the  second  uroneural  pair,  and  the  second 
ural  centrum  was  deeply  stained.  The  second 
uroneural  lay  just  posterior  to  the  second  ural 
vertebra  along  the  plane  of  the  notochord.  The 
first  uroneural  originated  above  an  area  that 
became  the  first  preural  centrum,  but  there  was 
no  indication  of  the  centrum  at  11.9  mm.  The 
first  uroneural  extended  along  the  notochord 
over  the  second  ural  centrum  and  ended  midway 
along  the  second  uroneural.  The  second  uroneural 
extended  from  the  second  ural  centrum  to  the 
origin  of  the  sixth  hypural.  Two  other  structures 
were  discernible  but  not  stained  at  11.9  mm — 
the  hemal  spines  of  the  second  and  third  preural 
vertebrae  and  the  posteriormost  ventral  secon- 
dary caudal  fin  ray. 

In  the  12.0-mm  specimen,  little  change  oc- 
curred. In  the  12.4-mm  specimen,  all  the  struc- 
tures mentioned  above  were  more  deeply  stained, 
and  the  neural  and  hemal  spines  of  the  second 
preural  vertebra  (though  this  vertebra  is  undif- 
ferentiated) were  stained  (Figure  6C).  Of  partic- 
ular interest  in  this  specimen  was  the  marked 
similarity  of  the  hemal  spine  of  the  second 
preural  vertebra  to  the  parhypural.  Nybelin 
(1963)  considered  the  parh3TJural  to  be  a  hemal 
spine,  and  our  observation  bears  this  out  in  as 
much  as  the  caudal  artery  goes  through  this  bone 
rather  than  over  it.  Monod  (1968)  has  referred 
to  the  hemal  spine  of  the  first  preural  centrum 
as  the  parhypural  bone  and  Hollister  (1936) 
considered  this  bone  to  be  a  hypural.  We  use  the 
term  parhypural  because  it  has  characteristics 
of  both  a  hypural  bone  and  a  hemal  spine. 
During  its  development,  it  closely  resembles  a 
hypural  and  in  fact  is  joined  to  the  first  hypural 
(see  Figure  6D),  and  it  bears  two  principal 
caudal  rays.  Both  spines  of  the  two  preural 
vertebrae  are  flattened  bones  with  developing 
hemal  arches  between  the  spine  base  and  the 
notochord.  In  the  14.0-mm  specimen,  the  first 
preural  centrum  and  the  two  ural  centra  were 
stained  as  was  the  lower  portion  of  the  second 
preural  centrum.  The  posteriormost  ventral 
secondary  caudal  ray  was  stained.  A  neural  arch 
was  visible,  though  unstained  on  the  first  pre- 


1113 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


B 


I- 


1  mm 

Figure  6. — Development  of  the  caudal  fin  structures  in  larvae  oi Harengula  jaguana.  Fin  rays  are  omitted  from 
the  illustrations  to  show  the  supporting  structures  more  clearly.  Standard  length  of  specimens:  A,  9.9  mm;  B,  11.5 
mm;  C,  12.4  mm;  D,  14.9  mm;  E,  18.0  mm;  F,  19.3  mm.  Abbreviations:  HYj^  =  hypurals,  Ep,.3  =  epurals,  Uj  and 
U2  =  ural  vertebrae,  P^  and  Pyj  =  preural  vertebrae,  Hs  =  hemal  spine,  Nc  =  notochord,  Un-Urs  =  uroneurals, 
Ns  =  neural  spine,  Na  =  neural  arch,  Ph  =  parhypural. 


1114 


HOUDE,  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


ural  centrum  and  was  not  connected  to  the  first 
uroneural  base. 

In  the  14.9-mm  specimen  major  features  in- 
cluded an  ossified  area  on  the  notochord  posterior 
to  the  sixth  hypural  (Figure  6D).  This  structure 
apparently  was  temporary;  it  was  not  the  third 
uroneural  and  it  was  not  as  clearly  observed 
in  larger  specimens.  Four  upper  secondary  caudal 
rays  were  visible  though  only  the  posteriormost 
was  stained.  Three  lower  secondary  caudal  rays 
also  were  present  with  only  the  posteriormost 
stained.  Two  epurals  were  barely  discernible  and 
were  not  stained.  The  "hemal  archlike"  bone  of 
the  parhypural  changed  shape  and  appeared  as 
a  forked  bone  which  received  the  spine  of  the 
parhypural  between  its  forks.  This  small  hemal 
archlike  bone  also  supported  the  first  hypural 
and  abutted  the  first  preural  centrum,  the  noto- 
chord between  the  first  preural  centrum  and  the 
first  ural  centrum,  and  the  first  ural  centrum 
itself.  The  third  hypural  abutted  the  second  ural 
centrum,  and  the  remaining  hypurals  abutted 
the  notochord.  At  this  stage,  it  was  obvious 
that  the  first  uroneural  was  fused  to  the  first 
preural  centrum.  The  second  uroneural  was  free 
and  never  fused  with  any  bone. 

In  the  15.6-mm  specimen,  seven  upper  secon- 
dary caudal  rays  and  four  ventral  secondary 
caudal  rays  were  stained.  Two  epurals  were 
visible  but  weakly  stained.  An  anteriorly  directed 
flange  or  expansion  had  developed  on  the  base 
of  the  parhypural.  Its  supporting  hemal  arch 
structure  was  distinct  and  not  fused  with  the 
flange.  The  neural  arch  on  the  first  preural 
vertebra  was  beginning  to  ossify.  In  the  16.6-mm 
specimen,  the  third  uroneural  was  visible,  lying 
lateral  to  the  second  uroneural.  It  was  shaped 
like  the  second  uroneural  but  was  much  smaller 
and  appeared  as  a  well  ossified  splintlike  bone. 
The  ossified  area  above  the  sixth  hypural  that 
was  noted  in  the  14.9-mm  specimen  was  not 
present.  Three  epurals  were  visible  but  not  ossi- 
fied. The  full  complement  of  secondary  caudal 
rays  was  present — eight  upper,  seven  lower. 

In  the  18.0-mm  specimen,  several  significant 
changes  were  evident  (Figure  6E).  First,  only 
two  epurals  were  present,  and  they  were  slightly 
stained.  This  probably  was  the  result  of  indi- 
vidual variation  since  three  were  observed  in  the 
16.6-mm  specimen.  The  neural  arch  of  the  first 
preural  vertebra  had  developed  an  upward  pro- 
jecting spinelike  process.  This  neural  arch  lay 


over  the  posterior  dorsal  surface  of  the  first 
preural  centrum  between  the  bases  of  the  left 
and  right  first  uroneural.  We  did  not  verify 
that  the  dorsal  nerve  passes  through  this  arch; 
thus  this  neural  arch  and  spine  of  the  first 
preural  vertebra  could  be  some  other  bone.  Fusion 
had  not  taken  place  between  the  neural  arch  and 
the  first  uroneural  bases  in  this  specimen.  The 
first  hypural  no  longer  touched  the  first  preural 
centrum,  and  a  remnant  of  its  hemal  archlike 
base  remained  between  the  vertebra  and  the 
hypural.  The  first  or  anteriormost  upper  and  lower 
secondary  caudal  fin  rays  lay  parallel  to  the 
body  axis  rather  than  slightly  vertical  as  in 
smaller  specimens.  The  third  uroneural  lay 
immediately  above  and  posterior  to  the  second 
uroneural. 

Little  difference  was  noted  between  the 
19.3-mm  and  the  18.0-mm  specimen  except  for 
the  complete  absence  of  the  hemal  archlike 
support  of  the  first  hypural  in  the  larger  speci- 
men (Figure  6F).  Three  epurals  were  present 
but  were  still  only  faintly  stained.  Without  doubt, 
these  were  the  last  components  of  the  caudal 
fin  to  ossify.  In  this  specimen,  there  were  nine 
upper  and  seven  lower  secondary  caudal  rays. 
The  second  preural  vertebra  had  the  anomalous 
condition  of  bearing  two  neural  spines. 

All  three  uroneurals  are  paired  and  obviously 
provide  rigid  support  for  the  notochord  as  the 
tail  develops.  As  a  result,  the  first  and  second 
uroneurals  are  among  the  first  tail  bones  to 
ossify.  The  ossified  first  uroneural  fuses  to  the 
first  preural  centrum  after  the  centrum  becomes 
ossified.  The  other  uroneurals  were  not  fused  to 
any  bone  in  the  Harengula  we  examined  nor 
were  they  fused  to  other  bones  in  large  larvae 
of  Opisthonema  (Richards,  Miller,  and  Houde, 
1974). 

Dorsal  and  Anal  Fins 

Ossification  of  dorsal  fin  rays  was  first  ob- 
served in  the  11.9-mm  specimen.  Twelve  rays  in 
the  midregion  of  the  developing  fin  were  faintly 
stained.  Supporting  pterygiophores  for  these 
rays  also  were  faintly  stained.  About  eight  un- 
stained anal  rays  were  visible,  but  no  supporting 
pterygiophores  were  seen.  In  the  12.4-mm  speci- 
men, 12  dorsal  rays  also  were  stained  but  these 
were  the  last  12  rays  of  the  fin.  Supporting 
pterygiophores  for  these  rays  also  were  stained. 


1115 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


The  anal  fin  rays  showed  only  slight  staining. 
The  14.0-mm  specimen  had  15  ossified  dorsal 
rays  and  pterygiophores;  the  anal  had  11  un- 
stained rays  and  pterygiophores.  At  this  size, 
the  vertebrae  were  countable  and  the  dorsal  rays 
were  over  the  24th  to  29th  vertebrae.  The  anal 
fin  was  beneath  the  34th  to  38th  vertebrae.  In 
the  14.9-mm  specimen,  17  ossified  dorsal  rays 
were  present  and  were  over  the  20th  to  27th 
vertebrae.  The  anal  fin  had  15  faintly  stained 
rays  and  visible  but  unstained  pterygiophores. 
This  fin  was  under  the  33rd  through  38th 
vertebrae.  In  the  15.6-mm  specimen,  the  anal 
fin  pterygiophores  were  well  ossified.  Seventeen 
dorsal  pterygiophores  supported  18  rays  (1  ptery- 
giophore  supported  the  first  2  rays),  and  14  anal 
pterygiophores  supported  15  ossified  anal  rays 
(1  pterygiophore  supporting  the  first  2  rays). 
In  that  specimen,  the  dorsal  fin  was  over  the 
19th  to  27th  vertebrae,  the  anal  under  the  33rd 
to  37th  vertebrae.  In  the  16.4-mm  specimen,  18 
dorsal  and  16  anal  ossified  rays  were  present. 
The  first  few  pterygiophores  of  each  fin  were 
faintly  stained.  The  dorsal  fin  was  over  the  18th 
to  25th  vertebrae,  the  anal  under  the  32nd  to 
38th  vertebrae.  In  the  18.0-mm  specimen,  there 
were  two  ural  vertebrae  in  the  caudal  region.  In 
the  12.0-mm  specimen,  the  middle  vertebrae  were 
visible  because  the  ventral  portions  of  their  centra 
were  ossified.  In  the  12.4-mm  specimen,  20  verte- 
brae anterior  to  the  dorsal  fin  were  ossified. 
Neither  the  first  few  vertebrae  nor  the  last  several 
were  ossified.  The  14.0-mm  specimen  had  the  first 
vertebra  faintly  stained,  the  next  36  were  com- 
plete, the  next  3  were  visible  but  unstained,  and 
the  last  had  only  the  lower  half  of  the  centrum 
stained.  In  this  specimen,  a  few  neural  arches  near 
the  middle  of  the  vertebral  column  were  lightly 
stained.  The  first  10  hemal  spines  also  were 
slightly  stained  as  were  the  2  preceding  the 
parhypural.  In  the  14.9-mm  specimen,  all  neural 
spines  and  hemal  spines  were  lightly  stained. 
Pleural  ribs  were  first  observed  in  the  15.6-mm 
specimen  on  the  8th  to  16th  vertebrae.  From  den- 
sity of  stain,  it  appears  that  they  develop  in  a 
posterior  to  anterior  direction. 


completed  for  the  related  Atlantic  thread  herring, 
Opisthonema  oglinum  (Richards  et  al.,  1974). 
The  maxillaries  and  dentaries  of  scaled  sardines 
ossified  at  11.5  mm.  At  this  time,  the  maxillary 
bore  five  small  teeth.  These  teeth  were  too  small 
to  be  shown  in  the  illustrations.  Teeth  were  added 
with  growth — 8  teeth  at  14.0  mm,  14  teeth  at 
14.9  mm,  17  teeth  at  15.6  mm.  Teeth  were 
observed  on  the  dentary  only  on  the  15.6-mm 
specimen,  where  two  were  observed.  Dentary 
teeth  apparently  are  a  temporary  feature.  Teeth 
also  were  present  on  the  basihyal;  the  15.6-mm 
specimen  had  two  large  teeth,  and  the  16.6-mm 
specimen  had  three  teeth  on  this  bone.  These 
teeth,  like  the  dentary  teeth,  apparently  are 
temporary  larval  structures.  They  were  also 
seen  as  temporary  structures  in  the  larvae  of 
O.  oglinum  (Richards  et  al.,  1974).  The  pre- 
maxillaries  were  first  visible  in  the  14.9-mm 
specimen,  and  the  posterior  supramaxillaries 
were  first  seen  in  the  16.6-mm  specimen.  The 
anterior  supramaxillaries  and  the  hypomaxil- 
laries  had  still  not  developed  in  our  19.3-mm 
specimen  but  were  present  in  our  22.4-mm  speci- 
men. Berry  (1964a)  reported  hypomaxillaries  to 
be  developed  in  a  16-mm  specimen  of  Harengula 
thrissina  from  the  eastern  Pacific. 

Pigmentation 

Melanophore  distribution  on  preserved  scaled 


/  / 


Head  Bones 

The  many  skull  bones  were  difficult  to  de- 
scribe. A  detailed  analysis  of  general  develop- 
mental changes  in  skull  development  has  been 


Figure  7. — Late  stage  egg  o( Harengula  jaguana. 


1116 


HOUDE,  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


sardine  larvae  is  similar  to  that  of  other  clupeid 
larvae.  Pigmentation  varied  somewhat  among 
individuals  of  the  same  size,  but  a  general 
pattern  was  always  present.  Some  variation  re- 
sulted because  individual  melanophores  could  be 
in  either  a  contracted  or  expanded  state.  Illus- 
trated specimens  have  pigmentation  that  is  typi- 
cal of  most  larvae  of  those  sizes  (Figures  8  to 
10).  In  life,  numerous  yellow  chromatophores 
were  present,  usually  as  internal  pigmentation, 
but  these  were  not  illustrated. 

Head  Region 

Pigmentation  was  sparse  on  the  head  of  scaled 
sardine  larvae  until  they  attained  15  mm.  Eyes 
became  pigmented  when  larvae  were  4  to  5  mm, 
at  30  to  40  h  after  hatching.  At  the  same  time, 
from  two  to  four  melanophores  developed  near 
the  pectoral  symphysis.  These  usually  consisted 


of  one  just  anterior  to  the  symphysis  and  a  pair 
immediately  posterior  to  it.  They  were  retained 
throughout  larval  development.  One  or  two 
melanophores  usually  were  present  at  the  base 
of  the  pectoral  fins  when  larvae  were  6.5  mm  or 
longer.  From  one  to  four  stellate  melanophores 
first  appeared  over  the  hindbrain  at  7  to  8  mm. 
This  number  gradually  increased  as  larvae  grew, 
but  some  specimens  had  only  a  single  melano- 
phore  at  14  mm.  On  specimens  longer  than  15  mm, 
melanophores  became  numerous  over  the  mid- 
brain and  hindbrain.  One  or  two  deeply  im- 
bedded melanophores  were  visible  through  the 
otic  capsules  on  most  specimens  longer  than 
8  mm.  One  or  two  stellate  melanophores  fre- 
quently appeared  on  the  cheek  when  larvae  were 
14  mm.  This  number  often  increased  to  several 
at  15  to  18  mm.  Tiny  melanophores  developed 
on  the  snout  and  lower  jaw  of  larvae  that  were 
14  to  17  mm.  Melanophore  numbers  increased 


# 


^ 


-JL^--'  '~^ 


Figure  8. — Larvae  oi Harengula  jaguana:  A,  4.4  mm  SL;  B,  4.5  mm  SL;  C,  6.0  mm  SL. 


1117 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


■T» — jr->— 


_*^.A__i-_4 * —  -   «- It — »^ i^_^i---«-.*,.. 


Figure  9. — Larvae  of  Harengula  jaguana:  A,  8.9  mm  SL;  B,  11.5  mm  SL. 


rapidly  on  specimens  longer  than  18  mm,  al- 
though there  was  much  individual  variation. 
Numerous  stellate  melanophores  were  present 
over  the  brain,  on  the  snout,  jaws,  and  cheek 
region  of  specimens  between  18  and  24  mm. 

Gut  and  Trunk  Region 

Paired  series  of  melanophores,  typical  of 
clupeid  larvae,  developed  over  the  dorsolateral 
surface  of  the  foregut  region  and  along  the 
ventral  surface  of  the  hindgut  at  about  4.5  mm. 
Numbers  of  pairs  in  the  series  were  variable, 
ranging  from  7  to  12  along  the  foregut  and  from 
8  to  14  along  the  hindgut.  Those  on  the  foregut 
usually  were  more  evenly  paired  than  those  on 
the  hindgut.  In  specimens  where  the  melano- 
phores were  contracted,  pairs  were  easily  dis- 
tinguished, but  when  dispersed,  the  pairs  often 
tended  to  coalesce  forming  streaky  lines  of  pig- 
ment. The  two  series  were  retained  until  larvae 
were  21  mm,  but  became  indistinct  on  some 
larvae  between  18  and  21  mm.  No  distinct  series 
could  be  distinguished  on  specimens  longer  than 
21  mm. 

Two  series  of  melanophores  were  present  in- 
ternally. One  series  was  found  dorsal  to  the  gut 
and  the  second  extended  from  the  hindbrain  pos- 
teriorly along  the  vertebral  column.  Two  melano- 
phores appeared  near  the  dorsal  surface  of  the  gut 
near  the  anus  at  4  to  5  mm,  from  which  the 


series  of  melanophores  dorsal  to  the  hindgut 
began  to  develop  at  5  to  6  mm.  The  number 
gradually  increased  from  as  few  as  2  to  5  to 
as  many  as  34  when  larvae  were  12  to  15  mm. 
The  first  melanophores  in  this  series  developed 
near  the  posterior  of  the  hindgut;  additional 
melanophores  developed  anterior  to  those.  The 
series  along  the  vertebral  column  first  appeared 
at  10  to  12  mm,  and  numbers  gradually  in- 
creased to  about  25.  Melanophores  in  this  series 
first  appeared  just  posterior  to  the  hindbrain; 
additional  melanophores  developed  posterior  to 
them.  The  vertebral  series  was  difficult  to 
distinguish  in  most  specimens  and  was  not  in- 
cluded in  illustrations.  Both  series  became  in- 
distinct on  specimens  longer  than  18  mm  because 
larvae  increased  in  body  thickness. 

Two  stellate  melanophores  developed  at  the 
anal  fin  base  between  11  and  13.5  mm.  The 
number  increased  as  larvae  grew.  At  14  to  15  mm, 
stellate  melanophores  appeared  at  the  dorsal 
fin  base,  the  numbers  increasing  from  one  oi 
two  to  eight  or  more  at  18  mm.  Between  18  and 
21  mm,  a  few  melanophores  developed  in  the 
dorsal  fin  of  most  individuals,  and  a  paired 
series  of  stellate  melanophores  developed  pos- 
terior to  the  dorsal  fin  along  the  dorsal  midline. 
One  or  two  melanophores  were  present  at  the 
bases  of  the  pelvic  fins  in  larvae  longer  than 
15  mm. 

Stellate  melanophores  began  to  appear  on  the 


1118 


HOUDE.  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


J^ 


•  j»**^~^.'' 


•.■e,N 


Figure  10. — Larvae  of  Harengula  jaguana:  A,  16.1  mm  SL;  B,  18.8  mm  SL;  C,  21.3  mm  SL. 


sides  of  most  larvae  between  16  and  17  mm. 
The  first  of  these  developed  posterior  to  the 
dorsal  fin  along  the  lateral  midline  of  larvae. 
Numbers  increased  as  larvae  grew,  spreading 
anteriorly,  dorsally,  and  ventrally  so  that  most 
individuals  had  numerous  melanophores  scat- 
tered over  their  sides  by  22  mm.  The  epaxial 
myomeres  of  specimens  longer  than  22  mm  usu- 
ally were  outlined  by  melanophores  that  were  con- 
centrated along  the  myosepta.  Silver  coloration 
began  to  appear  along  the  ventral  and  ventro- 
lateral areas  of  the  trunk  at  22  to  24  mm.  By 
28  mm  few  melanophores  could  be  discerned 
below  the  midline  on  sides  of  juveniles  because 
of  the  accumulation  of  guanine  in  that  area. 


At  this  stage,  scaled  sardines  resemble  large 
juveniles  and  adults  because  of  their  predomi- 
nantly silver  color. 

Caudal  Region 

Newly  hatched  larvae,  4  to  4.5  mm,  had  three 
or  four  melanophores  along  the  dorsal  tip  of  the 
notochord.  In  the  first  48  h  after  hatching,  the 
number  of  melanophores  in  that  area  ranged 
from  three  to  six.  During  the  same  time  from 
one  to  three  melanophores  developed  along  the 
ventral  tip  of  the  notochord  in  some  specimens. 
As  caudal  rays  began  to  develop  at  8  to  10  mm, 
pigment  migrated  from  the  notochord  tip  to  the 

1119 


FISHERY  BULLETIN:  VOL.  72,  NO,  4 


area  surrounding  the  rays.  From  one  to  three 
deeply  imbedded  melanophores  were  present  near 
the  hypural  plate  when  larvae  reached  11  to 
16  mm.  Larger  specimens  had  similar  pigmenta- 
tion in  the  caudal  region  except  that  the  number 
of  melanophores  surrounding  the  caudal  rays 
continued  to  increase  as  larvae  grew. 

Transformation 

Transformation  of  larvae  apparently  was  com- 
plete between  22  and  24  mm.  Scaled  sardines 
of  22  mm  conformed  to  descriptions  of  juveniles 
and  adults  in  most  respects  (Storey,  1938;  Rivas, 
1950,  1963).  Proportional  measurements  relating 
preanal  length,  predorsal  length,  head  length, 
and  eye  diameter  to  standard  length  became  con- 
stant at  22  to  24  mm  (Table  1).  Only  body 
depth  continued  to  increase  relative  to  stan- 
dard length  for  larger  individuals.  The  slender 
rodlike  shape  of  larvae  was  replaced  by  the 
deeper  bodied,  laterally  compressed  shape  of 
juveniles  during  transformation.  Also,  the  rela- 
tion between  standard  length  and  total  length 
became  constant  when  scaled  sardines  were  22 
to  24  mm  (Table  1).  Full  fin  ray  complements 
were  present  by  19.5  mm  (Table  3),  slightly 
before  the  dorsal  and  anal  fins  had  completed 
their  movements  during  transformation.  Scales 
first  developed  at  21  to  22  mm,  and  the  typical 
silvery  coloration  of  juveniles  was  apparent  at 
22  to  24  mm.  Some  outstanding  features  during 
transformation  were  forward  movement  of  the 
dorsal  fin,  shortening  of  the  gut,  forward  move- 
ment of  the  anal  fin,  and  relative  increases  in 
head  length,  snout  length,  eye  diameter,  and  body 
depth. 

COMPARISONS 

Eggs  and  larvae  of  scaled  sardines  can  be 
distinguished  from  those  of  similar  genera  in 
south  Florida  marine  waters.  Houde  and  Fore 
(1973)  have  prepared  a  guide  that  will  help  to 
identify  eggs  and  larvae  of  some  clupeid  fishes, 
including  scaled  sardines,  from  the  Gulf  of  Mexico. 

Scaled  sardine  eggs  are  larger  than  those  of 
other  clupeid  genera  from  south  Florida.  Only 
scaled  sardines  have  eggs  larger  than  1.50  mm 
diameter.  Eggs  of  Opisthonema  oglinum,  Sar- 
dinella  anchovia,  Brevoortia  spp.,  and  Etrumeus 
teres  rarely  exceed  1.35  mm  diameter.  The  oil 


globule  of  scaled  sardine  eggs  is  smaller  than 
that  reported  for  other  clupeid  genera.  Eggs  of 
Etrumeus  have  no  oil  globule  and  cannot  be 
confused  with  scaled  sardines.  Two  other  species 
o{ Harengula  may  occur  near  Miami.  Harengula 
humeralis  and  H.  clupeola  are  not  common 
compared  to  H.  jaguana,  but  their  eggs  may  be 
similar  to  those  of  scaled  sardines.  Eggs  of 
Jenkinsia  spp.  are  undescribed  and  cannot  be 
compared  to  scaled  sardine  eggs. 

Scaled  sardine  larvae  can  be  distinguished 
from  all  other  genera  of  clupeids  with  which 
they  might  cooccur,  except  perhaps  for  Jenkinsia 
spp.,  which  are  undescribed.  Myomeres  do  not 
exceed  42  in  Harengula  larvae,  but  number  45 
or  more  in  other  genera,  except  for  Jenkinsia 
which  has  myomere  numbers  similar  to  Haren- 
gula. Larvae  of//,  humeralis  and  //.  clupeola 
are  undescribed,  but  probably  are  similar  to  those 
of  scaled  sardines.  Caudal  pigmentation  of  larvae 
less  than  9  mm  serves  to  separate  scaled  sardine 
larvae  of  those  sizes  from  larvae  o{  Opisthonema 
and  Sardinella.  Those  two  genera  have  melano- 
phores only  on  the  ventral  side  of  the  notochord 
tip  while  scaled  sardines  always  have  melano- 
phores on  the  dorsal  side  of  the  notochord  tip 
and  frequently  on  the  ventral  side  as  well. 
Brevoortia  larvae  have  caudal  pigmentation  like 
that  o^  Harengula,  but  they  rarely  have  fewer 
than  45  myomeres. 

Eggs  and  larvae  of  two  species  that  Berry 
(1964a)  and  Whitehead  et  al.  ( 1966)  would  assign 
to  the  genus  Sardinella  have  been  described 
as  Harengula  zunasi  (Uchida  et  al.,  1958;  Takita, 
1966)  and  //.  rouxi  (Marchal,  1967).  Eggs  and 
larvae  of//,  zunasi  from  Japanese  waters  (Uchida 
et  al.,  1958;  Takita,  1966)  closely  resemble  those 
of  //.  jaguana.  Egg  diameters  and  oil  globule 
diameters  of  H.  zunasi  average  slightly  larger 
than  for  //.  jaguana ,  but  the  very  wide  pervitel- 
line  space  and  exceptionally  small  oil  globule 
are  similar  in  the  two  species.  Pigmentation  is 
present  only  on  the  ventral  side  of  the  notochord 
tip  in  H.  zunasi  larvae,  thus  differing  from 
//.  jaguana.  Both  //.  zunasi  and  H.  jaguana 
larvae  have  less  than  45  myomeres — 43  in 
H.  zunasi,  usually  40  or  41  in  //.  jaguana. 
Marchal's  (1967)  Harengula  (=  Sardinella)  rouxi 
eggs  and  larvae  also  more  closely  resemble  those 
of  H.  jaguana  than  other  clupeid  eggs  and  larvae 
that  we  have  observed  from  Florida  waters. 
Eggs  of//,  rouxi  are  smaller  than  //.  jaguana. 


1120 


HOUDE,  RICHARDS,  and  SAKSENA:  EGGS  AND  LARVAE  OF  SCALED  SARDINE 


but  relative  widths  of  the  pervitelHne  space  and 
the  oil  globule  diameters  are  similar.  H.  rouxi 
andH.jaguana  larvae  have  similar  pigmentation 
at  the  notochord  tip.  Myomeres  range  from  43 
to  45  in  H.  rouxi,  which  is  higher  than  for 
H.  jaguana  but  lower  than  the  number  observed 
in  most  other  clupeids. 

ACKNOWLEDGMENTS 

Barbara  Palko  assisted  in  rearing  eggs  and 
larvae  used  for  this  report.  Thomas  Potthoff 
cleared  and  stained  specimens  used  to  describe 
osteological  development.  Grady  Reinert  illus- 
trated eggs  and  larvae,  and  Claire  Ulanoff  the 
caudal  fin  structures.  A  draft  of  the  manuscript 
was  reviewed  and  criticized  by  E.  H.  Ahlstrom. 
P.  J.  P.  Whitehead  brought  to  our  attention  the 
nomenclature  change  of  H.  pensacolae  to  H. 
jaguana  and  provided  information  regarding  the 
systematic  problems  related  to  Harengula.  To 
all  of  them  we  extend  our  sincere  thanks. 

Partial  financial  support  of  research  leading  to 
this  report  was  provided  by  National  Science 
Foundation  Grant  GY-8560  to  V.  P.  Saksena. 
Additional  financial  support  was  derived  through 
NOAA  Sea  Grant  04-3-158-27  Sub.  3  to  the 
University  of  Miami. 

LITERATURE  CITED 

Ahlstrom,  E.H. 

1968.  Book  review  of:  Mansueti,  A.  J.  and  J.  D.  Hardy,  Jr. 
1967.  Development  of  fishes  of  the  Chesapeake  Bay  re- 
gion, an  atlas  of  egg,  larval,  and  juvenile  stages.  Part  I. 
Copeia  1968:648-651. 
Berry,  F.  H. 

1964a.   A  hypomaxillary  bone   in  Harengula   (Pisces: 

Clupeidae).  Pac.  Sci.  18:373-377. 
1964b.  Review  and  emendation  of  Family  Clupeidae  by 
Samuel  F.  Hildebrand.  Copeia  1964:720-730. 
Berry,  F.  H.,  and  P.  J.  P.  Whitehead. 

1968.   A  new  species  of  sardine  (Sardinella ,  Clupeidae)  from 
the  Marquesas  Islands.  Proc.  Biol.  Soc.  Wash.  81:209-222. 
Briggs,  J.  C. 

1958.  A  list  of  Florida  fishes  and  their  distribution.  Bull. 
Fla.  State  Mus.,  Biol.  Sci.  2:225-318. 
Detwyler,  R.,  and  E.  D.  Houde. 

1970.  Food  selection  by  laboratory-reared  larvae  of  the 
scaled  sardine  Harengula  pensacolae  (Pisces,  Clupeidae) 
and  the  bay  anchovy  Anchoa  mitchilli  (Pisces,  En- 
graulidae).  Mar.  Biol.  (Berl.)  7:214-222. 

HOLUSTER,  G. 

1936.  Caudal  skeleton  of  Bermuda  shallow  water  fishes.  I. 
Order  Isospondyli:  Elopidae,  Megalopidae,  Albulidae, 
Clupeidae,  Dussumieriidae,  Engraulidae.  Zoologica 
(N.Y.)  21:257-290. 


Houde,  E.  D.,  and  P.  L.  Fore. 

1973.  Guide  to  identity  of  eggs  and  larvae  of  some  Gulf  of 
Mexico  clupeid  fishes.  Fla.  Dep.  Nat.  Resour.  Mar.  Res. 
Lab.  Leafl.  Ser.  4  (part  1,  no.  23),  14  p. 

Houde,  E.  D.,  and  B.  J.  Palko. 

1970.  Laboratory  rearing  of  the  clupeid  fish  Harengula 
pensacolae  from  fertilized  eggs.  Mar.  Biol.  (Berl.) 
5:354-358. 

Klima,  E.  F. 

1959.  Aspects  of  the  biology  and  the  fishery  for  Spanish 
mackerel,  Scomberomorus  maculatus  (Mitchill),  of  south- 
ern Florida.  Fla.  State  Board  Conserv.  Tech.  Ser. 
27,  39  p. 

Marchal,  E.  G. 

1967.  Cle  provisoire  de  determination  des  oeufs  et  larves 
des  clupeides  et  engraulides  Quest- Africains.  Cent.  Rech. 
Oceanogr.,  Repub.  Cote  D'lvoire,  Doc.  Sci.  Provisoire  No. 
014  S.R.  4  p.  +  plates. 

Martinez,  S. 

1972.  Fecundity,  sexual  maturation  and  spawning  of  scaled 
sardine  (Harengula  pensacolae).  Masters's  Thesis,  Univ. 
Miami,  Miami,  Fla.,  51  p. 
Matsuura,  Y. 

1972.   Egg  development  of  scaled  sardine  Harengula 
pensacolae,  Goode  &  Bean  (Pisces,  Clupeidae).  Bol.  Inst. 
Oceanogr.  21:129-135. 
Monod,  T. 

1968.  Le  complexe  urophore  des  poissons  teleosteens.  Mem. 
Inst.  Fond.  Afr.  Noire  81,  705  p. 

Nybelin,  O. 

1963.  Zur  morphologie  und  terminologie  des  Schwanz- 

skelettes  der  Actinopterygier.   Ark.   Zool.,  Ser.   2, 

15:485-516. 
Richards,  W.  J.,  R.  V.  Miller,  and  E.  D.  Houde, 

1974.  Egg  and  larval  development  of  the  Atlantic  thread 
herring,  Opisthonema  oglinum.  Fish.  Bull.,  U.S. 
72:1123-1136. 

RivAS,  L,  R. 

1950.  A  revision  of  the  American  clupeid  fishes  of  the  genus 
Harengula,  with  descriptions  of  four  new  sub-species. 
Proc.  U.S.  Natl.  Mus.  100:275-309. 
1963.  Genus  Harengula  Cuvier  and  Valenciennes  1847. 
Sardines.  In  H.  B.  Bigelow  (editor),  Fishes  of  the  western 
North  Atlantic,  Part  3,  p.  386-396.  Mem.  Sears  Found. 
Mar.  Res.  Yale  Univ.  1. 
Saksena,  V.  P.,  and  E.  D.  Houde. 

1972,  Effect  of  food  level  on  the  growth  and  survival  of 
laboratory-reared  larvae  of  bay  anchovy  (Anchoa  mitch- 
illi Valenciennes)  and  scaled  sardine  (Harengula  pen- 
sacolae Goode  &  Bean).  J,  Exp,  Mar,  Biol,  Ecol, 
8:249-258. 
Saksena,  V.  P.,  C.  Steinmetz,  Jr.,  and  E.  D.  Houde. 

1972.   Effects  of  tempyerature  on  growth  and  survival  of 
laboratory-reared  larvae  of  the  scaled  sardine,  Harengula 
pensacolae  Goode  and  Bean.  Trans.  Am.  Fish.  Soc. 
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Storey,  M. 

1938.  West  Indian  clupeid  fishes  of  the  genus  Harengula . 
Stanford  Ichthyol.  Bull,  1:3-56, 
Takita,  T, 

1966.  Egg  development  and  larval  stages  of  the  small 
clupeoid  fish,  Harengula  zunasi  Bleeker  and  some  infor- 
mations about  the  spawning  and  nursery  in  Ariake 
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1121 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 

Taylor,  W.  R.  Whitehead,  P.  J.  P. 

1967.  An  enzyme  method  of  clearing  and  staining  small  1973.  The  clupeoid  fishes  of  the  Guianas.  Bull.  Br.  Mus. 

vertebrates.  Proc.  U.S.  Natl.  Mus.  122(3596):  1-17.  Nat.  Hist.  (Zool.),  Suppl.  5. 
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1958.  Studies  on  the  eggs,  larvae  and  juveniles  of  Japanese  1966.  The  types  of  Bleeker's  Indo-Pacific  elopoid  and 

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1122 


EGG  AND  LARVAL  DEVELOPMENT  OF  THE 
ATLANTIC  THREAD  HERRING,  OPISTHONEMA  OGLINVM^^^ 

William  J.  Richards,^  Robert  Victor  Miller,''  and  Edward  D.  Houde^ 

ABSTRACT 

The  egg  and  larval  development  of  Atlantic  thread  herring,  Opisthonema  oglinum,  is  described, 
based  on  wild-caught  eggs  and  laboratory-reared  larvae.  This  description  includes  morphological 
details  of  the  egg  and  osteological  development,  changes  in  body  shape  and  pigmentation,  and 
significant  features  of  transformation  of  the  larval  development  stages.  The  egg  is  1.10  to  1.28  mm 
in  diameter  with  a  single  oil  globule.  Ossification  commences  in  the  larvae  when  they  attain 
10  mm  in  standard  length  and  all  bones  have  at  least  begun  to  ossify  by  20  mm.  During  trans- 
formation (15  to  25  mm),  the  larvae  assume  juvenile  characteristics;  particularly  evident  during 
this  period  is  the  anterior  movement  of  the  dorsal  and  anal  fins  from  their  posterior  larval 
positions  to  their  medial  adult  positions. 


The  Atlantic  thread  herring,  Opisthonema  ogli- 
num (Lesueur),  is  a  clupeid  fish  commonly  found 
in  the  subtropical  and  tropical  waters  of  the 
western  Atlantic  Ocean,  but  the  eggs  and  larvae 
of  this  species  have  not  been  described  previously. 
In  1968,  Atlantic  thread  herring  were  reared 
from  eggs  in  the  Tropical  Atlantic  Biological 
Laboratory,  Miami,  Fla.  (now  the  Southeast 
Fisheries  Center),  and  a  complete  developmental 
series  was  obtained  (Richards  and  Palko,  1969). 
This  paper  describes  the  egg  and  morphological 
development  of  the  reared  larvae.  We  used  a 
dynamic  approach,  similar  to  that  of  Moser  and 
Ahlstrom  (1970),  to  describe  the  sequential 
development  of  characters,  instead  of  a  static 
approach  in  which  a  few  selected  sizes  of  larvae 
are  described  in  detail.  Larvae  reared  under 
laboratory  conditions  provide  unusually  good 
specimens  for  studies  of  this  kind. 

The  major  purpose  of  describing  eggs  and  larvae 
is  to  provide  information  so  that  they  may  be 
identified  in  field  collections.  Identification  is  very 
difficult  among  the  clupeids  because  all  of  the 
larvae  are  very  similar  in  appearance.  This  group 
is  further  complicated  by  the  many  species  that 


'Contribution  No.  236,  Southeast  Fisheries  Center,  National 
Marine  Fisheries  Service,  NOAA,  Miami,  FL  33149. 

^Contribution  No.  1790,  Rosenstiel  School  of  Marine  and  At- 
mospheric Science,  University  of  Miami,  Miami,  FL  33149. 

^Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Miami,  FL  33149. 

"Southeast  Fisheries  Center,  National  Marine  Fisheries 
Service,  NOAA,  Miami,  FL  33149;  present  address:  National 
Marine  Fisheries  Service,  NOAA,  Washington,  DC  20235. 

^Rosenstiel  School  of  Marine  and  Atmospheric  Science, 
University  of  Miami,  Miami,  FL  33149. 


Manuscript  accepted  October  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 


occur.  In  the  western  North  Atlantic  15  genera, 
representing  about  36  species,  are  found.  Three 
genera  are  distinctive  since  they  are  found  in 
fresh  water,  or  at  least  spawn  and  develop  in 
fresh  to  brackish  water.  Five  other  genera  are 
distinctive  because  of  their  long  anal  fin,  and  one 
poorly  known  genus  because  of  its  very  few 
vertebrae.  However,  approximately  17  species  re- 
main represented  by  seven  genera,  which  are 
very  similar  in  appearance.  These  genera  are 
Clupea  (one  species),  Etrumeus  (one  species), 
Jenkinsia  (three  species), Sreuoor^m  (four  species), 
Opisthonema  (two  species),  Harengula  (three 
species),  and  Sardinella  (three  species).  Some 
species  within  these  genera  are  imperfectly 
known  (Berry,  1964).  At  our  laboratories,  three 
other  species  have  now  been  reared  besides 
O.  oglinum — Sardinella  anchovia,  Brevoortia 
smithi,  and  Harengula  jaguana — and  descrip- 
tions of  these  are  in  preparation.  Except  for 
Sardinella,  it  appears  now  that  O.  oglinum  can  be 
separated  from  all  of  the  other  genera  on  the  basis 
of  meristic  characters.  Brevoortia  is  similar  in 
most  meristic  characters,  but  its  anal  fin  is  found 
nearly  below  the  posterior  end  of  the  dorsal  fin, 
unlike  Opisthonema.  The  eggs  are  very  similar  to 
one  another,  but  size  and  spawning  times  are  help- 
ful in  separating  the  species.  Much  detailed  work 
is  needed  to  work  out  these  identification  prob- 
lems, not  only  for  the  eggs  and  larvae  but  for  the 
adults  as  well.  A  recent  paper  gives  useful  infor- 
mation on  these  identification  problems  (Houde 
and  Fore,  1973). 

1123 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


MATERIALS  AND  METHODS 

Eggs  that  were  used  for  descriptive  purposes 
were  collected  in  1971  and  1972  during  ichthyo- 
plankton  surveys  in  the  eastern  Gulf  of  Mexico. 
Twenty-three  eggs  in  varying  stages  of  develop- 
ment were  examined  and  measured.  Eggs  from 
the  laboratory  rearing  experiment  were  lost  and 
consequently  could  not  be  described. 

We  selected  only  the  best  specimens  for  this 
study  by  eliminating  fish  with  pronounced  body 
curvature  and  those  in  poor  condition.  We  used 
53  of  the  197  available  specimens.  Forty-two  of 
these  specimens  were  measured  with  an  ocular 
micrometer  of  a  dissecting  microscope  to  provide 
data  on  body  proportions.  Seventeen  of  the  speci- 
mens were  cleared  and  stained  to  provide  meristic 
data  and  osteological  data.  Specimens  shown  in 
the  illustrations  were  among  those  cleared  and 
stained  for  verification  of  the  fin-ray  counts. 
Staining  procedures  followed  those  of  Taylor 
(1967). 

During  development,  O.  oglinum  undergoes 
some  pronounced  changes  in  structure.  These 
changes  are  difficult  to  adequately  define,  par- 
ticularly the  metamorphic  stages.  We  have  fol- 
lowed the  definitions  used  by  Moser  and  Ahlstrom 
(1970),  and  we  have  also  taken  into  account 
Ahlstrom's  (1968)  comments  on  the  subject.  Our 
yolk-sac  larvae  were  lost,  so  our  description 
commences  with  the  larval  period.  The  period 
between  the  larval  period  and  juvenile  period 
is  termed  the  transitional  stage,  following  Moser 
and  Ahlstrom  (1970).  At  the  beginning  of  the 
transitional  period  (about  15  mm  standard 
length),  the  animals  commence  metamorphosis 
into  juveniles. 

Our  methods  of  counting  and  measuring  closely 
follow  Moser  and  Ahlstrom,  but  for  convenience 
are  defined  as  follows: 

Body  length — In  early  stage  larvae  and  in 
those  undergoing  notochord  flexion,  the  body 
length  is  the  distance  from  the  tip  of  the  snout 
to  the  tip  of  the  notochord.  After  the  hypural 
complex  is  developed  the  standard  length  mea- 
surement is  used,  i.e.,  the  distance  from  the  tip 
of  the  snout  to  the  posterior  margin  of  the  hypural 
elements.  While  the  notochord  is  undergoing 
flexion  and  the  hypural  elements  are  developing, 
this  estimated  standard  length  measurement  is 
denoted  in  the  tables. 


Eye  diameter — Maximum  width  of  the  pig- 
mented eye  measured  on  the  horizontal  axis. 
Snout  length — Distance  from  the  tip  of  the 
snout  to  the  anterior  edge  of  the  orbit. 

Head  length — Distance  from  the  tip  of  the  snout 
to  the  posterior  edge  of  the  opercle. 

Length  of  dorsal  and  anal  fin  bases — Distance 
from  the  origin  of  the  first  ray  to  the  point 
where  the  posterior  part  of  the  last  ray  con- 
tacts the  body. 

Snout  to  origin  of  dorsal  fin — Identical  to  the 
predorsal  length  defined  by  Hubbs  and  Lagler 
(1958). 

Snout  to  origin  of  pelvic  fin — Distance  from  the 
tip  of  the  snout  to  the  pelvic  fin  base. 

Snout  to  origin  of  anal  fin — Distance  from  the 
tip  of  the  snout  to  the  origin  of  the  anal  fin 
(in  small  larvae,  before  the  anal  fin  develops, 
this  measurement  is  defined  as  the  distance  from 
the  tip  of  the  snout  to  the  end  of  the  gut;  it  can 
be  used  as  gut  length  for  all  larvae  and  small 
juveniles). 

Origin  of  dorsal  fin  to  base  of  caudal  rays — 
Distance  from  origin  of  the  dorsal  fin  to  the  end 
of  the  hypural  plate. 

Body  depth — Vertical  depth  of  the  body  mea- 
sured at  the  origin  of  the  pelvic  fins  (in  larvae 
that  have  not  developed  pelvic  fins,  the  mid- 
point of  the  body  is  used). 

Origin  of  anal  fin  to  base  of  caudal  rays — Dis- 
tance from  ori^n  of  the  anal  fin  to  the  end  of 
the  hypural  plate. 

Origin  of  pelvic  fin  to  base  of  caudal  rays — 
Distance  from  origin  of  the  pelvic  fin  to  the  end 
of  the  hypural  plate. 

DESCRIPTION  OF  THE  EGGS 

Twenty-three  eggs  ranged  from  1.10  to  1.28  mm 
in  diameter  (mean  =  1.19  mm).  The  chorion 
is  thin  and  fragile,  unsculptured,  and  unpig- 
mented.  A  single  oil  globule  is  present,  ranging 
from  0.12  to  0.16  mm  in  diameter  (mean  =  0.15 
mm).  As  in  most  clupeid  eggs,  the  perivitelline 
space  is  wide,  and  the  yolk  mass  is  vaguely 
segmented.  For  10  embryos  at  the  blastodisc 
stage  the  yolk  diameter  averaged  59%  of  the 
egg  diameter,  while  for  13  advanced  embryos 
the  yolk  diameter  averaged  only  539^  of  the  egg 
diameter.  A  paired  dorsolateral  series  of  tiny 
melanophores  is  present  on  embryos  that  are 
about  to  hatch  (Figure   1).  Opisthonema   eggs 


1124 


RICHARDS,  MILLER,  and  HOUDE:  DEVELOPMENT  OF  THREAD  HERRING 


Figure  1. — Opisthonema  oglinum  egg. 

are  similar  to  those  of  most  other  clupeids  (e.g., 
Reintjes,  1962;  Simpson  and  Gonzalez,  1967) 
but  differ  markedly  in  total  egg  diameter  and 
oil  globule  diameter  from  Harengula  spp.,  with 
which  they  may  cooccur.  Houde,  Richards,  and 
Saksena  (1974)  reported  that  the  diameter  of 
Harengula  jaguana  eggs  was  never  less  than 
1.50  mm,  and  that  the  oil  globule  diameter  never 
exceeded  0.10  mm. 

MORPHOLOGY  OF  LARVAE 

Meristic  values  were  obtained  and  these  are 
shown  in  Table  1.  To  describe  the  change  in 
shape  and  to  note  changes  in  various  structures, 
13  measurements  were  made.  These  are  shown  in 
Table  2.  The  larvae  are  also  illustrated  for  several 
selected  sizes  (Figures  2  to  8).  Opisthonema 
oglinum  larvae,  prior  to  the  start  of  the  transi- 
tion to  juveniles,  are  very  slender  larvae  with  a 
well-developed  finfold  and  long  gut.  Prior  to 
notochord  flexion  gut  length  averages  about 
86%  of  the  body  length.  During  notochord  flexion 
this  increases  to  91%  because  body  length  is 
slightly  reduced.  The  abruptness  of  this  flexing 
is  evidenced  in  the  measurement  of  origin  of 
anal  fin  to  base  of  caudal  rays  in  Table  2.  After 
notochord  flexion  this  distance  is  smaller  due  to 
the  upturning  of  the  notochord.  Following  flexion 
(10  mm  SL)  the  gut  averages  927r  of  standard 
length  up  until  transformation  commences  at 
15  mm  SL.  At  that  time  there  is  a  gradual 
shortening  of  the  gut  until  it  becomes  about 


75%  of  the  standard  length  as  a  juvenile.  The 
large  finfold  decreases  at  about  the  time  of  noto- 
chord flexion  and  is  almost  lost  by  the  time  the 
anal  fin  is  well  differentiated  at  13  mm  SL, 
except  for  a  remnant  beneath  the  foregut  (Fig- 
ures 2  to  4). 

The  first  fin  to  form  is  the  pectoral  fin  but,  as 
described  later  under  the  osteology  section,  it  is 
not  the  ossified  pectoral  fin  of  the  juvenile.  The 
caudal  fin,  dorsal  fin,  and  anal  fin  all  develop 
within  the  finfold  itself,  and  their  development 
is  discussed  in  the  osteology  section.  The  pelvic 
fin  is  the  last  fin  to  be  discernible  as  a  small 
fleshy  protuberance  at  14  mm  SL. 

At  first,  the  gut  is  a  straight  simple  tube.  At 
5  mm  SL  it  can  be  differentiated  into  a  foregut 
and  hindgut.  The  hindgut  becomes  ridged  or 
banded  with  tissue,  which  is  quite  evident  in 
Figure  4  of  a  13.7-mm  SL  specimen.  This  ridging 
is  still  evident  through  much  of  the  transitional 
period  (Figure  5). 

The  most  striking  feature  of  development  is  the 
anterior  migration  of  the  dorsal  fin  during  trans- 
formation. The  fin  nearly  has  its  full  comple- 
ment of  rays  before  this  commences  and  like 
the  shortening  of  the  gut  and  anterior  advance- 
ment of  the  anal  fin,  it  is  a  rapid  change.  It  is 
more  striking  than  the  latter  since  the  fin  is  so 
visible.  The  predorsal  length  averages  more  than 
60%  of  the  body  length  until  about  17  mm,  then 
it  rapidly  decreases  to  an  average  of  43%  of  body 
length  when  transformation  is  completed.  The 
position  of  both  the  dorsal  and  anal  fin  in  rela- 
tion to  the  vertebrae  also  vividly  demonstrates 
this  movement  (Table  3).  The  fin  movement 
begins  at  15  mm.  At  that  size,  the  anal  fin 
origin  begins  to  move  forward  from  its  position 
under  vertebra  38  (Table  3  and  Figure  6)  to  its 
final  position  under  vertebrae  33  to  34  at  24  mm 
(Table  3  and  Figure  7).  Similarly,  the  origin  of 
the  dorsal  fin  is  transferred  forward  over  vertebra 
23  (Table  3  and  Figure  6)  to  over  vertebra  15 
when  larvae  measure  19  and  25  mm  (Table  3  and 
Figure  7).  To  about  20  mm,  there  are  21  pre- 
dorsal myomeres  and  no  ossified  predorsal  bones 
(free  interneurals),  but  shortly  thereafter  eight 
predorsals  become  ossified. 

One  character  which  may  be  instrumental  in 
separating  the  various  genera  and  possibly 
species  of  clupeids  is  the  distance  between  the 
dorsal  and  anal  fins.  For  practical  reasons,  the 
best  way  to  determine  this  distance  is  to  count 


1125 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Table  1. — Meristic  characters  of  larval  and  juvenile  Opisthonema  oglinum. 


Length  of  last 

Gillrakers 

Scutes 

Pec- 

Pel- 

dorsal ray  as 

Caudal 

Dorsal 

Anal 

toral 

vic 

fraction  of 

Epi- 

Cerato- 

Hypo- 

Pre- 

Post- 

SL(mm) 

rays 

rays 

rays 

rays 

rays 

prior  longest  ray 

branchial 

branchial 

branchial 

pelvic 

pelvic 

Vertebrae 

3.8-7.4 

Nothing 

countable  on 

4  specimens  In  this  size  range. 

8.4 

17 

11 

— 

— 

— 

— 

— 

— 

— 







9.0 

18 

9 

— 

— 

— 

— 

— 

— 

— 





46 

9.6 

18 

9 

— 

— 

— 

— 

— 

— 

— 





44 

10.0 

19 

13 

— 

— 

— 

— 

— 

— 

— 

— 



10.4 

19 

15 

— 

— 

— 

— 

— 









45 

10.5 

19 

— 

9+ 

— 

— 

— 

— 

— 

— 







10.7 

19 

13 

— 

— 

— 

— 

— 

— 

— 

— 

— 

46 

12.1 

18 

15 

— 

— 

— 

— 

— 

— 

— 

— 

— 

— 

12.5 

— 

16 

7± 

— 

— 

— 

— 

10 

— 

— 

— 

45 

13.5 

19 

17 

12 

— 

— 

— 

— 

— 

— 

— 

— 

— 

13.7 

19 

17 

16 

— 

— 

0.5X 

— 

— 

— 

— 

— 

— 

14.2 

19 

16 

14 

— 

— 

— 

— 

— 

— 

— 

— 

— 

14.3 

19 

14 

— 

— 

— 

— 

— 

8 

— 

— 

— 

— 

14.3 

19 

17 

10 

— 

— 

— 

— 

— 

— 

— 

— 

46 

curved 

19 

16 

16 

— 

4 

— 

— 

10 

— 

— 

— 

— 

15.5 

19 

20 

19 

— 

— 

— 

— 

— 

— 

— 

— 

— 

15.6 

19 

20 

14 

— 

5 

— 

3 

13 

2 

— 

— 

45 

16.2 

19 

19 

19 

— 

6 

0.5X 

— 

— 

— 

— 

— 

— 

16.9 

19 

17 

17 

— 

4 

— 

— 

— 

— 

— 

— 

46 

17.1 

19 

19 

19 

— 

5 

— 

— 

10 

— 

— 

— 

45 

17.2 

19 

18 

18 

5 

5 

— 

— 

— 

— 

— 

— 

45 

17.4 

19 

18 

19 

— 

6 

— 

— 

— 

— 

— 

— 

— 

17.7 

19 

19 

19 

— 

6 

0  5X 

— 

— 

— 

— 

— 

— 

17.7 

19 

18 

16 

— 

4 

— 

— 

— 

— 

— 

— 

— 

18.4 

19 

19 

19 

— 

5 

— 

3 

13 

— 

— 

— 

46 

19.3 

19 

19 

17 

9 

6 

0.5X 

6 

12 

6 

— 

— 

— 

19.7 

19 

20 

21 

15 

8 

0.6X 

6 

13 

4 

— 

— 

45 

20.3 

19 

21 

19 

13 

8 

0.7X 

8 

12 

8 

8 

0 

— 

21.1 

19 

20 

21 

14 

8 

0.6X 

10 

17 

10 

11 

2 

46 

23.4 

19 

20 

22 

16 

8 

0.7X 

10 

15 

9 

7 

0 

— 

23.8 

19 

20 

21 

15 

6 

0.7X 

11 

16 

10 

12 

9 

— 

24.4 

19 

20 

21 

14 

8 

— 

11 

16 

7 

14 

2 

45 

24.8 

19 

22 

23 

16 

8 

o.ax 

12 

16 

11 

18 

13 

— 

25.3 

19 

18 

21 

16 

8 

0.7X 

10 

15 

12 

13 

5 

— 

25.9 

19 

20 

20 

15 

8 

0.7X 

13 

16 

11 

17 

13 

46 

26.2 

19 

20 

21 

16 

8    ■ 

0.5X 

13 

16 

13 

18 

15 

46 

27.0 

— 

21 

24 

16 

8 

1.3X 

16 

20 

16 

18 

15 

46 

27.1 

— 

20 

23 

16 

— 

1.0X 

14 

18 

16 

17 

14 

46 

27.1 

— 

20 

23 

15 

— 

1.0X 

15 

19 

15 

18 

15 

46 

27.3 

— 

20 

23 

16 

— 

1.1X 

15 

18 

14 

18 

15 

46 

28.2 

— 

20 

21 

17 

— 

— 

15 

18' 

14 

18 

15 

46 

30.0 

— 

22 

22 

16 

8 

1.1X 

15 

18 

14 

19 

14 

— 

30.8 

19 

21 

21 

17 

8 

1.2X 

18 

18 

16 

17 

14 

45 

34.9 

19 

22 

23 

17 

8 

1.8X 

20 

22 

20 

18 

16 

46 

46.8 

— 

21 

21 

15 

8 

2.0X 

31 

25 

32 

16 

16 

— 

54.0 

19 

20 

25 

16 

8 

2.5X 

34 

27 

32 

18 

16 

47 

the  number  of  myomeres  between  the  end  of  the 
dorsal  fin  to  the  origin  of  the  anal  fin.  In  O. 
oglinum  larvae  less  than  16  mm,  we  counted  8, 
9,  or  10  myomeres  between  the  two  fins.  Trans- 
forming larvae  and  small  juveniles  (17  to  25  mm) 
had  from  5  to  7  myomeres  between  the  fins.  We 
were  unable  to  count  these  numbers  with  accuracy 
in  specimens  longer  than  26  mm. 

In  life  the  larvae  are  very  transparent  and 
gradually  become  opaque  during  transformation 
because  of  an  increase  in  pigmentation  and  a 
compacting  of  the  visceral  cavity.  Other  than  the 
gross  features  of  the  gut  mentioned  above,  the 
development  of  the  visceral  organs  was  not 
considered  in  the  present  study,  but  we  assume 
that  abrupt  changes  take  place.  The  swim  bladder 
first  appears  during  transformation.   Before 


transformation,  a  cavity  develops  above  the 
anterior  end  of  the  hindgut  (just  posterior  to  the 
pelvic  fins)  in  larvae  as  small  as  10  mm,  but  a 
definite  swim  bladder  is  not  apparent  until  the 
larvae  are  15  mm  long.  In  living  larvae  the 
swim  bladder  is  well  defined. 

OSTEOLOGICAL  DEVELOPMENT 

Larvae  of  O.  oglinum  undergo  no  ossification 
of  any  parts  before  they  measure  about  10.0  mm 
SL  (all  body  lengths  will  be  given  in  standard 
length  unless  otherwise  indicated).  In  the  young- 
est cleared  and  stained  larva  examined  (4.1  mm 
TL,  total  length),  the  cranial  bulb  was  outlined, 
as  were  the  lower  jaw,  hyoid  apparatus,  and 
dorsal  and  caudal  fin  lobes  (Figure  2).  All  these 


1126 


RICHARDS,  MILLER,  and  HOUDE:  DEVELOPMENT  OF  THREAD  HERRING 

Table  2. — Measurements  of  larvae  and  juveniles  oi  Opisthonema  oglinum.  Specimens  between  dashed  lines  are  undergoing 

notochord  flexion. 


mi; 

o3 
a! 

O   CT 

c  c 

^1 

a) 
tn 
ra 
.Q 

o  c 

<D   O 
-1  -o 

(0 

o-Q 

c  ro 

—1    (0 

Snout  to  origin 
of  dorsal  fin 
(predorsal) 

c 

O) 

1-  c 
O  '-^ 
O   <J 

z.  > 

U   0) 
O   Q. 

«  o 

c 
o  c 

O   CO 

c  „_ 

<n  o 

Origin  of  dorsal 
fin  to  base  of 
caudal  rays 

CD  -o 

Origin  of  anal 
fin  to  base  of 
caudal  rays 

Origin  of  pelvic 
fin  to  base  of 
caudal  rays 

3.6 

0.20 

0.10 

060 









3,1 



0.20 

0.50 

_ 

4.1 

0.18 

0-10 

0.53 



— 

— 

1.9 

3.4 

— 

0.25 

0.63 

2.0 

4.6 

0.20 

0.10 

0.60 

— 

— 

— 

2.0 

'     3.9 

— 

0,20 

0.63 

2.5 

5.2 

0.23 

0.13 

0.73 

— 

— 

— 

2.4 

4.4 

— 

0.33 

0.63 

2.7 

7.3 

0.25 

0.18 

0,90 

0,35 

— 

4.8 

3.2 

6.5 

2.2 

0.50 

0.75 

4.1 

7.4 

0.25 

0.18 

1.0 

0.38 

— 

5.0 

3.3 

6.6 

2.3 

0.60 

0.78 

4.1 

9.1 

0.35 

028 

1.1 

0.75 



5.9 

4.0 

8.1 

3.4 

0.95 

0.95 

5.0 

9.7 

035 

0.30 

1.2 

0.85 

— 

6.5 

4.2 

8.8 

3.3 

0.85 

0.95 

5.4 

10.0 

0.35 

0.27 

12 

0,94 

— 

6.8 

4.4 

9.2 

3.4 

0.95 

0.95 

5.6 

10.1 

0.43 

0.38 

1.5 

1.3 

.__ 

6.4 

4.4 

9.4 

3.9 

1.0 

0.63 

5.6 

10.4 

0.38 

035 

1.7 

1.5 

0.25 

6.3 

4.6 

9.6 

3.9 

1.1 

0.83 

5.8 

10.7 

0.40 

0.40 

1,7 

1.3 

0.35 

6.7 

4.7 

9.7 

3.9 

1.0 

1.0 

6.0 

12.1 

0.45 

— 

— 

— 

— 

7.9 

5.2 

11.1 

— 

— 

1.0 

6.9 

12.8 

0.50 

048 

2.0 

1.7 

0.45 

8.1 

5.8 

11.6 

4.9 

1.1 

1,2 

7,2 

12.9 

0.53 

0.48 

2.1 

1.9 

0.75 

8.2 

5.9 

11.4 

5.2 

1.3 

1,6 

7,2 

13.7 

0.55 

0.73 

2.8 

1.9 

0.63 

8.9 

6.2 

12.4 

5.0 

1.6 

1.4 

7.6 

14.0 

— 

— 

— 

— 

— 

9.0 

6.3 

12.6 

5.3 

— 

— 

8.0 

14.0 

0.58 

0.63 

2.6 

2.1 

0.60 

8.8 

5.8 

12.9 

5.5 

1.7 

1.4 

8.5 

15.0 

0.63 

0.68 

2.7 

2.1 

0.95 

9.0 

6.7 

13.2 

6.0 

1.6 

1.8 

8.4 

15.8 

0.63 

0.78 

3.0 

2.2 

0.88 

10.0 

7.1 

13.8 

6.3 

1.7 

1.9 

8.8 

16.2 

0.63 

0.60 

3.0 

2.4 

1.0 

9.7 

7.0 

13.9 

6.5 

1.7 

2.1 

8.9 

16.8 

0.80 

0.68 

3.2 

2.6 

1,1 

10.2 

7.7 

14.9 

6.9 

1.9 

2.2 

9.1 

17.1 

0.65 

0.73 

3.1 

2,6 

1,0 

10.0 

7.4 

15.3 

6.9 

1.9 

21 

9.5 

17.7 

0.70 

0.75 

3.3 

2.7 

1,2 

10.7 

8.5 

15.3 

7.1 

2.0 

2.4 

9.2 

17.7 

0.80 

0.85 

— 

— 

— 

10.4 

8.1 

15.4 

— 

— 

2.3 

9.6 

18.4 

0.83 

0.76 

3.5 

2.9 

1.3 

10.9 

8.8 

16.1 

7.8 

2.5 

23 

9.6 

19.3 

1.1 

— 

— 

— 

— 

10.9 

9.3 

16.3 

— 

— 

3.0 

10.0 

19.7 

1.1 

0.85 

3.9 

3.1 

1.8 

10.5 

9.0 

16.6 

9.2 

2.6 

3.1 

10.7 

20.3 

1.2 

1.1 

4.9 

3.5 

2,1 

10.0 

9.8 

16.8 

100 

3.3 

3,5 

10.5 

23.4 

1.4 

1.5 

6.0 

4.0 

3.4 

10,7 

11,5 

18.0 

13.1 

4.6 

5,4 

11.9 

23.8 

1.7 

1.6 

6.1 

40 

3-7 

10,7 

12,1 

18.1 

13.0 

4.7 

5.7 

11.7 

24.4 

1.5 

1.6 

6.4 

3.7 

3.6 

12.0 

11.9 

18.6 

12.5 

4.4 

5.8 

12.5 

24.8 

1.7 

1.9 

6.7 

4,4 

4,5 

11.0 

13.0 

18.7 

14.0 

5.5 

6.1 

11.8 

25.3 

1.7 

1,7 

6.6 

4,5 

4,2 

11.5 

12.7 

18.9 

14.0 

4.8 

6.4 

12.6 

26.2 

1.5 

1.8 

6.6 

4,0 

3.9 

12.0 

12.6 

19.7 

14,2 

4.8 

65 

13.6 

27.0 

1.9 

1.6 

6.4 

4,3 

4.3 

12.3 

13.5 

19.7 

14.7 

5.7 

7.3 

13.5 

27.1 

1.8 

1.9 

7,3 

4.4 

4,4 

11.6 

14.2 

20.2 

15.5 

5.8 

6,9 

12.9 

27.1 

1.9 

1.7 

6.7 

4,0 

4.0 

11.4 

13.3 

20.3 

15.8 

4.5 

6,8 

13.8 

27.3 

1.6 

1.8 

6.8 

4,1 

4.3 

11.8 

14.0 

19.9 

15.5 

5.0 

7.0 

13.3 

28.2 

1.9 

1.9 

7.3 

4,3 

42 

12.5 

14.3 

20.7 

16.7 

5.0 

7.0 

13.9 

30.0 

2.3 

2.4 

8.5 

5,0 

5.0 

130 

15.5 

22.8 

16.8 

8.3 

8.2 

14.5 

30.8 

2.2 

2.4 

8,0 

50 

5,0 

13.4 

15,7 

229 

17.3 

7.7 

7,9 

15.1 

structures  were  clear,  however,  indicating  no 
ossification.  The  first  structures  to  ossify  were 
the  dentaries  and  maxillaries  when  specimens 
measured  about  10.0  mm  (bone  nomenclature 
follows  Mead  and  Bradbury,  1963).  Almost  simul- 
taneously, the  very  thin  cleithral  ring  (cleithrum, 
supra-cleithrum,  and  postcleithrum)  and  the 
hypurals  began  to  ossify  very  slightly.  At  sizes 
between  12  and  13  mm,  the  skull  bones  began 
to  ossify,  as  did  the  vertebral  rings.  As  size 
increased,  various  other  parts  of  the  fish  began 
to  ossify — the  caudal  fin  rays,  parts  of  the 
branchial  apparatus  (ceratobranchials,  hypo- 
branchials,  epibranchials),  and  the  dorsal  and 
anal  fin  rays;  skull  bones  ossified  further  (Figure 
3).  At  about  20  to  22  mm,  essentially  all  bony 


structures  of  the  larvae  had  at  least  begun  to 
ossify,  and  some  were  well  developed. 

Vertebral  development 

No  ossification  took  place  before  10  mm,  but 
cartilaginous  structures  were  visible.  At  the  time 
of  notochord  flexion,  seven  hypural  elements 
were  formed  (four  superior  and  three  inferior 
elements  including  the  parhypural).  In  specimens 
measuring  10.5  mm,  the  hypurals  were  weakly 
ossified  but  the  seven  elements  were  distinct. 
The  first  vertebral  centra  to  ossify  was  the  first 
preural  centrum  and  the  ventral  portion  of  the 
centra  of  the  first  and  second  ural  centra.  This 
differs  somewhat  from  the  development  noted  in 


1127 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  2. — Opisthonema  ogUnum  larva  4.0  mm  total  length. 


5 


Figure  3. — Opisthonema  oglinum  larva  10.7  mm  standard  length. 


H.  jaguana  by  Houde  et  al.  (1974).  They  noted 
that  the  second  ural  vertebra  ossified  first. 
Epural  development  displayed  some  variation 
(tw^o  instead  of  the  normal  three  in  some  speci- 
mens), as  was  also  noted  in  Harengula  by  Houde 
et  al.  (1974).  Holhster  (1936)  noted  this  varia- 
tion in  Harengula  but  not  in  Opisthonema. 
Other  than  these  differences,  caudal  develop- 
ment was  essentially  the  same  for  Opisthonema 
and  Harengula.  For  a  more  complete  account, 
consult  Houde  et  al.  (1974). 


At  10.5  mm,  ossification  also  started  on  verte- 
brae 12  through  40.  This  ossification  starts  on 
the  dorsal  and  ventral  surfaces  of  the  centra, 
thus  making  it  quite  easy  to  count  vertebrae. 
The  degree  of  ossification  of  these  vertebrae 
indicates  that  the  middle  ones  were  most  ossified, 
with  ossification  proceeding  anteriorly  and  pos- 
teriorly. By  12.5  mm,  dorsal  and  ventral  ossi- 
fication of  the  centra  is  complete  on  vertebrae 
2  through  41,  while  only  the  ventral  centrum 
surface  has  ossified  on  the  first  vertebra  and  the 


1128 


RICHARDS,  MILLER,  and  HOUDE:  DEVELOPMENT  OF  THREAD  HERRING 


Figure  4. — Opisthonema  oglinum  larva  13.7  mm  standard  length. 


--  ^^^  r^-K-^^'^^v^^-  ^.'rrx^^- 


Figure  5. — Opisthonema  oglinum  larva  17.1  mm  standard  length. 


three  preceding  the  ural  centra.  These  three 
centra  immediately  anterior  to  the  first  preural 
were  wider  ventrally  and  had  large  spaces  be- 
tween the  vertebral  segments.  At  15.5  mm,  all 
vertebral  centra  were  partially  ossified  and  evenly 
spaced  with  narrow  spaces  between.  In  the  first 
preural  and  ural  centra,  the  three  rings  of  ossi- 


fication had  widened,  but  the  middle  ring  was 
still  wider  ventrally  than  dorsally.  (This  asym- 
metrical shape  of  the  ossified  rings  of  the  verte- 
brae associated  with  the  caudal  region  obviously 
corresponds  to  flexion  of  the  notochord.  The 
ventral  surface  is  longer  after  flexion  than  the 
dorsal  surface  and,  consequently,  to  keep  the 


1129 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


SSSSISSiSlSSMa^r: 


Figure  6. — Opisthonema  oglinum  larva  19.7  mm  standard  length. 


spaces  between  ossified  segments  equal,  the  seg- 
ments ossify  in  a  wedgelike  shape.)  By  17.1  mm, 
the  three  rings  had  widened  appreciably  and 
the  spaces  had  narrowed. 

Neural  and  hemal  spines  ossify  in  a  posterior 
to  anterior  direction.  Neural  spines  are  well 
formed  over  the  last  three  centra,  which  precede 
the  first  preural  well  before  ossification  on  the 
centra  is  completed.  By  17.1  mm,  ossification  of 
these  elements  is  just  complete  to  below  the  dorsal 
fin,  and  by  22  mm  they  are  all  ossified. 

Fin  Development 

The  earliest  fin  development  was  of  the  caudal 
and  dorsal  fins,  more-or-less  as  lobes,  at  about 
4  mm  TL.  This  early  development  may  be  due 
to  a  rearing  abnormality  since  fin  development 
is  seldom  seen  in  field-caught  larvae  less  than 
7  mm  SL.  Increasing  numbers  of  caudal  and 
dorsal  rays  were  defined  at  lengths  from  6  to 
8.4  mm,  but  were  not  clear  enough  to  count 
until  our  8.4-mm  specimen  (17  caudal  and  11 
dorsal  rays,  Table  1  and  Figure  3).  Between  8.4 
and  10.0  mm,  the  final  two  caudal  rays  were 


differentiated  to  complete  the  adult  complement 
of  19  principal  cartilaginous  rays  (10  superior 
and  9  inferior). 

Rays  continued  to  be  added  to  the  dorsal  fin: 
16  were  present  at  12.5  mm  and  18  to  20  were 
present  from  15  to  20  mm  (Table  1,  Figures  4 
through  7).  As  growth  proceeded,  one  or  two  more 
rays  were  added  to  complete  the  adult  comple- 
ment of  21  or  22  dorsal  rays  (Figure  8).  In  adult 
Opisthonema ,  the  last  ray  of  the  dorsal  fin  is 
elongate — more  than  twice  as  long  as  the  next 
longest  ray.  Until  about  larval  size  of  20  mm,  the 
last  ray  was  half  as  long  as  the  longest  ray, 
but  from  then  on  it  began  to  elongate.  From 
about  27  mm,  the  last  ray  grew  longer  than  the 
prior  longest  ray  (Table  1). 

The  anal  fin  formed  later  than  the  dorsal, 
from  a  thickening  of  the  ventral  finfold  in  the 
relatively  short  space  between  the  anus  and  the 
caudal  fin  (Figure  3).  At  10.5  mm,  the  fin  rays 
had  begun  to  differentiate  and  nine  rays  could 
be  counted.  Ossified  rays  increased  rapidly  to 
14,  15,  or  16  at  about  14  mm,  after  which  rays 
were  added  more  slowly  to  sizes  from  15  to  20  mm. 
Between  14  and  20  mm,  counts  of  17  to  20  rays 


1130 


RICHARDS,  MILLER,  and  HOUDE:  DEVELOPMENT  OF  THREAD  HERRING 


Figure  7. — Opisthonema  oglinum  juvenile  24.4  mm  standard  length. 


were  produced  (Figure  7).  Only  about  three  or 
four  more  rays  were  added,  from  20  mm,  until 
the  adult  complement  of  21  to  25  anal  rays  was 
reached  at  30  mm  and  over  (Table  1,  Figure  8). 

The  pectoral  fin  appeared  as  a  small,  fan-shaped 
structure  just  behind  the  cleithral  ring,  but  this 
structure  enlarged  gradually  (Figures  2  to  7). 
[Within  the  fan,  "ray  areas"  differentiated  soon 
thereafter,  but  these  had  no  apparent  relation 
to  where  rays  actually  ossify.]  Ossified  rays  first 
appeared  at  about  17  mm  (five  rays;  see  Table  1) 
and  quickly  increased  to  about  10  rays  at  19  mm. 
The  rounded  fan  shape  of  the  pectoral  fin  changed 
into  the  pointed  shape  characteristic  of  adults 
between  19  and  23  mm  (Figure  7).  At  21  mm, 
specimens  had  about  13  or  14  rays,  and  the 
adult  complement  of  15  to  17  rays  was  reached 
at  23  to  25  mm.  The  sequence  of  ray  ossifica- 
tion was  in  a  dorsal  (uppermost)  to  ventral 
(lowermost)  direction. 

Ossified  pelvic  rays  appeared  earlier  than  the 
pectoral  rays.  At  about  13  mm,  larvae  had  about 
four  rays  (Table  1),  and  at  about  15  mm  they 
had  five  or  six  (Figure  5).  The  number  of  rays 


seemed  to  remain  static  for  about  the  next  5  mm 
of  growth  (10  specimens  in  the  15  to  20  mm  size 
range),  but  rather  suddenly  two  more  rays  ap- 
peared at  about  20  mm  (Table  1,  Figure  7).  The 
pelvic  ray  count  held  constant,  though  size  in- 
creased to  50  mm,  but  in  adults  a  ninth  ray  is 
added  as  a  flattened,  segmented  ray  closely 
adnate  to  the  second  (formerly  most  lateral)  ray 
to  produce  nine  total  rays.  In  our  larger  (30  to 
54  mm)  specimens  (Figure  8)  the  flattened  first 
ray  does  not  appear  to  be  present.  If  it  is,  the 
ray  is  so  tightly  attached  to  the  second  ray  that 
the  two  seem  to  be  a  single  unit. 

Cephalic  Development 

No  ossification  of  any  bones  appeared  before 
specimens  reached  about  10.0  mm.  In  larvae  as 
small  as  4.1  mm  TL,  the  cranial  bulb,  dentaries, 
and  hyoid  bones  were  visible  as  cartilaginous 
elements.  At  about  10.0  mm,  the  maxillaries 
and  dentaries  were  easily  distinguished  and 
began  to  show  slight  ossification  (by  stain  uptake). 
The  jawbones  more-or-less  steadily  increased  in 


1131 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Figure  8. — Opisthonema  oglinum  juvenile  30.8  mm  standard  length. 


size  and  became  more  heavily  ossified;  at  about 
14  mm,  small  teeth  v^ere  found  on  the  ventral 
edge  of  the  maxillaries  and  the  anterodorsal 
edge  of  the  dentaries.  Concommitantly,  the  hyoid 
apparatus  continued  to  develop  steadily,  particu- 
larly the  ceratohyals  and  hypohyals,  which  were 
quite  distinct  and  slightly  ossified  by  14  mm. 
By  about  17  mm,  the  two  supramaxillaries  were 
differentiated  and  partly  ossified  but  had  not 
obtained  their  characteristic  adult  shapes.  The 
premaxillaries  also  were  partly  formed  and  ossi- 
fied as  two  distinctly  separate  units  close  to  the 
anterior  tips  of  the  maxillaries.  By  19  mm,  the 
articular  was  well  developed  but  not  fully  ossi- 
fied. The  posterior  supramaxillary  was  almost 
completely  ossified  but  not  the  anterior  supra- 
maxillary. Maxillaries  maintained  an  ossified 
posterior  edge  (the  region  of  growth),  and  the 
teeth  on  the  ventral  edges  were  still  prominent. 
The  ceratohyals  and  urohyal  were  more  ossified, 
and  two  small  centers  of  heavy  ossification  were 


present  in  the  hypohyals.  One  structure  of  interest 
was  the  presence  of  teeth  on  a  few  specimens 
on  the  basihyal.  In  a  12.0-mm  specimen,  two 
large  erect  teeth  were  noted;  a  15.6-mm  specimen 
had  one  such  tooth,  which  was  also  present  on 
a  17.1-mm  specimen.  No  such  teeth  were  evident 
on  a  25.9-mm  specimen,  indicating  that  these 
teeth  may  be  variable  and  limited  in  occurrence. 
Houde  et  al.  (1974)  noted  the  presence  of  these 
temporary  teeth  in  Harengula.  The  branchio- 
stegals  ossified  in  the  following  sequence:  fourth 
branchiostegal  slightly  ossified  at  15.5  mm;  fourth 
well  ossified  at  17.1  mm;  fourth,  third,  and 
second  ossified;  first  visible  as  cartilage;  fifth 
and  sixth  not  visible  at  19.7  mm.  By  the  time 
specimens  reached  24  mm,  six  well-ossified 
branchiostegals  were  present,  the  supramaxil- 
laries were  ossified  but  the  posterior  supra- 
maxillary had  not  reached  a  complete  adult 
shape,  all  the  hyals  were  partly  ossified,  the 
well-developed  premaxillaries  were  ossified  and 


1132 


RICHARDS.  MILLER,  and  HOUDE:  DEVELOPMENT  OF  THREAD  HERRING 


Table  3. — Position  of  dorsal  and  anal  fins  during  the  transformation  period  in 
larvae  of  Opisthonema  oglinum. 


Dorsal 

2d  dorsal 

Anal 

1st  anal 

SL 

(mm) 

origin 

over 

vertebra 

pterygiophore 

opposite 

neural  arch 

origin 

under 

vertebra 

pterygiophore 

opposite 
haemal  arch 

15.5 

25 

21 

38 

36 

17.1 

23 

— 

37 

35 

17.2 

22-23 

20 

38-39 

36 

18.4 

23 

20 

38 

35-36 

19.7 

20 

17 

36 

34 

21.1 

16 

12 

— 

— 

24.4 

16 

11 

33 

30 

25.9 

15-16 

11 

33 

30 

26.2 

16 

11 

33-34 

30 

270 

14 

9 

32 

29 

27.1 

15 

11 

33 

30 

27.1 

15 

10 

33 

30 

27.3 

14 

10 

33 

30 

28.2 

15 

10 

33 

30 

30.8 

15-16 

10 

33 

30 

34.9 

15 

10 

34 

30 

540 

15 

9 

34 

30 

joined  at  the  anterior  tip  of  the  upper  jaw,  and 
the  maxillaries  appeared  to  be  fully  formed. 

At  about  10  mm,  the  cleithral  ring  was  obvious 
as  a  thin  ring  of  ossified  bone  almost  encircling 
the  head  and  forming  a  posterior  line  of  de- 
markation.  The  three  bones  that  actually  form 
bhis  ring  are  the  supracleithrum,  cleithrum, 
and  postcleithrum,  which  developed  fairly  uni- 
formly to  about  the  time  the  pectoral  fin  began 
to  develop  ossified  rays  (about  15  to  17  mm). 
Thereafter,  the  cleithrum  became  the  dominant 
element. 

A  cartilaginous  cranial  bulb  was  visible  in 
our  smallest  larvae,  but  no  elements  were  dif- 
ferentiated or  ossified  until  about  12  mm.  At 
that  size,  bone  elements  (e.g.,  the  sphenotics, 
parietals,  epiotics,  and  pterotics)  were  slightly 
outlined.  Between  12  and  13  mm,  the  vomer  and 
parasphenoid  began  to  show  considerable  ossi- 
fication, and  the  pterotic  and  prootic  bullae  were 
differentiated  by  ossification  of  the  surrounding 
bones.  The  frontals  began  to  form  when  speci- 
mens measured  about  15  mm,  and  about  19  mm 
they  were  partly  ossified  (but  not  fully  formed), 
and  sensory  canals  were  present  within  the  bones. 
Canals  also  formed  at  the  19-mm  size  in  the 
prootics  and  sphenotics,  and  the  prootic  bulla 
was  the  most  obvious  structure  in  the  skull  be- 
cause of  the  heavily  ossified  bone  around  it. 

The  quadrate  and  the  pterygoids  had  begun 
to  form  by  19  mm,  and  the  articular  had  in- 
creased in  size  but  was  not  yet  fully  ossified. 
At  about  21  mm,  the  nasals  began  to  form  as 


thin,  small  plates  at  the  anterior  ends  of  the 
frontals.  Formation  of  supraorbitals  had  also 
begun,  the  anterior  one  being  moderately  well 
developed  and  quite  separate  from  the  posterior 
one.  At  the  21-mm  size,  it  also  appeared  that 
most  of  the  head  bones  were  at  least  partly 
formed,  and  ossification  ranged  from  slight  to 
considerable.  By  25  mm,  the  prootic  bulla  was 
well  encased  in  heavy  bone,  the  sclerotics  had 
begun  to  ossify  along  with  the  supraorbitals, 
the  ethmoids  had  begun  to  form  and  ossify  at 
the  anterior  ends  of  the  frontals  and  just  behind 
and  above  the  premaxillaries,  the  vomer  was 
quite  large  and  well  ossified,  most  sensory  canals 
were  partly  to  fully  formed  and  encased  in  bone, 
the  postorbitals  had  begun  to  form,  and  the 
pterotic  bulla  (which  lagged  far  behind  the  pro- 
otic in  development)  began  to  grow  larger.  From 
25  mm  through  the  juvenile  period,  growth  of 
the  skull  bones  was  restricted  primarily  to  an 
increase  in  size  and  consolidation  within  the 
several  multibone  complexes;  the  dorsal  and 
lateral  frontoparietal  foramina  decreased  in  size 
as  the  bones  increased,  and  the  characteristic 
striae  of  the  dorsal  surface  of  the  frontoparietals 
began  to  form;  the  pterotic  bulla  finally  became 
larger  than  the  prootic  by  about  34  mm;  and 
the  palatines  began  to  ossify.  During  the  30-  to 
50-mm  range,  most  of  the  cranial  structures 
assumed  their  adult  configuration,  the  dorsal 
frontoparietal  foramina  completely  closed  up, 
and  the  lateral  foramina  became  reduced  in  rela- 
tive size. 


1133 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


The  elements  of  the  opercular  complex — pri- 
marily the  opercle  and  preopercle — began  to  dif- 
ferentiate at  about  15  mm.  Shortly  thereafter 
the  subopercle  and  interopercle  began  to  form 
and  by  21  mm  most  of  the  opercular  series 
appeared  to  be  about  halfway  ossified;  the  inter- 
opercle seemed  to  be  the  most  weakly  ossified. 
By  25  to  26  mm,  the  interopercle  had  grown  to 
articulate  with  the  quadrate  and  angular  and 
the  hyals.  The  other  opercular  bones  had  be- 
come quite  well  developed,  but  the  postero- 
ventral  edges  remained  unossified,  evidently  to 
permit  continuous  growth. 

Branchial  Development 

The  ceratobranchials  were  the  first  elements  to 
develop  in  the  branchial  system,  becoming  evi- 
dent at  about  10  mm.  By  about  12  to  13  mm, 
the  ceratobranchials  showed  a  slight  uptake  of 
stain,  indicating  that  they  had  begun  to  ossify. 
At  14  mm,  the  hypobranchials  had  begun  to 
differentiate,  and  a  few  unossified  rakers  were 
visible  on  the  ceratobranchials. 

The  ceratobranchials,  the  first,  second,  and 
third  epibranchials,  and  the  hypobranchials  all 
developed  as  more-or-less  straight  rods  (although 
the  epibranchials  also  developed  small  dorsal 
extensions  for  attachment  of  suspensory  liga- 
ments). The  first  rakers  appeared  on  the  cerato- 
branchials at  about  12  mm  (Table  1)  and  held 
almost  constant  between  10  to  13  rakers  to 
about  17  mm.  Two  or  three  rakers  appeared 
on  the  epibranchials  and  hypobranchials  when 
larvae  reached  about  15  mm.  The  numbers  of 
rakers  on  all  three  elements  gradually  increased 
with  the  numbers  on  the  epibranchials  and  hypo- 
branchials almost  equal  but  from  two  to  four 
lower  than  on  the  ceratobranchials,  up  to  about 
30  mm  (Table  1).  At  the  30-mm  size,  all 
three  bones  had  an  equal  number  of  rakers,  but 
beyond  that  size  the  ceratobranchials  seemed  to 
lag  behind  the  epibranchials  and  hj^Dobranchials 
by  five  or  six  rakers.  In  adults,  the  hypobranchials 
and  ceratobranchials  are  almost  equal  in  numbers 
of  rakers  (30  to  45),  producing  lower  branch 
counts  of  60  to  90,  but  the  epibranchial  rakers 
almost  equal  the  combined  lower  branch  counts. 

The  fourth  epibranchial  (E4)  was  the  first  to 
develop  a  slight  vertical  extension  when  speci- 
mens measured  about  14  mm;  the  shape  of  the 
fourth  epibranchial  at  this  stage  is  more-or-less 


like  an  inverted  "T" — the  crossbar  (the  basal 
shaft)  is  ventral  and  the  vertical  segment  extends 
dorsally  from  it.  On  the  dorsal  and  posterior 
edges  a  developing  cartilaginous  capsule  (see 
Miller,  1969;  Figure  2,  for  the  adult  configura- 
tion of  the  capsule)  is  fused  to  the  developing 
E4  bone;  this  capsule  is  also  joined  to  the  epi- 
ceratobranchial  "elbow."  A  vertical  slit  is  present 
in  the  posterior  side  of  the  capsule,  and  the  two 
raker  series  that  will  eventually  grow  through- 
out the  length  of  the  lumen  of  the  epibranchial 
organ  begin  growing  along  the  sides  of  the 
posterior  slit.  Dual  fourth  epibranchial  raker 
series  are  present,  with  the  lateral  series  grow- 
ing along  the  ventrolateral  edge  of  the  fourth 
epibranchial  bone,  outside  the  epibranchial 
organ,  and  the  medial  fourth  epibranchial  series 
is  enclosed  in  the  organ  along  the  anterolateral 
edge  of  the  slit  in  the  cartilaginous  capsule. 
The  single  fifth  epibranchial  series  grows  along 
the  posteromedial  edge  of  the  slit.  By  15.5  mm, 
the  vertical  extension  on  E4  had  grown  much 
heavier  and  the  characteristic  posterior  foramen 
had  formed  (see  Miller,  1969;  Figures  2  and  4). 
Three  raker  tubercles  were  present  along  the 
edges  of  the  posterior  slit  (which  had  just  begun 
to  form).  By  17  mm,  the  cartilaginous  capsule 
had  begun  to  increase  in  size,  and  by  19  mm 
there  were  four  or  five  raker  tubercles  in  the 
posterior  slit.  Almost  no  ossification  had  yet 
appeared  on  the  fourth  epibranchial,  and  the  pos- 
terior foramen  was  quite  large.  Ossification 
began  at  about  20  mm,  and  by  about  25  mm 
the  posterior  end  of  the  basal  shaft  had  expanded 
vertically  (it  resembled  an  axe  blade),  and  the 
vertical  shaft  had  also  broadened  and  ossified 
quite  heavily.  At  this  stage  there  were  about 
eight  rakers  along  the  edges  of  the  posterior 
slit.  When  larvae  measured  26  mm,  the  lumen 
of  the  organ  had  begun  to  form;  it  extended 
anterodorsally  within  the  cartilaginous  capsule 
from  the  bridge  of  the  posterior  slit,  and  10 
rakers  appeared  along  each  edge.  One  or  two 
rakers  were  present  in  the  developing  lumen. 
By  30  mm,  the  lumen  had  elongated  to  about 
one-third  of  a  full  loop  [the  epibranchial  organ 
in  Opisthonema  is  the  continuous-tube  type 
(see  Bertmar,  Kapoor,  and  Miller,  1969;  Miller, 
1969)  in  which  the  lumen  and  included  rakers 
extend  for  a  full  loop  in  adults]  and  there  were 
about  15  to  20  rakers  in  the  lumen.  By  35  mm, 
the  lumen  was  about  a  half  of  a  full  loop  and 


1134 


RICHARDS,  MILLER,  and  HOUDE:  DEVELOPMENT  OF  THREAD  HERRING 


had  curved  anteriorly  beyond  the  width  of  the 
vertical  shaft  of  E4.  About  30  rakers  were 
present  in  each  series  at  this  stage  and  the 
epibranchial  organ  and  E4  bone  were  assuming 
adult  configuration.  Estimates  made  on  adult 
specimens  indicate  that  in  a  full-loop,  continuous- 
tube  epibranchial  organ,  the  definitive  number 
of  rakers  in  the  included  medial  E4  and  single 
E5  series  each  at  least  equal  the  total  of  rakers 
on  the  whole  first  gill  arch.  There  are  about 
120  rakers  in  adults  100  mm  or  longer  (Berry 
and  Barrett,  1963).  We  may  therefore  infer  that 
the  number  of  rakers  in  the  epibranchial  organ 
increases  gradually  with  increasing  size  of  the 
fish,  to  about  120  or  moi-e  in  each  series. 


PIGMENTATION 

Melanophores  were  present  along  the  ventral 
midline  in  the  smallest  specimens  studied  (4  mm) 
— one  or  two  melanophores  beneath  the  heart 
just  anterior  to  the  pectoral  symphysis,  and  a 
paired  row  along  the  base  of  the  hindgut  (that 
portion  of  the  gut  posterior  to  the  site  of  the 
pelvic  fins)  continuing  to  the  anus,  and  a  row  on 
the  ventral  midline  posterior  to  the  anus.  A 
dorsolateral  row  of  melanophores  occurred  on 
each  side  of  the  foregut  (that  portion  of  the  gut 
anterior  to  the  pelvic  fin  region).  The  eye  was 
pigmented  but  no  other  melanophores  were  pres- 
ent (Figure  2).  By  10  mm,  the  posterior  ventral 
row  was  distributed  along  the  posterior  edge  of 
the  hypural  bones,  and  a  few  internally  placed 
melanophores  appeared  dorsolaterally  on  each 
side  of  the  hindgut.  The  remaining  melanophore 
pattern  was  basically  unchanged  (Figure  3). 
By  15  mm,  the  melanophores  had  developed  into 
streaks  of  pigment  along  the  base  of  the  isthmus, 
dorsolaterally  along  the  anterior  gut,  along  the 
base  of  the  posterior  gut,  and  on  each  side  of 
the  base  of  the  anal  fin.  Internal  melanophores 
above  the  posterior  gut  had  taken  on  a  well- 
defined,  broken-lined  pattern  and  had  begun  to 
advance  anteriorly,  particularly  forming  a  slight 
arch  in  the  area  of  the  swim  bladder  (Figure  4). 
Melanophores  appeared  on  the  cleithrum  near 
the  hindbrain,  and  the  hypural  melanophores  at 
first  clustered  on  the  bases  of  the  lower  lobe 
of  the  caudal  fin  but,  by  17  mm,  melanophores 
appeared  on  both  lobes  of  the  caudal  fin.  Between 
15  and  24  mm  (transformation  period),  melano- 
phores varied  somewhat  in  time  of  appearance. 


In  some  specimens  a  melanophore  appeared 
medial  to  the  left  nostril  (Figure  5,  dorsal  view). 
Melanophores  appeared  both  dorsally  and  ven- 
trally  on  the  swim  bladder  as  it  developed 
(Figure  6).  During  this  period  melanophores 
also  began  to  appear  on  the  dorsum,  first  pos- 
terior to  the  dorsal  fin,  then  anteriorly.  Melano- 
phores also  appeared  along  the  lateral  midline 
and  over  the  hypural  bones  internally.  The 
internal  pigment  associated  with  the  vertebral 
column  of  these  larvae  is  quite  pronounced,  par- 
ticularly during  transformation.  A  few  internal 
melanophores  over  the  posterior  centra  were 
first  noted  in  a  cleared  and  stained  12.1-mm 
specimen.  By  15  mm,  one  or  two  melanophores 
or  groups  of  melanophores  were  noted  above 
each  vertebra.  The  melanophores  over  the 
anterior  vertebrae  are  lost  or  reduced  by  19  mm. 
Some  individual  variation,  however,  is  evident 
in  both  the  internal  and  external  pigmentation. 
The  dorsal  external  pigmentation  is  noticeably 
reduced  in  the  19.7-mm  specimen  (Figure  6)  as 
compared  to  the  17.1-mm  specimen  (Figure  5). 
The  expanded  state  of  most  melanophores  (a 
probable  result  of  rearing  under  continuous  illu- 
mination) makes  detailed  counts  of  melanophore 
patches  quite  difficult.  Following  transforma- 
tion, melanophores  were  visible  over  the  brain 
and  on  the  jaws  as  well  as  in  increasing  quan- 
tities on  the  dorsum,  lateral  midline,  over  the 
gut,  and  in  the  caudal  fin  rays  (Figure  7).  By 
30  mm,  the  dorsal  pigment  had  increased,  the 
foregut  pigment  was  lost,  and  melanophores 
were  seen  in  the  dorsal  fin — essentially  the  adult 
pattern  (Figure  8). 

In  life,  the  larvae  are  transparent  and  the 
only  noticeable  features  are  the  heavily  pig- 
mented eyes.  The  gut  is  usually  noticeable  be- 
cause of  the  food  contained  in  it.  In  larger 
larvae,  the  swim  bladder  is  decidedly  noticeable 
as  a  bubble  above  the  gut  (Figure  6).  Melano- 
phores are  invisible  until  the  specimen  is  exam- 
ined under  magnification. 

ACKNOWLEDGMENT 

Elbert  H.  Ahlstrom  (Southeast  Fisheries  Cen- 
ter, National  Marine  Fisheries  Service,  NOAA, 
La  Jolla,  Calif)  and  Peter  J.  Whitehead  [British 
Museum  (Natural  History)]  reviewed  the  manu- 
script and  their  helpful  comments  and  criticism 
are  greatly  appreciated. 


1135 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


LITERATURE  CITED 


Ahlstrom,  E.  H. 

1968.  Review  of  "Development  of  fishes  of  the  Chesa- 
peake Bay  region,  an  atlas  of  egg,  larval,  and  juvenile 
stages,  Part  I."    Copeia  1968:648-651. 

Berry,  F.  H. 

1964.     Review  and  emendation  of:  Family  Clupeidae. 
'  Copeia  1964:720-730. 
Berry,  F.  H.,  and  I.  Barrett. 

1963.     Gillraker  analysis  and  speciation  in  the  thread 
herring  genus  Opisthonema .  [In  Engl,  and  Span.]    Bull. 
Inter-Am.  Trop.  Tuna  Comm.  7:113-190. 
Bertmar,  G.,  B.  G.  Kapoor,  and  R.  V.  Miller. 

1969.  Epibranchial  organs  in  lower  teleostean  fishes — 
an  example  of  structural  adaptation.  Int.  Rev.  Gen. 
Exp.  Zool.  4:1-48. 

Hollister,  G. 

1936.  Caudal  skeleton  of  Bermuda  shallow  water  fishes. 
I.  Order  Isospondyli:  Elopidae,  Megalopidae,  Albulidae, 
Clupeidae,  Dussumieriidae,  Engraulidae.  Zoologica 
(N.Y.)  21:257-290. 

HouDE,  E.  D.,  AND  P.  L.  Fore. 

1973.  Guide  to  identity  of  eggs  and  larvae  of  some  Gulf 
of  Mexico  clupeid  fishes.  Fla.  Dep.  Nat.  Resour.  Mar. 
Res.  Lab.  Leafl.  Ser.  4  (part  1,  no.  23),  14  p. 

Houde,  E.  D.,  W.  J.  Richards,  and  V.  P.  Saksena. 

1974.  Description  of  eggs  and  larvae  of  scaled  sardine, 
Harengula  jaguana.   Fish.  Bull.,  U.S.  72:1106-1122. 


HUBBS,  C.  L.,  AND  K.  F.  Lagler. 

1958.     Fishes  of  the  Great  Lakes  region.  Revised  ed. 
Cranbrook  Inst.  Sci.,  Bull.  26,  213  p. 
Mead,  G.  W.,  and  M.  G.  Bradbury. 

1963.     Name  of  bones.  In  H.  B.  Bigelow  (editor).  Fishes 
of  the  western  North  Atlantic,  Part  3,  p.  20-23.     Mem. 
Sears  Found.  Mar.  Res.,  Yale  Univ.  1. 
Miller,  R.  V. 

1969.  Constancy  of  epibranchial  organs  and  fourth 
epibranchial  bones  within  species  groups  of  clupeid 
fishes.    Copeia  1969:308-312. 

Moser,  H.  G.,  and  E.  H.  Ahlstrom. 

1970.  Development  of  lanternfishes  (family  Myctophidae) 
in  the  California  Current.  Part  I.  Species  with  narrow- 
eyed  larvae.  Bull.  Los  Ang.  Cty.  Mus.  Nat.  Hist. 
Sci.  7,  145  p. 

Reintjes,  J.  W. 

1962.     Development  of  eggs  and  yolk-sac  larvae  of 
yellowfin  menhaden.     U.S.  Fish  Wildl.  Serv.,  Fish. 
Bull.  62:93-102. 
Richards,  W.  J.,  and  B.  J.  Palko. 

1969.     Methods  used  to  rear  the  thread  herring,  Opis- 
thonema oglinum,  from  fertilized  eggs.    Trans.  Am.  Fish. 
Soc.  98:527-529. 
Simpson,  J.  G.,  and  G.  Gonzalez. 

1967.    Some  aspects  of  the  early  life  history  and  environ- 
ment of  the  sardine,  Sardinella  anchovia,  in  eastern 
Venezuela.     Ser.   Recursos  Explot.   Pesq.   l(2):38-93. 
Taylor,  W.  R. 

1967.  An  enzyme  method  of  clearing  and  staining  small 
vertebrates.     Proc.  U.S.  Natl.  Mus.   122(3596),  17  p. 


1136 


THE  INFLUENCE  OF  TEMPERATURE  ON  LARVAL  AND 
JUVENILE  GROWTH  IN  THREE  SPECIES  OF  SOUTHERN 

CALIFORNIA  ABALONES^ 


David  L.  Leighton^ 


ABSTRACT 

Larvae  of  the  abalones //a/ioijs  rufescens,  H.  corrugata,  and  H.  fulgens  displayed  most  rapid  growth 
and  best  survival  at  15°-18°,  18°-21°,  and  20°-23°C,  respectively.  Survival  of  larvae  and  postlarvae  was 
poor  above  these  optimal  ranges.  However,  juveniles  3  mo  to  1  yr  old  were  tolerant  of  a  broader 
temp)erature  range.  The  warm- water  species,  H.  fulgens,  increased  in  shell  length  at  an  average  rate  of 
88  fi  per  day  at  26°C.  Mean  shell  elongation  rates  were  77  and  64  /z  per  day  in  H.  rufescens  and  in  H. 
corrugata  at  their  respective  optima. 


An  expanding  body  of  literature  exists  concerning 
aspects  of  the  biology  and  culture  of  the  abalone 
Haliotis  (e.g.,  Sakai,  1962;  Oba,  1964;  Tamura, 
1966;  Imai,  1967;  Tanaka,  1969;  Shibui,  1971a; 
and  McBeth,  1972,  which  succeeded  the  pioneer- 
ing studies  of  Murayama,  1935,  and  Ino,  1952).  In 
these  studies  little  attention  was  directed  to  prob- 
lems of  larval  development,  and  essentially  no 
information  has  been  obtained  on  the  limitations 
imposed  by  temperature  on  growth  and  survival  of 
larvae  and  postlarvae  with  the  single  exception  of 
the  observations  on  H.  sorenseni,  reported  by 
Leighton  (1972).  In  1962,  Kan-no  and  Kikuchi 
related  results  of  a  3-wk  experiment  in  which 
juvenile  H.  discus  hannai  were  reared  at  five  dif- 
ferent temperatures,  but  most  investigators  have 
merely  reported  the  range  of  temperature  prevail- 
ing during  observations  (e.g.,  Oba,  1964;  Shibui, 
1971b). 

This  paper  describes  results  of  experiments  in 
which  groups  of  larvae,  postlarvae,  and  juveniles 
were  reared  at  a  series  of  temperatures  encompas- 
sing the  natural  range  to  examine  the  influence  of 
these  factors  on  development  and  survival.  Larvae 
were  obtained  from  three  American  west  coast 
species  spawned  in  the  laboratory:  The  red 
abalone,  H.  rufescens,  the  pink  abalone,  H.  cor- 
rugata, and  the  green  abalone,  H.  fulgens. 


'This  work  is  a  result  of  research  sponsored  by  NOAA  Office  of 
Sea  Grant  U.S.  Department  of  Commerce,  under  Grant  #UCSD 
2-35208  with  the  Institute  of  Marine  Resources  in  cooperation 
with  California  Marine  Associates,  Cayxicos,  Calif  The  study 
was  carried  out  in  the  aquarium  laboratory  of  the  Southwest 
Fisheries  Center,  National  Marine  Fisheries  Service,  NOAA,  La 
Jolla,  Calif 

^Scripps  Institution  of  Oceanography,  University  of  California 
at  San  Diego,  La  Jolla,  CA  92037;  present  address:  California 
Marine  Associates,  P.O.  Box  136,  Cayucos,  CA  93430. 


MATERIAL  AND  METHODS 

Ripe  abalone  were  collected  off  southern 
California  by  diving.  In  transportation  to  the 
laboratory,  care  was  taken  to  avoid  subjecting  the 
animals  to  desiccation  or  other  physical  shock 
which  might  have  induced  premature  release  of 
gametes.  Adult  abalone  were  allowed  a  laboratory 
"conditioning  period"  of  about  2  wk  before  at- 
tempts were  made  to  induce  spawning.  Water 
temperature  in  tanks  containing  abalone  of  both 
sexes  was  raised  approximately  5°-8°C  above  am- 
bient, following  the  thermal  shock  method  of  Ino 
( 1952)  and  Oba  (1964);  a  procedure  which  was  only 
occasionally  successful.  Most  productive  spawn- 
ings in  terms  of  quantity  and  viability  were  those 
which  occurred  spontaneously  in  the  laboratory. 
Natural  cues  and  events  associated  with  "mass 
spawnings"  are  not  well  understood  (Owen  and 
Meyer,  in  press)  and  were  not  investigated  in  this 
study. 

Fertilized  eggs  were  collected  as  soon  as  possible 
after  their  release.  The  eggs,  which  settle  rather 
rapidly,  were  siphoned  or  pipetted  into  freshly 
filtered  seawater  (Cuno  filter  unit,^  ca.  5  yu )  at 
the  same  temperature  as  that  of  the  spawning 
environment.  Repetition  of  the  process  several 
times,  each  time  using  freshly  filtered  seawater, 
was  usually  sufficient  to  wash  eggs  free  of  excess 
sperm  and  debris.  Incubation  was  carried  out  at 
ambient  temperatures  and  larvae  treated  as  de- 
scribed elsewhere  (Leighton,  1972). 

While  some  experiments  were  performed  with 
eggs  at  early  cleavage  stages,  most  observations 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72.  NO.  4,  1974. 


^Reference  to  trade  names  does  not  imply  endorsement  by  the 
National  Marine  Fisheries  Service,  NOAA. 


1137 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


were  initiated  with  newly  hatched  trochophore 
larvae.  Trochophores  normally  hatched  from  eggs 
at  15°-18°C  within  12  to  18  h.  Shortly  after  hatch- 
ing, larvae  swim  to  the  surface  ( negative  geotaxis) 
and  are  easily  drawn  into  a  pipette  for  transfer  to 
experimental  containers. 

Thermal  influence  on  development  and  survival 
of  larvae  and  postlarvae  was  observed  using  a 
temperature  gradient  apparatus;  an  aluminum 
block  (30  X  15  X  150  cm)  bored  to  accommodate 
replicate  series  of  test  tubes  (25  ml).  Cooling  coils 
and  heating  elements  at  opposite  ends  maintained 
a  temperature  differential  (range:  7°-31°C)  with 
but  slight  fluctuation  (±0.5°C  per  gradient  posi- 
tion) over  the  course  of  the  average  experiment 
(2-4  wk).  The  apparatus  is  similar  to  that  used 
with  H.  sorenseni  larvae  (Leighton,  1972)  and  has 
been  thoroughly  described  elsewhere  (Thomas, 
Scotten,  and  Bradshaw,  1963). 

In  the  typical  experiment  duplicate  series  of  10 
tubes,  each  tube  containing  20  ml  of  seawater, 
were  placed  in  the  thermal  gradient  with  50  eggs 
or  larvae.  Incubation  was  carried  out  in  darkness. 
A  foam  urethane  cover  insulated  the  apparatus. 
Inspection  of  the  tubes  was  made  daily  during  the 
first  week  and  on  alternate  days  thereafter  to  de- 
termine the  stage  of  development  attained.  As 
abalone  larvae  are  lecithotrophic,  feeding  was  not 
necessary  until  settlement.  At  that  time  a  mixture 
of  three  species  of  pennate  diatoms  (Nitzschia 
spp.)  was  supplied. 

Studies  on  postlarvae  were  also  conducted  using 
the  temperature  gradient  block.  Between  two  and 
five  individuals  were  placed  in  each  tube.  Postlar- 
vae 1-2  mo  of  age  were  picked  individually  from 
walls  of  culture  containers  (Pyrex  beakers  or 
polyethylene  pails)  using  a  finely  bevelled  ap- 
plicator stick.  Several  drops  of  the  diatom  culture 
were  added  to  each  tube  twice  weekly  over  the 
usual  2-wk  observation  period. 

To  examine  the  effect  of  temperature  on  the 
success  of  juveniles,  groups  of  8-12  individuals 
were  reared  in  six  10-liter  polyethylene  contain- 
ers maintained  at  12°,  15°,  18°,  21°,  24°,  and  27°C 
(±1.0°).  Water  was  continuously  aerated  and  the 
entire  volume  exchanged  once  a  week.  Food  was 
either  a  mixture  of  unicellular  and  filamentous 
algae  cultured  within  each  container  under  il- 
lumination of  a  fluorescent  lamp  or  fronds  of  the 
brown  alga,  Egregia  laevigata,  collected  in  fresh 
condition  every  3-4  days.  Growth  of  juvenile 
abalones  was  measured  for  month-long  intervals 
in  these  experiments. 


Progeny  of  each  spawning  were  maintained  in 
the  laboratory  for  over  1  yr  providing  comparative 
information  on  juvenile  growth  rate  in  aquaria. 
Diatoms  and  minute  filamentous  algae  served  as 
food  during  their  first  few  months.  Older  juveniles 
were  provided  larger  algae,  Egregia  laevigata, 
Eisenia  arborea,  Macrocystis  pyrifera,  and 
Laminaria  farlowii. 

DEVELOPMENTAL  FEATURES  OF 

LARVAE,  POSTLARVAE,  AND 

JUVENILES 

While  morphogenesis  is  gradual  and  does  not 
progress  in  a  stepwise  manner,  various  stages  of 
larval  and  postlarval  development  are  recogniz- 
able. Development  rate  was  measured  in  terms  of 
the  time  required  for  larvae  to  first  gain  features 
distinctive  to  each  stage.  Eleven  such  stages  are 
passed  from  trochophore  larva  to  circular-shelled 
postlarva  (Figure  1).  Settlement  (the  crawling 
stage)  marks  the  end  of  larval  life.  Postlarval  de- 
velopment then  begins  with  the  deposition  of 
peristomial  shell  and  persists  to  formation  of  the 
first  respiratory  pore  ("notch  stage,"  Leighton, 
1972)  at  an  age  of  1-3  mo.  Thenceforth  to  first 
sexual  maturity  the  abalone  may  be  regarded  as 
juvenile. 


Figure  1.— 1)  Trochophore  larva  after  hatching.  2)  Cap-shell 
early  veliger  larva.  3)  Inflate-shell  veliger  (torsion  stage).  4) 
Early  operculate  veliger  (preeye  spot).  5)  Incipient  cephalic  ten- 
tacle stage  operculate  veliger.  6)  Midformed  cephalic  tentacle 
stage.  7)  Digitate  or  branched  cephalic  tentacle  stage.  8)  Crawl- 
ing and  settling  stage.  9)  Peristomial  shell  stage  postlarva.  10) 
Midasymmetric  shell  postlarva.  11)  Circular-shell  postlarva. 


Labelled  structures: 

c-g-, 

ciliated  girdle 

c.t.. 

cephalic  tentacle 

cten.. 

ctenidium 

d.g., 

digestive  gland 

e.. 

eye  spot 

e.t.. 

epipodial  tentacle 

f., 

foot 

int., 

intestine 

1.  sh.. 

larval  shell 

m., 

mantle 

m.o.. 

mouth  with  odontophor 

op.. 

operculum 

p.s.. 

peristomial  shell 

r.m., 

retractor  muscle 

r.s.m., 

right  shell  muscle 

v., 

velum 

vis., 

viscera 

1138 


LEIGHTON:  INFLUENCE  OF  TEMPERATURE  ON  ABALONES 


r.  m. 


r.  s.  m. 


1139 


FISHERY  BULLETIN;  VOL.  72,  NO.  4 


RESULTS 

In  the  course  of  the  study  six  batches  of  larvae 
were  obtained  from  Haliotis  rufescens,  while  three 
productive  spawnings  occurred  with//,  corrugata 
and H.fulgens.  Year-round  spawning  in//,  rufes- 
cens was  predicted  by  Boolootian,  Farmanfar- 
maian,  and  Giese  (1962)  and  Young  and  DeMar- 
tini  (1970)  from  field  sampling  for  gonad  indices.  I 
found  spawning  adults  every  month  of  the  year 
(1969-71)  in  samples  taken  from  Estero  Bay  (cen- 
tral California)  and  in  the  present  study  with  //. 
rufescens  from  southern  California,  laboratory 
spawnings  were  obtained  in  January,  February, 
April,  September,  November,  and  December. 
Haliotis  corrugata  and  H.  fulgens  spawned  only 
during  the  months  of  April,  June,  and  October. 
Members  of  the  shallowwater  species,  //. 
cracherodii,  held  in  the  laboratory  for  another 
study,  spawned  in  early  spring  and  early  fall. 
Haliotis  sorenseni  produced  viable  gametes  only 
during  late  winter  (Leighton,  1972). 

DEVELOPMENT  AND  HATCHING 
IN  EGGS 

At  14°-16°C  (ambient  for  La  Jolla  during  most  of 
the  year)  eggs  of  all  species  hatched  within  18-24 
h.  Generally,  development  to  hatching  appeared 
normal  over  a  rather  broad  thermal  range.  At 
hatching,  however,  consequences  of  inappropriate 
incubation  temperatures  became  pronounced  as 
trochophore  larvae  at  and  near  thermal  limits  be- 
came highly  abnormal  in  appearance  and  be- 
havior and  usually  succumbed  within  48  h,  par- 
ticularly at  higher  temperatures.  Bizarre  ciliated 
bodies  predominated  at  high  extremes  of  tempera- 
ture while  retardation  and  paralysis  occurred  at 
lowest  temperatures.  Commonly  torsion  was  in- 
complete in  larvae  held  at  subnormal  tempera- 
tures. A  consequence  of  ensuing  abnormality  and 
mortality  near  thermal  limits  is  apparent  in  the 
series  of  curves  generated  for  development  during 
the  first  several  days  of  larval  life.  Attrition  at 
upper  and  lower  extremes  and  relatively  high 
survival  and  rapid  growth  at  optimal  tempera- 
tures is  reflected  in  the  sharply  peaked  curves  for 
larval  development  rate  versus  temperature.  In 
H.  rufescens,  for  example,  eggs  developed  in  an 
apparently  normal  manner  over  the  range 
10°-23°C,  but  larval  grovvd:h  after  hatching  became 
restricted  to  the  comparatively  narrow  range 
13.5°-20.0°C  (Figure  2).  The  apparent  shift  of  the 


Incipient 
Cephalic  Tentacle 

Operculate 
Veliger 

Inflote-stiell 
Veliger 

Cop-shel  I 
Veliger 

Troctiophore 
Larva 


48  hours 


15  20 

TEMPERATURE  (°C) 

Figure  2. — Development  of  eggs  of  Haliotis  rufescens  held  at 
different  temperatures  over  a  period  of  48  h.  Mortality  occurred 
above  20°C  after  14  h. 


3- 


2- 


>- 
< 


O  H.  rufescens 
A  H.  corruggtg 
D  H    fulgens 


10  15  20 

TEMPERATURE  CO 


25 


30 


Figure  3. 


-Hatching  time  for  eggs  of  three  species  of  Haliotis 
incubated  at  several  temperatures. 


peaks  of  curves  with  time  to  suggest  true  optima 
at  temperatures  about  2°C  lower  than  observed  in 
trochophore  larvae  was  found  in  all  species 
studied  due  to  supraoptimum  mortality. 

Hatching  time  was  strongly  dependent  on 
temperature  and  ranged  between  10  and  72  h. 
Both  H.  corrugata  and  //.  fulgens,  at  tempera- 
tures supporting  rapid  but  normal  growth  (their 
respective  thermal  optima),  reached  the  point  of 
hatching  sooner  than  did  //.  rufescens  (Figure  3). 
Strongest  contrast  in  specific  development  rate  is 
seen  in  the  stage  attained  at  supraoptimum  tem- 
peratures (2°-3°C  above  optimum).  In  2  days:  //. 


1140 


LEIGHTON:  INFLUENCE  OF  TEMPERATURE  ON  ABALONES 


rufescens  (near  19°C)  reached  the  early  (preeye 
spot)  operculate  stage,  H.  corrugata  (near  23°C) 
had  formed  eyespots  and  cephahc  tentacle  buds, 
and  H.  fulgens  (near  25°C)  had  become  mid- 
cephalic  tentacle  operculates.  In  the  latter,  set- 
tling was  observed  as  early  as  3  days  after  fertili- 
zation. 

OBSERVATIONS  ON 
TROCHOPHORE  LARVAE 

When  swimming  trochophore  larvae  rather 
than  developing  eggs  were  introduced  to  the 
thermal  gradient  system,  survival  was  improved. 
In  experiments  initiated  with  fertilized  eggs,  sur- 
vival beyond  3  days  in  the  20-ml  tubes  was  low 
despite  routine  addition  of  dihydrostreptomycin 
sulfate  and  sulfanilamide  (to  final  concentration, 
10  ppm).  Substances  within  the  periviteliine  space 
(including  excess  sperm)  are  liberated  at  rupture 
of  the  albumen  membrane,  frequently  promoting 
fouling.  Temperature  block  studies  in  which 
trochophore  or  veliger  larvae  were  freed  of  con- 
taminants by  repeated  transfer  and  then  ad- 
mitted to  the  tubes  showed  reduced  mortality. 

Haliotis  rufescens  larvae  settled  approximately 
4  days  after  fertilization  (18°C).  However,  after  3 
wk  in  the  temperature  block,  only  those  groups 
between  14°  and  18°C  had  reached  advanced  post- 
larval  stages  (Figure  4).  Settling  occurred  in  some 
H.  corrugata  larvae  within  3.5  days,  but  postlar- 
vae  did  not  survive  (22°-23°C).  Most  rapid  growth 
and  best  survival  in  H.  corrugata  was  at  21°-22°C; 
the  circular-shell  postlarval  stage  was  reached  in 
17  days  (Figure  5).  Settlement  began  in  larvae  of 
H.  fulgens  at  25.5°C  in  slightly  less  than  3  days, 
but  again,  subsequent  success  was  poor.  Those  at 
22°-23°C,  however,  settled  by  the  fourth  day  and 
progressed  to  the  circular-shell  stage  in  15  days 
(Figure  6).  There  was  a  close  correspondence  of 
curves  for  development  rate  vs.  temperature  ob- 
tained with  progeny  from  different  spawnings  and 
parentage.  Optima  described  graphically  for  each 
species  varied  within  only  1°C  for  H.  corrugata, 
1.5°C  for  H.  fulgens,  and  2°C  for  H.  rufescens. 

Larvae  introduced  to  a  thermal  gradient  as 
operculate  veligers  exhibited  tolerance  to  a 
broader  temperature  range.  Subsequent  de- 
velopment rate  was,  however,  slowed.  The  general 
retardation  may  be  a  shock  response  to  environ- 
mental change.  The  greatly  reduced  volume  pro- 
vided in  the  20-ml  tubes  and  the  totally  darkened 
conditions  in  the  temperature  block  contrast  with 


Circular- 
Shelled 

Mid  Asymmetric     — 

Eorly 
Asymmetric 

Crawling 
(Settling) 

Branched 
Cephalic  Tentacle 

Mid  Cephalic 
Tentocle 

Incipient 
Cepholic  Tentacle 

Operculote 
Veliger 

Inf  late-shell 
Veliger 

Cap-shell 
Veliger 

Trochophore 
Larva 


10  15  20  25 

TEMPERATURE  (°C) 


30 


Figure  4. — Development  of  larvae  of  Haliotis  rufescens  at  a 
series  of  temperatures  when  introduced  to  the  thermal  gradient 
as  trochophores. 


Circular  ■ 
Shelled 


Mid  Asymmetric     - 


Early 
Asymmetric 

Crawling 
(Settling) 

Branched 
Cephalic  Tentacle 

Mid  Cephalic 
Tentacle 

Incipient 
Cephalic  Tentacle 

Operculate 
Veliger 

Inflote-shell 
Veliger 

Cop- shell 
Veliger 

Trochophore 
Larva 


15  20 

TEMPERATURE  CO 


30 


Figure  5. — Stages  attained  by  larvae  of  Haliotis  corrugata  over 
a  period  of  17  days.  Larvae  were  placed  in  the  thermal  gradient 
at  the  trochophore  stage. 

the  10-liter  volume  and  illumination  in  the  plastic 
rearing  containers.  In  an  experiment  illustrating 
the  point,  H.  corrugata  eggs,  trochophores  and 
operculate  veligers  were  placed  in  the  gradient  for 
5  days  in  each  case.  At  20°-22°C,  eggs  developed 
rapidly  and  early  postlarval  stages  reached  in  5 
days.  However,  operculate  veligers  had  not  yet 
reached  the  crawling  stage  at  an  age  of  7  days 
(Figure  7). 

In  temperature  block  experiments,  survival 
through  settling  usually  ranged  between  50  and 


1141 


FISHERY  BULLETIN:  VOL.  72,  NO.  4 


Circular - 
Shelled 

Mid  Asymmetric     - 

Early 
Asymmetric 

Crawling 
(Settling) 

Branched 
Cepholic  Tentocle 

Mid  Cepholic        _ 
Tentacle 

Incipient 
Cephalic  Tentacle 

Operculate 
Veliger 

Inflole-shell 
Veliger 

Cap- shell 
Veliger 

Trochophore 
Lorvo 


10  15  20 

TEMPERATURE  CO 


25 


30 


Figure  6. — Stages  attained  by  Haliotisfulgens  larvae  incubated 
at  several  temperatures  for  15  days.  The  experiment  was  ini- 
tiated with  trochophore  larvae. 


Circular- 
Shelled 

Mid  Asymmetric    — 

Early 
Asymmetric 

Crawling 
(Settling) 

Branched 
Cephalic  Tentacle 

Mid  Cephalic 
Tentocle 

Incipient 
Cepholic  Tentacle 

Operculate 
Veliger 

Inflote-shell 
Veliger 

Cop-shel  I 
Veliger 

Trochophore 
Lorwo 


O  5  doys,  in  as  Zygotes 

A  6  days,  m  as  Trochophores 

D  7  doys,  in  os  Operculotes 


10  15  20 

TEMPERATURE   CO 


25 


30 


Figure  7. — Comparison  of  development  rate  and  tolerated 
thermal  range  in  larvae  of  Haliotis  corrugata  placed  in  the 
temperature  block  at  1,  20,  and  48  h  after  fertilization. 

80%  within  the  physiologically  acceptable  tem- 
perature range.  High  mortality  near  the  upper 
limit  might  have  been  due,  in  part,  to  oxygen 
exhaustion.  This  was  tested  by  sampling  open-top 
tubes  in  the  block  at  22°  and  24°C  for  oxygen 
content  after  holding  approximately  150  larvae 
(H.  rufescens)  for  48  h.  A  decline  from  5.8  to  2.9  ml 
02/liter  was  observed  at  22°C  in  48  h.  Routinely, 
therefore,  only  25  to  50  larvae  or  eggs  were  admit- 
ted to  each  tube  and  once  daily  tubes  were  mixed 
to  assure  adequate  oxygen  was  available.  Subse- 


quently oxygen  depletion  was  not  a  cause  of  mor- 
tality. 

THERMAL  TOLERANCE  OF 
POSTLARVAE 

Postlarvae  ranging  in  age  from  1  to  2  mo  were 
placed  (2-5/tube)  in  the  thermal  gradient  block 
and  provided  each  3-4  days  a  mixture  of  three 
species  of  diatoms  (Nitzschia  spp.).  Tubes  were 
checked  for  survival  and  growth  of  postlarvae  over 
periods  of  2  wk.  Survival  was  good  in  all  species  at 
colder  temperatures,  but  those  at  10°-12°C  invari- 
ably were  lethargic  and  could  not  right  them- 
selves once  overturned.  Haliotis  rufescens 
survived  over  the  range  10°-19.5°C.  Haliotis  cor- 
rugata and  H.  fulgens  were  tolerant  to  the  same 
lower  temperatures  but  had  different  upper 
limits,  23.5°  and  26.0°C,  respectively.  Typically 
survival  was  nearly  100%  over  a  broad  inter- 
mediate range  of  temperatures,  but  declined 
sharply  within  2°  of  the  extremes. 

POSTLARVAL  AND  JUVENILE 
GROWTH 

Specific  differences  in  growth  rate  of  both  post- 
larvae and  juveniles  under  laboratory  conditions 
were  measured.  When  its  postlarvae  were  pro- 
vided near  optimal  thermal  and  feeding  environ- 
ments, H.  fulgens  formed  the  first  respiratory  pore 
in  about  half  the  time  required  by  the  other 
species.  As  the  pore  is  formed,  a  notch  is  first  seen 
on  the  anterior  right  shell  margin.  The  feature  is 
conspicuous  and  serves  as  a  convenient  point  of 
comparison.  The  "notch  stage"  was  reached  in 
some  rapid-growing  H.  fulgens  at  an  age  of  30 
days  (Table  1). 

Variability  in  growth  rate  was  marked.  Groups 
of  juveniles  of  identical  parentage,  age,  and  rear- 
ing environment  sampled  periodically  for  shell 
length  distribution  reflected  a  broad  range  and 
age-increasing  standard  deviation  (Table  2).  Shell 

Table  1. — Age  and  shell  length  of  postlarval  Haliotis  at  forma- 
tion of  the  first  respiratory  pore. 


Stiell 

Temper- 

Age 

length! 

ature 

Species 

(days) 

(mm) 

(°C) 

H.  rufescens 

60-70 

15-18 

14-18 

H.  corrugata 

50-60 

2.0-2.5 

15-22 

H.  fulgens 

30-40 

1,7-2  0 

16-24 

H.  sorenseni 

55-65 

2.0-2.1 

'14-18 

'Leigtiton,  1972 


1142 


LEIGHTON:  INFLUENCE  OF  TEMPERATURE  ON  ABALONES 

length  at  1  yr  of  age  in  four  species  reared  in  the 
laboratory  varied  over  a  range  greater  than  10mm 
(Table  3). 

INFLUENCE  OF  TEMPERATURE  ON 
GROWTH  RATE  OF  JUVENILES 

Several  growth  experiments  were  conducted 
with  juveniles  of  the  three  species  of  abalones  to 
gain  comparative  data  and  to  establish  respective 
temperatures  of  maximum  growth  rate.  Juveniles 
were  reared  for  month-long  periods  in  10-liter 
plastic  containers  held  at  six  temperatures  be- 
tween 12°  and  30°C.  Both  H.  corrugata  and  H. 
fulgens  displayed  enhanced  growth  rate  above 
20°C.  Haliotis  rufescens,  however,  grew  best 
below  20°C  and,  in  fact,  grew  but  slightly  less  at 
the  coldest  temperature,  12.5°C  (Table  4,  Figure 
8).  H.  fulgens  again  showed  a  superior  growth 
rate.  While  a  mean  daily  shell  growth  approach- 
ing 90  A'  was  observed  at  its  temperature  of 
maximum  growth  rate  (26°C),  some  individuals 
increased  in  shell  length  as  much  as  130  n  per 
day. 

DISCUSSION 

Seven  species  of  Haliotis  occur  in  southern 
California  waters  ranging  vertically  from  the  in- 


Table  2. — Variation  in  size  of  juvenile  Haliotis  of  identical 
parentage,  age,  and  growing  environment. 


Shi 

sll  length  (mm) 

Age 

Soecies 

(months) 

Number 

Mean 

Range            SD 

H.  rufescens 

3.7 

18 

4.4 

2.6-6.1            1.06 

H.  corrugata 

5,0 

27 

9.2 

6.8-14.1          2.42 

H.  fulgens 

4.7 

70 

7.1 

3  6-12.0         2.00 

H.  sorensenl 

3.3 

19 

4.3 

3.0-5.6           0.64 

Table  3. — Size  of  Haliotis  at  completion  of  first  year  growth  in 
the  laboratory. 


Shell  1 

ength  ( 

mm) 

Species 

Mean 

Range 

Number 

H.  rufescens 
H.  corrugata 
H.  fulgens 
H.  sorensenl 

15.6 
18.3 
32.8 
13.4 

9.9-20.0 
12.2-26.4 
30  5-389 

8.0-21.0 

50 
18 
'3 
19 

'Recent  observations  on  growth  of  over  100  juvenile  H.  fulgens  suggest 
the  three  individuals  represented  here  were  exceptionally  rapid  growers. 
Projection  of  growth  of  juveniles  presently  8  mo  old  suggest  the  mean  size 
at  1  yr  under  laboratory  conditions  may  fall  closer  to  25  mm. 

tertidal  to  depths  over  35  m.  Depth  distribution  is 
stratified  specifically,  although  in  certain  areas 
(i.e.,  in  the  presence  of  localized  upwelling)  over- 
lapping does  occur.  Vertical  and  latitudinal  dis- 
tribution appears  most  closely  related  to  tempera- 
ture. The  Point  Loma  (San  Diego)  shelf  from  0  to 
35  m  supports  all  California  abalone  species 
(Table  5).  Colder  water  species  may  be  found  in- 
tertidally  in  northern  California  (H.  rufescens,  H. 


Table  4. — Daily  shell  elongation  rate  for  groups  of  juvenile  Haliotis  reared  for  month-long  jjeriods  at  different 

temperatures  (microns/day). 


Species  and 
date 


Temperature  (°C  ±  1.5°; 


12 


15 


18 


21 


24 


27 


30 


H.  rufescens 

Oct.  1971 
Jan.  1972 
Mar.  1972 
Dec.  1972 

Mean 


91 

61 

90 

45 

32 

36 

41 

68 

61 

29 

70 

64 

84 

79 

35 

46 

92 

67 

95 

13 

609 


64.5 


77.3 


70.0 


27.3 


(') 


H.  corrugata 

Jun.  1972 
May  1973 
Jun.  1973 

Mean 


26 

57 


41.5 


29 
55 
45 

43.0 


30 
62 
72 

54.7 


46 
54 
91 

63.7 


53 

60 
63 

58.7 


28 
68 

48.0 


14 

14.0 


H.  fulgens 

Mar.  1973 
May  1973 
Jun.  1973 

Mean 


23 
21 


22.0 


29 
21 

21 

237 


63 

55 
56 

580 


77 

119 

64 

74 

88 

114 

60 

50 

86 

70.3 


858 


88.0 


54 
54.0 


'H.  rufescens  did  not  survive  in  the  27'C  containers. 

These  data  are  averages  for  groups  of  8  to  15  individuals  reared  in  each  of  six  1 0-liter  plastic  drums.  In  the  case  of  H.  corrugata 
and  H.  fulgens.  temperatures  were  raised  throughout  for  the  third  experiment  to  cover  the  supraoptimal  range.  Juveniles  used  in 
these  experiments  ranged  from  5  to  20  mm. 


1143 


FISHERY  BULLETIN:  VOL.   72,  NO.  4 


lOOr 


80 


<x 


en 
o 


60 


40 


20 


H.   fulgens 
q 


H,   corrugoto 


1 


_L 


18  21  24 

"Cdl.S") 


27 


30 


Figure  8. — Growth  rate  of  juvenile  abalone  held  for  month-long 
periods  at  different  temperatures.  Points  are  averages  for  groups 
of  8  to  15  individuals  (see  Table  4). 

Table  5. — Approximate  depth  distribution  oiHaliotis  species  off 
Point  Loma  (San  Diego,  Calif). 


Species 


Depth  range 
(m) 


H.  cracherodii 
H.  fulgens 
H.  corrugata 
H.  rufescens 
H.  k.  assimilis 
H.  sorenseni 
H.  walallensis 


0-2 
0-5 
1-20 
10-25 
10-30 
15-35 
15  35 


kamtschatkana,  and  H.  walallensis  together  with 
the  generally  shallow  water  and  intertidal  H. 
cracherodii). Haliotis  sorenseni, H.  corrugata,  and 
H.  fulgens  range  from  Pt.  Conception  to  central 
Baja  California.  Haliotis  cracherodii  and//,  rufes- 
cens occur  throughout  California  and  northern 
Baja  California,  while//,  k.  assimilis  replaces  //. 
kamtschatkana  in  southern  California  (McLean, 
1966). 

This  study  has  shown  that  the  thermal  re- 
quirements, particularly  for  eggs  and  early  lar- 
vae, are  exacting.  Field  distribution  of  juvenile 
and  adult  members  of  each  species  correspond 
with  the  thermal  tolerance  range  observed  in  lar- 
vae in  the  laboratory.  The  range  of  tolerance  in- 
creased with  larval  age.  Larvae  of  //.  corrugata 
placed  in  the  thermal  gradient  as  operculate  veli- 
gers  survived  a  range  of  18°  (from  8°  to  26°C), 
while  those  resulting  from  eggs  placed  in  the  same 
situation  were  tolerant  of  a  range  of  only  8°  (from 
15°  to  23°C).  The  observation  is  not  new  nor  lim- 
ited to  Haliotis  (Loosanoff  and  Davis,  1963). 
Thus,  survival  of  larvae  dispersed  in  nature  is 


likely  dependent  on  their  remaining  within  a 
water  mass  of  appropriate  temperature  and 
further,  settling  in  areas  over  which  temperature 
change  will  not  be  extreme.  Recruitment  to  mar- 
ginal environments  may  rely  on  the  timely  influx 
of  advanced  veliger  larvae.  The  situation  is  com- 
plicated, no  doubt,  by  acclimation  of  mature 
adults  near  distribution  limits. 

Most  studies  in  abalone  culture  have  been  con- 
ducted by  Japanese  workers  concentrating  on  the 
species  native  to  northern  Japan,  //.  discus  han- 
nai.  Its  broad  thermal  tolerance  (approximately 
5°-30°C)  and  relatively  rapid  growth  at  elevated 
temperatures  have  attracted  the  interest  of 
mariculturists.  The  species  exhibits  rapid  larval 
development,  settling  in  3  days  at  25°C  and  reach- 
ing the  notch  stage  in  42  days  (Kan-no  and 
Kikuchi,  1962).  When  reared  at  five  temperatures 
between  5°  and  25°C,  juvenile  //.  d.  hannai 
displayed  daily  increments  in  shell  length  of  1, 
2,  32,  68,  and  95 m  ,  respectively,  according  to  the 
same  report.  During  winter  months  when  sea 
temperatures  at  the  coastal  hatchery  drop  below 
10°C,  cultured  juvenile  abalone  are  transferred  to 
a  site  adjacent  the  Yogasaki  Electric  Generating 
Plant  using  26°C  water  detoured  from  the  effluent 
stream  (Kan-no,  pers.  commun.,  McBeth,  1972). 

Thermal  tolerance  and  growth  characteristics 
of  larvae  and  juveniles  of  the  Japanese  species  are 
similar  to  that  observed  in  the  present  study  in  //. 
fulgens.  Of  the  American  species  considered  here, 
only  //.  fulgens  could  be  recommended  for  heated 
effluent  mariculture. 

First  year  growth  measured  in  this  study  is  not 
considered  to  approximate  growth  in  nature. 
Artificial  lighting,  synthetic  materials  in  rearing 
tanks,  and  other  factors  may  have  infiuenced 
growth,  and  the  growth  rate  estimates  are  likely 
conservative.  The  general  observation  of  rapid, 
moderate,  and  slow  growth  in  //.  fulgens,  H. 
rufescens  and  //.  corrugata,  respectively,  is  con- 
cluded to  reflect  specific  differences  in  growd:h 
potential. 

LITERATURE  CITED 

BooLOOTiAN,  R.  A.,  A.  Farmanfarmaian,  and  a.  C.  Giese. 
1962.   On  the  reproductive  cycle  and  breeding  habits  of  two 
western  species  of  Haliotis.  Biol.  Bull.  (Woods  Hole) 
122:183-193. 
Imai,  T. 

1967.  Mass  production  of  molluscs  by  means  of  rearing  the 
larvae  in  tanks.  [In  Engl.,  Jap.  summ.]  Venus  25: 159-167. 
Ino,  T. 

1952.  Biological  studies  on  the  propagation  of  Japanese 


1144 


LEIGHTON:  INFLUENCE  OF  TEMPERATURE  ON  ABALONES 


abalone  (genus  Haliotis).  [In  Jap.,  Engl,  summ.]  Bull. 
Tokai  Reg.  Fish.  Res.  Lab.  5,  102  p. 
Kan-no,  H.,  and  S.  Kikuchi. 

1962.  On  the  rearing  of  Anadara  broughtonii  (Schrenk) 
and  Haliotis  discus  hannai  Ino.  Bull.  Mar.  Stn.  Asamushi 
ll(2):71-76. 

Leighton,  D.  L. 

1972.  Laboratory  observations  on  the  early  growth  of  the 
abalone,  Haliotis  sorenseni,  and  the  effect  of  temperature 
on  larval  development  and  settling  success.  Fish.  Bull., 
U.S.  70:373-381. 

LOOSANOFF,  V.  L.,  AND  H.  C.  DaVIS. 

1963.  Rearingofbivalvemollusks.  Adv.  Mar.  Biol.  1:1-136. 
McBeth,  J.  W. 

1972.  The  growth  and  survival  of  the  California  red 
abalone   in  Japan.    [In   Engl.,  Jap.   summ.]   Venus 
31:122-126. 
McLean,  J.  H. 

1966.  West  American  prosobranch  gastropoda:  Super- 
families  Patellacea,  Pleurotomariacea  and  Fissurellacea. 
Ph.D.  Thesis,  Stanford  Univ.,  272  p. 
Murayama,  S. 

1935.   On  the  development  of  the  Japanese  abalone, 
Haliotis  gigantea.  J.  Coll.  Agric,  Tokyo  Imp.  Univ. 
13:227-233. 
Oba,  T. 

1964.  Studies  on  the  propagation  of  an  abalone,  Haliotis 
diversicolor  supertexta  Lischke — II.  On  the  development. 
[In  Jap.,  Engl,  synop.]  Bull.  Jap.  Soc.  Sci.  Fish. 
30:809-819. 


Owen,  B..  and  R.  Meyer. 

In  press.  Laboratory  hybridization  of  California  abalone 
(Haliotis). 
Sakai,  S. 

1962.  Ecological  studies  on  the  abalone,  Haliotis  discus 
hannai  Ino — IV.  Studies  on  the  growth.  [In  Jap.,  Engl, 
synop.]  Bull.  Jap.  Soc.  Sci.  Fish.  28:899-904. 

Shibui,  T. 

1971a.  Experimental  studies  on  the  predatory  animals  of 
young  abalones.  [In  Jap.,  Engl,  summ.]  Bull.  Jap.  Soc.  Sci. 
Fish.  37:1173-1176. 
1971b.  Studies  on  the  transplantation  of  red  abalone  and  its 
growth  and  development.  [In  Jap.,  Engl,  summ.]  Bull. 
Jap.  Soc.  Sci.  Fish.  37:1168-1172. 
Tamura,  T. 

1966.  Marine  aquaculture.  [Transl.  by  M.  I.  Watanabe]. 
Natl.  Tech.  Inf.  Serv.,  Springfield,  Va.,  1052  p. 
Tanaka,  Y. 

1969.  Studies  on  reducing  mortality  of  larvae  andjuveniles 
in  the  course  of  the  mass-production  of  seed  abalone — I. 
Satisfactory  result  with  streptomycin  to  reduce  intensive 
mortality.  [In  Jap.,  Engl,  summ.]  Bull.  Tokai  Reg.  Fish. 
Res.  Lab. 

Thomas,  W.  H.,  H.  L.  Scotten,  and  J.  S.  Bradshaw. 

1963.  Thermal  gradient  incubators  for  small  aquatic  or- 
ganisms. Limnol.  Oceanogr.  8:357-360. 

Young,  J.  S.,  and  J.  D.  DeMartini. 

1970.  The  reproductive  cycle,  gonadal  histology,  and 
gametogenesis  of  the  red  abalone,  Haliotis  rufescens 
(Swainson).  Calif.  Fish  Game  56:298-309. 


1145 


LABORATORY  STUDY  OF  BEHAVIORAL  INTERACTIONS  BETWEEN 

THE  AMERICAN  LOBSTER,  HOMARUS  AMERICANUS,  AND 

THE  CALIFORNIA  SPINY  LOBSTER,  PANULIRUS  INTERRUPTUS, 

WITH  COMPARATIVE  OBSERVATIONS  ON 

THE  ROCK  CRAB,  CANCER  ANTENNARIUS^ 

C.  O'Neil  Krekorian,  David  C.  Sommerville,  and  Richard  F.  Ford^ 

ABSTRACT 

Behavioral  interactions  between  Homarus  americanus  and  Panulirus  interruptus,  with  comparative 
observations  on  Cancer  antennarius,  were  studied  in  order  to  determine  the  possible  effects  an 
introduced  population  of  H.  americanus  would  have  on  the  southern  California  population  of 
P.  interruptus.  Subjects  were  placed  in  tanks  3  m  in  diameter  with  observational  windows 
equally  spaced  around  the  tank  perimeter.  Three  30-min  observation  periods  were  conducted  on  the 
lobsters  each  day  for  a  5-day  precontrol  period  (H.  americanus  absent),  a  10-day  experimental  period 
(H.  americanus  present),  and  a  5-day  postcontrol  period  (H.  americanus  absent).  Five  replicates 
of  a  shelter  and  no  shelter  condition  were  made  with  five  naive  P.  interruptus  and  one//,  americanus 
for  each  replicate.  Agonistic  action  patterns  were  recorded  for  actors  and  reactors,  along  with  various 
other  behaviors,  on  data  sheets  partitioned  into  1-min  intervals.  A  large  percentage  of  Homarus- 
initiated  behavioral  actions  in  the  shelter  (44%)  and  no  shelter  (39%)  conditions  involved  threat 
and  attack  by  H.  americanus.  In  //omarus-initiated  interactions,  P.  interruptus  was  displaced  by 
H.  americanus  61%  of  the  time  in  the  shelter  condition  and  63%  of  the  time  in  the  no  shelter 
condition.  Although  Panii/irws-initiated  interactions  occurred  much  less  frequently,  the  results  were 
similar  to  the  //omarus- initiated  interactions  in  that  P.  interruptus  was  ultimately  displaced  by 
threatening  and  attacking//,  americanus  92%  of  the  time  in  the  shelter  condition  and  76%  of  the  time 
in  the  no  shelter  condition.  Our  results,  and  those  of  other  studies,  are  discussed  with  respect  to  the 
potential  adverse  effects  of  introducing//,  americanus  into  southern  California  waters.  The  evidence 
suggests  that  such  an  introduction  is  inadvisable. 


At  the  present  time,  there  is  strong  interest  from 
the  private  sector  in  introducing  the  American 
lobster,  Homarus  americanus,  into  California 
waters.  This  interest  arises  primarily  from  the 
marked  downward  trend  in  annual  landings  of 
the  California  spiny  lobster,  Panulirus  inter- 
ruptus, and  the  high  unit  value  and  continuing 
demand  for  lobster  species  in  general  and  in 
particular  for  the  American  lobster,  which 
supports  one  of  the  most  valuable  fisheries  in 
North  America.  Conditions  along  the  entire 
California  coast  appear  well  within  the  limits 
tolerated  by  larvae,  juveniles,  and  adults  of  H. 
americanus.  Thus,  with  the  recent  development  of 
successful  mass  culture  techniques  (Hughes, 
1968;  Ghelardi  and  Shoop,  1968;  Kensler,  1970), 


'This  work  is  a  result  of  research  sponsored  by  the  National 
Oceanic  and  Atmospheric  Administration  Office  of  Sea  Grant, 
U.S.  Department  of  Commerce,  under  Grants  No.  USDC 
2-35208  and  USDC  04-3-158-22. 

^Biological  Sciences,  San  Diego  State  University,  San  Diego, 
CA  92115. 


the  species  probably  could  be  established,  at 
least  by  means  of  continued  stocking  (Ghelardi 
and  Shoop,  1972). 

Despite  the  apparent  value  of  the  American 
lobster  as  a  Pacific  Coast  fishery,  there  are 
several  potential  detrimental  effects  of  intro- 
ducing it  into  the  Pacific  which  must  be  considered 
(Rathbun,  1888;  Ghelardi,  1967).  These  are:  1)  the 
introduction  of  disease,  parasitic  organisms,  or 
other  microfauna  and  microflora  harmful  to 
native  species  and  2)  the  elimination  or  reduc- 
tion in  abundance  of  ecologically  similar  forms, 
such  as  P.  interruptus,  in  areas  where//,  ameri- 
canus might  become  established. 

Introductions  of  some  foreign  animals  and  ~ 
plants  have  had  very  serious  effects  on  native 
species  (Elton,  1958).  Thus,  there  is  a  great  need 
for  effective  evaluation  and  control  of  exotic 
species  introductions,  as  recently  discussed  by 
Lachner,  Robins,  and  Courtenay  (1970).  There 
have  been  at  least  23  attempts  to  introduce 


Manuscript  accepted  December  1973. 
FISHERY  BULLETIN:  VOL.  72,  NO.  4,  1974. 

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KREKORIAN,  SOMMERVILLE,  and  FORD:  LOBSTER  BEHAVIORAL  INTERACTIONS 


H.  americanus  between  Monterey  Bay  and  British 
Columbia  (Ghelardi  and  Shoop,  1968).  The  exact 
reasons  for  the  failure  of  these  introductions  are 
unknown.  However,  three  possible  causes  were: 
1)  low  stocking  density,  2)  unsuitability  of  the 
locations  used  for  introductions,  and  3)  possible 
injuring  or  weakening  of  lobsters  through  mis- 
handling or  disease  before  the  introductions 
(Ghelardi  and  Shoop,  1968).  In  the  lobster  trans- 
plants, as  in  virtually  all  other  attempts  to  trans- 
plant species,  there  has  been  little  or  no  effort 
to  evaluate  the  impact  the  exotic  would  have  on 
native  species  or  to  control  pathogens  and  other 
potentially  harmful  organisms  associated  with  it. 
Only  the  recent  pilot  introduction  in  British 
Columbia  by  Ghelardi  and  Shoop  (Ghelardi,  1967; 
Ghelardi  and  Shoop,  1972)  considered  potential 
detrimental  effects  and  was  conducted  on  a  truly 
scientific  basis. 

While  it  might  be  argued  that  one  can  never 
determine  what  the  effects  of  an  exotic  intro- 
duction will  be  until  it  takes  place,  we  feel 
that  a  serious  attempt  must  be  made  to  evaluate 
potential  adverse  effects  by  laboratory  studies 
before  even  a  small-scale  pilot  transplant  is 
attempted.  During  the  period  1970-73  we,  and 
others  of  our  group,  have  conducted  a  series  of 
studies  on  the  social  interactions  of  H.  ameri- 
canus with  ecologically  similar  decapod  crusta- 
ceans from  southern  California  waters.  This  paper 
describes  the  results  of  one  of  our  studies  con- 
cerning interactions  between  H.  americanus  and 
P.  interruptus  with  comparative  observations  on 
P.  interruptus  and  the  rock  crab,  Cancer  anten- 
narius.  In  it,  we  have  primarily  considered 
agonistic  interactions.  Other  studies  have  shown 
that  interspecific  aggression  can  be  important 
in  regulating  the  lives  of  sympatric  species 
(see  Aspey,  1971;  also  Myreberg,  1972a). 

METHODS  AND  MATERIALS 

American  lobsters  were  purchased  in  San 
Diego  from  the  Gulf  of  Maine  Lobster  Corpora- 
tion. They  were  quarantined  2  wk  in  a  large 
holding  tank  (0.5  x  1.2  x  2.3  m)  for  effects  of 
gaffkemia  or  other  diseases  before  being  intro- 
duced to  experimental  tanks.  California  spiny 
lobsters  and  rock  crabs  were  trapped  in  shallow 
water  off  the  San  Diego  coast  and  were 
either  introduced  directly  into  experimental 
tanks  or  maintained  for  short  periods  in  holding 
tanks  of  the  same  size  employed  for//,  americanus. 


Holding  tanks  were  supplied  with  fresh  run- 
ning seawater  from  the  Scripps  Institution  sys- 
tem. The  temperature  of  the  water  in  tanks 
varied  throughout  the  year  in  close  correspon- 
dence with  ambient  ocean  temperatures,  from  a 
minimum  of  14°C  in  January  to  a  maximum  of 
23°C  in  August.  The  study  began  in  July  1972 
and  ended  in  April  1973.  Lobsters  and  crabs 
in  holding  tanks  were  fed  frozen  squid,  Loligo 
opalescens,  and  northern  anchovy,  Engraulis 
mordax,  twice  a  week.  No  attempt  was  made  to 
control  the  photoperiod  for  these  individuals  while 
in  the  holding  tanks.  However,  they  were  exposed 
to  the  normal  day-night  cycle  during  this  period 
from  light  entering  through  the  walls,  roof,  and 
building  openings. 

Three  experimental  tanks  were  used,  each  3.04 
m  in  diameter  and  1.22  m  in  height,  with  a 
capacity  of  approximately  9,000  liters.  Each  tank 
had  four  observation  windows  68.5  x  48.0  cm 
positioned  equidistant  around  the  perimeter. 
The  tanks  were  enclosed  in  lightproof  tents  made 
of  black  Mobil  Kordite^  polyethylene  sheeting  of 
6-mil  thickness.  Lobsters  in  the  experimental 
tanks  received  11  h  of  light  daily  from  0400 
to  1500  P.s.t.  (Pacific  standard  time),  supplied 
by  two  75-W  General  Electric  floodlights.  The 
experimental  subjects  were  not  fed  while  in  the 
experimental  tanks  so  as  to  eliminate  the  variable 
of  interactions  for  food. 

Three  experimental  conditions  were  studied. 
These  were:  1)  social  interaction  between  P. 
interruptus  and  H.  americanus  in  the  absence  of 
shelter,  2)  social  interaction  between  P.  inter- 
ruptus and  //.  americanus  with  more  shelters 
than  lobsters,  and  3)  social  interaction  between 
P.  interruptus  andC.  antennarius  without  shelter. 
Seven  shelters  were  provided  for  the  experimental 
condition  involving  interaction  between  P.  inter- 
ruptus and  //.  americanus  with  shelter.  The 
shelters,  which  measured  25  cm  in  width,  38  cm 
in  length,  and  14  cm  in  height,  were  made  by 
cutting  76-cm  sections  of  concrete  conduit  length- 
wise and  then  into  38-cm  lengths. 

In  each  experimental  condition,  five  California 
spiny  lobsters  and  either  one  American  lobster  or 
one  rock  crab  were  employed.  Five  replicates  of 
each  experimental  condition  were  made  using 
naive  animals  for  each  replicate.  The  5:1  ratio 
used  for  the  P.  interruptus  and  //.  americanus 


^Reference  to  trade  names  does  not  imply  endorsement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


1147 


FISHERY  BULLETIN:  VOL  72,  NO.  4 


interactions  was  a  compromise  between  a  repre- 
sentative density  which  might  result  from  a  large 
stocking  of//,  americanus  in  natural  habitats  on 
the  southern  California  coast  and  the  physical 
limitations  of  the  experimental  tanks  which 
prevented  using  more  P.  interruptus.  Both  males 
and  females  of  each  lobster  species  were  used 
for  experiments.  However,  only  male  C.  anten- 
narius  were  used  because  all  females  obtained 
were  carrying  eggs  at  the  time  these  experiments 
were  conducted. 

Interaction  experiments  involving  P.  inter- 
ruptus and  C.  antennarius  were  employed  to 
help  in  the  process  of  assessing  potential  effects 
H.  americanus  might  have  on  P.  interruptus. 
That  is,  we  wanted  to  establish  a  behavioral 
base  line  by  using  a  clawed  decapod  crustacean 
which  is  naturally  sympatric  with  P.  inter- 
ruptus. Thus,  the  5:1  ratio  used  for  the  C. 
antennarius  and  P.  interruptus  interactions 
was  employed  for  comparative  purposes. 

The  P.  interruptus  subjects  used  ranged  in 
weight  from  209  to  911  g,  with  a  mean  of 
436  g.  Homarus  americanus  used  weighed  from 
417  to  635  g,  with  a  mean  of  471  g.  Cancer 
antennarius  used  ranged  in  weight  from  560  to 
840  g,  with  a  mean  of  673  g.  California  spiny 
lobsters  were  assigned  to  groups  by  a  randomiza- 
tion process.  Each  group  usually  consisted  of 
both  sexes  and  individuals  which  were  larger, 
smaller,  and  the  same  size  as  the  single 
American  lobster  tested.  Cancer  antennarius 
used  in  the  experiments  weighed  more  than  most 
of  the  California  spiny  lobster  subjects  with 
which  it  was  tested.  An  attempt  was  made  to 
use  P.  interruptus  that  weighed  between  400  and 
600  g  for  all  experiments  so  that  their  weight 
matched  the  weight  of  the  H.  americanus  avail- 
able to  us.  As  a  result  of  poor  trap  catches, 
however,  we  were  sometimes  forced  to  use  P. 
interruptus  that  were  either  smaller  or  larger 
than  the  H.  americanus  subjects. 

Each  of  the  15  separate  experiments  consisted 
of  three  observation  periods.  These  were  called 
the  precontrol,  experimental,  and  postcontrol 
periods.  For  the  social  interaction  experiments 
involving  P.  interruptus  and  //.  americanus, 
precontrol  observations  were  taken  for  5  days, 
experimental  observations  were  taken  for  10 
days,  and  postcontrol  observations  were  taken 
for  5  days.  For  the  experiments  involving  social 
interactions  between  P.  interruptus  andC.  anten- 


narius, the  precontrol,  experimental,  and  post- 
control  observation  periods  were  all  5  days  in 
duration.  For  the  precontrol  observation  period, 
only  individuals  of  P.  interruptus  were  present 
in  the  experimental  tanks.  Upon  completion 
of  the  precontrol  period,  an  H.  americanus  or 
C  antennarius  was  introduced  into  the  tank. 
Following  the  experimental  observation  period, 
the  H.  americanus  or  C.  antennarius  was  re- 
moved and  the  postcontrol  observations  of  P. 
interruptus  taken. 

For  P.  interruptus  and  H.  americanus  experi- 
ments, three  30-min  observation  periods  were 
conducted  daily  for  each  tank.  These  30-min 
observation  periods  were  taken  between  0800  and 
1000  (4-6  h  after  the  onset  of  the  lights), 
1200  and  1400  (8-10  h  after  the  onset  of  the 
lights),  and  1510  and  1700  h  (10  min-1  h  50 
min  after  the  lights  went  off)  P.s.t.  for  pre- 
control, experimental,  and  postcontrol  periods.  In 
the  experiment  involving  P.  interruptus  and 
C.  antennarius,  only  two  20-min  observation 
periods  were  taken  daily.  One  was  taken  between 
0800  and  1000  and  the  other  between  1510 
and  1700.  The  1200-1400  observation  period  was 
omitted  because  of  the  low  frequency  of  inter- 
actions shown  by  these  species  during  initial 
observations.  Table  1  summarizes  the  experi- 
mental paradigm  used  for  this  study. 

Observations  taken  between  1510  and  1700 
were  made  using  two  100-W  red  lights  with  a 
spectral  distribution  between  550  and  720  nm. 
Most  of  the  red  light  (75%)  fell  within  600- 
650  nm.  Spectral  sensitivity  of  H.  americanus 
ranges  from  400  to  600  nm  with  peak  sensi- 
tivity at  520-525  nm  (Kennedy  and  Bruno,  1961). 
At  present  no  information  exists  on  the  spectral 
sensitivity  of  P.  interruptus,  but  the  assumption 
was  made  that  this  species  also  is  insensitive  to 
light  within  this  spectral  range.  During  the  study, 
we  observed  no  evidence  that  movement  and 
social  behavior  of  either  species  was  inhibited  by 
the  use  of  red  lights. 

TERMINOLOGY 

The  frequency  and  type  of  behavioral  inter- 
actions between  P.  interruptus  and//,  americanus 
or  C.  antennarius  were  recorded  on  a  data  sheet 
which  was  partitioned  into  1-min  intervals.  The 
behavior  of  the  actor  (the  individual  presenting 
the  stimuli  or  initiating  the  interaction)  and  the 
subsequent  response  of  the  reactor  (the  individual 


1148 


KREKORIAN,  SOMMERVILLE,  and  FORD:  LOBSTER  BEHAVIORAL  INTERACTIONS 


Table    1. — Experimental    paradigm   for   social    interaction   study   between  Homarus   americanus,  Panulirus   interruptus,   and 

Cancer  antennarius 


Precontrol 

Experimental 

Postcontrol 

Experimental 
condition 

Number 

of 

days 

Length  of 

observation 

periods 

(min) 

Time  of 
observations 

Number 

of 

days 

Length  of 

observation 

periods 

(min) 

Time  of 
observations 

Number 

of 

days 

Length  of 

observation 

periods 

(min) 

Time  of 
observations 

H.  americanus 

vs. 
P.  interruptus 
No  shelter 

5 

30 

0800-1000 
1200-1400 
1510-1700 

10 

30 

0800-1000 
1200-1400 
1510-1700 

5 

30 

0800-1000 
1200-1400 
1510-1700 

H.  americanus 

vs. 
P.  interruptus 
Shelter 

5 

30 

0800-1000 
1200-1400 
1510-1700 

10 

30 

0800-1000 
1200-1400 
1510-1700 

5 

30 

0800-1000 
1200-1400 
1510-1700 

P.  interruptus 

vs. 

C.  antennarius 

No  shelter 

5 

20 

0800-1000 
1510-1700 

5 

20 

0800-1000 
1510-1700 

5 

20 

0800-1000 
1510-1700 

responding  to  the  stimuli)  were  both  recorded  in 
the  predetermined  categories  described  below.  In 
addition,  the  amount  of  locomotion  displayed  by 
subjects,  their  location  in  the  tank  with  respect 
to  the  wall,  and  the  number  of  individuals  in 
shelters,  when  present,  were  recorded.  The 
behavioral  action  patterns  of  P.  interruptus,  H. 
americanus,  and  C.  antennarius  described 
by  previous  workers  were  employed  in  this  study 
where  possible. 

I.  The  following  categories  were  employed  for 
the  actor:  A)  Approach,  B)  Threat,  C)  Attack, 
and  D)  Social  contact.  These  terms  are 
defined,  in  most  cases,  separately  for  each 
of  the  three  species  considered. 

A)  Approach — Movement  of  the  actor 
directly  toward  a  moving  or  stationary 
heterospecific.  During  approach,  the 
actor  compensates  for  changes  in  the 
direction  of  movement  of  a  moving 
heterospecific  so  that  the  actor  is  always 
moving  directly  toward  the  heterospeci- 
fic. No  implication  of  function  is 
intended  in  our  use  of  the  term 
approach. 

B)  Threat 

1)    Homarus  americanus 

Meral  spread — In  this  study  only 
the  display  described  by  Schrivener 
(1971)  as  meral  spread  was  re- 
corded as  threat.  Schrivener's 
description  of  this  behavior  is  as 
follows:  "During  meral  spread,  the 
lobster  stands  on  its  walking  legs 
with  its  body  raised  from  4  to  5 
cm  off  the  bottom.  The  abdomen  is 


usually  fully  extended,  with  the 
cephalothorax  angled  slightly  up- 
wards from  the  horizontal.  The 
chelae  are  held  about  5  cm  off  the 
bottom  spread  wide  apart  with 
their  long  axes  pointing  directly  at 
the  opponent.  Some  animals  hold 
the  claws  fully  extended,  wide 
apart,  and  as  high  off  the  bottom 
as  possible." 
2)     Cancer  antennarius 

Lateral  Merus  Display — The 
merus  of  the  chelipeds  is  extended 
laterally,  with  the  distal  end  of  the 
meri  raised  and  extended  some- 
what anteriorad.  The  higher  the 
intensity  of  the  display,  the  greater 
is  the  lateral  spreading  of  the 
chelipeds  (Schone,  1968;  Wright, 
1968).  Wright  (1968)  subdivides 
the  Lateral  Merus  Display  into 
three  subtypes  based  on  the 
position  of  the  chelae.  These  are: 
1)  the  High-Intensity  Merus  Dis- 
play in  which  the  chelae  are  un- 
flexed  (maximum  adduction)  with 
the  tips  held  laterally;  2)  the  Mid- 
Intensity  Merus  Display  in  which 
the  chelae  are  half  flexed  so  that 
the  tips  point  forward;  and  3)  the 
Low-Intensity  Merus  Display 
in  which  the  chelae  are  flexed,  with 
their  tips  medial.  All  intensities  of 
the  meral  spread  were  observed, 
but  these  were  simply  recorded  to- 
gether as  threat  in  our  study. 


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FISHERY  BULLETIN:  VOL  72,  NO.  4 


3)    Panulirus  interruptus 

Two  of  the  aggressive  postures 
described  by  Roth  (1972)  were  used 
in  this  study.  These  aggressive  pos- 
tures are  body  raise  and  rear-up. 
We  observed  that  these  are  the 
most  common  and  morphologically 
distinct  aggressive  postures  ex- 
hibited by  P.  interruptus. 

a)  Body  raise — Raising  the  body 
off  the  substrate  by  partial 
extension  of  the  walking  legs. 
This  corresponds  to  Roth's  term 
Rise  Up  (Ri). 

b)  Rear-up — Raising  the  body  off 
the  substrate  by  full  extension 
of  the  third,  fourth,  and  fifth 
walking  legs.  The  anterior  part 
of  the  body  is  raised  much 
higher  than  the  posterior  part 
of  the  body.  This  was  also 
called  Rise  Up  by  Roth  (R2 
and  R3).  However,  we  have 
combined  his  R^  and  R3  into  a 
separate  category,  rear-up, 
because  they  appear  to  be  dif- 
ferent intensities  of  the  same 
behavior  action  pattern,  which 
is  distinct  from  Ri . 

C)     Attack 

1)    Homarus  americanus  and  Cancer 
antennarius 

Four  actions  were  included  under 
attack.  These  were  pinch,  push, 
scissoring,  and  chase. 

a)  Pinch — Rapid  gripping  and  re- 
lease of  any  part  of  a  Cali- 
fornia spiny  lobster's  body 
with  one  or  both  chelipeds. 

b)  Push — Contact  between  the 
chelipeds  and  any  part  of  a 
California  spiny  lobster's  body 
when  the  chelipeds  are  thrust 
forward  while  the  body  remains 
stationary  or  the  chelipeds  are 
extended  or  in  a  meral  spread 
in  a  stationary  position  during 
locomotion. 

c)  Scissoring — As  described  by 
Schrivener  (1971)  for//,  ameri- 
canus, "This  occurs  when  one 
lobster  faces  its  opponent,  with 


the  chelae  in  the  meral  spread 
posture  (spread  wide  apart, 
long  axes  of  the  palms  point- 
ing at  the  adversary).  The 
chelae  are  then  rapidly  brought 
together  in  a  scissoring  motion. 
As  a  result,  they  either  strike 
or  pass  rapidly  in  front  of  the 
other  animal." 
d)  Chase — During  chase  the  actor 
moves  rapidly  toward  a  hetero- 
specific  that  in  turn  is  usually 
moving  rapidly  and  is  ob- 
viously trying  to  remove  itself 
from  the  vicinity  of  the  lobster 
following  it.  Chase  was  re- 
corded only  after  the  actor 
and  reactor  had  been  within  30 
cm  from  one  another.  Frequent- 
ly, chase  precedes  a  push  or 
pinch  and  follows  an  initial 
lunge  by  an  actor  towards  the 
reactor.  During  chase//,  amer- 
icanus usually  displays  meral 
spread. 
2)     Panulirus  interruptus 

Two  actions  were  included  under 
attack.  These  were  physical  con- 
tact and  chase. 

a)  Physical  contact — This  in- 
volves colliding  with  some  part 
of  a  heterospecific's  body;  in 
some  cases  clasping  of  the  op- 
ponent with  the  first  three 
pairs  of  walking  legs  or  a  bite 
may  occur.  This  includes  Roth's 
(1972)  low  intensity  attack 
(Ai),  high  intensity  attack 
(A2),  and  clasp  (CD. 

b)  Chase — Rapid  locomotion  to- 
ward a  reactor  while  it  is 
removing  itself  from  the  vicin- 
ity of  the  lobster  following  it. 

D)  Social  contact — Two  heterospecifics 
were  recorded  as  having  social  con- 
tact when  one  of  the  following  events 
occurred. 

1)  Two  or  more  heterospecifics  came 
within  30  cm  of  one  another  during 
movement  about  the  tank  without 
aggressive  interaction  occurring. 
This     category     was     recorded 


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KREKORIAN,  SOMMERVILLE,  and  FORD:  LOBSTER  BEHAVIORAL  INTERACTIONS 


whether  one  or  both  animals  were 
moving,  and  in  some  cases  direct 
physical  contact  was  made. 
2)  Two  or  more  heterospecifics  were 
touching  or  within  30  cm  of  one 
another,  were  not  moving,  and 
exhibited  no  aggressive  interaction. 
Social  contact  during  movement 
was  distinguished  from  approach 
by  the  absence  of  direct  movement 
of  heterospecifics  toward  one 
another.  That  is,  the  animals  were 
not  on  a  collision  course. 

II.  The  following  categories  were  employed  for 
the  reactor:  A)  No  response,  B)  Walk  away, 
C)  Abdomen  flex,  D)  Threat,  and  E)  Attack. 

A)  No  response — No  change  in  the  overt 
behavior  of  the  reactor. 

B)  Walk  away — Movement  away  from  an 
approaching,  threatening,  or  attacking 
heterospecific,  using  the  walking  legs. 

C)  Abdomen  flex — Movement  away  from 
an  approaching,  threatening,  or  attack- 
ing heterospecific,  using  rapid  flexion 
of  the  abdomen. 

D)  Threat— The  description(s)  of  threat 
used  for  H.  americanus,  P.  interrup- 
tus,  and  C.  antennarius  provided  above 
for  actors  (I-B)  was  also  used  for  the 
reactor. 

E)  Attack — The  description(s)  of  attack 
used  for//,  americanus,  P.  interruptus, 
and  C.  antennarius  provided  above  for 
actors  (I-C)  was  also  used  here  for  the 
reactor. 

III.  Additional  categories  used  on  the  data  sheet 
and  their  definitions  were  as  follows: 

A)  Roaming — Slow  or  moderate  walking 
about  the  tank.  During  roaming,  direct 
interaction  between  heterospecifics  or 
conspecifics  does  not  occur.  For  P. 
interruptus,  roaming  by  an  individual 
was  recorded  only  if  it  occurred  for  31s 
or  more  during  a  1-min  interval.  For 
H.  americanus  and  C  antennarius, 
the  amount  of  time  they  were  observed 
roaming  during  each  1-min  interval 
was  recorded. 

B)  Wall — Like  many  decapods,  P.  inter- 
ruptus exhibits  thigmotactic  behavior. 
When  shelter  is  absent  individuals  are 


found  with  their  bodies  in  contact  with 
a  solid  object.  In  our  no  shelter  con- 
dition, the  tank  wall  was  the  only  solid 
object  present.  A  lobster  that  had  some 
part  of  its  body,  excluding  the  antennae, 
within  30  cm  of  the  side  of  the  tank  for 
31  s  or  more  of  each  1-min  interval 
was  recorded  as  wall.  The  location  of  a 
lobster  within  the  tank  that  was  greater 
than  30  cm  from  the  side  of  the  tank 
for  31  s  or  more  of  each  1-min  interval 
was  recorded  as  no  wall. 
C)  Group — A  congregation  of  two  or  more 
subjects,  each  within  30  cm  of  one 
another.  Thus,  in  a  group  of  five 
P.  interruptus,  a  maximum  distance  of 
120  cm  would  separate  lobsters  at 
opposite  ends  of  a  group. 

RESULTS  AND  DISCUSSION 
Agonistic  Behavior 

The  frequency  and  outcome  of  agonistic  behav- 
ioral interactions  between  //.  americanus  and 
P.  interruptus  for  conditions  involving  shelter 
and  no  shelter  are  shown  in  Table  2.  Similar 
data  also  are  presented  in  this  table  for  interac- 
tions between  P.  interruptus  and  C.  antennarius. 

Homarus  vs.  Panulirus  with  No  Shelter 

There  were  a  total  of  2,515 //omarws-initiated 
behavioral  interactions  by  actors  for  the  five  repli- 
cate H.  americanus-P.  interruptus  no  shelter 
experiments.  Twenty  percent  of  the  behavioral 
interactions  were  classed  as  social  contact,  40% 
as  Homarus  approach,  24%  as  Homarus  threat, 
and  15%  as  Homarus  attack  (Table  2).  Sixty- 
eight  percent  (1,700)  of  the  //omarus-initiated 
behavioral  interactions  occurred  during  the  1510- 
1700  h  observation  period  (lights  off). 

There  were  a  total  of  1,683  responses  by 
reactors  to  //omarus-initiated  interactions. 
Thirty  seven  percent  of  these  were  classed  as  no 
response,  49%  Panulirus  walk  away,  and  14% 
Panulirus  abdomen  flex  (Table  2).  Thus,  P. 
interruptus  was  displaced  a  total  of  63%  of  the 
time  when  //.  americanus  initiated  a  behavioral 
interaction.  Panulirus  interruptus  was  never 
observed  to  threaten  or  attack  H.  americanus  in 
//omarws-initiated  behavioral  interactions. 

A  total  of  227  Panulirus-ivaiiaied  behavioral 
interactions  were  recorded  in  the  five  replicate 


1151 


FISHERY  BULLETIN:  VOL  72,  NO.  4 

Table  2. — The  total  number  of  behavioral  interactions  between  Homarus  americanus  and  PanuUrus  interruptus  during  10-day 
experimental  periods  for  the  shelter  (n  =  5  groups)  and  no  shelter  («  =  5  groups)  conditions,  and  between  P.  interruptus  and  Cancer 
antennarius  during  5-day  periods  for  a  no  shelter  condition  (n  =  5  groups).  Social  contact  (SC)  and  no  response  (NR)  for 
Homarus-initiated  interactions  include  hoth  Homarus  and  PanuUrus  actions  where  only  social  contact  occurred.  HA  =  Homarus 
approach;  HT  =  Homarus  threat;  HAT  =  Homarus  attack;  PWA  =  PanuUrus  walk  away;  PAF  =  PanuUrus  abdomen  flex;  PA  = 
PanuUrus  approach;  PT  =  PanuUrus  threat;  PAT  =  PanuUrus  attack;  HWA  =  Homarus  walk  away;  HAF  =  Homarus  abdomen  flex; 
CA  =  Cancer  approach;  CT  =  Cancer  threat;  CAT  =  Cancer  attack;  CWA  =  Cancer  walk  away. 


P.s.t. 


Experimental 
condition 


SC 


Homarus-initiated  interactions 


Actor 


HA 


HT         HAT 


NR 


Reactor 


PWA 


PAF 


0800 
1200 
1510 
Totals 


No  shelter 
Shelter 

No  shelter 
Shelter 

No  shelter 
Shelter 

No  shelter 
Percent 

Shelter 
Percent 


177 

172 

106 

56 

7 

6 

1 

2 

97 

97 

63 

47 

6 

2 

1 

1 

238 

748 

438 

276 

2  = 

--  1,700 

(68%) 

24 

104 

74 

41 

I  = 

=     243 

(90%) 

512 

1,017 

607 

379 

7.  - 

=  2,515 

20 

40 

24 

15 

37 

112 

76 

44 

2  = 

=     269 

14 

42 

28 

16 

207 

156 

24 

8 

5 

1 

128 

92 

43 

7 

3 

1 

299 

572 

162 

S  =  1,033 

(61%) 

53 

72 

27 

2  =     152 

(86%) 

634 

820 

229 

£  =  1 .683 

37 

49 

14 

68 

80 

29 

S=      177 

38 

45 

16 

P.s.t. 


Experimental 
condition 


Panu/(>us-initiated  interactions 


PA 


Actor 


PT 


PAT 


NR 


HWA 


Reactor 


HAF 


HT 


HAT 


0800 


1200 


1510 


Totals 


No  shelter 
Shelter 

No  shelter 
Shelter 

No  shelter 
Shelter 

No  shelter 
Percent 

Shelter 
Percent 


36 

0 

3 

0 

83. 

1 

3 

0 

107 

0 

22 

0 

226 

1 

100 

0 

28 

0 

100 

0 

3 

1 

0 

29 

16 

0 

0 

0 

3 

0 

7 

3 

1 

65 

26 

1 

0 

0 

2 

1 

6 

41 

4 

54 

21 

0 

2 

0 

20 

5 

16 

45 

5 

148 

63 

6 

16 

2 

53 

23 

1 

2 

0 

25 

6 

3 

6 

0 

74 

18 

Cancer-Panulirus  interactions 


Actor 


Reactor 


P.s.t. 

Experimental 
condition 

SC 

CA 

PA 

CT 

PT 

CA 

0800 

130 

4 

16 

2 

0 

5 

1510 

37 

8 

20 

2 

3 

2 

Total 

No  shelter 
Percent 

167 
73 

12 

5 

36 
16 

4 
2 

3 
1 

7 
3 

NR        CWA       PWA       PAF         CT  PT         CAT 


1=  229 


145 

0 

6 

0 

2 

0 

2 

49 

0 

15 

0 

9 

0 

3 

194 

0 

21 

0 

11 

0 

5 

84 

0 

9 

0 

5 

0 

2 

S  =  231 


experiments.  Of  these,  226  were  PanuUrus 
approach  while  only  1  was  PanuUrus  threat 
(Table  2).  There  was  a  total  of  277  responses 
by  the  reactors  (Homarus).  Sixteen  (6%)  of  these 
were  classed  as  no  response,  45  (16%)  as  Homarus 
walk  away,  5  (2%)  as  Homarus  abdomen  flex, 
148  (53%)  as  Homarus  threat,  and  63  (23%)  as 
Homarus  attack  (Table  2).  Thus,  76%  of  H. 


americanus  responses  to  P.  interruptus  approach 
were  threat  and  attack.  These  threats  and  attacks 
by  H.  americanus  subsequently  resulted  in  dis- 
placement of  P.  interruptus  from  the  immediate 
area. 

The  number  of  behavioral  actions  by  both  the 
actor  (primarily //omarws)  and  reactor  (primarily 
PanuUrus )  decreased  with  time,  as  shown  in  Table 


1152 


KREKORIAN,  SOMMERVILLE,  and  FORD:  LOBSTER  BEHAVIORAL  INTERACTIONS 


3.  There  was  a  significant  reduction  in  Homarus- 
initiated  actions  with  time  as  indicated  by  the 
resuhs  of  a  Spearman  Rank  Correlation  Analysis 
(r,  =  -0.66,  P  <  0.05;  Siegel,  1956).  Social 
contact  was  excluded  from  the  statistical  analysis 
of  actor  actions  because  it  included  and  did 
not  differentiate  H.  americanus  and  P.  inter- 
rap^us- initiated  interactions.  Most  social  contact, 
however,  was  initiated  hy  H.  americanus.  There 
also  was  a  significant  decrease  in  behavioral 
actions  with  time  for  P.  interruptus  responses 
{r,  =  -0.82,  P  <  0.01).  Only  Panulirus  walk 
away  and  abdomen  flex  were  considered.  No 
response  was  excluded  from  the  statistical  analy- 
sis of  reactor  actions  because  it  included  both 
H.  americanus  and  P.  interruptus  responses. 

In  the  absence  of  shelter,  some  H.  americanus 
excavated  a  depression  in  the  sand  where  they 
remained  when  they  were  not  roaming.  When  a 
P.  interruptus  approached  an  H.  americanus  in 
its  sand  depression,  the  likelihood  of  attack 
increased,  and  the  attacks  appeared  to  last  longer 
and  involve  more  pinching. 

Homarus  vs.  Panulirus  with  Shelter 

The  addition  of  seven  shelters  reduced  the 
number  of  //omart/s-initiated  interactions  as 
compared  with  the  no  shelter  condition.  A  com- 
parison of  all  Homari/s-initiated  interactions 
(both  actor  and  reactor)  between  the  shelter  and 
no  shelter  conditions  indicated  that  Homarus- 
initiated  interactions  for  the  shelter  condition 
were  significantly  reduced  (P  =  0.01,  Wilcoxon 
matched- pairs  test;  Siegel,  1956).  There  were  a 
total  of  269  behavioral  actions  by  actors  and  177 
by  reactors  (Table  2).  Ninety  percent  (243)  of 


the  behavioral  actions  by  actors  and  86%  (152) 
of  behavioral  actions  by  the  reactors  occurred  in 
the  1510-1700  h  observation  period. 

Fourteen  percent  of  the  //omarus-initiated 
interactions  of  actors  were  classed  as  social  con- 
tact, 42%  as  Homarus  approach,  289c  as  Homarus 
threat,  and  169c  as  Homarus  attack.  The  be- 
havioral actions  of  the  reactors  were  38%  no 
response,  45%  Panulirus  walk  away,  and  16% 
Panulirus  abdomen  flex. 

There  was  a  total  of  28  Pa/iw/i>us-initiated 
behavioral  actions  for  the  five  replicate  experi- 
ments. All  were  classed  as  Panulirus  approach. 
Thirty-four  behavioral  actions  by  H.  americanus 
(reactor)  resulted.  Of  these,  1  was  classed  no 
response,  2  Homarus  walk  away,  25  Homarus 
threat,  and  6  Homarus  attack.  Thus,  92%  of 
these  responses  of  H.  americanus  to  Panulirus 
approach  involved  threat  and  attack. 

Most  of  the  behavioral  interactions  that 
occurred  in  the  Homarus-Panulirus  shelter 
condition  took  place  when  the  lobsters  were  out 
of  their  shelters.  On  some  occasions,  however, 
H.  americanus  attacked  P.  interruptus  while  they 
were  in  shelters.  When  this  occurred  H.  ameri- 
canus entered  the  shelter  through  the  front 
entrance,  the  attack  ensued,  and  P.  interruptus 
fled  through  the  back  entrance  which  was  nearly 
flush  against  the  side  of  the  tank.  The  amount  of 
time  H.  americanus  remained  in  the  shelter  of 
the  displaced  P.  interruptus  varied  greatly.  Some 
H.  americanus  left  the  shelter  within  1  min  and 
either  roamed  or  displaced  another  P.  interruptus 
from  its  shelter.  Others  remained  in  the  shelter 
longer,  and  some  for  the  duration  of  the  observa- 
tion period.  Panulirus  interruptus  that  ap- 
proached//, americanus  in  a  shelter  were  usually 


Table  3. — The  total  number  of  Homarus  americanus -initiated  behavioral  interactions  vnth  Panulirus  interruptus  by  day  for  the  no 
shelter  condition  {n  =  5  groups).  These  totals  include  data  from  morning,  noon,  and  evening  observations.  Social  contact  (SC)  and  no 
response  (NR)  totals  include  both//,  americanus  and  P.  interruptus  actions.  However,  the  great  majority  of  SC  is  Homarus  initiated, 
and  the  great  majority  of  NR  is  derived  from  Panulirus.  HA  =  Homarus  approach;  HT  •=  Homarus  threat;  HAT  =  Homarus  attack; 
PWA  =  Panulirus  walk  away;  PAF  =  Panulirus  abdomen  flex. 


Actor 

Reactor 

Day 

SC 

HA 

HT 

HAT 

Total 

TotaP 

NR 

PWA 

PAF 

Total 

TotaP 

1 

113 

234 

116 

65 

528 

415 

146 

185 

38 

369 

223 

2 

48 

112 

93 

61 

314 

266 

59 

92 

22 

173 

114 

3 

25 

85 

56 

37 

203 

178 

32 

78 

29 

139 

107 

4 

32 

85 

73 

55 

245 

213 

42 

72 

28 

142 

100 

5 

49 

79 

18 

15 

161 

112 

53 

68 

12 

133 

80 

6 

40 

92 

51 

26 

209 

169 

45 

84 

16 

145 

100 

7 

37 

108 

59 

36 

240 

203 

54 

72 

29 

155 

101 

8 

93 

109 

72 

48 

322 

229 

105 

75 

32 

212 

107 

9 

53 

75 

46 

19 

193 

140 

66 

65 

10 

141 

75 

10 

22 

38 

23 

17 

100 

78 

34 

29 

13 

76 

42 

'These 

totals  exclude 

SC 

2These 

totals  exclude 

NR. 

1153 


FISHERY  BULLETIN:  VOL  72,  NO.  4 


quickly  threatened  or  attacked.  However,  this 
event  was  rare. 

When  H.  americanus  pinched  P.  interruptus, 
in  both  the  shelter  and  no  shelter  condition, 
the  pincer  claw  appeared  to  be  the  only  one 
used.  Panulirus  interruptus  that  had  been 
attacked,  and  especially  those  pinched  by  H. 
americanus,  appeared  to  move  away  from  an 
approaching  Hornarus  in  subsequent  encounters 
at  greater  distances  than  they  did  initially  before 
they  had  been  attacked. 

Panulirus  vs.  Cancer  with  No  Shelter 

There  was  little  aggression  shown  in  behavioral 
interactions  between  P.  interruptus  andC.  anten- 
narius,  species  which  commonly  occur  together 
in  nature.  A  total  of  229  behavioral  actions  were 
initiated  by  actors.  Of  these,  73%  (167)  were 
classed  as  social  contact,  5%  (12)  as  Cancer 
approach,  16%  (36)  as  Panulirus  approach,  2%  (4) 
as  Cancer  threat,  1%  (3)  as  Panulirus  threat  and 
3%  (7)  as  Cancer  attack  (Table  2).  There  was  a 
total  of  231  responses  by  the  reactors.  Eighty- 
four  percent  (194)  of  these  were  classed  as  no 
response,  9%  (21)  were  classed  as  Panulirus  walk 
away,  5%  (11)  as  Cancer  threat,  and  2%  (5) 
as  Cancer  attack. 

One  of  us  (Krekorian)  observed  P.  interruptus 
walk  over  C.  antennarius  21  times  with  no 
response  from  the  latter  species.  This  was  never 
observed  between  P.  interruptus  and  H.  ameri- 
canus. In  addition,  on  63  occasions  noninteracting 
groups  were  observed  composed  of  two  or  more 
P.  interruptus  and  C  antennarius  within  30  cm  of 
one  another,  and  on  50  other  occasions  similar 
groups  were  observed  consisting  of  C.  antennarius 
and  one  P.  interruptus.  In  contrast,  we  never 
observed  groups  composed  of//,  americanus  and 
P.  interruptus. 

Discussion  of  Agonistic  Behavior 

These  results  show  that  a  large  percentage  of 
//omaras -initiated  behavioral  interactions  in  the 
shelter  (44%)  and  no  shelter  (39%)  conditions 
involved  aggressive  behavior  (Homarus  threat 
+  Homarus  attack.  Table  2).  The  response  of 
P.  interruptus  to  Homarus  approach  and  aggres- 
sive acts  was  usually  defensive.  In  the  shelter 
condition  P.  interruptus  was  displaced  by  //. 
americanus  61%  of  the  time.  Panulirus  either 
walked  away  or  used  an  abdomen  flex  to  remove 


itself  from  the  area  occupied  by  Homarus.  In 
the  no  shelter  condition  P.  interruptus  was  dis- 
placed 63%  of  the  time.  Although  shelter  reduced 
the  total  number  of  behavioral  interactions 
initiated  by//,  americanus,  the  percentages  for 
aggressive  and  defensive  acts  remained  about  the 
same  (Table  2). 

The  number  of  Pa/i«/irus-initiated  behavioral 
interactions  was  far  less  than  the  number  of 
behavioral  interactions  initiated  by  Homarus. 
However,  the  result  of  the  interactions  which 
followed  were  qualitatively  the  same.  That  is,  P. 
interruptus  was  ultimately  displaced  by  threaten- 
ing and  attacking  //.  americanus  in  the  shelter 
(92%  of  the  time)  and  no  shelter  (76%  of  the 
time)  conditions. 

Grasping  of  one//,  americanus  by  another  was 
rarely  involved  in  the  agonistic  encounters  ob- 
served by  Schrivener  (1971).  In  contrast  to  this, 
we  frequently  observed  H.  americanus  pinching 
P.  interruptus.  Pinching  by  //.  americanus  is 
typical  of  its  predation  behavior.  At  no  time  in 
our  study  did  we  observe  P.  ifiterruptus  attack 
H.  americanus  or  C.  antennarius. 

Studies  by  other  members  of  our  group  have 
shown  that  the  laboratory  activity  rhythms  of  P. 
interruptus  and  //.  americanus  over  a  24-h 
period  are  very  similar,  both  species  exhibiting 
their  highest  levels  of  activity  during  the  first 
4  h  of  darkness  (Van  01st  and  Carlberg,  pers. 
commun.).  This  similarity  in  the  timing  of  activ- 
ity probably  would  intensify  interactions  between 
the  two  species  in  the  field.  Such  interactions 
could  result  in  P.  interruptus  being  displaced 
from  areas  occupied  or  frequented  by  //.  ameri- 
canus, and/or  being  placed  under  considerable 
stress  due  to  possible  competition  for  food,  suit- 
able refuges,  or  other  aspects  of  space  within 
the  habitat.  In  the  laboratory,  //.  americanus 
displaced  P.  interruptus  when  there  was  only  one 
shelter  for  two  lobsters  (Lester,  pers.  commun.) 
and  inhibited  P.  interruptus  from  feeding  when 
food  was  limited  (Needham,  pers.  commun.). 

Assuming  that  the  behavior  displayed  by  the 
two  lobster  species  in  the  laboratory  would  be 
similar  to  that  occurring  in  the  field,  one  would 
expect  considerable  agonistic  interaction  between 
the  two  species  if  they  were  to  occupy  the  same 
habitat.  Although  there  have  been  few  studies 
that  have  thoroughly  compared  the  behavior  of 
animals  in  the  laboratory  with  their  behavior  in 
the  field,  there  are  some  data  that  suggest  the 


1154 


KREKORIAN,  SOMMERVILLE,  and  FORD:  LOBSTER  BEHAVIORAL  INTERACTIONS 


two  are  very  similar,  at  least  where  species  other 
than  primates  are  involved.  For  example,  a  recent 
study  by  Myrberg  ( 1972b),  involving  such  a  direct 
comparison,  showed  that  the  agonistic  and  other 
social  behavior  of  the  bicolor  damselfish,  Eupo- 
macentrus  partitas,  in  the  laboratory  was  very 
similar  to  its  field  behavior  both  qualitatively 
and  quantitatively.  In  another  study,  Hazlett 
and  Bossert  (1965)  similarly  detected  no  quali- 
tative differences  between  the  laboratory  and  field 
behavior  of  some  pagurid  and  diogenid  crabs. 
As  a  result  of  this,  they  chose  to  study  the  behavior 
of  these  crabs  in  the  laboratory  where  conditions 
were  more  uniform  and  controllable. 

There  have  been  surprisingly  few  studies  con- 
cerned with  interspecific  aggression.  This  is 
especially  true  of  many  decapod  crustaceans  for 
which  most  of  the  studies  have  been  rather 
superficial  (Reese,  1964).  It  is  rapidly  becoming 
apparent  from  the  few  studies  that  have  been 
made,  however,  that  interspecific  aggression  may 
be  very  important  in  regulating  the  distribution 
and  abundance  of  many  marine  animal  popula- 
tions. Myrberg  (1972a)  has  found  that  in  the  bi- 
color damselfish  interspecific  chases  accounted  for 
approximately  40%  or  more  of  the  chases  carried 
out  by  territorial  males.  Interspecific  aggression 
was  displayed  by  both  sexes  and  occurred  through- 
out the  year. 

In  laboratory  experiments.  Teal  (1958)  found 
that  the  fiddler  crab,  Uca  pugnax,  reduced  the 
number  of  burrows  dug  by  U.  pugilator  and 
U.  minax.  In  field  studies,  described  by  Aspey 
(1971),  it  was  found  that  where  U.  pugnax  and 
U.  pugilator  existed  in  overlapping  areas,  the 
number  of  burrows  per  square  meter  was  signifi- 
cantly less  than  in  areas  inhabited  only  by  U. 
pugilator.  The  reduction  in  the  number  of  burrows 
dug  by  other  species  of  Uca  when  paired  with 
U.  pugnax  appears  to  be  due  to  the  greater 
frequency  of  agonistic  display  exhibited  by  U. 
pugnax  (Aspey,  1971). 

In  contrast  to  the  results  of  the  Panulirus- 
Homarus  experiments,  very  little  behavioral 
interaction  or  aggression  occurred  between  C. 
antennarius  and  P.  interruptus.  Seventy-three 
percent  of  actor  behavior  involved  nonaggressive 
actions  (social  contact),  and  84%  of  the  reactor 
responses  involved  no  change  in  behavior  (no 
response).  In  addition,  C  antennarius  frequently 
remained  in  close  proximity  to  P.  interruptus, 
and  P.  interruptus  frequently  walked  over  C 
antennarius  when  moving  from  one  area  in  the 


tank  to  another  area.  These  events  were  never 
observed  inHomarus-Panulirus  experiments.  The 
laboratory  observations  on  Panulirus-Cancer 
interactions  agree  with  observations  made  in  the 
field  where  C.  antennarius  is  sometimes  found 
sharing  the  same  refuges  with  P.  interruptus. 

Our  data  also  show  that  even  though  the 
number  of  Homarus-Panulirus  interactions 
decreased  with  time,  there  was  still  a  large 
number  of  behavioral  interactions  between  P. 
interruptus  and  H.  americanus  on  day  10  in  the 
no  shelter  condition.  This  is  most  clearly  seen 
when  the  number  of  interactions  on  day  10  are 
compared  with  the  total  number  of  Cancer- 
Panulirus  interactions.  The  percentage  of  aggres- 
sion shown  by  Homarus  {Homarus  threat  + 
Homarus  attack)  on  day  10  (40% )  was  very  similar 
to  the  total  percentage  of  aggression  (39%). 
Likewise,  the  amount  of  fleeing  (Panulirus  walk 
away  -I-  Panulirus  abdomen  flex)  shown  by 
Panulirus  on  day  10  (55% )  was  similar  to  the 
total  percentage  of  fleeing  (63%).  Thus,  although 
the  absolute  number  of  behavioral  interactions 
decreased  with  time,  the  relative  amounts  of 
Homarus  aggression  and  Panulirus  fleeing 
remained  the  same  as  the  total  percentages. 
These  data  suggest  that,  even  if  the  number  of 
encounters  in  the  field  between  introduced  H. 
americanus  and  P.  interruptus  were  small,  the 
behavioral  actions  by  H.  americanus  would  be 
largely  aggressive  and  the  responses  by  P. 
interruptus  defensive. 

Locomotion 

Homarus  vs.  Panulirus  with  No  Shelter 

The  total  numbers  of  P.  interruptus  observed 
roaming  during  the  three  observation  periods, 
precontrol  1,277,  experimental  1,271,  and  post- 
control  1,171,  were  not  significantly  different 
(Table  4;  P  <  0.05,  Kruskal-Wallis  One-Way 
Analysis  of  Variance  by  Ranks).  A  comparison  of 
the  three  observation  periods  showed  that  the  ma- 
jority of  this  roaming  by  both  P.  interruptus  and 
H.  americanus  occurred  during  the  1510-1700  h 
observation  period.  In  P.  interruptus,  62%  of  the 
roaming  occurred  during  this  period.  In//,  ameri- 
canus, 81%  of  the  roaming  occurred  during  the 
1510-1700  h  observation  period. 

The  relationship  between  the  amount  of  time 
spent  roaming  hyH.  americanus  and  the  number 
of  i/omarus-initiated  behavioral  actions  is  shown 


1155 


FISHERY  BULLETIN:  VOL  72,  NO.  4 


Table  4. — The  total  number  of  Panulirus  interruptus  roaming 
during  precontrol  (Homarus  absent),  experimental  (Homarus 
present),  and  postcontrol  (Homarus  absent)  periods  for  shelter 
and  no  shelter  conditions.  Values  for  the  experimental  period  are 
one-half  the  10-day  total  so  that  the  totals  shown  for  the  three 
periods  are  comparable.  The  maximum  number  of  roaming  lob- 
sters possible  for  each  group,  during  each  period  and  for  each 
condition  (shelter  or  no  shelter)  was  2,250. 


Precontrol 

ExDerimental 

Postcontrol 

Group 

Shelter 

No  shelter 

Shelter 

No  shelter 

Shelter 

No  shelter 

1 

27 

214 

97 

197 

30 

308 

2 

99 

361 

56 

252 

12 

125 

3 

168 

55 

132 

213 

106 

358 

4 

282 

89 

156 

207 

63 

62 

5 

129 

558 

125 

402 

154 

318 

Totals 

705 

1,277 

566 

1,271 

365 

1,171 

in  Table  5.  There  was  a  significant  correlation 
(r^  =  +0.90, P  =  0.05)  between  the  total  roaming 
time  of  each  H.  americanus  {N  =  5)  and  the  num- 
ber of  //omaras-initiated  behavioral  actions. 
That  is,  the  greater  the  total  roaming  time,  the 
greater  was  the  number  of  behavioral  actions. 

Table  5. — Total  i/omarus-initiated  behavioral  actions  and 
roaming  time  for  shelter  and  no  shelter  conditions, 
//omarus -initiated  behavioral  actions  include  social  contact, 
Homarus  approach,  Homarus  threat,  and  Homarus  attack.  So- 
cial contact  includes  somePa?ia/in^s-initiated  actions;  however, 
the  great  majority  of  the  total  is  due  to/Zomart^s-initiated  ac- 
tions. 


the  shelter  condition  was  not  significantly  corre- 
lated with  the  number  of  //omarws-initiated 
behavioral  actions  (Table  5;r,  =  +0.60, P  >0.05). 
The  amount  of  P.  interruptus  roaming  without 
shelter  was  significantly  greater  than  the  amount 
of  roaming  with  shelter  (Table  4;  P  =  0.028, 
Mann-Whitney  U  test).  Similarly,  the  amount  of 
H.  americanus  roaming  without  shelter  was  also 
significantly  greater  than  the  amount  of  roaming 
with  shelter  (Table  5;  P  =  0.004,  Mann-Whitney 
U  test). 

Panulirus  vs.  Cancer  with  No  Shelter 

The  number  of  P.  interruptus  roaming  during 
the  three  observation  periods  was:  precontrol 
532,  experimental  534,  and  postcontrol  549 
(Table  6).  There  were  no  significant  differences  in 
the  amount  of  roaming  during  the  three  observa- 
tion periods  (P  >  0.05,  Kruskal-Wallis  One-Way 
Analysis  of  Variance  by  Ranks). 

Table  6. — The  total  number  of  Panulirus  interruptus  roaming 
and  within  30  cm  of  the  wall  during  the  precontrol  (Cancer 
absent),  experimental  (Cancer  present),  and  postcontrol  (Cancer 
absent)  periods  for  the  Panulirus  vs.  Cancer  no  shelter  condition. 
The  maximum  number  of  roaming  lobsters  for  each  group  during 
each  period  was  1,000.  The  maximum  number  of  wall  +  no  wall 
positions  for  each  group  during  each  period  was  also  1,000. 


I 


Precontrol 


Experimental 


Postcontrol 


Shelter 

No  shelte 

r 

Group 

Wall 

Roaming 

Wall 

Roaming 

Wall 

Roaming 

Size 

Roaming 

Behavioral 

Size 

Roaming 
(s) 

Behavioral 

Group 

Sex 

(g) 

(s) 

actions 

Sex 

(g) 

actions 

1 
2 

967 
873 

11 
168 

956 
828 

44 
169 

997 
748 

20 

196 

1 

6 

419 

6,435 

72 

2 

480 

15,665 

442 

3 

925 

127 

952 

112 

901 

104 

2 

2 

469 

2,785 

84 

2 

635 

33,590 

541 

4 

922 

160 

913 

118 

909 

76 

3 

S 

457 

1.650 

55 

-^ 

467 

20,005 

514 

5 

953 

66 

865 

91 

810 

153 

4 

S 

471 

1,735 

26 

r^ 

457 

23,125 

725 

5 

5 

430 

2,025 

32 

2 

417 

9,435 

293 

Totals 

4,640 

532 

4,514 

534 

4,365 

549 

Homarus  vs.  Panulirus  with  Sheher 


Distribution  of  Panulirus 


The  numbers  of  P.  interruptus  roaming  during 
the  three  observation  periods  were:  precontrol 
705,  experimental  566,  and  postcontrol  365  (Table 
4).  The  differences  between  the  three  test  periods 
were  not  significant  (P  >  0.05,  Kruskal-Wallis 
One- Way  Analysis  of  Variance  by  Ranks). 

The  majority  of  roaming  that  occurred  in  both 
P.  interruptus  and  H.  americanus  took  place 
during  the  1510-1700  h  observation  period  as  in 
the  no  shelter  condition.  Seventy-seven  percent 
of  P.  interruptus  roaming  and  78%  of  H.  ameri- 
canus roaming  occurred  during  this  period.  The 
amount  of  roaming  done  by  H.  americanus  in 


Homarus  vs.  Panulirus  with  No  Sheher 

The  displacement  effect  H.  americanus  had  on 
P.  interruptus  is  clearly  shown  in  Table  7.  During 
the  precontrol  observation  period  (Homarus 
absent)  P.  interruptus  was  most  frequently  found 
within  30  cm  of  the  wall.  In  all  five  replicate 
experiments  the  subjects  spent  the  majority  of 
their  time  near  the  wall.  Group  5  was  observed 
within  30  cm  of  the  wall  three  times  more  fre- 
quently than  it  was  observed  away  from  the  wall. 
The  other  groups  exhibited  even  greater  wall — 
no  wall  differences.  For  example.  Group  3  was 


1156 


KREKORIAN,  SOMMERVILLE,  and  FORD:  LOBSTER  BEHAVIORAL  INTERACTIONS 


observed  within  30  cm  of  the  wall  13  times  more 
frequently  than  it  was  observed  away  from  the 
wall  (Table  7). 

Table  7, — The  total  number  ofPanulirus  interruptus  within  30 
cm  of  the  wall  during  the  precontrol  (Homarus  absent),  experi- 
mental (Homarus  present),  and  postcontrol  (Homarus  absent) 
periods  for  the  no  shelter  condition.  The  maximum  number  of 
positions  (wall  +  no  wall)  for  each  group  during  each  period  was 
2,250.  Values  for  the  experimental  period  are  one-half  the 
10-day  total  so  that  the  totals  shown  for  the  three  periods  are 
comparable. 


control  observation  periods  for  the  number  of 
P.  interruptus  observed  in  shelters  (P  >  0.05, 
Kruskal-Wallis  One-Way  Analysis  of  Variance  by 
Ranks). 

Table  8, — The  total  number  ofPanulirus  interruptus  in  shelters 
or  within  30  cm  of  the  wall  during  the  precontrol  (Homarus 
absent),  experimental  (Homarus  present)  and  postcontrol 
(Homarus  absent)  periods  for  the  shelter  condition.  The  max- 
imum number  of  positions  (shelter  +  wall  -i-  no  wall)  for  each 
group  during  each  period  was  2,250.  Values  for  the  experimental 
period  are  one-half  the  10-day  total  so  that  the  totals  shown  for 


Precontrol 

Experimental 
Wall        No  wall 

Postcontrol 
Wall        No  wall 

the  three  periods 

are  comparable. 

Group 

Wall 

No  wall 

Group 

Precontrol 

Experi 

mental 

Postcontrol 

1 
2 
3 
4 
5 

1,998 
1,967 
2,094 
2,011 
1,684 

252 
283 

156 
239 
566 

360 
500 
723 
964 
1,496 

1,890 
1,750 
1,527 
1,286 
754 

1,959 
713 
1,592 
2,162 
1,432 

291 

1,537 

658 

88 

818 

Shelter 

Wall 

Shelter 

Wall 

Shelter        Wall 

1 
2 
3 
4 
5 

2,217 
2,076 
1,372 
1,639 
1,862 

23 
110 
694 
490 
356 

2,036 
1,635 
1,449 
1,714 
1,893 

166 
434 
643 
427 
285 

2,163             86 
2,160             66 
1,982           255 

1,780           298 
1 ,966           252 

During  the  experimental  observation  period 
(Homarus  present)  P.  interruptus  was  usually 
found  in  the  center  of  the  tank  (no  wall). 
Four  of  the  five  groups  were  observed  more  fre- 
quently in  the  center  of  the  tank  than  within  30 
cm  from  the  wall.  Only  Group  5  was  observed 
near  the  wall  more  frequently  than  in  the 
center.  However,  Group  5  spent  less  time  near  the 
wall  during  the  experimental  period  than  in  the 
precontrol  period. 

During  the  postcontrol  period,  four  out  of  five 
groups  were  observed  within  30  cm  of  the  wall 
more  frequently  than  in  the  center  (Table  7). 
Group  2  spent  approximately  twice  as  much  time 
in  the  center  than  within  30  cm  of  the  wall. 

The  wall-no  wall  distribution  of  P.  interruptus 
during  the  three  observation  periods  was  signifi- 
cantly different  (P  =  0.009,  Kruskal-Wallis 
One- Way  Analysis  of  Variance  by  Ranks).  The 
sums  of  ranks  for  the  three  observation  periods 
were:  precontrol  59,  experimental  19,  and  post- 
control  42.  These  sums  of  ranks  indicate  that  the 
differences  are  between  the  experimental  and 
control  periods.  There  were  no  significant  dif- 
ferences between  the  precontrol  and  postcontrol 
periods  (P  >  0.05,  Mann-Whitney  U  test;  Siegel, 
1956). 

Homarus  vs.  Ponulirus  with  Shelter 

In  the  shelter  condition  individuals  of  all  five 
groups  spent  most  of  their  time  in  the  shelters 
(Table  8).  There  were  no  significant  differences 
between  the  precontrol,  experimental,  and  post- 


The  wall-no  wall  distribution  of  P.  interruptus 
for  the  three  observation  periods  also  was  not 
significantly  different  (Table  8;  P  >  0.05,  Kru- 
skal-Wallis One-Way  Analysis  of  Variance 
by  Ranks).  The  greatest  number  of  P.  inter- 
ruptus found  outside  the  shelters  (wall  and  no 
wall  condition)  occurred  during  the  1510-1700 
h  observation  period. 

Fanulirus  vs.  Cancer  with  No  Shelter 

During  the  precontrol,  experimental,  and  post- 
control  periods,  individuals  of  all  five  groups  of 
P.  interruptus  were  observed  within  30  cm  of  the 
wall  much  more  frequently  than  in  positions  30 
cm  away  from  the  wall  (Table  6).  The  groups 
were  observed  near  the  wall  from  approximately 
3  (Group  2  postcontrol)  to  332  (Group  1,  post- 
control)  times  more  frequently  than  away  from 
the  wall.  Group  1  spent  nearly  all  its  time  near 
the  wall  during  the  postcontrol  period.  There 
were  no  significant  differences  in  the  number  of 
lobsters  found  near  the  wall  for  the  three  periods 
(P  >  0.05,  Kruskal-Wallis  One-Way  Analysis  of 
Variance  by  Ranks). 

Discussion  of  Lobster 
Distribution  and  Locomotion 

The  effect  of  the  presence  of  H.  americanus 
on  the  distribution  of  P.  interruptus  in  a  tank 
without  shelter  is  quite  evident.  Homarus  ameri- 
canus displaced  P.  interruptus  from  its  preferred 


1157 


FISHERY  BULLETIN:  VOL  72,  NO.  4 


areas  (areas  within  30  cm  of  the  wall).  There 
was  a  reversal  of  the  precontrol  wall  position  of 
four  out  of  five  P.  interruptus  groups  during  the 
experimental  period  (Table  7).  When  H.  ameri- 
canus  was  removed  for  the  postcontrol  period, 
three  of  the  four  groups  which  had  reversed 
their  precontrol  position  during  the  experimental 
period  moved  back  to  the  wall  position.  Group 
2  remained  in  the  no  wall  position  during  the 
postcontrol.  The  exact  reason  for  this  is  unknown, 
but  perhaps  this  group's  encounters  with  H. 
americanus  were  somehow  more  intense  and  thus 
the  enounters  had  a  more  lasting  effect  on  the 
behavior  of  Group  2.  The  individual  used  in  this 
group  was  by  far  the  most  active  H.  ameri- 
canus tested  for  both  the  shelter  and  no  shelter 
condition  and  initiated  the  second  highest  number 
of  behavioral  actions  (Table  5). 

Group  5  remained  in  the  wall  position  more 
than  the  no  wall  position  during  all  three  test 
periods.  Thus,  the  H.  americanus  introduced  to 
this  group  had  little  effect  on  its  distribution 
within  the  tank.  The  reason  for  this  is  probably 
the  low  level  of  activity  and  aggression  shown 
by  this  individual.  It  showed  the  least  amount  of 
roaming  (approximately  one-half  the  value  shown 
by  the  next  least  active  individual)  and  the  lowest 
number  of  behavioral  actions  of  any  lobster  in 
the  no  shelter  condition.  It  directed  only  16 
attacks  at  P.  interruptus,  less  than  one-half  of 
those  shown  by  the  next  least  aggressive  H. 
americanus. 

In  contrast  to  the  above,  C.  antennarius  had 
no  effect  on  the  distribution  of  P.  interruptus  in 
the  absence  of  shelter.  All  five  groups  of  P. 
interruptus  spent  nearly  all  their  time  near  the 
wall  during  each  of  the  three  test  periods 
(Table  6).  That  is,  P.  interruptus  groups  were 
never  observed  spending  more  time  in  the 
no  wall  position  than  in  the  wall  position  when 
paired  with  C.  antennarius. 

Douglis  (1946)  found  that  when//,  afnericanus 
was  present  in  a  large  aquarium  tank  with  one  or 
more  blue  crab,  Callinectes  sapidus,  spider  crab, 
Libinia  emarginata,  or  hermit  crab,  Pagurus 
polycarus,  "it  tended  by  pushing  and  fighting  to 
keep  the  crabs  on  the  opposite  side  of  the  tank 
from  itself."  Thus,  although  details  were  not 
given,  it  appears  that  H.  americanus  displaced 
crabs  that,  by  virtue  of  their  claws,  would 
seem  to  be  much  better  prepared  to  cope  with 
H.  americanus  than  is  P.  interruptus. 


The  presence  of  more  shelter  than  was  neces- 
sary for  the  number  of  lobsters  in  a  tank  sub- 
stantially decreased  the  number  of  P.  interrup- 
tus displaced  from  the  wall  position.  This  was 
primarily  due  to  the  fact  that  when  shelter  was 
present,  all  lobsters  spent  the  majority  of  their 
time  in  the  shelter.  This  interpretation  is  sup- 
ported by  comparing  data  on  the  roaming  time 
for  the  shelter  and  no  shelter  conditions.  The 
presence  of  shelter  significantly  reduced  the 
amount  of  roaming  in  both  P.  interruptus  and 
H.  americanus. 

The  greater  frequency  of  agonistic  interactions 
observed  between//,  americanus  and  P.  interrup- 
tus during  the  1510-1700  h  observation  period, 
as  compared  with  the  0800-1000  and  1200-1400  h 
observation  periods,  was  also  no  doubt  due  to 
the  higher  level  of  locomotion  during  this  period. 

A  great  amount  of  variability  in  the  activity 
and  aggression  of  individual  H.  americanus  was 
also  observed  in  our  study.  Some  individuals 
were  very  active  and  aggressive,  while  others 
were  neither.  In  our  study  these  variables  were 
not  related  to  the  sex  or  size  of//,  americanus. 
In  the  shelter  condition,  a  female  exhibited  the 
greatest  number  of  behavioral  actions,  while  in 
the  no  shelter  condition,  it  was  a  male.  Of  the 
10  H.  americanus  tested,  these  lobsters  ranked 
fourth  and  seventh  in  size  (Table  5). 

CONCLUSIONS 

Although  we  cannot  predict  with  certainty  the 
effect  a  large  introduced  population  of//,  ameri- 
canus would  have  on  P.  interruptus  and  other 
decapod  crustaceans  native  to  southern  Cali- 
fornia, our  data  suggest  that  an  adverse  outcome 
from  such  an  introduction  could  occur.  The  types 
of  behavioral  interactions  we  observed  in  the 
laboratory  between  H.  americanus  and  P.  inter- 
ruptus would  most  likely  also  occur  in  the  field. 
This  conclusion  is  strengthened  by  the  studies 
and  observations  of  other  workers  who  have  com- 
pared and  found  close  agreement  between  the 
laboratory  and  field  behavior.  Our  data  show  that 
a  large  percentage  of  the  behavioral  actions  of 
H.  ainericanus  toward  P.  interruptus  probably 
would  involve  aggressive  actions.  Assuming  that 
individuals  of  these  two  species  came  in  con- 
tact with  one  another  in  nature,  these  aggres- 
sive actions  could  have  direct  or  indirect  effects 
on  the  distribution  and  abundance  of  P.  inter- 
ruptus. Thus,  our  evidence  suggests  that  it  would 


1158 


KREKORIAN,  SOMMERVILLE.  and  FORD:  LOBSTER  BEHA\aORAL  INTERACTIONS 


be    inadvisable    to    introduce    H. 
into  southern  California  waters. 


americanus 


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SCHONE,  H. 

1968.     Agonistic  and  sexual  display  in  aquatic  and  semi- 
terrestrial  brachyuran  crabs.  Am.  Zool.  8:641-654. 
Scrivener,  J.  C.  E. 

1971.  Agonistic  behavior  of  the  American  lobster 
Homarus  americanus  (Milne-Edwards).  Fish.  Res.  Board 
Can.,  Tech.  Rep.  235,  128  p. 

Siegel,  S. 

1956.     Nonparametric  statistics  for  the  behavioral  sciences. 
McGraw-Hill,  N.Y.,  312  p. 
Teal,  J.  M. 

1958.     Distribution  of  fiddler  crabs  in  Georgia  salt  marshes. 
Ecology  39:185-193. 
Wright,  H.  O. 

1968.  Visual  displays  in  brachyuran  crabs:  Field  and 
laboratory  studies.     Am.  Zool.  8:655-665. 


1159 


MERCENARIA  MERCENARIA  (MOLLUSCA:  BIVALVIA): 
TEMPERATURE-TIME  RELATIONSHIPS  FOR  SURVIVAL 

OF  EMBRYOS  AND  LARVAE^ 

V.  S.  Kennedy,^  W.  H.  Roosenburg,^  M.  Castagna,'*  and  J.  A.  Mihursky^' 

ABSTRACT 

To  estimate  the  effects  of  entrainment  of  Mercenaria  mercenaria  embryos  and  larvae  in  the  cooling- 
water  systems  of  steam-electric  power  plants,  we  used  a  thermal  gradient  apparatus.  Cleavage 
stages,  trochophore  larvae  and  straight-hinge  veliger  larvae  were  subjected  to  11  different 
temperatures  for  8  different  time  periods.  There  was  a  direct  relationship  of  mortality  with  tempera- 
ture increase  and,  at  higher  temperatures,  with  increase  in  time  exposure.  As  the  clams  aged, 
temperature  tolerance  increased,  with  cleavage  stages  most  sensitive  to  higher  temperature  and 
straight-hinge  larvae  least  sensitive.  Multiple  regression  analyses  of  percentage  mortality  on 
temperature  and  time  produced  estimating  equations  that  allow  prediction  of  percentage 
mortality  under  different  conditions  of  temperature  and  time  exposure.  Entrainment  of  M .  mercenaria 
embryos  and  larvae  in  cooling  systems  of  power  plants  should  be  as  short  as  possible  if  mortality 
is  to  be  held  to  a  minimum. 


Passage  of  plankton  through  the  coohng  system 
of  steam-electric  power  plants  is  a  matter  of 
concern  (Coutant,  1970).  Mortality  caused  by  such 
entrainment  (e.g.  Marcy,  1971)  might  lead  to  loss 
of  species  from  the  vicinity  of  a  power  plant,  with 
various  ecological  and  economic  consequences.  It 
is  estimated  that  increased  demand  for  cooling 
water  may  necessitate  the  location  of  power  plants 
in  estuarine  and  marine  environments  (Tarzwell, 
1972).  Thermal  tolerances  of  planktonic  organ- 
isms in  these  environments  must  be  determined  to 
allow  estimation  of  lengths  of  entrainment  and 
increases  in  temperature  that  are  least  harmful 
to  entrained  organisms. 

The  hard  clam,  Mercenaria  mercenaria  (L.), 
is  an  abundant  and  commercially  important 
bivalve  found  in  shallow  inshore  waters  of  the  east 
coast  of  North  America.  It  is  easily  spawned  in 
the  laboratory  and  has  been  the  subject  of  nu- 
merous investigations  on  the  influence  of  various 
factors  on  its  larval  biology  (see  Loosanoff  and 
Davis,  1963;  Calabrese  and  Davis,  1970  for  appro- 


'Contribution  No.  565  of  the  Natural  Resources  Institute, 
University  of  Maryland  and  Contribution  No.  552  of  the  Vir- 
ginia Institute  of  Marine  Science. 

^Natural  Resources  Institute,  University  of  Maryland,  Ches- 
apeake Biological  Laboratory,  Solomons,  Md.;  present  address: 
Fisheries  Research  Board  of  Canada,  Biological  Station,  St. 
John's,  Newf ,  Can. 

^Natural  Resources  Institute,  University  of  Maryland,  Chesa- 
peake Biological  Laboratory,  Solomons,  MD  20688. 

''Virginia  Institute  of  Marine  Science,  Eastern  Shore  Labora- 
tory, Wachapreague,  VA  23480. 


priate  references).  We  used  an  aluminum  thermal 
gradient  apparatus  (Thomas,  Scotten,  and  Brad- 
shaw,  1963)  to  determine  thermal  tolerances  of 
hard  clam  embryos  and  larvae  at  different  com- 
binations of  temperature  and  time  exposure.  This 
simulated  exposure  of  these  organisms  to  heat 
for  varying  time  periods  in  power  plant  cooling 
systems.  The  research  was  undertaken  in  the 
summer  of  1972  and  spring  of  1973  at  the  Eastern 
Shore  Laboratory,  Virginia  Institute  of  Marine 
Science,  Wachapreague,  Va.  Similar  experiments 
have  been  made  on  embryos  and  larvae  of  the 
coot  clam,  Mulinia  lateralis  (Say)  (Kennedy  et 
al.,  1974).  Reference  should  be  made  to  that  paper 
for  fuller  details  of  experimental  apparatus  and 
techniques. 

MATERIALS  AND  METHODS 

Mercenaria  mercenaria  were  stimulated  to 
spawn  by  fluctuating  water  temperatures  (Loo- 
sanoff and  Davis,  1963)  over  the  range  of  22°  to 
30°C.  Gametes  from  3  to  32  females  and  2  to  30 
males  were  pooled  in  each  experiment  to  provide 
genetic  diversity  (Calabrese  and  Davis,  1970).  We 
used  three  developmental  stages:  early  cleavage 
stages  (2  h  old);  trochophore  larvae  (10-11  h); 
straight-hinge  veliger  larvae  (32-50  h). 

Wild  stock  collected  as  needed  in  the  summer 
near  Wachapreague  provided  the  gametes.  After 
the  experiments  ended  in  1972,  the  preservative 


Manuscript  accepted  February  1974. 
FISHERY  BULLETIN:  VoL  72,  No.  4,  1974. 

1160 


KENNEDY  ET  .-XL.:  TEMPER.ATURE-TIME  REL.^TIONSHIPS 


Table  1. — Percentage  mortality  of  cleavage  stages  of  Mercenaria  mercenaria  under  different  temj>erature-time  combinations. 
Values  in  parentheses  are  temperatures  corrected  for  the  influence  of  injection  water. 


Tem 

perature 

=C 

Time 

(min) 

17.5 

20.2 

22.7 

25  1 

27.6 

30.0 

32,5 

34.9 

37.4 

39.7 

42.4 

1 

0 

39 

14 

12 

12 

35 

0 

0 

3 

26 

85 

(18.8) 

(21.5) 

(23.3) 

(31.6) 

(34.0) 

(35.8) 

(37.7) 

(39.4) 

5 

26 

0 

24 

11 

21 

0 

0 

12 

64 

99 

100 

(18.4) 

(21.1) 

(22.7) 

(31.9) 

(34.3) 

(36.4) 

(38.5) 

(40.3) 

10 

22 

(18.3) 

0 
(21.0) 

12 

0 

16 

0 

0 

78 
(34.1) 

98 
(36.4) 

100 
(38.5) 

100 
(40.8) 

30 

0 

16 

1 

0 

8 

40 

63 

100 

100 

100 

100 

60 

11 

0 

12 

0 

22 

46 

88 

100 

100 

100 

100 

120 

0 

0 

10 

0 

16 

0 

91 

100 

100 

100 

100 

180 

0 

7 

0 

28 

0 

54 

72 

100 

100 

100 

100 

360 

21 

0 

0 

0 

0 

0 

98 

100 

100 

100 

100 

Table  2.- 

—Percentage  mortality  of  trochophore 

larvae  of  Mercenaria 

mercenaria 

under  different  temperature-time  combinations. 

Values 

in  parentheses  are 

temperatures 

,  corrected  for  the  influence  of 

injection  water. 

Tem 

perature 

'C 

Time 

(mm) 

17.6 

20  1 

226 

250 

27.5 

299 

32.4 

348 

373 

397 

42,3 

1 

29 

19 

14 

0 

0 

2 

11 

0 

0 

14 

20 

(18.9) 

(21.4) 

(23.2) 

(31.5) 

(33.9) 

(35.7) 

(37.7) 

(39.3) 

5 

25 

30 

19 

14 

0 

0 

0 

0 

0 

41 

93 

(18.5) 

(21.0) 

(22.6) 

(31.8) 

(34.2) 

(36.3) 

(38.5) 

(40.2) 

10 

25 
(18.4) 

21 
(21.1) 

2 

3 

1 

0 

0 

0 

(34.1) 

2 
(36.3) 

86 

(38.5) 

100 
(40.7) 

30 

20 

13 

0 

17 

8 

1 

2 

10 

55 

100 

100 

60 

20 

0 

5 

7 

6 

0 

0 

0 

100 

100 

100 

120 

17 

0 

0 

0 

0 

0 

0 

63 

100 

100 

100 

180 

18 

1 

0 

0 

0 

0 

0 

100 

100 

100 

100 

360 

11 

8 

7 

10 

0 

3 

47 

100 

100 

100 

100 

Table  3. — Percentage  mortality  of  straight-hinge  larvae  of  Mercenaria  mercenaria  under  different  temperature-time  combinations. 
Values  in  parentheses  are  temperatures  corrected  for  the  influence  of  injection  water. 


Te 

Tiperature  'C 

Time 

(mln) 

18.3 

21.0 

23.5 

26.1 

285 

30,9 

33.4 

35.8 

38.2 

40.7 

43.1 

1 

3 

2 

3 

2 

2 

3 

4 

4 

3 

5 

4 

(19.6) 

(21.6) 

(30.0) 

(32.5) 

(34.2) 

(36.4) 

(38.4) 

(40.1) 

5 

3 

3 

3 

5 

5 

4 

6 

4 

4 

4 

5 

(19.2) 

(30.3) 

(32.8) 

(34.8) 

(37.0) 

(39.2) 

(41.0) 

10 

3 

(19.1) 

3 

3 

4 

3 

4 

3 

5 
(35.0) 

5 
(37.2) 

5 
(39.5) 

7 
(41.5) 

30 

3 

2 

3 

3 

4 

3 

5 

5 

8 

5 

29 

60 

5 

4 

2 

4 

4 

4 

5 

7 

5 

47 

76 

120 

3 

3 

5 

2 

5 

4 

5 

3 

9 

13 

99 

180 

5 

4 

4 

4 

6 

3 

3 

11 

6 

12 

96 

360 

4 

4 

4 

5 

5 

6 

4 

8 

9 

97 

98 

in  most  of  the  vials  containing  the  cleavage  stages 
and  trochophores  was  found  to  have  developed  a 
precipitate  that  hindered  microscopic  analysis  of 
the  results.  Consequently,  in  March  1973  we 
spawned  2-yr-old  individuals  of  the  Fo  generation 
produced  in  the  hatchery  in  1971  from  the  same 
local  wild  stock.  These  clams  had  been  held  in 
beds  near  the  hatchery.  They  were  conditioned  for 
6  wk  in  warm  water  before  being  spawned  (Loo- 
sanoff  and  Davis,  1963)  and  provided  us  with  re- 
placement cleavage  stages  and  trochophore 
larvae.  Results  of  experiments  using  these  re- 
placements did  not  appear  to  differ  from  prelimi- 
nary results  of  the  1972  experiments. 


Embryos  and  larvae  not  used  immediately  in 
experiments  were  held  at  ambient  temperatures 
in  60-liter  plastic  containers  at  a  density  of  about 
33/ml  (cleavage  stages,  trochophores)  or  about 
17/ml  (straight-hinge)  with  the  seawater  changed 
daily.  Development  appeared  normal  with  no  high 
mortalities  observed.  Larvae  not  used  in  our 
experiments  were  successfully  carried  through  to 
metamorphosis. 

We  used  clarified,  ultraviolet  irradiated  sea- 
water  (28-31"/oo)  in  the  experiments.  The  cast 
aluminum  block,  bored  to  hold  88  test  tubes 
(25  mm)  in  an  8  )(  11  matrix  (see  Figure  1, 
Kennedy  et  al.,  1974)  provided  a  thermal  gradient 


1161 


FISHERY  BULLETIN:  VOL.  72.  NO.  4 


that  was  approximately  linear,  varying  by  2.3° 
to  2.7°C  from  one  column  of  test  tubes  to  the  next. 
Each  of  the  11  columns  in  the  block  represented 
a  different  temperature  level  (Tables  1-3).  Tem- 
peratures rarely  varied  more  than  ±  0.3°C  either 
within  a  test  tube  or  from  one  test  tube  to  another 
in  a  column.  The  eight  rows  represented  different 
time  exposures  (1,  5, 10,  30,  60, 120, 180, 360  min). 
There  were  a  total  of  88  different  temperature- 
time  combinations  or  treatments. 

Twenty-six  milliliters  of  water  placed  in  each 
test  tube  were  brought  to  stable  temperature 
levels.  Four  milliliters  of  water  containing  the 
appropriate  developmental  stages  were  injected 
into  each  test  tube  to  give  a  concentration  of  about 
9  to  12  animals/ml.  We  inoculated  the  11  test 
tubes  in  any  row  simultaneously,  using  an 
apparatus  holding  11  syringes  whose  plungers 
were  depressed  together  (see  Figure  1,  Kennedy 
et  al.,  1974). 

Eighty-eight  plastic  beakers,  each  holding 
about  340  ml  of  sea  water,  were  placed  in  an  8  x  11 
matrix  in  a  water  bath  at  25°  to  26°C.  When 
a  time  period  in  the  block  ended,  we  removed  the 
appropriate  row  of  11  test  tubes  at  once  and 
washed  the  contents  of  each  test  tube  into  its 
corresponding  beaker.  Survivors  were  incubated 
in  the  beakers  for  19  h  (trochophores)  or  23  h 
(cleavage  stages,  straight-hinge)  after  the  experi- 
ments ended.  Preliminary  experiments  indicated 
that  this  allowed  surviving  cleavage  stages  and 
trochophores  to  develop  to  the  straight-hinge 
stage  and  bacteria  to  decompose  dead  individuals. 
It  also  allowed  bacteria  to  decompose  the  meat  of 
dead  straight-hinge  larvae. 

At  the  end  of  the  incubation  period,  the  animals 
in  each  beaker  were  preserved  in  1%  buffered 
Formalin."*  Numbers  of  straight-hinge  larvae  that 
were  alive  or  dead  at  the  end  of  an  experiment 
were  counted  for  each  treatment.  Indications 
of  death  included  an  empty  shell  or  decomposing 
meats  within  a  shell.  For  each  experiment,  we 
used  10  control  test  tubes  held  at  room  tempera- 
ture, with  the  experimental  animals  treated  to  all 
handling  described  except  exposure  in  the  block. 
Three  experiments  were  made  on  each  of  the  three 
developmental  stages. 

Temperature  of  the  injected  water  was  about 


^Reference  to  trade  names  does  not  imply  endorsement  by 
the  National  Marine  Fisheries  Service,  NOAA. 


23°  to  25°C.  This  altered  the  temperature  in  the 
test  tubes  at  the  cold  and  warm  ends  of  the  block 
for  a  short  period  of  time  after  injection.  We  made 
approximate  corrections  for  these  changes 
(Kennedy  et  al.,  1974),  and  the  corrected  temper- 
atures are  noted  in  Tables  1  to  3.  No  corrections 
were  made  for  periods  longer  than  10  min. 

In  a  separate  experiment,  we  measured  oxygen 
levels  in  the  test  tubes  over  a  6-h  period  using 
straight-hinge  larvae  of  M.  mercenaria .  Num- 
bers of  larvae  were  similar  to  numbers  used  in 
temperature-time  experiments.  Over  the 
temperature  range  of  18°  to  43°C,  dissolved 
oxygen  levels  remained  near  saturation,  with 
almost  no  change  during  the  6  h.  We  concluded 
that  there  would  be  no  stress  from  low  oxygen 
levels  (Morrison,  1971)  so  we  did  not  aerate  during 
the  experiments. 

Multiple  regression  analyses  of  percentage 
mortality  on  temperature  and  time  were 
calculated  by  a  UNIVAC  1108  using  a  BMD02R 
stepwise  regression  program,  version  of  2  May 
1966,  from  the  Health  Sciences  Computing 
Facility,  University  of  California  at  Los  Angeles. 

Davis  and  Calabrese  (1964)  indicated  that 
accuracy  in  experiments  involving  sampling  and 
handling  bivalve  larvae  is  about  ±  10%.  Thus, 
differences  of  less  than  207c  in  percentage  mor- 
tality from  one  treatment  to  another  may  not  be 
meaningful. 


RESULTS 

There  was  a  direct  relationship  of  mortality 
with  temperature  increase  and,  at  higher 
temperatures,  with  increase  in  time  exposure 
(Tables  1-3;  Figures  1-3).  As  the  animals  aged, 
temperature  tolerance  increased,  with  cleavage 
stages  most  sensitive  to  higher  temperature  and 
straight-hinge  larvae  least  sensitive  (Tables 
1-3;  Figures  1-3). 

The  general  mortality  patterns  for  the  tripli- 
cated experiments  at  each  developmental  stage 
were  scrutinized  and  judged  to  be  similar  so  the 
data  were  combined.  Over  the  (approximately) 
20°  to  26°C  interval  (columns  2  to  4  in  the  block), 
survival  was  high  at  each  temperature  level.  The 
average  number  of  straight-hinge  larvae  found 
alive  in  each  of  these  columns  and  in  the  controls 
were  compared,  with  no  significant  differences 
found  (P  >  0.05).  Therefore  there  was  no  unusual 


1162 


KENNEDY  ET  AL.:  TEMPERATURE-TIME  RELATIONSHIPS 


Mercenana   mercenana 
cleavage   stages 


Mercenana   mercenana 
straight  ■  hinge    larvae 


Figure  1. — Mercenaria  mercenaria  cleavage  stages.  Response 
surface  generated  from  multiple  regression  analysis  of  per- 
centage mortality  on  temperature  and  time.  Refer  to  Table  1 
for  appropriate  temperatures. 


Mercenana    mercenaria 
trochophore   larvae 


Figure  3. — Mercenaria  mercenaria  straight-hinge  larvae.  Re- 
sponse surface  as  in  Figure  1.  Refer  to  Table  3  for  appropriate 
temperatures. 


mortality  associated  with  exposure  in  the  block 
at  normal  temperatures  (Kennedy  et  al.,  1974). 
Percentage  mortality  data  for  each  developmental 
stage  were  determined  as  for  Mulina  lateralis 
(Kennedy  et  al.,  1974)  and  are  presented  in  Tables 
1  to  3.  The  stepwise  multiple  regression  program 
transformed  these  data  to  arcsine  square  root  of 
the  percentage  mortality  to  allow  the  distribution 
to  approximate  the  normal.  First,  second,  and 
third  order  terms  for  main  effects  (temperature, 
time)    and    all    possible    interactions    were 


'Figure   2. — Mercenaria   mercenaria   trochophore  larvae.  Re- 
'\  sponse  surface  as  in  Figure  1.  Refer  to  Table  2  for  appropriate 
.temperatures. 


scrutinized.  Only  those  terms  (variables)  withF  ^ 
3.96  (P  =  0.05,  d.f.  1,  80)  were  entered  in  the  final 
equation.  The  program  selected  variables  making 
greatest  reduction  in  residual  sum  of  squares  until 
no  further  variables  satisfied  the  acceptance 
criteria.  The  final  empirical  models  appeared  to  be 
good  predictive  equations  for  all  three  stages 
(Table  4).  The  derived  constant  and  variables 
selected  for  each  stage  are  presented  in  Table  5, 
along  with  other  statistics.  The  equations  incor- 
porating these  constants  and  variables  allow  cal- 
culation of  predicted  percentage  mortality  for  dif- 
ferent combinations  of  temperature  and  time.  The 
resulting  estimates  are  in  transformed  form  and 
must  be  converted  to  untransformed  values  ( Sokal 
and  Rohlf,  1969).  Figures  1  to  3  were  constructed 
using  these  equations  and  seven  temperature 
levels  to  outline  the  basic  pattern  of  the  estimated 
response  surface. 

For  each  stage,  the  coefficient  of  determination 
ranged  between  lY7c  to  SCK^r  when  all  the  variables 
were  selected  (Table  5),  indicating  that  most  of 
the  variation  in  mortality  can  be  explained  by 
these  variables  (Steel  and  Torrie,  1960).  For 
cleavage  stages  and  trochophore  larvae,  T^,  by 
itself,  was  the  best  single  predictor  of  percentage 
mortality.  This  was  also  true  for  straight-hinge 
larvae  although  T^  was  eventually  eliminated 
by  the  program  as  new  variables  entered.  In 
combination  with  the  other  variables  in  the  final 
predictive  equation,  T^  continued  to  be  the  most 
useful  variable  in  estimating  or  predicting  per- 
centage mortality  for  trochophore  larvae,  as 


1163 


FISHERY  BULLETIN;  VOL,  72.  NO.  4 


Table  4. — Analysis  of  variance  of  multiple  regression  of  percentage  mortality 
on  temperature  and  time  for  embryos  and  larvae  of  Mercenaria  mercenaria. 
***  —  significant  at  the  0.001  level;  d.f.  —  degrees  of  freedom;  MS  —  mean  squares. 


Source  of 
variation 

Cleavage  stages 
,/./■.                   MS 

Trochophore 

Straight-hinge 
d.f.                  MS 

Regression 
Residual 

4           20557.780*** 
84                399.213 

3           23484.304*** 
84                332.115 

6              2903.295*** 
81                  54.931 

indicated  by  the  values  of  the  standard  partial 
regression  coefficients  (Table  5).  However,  for 
cleavage  stages,  in  the  final  predictive  equation 
T^  became  relatively  less  important  (Snedecor, 
1956;  Steel  and  Torrie,  1960). 

The  88  residuals  were  tested  for  skewness 
(g^)  and  kurtosis  (g^)  (Sokal  and  Rohlf,  1969). 
Both  statistics  were  normally  distributed  for 
cleavage  stages  (g^^  =  -1.02;  ^2  ""  -1-78).  They 
were  as  follows  for  trochophore  larvae:  g^  = 
2.02*;  g^  =  0.90  and  for  straight-hinge  larvae: 
g^  =  -0.12;^2  =  5.92**  (*  P  =  0.05;  **P  =  0.01). 

We  estimated  temperature  levels  for  10%,  50%, 
and  90%  mortality  for  each  period  of  time 
exposure  by  plotting  percentage  mortality  from 
Tables  1  to  3  against  log  temperature  on  prob- 
ability paper.  These  values  (Figure  4)  allow  us  to 
estimate  the  possible  effects  of  temperature  eleva- 
tion over  time  on  the  survival  of  the  different 
stages. 


DISCUSSION 

Early  cleavage  stages  of  molluscs  appear  to 
have  a  narrower  range  of  tolerable  temperatures 
than  older  stages  (Pelseneer,  1901;  Loosanoff,  Mil- 
ler, and  Smith,  1951;  Loosanoff  and  Davis,  1963; 


Goodwin,  1970;  Kennedy  et  al.,  1974).  Results  for 
Mercenaria  mercenaria  indicate  that  increased 
temperature  tolerance  occurred  as  early  as  the 
trochophore  stage.  This  is  in  agreement  with  our 
results  for  Mulinia  lateralis  (Kennedy  et  al., 
1974). 

Cleavage  stages  of  Mercenaria  mercenaria  were 
generally  more  temperature  sensitive  than  those 
of  Mulinia  lateralis  (Kennedy  et  al.,  1974). 
Trochophore  larvae  of  both  species  were  generally 
similar  in  their  thermal  tolerances.  Straight- 
hinge  larvae  of  the  hard  clam  were  more  tempera- 
ture tolerant. 

The  sensitive  cleavage  stages  of  the  hard  clam 
are  of  primary  importance  in  relation  to  the 
effects  of  entrainment  and  exposure  to  high 
temperature  in  cooling  systems.  If  the  cleavage 
stages  are  killed,  obviously  it  does  not  matter 
that  the  next  stages  would  be  more  temperature 
tolerant.  The  hard  clam  spawns  during  the 
summer  throughout  its  geographical  range  (e.g. 
Loosanoff,  1937;  Landers,  1954;  Carriker,  1961; 
Porter,  1967;  Chanley  and  Andrews,  1971). 
However,  little  precise  information  exists  as  to 
the  temperature  range  for  spawning.  Carriker 
(1961)  found  that  hard  clams  spawned  between 
22°  and  30°C  in  Little  Egg  Harbor,  N.J.,  with 
maximum  frequency  over  the  range  of  24°  to  26°C. 
This  is  in  general  agreement  with  the  sparse 


Table  5. — Statistics  of  multiple  regression  of  percentage  mortality  on  temperature  and  time.  M  =  minutes; 
T  =  °C;  b  =  regression  coefficient;  Sf,  =  standard  error  of  fe;  lOOR^  =  coefficient  of  determination  (increases 
as  each  new  variable  is  added);  Srs  -  standard  error  of  the  response  surface  (decreases  as  each  new  variable 
is  added);  b'  =  standard  partial  regression  coefficient  (absolute  values). 


Developmental 
stage 


Constant 


Variable 


lOOfl' 


Cleavage 
stages 


Trochophore 
larvae 

Straight-hinge 
larvae 


-3.6 


152.6 


8.7 


p 

1.05  .^ 

10-= 

1.40 

V 

10-" 

67.1 

21.01 

061 

MP 

1.36  X 

10-^ 

4.90 

X 

10-  = 

68.2 

20.76 

1.90 

M^P 

-9.24  X 

10-" 

4.11 

X 

io-» 

69.9 

20,34 

4,40 

M^P 

1.61    X 

10-'o 

7.96 

X 

10-" 

71.3 

19.98 

2,74 

r^ 

3.78  X 

10-= 

4.40 

10-" 

48.4 

24,28 

2.38 

T 

-8.33 

1.23 

65.9 

19.87 

1.85 

M-P 

1.82  X 

10-' 

4.40 

' 

10-' 

71.6 

18.22 

0,27 

M73 

5.00  X 

10-' 

5.87 

X 

10-  = 

44.2 

11.91 

17.10 

MT^ 

-2.48  X 

10-  = 

3.40 

X 

10-" 

61.7 

9.92 

21.74 

MT 

3.43   ■ 

10-^ 

5.91 

X 

10-  = 

69.7 

8.88 

8.20 

Mn^ 

-5.90   ■ 

10'" 

1.10 

X 

io-« 

74.8 

8.19 

6.89 

Mn^ 

4.98   ■ 

10' 

1.11 

X 

10-' 

77.6 

7.78 

5.48 

M^ 

-1.26  ^ 

10-^ 

4.33 

X 

10-' 

79.7 

7.41 

1.21 

1164 


KENNEDY  ET  AL.:  TEMPERATURE-TIME  RELATIONSHIPS 


reports  elsewhere  (Nelson,  1928;  Belding,  1931; 
Loosanoff,  1937;  Porter,  1967).  No  temperatures 
have  been  published  for  spawning  in  Maryland  or 
Virginia  waters.  We  will  assume  conservatively 
that  the  range  of  23°  to  29°C  would  apply  in 
these  waters  and  that  hard  clam  embryos  and 
larvae  would  be  present  in  the  plankton  under 
these  conditions.  Coutant  (1970)  estimated  that 
the  average  temperatui'e  increase  expected  in 
cooling  water  carrying  entrained  organisms 
through  a  nuclear  power  plant  would  be  10.8°C. 

Therefore,  entrained  embryos  and  larvae  of  hard 
clams  could  be  subjected  to  temperatures  of 
33.8°  to  39.8°C  while  passing  through  such  a 
facility.  In  spring  (Figure  4),  9(K^  of  the  cleavage 
stages  could  be  eliminated  if  entrained  for  about 
30  min.  Fifty  percent  could  be  killed  in  about 
13  min  and  10%  in  about  6  min.  For  trochophores, 
10%  could  be  killed  in  about  25  min,  perhaps 
longer.  Straight-hinge  larvae  would  appear  to  be 


unaffected  by  the  temperature  increase  in  spring. 
In  late  summer,  90%  of  the  cleavage  stages 
might  be  killed  in  1  min  or  less,  with  90%  of  the 
trochophores  dying  in  less  than  5  min.  Over  180 
min  of  exposure  would  be  needed  to  kill  90%  of 
the  straight-hinge  larvae. 

The  equations  we  have  developed  should  allow 
predictive  evaluations  to  be  made  concerning  the 
effects  of  entrainment  of  hard  clam  embryos  and 
larvae  in  Maryland  and  Virginia  waters  and 
elsewhere.  Discharge  canals  of  steam-electric 
power  plants  are  usually  located  to  avoid  directing 
heated  water  over  beds  of  commercial  bivalves. 
It  appears  that  it  is  also  important  to  avoid 
taking  in  water  that  might  come  from  the  area 
of  a  bed  of  hard  clams  during  spawning  season. 
Should  such  water  contain  embryos  and  larvae  of 
hard  clams,  long  exposures  in  the  cooling  system 
of  the  plant  (whether  within  the  facility  or  in  a 
discharge  canal)  could  be  lethal  to  the  entrained 


50 


40 


30 


Mercenaria    mercenaria 


g 


straight  -  hinge     larvae 


-1 1 — I — I— _i i_j_ 


^     4 

o 


a> 
a 

I     30 


i 


trochophore     larvae 


-1 1 I L_ 


30- 


cleavage     stages 


5     6    7  8  9  10 


20  30      40    50 

Minutes 


100 


200       300    400  500 


1000 


Figure  4. — Estimates  of  three  percentage  mortality  levels  for  different  exposure  times.  Percentage  mortality  for  trochophore 
larvae  and  straight-hinge  larvae  was  estimated  to  be  less  than  lO^f  at  1  min  and  up  to  30  min,  respectively.  For  each  stage, 
the  dashed  lines  represent  an  increment  of  10.8°C  over  estimated  spawning  temperature  in  spring  (23°C  -  lower  dashed 
Une)  and  late  summer  (29°C  -  upper  dashed  line)  in  Maryland  and  Virginia  waters. 


1165 


FISHERY  BULLETIN:  VOL,  72,  NO,  4 


organisms.  Whether  such  mortality  would  affect 
the  continued  existence  of  the  local  hard  clam 
resource  depends  upon  local  circumstances. 
Minimum  destruction  of  the  resource  during  use 
of  cooling  water  from  the  vicinity  of  hard  clam 
habitat  requires  that  entrainment  of  embryos  and 
larvae  be  as  short  as  possible.  The  thermal 
discharge  should  be  mixed  with  receiving  water 
as  quickly  as  possible  to  provide  a  rapid  return  to 
ambient  temperature.  In  making  evaluations  it 
should  be  remembered  that  organisms  passing 
through  cooling  systems  are  also  subject  to 
various  stresses  due  to  pressure  changes,  mechani- 
cal effects,  and  chlorination,  in  addition  to 
temperature. 


ACKNOWLEDGMENTS 

H.  Hidu  was  closely  involved  in  early  experi- 
mentation using  the  thermal  gradient  apparatus. 
We  thank  L.  Douglass  for  his  helpful  advice  on 
the  computer  program  and  associated  statistical 
matters.  K.  Drobeck  kindly  supplied  the  appara- 
tus for  simultaneous  injections  of  larvae  into  the 
test  tubes.  Other  associates  lent  essential  equip- 
ment as  needed.  H.  Zion  and  R.  Karney  helped 
us  greatly  in  the  course  of  the  experiments. 
N.  Lewis  provided  us  with  the  embryos  and 
larvae.  F.  Younger  drew  the  figures.  Financial 
support,  in  part,  came  from  U.S.  Department  of 
the  Interior  Water  Resources  Research  Center, 
University  of  Maryland,  Project  A-OllMD,  and 
from  Maryland  Department  of  Natural  Resources. 


LITERATURE  CITED 

Belding,  D,  L. 

1931.     The  quahaug  fishery  of  Massachusetts,  Mass,  Dept. 
Conserv.,  Div.  Fish  Game,  Mar.  Fish.  Serv,  2,  41  p, 
Calabrese,  a,,  and  H.  C,  Davis. 

1970,  Tolerances  and  requirements  of  embryos  and  larvae 
of  bivalve  molluscs.  Helgolander  wiss.  Meeresunters. 
20:553-564, 

Carriker,  M,  R, 

1961.  Interrelation  of  functional  morphology,  behavior, 
and  autecology  in  early  stages  of  the  bivalve  Mercenaria 
mercenaria.     J,  Elisha  Mitchell  Sci,  See,  77:168-241, 

Chanley,  P,,  and  J,  D.  Andrews. 

1971,  Aids  for  identification  of  bivalve  larvae  of  Virginia, 
Malacologia  11:45-119, 

Coutant,  C,  C, 

1970,  Biological  aspects  of  thermal  pollution,  I,  Entrain- 
ment and  discharge  canal  effects,  CRC  Crit,  Rev, 
Environ,  Control  1:341-381, 


Davis,  H,  C,  and  A,  Calabrese, 

1964,     Combined  effects  of  temperature  and  salinity  on 
development  of  eggs  and  growth   of  larvae  of  M, 
mercenaria    and  C,   virginica.     U,S.  Fish  Wildl,  Serv., 
Fish.  Bull.  63:643-655, 
Goodwin,  C.  L, 

1970,     Some  observation  on  laboratory  spawning  of  the 
geoduck,  Panope  generosa,  and  the  culture  of  its  larvae. 
Proc.  Natl,  Shellfish,  Assoc,  60:13-14, 
Kennedy,  V.  S,,  W,  H,  Roosenburg,  H,  H,  Zion,  and 
M,  Castagna, 

1974,     Temperature-time  relationships  for  survival  of  em- 
bryos and  larvae  of  Mulinia  lateralis  (Mollusca:  Bivalvia). 
Mar.  Biol,  (Berl,)  24:137-145, 
Landers,  W,  S. 

1954,  Seasonal  abundance  of  clam  larvae  in  Rhode  Island 
waters,  1950-52,  U,S,  Fish  Wildl,  Serv.,  Spec,  Sci, 
Rep,  Fish,  117,  29  p, 

LOOSANOFF,  V,  L, 

1937,  Spawning  of  Venus  mercenaria  (L,),  Ecology 
18:506-515, 

LOOSANOFF,  V,  L.,  AND  H,  C,  DaVIS, 

1963,     Rearing  of  bivalve  mollusks,     Adv,  Mar,   Biol, 
1:1-136, 
LOOSANOFF,  V,  L,,  W,  S,  Miller,  and  P,  B,  Smith, 

1951.     Growth  and  setting  of  larvae  of  Venus  mercenaria  in 
relation  to  temperature,  J,  Mar,  Res,  10:59-81, 
Marcy,  B,  C,  Jr. 

1971,     Survival  of  young  fish  in  the  discharge  canal 
of  a  nuclear  power  plant,     J,  Fish,  Res,  Board  Can, 
28:1057-1060, 
Morrison,  G, 

1971,  Dissolved  oxygen  requirements  for  embryonic  and 
larval  development  of  the  hardshell  clam,  Mercenaria 
mercenaria.     J,  Fish,  Res,  Board  Can,  28:379-381. 

Nelson,  T,  C, 

1928,  On  the  distribution  of  critical  temperatures  for 
spawning  and  for  ciliary  activity  in  bivalve  molluscs. 
Science  (Wash,,  DC)  67:220-221, 

PE1.SENEER,  P, 

1901,     Sur  le  degre  d'eurythermie  de  certaines  larves 
marines.  Bull.  Acad,  R,  Belg,  CI.  Sci,,  p,  279-292. 
Porter,  H.  J. 

1967.     Seasonal    gonadal    changes    of   adult    clams, 
Mercenaria  mercenaria   (L.),  in  North  Carolina.  Proc, 
Natl.  Shellfish,  Assoc.  55:35-52. 
Snedecor,  G.  W. 

1956.  Statistical  methods  applied  to  experiments  in 
agriculture  and  biology.  5th  ed.  Iowa  State  Univ. 
Press,  Ames,  534  p. 

SOKAL,  R,  R,,  AND  F,  J,  ROHLF. 

1969.     Biometry;  the  principles  and  practice  of  statistics 
in  biological  research.     W.  H.  Freeman,  San  Franc, 
776  p. 
Steel,  R,  G,  D,,  and  J,  H,  Torrie, 

1960,     Principles  and  procedures  of  statistics:  with  special 
reference  to  the  biological  sciences,     McGraw-Hill, 
N.Y,,  481  p, 
Tarzwell,  C.  M, 

1972,  An  argument  for  the  open  ocean  siting  of  coastal 
thermal  electric  plants,     J.  Environ.  Qual.  1:89-91. 

Thomas,  W.  H,,  H.  L.  Scotten,  and  J.  S.  Bradshaw, 

1963,  Thermal  gradient  incubators  for  small  aquatic 
organisms,  Limnol.  Oceanogr.  8:357-360. 


1166 


INDEX 


Fishery  Bulletin  Vol.  72,  No.  1-4,  1974 


Abalone 
southern  California,  temperature  influence 

Haliotis  corrugata 1137 

Haliotis  fulgens 1137 

Haliotis  rufescens  1137 

"Ability  of  male  king  crab,  Paralithodes  cam- 
tschatica,  to  mate  repeatedly,  Kodiak,  Alaska, 
1973,"  by  Guy  C.  Powell,  Kenneth  E.  James,  and 
Charles  L.  Kurd  171 

Abudefduf  abdominalis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 980 

Abudefduf  imparipennis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 980 

Abudefduf  sindonis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 979 

Abudefduf  sordidus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 979 

"Abundance  of  pelagic  fish  during  the  19th  and 
20th  centuries  as  recorded  in  anaerobic  sedi- 
ment off  the  Californias,"  by  Andrew  Soutar 
and  John  D.  Isaacs 257 

Acanthurus  thompsoni 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1000 

"Acoustic  telemetry  from  fish,"  by  John 
Kanwisher,  Kenneth  Lawson,  and  Gunnar 

Sundness 251 

Acoustic  telemetry — see  Telemetry 

ADRON,  J.  W.,  A.  BLAIR,  and  C.  B.  COWEY, 
"Rearing  of  plaice  [Pleuronectes  platessa)  Isirvae 
to  metamorphosis  using  an  artificial  diet"   353 

Aetideus 

calanoid  copepod  from  Gulf  of  Mexico 

Aetideus  acutus  Farran 217 

Aetideus  giesbrechti  Cleve 220 

Aetideus  mexicanus,  new  species 215 

"(The)  age  composition  of  striped  bass  catches 
in  Virginia  rivers,  1967-1971,  and  a  description 
of  the  fishery,"  by  George  C.  Grant 193 

AHLSTROM,  ELBERT  H.— see  MOSER  and 
AHLSTROM 


Aholehole 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Kuhlia  sandvicensis 948 

Alaminos — see  Vessels 

Alaska 

Kodiak 171 

Alaska — see  Vessels 

Albatross — see  Vessels 

Albatross  IV — see  Vessels 

AUelochemics 

marine,  and  evolution 1 

ALVARINO,  ANGELES,  "Distribution  of  si- 
phonophores  in  the  regions  adjacent  to  the  Suez 
and  Panama  canals"   527 

"American  lobsters  tagged  by  Maine  commercial 
fishermen,  1957-59,"  by  Robert  L.  Dow  622 

"Analysis  of  migrations  and  mortality  of  bluefin 
tuna,  Thunnus  thynnus ,  tagged  in  the  northwest- 
ern Atlantic  Ocean,"  by  F.  J.  Mather  III,  B.  J. 
Rothschild,  G.  J.  Paulik,  and  W.  H.  Lenarz  ....      900 

Anampses  cuvier 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 992 

ANAS,  RAYMOND  E.,  "Heavy  metals  in  the 
northern  fur  seal,  Callorhinus  ursinus,  and 
harbor  seal,  Phoca  vitulina  richardi"  133 

Anchovy 

swimming  energetics  of  larval   885 

Ancylopsetta  quadrocellata — see  Flounder,  ocel- 
lated 

Angelfish 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 

angelfish 964 

potter's  angelfish 964 

Aphareus  furcatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 955 

Apogon  erythrinus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 950 

1167 


Apogon  menesemus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 951 

Apogon  snyderi 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 951 

APRIETO,  VIRGINIA  L.,  "Early  development 
of  five  carangid  fishes  of  the  Gulf  of  Mexico  and 
the  south  Atlantic  coast  of  the  United  States"  . .      415 

Arcturus — see  Vessels 

Argo — see  Vessels 

Argosy — see  Vessels 

Arothron  hispidus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1012 

Arothron  meleagris 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1012 

Arrow — see  Vessels 

Artificial  structures 

evaluation  of  mid-water  for  attracting  fishes 

behavior  observations  at  structures   188 

behavioral  mechanisms 189 

comparison  of  day  and  night  collections  ....  187 

diver  estimates  of  numbers  and  species  ....  184 

purse  seine  operations 190 

recruitment  patterns  and  production  186 

responses  to  moving  structures 188 

size  and  color  evaluation   187 

Askoy — see  Vessels 

Atlantic  Ocean 

zoogeography  of  the  genus  Nematoscelis   1039 

Atlantis — see  Vessels 

Atlantis  II — see  Vessels 

Aulostomus  chinensis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 942 

Auxis  sp. — see  Mackerel,  frigate 


BAKKALA,  RICHARD  G.— see  FRENCH  and 
BAKKALA 

BAKUN,  ANDREW,  DOUGLAS  R.  MCLAIN, 
and  FRANK  V.  MAYO,  "The  mean  annual  cycle 
of  coastal  upwelling  off  western  North  America 
as  observed  from  surface  measurements"  843 

BALDRIDGE,  ALAN,  "Migrant  gray  whales  with 
calves  and  sexual  behavior  of  gray  whales  in  the 
Monterey  area  of  central  California,  1967-73"  . .      615 


Balloonfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Arothron  hispidus 1012 

Arothron  meleagris 1012 

Bass,  sea — see  Sea  bass 

Bass,  striped 

age  composition  and  fishery  in  Virginia  rivers 

cycles  of  abundance 197 

description  of  fishery 193 

differences  in  age  composition  between  years 

and  rivers 196 

seasonal  age  composition 195 

seasonal  and  annual  age  composition  of 
river  catches 197 

BEITINGER,  THOMAS  L.,  "Thermoregulatory 
behavior  and  diel  activity  patterns  of  bluegill, 
Lepomis  macrochirus ,  following  thermal  shock"    1087 

BEJDA,  ALLEN  J.— see  OLLA  et  al. 

BELL,  FREDERICK  W.— see  FULLENBAUM 
and  BELL 

BEN-YAMI,  M.,  and  T.  GLASER,  "The  invasion 
of  Saurida  undosquamis  (Richardson)  into  the 
Levant  Basin  -  an  example  of  biological  effect  of 
interoceanic  canals" 359 

BENIGNO,  JOSEPH  A.— see  KEMMERER  et  al. 

Bigeye 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 948 

"Bioeconomic  contribution  of  Columbia  River 
hatchery  coho  salmon,  1965  and  1966  broods, 
to  the  Pacific  salmon  fisheries,"  by  Roy  J.  Wahle, 
Robert  R.  Vreeland,  and  Robert  H.  Lander 139 

BLAIR,  A.— see  ADRON  et  al. 

Blake — see  Vessels 

Blue  Goose — see  Vessels 

Bluegill 

thermoregulatory  behavior  and  diel  activity 
patterns  following  thermal  shock 1087 

Bodianus  bilunulatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 989 

Boreogadus  saida — see  Cod,  Arctic 

Bothus  mancus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1005 

"Bothus  thompsoni  (Fowler)  1923,  a  valid  species 
of  flatfish  (Pisces:  Bothidae)  from  the  Hawaiian 
Islands,"  by  Paul  Struhsaker  and  Robert  M. 
Moncrief 237 


1168 


I 


Bothus  thompsoni 

a  valid  species  of  flatfish 

comparison  with  other  species  of  Bothus  .  .  .  243 

description   237 

ecology 245 

material  examined 245 

George  M.  Bowers — see  Vessels 

BOWMAN,  THOMAS  E.— see  WILLIAMS  et  al. 

Boxfish 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Ostracion  meleagris  1011 

Brevoortia  patronus — see  Menhaden,  Gulf 

BROOKS,  A.  L.,  C.  L.  BROWN,  JR.,  and  P.  H. 
SCULLY-POWER,  "Net  filtering  efficiency  of  a 
3-meter  Isaacs-Kidd  Midwater  Trawl" 618 

Brotula 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Brotula  multiharbata 930 

Brotula  multibarbata 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 930 

BROWN,  C.  L.,  JR.— see  BROOKS  et  al. 

Anton  Bruun — see  Vessels 

Butte  rflyfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

blackface 969 

blue-striped   975 

Chaetodon  auriga  975 

Chaetodon  corallicola 969 

Chaetodon  miliaris 969 

Forciper  longirostris 965 

Forcipiger  flauissimus  965 

four-spot   971 

Hemitaurichthys  thompsoni 967 

masked    976 

one-spot 972 

ornated    973 

pebbled   972 

CABLE,  WAYNE  D.,  and  WARREN  S.  LAN- 
DERS, "Development  of  eggs  and  embryos  of 
the  surf  clam,  Spisula  solidissima,  in  synthetic 
seawater"   247 

"Calanoid  copepods  of  the  genus  Aetideus  from 

the  Gulf  of  Mexico,"  by  Taisoo  Park 215 

California 

Del  Mar 670 

La  Jolla 295 

Callorhinus  ursinus — see  Seal,  fur 

Calypso — see  Vessels 


Cameron — see  Vessels 

Canals 
interoceanic 

example  of  biological  effect  of 359 

Cancer  antennarius — see  Crab,  rock 

Cantherines  dumerili 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1009 

Cantherines  sandwichiensis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1009 

Canthigaster  amboinensis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1013 

Ca  n  th  igaster  jacta  tor 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1014 

Cape  St.  Mary — see  Vessels 

Carangidae 

distinguishing  features 

banded  rudderfish 422 

leatherjacket  435 

lookdown 431 

rainbow  runner 419 

round  scad    427 

distribution  and  spawning 

banded  rudderfish 426 

leatherjacket  439 

lookdown 435 

rainbow  runner 421 

round  scad   429 

fin  development 

banded  rudderfish 426 

leatherjacket   438 

lookdown 434 

rainbow  runner 420 

round  scad    429 

literature 

banded  rudderfish 422 

leatherjacket  435 

lookdown 431 

rainbow  runner 417 

round  scad   426 

morphology 

banded  rudderfish 422 

leatherjacket  435 

lookdown 431 

rainbow  runner 419 

round  scad    427 

pigmentation 

banded  rudderfish 423 

leatherjacket  438 

lookdown 433 

rainbow  runner 420 

round  scad   427 


1169 


Caranx  mate — see  Omaka 

Caranx  melampygus — see  Ulua,  blue 

Cardinalfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Apogon  erythrinus    950 

Apogon  menesemus    951 

Apogon  snyderi  951 

CASTAGNA,  M.— see  KENNEDY  et  al. 

Centropyge  potteri 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 964 

Cephalopholis  argus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 947 

Chaetodon  auriga 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 975 

Chaetodon  corallicola 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 969 

Chaetodon  fremblii 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 975 

Chaetodon  lunula 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 976 

Chaetodon  miliaris 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 969 

Chaetodon  multicinctus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 972 

Chaetodon  ornatissimus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 973 

Chaetodon  quadrimaculatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 971 

Chaetodon  unimaculatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 972 

Chain — see  Vessels 

"Changes  in  the  amount  and  proportions  of  DDT 
and  its  metabolites,  DDE  and  DDD,  in  the 
marine  environment  off  southern  California, 
1949-72,"  by  John  S.  MacGregor  275 

Cheilinus  rhodochrous 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 989 


"Chemical  signals  in  the  sea:  marine  allelo- 
chemics  and  evolution,"  by  J.  S.  Kittredge, 
Francis  T.  Takahashi,  James  Lindsey,  and 
Reuben  Lasker   1 

Chemical  signals 
in  the  sea 

allelochemics 1 

marine  kairomones   4 

pheromones    5 

Chromis  leucurus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 982 

Chromis  ovalis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 984 

Chromis  vanderbilti 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 982 

Chromis  verater 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 984 

Chub,  sea — see  Sea  chub 

Cirrhitops  fasciatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 988 

Cirrhitus  pinnulatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 988 

Cirripectus  variolosus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 999 

Citharichthys  spilopterus — see  Whiff,  bay 

Clam,  hard 
temperature-time  relationships  for  survival  of 
embryos  and  larvae 1160 

Clam,  soft-shell 

reproductive  cycle  at  Skagit  Bay,  Washington 

description  of  area  648 

females    649 

immature   652 

males 649 

1971  reproductive  cycle 652 

1972  reproductive  cycle 654 

Clam,  surf 

eggs  and  embryos 

development  of,  in  synthetic  seawater 247 

CLARKE,  THOMAS  A.,  "Some  aspects  of  the 
ecology  of  stomiatoid  fishes  in  the  Pacific  Ocean 
near  Hawaii" 337 

CLARKE,  WILLIAM  D.— see  ROSENTHAL  et  al. 


1170 


Coastal  upwelling 
off  western  North  America 
mean  annual  cycle  as  observed  from  surface 
measurements 843 

John  N.  Cobb — see  Vessels 

Cod,  Arctic 

density  distribution  of  juveniles  in  Chukchi 

Sea 

horizontal  density  distribution 1101 

possible  causes  of  density  structure  and 

its  vertical  displacement 1099 

Cololabis  saira — see  Saury,  Pacific 

Combat — see  Vessels 

Combtooth  blennies 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Cirripectus  variolosus    999 

Exallias  brevis 998 

sabre-toothed 999 

Conger  marginatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 929 

Coquette — see  Vessels 

Coris  gaimard 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 993 

Cornetfish 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Fistularia  petimba    944 

COWEY,  C.  B.— see  ADRON  et  al. 

Crab,  king 

ability  of  male  to  mate  repeatedly  near  Kodiak, 

Alaska 171 

distribution  and  relative  abundance  of  larvae 
in  southeastern  Bering  Sea,  1969-70 

distribution 810 

larval  release  areas 811 

relation  between  distribution  of  larvae  and 

current  patterns  812 

relative  abundance 810 

Crab,  rock 
laboratory  study  of  behavioral  interactions 
with  the  California  spiny  lobster 1146 

Crabs 

swimming,  of  genus  Callinectes 

Callinectes  arcuatus 752 

Callinectes  bellicosus  761 

Callinectes  bocourti    766 

Callinectes  danae    746 

Callinectes  exasperatus   757 

Callinectes  gladiator    735 


Callinectes  latimanus 775 

Callinectes  maracaiboensis 773 

Callinectes  marginatus   722 

Callinectes  ornatus 739 

Callinectes  rathbunae    772 

Callinectes  sapidus 778 

Callinectes  similis 731 

Callinectes  toxotes 764 

characters  of  systematic  value  687 

fossil  record   715 

genus  Callinectes    719 

history 685 

key  to  species  of  Callinectes 720 

larval  development 713 

key  to  species  of  Callinectes 720 

larval  development 713 

measurements 689 

modern  distribution 717 

questionable  species 791 

CRAWFORD,  L.,  D.  W.  PETERSON,  M.  J. 
KRETSCH,  A.  L.  LILYBLADE,  and  H.  S. 
OLCOTT,  "The  effects  of  dietary  a  -tocopherol 
and  tuna,  safflower,  and  linseed  oils  on  the 

flavor  of  turkey" 1032 

Croaker,  Atlantic 

electrical  threshold  response  of 851 

Townsend  Cromwell — see  Vessels 

GUSHING,  D.  H.,  "A  link  between  science  and 

management  in  fisheries" 859 

"Daily  activity,  movements,  feeding,  and  sea- 
sonal occurrence  in  the  tautog,  Tautoga  onitis" 
by  Bori  L.  Olla,  Allen  J.  Bejda,  and  A.  Dale 

Martin 27 

DAMKAER,  DAVID  M.— see  WILLIAMS  et  al. 

Damselfish 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 

Abudefduf  abdominalis 980 

Abudefduf  imparipennis 980 

Abudefduf  sindonis    979 

Abudefduf  sordidus  979 

Chromis  leucurus  982 

Chromis  ovalis 984 

Chromis  vanderbilti 982 

Chromis  verater 984 

Dascyllus  albisella   982 

Plectroglyphidodon  johnstonianus  978 

Pomacentrus  jenkinsi 979 

Dascyllus  albisella 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 982 

DAYTON.  PAUL  K.— see  ROSENTHAL  et  al. 


1171 


DDT 

changes  in  amount  and  proportions  of,  and  its 
metabolites  in  marine  environment  off  south- 
ern California,  1949-72 275 

Decapterus  punctatus — see  Scad,  round 

Delaware — see  Vessels 

Del  Mar,  California 670 

"Density  distribution  of  juvenile  Arctic  cod, 
Boreogadus  saida,  in  the  eastern  Chukchi  Sea 
in  the  fall  of  1970,"  by  Jay  C.  Quast 1094 

"Description  of  eggs  and  larvae  of  scaled  sardine, 
Harengula  jaguana"  by  Edward  D.  Houde,  Wil- 
liam J.  Richards,  and  Vishnu  P.  Saksena 1106 

"Development  and  distribution  of  larvae  and 
juveniles  of  Sebastolobus  (Pisces;  Family  Scor- 
paenidae),"  by  H.  Geoffrey  Moser   865 

"Development  of  eggs  and  embryos  of  the  surf 
clam,  Spisula  solidissima,  in  synthetic  seawa- 
ter,"  by  Wayne  D.  Cable  and  Warren  S.  Landers       247 

"Development  of  eggs  and  larvae  of  Caranx 
mate  (Carangidae),"  by  John  M.  Miller  and 
Barbara  Y.  Sumida   497 

Diamantina — see  Vessels 

Diodon  holocanthus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1015 

Diodon  hystrix 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1015 

Discovery — see  Vessels 

"Distribution  and  relative  abundance  of  larvae  of 
king  crab,  Paralithodes  camtschatica,  in  the 
southeastern  Bering  Sea,  1960-70,"  by  Evan  B. 
Haynes 804 

"Distribution  of  siphonophores  in  the  regions 
adjacent  to  the  Suez  and  Panama  canals,"  by 
Angeles  Alvarino  527 

Distribution,  variation,  and  supplemental  de- 
scription of  the  opossum  shrimp,  Neomysis 
americana  (Crustacea:  Mysidacea),"  by  Austin  B. 
Williams,  Thomas  E.  Bowman,  and  David  M. 
Damkaer 835 

Dolphin — see  Vessels 

Dorsetshire — see  Vessels 

DOW,  ROBERT  L.,  "American  lobsters  tagged 

by  Maine  commercial  fishermen,  1957-59" 622 

DURKIN,  JOSEPH  T.,  and  DAVID  A.  MISI- 
TANO,  "Occurrence  of  a  ratfish  in  the  Columbia 
River  estuary" 854 

1172 


"Early  development  of  five  carangid  fishes  of  the 
Gulf  of  Mexico  and  the  south  Atlantic  coast  of 
the  United  States,"  by  Virginia  L.  Aprieto 415 

Echidna  zebra 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 928 

"Ecology  and  natural  history  of  a  stand  of  giant 
kelp,  Macrocystis  pyrifera,  off  Del  Mar,  Cali- 
fornia," by  Richard  J.  Rosenthal,  William  D. 
Clarke,  and  Paul  K.  Dayton  670 

Ecosystems — see  Marine  ecosystems 

Eel 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

broad-banded  moray   928 

Gyninothorax  eurostus 927 

Gymnothorax  flavimarginata 927 

spotted  moray  926 

white   929 

zebra  moray 928 

"(The)  effects  of  dietary  a -tocopherol  and  tuna, 
safflower,  and  linseed  oils  on  the  flavor  of  tur- 
key," by  L.  Crawford,  D.  W.  Peterson,  M.  J. 
Kretsch,  A.  L.  Lilyblade,  and  H.  S.  Olcott 1032 

"Effects  of  oil  on  marine  ecosystems:  a  review 
for  administrators  and  policy  makers,"  by  Dale 
R.  Evans  and  Stanley  D.  Rice 625 

"Egg  and  larval  development  of  the  Atlantic 
thread  herring,  Opisthonema  oglinum"  by  Wil- 
liam J.  Richards,  Robert  Victor  Miller,  and 
Edward  D.  Houde 1123 

Elagatis  bipinnulata — see  Runner,  rainbow 

"Electrical  threshold  response  of  some  Gulf  of 
Mexico  fishes,"  by  Edward  F.  Klima 851 

"Electrophoretic  comparison  of  five  species  of 
pandalid  shrimp  from  the  northeastern  Pacific 
Ocean,"  by  AUyn  G.  Johnson,  Fred  M.  Utter, 
and  Harold  O.  Hodgins 799 

Embryos 
hard  clam 

temperature-time  relationships  for  survival    1160 

Emilia — see  Vessels 

Engraulis  mordax — see  Anchovy 

Ensign — see  Vessels 

Eschrichtius  robustus — see  Whale,  gray 

Etropus  crossotus — see  Flounder,  fringed 

Euthynnus  alletteratus — see  Tuna,  little  tunny 

"(An)  evaluation  of  mid-water  artificial  struc- 
tures for  attracting  coastal  pelagic  fishes,"  by 
Donald  A.  Wickham  and  Gary  M.  Russell 181 


i 


EVANS,  DALE  R.,  and  STANLEY  D.  RICE, 
"Effects  of  oil  on  marine  ecosystems:  a  review 
for  administrators  and  policy  makers" 625 

Evolution 

and  marine  allelochemics 1 

ExaUias  brevis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 998 

"(An)  examination  of  the  yield  per  recruit 
basis  for  a  minimum  size  regulation  for  Atlantic 
yellowfin  tuna,  Thunnus  albacares,"  by  W.  H. 
Lenarz,  W.  W.  Fox,  Jr.,  G.  T.  Sakagawa,  and 
B.  J.  Rothschild 37 

FAHAY,  MICHAEL  P.,  "Occurrence  of  silver 
hake,  Merluccius  bilinearis,  eggs  and  larvae 
along  the  middle  Atlantic  continental  shelf 
during  1966"   813 

"Feeding  relationships  of  teleostean  fishes  on 
coral  reefs  in  Kona,  Hawaii,"  by  Edmund  S. 
Hobson 915 

Filefish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Cantherines  dumerili 1009 

Cantherines  sandwichiensis 1009 

Pervagor  spilosoma 1010 

Fish 
abundance  of  pelagic  during  19th  and  20th 

centuries  off  the  Californias   257 

electrical  threshold  response  of  some  Gulf  of 
Mexico 

Atlantic  croaker  851 

chub  mackerel 851 

longspine  porgy 851 

scaled  sardine   851 

spot 851 

feeding  relationships  of  teleosts  on  coral  reefs 
in  Kona,  Hawaii 

aholehole 948 

angelfish 964 

assessing  nocturnal  colorations   917 

balloonfish    1012 

bigeye 948 

boxfish 1011 

brotulas 930 

butterflyfish  964 

cardinalfish 950 

combtooth  blennies 998 

conger  eel 929 

coral  reefs  as  a  habitat 1017 

cornetfish    944 

damselfish 978 

filefish  1009 

fishes  observed  on  transect  lines   923 

food  habits   916 


generalized    carnivores:    main    line    of 

evolution 1018 

goatfish  957 

hawkfish 986 

inshore  habitats  and  their  characteristic 

fishes  918 

jacks 954 

left-hand  flounder 1005 

lizardfish 929 

moorish  idol 1003 

moray  eel   926 

parrotfish   995 

porgy  956 

scorpionfish 944 

sea  bass 947 

sea  chubs 964 

sharpbacked  puffer 1013 

silversides 931 

snapper  955 

specialized  offshoots  from  the  main  line  of 

evolution 1022 

spiny  puffer  1015 

squirrelfish 932 

surgeonfish 1000 

transect  counts  for  habitat  categories 917 

triggerfish 1005 

trumpetfish 942 

wrasse  989 

Fish  harvesting  systems 

experiments  with  coastal  pelagic  fishes  to 

establish  design  criteria  for  electrical 

captured  fish   660 

description  of  test  equipment  658 

mid-water  trawling  mode 667 

netless  fish  harvesting  mode 664 

120-KVA  pulse  generator  design 664 

test  procedure   658 

wild  fish 661 

Fish  Hawk — see  Vessels 

Fish  larvae 
and  eggs 

omaka   497 

Fish  protein  concentrates 

composition  of  residual  lipids  845 

Fish,  stomiatoid 
some  aspects  of  ecology  near  Hawaii 

Aristostomias  grimialdii 346 

Aristostomias  lunifer 346 

Aristostomias  polydactylus 346 

Aristostomias  tittmanni 346 

Astronesthes  cyaneus  343 

Astronesthes  gemmifer 344 

Astronesthes  indicus    343 

Astronesthes  lucifer   344 

Astronesthes  luetkeni 344 


1173 


Astronesthes  splendidus   344 

Bathophilus  brevis   345 

Bathophilus  digitatus 345 

Bathophilus  kingi 345 

Bathophilus  longipinnis   345 

Bathophilus  pawneei   345 

Chauliodus  sloani 342 

Danaphos  oculatus 342 

Diplophos  taenia  338 

Echiostoma  barbatum   345 

Eustomias  bibulbosus    344 

Eustomias  bifilis  345 

Eustomias  gibbsi 345 

Flagellostomias  boureei 345 

Gonostoma  atlanticum 340 

Gonostoma  ebelingi    341 

Gonostoma  elongatum  341 

Heterophotus  ophistoma    344 

Ichthyococcus  ovatus    340 

Idiacanthus  fasciola 346 

Malacosteus  niger 346 

Margrethia  obtusirostra    342 

Neonesthes  microcephalus    344 

Pachystomias  microdon 345 

Photonectes  achirus    345 

Photonectes  albipennis 345 

Photonectes  caerulescens 345 

Photonectes  fimbria    345 

Photostomias  guernei 346 

Stomias  danae 343 

Thysanactis  dentex 345 

Valenciennellus  tripunctulatus  342 

Vinciguerria  nimbaria 339 

Vinciguerria  poweriae 340 

Woodsia  nonsuchae    342 

Fishery  management 

bioeconomic  model:  American  lobster  fishery 

demand  function  for  lobsters 19 

economic  impact  of  selected  management 

alternatives   21 

how  the  model  works 20 

production  function  and  supply  of  lobsters  .  16 

quadratic  example  of  resource  use  model    . .  14 

specification  of  general  resource  use  model  .  13 

link  between  science  and 

analytic  model 860 

descriptive  model  859 

nature  of  fisheries  science   863 

science  and  management  in  the  fishery 

commissions 862 

stock  and  recruitment 861 

Fistularia  petimba 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 944 

Flatfish — see  Bothus  thompsoni 


FLEMINGER,  A.,  and  K.  HULSEMANN,  "Sys- 
matics  and  distribution  of  the  four  sibling  species 
comprising  the  genus  Pontellina  Dana 
(Copepoda,  Calanoida)" 63 

Florida 
Panama  City 18  1,  657 

Flounder 

food  habits  of  four  species  of  Georgia 515 

Flounder,  fringed 
Georgia 
food  habits  of 520 

Flounder,  left-hand 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Bothus  mancus   1005 

Flounder,  ocellated 
Georgia 

food  habits  of 521 

"Food  habits  of  Georgia  estuarine  fishes.  I.  Four 
species  of  flounders  (Pleuronectiformes:  Bothi- 
dae),"  by  Robert  R.  Stickney,  Gary  L.  Taylor, 
and  Richard  W.  Heard  HI   515 

Forcipiger  flauissimus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 965 

Forcipiger  longirostris 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 965 

FORD,  RICHARD  F.— see  KREKORIAN  et  al. 

FOX,  W.  W.,  JR.— see  LENARZ  et  al. 

Freelance — see  Vessels 

FRENCH,  ROBERT  R.,  and  RICHARD  G.  BAK- 
KALA,  "A  new  model  of  ocean  migrations  of 
Bristol  Bay  sockeye  salmon" 589 

Frobisher — see  Vessels 

FULLENBAUM,  RICHARD  F.,  and  FRED- 
ERICK W.  BELL,  "A  simple  bioeconomic  fishery 
management  model:  a  case  study  of  the  American 
lobster  fishery"   13 

Fundulus  diaphanus  diaphanus — see  Killifish, 
eastern  banded 

Gascoyne — see  Vessels 
Theodore  N.  Gill — see  Vessels 
Glacier — see  Vessels 

GLASER,  T.— see  BEN-YAMI  and  GLASER 

Goatfish 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Mulloidichthys  auriflamma  957 


1174 


Mulloidichthys  samoensis 957 

Parupeneus  bifasciatus   960 

Parupeneus  chryserydros    958 

Parupeneus  multifasciatus 958 

Parupeneus  porphyreus 961 

Gomphosus  varius 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 994 

GOPALAKRISHNAN,  K.,  "Zoogeography  of  the 
genus  Nematoscelis  (Crustacea,  Euphausiacea)"    1039 

GRANT,  GEORGE  C.,  "The  age  composition  of 
striped  bass  catches  in  Virginia  rivers,  1967- 
1971,  and  a  description  of  the  fishery" 193 

Gulf  Ranger — see  Vessels 

Gymnothorax  eurostus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 927 

Gymnothorax  flavimarginata 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 927 

Gymnothorax  meleagris 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 926 

Gymnothorax  petelli 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 928 

Hake,  red 
seasonal  distribution  of  siblings  in  New 
England 481 

Hake,  silver 

occurrence  of  eggs  and  larvae  along  middle 

Atlantic  continental  shelf  during  1966 

distribution  of  eggs    816 

distribution  of  larvae 822 

Hake,  white 

seasonal   distribution  of  siblings  in   New 
England 481 

Hakes 

seasonal  distribution  of  siblings  in  New 

England 

analysis  of  temperature  and  distribution  .  .  .  485 

distribution  with  substrate   492 

life  history  stage  by  sampling  strata    484 

life  history  stages 483 

natural  divisions  of  study  area 483 

sampling  procedures  482 

seasonal  distribution 485 

temperature 484 

topography 483 

Halichoeres  ornatissimus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 991 


Haliotis  corrugata 

southern  California,  temperature  influence   . .    1137 

Haliotis  fulgens 

southern  California,  temperature  influence   . .    1137 

Haliotis  rufescens 

southern  California,  temperature  influence  . .    1137 

Harengula  jaguana — see  Sardine,  scaled 

Harengula  pensacolae — see  Sardine,  scaled 

Hassler — see  Vessels 

Hawaii 

feeding  relationships  of  teleostean  fishes  on 
coral  reefs  in  Kona,  June  1969  to  August  1970      915 

Hawkfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Cirrhitops  fasciatus    988 

Cirrhitus  pinnulatus    988 

Paracirrhites  forsteri   986 

HAYNES,  EVAN  B.,  "Distribution  and  relative 
abundance  of  larvae  of  king  crab,  Paralithodes 
camtschatica,  in  the  southeastern  Bering  Sea, 
1969-70"  804 

HEARD,  RICHARD  W.  Ill— see  STICKNEY  et  al. 

"Heavy  metals  in  the  northern  fur  seal,  Cal- 
lorhinus  ursinus,  and  harbor  seal, PAoca  vitulina 
richardi,"  by  Raymond  E.  Anas 133 

Hemitaurichthys  thompsoni 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 967 

Hemitaurichthys  zoster 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 969 

Herring,  Atlantic  thread 
egg  and  larval  development 

branchial  development  1134 

cephalic  development 1131 

description  of  eggs  1124 

fin  development 1130 

morphology  of  larvae 1 125 

pigmentation 1135 

vertebral  development 1127 

HIROTA,  JED,  "Quantitative  natural  his- 
tory   of    Pleurobrachia     bachei     in     La    Jolla 

Bight"   295 

HOBSON,  EDMUND  S.,  "Feeding  relationships 
of  teleostean  fishes  on  coral  reefs  in  Kona, 
Hawaii" 915 

HODGINS,  HAROLD  O.— see  JOHNSON  et  al. 

Holacanthus  arcuatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 964 


1175 


Holocentrus  diadema 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 934 

Holocentrus  lacteoguttatum 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 937 

Holocentrus  sammara 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 932 

Holocentrus  spinifera 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 932 

Holocentrus  Here 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 934 

Holocentrus  xantherythrus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 934 

Holotrachys  lima 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 938 

Homarus  americanus — see  Lobster,  American 

Horizon — see  Vessels 

HOUDE,  EDWARD  D.— see  RICHARDS  et  al. 

,  WILLIAM  J.  RICHARDS,  and  VISHNU 

P.  SAKSENA,  "Description  of  eggs  and  larvae 

of  scaled  sardine,  Harengula  jaguana" 1106 

HUGHES,  STEVEN  E.,  "Stock  composition, 
growth,  mortality,  and  availability  of  Pacific 
saury,  Cololahis  sajra,  of  the  northeastern  Pacific 
Ocean" : 121 


HULSEMANN, 
HULSEMANN 


K.— see    FLEMINGER   and 


Hunt — see  Vessels 

HURD,  CHARLES  L.— see  POWELL  et  al. 

Hydrolagus  colliei — see  Ratfish 

"In  situ  experiments  with  coastal  pelagic  fishes 
to  establish  design  criteria  for  electrical  fish 
harvesting  systems,"  by  Wilber  R.  Seidel  and 
Edward  F.  Klima  657 

Indian  Ocean 

zoogeography  of  the  genus  Nematoscelis   1039 

"(The)  influence  of  temperature  on  larval  and 
juvenile  growth  in  three  species  of  southern 
California  abalones,"  by  David  L.  Leighton  ....    1137 

"(The)  invasion  of  Saurida  undosquamis 
(Richardson)  into  the  Levant  Basin  -  an  example 


of  biological  effect  of  interoceanic  canals,"  by 

M.  Ben-Yami  and  T.  Glaser 359 

ISAACS,  JOHN  D.— see  SOUTAR  and  ISAACS 

Isaacs-Kidd  Midwater  Trawl 

net  filtering  efficiency  of  a  3-meter 618 

Islander  VI — see  Vessels 

Jacks 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
blue  ulua 954 

JAMES,  KENNETH  E.— see  POWELL  et  al. 

JOHNSON,  ALLYN  G.,  FRED  M.  UTTER,  and 
HAROLD  O.  HODGINS,  "Electrophoretic  com- 
parison of  five  species  of  pandalid  shrimp  from 
the  northeastern  Pacific  Ocean" 799 

JOHNSON,  MARTIN  W.,  "On  the  dispersal  of 
lobster  larvae  into  the  east  Pacific  barrier 
(Decapoda,  Palinuridea)"  639 

David  Starr  Jordan — -see  Vessels 

Kagoshima  Maru — see  Vessels 

KANWISHER,  JOHN,  KENNETH  LAWSON, 
and  GUNNAR  SUNDNES,  "Acoustic  telemetry 
from  fish"   251 

KAPLAN,  EUGENE  H.,  J.  R.  WELKER,  and 
M.  GAYLE  KRAUS,  "Some  effects  of  dredging 
on  populations  of  macrobenthic  organisms"  ....      445 

Katsuwonus  pelqmis — see  Tuna,  skipjack 

Kelp,  giant 
ecology  and  natural  history  of 

algal  association 672 

causes  of  plant  mortality  673 

components  of  the  epifauna 677 

epibenthic  invertebrates 677 

germination 675 

observations  on 672 

plant  longevity   676 

recruitment   675 

survivorship 675 

KEMMERER,  ANDREW  J.,  JOSEPH  A. 
BENIGNO,  GLADYS  B.  REESE,  and  FRED- 
ERICK C.  MINKLER,  "Summary  of  selected 
early  results  from  the  ERTS-1  menhaden  ex- 
periment"        375 

KENNEDY,  V.  S.,  W.  H.  ROOSENBURG,  M. 
CASTAGNA,  and  J.  A.  MIHURSKY,  "Mercen- 
aria  mercenaria  (Mollusca:  Bivalvia):  tempera- 
ture-time relationships  for  survival  of  embryos 
and  larvae" 1 160 


1176 


Killifish,  eastern  banded 

unusual  occurrence  in  the  lower  Columbia 
River   855 

Kistna — see  Vessels 

KITTREDGE,  J.  S.,  FRANCIS  T.  TAKAHASHI, 
JAMES  LINDSEY,  and  REUBEN  LASKER, 
"Chemical  signals  in  the  sea:  marine  allelo- 
chemics  and  evolution" 1 

KLIMA,  EDWARD  P.,  "Electrical  threshold 
response  of  some  Gulf  of  Mexico  fishes" 851 

—see  SEIDEL  and  KLIMA 

Kodiak,  Alaska 171 

Kona,  Hawaii 

feeding  relationships  of  teleostean  fishes  on 
coral  reefs,  June  1969  to  August  1970 915 

Kayo  Maru — see  Vessels 

KRAUS,  M.  GAYLE— see  KAPLAN  et  al. 

KREKORIAN,  C.  O'NEIL,  DAVID  C.  SOM- 
MERVILLE,  and  RICHARD  F.  FORD,  "Labora- 
tory study  of  behavioral  interactions  between  the 
American  lobster,  Homarus  americanus,  and  the 
California  spiny  lobster,  Panulirus  interruptus , 
with  comparative  observations  on  the  rock  crab, 
Cancer  antennarius"  1 146 

KRETSCH,  M.  J.— see  CRAWFORD  et  al. 

Kuhlia  sanduicensis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 948 

Kyphosus  cinerascens 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 964 

La  Jolla,  California  295 

"Laboratory  study  of  behavioral  interactions 
between  the  American  lobster,  Homarus  ameri- 
canus, and  the  California  spiny  lobster, 
Panulirus  interruptus,  with  comparative  obser- 
vations on  the  rock  crab.  Cancer  antennarius ,"  by 
C.  O'Neil  Krekorian,  David  C.  Sommerville,  and 
Richard  F.  Ford 1146 

Labroides  phthirophagus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 989 

LANDER,  ROBERT  H.— see  WAHLE  et  al. 

LANDERS,  WARREN  S.— see  CABLE  and 
LANDERS 

Larvae 

development  and  distribution  o{  Sebastolobus      865 
hard  clam 

temperature-time  relationships  for  survival    1160 


king  crab 

distribution  and  relative  abundance  in 
southeastern  Bering  Sea,  1969-70 804 

lobster 
dispersal  into  the  East  Pacific  Barrier 639 

plaice 

rearing  to  metamorphosis  using  an  arti- 
ficial diet 353 

silver  hake 
occurrence  along  middle  Atlantic  con- 
tinental shelf  during  1966 813 

swimming  energetics  of  anchovy 885 

Larvae,  fish — see  Fish  larvae 

"Larval  fishes  of  Yaquina  Bay,  Oregon:  a  nursery 
ground  for  marine  fishes?"  by  William  G.  Pearcy 
and  Sharon  S.  Myers 201 

LASKER,  REUBEN— see  KITTREDGE  et  al. 

LAWSON,  KENNETH— see  KANWISHER  et  al. 

Leatherjacket 

early  development  435 

LEIGHTON,  DAVID  L.,  "The  influence  of 
temperature  on  larval  and  juvenile  growth  in 
three  species  of  southern  California  abalones"  . .    1137 

Leiostomus  xanthurus — see  Spot 

LENARZ,  WILLIAM  H.,  "Length-weight  rela- 
tions for  five  eastern  tropical  Atlantic  scombrids"      848 

—see  MATHER  et  al. 

,  W.  W.  FOX,  JR.,  G.  T.  SAKAGAWA, 

and  B.  J.  ROTHSCHILD,  "An  examination  of 
the  yield  per  recruit  basis  for  a  minimum  size 
regulation  for  Atlantic  yellowfin  tuna,  Thunnus 
albacares" 37 

"Length-weight  relations  for  five  eastern  tropical 
Atlantic  scombrids,"  by  William  H.  Lenarz   ....      848 

Lepomis  macrochirus — see  Bluegill 

LIGHTNER,  DONALD  V.,  "Normal  postmortem 
changes  in  the  brown  shrimp,  Penaeus  aztecus"      223 

LILYBLADE,  A.  L  — see  CRAWFORD  et  al. 

LINDSEY,  JAMES— see  KITTREDGE  et  al. 

"(A)  link  between  science  and  management  in 
fisheries,"  by  D.  H.  Gushing  859 

LINN,  JAMES  S.— see  SMITH  et  al. 

Linseed  oil 
effects  on  the  flavor  of  turkey 1032 

Lionfish 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 944 

Lipids 

composition    of   residual    in    fish    protein 
concentrates 845 

1177 


Lizardfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Saurida  gracilis    929 

Synodus  variegatus    929 

Lizardfish,  Red  Sea 

invasion  into  the  Levant  Basin 
commercial  fish  populations  as  indicators  of 

the  biological  effect  360 

commercially  important  Red  Sea  migrants 

and  their  Mediterranean  competitors 360 

ecological  barriers  to  migrating  species  ....  368 

fishery  statistics  360 

food  and  habitat  364 

growth 366 

hake  as  a  competitor  of 367 

human  interference  may  facilitate  invasion  369 

invasion 364 

meteorology  363 

population  explosion  369 

Red  Sea  migrants  as  prey  of 367 

relation  with  relative  species   366 

relative  importance  359 

role  of  environmental  factors   370 

sea  temperature  361 

spawning 366 

Lobster,  American 

laboratory  study  of  behavioral  interactions 

with  the  California  spiny  lobster 1146 

tagged  by  Maine  commercial   fishermen, 
1957-59 622 

Lobster,  California  spiny 

laboratory  study  of  behavioral  interactions 

with  the  American  lobster 1146 

the  laboratory  study  of  behavioral  interactions 
with  the  rock  crab  1146 

Lobster  larvae 

dispersal  into  the  East  Pacific  Barrier 

cruise  results 640 

procedure   640 

Long  Island,  New  York 27 

Lookdown 
early  development  431 

Lyman — see  Vessels 

MacGREGOR,  JOHN  S.,  "Changes  in  the  amount 
and  proportions  of  DDT  and  its  metabolities, 
DDE  and  DDD,  in  the  marine  environment  off 
southern  California,  1949-72" 275 

Mackerel,  chub 

electrical  threshold  response  of 851 

Mackerel,  frigate 

length- weight  relations  for  five  eastern  tropical 
Atlantic  scombrids 848 


McLAIN,  DOUGLAS  R.— see  BAKUN  et  al. 

Macrobenthic  organisms 

effects  of  dredging  on  populations  of 

changes  in  land  usage  patterns   458 

chi-square  analysis  of  number  of  species 

and  specimens 462 

comparison  of  standing  crop  with  other  areas  464 

current  velocity 451 

dissolved  nutrients 453 

effects  of  wind-driven  currents  on  sediment 

deposition 455 

estimate  of  productivity  of  marsh  468 

light  penetration 450 

mass  movement  of  water  452 

mechanical  analysis  of  the  sediment 454 

Mercenaria  survey   457 

pH 450 

population  dynamics  and  distribution  of 

organisms 465 

previous  dredging  of  Goose  Creek 447 

productivity  468 

relationship  of  current  velocity  to  charac- 
teristics of  sediment  and  distribution  of 

organisms 470 

relationship  of  substratum  to  distribution 

of  organisms 470 

salinity    450 

standing  crop  estimates   463 

study  area 445 

water  temperature 450 

Macrocystis  pyrifera — see  Kelp,  giant 

Macropharyngodon  geoffroy 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 994 

Marine  ecosystems 
effects  of  oil  on 

biodegradation 628 

biological  differences 628 

biological  effects 630 

carcinogenicity    631 

description  of  oil 626 

environmental  differences  627 

hydrocarbons  in  marine  food  web    630 

natural  physical  processes  affecting  oil  in 

water  column 627 

observed  toxic  effects 631 

oil  in  sediments 629 

sublethal  and  chronic  effects  of  oil  pollution  634 

MARTIN,  A.  DALE— see  OLLA  et  al. 

MATHER,  F.  J.,  HI,  B.  J.  ROTHSCHILD,  G.  J. 
PAULIK,  and  W.  H.  LENARZ,  "Analysis  of  mi- 
grations and  mortality  of  bluefin  tuna,  Thunnus 
thynnus,  tagged  in  the  northwestern  Atlantic 
Ocean" 900 

MAYO,  FRANK  V.— see  BAKUN  et  al. 


1178 


"(The)  mean  annual  cycle  of  coastal  upwelling 
off  western  North  America  as  observed  from 
surface  measurements,"  by  Andrew  Bakun, 
Douglas  R.  McLain,  and  Frank  V.  Mayo 843 

Melichthys  niger 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii  1005 

Menhaden,  Gulf 

early  results  from  ERTS-1  experiment 
analytical  rationale  and  data  limitations   . .      378 

commercial  fishing  data 378 

ERTS-1  and  aircraft  environmental  sensors      377 
ERTS-1    imagery   and   fish   distribution 

relationships    382 

ERTS-1  imagery  and  oceanographic  param- 
eter relationships 385 

experimental  rationale 376 

fisheries  data 378 

oceanographic  parameter-fish  distribution 

relationships   379 

prediction  models  for  resource  management 

and  utilization 385 

sea-truth       oceanographic       parameter 

measurements 377 

study  area  and  fishery 376 

"Mercenaria  mercenaria  (Mollusca:  Bivalvia): 
temperature-time  relationships  for  survival  of 
embryos  and  larvae,"  by  V.  S.  Kennedy,  W.  H. 
Roosenburg,  M.  Castagna,  and  J.  A.  Mihursky    1160 

Mercenaria  mercenaria — see  Clam,  hard 

Merluccius  bilinearis — see  Hake,  silver 

Meteor — see  Vessels 

Micropogon  undulatus — see  Croaker,  Atlantic 

"Migrant  gray  whales  with  calves  and  sexual 
behavior  of  gray  whales  in  the  Monterey  area  of 
central  California.  1967-73,"  by  Alan  Baldridge      615 

MIHURSKY,  J.  A.— see  KENNEDY  et  al. 

MILLER,  JOHN  M.,  and  BARBARA  Y.  SUMIDA, 
"Development  of  eggs  and  larvae  ofCaranx  mate 
(Carangidae)" 497 

MILLER,  ROBERT  VICTOR— see  RICHARDS 

et  al. 

MINKLER,  FREDERICK  C— see  KEMMERER 
et  al. 

MISITANO,  DAVID  A.— see  DURKIN  and 
MISITANO 

,  and  CARL  W.  SIMS,  "Unusual  occur- 
rence of  an  eastern  banded  killifish  in  the  lower 
Columbia  River" 855 

MONCRIEF,  ROBERT  M.— see  STRUHSAKER 
and  MONCRIEF 


Monognathus 

metamorphic  forms  of 553 

three  new  species 

Monognathus  ahlstromi    551 

Monognathus  isaacsi  548 

Monognathus  Jesse  552 

Monotaxis  grandoculis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 956 

Moorish  idol 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1003 

Morone  saxatilis — see  Bass,  striped 

MOSER,  H.  GEOFFREY,  "Development  and 
distribution  of  larvae  and  juveniles  of  Sebastolo- 
bus  (Pisces;  Family  Scorpaenidae)" 865 

,  and  ELBERT  H.  AHLMSTROM, 

"Role  of  larval  stages  in  systematic  investiga- 
tions of  marine  teleosts:  the  Myctophidae,  a  case 
study" 391 

Mulloidichthys  auriflamma 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 957 

Mulloidichthys  samoensis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 957 

MUSICK,  JOHN  A.,  "Seasonal  distribution 
of  sibling  hakes,  Urophycis  chuss  and  U.  tenuis 
(Pisces,  Gadidae)  in  New  England" 481 

Mya  arenaria — see  Clam,  soft-shell 

Myctophidae 
role  of  larval  stages  in  systematic  investiga- 
tions 

some  evolutionary  considerations    409 

subfamily  Lampanyctinae  403 

subfamily  Myctophinae 392 

MYERS,  SHARON  S.— see  PEARCY  and 
MYERS 

Myripristis  amaenus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 940 

Myripristis  kuntee 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 938 

Myripristis  murdjan 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 939 

Naso  hexacanthus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1001 

Natal — see  Vessels 


1179 


Nematoscelis 

International  Indian  Ocean  Expedition  collec- 
tion, 1960-65 

zoogeography  of  the  genus 1039 

Neomysis  americana — see  Shrimp,  opossum 

"Net  filtering  efficiency  of  a  3-meter  Isaacs- 
Kidd  Midwater  Trawl,"  by  A.  L.  Brooks,  C.  L. 
Brown,  Jr.,  and  P.  H.  Scully-Power 618 

"(A)  new  model  of  ocean  migrations  of  Bristol 
Bay  sockeye  salmon,"  by  Robert  R.  French  and 
Richard  G.  Bakkala 589 

New  York 
Long  Island   27 

"Normal  postmortem  changes  in  the  brown 
shrimp,  Penaeus  aztecus,"  by  Donald  V.  Lightner      223 

North  America 
coastal  upwelling  off  western 

mean    annual    cycle    as    observed    from 
surface  measurements 843 


"Occurrence  of  a  ratfish  in  the  Columbia  River 
estuary,"  by  Joseph  T.  Durkin  and  David  A. 
Misitano   854 

"Occurrence  of  silver  hake,  Merluccius  bilinearis, 
eggs  and  larvae  along  the  middle  Atlantic  con- 
tinental shelf  during  1966,"  by  Michael  P.  Fahay      813 

Oil 
effects  of  dietary    a -tocopherol  and  tuna, 
safflower,  and  linseed  oils  on  the  flavor  of 
turkey   1032 

OLCOTT,  H.  S.— see  CRAWFORD  et  al. 

—see  SMITH  et  al. 

Oligoplites  saurus — see  Leatherjacket 

OLLA,  BORI  L.,  ALLEN  J.  BEJDA,  and  A. 
DALE  MARTIN,  "Daily  activity,  movements, 
feeding,  and  seasonal  occurrence  in  the  tautog, 
Tautoga  onitis"  27 

Omaka 
development  of  eggs  and  larvae 

body  proportions 511 

cultures 498 

definitions,  meristics,  and  morphometries  .  .  499 

egg  development 499 

growth 510 

larvae  fin  development 507 

larvae  pigmentation 504 

morphological  development  of  yolk  sac  larvae  504 

ossification  509 

yolk  sac  larvae  pigmentation   502 

"On  the  dispersal  of  lobster  larvae  into  the  East 
Pacific  Barrier  (Decapoda,  Palinuridea),"  by 
Martin  W.  Johnson    639 

1180 


Oncorhynchus  kisutch — see  Salmon,  coho 

Oncorhynchus  nerka — see  Salmon,  sockeye 

Opisthonema  oglinum — see  Herring,  Atlantic 
thread 

Oregon 
Yaquina  Bay  201 

Oregon — see  Vessels 

Oshoro  Maru — see  Vessels 

"Ostelogical  development  and  variation  in  young 
tunas,  genus  Thunnus  (Pisces,  Scombridae), 
from  the  Atlantic  Ocean,"  by  Thomas  Potthoff  .      563 

Ostracion  meleagris 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1011 

Pacific  Ocean 

variation  of  surface  geostrophic  flow 

data   1075 

eastern  boundary  currents  in  the  Northern 

Hemisphere   1079 

North  Equatorial  Countercurrent  1080 

North  Equatorial  Current  region 1083 

Peru  Current 1078 

South  Equatorial  Current  region 1077 

zoogeography  of  the  genus  Nematoscelis   1039 

Panama  City,  Florida   181,  657 

Pandalopsis  dispar — see  Shrimp,  pandalid 

Pandalus  borealis — see  Shrimp,  pandalid 

Pandalus  goniurus — see  Shrimp,  pandalid 

Pandalus  hypsinotus — see  Shrimp,  pandalid 

Pandalus  jordani — see  Shrimp,  pandalid 

Panulirus  interruptus — see  Lobster,  California 
spiny 

Paracirrhites  arcatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 986 

Paracirrhites  forsteri 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 986 

Paralithodes  camtschatica — see  Crab,  king 

PARK,  TAISOO,  "Calanoid  copepods  of  the 
genus  Aetideus  from  the  Gulf  of  Mexico" 215 

Parrotfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Scarus  rubroviolaceus  996 

Scarus  sordidus 995 

Scarus  taeniurus 995 

Parupeneus  bifasciatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 960 


Parupeneus  chryserydros 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 962 

Parupeneus  multifasciatus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 958 

Parupeneus  porphyreus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 961 

Patanela — see  Vessels 

PAULIK,  G.  J.— see  MATHER  et  al. 

PEARCY,  WILLIAM  G.,  and  SHARON  S. 
MYERS,  "Larval  fishes  of  Yaquina  Bay,  Ore- 
gon: a  nursery  ground  for  marine  fishes?" 201 

Pelican — see  Vessels 

Penaeus  aztecus — see  Shrimp,  brown 

Pervagor  spilosoma 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1010 

PETERSON,  D.  W.— see  CRAWFORD  et  al. 

Phoca  vitulina  richardi — see  Seal,  harbor 

Pillsbury — ^see  Vessels 

Pioneer — see  Vessels 

Plagiotremus  goslinei 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 999 

Plaice 

rearing  of  larvae  to  metamorphosis  using 

an  artificial  diet 353 

Plectroglyphidodon  johnstonianus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 978 

Pleurobrachia  bachei 

quantitative  natural  history 

demography  and  net  production 325 

growth  in  culture  and  metabolic  rates 297 

physical  parameters  and  distribution 304 

seasonal  variations  in  parasites,  predators, 

and  prey   313 

significance  of,  in  plankton   332 

study  area 300 

Pleuronectes  platessa — see  Plaice 

Pomacentrus  jenkinsi 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 979 

Pontellina 

systematics  and  distribution  of  sibling  species 

abundance 106 

developmental  stages  and  breeding 86 

geographical  distribution Ill 


geographical  variation  and  sympatry 103 

measurements 64 

phylogenetic  relationships 93 

Pontellina  morii  sp.  n 79 

Pontellina  platychela  sp.  n 75 

Pontellina  plumata  (Dana) 71 

Pontellina  sobrina  sp.  n. 84 

sample  analysis 64 

seasonal  occurrence  and  breeding  93 

specimen  analysis 64 

vertical  distribution 105 

Porgy 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Monotaxis  grandoculis 956 

Porgy, longspine 

electrical  threshold  response  of 851 

PORTER,  RUSSEL  G.,  "Reproductive  cycle  of 
the  soft-shell  clam,  Mya  arenaria,  at  Skagit  Bay, 
Washington"    648 

POTTHOFF,  THOMAS,  "Osteological  develop- 
ment and  variation  in  young  tunas,  genus 
Thunnus  (Pisces,  Scombridae),  from  the  Atlantic 
Ocean" 563 

POWELL,  GUY  C,  KENNETH  E.  JAMES, 
and  CHARLES  L.  HURD,  "Ability  of  male  king 
crab,  Paralithodes  camtschatica,  to  mate  re- 
peatedly, Kodiak,  Alaska,  1973"  171 

Pranesus  insularum 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 931 

Priacanthus  cruentatus — see  Bigeye 

Prince — see  Vessels 

Pseudocheilinus  octotaenia 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 989 

Pterios  sphex — see  Lionfish 
Puffer,  sharpbacked 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 

Canthigaster  amboiriensis 1013 

Canthigaster  jactator 1014 

Puffer,  spiny 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 

Diodon  holocanthus  1015 

Diodon  hystrix 1015 

"Quantitative  natural  history  o^  Pleurobrachia 
bachei  in  La  JoUa  Bight,"  by  Jed  Hirota 295 

QUAST,  JAY  C,  "Density  distribution  of 
juvenile  Arctic  cod,  Boreogadus  saida,  in  the 
eastern  Chukchi  Sea  in  the  fall  of  1970" 1094 


1181 


RAJU,  SOLOMON  N.,  "Three  new  species  of 
the  genus  Monognathus  and  the  leptocephali  of 
the  order  Saccopharyngiformes" 547 

Ratfish 
occurrence  in  the  Columbia  River  estuary  . . .      854 

"Rearing  of  plaice  (Pleuronectes  platessa)  larvae 
to  metamorphosis  using  an  artificial  diet,"  by 
J.  W.  Adron,  A.  Blair,  and  C.  B.  Cowey 353 

REESE,  GLADYS  B.— see  KEMMERER  et  al. 

"Reproductive  cycle  of  the  soft-shell  clam,  Mya 
arenaria,  at  Skagit  Bay,  Washington,"  by 
Russell  G.  Porter   648 

"(The)  residual  lipids  of  fish  protein  concen- 
trates," by  Vega  J.  Smith,  James  S.  Linn,  and 
Harold  S.  Olcott  845 

Rhinecanthus  rectangulus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1006 

RICE,  STANLEY  D.— see  EVANS  and  RICE 

RICHARDS,  WILLIAM  J.— see  HOUDE  et  al. 

,  ROBERT  VICTOR  MILLER,  and 

EDWARD  D.  HOUDE,  "Egg  and  larval  develop- 
ment of  the  Atlantic  thread  herring,  Opistho- 
nema  oglinum"   1123 

Rockaway — see  Vessels 

"Role  of  larval  stages  in  systematic  investiga- 
tions of  marine  teleosts:  the  Myctophidae,  a 
case  study,"  by  H.  Geoffrey  Moser  and  Elbert 
H.  Ahlstrom 391 

ROOSENBURG,  W.  H.— see  KENNEDY  et  al. 

ROSENTHAL,  RICHARD  J.,  WILLIAM  D. 
CLARKE,  and  PAUL  K.  DAYTON,  "Ecology 
and  natural  history  of  a  stand  of  giant  help, 
Macrocystis  pyrifera ,  off  Del  Mar,  California"  .  .      670 

ROTHSCHILD,  B.  J.— see  LENARZ  et  al. 

—see  MATHER  et  al. 

Rudderfish,  banded 

early  development  422 

Runner,  rainbow 

early  development  417 

RUSSELL,  GARY  M.— see  WICKHAM  and 
RUSSELL 


Saccopharyngiformes 
leptocephali  of 

affinities  of  Saccopharyngoidei  within  the 

Anguilliformes 560 

Leptocephalus  latissimus    555 

Leptocephalus  pseudolatissimus  557 

1182 


metamorphic  form  of  Eurypharynx  pele- 

canoides 558 

metamorphic  form  of  Saccopharynx   557 

Safflower  oil 

effects  on  the  flavor  of  turkey 1032 

SAKAGAWA,  G.  T.— see  LENARZ  et  al. 

SAKSENA,  VISHNU  P.— see  HOUDE  et  al. 

Salmon,  coho 

bioeconomic  contribution  of  Columbia  River 

hatchery 

economic  evaluation 152 

estimation  of  total  catch  from  hatcheries   . .      145 

experimental  design 140 

field  operations  144 

Salmon,  sockeye 

new  model  of  ocean  migrations  of  Bristol  Bay 
distribution  and  migration  inferred  from 

high-seas  catches   592 

distribution  as  determined  by  coastal  tag 

returns 590 

influence  of  water  areas  and  currents 609 

model 610 

Sardine,  scaled 

description  of  eggs  and  larvae 

comparisons 1120 

description  and  occurrence  of  embryos 1107 

description  of  larvae    1108 

meristics 1110 

morphometries 1107 

osteological  development   1112 

pigmentation  1116 

scales 1112 

transformation 1120 

electrical  threshold  response  of 851 

Saurida  gracilis 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii  929 

Saurida  undosquamis — see  Lizardfish,  Red  Sea 

Saury,  Pacific 

northeastern  Pacific  Ocean 

availability  of  fishable  concentrations   128 

growth 126 

length-weight  relation 126 

mortality 128 

status  of  knowledge 121 

stock  composition 123 

Scad,  round 

early  development   426 

Scarus  rubroviolaceus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 996 

Scarus  sordidus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 995 


Scar  us  taeniurus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 995 

Scomber  japonicus — see  Mackerel,  chub 

Scombrids 

length-weight  relations  for  five  eastern  tropical 

Atlantic 

bigeye  tuna ; 848 

frigate  mackerel  848 

little  tunny 848 

skipjack  tuna 848 

yellowfin  tuna 848 

Scophthalmus  aquosus — see  Windowpane 

Scorpaena  coniorta 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 945 

Scorpaenopsis  cacopsis 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 946 

Scorpionfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

lionfish ■ 944 

Scorpaena  coniorta 945 

Scorpaenopsis  cacopsis    946 

SCULLY-POWER,  P.  H.— see  BROOKS  et  al. 

Sea  bass 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Cephalopholis  argus 947 

Sea  chub 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Kyphosus  cinerascens 964 

Seal,  fur 

heavy  metals  in 

age  determinations 135 

analyses  of  samples 134 

collection  of  samples   134 

heavy  metal-age  comparison 136 

tissues  135 

Seal,  harbor 
heavy  metals  in 

age  determinations 135 

analyses  of  samples :  134 

collection  of  samples   134 

heavy  metal-age  comparison 136 

mercury  in  livers   136 

tissues  135 

"Seasonal  distribution  of  sibling  hakes,  Uro- 
phycis  chuss  and  U.  tenuis  (Pisces,  Gadidae)  in 
New  England,"  by  John  A.  Musick 481 


Sebastolobus 

development  and  distribution  of  larvae  and 
juveniles 

distinguishing  features 871 

distribution : .      880 

fin  development 876 

general  morphology 871 

pigmentation 879 

SEIDEL,  WILBER  R.,  and  EDWARD  F.  KLIMA, 
"In  situ  experiments  with  coastal  pelagic  fishes 
to  establish  design  criteria  for  electrical  fish 
harvesting  systems" 657 

Selene  vomer — see  Lookdown 

Seriola  zonata — see  Rudderfish,  banded 

Shrimp,  brown 

normal  postmortem  changes 

antennal  gland  232 

gills 231 

gonadal  tissue 232 

gross  observations   224 

heart  and  major  vessels  229 

histological  observations 225 

integument 229 

musculature 229 

nerve  tissue  232 

Shrimp,  opossum 

distribution,  variation,  and  supplemental 

description 

distribution 841 

morphological  analysis 836 

supplemental  description 838 

Shrimp,  pandalid 

electrophoretic  comparison  of  five  species  from 

the  northeastern  Pacific  Ocean 

Pandalopsis  dispar 799 

Pandalus  borealis 799 

Pandalus  goniurus 799 

Pandalus  hypsinotus   799 

Pandalus  jordani    799 

Silas  Bent — see  Vessels 

Silver  Bay — see  Vessels 

Silversides 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Pranesus  insularum 931 

"(A)  simple  bioeconomic  fishery  management 
model:  a  case  study  of  the  American  lobster 
fishery,"  by  Richard  F.  Fullenbaum  and  Frederick 
W.  Bell 13 

SIMS,  CARL  W.— see  MISITANO  and  SIMS 

Siphonophores 
distribution  adjacent  to  Suez  and  Panama 
canals 


1183 


Ahyla  carina 544 

Abyla  haeckeli  544 

Abyla  schmidt 544 

Abylopsis  eschscholtzi   542 

Abylopsis  tetragona    542 

Agalma  elegans 542 

Agalma  okeni 542 

Amphicaryon  acaule 542 

Amphicaryon  ernesti    542 

Anthophysa  rosea  542 

Apolemia  uvaria  542 

Athoribya  rosacea 542 

Bassia  bassensis   542 

Ceratocymba  dentata  544 

Ceratocymba  leuckarti 544 

Ceratocymba  sagittata  542 

Chelophyes  appendiculata 541 

Chelophyes  contorta  541 

Clausophyes  ovata 541 

Cordagalma  cordiformis 542 

Dimophyes  arctica 543 

Diphyes  bojani 541 

Diphyes  chamissonis    541 

Diphyes  dispar 541 

Diphyopsis  mitra 541 

distribution  in  eastern  Mediterranean  and 

Red  Sea 529 

distribution  in  western  Caribbean  and  cen- 
tral American  Pacific 534 

Enneagonum  hyalinum 542 

Eudoxia  russelli    541 

Eudoxoides  spiralis    541 

Forskalia  edwardsi 542 

Hippopodius  hippopus 542 

Lensia  campanella   541 

Lensia  challengeri 543 

Lensia  conoidea 541 

Lensia  cossack  543 

Lensia  fowleri    541 

Lensia  hotspur 541 

Lensia  lelouveteau 543 

Lensia  meteori  541 

Lensia  multicristata 541 

Lensia  subtilis  541 

Lensia  subtiloides 541 

Melophysa  melo 544 

Muggiaea  atlantica 541 

Muggiaea  kochi 541 

Nanomia  cara    542 

Nectopyramis  natans  544 

Physophora  hydrostatica 542 

Praya  cymbiformis  542 

Rhizophysa  filiforrnis 542 

Rosacea  plicata   542 

Sphaeronectes  spp 541 

Stephanomia  bijuga 542 

Stephanomia  rubra 542 

Sulculeolaria  angusta   541 


Sulculeolaria  bigelowi 543 

Sulculeolaria  biloba 541 

Sulculeolaria  chuni    542 

Sulculeolaria  monoica 544 

Sulculeolaria  quadrivalvis 542 

Sulculeolaria  turgida 542 

Vogtia  glabra 542 

Vogtia  pentacantha 542 

Vogtia  spinosa 542 

Skagit  Bay,  Washington 648 

SMITH,  VEGA  J.,  JAMES  S.  LINN,  and  HAR- 
OLD S.  OLCOTT,  "The  residual  lipids  of  fish 
protein  concentrates" 845 

Snapper 

feeding    relationships    on    coral    reefs    in 
Kona,  Hawaii 
Aphareus  furcatus    955 

Solimoes — see  Vessels 

"Some  aspects  of  the  ecology  of  stomiatoid  fishes 
in  the  Pacific  Ocean  near  Hawaii,"  by  Thomas 
A.  Clarke    337 

"Some  effects  of  dredging  on  populations  of 
macrobenthic  organisms,"  by  Eugene  H.  Kaplan, 
J.  R.  Welker,  and  M.  Gayle  Kraus   445 

SOMMERVILLE,  DAVID  C— see  KREKORIAN 
et  al. 

SOUTAR,  ANDREW,  and  JOHN  D.  ISAACS, 
"Abundance  of  pelagic  fish  during  the  19th  and 
20th  centuries  as  recorded  in  anaerobic  sediment 
off  the  Californias" 257 

Spisula  solidissima — see  Clam,  surf 

Spot 
electrical  threshold  response  of 851 

Squirrelfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Holocentrus  diadema 934 

Holocentrus  lacteoguttatum    937 

Holocentrus  sammara   932 

Holocentrus  spinifera 932 

Holocentrus  tiere 934 

Holocentrus  xantherythrus  934 

Holotrachys  lima 938 

Myripristis  amaenus    940 

Myripristis  kuntee 938 

Myripristis  murdjan 939 

Stenotomus  caprinus — see  Porgy,  longspine 

Stethojulis  balteata 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 992 


1184 


STICKNEY,  ROBERT  R.,  GARY  L.  TAYLOR, 
and  RICHARD  W.  HEARD  III,  "Food  habits  of 
Georgia  estuarine  fishes.  I.  Four  species  of 
flounders  (Pleuronectiformes:  Bothidae)" 515 

"Stock  composition,  growth,  mortality,  and  avail- 
ability of  Pacific  saury,  Cololabis  saira,  of  the 
northeastern  Pacific  Ocean,"  by  Steven  E. 
Hughes   121 

Stranger — see  Vessels 

STRUHSAKER,  PAUL,  and  ROBERT  M.  MON- 
CRIEF,  "Bothus  thompsoni  (Fowler)  1923,  a 
valid  species  of  flatfish  (Pisces:  Bothidae)  from 
the  Hawaiian  Islands" 237 

Sufflamen  bursa 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1008 

SUMIDA,  BARBARA  Y.— see  MILLER  and 
SUMIDA 

"Summary  of  selected  early  results  from  the 
ERTS-1  menhaden  experiment,"  by  Andrew  J. 
Kemmerer,  Joseph  A.  Benigno,  Gladys  B.  Reese, 
and  Frederick  C.  Minkler 375 

SUNDNES,  GUNNAR— see  KANWISHER  et  al. 

Surgeonfish 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 

Acanthurus  thompsoni    1000 

Naso  hexacanthus 1001 

Suriname  Rivier — see  Vessels 

"(The)  swimming  crabs  of  the  genus  Callinectes 
(Decapoda:  Portunidae),"  by  Austin  B.  Williams      685 

"Swimming  energetics  of  the  larval  anchovy, 
Engraulis  mordax,"  by  W.  J.  Vlymen 885" 

Synodus  uariegatus 
feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii  929 

"Systematics  and  distribution  of  the  four  sibling 
species  comprising  the  genus  Pontellina  Dana 
(Copepoda,  Calanoida),"  by  A.  Fleminger  and 
K.  Hulsemann 63 

TAKAHASHI,  FRANCIS  T.— see  KITTREDGE 
et  al. 

Talisman — see  Vessels 

Tautog 

Long  Island,  New  York 

activity  and  movements 29 

feeding 31 

seasonal  movements   33 

Tautoga  onitis — see  Tautog 

TAYLOR,  GARY  L.— see  STICKNEY  et  al. 


Telemetry 

acoustic,  from  fish 

behavior   954 

depth  transmitter 252 

heartbeat  transmitters  252 

physiological  response 254 

receiver 253 

sound  as  telemetry  medium 251 

Teritu — see  Vessels 

Thalassoma  duperrey 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii '      990 

Thalassoma  fuscus 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii ggj 

"Thermoregulatory  behavior  and  diel  activity 
patterns  of  bluegill,  Lepomis  macrochirus ,  fol- 
lowing thermal  shock,"  by  Thomas  L.  Beitinger     1087 

"Three  new  species  of  the  genus  Monognathus 
and  the  leptocephali  of  the  order  Saccopharyngi- 
formes,"  by  Solomon  N.  Raju 547 

Thunnus  albacares — see  Tuna,  yellowfin 

Thunnus  obesus — see  Tuna,  bigeye 

Thunnus  thynnus — see  Tuna,  bluefin 

Torrey  Canyon — see  Vessels 

Trawl — see  Isaacs-Kidd  Midwater  Trawl 

Triggerfish 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Melichthys  niger 1005 

Rhinecanthus  rectangulus   1006 

Sufflamen  bursa    1008 

Xanthichthys  ringens 1006 

Trumpetfish 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 
Aulostomus  chinensis    942 

TSUCHIYA,  MIZUKI,  "Variation  of  the  surface 
geostrophic  flow  in  the  eastern  intertropical 
Pacific  Ocean" 1075 

Tuna 

osteological  development  and  variation  in 
young  from  Atlantic  Ocean 

bones  and  rakers  of  the  first  gill  arch 578 

fins  and  fin  supports   572 

identification  584 

lateral  line  scales 583 

vertebral  column 564 

Tuna,  bigeye 

length-weight  relations  for  five  eastern  tropical 
Atlantic  scombrids 848 


1185 


Tuna,  bluefin 

analysis  of  migrations  and  mortality  of  tagged 

estimates  of  fishing  and  other  losses 909 

method  of  release 905 

migrations    900 

total  mortality  estimates — Chapman  and 

Robson  method  906 

total    mortality    estimates — regression 
method 911 

Tuna,  little  tunny 

length- weight  relations  for  five  eastern  tropical 
Atlantic  scombrids 848 

Tuna,  skipjack 

length-weight  relations  for  five  eastern  tropical 
Atlantic  scombrids 848 

Tuna,  yellowfin 

examination  of  yield  per  recruit  basis  for 

minimum  size  regulation  for 
approaches  to  yield-per-recruit  analysis  ....        39 

computer  programs    40 

data   39 

definitions  of  minimum  size 38 

dispersion  of  gear  and  yield  per  recruit  ....        58 
interaction  between  minimum  size  and  catch 

quota  regulations 58 

knife-edged  recruitment  approach 41 

parameters 40 

relation  between  fleet  composition  and 

optimum  size  at  recruitment 57 

size-specific  F  approach 45 

length-weight  relations  for  five  eastern  tropical 

Atlantic  scombrids 848 

Tuna  oil 

effects  on  the  fiavor  of  turkey 1032 

Ulua,  blue 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 954 

Umitaka  Maru — see  Vessels 

Undaunted — see  Vessels 

"Unusual  occurrence  of  an  eastern  banded  killi- 
fish  in  the  lower  Columbia  River,"  by  David  A. 
Misitano  and  Carl  W.  Sims 855 

Upwelling — see  Coastal  upwelling 

Urophycis  chuss — see  Hake,  red 

Urophycis  tenuis — see  Hake,  white 

UTTER,  FRED  M.— see  JOHNSON  et  al. 

"Variatioan  of  the  surface  geostrophic  flow  in  the 
eastern  intertropical  Pacific  Ocean,"  by  Mizuki 
Tsuchiya 1075 

Varuna — see  Vessels 

Velero—see  Vessels 


Velero  III — see  Vessels 

Vessels 

Alarninos 1076 

Alaska  66 

Albatross 749 

Albatross  IV 482 

Arcturus    750 

Argo 66,  1042,  1076 

Argosy  756 

Arrow 625 

Askoy 756 

Atlantis  749 

Atlantis  II 66, 1043 

Silas  Bent 66 

Blake    729 

Blue  Goose   743 

George  M.  Bowers 660,  733 

Anton  Bruun   66 

Calypso    729 

Cameron    482 

Cape  St.  Mary   744 

Chain    66,  1043 

John  N.  Cobb  130 

Combat 733 

Coquette  743 

Townsend  Cromwell 66,  237,  350,  640 

Delaware 66,  1043 

Diamantina    66 

Discovery 67 

Dolphin  814 

Dorsetshire  744 

Emilia   746 

Ensign  734 

Fish  Hawk    749 

Freelance 742 

Frobisher 744 

Gascoyne 66 

Theodore  N.  Gill 66,  835 

Glacier 1105 

Gulf  Ranger 182 

Hassler 729 

Horizon  66 

Hunt 66 

Islander  VI 67 

David  Starr  Jordan 66,  640,  1076 

Kagoshima  Maru    67 

Kistna    67,  1042 

Koyo  Maru    67,  1047 

Lyman  786 

Meteor   67 

Natal    67,  1042 

Oregon 66,  727 

Oshoro  Maru    67 

Patanela    1042 

Pelican 733 

Pillsbury  730 

Pioneer 67 


1186 


Prince 482 

Rockaway   66,  1076 

Silver  Bay 733 

Solimoes    746 

Stranger   66 

Suriname  Rivier 746 

Talisman 729 

Teritu 350 

Torrey  Canyon 625 

Umitaka  Maru 67 

Undaunted  1076 

Varuna    67 

Velero 787 

Velero  III 728 

Vidal   729 

Vitiaz 67 

Thomas  Washington 66,  528,  1076 

Zaca  756 

Vidal — see  Vessels 

Vitiaz — see  Vessels 

VLYMEN,  W.  J.,  "Swimming  energetics  of  the 
larval  anchovy,  Engraulis  mordax" 885 

VREELAND,  ROBERT  R.— see  WAHLE  et  al. 

WAHLE,  ROY  J.,  ROBERT  R.  VREELAND, 
and  ROBERT  H.  LANDER,  "Bioeconomic  con- 
tribution of  Columbia  River  hatchery  coho 
salmon,  1965  and  1966  broods,  to  the  Pacific 
salmon  fisheries" 139 

Washington 
Skagit  Bay 648 

Thomas  Washington — see  Vessels 

WELKER,  J.  R.— see  KAPLAN  et  al. 

Whale,  gray 

migrants  with  calves  and  sexual  behavior  off 
central  California 

northward  migration 615 

sexual  behavior 616 

WhifF,  bay 
Georgia 
food  habits  of 522 

WICKHAM,  DONALD  A.,  and  GARY  M.  RUS- 
SELL, "An  evaluation  of  mid-water  artificial 
structures  for  attracting  coastal  pelagic  fishes"  .      181 


WILLIAMS,  AUSTIN  B.,  "The  swimming  crabs 

of  the  genus  Callinectes  (Decapoda:  Portunidae)"      685 

,  THOMAS  E.  BOWMAN,  and  DAVID  M. 

DAMKAER,  "Distribution,  variation,  and  supple- 
mental description  of  the  opossum  shrimp,  Neo- 
mysis  americana  (Crustacea:  Mysidacea)" 835 

Windowpane 
Georgia 
food  habits  of 523 

Wrasse 

feeding  relationships  on  coral  reefs  in  Kona, 

Hawaii 

Anampses  cuvier 992 

bird 994 

Bodianus  bilunulatus    989 

Cheilinus  rhodochrous 989 

Coris  gaimard 993 

Halichoeres  ornatissimus   991 

Labroides  phthirophagus    989 

Macropharyngodon  geoffroy 994 

Pseudocheilinus  octotaenia 989 

Stethojulis  balteata 992 

Thalassoma  duperrey 990 

Thalassoma  fuscus 991 

Xanthichthys  ringens 

feeding  relationships  on  coral  reefs  in  Kona, 
Hawaii 1006 

Yaquina  Bay,  Oregon 
larval  fishes  of 

description  of  estuary  201 

estuary  as  a  nursery  208 

horizontal  variations 205 

relative  abundances  of  larvae 203 

sampling  methods 202 

seasonal  variations 204 

species  composition   203 

tidal-diel  variations 208 

Zaca — see  Vessels 

Zanclus  canescens — see  Moorish  idol 

"Zoogeography  of  the  genus  Nematoscelis  (Cru- 
stacea, Euphasiacea),"  by  K.  Gopalakrishnan  . .    1039 


1187 


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In  the  text,  Fishei-y  Bi(Ueti)i  style,  for  the 
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lication No.  6,  A  List  of  Com  moil  and  Scieiitific 
Names  of  Fishes  from  the  United  States  a)id 
Canada,  Third  Edition,  1970.  The  Merviam- 
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oped by  the  American  Standards  Association.) 

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as  mm,  m,  g,  ml,  mg,  °C  (for  Celsius),  7c.  "/oo 
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measure  only  when  used  with  numerals.  Periods 
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APPENDIX 

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(Contents-continued) 


KENNEDY,  V.  S.,  W.  H.  ROOSENBURG,  M.  CASTAGNA,  and  J.  A.  MIHURSKY. 
Mercenaria  mercenaria  (Mollusca:  Bivalvia):  Temperature-time  relationships  for 
survival  of  embryos  and  larvae 1160 


INDEX,  VOLUME  72  1167 


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nWlilllS'S,?.'   LIBRARY 


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